JP2020005672A - Ocular fundus imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fundus photography device for acquiring a fundus image in which artifacts are suppressed. SOLUTION: The fundus photographing apparatus includes an irradiation optical system that irradiates the fundus with illumination light via an objective lens, a light receiving element that shares the objective lens with the irradiation optical system, and further receives light reflected from the fundus of the fundus of the illumination light. It has a light receiving optical system and a photographing optical system including the light receiving optical system, and acquires a fundus image based on a signal from the light receiving element. The control unit acquires refractive index information, which is information regarding the refractive index of the eye to be inspected, and executes an artifact suppression process for suppressing the generation of artifacts based on the reflection of the illumination light by the objective lens according to the refractive index. Specifically, the shooting mode is based on the refractive power between the first mode in which the artifact suppression process is not executed when the fundus image is taken and the second mode in which the artifact suppression process is executed when the fundus image is taken. Can be switched. [Selection diagram] FIG. 12

Description

  The present disclosure relates to a fundus photographing apparatus for obtaining a front image of the fundus.

  2. Description of the Related Art A fundus imaging apparatus that captures a front image of the fundus of a subject's eye is widely used in the ophthalmology field. Examples of the fundus photographing apparatus include the following apparatuses in addition to the fundus camera and the scanning laser ophthalmoscope. For example, in Patent Literature 1, a front image of the fundus is obtained by scanning slit-shaped illumination light on the fundus and sequentially projecting the illuminated image of the fundus region on a two-dimensional imaging surface according to the scanning. An apparatus is disclosed. In many fundus imaging apparatuses, illumination light is projected and received through an objective lens.

JP-B-61-48940

  In an apparatus having an objective lens, reflected light generated on the front surface or the back surface of the objective lens may be reflected as an artifact in a fundus image under at least some shooting conditions. The artifact appears as a bright point image (reflection image) near the center of the fundus image. The bright spot image can be an obstacle to diagnosis and observation.

  The present disclosure has been made in view of at least one of the problems of the related art, and has an object to provide a fundus imaging apparatus capable of acquiring a fundus image in which artifacts are suppressed.

  A fundus imaging apparatus according to a first aspect of the present disclosure provides an illumination optical system that irradiates illumination light to the fundus of an eye to be examined via an objective lens, and the objective lens is shared with the illumination optical system. A fundus photographing apparatus that has a photographing optical system that includes a light receiving element that receives fundus reflected light of light, and that acquires a fundus image based on a signal from the light receiving element. A refractive power information acquisition unit that obtains refractive power information that is information on power, and a control unit that executes an artifact suppression process for suppressing the occurrence of an artifact based on the reflection of the illumination light by the objective lens, The control means includes: a first mode in which an artifact suppression process is not performed when capturing a fundus image; and a second mode in which the artifact suppression process is performed when capturing a fundus image. When switches based shooting mode between the refraction power.

  According to the present disclosure, it is possible to acquire a fundus image in which artifacts are suppressed.

FIG. 1 is a diagram illustrating an external configuration of an apparatus according to one embodiment. FIG. 3 is a diagram illustrating an optical system housed in the photographing unit according to the embodiment. FIG. 2 is a block diagram illustrating a control system of the device according to the embodiment. It is a figure for explaining operation of a diopter correction optical system according to a refractive power of an eye to be examined, and is a figure showing a state of diopter correction when a refractive power is in the 1st range. It is a figure for explaining operation of a diopter correction optical system according to a refractive power of an eye to be examined, and is a figure showing a state of diopter correction when a refractive power is in a 2nd range. It is a figure for explaining an outline of the 2nd artifact suppression processing. It is a figure for explaining an outline of the 3rd artifact suppression processing. FIG. 3 is a diagram illustrating a manner of irradiating illumination light to the fundus and scanning by the optical system of FIG. 2. FIG. 3 is a diagram illustrating a manner of irradiating illumination light to the fundus and scanning by the optical system of FIG. 2. It is a figure for explaining the outline of the 4th artefact suppression processing, and shows a fundus image obtained when irradiating illumination light from two projection areas simultaneously. It is a figure for explaining the outline of the 4th artefact suppression processing, and shows a fundus image obtained when illumination light is irradiated selectively from one of two projection areas. It is a figure for explaining the outline of the 5th artifact control processing. FIG. 3 is a diagram illustrating an optical chopper applicable as a scanning unit in the optical system of FIG. 2. 6 is a flowchart illustrating a photographing operation of the device.

"Overview"
Hereinafter, an embodiment of a fundus imaging apparatus according to the present disclosure will be described with reference to the drawings. In the following, in each of the first and second embodiments, an apparatus is disclosed in which artifacts caused by reflection and scattering inside the eye to be inspected or inside the apparatus are suppressed. Each embodiment can appropriately utilize a part or all of the other embodiments.

<First embodiment>
First, a first embodiment will be described. In the first embodiment, the fundus imaging apparatus (see FIG. 1) has at least an imaging optical system (for example, see FIG. 2) and a control unit (for example, see FIG. 3). The ophthalmologic photographing apparatus may additionally have a refractive power information acquisition unit.

<Control unit>
The control unit is a processing device (processor) that performs control processing of each unit in the fundus imaging apparatus and arithmetic processing. For example, the control unit is realized by a CPU (Central Processing Unit), a memory, and the like. In the present embodiment, the control unit may also serve as the image processing unit. The image processing unit performs at least one of generation of a fundus image and various types of image processing on the fundus image.

<Shooting optical system>
The photographing optical system is used for projecting and receiving illumination light to and from the fundus of the subject's eye via an objective lens to photograph a fundus image. In the first embodiment, the photographing optical system has an irradiation optical system, a light receiving optical system, and a diopter correction optical system (see FIGS. 2, 4A, and 4B).

  The irradiation optical system irradiates illumination light to the fundus of the subject's eye via the objective lens. Additionally, the illumination optical system may include a light source that emits illumination light (illumination light source). The light receiving optical system has a light receiving element that receives the fundus reflected light of the illumination light. The signal from the light receiving element is input to the image processing unit. The image processing unit acquires (generates) a fundus image of the subject's eye based on a signal from the light receiving element. In the present disclosure, a front image of the fundus is referred to as a “fundus image”.

  The irradiation optical system and the light receiving optical system share at least an objective lens. In addition, the irradiation optical system and the light receiving optical system may share an optical path coupling unit. The optical path coupling unit couples and separates a projection optical path of the illumination light and a light reception optical path of the fundus reflection light. In this case, the objective lens is arranged on a common optical path formed by the light path coupling section and the light projecting light path and the light receiving light path.

  The imaging optical system may be a scanning optical system that performs imaging by scanning illumination light on the fundus. Further, the imaging optical system may be a non-scanning optical system. Examples of a scanning optical system include a spot scan optical system and a line scan optical system. In a spot scan type optical system, spot-like illumination light is two-dimensionally scanned on the fundus. In a line scan type optical system, linear illumination light is scanned in one direction. For example, the linear illumination light may be linearly scanned on the fundus, or may be rotationally scanned on the fundus. In the case of rotational scanning, the center of rotation may be the optical axis of the imaging optical system. In the scanning optical system, any one of a point light receiving element, a line sensor, a two-dimensional light receiving element (photographing element), and the like can be appropriately adopted as the light receiving element. An example of a non-scanning optical system is an optical system of a general fundus camera.

<Diopter correction optical system>
The diopter correction optical system (see FIGS. 2, 4A, and 4B) is used to correct the diopter of the photographing optical system according to the refractive power of the eye to be inspected. The refractive power of the subject's eye is also referred to as a refractive error and a diopter value. In the present embodiment, the diopter correction optical system includes a diopter correction amount in the irradiation optical system (hereinafter, referred to as “irradiation-side correction amount”) and a diopter correction amount in the light-receiving optical system (hereinafter, “light-receiving-side correction amount”). ) Are adjusted independently.

  The diopter correction optical system may be separately arranged at two or more locations of the photographing optical system. In this case, the diopter correction optical system may include a first diopter correction optical system and a second diopter correction optical system. The diopter correction amount in the first diopter correction optical system and the diopter correction amount in the second diopter correction optical system are set independently. For example, the first diopter correction optical system may be disposed on one optical path of the irradiation optical system and the light receiving optical system, and in this case, the second diopter correction optical system may be disposed on the other optical path with respect to one. Alternatively, they may be arranged on a common optical path of the irradiation optical system and the light receiving optical system.

  In the present embodiment, a first driver (first driver) and a second driver (second driver) may be provided. The first drive unit and the second drive unit are independently controlled by the control unit. The first drive unit drives at least one optical element included in the first diopter correction optical system. The second drive unit drives at least one optical element included in the second diopter correction optical system.

  When the second diopter correction optical system is arranged in the common optical path, the diopter correction amount in the other optical system is the diopter correction amount in the first diopter correction optical system and the diopter correction amount in the second diopter correction optical system. And the diopter correction amount at For convenience of explanation, one or both of the first diopter correction optical system and the second diopter correction optical system that affect the diopter of the irradiation optical system are referred to as an “irradiation-side diopter correction optical system” and receive light. One or both that affect the diopter of the optical system may be referred to as a “light-receiving-side diopter correction optical system”.

  By the way, the position conjugate with the fundus of the objective lens (that is, the position of the intermediate image plane of the fundus) is displaced according to the refractive power (mainly, the spherical power) of the eye to be examined. In FIGS. 4A and 4B, the position of the intermediate image plane is indicated by reference numeral J. In the present embodiment, the diopter correction optical system disposed between the objective lens and the light receiving surface is driven such that the intermediate image plane and the light receiving surface of the light receiving optical system have a conjugate relationship, thereby forming a fundus. Is well formed on the light receiving surface.

  In the present disclosure, “conjugate” is not necessarily limited to a perfect conjugate relationship, but includes “substantially conjugate”. In other words, a case where the components are displaced from a perfect conjugate position within a range permitted in relation to the technical significance of each unit is also included in the “conjugate” in the present disclosure.

  Also, if diopter correction is performed in the irradiation optical system, it is considered that, for example, errors in the illumination range are suppressed, and the light amount distribution of the illumination light on the fundus becomes easy to be uniform. However, the condensing position in the irradiation optical system is displaced along the optical axis according to the irradiation-side correction amount. Specifically, as the irradiation-side correction amount shifts to the minus diopter side, it is considered that the condensing position approaches the objective lens. In FIGS. 4A and 4B, the light condensing position is indicated by a symbol K. When the focusing position approaches the surface of the objective lens, the reflection of the illumination light by the objective lens may be easily reflected in the fundus image as an artifact. That is, if the irradiation-side correction amount is adjusted in accordance with the refractive power, the more the refractive power of the eye to be examined is a value on the minus diopter side (for example, the more the myopic eye has a higher power), Artifacts are likely to occur.

<Artifact suppression by making the irradiation-side correction amount and the light-receiving-side correction amount inconsistent>
On the other hand, the control unit may adjust the irradiation-side correction amount and the light-receiving-side correction amount to different values by controlling the diopter correction optical system (see FIG. 4B). For example, the control unit may adjust the light-receiving-side correction amount according to the refractive power of the eye to be inspected. More specifically, the light-receiving-side correction amount may be adjusted to a diopter substantially equal to the refractive power.

  At this time, the control unit may further adjust the focusing position of the illumination light via the diopter correction optical system with reference to the intermediate image of the fundus oculi formed via the objective lens (see FIG. 4B). More specifically, the irradiation-side correction amount may be adjusted such that the light-converging position is arranged at a position further away from the objective lens with respect to the intermediate image. Thus, the image of the fundus is favorably formed on the imaging surface of the light receiving optical system, and the occurrence of artifacts due to the reflection of the objective lens is suppressed. As a result, a good fundus image is captured.

  At this time, the irradiation-side correction amount may be adjusted so that the absolute value is smaller than the light-receiving-side correction amount. As the difference between the irradiation-side correction amount and the light-receiving-side correction amount increases, various effects such as a decrease in the amount of received light are more likely to occur. Therefore, by limiting each correction amount so that a large difference does not occur between the irradiation-side correction amount and the light-receiving-side correction amount, it is possible to obtain a fundus image with good image quality while suppressing the occurrence of artifacts. Can be.

  When adjusting the irradiation-side correction amount and the light-receiving-side correction amount to values different from each other, the control unit may adjust the irradiation-side correction amount to a constant value regardless of the light-receiving-side correction amount. However, the present invention is not necessarily limited to this, and in the same case, the irradiation-side correction amount may be adjusted to a different value for each light-receiving-side correction amount.

  However, it is not necessary to always adjust each irradiation so that the irradiation-side correction amount and the light-receiving-side correction amount have different values. For example, under predetermined imaging conditions, the irradiation-side correction amount and the light-receiving-side correction amount may match each other. Here, the imaging conditions under which the artifact does not matter can be checked in advance by experiments, optical simulations, and the like. For example, the range of the diopter correction amount in which the artifact does not occur when the irradiation-side correction amount and the light-receiving-side correction amount are matched may be predetermined as the imaging condition. When the irradiation-side correction amount and the light-receiving-side correction amount match each other, each of the irradiation-side correction amount and the light-receiving-side correction amount may be adjusted to a diopter substantially equal to the refractive power.

<Switching the shooting mode according to the refractive power>
In the present embodiment, the control unit determines whether the irradiation-side correction amount and the light-receiving-side correction amount are different from each other in a first imaging mode (see FIG. 4A) in which imaging is performed with the irradiation-side correction amount and the light-receiving-side correction amount being matched with each other. The imaging mode of the apparatus may be switched in accordance with the refractive power of the eye to be examined, between a second imaging mode (see FIG. 4B) in which imaging is performed in a state where the eye is left. The refractive power may be roughly divided into a first range and a second range on the minus diopter side with respect to the first range. That is, the second range is different from the first range in the intermediate image plane of the fundus reflection light formed via the objective lens (mainly, the intermediate image plane formed closest to the objective lens). Is a range that is closer to the rear surface of the objective lens. 4A and 4B, the range of the diopter correction amount corresponding to the first range is the range illustrated by reference numeral A1, and the range of the diopter correction amount corresponding to the second range is reference numeral A2. Is the range shown in FIG. The shooting mode may be switched between a case where the refractive power is in the first range and a case where the refractive power is in the second range. The control unit may switch to the first photographing mode when the refractive power is within the first range. In this case, the control unit may photograph the fundus in a state where the irradiation-side correction amount and the light-receiving-side correction amount match each other. At this time, both the irradiation-side correction amount and the light-receiving-side correction amount may be adjusted to values according to the refractive power. Further, the control unit may switch to the second shooting mode when the refractive power is in the second range. In this case, the control unit may adjust the light-receiving-side correction amount according to the refractive power of the eye to be inspected, and set the irradiation-side correction amount to a value having a smaller absolute value than the light-receiving-side correction amount.

  The value of the refractive power serving as the threshold between the first range and the second range can be checked in advance by, for example, experiments and optical simulations. For example, when changing the diopter correction amount in the diopter correction optical system from the plus diopter side to the minus diopter side while matching the irradiation side correction amount and the light receiving side correction amount, the reflection of the objective lens causes A value at which an artifact starts to occur may be determined as a threshold.

<Scanning imaging optical system>
Meanwhile, as a scanning type imaging optical system, an apparatus having a harmful light removing unit and a scanning unit is known. In a scanning type imaging optical system, an illumination optical system forms a local illumination area in a part of an imaging range on a fundus. As a typical example, an apparatus that forms an illumination area in a slit shape or a spot shape is known.

  The harmful light removing unit is disposed on the optical path of the light receiving optical system with the diopter correction optical system interposed between the harmful light removing unit and the objective lens, for example. In this case, the harmful light removing unit may be arranged at a position conjugate with the fundus with respect to at least the objective lens and the diopter correction optical system in a state where the correction amount on the light receiving side according to the refractive power of the eye to be inspected is set.

  The harmful light removing unit causes the light receiving element to receive fundus reflected light from a local imaging region (hereinafter, referred to as an “effective region”) that is a part of the imaging range. The harmful light removing unit is used for removing light from areas other than the effective area. The harmful light removing unit may be, for example, an aperture. A typical stop in a spot scan type apparatus is a pinhole, and a typical stop in a slit scan type apparatus is a slit. In this case, the fundus reflection light from the effective area corresponding to the aperture of the stop in the entire photographing range on the fundus is selectively guided to the light receiving element, and is acquired as an effective image. In particular, in a slit scan type device, the light receiving element itself may be used as a harmful light removing unit. In this case, a line sensor whose shape itself is formed in a slit shape may be used as the light receiving element, or line exposure is performed on a two-dimensional imaging surface (in other words, has a rolling shutter function). CMOS may be used. In this case, the fundus reflection light from the effective area corresponding to the line-shaped effective pixel in the entire fundus imaging range is selectively guided to the light receiving element, and is acquired as an effective image.

  The scanning unit scans the local illumination region and the effective region (local imaging region) on the fundus in synchronization with each other. The scanning unit may be, for example, an optical scanner shared between the irradiation optical system and the light receiving optical system. In this case, the optical scanner is arranged on a common optical path of the irradiation optical system and the light receiving optical system.

  The scanning unit may include a first scanning unit provided in the irradiation optical system and a second scanning unit provided separately from the first scanning unit and provided in the light receiving optical system. In this case, in an example of the slit scan type device, a first slit-shaped member may be arranged on the optical path of the irradiation optical system in order to form a local illumination region in a slit shape. The first scanning unit may include a first slit-shaped member and a driving unit that moves the first slit-shaped member in a direction intersecting the optical axis. Further, when the second slit-shaped member is used as the harmful light removing unit, the second scanning unit includes a second slit-shaped member and a driving unit that moves the second slit-shaped member in a direction intersecting the optical axis. It may be. The driving unit of the first scanning unit and the driving unit of the second scanning unit may be separate devices or may be a common device.

  In the case where a CMOS is used as the light receiving element in the slit scan type device, the CMOS may be used as the second scanning unit in the second scanning unit. That is, the line exposure by the rolling shutter function may be controlled in synchronization with the first scanning unit. In this case, the CMOS which is the light receiving element also serves as the harmful light removing unit and the second scanning unit. Thereby, the number of parts of the optical system is suppressed.

<Suppression of image height change due to diopter correction>
In the scanning type imaging optical system as described above, if the position of the area irradiated with the illumination light on the fundus deviates from the position of the effective area, the amount of received light decreases or an image cannot be obtained at all. It is possible that you may not be able to do it.

  On the other hand, the diopter correction optical system performs diopter correction in each of the irradiation optical system and the light receiving optical system between when the irradiation-side correction amount and the light-receiving-side correction amount match and when they are different from each other. A telecentric optical system that maintains an image height in a region closer to the image than the optical system may be included. (However, in both the irradiation optical system and the light receiving optical system, the eye to be examined is referred to as the object side, and the side opposite to the eye to be examined with the diopter correction optical system therebetween is referred to as the image side.) Even when the side correction amount and the light receiving side correction amount do not match, a difference between the position of the area irradiated with the illumination light on the fundus and the position of the effective area hardly occurs. Therefore, the above-described telecentric optical system has an effect that, in an apparatus having a scanning-type photographing optical system, a fundus image can be photographed favorably when the occurrence of artifacts is suppressed. However, the telecentric optical system may be a substantially telecentric optical system within an allowable accuracy range.

  Note that, more specifically, the telecentric optical system may include a first telecentric optical system and a second telecentric optical system. The first telecentric optical system maintains an image height in a region closer to the image than the diopter correction optical system regardless of a change in the light-receiving-side correction amount. The second telecentric optical system maintains the height of the principal ray of the illumination light on the fundus irrespective of a change in the irradiation-side correction amount.

  The above-described telecentric optical system is also useful for a non-scanning optical system. That is, a change in magnification of the fundus image and a change in illumination unevenness due to diopter correction are suppressed by the telecentric optical system.

<Adjustment of shooting conditions according to diopter correction amount>
The irradiation-side correction amount is adjusted to a value different from the light-receiving-side correction amount in order to suppress the occurrence of artifacts. As a result, the outer edge of the area on the fundus where the illumination light is irradiated is blurred or the illumination light is irradiated. There is a case where the position of the area is shifted from the position of the effective area. In these cases, the amount of received light is more likely to be reduced than in the case where the irradiation-side correction amount matches the light-receiving-side correction amount.

  In contrast, in the present embodiment, between the case where the irradiation-side correction amount and the light-receiving side correction amount match each other, and the case where the irradiation-side correction amount and the light-receiving side correction amount are different from each other. The control unit may execute switching control for switching at least one of the amount of illumination light irradiated to the fundus, the gain of the light receiving element, and the exposure time. More specifically, when the irradiation-side correction amount and the light-receiving-side correction amount are different from each other, when the irradiation-side correction amount and the light-receiving-side correction amount are different from each other, the amount of illumination light, At least one of the gain of the light receiving element and the exposure time is increased. Thus, even when the irradiation-side correction amount and the light-receiving-side correction amount do not match, a fundus image with a wide dynamic range can be obtained. This switching control may be linked with the switching of the shooting mode. Note that the control unit may reduce the scanning speed to increase the exposure time. Further, in an apparatus that continuously captures a plurality of fundus images and adds a plurality of images to capture one captured image, increasing the number of fundus images used for addition increases the exposure time. Can be substantially increased.

<Refractive power acquisition unit>
The refractive power information obtaining unit obtains refractive power information as information on the refractive power of the subject's eye. For example, the refractive power information obtaining unit may be a measuring unit that obtains refractive power information by measuring the eye to be inspected. In this case, at least a part of the imaging optical system may be used for the measurement unit that is the refractive power information acquisition unit. For example, the refractive power information acquisition unit may detect a focus state in the light receiving optical system, and acquire refractive power information based on a detection result of the focus state. More specifically, the focus state is detected while changing the light-receiving-side correction amount, which is the diopter correction amount in the light-receiving optical system, and the value of the light-receiving-side correction amount when the best focus state is obtained is determined by the refraction. It may be acquired as frequency information. However, the correction amount is not limited to the light-receiving-side correction amount. The driving amount in the driving unit driven to change the light-receiving-side correction amount (or the irradiation-side correction amount), and the position information of the optical element displaced by the driving unit , Etc. may be acquired as the refractive power information. The focus state may be detected based on a fundus image acquired via the photographing optical system. In this case, the focus state may be detected as contrast information of the fundus image. Further, the focus state may be detected based on a fundus image in which the index image of the focus index is reflected. As an example of the focus index, a split index is known (see FIG. 2). The split target is projected on the fundus as two target images separated by the prism. The focus state may be detected based on the positional relationship between the two index images. In this case, the refractive power information acquisition unit includes an index projection unit that projects the focus index.

  Note that the refractive power information acquisition unit is not necessarily limited to the measurement unit. For example, the refractive power information acquiring unit may be configured to receive refractive power information measured in advance by a device separate from the fundus photographing device, and to thereby acquire the refractive power information. In this case, the refractive power information acquisition unit may include a control unit and a port for connecting any of a separate device, an external storage medium, a user interface, and the like to the ophthalmologic measurement device. . As a separate device, for example, there is a subjective or objective refraction inspection device. The external storage medium may store refractive power information in advance, and the control unit may read the refractive power information from the storage medium to acquire the information. Also, the user interface may be used to manually enter refractive power information. In this case, the refractive power information may be acquired as an input result by the examiner.

<Second embodiment>
Next, a second embodiment will be described.

  In the fundus imaging apparatus according to the second embodiment, processing for suppressing artifacts due to reflection of the objective lens (hereinafter, artifact suppression processing) is executed. In the second embodiment, the artifact suppression processing is automatically executed when the refractive power of the subject's eye falls within a predetermined range, and is not executed when the refractive power is outside the predetermined range. In other words, the control unit sets the shooting mode between the first mode in which the artifact suppression process is not performed when capturing the fundus image and the second mode in which the artifact suppression process is performed when capturing the fundus image. , Based on the refractive power.

  As described in the first embodiment, when diopter correction according to the refractive power is performed in both the irradiation optical system and the light receiving optical system, artifacts are more likely to occur as the refractive power is on the minus diopter side. . Therefore, in the second embodiment, the first mode is set in the former case between the case where the refractive power is included in the first range and the case where the refractive power is included in the second range. In this case, the second mode may be set. As a result, a fundus image in which the occurrence of artifacts is suppressed is obtained regardless of the refractive power of the eye to be examined. In addition, when photographing an eye to be inspected in which the refractive power is relatively on the plus diopter side and artifacts are unlikely to occur, the influence on the fundus image based on the artifact suppression processing, and the burden on the examinee due to the imaging, etc. At least one is prevented.

  In addition, the diopter correction optical system for setting the irradiation-side correction amount (the diopter correction amount in the irradiation optical system) and the light-receiving-side correction amount (the diopter correction amount in the light receiving optical system) in the first embodiment to a mismatch state. Driving the system corresponds to one of various artifact suppression processes. However, the artifact suppression processing in the second embodiment is not necessarily limited to this. For example, in the artifact suppression process, a plurality of fundus images having different positions of the artifact with respect to the tissue of the eye to be examined may be captured, and a plurality of fundus images may be combined to generate a combined image (for example, Second and fifth artifact suppression processes). Further, various operations exemplified in the following description may be adopted.

  Hereinafter, the detailed configuration of the second embodiment will be described focusing on the differences from the first embodiment. The fundus imaging apparatus according to the second embodiment has at least an imaging optical system, an image processing unit, a refractive power acquisition unit, and a control unit. For each of these components, the items of <control unit>, <image processing unit>, <photographing optical system>, and <refractive power acquisition unit> in the description of the first embodiment can be used as appropriate.

<Second artifact suppression processing>
In the second artifact suppression processing, the fundus image is photographed at least twice by switching the positional relationship between the optical axis of the photographing optical system and the visual axis of the subject's eye. Further, a plurality of fundus images obtained by at least two shootings are combined by the image processing unit. As a result, the device acquires a composite image that is a fundus image in which artifacts are suppressed (see FIG. 5). In FIGS. 5 to 10, artifacts are indicated by reference numeral N or reference numerals N1 and N2. The image processing unit is configured to convert an area including an artifact in at least one of the plurality of fundus images (referred to as a first fundus image) into an image area having the same positional relationship with respect to the fundus tissue and the other fundus image. A complementary image is generated by performing complementation using the image area. More specifically, a region including an artifact in at least one of a plurality of fundus images may be replaced with a corresponding image region in another image. Further, an area including an artifact may be complemented by image addition of a plurality of fundus images.

  In order to execute the second artifact suppression processing, the fundus imaging apparatus may include a position adjustment unit. The position adjustment unit adjusts an occurrence position of an artifact with respect to a fundus tissue in a fundus image by changing a positional relationship between an optical axis of an imaging optical system and a visual axis of an eye to be inspected. The position adjustment unit may include a fixation optical system. The fixation optical system presents a fixation target to the eye to be examined. The fixation optical system may be capable of switching the presentation position of the fixation target to a plurality of positions in a direction intersecting the optical axis of the imaging optical system. In addition, the position adjustment unit may include a driving unit that moves the imaging optical system with respect to the eye to be inspected. For example, the driving unit may change the positional relationship between the optical axis of the imaging optical system and the visual axis of the eye by rotating the imaging optical system around the anterior segment of the eye. Of course, the position adjustment unit may include both the fixation optical system and the drive unit.

  For more detailed contents regarding the second artifact suppression processing, refer to, for example, Japanese Patent Application Laid-Open No. 2017-184787 by the present applicant.

<Third artifact suppression processing>
In the third artifact suppression process, a background difference based on the fundus image and the background image is executed by the image processing unit, and as a result, a fundus image in which artifacts are suppressed is generated (see FIG. 6). The background image referred to here is a background image for the fundus image, and includes at least an artifact due to the objective lens. The background image may be an image captured with the front side of the objective lens covered with a lens cover or the like.

  For more details regarding the third artifact suppression processing, refer to, for example, Japanese Patent Application Laid-Open No. 2017-217076 by the present applicant.

<Apparatus Configuration as Premise of Fourth and Fifth Artifact Suppression Processing>
All of the fourth and fifth artifact suppression processes are based on the premise that the imaging optical system has the following configuration. That is, the photographing optical system is a slit scan type optical system. For example, the optical system shown in FIG. 2 may be used. The imaging optical system has at least a slit forming unit, a scanning unit, and a light emitting / receiving unit. In addition, the imaging optical system may include a light source, an image sensor, an optical path branching unit, and the like.

  The slit forming unit forms the illumination light in a slit shape on the fundus of the eye to be inspected. The slit forming portion may be, for example, a slit-shaped light transmitting portion (for example, an opening) arranged in a plane conjugate with the fundus.

  The scanning unit scans the illumination light formed in a slit shape on the fundus in a direction intersecting the slit. As shown in FIGS. 2 and 7, the scanning unit scans the illumination light formed in a slit shape on the fundus in a direction intersecting the slit (specifically, a direction intersecting the longitudinal direction of the slit). . The scanning unit may scan the illumination light by moving the slit forming unit in a direction intersecting the slit. Examples of this type of scanning unit include a mechanical shutter, a liquid crystal shutter, an optical chopper, and a drum reel.

  The scanning direction of the slit is preferably a direction orthogonal to the slit. However, the direction may be oblique to the direction orthogonal to the slit.

  Further, the scanning unit may be a member that changes the direction of light passing through the slit forming unit. For example, various optical scanners such as a galvano scanner may be used as the scanning unit. A scanning unit of a type that scans by rotating light may be placed at a position conjugate with the pupil of the eye to be examined.

  The imaging optical system may further include an optical path coupling unit and an objective lens.

  The optical path coupling unit couples and separates the projection optical path of the illumination light and the light reception optical path of the fundus reflection light. The objective lens is arranged on a common optical path formed by the optical path coupling section and the light transmitting optical path and the light receiving optical path. At this time, it is desirable that the optical axis of the photographing optical system (hereinafter, also referred to as “photographing optical axis”) coincides with the optical axis of the objective lens.

  Various beam splitters can be used as the optical path coupling unit. In this case, the optical path coupling unit may be a perforated mirror, a simple mirror, a half mirror, or another beam splitter.

  The light projection / reception separating unit separates, on the pupil of the subject's eye, an area where the illumination light is projected (light projection area) and an area where the fundus reflection light by the illumination light is extracted (light reception area).

  Specifically, as shown in FIGS. 2 and 8, the light projecting / receiving part forms two light projecting regions separated from each other in the scanning direction of the illumination light. The two light projecting regions may be formed so as to sandwich the photographing optical axis. In the first embodiment, the light-projecting / receiving separation unit may be one that forms at least two light-projecting regions, and may be one that forms three or more light-projecting regions. The illumination light that has passed through each light projecting area illuminates the same slit-shaped area on the fundus. Then, as the scanning unit is driven, the slit-shaped area is scanned.

  As shown in FIG. 8, the light receiving / receiving section is formed so as to be sandwiched between the two light emitting areas by the light emitting / receiving section. That is, the regions are formed in a line in the order of one light emitting region, light receiving region, and the other light emitting region. Further, the light receiving region may be formed on the photographing optical axis. The light emitting area and the light receiving area may be arranged so as not to overlap each other. In that case, it is reduced that a part of the illumination light is reflected and scattered in the cornea and the intermediate light transmitting body, and flare is generated in the fundus image.

  The light projection / reception separation unit may include a plurality of members arranged on the light projection light path of the illumination light and the light reception light path, respectively.

  The light-projection / light-receiving separation unit partially sets the irradiation position of the illumination light at at least two positions separated from each other with respect to the scanning direction of the illumination light, for example, on a pupil conjugate plane in the light-projecting optical path of the illumination light. There may be. In this case, a light source that emits illumination light may be disposed at each of the two irradiation positions, and an opening that allows illumination light to pass therethrough may be disposed at each of the two irradiation positions.

  In other words, the light projection / reception separation unit includes at least two illumination light sources or two apparent illumination light sources that are arranged at positions different from each other in the scanning direction at a position conjugate with the pupil of the subject's eye. There may be. As a result, the light projection area is formed at two positions separated from each other in the scanning direction of the illumination light. More preferably, the two illumination light sources, or the two apparent illumination light sources, may be arranged symmetrically with respect to the imaging optical axis. Thereby, two light projection areas can be formed symmetrically with respect to the photographing optical axis. The state of light emission from two light sources or two apparent light sources may be controllable for each light source by a control unit described later. As a result of controlling the light projection state for each light source, whether or not to transmit the illumination light is individually set for each light projection area. Of course, the light projecting / receiving separation unit may include three or more illumination light sources, or three or more apparent illumination light sources.

  Note that the light projection state may include at least two types of states: a state in which illumination light from a light source or an apparent light source reaches the subject's eye and a state in which illumination light does not reach the eye. The switching of the projection state may be realized by controlling the lighting of the light source. The light projection state may be switched by driving and controlling a light source or a shutter that selectively blocks a light beam from the apparent light source toward the subject's eye.

  In addition, the light-projecting / receiving separation unit partially passes the fundus reflection light from the light-receiving area, which is an area sandwiched between the two light-projecting areas, on the pupil conjugate plane in the light-receiving optical path of the illumination light to the imaging surface side. Alternatively, other light may be prevented from passing through to the imaging surface side. For example, the light projection / reception separation unit may include a light blocking member that allows the fundus reflection light from the light reception area to pass to the imaging surface side and blocks other light. The light blocking member may be arranged on the pupil conjugate plane in the light receiving optical path, for example. For example, when a stop having an opening centered on the photographing optical axis is provided as a light blocking member, a light receiving region is formed by an opening image of the stop.

  When a light-shielding member is included in the light-projecting / receiving separation unit, the light-shielding member may be shared with the above-described optical path coupling unit or may be a separate unit.

<Fourth artifact suppression processing>
In the above-described apparatus configuration, the control unit may individually set whether or not to transmit the illumination light for the two light-projection regions on the pupil of the subject's eye. In this case, the control unit may capture a fundus image based on the illumination light selectively projected from one (any one) of the two projection areas.

  By the way, in the vicinity of the photographing optical axis in the fundus image, a reflected image (a kind of bright spot image or a kind of artifact) may be generated due to the reflection of the illumination light at the center of the lens surface of the objective lens. Since the light projection area is far from the photographing optical axis, the reflected image is likely to appear at a position slightly deviated from the position of the photographing optical axis in the fundus image. As an example, FIG. 9A shows a fundus image captured by simultaneously projecting illumination light from both of the two projection areas. As shown in FIG. 9A, corresponding to the two light projecting regions, reflected images (indicated by reference numerals N1 and N2) may be generated at two places across the photographing optical axis in the central portion of the fundus image. The two reflection images appear side by side in the scanning direction (that is, at different positions in the scanning direction).

  In contrast, in the present embodiment, the illumination light is selectively projected from one of the two projection areas to the fundus, and a fundus image is captured. As a result, the position of the objective lens where a reflected image is generated is reduced by half compared to the above case. As a result, as shown in FIG. 9B, the reflection image in the fundus image can be reduced by half. As described above, selectively projecting the illumination light from one of the two light projecting regions on the pupil of the subject's eye to the fundus and photographing the fundus image is advantageous in reducing artifacts. is there.

<Fifth Artifact Suppression Processing>
The control unit selectively emits illumination light to the fundus from one of the two light projection areas to capture the first fundus image, and further sets the light emission area where the illumination light is projected to the other. To the second fundus image by selectively projecting illumination light from the other side. By performing such two shootings, two fundus images are obtained in which the appearance positions of artifacts such as a reflection image by the objective lens are different from each other depending on the projection area used for the shooting. The imaging may be performed between the first imaging and the second imaging without changing the positional relationship between the subject's eye and the imaging optical system. Further, it is desirable that the photographing of the second fundus image be performed continuously and automatically from the photographing of the first fundus image.

  In the present embodiment, when two fundus images are taken, there is no need to change the positional relationship between the subject's eye and the imaging optical system, and the light source is switched on or off, or the shutter is driven. The light projection area on the pupil of the subject's eye can be switched in a short time. Therefore, two fundus images can be captured in a short time. As a result, even if the first fundus image and the second fundus image are continuously photographed, the burden on the subject is suppressed. Even if the illumination light is visible light, the second image is taken immediately after the first image is taken, so that the miosis caused by the first image is given in the second image. The effect can be suppressed.

  Here, examples of the effect of the miosis include that the illumination light and the fundus reflection light are vignetted by the iris, thereby darkening the fundus image. The effect of vignetting (change in brightness) between the center of the image and the periphery of the image is not always uniform. For example, the periphery of an image may be more susceptible to vignetting as the shooting angle of view increases.

  In the fifth artifact suppression process, a single fundus image (hereinafter, referred to as a “combined image”) may be generated by performing a combining process on these two fundus images. The combining process is performed by the image processing unit. In the present embodiment, a combining process is performed to obtain an image in which the influence of the artifact is suppressed. There are various synthesis methods as exemplified below.

  For example, a composite image may be generated by replacing a region including an artifact in one fundus image of two fundus images with a part of the other fundus image corresponding to the region (see FIG. 10). ). At this time, replacement may be performed in units of scanning lines. For example, when the above-described reflection image occurs as an artifact, a composite image may be generated by replacing a reflection image generated at the image center of one fundus image with a corresponding region in the other fundus image.

  Further, a composite image may be generated as an average image of two fundus images. In this case, the averaging process may be performed by giving different addition ratios between the reflection image and the other regions.

  The area where the reflection image occurs is a substantially constant range based on the photographing optical axis although there is some variation depending on the diopter. For this reason, in the two fundus images, the region to be combined with the other image in the combining process may be determined in advance. However, the present invention is not limited to this, and the detection processing of the reflection image may be performed on the fundus image, and the regions to be combined may be individually set based on the result of the detection processing. Further, an area to be combined may be set according to the diopter.

  In addition, the control unit captures the first fundus image based on scanning of only a part of the scanning range corresponding to the composite image, switches the light projection area, and then performs control based on the remaining part of the scanning. A composite image may be generated by taking a second fundus image and combining (collage) the fundus images. In this case, it is preferable that the scanning range is divided into two around the photographing optical axis, and a fundus image is photographed in each of the two divided scanning ranges. Note that, in this case, the synthesis processing is not necessarily limited to image processing. For example, a composite image can be formed on the imaging surface by switching the projection area where the illumination light is projected at the timing when the illumination light arrives at the division position of the scanning range.

  In this case, between the two fundus images, it is preferable that the relationship between the scanning range on the fundus and the projection area where the illumination light is projected intersects between the two fundus images. For example, when the two light projecting regions are arranged side by side in the vertical direction, and the illumination light is scanned on the fundus in the vertical direction, when passing the illumination light from the upper light projecting region, the lower half of the fundus is used. When the first fundus image is photographed based on the scanning, and the illumination light is allowed to pass from the lower light projecting area, the second fundus image is photographed based on the scanning of the upper half of the fundus. A composite image may be generated. In this case, in relation to each projection area, the reflected image of the objective lens and the images obtained by photographing the portion where the artifact such as flare is hardly included are combined. Therefore, it is possible to obtain a composite image in which artifacts are suppressed.

  The following shooting control may be executed instead of the synthesis processing. That is, the projection area may be switched by the control unit at the timing when the illumination light that scans on the fundus at the time of photographing reaches the boundary position of the two divisions. A composite image in which a reflection image is suppressed is generated without requiring a composite process.

"Example"
Next, an example of the fundus imaging apparatus according to the first embodiment and the second embodiment will be described with reference to FIGS. 1 to 4, 11, and 12.

  The fundus imaging apparatus 1 (hereinafter, simply referred to as “imaging apparatus 1”) forms illumination light in a slit shape on the fundus of the eye to be inspected, scans the slit-shaped area on the fundus, and illuminates. A front image of the fundus is captured by receiving light reflected by the fundus.

<Appearance>
With reference to FIG. 1, an external configuration of the photographing apparatus 1 will be described. The photographing device 1 has a photographing unit 3. The photographing unit 3 mainly includes the optical system shown in FIG. The photographing apparatus 1 has a base 7, a drive unit 8, a face support unit 9, and a face photographing camera 110, and adjusts the positional relationship between the subject's eye E and the photographing unit 3 using these.

  The drive unit 8 can move in the left-right direction (X direction) and the front-back direction (Z direction, in other words, the working distance direction) with respect to the base 7. Further, the driving unit 8 further moves the photographing unit 3 on the driving unit 8 in the three-dimensional direction with respect to the eye E to be inspected. The drive unit 8 includes an actuator for moving the drive unit 8 or the imaging unit 3 in each of the predetermined movable directions, and is driven based on a control signal from the control unit 80. The face support unit 9 supports the face of the subject. The face support unit 9 is fixed to the base 7.

  The face photographing camera 110 is fixed to the housing 6 so that the positional relationship with the photographing unit 3 is constant. The face photographing camera 110 photographs the face of the subject. The control unit 100 specifies the position of the eye E from the captured face image and controls the driving of the driving unit 8 to align the imaging unit 3 with the specified position of the eye E.

  Further, the imaging device 1 further includes a monitor 120. The monitor 120 displays a fundus observation image, a fundus photographing image, an anterior segment observation image, and the like.

<Optical System of Example>
Next, an optical system of the photographing apparatus 1 will be described with reference to FIG. The imaging device 1 includes an imaging optical system (fundus imaging optical system) 10 and an anterior ocular segment observation optical system 40. These optical systems are provided in the photographing unit 3.

  In FIG. 2, a position conjugate to the pupil of the subject's eye is indicated by “△” on the imaging optical axis, and a fundus conjugate position is indicated by “×” on the imaging optical axis.

  The photographing optical system 10 has an irradiation optical system 10a and a light receiving optical system 10b. In the embodiment, the irradiation optical system 10a includes a light source unit 11, a lens 13, a slit member 15a, lenses 17a and 17, a mirror 18, a perforated mirror 20, and an objective lens 22. The light receiving optical system 10b has an objective lens 22, a perforated mirror 20, lenses 25a and 25b, a slit-shaped member 15b, and an image sensor 28. The perforated mirror 20 is an optical path coupling unit that couples the optical paths of the irradiation optical system 10a and the light receiving optical system 10b. The perforated mirror 20 reflects the illumination light from the light source toward the eye E, and allows a portion of the fundus reflection light from the eye E that has passed through the opening to pass to the image sensor. Various beam splitters other than the perforated mirror 20 can be used. For example, instead of the perforated mirror 20, a mirror in which the perforated mirror 20, the light transmitting portion, and the reflecting portion are reversed may be used as the optical path coupling portion. However, in this case, an independent optical path of the light receiving optical system 10b is provided on the reflection side of the mirror, and an independent optical path of the irradiation optical system 10a is provided on the transmission side of the mirror. Further, the perforated mirror and the mirror as an alternative means can be further replaced by a combination of a half mirror and a light shielding unit.

  In this embodiment, the light source unit 11 has a plurality of types of light sources having different wavelength bands. For example, the light source unit 11 has visible light sources 11a and 11b and infrared light sources 11c and 11d. Thus, the light source unit 11 of the present embodiment is provided with two light sources for each wavelength. Two light sources having the same wavelength are arranged apart from the imaging optical axis L on the pupil conjugate plane. The two light sources are arranged along the X direction, which is the scanning direction in FIG. 2, and are arranged axially symmetric with respect to the imaging optical axis L. As shown in FIG. 2, the outer peripheral shape of the two light sources may be a rectangular shape in which the direction intersecting the scanning direction is longer than the scanning direction.

  Light from the two light sources passes through the lens 13 and irradiates the slit member 15. In the present embodiment, the slit-shaped member 15a has a light-transmitting portion (opening) formed elongated along the Y direction. As a result, the illumination light is formed in a slit shape on the fundus conjugate plane (a region illuminated in a slit shape on the fundus is shown as reference B).

  In FIG. 2, the slit-shaped member 15a is displaced by the driving unit 15c such that the light transmitting unit crosses the photographing optical axis L in the X direction. Thereby, the scanning of the illumination light in the present embodiment is realized. In the present embodiment, scanning by the slit-shaped member 15b is also performed on the light receiving system side. In the present embodiment, the slit members on the light emitting side and the light receiving side are driven by one driving unit (actuator) in an interlocked manner.

  In the irradiation optical system 10a, the image of each light source is relayed by the optical system from the lens 13 to the objective lens 22, and is formed on the pupil conjugate plane. That is, on the pupil conjugate plane, images of the two light sources are formed at positions separated in the scanning direction. Thus, in the present embodiment, the two light projection areas P1 and P2 on the pupil conjugate plane are formed as images of the two light sources.

  The slit-shaped light passing through the slit-shaped member 15a is relayed by an optical system from the lens 17a to the objective lens 22, and forms an image on the fundus Er. Thereby, the illumination light is formed in a slit shape on the fundus Er. The illumination light is reflected on the fundus Er and is extracted from the pupil Ep.

  Here, since the aperture of the perforated mirror 20 is conjugate with the pupil of the eye to be inspected, the fundus reflection light used for photographing the fundus image passes through the image of the aperture of the perforated mirror (pupil image) on the pupil of the eye to be inspected. You are limited to some. Thus, the image of the opening on the pupil of the subject's eye becomes the light receiving region R in the present embodiment. The light receiving region R is formed between two light projecting regions P1 and P2 (images of two light sources). Further, as a result of appropriately setting the imaging magnification of each image, the diameter of the aperture, and the arrangement interval of the two light sources, the light receiving region R and the two light projecting regions P1 and P2 do not overlap each other on the pupil. Formed. Thereby, the occurrence of flare is favorably reduced.

  The fundus reflection light passing through the objective lens 22 and the aperture of the perforated mirror 20 forms an image of the slit-shaped region of the fundus Er at the fundus conjugate position via the lenses 25a and 25b. At this time, the harmful light is removed by disposing the translucent portion of the slit-shaped member 15b at the position of the image formation.

  The image sensor 28 is arranged at a fundus conjugate position. In the present embodiment, the relay system 27 is provided between the slit-shaped member 15b and the image sensor 28, whereby both the slit-shaped member 15b and the image sensor 28 are arranged at the fundus conjugate position. As a result, both the removal of the harmful light and the imaging are performed favorably. Instead of this, the relay system 27 between the imaging element 28 and the slit-shaped member 15b may be omitted, and both may be arranged close to each other. In this embodiment, a device having a two-dimensional light receiving surface is used as the image sensor 28. For example, a CMOS or a two-dimensional CCD may be used. The image of the slit-shaped region of the fundus Er, which is formed by the light-transmitting portion of the slit-shaped member 15b, is projected on the image sensor 28. The image sensor 28 has sensitivity to both infrared light and visible light.

  In this embodiment, as the slit-shaped illumination light is scanned on the fundus Er, an image (slit-shaped image) of the scanning position on the fundus Er is sequentially projected for each scanning line of the image sensor 28. Thus, the entire image of the scanning range is projected on the image sensor in a time-division manner. As a result, a front image of the fundus Er is captured as an entire image of the scanning range.

  In the embodiment, the scanning unit in the light receiving system is a device for mechanically scanning the slit, but is not necessarily limited to this. For example, the scanning unit on the light receiving optical system side may be a device that electronically scans the slit. As an example, when the imaging element 28 is a CMOS, the scanning of the slit may be realized by a rolling shutter function of the CMOS. In this case, by displacing the area to be exposed on the imaging surface in synchronization with the scanning unit in the light projection system, it is possible to efficiently capture an image while removing harmful light. In addition, a liquid crystal shutter or the like can be used as a scanning unit that electronically scans the slit.

  The imaging optical system 10 has a diopter correction unit. In the present embodiment, a diopter correction unit (diopter correction optical systems 17 and 25) is provided in each of the independent optical path of the irradiation optical system 10a and the independent optical path of the light receiving optical system 10b. Hereinafter, for convenience, the irradiation-side diopter correction optical system is referred to as an irradiation-side diopter correction optical system 17, and the light-receiving-side diopter correction optical system is referred to as a light-receiving-side diopter correction optical system 25. The irradiation-side diopter correction optical system 17 of this embodiment includes a lens 17a, a lens 17b, and a drive unit 17c (see FIG. 3). Further, the light-receiving-side diopter correction optical system 25 of the present embodiment includes a lens 25a, a lens 25b, and a drive unit 25c (see FIG. 3). In the irradiation-side diopter correction optical system 17, the distance between the lens 17a and the lens 17b is changed, and in the light-receiving diopter correction optical system 25, the distance between the lens 25a and the lens 25b is changed. Thereby, diopter correction is performed in each of the irradiation optical system 10a and the light receiving optical system 10b.

  The driving unit 17c of the irradiation optical system 10a and the driving unit 25c of the light receiving optical system 10b can be driven independently. As a result, in the present embodiment, as shown in FIG. 4B, the irradiation-side correction amount that is the diopter correction amount in the irradiation optical system 10a and the light-receiving-side correction amount that is the diopter correction amount in the light-receiving optical system 10b are: Each can be set independently.

  In this embodiment, each of the irradiation-side diopter correction optical system 17 and the light-receiving-side diopter correction optical system 25 includes a telecentric optical system. Each telecentric optical system maintains the image height in the image-side area even if the diopter correction amount changes. Thus, the positional relationship between the slit opening of the irradiation optical system and the slit opening of the light receiving optical system on the fundus can be kept constant regardless of the balance between the irradiation-side correction amount and the light-receiving-side correction amount. For this reason, the slit opening of the irradiation optical system and the slit opening of the light receiving optical system on the fundus can always be matched regardless of the balance between the irradiation-side correction amount and the light-receiving-side correction amount. Further, it is possible to suppress a change in image size according to a change in the diopter correction amount.

  As shown in FIG. 2, the imaging optical system 10 further includes a split target projection optical system 50 as an example of a focus target projection optical system. The split target projection optical system 50 projects two split targets on the fundus. The split index is used for detecting a focus state. In this embodiment, the refractive power of the eye E is acquired from the detection result of the focus state.

  The split index projection optical system 50 may include at least a light source 51 (infrared light source), an index plate 52, and a deflection prism 53, for example. In the present embodiment, the index plate 52 is arranged at a position corresponding to the imaging surface of the light receiving optical system 50. Similarly, each of the slit members 15a and 15b is arranged at a corresponding position. Specifically, when the diopter correction amounts on the irradiation side and the light receiving side are 0D, the optotype plate 52 is arranged at a position substantially conjugate with the fundus of the normal eye (0D eye). The deflection prism 53 is disposed closer to the index plate 52 on the side of the subject's eye than the index plate 52.

  The index plate 52 is formed using, for example, slit light as an index. The deflection prism 53 separates the index light beam passing through the optotype plate 52 to form a split index. The separated split index is projected onto the fundus of the subject's eye via the irradiation-side diopter correction optical system 17 and the objective lens 22. For this reason, the split index is reflected in a fundus image (for example, a fundus observation image).

  When the index plate 52 is displaced from the fundus conjugate position, the two split indices are separated on the fundus, and when the index plate 52 is located at the fundus conjugate position, the two split indices match. The conjugate relationship is adjusted by the irradiation-side diopter correction optical system 17 disposed between the deflection prism 53 and the eye to be examined Er. Therefore, in the present embodiment, defocusing is performed while making the irradiation-side diopter correction amount and the light-receiving-side diopter correction amount coincide with each other. At this time, the split state of the split index indicates the focus state. By adjusting each of the diopter correction amounts on the irradiation side and the light receiving side so that the two split indices match, each of the imaging surface and each of the slit-shaped members 15a and 15b is conjugated with the fundus. Becomes

  The refractive power of the eye E can be derived from the diopter correction amount when each of the imaging surface and the slit members 15a and 15b has a conjugate positional relationship with the fundus. Therefore, in the present embodiment, an encoder (not shown) for reading any one of the interval between the lens 17a and the lens 17b or the interval between the lens 25a and the lens 25b may be further provided. The refractive power of the eye E may be acquired on the basis of the signal from.

  The scanning unit may be, for example, an optical chopper as shown in FIG. The optical chopper has a wheel having a plurality of slits formed on the outer periphery, and can rotate the wheel to scan the slits at high speed.

  Here, in FIG. 2, the components from the light source unit 11 of the irradiation optical system 10a to the mirror 18 and the components of the light-receiving optical system 10b from the perforated mirror 20 to the image sensor 28 are arranged in parallel in the X direction. By rotating the directions of the opening mirror 20 and the mirror 18 by 90 degrees from the state shown in the figure and arranging them in parallel in the Y direction, the optical chopper can be used as a scanning unit. In this case, the optical axis of the irradiation optical system 10a and the optical axis of the light receiving optical system 10b are respectively traversed at two points, the upper end and the lower end of the wheel, so that the optical projecting system and the light receiving system Scanning can be easily synchronized.

<Anterior eye observation optical system>
Next, the anterior ocular segment observation optical system 40 will be described. The anterior ocular segment observation optical system 40 shares the objective lens 22 and the dichroic mirror 43 with the imaging optical system 10. The anterior ocular segment observation optical system 40 further includes a light source 41, a half mirror 45, an image sensor 47, and the like. The image sensor 47 is a two-dimensional image sensor, and is arranged, for example, at a position optically conjugate with the pupil Ep. The anterior segment observation optical system 40 illuminates the anterior segment with infrared light and captures a front image of the anterior segment.

  Note that the anterior ocular segment observation optical system 40 illustrated in FIG. 2 is merely an example, and the anterior ocular segment may be imaged using an optical path independent of other optical systems.

<Control system of embodiment>
Next, a control system of the photographing apparatus 1 will be described with reference to FIG. In this embodiment, the control unit 100 controls each unit of the image capturing apparatus 1. For convenience, the image processing of various images obtained by the photographing apparatus 1 is also performed by the control unit 100. In other words, in the present embodiment, the control unit 100 also serves as the image processing unit.

  The control unit 100 is a processing device (processor) having an electronic circuit that performs control processing of each unit and arithmetic processing. The control unit 100 is realized by a CPU (Central Processing Unit), a memory, and the like. The control unit 100 is electrically connected to the storage unit 101 via a bus or the like.

  The storage unit 101 stores various control programs, fixed data, and the like. Further, the storage unit 101 may store temporary data and the like.

  The image captured by the image capturing apparatus 1 may be stored in the storage unit 101. However, the present invention is not necessarily limited to this, and the captured image may be stored in an external storage device (for example, a storage device connected to the control unit 100 via LAN and WAN).

  The control unit 100 includes the driving unit 8, the light sources 11a to 11d, the driving unit 15c, the driving unit 17c, the driving unit 25c, the imaging device 28, the light source 41, the imaging device 47, the light source 51, the input interface 110, the monitor 120, and the like. Are electrically connected to each other.

  Further, the control unit 100 controls each of the above-described members based on an operation signal output from the input interface 110 (operation input unit). The input interface 110 is an operation input unit that receives the operation of the examiner. For example, a mouse and a keyboard may be used.

<Description of operation of the embodiment>
Next, the photographing operation will be described based on the flowchart of FIG.

  The image capturing apparatus 1 may automatically start an image capturing operation when the face of the subject is placed on the face supporting unit 9 and included in the image capturing range of the face detection camera 110.

  First, photographing by the face detection camera 110 and the anterior ocular segment observation optical system 40 is performed in parallel (S1), and alignment adjustment using the photographing results of both is performed (S2).

  Specifically, the control unit 100 detects one position of the left and right eyes included in the face image, and drives the driving unit 8 based on the position information. Thereby, the position of the photographing unit 4 is adjusted to a position where the anterior eye part observation is possible.

  Next, an alignment reference position is set based on the anterior ocular segment front image, and alignment is guided to the set alignment reference position. In the present embodiment, the positional relationship between the subject's eye E and the imaging unit 3 is adjusted by the control unit 100 based on the anterior segment front image. In the present embodiment, based on the signal from the image sensor 47, the control unit 100 determines the position where the center of the pupil in the anterior ocular segment observation image and the image center (in this embodiment, the position of the photographing optical axis L) substantially match. A first reference position targeting a relationship is set. Then, an alignment shift from the first reference position is detected, and the photographing unit 4 is moved in the up, down, left, and right directions in a direction in which the alignment shift is eliminated. At this time, for example, the misalignment between the first reference position and the pupil center on the anterior ocular segment observation image may be detected based on the amount of deviation between the pupil center and the imaging optical axis. In addition, when the fundus imaging apparatus 1 has, for example, an alignment projection optical system that projects an alignment index onto a cornea vertex, an alignment shift may be detected based on a deviation amount between the alignment index and the imaging optical axis. .

  The control unit 100 also moves the photographing unit 4 in the front-back direction so that the anterior eye observation image is focused on the pupil Ep. Thereby, the distance from the apparatus to the subject's eye is adjusted to a predetermined working distance.

  As described above, in the present embodiment, as a result of the alignment adjustment in S2, the positional relationship between the subject's eye and the photographing unit 4 is such that the center of the light receiving region R on the pupil of the subject's eye (that is, the photographing optical axis) is the pupil center. (The first reference position in the present embodiment).

  After the first shooting mode is set, the control unit 100 starts shooting and displaying a fundus oculi observation image (S3). More specifically, the control unit 100 simultaneously turns on the light sources 11c and 11d and starts driving the driving unit 15c, so that the slit-shaped illumination light is repeatedly scanned in a predetermined range on the fundus Er. At every predetermined number of scans (at least once), a fundus image captured substantially in real time is generated as a fundus observation image at any time based on a signal output from the image sensor 28. The control unit 100 may cause the monitor 120 to display the fundus oculi observation image as a substantially real-time moving image.

  Next, the focus state in the irradiation optical system and the light receiving optical system is adjusted based on the fundus observation image (S4). In this embodiment, after the alignment is completed, the diopter correction optical system is driven to perform focus adjustment. At this time, in this embodiment, both the irradiation-side diopter correction optical system 17 and the light-receiving-side diopter correction optical system 25 are driven.

  In the focus adjustment processing, first, the control unit 100 starts projection of the split index on the fundus by turning on the light source 51. The control unit 100 performs defocusing by changing the correction amount while making the irradiation-side diopter correction amount and the light-receiving-side diopter correction amount coincide. Further, every time the correction amount changes, the control unit 100 detects the split state of the split index from the fundus observation image, and determines the irradiation-side diopter correction amount and the light-receiving-side diopter correction amount until the split index matches. adjust. As a result of such adjustment, the imaging surface and each of the slit-shaped members 15a and 15b have a conjugate positional relationship with the fundus.

  Further, in the present embodiment, the diopter correction amount when the split index matches is acquired by the control unit 100 as refractive power information (S5).

  Next, the control unit 100 sets the shooting mode based on the refractive power information. First, the diopter correction amount, which is refractive power information, is compared with a predetermined threshold (S6). In this embodiment, assuming that an artifact occurs when each of the irradiation-side correction amount and the light-receiving-side correction amount is on the minus diopter side with respect to −12D, “−12D” is set as the threshold of the refractive power. Has been adopted. In other words, the first range indicated by reference numeral A1 in FIG. 4B is a range on the plus diopter side from "-12D" in the present embodiment. The second range indicated by reference numeral A2 is “−12D” in the present embodiment and a range on the minus diopter side thereof. However, the range of the diopter in which an artifact due to the reflection of the objective lens 22 is different depending on the optical design of the device, a value according to the optical design of the device may be used as the threshold.

  In the present embodiment, if the refractive power of the subject's eye is a value on the plus diopter side from "-12D", the first photographing mode is set (S6: No). On the other hand, if the refractive power of the subject's eye is “−12D” or a value on the negative diopter side, the second imaging mode is set (S6: Yes).

  In the first shooting mode, the process proceeds to S8, where shooting conditions other than the diopter correction amount are adjusted according to the shooting mode (S8). After the adjustment, a fundus image is captured (S9). At this time, the light emission from the observation light sources 11c and 11d may be stopped, and then the imaging light sources 11a and 11b may be turned on. In this case, a photographed image of the fundus is obtained as a photographing result based on the visible light emitted from the light sources 11a and 11b.

  In the present embodiment, in the first imaging mode, a fundus image is imaged in a state where the irradiation-side correction amount and the light-receiving-side correction amount match each other (see FIG. 4A). At the time of photographing, the irradiation-side correction amount and the light-receiving-side correction amount are values immediately after adjustment in the focus adjustment processing (S5). Therefore, the diopter correction amount is in a range where the artifact is not a problem, and the fundus is photographed in a state where each of the imaging surface and each of the slit-shaped members 15a and 15b has a conjugate positional relationship with the fundus. Therefore, a good fundus image is captured.

  On the other hand, in the second imaging mode, the irradiation-side correction amount is shifted to the plus diopter side with respect to the value when the split index matches (see FIG. 4B). As a result, the focus position of the illumination light moves away from the objective lens, so that artifacts due to the reflection of the objective lens 22 are less likely to occur. In this embodiment, the value of the irradiation-side correction amount after the transition may be a fixed value, or may vary according to the light-receiving-side correction amount in a range that does not match the light-receiving-side correction amount. In this embodiment, the irradiation-side correction amount is shifted to “−10D” which is a value on the plus diopter side from the threshold. However, the present invention is not necessarily limited to this, and may be shifted to a threshold.

  Next, shooting conditions other than the diopter correction amount are adjusted according to the second shooting mode. At this time, since the diopter correction amount in the irradiation optical system is deviated from the best focus, the slit light irradiated as the illumination light is blurred on the fundus. As a result, the fundus reflection light passing through the opening of the slit 15b in the light receiving optical system is reduced, so that the received light amount is reduced.

  Therefore, the control unit 100 sets one of the amount of illumination light output from the light sources 11a and 11b or the light sources 11c and 11d, the gain of the Increase in the shooting mode. This suppresses a decrease in image quality due to the fact that slit light emitted as illumination light is blurred on the fundus as a result of the processing in S7.

  Then, the control unit 100 captures a fundus image after adjusting the capturing conditions (S9). In the second imaging mode, a fundus image is captured in a state where the irradiation-side correction amount and the light-receiving-side correction amount do not match. As a result, in the present embodiment, even when a myopic eye is photographed, the occurrence of artifacts is suppressed. At the time of shooting, the diopter correction amount in the light receiving optical system 10b is a value immediately after adjustment in the focus adjustment processing (S5). Therefore, since the fundus and the imaging surface are conjugate, out-of-focus in the fundus image is suppressed. Further, in the second imaging mode, the slit 15a is arranged in a non-conjugated positional relationship with the fundus Er, so that the slit light irradiated as illumination light is blurred on the fundus. However, any one of the imaging conditions among the light intensity of the illumination light, the gain of the imaging element 28, and the exposure time is increased compared to the first imaging mode, so that a fundus image having an appropriate dynamic range is easily obtained.

  In the method of suppressing an artifact on a fundus image by image processing, a trace of the image processing may be left in the image. On the other hand, in the present embodiment, image processing for suppressing artifacts is not necessarily required, and thus in the fundus image, the tissue of the fundus is more naturally depicted.

  In addition, in the second mode, it is considered that the burden on the subject is increased as compared with the first mode by increasing the illumination light amount or the exposure time. However, since the time from the start of shooting (start of irradiation of illumination light for shooting) to completion is relatively short, the increase in the burden is considered to be relatively small. Therefore, even when imaging the eye to be examined having a high degree of myopia, a fundus image in which artifacts are suppressed can be imaged without imposing a large burden on the subject.

  As described above, the description has been given based on the embodiment. However, in implementing the present disclosure, the content of the embodiment can be appropriately changed.

<Transformation example of diopter correction optical system>
For example, in the above-described embodiment, as the diopter correction optical systems 17 and 25, an optical system in which a diopter correction amount is set according to a lens interval has been described as an example. However, the diopter correction optical system is not necessarily limited to this, and various optical systems can be adopted. For example, in the case of the optical system shown in FIG. 2, the diopter correction in the irradiation optical system 10a becomes possible by displacing the slit-shaped member 15a in the optical axis direction instead of the lens 17a. When the slit-shaped member 15a is displaced in the optical axis direction, the position of the condensing point K is displaced in the optical axis direction. Similarly, by displacing the slit-shaped member 15b in the optical axis direction instead of the lens 25b, diopter correction in the light receiving optical system 10b becomes possible. In this case, the lens 27 and the image sensor 28 may be moved in conjunction with the slit-shaped member 25b. Further, in this case, it is difficult for one driving unit to perform scanning by the slit-shaped member 15a and scanning by the slit-shaped member 15b, so that the slit-shaped members 15a and 15b , May each have a drive unit.

<Shooting control during fluorescent shooting>
Further, for example, in each of the above embodiments, the fundus imaging apparatus not only captures a fundus image based on the fundus reflected light, but also captures a fluorescent fundus image that is a fundus image based on fluorescence emitted from the fundus. Good.

  In this case, illumination light is emitted from the irradiation optical system as excitation light. The wavelength range of the illumination light can be appropriately set according to the intended fluorescent substance. The fluorescent substance may be a contrast agent (for example, indocyanine green and fluorescein) or a spontaneous fluorescent substance (for example, lipofuscin) accumulated in the fundus.

  In the light receiving optical system, fluorescence from the fundus based on the excitation light is guided to the light receiving element. When fluorescence imaging is performed, a barrier filter is arranged on an independent optical path of the light receiving optical system. The barrier filter has spectral characteristics such that light in the same wavelength range as the excitation light is blocked and fluorescence is transmitted. As a result, of the fundus reflection light of the excitation light and the fluorescence from the fundus, the fluorescence is selectively received by the light receiving element. As a result, a fundus fluorescent image can be favorably obtained. The fundus imaging apparatus may include a driving unit for inserting and removing the barrier filter. The insertion and removal of the barrier filter may be controlled by the control unit.

  The control unit may switch the shooting mode between the normal shooting mode and the fluorescence shooting mode. The normal photographing mode is set to photograph a fundus image based on the fundus reflection light. The fluorescent imaging mode is set to capture a fluorescent fundus image. The control unit may control insertion / removal of the barrier filter according to the shooting mode. In this case, the control unit retracts the barrier filter in the normal shooting mode. Further, the control unit causes the barrier filter to be inserted in the fluorescence imaging mode. Here, in the fluorescent imaging mode, not only the fundus reflection light of the excitation light but also the reflection light by the objective lens is blocked by the barrier filter. Therefore, it is not necessary to execute the various artifact suppression processes described in the above embodiment in the fluorescence imaging mode. Therefore, in the fluorescence imaging mode, the artifact suppression processing need not be performed by the control unit regardless of the refraction error of the eye to be inspected. For example, in a device that suppresses the occurrence of artifacts by making the diopter correction amount (irradiation-side correction amount) in the irradiation optical system and the diopter correction amount (light-receiving-side correction amount) in the light receiving optical system inconsistent. In the fluorescence imaging mode, each value is adjusted according to the refraction error so that the irradiation-side correction amount and the light-receiving-side correction amount match.

Reference Signs List 1 fundus photographing device 10 photographing optical system 10a irradiation optical system 10b light receiving optical system 22 objective lens 100 control unit E eye to be examined Er fundus

Claims (8)

An irradiation optical system that irradiates the fundus of the subject's eye with illumination light via an objective lens, and a light receiving element that shares the objective lens with the irradiation optical system and further includes a light receiving element that receives fundus reflection light of the illumination light An imaging system including an optical system,
A fundus imaging apparatus that acquires a fundus image based on a signal from the light receiving element,
Refractive power information obtaining means for obtaining refractive power information that is information on the refractive power of the eye to be examined,
Control means for performing an artifact suppression process for suppressing the occurrence of artifacts based on the reflection of the illumination light by the objective lens,
The control means sets the refraction power between a first mode in which an artifact suppression process is not performed when capturing a fundus image and a second mode in which the artifact suppression process is performed when capturing a fundus image. Fundus imaging device that switches based on The refractive power of the eye to be examined is roughly divided into a first range and a second range on the minus diopter side with respect to the first range,
The control means switches to a first photographing mode when the refractive power of the subject's eye is in the first range, and switches to a second photographing mode when the refractive power of the subject's eye is in the second range. Item 7. A fundus photographing apparatus according to item 1. The irradiation optical system emits illumination light to the fundus as excitation light, thereby generating fluorescence from a fluorescent substance present in the fundus,
In the light receiving optical system, a barrier filter that shields the illumination light and allows the fluorescence to pass is disposed so as to be freely inserted and removed on an independent optical path of the light receiving optical system,
The control unit controls the insertion and removal of the barrier filter, and when the barrier filter is inserted on the independent optical path, sets the imaging mode to the first imaging mode regardless of the refractive power. The fundus photographing apparatus according to claim 1. The control means,
In the second shooting mode,
As the artifact suppression processing,
4. The composite image according to claim 1, wherein a plurality of fundus images having different positions of the artifact with respect to the tissue of the subject eye are captured, and a composite image is generated by combining the plurality of fundus images. 5. Fundus imaging device. The imaging optical system includes:
A slit forming unit that forms illumination light in a slit shape on the fundus of the eye to be examined,
A scanning unit that scans illumination light formed in a slit shape on the fundus in a direction crossing the slit,
A projection area through which the illumination light passes on the pupil of the eye to be examined is formed at two positions separated from each other in the scanning direction of the illumination light, and the fundus reflection light of the illumination light is extracted on the pupil of the eye to be examined. Light-receiving area to be formed so as to be sandwiched between the two light-emitting areas,
The fundus imaging apparatus according to any one of claims 1 to 4, wherein a fundus image is captured based on the fundus reflection light extracted from the light receiving region. The control means,
In the second shooting mode,
As the artifact suppression processing,
The control means includes: a first fundus image that is a fundus image based on the illumination light projected from one of the two light projection areas; and the illumination light projected from the other of the two light projection areas. The fundus imaging apparatus according to claim 5, wherein a second fundus image, which is a fundus image based on the image, is captured, and a composite image is generated using at least two of the first fundus image and the second fundus image. The control means,
In the first shooting mode, a fundus image is shot based on the illumination light projected simultaneously from both of the two projection areas,
In the second photographing mode, as the artifact suppression processing, whether or not to pass the illumination light is individually set for the two light projecting regions, and selectively from any of the two light projecting regions. The fundus photographing apparatus according to claim 5, wherein the fundus image is photographed based on the projected illumination light. Position adjusting means for changing the positional relationship between the optical axis of the imaging optical system and the visual axis of the eye to be inspected to adjust the position of the artifact with respect to the tissue of the eye to be inspected in the fundus image; ,
The fundus photographing apparatus according to claim 4, wherein the control unit photographs the plurality of fundus images by changing the positional relationship for each photographing in the second photographing mode.

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