JPS623215A - focus detection device - Google Patents

Abstract

PURPOSE:To perform focus detection with high precision at any time by providing a pupil-dividing and deflecting means which has both a splitting means for dividing the pupil of an objective lens into plural areas and a defelcting means for deflecting luminous flux at right angles to the dividing direction of the pupil. CONSTITUTION:An image re-formation system 13 is provided with the polarizing means of prisms 15a and 15b slanted in the mutually opposite direction so that the pupil of the objective lens consisting of converging lenses 14a and 14b placed symmetrically about an optical axis 9 is divided into plural areas on the side of a field lens 4 and light is deflected at right angles to the dividing direction of the pupil on the side of a sensor. Luminous flux 16a passed through the exit pupil 2a of the objective lens 1 by the image re-formation system forms an image nearby an expected image formation surface 3 temporarily and then re-forms an image through the field-lens side converging lens 14a of the image re-formation system 13. In this case, the light is deflected by the exit-pupil prism 15a of the image re-formation system 13 at right angles to the dividing direction of the pupil to form an image at a position 8a' displaced from the optical axis in the same direction. Consequently, even if the quantity of deforcing increases focus detection is possible at any time.

Description

Detailed Description of the Invention (Industrial Field of Application) Misfire 8A relates to a focus detection device for a camera, etc., and in particular, it divides the head of the objective lens of the camera into a plurality of regions and uses the light flux passing through each region to The present invention relates to a focus detection device that forms a plurality of secondary object images and detects the focal position of a smart lens based on the relative positional relationship of these secondary object images.

(Prior art) Conventionally, a re-imaging system having a pupil division means is placed on the image plane side of the objective lens, the pupil of the objective lens is divided into a plurality of parts by the pupil division means, and the light beams from these @ areas are used. A plurality of secondary object images are formed from the primary object image formed by the objective lens, and the focal state of the objective lens is detected by detecting the relative positional relationship of these secondary object images. For example, a focus detection device using a so-called re-imaging system was disclosed in Japanese Patent Application Laid-open No. 5
This is proposed in Japanese Patent No. 2-95221.

FIG. 1 is a schematic diagram of an optical system of a focus detection device using a conventional reimaging system.

In the figure, l is the objective lens, 2 is the exit heel of objective lens 1, and 3
is the planned imaging plane of the objective lens l, 4 is the field lens,
5 is a field mask, 6a and 6b are objective lenses 10, respectively.
A set of reimaging systems 7g placed symmetrically about the optical axis 9
, 7b are provided in each re-imaging system, and nine apertures, 8a
, 8b indicate photoelectric conversion means, so-called senna, placed near the imaging planes of the re-imaging systems 6a, 6b, respectively. Here, the apertures 7a and 7b are field lenses 4
The relative position of the image on the senna 8m and Bb changes depending on the position of the imaging point 10 of the objective lens 1 in Fig. From this, the focal state of the objective lens is detected. For example, in a so-called front-focus state where the imaging point of the objective lens 1 is at point 11, the images on the sensors 8m and 8b are respectively indicated by arrows 11m'.

11b, and conversely, in a so-called rear-focus state where the imaging point of the objective lens 1 is at the point 12, the images on the senna 9m and gb are respectively indicated by the arrow 1.
It moves relatively in the directions of 2a and 12b. deer
Also, the distance between the imaging point of the objective lens and the planned imaging plane 3,
In other words, since there is a uniquely determined relationship between the amount of defocus and the relative deviation of the two images, by detecting this amount and direction, the amount of defocus and its direction can be calculated. Detected. However, with this method, as the amount of defocus increases, the amount of relative movement of the two images increases, and the common parts contained in the two images decrease, it becomes difficult to accurately defocus. 7. Detection of the amount of orcus becomes increasingly difficult. The degree of defocus fl- that can be detected depends on the calculation method for detecting the relative shift, but it is essential that at least a common portion of the two images remains. That is, in order to be able to detect a large amount of defocus, it is advantageous for the field of view seen by the imaging optical systems 6m and 6b to be as long as possible.

However, in the configuration shown in FIG. 1, because the separation direction of the two images and the moving direction of the six images are the same,
The length of the image on the senna plane is constrained by the fact that the two images do not overlap each other, and therefore the length of the field of view is also t, b.
It can be said that it is a structure that cannot be taken for a long time.

FIG. 2 is an explanatory diagram of the vicinity of the re-imaging system 6b in FIG. 1.

In the same figure, the distance between the planned imaging plane 3 and the sensor plane is t1
The inclination of the light 1iJ130 with respect to the optical axis 9 passing through the center of the re-imaging system 6b is expressed as 2'-. The length of the field of view on the planned imaging plane corresponding to the maximum flame of the image that can be taken is LFi βFNO・5 tomuyu. Therefore, in order to increase L, it is sufficient to configure the system in the following directions: (a) increase the total length t, (c) decrease the magnification β, and (c) decrease FNO.
However, method (a) increases the size of the system, and method (b) reduces the radius of curvature of the reimaging system.
.

The method (c) requires a large eccentricity of the re-imaging system, which is difficult in terms of production and performance.

(Problems to be Solved by the Invention) The present invention provides a high-precision focus detection device that uses a re-imaging system and is capable of always detecting focus even when the amount of defocus increases. With the goal.

(Means for solving the problem) The pupil of the objective lens is divided into a plurality of regions on the image plane side of the objective lens, and further divided into a plurality of regions, and a plurality of secondary object images are generated from the light flux passing through the nine regions. A re-imaging system is disposed to form a re-imaging system, a photoelectric conversion means constituted by a plurality of light receiving elements is disposed near the image plane of the re-imaging system, and the photoelectric conversion means forms a plurality of secondary objects. By detecting the relative positional relationship of the images,
In the focus detection device for detecting the focal position of the objective lens, the re-imaging system includes dividing means for dividing the pupil of the objective lens into a plurality of regions, and deflection means for deflecting a light beam in a direction perpendicular to the direction in which the pupil is divided. The present invention has a pupil division/deflection means having both means.

Other features of the invention are described in the Examples.

(Example) FIG. 3, a3) is a schematic diagram of an optical system according to one embodiment of the present invention. Figure 2 is a plan view, and figure ■ is a front view.

In this figure, members having the same functions as those shown in FIG. 1 are given the same reference numerals. 13 in the figure is from Figure 1 (O
This is a refocusing image system which is a pupil division and deflection means which is a feature of this embodiment and has the shape shown in FIG.

In this re-imaging system 13, a field lens
□Convergent lens 1 placed symmetrically with respect to the optical axis 9 on the 4th side
The division means for dividing the pupil of the objective lens consisting of 4a and 14b into a plurality of regions is the same as the conventional reimaging system shown in Figure 1, but the sensor side is perpendicular to the pupil separation direction. They differ in that they have polarizing means in the form of prisms 15 and 15b tilted in opposite directions so as to deflect light in the opposite directions.

By using a re-imaging system as shown in FIG. Convergent lens on the field lens side of the re-imaging system 13 □1
At 4a, it is reimaged. At this time, the prism 15a on the exit side of the re-imaging system 13 deflects the beam in a direction perpendicular to the separation direction of the stems, and the position B is displaced in the same direction with respect to the optical axis (i.e., downward in FIG. 3). , I.

Similarly, the light beam passing through the incident illumination ill 2b on the opposite side is imaged at the oppositely displaced position 8b'.

FIG. 4 is an explanatory diagram showing the image formation state of the field mask on the sensor surface of this system. 8a' and 8b' are sensors, 1
6 m + 16 b is the image of the field mask.

As is clear from this figure, on the Senna plane, the two images are displaced in the direction perpendicular to the Senna row direction (y-axis direction), so the two images do not overlap, and the re-imaging system The sensor, ie, the field of view length, can be freely lengthened within a range that allows for aberrations. Therefore, detection up to a larger amount of defocus becomes possible.

FIG. 5 is a schematic diagram of an optical system according to a second embodiment of the present invention, and is a front view corresponding to (6) in FIG. 3. The difference between this implementation sequence and the first implementation sequence is reconnection.

The point is that the directions of the converging lenses 13a and 13b of the image system are reversed.

In other words, the prism is located on the field lens side, and the convergent lens is located on the sensor side. This kind of placement money is very
The objectives of the invention are achieved.

In the above embodiments, the apertures 7a and 7b are provided on the field lens side of the re-imaging system, but they can also be provided on the senna side.

In the above embodiments, the re-imaging system is shown as one in which one set of converging lenses and one set of prisms are integrated, but these may be arbitrarily separated and configured as a single optical member. Further, as shown in FIG. 6, (5), for the purpose of obtaining good optical performance, the converging lens, prism, etc. in the re-imaging system may be composed of a plurality of optical members.

In the focus detection device using the re-imaging system of this embodiment, the two images on the sensor are not symmetrically shifted on the front focus side and the rear focus side of the objective lens. Generally, if the amount of defocus is the same, the amount of deviation on the sensor on the front focus side is large due to optical properties.

For this reason, in this embodiment, each sensor is lengthened in the direction in which the image shifts during front focus, in an attempt to increase the amount of defocus that can be detected.

FIG. 7 is a schematic diagram of one embodiment of the senna at this time.

The first row corresponds to the senna extended in the direction in which the image shifts when the front is in focus in FIG. 4.

Along with this, sensors 8&', 8b' and field mask 1
The centers of 6a and 16b do not coincide, and are shifted from each other. By doing so, it becomes possible to equalize the maximum detectable defocus amount on the front focus side and the rear focus side.

In the first embodiment shown in FIG. 3 of the present invention, since the centers of the two cells are originally shifted from the center in the rear focus direction, the sensor is extended in the front focus direction and No new space is required and the compatibility with this implementation is very good.

Furthermore, by design manipulation, it is possible to arrange the two sensors so that they do not deviate at all in the column direction, and more effective use of the sensor space is realized. In addition to making the maximum detectable focus amount equal on the front focus side and the rear focus side as in this embodiment, it is also possible to balance them depending on the purpose. For example, when the objective lens has a focus adjustment method other than full extension, such as front focus or rear focus, the maximum defocus t on the front focus side and the rear focus side are generally different. By doing so, it becomes possible to optimize the Senna length.
□ (Effects of the Invention) According to the present invention, it is possible to achieve a focus detection device using a re-imaging system that can always perform focus detection even when the amount of defocus increases. It is possible to achieve a focus detection device that can make the maximum □' defocus amount on the front focus side and the rear focus side equal or appropriately balanced.

[Brief explanation of drawings]

1 and 2 are schematic diagrams of an optical system of a focus detection device using a conventional re-imaging system, FIG. 3 is a schematic diagram of an optical system according to an embodiment of the present invention, and FIG. 4 is a schematic diagram of an optical system according to an embodiment of the present invention. FIG. 5 is a schematic diagram of an optical system of another embodiment of the present invention; FIG. 6 is an explanatory diagram of another embodiment of a part of the present invention; FIG.
The figure is an explanatory diagram showing changes in the field of view length in the senna according to the present invention. In the figure, 1 is an objective lens, 2 is an exit pupil, 3 is a planned imaging plane, 4 is a field lens, 5 is a field mask, 1
3 is the re-imaging system, 81°8b, 8a', 8b'
are each senna.

Claims (4)

[Claims] (1) A re-imaging system is provided on the image plane side of the objective lens, which divides the pupil of the objective lens into a plurality of regions, and further forms a plurality of secondary object images from the light flux passing through the divided pupil regions. and arranging a photoelectric conversion means consisting of a plurality of light receiving elements near the image plane of the re-imaging system, and detecting the relative positional relationship of the plurality of secondary object images by the photoelectric conversion means, In the temporary focus detection position for detecting the focal position of the objective lens, the re-imaging system includes dividing means for dividing the pupil of the objective lens into a plurality of regions, and a deflector for deflecting a light beam in a direction perpendicular to the direction in which the pupil is divided. What is claimed is: 1. A focus detection device comprising a pupil division deflection means having both means. (2) A patent claim characterized in that the dividing means is constituted by a lens system arranged symmetrically with respect to the optical axis of the objective lens, and the deflecting means is constituted by a prism arranged symmetrically with respect to the optical axis of the objective lens. The focus detection device according to item 1. (3) A patent characterized in that the position on the photoelectric conversion means at which an object point on the optical axis forms an image when the objective lens is focused does not match the center of the photoelectric conversion means. A focus detection device according to claim 1. (4) A secondary object image when the objective lens is in front focus, with the center of the photoelectric conversion means being set relative to the position on the photoelectric conversion means where an object point on the optical axis forms an image when the objective lens is in focus. 4. The focus detection device according to claim 3, wherein the focus detection device is shifted in the direction of movement.