JPS641137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fundus camera that can selectively perform fluorescent fundus photography and color or monochrome photography (referred to as general photography), and particularly relates to a device that enables good image quality.

The angle of view of non-contact fundus cameras has traditionally been around 30 degrees for a long time, but in recent years, the angle of view has increased to 45 degrees due to the development of wide-angle objective lenses and advances in methods for eliminating harmful reflections and scattering of illumination light beams. It is starting to exceed the However, if wide-angle imaging is performed, it becomes possible to image a wide range with fewer imaging times, and if the number of imaging operations is reduced, pain to the patient is also reduced, so there is a strong desire for further wide-angle imaging. One of the important requirements for widening the field of view is the removal of the harmful light mentioned above, but in fundus cameras in which the imaging system and illumination system are arranged coaxially, part of the illumination system is reflected by the cornea. In order to prevent light from entering the imaging system, a method has long been practiced in which a sunspot is provided in the illumination optical path to block the light reflected by the cornea in advance. However, as objective lenses became wider (45 degrees), harmful light reflected by the crystalline lens became a problem. This is because with a conventional narrow-angle retinal camera (30°), the sunspot shadow, or image, covered not only the reflective area of the cornea but also the crystalline lens. This is because the shadow is shortened and harmful light is also generated in the crystalline lens.

As a countermeasure, Japanese Patent Publication No. 51-24249 removes the light reflected by the lens surface by forming a sunspot image on the front surface or between the front and back surfaces of the crystalline lens, and Japanese Utility Model Publication No. 1971-107140 removes the reflected light from the lens surface. A conjugate sunspot is provided in the illumination system to eliminate scattered light within the crystalline lens and the posterior surface of the crystalline lens.

By the way, in the case of a fundus camera, there is a restriction that the fundus illumination beam enters through the pupil of the eye to be examined, so it is desirable to increase the pupil diameter. It becomes difficult to dilate the pupils, so it is necessary to assume that the pupil diameter that can actually be selected is quite small. In addition, in the case of the method for removing harmful light as described above, as the angle of view expands, the area that must be blocked increases, which, combined with the restriction of pupil diameter, makes it difficult to completely remove harmful light. If the fundus of the eye is illuminated beyond the range to be photographed during fundus illumination, there is a risk that the excess light will be scattered and become harmful light.

On the other hand, a normal fundus camera can perform fluorescent fundus photography in addition to general photography. In fluorescence fundus photography, the fundus is illuminated with excitation light of a wavelength near blue, timing the time when frioretsen sodium, etc. injected through the cubital vein reaches the intraocular circulation system, and fluorescence is generated from the blood columns. Photographing only the fluorescent light from among the reflected light from the subject's eye is performed. At this time, a barrier filter is installed in the photographing optical path and an exciter is installed in the illumination optical path to separate wavelengths.

The present applicant previously wrote in Japanese Patent Application Laid-Open No. 55-26959,
Focusing on the fact that the wavelengths of illuminating light and photographing light are separated during fluorescence photography, we proposed increasing the amount of illuminating light by removing the light-shielding plate for removing harmful light. That is, as a result of wavelength separation, light in the illumination wavelength range is blocked by the barrier filter, so even if harmful light within that wavelength range is generated, it will not cause any problems.

The first object of the present invention is to enable fluorescence photography with a wide angle of view, and the second purpose is to make general photography advantageous in terms of resolution and to improve the image quality of general photography. The configuration is such that the imaging magnification during general imaging is greater than the imaging magnification during fluorescence imaging, and more preferably, the imaging range on the fundus during general imaging substantially matches the illumination range. .

Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows a case where the photographing magnification is small (wide-angle) for fluorescence photography, and Figure 2 shows a case where the photographing magnification is small (wide-angle) for fluorescence photography. The case where is large (narrow angle) is shown. In the figure, E indicates the eye to be examined, and Ef indicates the fundus. Also, 1 is an objective lens,
2 is a perforated mirror, 3 is an imaging lens, and 4 is a photographic film. The objective lens 1, the imaging lens 3, the photographic film 4, and the photographic aperture constitute a photographing system.The objective lens 1 has the function of forming an image Ef' of the fundus, and the imaging lens 3 has the function of forming the image Ef'. film 4
re-image. 5 is a photographing field diaphragm plate.

The imaging lens 3 of this embodiment includes a focusing lens 3, a positive front fixed lens 3b, a negative variator lens 3c movable in the optical axis direction to change the imaging magnification (focal length), and a fixed front fixed lens 3b. It is composed of a relay lens 3d. Although the variator lens 3c is designed to focus at two locations within its movement range, a compensator may be added to enable focus to be achieved over the entire range.

Further, reference numeral 6 denotes a quick return mirror, which is installed obliquely in the optical path during observation and is retracted out of the optical path during photographing. 7 is a mirror for bending the optical path, 8 is an eyepiece lens, and members 6 to 8 constitute a finder.
Next, 10 and 11 are relay lenses, 12 is a mirror for bending the optical path, 13 is a ring slit, 14 is a condenser lens, 15 is a photography light source such as a xenon flash tube, 16 is another condenser lens,
17 is a light source for observation such as a halogen bulb. Here, the members 10 to 17, the objective lens 1, and the perforated mirror 2 constitute an illumination system, and the luminous flux emitted from both light sources is condensed onto the ring slit 13 by the action of a condenser lens, while the ring slit Rituto is
The pupil of the eye to be examined with respect to the mirror surface of the mirror 12, the relay lenses 10 and 11, the mirror surface of the perforated mirror 2, and the objective lens 1.
Since it is arranged conjugately with Ep, a light ring, which is an image of the slit part of the ring slit, is formed on the pupil plane, and the light ring spreads and illuminates the fundus of the eye. l ₁ is the chief ray when the angle is wide, and l ₂ is the chief ray when the angle is narrow.

On the other hand, numeral 18 is an illumination field diaphragm, which has the function of narrowing down the fundus illumination flux as shown in Figure 2.
As a result of being arranged conjugately with Ef, the periphery of the illumination part on the fundus is shielded from light. Note that the photographing field on the fundus when the variator lens 3c of the imaging lens 3 is moved to the long focal point side and the illumination field when the aperture 18 is stopped down are made to match, and the light flux that illuminates the fundus after going beyond the photographing field This prevents the light from being scattered and reflected on the fundus of the eye and mixed into the photographing light beam, resulting in flare. This diaphragm 18 may have a structure that narrows down the iris diaphragm, or may have a structure in which a light shielding plate with a circular aperture is inserted into or removed from the light beam, and the diaphragm 18 is arranged at a position conjugate with the fundus of a normal eye. However, for example, if the aperture is set to 18 in conjunction with the focusing X of the focusing lens 3,
It is preferable to configure the lens so that it moves in the optical axis direction and set it to be conjugate with the fundus regardless of the diopter of the eye to be examined. 19 is a control mechanism for this purpose.

Next, 20 is an exciter filter, which can be inserted into the illumination optical path (Fig. 1) and removed from it (Fig. 2), and 21 is a barrier filter, which can be inserted into and removed from the photographing optical path. . It is of course possible to attach and detach both filters separately, but it is more convenient to link them together.In conjunction with the insertion of these fluorescent photography filters, the variator lens 3c is set to the short focus side (low magnification), and Figure Y) It is convenient to set it to the long focus side (high magnification) in conjunction with the removal of the filter (Figure 2). It is also convenient to open or remove the illumination field diaphragm 18 in conjunction with the insertion of the fluorescent photographing filter, and to narrow it down in conjunction with the withdrawal of the filter (FIG. 2). In addition,
In order to compensate for changes in the optical path length when the fluorescent photography filter is removed, a translucent flat plate may be inserted instead.

In the above configuration, when performing fluorescence photography, the exciter filter 20 and the barrier filter 21 are inserted into each optical path, and the variator lens 3c
If you set it to the short focus side, you can take pictures using the same handling as a conventional fundus camera.

Exciter filter 20 for general photography
When the barrier filter 21 is removed from the optical path, the variator lens 3c moves to the long focal point side, increasing the magnification of the photographing system, and the illumination field diaphragm 18 is narrowed down. When the focusing lens 3a is adjusted according to the eye to be examined, the aperture 18 is linked and the camera focuses on the fundus, and the aperture 18 and the fundus are
Ef becomes conjugate. Here light source 15 or 17
The illumination angle obtained when the light is turned on is equal to the shooting angle of view of the shooting system. In addition, even when the shooting angle of view becomes narrow, if the harmful light from the crystalline lens deteriorates the image quality, it is necessary to remove light from the mirror 12 and the ring slit in the optical path between the perforated mirror 2 and the light source, which is conjugate with the fundus side of the crystalline lens. A sunspot B is placed between the ring slits 13, but since it is not necessary during fluorescence photography, it is removed out of the optical path or moved in the direction of the optical axis and overlapped with the central light-shielding part of the ring slit 13.
Disables the shading effect to save the amount of illumination light.

Fig. 3 shows a modification, in which instead of moving the variator lens 3c of Fig. 1, a telephoto BRAVAIS attachment lens 3f is attached and detached behind the fixed lens 3e. When the lens 3f is inserted with its optical axis aligned, the magnification of the photographing system increases and the angle of view becomes narrow. Note that it is convenient if the insertion of this attachment lens and the narrowing down of the illumination field diaphragm 18 are linked.

On the other hand, the photographed area is narrower than when photographing with fluorescent light, but if you want a photograph with the same magnification, leave the attachment lens 3f out of the optical path or fix the variator lens 3c on the short focus side. It is preferable to narrow down the illumination field diaphragm 18 and further narrow down the photographing field diaphragm 22 according to the range to be photographed, or to replace the film camera body with a camera body equipped with a different photographic field diaphragm.

According to the present invention described above, it is possible to perform fluorescence photography with a significantly wide angle of view, and also to obtain high-contrast photographs in general photography, or to reduce the area in which images are formed by increasing the photographic magnification. Since it is the same as when zooming in at 2x (wide-angle), it has the advantage of allowing you to use the film without wasting it, and in particular reduces deterioration in resolution due to graininess of the film compared to when enlarging a color image without changing the shooting magnification. It is extremely effective in that it allows you to

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are sectional views each showing an embodiment of the present invention. FIG. 3 is a sectional view showing a modification. In the figure,
1 is an objective lens, 3 is an imaging lens, 3c is a variator lens, 5 is a photographing field diaphragm, 18 is an illumination field diaphragm, 20 is an exciter filter, 21 is a barrier filter, and 3f is an attachment lens.

Claims (1)

[Scope of Claims] 1. Equipped with a fundus illumination optical system and a fundus photography system, capable of general photography and fluorescence photography, and during general photography, the fundus illumination light and the fundus photography light are spatially separated at the anterior segment of the subject's eye. In addition, in a fundus camera, in which the fundus illumination light and the fundus photographing light are separated in terms of wavelength during fluorescence photography, and the fundus photographing system has a variable magnification optical system that changes the photographing magnification, In this case, a photographing field diaphragm is provided at a position optically conjugate with the fundus of the examined eye and regulates the photographing field range in which the fundus image is formed, and the photographing field diaphragm above the fundus of the examined eye is used during fluorescence photography compared to during general photography. A fundus camera comprising means for changing the magnification of the variable magnification optical system so as to expand a field of view in which a fundus image is formed. 2 Equipped with a fundus illumination optical system and a fundus photography system, it is capable of general photography and fluorescence photography, and for general photography, the fundus illumination light and fundus photography light are spatially separated at the anterior segment of the subject's eye, and for fluorescence photography. In a fundus camera that separates fundus illumination light and fundus imaging light in terms of wavelength, and in which the fundus imaging system has a variable magnification optical system that changes the imaging magnification, the fundus imaging system has a variable magnification optical system that changes the imaging magnification; a photographing field diaphragm provided at a position optically conjugate with the fundus of the eye to regulate a photographing field range in which a fundus image is formed; , an illumination field diaphragm that regulates an illumination field range on the fundus of the subject's eye, and a change in the field of view in which a fundus image is formed by the photographic field diaphragm on the fundus of the subject's eye during fluorescence photography compared to during general photography. means for changing the magnification of the magnification optical system; and means for expanding the illumination field range by the illumination field diaphragm on the fundus of the subject's eye during fluorescence imaging to be greater than or equal to the expanded imaging field range, compared to during general imaging. A fundus camera characterized by: 3. The fundus camera according to claim 2, wherein the illumination field range by the illumination field diaphragm on the fundus of the examinee's eye during fluorescence imaging is made to coincide with the enlarged photographing field range during fluorescence imaging compared to during general imaging.