JPS5977831A - Eye bottom camera - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention enables focusing, working distance adjustment, and optical axis alignment to be performed using a single focusing optical system.
It is an object of the present invention to provide a fundus camera that has improved operability, simplified construction, and miniaturized construction.

In a fundus camera, focusing is generally performed while observing an aerial image using a transparent focus plate provided with a single line or the like. Unfortunately, accurate focusing requires considerable skill and also places a heavy burden on examiners such as doctors.

To solve this problem, a fundus camera has recently been proposed in which an index is projected onto the fundus from inside the fundus camera, and the examiner adjusts the focus while observing this projected image. Since the observation and photographing light beams were separated from each other, additional mechanisms were required to adjust the working distance (distance M between the cornea of the eye being examined and the objective lens) and the optical axis, resulting in poor operability. However, there were problems in that the structure was complicated and the entire fundus camera became large. To explain this in detail, FIG. 1 shows a conventional optical system, in which 1 is a light source for observation, 2 is a condenser lens, and 3 is a light source for observation provided by the condenser lens 2 at the position of the image of the light source for observation. 4 is a condensing lens, 5 is a ring slit having an annular opening, 6 is a relay lens, and 7 is left and right as shown in FIG. 2 (perpendicular to the drawing in FIG. 1).
8 is an objective lens, 9 is an eye to be examined, and 10 is an on-axis entrance 10a and its right and left sides as shown in FIG. an aperture diaphragm having a pair of off-axis apertures 10b located perpendicularly to the objective lens 8 and located at a position conjugate with the pupil of the subject's eye 9; 11 is a photographing lens including a focusing lens lla; 12 is a flip-up mirror for switching between the photographing optical path and the observation optical path; 13 is a film surface; 14
15 is a focusing plate, and 16 is an eyepiece.

Since the conventional example is configured as described above, the illumination light emitted from the observation light source 1 or the photographing light source 3 is focused onto the ring slit 5 by the condenser lens 4. The light passing through the ring slit 50 is condensed near the perforated mirror 7 by the lacing 6, and then reflected by the perforated mirror 7, and then reflected by the objective lens 8 onto the cornea 9a of the eye 9 to be examined. The light is focused in the vicinity of and illuminates the fundus 9b. Next, the light emitted from the fundus 9b is passed through the objective lens 8 to the perforated mirror 70.
The fundus image is formed in front of the eye, and the light emitted from the fundus image is transmitted through the open lower a of the perforated mirror 7 and the axial aperture 10a' of the aperture stop 10.
During observation, it is subjected to the action of the photographing lens 11, and is sequentially reflected by the flip mirror 121 and the reflecting mirror 14, and then the focus plate 1.
5 and observed through the eyepiece lens 16, and when photographing, the image is formed on the film surface 13 by the photographic lens 11.

- On the other hand, the index light beam for focusing is emitted from the index optical system (not shown) and then passes through the pair of off-axis apertures 10b of the aperture stop 10 and the left and right notches of the open lower a of the perforated mirror 7. Thereafter, the objective lens 8 forms an image on the fundus 9b of the eye 9 to be examined as an index image.

Then, this index image is observed through the rear eyepiece lens 16, which follows the same path as the fundus image after leaving the fundus 9b.

Therefore, focusing can be performed by fully adjusting the position of the focusing lens lla while observing this index image ff. Focusing is performed in this way, but as mentioned above, in the past, the index light beam and the photographing/observation light beam were separated to avoid the occurrence of flare and ghosts due to surface reflection of the index light on the lens surface, etc., so the working distance adjustment was difficult. Also, a separate mechanism was required for optical axis alignment.

In view of the above-mentioned problems, the present invention projects an index onto the fundus of the eye by superimposing an index light beam and a photographing/observation light beam, and uses the reflected light from the cornea to adjust the working distance and optical axis. The purpose of the present invention is to provide a fundus camera with improved operability, simplified structure, and miniaturization. To explain this by assigning the same reference numerals to the members, the perforated mirror 7 and the aperture stop 10 are provided with only perfect circular center-to-center lowers a and 10a, as shown in FIGS. 5 and 6. ing. 17 is a polarizing beam splitter disposed between the flip-up mirror 12 and the reflecting mirror 14, and this plays the role of removing surface reflection of the index light on the cornea 9a and each lens surface. In order to have this effect, the ability to separate the two polarized light components is slightly weakened. 18 is a concave lens; 19 is a focus index having a shape as shown in FIG. 7 and provided at a position optically conjugate with the film surface 13 or focal plate 15; 20 is a condenser lens; 21 is a working distance. When the index light passes through the objective lens 8 and is reflected by the cornea 9a of the eye 9 to be examined, the position where the index light is formed as an image by the objective lens 8 is the fundus image position formed by the objective lens 8. An aperture stop for an index, 22 a condensing lens, and 23 a light source for an index, which are arranged to coincide with each other, constitute an optical system for an index together with the polarizing beam splitter 17.

Since the fundus camera according to the present invention is configured as described above, is it possible to use an index light? The light emitted from IJi, 23 is sent to the condenser lens 2.
2. Index aperture 21. The light passes through the condensing lens 20 and illuminates the index 19 . After the index light emitted from the index 19 passes through the concave lens 18, almost only the S component is reflected by the polarizing beam splitter 17 and enters the observation optical system.Then, the index light passes through the observation optical system in the opposite direction to the observation direction and is reflected in the eye 9 to be examined. It reaches the fundus 9a.

Here, since the index 19 is optically conjugate with the film plane 13 or the focusing plate 15, when the fundus 9bT/c is correctly focused by the focusing lens lla,
The image of index 19 also correctly images the fundus 9bK.

At this time, the polarized index light is reflected by the fundus 9bK and loses its polarization, and a part of it passes through the observation optical system.
The light is reflected by the bouncing mirror 12 and directed toward the polarizing beam splitter 17 . In addition, the index light, which remains as an S component and is reflected by the lens and the surface of the cornea 9a on the way to the fundus 9b, also heads toward the polarizing beam splitter 17. Since this polarized beam brick 17 has the property of passing the P component and reflecting almost the S component, the P component of the index light reflected by the fundus 9b is reflected by the lens and cornea 92. A small portion of the index light, which remains the S component, passes through and heads toward the focus plate 15. Therefore, a fundus image, an index image, a lens surface reflection image of the index light, and a corneal reflection image are obtained through the eyepiece lens 16, but among these, the lens surface reflection light is determined by selecting the curvature of each lens and by adjusting the fundus illumination system. This can be removed by employing surface anti-reflection black dots. Further, since the corneal reflected light is considerably stronger than the fundus reflected light, the rate of decrease in the separation ability of the polarizing beam splitter 17 for one minute between the two polarization methods required to create a corneal reflected image may be small.

Thus, by moving and adjusting the position of the focusing lens lla so that the target image is properly focused while observing the target image, the fundus image will also be in focus. Also, subject 111i! If the working distance of the fundus camera with respect to 9K is correct, the line of the index aperture diaphragm 21 will be clearly visible, and when the optical axis of the fundus camera is correctly aligned, the image of the index aperture diaphragm 21 will be visible at the center of the field of view. Figures 8 to 11 show various states during adjustment, and Figure 8 shows focus.

Fig. 9 shows a state in which the working distance and optical axis are all aligned correctly, Fig. 9 shows a state in which the working distance and optical axis are aligned correctly but the focus is poor, and Fig. 10 shows a state in which the focus is incorrect.

FIG. 11 shows a state in which the optical axis is correctly aligned but the working distance is defective, and FIG. 11 shows a condition in which the focus and working distance are correctly aligned but the optical axis is defective. In this way, the single focusing optical system adjusts the focusing 2 working distance Nf,
Since the optical axis can be aligned, the operability is improved, the structure is simple, the device is compact, and the manufacturing cost is also reduced.

Note that the same effect can be obtained not only by using the index 19 but also by adopting a split R type index optical system. Further, the polarizing beam splitter 17 may be configured so that it can be switched to a crow or block for optical path length correction when it is not needed.

FIG. 12 shows the optical system of the second embodiment, in which the focus, optical axis deviation, and working distance are detected by a detector. In this figure, 27 is a dichroic mirror that transmits all visible light and reflects infrared light, 18 is a concave lens, 24 is a polarizing beam splitter, 120 is a condensing lens, 25 is a mask, 26 is a focus detector, 28 is a half mirror, 129 is a working distance/optical axis deviation detector, 19 is a focus index, and 21 is arranged so that when the fundus camera is at a proper working distance, the index light reflected by the cornea forms an image on the detector 29. 22 is a condensing lens, 23 is an infrared light source for index such as an infrared LED, and these constitute the focusing optical system'. Here, the index 19 and the mask 25 are, for example, shown in FIG.
As shown in A) and (B)K, the shapes and sizes are exactly the same, but the transmitting part and the light shielding part are provided in completely opposite directions, and the parfocal position is the same as that of the film surface 13 or focusing plate 15, respectively. It is located in The detector 29 is a five-segment element as shown in FIG. 14, and the diameter of the central portion 29e is equal to the diameter of the image of the index aperture 21 when it is correctly formed thereon. They almost coincide, and each peripheral portion 29a to 29d is arranged symmetrically with respect to the optical axis. 30 is a focusing plate 15
This is a working distance, optical axis deviation, and focus status display device installed near the outer periphery of the camera. Further, FIG. 15 shows the field of view/hill of the eyepiece lens 16, 31a to 31d are optical axis deviation indicators, 31e is a working distance indicator, and 32 is a focus indicator. FIG. 16 shows a block diagram of a signal processing circuit that processes signals from each detector, and 33 is an amplifier;
34 is a control circuit, 35 is an index light source driving section, and 36 is a display device driving section.

Since the second embodiment is configured as described above, the light emitted from the index light source 23 is transmitted to the condenser lens 22. After passing through the entire index aperture stop, the index 19 is illuminated. Index 19'f: The emitted index light passes through the half mirror 28 and the condensing lens 20, and only the polarized light of the S component is selectively reflected by the rear light beam musblitter 24, passes through the concave lens 18, and then The light is reflected from the dichroic mirror 27VC and enters the observation optical system. Thereafter, the observation optical system advances in the opposite direction to that during observation, and reaches the fundus 9b of the eye 9 to be examined. With this ζ, index 19
Since the film, the mirror surface 13, or the focusing plate 15 are optically conjugate, the fundus 9b is focused by the focusing lens lla.
When the eye is in focus correctly, the image of the index 19 is also correctly formed on the fundus 9bK. Then, the polarization of the index light is disrupted in the fundus 9b, and a portion of it travels through the observation optical system and bounces off the mirror 12. The light is sequentially reflected by the dichroic mirror 27 and returns to the focusing optical system. Further, a part of the index light reflected by the lens and the surface of the cornea 9a on the way to the fundus 9b also returns to the focusing optical system. Thereafter, these lights head toward the polarizing beam splitter 24, but due to the action of the polarizing beam splitter 24, only the polarized light of the P component of the index light emitted from the fundus 9M+- passes through and is focused on the mask 25. Image. In this case, the index 19 and the mask 25 have the relationship as shown in FIGS. 13(A) and 13(B)K, and are provided at the parfocal position W, so that
When the fundus 9b is in focus, the index image completely overlaps the light-shielding portion of the mask 25, and as a result, the index light is directed to the mask 25.
It is completely blocked and does not enter the focus detector 26 at the rear. Therefore, by detecting the amount of light incident on this detector 26, focus can be detected. On the other hand, other light is reflected by the polarizing beam splitter 24 and then reflected by the half mirror 28 and enters the working distance/optical axis deviation detector 29. Here, the reflected light on each lens surface can be removed by the method described in the first embodiment,
Even if there is light, it does not affect the measurement because it is a constant light.

Furthermore, the polarized light of the S component of the index light also enters the detector 29;
If this also does not spread beyond the center part 29e when out of focus,
Since there is no change in the amount of light incident on each light receiving element, there is no effect. Then, when the corneal reflected light indicates that the working distance is correct, the detector 2
9 as a sharp aperture diaphragm image, and when the optical axis is correctly aligned, the image will be centered. Therefore,
By detecting the amount and ratio of light incident on each light receiving element of the detector 29, the working distance and optical axis deviation can be detected.

Fig. 17 to Fig. 19 show various states during adjustment, Fig. 17 shows a state in which the optical axis 1 working distances are both correctly aligned, and Fig. 18 shows a state in which the optical axes are correctly aligned but the operation is not performed. A state in which the distance is <6 is shown, and FIG. 19 shows a state in which the working distance is correctly matched but the optical axis is misaligned.

Thus, the signals of the detectors 26 and 29 are transmitted to the signal processing circuit (
16) within the field of view of the eyepiece 16 (the first
5), the examiner can easily and accurately perform positive aVC focusing, 2nd working distance adjustment, and optical axis adjustment.

In this embodiment, a part of the light beam forming the fundus image also goes to the detectors 26 and 29, but the influence of these can be eliminated by an optical bandpass filter, modulation of the index light, or an electrical filter. Furthermore, it would be even more useful if the focusing lens and fundus camera main body's longitudinal and horizontal movement and L-down movement mechanisms were configured to be driven based on the above-mentioned signals.

Further, each of the embodiments described above can be applied to a so-called non-mydriatic camera that observes the eye to be examined using invisible light and photographs the eye using visible light. To do this, in the first embodiment, it is sufficient to change the index light wavelength, and in the second embodiment, the separation wavelength of reflection and transmission of the dichroic mirror is changed in relation to the sensitivity wavelength range of the night vision tube. That's fine.

As described above, the fundus camera according to the present invention has important practical advantages such as improved operability, simple structure, miniaturization, and low manufacturing cost.

[Brief explanation of drawings]

FIG. 1 shows the optical system of a conventional fundus camera, FIGS. 2 and 3 are front views of the perforated mirror and aperture stop of the conventional example, and FIG. 4 shows a fundus camera according to the present invention. Figures 5, 6 and 7 are front views of the perforated mirror, aperture stop and index of the above embodiment, respectively, and Figures 8 to 11 are diagrams showing the optical system of the embodiment. Diagrams showing various states during adjustment,
Fig. 12 is a diagram showing the optical system of the second embodiment, Fig. 13 is a text indicating the index and mass dandruff of the above second embodiment, and Fig. 14 is a diagram showing the working distance and optical axis deviation of the above second embodiment. A front view of the detector, FIG. 15 is a diagram showing the field of view of the second embodiment, and the first
Figure 6 is a block diagram of the signal processing circuit of the second embodiment,
FIGS. 17 to 19 are diagrams showing various states during adjustment of the second embodiment. 7...Perforated mirror, 8...Objective lens, 9...
...Eye to be examined, 10..Aperture stop, 11..Photographing lens, 17..Polarizing beam splitter-119.
...Indicator, 21...Aperture stop for indicator, 23...
- Index light source, 15... focus plate. Figure 2 Figure 3 0a Figure 113 (A) (B') Figure 14? [Fig. 7, Fig. 18, ff, Fig. 19, Fig. 16]

Claims (1)

[Claims] A fundus camera characterized in that the fundus camera is configured to also align the photographing and observation optical axis with the index light beam.