JPS6143053B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ophthalmological apparatus that allows easy adjustment of the working distance between the apparatus and the eye to be examined.

When photographing the fundus, delicate relative positioning of the eye to be examined and the fundus camera is required. In particular, the adjustment of the working distance between the eye to be examined and the fundus camera, the so-called working distance, is delicate, and if this working distance is inappropriate, the illumination light flux from the fundus camera will not effectively enter the eye to be examined. Furthermore, if the working distance is not appropriate, flare may be mixed in, resulting in a reduction in image quality.

In particular, in the case of a non-mydriatic method in which the fundus camera is focused and the field of view is set without adding mydriatic agents to the eye being examined, the fundus is examined by observing a low-resolution image on a display device, such as an image on a cathode ray tube. Since the camera is adjusted, it is difficult to visually recognize the flare caused by the above-mentioned inappropriate working distance. On the other hand,
During focus adjustment, the subject's eye often moves slightly, which disrupts the working distance, and the negative effects become more pronounced as the angle of view of the imaging system expands.

An object of the present invention is to obtain a clear fundus photograph without deterioration of image quality due to inappropriate working distance in a fundus camera or the like that observes and focuses on a displayed image on a display device.

FIG. 1 shows an embodiment of the present invention. In the figure, 1 is a tungsten bulb, 2 is a condenser lens, 3 is an infrared/near infrared transmission filter, 4 is a strobe tube, 5 is a condenser lens, 6 is a ring slit, and tungsten bulb 1 and strobe tube 4 are condensers. Conjugate with respect to the lens 2, the image of the tungsten sphere and the strobe tube 4 are also conjugate with the ring slit 6 with respect to the condenser lens 5.

7 and 12 are relay lenses, 13 is a ring slit plate, and only one of 6 or 13 may have a ring slit. 14 is a perforated mirror with a circular aperture, and 15 is an objective lens. 17 is the aperture,
Blocks light other than the shooting light beam. Reference numerals 18 and 18a are imaging lenses serving as an imaging optical system for adjusting the focus, and the element 18a functions to adjust the focus by moving in the optical axis direction. 19 is the film surface, 2
0 is a flip-up mirror, 21 is a field lens, 2
2 is a photographic lens, 23 is an infrared vidicon, 24
is a cathode ray tube.

Further, R is a secondary light source for adjusting the working distance, and uses the tip of the optical fiber 25. 26
27 is a tungsten bulb, and 27 is an infrared filter, which makes infrared rays enter the other end of the fiber 25.

Elements 12 to 24, tungsten bulb 30, infrared filter 31, condenser lens 32, slit plate 33, split prism 3
4. A focusing system consisting of a relay lens 35 and a transparent flat plate 36 equipped with a small mirror surface 36a is disclosed in Japanese Patent Application Laid-open No. 51
-As proposed in No. 330. That is, the slit plate 33 having the rectangular opening 33 serving as a focusing index and the split prism 34 have shapes as shown in FIG. 2, and are actually close to each other. Tungsten ball 30
and the slit plate 33 are conjugate with respect to the condenser lens 32, and the intersection of the optical axis of the relay lens 12 and the small mirror surface 36a is conjugate with the slit plate 33 with respect to the relay lens 35. Furthermore, element 30
Elements 1 to 35 are movable in the optical axis direction.
In conjunction with the movement of 8a, the film surface 1 with respect to the fundus
9 and the slit plate 33 are maintained conjugate.

Next, to explain the operation, as shown in the optical path _L1 in FIG.
2, the image of the ring slit 6 is superimposed on the ring slit 13, and then reflected by the perforated mirror 14 and transmitted through the objective lens 15 to the angle EC of the eye E to be examined.
A ring slit image is formed nearby, and the fundus Ef
to illuminate. The light beam for photographing from the fundus Ef is transmitted to the first lens by the objective lens 15 as shown in the optical path _L2 .
After being imaged on the conjugate plane 16 of the fundus, it sequentially passes through the hole of the perforated mirror 14 and the diaphragm 17, and is imaged on the conjugate plane 19 of the fundus by the taking lens 18.

Furthermore, a flip-up mirror 20 is provided between the photographing lens 18 and the film surface 19, and the film surface (second
The state of convergence of the photographing light beam on the fundus conjugate plane) 19 can be observed on the cathode ray tube 24. The optical paths L ₁ and L ₂ indicated by the dotted lines above represent an illumination optical system and a photographing optical system conventionally used in a general fundus camera. The optical path indicated by the solid line _L3 indicates the optical path according to the present invention, in which the light flux from the index light source P passes through the objective lens 15, is reflected at the corneal surface EC of the eye to be examined, and then is converted into an image of the index light source P by the objective lens again.
form P′. At this time, if the working distance between the eye to be examined and the objective lens is appropriate, the index light source P is set such that an image P' of the index light source is formed on the first conjugate plane 16.
The position of is set. The light beam from the image P' of the index light source passes through the hole of the perforated mirror 14, the diaphragm 17, and the photographing lens 18 in order and reaches the second conjugate surface 19. Observe the index light source image P'' of a plane that is conjugate with respect to the conjugate plane 19 and flip-up mirror 20.If the working distance is not appropriate, the index light source image will appear blurry, so make sure that the index light source image is clear. The entire fundus camera is moved to appropriately adjust the working distance.

In the above embodiment, the position of the index light source P is provided near the perforated mirror 14, but if the position is optically conjugate with the position of this P, the illumination optical system between the light source 1 and the perforated mirror 14 is provided. (FIG. 4) Alternatively, it may be introduced into the optical system between the vidicon 23 and the perforated mirror 14 of the observation section (FIG. 5).

Next, the shape of the target light source to be projected may be simply the light source itself, or a method of providing a target with an arbitrary shape and illuminating the target using an illumination optical system is also possible.

Although only one index light source is shown in Figure 1, by arranging multiple index light sources approximately symmetrically around the optical axis, the optical axis of the fundus camera can be adjusted for people with normal corneal curvature. It can be used as an auxiliary means to align the optical axis of the eye to be examined. FIG. 3 is a diagram showing what is observed when four index light sources are used and the optical axes of the fundus camera and the eye to be examined are aligned. If the optical axes of the eye to be examined and the fundus camera are aligned, the image P'' of the index light source will appear approximately symmetrical around the center of the observation field, but if they are not aligned, it will appear asymmetrical or Since they do not appear or appear a predetermined number of times, it is possible to easily detect the state of alignment between the eye to be examined and the fundus camera.

The above-mentioned index light source is usually installed at a position slightly away from the optical axis so that it does not interfere with observation and photography, but when measuring the coincidence of working distance and alignment with a single index light source, it is necessary to use the index light source. It may be provided on the optical axis.

Next, a rough guideline for the location of the index light source will be described. Although the diopter of the subject usually varies, the light flux emitted from the fundus of the subject's eye and incident on the objective optical system can be considered to be approximately an afocal light flux. Therefore, when the working distance is appropriate, the position where the objective optical system can take a fixed image of the subject's eye can be considered to be a substantially constant position regardless of the subject. Therefore, the index light source may be provided at a position where the light beam reflected on the corneal surface of the eye to be examined becomes approximately afocal when the working distance is appropriate. In other words, if the corneal surface is approximately spherical, in order for the light beam reflected on the corneal surface of the subject's eye to become an approximately afocal light beam, when the working distance is appropriate, the light beam from the index light source must be The index light source is provided so that the light is incident toward the midpoint between the center of the radius of curvature of the cornea and the corneal surface.

Next, focusing will be explained.

The light beam emitted from the tungsten bulb 30 becomes infrared rays through a filter 31, and is condensed onto a split prism 34 by the action of a condenser lens 32.

At this time, the light beam passing through the rectangular aperture 33a (focusing index) of the slit plate 33 is separated into two upper and lower beams by the action of the prism, and further reproduces the image of the index on the small mirror surface 36a by the relay lens 35. Note that the order of arrangement of the slit plate 33 and the prism 34 may be reversed.

Now, objective lens 15, photographing lens 18, 18a
When the focus of the photographing system consisting of the film 19 matches the fundus Ef, the intersection of the extension of the optical axis of the relay lens 12 and the small mirror surface 36a is determined by the relay lens 12, the perforated mirror 14, and the objective lens 15.
If you set it so that it is conjugate with the fundus,
When the fundus is in a predetermined position, the image of the index is reproduced. If the fundus is located before or after the predetermined position, the index image will be separated from the center because it will be reflected at the fundus before or after the two light beams intersect.

The index light beam reflected from the fundus is passed through the objective lens 15,
After passing through the photographic lenses 18 and 18a and the flip-up mirror 20 and once converging onto the field lens 21, the light enters the pidicon 23 via the photographic lens 22.
Therefore, as shown in FIG. 3, on the cathode ray tube 24, an index image 33a' corresponding to 33a and an index light source image for adjusting the working distance are displayed superimposed on the fundus image.
In the illustrated example, the index images are separated, so the operator can see that the imaging system is out of focus.

Therefore, the operator moves the element lens 18a to adjust the focus, but at this time the element 3
While the systems 0 to 35 move together, they are maintained conjugate to the fundus through optical elements that relay the film surface 19 and the slit plate 33, respectively, so the lens 18a remains until the image of the index matches.
By moving the camera, you can focus the camera. Note that instead of moving the lens, elements 19 to 23
The focus may be adjusted by moving the two together in the optical axis direction.

Furthermore, in the above example, a plurality of light beams form a single index image, but the split prism 3
4 may be removed and the index may be projected onto the fundus as it is.

When the focus and working distance are satisfied at the same time through the above adjustment steps, the operator leaves the flip-up mirror 20 and the flat plate 36, fires the strobe 4, and opens the shutter (not shown) to release the film. 19 is exposed.

4 and 5 are partial modifications of the embodiment shown in FIG. 1, in which a tube 106 protruding inward from the slit opening 6a of the ring slit 6 is attached;
An infrared filter 107 is provided at its tip to serve as a light source P as a working distance indicator. This point P is placed conjugate to the point P in FIG. Note that the reason for providing the filter is to prevent it from interfering with flash photography.

In FIG. 5, a light source P is provided at a position conjugate to point P in FIG. 1 via a semi-transparent mirror 108 and a lens 109, which are provided behind the perforated mirror 14 and can be freely removed and installed obliquely.

Further, the image of the annular secondary light source is reflected by the semi-transparent mirror 108 and projected toward the cornea, and the image displayed on the cathode ray tube 24 (FIG. 3) is an index image 33 for focus adjustment.
It is also advisable to make an annular indicator for adjusting the working distance appear close to and surrounding a'.

According to the present invention described above, since the focus adjustment can be performed simultaneously with the working distance, it is possible to obtain a photograph that is in focus and has no flare at the same time.

Further, according to the present invention, since corneal reflection is used to adjust the working distance, the position of the index light source image formed by the objective optical system changes greatly with a slight change in the working distance, causing the working distance to be adjusted. Can be adjusted sensitively.

Furthermore, in addition to the fundus of the subject's eye (for example, capillaries), an index image for focus adjustment can be used as a guide for focus adjustment, making it easier to adjust focus.

Furthermore, the working distance can be adjusted without adding an auxiliary lens or a detour optical path, and the optical system can be simplified or made more compact.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention. FIG. 2 is a perspective view for explaining the shape of a split prism. FIG. 3 is a diagram showing a display screen on a cathode ray tube. 4 and 5 are sectional views each showing a partially modified example of the embodiment of FIG. 1. In the figure, 15 is an objective lens;
18 is a photographing lens, 19 is a film, 24 is a cathode ray tube, P is a light source for an index, and 33 is a slit plate for an index.

Claims (1)

[Claims] 1. An objective optical system provided in order from the eye to be examined side;
In an ophthalmological apparatus that observes or photographs the fundus of an eye to be examined via an imaging optical system that performs focus adjustment so that the fundus image by the objective optical system is focused on a predetermined imaging plane, an index for focus adjustment is provided on the fundus of the eye to be examined. a projection optical system that projects the image; and, when a predetermined working distance from the eye to be examined is taken, an image that is an index light source and is projected onto the eye to be examined by the objective optical system, is reflected by the cornea of the eye to be examined, and is imaged by the objective optical system; an index light source arranged so that its position substantially coincides with a fundus conjugate plane formed by the objective optical system, an index image for focus adjustment reflected from the fundus of the subject's eye, and an index light source for working distance adjustment reflected from the cornea of the subject's eye; An ophthalmological apparatus comprising an observation means capable of observing an image superimposed on a fundus image via the objective optical system and the imaging optical system.