JPS62186839A - Eyeground 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 [Industrial Field of Application] The present invention relates to a fundus camera that captures an image of the fundus of an eye to be examined.

[Prior Art] A fundus camera that examines and photographs the fundus of the eye has become indispensable for ophthalmological diagnosis. For example, this fundus camera is used to examine the circulatory system using fluorescent angiography, diagnose the intraocular retina, diagnose vascular disorders in urology, and diagnose retinal detachment, but in all cases it also diagnoses the vascular structure. There are difficulties in obtaining possible images.

However, for diagnostic reasons, it is desired to obtain fundus images with even better resolution and contrast in a direction that places as little burden on the patient as possible. An attempt to do this is described in US Pat. No. 4,213,678. FIG. 2 shows the known device, in which a laser beam emitted from a laser light source 1 and horizontally and vertically deflected by galvano mirrors 2a and 2b passes through a mirror 3, a lens 4, etc. to the fundus Er of the eye E to be examined. is scanned continuously in the form of a linear raster. Further, the laser beam reflected by the fundus Er is received by the light receiving element 6 through the lens 5 or the like through the pupil Ep, and becomes an electric signal. By synchronizing this signal with the scanning signal, the fundus image is displayed on a television monitor.

This known device uses galvano mirrors 2a and 2b for vertical and horizontal deflection of the laser beam.

Although this is advantageous in reducing the size of the device, its characteristics make it unsuitable for high-speed scanning, and it is impossible to obtain a signal equivalent to a normal NTSC television signal. Therefore, in order to obtain a standard television signal from this type of device, faster horizontal scanning is required.

Currently practical high-speed deflectors include polygon mirrors and acousto-optic deflectors (AODs).
9-115024 is known. This device dramatically improved the performance of the previous device, but the high-speed polygon mirror required advanced technology such as the use of air bearings to compensate for its accuracy, and the device It has the disadvantages of being expensive and large.

On the other hand, considering the use of an acousto-optic deflector, the above-mentioned drawbacks can be solved, but when driven in continuous sweep, its resolving power is basically lower than that of a polygon mirror, so it has the following drawbacks: 0 It is natural that there is a desire to observe the affected area more magnified in normal diagnosis, and when enlarging and observing a part of the fundus image observed with the above-mentioned known device, it is necessary to use laser light. The scanning range is limited by making the scanning signal variable, and the monitor screen is reconstructed using the scanning signal and the output from the light receiving device. However, the resolution of the monitor image in the horizontal continuous scanning direction is determined by the characteristics of the scanning optical system if the resolution of the monitor is high enough. is only valid for
It cannot be used when using an acousto-optic deflector.

[Object of the Invention] The object of the present invention is to extract a standard television signal as an output signal by using an acousto-optic deflector for high-speed continuous scanning, and to effectively take advantage of the advantages of miniaturization. Another object of the present invention is to provide a fundus camera that has a variable observation magnification and does not cause a decrease in the resolution of an observed image even when the magnification is changed.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to scan a light beam emitted from a laser light source on the fundus surface of the eye to be examined using a scanning optical system, and to scan the light beam reflected from the fundus. In an apparatus for guiding light to a light receiving element by a light receiving optical system and synthesizing a fundus image using a signal from the light receiving element and a scanning signal from the scanning optical system, the scanning optical system and the light receiving optical system include an objective lens facing the eye to be examined. A fundus camera, characterized in that the scanning optical system is equipped with at least an acousto-optic deflector and a variable magnification optical system that changes the size of the scanning beam diameter in proportion to the fundus scanning area of the eye to be examined. be.

[Embodiments of the Invention] The present invention will be explained in detail based on the embodiment shown in FIG.

FIG. 1 shows an embodiment of the present invention, in which a laser controller 10. The beam emitted from the laser head 12 to which the laser light source 11 is connected is transmitted through a beam expander 13,
Acousto-optic deflector (hereinafter referred to as AOD) 14, imaging lens 15. A relay lens 17 with a vertical scanning galvanometer mirror 16 in the middle, a field lens 18, a mirror 19, a variable relay lens 20, a perforated mirror 21. Objective lens 2
2 to reach the eye E to be examined. Also,
On the side of the perforated mirror 21 that reflects the light beam from the objective lens 22 direction, there is a relay lens 24 having a small sunspot 23 in the middle.
, small light shield 25. Ring slit 26, small light shield 27,
Mirror 28, condenser lens 29. The light receiving elements 30 are arranged sequentially.

40 is an electrical controller, AOD driver 4
Sending a control signal to the AOD l 4 via the galvano mirror driver 42 and to the galvano mirror 16 via the galvano mirror driver 42;
A signal is sent from the light receiving element 30 to the controller 40 via an amplifier 43. Furthermore, an image signal is transmitted from the controller 40 to the television monitor 44.

First, I will explain the observation method using laser beam flux.
The laser beam emitted from the laser beam expander 13 is aligned with the aperture of the AOD 14 and is incident thereon. The AOD 14 is controlled by the signal from the AOD driver 41.
The laser beam is deflected at high speed, that is, continuously swept, as shown in L1 to L1°.

In reality, this deflection is perpendicular to the plane of the paper, but in the drawing it is shown parallel to the plane of the paper. The laser beam deflected by the AOD 14 forms a one-dimensional point sequence on Sl by the imaging lens 15, and these point sequences are formed on the scanning plane S2 of f51 by the vertical scanning galvanometer mirror 16 and the relay lens 17. form a linear raster. At this time, the galvano mirror 16 is driven by a galvano mirror driver 42, and the input signal to the AOD driver 41 and the input signal to the galvano mirror driver 42 are synchronized by the controller 40.

The scanning plane S2 corresponds to the film plane of the fundus camera, and is made conjugate with the second scanning plane S3 via the mirror 19 by the variable magnification relay lens 20, and by changing the magnification of the variable magnification relay lens 20, the relay The magnification is variable. Furthermore, since S3 is made conjugate with the fundus Er of the eye E by the objective lens 22 and the optical system of the eye E, the first
The linear raster of the scanning plane S2 can scan the fundus Er of the eye E to be examined at different magnifications due to the action of the variable magnification relay lens 20. On the other hand, the laser beam reflected by the fundus Er passes through the pupil Ep of the eye E to be examined, passes through the objective lens 22 that is common to the scanning optical system, and then passes through the pupil Ep by the objective lens 22.
The light is reflected downward by the perforated mirror 21 arranged at the conjugate point P1 of the light beam, and is focused on the light receiving surface P3 of the light receiving element 30 by the relay lens 24, mirror 28, and condenser lens 29.

Here, pupils Ep, Pi, P2. P3 are each optically conjugate, and P2 is provided with a ring slit 26 that forms an image in the hole of the perforated mirror 21, and the scanning optical system and the light receiving optical system are combined in a pupil-splitting format. This is similar to a conventional fundus camera. In addition, the relay lens 24
There are small black dots 23 that remove reflected light from each surface of the objective lens 22, and points approximately conjugate to the cornea and crystalline lens positions of the subject's eye E before and after P2 remove reflected light from the same areas.
Small light shielding objects 25 and 27 are arranged to cut scattered light.

In this way, the light receiving element 30 can receive only the reflected light from the fundus Er, with various harmful reflected lights and scattered lights removed. The output of the light receiving element 30 is inputted to the controller 40 via an amplifier 43, and then inputted to the controller 40.
0 to the AOD driver 41 and galvano mirror driver 42. It is synthesized with a synchronization signal that is always constant for magnification changes, and becomes a standard TV signal on the TV monitor 4.
4 is output. The TV monitor 44 is the controller 40
A fundus image Er' is projected in response to a signal from the fundus oculi.

Furthermore, all the components within the broken line are housed in the same housing, and can be aligned front to back, left to right, and up and down with respect to the eye E to be examined. That is, since the optically coupled components are integrally formed, no special consideration is required for one-position alignment.

Let us consider the case where magnification is changed in the embodiment of the present invention configured as described above. As described above, the scanning optical system maps the first scanning plane S2 to the eye Er at different magnifications by the action of the variable magnification relay lens 20. Here, if there is no vignetting in the optical system after the first scanning surface S2 and the aberrations of the optical system are sufficiently corrected, the resolution of the linear raster formed with the fundus E of the eye E, In other words, the total number of pixels resolved within the screen is
The resolution is the same as that of . This is reasonable considering that observation is performed on the same television monitor 44 regardless of its magnification. And its resolution ff4fAOD1
4. It is almost determined by the size of the aperture of the galvano mirror 16 and the screen size on the first scanning plane S2. In other words, even when the observation magnification is changed, the performance of the scanning element consisting of the AOD 14 and the galvano mirror 16 is always fully demonstrated. As mentioned earlier.

This is extremely important considering that the resolving power of the AOD 14 is slightly inferior to that of polygon mirror systems, etc., and can be said to be an essential condition for maintaining sufficient resolution even when performing magnified observation.

Due to the above-described unique configuration of the present invention, a high-speed scanning system using the AOD 14 can be employed, and all the optical systems from the laser head 12 to the light receiving element 30 can be integrally combined.

In other words, a high-speed scanning system using a polygon mirror is very large and heavy, so if all the optical systems are combined together, there will be a large inertia when positioning this optical system with respect to the eye E. This is because delicate positional alignment becomes impossible.

Note that if the pupil position is significantly moved by the variable magnification relay lens 20, it is preferable to move the field lens 18 in and out as necessary.

[Effects of the Invention] As explained above, by adopting the configuration of the fundus camera according to the present invention, it is possible to create a laser scanning fundus camera that has sufficiently high resolution even during magnified observation, is compact, and is capable of high-speed continuous scanning. Obtainable. This miniaturization is achieved by using an AOD, which for the first time makes it possible to form the entire optical system in one piece.
It can be made to have the same operability as a normal fundus camera. Furthermore, it becomes possible to directly apply the methods used in conventional fundus cameras for widening the angle of view, removing harmful reflections, and removing scattered light, which has a remarkable effect on improving the contrast of the observed image.

[Brief explanation of drawings]

FIG. 1 shows a configuration diagram of an embodiment of a fundus camera according to the present invention, and FIG. 2 is a configuration diagram of a conventional device. 11 is a laser light source, 12 is a laser head, 14
is an AOD, 16 is a galvanometer mirror, 120 is a variable magnification relay lens, -21 is a perforated mirror, 22 is an objective lens, 30
4 is a light receiving element, 4o is a controller, and 44 is a television monitor.

Claims (1)

[Scope of Claims] 1. A scanning optical system is used to scan the light beam emitted from a laser light source on the fundus surface of the eye to be examined, and a light receiving optical system guides the light beam reflected from the fundus to a light receiving element. In an apparatus for synthesizing a fundus image using a signal from an element and a scanning signal from the scanning optical system, the scanning optical system and the light-receiving optical system share an objective lens facing the eye to be examined, and the scanning optical system includes at least A fundus camera comprising an acousto-optic deflector and a variable magnification optical system that changes the diameter of a scanning beam in proportion to the fundus scanning area of an eye to be examined. 2. The variable magnification optical system relays the first scanning plane in the scanning optical system to the second scanning plane, and the objective lens relays the first scanning plane in the scanning optical system to the second scanning plane.
The fundus camera according to claim 1, wherein the scanning plane of the fundus is projected onto the fundus of the eye to be examined. 3. The light-receiving optical system is coupled to the scanning optical system in a pupil-dividing manner using a perforated mirror arranged on a plane substantially conjugate to the pupil of the eye to be examined by the objective lens. fundus camera. 4. The laser light source, the scanning optical system, the light-receiving optical system, and the light-receiving element are mechanically coupled to each other and housed in an integrated housing, and the housing is adjustable in position forward and backward, left and right, and up and down with respect to the eye to be examined. A fundus camera according to claim 1.