JPS6349505B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a fundus camera.

In recent years, non-mydriatic fundus cameras have become popular. This involves illuminating the fundus of the subject's eye, which has dilated pupils due to dark adaptation in the dark, using light of wavelengths that are invisible to the human eye, such as infrared light, and capturing the reflected light from the fundus using an imaging tube. It receives light, displays the fundus image on a monitor TV based on its output, and while looking at this fundus image, performs camera adjustments such as focusing, adjusting the working distance, and aligning the axes of the eye and objective lens to take pictures. Set the state compatible with. In this state, the fundus image is recorded on the film by emitting light, such as visible light (white light), from a strobe, for example. Since such a fundus camera does not use a mydriatic agent, it is suitable for photographing the fundus without causing discomfort to the subject.

By the way, when taking fundus photographs using a fundus camera, the adjustment of the relative position between the subject's eye and the camera is generally very delicate, and flare may occur in the fundus photograph due to a slight adjustment error or minute movement of the subject's eye just before photography. It is easy to get mixed in and cause uneven lighting.
For this reason, many shooting failures occur. In particular, in the above-mentioned non-mydriatic fundus camera, the monitor TV is usually monochrome, and furthermore, the contrast of the fundus image displayed on the monitor is very poor because of the illumination using infrared light. For this reason, it is noticeable that () it is difficult to focus, () it is impossible to observe the details of the fundus, and () it is difficult to distinguish the presence of flare even if it is mixed in, and even experienced photographers still often fail in taking pictures. However, at present, it is impossible to tell whether or not the shooting has failed until the film is developed. Therefore, in the event of a failure, it takes time and effort to retake the photograph, which is very troublesome. Particularly in recent years, fundus photography is often performed not only for the purpose of curing patients with eye diseases, but also in groups for internal medical diagnosis, and it may be virtually impossible to retake the photograph.

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned problems, the present invention has been made for the purpose of providing a fundus camera that can quickly and easily confirm the condition of a fundus image recorded on a film or the like.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment in which the present invention is applied to a non-mydriatic fundus camera using infrared illumination. A light bulb 1 used as an observation light source, an infrared filter (transmits light with a wavelength of 800 mm or more and blocks light with a wavelength shorter than 800 mm), a condenser lens 3, a strobe tube 4 used as a photography light source, a ring slit 5. Relay lenses 6 are sequentially arranged on the optical axis 7, and together with the perforated mirror 8 and the objective lens 9 constitute an illumination optical system. Here, the light bulb 1 and the strobe tube 4 are conjugate to each other with respect to the condenser lens 3. On the other hand, on the optical axis 10, in order from the one closest to the eye 11 to be examined, there is an objective lens 9, a perforated mirror 8, and an imaging lens 1.
2, beam splitter 13, shutter 14,
A film 15 is disposed to constitute a photographing optical system. Further, on the optical axis 16 bent by the beam splitter 13, a window lens 17, a movable mirror 18, a monitor lens 19, and an image pickup tube 20 (for example, an infrared light vidicon) are arranged in order, and the output of the image pickup tube is It is connected to a monitor television 21 to constitute an observation optical system. Further, when the movable mirror 18 is moved out of the optical path as shown by the broken line, the monitor lens 22 and the image pickup tube 23 (for example, a white light vidicon) are located on the optical axis 16. The output of the image pickup tube 23 is also connected to the monitor television 21. here,
The beam splitter 13 reflects all infrared light,
Regarding visible light, it has the property of partially reflecting and partially transmitting visible light. Such a beam splitter can be obtained by overlapping coating films of a half mirror and a dichroic mirror. Further, the window lens 17 is provided to adjust the exit pupil position of the imaging lens, and has a substantially conjugate relationship with the film 15.

When photographing the fundus using the fundus camera as described above, it is first necessary to adjust the camera while viewing the fundus image. When the light bulb 1 is turned on, the emitted light passes through an infrared filter 2 to remove visible components and becomes an infrared beam. This infrared light beam is once focused on the strobe tube 4 by a condenser lens 3. The luminous flux passes through the ring slit 5
When the light passes through the annular aperture 24, it becomes an annular light flux, and an image of the ring slit 5 is formed near the perforated mirror 8 by the relay lens 6. That is, the ring slit 5 and the perforated mirror 8 are substantially conjugate with respect to the relay lens 6. The ring slit image is projected near the iris 25 of the eye 11 to be examined by the objective lens 9. The fundus 26 of the eye 11 to be examined is illuminated by the light beam passing through this ring slit image.

The light reflected by the fundus 26 passes through the crystalline lens 27 of the eye 11 to be examined, emerges from the cornea 28 as a substantially parallel beam of light, enters the objective lens 9, and forms an image of the fundus 26 near the rear focal point F. . This fundus image passes through the hole 29 of the perforated mirror 8, is relayed by the imaging lens 12, and is imaged near the window lens 17. This image is further reflected by the movable mirror 18, and the monitor lens 1
9 forms an image on the image receiving surface of the image pickup tube 20. A fundus image can be displayed on a cathode ray tube of a monitor television 21 based on the output signal from the image pickup tube 20, and the person operating the camera can adjust the camera and observe the fundus image while looking at the screen.

Next, a photograph is taken. In this case, the strobe tube 4 is first made to emit light, and at the same time the shutter 14 is opened and the movable mirror 18 is moved out of the optical path as shown by the broken line. The light beam emitted from the strobe tube 4 illuminates the fundus 26 of the eye 11 to be examined in the same manner as the light beam emitted from the light bulb 1 described above, and forms an image near the rear focal point F of the objective lens 9. This image passes through the hole 29 of the perforated mirror 8 and is relayed by the imaging lens 12, and a part of the visible component is transmitted to the beam splitter 1.
3 and forms an image on a film 15 to record a fundus image. The remaining visible and infrared components are reflected by the beam splitter 13 and passed through the window lens 17.
After being imaged in the vicinity, the image is further formed on the image receiving surface of the image pickup tube 23 by the monitor lens 22 . Image tube 23
A fundus image can be displayed on the cathode ray tube of the monitor television 21 based on the output signal from the monitor.

Here, the image projected on the monitor TV screen is exactly the same as that recorded on film 15, and the image obtained using visible light has a much higher contrast and is clearer than the image using infrared light. . Therefore, if you look at this video, film 1
It is possible to easily check whether flare is mixed in the fundus photograph recorded in step 5 or whether the focus is correct or not, and measures such as retaking the photograph can be taken immediately as necessary.

However, when the light emitted from the strobe tube 4 is used as is, the time for which the fundus image is displayed on the monitor television 21 is very short, so the above confirmation is often insufficient or impossible.

FIG. 2 shows an example of a circuit configuration for eliminating such inconveniences and ensuring the above confirmation. In the figure, numerals 4 and 23 represent the strobe tube 4 and the imaging tube 23 in FIG. 1, respectively. The output of the image pickup tube 23 is connected to an input terminal of an analog-to-digital (A/D) conversion circuit 30, and the output of this A/D conversion circuit 30 is connected to an input terminal of a frame memory 31. The output of the frame memory 31 is connected to the input terminal of the monitor television 21. 32 is a control circuit;
From here, control signal lines a, b, c, d, and e are connected to the image pickup tube 23, A/D conversion circuit 30, frame memory 31, flip-flop 33, strobe tube 4, and flip-flop 34, respectively. Further, the other input terminal of the flip-flop 34 is connected to a signal line f for sending out a vertical synchronizing signal from the control circuit 32. The output of this flip-flop 34 is connected to one input terminal of an AND circuit 39. Reference numeral 35 denotes a light receiving element, and for example, as shown by the broken line in FIG.
6 is provided and arranged on the optical axis bent by this half mirror. 37 is a reference voltage generation circuit;
The output thereof and the output of the light receiving element 35 are connected to an input terminal of a comparator circuit 38. The output of the comparator circuit 38 is the flip-flop 3
It is connected to the input terminal of 3. The output of flip-flop 33 is connected to the other input terminal of AND circuit 39 and also to control circuit 32. The output of the AND circuit 39 is connected to the frame memory 31.

First, the control circuit 32 operates the image pickup tube 23 through the signal line a to start scanning, and the A/D conversion circuit 3 through the signal lines b and c.
0 and frame memory ready for operation. It also resets the flip-flop 34 through the signal line e. Here, the control circuit 32 outputs a strobe light emission signal through the signal line d, causing the strobe tube 4 to emit light and resetting the flip-flop 33. The light emitted from the strobe tube 4 is directed to the fundus 26 of the eye 11 by the illumination optical system.
A portion of the light is reflected by the beam splitter 13 and travels along the optical axis 16 to form a fundus image on the image receiving surface of the image pickup tube 23. This fundus image is scanned and sequentially output as a photoelectric signal.
The signal is input to the D conversion circuit 30, converted into a digital signal, and supplied to the frame memory 31. On the other hand, some of the light is further reflected by the half mirror 36 and enters the light receiving element 35. Comparator circuit 38
Now, the output of the light receiving element 35 and the reference voltage generation circuit 37
When the output of the light receiving element 35 becomes larger than the reference voltage, that is, when the amount of light emitted from the strobe tube 4 becomes brighter than a predetermined value, an inverted signal is output. The output is "1".
This output is input to the control circuit 32, and in response, the control circuit 32 immediately supplies a vertical synchronizing signal to the flip-flop 34 through the f line. As a result, the output of the flip-flop 34 becomes "1", so the output of the AND circuit 39 becomes "1", and in response to this, the frame memory 31 starts a storage operation. When the next vertical synchronization signal is supplied from the control circuit 32 to the flip-flop 34, the output of the flip-flop 34 becomes "0".
The output of the AND circuit 39 also becomes "0", and in response to this, the frame memory 31 ends the storage operation. That is, by the above-mentioned operation, the A/
Of the digital image signals supplied via the D conversion circuit 30, just one screen worth of signals is stored in the frame memory. If this memory content is projected onto the cathode ray tube of the monitor television 21, the fundus image obtained by the light emission of the strobe tube 4 will be displayed on the monitor television 21.
1 as a still image, making it possible to fully confirm the same fundus image as recorded on film.

Although the above-described embodiment uses an image pickup tube as the imaging means, a solid-state image sensor such as a CCD, which has been put into practical use in recent years, may also be used as the image pickup means.

FIG. 3 shows such an embodiment.
In this embodiment, the outline of the optical system is the same as that of the embodiment shown in FIG. Therefore, the same numbers are given to the components having the same function, and the explanation thereof will be omitted.

In FIG. 3, a reflecting mirror 41 is arranged on the optical axis 16 behind the window lens 17, and a monitor lens 19 is placed on the optical axis bent by this reflecting mirror.
A CCD 42 is arranged next to the CCD 42, and its output is connected to the monitor television 21. Further, an infrared cut filter 43 is arranged between the monitor lens 19 and the CCD 42 on the optical axis 16 so as to be freely insertable and removable.

If the light bulb 1 is turned on with the infrared cut filter 43 removed from the optical path, the luminous flux emitted from the light bulb becomes infrared light in the infrared filter 2, and then, in the case of the embodiment shown in FIG. Similarly, CCD42
An image of the fundus 26 of the eye 11 to be examined is formed on the image receiving surface of the eye. Since the CCD 42 has sensitivity ranging from the visible region to the infrared region, the CCD 42 outputs a photoelectric signal according to the intensity distribution of the fundus image formed by the above-mentioned infrared light beam, and based on the output, the CCD 42 outputs a photoelectric signal to the cathode ray tube of the monitor television 21. An image of the fundus 26 can be projected. Therefore, it is possible to adjust the camera and observe the fundus while looking at this.

Next, when the infrared cut filter 43 is inserted into the optical path and the strobe tube 4 is made to emit light, the light beam emitted from the strobe tube illuminates the fundus 26, and part of the visible component of the light beam reflected by the fundus 26 is The light passes through the beam splitter 13 and forms a fundus image on the film 15. The remaining visible components and infrared components are reflected by the beam splitter 13, once formed into an image near the window lens 17, further reflected by the reflecting mirror 41, and passed through the infrared cut filter 43 while being converged by the monitor lens 19. This results in only visible components forming a fundus image on the image receiving surface of the CCD 42. Depending on the intensity distribution of this image
Based on the photoelectric signal output from the CCD 42, it is possible to clearly display the same fundus image recorded on the film on the monitor television 21, so by viewing this image, you can see the condition of the fundus image recorded on the film. Can be easily confirmed.

The purpose of inserting the infrared cut filter 43 here is to obtain a high-contrast image using only visible light, but if the thickness of this filter is set appropriately, the infrared cut filter 43 can be It is also possible to provide the lens with a function of correcting a shift in the imaging position due to chromatic aberration. Further, although an infrared cut filter is used in this embodiment, a blue or green filter may be used as necessary depending on the characteristics of the image sensor.

When obtaining a still image using the fundus camera shown in Figure 3, the CCD can accumulate the light intensity of the fundus image and once hold it before outputting it, so the flip-flop, etc. for timing shown in Figure 2 is not needed. The configuration is simple as shown in Figure 4. Here, 42 represents the CCD 42 in FIG.
The output of the CCD 42 is displayed on a monitor television 21 via an A/D conversion circuit 30 and a frame memory 31. 44 is a control circuit, and control signal lines g, h, and k are CCD 42 and A/D conversion circuit 3, respectively.
0, connected to the frame memory 31.

First, when the CCD 42 is made ready to receive light through the g line and the control circuit 44 outputs a strobe light emission signal to cause the strobe tube 4 to emit light, the light emitted from the strobe tube 4 causes the CCD 42 to emit light.
The fundus of the eye is formed on the image receiving surface, and its image intensity distribution is stored in the CCD 42 as a photoelectric signal. After a predetermined period of time has elapsed, the A/D conversion circuit 30 is operated through the h line, and the image storage of the CCD 42 is stopped through the g line, and the accumulated photoelectric signals are sequentially transferred and output and converted into digital data by the A/D conversion circuit 30. Convert to signal. This digital signal is stored in the frame memory 31 through the k line, and when all the photoelectric signals have been stored, if these are displayed on the monitor television 21 as image signals for one screen, a still image of the fundus 26 can be obtained. . Therefore, by viewing this image, the condition of the fundus image recorded on the film 15 can be fully confirmed.

In this embodiment, if the infrared component of the light beam directed toward the CCD 42 is sufficiently weak compared to the visible component, the filter 43 is not necessary.

As is clear from the above description, in the present invention, the same fundus image recorded on film can be displayed with high contrast on the cathode ray tube of a monitor television, so that failures in imaging can be immediately discovered. Therefore, by simply waiting a few minutes until the eye to be examined undergoes dark adaptation and mydriasis again, the image can be immediately retaken.

In the present invention, the film 1 can be detected by detecting the magnitude of the output signal of the CCD 42, for example.
Underexposure and overexposure of the photograph recorded in 5 can be detected. Further, by using this output signal to control the light emission time of the strobe tube, auto strobe photography can be performed. In addition, the image signals obtained by the image pickup tube 23 and CCD 42 can be not only displayed on a monitor television, but also recorded on a video signal recording device such as a video tape recorder and used as needed. Depending on the circumstances, you may be able to omit taking photos and just record a video. Furthermore, if the fundus image is obtained as a color image, even better fundus observation can be performed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing a circuit configuration for obtaining a still image in the embodiment shown in FIG. 1, and FIG. 3 is a diagram showing another embodiment of the present invention. FIG. 4 is a diagram showing a circuit configuration for obtaining a still image in the embodiment shown in FIG. 1... Light bulb, 4... Strobe tube, 8... Perforated mirror, 9... Objective lens, 11... Eye to be examined, 12...
...Imaging lens, 15...Film, 20, 23...
...Image tube, 21...Monitor TV, 42...
C.C.D.

Claims (1)

[Claims] 1. Of the light flux emitted from the observation light source, a component belonging to a wavelength range different from the visible spectrum range is irradiated onto the eye to be examined, and the light flux reflected at the fundus of the eye is guided onto the imaging means as observation light, and displayed based on the output of the imaging means. While adjusting the camera by looking at the fundus image of the eye to be examined formed on the means, the eye to be examined is irradiated with a component belonging to the visible spectrum of the light beam emitted from the photographing light source, and the light beam reflected by the fundus is collected. In a fundus camera that records the fundus image of the subject's eye by guiding it as photographing light onto a recording means, a light splitting means for dividing a luminous flux in the visible spectrum into two is provided in the optical path of the photographing light, and the light dividing means A portion of the photographing light is guided onto an imaging means sensitive to light in the visible spectrum range, which is disposed in an optical path branched from the photographing optical path, and the image of the eye to be examined is displayed on the display means based on the output of the imaging means. A fundus camera characterized in that it displays a fundus image and records the fundus image of the eye to be examined by guiding the remainder of the photographing light onto the recording means.