JPS6034378B2 - fundus camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fundus camera that allows accurate and easy focus adjustment of the fundus.

Fundus examination is used not only in ophthalmology but also in a wide range of fields such as internal medicine and neurosurgery for the early detection and diagnosis of various diseases.
With advances in preventive medicine to combat adult diseases, it has come to be widely adopted in mass medical examinations.

Fundus cameras have a wide range of applications in this field because of their large processing capacity during mass medical examinations, the preservation of photographs taken, and the precision of examinations. In order to take precise photographs of the fundus, it is necessary to accurately focus the fundus camera on the subject, the fundus, but with conventional fundus cameras, the camera operator directly observes the fundus image with his or her eyes through the viewfinder optical system. Not only does it require skill to determine the target, but it also has the disadvantage that focusing errors due to parallax occur because the aerial image is directly observed. The aim of the invention is to eliminate the drawbacks of conventional fundus cameras.

FIG. 1 shows an optical system according to an embodiment of the present invention.

In the figure, 1 is an objective lens, 2 is a relay lens, 3 is a film surface, and 4 is a closed aperture, and these four components constitute a photographing system. E is an eyeball placed at a predetermined position in front of the fundus camera.The objective lens 1 forms an image of the fundus worm f on this eyeball E as an aerial image, and the relay lens 2 transfers this aerial image to the film plane 3 and the inverted image. The image is re-imaged on a symmetrical plane F3 (described later) of the film plane 3 with respect to the mirror 2. A color film or the like is placed on the film surface 3 to record the fundus Ef image. 5
is a focus index light source, 6 is an aperture, 7 is a condenser lens, 8 is an infrared transmitting visible light reflection filter, 9 is a split image prism, and 1 is a focus index (in this example, as shown in Figure 2) 11 is a slit (in this example, it is a two-hole slit as shown in Figure 2), 12 is a relay lens, and 13 is a partially reflective transparent plate (in this example, it is a two-hole slit as shown in Figure 2). As shown in the figure, it is a partially reflective transparent plate in which a small area of the transparent plate is coated with a reflective film 13'), 14 is a relay lens, and 15 is an optical path splitting means (
In this example, it is a perforated mirror as shown in FIG. 2), and the above eleven elements and the objective lens constitute a focus index projection system.

In the embodiment of FIG. 1, the relay lenses 2, 14 are optically equivalent and are arranged symmetrically with respect to the perforated mirror 15. The light emitted from the focus indicator light source 5 passes through a closed aperture 6 and is focused by a condenser lens 7 onto a focus indicator. An infrared transmitting and visible light reflecting filter 8 is disposed between the condenser lens 7 and the focus index 10. Therefore, in the optical path of the focus index projection system after this filter 8, the visible component is removed from the beam, leaving only the infrared beam. No beam is sensed by the eyeball E from the focus index projection system. A split image prism 9 (in this example, it has a shape as shown in FIG. 3 and divides one beam into two beams) is arranged near the focus index 10, and therefore the split image prism 9 The infrared beam passing through the focus indicator slit 10 is divided into two to become a focusing infrared beam lp. A perspective view of the arrangement from the focus indicator light source 5 to the two-hole slit 11 is shown in FIG. The relay lens 12 partially reflects the image of the focus index 10 through the reflecting portion 13' of the transparent plate 13.
image is formed. This imaging point F is located on a conjugate plane of the film surface 3. (In this example, relay lenses 2 and 1
4 is optically equivalent and is arranged symmetrically with respect to the apertured mirror) The infrared beam lp reflected here passes through the relay lens 14, passes through the slit part of the ring slit 27 (described later), and passes through the apertured mirror. The light is reflected by the mirror 15 and focused at or near the rear focal point F2 of the objective lens, and then passes through the objective lens and the crystalline lens EI of the eyeball E, and is projected onto the fundus Ef. If the focus of the eyeball E is adjusted to infinity and the focusing infrared beam lp is focused on the back focal point F2 of the objective lens, the beam lp that has passed through the objective lens becomes a parallel beam, Therefore, the light is accurately focused on the fundus Ef, and as shown in FIG. 4A, the focus index 1
An image 10' of 0 is formed on the fundus Ef. If the focus index 10 cannot be accurately imaged on the fundus due to an abnormality in the refractive power of the eyeball E, the image of the focus index 10 will be reflected by the two-hole slit 11 on the pupil as shown in FIGS. 4B and C. The two holes of the image are separated according to the angle at which a point on the eyeball Ef is viewed, resulting in an image of 10". In order to make the separated focus index image 10" match the shape of the focus index 10, infrared beam l
The light condensing position by the relay lens 14 of p may be moved by an appropriate distance along the optical axis by the rear focal point F2 of the objective lens. Here, the two-hole slit 11 is placed at the back focal position of the relay lens 12, and the two holes are the ring slit 27 (
The ring slit 27 is included in the slit portion of the image (described later), and is arranged so that a straight line connecting the centers of the two holes lies on the diameter of the image of the ring slit 27. In addition, the closing diaphragm 6 has a focus indicator light source 5 separated into two parts by a split image prism 9.
The size of the opening is determined so that the light beams from the two-hole slit 11 pass through separate holes of the two-hole slit 11 and do not interfere with each other, and the two-hole slit 11 is arranged near the position where the image is formed by the condenser lens 7. 16 is a light source for fundus illumination, 18 is an infrared transmissive viewing light reflection filter, 19 is a condenser lens or inverting mirror, 21 is a strobe light source, 23 is a condenser lens, 25 is a ring slit, 26 is a relay lens, and 27 is a ring. The above nine elements, the relay lens 14, the perforated mirror 15, and the objective lens constitute a fundus illumination system.

The light emitted from the fundus illumination light source 16, including a portion of the light reflected by the concave mirror 17, passes through a condenser lens 19, an inverting mirror 20, and a field lens, and then passes through a ring slit 2.
It is collected on 5. The light whose secondary light source is one point on the ring slit 25 is placed so that its rear focal point is at the point that intersects with the optical axis of the ring slit 25, or once it is turned into parallel light by the Ray lens 26, it is focused on the total reflection surface. The illumination system relay lens 1 passes through the transparent part of the partially reflective transparent plate 13 held in one part.
4, the ring slit 27 is placed in its front focal plane.
Once an image is formed above, it is reflected by a perforated mirror 15 disposed obliquely in the optical path of the photographing system, and is imaged by the objective lens onto the pupil of the eye E to be examined, thereby illuminating the fundus illumination light source. The ring slit 25 is imaged by the relay lenses 26 and 14 so that the ring portion coincides with the ring slit 27, and the ring slit 27 is further imaged onto the pupil of the eyeball E by the objective lens. The illumination beam is parallel between the relay lenses 26 and 14, and is optically equivalent to the relay lenses 14 and 2 and arranged symmetrically with respect to the perforated mirror 15. Therefore, the part of the fundus image formed on the film surface 3 corresponding to the center of the ring is dark, and therefore the contrast of the focus index projected on this part is high. Furthermore, ring slits 25 and 27 are provided in the illumination beam optical path.
By arranging this, the reflected light of the illumination beam by the objective lens and the cornea is prevented from traveling to the film surface 3 based on the principle of the usual ring illumination method. Further, since the infrared transmitting visible light reflecting filter 18 is disposed between the fundus illumination light source 16 and the condenser lens 19, the light that illuminates the fundus Ef is infrared rays and is not sensed by the eye as described above. After focusing and determining the imaging field, the reversing mirror 20 and the partially reflective transparent plate 13 are removed from the illumination optical path as indicated by broken lines 20 and 13, respectively, and the fundus illumination light source 16, concave mirror 17, and condenser lens 1 are removed.
A strobe light source 21 disposed at a position optically equivalent to 9.
, a concave mirror 22, and a condenser lens 23 to momentarily illuminate the fundus of the eye and photograph it.

At this time as well, an infrared filter may be placed in front of the strobe light source 21 and an infrared film may be exposed using infrared rays, but in order to ensure a precise examination, color photography is preferable.
Therefore, in the embodiment shown in FIG. 1, no infrared transmitting and visible light reflecting filter is disposed in front of the strobe light source 21.
28 is an optical path splitting means, and in this example, a reversing mirror, 30
31 is a relay lens, and 31 is an infrared imaging tube 32 which is a monitor television. The above four elements, the objective lens 1, and the relay lens 2 constitute an observation system.

When the imaging system is focused on the fundus Ef, the light from the fundus Ef forms an aerial image at or near the back focal point F2 of the objective lens, and then passes through the hole of the perforated mirror 15 to the relay lens. By 2, the film surface 3 is
The image is re-imaged on the symmetry plane F3 of the film surface 3 with respect to the reversing mirror 28 interposed in the optical path of the photographing system. During the focus adjustment operation, the reversing mirror 28 is placed in the optical path of the photographing system. Therefore, the infrared rays emitted from the focus index photographing system and the fundus illumination system and reflected by the fundus Ef travel backward through the objective lens 1, pass through the relay lens 2, are reflected by the reversing mirror 28, and are focused on the symmetry plane F3. image and further field lens 29
The light passes through three relay lenses and forms an image on the light receiving surface of the image pickup tube 31. The infrared image pickup tube 31 electrically converts infrared information and applies it to the monitor television 32. The monitor television 32 converts the electrical signal into a television image and displays the infrared image as a visible image. Instead of the image pickup tube 31 and monitor television 32, other means for converting an infrared image into a visible image, such as an infrared image tube, may be used. As described above, the focus indicator projection system and fundus illumination system share an optical path with the imaging system through the perforated mirror 15, and the observation system through the reversing mirror 28.

Focus adjustment operations and shooting field determination operations are performed using the reversing mirror 20.
, 28. The partially reflective transparent plate 13 is placed in the optical path of the illumination system and imaging system as shown by the solid line in FIG. This is performed by irradiating the fundus Ef with the infrared rays reflected by the fundus Ef and visualizing the infrared rays reflected by the fundus Ef using an observation system.

An image as shown in FIG. 4 is observed on the image display surface of the monitor 32. For focus adjustment, for example, as mentioned earlier, the two IJ Ray lenses 2 and 14 are optically equivalent, so if one lens is moved manually or automatically, the two lenses 2 and 14 can be adjusted to be equivalent. If we give a motion relationship so that the other lens also moves, we can simultaneously move the relay lens 14 along the optical path so that the index image on the fundus Ef matches the shape of the index 10. In response to this, the relay lens 2 moves optically equivalent to the movement of the lens 14. Therefore, the focus of the photographing system can be brought into exact alignment with the fundus by a simple operation of moving one of the lenses 2, 14 a suitable distance while observing the focus index image displayed on the monitor television 32. However, as shown in the example in Figure 1, the fundus illumination system, focus index projection system, and pointy-ray lens 1
4, the illumination condition of the fundus may change by moving the relay lens 14, so although it is not shown in the example of FIG. Mechanical or electrical movement means is installed to optically move both the film surface 3 where the focus index is focused and the point F on the conjugate surface along the optical path, and the monitor The imaging system can be focused accurately on the fundus by simply moving one of the film planes 3 (or the imaging point F) by an appropriate distance so that the index image displayed on the television 32 becomes as shown in FIG. 4A. I can do it. Therefore, at this time, the plane of symmetry F3, the field lens 29,
The imaging system including the IJ Ray lens 30 and the image pickup tube 31 is moved simultaneously with the movement of the film surface 3 in an optically equivalent manner. Monitor the focus index image on TV 3
By adjusting the photographing system and the focus index projection system in this manner while observing in step 2, the photographing system can be focused on the fundus Ef. Also monitor TV 32
In addition to the focus index image, the fundus image illuminated over a wide area by the fundus illumination system is displayed.
The photographic field of view is determined by changing the relative direction of the photographing system and the eyeball E, for example, by changing the direction of the camera with respect to the fixed eye, or by changing the direction of the eyeball that the subject is gazing at relative to the target eyeball. can do. This is because the optical paths of the observation system and the photographing system coincide (the above-mentioned systems are assembled into one body, for example, and are movable and rotatable on the camera stand). By the way, in order not to use mydriatics to open the pupils, it is necessary to adjust the focus of the fundus camera and determine the field of view.
Eyeball E must be shielded from visible light.

Therefore, pupil alignment, which is the adjustment of the direction and position of the pupil to prevent the film surface 3 from harmful reflected light from the pupil and to ensure that the objective lens is at a predetermined distance from the pupil, is also invisible. It must be done using light. In the embodiment of FIG. 1, pupil alignment is performed using infrared light.

Reference numeral 33 denotes a light source for pupil positioning, which is arranged so as to face the pupil of the eyeball E with an infrared transmitting visible light reflecting filter 34 in between.

Reversing mirrors 35 and 36 are placed in the optical path between the objective lens and the aperture 4 and between the relay lens 2 and the film surface 3 to bypass the relay lens 2 during pupil alignment operations. Open a light path.

37 is an objective auxiliary lens, 38 is a field lens, 39
is a transparent chart on which a line diagram as shown in FIG.

Mirrors 42 and 43 bend the optical path for pupil alignment.

40 and 41 are relay lenses, which are shown in chart 39 above.
The pupil image formed above is re-imaged onto a symmetrical plane F3 with respect to the reversing mirror 28 disposed in the optical path of the film plane 3.

Light from the pupil of the eyeball E passes through the objective lens, is reflected by a reversing mirror 35 disposed in the optical path of the photographing system, is directed to an auxiliary objective lens 37, and is imaged on a chart 39. The light from this image is reflected by the mirror 42, passes through the relay lenses 40, 41, is reflected by the mirror 43, and the reversing mirrors 36, 28 arranged in the optical path of the imaging system, and is focused on the symmetry plane F3. Image. This image is re-formed on the light receiving surface of the image pickup tube 31 by the relay lens 30, so that the image of the pupil is displayed on the monitor television 32. In the embodiment in which the film plane 3 is moved to focus on the fundus, the plane of symmetry F3 also moves, but the relay lens 41 moves along the optical axis in correlation with this movement, so that the pupil image is always maintained. is imaged on the plane of symmetry F3. Therefore, the pupil image displayed on the monitor television 32 is always in focus. Chart 39 displayed on monitor TV 32
The pupil position alignment can be performed by observing the pupil image and changing the relative position of the camera eyeball E with respect to the pupil in consideration of the position of the pupil image with respect to the diagram of the chart 39. 1st
In order to photograph the fundus of a subject with the fundus camera of the embodiment shown in the figure, first, the reversing mirrors 35, 36, and 28 are placed in the optical path of the photographing system, the light source for pupil positioning is turned on, and the monitor The pupil position is adjusted while observing the pupil image displayed at 32, and then the reversing mirrors 35 and 36 are removed from the optical path, and the partially reflecting transparent plate 13 and the reversing mirror 20 are moved to the first
As shown by the solid line in the figure, it is placed in the optical path of the illumination system to illuminate the fundus with infrared rays over a wide area, and also projects a focus index, and then observes the fundus image and focus index image on a monitor TV to determine the field of view and adjust the focus. Then, the reversing mirrors 20 and 28 and the partially reflective transparent plate 13 are removed from the optical path, and the strobe light source 21 emits light to expose the fundus image on the photographic film placed on the film surface 3. Although not shown in FIG. 1, lighting of each light source, reversal of each mirror, etc. are performed according to a predetermined interlocking relationship by mechanical or electrical means. As is clear from the above, according to the fundus camera of the present invention, focus adjustment can be performed while observing the focus index image, making it accurate and easy. separated to the east;
In other words, spatial separation is used instead of temporal separation as known in U.S. Pat. No. 3,614,214, and the focus index and its image have the same shape without lateral deviation only when focusing, making focus adjustment easy, and fundus photography. Since it is possible to adjust the focus while observing the range and confirming the presence or absence of ghost fear, there is no chance of failure in taking pictures, which is of great benefit in medical fields such as fundus examinations.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of one embodiment of the present invention, and Figures 2 A to 1 are illustrations of the first embodiment.
Figure 3 is a perspective view of a part of the optical system in Figure 1. Figures 4 A to C are the fundus image and focus index image displayed on the monitor TV. This is an example. In the figure, 1 is an objective lens, 2 is a relay lens, 3 is a film surface, 5 is a focus index light source, 9 is a split image prism, 10 is a focus index, 14 is a relay lens, 15
16 is a perforated mirror, 16 is a light source for fundus illumination, 21 is a strobe light source, 28 is an inverted mirror, 31 is an image pickup tube, and 32 is a monitor television. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. An illumination system that illuminates the fundus of the examinee's eye, a first imaging optical system whose focus is adjustable for forming a fundus image of the examinee's eye at a predetermined position, and an optical system that illuminates the fundus of the examinee's eye at a predetermined position. A fundus camera having an observation system for observing an ocular fundus image includes a second imaging optical system whose focus is adjustable for forming a predetermined index and the index image on the fundus of the subject's eye, and a second imaging optical system that is substantially conjugate with the fundus of the subject's eye. a light beam separating means is provided for separating the light beam from the index into a plurality of light beams, and when the focus of the first imaging optical system is not adjusted, the index image becomes separated on the fundus of the eye and is brought into focus. A fundus camera, characterized in that the fundus camera comprises means for interlocking at least a portion of the first and second imaging optical systems so that the index image is not separated on the fundus when the eye is in the fundus.