JPS5912291B2 - Fundus camera with built-in focusing chart - Google Patents

Description

[Detailed Description of the Invention] A fundus camera generally consists of an illumination system for the fundus, a photographing system, and a monitor system derived from the middle of the photographing system for focusing and determining the field of view. However, because it is difficult to obtain sufficient brightness for the image on a monitor system, it is not possible to use a focusing glass such as a diffuser plate for focusing, and instead a transparent plate with crosshairs etc. is used. Usually, a means is used to match the aerial image taken by the photographing system with this image.

However, focusing using such means requires considerable skill and is inefficient.

In addition, in devices that use invisible light such as infrared rays for illumination during observation such as focusing, and use an image pickup tube such as an infrared vidicon for the monitor system, the monitor system is monochromatic rather than multicolored, so the hue contrast in the fundus is utilized. This makes it even more difficult to focus on the dark fundus itself as a target.

The present invention is an attempt to eliminate such inconveniences in conventional fundus cameras, by inserting a special chart into the illumination system during observation at a position conjugate with the final imaging film plane of the imaging system. is projected onto the fundus of the eye, and this chart is moved relative to the fundus in conjunction with the focus adjustment of the imaging system.During this adjustment, the success or failure of focus is determined based on the specificity of how the chart image appears on the fundus. It is designed to be judged.

To explain this regarding the figures, 1 in Figure 1 is the subject's eye, 2
is an objective lens, 3 is a perforated oblique mirror with a small hole in the center, and 4 is an oblique mirror with a small hole in the center.
5 is a relay lens, and 5 is a photographic film surface, which together constitute a photographing system.

6 is a light source for illumination during observation, 7 is a condenser lens, 8
numeral 9 is a ring slit, and numeral 10.11 is a relay lens. These and the oblique mirror 3 to the eye 1 constitute an observation illumination system.

Reference numeral 12 denotes a flash light source for illumination during photographing, and numeral 13 denotes a condenser lens. These and the illumination system after the ring slit 9 constitute an illumination system for photographing.

14 is an oblique mirror for guiding the monitor optical path, which is rotatable in the optical path of the photographing system by the front force of the film surface 5; 15 is an eyepiece;
Reference numeral 16 denotes the observer's eyes, and these and a photographing system in front of the oblique mirror 14 constitute a monitor system.

The above is the same as in a general fundus camera, and the outline of its operation is that the light emitted from the observation light source 6 passes through the condenser lens 7 and the oblique mirror 8, and is once focused on the ring slit 9, then the relay The image of the ring slit 9 is formed near the perforated oblique mirror 3 by the lens 10.11, and the image is further reflected by the lens 10, 11, passes through the objective lens 2, the crystalline lens 1' of the eye 1, and other lens-acting parts to the fundus 1''. Illumination over a wide area.

The reflected light from the illuminated fundus travels backward along the incident optical path to form an image of the fundus on the front side of the perforated oblique mirror 3, and is then re-imaged on the film surface 5 by the relay lens 4. During observation, the monitor oblique mirror 14 is placed in the optical path and produces a fundus image at a position conjugate with the film surface 5, which is observed by the eye 16 via the eyepiece 15.

In this case, the fundus image often deviates from the film plane due to differences in the refractive power of the eyes themselves, so it is necessary to adjust the focus.

For focus adjustment, the relay lens 4 may be moved back and forth, but the film surface 5 and the monitor system after the oblique mirror 14 may be moved back and forth as a unit, as shown by the chain line A.

When preparations for photographing are thus completed, the monitor oblique mirror 14 and the illumination system oblique mirror 8 are retracted as shown by chain lines (if they are semi-transparent mirrors, they remain as they are), and the flash light source 12 for illumination during photographing is emitted to take a photograph.

In the fundus camera as described above, the present invention inserts a special chart 17 as described later in the optical path of the illumination system at a position conjugate with the film surface 5 of the imaging system, and projects this onto the fundus 1'' by the illumination system. When adjusting the focus, this chart is moved while maintaining a conjugate relationship with the film plane, so that the success or failure of focus can be determined by how the chart image appears on the fundus.

An example of the structure of the chart 17 is as shown in FIGS. 2 and 3, in which a main mark line 17o made of an opaque line such as a thin metal wire is provided in a short cylindrical frame 18, orthogonal to the optical axis of the illumination system. Attach the auxiliary marks 171.17□ with approximately the same thickness as the main mark line in the front and rear planes that include this main mark line and are parallel to the plane perpendicular to the optical axis. The frame bodies 18 are arranged so that they do not overlap with each other or with the main mark line when viewed from the direction.
, and the spacing l'1. of the 3,000-line plane including these three types of gauge lines. l'2 means that when the specifications of the imaging system including the eye to be examined are in the standard state, if the correct position of the in-focus film surface 5 is the solid line position, this film surface is moved forward or backward. Position 51 where blur begins to be recognized
, 5□, respectively, are optically equal to or slightly larger than the distances corresponding to distances 11 and 12.

This distance l'1. In other words, l'2 corresponds to a distance slightly outside the distance corresponding to the depth of focus in this system.

Note that the distance l'1.corresponding to the distance 11.12. l'2 correspond to each other in an optical conjugate relationship.

The front and rear auxiliary marks 171°17□ are the main marks 1 as in the above example.
Not limited to those provided at different levels across 7o, Fig. 5,
As shown in FIG. 6, both auxiliary marked lines 171.
17□ may form a straight line.

Furthermore, the marking lines do not necessarily have to be parallel, and it is sufficient that they do not overlap as a whole when viewed from the optical axis direction, and in extreme cases, they may even intersect with each other.

The chart 17 is also made by bonding two transparent glass plates 191.19□ together as shown in FIG. The front and rear auxiliary marks 1 are provided on the front and rear outer surfaces.
70, 17□ may also be provided by similar means.

FIG. 8 shows the same arrangement of marked lines as the example in FIG. 2, and FIG. 9 shows the same arrangement as in the example in FIG.

In this case, the thicknesses 1 and 1t2 of both glass plates are the optical thicknesses l'1 and 1t2 above, considering their refractive index. Let it be determined so that l'2.

An example of the linkage between the chart 17 and the focus adjustment mechanism of the photographing system is the slider 2 that moves along the optical axis of the illumination system on the aircraft body 20.
1 holds the chart 17, and this slider is connected to the lever 23 on the setting shaft 22 and the bell crank 25 on the setting shaft 24.
are successively connected to the focus adjustment mechanism A through a long hole 26, pin 27, etc., and by appropriately determining the length of each arm of the lever 23 and bell crank 25, the conjugate relationship between the chart 17 and the film surface 5 is established. Let's keep this and move this.

In the fundus camera of the present invention as described above, when the fundus 1'' is illuminated by the light source 6 for observation, three types of gauge lines 17...171 on the chart 17,
17□ is projected as a shadow image on the fundus of the eye.

When the projected image is in focus, the main mark line image 28° appears most clearly as shown in Figure 10■ or 11■, and the images of the front and rear auxiliary mark lines 281°2B□ appear most clearly. Appears slightly blurred to approximately the same extent.

In addition, in the case of the front bin, as shown in Figure 1, the front auxiliary mark line image 281 is the clearest, the main mark line image 28o is moderately blurred, the rear auxiliary mark line image 28□ is largely blurred, and the rear In the case of a pin, the image 282 of the rear auxiliary mark line appears as the clearest, the image 2B of the main mark line appears as a medium blur, and the image 2B of the front auxiliary mark line appears as a large blur, as shown in (3) in the same figure.

The principal mark line 17o of the chart 17 is located at a conjugate position with the film surface 5, and a similar chart image is also located in the optical path of the monitor system when the oblique mirror 14 enters the optical path. appears, it can be observed on the monitor, and by adjusting the focus adjustment mechanism and the position of the moving chart 17 so that the chart image appears to be in focus, the desired number 2'/1 can be adjusted.

This focusing eliminates the trouble of aligning the aerial image with the crosshairs as in the conventional method, and the contrast of this CH-1 image is much higher than when looking only at the fundus due to simple illumination. It is easy to tell from the above, and it is easy to judge whether the focus is correct or not by looking at the difference in the force that appears on the marked line of 3 (Φ).

Particularly, in the case of the charts shown in FIGS. 5 and 9, the images of the front and rear auxiliary marked lines are brought into contact with each other at their respective ends, making comparison easy.

Although the chart image on the fundus of the eye is effective for focusing, it also poses an inconvenience in that it obstructs the overall observation or photographing of the fundus of the eye.

To deal with this, it is preferable to move the chart out of the illumination optical path manually or automatically in conjunction with the photographing operation as necessary.

One example of this means is as shown in FIGS. 12 and 13, in which an electromagnetic mechanism 29 such as a rotating solenoid having a rotating shaft is connected to the slider 2.
The chart 17 is held by the shaft 30, and the chart is evacuated by operating this electromagnetic mechanism.

In the above explanation, in the case of focus adjustment regarding the chart and film surface, we have described the method in which these are moved relative to the subject's eye, but for focus adjustment, the film surface 5 remains fixed as shown in FIG. 14, and the relay lens 4 The interlocking mechanism 31 is provided with a focus adjustment mechanism for each of the chart 17 and the chart 17, and the interlocking mechanism 31 is used to adjust the focus of the chart 17 and the film surface 5 on the fundus without destroying the conjugate relationship between the chart 17 and the film surface 5.
The same purpose can also be achieved by providing a.

In this case, the movement relationship between the lens 4 and the chart 17 is such that when the lens 4 approaches the eye 1 to be examined, the chart 17 moves away from it, and the amount of movement generally does not have a linear proportional relationship.

Therefore, both movement mechanisms 31 must also include a mechanism for performing low-volume conversion of the cam to maintain a conjugate relationship between the chart and the film surface.

Note that it is convenient to configure the relay lens 4 with a zoom lens, since the size of the photographed image can also be changed.

In Figure 15, infrared light is used for illumination during observation, and an image pickup tube such as an infrared vidicon tube is used for the monitor system to form an infrared image of the fundus on its light receiving surface, which is then converted into a visible image. This shows an example of a fundus camera for displaying, in which 32 is a filter that excludes visible light from the observation light source 6 and allows only infrared light, and 33 is a light-receiving surface 34 at a conjugate position with the film surface 5.
35 is a visible image display device connected to the image pickup tube, and other parts and functions are the same as those in the example shown in FIG.

Unlike direct observation using only visible light, the observation power method that uses infrared light cannot utilize the hue contrast in the fundus, making it more difficult to focus only on the dark fundus. However, if the marked line image is used as the target for focusing as in the present invention, there is an effect that focusing can be performed easily, quickly and accurately.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of essential parts showing one embodiment of the fundus camera of the present invention, FIG. 2 is a perspective view showing an example of a chart, and FIG. 3 is a front view of the same. II and I are cross-sectional front views at each marked line in Figure 1, respectively, and Figure 5 is another one of the charts.
A slope view showing an example, Figure 6 is a front view of the same as above, Figures 7 I and II
, I are cross-sectional front views of each marked line in FIG. 5, FIGS. 8 and 9 are slope views of further charts, and FIG. II and I are respectively the example in Figure 2,
Fig. 8 is a diagram showing how the front focus, correct focus, and rear focus appear in the projected image of the chart in the example, Fig. 11 1・■,
(2) is the same diagram as above for the chart in the example of Figure 5 and Figure 9, respectively; Figure 12 is a side view showing one example of the chart retraction device; Figure 13 is a front view of the same as above; Figure 14 is the fundus camera of the present invention. FIG. 15 is a layout diagram of the main parts showing another embodiment of the fundus camera of the present invention, which uses infrared light during observation.
FIG. 2 is a layout diagram of main parts showing an example. 1: Eye to be examined, 2: Objective lens, 3: Perforated oblique mirror, 4: Relay lens, 5: Film surface, 6: Observation illumination light source, 7
: Condenser lens, 8: Oblique mirror, 9 Nilinger lens, 10, 11: Relay lens, 12: Flash light L1
3: Condenser lens, 14: Oblique mirror, 15: Eyepiece, 17: Chart, 17o: Main mark line, 171: Front auxiliary mark line, 17□: Rear auxiliary mark line, 18: Frame, 191,
192 glass plate, 20: fuselage, 21: slider, 22:
Setting axis, 23 Nlever, 24: Setting axis, 25: Bell crank, 28o=28□, 28□: Image of marked line, 29: Electromagnetic mechanism, 30: Rotation axis, 31: Interlocking mechanism.

Claims (1)

[Scope of Claims] 1. In a fundus camera in which a fundus illumination system that shares a part of the optical path of the imaging system with respect to the fundus is introduced from the middle of the optical path of the imaging system, and a monitor system for imaging is derived from the middle of the imaging system optical path, the imaging system optical path A chart with a main index is inserted at a position conjugate to the photographing film plane, which is the final image forming plane of the photographing system, in the optical path that merges with the camera. The distance l'1. which is optically equal to or slightly smaller than the distance corresponding to distances 11 and 12 from which the film is moved forward and backward from the correct focus position to the position where blurring begins to be observed. Front and rear auxiliary indicators are provided in the plane forward and backward from the main indicator by l'2 so that they do not overlap each other or the main indicator when inspected in the optical axis direction, and the illumination system is used to illuminate the front and rear auxiliary indicators. The chart is projected onto the fundus of the eye, and the blurring of the image of each index appears in stages depending on whether the focus is correct or not. This is used to determine whether the focus is correct or not, and the focus adjustment mechanism of this chart and the focus adjustment of the imaging system are used. A fundus camera with a built-in focusing mechanism, which is linked to the mechanism so that adjustment can be made while maintaining the conjugate relationship between the film surface and the chart. 2. In the fundus camera described in claim 1, the chart is disposed in the fundus illumination system, and the chart is comprised of opaque lines extending perpendicularly to the optical axis within a short cylindrical frame. A main mark line is provided, and in the front and rear planes that include the main mark line and are parallel to the plane orthogonal to the optical axis, auxiliary mark lines of approximately the same thickness as the main mark line are placed within the above frame. Focusing chart 1 that uses something installed inside the body
・Built-in fundus camera. 3. In the fundus camera according to claim 1, the chart placed in the illumination system is moved out of the optical path manually as necessary or automatically in conjunction with the operation during photographing. Fundus camera with built-in focusing chart. 4. In the fundus camera described in claim 1, the chart is arranged in the fundus illumination system, and the chart is made by laminating two transparent plates and placing one of the laminated surfaces on one side. A fundus camera with a built-in chart for human alignment, which uses a main mark line and auxiliary mark lines each having a thickness approximately equal to the main mark line on the front and rear outer surfaces.