JPS6139050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focusing device for a fundus camera.

In general, a fundus camera includes a fundus illumination system, a photographing optical system, and a finder system for determining and focusing a photographic field of view. Conventional fundus cameras use a transparent plate with a target line, such as a crosshair, on the focusing surface, and by aligning the aerial image formed by the imaging optical system with this target line, the state of focus can be determined. However, when using this method, the examiner's diopter may shift during focusing, so it requires considerable skill to accurately focus, and it is a burden on the examiner. There is also the problem that it also gets larger.

As a means to overcome these drawbacks, it has already been proposed to provide an index projection system using, for example, an angle prism in the optical path of the illumination system, and to perform focusing based on the state of the index projected onto the fundus. . According to this method, focusing itself is easy, but a complicated mechanism using a cam etc. is required to link the photographing optical system and the index projection system and maintain a conjugate relationship in relation to each other. . moreover,
When a lens for an illumination system is used in common as a relay lens for target projection, there is a problem in that the illumination conditions change depending on the focusing operation. Furthermore, when an index projection system is provided in the optical path of the illumination system, there is also the inconvenience that only one part of each part of the fundus can be focused.

The present invention solves the above-mentioned problems with conventional fundus cameras and provides a focusing device for a fundus camera that has a simple structure and can easily perform focusing.

That is, the present invention provides a fundus camera having a photographing optical system and an illumination optical system, in which an objective lens is positioned behind a perforated mirror installed diagonally in the photographing optical path to reflect the illumination light beam toward the fundus. An optical path dividing means such as an oblique reflecting mirror is provided near a position conjugate with the pupil of the target, and an index projection system is arranged along the divided optical path divided by the optical path dividing means.

In the present invention, since the index projection system is provided not in the illumination optical system but along the divided optical path divided by the optical path dividing means from the optical path of the photographing optical system, the operation for focusing affects the illumination conditions. Moreover, the target projection system and the focusing section of the photographing optical system can be linked together very easily. For example, by making the optical path of the index projection system parallel to the optical path of the photographing optical system using an oblique reflecting mirror, etc., and placing the index at a position conjugate with the imaging film surface of the photographing optical system, the relay lens of the index projection system and the index It is possible to perform focusing by moving the focusing unit of the photographing optical system by the same distance in the same direction. Furthermore, the present invention uses infrared light to perform projection from the index projection system.
The effect is particularly remarkable when used in so-called non-mydriatic fundus cameras, which have come to focus without using mydriatic drugs or the like. In other words, focusing using infrared light is performed by observing the reflected image of the fundus through a visible image converting means such as a night vision tube. , it is difficult to judge the focus state. However, when using the focusing device of the present invention, it is possible to determine the focus very easily based on the image formation state of the index projected on the fundus, and the mechanism for this is also very simple compared to conventional ones. It gets easier.

The embodiments of the present invention will now be described with reference to the drawings.
First, in FIG. 1, the photographing optical system includes an objective lens 1 disposed with respect to the eye E to be examined;
In contrast, it consists of an aperture 2, a focusing lens 3, an imaging lens 4, and a film 5, which are placed near a position conjugate to the pupil E _P of the subject's eye. It is an optical system. A finder optical system is formed by an oblique reflecting mirror 22 provided in front of the film 5, a field lens 23 provided on the reflection optical path of the reflecting mirror 22, a reflecting mirror 24, and an eyepiece 25.

The illumination optical system includes a diagonal perforated mirror 6 inserted into the optical path of the photographing optical system in front of the diaphragm 2, a relay lens 7 provided in the reflection optical path of the perforated mirror 6, a condensing lens 9, and a ring-shaped mirror. Slits 10,
A flash tube 11 that serves as a light source for photography, and a heat shield filter 1
2. Consists of a condensing lens 13 and a light source 14 for ordinary illumination, and the illumination light from the light source 14 is transmitted through a perforated mirror 6.
The light hits the reflective surface of the eye in a ring shape and is reflected, and passes through the objective lens 1 to illuminate the fundus E _R .

The index projection system that facilitates focusing for photographing the fundus includes an oblique reflector 15 and a reflector 1 provided in the optical path of the photographing optical system behind the diaphragm 2.
6. Relay lens 17, slit-like index 18, deflection prism 1 disposed in close contact with index 18
9, consisting of a condensing lens 20 and a light source 21. The light from the light source 21 passes through the condensing lens 20 and illuminates the slit-shaped index 18, and the slit-shaped index is closely fitted with a deflection prism 19 that divides the slit into two and directs the light in different directions. Because of this arrangement, the light passing through the upper half of the slit and the light passing through the lower half become light fluxes that are symmetrical with respect to the optical axis and directed in opposite directions. The light transmitted through the slit passes through the relay lens 17, the reflecting mirrors 16 and 15, the diaphragm 2, and the hole in the perforated mirror 6, and once forms an image with respect to the lenses 3 and 4 at a position F that is conjugate with the film 5. The light enters the eye E through the lens 1.

The light transmitted through the slit that enters the eye E is focused on the fundus E _R in the same formation as the slit index 18 (Fig. 3a), and when it is out of focus, the light passes through the slit in the upper and lower halves of the slit. The image becomes a separated image (Fig. 3 b, c).

A reflecting mirror 15 is arranged in the optical path of the photographing optical system in order to reflect the slit-transmitted light projected symmetrically with respect to the optical axis bisected by the deflection prism 19 toward the objective lens 1 as described above. As shown in FIG. 2, it consists of two reflecting parts 15a and 15b arranged symmetrically on both sides of the optical axis. Therefore, the reflecting mirror 15 does not interfere with the effective light beam of the photographing system that is reflected by the fundus E _R and directed toward the film 5 . The aperture 2 also has a central aperture hole 2a for the photographic light beam and aperture holes 2b and 2c for the slit-transmitted light beam on both sides, in order to pass the photographing light beam along the optical axis of the photographic optical system and the slit-transmitted light beam. have
Further, the perforated mirror 6 also has a hole with projecting portions on both sides so that light transmitted through the slit can pass therethrough.

In order to increase the contrast of the slit index image projected onto the fundus _ER , it is desirable to block background illumination in the projection area. For this purpose, in this example, a light shielding plate 8 of a size that can cover the index image is provided in the illumination system at a position conjugate with the fundus E _P so as to be freely removable.

In the optical system shown in FIGS. 1 and 2,
a focusing lens 3 and a relay lens 17 of the index projection system;
Focusing is performed by moving the slit index 18, deflection prism 19, condensing lens 20, and light source 21 together in the optical axis direction, and the focus on the film 5 is determined by the state of the slit index image formed on the fundus E _R. You can know the status.

As described above, in the present invention, in a fundus camera having a photographing optical system and a fundus illumination system, an optical path splitting means is provided behind the perforated mirror provided in the optical path of the photographing optical system for introducing the illumination light flux. Since the index projection system is provided in this divided optical path, the operation for focusing does not affect the illumination conditions, and the coordination between the index projection system and the focusing section of the photographing optical system is improved. A very simple design is possible. Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the optical system as shown in the drawings, but is applicable to focusing of a fundus camera provided with an index projection system independent of the fundus illumination system. This includes all equipment.
Note that when the present invention is applied to a focusing device using infrared light, an infrared transmitting filter is inserted in front of the target projection light source 21, and the infrared transmitting filter is used in place of the heat shielding filter 12 of the fundus illumination system. The image of the finder system can be received by a night vision tube. In the present invention, it is also possible to easily change the relative positional relationship between the target projection system and the focusing section of the photographing optical system, and by changing this relative positional relationship, the target image is deviated from the target imaging position on the fundus. It also becomes possible to focus the imaging optical system on the body part.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of an optical system of a fundus camera showing an embodiment of the present invention, FIG. 2 is a plan view of its index projection system, and FIG. 3 is a diagram showing a projected slit image. 1... Objective lens, 2... Aperture, 3... Focusing lens, 4... Imaging lens, 5... Film, 6...
...Perforated mirror, 14...Light source for illumination, 15,1
6...Reflector, 18...Slit index, 19...
Deflection prism, 21... light source.

Claims (1)

[Scope of Claims] 1. A fundus camera comprising a photographing optical system and a fundus illumination system that illuminates the fundus through a perforated mirror installed obliquely in the optical path of the photographing optical system, in which an optical path dividing means is provided behind the perforated mirror. and an index projection system for freely projecting an index image onto the eye to be examined along the divided optical paths divided by the optical path splitting means. A focusing device for fundus cameras that allows you to know the focus state of the photographic optical system. 2 In the above item 1, the photographing optical system consists of an objective lens, a focusing lens and an imaging lens arranged behind the perforated mirror, and the optical path splitting means is arranged between the perforated mirror and the focusing lens. A focusing device for a fundus camera placed at a position approximately conjugate to the pupil of the eye. 3 In the above item 1, the index projection system is provided with an oblique mirror and a relay lens for directing its optical path parallel to the optical path of the projection optical system, and the index is arranged at a position conjugate with the imaging film surface. Focusing device for fundus camera. 4. In item 3 above, the indicator is combined with a deflection prism so that at least two divided parts of the indicator are oriented in opposite directions with respect to the optical axis, and the optical path splitter is configured to: A focusing device for a fundus camera configured as an oblique mirror having at least two reflecting portions that are offset in the polarization direction of a polarization prism and spaced apart from each other with respect to the optical axis of a photographing optical system. 5. The focusing device for a fundus camera according to item 1 above, wherein the fundus illumination system is provided with a light-shielding plate that can be freely inserted and removed to block light from a portion corresponding to the target projection area by the target projection system. 6. A focusing device for a fundus camera according to item 1 above, wherein the target projection system projects the target using infrared light.