JPS61293424A - Optical apparatus for projecting cornea image - 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 Application Field] The present invention is used for a placido image photographing device used in ophthalmology to measure corneal radius of curvature, corneal shape, etc., or to analyze corneal shape. The present invention relates to a corneal image projection optical device for forming an image.

[Prior Art] Two types of placido image projection optical systems, which project concentric placido images produced by a light source onto the cornea for corneal measurements, are conventionally known: dish-shaped and cylindrical. Among these, the dish type allows a large working distance, so even if there is some error in working distance alignment, it will hardly affect the size of the image, so it is suitable for obtaining high accuracy and analytical photographs. ,
On the other hand, it has the disadvantage that the device must be made larger.

In addition, although the latter cylindrical type can be made smaller, the accuracy is lower due to the short distance between the multiple ring-shaped diffuse reflection surfaces arranged in parallel between the strobe light source and the eye to be examined and the cornea, that is, the working distance. It has the disadvantage that it is unsuitable for obtaining photographs for analysis.

[Object of the invention] The object of the present invention is to improve the drawbacks of the conventional and conventional examples,
It is an object of the present invention to provide a corneal image projection optical device that has high accuracy, can be made compact, and can obtain a large Placido image at a small angle of incidence.

[Summary of the Invention] The gist of the present invention for achieving the above object is to provide a light source;
The apparatus has a ring-shaped optical reflection surface installed around the optical axis of the optical system of the apparatus, and the cornea of the eye to be examined is illuminated by the ring-shaped light beam of the light source reflected by the optical reflection surface. This is a corneal image projection optical device characterized by the following.

[Embodiments of the invention] The present invention will be explained in detail based on illustrated embodiments.

FIG. 1° shows a first embodiment of the present invention, in which light emitted from a point light source l such as an incandescent lamp having a small filament is split into a light beam disposed obliquely on the optical axis 0 of the optical system of the device. It is reflected by the member 2 in the direction of the eye E to be examined, and further reflected by the ring-shaped optical reflection surface 3 provided around the optical axis 0 to form a ring-shaped image. Each optical member is arranged so as to illuminate Ec.

The ring-shaped image P formed by the reflecting surface 3 of the point light source l is the cornea Ec
The point light source 1 is formed in a large area in the opposite direction of the reflected light rays directed toward the point light source 1 and at a distance from the reflecting surface 3 to the point light source 1. The ring-shaped Placido image formed on the cornea Ec is received by the lens system 4 on the optical axis 0 and guided to the measuring and photographing device 5, where it is used for measuring the angle 11Ec, photographing, etc.

FIG. 2 shows a second embodiment, in which the light emitted from a ring-shaped light source 6, such as a circular fluorescent lamp, is arranged with the optical axis 0 as the center. The light is reflected by three ring-shaped optical reflection surfaces 3a, 3b, and 3C to form three Placido images Pa, Pb, and Pc, which concentrically illuminate the cornea Ec. A ring-shaped light source image of Ig is guided to a measuring and photographing device 5 through a lens system 4.

The reflecting surfaces 3a, 3b, and 3c have different illumination angles to obtain information on different parts of the cornea Ec. Among these, one reflective surface 3c is located at the closest position to the eye E and can irradiate the cornea Ec with a light beam at a large angle, but the light source image formed by this optical reflective surface 3C is relatively Since the distance is long, changes in the size of the resolved ring-shaped image Pc due to errors in adjusting the working distance are relatively small, resulting in good accuracy. Moreover, since the reflecting surface 3c is not large, this is even more convenient.

FIG. 3 shows a third embodiment, in which a ring-shaped light source 7 is provided with a ring-shaped diaphragm 8 having a slit, and this ring-shaped diaphragm 8 serves as a substantial light source. Further, the ring-shaped optical reflection surface 3d provided around the optical axis 0 has a curvature in the cross-sectional direction, and the ring-shaped aperture 8 is the focal point of this reflection surface 3d, and the reflected light flux to the cornea Ec is become parallel. Therefore, since the ring-shaped light beam onto the cornea Ec is projected from an infinite distance, the size of the brachid image is constant regardless of the working distance, and high accuracy can be obtained.

[Effects of the Invention] As explained above, the corneal image projection optical device according to the present invention can obtain a large image at a small angle of incidence, and can resolve a ring-shaped image, that is, a Placido image, even if there is some error in adjusting the working distance. Since it has almost no effect on the size, it has the advantage of being excellent in accuracy, being able to obtain high-quality images for analysis, and being able to miniaturize the apparatus.

[Brief explanation of the drawing]

The drawings show an embodiment of the corneal image projection optical device according to the present invention, and FIGS.
FIG. 6 is an optical layout diagram of second and third embodiments. 1 is a point light source, 2 is a light splitting member, 3 is an optical reflection surface, 4 is an apparatus optical system, 5 is a measuring and photographing device, 6.7 is a ring-shaped light source, and 8 is a ring-shaped diaphragm. Patent applicant Canon Co., Ltd. Figure 1

Claims (1)

[Claims] 1. It has a light source and a ring-shaped optical reflection surface installed around the optical axis of the device optical system, and the ring-shaped light beam of the light source reflected by the optical reflection surface A corneal image projection optical device characterized in that the cornea of an eye to be examined is illuminated. 2. The corneal image projection optical device according to claim 1, wherein the light source is a point light source. 3. Claim 1 in which the light source is a ring-shaped light source
The corneal image projection optical device described in 2. 4. The corneal image projection optical device according to claim 3, wherein the ring-shaped light source is provided with a ring-shaped slit. 5. The corneal image according to claim 4, wherein the ring-shaped optical reflection surface has a curvature, and the light beam emitted through the ring-shaped slit illuminates the cornea as a ring-shaped parallel light beam. Projection optical device.