JPS6148336A - Apparatus for measuring shape of cornea - 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 provides a light receiving means for measuring the corneal shape of an eyeball.
The present invention relates to a corneal shape measuring device using a plurality of one-dimensional light receiving elements.

[Prior art] Conventionally, the shape of the cornea has been measured by projecting a Mayer optotype onto the cornea and measuring the reflected image to calculate the shape of the cornea. For example, a common method is to determine the position and spacing of optotype images on a -dimensional COD (charge coupled device).

Of course, in order to precisely calculate the shape of the cornea, it is necessary to measure as many positions as possible, so it is necessary to use a large number of one-dimensional CODs as light receiving means, but this requires Considering the above problem and cost, there is a certain limit.

[Object of the Invention] An object of the present invention is to improve the measurement accuracy of the stomach angle j1 and the shape i11! by making it possible to measure the positions of many optotype images using a limited number of light receiving elements. An object of the present invention is to provide a device 4 for determining the quality of data.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to provide a light receiving means consisting of a plurality of one-dimensional light receiving elements, and a corner-reflected image of a target projected toward the cornea of the eye to be examined. The corneal shape measuring device is characterized in that it has a projection means for projecting onto the light receiving means, and the projection means forms corneal reflection images that are in an inverted or rotational positional relationship with respect to each other.

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

FIG. 1 shows a first embodiment of the corneal shape measuring device according to the present invention, where E is the subject's eye undergoing examination, and Ec
indicates the cornea.

On the optical axis ○, in order from the eye E side to be examined, there is a ring-shaped light source l, an objective lens 2, and a first hole listening lens 3 having an aperture 3a.
, a second perforated lens 4 having an opening 4a, a projection lens 5, and five one-dimensional CCDs 6a to 6e are arranged, and the -dimensional CCDs 6a to 6e are aligned with the optical axis O, as illustrated in FIG. They are arranged radially at equal angles around the center.

In FIG. 1, the light emitted from the ring-shaped light rA1 is reflected at each corner Ec of the eye E to be examined, forming a ring-shaped reflected image M. The light from this reflected image M is once focused on a point P by the objective lens 2 and the lens section of the first aperture lens 3, and then further focused on the point P by the lens section of the second aperture lens 4 and the projection lens 5. As shown in FIG. 2, reflected images M1 are formed on five one-dimensional CCDs 6a to 6e.

Also, of the light flux from the reflected image M, the portion that passes through the objective lens 2 and the aperture 3a of the first aperture lens 3 becomes an afocal light flux, and the part that passes through the aperture 3a of the second aperture lens 4 and the projection lens 5 to form a reflected image M2 on -dimensional CCDs 6a to 6e.

Here, the two reflected images old and M2 are the odd number of CCDs 5a~
Since the vertical and horizontal directions are reversed on CCD 6e and the projection magnification is different, measurements are performed in 10 directions on CCD 6a to 6e, and from the coordinates and magnification on CCD 6a to 6e, the corneal Ec The shape of can be calculated.

FIG. 3 shows a second embodiment of the present invention, in which from the side of the eye E to be examined, the link-shaped light source l, the objective lens 7, and the two as shown in FIG.
Aperture stop 8. having apertures 8a, 8b. A trapezoidal prism 9, a first half-moon lens 10, and a second half-moon lens 11 are arranged in an arrangement δ.

The trapezoidal prism 9 and the second half-moon lens 11 are the objective lens 7.
The first half-moon lens 10 is provided on one side of the optical axis O at the position of the light beam passing through the aperture 8b of the aperture stop 8, and the first half-moon lens 10 is provided at the position of the light flux passing through the aperture 8a of the aperture stop 8 on the opposite side.

In this case, the light emitted from the reflected image M of the ring-shaped light source l on the cornea Ec is made into an afocal light beam by the objective lens 7, and the light passing through the aperture 8a of the aperture diaphragm 8 is
A projected image is formed on the CCDs 6a to 6e by the half-moon lens 10, and the light passing through the other aperture 8b is transmitted to the trapezoidal prism 9.
After inverting the reflected image M, a second half-moon lens 11 forms a projected image on the CCDs 6a to 6e.

In this way, similarly to the first embodiment, five one-dimensional C
Measurements can be performed in 10 directions on the CDs 6a to 6e, and the shape of the cornea can be determined from the coordinates and magnification on the CCDs 6a to 6e.

FIG. 5 shows a third embodiment of the present invention, in which the aperture stop 8 in the second embodiment described above has two apertures 8a,
8b, whereas here the aperture stop 8 has only one aperture 8C and is moved perpendicularly to the optical axis O as shown by the arrow to change the aperture 8C to 8c''.
It is said to be a movable type that can change its position, and there is also a second
One projection lens 12 is used instead of the first and second half-moon lenses 10.11 in the embodiment.

In the case of this embodiment, the angle DA E C of the ring-shaped light source 1
The light flux emitted from the reflected image M at is turned into an afocal light flux by the objective lens 7. Then, the light passes through the aperture 8c of the aperture stop 8 and forms a projected image M3 on the one-dimensional CCDs 6a to 6e by the projection lens 12 as shown in FIG. Also, the position of the aperture 8c of the aperture stop 8 is 8 in FIG.
When moving to the position c', the light passing through the aperture 8c' passes through the trapezoidal prism 9 and then forms a projected image M4 on the one-dimensional CCDs 6a to 6e by the projection lens 12. Here 2
The two projected images M3 and M4 are equal-sized images whose top, bottom, left, and right sides are simply reversed, and they are distinguished by a projection time difference. In this embodiment, the time difference is provided by moving the aperture diaphragm 8, but it is also possible to provide a time difference by adding a shutter function to each luminous flux.

In addition, the inversion using the trapezoidal prism 9 can be performed by combining multiple prisms with different angles, and the projection method can be used in accordance with Fig. 1 to properly select the focal length of the lens and make the magnification equal. It can also be done by

In the above-mentioned embodiment, only the case where the reflected image is inverted was explained; however, one reflected image is transferred to the optical axis O of the objective lens 7
For example, the trapezoidal prism 9 may be slightly displaced in the direction perpendicular to the paper plane of the pfJS diagram in FIG. Although only the case where five pieces are used is shown, the number is not necessarily limited.

[Effects of the Invention] As explained above, corneal shape measurement according to the present invention
□ When the apparatus projects the image of the optotype reflected on the cornea onto the light receiving means, by inverting or rotating the image, it is possible to obtain more information than the number of light receiving elements for the fixedly arranged light receiving means. Therefore, a large number of positions can be measured using a limited number of light receiving elements, and measurement accuracy can be significantly improved.

[Brief explanation of drawings]

The drawings show an embodiment of the corneal shape measuring device according to the present invention. FIG. 1 is an optical layout diagram of the first embodiment, and FIG. 2 is a diagram showing the light receiving means and the angle I+! ,! An explanatory diagram of the positional relationship with the reflected image, Fig. 3 is an optical arrangement diagram of the second embodiment, Fig. 4 is a front view of the aperture stop, Fig. 5 is an optical arrangement diagram of the third embodiment, and Fig. 6
The figure is an explanatory diagram of the positional relationship between the light receiving means and the corneal reflection image. 1 is a ring-shaped light source, 2.7 is an objective lens, 3.4 is a hole lens, 5.12 is a projection lens, 6a to 6e are one-dimensional CCDs, 8 is an aperture stop, 9 is a trapezoidal prism, 1o,
11 is a half-moon lens. Patent applicant: Canon Co., Ltd. Drawings Figure 1 Figure 21 Figure 5 Figure 4 ε; Figure S6

Claims (1)

[Scope of Claims] 1. A light-receiving means comprising a plurality of one-dimensional light-receiving elements, and a projection means for projecting a corneal reflection image of a target projected toward the cornea of the eye to be examined onto the light-receiving means. A corneal shape measuring device characterized in that the projection means forms corneal reflection images that are inverted or rotated relative to each other. 2. The corneal shape measuring device according to claim 1, wherein the light receiving element is a radially arranged one-dimensional light receiving element. 3. The corneal shape measuring device according to claim 1, wherein the projection means projects the corneal reflected image at a different magnification. 4. A device according to claim 1, wherein a plurality of means for inverting or rotating the corneal image are provided, and the directions of the images formed by each of the means on the one-dimensional light-receiving probe are different from each other. Corneal topography measurement device. 5. The corneal shape measuring device according to claim 1, further comprising means for giving a time difference to the light flux passing through the projection means.