JPS5819225A - Cornea meter - 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 The present invention relates to an apparatus for measuring the anterior radius of curvature of the cornea.

Conventionally, corneal needles have been called ophthalmometers, keratometers, and the like, and have been widely used as testing instruments for contact lens wearers and for detecting corneal inflection abnormalities. .

However, in both cases, the measurements are manual and time consuming, and it is extremely difficult to keep the eyeballs from moving during the measurements, resulting in a lack of accuracy.

There are also some that require a photo shoot, but this requires extremely troublesome post-processing.

The keratometer of the present invention has been made in view of the above points, and includes a method in which the rear focal position of the main lens and the front focal position of the sub-lens are made to coincide with each other, and an aperture is placed at that position.
A light projection system consisting of a collimator lens, a slit, and a light source is provided at a plurality of positions facing the cornea at different angles with respect to the optical axis of the main lens, and the light projection system includes a collimator lens, a slit, and a light source. A photographic element or the like is arranged at a position conjugate with the reflective bone of the slit, and the distance between the reflective bones of the slit is read by the photographic element or the like, and the radius of curvature of the anterior surface of the cornea is measured. .

Embodiments of the present invention will be described below with reference to the drawings.

No. 11EI is a schematic optical path diagram showing an embodiment of the present invention, FIG. 2 is a perspective view of the embodiment of the present invention, and FIGS. 3 and 4.

FIG. S is a diagram of the principle of the present invention.

In the figure, 1 is the main lens, 3 is a sub-lens, 2 is an aperture consisting of a perforated reflector placed near the rear focal position of the main lens 1 and the front focal position of the sub-lens 3, and the instrument is the diaphragm 2.
and an image pickup device placed at a position conjugate with the cornea 40 at the end of measurement with respect to the main lens 1 and the sub-lens 3.

Similarly, 8 is a 7゛TT infrafocus placed at a position conjugate to the reflection range of the cornea 4 to be measured, sandwiching the diaphragm 2, the main lens 1 and the sub-lens 3, and 9 is a ***. /'s.

7 is a half mirror for dividing the optical path into the camera element S and the finder focusing plate 81I, and is placed in front of the sub-lens 3 as shown in FIG. This may be between the sub-lens 3 and the image sensor 5 shown in FIG.

6.6' is a light projecting system, which faces the cornea 4, and has θI* with respect to the focal point F on the optical axis A of the cornea 4, as shown in FIG.
It is placed at a position having an angle of L'l. 8m.

6&' is a light projection lens, 6b and 6b' are lenses placed at the focal point of the light projection lens 61°6.1), and 6e and 6c' are light sources.

In Fig. 2, 10 is the illumination system, and the illumination lens is 10 m.
, the index consists of a diffuser plate 10b and an illumination light source 10c.

The operation of the keratometer in the present invention will be explained below.

First, a method of determining the distance between the cornea 4 to be measured and the main lens 1 will be explained.

The light from the illumination system 10 is transmitted from the illumination light source 10e, through the index or the diffuser plate tab, through the illumination lens 10m, and into the hole #.
) and reaches an aperture 2 consisting of a reflective mirror.

Then, the reflected light from the diaphragm 2 passes through the main lens 1 and is projected onto the cornea 4, and the reflected light returns to the main lens 1.
The light passes through the aperture 2 and reaches the half mirror 7. As a result, the optical path is divided into two, one being the finder focus plate 8.
The other one passes through the sub-lens 3 and reaches the image sensor 3.

At this time, in the finder focusing plate 8, if the aperture OS is in focus, the cornea 40, the anti-reflection color image sensor 5, and the finder focusing plate 8 are conjugated, and the projection system 6 is in focus (6b, 6b'). is also conjugate.

In this state, the light from the light projection systems 6 and 6' is reflected by the cornea 4, passes through the main lens 1 and the aperture 2, and passes through the nofora 7.
One of them passes through the finder focus plate 8, and the other passes through the sub-lens 3 and reaches the image pickup device 5. At this time, it goes without saying that the projection system 6, 6b and 6b' are formed on the image pickup element s.

By the way, the distance between the points where the light from the light projection systems 6, 6' is reflected on the cornea 4 is the distance from the optical axis A, respectively. If we assume h, then we get .

Thus, 8 is the radius of curvature of the front surface of the cornea 4.

The power ratio of main lens 1 and sub lens 3 is M
Then, we get 1'I-Mh, and the formula (2) is obtained.

Here, before 4 appears on Ha's camera element s, the light projection system 6.6
The distance between the reflection bones of 6b and 6b' is O. Also, the bit pitch of the image sensor 5 is P1 The number of pits is N
Then, we get H-PN and the formula 0.

P @ M @ ('I * e@ is a known constant, so by counting the number of bits N on the imaging element s, the radius of front curvature R of the cornea can be measured.

Next, the principle of the present invention will be explained with reference to FIGS. 4 and 5.

Figure 4 shows the case where the cornea 4 is shifted perpendicular to the optical axis A, as shown by the dotted line. In this case, the chief ray after corneal reflection is parallel to the optical axis A, so it becomes h - h' and is measured. There is no error.

FIG. 5 shows a case where the cornea 4 is displaced in the optical axis direction as shown by the dotted line. In this case, the chief ray after corneal reflection is stationary and the center of my blur on the camera element 5. If you take , there is no measurement error.

As described above, in the present invention, there is no measurement error even if the focusing is slightly shifted in the direction of the optical axis and in the direction perpendicular thereto (the plane where the light projection system is located).

The explanation so far has been based on the case where there are two light emitting systems on both sides, but the same applies if there are multiple light emitting systems, and in that case, the curvature of each part of the corneal cross section can be measured. You can also check the shape of the corneal cross section by stirring. Furthermore, by rotating this device ecP, it is possible to measure the vertical curvature of the cornea, and by combining it with a mechanism that detects the rotation angle, it is also possible to measure the direct visual power and the visual axis.

[Brief explanation of drawings]

FIG. 1 is a schematic optical path diagram showing an embodiment of the present invention, FIG. 3 is a perspective view of the embodiment of the present invention, and FIGS. 3 and 4. FIG. S is a diagram of the principle of the present invention. l...Main lens, 2...Aperture, 3...Sub lens, 4...Cornea, 5...Photographing element, 6.6'...
- Light projection system, 6a. 6m'...Light projection lens, 6b, 6b'...Slit, 6c. 6(+'...Light source, r...Harnra, 8...
Finder focusing plate, 9... Eyepiece lens, 10... Illumination system, loa... Illumination lens, 10b... Index or diffuser plate, 10a... Illumination light source.

Claims (1)

[Claims] (1) The rear focal position of the main lens and the front focal position of the sub-lens are approximately aligned, and the diaphragm is placed at that position, and then placed at multiple positions facing the cornea at different angles with respect to the optical axis of the main lens. , a light projection system consisting of a collimator lens, a slit, and a light source is provided, and a photographing element or the like is disposed at a position conjugate with the reflection of the slit of the light projection system by the cornea with respect to the main lens and the sub-lens, and the photographing element is A corneal needle characterized in that it reads the distance between the reflective bones of the slit and measures the radius of curvature of the anterior surface of the cornea.