JPH0431253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a corneal topography measuring device used in ophthalmology to measure the radius of curvature of the corneal surface.

[Prior Art] Conventional corneal shape measuring devices include a so-called off-salmometer that projects an index onto the eye to be examined and optically and manually measures the size of the corneal reflected image;
A device called a keratometer is widely known. Further, as methods for automatically measuring the shape of the cornea, Japanese Patent Application Laid-open Nos. 58-73335 and 58-54927 are known.

However, these measurement devices have a problem in that they require a plurality of one-dimensional position detection elements arranged in a precisely adjusted manner and a two-dimensional imaging element for alignment.

[Object of the invention] The object of the present invention is to eliminate the above-mentioned problems and to
An object of the present invention is to provide a corneal shape measuring device in which two two-dimensional image sensors can be used for alignment and corneal shape measurement, and the amount of light reaching the two-dimensional image sensors or signals from the two-dimensional image sensors can be adjusted.

[Summary of the invention] The gist of the present invention for achieving the above object is as follows:
an index projection system that projects a predetermined index onto the cornea of the eye to be examined;
an imaging optical system that forms a corneal reflection image of the predetermined index on a two-dimensional imaging device; a measuring device that measures a corneal shape based on a corneal reflection signal from the two-dimensional imaging device; and the two-dimensional imaging device. The amount of light reaching the two-dimensional imaging device is determined between the detection means that detects the state of alignment with the eye to be examined based on the corneal reflection image signal from the element, the measurement of the corneal shape, and the detection of the state of alignment. or a control means for adjusting the signal from the two-dimensional image sensor.

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

FIG. 1 shows a configuration diagram of the optical system, in which an objective lens 1 is arranged facing the cornea Ec of the eye E to be examined, and behind the objective lens 1, an aperture 2 and an image sensor 3 are provided. Additionally, as shown in Figure 2, around the objective lens 1 there are four
light sources 4a to 4d are arranged, each of these light sources 4a to 4d is arranged, and each of these light sources 4a to 4
Indices 5a to 5d each having a punctate opening are inserted between d and the cornea Ec of the eye E to be examined.

The indicators 5a to 5d are illuminated by the light sources 4a to 4d and project a luminous flux onto the cornea Ec of the eye E to be examined. 4
A to 4D are images reflected by the cornea Ec of this light beam, and these corneal reflection images 4A to 4D are formed on the image pickup device 3 via the objective lens 1 and the aperture 2.

Further, the entire device is positioned on a movable part (not shown), so that the examiner can align it with the eye E to be examined. Further, as disclosed in Japanese Patent Application Laid-Open No. 61-249432, the diaphragm 2 corrects the change in the size of the corneal reflection images 4A to 4D due to the change in the distance between the apparatus and the eye to be examined, and the image sensor 3 It is arranged at a position that specifies and transmits only the chief ray in the direction in which the size of the corneal reflection images 4A to 4D remains unchanged, and the light beam centered on this chief ray.

FIG. 3 is a block circuit diagram of the present invention, in which the output of the image sensor 3 is connected to a frame memory 11 and a display 12 via a drive circuit 10, and the frame memory 11 is connected to an MPU (microprocessor unit).
It is connected to 13. Further, the output of the MPU 13 is connected to the light sources 4a to 4d via the light source control circuit 14. The drive circuit 10 outputs a video signal, the frame memory 11 is a memory that digitizes and stores the video signal according to a control signal from the MPU 13, and the display 12 outputs a video signal, for example.
Video signals from a CRT monitor, etc. can be directly displayed, and the light source control circuit 14 is connected to the MPU 13.
By adjusting the amount of current supplied to the light sources 4a to 4d based on the control signal from the light sources 4a to 4d,
4d is designed to control the amount of emitted light.

When a control signal is input from the MPU 13 to the light source control circuit 14, the light sources 4a to 4d are caused to emit light, and the light is projected onto the cornea Ec of the eye E as shown in FIG. Then, reflected images 4A to 4D by the cornea Ec are formed on the image sensor 3, and the formed images are converted into video signals in the drive circuit 10, and displayed in real time on the display 12, as well as in the frame memory 11.
is input. From MPU13 to frame memory 1
When a control signal is output to frame memory 1,
1 digitizes and stores the input video signal. Next, the MPU 13 performs calculations based on the digital data stored in the frame memory 11, and performs control corresponding to the results.

FIG. 4 is a flowchart of a program built into the MPU 13. First, in step 20, the MPU 13 initializes the frame memory 11 and outputs a control signal to the light source control circuit 14 to maximize the amount of light emitted from the light sources 4a to 4d.
Then, since the light sources 4a to 4d emit a large amount of light to the image sensor 3, the cornea of the eye E at the indices 5a to 5d is
In addition to the reflected images 4A to 4D by Ec, an anterior segment image that is a diffuse reflected image is formed and displayed on the display 12. In step 21, the MPU 13 stores the video signal of the image formed on the image sensor 3 in the frame memory 11, and in step 22 stores the corneal reflection images 4A to 4D of the index in the image data stored in the frame memory 11. Count the number of light sources 4
Compare with the number of pieces a to 4d, that is, 4 pieces. and,
If they match, the process advances to step 23; if they do not match, the process returns to step 21.

Number of corneal reflection images 4A to 4D and light sources 4a to 4d
The reason why the numbers do not match is because the positional relationship between the eye E and the measurement device is incorrect.
The numbers of light sources 4a to 4d are made to match A to 4D.
In this way, in steps 21 and 22, the eye E to be examined and the corneal shape control device are aligned.

Next, in step 23, the MPU 13 outputs a control signal to the light source control circuit 14, and the light sources 4a to 4d
In step 24, the video signal from the image sensor 3 is stored in the frame memory 11. In step 25, similarly to step 22, the number of corneal reflection images 4A to 4D in the image data stored in the frame memory 11 is compared with the number of light sources 4a to 4d, and if they match, the process proceeds to step 26.
Then, it is determined whether the illuminance of the corneal reflection images 4A to 4D formed on the image sensor 3 is at an appropriate level. This adjusts the amount of light emitted from the light sources 4a to 4d, removes the anterior segment image which is an unnecessary diffuse reflection image, and forms only the necessary corneal reflection images 4A to 4D on the image sensor 3. Corneal reflection image 4A~
This is to prevent halation or flare from occurring in the corneal reflection images 4A to 4D on the image sensor 3 since the measurement is performed with high precision at the imaging position on the 4D image sensor 3. Furthermore, since there are individual differences in the reflectance of the cornea Ec, the amount of light emitted from the light sources 4a to 4d is adjusted to produce corneal reflection images 4A to 4 on the image sensor 3.
This is to set the illuminance of D to an appropriate level.

If it is determined in step 26 that the illuminance of the corneal reflection images 4A to 4D formed on the image sensor 3 is not at an appropriate level, the process returns to step 23 and the output amount and light amount of the light sources 4a to 4d are adjusted again. If the level is appropriate, proceed to step 27. In step 27, it is checked whether a measurement start signal has been input to the MPU 13 from a circuit (not shown), and if it has not been input, the process returns to step 23 and the light source 4a is turned on again.
Adjust the amount of emitted light from ~4d. If the measurement start signal is input in step 27, the process proceeds to step 28, where the center of gravity of the corneal reflection images 4A to 4D is calculated based on the image data stored in the frame memory 11, and in step 29, the center of gravity of the corneal reflection images 4A to 4D is calculated. The shape of the cornea Ec is calculated from the calculated center of gravity value.
Note that the calculations for determining the center of gravity and the calculations for calculating the shape of the cornea Ec in steps 28 and 29 are well known and will not be described here.

FIGS. 5 and 6 show a second embodiment, in which the parts other than the block circuit diagram and frame memory 11 shown in FIG. 3 have the same structure as the first embodiment. FIG. 5 is a configuration diagram of the frame memory 11, in which the output of the drive circuit 10 is connected to a binarization circuit 20, and the output of this binarization circuit 20 is sent to the MPU 1 via a memory controller 21 and a binarization memory 22.
Connected to 3. In addition, the binarization circuit 20
The output of the MPU 13 is input via the D/A converter 23, and the MPU 13 is also input to the memory controller 21.
output is connected.

In the frame memory 11 configured in this manner, the binarization circuit 20 binarizes the video signal input from the drive circuit 10 using the voltage input from the MPU 13 via the D/A converter 23 as a reference voltage. , is output to the memory controller 21. The memory controller 21 stores the binarized video signal in the binarization memory 22 in synchronization with the control signal from the MPU 13. Furthermore, the memory controller 21 outputs the binarized image signal from the binarization memory 22 to the MPU 13 based on another control signal from the MPU 13 .

Next, the operation of this second embodiment will be explained with reference to the flowchart shown in FIG. Note that steps with the same symbols as in FIG. 4 perform the same operations. First, in step 30, the MPU 13 initializes the reference voltage output from the frame memory 11 and the D/A converter 23, and maximizes the amount of light emitted from the light sources 4a to 4d. In step 31, the video signals of the corneal reflection images 4A to 4D formed on the image sensor 3 are binarized and stored in the binarization memory 22, and in step 32, the corneal reflection images from the image signals in the binarization memory 22 are The number of images 4A to 4D is the light source 4a to 4d.
Check whether it matches the number of items. If they match, the process advances to step 33; if they do not match, the process returns to step 31.

In step 31, the examiner aligns the eye E to be examined with the corneal shape measuring device, thereby matching the number of corneal reflection images 4A to 4D with the number of light sources 4a to 4d. In step 33, the light sources 4a to 4d
The output light intensity is adjusted to a predetermined light intensity for corneal shape measurement. In step 34, the D/A converter 23
At step 35, the video signals of the corneal reflection images 4A to 4D are binarized and stored in the binarization memory 22. In step 36, corneal reflection images 4A to 4A are obtained from the image signals in the binarized memory 22.
The number of light sources 4D and the number of light sources 4a to 4d are compared, and if they do not match, the process returns to step 30 to align the eye E and the corneal shape measuring device, and if they match, the process proceeds to step 37. In step 37, the diameters of the corneal reflection images 4A to 4D in the image signal of the binarized memory 22 are determined, and if the diameters are within the allowable range, the process proceeds to step 38. In step 38, select MPU1 from the circuit not shown.
Check whether the measurement start signal is input to 3.
If no input has been made, the process returns to step 34; if it has been input, the process proceeds to steps 28 and 29. In steps 28 and 29, the center of gravity and shape of the cornea Ec are calculated from the image data stored in the binarized memory 22.

In addition, in the embodiment described above, the light sources 4a to
The amount of light emitted from the light source 4d is controlled by the amount of current from the light source control circuit 14, but it is also possible to control the amount of light emitted from the light source 4d by mechanical control by inserting an optical filter or a light flux diaphragm between the light sources 4a to 4d and the indicators 5a to 5d. You can go with it.
Moreover, the light intensity adjustment of the light sources 4a to 4d is performed using the light sources 4a to 4.
The number of lights d may be varied, and the amount of light from another light source may be transmitted to the light source that is turned off using a mirror or the like.
Furthermore, light sources may be additionally provided for observing the anterior segment of the eye other than the light sources 4a to 4d, and the light amount may be adjusted by combining these light sources. Further, the amount of light emitted from the light sources 4a to 4d is kept constant, and the image sensor 3
A similar effect can be obtained even if the sensitivity is electrically variable.

[Effects of the Invention] As explained above, the corneal shape measuring device according to the present invention can measure one two-dimensional shape by relatively adjusting the amount of light irradiated to the two-dimensional image sensor and the sensitivity of the two-dimensional image sensor. It becomes possible to perform alignment with the eye to be examined and measurement of the corneal shape using the image sensor.

[Brief explanation of drawings]

The drawings show an embodiment of the corneal shape measuring device according to the present invention, and FIG. 1 is a block diagram of the first embodiment, FIG. 2 is a light source arrangement diagram, and FIG. 3 is a block circuit diagram.
FIG. 4 is a flowchart of the first embodiment, and FIG.
The figure is a block circuit diagram of the second embodiment, and FIG. 6 is a flowchart of the second embodiment. 1 is an objective lens, 2 is an aperture, 3 is an image sensor, 4a to 4d are light sources, 5a to 5d are indicators, 10
is a drive circuit, 11 is a frame memory, 12 is a display, 13 is an MPU, 14 is a light source control circuit, 20 is a binarization circuit, 21 is a memory controller, 22 is a binarization memory, 23 is a D/A converter It is.

Claims (1)

[Scope of Claims] 1. An index projection system that projects a predetermined index onto the cornea of the eye to be examined; an imaging optical system that forms a corneal reflection image of the predetermined index on a two-dimensional image sensor; a measuring means for measuring the shape of the cornea based on the corneal reflection signal from the two-dimensional imaging device; a detecting means for detecting the state of alignment with the eye to be examined based on the corneal reflection image signal from the two-dimensional imaging device; and measuring means for measuring the shape of the cornea. and a control means for adjusting an amount of light reaching the two-dimensional image sensor or a signal from the two-dimensional image sensor between the detection of the alignment state and the detection of the alignment state. 2. The corneal shape measuring device according to claim 1, wherein the control means adjusts the amount of light irradiated onto the cornea of the eye to be examined by the target projection system. 3. The corneal shape measuring device according to claim 1, wherein the control means adjusts the amount of light irradiated to the cornea of the eye to be examined by inserting and removing an optical filter into the optical path of the target projection system. . 4. Claim 1, wherein the control means adjusts the amount of light irradiated onto the cornea of the eye to be examined by arranging a variable aperture in the optical path of the target projection system.
The corneal topography measuring device described in 2. 5. When the corneal reflection image formed on the two-dimensional image sensor reaches a predetermined position when detecting the alignment state, the measurement of the corneal shape is automatically started. The corneal topography measuring device described in 2.