JP2691271B2 - Corneal shape measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corneal shape measuring apparatus used in an ophthalmological clinic or the like to perform optical measurement on an eye to be inspected. In the conventional corneal shape measuring apparatus, the cornea measurement and the alignment are performed using different optical systems. SUMMARY OF THE INVENTION An object of the present invention is to provide a corneal shape measuring apparatus capable of performing corneal shape measurement and accurate alignment with a simple structure. A corneal shape measuring apparatus according to the present invention for achieving the above object comprises a ring-shaped light source provided around the optical axis and a cornea of the eye to be examined by the ring-shaped light source. Image pickup means for picking up a reflected image together with an anterior segment including the iris of the eye to be inspected, display means for displaying an image picked up by the image pickup means, and alignment mark for displaying an alignment mark for alignment of the eye to be inspected on the display means Means for performing corneal shape measurement from the intersection of at least three lines in the image captured by the imaging means and the corneal reflection image of the ring-shaped light source. In order to facilitate understanding of the present invention, a detailed description will be given based on an example on which the following embodiments will be described. FIG. 1 is an optical configuration diagram. In front of the eye E to be inspected, an objective lens 1, a light splitting member 2, a diaphragm 3, and a two-dimensional optical sensor 4 are sequentially arranged along the optical axis O1 from the eye E side. A ring-shaped light source 5 is arranged around the objective lens 1. Further, an optical axis O2 which is orthogonal to the optical axis O1 and passes through the light splitting member 2
A light source 6, an alignment target 7, a lens 8, a light splitting member 2, a lens 9 and a television camera 10 are sequentially arranged on the upper side, and an output of the television camera 10 is connected to a television monitor 11. The objective lens 1 and the lens 9 from the eye E to be examined to the television camera 10 are of a telecentric system. A reflection image from the cornea Ec of the eye E to be inspected of the ring-shaped light source 5 is formed on the two-dimensional optical sensor 4 through the objective lens 1, the light splitting member 2 and the diaphragm 3, the size of which will be described later. The radius of curvature of the cornea Ec can be obtained by measuring with a means. On the other hand, as shown in FIG. 2A, an image of the anterior segment of the eye E is projected on the television monitor 11 by the television camera 10, and the anterior segment is illuminated by a visible external light source (not shown). ing. Alignment target 7 is visible light source 6
And the television camera 1 through the lenses 8 and 9
0 is photographed. An iris image Pi, an image Pr of the ring-shaped light source 5, an image Pa of the alignment target 7, a pupil image Pp, and an external eye illumination light source image Ps are displayed on the television monitor 11 in FIG. Since the optical system reaching the television camera 10 in this case is a telecentric system, even if there is a blur, it does not affect the reading measurement accuracy. When the video signal of the scanning line 1 is shown in FIG. 2 (b), the sclera Es has strong reflection and the iris Ei is dark and low in level. If the level L is set in the middle, the signal can be binarized. If the distance between the intersections a and b is obtained by means described later, the size of the iris image Pi can be determined. The reason why the scanning line 1 is deviated from the center of the eye E is to avoid the light source image Ps. If the shift amount is determined in advance, it can be converted into the diameter of the iris image Pi. FIG. 3 shows an electrical block circuit configuration diagram.
First, the measurement unit of the corneal radius of curvature will be described. The analog signal read from the two-dimensional optical sensor 4 is amplified by the amplifier 20 and temporarily held at the signal level by the sample value holding circuit 21, and then the next stage. The digital signal is converted by the A / D converter 22. The optical sensor 4 is controlled by a clock signal from the driver 23. A
The digital signal output from the / D converter 22 is passed through an interface 24 to a RAM (Random Access Memory).
25. Reference numeral 26 denotes a ROM (Read Only Memory) in which a control program for operating the microprocessor 27 is written. The position of the ring image formed on the two-dimensional optical sensor 4 is obtained from the data in the RAM 25,
The radius of curvature of the cornea is determined by fitting to a general formula of an ellipse or the like, and is displayed on a result display 28 and output to a printer 29 as necessary. Next, the corneal diameter measuring unit will be described. The video signal of the anterior ocular segment image of the subject's eye E captured by the television camera 10 is supplied to the television monitor 11, the amplifier 30, and
The signal is input to the period separation circuit 31 to operate the scanning line counter 32. The output c from the scanning line counter 32 is connected to the interface 24. The video signal amplified by the amplifier 30 is input to comparators 34 and 35 and a sample value hold circuit 36,
Is input to the sample value hold circuit 36 via the monostable multivibrator 37. Comparator 3
5 is connected to a pupil level setting signal d, an output e of which drives a monostable multivibrator 37, and an output f of which outputs a sample value hold circuit 3.
The output signal h is added to a predetermined voltage signal g via an adder 38 via an adder 38, and the output signal h is connected to an input terminal of a comparator 34. The output i of the comparator 34 is connected to the gate input of the counter 39, and count control is performed by the clock output j of the oscillator 40. The count output k of the counter 39 is input to the interface 24, and the control signal m of the counter 39 is sent from the interface 24 to the counter 39. Further, the ring-shaped light source 5 and the light source 6 are connected to the interface 24, and the turning on / off control is performed. The operation of the corneal diameter measuring unit will be described with reference to FIG. 4. Since the pupil image Pp is close to a black level and there is no individual difference, the pupil level setting signal d may be constant. If the monostable multivibrator 37 is driven by the fall of the output signal e from the comparator 35 and the video signal at the time of the fall of the signal e is held as a sample value, the level Li of the iris image Pi is determined and the individual difference Can be suppressed. A predetermined level g is added to this level Li, and the level h and the output signal of the TV camera 10 are compared by the comparator 34.
By comparison, the iris signal i can be extracted. The signal h from the adder 38 is output for each scanning line while the screen of the television monitor 11 has a pupil. On the basis of the output c from the scanning line counter 32, a counter control signal m is output when a predetermined scanning line is reached, the width of the iris signal i is counted by the clock output j, and the output k is read, whereby the scanning line is read. The corneal diameter can be obtained by converting the diameter of the iris image Pi on 1. The measurement operation procedure is as follows:
First, while aligning the ring image Pr with the target image Pa with good focus while pressing the measurement button (not shown), the light sources 5 and 6 are turned off and the iris diameter, that is, the cornea diameter is measured. While lit, the radius of curvature of the cornea is measured, but the procedure may be reversed. In addition, it is easier to perform the signal processing when the ring-shaped light source 5 is turned off when measuring the iris diameter.
Also, since the iris has a high reflectance with infrared light, it is desirable to use visible light for external eye illumination. On the assumption of the configuration of the above example, in the embodiment, a ring-shaped corneal reflection image Pr by the light source 5 is projected on the television monitor 11, and this image Pr is generally represented by an ellipse. Therefore, by using at least three scanning lines of the ring-shaped image Pr and finding the intersection of the rings, this ellipse can be calculated, and the radius of corneal curvature in each radial direction can be calculated. It can be calculated. Furthermore, the microprocessor 27 may calculate the base curve of the contact lens based on the measurement results of the radius of curvature of the cornea and the diameter of the cornea, and output the result to the result display 28 and the printer 29. As described above, according to the corneal shape measuring apparatus of the present invention, the accurate alignment using the anterior segment image including the iris displayed together with the alignment mark and the corneal shape measurement can be performed. Can be performed by a common image pickup unit, and therefore, excellent corneal shape measurement can be performed with a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example which is a premise for explaining an embodiment of the present invention and an optical configuration which is a basis of the embodiment of the present invention. FIG. 2 is a front view of a television monitor and a waveform diagram of a video signal of a specific scanning line. FIG. 3 is a block circuit configuration diagram. FIG. 4 is a signal waveform diagram of a block circuit configuration diagram. [Description of Signs] 1 Objective lens 2 Light splitting member 3 Aperture 4 Optical sensor 5 Ring light source 6 Light source 7 Alignment target 11 TV monitor 21, 36 Sample value hold circuit 22 A / D converter 25 RAM 26 ROM 27 Microprocessor 34 , 35 comparator 37 monostable multivibrator 38 adder 39 counter

Claims (1)

(57) [Claims] A ring-shaped light source provided around the optical axis, an imaging unit that images a corneal reflection image by the subject's eye of the ring-shaped light source together with an anterior segment including the iris of the subject's eye, and an image captured by the imaging unit. A display unit for displaying and an alignment mark unit for displaying an alignment mark for alignment of the eye to be inspected on the display unit are taken by the image pickup unit .
Of at least three lines in the image and the ring-shaped light source
A corneal shape measuring apparatus, characterized in that a corneal shape measurement is executed from an intersection of corneal reflection images .