JP2940955B2 - Optical measuring device for eye examination - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an optical measurement apparatus for eye examination that automatically measures various optical characteristics (eye refractive index, corneal curvature, etc.) of an eye to be examined.

[Prior art and its problems]

As the above-described optical measuring device for eye examination, for example, devices such as an auto-refractometer (automatic eye refractometer) and an auto-keratometer (automatic corneal curvature measuring device) are known. In each of these devices, a measurement optical system including the eye to be inspected is formed by arranging the eye to be inspected at a predetermined position on the optical axis of the device. The arrangement of the eye to be inspected is such that the optical axis of the apparatus is coincident with the optical axis of the eye to be inspected, that is, aiming is performed, and the focus of the monitor camera optical system itself in the apparatus is the position of the eye to be inspected of the measurement optical system. In other words, two conditions must be satisfied: matching is achieved. Taking the auto-refractometer as an example, the principle of the device of the refractometer is that the optical target (measuring light) imaged on the fundus of the eye to be examined, ie, on the retina, is observed through an optical system, and the refraction of the eye is measured. And
The auto-refractometer performs the measurement automatically, but in order to actually perform the measurement, the positional relationship between the measurement optical system on the device side and the eye to be inspected is required as a preparation step before the measurement light is emitted. Is adjusted to a state in which can be measured (a state in which aiming and distance adjustment have been achieved). In such a pre-adjustment operation in a conventional auto-refractometer, the measuring device itself is placed on the subject's eye so that the aiming mark (reticle pattern) displayed on the monitor screen matches the position of the corneal reflection image of the aiming light source. By operating up, down, left and right, aiming is performed, and by adjusting the distance between the apparatus and the subject's eye, the focal point of the monitor camera optical system itself is matched with the position of the subject's eye in the measurement optical system. In this way, the measurer recognizes that aiming and distance adjustment have been achieved on the monitor screen, and then the measurer turns on the measurement start switch to perform actual measurement. However, when the measurement is started by the aiming / distance adjustment method as described above, first, it is difficult for the subject to keep the aiming / distance adjustment state constant. It takes a lot of skill to turn on the switch, and it is extremely difficult to turn on the switch at the timing when the aiming and the distance adjustment are actually completed.

[Object of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical inspection apparatus for eye examination provided with an aiming / distance adjustment mechanism that does not miss measurement timing.

[Means for Solving the Problems]

An optical measurement apparatus for an eye inspection according to the present invention is provided with the following configuration in order to solve the above-described problems of the related art and achieve the object. That is, the optical measuring device includes a measuring light projecting system for projecting measuring light toward an eye to be inspected, a measuring light receiving system including a light receiving sensor for receiving reflected light from the eye to be inspected, and an optical measurement for eye inspection on the eye to be inspected. Aiming and distance adjusting means including an aiming and distance adjusting optical system for aiming and distance adjusting of the apparatus, and projecting measurement light to the eye to be inspected and based on reflected light of the eye to be inspected obtained by the measuring light receiving system. Measuring means for measuring the eye to be examined. The light receiving sensor is arranged so that the light receiving system optical axis of the measuring light receiving system coincides with the intersection of the X axis and the Y axis on the light receiving sensor. The aiming and distance adjusting optical system has a pair of aiming light source means for irradiating a light beam toward the subject's eye, and the pair of aiming light source means is symmetric in the X-axis direction with respect to a light receiving system optical axis. And irradiates the cornea of the eye to be examined with a sufficiently thin light beam, and only when the distance adjustment and the aiming are achieved within a predetermined range, each of the corneal reflected lights is received by the light receiving section. It is arranged to be received by a sensor. The aiming / distance adjusting means includes: comparing means for comparing the signal level of the two corneal reflected light images formed on the light receiving sensor with a reference value; A determination unit for determining whether two corneal reflection images are received on the X axis of the light receiving sensor when it is determined to be larger than the value; and two corneal reflections received on the X axis of the light receiving sensor. Calculating means for calculating the distance between the image and the Y-axis of the light receiving sensor; and comparing the two distances calculated by the calculating means, and when the difference is within an allowable range, start measuring light projection to the measuring device. Second comparing means for outputting a signal.

[Action / Effect]

In the above configuration, if the distance adjustment of the measurement device to the eye to be examined is inappropriate, the corneal reflected light of the aiming light is not received by the light receiving sensor, or even if it is received, the corneal reflection of the aiming light from the light receiving sensor is performed. This state where the signal level of the reflected image is lower than the reference value is determined by the first comparing means. Thereby, distance adjustment can be achieved. Also, when the error of aiming of the measuring device with respect to the eye to be examined is large, the corneal reflected light of the aiming light is not received by the light receiving sensor, and this state is determined by the first comparing means. When the aiming error is very small, two states of the X-axis direction shift and the Y-axis direction shift can be considered in the light receiving sensor, but the Y-axis direction shift is determined by the determination unit.
The displacement in the X-axis direction is determined by the calculating means and the second comparing means, whereby accurate aiming is performed. Then, the measurement light projection start signal is output from the second comparison means to the measurement device when both the distance adjustment and the aim adjustment are achieved. Therefore, according to the above configuration, when the distance adjustment and the aiming adjustment are achieved, the measurement is automatically started immediately, so that the optimal measurement timing can always be obtained.

【Example】

Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. 1 to 9. FIG. 1 is a view schematically showing an entire optical system of an auto-refractometer as one embodiment according to the optical measuring apparatus for eye examination of the present invention. FIG. 2 is a schematic diagram of the measuring light projecting optical system in FIG. 1, FIG. 3 is a schematic diagram of the measuring light receiving optical system in FIG. 1, and FIG. Show. The projection system optical axis A of the measurement light projection optical system 1 extends from the light source 2 toward the first half mirror 3 and the first half mirror 3
At a right angle and extends toward the subject's eye E.
The light source 2 uses an infrared light emitting diode. Various optical elements along the optical axis portion a ₁ extending to the straight upward from the light source 2 to the first half mirror 3 is disposed. Then, the measurement light reflected at a right angle by the first half mirror 3 exits the apparatus along the optical axis portion a _2. Thus, by locating the optical axis aE of the eye E on the optical axis a _2, it is possible to project a measuring beam into the eye E. On the optical axis portion a ₁ between the light source 2 and the first half mirror 3, a collimator lens 4, a pyramid-shaped quadrangular pyramid prism 5, a diaphragm 6, a light projecting relay lens 7, and a four-hole mirror are arranged in this order from the light source 2 side. 8, an eyepiece 9 is arranged. The quadrangular pyramid prism 5 transmits the infrared light from the light source 2 through the collimator lens 4 to the optical axis to form a spot pattern of four points of the measurement light.
Four high-speed separations at a central angle of 90 ° around a ₁ are performed. The stop 6 is disposed at the focal position of the light-projecting relay lens 7. Four light beams emitted from the quadrangular pyramid prism 5 enter the light-projecting relay lens 7 after passing through the stop 6, and each of them has an optical axis portion a. _{As a} light beam parallel to ₁ , four spot patterns are formed. 4 hole mirror 8, a mirror for reflecting at a right angle to the measuring beam is a retinal reflection light on the light-receiving optical system 10 of the measuring light to be described later, 45 reflective surface of the upper with respect to the optical axis portion a ₁゜ The projection optical system 1 is inclined
In order to prevent the light path of the light spot pattern from being interrupted, four small holes are formed in a portion corresponding to the light path. Therefore, the measurement light passing through each hole of the four-hole mirror 8 enters the eyepiece 9 as a four-point spot pattern, is reflected at right angles by the first half mirror 3, and enters the eye E to be examined. The optical axis portions b ₁ and b ₂ of the light receiving system optical axis B from the eye E to the four-hole mirror 8 are the optical axis portions a ₂ and b ₂ of the light projecting optical axis A.
a matches ₁ . In the measuring light receiving optical system 10, the retinal reflected light of the measuring light travels backward from the eye E to the four-hole mirror 8 along the optical axis portions b ₁ and b ₂ , and is reflected at a right angle by the four-hole mirror 8. On this optical axis b ₃ is the reflected light, and the micro-mirror 11 is arranged with a reflecting surface parallel with the four-hole mirror 8, the micromirror 11
This causes the measured reflected light to be reflected further downward at right angles.
Below the micromirror 11 light-receiving sensor 13 constituted by a CCD (charge-coupled device) is arranged as an imaging lens 12 and the imaging element matrix along the optical axis portion b _4. Light receiving sensor 13, since it is arranged to pass through the optical axis portion b ₄ at its center, the planar extent of the space traveled by the light receiving sensor 13 can detect the object scene, the object scene center The light receiving optical system 10 is located on the light receiving system optical axis B. In other words, the optical axis b _4, i.e. the optical axis B is coincident with the intersection of the X and Y axes of the light receiving sensor 13. In aiming and distance adjustment optical system 15, aiming light sources 21 of a pair consisting of infrared light emitting diodes are arranged axially symmetrical positions in the horizontal direction with respect to the optical axis portion a _2, aiming light sources of axisymmetric The direction of the straight line passing through 21 is made to coincide with the direction in which the object field is scanned by the light receiving sensor 13 described above. Normally, when monitoring this image, the scanning line moves from top to bottom while scanning in the horizontal direction of the monitor screen, but the scanning direction here is intended to be the horizontal direction. In this embodiment, the scanning direction is from left to right toward the subject's eye. The aiming light emitted from the aiming light source 21 is converted into a sufficiently thin beam light beam by a collimator lens 22 disposed in front of the aiming light source 21, and the corneal reflection is applied to the eye E at an appropriate position for measurement. The light is detected by the light receiving sensor 13 as a light beam taking an optical path parallel to the optical axis portions a ₂ and b ₁ . FIGS. 5 (a), (b) and (c) show the aiming light sources, respectively.
FIG. 7 is a diagram showing various reflection directions of reflected light depending on the positional relationship between 21 and an eye E to be inspected. FIG. 5A shows a case where the distance between the aiming light source 21 and the eye E is too long, and FIG. 5B shows a case where the distance between the aiming light source 21 and the eye E is just right.
FIG. 5C shows a case where the distance between the aiming light source 21 and the eye E is too short. As can be seen from each figure, the beam light of each aiming light source is sufficiently thin, and the spot where the beam light source hits the cornea of the eye E is very small, and the corneal reflected light is also thin and does not spread. its corneal reflection light be too close or too far with respect to the eye E went away from the optical axis a _2, a light receiving sensor 13 proceeds parallel generally to the optical axis a _2, b ₁ at the position of just the right distance To reach. In the present embodiment, in the state shown in FIG. 5 (b), the focal point of the monitor camera optical system itself is configured to coincide with the eye E to be inspected. However, if the error of the distance adjustment is very small, the light is received by the light receiving sensor 13 even if the aim is set. Also, even when the aiming error is large, the light receiving sensor 13 does not receive the light similarly to the above. Hereinafter, a description will be given of a portion forming an optical path of corneal reflected light (hereinafter, referred to as aiming light) of the aiming light source 21. The aiming light partially transmitted through the first half mirror 3 is reflected downward at right angles by the second half mirror 14 and passes through the monitor relay lens 16. The first under the monitor relay lens 16
A 45 ° mirror 17 is disposed, and a reticle plate 18 of transparent glass on which a reticle pattern is written is disposed on the reflected light path. This reticle plate 18 is a monitor relay lens
The lens 16 is arranged at a position conjugate with the eye E. At a position where the reticle plate 18 has passed from the first 45.degree. Mirror 17, a second 45.degree. Mirror 19 is disposed so as to reflect the aiming light incident on the mirror at right angles downward. Optical axis portion below the second 45 ° mirror 19 is a micro-mirror 11 below the optical axis portion b ₄ common in measuring light receiving optical system 10, also common imaging lens 12 and the light receiving sensor 13 It has become. Therefore, the aiming / distance adjusting optical system 15 is configured such that the monitor reticle optical system is incorporated in the monitor camera optical system. In addition, aiming and distance adjustment optical system
At 15, the micromirror 11 is extremely small and its aiming light passes through its periphery, so its presence does not hinder. In Figure 1, what is placed on the extension of the optical axis a ₂ of the projection optical system 1 of the measuring light is an indicator 20 for causing viewed far point to the subject's eye at the time of measurement. FIG. 6 is a block circuit diagram of the present auto-refractometer. Both the reflected light from the eye and the aiming light of the measurement light are light receiving sensors
The light is detected by the light receiving sensor 13 and sequentially converted into an image signal (electric signal) by the scanning of the light receiving sensor 13. This image signal is input to the comparator 31, the synchronization separation circuit 34, the image processing device 52, and the monitor 53 together with the scanning synchronization signal. The image signal input to the comparator 31 is obtained by binarizing an image signal of a higher level and an image signal of a lower level than a reference value corresponding to the luminance of the aiming light source set in the comparator 31, and extracting the image signal. Output to the circuit 33.
That is, the image signal of the reflection image of the eye to be examined is at a level lower than the reference value, and the image signal of the aiming light reflection image is at a level higher than the reference value. On the other hand, the synchronization signal input to the synchronization separation circuit 32 is separated into a horizontal synchronization signal and a vertical synchronization signal, the horizontal synchronization signal is sent to the X-axis reference generation circuit 34 and the Y-axis reference generation circuit 35, and the vertical synchronization signal is sent to the X-axis reference generation circuit 35. Each is input to the axis reference generation circuit 34. In the X-axis reference generating circuit 34, a timing signal indicating the X-axis passing through the center of the optical axis is generated from both the horizontal synchronizing signal and the vertical synchronizing signal, and is input to the AND circuit 33. On the other hand, the Y-axis reference generation circuit 35 includes a clock pulse generation circuit and a pulse counter, and indicates the Y-axis when the number of pulses from the horizontal synchronization signal input time coincides with the Y-axis passing through the optical axis center. The timing signal is input to the AND circuit 41 and the Y-axis-right reflection image width counter 38. The AND circuit 33 outputs the signal to the right reflected image detection circuit 3 only when the output signal from the comparator 31 is on the X-axis reference.
6. Output to the left reflected image detection circuit 37 and the left reflected image-Y axis width counter 39. The signal of the corneal reflected light of one (right) of the pair of aiming light sources 21 is output from the right reflected image detection circuit 36 for detecting the position, and the signal of the corneal reflected light of the other (left) is reflected in the left reflected image. Output from the detection circuit 37.
That is, the left reflection image detection circuit 37 is configured by a one-value counter, and outputs a pulse signal to the AND circuit 41 when one pulse signal is input from the AND circuit 33.
The right reflection image detection circuit 36 is constituted by a binary counter. When two pulse signals are input from the AND circuit 33, the pulse signal is converted to a Y-axis-right reflection image width counter.
Output to 38. Each counter 38, 39 measures the distance between the Y axis and each corneal reflection image. In the counter 39, the measurement is started by the signal from the AND circuit 33, and the measurement is stopped by the signal from the AND circuit 41. The AND circuit 41 outputs a stop signal to the counter 39 when signals are input from both the detection circuit 37 and the Y-axis reference generation circuit 35. This allows the counter
The calculation of 39 is stopped. The counter 39 outputs a count value corresponding to the distance from the left corneal reflection image to the Y axis to the comparison circuit 40. On the other hand, in the counter 38, the Y-axis reference generation circuit 35
The counting is started by the signal from the detecting circuit 36, and the counting is stopped by the signal from the detecting circuit 36. The counter 38 outputs a count value corresponding to the distance from the Y axis to the right corneal reflection image to the comparison circuit 40. The comparison circuit 40 determines whether or not the two count values are close to each other within an allowable range, that is, whether the left and right corneal reflection images are symmetrical with respect to the Y axis. A signal for instructing the start of measurement is output to. From the microcomputer 51, a signal for instructing the measurement light projecting system 1 to project the measurement light is output. 7 to 9 show a monitor display image (a) projected on the monitor 53, an image signal (b) on the X-axis reference (to be described later) of the light receiving sensor 13 in each state of aiming and distance adjustment, and the image thereof. FIG. 7 is a diagram showing each of the binarized signals (c) of the signal, FIG. 7 shows a state in which both the aiming and the distance are matched, FIG. 8 shows a state in which the distance is matched but the aiming is not matched, FIG. FIG. 9 shows a state in which the aim has been adjusted but the distance has not been adjusted. In the state where the aim and the distance are matched, both the eye to be examined and the image of the aiming light clearly appear at the center of the monitor image, as shown in FIG. The point light source patterns P _1,2 clearly appear at two points. That is, the signal of the point light source pattern _P1,2 (the signal from the light receiving sensor 13)
FIG. 7 (b) shows peaks PL1, ₂ of which the level is clear in the point light source pattern portion for every two points, and sets an appropriate reference value TL to the comparator 31 to output a signal of 2 points. By making the values (signals of the comparator 31), two pulse signals PS1, ₂ corresponding to each point light source pattern as shown in FIG. 7C are obtained on the basis of the X width (the AND circuit 33).
More signal). If the aiming error is very small even if there is an aiming error, two pulse signals PS _{1, 2} are output from the comparator 31 as in the cases of FIGS. 7 (b) and 7 (c). However, in this case, if the error is in the Y-axis direction, the image of the aiming light is not on the X-axis, so that no pulse is output from the AND circuit 33. Thereby, aiming in the Y-axis direction is determined. On the other hand, if the difference is thereafter in the X-axis direction, the distance between the image of each aiming light and the Y-axis is determined by the comparison circuit 40.
Are compared with each other, whereby the aiming in the X-axis direction is determined. Also, in a state where the distance is correct but the aim is not aligned (except when the aiming error is very small), when the error is large, the image of the eye to be examined clearly appears on the monitor screen, The light image does not appear on the monitor screen. Therefore, the image signal taken on the X-axis reference is almost flat or even with some peak signals,
As shown in FIG. 8 (b), a signal having a remarkable level peak exceeding the reference value in the comparator 31 is not obtained, and even in the case of the binarized signal, as shown in FIG. 8 (c). No pulse is obtained. Next, in a state where the aiming is performed but the distance is not, as shown in FIG. 9 (a), the image of the eye to be inspected appears at the center of the monitor screen but in a blurred state. No image appears. This is because the corneal reflection image does not reach the light receiving sensor 13 as described above with reference to FIG.
Therefore, the signal taken on the X axis reference is shown in FIG.
As shown in FIG. 9, only a signal having a low level and almost no peak is generally obtained, and no pulse is obtained in the binarized signal as shown in FIG. 9 (c). However, when the distance alignment error is very small, the aiming light appears on the monitor screen and a signal having a certain peak is input to the comparator 31.The peak value is smaller than the reference value, and the comparator 31 outputs a pulse. Is not output. As described above, in the auto-refractometer having the aiming / distance adjusting mechanism configured and operated, the measurer operates the apparatus so that the state of FIG. 8 or FIG. 9 changes from the state of FIG. Just by moving the main body back and forth and right and left, the measurement is automatically started at the timing when the aim and the distance are matched, so that the measurement can be performed without missing a good measurement timing.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an optical system of an auto-refractometer of an optical measuring device for eye examination according to one embodiment of the present invention;
FIG. 2 is a diagram schematically showing a light projecting optical system for measuring light in FIG. 1, FIG. 3 is a diagram schematically showing a light receiving optical system for measuring light in FIG. 1, and FIG. 4 is FIG. 5 (a), 5 (b), and 5 (c) schematically show the aiming / distance adjusting optical system in FIG.
(C) is a diagram showing the positional relationship between the aiming light source and the eye to be examined in the auto-refractometer of FIG. 1, FIG. 6 is a block circuit diagram of the auto-refractometer of FIG. 1,
7A and 7B show a state in which both the aim and the distance are matched, FIG. 7A shows a monitor image, FIG. 7B shows an image signal on the X-axis reference, and FIG. FIG. 8 shows a state where the distance is correct but the aim is not aligned, FIG. 8 (a) is a view showing a monitor image, and FIG. FIG. 9C is a diagram showing an image signal, FIG. 9C is a diagram showing a binarized image signal on the X-axis reference, FIG.
(A) is a diagram showing a monitor image, (b) is a diagram showing an image signal on the X-axis reference, and (c) is a diagram showing a binarized image signal on the X-axis reference. E: Eye to be examined, aE: Optical axis of eye to be inspected, a ₂ : Optical axis of measurement light, 13: Light receiving sensor, 15: Optical system for aiming and distance adjustment, 21: Optical source for aiming, 40 ... Comparison circuit

Claims (2)

(57) [Claims] A measuring light projecting system for projecting measuring light toward an eye to be inspected; a measuring light receiving system including a light receiving sensor for receiving reflected light from the eye; An aiming / distance adjusting means including an aiming / distance adjusting optical system (15) for aiming and adjusting the distance of the optical measuring device for eye inspection with respect to the eye to be inspected (E), and projecting the measuring light to the eye to be inspected. A measuring means for measuring the subject's eye based on the reflected light of the subject's eye obtained by the measuring light receiving system (10), and the light receiving sensor (13) comprises: The light receiving system optical axis (B) of (10) is arranged so as to coincide with the intersection of the X axis and the Y axis on the light receiving sensor (13). A pair of aiming light source means (21, 22) for irradiating a light beam toward They are arranged symmetrically to the X-axis direction with respect to the light receiving system optical axis (B), and,
The cornea of the eye to be inspected (E) is irradiated with a sufficiently thin light beam, and only when the distance adjustment and the aiming are achieved within a predetermined range, the respective corneal reflected lights are emitted from the aiming light sources (21). , 22) are arranged to be received by the light receiving sensor (13) through an optical axis parallel reflection path different from the aiming path of the light receiving sensor (13). First comparing means (31) for comparing the signal level of the image of the corneal reflected light with a reference value
When the first comparing means (31) determines that the signal levels of the two corneal reflection images are higher than the reference value, whether the two corneal reflection images are received on the X axis of the light receiving sensor (13) Determining means (31, 32, 33, 34) for determining whether or not the distance between each of the two corneal reflection images received on the X axis of the light receiving sensor (13) and the Y axis of the light receiving sensor (13) is obtained; The two distances calculated by the calculation means (35, 36, 37, 38, 39, 41) and the two distances calculated by the calculation means (35, 36, 37, 38, 39, 41) are compared, and the difference is calculated. A second output of a measurement light projection start signal to the measurement device when within the allowable range;
An optical measurement device for an eye examination, comprising: a comparison unit (40). 2. A measuring light projecting system (1) for projecting measuring light toward an eye to be inspected (E), and a measuring light receiving system (10) including a light receiving sensor (13) for receiving reflected light from the eye to be inspected. An aiming / distance adjusting means including an aiming / distance adjusting optical system (15) for aiming and adjusting the distance of the optical measuring device for eye inspection with respect to the eye to be inspected (E), and projecting the measuring light to the eye to be inspected. A measuring means for measuring the subject's eye based on the reflected light of the subject's eye obtained by the measuring light receiving system (10), and the light receiving sensor (13) comprises: The light receiving system optical axis (B) of (10) is arranged so as to coincide with the intersection of the X axis and the Y axis on the light receiving sensor (13). A pair of aiming light source means (21, 22) for irradiating a light beam toward They are arranged symmetrically to the X-axis direction with respect to the light receiving system optical axis (B), and,
The cornea of the eye to be inspected (E) is irradiated with a sufficiently thin light beam, and only when the distance adjustment and the aiming are achieved within a predetermined range, the respective corneal reflected lights are emitted from the aiming light sources (21). , 22) are arranged to be received by the light receiving sensor (13) through an optical axis parallel reflection path different from the aiming path of the light receiving sensor (13). And a comparator (31) for outputting an image signal representing a first and second corneal reflected light image corresponding to each light beam emitted from the first and second aiming light source means as a pulse signal by comparing the reference value with a reference value. A synchronization separation circuit (32) for separating a synchronization signal output together with an image signal from the light receiving sensor (13) into a horizontal synchronization signal and a vertical synchronization signal; and a horizontal synchronization signal and a vertical synchronization signal from the synchronization separation circuit (32). Based on the light receiving sensor ( An X-axis reference generation circuit (34) for generating an X-axis reference signal indicating that the image signal from 13) is on the X-axis of the light receiving sensor (13), a pulse signal from the comparator (31) and an X-axis reference A first AND circuit (33) for outputting a pulse signal when the X-axis reference signal from the generation circuit (34) is input; and a pulse signal from the first AND circuit (33). A first reflection image detection circuit (37) that outputs a pulse signal when the pulse signal is counted, and an image signal from the light reception sensor (13) is detected based on a horizontal synchronization signal from the synchronization separation circuit (32). (13) Y
A Y-axis reference signal generation circuit (35) for generating a Y-axis reference signal indicating on-axis; a pulse signal from the first reflected image detection circuit (37); and a Y signal from the Y-axis reference generation circuit (35) A second AND circuit (41) that outputs a stop signal when the axis reference signal is input; and a counting operation is started by a pulse signal from the first AND circuit (33), while a stop from the second AND circuit (41) is performed. A first reflection image-Y axis width counter (39) for outputting a first distance signal indicating the distance between the first corneal reflection image (P ₁ ) and the Y axis after stopping counting by a signal, and a first AND circuit ( 33) counting the pulse signal from the above, and outputting the pulse signal when the second pulse signal is counted.
The counting is started by the reflection image detection circuit (36) and the Y-axis reference signal from the Y-axis reference generation circuit (35), while the counting is stopped by the pulse signal from the second reflection image detection circuit (36). a second image of corneal reflection (P ₂₎ and the second reflecting image -Y axis width counter which outputs a second distance signal indicating the distance between the Y-axis (38), first, second reflection images -Y axis width Number from the counter (39,38)
A comparison circuit (40) for comparing the first distance with the second distance based on the second distance signal and outputting a measurement light projection start signal to the measuring device when the difference is within an allowable range; An optical measurement device for eye examination, comprising: