JPH0254B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for objectively and automatically measuring the refractive power of an eye. As an example of a conventional objective automatic eye refractive power measurement device, a measurement target projected onto the fundus of the eye to be examined is moved in the optical axis direction, a position where the measurement target is conjugate with the fundus is detected, and the measurement target at this time is There are known devices that calculate refractive power from the amount of movement. In this case, in order to measure the degree of astigmatism, this measurement must be carried out in each radial direction.
With this device, it is necessary to move the measurement target each time to measure the refractive power in each radial direction, which takes time, and the eye to be examined moves or the state of accommodation changes during the measurement. In addition, instructions to not move the eyes for a certain period of time make the examinee nervous, causing the examinee's eye to enter a different state of accommodation than usual, which results in the examinee suffering from long-term measurements and increasing the accuracy of the measurement. The decline is inevitable.

As another example, an apparatus is known that projects a pair of measurement beams onto the fundus of the eye to be examined and measures refractive power based on the amount of separation of the measurement beams on the fundus. However, in this case, there is a drawback that the amount of separation increases depending on the refractive power of the eye to be examined, resulting in a decrease in measurement accuracy. In other words, it is a measuring device with a substantially narrow measuring range.

The present invention aims to eliminate the drawbacks of the conventional objective type automatic eye refractive power measurement device, and its structural feature is that the two objects are at an angle to each other from the measurement target. A measurement target projection optical system that projects a plurality of light beams onto the fundus of the eye to be examined; a target imaging optical system that forms light from the measurement target image projected onto the fundus of the eye to be examined; A detection device detects the position of each target image formed from the light beam, and the target is fixed at a predetermined position on the optical axis, and the target is moved to a position substantially conjugate with the fundus of the eye to be examined using an electric signal from the detection device. a target position control system that moves the target, and further calculates the spherical power, astigmatic power, and astigmatic axis based on signals from the detecting device in at least three radial directions when the light beam from the moved target is rotated around the optical axis. and a refractive power calculation section. That is, in the present invention, the measurement target is fixed at a specific position, the refractive power in the radial direction is measured in this state, and the measurement target is moved and fixed based on the measurement results. In this state, refractive power is detected in at least three radial directions, and the spherical power, astigmatic power, and astigmatic axis are calculated from the detected values. As described above, the present invention has a fast measurement time, and by performing so-called preliminary measurements before the main measurement, it is possible to widen the measurement range of the refractive power of the eye to be examined and to perform highly accurate measurements for any refractive power. This is what I did.

Embodiments of the present invention will be described below with reference to the drawings. First, the measurement procedure in the apparatus of the example will be explained based on FIG. 1. The power switch is turned on, thereby fixing the measurement target and the fixation target at predetermined positions, and also fixing the light source of the optical system for projecting the measurement target at a fixed rotational position. A preliminary measurement is performed in this state, and the approximate spherical power is measured. Next, based on the measured values of the preliminary measurements,
The measurement target is moved and fixed at a position substantially conjugate with the fundus of the eye to be examined, and the fixation target is placed at a position farther than the measurement target to fog the eye to be examined. The main measurement is performed in this state. In this measurement, the light source of the optical system for projecting the measurement target is rotated around the optical axis, and measurements are made in at least three radial directions. Next, the spherical power, astigmatic power, and astigmatic axis are calculated from these measured values, and the results are displayed and the measurement is completed.

Next, the measurement principle of the present invention, specifically the principle of calculating the refractive power in a predetermined radial direction, will be explained. In FIG. 2, the deviation amount δ of two light beams that are separated and projected from the measurement target T through the light transmission objective lens 1 in an arbitrary radial direction θ of the pupil of the eye E to be examined and reach the fundus of the eye E differs depending on whether it is a refractive error, which is a refractive error in the crystalline lens of the eye to be examined, or an axial abnormality, which is an abnormality in the distance from the crystalline lens to the fundus of the eye. The angle β〓 formed by a line connecting two deviated points on the fundus from the center of the pupil of the subject's eye is tanβ〓=X(D〓−D _T ) in both cases of refractive and axial abnormalities. (1) X: Distance between two light beams in the pupil of the eye to be examined D〓: Refractive power of the eye to be examined in the radial direction θ in the pupil of the eye to be examined D _T : Diopter conversion value of the measurement target position.

Therefore, in the optical system shown in FIG. 3, if the aperture S is placed at a position that is conjugate with the pupil P of the eye E to be examined through the light-receiving objective lens 2, and the aperture S is placed at the front focal position of the relay lens 3, The reflected light from the two deviated points O ₁ and O ₂ on the fundus of the subject's eye can be extracted as a luminous flux whose principal ray passes through the pupil center P of the subject's eye, and the exit angle created by this luminous flux is at the pupil center of the subject's eye. It corresponds to the angle β formed by the line connecting P and O ₁ and O ₂ of the fundus. Here, the aperture S for the eye P to be examined is
The imaging magnification of is m, and the focal length of relay lens 3 _{is 3.}
When , the reflected light from O ₁ and O ₂ of the fundus of the examinee's eye forms an image off the optical axis created by the relay lens 3, and the image height △ from the optical axis is △ = ₃ tanmβ ... (2 ) becomes. Note that this image height Δ does not change even before and after the imaging position of the relay lens 3, since the aperture S of the relay lens 3 has a telecentric aperture relationship. When β is small or m=1, equation (2) can be set as △=m ₃ tanβ ...(3), and from equations (1) and (3), △=m ₃ D _T ) ...(4) Then, if the image height △ of the relay lens 3 is measured,
The refractive power D of the eye to be examined in the radial direction θ can be calculated.

As shown in FIG. 4, this apparatus based on the above principle includes a target projection optical system 50 that projects a measurement target onto the fundus of the eye to be examined, and a target light receiving optical system that projects an image of the measurement target on the fundus of the eye to be examined onto a measurement optical system 51. 52, consisting of a measurement optical system 51 that detects refractive power from a measurement target image, a fixation target system 53 that fixes the line of sight of the eye to be examined, and an aiming optical system 54 that indicates the positional relationship between the eye to be examined and this device; Each optical system will be explained in detail below.

As shown in FIG. 4, the target projection optical system 50 includes a pair of infrared light sources 1a and 1b arranged around the optical axis, a condenser lens 2a that focuses the light from the infrared light sources 1a and 1b, respectively, and 2b, a collimator lens 3 for producing parallel light, a measurement target 5 having a circular aperture stop 4, an imaging lens 6, a projection imaging lens 7, a half mirror 8 for infrared light, and a mirror for reflecting infrared light in the long wavelength region. It is composed of a dichroic mirror 9 having a characteristic of transmitting a visible part and infrared light in the vicinity thereof. The pair of infrared light sources 1a, 1b are turned on alternately at a high speed, and the two sources 1a, 1b are integrally configured to be rotatable around the optical axis, and the measurement target 5 is moved in the optical axis direction. configured as possible.

In the above configuration, a pair of infrared light sources 1a, 1
The light from b is condensed by condensing lenses 2a and 2b, respectively, and further converted into parallel light by a collimator lens 3, which obliquely enters a circular aperture stop 4. The light that has passed through the circular aperture diaphragm 4 is imaged at a point _P1 by the imaging lens 6, and then enters the eye E through the projection imaging lens 7, half mirror 8, and dichroic mirror 9. . Here, the images of the infrared light sources 1a and 1b are formed at the pupil position of the eye E to be examined, and the circular aperture diaphragm 4 of the measurement target 5 is formed.
The image is formed on the fundus _P2 of the eye to be examined. When the measurement target 5 and the fundus _P2 of the eye E are in a conjugate positional relationship, the image of the circular aperture diaphragm 4 illuminated by the light from the infrared light source 1a and the light from the infrared light source 1b are combined. The thus illuminated image of the circular aperture stop 4 is formed at the same position on the fundus _P2 . On the other hand, the measurement target 5 and the fundus of the eye E to be examined
When _P2 is not in a conjugate positional relationship, the images of the circular aperture stop 4 illuminated by the light from each of the infrared light sources are connected to two separate locations on the fundus _P2 . In the present invention, the fundus of the circular aperture diaphragm 4 of the measurement target 5 fixed on the optical axis is
Distinguishing whether the images at P ₂ match or separate by alternately lighting the infrared light sources 1a and 1b;
When they are separated, the separation distance is measured, and the refractive power of the eye to be examined is calculated from the measured value and the position of the measurement target at that time.

As shown in FIG. 4, the target light receiving optical system 52 is arranged at a position conjugate with the cornea of the eye to be examined with respect to the dichroic mirror 9, the half mirror 8, the light receiving objective lens 10, the mirror 11, and the light receiving objective lens 10. It is composed of a corneal reflected light blocking diaphragm 12 and a relay lens 13. As shown in FIG. 5, the corneal reflected light blocking diaphragm 12 is a diaphragm plate that is a substantially circular hole and has two protruding light blocking portions 12a and 12b symmetrical with respect to the optical axis passing position. Further, the corneal reflected light blocking diaphragm 12 is configured to rotate in conjunction with the rotational movement of the infrared light sources 1a and 1b when they rotate around the optical axis.
Further, the corneal reflected light blocking diaphragm 12 is arranged at the front focal point of the relay lens 13, and the projection optical system using the relay lens 13 is constructed in a telecentric optical manner. The relay lens 13 is configured to be movable in the optical axis direction in conjunction with the measurement target.

In the above configuration, the measurement target image of the fundus P ₂ of the eye to be examined includes the dichroic mirror 9, the half mirror 8, the light receiving objective lens 10, the mirror 11,
It is projected by the relay lens 13 into the measurement optical system 51, which will be explained in detail later. At this time, harmful reflected light from the cornea of the eye to be examined is removed by the protruding blocking portions 12a and 12b of the reflected light blocking diaphragm 12. Also,
Since the corneal reflected light blocking diaphragm 12 and the relay lens 13 constitute a telecentric optical system, the measurement target image formed on the measurement optical system 51 is composed of a luminous flux from the principal ray parallel to the optical axis. The central position of the circular hole image, which is the measurement target image, does not shift even before and after the imaging position.

As shown in FIG. 6, the measurement optical system 51 includes an X-direction detection system 56 consisting of a half mirror 15, a mirror 16, a relay lens 17, a mirror 18, a chopper 19, a condenser lens 20, and a light receiving element 21; Mirror 22, relay lens 23,
Chopper 19, condensing lens 24 and light receiving element 2
A Y direction detection system 57 consisting of 5, a light emitting element 26,
It is composed of condensing lenses 27 and 28 and a reference signal generation system 58 consisting of a light receiving element 29. The chopper 19 has a group of continuous slits in the circumferential direction and rotates around the optical axis.

In the above configuration, a measurement target image of the fundus P ₂ of the eye to be examined is projected near the upper part 19 a of the chopper 19 by the target light receiving optical system 52 and the X-direction detection system 56 . At the same time, a measurement target image of the fundus P ₂ of the eye to be examined is projected near the side 19b of the chopper 19 by the target light receiving optical system 52 and the Y-direction detection system 57. Here, the measurement target 5 and the fundus of the examined eye P ₂
If they are not in a conjugate relationship, as shown in FIG.
It is projected onto a group of slits separated by Δx in the X direction and Δy in the Y direction.

In the above configuration, the signal from the light receiving element 21 when the infrared light source 1a is turned on and the circular aperture image 30a created by the light is scanned by the chopper 19, and the circular aperture image created by the light when the infrared light source 1b is turned on. Δx is calculated from the phase difference between the signal from the light receiving element 21 and the signal from the light receiving element 21 when the chopper 19 scans the signal 30b. Similarly, Δy is calculated from the phase difference between the signals from the light receiving element 25 when the chopper 19 scans the circular aperture images 30a' and 30b'. Here, the conjugate relationship between the measurement target 5 and the fundus P ₂ of the eye to be examined, the degree of astigmatism of the eye E to be examined, and the circular aperture images 30 a and 30 on the stopper 19 are explained.
Explain the relationship b. It is assumed that the light sources 1a and 1b are arranged side by side at positions rotated by θ from the vertical direction. That is, it is assumed that the measurement radial direction is a direction rotated by θ from the vertical direction.

(1) When the measurement target 5 and the fundus _P2 of the eye to be examined are in a conjugate relationship and the eye E to be examined does not have astigmatism, circular aperture images 30a and 30b are formed on the stopper 19 as shown in FIG. 8A. It is projected to overlap the optical axis passing position. That is, △x=
Δy=0.

(2) When the measurement target 5 and the fundus P ₂ of the eye to be examined are not in a conjugate relationship, and the eye E to be examined does not include astigmatism or includes astigmatism, the principal axis of the eye to be examined E and the diameter measured by the light sources 1a and 1b. When the line directions match, the circular aperture images 30a and 30b are projected separately in the measurement radial direction on the chopper 19, as shown in FIG. 8B.

(3) When the measurement target 5 and the fundus P ₂ of the eye to be examined are not in a conjugate relationship, the eye E to be examined includes astigmatism, and the main meridian of the eye E to be examined and the direction of the measurement meridian consisting of the light sources 1a and 1b are different. As shown in FIG. 8C, circular aperture images 30a and 30b are separately projected on the chopper 19 in the measurement radial direction and in a direction perpendicular thereto.

In this embodiment, as shown in FIG. 8, the separation amounts △x and △y in the horizontal and vertical directions are detected, and the detection results are converted into separation amounts in the measurement radius direction.
This is to detect the eye refractive power in the measurement radial direction.

By performing the above conversion, the light sources 1a and 1b
By simply rotating the lens, the eye refractive power in each measurement radial direction can be determined.

As shown in FIG. 4, the fixation target system 53 includes a visible light source 31, a condenser lens 32, a fixation target 33 movable in the optical axis direction, a mirror 34, a projection lens 35, and a red light source that reflects visible light. It is composed of a dichroic mirror 36 that transmits external light.

In the above configuration, the light from the visible light source 31 is directed to the fixation target 33 via the condensing lens 32.
to illuminate. The light from the fixation target 33 passes through a mirror 34, a projection lens 35, a dichroic mirror 36, and the dichroic mirror 9, and is projected onto the eye E to be examined. The subject is
The collimation direction is fixed by gazing at the fixation target 33. Further, the eye to be examined is required to always be in a far-viewing state, and the fixation target 33 is movable in the optical axis direction and adjusted to a position where the eye to be examined is in a far-viewing state.

The aiming optical system 54 includes a half mirror 9, a dichroic mirror 36, a projection lens 36', a half mirror 37, and an image pickup tube 38 arranged on the same optical axis.
In addition, a light source 40 is placed on the reflection optical axis of the half mirror 37,
It is configured by arranging a condenser lens 41, a collimating plate 42, a mirror 44, and a projection lens 45. Image tube 38
is connected to a monitor television 39. As shown in FIG. 9, the collimating plate 42 has a collimating scale 43 having a circle in the center and radiation around the circle.

In the aiming optical system configured as above,
An image of the anterior segment of the eye E to be examined by the projection lens 36' and an image of the collimation scale 43 by the projection lens 45 are projected onto the image pickup tube 38 in a superimposed manner. The examiner sees on the monitor television 39 that the center of the pupil image of the eye to be examined and the image of the collimation scale 43 are aligned, and the optical axis of the eye to be examined and the optical axes of the target projection optical system 50 and the target light receiving optical system 52 are aligned. Move the device vertically, horizontally, and horizontally relative to the eye to be examined so that the

Next, the configuration of the electric circuit of this device will be explained based on the block diagram of FIG. The control circuit 101 is
Power switch 102, measurement switch 103, chopper drive circuit 104, light source drive circuit 105, measurement target drive circuit 106, fixation target drive circuit 107, measurement target light source rotation drive circuit 108, measurement detection section 109, and arithmetic processing section 110
and are controlled by a predetermined program.

The chopper drive circuit 104 is connected to and drives a motor 112 that rotates the chopper 19. The light source driving circuit 105 is connected to the reference signal light emitting element 26 and the measurement target light sources 1a and 1b, and lights them. Measurement target drive circuit 1
06 is connected to and drives a motor 114 that moves the measurement target 5 on the optical axis. A fixation target drive circuit 107 is connected to and drives a motor 116 that moves the fixation target on the optical axis. The measurement target light source rotation drive circuit 108 is connected to a motor 118 that rotates the measurement target 5 around the optical axis. The light receiving element 29 receives the light emitted by the reference signal light emitting element 26 and passing through the chopper 19.
A reference signal is input to the amplifier circuit 120. The amplifier circuit 120 includes a waveform shaping circuit 122 and a waveform shaping circuit 1.
22 is connected to a first phase difference detection circuit 124 and a second phase difference detection circuit 126. A light receiving element 21 that receives the light emitted by the measurement target light sources 1a and 1b and passed through the upper part 19a of the chopper 19.
is connected to the amplifier circuit 127, and the amplifier circuit 127 is connected to the AGC circuit 128.
is connected to the waveform shaping circuit 130, and the waveform shaping circuit 130 is connected to the first phase difference detection circuit 124. Similarly, a light receiving element 25 that receives the light emitted by the measurement target light sources 1a and 1b and passed through the side part 19b of the chopper 19 is connected to an amplifier circuit 132, and the amplifier circuit 132 is further connected to an AGC circuit 134.
The AGC circuit 134 connects the waveform shaping circuit 136 to
The waveform shaping circuit 136 is the second phase difference detection circuit 126
is connected to. The first phase difference detection circuit 124 detects the phase difference between the reference short rectangular wave output from the waveform shaping circuit 122 and the rectangular wave output from the waveform shaping circuit 130, and outputs it as a phase difference signal X _a . Similarly,
The second phase difference detection circuit 126 is a waveform shaping circuit 122
The phase difference between the reference rectangular wave and the rectangular wave output from the waveform shaping circuit 136 is detected and output as a phase difference signal Y _a . The first phase difference detection circuit 124 and the second phase difference detection circuit 126 are connected to a comparison circuit 138, and the comparison circuit 138 is further connected to the arithmetic processing section 110.
is connected to.

The comparison circuit 138 includes light emitting elements 1a and 1b.
The phase difference ΔX between the phase difference signals X _a and X _b output by the first phase difference detection circuit 124 when the first phase difference detection circuit 124 is turned on, and the second phase difference ΔX when the light emitting elements 1a and 1b are turned on
Phase difference signal Y _a outputted by the phase difference detection circuit 126
The phase difference ΔY between and Y _b is calculated.

These phase differences ΔX and ΔY correspond to the separation amounts Δx and Δy of the circular aperture images 30a and 30b in the X and Y directions in FIG. 8, respectively. Arithmetic processing unit 110
is the separation amount in the measurement meridian direction from the rotational position angle θ _i of the measurement target light source, which is a signal from the target light source drive circuit, and the above phase differences △X _i , △Y _i using the following equation (5). _The phase _{difference △ P pi} corresponding _to The refractive power Dθ of the eye to be examined in the measurement meridian direction θ is calculated according to the equation (4) described above based on the principle of calculation based on the power. In the case of this measurement, Dθ (D ₁ , D ₂ , D ₃ ) in at least three radial directions is calculated, and from this result, the spherical refractive power, astigmatic power, and astigmatic axis of the eye to be examined are determined and displayed on the display 142. Output.

The operation of the electric circuit configured as described above is as follows. The power switch 102 is turned on, and the optical axis of the subject is made to coincide with the optical axes of the target projection optical system 50 and the target light receiving optical system 52 using the aiming optical system 54. Also, the control circuit 1
01, the chopper 19 rotates, the reference optical element 26 lights up, and the light sources 1a and 1b of the target projection optical system alternately light up. These rotations and lighting continue until the measurement is completed. Furthermore, under the control of the control circuit 101, the measurement target drive circuit 106 drives the motor 114 to move the measurement target 5 to a predetermined position, for example, +6 diopters, and also moves the fixation target drive circuit 10
7 drives the motor 116 to move the fixation target 2
3 to a predetermined position, for example, +20 dayopter position, and then move the measurement target light source rotation drive circuit 1
08 drives the motor 118 to rotationally move the alignment and direction of the light sources 1a and 1b of the measurement target 5 to a vertical position (rotation angle θ=0). This completes the preparation for preliminary measurements.

Next, under the control of the control circuit 101, the light receiving element 2
1, 25, and 29 receive the respective signal lights,
According to the circuit configuration described above, the arithmetic processing unit 110 calculates a phase difference ΔPθ corresponding to the amount of separation of the aperture aperture images in the meridian plane (θ=0). This ΔPθ is converted into the separation amount of the hole aperture image, and the refractive power of the eye to be examined in the meridian plane (θ=0) is calculated from the position of the measurement target 5 at that time. This calculation result is converted into the amount of movement of the measurement target 5 and is sent to the control circuit 101.
is input. This signal causes the control circuit 101
controls the measurement target drive circuit 106, and uses the motor 114 to move the measurement target 5 to a position corresponding to the refractive power of the eye to be examined in the measurement connection direction at θ=0, that is, to a position where the measurement target 5 and the fundus of the eye to be examined have an approximately conjugate relationship. moved further away from the location. In this state, the measurement target 5 and the fixation target 23 are fixed, and the following main measurement begins. The position of the measurement target 5, which has been moved and fixed as a result of the preliminary measurement, is not changed during the main measurement.

The preliminary measurement described above is effective for further improving the accuracy of the following main measurement by setting the position of the measurement target 5 at a position that is substantially conjugate with the fundus of the eye to be examined.

In this measurement, the detection described in the preliminary measurement is performed in the same way. In this measurement, the measurement target light source rotation drive circuit 108 drives the motor 118 in response to a signal from the control circuit 101 to sequentially rotate the measurement target light sources 1a and 1b around the optical axis, so that the refractive power of the eye to be examined in the measurement meridian direction is Calculate Dθ. This measurement is performed in at least three meridian directions, and _the refractive powers of the eye to be examined at that time are Dθ ₁ , _{Dθ 2 , and} Dθ _{3 .} 2θ ₃ +α) From these results, the spherical power A, the astigmatic power B, and the astigmatic axis α are calculated, and the final measurement result is displayed on the display 142. The greater the number of measurement meridian directions, the higher the measurement accuracy, and A, B, and C are calculated by the least divert method. In this embodiment, preliminary measurements were carried out in one meridian direction, but it goes without saying that measurements may be carried out in three meridian directions. Further, after performing a preliminary measurement in one meridian direction, it is also possible to perform preliminary measurements again in three meridian directions to further improve the accuracy of the main measurement.

As described above, according to the present invention, the measurement speed can be increased by performing measurements with the measurement target fixed, and by performing preliminary measurements before the actual measurement, the measurement range can be expanded and the measurement speed can be increased. This makes it possible to measure accuracy.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the measurement procedure of the embodiment of the present invention, Figs. 2 and 3 are explanatory diagrams of the measurement principle of the embodiment, Fig. 4 is an optical diagram of the embodiment, and Fig. 5 is a diagram of the embodiment. A front view of the corneal reflected light blocking diaphragm, FIG. 6 is an optical diagram of the measurement optical system of the example, FIG. 7 is an explanatory diagram of the measurement principle of the measurement optical system shown in FIG. 6, and FIG. 8 is the same measurement optical system. FIG. 9 is a front view of the fixation target of the embodiment, and FIG. 10 is a block diagram of the electric circuit of the embodiment. 1a, 1b... Infrared light source, 4... Circular aperture stop, 7... Imaging lens for projection, 8... Half mirror related to infrared light, 9... Dichroic mirror, 21... Light receiving element, 29... Light receiving element, 50
... Target projection optical system, 51 ... Measurement optical system, 52 ... Target light receiving optical system, 53 ... Fixation target system, 54 ... Aiming optical system, 101 ... Control circuit, 102 ... Power switch, 103 ...Measurement switch, 104...Chopper drive circuit, 10
5...Light source drive circuit, 106...Measurement target drive circuit, 107...Fixation target drive circuit,
108...Measurement target light source rotation drive circuit, 1
09...Measurement detection section, 110...Arithmetic processing section, 1
42...Indicator.

Claims (1)

[Claims] 1. A measurement target projection optical system that projects a plurality of light beams having angles to each other from a measurement target onto the fundus of the eye to be examined, and a target imaging optical system that forms light from the measurement target image projected onto the fundus of the eye to be examined. , a detection device for detecting the position of each target image formed from a plurality of light beams by the target imaging optical system, and a detection device for detecting the target by an electric signal from the detection device by the target fixed at a predetermined position on the optical axis. a target position control system for moving the target to a position substantially conjugate with the fundus of the eye to be examined;
The spherical power, astigmatic power,
1. An objective automatic eye refractive power measurement device, comprising: a refractive power calculation unit that calculates an astigmatic axis.