JP2630956B2 - Automatic eye refractive power measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic eye refractive power measuring device that objectively and automatically measures the refractive power of a subject.

[Prior Art] Conventionally, a measurement target illuminated by near-infrared light is projected onto the fundus of the eye to be inspected, the projected image is photoelectrically detected, and the positions of the measurement target and the light receiving unit are defined as the fundus conjugate position with respect to one meridian. After moving the optical member in the direction of the optical axis so that it coincides with the optical member, the optical member is fixed, and the measurement target and the light receiving unit are rotated relative to the eye to be inspected. There is known a method (first method) of measuring the refractive power of the eye by detecting the amount of displacement of the eye.

In order to improve this, JP-A-61-259641
As described in Japanese Patent Application Laid-Open Publication No. H10-260, a method (second method) in which the point at which the optical member is moved and fixed in the optical axis direction is set to a position corresponding to the refractive power at the 45 ° or 135 ° meridian of the eye to be examined is proposed. Have been.

[Problems to be Solved by the Invention] However, according to the first method, when the astigmatism of the eye to be examined is large, that is, when the difference in refractive power in each meridian is large, the measurement target image on the light receiving section is large. As the amount of displacement increases and the conjugate relationship between the fundus and the light receiving unit is greatly disturbed, the measurement target image on the light receiving unit is blurred and becomes an unclear image. For this reason, there arises a problem that the detection accuracy for the deviation amount in the light receiving unit is reduced, and the measurement accuracy of the refractive power is deteriorated. In order to prevent this, there is a method to reduce the degree of blur by placing a small stop at the conjugate position with the cornea of the subject's eye and narrowing down the light beam incident on the light receiving unit, but the light amount is greatly reduced Therefore, there is a problem that a noise component from the light receiving unit relatively increases, which leads to a decrease in accuracy.

The second method is straight astigmatism (strong main meridian 90 ゜. Weak main meridian)
180 °) or astigmatism (strong main meridian 180; weak main meridian 90 °) is relatively large, so the accuracy is relatively better based on the refractive power at 45 ° or 135 ° in the middle. However, when the eye to be examined is obliquely astigmatic, there is no effect, and there is a problem that the measurement accuracy of the strongly obliquely astigmatic eye is reduced.

SUMMARY OF THE INVENTION In view of the above-described problems of the related art, an object of the present invention is to stably operate in a short time without adding a special mechanism, regardless of the astigmatic axis angle of the eye to be inspected, and always stably. The goal is to provide a way to minimize the amount.

Means for Solving the Problems In order to achieve the above object, the present invention provides an index projection optical system for projecting a measurement index onto the fundus of the eye to be inspected, a light beam reflected by the fundus of the eye to be inspected to a light receiving element, and a measurement index An index-of-index detecting optical system for detecting the position of the index, the two-meridian refractive power calculating means for measuring the refractive power in two orthogonal meridian directions based on the detection result of the index detecting optical system And an average refractive power calculating means for calculating an average of the refractive power in the two meridian directions by the two meridian refractive power calculating means, and for making the fundus of the eye to be examined substantially conjugate with the measurement index and the light receiving surface of the light receiving element. A moving means for moving the optical distance of the measurement index and the light receiving element to the fundus of the eye to be examined based on the average refractive power, with the measurement index and the light receiving element fixed at the position moved by the moving means. It is characterized by comprising a signal generating means for starting the main measurement, and a refractive power calculating means for calculating the refractive power of the eye to be examined based on the amount of movement of the moving means and the output of the light receiving element.

More specifically, the present invention is based on the following findings.

Assuming that the refractive power of the eye to be examined in the meridian in the θ direction is Dθ, the average spherical power is SE, the astigmatic power is C, and the astigmatic axis is Ax,
There is the following relationship.

Dθ = SE + Ccos (θ−Ax) where Dθ is the refractive power D (θ + 90) in the orthogonal direction.
゜) becomes D (θ + 90 °) = SE−Ccos (θ−Ax), Becomes

That is, the refractive power in any two orthogonal meridians is measured, and since the average is the average spherical power, the positions of the measurement target and the light receiving unit are moved to the corresponding positions and then fixed, and the measurement target and By rotating the light receiving unit with respect to the optical axis and measuring the refractive power of each meridian, the amount of blur on the light receiving unit can be minimized,
You can always obtain stable measurement accuracy.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an arrangement diagram showing an optical system of an eye refractive power measuring device utilizing the present invention.

In FIG. 1, 1 is a projection optical system, 2 is a light receiving optical system,
Reference numeral 3 denotes a target optical system, and reference numeral 4 denotes a shared optical system shared by the projection optical system 1 and the target optical system 3.

5 indicates an eye to be examined, 6 indicates a corneal position of the eye to be inspected, and 7 indicates a fundus position of the eye to be inspected.

The projection optical system 1 is connected to the target 8 via the shared optical system 4.
Is projected on the fundus 7 of the eye 5 to be examined. The light receiving optical system 2 functions to form a target image formed on the fundus 7 on the detection element 9. The index optical system 3 functions to project the fog chart 10 onto the fundus 7 via the shared optical system 4.

The projection optical system 1 emits near-infrared light, and includes infrared light sources 11a and 11b, a relay lens 12, and a target 8 which are located symmetrically with respect to the optical system optical axis. As shown in FIG. 2, the target 8 has a rectangular opening 36 formed therein, and its longitudinal direction is arranged at right angles to a line connecting the infrared light sources 11a and 11b. Further, the projection optical system 1 can rotate integrally with the optical axis.

Next, the index optical system 3 includes a lamp 13 that emits visible light, a condenser lens 14, and a fog chart 10. The fog chart 10 is directed to a cold mirror 15 in the shared optical system 4 and a target 8 in the projection optical system 1. It is located away from the strong point 16 by an amount corresponding to the amount of fog. Further, the visual acuity chart 18 can be arranged on the optical axis of the index optical system 3 by switching to the fog chart 10, and in this case, it is arranged at a position of a point 16 conjugate with the target 8.

The conjugate optical system 4 includes a cold mirror 15 that transmits infrared light and reflects visible light, and a concave cylindrical lens 1 for correcting astigmatism.
9, a convex lens 20, a prism 21, a relay lens 22, a prism 23 movable in the optical axis direction, an objective lens group 24, and a beam splitter 25. An image is formed on the fundus 7. Concave cylindrical lens 19 for correcting astigmatism, convex cylindrical lens
Reference numeral 20 denotes a cylindrical lens unit having the same power and a different sign, and constitutes a crosstalk cylindrical lens capable of continuously changing the astigmatic power by rotating the cylindrical axes relatively to each other, and includes an objective lens. The lens 24 and the relay lens 22 are arranged at positions conjugate to the cornea 6 of the subject's eye 5. The objective lens group 24 comprises a retrofocus type lens composed of a concave lens and a convex lens.
Since the principal point can be placed on the side of the subject's eye without changing the focal length as compared with a lens composed of two lenses, the distance between the subject's eye 5 and the beam splitter 25, that is, the working distance of the device can be increased. Will be possible.

The beam splitter 25 functions as a half mirror for transmitting visible light and for infrared light.

In the present embodiment, the cornea 6 of the eye 5 to be examined coincides with the image-side focal point of the objective lens 24, and the relay lens 22 is arranged so that the object-side focal point 26 of the objective lens 24 and the target 8 are conjugate and the projection magnification is equal. Have been. Therefore, even if the prism 23 moves, the object-side focal position of the relay lens 22 is always conjugate with the cornea 6 of the subject's eye 5, and the cylindrical lens is located at the conjugate position.
19 and 20 are arranged. Since the infrared light sources 11a and 11b are further conjugated to the object-side focal position of the relay lens 22 via the relay lens 12, the images of the infrared light sources 11a and 11b are always formed on the cornea 6 of the eye 5 to be inspected.

Next, the light receiving optical system is composed of a mirror 27, an objective lens group 28, a prism 29, a relay lens 30, a prism 31, an aperture 32, and a detection element 9, and the pair lens group 28 is composed of the objective lens group 24 of the conjugate optical system 4. The prism 29 has the same focal length as that of the optical system 4, and the prism 29 can move in the optical axis direction integrally with the prism 23 of the shared optical system 4.

The object-side focal point 33 of the objective lens group 28 is conjugate to the detection element 9 via the relay lens 30, and an aperture 32 is disposed at the focal position of the relay lens. For this reason, the diaphragm 32 is always conjugate with the cornea 6 to be examined, and as shown in FIG.
A black spot at a position conjugate with the infrared light sources 11a and 11b that form an image on the cornea 6
32a and 32b are arranged and function to cut corneal reflected light. By moving the prism 29, the detection element 9 always maintains a conjugate positional relationship with the fundus 7 of the non-optometric eye 5 with respect to the non-emmetropic eye. The detection element 9 is preferably a one-dimensional position detection element in the present embodiment, has a detection direction in a direction connecting the black points 32a and 32b of the stop 32, and the stop 32 and the detection element 9 rotate together with the projection optical system.

As shown in FIG. 4, the beam splitter 34 disposed on the common optical system 4 has an aperture 35 at a position conjugate with the focal length 26 of the objective lens group 24, and
, The light emitted from the aperture becomes parallel light and reaches the cornea 6, so that a light source image is formed on the fundus side by a distance of 1/2 of the corneal curvature radius.

Beam splitter 35 arranged on light receiving optical system 2
Is for guiding the anterior segment of the subject's eye 5 to the infrared TV camera 41, as shown in FIG. 5, and 40 is an imaging lens. Further, on the beam splitter 35, a reticle 43 illuminated by the infrared light 42 is imaged on the TV camera imaging surface 45 by the lens 44, so that the reticle 43 is formed on the cornea 6 by a TV monitor or the like (not shown). By adjusting the position of the eye-refractive-power measuring device so that the bright point of the opening 38 coincides with the center of the reticle 43, the eye 5 to be examined can be coincident with the measurement optical axis.

Next, the measurement principle of the eye refractive power measuring device based on the above configuration will be described.

In FIG. 1, when the target 8 and the fundus of the eye to be examined 7 are at the conjugate position, the image position when the infrared light source 11a is turned on is 1
The image position when 1b is turned on coincides with each other, but when the fundus of the eye to be examined 7 and the target 8 are in a non-conjugated position, they are separated from each other, and on the detection element 9, as shown in FIG. Is detected.

 Now, the refractive index of the eye to be examined is: D: the distance between the infrared light sources 11a and 11b: x: the amount of displacement on the detection element ... y: the imaging magnification of the relay lens 30 ... m: the focal length of the objective lens groups 24, 28 Let f be the following equation.

Furthermore, the amount of movement when the prisms 23 and 29 are moved in the optical axis direction to make the amount of displacement y on the detection element zero is:
It is expressed by the following equation.

From equations (1) and (2) Now, with respect to the subject's eye 5, the infrared light sources 11a and 11b
And the detection element 9 are arranged, the refractive power of the eye 5 to be examined in the horizontal meridian is obtained. If this is D, and the movement amount of the prisms 23 and 29 at this time is Z, from the equation (2), Is represented by

Then rotated integrally while fixing the projection optical system 1 and the sensing element 9 and the prism 23 and 29, it detects the shift amount y ₂ of on sensing elements 9 at this time. Eye power at this meridian
D ₂ is obtained from equations (1) and (4). Is represented by Similarly, the projection optical system and the detection element 9
And measure the refractive power of the eye at each meridian.

Assuming that the refractive power at each meridian having an angle of θ with respect to the horizontal direction is Dθ, the average spherical power SE, astigmatic power C, and astigmatic axis Ax of the subject's eye have the following relationship.

Dθ = SE + Ccos (θ−Ax) (6) Since the unknowns in equation (6) are three, SE, C, and Ax, it can be calculated by measuring the refractive power Dθ in at least three meridian directions. However, by obtaining S, C, and Ax by the least-squares method from the refractive power of more meridians, a highly reliable result can be obtained.

Next, an actual measurement operation including the operation of the index optical system 3 will be described.

1) Confirmation of naked eye visual acuity As a state before the start of the objective automatic measurement, the visual acuity chart 18 in FIG. 1 is switched to the conjugate position 16 with the target 8 on the index optical system 3, and the fog chart 10 is Set outside measurement optical axis.

Further, the prisms 23 and 29 are provided at the focal position 26 of the objective lens group.
And the target 8 are set to a conjugate position, that is, a position where the fundus 7 of the subject eye 5 and the position 16 of the visual acuity chart 18 are conjugate to the emmetropic eye. For this reason, the subject's eye 5
By observing the visual acuity chart 18, the naked eye visual acuity can be confirmed, and the subject can be made aware of the necessity of refraction inspection and refraction correction to be performed in the future.

2) Preliminary Measurement The operation related to the preliminary measurement will be described based on the flowchart shown in FIG.

After the examiner correctly positions the eye 5 and the measuring device, the examiner presses the measuring switch 50 in FIG.

At this time, the infrared light sources 11a and 11b and the detecting element 9 are set so as to be located in a direction perpendicular to the eye to be examined, unlike FIG. The prisms 23 and 29 are placed so that the target 8 is located at zero diopter. The chart is driven by a chart switching motor 57 via a drive circuit 56,
Switch to fog chart 10.

After that, the infrared light source 11a emits light via the light source driving circuit 52 according to a command from the CPU 51. The target image formed on the fundus 7 of the subject's eye 5 is reflected by the fundus and forms an image again on the detecting element 9 (step 100).

The charges accumulated in the detection element 9 which is a one-dimensional CCD are sequentially taken out, amplified by an amplifier 53, converted into a digital value by an A / D converter 54, and stored in a RAM 55. Next, similarly, the infrared light source 11b emits light, the signal from the detecting element 9 at this time is stored in the RAM 55, and the CPU 51 detects the displacement y in FIG. 6 based on each value (step 101).

In step 102, based on the equation (3), the prism 2
The movement amount Z of 3, 29 is calculated, and in step 103, the prism driving motor 59 is driven via the drive circuit 58 to move the prisms 23, 29 based on the calculated movement amount Z.

Next, the refractive power of the vertical meridian is calculated based on the amount of movement of the prism 23 (step 104).

At this time, since the fundus of the eye 5 to be examined is conjugate with the conjugate point 16 of the target 8, the cloud fog chart 10 is visually recognized as being blurred.

When the refractive error of the eye 5 is large (step 105)
Since the target image formed on the detection element 9 is unclear and the calculated movement amount Z is inaccurate, the infrared light sources 11a and 11b are turned on again after the movement, and the displacement amount y on the detection element 9
Is calculated, and the movement amount Z is calculated. The prisms 23 and 29 are shifted to the minus side so that the eye 5 to be examined can clearly see the fog chart 10 (step 106). This amount corresponds to half of the interval l between the conjugate point 16 and the fog chart 10.

Therefore, the movement amount of the prisms 23 and 29 is Becomes

The infrared light sources 11a and 11b are turned on again, and the vertical meridian refracting power Dv in a state where the subject's eye clearly sees the fog chart 10 is calculated from the equation (5).

Next, the projection optical system 1 and the detection element 9 are rotated by 90 ° by the drive circuit 60 and the motor 61 (step 107).

After rotating the projection optical system 1 and the detection element 9 by 90 °, the distance between target images on the horizontal meridian is detected by the light receiving element, similarly to the vertical meridian (step 108), and the refractive power of the horizontal meridian is calculated (step 109). ).

The average refractive power DSE is calculated from the values of Dv and DH, the amount of movement with respect to the average refractive power DSE is calculated by the equations (2) and (7), and the prisms 23 and 29 are moved (step 111). In this case, the conjugate point of the fundus 7 at the average refractive power of the eye 5 is
Since the target 8 is located at the distance 1 on the light source side and conjugate with the fog chart 10 and the minimum circle of confusion of the fog chart image coincides with the fundus 7, the eye 5 to be examined is the fog chart.
10 looks the sharpest.

3) Cloud fog Next, the prisms 23 and 29 are gradually moved to the right in FIG. 1, so that the eye 5 to be examined is adjusted and removed because the cloud fog chart is gradually blurred. The amount of movement is a point at which the conjugate point of the fundus 7 coincides with the target 8 in the average refractive power DSH of the eye 5 to be examined. At this time, the infrared light sources 11a and 11b are sequentially turned on, and the target on the detection element 9 is turned on. This can be realized by moving the prisms 23 and 29 so that the shift amount yH in the horizontal meridian of the image becomes an amount corresponding to the difference DH-DSH of the refractive power measured in the preliminary measurement. Thus, even when the eye 5 is exerting an accommodation force in the preliminary measurement, the cloud fog amount can always be maintained at the diopter DF corresponding to the distance l between the conjugate point 7 and the cloud fog chart 10. For example, vertical meridian +3
When preliminary measurement is performed in a state where the eye 5 of D, horizontal meridian + 5D exerts 4D accommodation force, Dv = -1D, DH = + 1D is obtained, and DSH = 0D, which is equivalent to DH-DSE = + 1D. In order to obtain the displacement yH on the detecting element 9, the prisms 23 and 29 corresponding to DF + 4D are moved.

4) Main measurement Next, the infrared rays 11a and 11b are sequentially turned on, the horizontal meridian refractive power DH is measured again, and the projection optical system 1 and the detection element 9 are measured.
And an angle θ, and the refractive power Dθ in the meridian direction corresponding to the angle θ is measured. This is repeated, and the refractive power at each meridian is measured. At this time, the prisms 23 and 29 are fixed, and when the eye to be inspected has astigmatism, the target image on the detection element 9 is blurred and a displacement amount y is generated. However, in preliminary measurement and fogging, the prisms 23 and 29 are set at positions corresponding to the average refractive power of the subject's eye. Therefore, the measurement accuracy is improved as compared with the case where the preliminary measurement is not performed. The calculation of the spherical power S, the astigmatic power C, and the astigmatic axis Ax of the subject's eye is verified by the CPU 51 according to the equation (6) and displayed on the display device 62 in FIG. Furthermore, the average refractive power of the eye Is calculated, and the fundus conjugate position based on this value is
Are moved to the left in FIG.

5) Re-measurement Since the eye 5 to be examined is a living eye, correct results may not be obtained by a single main measurement due to various factors, and sometimes several measurements are required. In this case, set the measurement switch 50 again.
By pressing, the above-described operations of 3) fog and 4) main measurement are repeated.

6) Visual acuity confirmation By pressing the visual acuity confirmation switch 68 after the objective measurement, the index is switched to the visual acuity chart 18 and the driving circuit 63
Drive the motors 64 and 65 through the
9. Rotate the concave cylindrical lens 20 to correct the astigmatic power. Further, the motor can be driven via the drive circuit to move the prisms 23 and 29 to correct the spherical power, thereby allowing the subject to check the corrected visual acuity based on the measurement result.

Now, the astigmatic power of the convex cylindrical lens is CA, and the astigmatic axis is θ.
A, assuming that the cylindrical power of the concave cylindrical lens is -CA and the axis of astigmatism is θB, the combined cylindrical power is given by the following equation.

CC = −2 CA sin (θA−θB) (8) Thus, the subject can compare the naked eye acuity and the corrected visual acuity before and after the measurement, so that the subject can understand the necessity of the correction. In addition, since the examiner can check the result of the objective test, for the test items of the subjective test performed by another device,
You can make a rough plan.

7) Measurement of the other eye As described above, the measurement of one eye is completed, the measurement unit is moved,
Perform alignment with the other eye. At this time, by detecting the switching to the other eye with the switch 69, the apparatus is set to the state of the confirmation of the naked eye visual acuity described in the above item 1), and the measurement is performed in the same manner.

8) Printing and Clearing of Data After the above operation is completed, the examiner presses the print switch 70, so that the data is printed by the printer 71, and the apparatus returns to the initial state, that is, the state of the item 1). Preparation for the next subject measurement is completed.

[Effects of the Invention] As described above, according to the present invention, before the main measurement, the refractive power of two orthogonal meridians is preliminarily measured, so that the measurement target and the light receiving unit are conjugated to the minimum confusion circle position of the eye to be examined. Since the amount of blurring of the measurement target image in the light receiving unit can be minimized irrespective of the astigmatic axis angle of the subject's eye, an eye refractive power measurement device with high measurement accuracy can be realized, and the measurement of the astigmatic power can be performed. The range can be doubled.

[Brief description of the drawings]

FIG. 1 is a diagram showing an arrangement of an optical system of an apparatus using one embodiment of the present invention, FIGS. 2 and 3 are diagrams for explaining the shapes of a target 8 and a stop 32, respectively, and FIG. FIG. 5 is an optical system layout diagram for guiding the anterior segment of the eye 5 to be inspected to the infrared TV camera 41, and FIG. FIG. 7 is a block diagram of the apparatus, and FIG. 8 is a flowchart of the preliminary measurement. DESCRIPTION OF SYMBOLS 1 ... Projection optical system, 2 ... Reception optical system 3 ... Index optical system 4, ... Common optical system 11a, 11b ... Infrared light source 23, 29 ... Prism 51 ... CPU, 55 ... RAM 60 …… Drive circuit, 66 …… ROM

Continuation of the front page (56) References JP-A-57-200128 (JP, A) JP-A-61-168331 (JP, A) JP-A-61-172535 (JP, A) JP-A-62-57534 (JP, A) JP-A-61-259639 (JP, A) JP-A-62-109541 (JP, A) JP-A-59-183726 (JP, A)

Claims (1)

(57) [Claims] 1. An automatic eye having an index projection optical system for projecting a measurement index to the fundus of the eye to be inspected, and an index detection optical system for guiding a light beam reflected by the fundus of the eye to the light receiving element to detect the position of the measurement index. In the refractive power measuring device, two meridian refractive power calculating means for measuring the refractive power in two orthogonal meridian directions based on the detection result of the index detection optical system, and the two meridian refractive power calculating means by the two meridian refractive power calculating means Average refractive power calculating means for calculating an average of the measurement index and the light receiving element based on the average refractive power to make the fundus of the subject's eye and the measurement index and the light receiving surface of the light receiving element substantially conjugate. Moving means for moving the optical distance with respect to the fundus of the eye to be examined, signal generating means for starting the main measurement in a state where the measurement index and the light receiving element are fixed at the position moved by the moving means, and moving amount of the moving means Fine wherein based on the output of the light receiving element and the refractive power calculating means for calculating a refractive power of the eye, the automatic eye refractive power measuring apparatus, characterized in that it comprises a.