JP2014151024A - Eye refractive power measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eye refractive power measuring apparatus capable of measuring an eye refractive power value by a method different from the conventional one.SOLUTION: The eye refractive power measuring apparatus comprises: a measuring optical system including a projection optical system for projecting a measurement index onto a fundus of a subject's eye, and a light receiving optical system for causing a light-receiving element to receive a reflected luminous flux from the fundus by the measurement index; and arithmetic means that acquires a first eye refractive power characteristic regarding a first pupil area of the subject's eye on the basis of a light receiving signal from the light receiving element, and a second eye refractive power characteristic regarding a second pupil area formed outside the first pupil area; and measures the eye refractive power of the subject's eye. The arithmetic means acquires a third eye refractive power characteristic by calculating a weighted average of the first eye refractive power characteristic and the second eye refractive power characteristic.

Description

  The present invention relates to an eye refractive power measuring apparatus that measures the eye refractive power of a subject's eye.

  The measurement light beam is projected onto the fundus of the subject's eye, and the reflected light from the fundus is taken out as a double ring image and picked up by a two-dimensional image sensor, and the daytime vision and nighttime vision are obtained from the two ring images as measurement results. An objective eye refractive power measuring device that measures the eye refractive power of an eye to be examined that presents information is known (see Patent Document 1).

JP 2012-75646 A

  In the eye refractive power measuring device of Patent Document 1, the eye refractive power obtained from two different light beams that have passed through different regions of the pupil is presented. By the way, the sensitivity of photoreceptor cells varies depending on the direction of incident light. For example, a light beam incident from the outside of the pupil is less sensitive to a light beam incident from substantially the center of the pupil. It is a technical object of the present invention to provide an eye refractive power measuring device that obtains an eye refraction value of an eye to be examined by a method different from the conventional one.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

  Based on a measurement optical system comprising: a projection optical system that projects a measurement index onto the fundus of the eye to be examined; a light receiving optical system that receives a reflected light beam from the fundus of the measurement index by a light receiving element; and a light reception signal from the light receiving element And calculating means for obtaining a first eye refractive power characteristic related to the first pupil area of the eye to be examined and a second eye refractive power characteristic related to the second pupil area formed outside the first pupil area, An eye refractive power measuring apparatus for measuring an eye refractive power of an eye to be examined, wherein the computing means obtains a weighted average of the first eye refractive power characteristic and the second eye refractive power characteristic to obtain a third Computation means for obtaining eye refractive power characteristics is provided.

  According to the present invention, the eye refractive power value can be measured by a method different from the conventional one.

It is a schematic block diagram of the optical system and control system in this apparatus. It is a block diagram of the ring lens in this apparatus. It is a figure explaining each ring light beam on a pupil. It is a figure explaining the measurement area | region when it rotates eccentrically. It is a figure shown about the ring image on an image sensor. It is the figure which showed each measurement area | region on a pupil. It is a figure explaining the relationship between a pupil diameter and a weighting coefficient.

  The best mode of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an optical system and a control system in the present apparatus. The measurement optical system 10 includes a projection optical system 10a and a light receiving optical system 10b. In this embodiment, the projection optical system 10a as a light projecting unit projects a measurement index from the center of the pupil of the eye to the fundus, and the light receiving optical system 10b as a light receiving unit reflects reflected light of the measurement index projected onto the fundus. A plurality of ring beams are extracted from the peripheral portion. In the present embodiment, the measurement index is projected as a spot-like light beam.

  In this embodiment, the projection optical system 10a serving as a light projecting unit includes a near-infrared point light source 11, a relay lens 12, a hall mirror 13, a prism 15, a first drive unit 23, and a measurement objective lens 14. It is arranged toward the eye to be examined. The near-infrared point light source 11 is an LED, SLD, or the like disposed on the measurement optical axis L1. The prism 15 is a light beam deflecting member. The first driving unit 23 is a rotating unit that drives the prism 15 to rotate about the optical axis L1. The light source 11 is conjugated with the fundus of the eye to be examined, and the hole portion of the Hall mirror 13 is conjugated with the pupil. The prism 15 is disposed at a position deviated from the position conjugate with the pupil of the eye E to be examined, and decenters the light beam passing therethrough with respect to the optical axis L1. A beam splitter 29, which is an optical path branching member, is disposed between the measurement objective lens 14 and the eye to be examined. The beam splitter 29 reflects the anterior ocular segment observation light and alignment light to the observation optical system 50 and guides the light flux of the fixation target optical system 30 to the eye to be examined.

  The fixation target optical system 30 is configured by the light source 31 to the observation system objective lens 36. On the optical axis L2 that is coaxial with the optical axis L1 by the beam splitter 29, an observation system objective lens 36, a half mirror 35, a dichroic mirror 34, a light projection lens 33, a fixation target 32, and a visible light source 31 are sequentially arranged. The The light source 31 and the fixation target 32 move in the direction of the optical axis L2 to release the adjustment of the eye to be examined. The light source 31 illuminates the fixation target 32, and the light flux from the fixation target 32 passes through the projection lens 33, the dichroic mirror 34, the half mirror 35, and the objective lens 36, and then is reflected by the beam splitter 29 toward the eye to be examined. The eye to be examined fixes the fixation target 32.

  An optical system 40 projects an alignment index from the front of the eye to be examined. Near-infrared light from the light source 41 is collected by a condenser lens 42 to be converted into a substantially parallel light beam through a dichroic mirror 34, a half mirror 35, and an objective lens 36, and then reflected by a beam splitter 29 to the eye to be examined. Projected.

  Reference numeral 50 denotes an observation optical system. On the reflection side of the half mirror 35, a photographing lens 51 and a CCD camera 52, which is an image sensor, are arranged. The output of the camera 52 is connected to the monitor 7 via the image processing unit 77. The anterior segment image of the eye to be examined is imaged on the image sensor surface of the camera 52 via the beam splitter 29, the objective lens 36, the half mirror 35, and the imaging lens 51, and the observation image is displayed on the monitor 7. The observation optical system 50 can also serve as an optical system for detecting an alignment index image formed on the cornea of the eye to be examined and an optical system for detecting the pupil position and pupil diameter. The position and pupil diameter are detected.

  In this embodiment, the light receiving optical system 10b serving as the light receiving means shares the measurement objective lens 14, the prism 15 and the hall mirror 13 of the projection optical system 10a, and is a relay lens arranged on the optical path in the reflection direction of the hall mirror 13. 16, a mirror 17, a light receiving diaphragm 18 disposed in an optical path in the reflection direction of the mirror 17, a collimator lens 19, a ring lens 20, and a two-dimensional image sensor 22 such as a CCD (hereinafter referred to as an image sensor 22). The light receiving diaphragm 18 and the image sensor 22 have a conjugate relationship with the fundus of the eye to be examined. The output of the image sensor 22 is connected to the control unit 70 via the image processing unit 77. In addition, a memory 75 is connected to the control unit 70 serving as a calculation unit, and a calculation program or the like for calculating eye refractive power based on a ring image can be stored. The control unit 70 controls the entire apparatus. For example, a 1/3 type 300,000 pixel CCD is used for the image sensor 22.

  The ring lens 20 is disposed at a position substantially conjugate with the anterior eye portion of the eye to be examined in the optical path of the measurement optical system 10, and reflects light from a minute region of the fundus illuminated by the projection optical system 10a at a distance from the measurement optical axis L1. The light beam is divided into a plurality of different measurement light fluxes, and is condensed on the image pickup surface of the image pickup device 22. As a result, a plurality of ring pattern images having different distances from the measurement optical axis are received by the image sensor 22.

  More specifically, as shown in FIGS. 2A and 2B, the ring lens 20 includes a first lens portion 20a and a second lens portion 20b in which two cylindrical lenses are formed in a ring shape on a flat plate, Other than the lens part, the light shielding part 20c is provided with a light shielding coating. The light shielding portion 20c forms a double ring opening in which two rings having different diameters are formed. And the annular | circular shaped 1st lens part 20a and 2nd lens part 20b corresponding to each ring opening are each formed in the concentric form with a different radius centering on the optical axis L1.

  In the present embodiment, the radius of the second lens portion 20b is configured to be larger than the radius of the first lens 20a. In the ring lens 20, for example, the light shielding part 20 c is conjugated with the eye pupil to be examined (the conjugated position does not have to be strictly conjugated but may be conjugated with accuracy required in relation to measurement accuracy). Is provided in the light receiving optical system. Therefore, the reflected light from the fundus is extracted in a ring shape with a size corresponding to the first lens unit 20a and the second lens unit 20b from the periphery of the pupil. When a parallel light beam enters the ring lens 20, a ring image having the same size as that of the ring lens 20 is condensed on the image sensor 22 arranged at the focal position. Note that the light shielding portion 20 c having a ring-shaped opening may be formed of a separate member in the vicinity of the ring lens 20.

  Further, the light source 11 of the projection optical system 10a, the light receiving diaphragm 18, the collimator lens 19, the ring lens 20, and the image sensor 22 of the light receiving optical system 10b are integrally movable in the optical axis direction as a movable unit 25. . The drive unit 26 moves a part of the measurement optical system 10 in the optical axis direction so that the outer ring light beam is incident on the image sensor 22 in each meridian direction. That is, the driving unit 26 is a driving unit that moves the movable unit 25 in the optical axis direction. By moving according to the spherical refraction error (spherical refractive power) of the eye to be examined, the spherical refraction error is corrected so that the light source 11, the light receiving diaphragm 18 and the image sensor 22 are optically conjugate with respect to the fundus of the eye to be examined. To. The moving position of the movable unit 25 is detected by a potentiometer 27. The Hall mirror 13 and the ring lens 20 are arranged so as to be conjugate with the pupil of the eye to be examined at a constant magnification regardless of the movement amount of the movable unit 25.

  In the above configuration, the near-infrared light emitted from the light source 11 passes through the relay lens 12, the hall mirror 13, the prism 15, the objective lens 14, and the beam splitter 29 to form a spot-like point light source image on the fundus of the eye to be examined. Form. At this time, the pupil projection image (projected light beam on the pupil) of the hall portion of the hall mirror 13 is eccentrically rotated at high speed by the prism 15 rotating around the optical axis.

  The point light source image projected onto the fundus is reflected and scattered to exit the eye to be examined, and is once condensed between the objective lens 14 and the prism 15 by the objective lens 14 and directed toward the prism 15. The light is condensed again at the position of the light receiving aperture 18 via the high-speed rotating prism 15, the hall mirror 13, the relay lens 16, and the mirror 17, and the collimator lens 19 and the ring lens 20 (first lens portion 20a and second lens portion 20b). As a result, a double ring image (double ring image) is formed on the image sensor 22 (see FIG. 5). An output signal from the image sensor 22 is detected and processed by the image processing unit 77.

  The prism 15 is disposed in a common optical path with the projection optical system 10a and the light receiving optical system 10b. For this reason, the reflected light beam from the fundus passes through the same prism 15 as the projection optics 10a. Therefore, in the subsequent optical system, the reverse scanning is performed as if there was no eccentricity of the projected light beam / reflected light beam (received light beam) on the pupil.

  Next, the measurement area on the pupil formed by the measurement optical system 10 will be described. FIG. 3 is a diagram for explaining each ring light beam on the pupil. FIG. 4 is a diagram for explaining the measurement region when it is eccentrically rotated. FIG. 5 is a diagram showing a ring image on the image sensor 22.

  As shown in FIG. 3A, out of the reflected light from the fundus, the first ring light beam 101 is extracted from above the pupil by the first lens unit 20a of the ring lens 20. At this time, the measurement optical axis L1 (the optical axis of the objective lens 14) is aligned with the approximate pupil center of the eye E. Therefore, when the prism 15 is eccentrically rotated by the first driving unit 23, the first ring light beam 101 is eccentrically rotated around the center Pc of the pupil Pu.

  Then, when the prism 15 is rotated at a high speed, the first ring light beam 101 moves at a high speed in the first measurement region T1 on the pupil as shown in FIG. Therefore, the first measurement region T1 (first pupil region) having a substantially circular shape is formed by the eccentric rotation of the ring light beam 101.

  At this time, the ring image on the imaging element 22 becomes a ring image at a different measurement position if an instant is captured. However, when the prism 15 is rotated at a high speed, finally, a first ring-shaped image (first ring image 105 in FIG. 5) obtained by integrating the ring images obtained at the respective positions is formed on the image sensor 22. Is received. Thereby, an average refractive power in the pupil region corresponding to the first measurement region T1 is obtained. Further, by obtaining refraction information at each position in the measurement region T1 even for abnormal eyes such as cataracts and small pupil eyes where calculation of measurement results is difficult with only some refraction information, Eye refractive power can be measured (for details, refer to JP-A-2005-185523). Note that the first ring image shows the inner ring image 105 of the double ring images formed on the image sensor 22 shown in FIG.

  As shown in FIG. 3B, the second ring light beam 102 is extracted from the pupil by the second lens portion 20b of the ring lens 20 in the fundus reflection light. At this time, the second ring light beam 102 is formed surrounding the first ring light beam 101 in an annular shape. When the prism 15 is eccentrically rotated by the first driving unit 23, the second ring light beam 102 is eccentrically rotated around the center Pc of the pupil Pu.

  Then, when the prism 15 is rotated at a high speed, the second ring light beam 102 moves on the pupil within the second measurement region T2 at a high speed as shown in FIG. 4B. Accordingly, a substantially annular second measurement region T2 (second pupil region) is formed outside the first measurement region T1 by the eccentric rotation of the ring light beam 102.

  At this time, the ring image on the imaging element 22 becomes a ring image at a different measurement position if an instant is captured. However, when the prism 15 is rotated at a high speed, finally, a second ring-shaped image (see the second ring image 106 in FIG. 5) obtained by integrating the ring images obtained at the respective positions becomes the image sensor 22. Light is received on the top. Thereby, an average refractive power in the pupil region corresponding to the second measurement region T2 is obtained. Further, with only a part of the refraction information, it is possible to measure eye refractive power by obtaining refraction information at each position in the measurement region T2 even for an abnormal eye such as a cataract. In this configuration, even if the pupil diameter is smaller than the second measurement region T2 and a part of the measurement light beam is blocked by the iris, the eye refractive power can be acquired based on the ring image of the measurement light beam that has passed through the pupil.

  FIG. 6 is a diagram showing each measurement region on the pupil as in the present invention. In the present embodiment, the first ring light beam 101 and the second ring light beam 102 are simultaneously eccentrically rotated at a high speed, so that a measurement region of φ (diameter) = 1.0 mm to φ = 6.0 mm can be measured. It has become. The first measurement region T1 formed by the rotation of the first lens unit 20a and the prism 15 is set so as to correspond to a region on the pupil that is inside φ = 4.0 mm. On the pupil, it is set so as to correspond to a region having an upper limit of φ = 3.0 to 4.0 mm. Note that the first measurement region T1 may include a region that is not measured at the center (for example, in a φ = 1.0 mm region). The second measurement region T2 formed by the rotation of the second lens unit 20b and the prism 15 is set so that the lower limit of the measurement region corresponds to any of φ = 3.0 to 4.5 mm on the pupil. Yes. Further, the second measurement region T2 is set so that the upper limit of the measurement region corresponds to any of φ = 4.5 to 6.5 mm.

  That is, the center-of-gravity diameter of the lens portion of the ring lens 20, the projection magnification of the lens portion of the ring lens 20 on the pupil (determined by the optical system of the measurement optical system 10), and the amount of eccentricity by the prism 15 are the first measurement region. A predetermined ring light beam is eccentrically rotated at T1, and another ring light beam is eccentrically rotated in a second measurement region T2 surrounding the first measurement region T1 in an annular shape.

  The measurement operation of the apparatus having the above configuration will be described. First, the face of the subject is fixed to a face support unit (not shown), and after instructing to fixate the fixation target 32, alignment with the eye to be examined is performed.

  The control unit 70 turns on the light source 11 and causes the first driving unit 23 to rotate the prism 15 at a high speed. The measurement light emitted from the light source 11 is projected onto the fundus oculi Ef via the relay lens 12 to the beam splitter 29, and the pupil projection image (projected light beam on the pupil) is eccentrically rotated at high speed.

  Then, the first ring light beam 101 and the second ring light beam 102 pass through the first measurement region T1 and the second measurement region T2, respectively. These ring light beams are extracted as ring-shaped light beams by the ring lens 20 through the objective lens 14 to the collimator lens 19 and detected as the first ring image 105 and the second ring image 106 from the imaging device 22.

  At this time, preliminary measurement of eye refractive power is first performed, and the light source 31 and the fixation target plate 32 are moved in the direction of the optical axis L2 based on the result of the preliminary measurement. It is done. Thereafter, the eye refractive power is measured for the eye to be inspected with cloud fog.

  Further, the control unit 70 controls the driving unit 26 based on the result of the preliminary measurement, and moves a part of the measurement optical system 10 so that the first ring image 105 has a size corresponding to the normal eye (0 diopter). Let Thereby, the diopter is corrected and the second ring image 106 can be prevented from being detached from the imaging surface of the imaging element 22. In this case, when diopter correction is performed, the second ring image 106 may be used.

  FIG. 5 is a double ring image captured by the image sensor 22 during measurement. An output signal from the image sensor 22 is stored in the image memory 71 as image data (measurement image). Then, the control unit 70 calculates the eye refractive power based on each ring image captured by the image sensor 22. For example, the control unit 70 specifies (detects) the position of each ring image in each meridian direction based on the measurement image stored in the image memory 71. In this case, the control unit 70 specifies the position of the ring image by edge detection. The position of each ring image is determined by cutting the waveform of the luminance signal at a predetermined threshold, and determining the waveform intermediate point, the peak of the luminance signal waveform, the barycentric position of the luminance signal, etc. May be.

  Next, the control unit 70 approximates the ellipse using the least square method or the like based on the identified image position of each ring image. And the control part 70 calculates | requires the refraction error of each meridian direction from the approximate ellipse shape. A calculation is performed to weight these refraction errors and the diopter correction amount by the drive unit 26 and the light flux passing through different areas of the pupil, which will be described later, and the eye refractive power of the eye to be examined, S (spherical power), C (columnar surface) Each value of (frequency) and A (astigmatic axis angle) is obtained, and the measurement result is displayed on the monitor 7 respectively.

  Here, in this embodiment, the monitor 7 displays the eye refractive power obtained from the first ring image 105 having the eye refractive power inside φ = 4.0 mm. Further, when the examiner gives a print instruction using an operation unit (not shown), measurement result data is printed by a print unit (not shown). In the measurement result data to be printed, the ocular refractive power for nighttime with the measurement area expanded to φ = 6.0, which will be described below, as well as the ocular refractive power for daytime which is displayed on the monitor 7 from φ = 4.0 mm inside. Is shown. The eye refractive power with the measurement area expanded to φ = 6.0 was obtained by weighting the first ring image 105 and the second ring image 106 based on the present invention, and the calculation method is as follows. Describe.

  Of the double ring images, the inner first ring image 105 and the outer second ring image 106 differ in the amount of change in the ring diameter caused by the diopter. Therefore, the control unit 70 calculates the eye refractive power in the first measurement region T1 and the second measurement region T2 based on the eye refraction value and the ring diameter set for each ring image. That is, it is necessary to set a diopter corresponding to the diameter of each ring image. Then, the eye refractive power of each ring is calculated based on the diopter set for each ring image of the inner first ring image 105 and the outer second ring image 106 and the set value of the ring image diameter. When measuring the eye refractive power of the inner first ring image 105, the control unit 70 detects the edge of the inner ring image and detects the diameter of the ring image. Next, a diopter corresponding to the detected ring diameter is calculated based on the diopter set exclusively for the inner ring image and the set value of the ring image diameter.

  Here, a calculation method for obtaining the eye refractive power from the light flux that has passed through a plurality of regions of the pupil according to the present invention will be described. First, as described above, S (spherical power), C (column surface power), and A (astigmatic axis angle) that are eye refractive powers are obtained for each ring image. Here, each ring image can also be expressed as a lens power by the following first formula. S is a spherical power, C is a columnar power, and A is an astigmatic axis angle.

Further, when the two lens powers P _A and P _B are combined, they can be expressed by the following second formula.

Here, when one eye refractive power (S, C, A) as a whole is calculated from two ring images (first ring image 105 and second ring image 106), the lens power calculated from each ring image is calculated. It can be obtained by synthesizing P _A and P _B. However, when the pupil size is different for each region, the influence on the obtained eye refractive power measurement value is different. In other words, this phenomenon is called a Style-Crawford Effect, and the influence of light incident from the outside of the pupil (sensitivity on the photoreceptor) is assumed to be small with respect to the central region of the pupil. Here, the sensitivity S of the photoreceptor cell when entering from a position separated by x from the optical axis can be expressed by the following third equation.

Considering the above-mentioned style Crawford phenomenon, the lens power (second eye refractive power characteristic) of the ring image of the second ring image 106 (the light beam that has passed through the second measurement region T2) is the first ring image 105 (the first eye refractive power characteristic). More accurate eye refracting power measurement by weighting the lens power (first eye refracting power characteristic) of the ring image of the light beam that has passed through one measuring region T1 and performing weighted averaging of the two lens powers A value can be calculated. That is, when the pupil diameter is large, the range of the second measurement region T2 is widened outward, so that the influence of the eye refraction characteristics calculated from this region can be considered to be relatively small compared to the inner ring. . One lens power (third eye refractive power characteristic) obtained by weighting two lens powers and calculating a weighted average has a weighting coefficient α (weighting of the second measurement region T2 relative to the first measurement region T1: <1). In the following, it can be calculated by the fourth equation. In this way, the calculation means (control unit 70) obtains the third eye refractive power characteristic by weighted averaging the first eye refractive power characteristic and the second eye refractive power characteristic.

In this embodiment, the pupil diameter of the eye E whose eye refractive power is being measured is detected, and a weighting coefficient based on the detected pupil diameter is set. More specifically, the control unit 70 detects the pupil diameter from the anterior segment image of the eye E captured by the CCD camera 52 of the observation optical system 50. Subsequently, a weighting coefficient corresponding to the detected pupil diameter is determined based on a table stored in the memory 75. The control unit 70 performs the calculation represented by the fourth equation, where α is the weighting coefficient value determined from the table. The eye refractive power based on the first measurement region T1 and the eye refractive power based on the second measurement region T2 are combined to generate one eye refractive power. The influence of the eye refractive power based on the second measurement region T2 is reduced in one eye refractive power.

More specifically, FIG. 7 shows the relationship between the pupil diameter and the weighting coefficient. When the pupil diameter increases, the weighting coefficient is determined so that the influence of the lens power by the second measurement region T2 is reduced in the weighted average lens power obtained by the fourth equation. In the present embodiment, when the pupil diameter is 3.5 mm to 6 mm, the weighting coefficient decreases linearly, and when the pupil diameter exceeds 6 mm, the weighting coefficient becomes constant. Note that the table shown in FIG. 7 starts from 3.5 mm based on the inner diameter of the second measurement region, and is not limited to this value. When the pupil diameter is 3.5 mm, the weighting coefficient is 0.8, and when the pupil diameter is 6 mm, the weighting coefficient is 0.55. In the present embodiment, the weighting coefficient is constant when the pupil diameter exceeds 6 mm, but may be reduced as the pupil diameter increases. In the present embodiment, the relationship between the pupil diameter and the weighting coefficient is configured with a straight line, but may be configured with a curve.
When combining the lens power, a method called a power vector is used. The first expression indicating the lens power described above is converted into the following fifth expression using a sin component, a cos component, and an equivalent spherical power.

J ₄₅ , J ₁₈₀ , and M are calculated for the first ring image 105 based on the first measurement region T1 and the second ring image 106 based on the second measurement region T2, respectively, and the above-described weighting is performed to produce one eye refractive power. By applying to the fourth equation for obtaining the above, it is possible to calculate by combining the lens powers of the two regions.

  In this way, the eye refractive power relating to each region is obtained from the light reception signals relating to different regions of the eye to be examined, and each eye refractive power is weighted and combined to obtain one eye refractive power, thereby corresponding to the pupil diameter of the eye E. The accurate eye refractive power can be obtained and presented. In addition, each eye refractive power combination is performed by weighted average, and the weighted average weighting coefficient can be changed, and a coefficient considering the style Crawford phenomenon that the sensitivity of photoreceptor cells decreases as the incident angle of light to the fundus increases. Use. Here, in consideration of the style Crawford phenomenon, the coefficient is set so that the influence on one eye refractive power to be obtained becomes smaller as the region where each eye refractive power is measured is further away from the measurement optical axis. Further, when obtaining one eye refractive power from a plurality of eye refractive powers, a power vector method is used. Further, the pupil diameter of the eye E being measured is detected, and the weighted average weighting coefficient is changed based on the detected pupil diameter. In this way, as a measurement result, it is possible to provide an eye refractive power corresponding to a pupil diameter that changes between daytime and nighttime.

  In the present embodiment, the combination of the two areas of the first measurement area T1 and the second measurement area T2 is calculated. However, even if there are three or more areas, the calculation can be performed by weighting in the same manner. For example, there may be three or more ring beams. Moreover, the structure which takes out an intermittent ring image instead of a continuous ring image may be sufficient. A configuration (for example, a six-point index) that extracts a fundus reflection image in which point images are arranged in a substantially ring shape may be used. The light receiving element is not limited to a two-dimensional image pickup element, but is an eye refractive power measuring device that rotates a light receiving element in which a plurality of photodiodes with divided regions are arranged at a position conjugate with the pupil of eye E. Is also applicable.

  In the present embodiment, the measurement light is projected from the central part of the pupil to the fundus and the reflected light from the fundus is extracted from the peripheral part (plural areas) of the pupil, but this is not restrictive. The measurement light may be projected onto the fundus from the periphery (plural areas) of the pupil, and the measurement light reflected from the fundus may be extracted from the center of the pupil. That is, the eye refractive powers at a plurality of locations of the eye E may be obtained, and the eye refractive powers at a plurality of locations may be weighted to obtain one combined eye refractive power.

  In the present embodiment, the weighting coefficient decreases as the distance from the measurement optical axis increases. However, the present invention is not limited to this. The eye refractive power may be obtained by weighting in consideration of the distribution of the amount of light corresponding to the angle or direction of the light beam incident on the photoreceptor cell. For example, when there is local opacity in the lens (substantially pupil) due to cataracts, it becomes difficult for the light flux of the turbid part to reach the fundus (macular area). Therefore, before or during the measurement, the turbidity and the degree of opacity of the translucent body (from the cornea to the retina) of the eye E are detected, and a weighting coefficient is applied to each of the light beams separated and received by the pupil based on the detected information. You only have to set it.

  Further, the weighting coefficient may be arbitrarily changed by the examiner. The examiner may set a weighting coefficient in advance by operating a switch of an operation unit (not shown).

  In the present embodiment, when the pupil diameter being measured is applied to the second measurement region T2, the weighting coefficient based on the pupil diameter of the eye E detected during the measurement is used in the fourth equation that weights and averages the two lens powers. However, it is not limited to this. The weighting coefficient of the fourth equation may be constant regardless of the pupil diameter detected during the measurement.

  In the present embodiment, weighting is performed in the calculation (fourth equation) for obtaining one eye refractive power from two lens powers (eye refractive power) based on two ring images picked up by the two-dimensional imaging device 22. However, the weighting coefficient is not limited to the calculation that combines the eye refractive powers. When the two eye refractive powers are obtained or before the two eye refractive powers are obtained, weighting based on the passing area of the pupil may be performed in advance. For example, the shape of the detected ring image may be combined after correction (deformation) based on a weighting coefficient.

7 monitor 10 measurement optical system 10a projection optical system 10b light receiving optical system 11 near infrared point light source 15 prism 20 ring lens 22 two-dimensional image pickup device 23 first drive unit 29 beam splitter 30 fixation target optical system 40 XY direction alignment index projection Optical system 50 Observation optical system 70 Control unit 75 Memory

Claims (7)

A measurement optical system comprising: a projection optical system that projects a measurement index onto the fundus of the eye to be examined; and a light receiving optical system that receives a reflected light beam from the fundus according to the measurement index by a light receiving element;
Based on the light reception signal from the light receiving element, the first eye refractive power characteristic related to the first pupil region of the eye to be examined and the second eye refractive power related to the second pupil region formed outside the first pupil region. An eye refractive power measuring device that includes a computing means for obtaining characteristics and measures the eye refractive power of the eye to be examined,
The calculation means includes calculation means for obtaining a third eye refractive power characteristic by obtaining a weighted average of the first eye refractive power characteristic and the second eye refractive power characteristic. measuring device.   The calculation means takes into account the style Crawford phenomenon that the sensitivity of the photoreceptor cell decreases as the incident angle of light with respect to the fundus increases, and the weighted average of the first eye refractive power characteristic and the second eye refractive power characteristic The eye refractive power measurement apparatus according to claim 1, wherein the third eye refractive power characteristic is obtained by obtaining   The eye refractive power measurement apparatus according to claim 1, wherein the calculation unit is capable of changing a weighting coefficient when obtaining the weighted average.   4. The eye refractive power measuring apparatus according to claim 3, wherein the calculating means reduces the weighting coefficient for obtaining the weighted average as the luminous flux is further away from the measurement optical axis. Having pupil diameter measuring means for measuring the pupil diameter of the subject eye when measuring the eye refractive power of the subject eye;
4. The eye refractive power measurement apparatus according to claim 3, wherein the calculation means changes a weighting coefficient for obtaining the weighted average based on a measurement result of the pupil diameter measurement means.   The said calculating means calculates | requires the said weighted average by adding the said 1st eye refractive power characteristic and the said 2nd eye refractive power characteristic with a power vector method, The any one of Claims 1-5 characterized by the above-mentioned. The eye refractive power measuring device according to 1. The measurement optical system is a light receiving optical system that receives a plurality of ring-shaped light fluxes having different passing regions in the eye pupil by a two-dimensional light receiving element,
The computing means obtains the first eye refractive power characteristic based on the inner ring-shaped light beam received by the two-dimensional light receiving element, and based on the outer ring-shaped light beam received by the two-dimensional light receiving element. The eye refractive power measuring apparatus according to claim 1, wherein the second eye refractive power characteristic is obtained.