JP5397893B2 - Eye refractive power measuring device - Google Patents

Description

  The present invention relates to an eye refractive power measuring apparatus that measures the eye refractive power of an eye to be examined.

  The eye refractive power measuring device projects measurement light onto the fundus and causes the fundus reflection light to be imaged on a two-dimensional image sensor as a predetermined index pattern image (for example, a ring image or Shack-Hartmann image). A device that measures the eye refractive power (including wavefront aberration) of an eye to be examined is known. (See Patent Document 1).

JP 2007-89715 A

  However, in the apparatus as described in Patent Document 1, if the measurement window (for example, an objective lens, a protective glass, etc.) arranged in front of the eye to be examined is dirty or cloudy due to condensation, the measurement light is reflected by the dirt. Then, there is a possibility that an extra index image other than the index image that should be detected originally may be detected, and the measurement result may be output based on an incorrect index image.

  In view of the above problems, an object of the present invention is to provide an eye refractive power measuring apparatus that can obtain a stable measurement result even when an index image that is measurement noise is detected.

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

(1) A measurement optical system that projects measurement light onto the fundus of the subject's eye and takes out the fundus reflection light as a predetermined index pattern image and images it on a two-dimensional image sensor, and an index pattern image captured on the two-dimensional image sensor An eye-refractive-power measuring apparatus comprising: an arithmetic control unit that measures the eye refractive power of the eye to be examined and outputs a measurement result, wherein the arithmetic control unit is index image data stored in advance in the storage unit. Te, and the index image data of the target pattern image formed by the reflected light from the optical member constituting the measurement optical system, an imaging result of the two-dimensional imaging device, a target pattern image by the fundus reflection light using a , And an index pattern image by the reflected light from the optical member, and based on the determination result, the index pattern image by the fundus reflected light and the finger by the reflected light from the optical member An index pattern image based on the fundus reflection light is specified from data in which a target pattern image is mixed, and a measurement result corresponding to the specified index pattern image is output.
(2) In the eye refractive power measurement device according to (1), the index pattern image by fundus reflected light and the index pattern image by reflected light from the optical member are ring images, and the storage means As the ring image data of the ring image by the reflected light from the optical member, the diameter of the ring image by the reflected light from the optical member or the refractive power corresponding to the ring image is stored, The ring image data closer to the diameter or the refractive power of the ring image stored in the storage means is used as ring image data based on the reflected light from the optical member, and the other ring image data is used as the ring image data based on the fundus reflected light. It is characterized by distinguishing as follows.
(3) In the eye refractive power measurement device according to (2), the calculation control unit further determines whether or not there are two ring images on the two-dimensional imaging device, and determines that there are two ring images. If it is, the fact that the measurement window has an abnormality due to dirt or fogging is output .

  According to the present invention, a stable measurement result can be obtained even if an index image serving as measurement noise is detected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an optical system and a control system of the present apparatus. The measurement optical system 10 includes a projection optical system 10a that projects a spot-like measurement index on the fundus oculi Ef of the eye E via the pupil central portion of the eye E, and fundus reflected light reflected from the fundus oculi Ef via the pupil periphery. And a light receiving optical system 10b for picking up a ring-shaped fundus reflection image on the two-dimensional imaging device.

  The projection optical system 10 a includes a measurement light source 11, a relay lens 12, a hall mirror 13, and an objective lens 14 that are disposed on the optical axis L <b> 1 of the measurement optical system 10. The light source 11 is optically conjugate with the fundus oculi Ef of the normal eye. The opening of the Hall mirror 13 is optically conjugate with the pupil of the eye E.

  In the light receiving optical system 10b, the objective lens 14 and the hall mirror 13 of the projection optical system 10a are shared, and the relay lens 16 and the total reflection mirror 17 disposed on the optical axis L1 in the reflection direction of the hall mirror 13 are totally reflected. It includes a two-dimensional imaging device 22 including a light receiving stop 18, a collimator lens 19, a ring lens 20, and an area CCD disposed on the optical axis L <b> 1 in the reflection direction of the mirror 17. The light receiving aperture 18 and the image sensor 22 are in a positional relationship optically conjugate with the fundus oculi Ef. The ring lens 20 includes a lens part formed in a ring shape and a light shielding part in which an area other than the lens part is coated with a light shielding coating, and has a positional relationship optically conjugate with the pupil of the eye E to be examined. It has become. An output from the image sensor 22 is input to the arithmetic control unit 70 via the image memory 71.

  The measurement optical system 10 is not limited to the above, and a ring-shaped measurement index is projected from the periphery of the pupil to the fundus oculi Ef, the fundus reflection light is extracted from the center of the pupil, and the ring-shaped fundus reflection is reflected on the two-dimensional imaging device. Well-known ones such as a configuration for receiving an image can be used. Moreover, the structure which takes out an intermittent ring image instead of a continuous ring image may be sufficient, and the structure which takes out the fundus reflection image in which the point images were arranged in the substantially ring shape may be sufficient.

  Between the objective lens 14 and the hall mirror 13, the fixation target luminous flux from the fixation target presenting optical system 30 is guided to the eye E, and the reflected light from the anterior eye part of the eye E to be examined is guided to the observation optical system 50. A dichroic mirror 29 is arranged. The dichroic mirror 29 transmits the wavelength of the measurement light beam used in the measurement optical system 10.

  The fixation target presentation optical system 30 includes a fixation target presentation visible light source 31, a fixation target plate 32 having a fixation target, a light projection lens 33, a dichroic mirror 29, and an objective lens 14. The light source 31 and the fixation target plate 32 are moved in the direction of the optical axis L2, thereby performing clouding of the eye E.

  A ring index projection optical system 45 that emits near-infrared light for projecting a ring index onto the cornea Ec of the eye E and an infinite distance index onto the cornea Ec of the eye E are projected in front of the anterior segment of the eye E. Accordingly, the working distance index projection optical system 46 that emits near-infrared light for detecting the alignment state in the working distance direction with respect to the eye to be examined is arranged symmetrically with respect to the observation optical axis. The ring projection optical system 45 is also used as anterior segment illumination for illuminating the anterior segment of the eye E. It can also be used as an index for corneal shape measurement.

  The observation optical system 50 shares the objective lens 14 and the dichroic mirror 29 of the fixation target presenting optical system 30, and includes a half mirror 35, an imaging lens 51, and a two-dimensional imaging element 52. An output from the image sensor 52 is input to the arithmetic control unit 70. As a result, the anterior segment image of the eye E is captured by the two-dimensional image sensor 52 and displayed on the monitor 7. The observation optical system 50 also serves as an optical system that detects an alignment index image formed on the cornea of the eye E, and the position of the alignment index image is detected by the arithmetic control unit 70.

  Connected to the arithmetic control unit 70 are an image memory 71, an image sensor 52, a memory 75, a monitor 7, a switch unit 80 having a plurality of switches and used for various measurement settings. The arithmetic control unit 70 controls the entire apparatus and calculates an eye refraction value, a corneal shape, and the like. The memory 75 can store an arithmetic program for calculating the eye refractive power based on the ring image.

  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 arithmetic control unit 70 turns on the light source 11 based on the input of the measurement start signal. The measurement light emitted from the light source 11 is projected onto the fundus oculi Ef via the relay lens 12 to the objective lens 14 to form a spot-like point light source image that rotates on the fundus oculi Ef.

  The light of the point light source image formed on the fundus oculi Ef is reflected and scattered, exits the subject eye E, is collected by the objective lens 14, and passes through the dichroic mirror 29 through the total reflection mirror 17 to the light receiving stop 18. The light is condensed again on the aperture, converted into a substantially parallel light beam (in the case of a normal eye) by the collimator lens 19, extracted as a ring-shaped light beam by the ring lens 20, and received by the image sensor 22 as a ring image.

  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.

  FIG. 2 is a 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). Thereafter, the arithmetic control unit 70 specifies (detects) the position of the ring image in each meridian direction based on the measurement image stored in the image memory 71. In this case, the calculation control unit 70 cuts the waveform of the luminance signal at a predetermined threshold, and obtains an intermediate point of the waveform at the cutting position, a peak of the waveform of the luminance signal, a gravity center position of the luminance signal, and the like. The position of the ring image is specified. Next, the arithmetic control unit 70 approximates the ellipse using the least square method or the like based on the specified image position of the ring image. The arithmetic control unit 70 obtains the refractive error in each meridian direction from the approximate ellipse shape, and based on this, the eye refraction value, S (spherical power), C (column surface power), A (astigmatism) of the eye to be examined. Each value of (axis angle) is calculated, and the measurement result is displayed on the monitor 7.

  Hereinafter, a process when the measurement window (in the following description, an objective lens is used as an example) is dirty will be described. Originally, the measurement light emitted from the light source 11 is applied to the fundus of the subject's eye via the objective lens 14, and the fundus reflection light is received by the image sensor 22 as a ring image. However, if the surface of the objective lens 14 on the eye side to be examined is dirty or cloudy, the light emitted from the light source 11 is reflected by the stain on the objective lens 14 and received by the imaging element 22 as another ring image. The Thereby, the ring image by the fundus reflection light and the ring image by the reflection light from the objective lens 14 are mixed, and two ring images may appear (see FIG. 3).

  In FIG. 3, the ring image due to the above-described dirt or clouding is denoted by S1, and the ring image due to reflection from the fundus is denoted by S2. The ring image S1 is picked up as a ring image having the same size as when an eye to be examined having a predetermined refractive power (for example, around −18D) is measured due to optical design. In addition, about -18D is based on this optical design, and in different optical design, it does not necessarily restrict to this.

  Since the size of the ring image S2 changes depending on the refractive power of the eye to be inspected, the ring image S2 appears outside the ring image S1 as shown in FIG. 3A or inside the ring image S1 as shown in FIG. May appear. At this time, when the amount of light reflected from the fundus (ring image S2) is larger than the amount of light reflected from the surface of the objective lens (ring image S1), the eye refractive power is measured based on the ring image S2. However, when the reflected light (ring image S1) on the objective lens surface is stronger than the reflected light from the fundus (ring image S2), the measurement result is calculated based on the ring image S1, and the eye refractive power of the eye to be examined is calculated. Can not be measured. In particular, when the amount of light reflected from the fundus is difficult to obtain due to intraocular turbidity such as cataract, the above-described erroneous detection is likely to occur. That is, the ring image formed by the reflected light from the optical member (for example, the objective lens 14) constituting the measurement optical system becomes measurement noise.

  In the following embodiment, as described above, index image data related to an index image (for example, a ring image) that becomes measurement noise is stored in the memory 75 in advance, and the imaging result by the image sensor 22 and the memory 75 are stored. A method of specifying index image data based on fundus reflected light using the index image data thus specified and outputting a measurement result corresponding to the specified index image data will be described. When the index image is a ring pattern image, the index image (ring image) data includes, for example, the refractive power corresponding to the ring image S1, the image data of the ring image S1, the ring diameter of the ring image S1, and the like. .

  FIG. 4 is a flowchart for explaining the first embodiment. The arithmetic control unit 70 detects each meridian edge in order in the 360 degree direction with reference to the center coordinates specified based on a part of the ring image. Here, as shown in FIG. 3, when there are two ring images, the distance between the center coordinate and each edge is divided into an edge corresponding to the inner ring and an edge corresponding to the outer ring (inner / outer conversion). ). Next, the arithmetic control unit 70 approximates the ellipse using the least square method or the like based on the identified inner edge position. Then, the calculation control unit 70 obtains a refraction error in each meridian direction from the approximate ellipse shape, calculates each value of the SCA corresponding to the inner ring image, and then proceeds to determination step 1.

  In determination step 1 (step 1 in FIG. 4), the arithmetic control unit 70 determines whether or not the refractive power of the inner ring is around −18D. Specifically, it is determined whether or not the refractive power of the inner ring is within a predetermined range (for example, ± 3D) set based on −18D in consideration of an error. The determination step 1 is a step for determining whether or not there is a possibility that the inner ring image is a ring image due to dirt or the like of the objective lens 14, and a predetermined refractive power (corresponding to the ring image due to dirt or the like ( −18D) is used. In this case, the refractive power corresponding to the ring image due to dirt or the like may be obtained in advance by experiments or the like and stored in the memory 75 (of course, as shown in FIG. Including the meaning included in the part).

  In the determination step 1, if the inner ring is not around -18D, the inner ring image is determined to be a ring image by fundus reflection light, and the measurement result corresponding to the inner ring image is displayed on the monitor 7 through the blink determination step 4. Displayed (may be printed out by a printer).

  On the other hand, if the inner ring is around -18D, it is determined that there is a possibility that the inner ring may be a ring image due to the aforementioned dirt or the like. Then, in determination step 2, the presence or absence of the outer ring image is determined. Specifically, the presence or absence of the outer ring image is determined based on whether or not the outer edge detection point is 1/3 or more (whether or not the outer circle is missing 2/3 or more of the whole).

  In the determination step 2, when it is determined that there is an outer ring, the arithmetic control unit 70 approximates an ellipse using the least square method or the like based on the outer edge position, and calculates an SCA corresponding to the outer ring image. calculate. Here, the calculation control unit 70 determines the ring image closer to −18D as a ring image due to dirt or the like, determines the other ring image as a ring image due to fundus reflection light, and performs measurement corresponding to the other ring image. Display the results. Therefore, if the inner ring is closer to −18D, the measurement result corresponding to the outer ring is output, and if the outer ring is closer to −18D, the measurement result corresponding to the inner ring is output.

  If it is determined in the determination step 2 that there is no outer ring, the ring image is determined to be only a ring image by fundus reflection light, and the measurement result based on the inner ring image through the blink determination step 3 and the determination step 4 Is displayed on the monitor 7. In this case, the measurement result corresponding to this ring image is displayed.

  By the determination step as described above, it is possible to determine whether the ring image on the image sensor 22 is a ring image due to fundus reflection light or a ring image due to contamination of the objective lens 14. Therefore, the measurement light is reflected by dirt, etc., and erroneous detection due to an extra ring image other than the ring image that should be detected can be prevented. Therefore, even when the measurement window is dirty, the eye refractive power of the eye to be examined is reduced. It is possible to calculate with certainty.

  The arithmetic control unit 70 determines whether or not there are two ring images on the image sensor 22, and if it is determined that there are two ring images, the objective lens 14 is abnormal due to dirt or cloudiness. May be reported on the monitor 7 (or printer) together with the measurement result.

  The determination step 3 and the determination step 4 will be briefly described. Determination step 3 (for the outside) and determination step 4 (for the inside) are steps for determining blink (or wrinkle), respectively. Specifically, in the determination step 2, when the outer edge detection point is 1/12 or more, it is determined as a blink error and displayed on the monitor 7 as a BLK error. On the other hand, if the detected point is smaller than 1/12, the process proceeds to decision step 4. When the inner edge detection point is ½ or more, the SCA of the inner ring is taken as the measurement value, and the measurement result is displayed on the monitor 7. If the edge detection point is smaller than 1/2, a BLK error is displayed and displayed on the monitor 7.

  In the above determination process, determination step 2 may be changed to an order prior to determination step 1, and the presence / absence of the outer ring and SCA calculation may be performed prior to determination step 1. In determination step 2 and determination step 4, the presence or absence of a ring formed on the light receiving element 22 was confirmed and an error was determined. A measurement value was obtained in advance, and then the measurement result was displayed together with the reliability coefficient. It does not matter if it is output. That is, the stain determination may be performed after the measurement result is calculated.

  In the above method, the determination is made based on whether or not the inner ring is around -18D, but the same determination may be performed based on the outer ring.

  In the first embodiment, the ring image data by the fundus reflection light and the ring image data by the reflection light from the objective lens 14 are discriminated using the refractive power corresponding to the ring image S1, but the present invention is not limited to this. Instead, any ring image data related to the ring image S1 may be used. For example, the above-described determination may be performed by comparing the ring diameter corresponding to the ring image S1 and the ring diameter of each ring image described above.

  Next, a second embodiment will be described with reference to FIG. In FIG. 5, a ring image due to dirt or cloudiness is denoted as S1, and a ring image due to reflection from the fundus is denoted as S2. FIG. 5A is a diagram when the eye to be measured is measured when the measurement window is clouded by dirt or condensation. Here, when the measurement window is dirty or cloudy due to condensation, the measurement light source 11 is turned on in a state where there is no subject eye or other reflecting object in front of the inspection window 29. In this case, the light emitted from the light source 11 is reflected by dirt on the objective lens 14, and the ring image is received by the imaging element 22 (see FIG. 5B). The arithmetic control unit 70 stores the image data of the ring image S1 (see FIG. 5B) from the light receiving element 22 in the memory 75 in advance. Next, measurement is performed in the presence of the eye to be examined. Here, when two rings are detected, the arithmetic control unit 70 causes the ring image (the eye to be examined and other reflecting objects to be in front of the ring image) stored in the memory 75 from the acquired image data (FIG. 5A). The brightness distribution corresponding to the ring image acquired in the absence (FIG. 5B) is removed. As a result, the ring image data based on the fundus reflection light is specified, so that the measurement result corresponding to the remaining ring image (FIG. 5C) is output.

  In the above description, the measurement optical system that acquires the ring pattern image by the fundus reflection light has been described as an example, but the present invention is not limited to this, and in order to obtain the eye refractive power of the subject's eye, The present invention can be applied to any configuration as long as the measurement light is projected and the fundus reflection light is captured by the two-dimensional imaging device as a predetermined index pattern image. For example, in order to obtain the wavefront aberration of the subject's eye, a measurement optical system that projects a spot index on the fundus of the subject's eye and detects the fundus reflected light using a Shack-Hartmann sensor may be used. In this case, as index image data related to the Shack-Hartmann image that is formed on the two-dimensional imaging device by the reflected light from the measurement window and becomes measurement noise, the refractive power corresponding to the Hartmann image, the Hartmann image data, the Hartmann image The interval of each dot image is used.

It is a schematic block diagram of the optical system and control system of this apparatus. It is a figure which shows the ring image imaged by the imaging device of the eye refractive power measurement optical system in the case of a measurement. It is a figure which shows a ring image when an objective lens has a stain | pollution | contamination etc. FIG. It is a flowchart explaining 1st Example. It is a figure for demonstrating 2nd Example.

7 Monitor 10 Measurement Optical System 10a Projection Optical System 10b Light Receiving Optical System 22 Two-Dimensional Image Sensor 70 Arithmetic Control Unit 75 Memory

Claims (3)

Based on a measurement optical system that projects measurement light onto the fundus of the subject's eye, takes out the fundus reflection light as a predetermined index pattern image, and images it on a two-dimensional image sensor, and an index pattern image captured on the two-dimensional image sensor In an eye refractive power measurement apparatus comprising: an arithmetic control unit that measures eye refractive power of an eye to be examined and outputs a measurement result;
The calculation control unit is index image data stored in advance in a storage unit, the index image data of an index pattern image formed by reflected light from an optical member constituting the measurement optical system, and the two-dimensional imaging The index pattern image by the fundus reflected light and the index pattern image by the reflected light from the optical member are discriminated using the imaging result by the element , and the index pattern by the fundus reflected light is determined based on the discrimination result and the image from the data and the index pattern image by the reflected light, are mixed from the optical member, said identifying a target pattern image by the fundus reflection light, and outputs the measurement result corresponding to the identified target pattern image An eye refractive power measuring device characterized by the above. In the eye refractive power measuring device according to claim 1,
The index pattern image by fundus reflected light and the index pattern image by reflected light from the optical member are ring images,
The storage means stores, as the ring image data of the ring image by the reflected light from the optical member, the diameter of the ring image by the reflected light from the optical member, or the refractive power corresponding to the ring image,
The calculation control means uses the ring image data closer to the diameter or the refractive power of the ring image stored in the storage means as ring image data by reflected light from the optical member, and the other ring image data as the ring image data. An eye refractive power measuring apparatus characterized by discriminating as ring image data by fundus reflection light . In the eye refractive power measuring device according to claim 2,
The arithmetic control unit further determines whether or not there are two ring images on the two-dimensional image sensor. If it is determined that there are two ring images, the measurement window is abnormal due to dirt or cloudiness. An eye refractive power measuring apparatus that outputs a certain effect .

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