JP2013005982A - Eye axial length measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eye axial length measuring device which can suitably measure the eye axial length of a cataract eye even if an inspector is not a skilled person.SOLUTION: The eye axial length measuring device has a measurement optical system which comprises: a light projection optical system for dividing light emitted from a light source and projecting a measuring beam to the bottom of an eye; a light receiving optical system for leading light formed by synthesizing one light reflected at the bottom of the eye and the other light to a light receiving element; and an optical member which is arranged in order to adjust a light passage difference. The eye axial length measuring device measures the eye axial length of the eye to be inspected on the basis of an interference signal outputted from the light receiving element, and also comprises: an imaging optical system which has an imaging element having an imaging face at a position almost conjugative with the anterior ocular segment of the eye to be inspected and images a diaphanoscopy image at the pupil of the eye to be inspected which is irradiated with eye-bottom reflection light; and a light transmittance region specifying means which acquires the two-dimensional distribution of an opaque part in a prescribed region which is set so that an S/N ratio of the interference signal may satisfies a permission value by processing the diaphanoscopy image acquired by the imaging element, and specifies a light transmittance region in the prescribed region on the basis of the acquired two-dimensional distribution.

Description

  The present invention relates to an axial length measuring device that optically measures the axial length of a subject's eye.

  An axial length measuring device that has an interference optical system that irradiates measurement light toward the eye to be examined and detects the reflected light as interference light by a light receiving element and measures the axial length of the eye to be examined is known ( For example, see Patent Document 1).

Special Table 2002-531205

  In such an apparatus, when measuring the axial length of a strong cataract eye, the measurement light is greatly scattered by the turbid portion of the cataract, and the S / N of the interference signal is greatly reduced. For this reason, the axial length may not be measured. In addition, the S / N of the interference signal also decreases as the measurement optical axis moves away from the corneal apex. Therefore, when an inexperienced examiner uses the axial length measuring device, a sufficient interference signal cannot be obtained, which may cause a measurement error.

  In view of the above problems, an object of the present invention is to provide an axial length measuring device that can suitably measure the axial length of a cataract eye even for an unskilled examiner.

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

(1) A light projecting optical system that divides light emitted from a light source and projects a measurement beam generated from one of the divided lights toward the fundus, one light reflected from the fundus, and the other A light-receiving optical system that guides light combined with light to a light-receiving element, and an optical member that is arranged to be movable in the optical axis direction in order to adjust the optical path difference between the one light and the other light. An imaging surface having an optical system and arranged at a position substantially conjugate with the anterior eye portion of the eye to be examined in an axial length measuring device that measures the axial length of the eye to be examined based on an interference signal output from the light receiving element Interference by processing the transillumination image acquired by the imaging optical system that captures the transillumination image in the eye pupil part of the eye to be examined illuminated by the fundus reflection light and the imaging element Predetermined so that the S / N ratio of the signal satisfies the allowable value An optical axis length measuring device, comprising: a light transmission region specifying means for obtaining a two-dimensional distribution of a turbid portion in a region and specifying a light transmission region in the predetermined region based on the obtained two-dimensional distribution. .
(2) Drive means for driving the measurement optical system with respect to the eye to be examined, and the drive means so that the optical axis of the measurement optical system is positioned in the light transmission area specified by the light transmission area specification means (1) The axial length measuring device according to (1), further comprising drive control means for controlling
(3) The light transmission region specifying unit divides the predetermined region into a plurality of regions, and compares the turbidity rate of each divided region using the calculation result of the two-dimensional distribution to thereby reduce the region with a low turbidity rate. (2) The axial length measuring apparatus characterized by specifying as a light transmissive area | region.
(4) The drive control unit operates the automatic alignment for the eye to be examined by controlling the drive unit based on the imaging signal output from the imaging device, and the optical axis of the measurement optical system is positioned in the light transmission region. The alignment position is changed so that the axial length measuring device according to (3) is characterized.
(5) The light projecting optical system includes a light source that emits coherent light, and the light source is a light projecting optical system that also serves as a transillumination light source, and is in an optical path of the light projecting optical system. (4) The axial length measurement device according to (4), further comprising speckle suppression means that optically suppresses speckle noise generated in the transillumination image.
(6) A switching signal for switching between a first mode for measuring the axial length by receiving interference light by the measurement optical system and a second mode for capturing the transillumination image by the imaging optical system. And a control means for stopping the operation of the speckle suppression means in the first mode and operating the speckle suppression means in the second mode based on a switching signal from the mode switching means. (5) The ophthalmologic measurement apparatus characterized by including.

  In view of the above problems, an object of the present invention is to provide an ophthalmologic measuring apparatus that can suitably measure the axial length of a cataract eye.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an external view of an ophthalmologic apparatus according to the present invention. This apparatus is provided with a base 2, a face support unit 4 attached to the base 2, a movable base 6 movably provided on the base 2, and a movable base 6, which will be described later. A measuring unit 8 that houses the optical system is provided. The movable table 6 is moved on the base 2 in the left-right direction (X direction) and the front-rear direction (Z direction) by operating the joystick 12. The measuring unit 8 is moved in the vertical direction (Y direction) by the drive mechanism 17 including a motor or the like when the rotary knob 12a is rotated. The movable table 6 is provided with a monitor 70 for displaying various information such as an observation image of the eye E and a measurement result, and an operation unit 90 on which switches for performing various settings are arranged.

  FIG. 2 is a schematic configuration diagram showing an optical system of the ophthalmologic apparatus according to the present embodiment. The present optical system includes an axial length measurement optical system (measurement unit) 10, a kerato projection optical system 50 that projects an index for measuring a corneal shape onto the cornea, an alignment projection optical system 40, and an anterior eye that captures an anterior ocular segment front image. The front image pickup optical system 30 is roughly divided. The following optical system is built in the measurement unit 8.

  The projection optical system 50 has a ring-shaped light source 51 disposed around the measurement optical axis L1, and measures a corneal shape (curvature, astigmatic axis angle, etc.) by projecting a ring index onto the eye cornea to be examined. Used for. As the light source 51, for example, an LED that emits infrared light or visible light is used.

  The projection optical system 40 is disposed inside the light source 51, has a projection light source 41 (for example, λ = 970 nm) that emits infrared light, and is used to project an alignment index onto the subject's eye cornea. The light source 51 and the light source 41 also serve as an anterior segment illumination light source.

  The imaging optical system 30 includes a dichroic mirror 33, an objective lens 47, a total reflection mirror 36, a filter 34, an imaging lens 37, and a two-dimensional imaging device 35, and is used for imaging a front image of the anterior eye portion of the eye to be examined. . The imaging element 35 is disposed at a position where the imaging surface is substantially conjugate with the anterior eye portion to be examined. Further, the imaging optical system 30 captures a transillumination image (an intra-pupil image) in the eye pupil portion illuminated by the fundus reflection light. The dichroic mirror 33 transmits most of the measurement light, reflects part of the measurement light, and reflects light from the light source 51 and the light source 41.

  The anterior ocular segment light reflected by the projection optical system 50 and the projection optical system 40 forms an image on the two-dimensional image sensor 35 through the dichroic mirror 33, the objective lens 47, the total reflection mirror 36, the filter 34, and the imaging lens 37. Is done.

  The axial length measurement optical system 10 includes a light projecting optical system 10a and a light receiving optical system 10b, and projects measurement light onto the eye to be examined and detects interference light due to the reflected light. The light projecting optical system 10a divides the light emitted from the measurement light source 1 (also serving as a fixation lamp in the present embodiment), and projects the measurement beam generated from one of the divided lights toward the fundus. To do. The light projecting optical system 10a includes a collimator lens 3 that converts a light beam emitted from the measurement light source 1 that emits low coherent light into a parallel light beam, a beam splitter (hereinafter referred to as a beam splitter) 5 that divides the light emitted from the light source 1, A first triangular prism (corner cube) 7 arranged in the transmission direction of the beam splitter 5, a second triangular prism 9 arranged in the reflection direction of the beam splitter 5, a polarizing beam splitter 11, a quarter wavelength plate 18, and light It has a diffusion plate 13 as an optical member that randomly diffuses.

  The diffusing plate 13 is disposed in the optical path of the light projecting optical system 10a, and is used as speckle suppressing means for optically suppressing speckle noise generated in the illumination image. In the present embodiment, the diffusion plate 13 is located at a position deviating from the optical path of the imaging optical system 30 and is disposed in a common optical path through which the first measurement light and the second measurement light pass. In other words, in order to remove speckle noise in the transillumination image, it is inserted into the optical path and vibrated in the direction perpendicular to the optical axis L1 during the transillumination image shooting. In the present embodiment, the diffusing plate 13 is configured to vibrate in a direction perpendicular to the optical axis L1, but may be rotated.

  The 1st drive part 16 has drive sources, such as a motor, and is arrange | positioned in order to insert / remove the diffuser plate 13 from an optical path. The second drive unit 15 has a drive source such as a motor, and is arranged to vibrate the diffusion plate 13 in a direction perpendicular to the optical axis after the diffusion plate 13 is inserted.

  The light receiving optical system 10 b guides the light, which is a combination of one light reflected from the fundus and the other light, to the light receiving element 21. The light receiving optical system 10 b includes a dichroic mirror 33, a quarter wavelength plate 18, a polarizing beam splitter 11, a condenser lens 19, and a light receiving element 21.

  The light (linearly polarized light) emitted from the light source 1 is collimated by the collimator lens 3 and then split by the beam splitter 5 into first measurement light and second measurement light. Then, the divided light is reflected by the triangular prism 7 (first measurement light) and the triangular prism 9 (second measurement light) and folded, and then combined by the beam splitter 5. The synthesized light is reflected by the polarization beam splitter 11, converted into circularly polarized light by the quarter-wave plate 18, and then passes through the diffusion plate 13 and the dichroic mirror 33 that vibrate in the direction perpendicular to the optical axis. Thus, at least the eye cornea and the fundus are irradiated. At this time, when the measurement light beam is reflected by the cornea and the fundus of the subject's eye, the phase is converted by ½ wavelength.

  The corneal reflection light and the fundus reflection light are transmitted through the dichroic mirror 33 (a part of the fundus reflection light is reflected) and the diffusion plate 13 and converted into linearly polarized light by the quarter wavelength plate 18. Thereafter, the reflected light transmitted through the polarization beam splitter 11 is collected by the condenser lens 19 and then received by the light receiving element 21.

  The triangular prism 7 is an optical member (optical path length changing member) arranged to be movable in the optical axis direction in order to adjust the optical path difference between one light and the other light. The triangular prism 7 is linearly moved in the optical axis direction with respect to the beam splitter 5 by driving of a driving unit 71 (for example, a motor). In this case, the optical path length changing member may be a triangular mirror. The driving position of the prism 7 is detected by a position detection sensor 72 (for example, a potentiometer, an encoder, etc.).

  In the above description, the corneal reflection light and the fundus reflection light are configured to interfere with each other. However, the present invention is not limited to this. That is, it has a beam splitter (light splitting member) that splits the light emitted from the light source, a sample arm, a reference arm, and a light receiving element for receiving interference light, and the eye to be examined via the sample arm. It may be an eye size measuring device provided with a light interference optical system that receives interference light due to the measurement light irradiated to the reference light from the reference arm by a light receiving element. In this case, the optical path length changing member is disposed on at least one of the sample arm and the reference arm.

  In the above configuration, the optical path length of the reference light is changed by moving the prism 7 linearly. However, the present invention is not limited to this, and the optical path length of the reference light is controlled by an optical delay mechanism using a rotating reflector. Even if it is the structure which changes this, application of this invention is possible (for example, refer Unexamined-Japanese-Patent No. 2005-160694).

  Further, the measurement light source 1 of the measurement optical system 10 is also used as a transillumination image light source, and is projected onto the fundus of the eye to be examined through the same optical path as the light projection optical system 10a. Then, the inside of the pupil of the eye to be examined is illuminated from behind by the fundus reflection light. The light emitted from the eye pupil to be examined is imaged by the two-dimensional image sensor 35 through the same path as the above-described anterior segment reflection light. Thereby, a transillumination image in the eye pupil to be examined is acquired.

  Next, the control system will be described. The control unit 80 controls the entire apparatus and calculates measurement results. The control unit 80 is connected to the light source 1, the light source 51, the light source 41, the drive mechanism 17, the first drive unit 16, the second drive unit 15, the light receiving element 21, the image sensor 35, the monitor 70, the memory 85, and the like. The control unit 80 is connected to an operation unit 90 for performing various input operations. In addition to various control programs, the memory 85 stores a software program for the control unit 80 to calculate the axial length and the like.

  The operation unit 90 includes, for example, a first mode in which interference light is received by the measurement optical system and the axial length is measured, and a second mode in which a transillumination image that is an image in the pupil is captured by the imaging optical system. Mode switching means (mode switching switch 90a) for issuing a switching signal for switching is provided. The operation unit 90 may be a general-purpose interface such as a mouse as an operation input unit, or may be a touch panel.

  Based on the switching signal from the mode switching unit, the control unit 80 stops the operation of the speckle suppression unit in the first mode and operates the speckle suppression unit in the second mode.

  More specifically, the control unit 80 controls the driving of the first driving unit 16 and the second driving unit 15 to control the attachment / detachment of the diffusion plate 13 and the operation of vibration. When measuring the axial length, the diffusion plate 13 is removed from the optical path, and the vibration is stopped.

  In the first mode, the diffusion plate 13 is removed from the optical path, and the operations of the first driving unit 16 and the second driving unit 15 are stopped. At the time of switching to the second mode, the control unit 80 operates the first drive unit 16 to insert the diffuser plate 13 on the optical path, and operates the second drive unit 15 to vibrate the diffuser plate 13. Is done. Note that when the mode is switched from the second mode to the first mode by operating the mode switch 90a, the control unit 80 stops the operation of the second drive unit 15 and stops the vibration of the diffusion plate 13. Then, the first driving unit 16 is operated to remove the diffusion plate 13 from the optical path. The control unit 80 stops the operation of the first driving unit 16 when the diffusing plate 13 is removed from the optical path.

  The operation of the apparatus having the above configuration will be described. First, a case where the first mode is set will be described. While examining the alignment state of the eye to be inspected displayed on the monitor 70, the examiner moves the apparatus up and down, left and right, and in the front-rear direction using an operating means such as the joystick 12, and moves the apparatus to the eye E with a predetermined amount. Place it in a positional relationship. In this case, the examiner fixes the fixation target to the eye to be examined.

  FIG. 3 is a diagram illustrating an anterior ocular segment observation screen on which an anterior ocular segment image captured by the image sensor 35 is displayed. At the time of alignment, the light source 41 and the light source 51 are turned on. Here, as shown in FIG. 3, the examiner performs vertical and horizontal alignment so that the reticle LT and the ring index R1 by the light source 41 are concentric. In this embodiment, the reticle LT is an electronic display of the alignment reference position set as a position where the corneal apex position and the optical axis L1 of the apparatus coincide. In addition, the examiner performs front-rear alignment so that the ring index R1 is in focus. A ring index R2 from the second light source 51 is displayed outside the ring index R1.

<Calculation of axial length>
After the alignment is completed, a trigger signal for starting measurement is automatically or manually output, and when the measurement light source 1 is turned on by the control unit 80, the measurement light is irradiated to the eye to be examined by the axial length measurement optical system 10, and Reflected light from the eye to be examined by the measurement light is incident on the light receiving element 21 of the light receiving optical system 10b.

  Further, the control unit 80 controls driving of the driving unit 71 to reciprocate the first triangular prism 7. Then, the control unit 80 calculates the axial length based on the timing when the interference light (interference signal) is detected by the light receiving element 21 based on the light reception signal output from the light receiving element 21.

  Information about the acquired axial length of the eye to be examined is stored in the memory 85. When the predetermined number of measurements are completed (or when a predetermined number of eye length values of the subject are obtained), the control unit 80 ends the reciprocating movement of the prism 7 and sets the moving position of the prism 7 to the initial position. Return. In the first mode, the corneal shape can be arbitrarily measured in addition to the axial length.

<Tetsuri shooting>
When the mode selector switch 90a for the second mode is selected by the examiner, the control unit 80 switches the mode from the first mode to the second mode. The control unit 80 may automatically switch from the first mode to the second mode. In the second mode, the control unit 80 operates the first driving unit 16 and inserts it on the optical path of the diffusion plate 13. Next, the second driving unit 15 is operated to vibrate the diffusion plate 13 on the optical path.

  Then, the light source 51 and the light source 41 are turned off, and the light source 1 is turned on. The light is emitted from the light source 1, passes through the diffusion plate 13, and is projected onto the fundus. Then, the fundus reflection light is emitted from the pupil after illuminating the crystalline lens of the eye E. The fundus reflection light emitted from the pupil is reflected by the dichroic mirror 33, picked up by the image pickup device 35 as a transillumination image, and displayed on the monitor 70. Thereby, in the site | part K with a cataract or opacity, a dark shadow is confirmed (refer FIG. 4).

  Here, considering the path of light emitted from the light projecting system, the surface such as the fundus of the eye to be examined has approximately the same or larger unevenness compared to the wavelength of light. For this reason, the light beams irradiated toward the fundus of the subject's eye may overlap with a complicated phase change on the fundus, and the light beams may interfere with each other. When a transillumination image is captured by the reflected light, spotted unevenness occurs on the transillumination image.

  Therefore, the spot-like unevenness on the transillumination image is removed by installing the diffusion plate 13 on the optical path where the unevenness on the speckle occurs when the transillumination image is taken. That is, the phase difference is generated for the measurement light traveling toward the fundus by vibrating the diffuser plate 13 in the direction perpendicular to the optical axis on the optical path. Thereby, the interference state of the measurement light on the fundus is changed, and as a result, the speckle pattern generated on the transillumination image is temporally changed. The pattern is averaged by the integration effect within the response speed of the light receiving system. In this case, for example, the diffusion plate 13 is vibrated at a sufficient speed so that the speckle pattern fluctuates several times within the time for acquiring one frame in the image sensor 35.

  When the switch 12 b provided on the joystick 12 is operated, a transilluminated image is acquired and stored in the memory 85. Further, such a transillumination image is output to the monitor 70, a printer, or the like. In the present invention, an image is acquired by operating the shooting switch 12b. However, a configuration may be adopted in which shooting is automatically performed.

  As described above, according to the present invention, it is possible to remove the spot-like unevenness of the entire image when the intra-pupil image such as the transillumination image is taken, and the examiner can remove the opacity due to the cataract and the spot-like unevenness. It is possible to confirm without erroneous recognition.

  Further, in the above description, by operating the diffuser plate 13 at the time of transillumination imaging, speckle noise of the transillumination image is removed, and a good transillumination image suitable for confirming the progress state of the cataract can be obtained. On the other hand, by stopping the operation of the diffusion plate 13 during the measurement of the axial length, the light coherence between the fundus reflection light and the other light is ensured, and the axial length can be measured accurately.

  In the present invention, the diffusing plate 13 is used as the optical member used for removing speckle noise, but the present invention is not limited to this. For example, a prism may be used. In the case of using a prism, the driving unit rotates the prism and rotates the light beam eccentrically, thereby changing the scattering state of the light beam on the fundus and removing speckle noise. It is also possible to reduce speckle noise by reducing the coherence by using a member such as a crystal depolarization plate, a bundle fiber, a photonic crystal, or a liquid crystal plate.

  In the above configuration, the diffusion plate 13 is inserted between the polarization beam splitter 11 and the dichroic mirror 33. However, the configuration is not limited to this, and any position outside the optical path of the imaging optical system 30 may be used.

  Furthermore, a common optical path (for example, between the light source 1 and the beam splitter 5) for the first measurement light and the second measurement light is preferable. Thereby, the entire measurement light beam is acted on by the optical member for removing speckle noise. On the other hand, if it is arranged in any one of the divided optical paths, the other light is not changed.

  In the case of using a prism, it is necessary to move the light beam on the fundus. Therefore, the arrangement position should be a position deviating from the optical path of the imaging optical system 30 and a position deviating from the fundus conjugate position. It becomes applicable with.

  In the present invention, an SLD that is a light source that emits low-coherent light is used as the measurement light source 1. However, the present invention is not limited to this, and any light source that emits coherent light may be used. For example, a multi-mode laser diode that is a highly coherent light source is also applicable. The present invention can also be applied to a configuration in which the axial length is measured by SS (Swept source) -OCT using a wavelength variable light source.

  In the above configuration, when a light beam deflecting member such as a prism is used as the speckle removing means, if it is arranged at the pupil conjugate position, even if the light beam deflecting member is operated during the measurement of the axial length, The movement of the corneal reflected light may be reduced and the reduction in coherence may be suppressed by a certain amount.

<Improvement of measurable rate>
With the configuration as described above, when an intra-pupil image such as a transillumination image is photographed, spotted unevenness of the entire image can be removed. The examiner can easily observe the turbidity due to cataracts, and thus can improve the measurable rate (measurement success rate) at the time of measuring the eye.

  For example, when there is a turbid portion at a position on the optical axis passing through the apex of the cornea, the measurement light of the apparatus may be scattered due to turbidity, and the measurement may fail. The control unit 80 changes the alignment position on the pupil to avoid the position where the measurement light is transmitted from the turbid portion. As a result, scattering of the measurement light is suppressed and the measurable rate is improved.

  Hereinafter, a method for improving the measurable rate at the time of measuring the eye to be examined will be described with reference to the flowchart shown in FIG.

  First, the axial length is measured. When the alignment to the center of the cornea is completed, a trigger signal for starting measurement is output automatically or manually. The control unit 80 calculates the axial length based on the trigger signal. The control unit 80 switches from the first mode to the second mode based on the obtained measurement result of the axial length.

  For example, the control unit 80 performs mode switching when the acquired S / N ratio of the axial length is equal to or less than a predetermined value. Of course, when the S / N ratio of the axial length is equal to or less than a predetermined value, the control unit 80 may display that fact on the monitor 70. The examiner selects whether to switch the mode.

  After the mode switching, the control unit 80 captures a transillumination image by the image sensor 35. The control unit 80 displays the captured illumination image on the monitor 70 (see FIG. 4). When an imaging start trigger signal is output automatically or manually, the control unit 80 acquires a transillumination image for analysis (a transillumination image). The control unit 80 analyzes the acquired transillumination image in order to change the alignment position.

  The control unit 80 processes the transillumination image acquired by the image pickup device 35, so that the turbidity part in a predetermined region centered on the corneal apex that is set so that the S / N ratio of the interference signal satisfies an allowable value. Find the two-dimensional distribution of. Based on the obtained two-dimensional distribution, the control unit 80 specifies a light transmission region within the predetermined region.

  For example, the control unit 80 divides the predetermined area set so that the S / N ratio of the interference signal satisfies the allowable value into a plurality of the illuminated images. The control unit 80 compares the turbidity for each divided region using the calculation result of the two-dimensional distribution. Based on the comparison result, the controller 80 identifies an area with a low turbidity rate as the light transmission area.

  This will be specifically described below. As illustrated in FIG. 6, the control unit 80 changes the alignment position based on the turbidity ratio in each of the divided regions P1 to P4 in the measurable region P of the transillumination image.

  The S / N ratio in the reflected light from the eye to be examined decreases with increasing distance from the corneal apex position. Since the acquisition of the interference signal becomes difficult due to the decrease in the S / N ratio, there is a possibility that the measured value of the axial length is not calculated.

  The measurable area P indicates an area that is a predetermined distance away from the corneal apex position. When measurement light is incident in the absence of turbidity, the S / N of an interference signal including reflected light from the eye to be examined is displayed. This is an area in which the ratio can be obtained above the allowable value (for example, an area of φ1.0 mm).

  For example, in the measurable region P on the pupil, the S / N ratio capable of measuring the axial length can be obtained when the measurement light beam (measurement light diameter is φ1.5 mm) passes a predetermined area or more. The S / N ratio of the interference signal caused by light in the vicinity of the optical axis L1 (the central portion of the measurement light beam) is the largest. If the light in the vicinity of the optical axis L1 can pass in the measurable region P, the measurement success rate becomes high.

  The measurable area P is set in advance by experiment, simulation, or the like. For example, the setter moves the optical axis L1 from the apex of the cornea and obtains an area in which the S / N ratio of the interference signal can be secured at a predetermined value or more (for example, an area away from the apex of the cornea by ΔD). Each divided area P1 to P4 is an area obtained by dividing the measurable area P into predetermined areas. The controller 80 changes the alignment position to any position in each region (details will be described later). The turbidity ratio indicates the ratio of the turbidity part to the entire area in each divided area.

  In the present embodiment, the measurable area P is set as a circular area, but is not limited to this. Any position where the S / N ratio of the interference signal can be acquired at a predetermined value or more is acceptable. The control unit 80 electronically displays a pattern indicating the measurable region P on the monitor 70 together with the illumination image. The pattern may be any shape, and is displayed, for example, as a circle or a square.

  The control unit 80 acquires the luminance information in the measurable region P of the transillumination image image in order to calculate the turbidity ratio in each of the divided regions P1 to P4. A method for calculating the turbidity will be described. For example, the control unit 80 detects the luminance value of each pixel in the measurable region P. The control unit 80 determines whether each pixel corresponds to a turbid portion or a non-turbid portion by determining whether or not the detected luminance value is equal to or less than a predetermined threshold value. When the luminance value of the pixel is equal to or less than a predetermined threshold, the control unit 80 determines that the pixel corresponds to the turbid portion. When the luminance value of a pixel is greater than a predetermined threshold, the control unit 80 determines that the pixel corresponds to a portion without turbidity.

  The control unit 80 performs the determination process as described above for all the pixels in the measurable region P. The control unit 80 calculates the number of pixels corresponding to the turbid portion in the total number of pixels in each of the divided regions P1 to P4. The control unit 80 calculates a turbidity rate in each divided region. For example, the turbidity is represented by a parameter of 0-100. The parameter of the turbidity ratio is closer to 100 as the number of pixels in the turbid part is larger in the region, and the parameter is closer to 0 as the number of pixels in the turbid part is smaller. When the parameter of the turbidity rate is 0, it indicates that the turbidity portion is completely absent in the region. When the turbidity parameter is 100, it indicates that the entire region is a turbid portion.

  Since the spotlight-like unevenness of the entire image is removed by the diffusion plate 13, the control unit 80 can detect the transillumination image without erroneously recognizing the turbidity due to the cataract and the spotted unevenness.

  The control unit 80 controls the drive mechanism 17 based on the imaging signal output from the imaging element 35 to operate the automatic alignment for the eye to be examined, and the optical axis L1 of the axial length measurement optical system 10 is located in the light transmission region. Change the alignment position so that it is positioned. For example, the control unit 80 changes the alignment position based on the calculated turbidity rate. The control unit 80 compares the turbidity rate parameters of the respective divided regions. Using the comparison result, the control unit 80 changes the alignment position so that the optical axis L1 of the apparatus passes through the divided region having the smallest turbidity parameter.

  FIG. 7 is a diagram illustrating an example of the transillumination image displayed on the screen on the monitor 70 when the turbidity ratio is calculated in each divided region.

The controller 80 uses the drive mechanism 17 to drive the axial length measurement optical system 10 with respect to the eye to be examined,
Control is performed so that the optical axis L1 of the optical axis length measurement optical system 10 is positioned in the specified light transmission region (for example, a divided region having the smallest turbidity parameter).

  The control unit 80 shifts the optical axis L1 from the vicinity of the corneal apex by moving the apparatus main body vertically and horizontally with respect to the eye to be examined. For example, the control unit 80 changes the alignment position so that the predetermined position (the center of gravity position of the divided area) of the divided area P1 having the smallest opacity parameter matches the optical axis L1 of the apparatus (see FIG. 8). The predetermined position is set, for example, at the center of gravity of the divided area.

  The reference position O is an alignment reference position for matching the corneal apex position with the optical axis L1. As shown in FIG. 8, the control unit 80 moves the alignment position from the reference position O to the alignment position O3 shifted by D2 leftward and D3 downward with respect to the eye to be examined. The shift amounts (D2, D3) are calculated in advance so that the measurement light passes through a predetermined position in each divided region by experiment, simulation, or the like. The calculated shift amounts (D2, D3) are stored in the memory 75.

  After changing the alignment position to the alignment position O3, the control unit 80 turns on the light source 51 and the light source 41 and turns off the light source 1, and further switches the monitor 70 to the anterior ocular segment front image.

The control unit 80 performs automatic alignment at the changed alignment position O3. After detecting the corneal apex position (corneal bright spot position) Mo1, the control unit 80 obtains a deviation amount Δd1 between the alignment position O3 and the corneal apex position Mo1 using the detection result.
As a result, the detected misalignment amount is offset by D2 and D3 with respect to the alignment reference position O that is the alignment position before the change.

  The controller 80 controls the drive of the drive mechanism 17 so that the deviation amount Δd1 enters the allowable range A2 set with the alignment position O3 as the center (operation of automatic alignment). The control unit 80 determines whether or not the deviation amount Δd is within the alignment completion allowable range A2 and continues for a certain time (for example, 10 frames of image processing or 0.3 seconds). The suitability of the alignment is determined.

  When it is determined that the alignment is appropriate, the control unit 80 stops driving the drive mechanism 17. Even after the alignment is completed, the control unit 80 may detect the deviation amount Δd1 as needed, and may resume automatic alignment when the deviation amount Δd1 exceeds the allowable range A2. The control unit 80 may perform control (tracking) for tracking the measurement unit 8 with respect to the subject's eye so that the deviation amount Δd1 satisfies the allowable range A2.

  As described above, the control unit 80 performs automatic alignment. After the alignment is completed, the control unit 80 calculates the axial length by outputting a trigger signal for starting measurement automatically or manually. The control unit 80 displays the measurement result of the axial length on the monitor 70 and ends the measurement.

  As described above, by changing the alignment position, the control unit 80 moves the position of the optical axis L1 of the apparatus to an area where the area of the turbid portion is small.

  More measurement light can pass through the movement of the optical axis L1. For example, the possibility that the light beam close to the central portion of the measurement light is scattered by the turbid portion is reduced. As a result of suppressing the decrease in the S / N ratio of the interference signal due to scattering at the turbid portion, the measurable rate is improved.

  Although the control unit 80 is configured to perform mode switching when the S / N ratio of the interference signal of the axial length is equal to or less than a predetermined value, the present invention is not limited to this. The mode may be switched based on the measurement result of the axial length. For example, when the control unit 80 does not acquire a predetermined number of measurement results as a result of measuring the axial length of a predetermined number of times (for example, the measurement result is acquired only twice in five measurements). The mode may be switched. The control unit 80 may be configured to switch the mode when the newly acquired measurement value of the axial length is out of the predetermined measurement value range (is an abnormal value).

  In the above description, the control unit 80 changes the alignment position based on the turbidity parameter, but the present invention is not limited to this. For example, the control unit 80 may be configured to change the alignment position by calculating an average luminance value for each divided region and comparing the average luminance value calculated in each divided region. In a region where there is much turbidity, the luminance value decreases due to turbidity, and therefore the average luminance value decreases. For this reason, the control unit 80 may calculate an average luminance value for each divided region, and move the alignment position to the divided region in which the luminance value having the largest average luminance value is calculated. As a result, the alignment position can be moved to a region with less turbidity.

  In the above description, the control unit 80 displays the turbidity ratio parameter on the still image of the acquired transillumination image, but is not limited thereto. For example, the control unit 80 may display the superimposed image on the monitor 70 by superimposing the analysis result of the transilluminated image on the moving image of the transilluminated image. For example, the turbidity parameter is superimposed on the transillumination moving image displayed on the monitor 70. Thereafter, the control unit 70 detects the movement of the transillumination image, thereby tracking the display of the parameter of the turbidity rate to the display of the transillumination image. In the superimposition process, for example, the pupil portion of the transillumination image stored in the memory 85 as the reference image and the pupil portion of each moving image of the transillumination image sequentially detected are detected and superimposed. Is done by.

  In the above description, the control unit 80 is configured to change the alignment position based on the turbidity, but the present invention is not limited to this. For example, the examiner confirms the turbidity rate parameter displayed on the monitor 70. After confirmation, the examiner changes the alignment position.

  When the alignment position is changed by the examiner, for example, the examiner uses the operation unit 90 (touch panel, joystick, etc.) to move the position of the optical axis L1 of the apparatus on the screen on the monitor 70 (measurement light is emitted). Position). When the selection is made by the examiner, the control unit 80 changes the alignment position so that the optical axis L1 of the apparatus passes through the selected region.

  The examiner may set the alignment position by using the observation result when the transillumination image is observed without using the turbidity parameter displayed on the monitor 70.

  In the above description, the turbidity parameter is displayed on the monitor 70, but it may not be displayed. For example, the control unit 80 may display the parameter on the monitor 70, call the turbidity rate parameter from the memory 85 or the like, and change the alignment position.

  In the above description, the divided region with the smallest turbidity is set as the light transmission region, and the alignment position is changed so that the optical axis L1 of the apparatus passes through the light transmission region. However, the present invention is not limited to this. The light transmission region in the present embodiment may be a region in which the measurement light beam can pass a predetermined area or more and an allowable S / N can be obtained. For example, the control unit 80 specifies a region corresponding to the turbidity rate at which an allowable S / N is obtained. The controller 80 may change the alignment position so that the optical axis L1 of the apparatus passes over the specified area.

  In the above description, the center of gravity position of the divided area is set as the predetermined position when the alignment position is changed, but the present invention is not limited to this. The predetermined position only needs to be able to move the optical axis L1 of the apparatus in each divided area, and it is only necessary that the optical axis L1 of the apparatus falls within the divided area. For example, it may be set at a position away from the corneal apex position by a predetermined distance with respect to each divided region.

  If the measurement result of the axial length is out of the predetermined allowable range after changing the alignment position, the control unit 80 further performs measurement after changing the alignment position again. Regarding the change of the alignment position, the alignment position may be changed by a predetermined amount within the same divided region, or may be changed to a predetermined position in a different divided region. When the alignment position is changed to a different divided area, the selection of the divided area to be changed may be performed based on the parameter of the turbidity rate or may be changed to a neighboring divided area.

  If the measurement result is not satisfactory or the measurement result is not calculated even if the alignment position is changed a predetermined number of times, the control unit 80 determines that the measurement error has occurred and stops measuring the axial length. The control unit 80 may display that effect on the monitor 70 or the like.

  In the above description, the process shifts to the alignment position changing process based on the obtained measurement result of the axial length, but the present invention is not limited to this. For example, a configuration in which a transillumination image is first taken and the alignment position is changed may be used.

  In the above description, the analysis is performed by acquiring the transilluminated image as a still image, but the present invention is not limited to this. For example, when the transillumination image is captured after the mode is switched from the first mode to the second mode, the control unit 80 is displayed on the monitor 70 in order to change the alignment position based on the cloudy portion. Analyzing the transillumination image. For example, the control unit 80 sequentially analyzes the transillumination image displayed on the monitor 70 to update the analysis result related to the transillumination image in real time.

  In the above description, the control unit 80 completes the alignment by automatic alignment after changing the alignment position, but is not limited to this. For example, the examiner may perform alignment manually. After changing the alignment position, the control unit 80 switches the image to be displayed on the monitor 70 to the front image of the anterior segment. The examiner performs alignment by confirming the front image of the anterior segment.

  In addition, the control part 80 is good also as a structure which changes and displays the transillumination image on the monitor 70, or the display magnification of a transillumination image. By doing so, the illuminated image becomes easier to observe.

1 is an external view of an ophthalmologic apparatus according to the present invention. It is a schematic block diagram shown about the optical system of the ophthalmologic apparatus which concerns on this embodiment. It is a figure which shows the anterior ocular segment observation screen on which the anterior ocular segment image was displayed. It is a figure which shows the transillumination image observation screen on which the transillumination image was displayed. It is a flowchart explaining the method to improve the measurable rate at the time of measuring the eye to be examined. It is a figure which shows each division area in the measurable area | region of a transillumination image. It is a figure which shows an example of the transillumination image displayed on the screen on a monitor when the turbidity rate is calculated in each division area. It is a figure explaining the case where an alignment position is changed so that the predetermined position of a division area and the optical axis L1 of an apparatus may correspond.

DESCRIPTION OF SYMBOLS 1 Measurement light source 10 Optical axis length measurement optical system 10a Light projection optical system 10b Light reception optical system 13 Diffusion plate 15 2nd drive part 16 1st drive part 30 Anterior eye part front imaging optical system 35 Two-dimensional image sensor 40 Alignment projection optical system 50 kerato projection optical system 70 monitor 80 control unit 85 memory 90 operation unit 90a mode change switch

Claims (6)

A projection optical system that divides the light emitted from the light source and projects a measurement beam generated from one of the divided lights toward the fundus;
A light receiving optical system that guides light, which is a combination of one light reflected from the fundus and the other light, to a light receiving element;
An optical member arranged to be movable in the optical axis direction in order to adjust the optical path difference between the one light and the other light, and based on an interference signal output from the light receiving element In the axial length measuring device for measuring the axial length of the eye to be examined,
An imaging optical system having an imaging element having an imaging surface arranged at a position substantially conjugate with the anterior eye part of the eye to be examined, and for imaging a transillumination image in the eye pupil part of the eye illuminated by the fundus reflection light;
By processing the transillumination image acquired by the image sensor, the two-dimensional distribution of the turbidity portion in a predetermined region set so that the S / N ratio of the interference signal satisfies the allowable value is obtained, and the obtained two-dimensional distribution is obtained. And a light transmission area specifying means for specifying a light transmission area in the predetermined area based on the above.   Drive means for driving the measurement optical system with respect to the eye to be examined, and controlling the drive means so that the optical axis of the measurement optical system is positioned in the light transmission area specified by the light transmission area specification means 2. The axial length measuring device according to claim 1, further comprising drive control means.   The light transmission region specifying means divides the predetermined region into a plurality of regions, and compares the turbidity rate of each divided region using the calculation result of the two-dimensional distribution to thereby select a region with a low turbidity rate as the light transmission region. The axial length measuring device according to claim 2, characterized by: The drive control means operates the automatic alignment for the eye to be examined by controlling the drive means based on the imaging signal output from the imaging element,
4. The axial length measuring device according to claim 3, wherein the alignment position is changed so that the optical axis of the measurement optical system is positioned in the light transmission region. The light projecting optical system has a light source that emits coherent light, and the light source is a light projecting optical system that also serves as a transillumination light source,
The ocular axial length measurement apparatus according to claim 4, further comprising speckle suppression means that is disposed in an optical path of the projection optical system and optically suppresses speckle noise generated in the transillumination image. A mode for generating a switching signal for switching between a first mode for receiving the interference light by the measurement optical system and measuring the axial length and a second mode for capturing the transillumination image by the imaging optical system. Switching means;
Based on a switching signal from the mode switching means, control means for stopping the operation of the speckle suppression means in the first mode and operating the speckle suppression means in the second mode;
The ophthalmic measurement apparatus according to claim 5, comprising: