JP2014188272A - Ophthalmological device, control method therein, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ophthalmological device in which speckle noise is reduced when reflected luminous flux from an eyeground is received by a two-dimensional light-receiving element.SOLUTION: An ophthalmological device includes: projection means for projecting coherent luminous flux on an eye to be inspected; light-receiving means for receiving a reflected luminous flux of the luminous flux from the eye to be inspected by a two-dimensional light-receiving element; and a shared optical system in which a part of optical paths of the projection means and the light-receiving means is shared. In the ophthalmological device, a transparent optical member is arranged on an optical axis of the shared optical system, and drive means is included for oscillating the optical member so that an inclination angle is generated in a plane substantially orthogonal to the optical axis.

Description

  The present invention relates to an ophthalmologic apparatus that projects a coherent light beam on an eye to be examined and receives reflected light, a control method thereof, and a program.

  Many ophthalmologic apparatuses using a coherent light source are known. Particularly, in recent years, semiconductor lasers and SLDs (super luminescent diodes) are often used in ophthalmologic apparatuses as small-sized and high-power light sources. However, there is a problem that not only the laser but also the SLD cannot completely eliminate the coherence, and the speckle noise becomes a noise component at the time of image detection and stable image data cannot be obtained.

It is considered that speckle noise generated when a coherent light beam is projected onto the fundus is generated by the following mechanism. When a light beam is irradiated on the fundus oculi, the reflected light beams interfere with each other due to subtle irregularities on the fundus oculi. The interfered light beam is detected as a speckle noise pattern, that is, a speckle pattern, on the two-dimensional light receiving element which is the fundus conjugate surface through the eye lens, the cornea, and the optical member of the apparatus.
When measurement is performed using the image data, measurement values cannot be stably obtained due to such speckle noise or speckle pattern.

In particular, in an eye refractive power measuring apparatus, as a first condition, a high output light source is necessary because the fundus reflection bundle is weak light. Further, when there is opacity of the intermediate translucent body such as an eye to be examined having a small pupil or a cataract, the cornea may be defective. For this reason, as a second condition, a light source with a narrow directivity angle is necessary to project the light beam on the fundus while avoiding it. Furthermore, as a third condition, it is desirable to use near infrared light that is not dazzling for the subject. From these three requirements, a light source with a high output of near-infrared wavelength and a low coherence is required.
However, in the above-described high-power SLD light source that satisfies these conditions, it is necessary to solve the problem related to speckle noise.

  As a method for removing such speckle noise, Patent Document 1 discloses an eye refractive power measuring device that rotates and removes a prism or a plane-parallel plate at high speed. In this document, an image is detected every 1/30 seconds, and an addition process is performed once or twice. Addition processing is disclosed in which the coordinates of images are matched to add luminance levels.

Japanese Patent No. 4666461

However, in the eye refractive power measurement apparatus disclosed in Patent Document 1, it is necessary to rotate a prism or a plane parallel plate at a high speed as a method for removing the speckle pattern. Therefore, it is necessary to always rotate the measurement time at a high speed. Even if the measurement time is 30 seconds, an image is detected every 1/30 seconds, and even if the addition process is performed once or twice, it is necessary to make at least one rotation in 1/30 seconds. Therefore, even if it is used for both eyes, 50 persons / day for 5 years, it will rotate 3.75 million, and it is difficult to maintain durability and reliability due to bearing wear and vibration.
In addition, it is complicated to arrange the means for driving the rotation mechanism in the optical path.

  The present invention has been made in view of the above situation, and an ophthalmologic apparatus capable of reducing speckle noise with a simple configuration and excellent durability and reliability, a control method thereof, and a program The purpose is to provide.

In order to achieve the above object, an ophthalmologic apparatus according to the present invention has a projection unit that projects a coherent light beam on a subject's eye, and causes a two-dimensional light receiving element to receive a reflected light beam of the coherent light beam from the eye to be examined. A light receiving means;
In an ophthalmologic apparatus having a shared optical system sharing a part of the optical path of the projection means and the light receiving means, an optical member disposed on the optical axis of the shared optical system, and an orthogonal plane of the optical axis of the service optical system Drive means for vibrating the optical member about a predetermined axis so that an inclination angle is generated.

  According to the present invention, when the optical element is vibrated as a means for reducing speckle noise, the durability of the driving means for the vibration can be maintained and the size can be reduced. Further, speckle noise or speckle patterns caused by speckle noise can be reduced by eliminating or blurring from the imaging range, and a stable ring image can be detected, and a highly reliable ophthalmologic apparatus can be provided.

It is an optical diagram of an eye refractive power measuring device explaining the present invention. It is explanatory drawing of the light beam which passes a parallel plane plate. It is an optical path explanatory drawing of the optical power measurement optical system of the present invention. It is drive explanatory drawing of the Example of this invention. It is explanatory drawing of the aperture stop in an optical path. It is drive explanatory drawing of another Example.

(First embodiment: eye refractive power measuring device)
An eye refractive power measuring apparatus according to a first embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a layout diagram of a measurement optical system of an eye refractive power measurement apparatus. A light source having a coherent light source wavelength of 880 nm, here an SLD will be described. On the optical path 01 from the eye refractive power measurement light source SLD 101 to the eye E to be examined, a lens 102, a diaphragm 103 almost conjugate with the pupil Ep of the eye E to be examined, a perforated mirror 104, a plane parallel plate 105, and an objective lens 106 are arranged. Has been. The light source 101 that emits the coherent light beam and these configurations described here function as projection means for projecting the light beam onto the eye to be examined in the present invention. Further, a dichroic mirror 107 that sequentially reflects visible light from the eye E side and partially reflects a light beam having a wavelength of 880 nm is sequentially arranged. On the optical path 02 in the reflection direction of the perforated mirror 104, a diaphragm 108, a light beam splitting prism 109, a lens 110, and an image sensor 111, each having an annular slit substantially conjugate with the pupil Ep, are sequentially arranged. The imaging element 111 functions as a two-dimensional light receiving element, and the configuration for guiding the reflected light beam of the coherent light beam from the eye to be examined to the imaging element 111 functions as a light receiving unit that causes the light receiving element to receive the reflected light beam. In addition, the configuration in which various optical elements in the projection unit and various optical systems in the light receiving unit share a part of an optical path such as a coherent light beam functions as a shared optical system in the present embodiment.

  The above-described optical system is for measuring eye refractive power, and the light beam emitted from the measurement light source 101 is primarily imaged by the lens 102 on the side of the objective lens 106 of the plane parallel plate 105 while the light beam is narrowed by the diaphragm 103. Then, the light passes through the objective lens 106 and the dichroic mirror 107 and is projected onto the pupil center of the eye E. The luminous flux forms an image on the fundus Er, and the reflected light enters the objective lens 106 again through the center of the pupil. The incident light beam is reflected around the perforated mirror 104 after passing through the objective lens 106.

The reflected light beam is pupil-separated by a stop 108 substantially conjugate with the eye pupil Ep to be examined, and is projected as a ring image on the light receiving surface of the image sensor 111. If the eye E is a normal eye, the ring image is a predetermined circle, and the curvature of the circle is small for the myopic eye, and the curvature of the circle is large for the hyperopic eye. When the subject eye E has astigmatism, the ring image becomes an ellipse, and the angle formed by the horizontal axis and the major axis of the ellipse becomes the astigmatism axis angle. The refractive power is obtained based on the coefficient of the ellipse.
On the other hand, in the reflection direction of the dichroic mirror 107, a fixation target projection optical system and an alignment light receiving optical system that shares anterior eye part observation and alignment detection of the eye to be examined are arranged.

  On the optical path 03 of the fixation target projection optical system, a lens 211, a dichroic mirror 212, a lens 213, a folding mirror 214, a lens 215, a fixation target 216, and a fixation target illumination light source 217 are sequentially arranged. At the time of fixation guidance, the projection light flux of the light source 217 for illuminating the fixation target illuminates the fixation target 216 from the back side, and the fundus of the eye E to be examined through the lens 215, the folding mirror 214, the lens 213, and the lens 211. Projected to Er. The lens 215 can be moved in the optical axis direction by a fixation guidance motor in order to guide the diopter of the eye E and realize a cloud state.

  In addition, an alignment prism 218, a lens 219, and an image sensor 220 are sequentially arranged on the optical path 04 in the reflection direction of the dichroic mirror 212, so that the anterior ocular segment observation and alignment detection of the eye to be examined can be performed. The alignment prism 218 can be inserted into the optical path of the optical axis 04 during alignment by a drive solenoid (not shown) together with a filter (not shown) that transmits a light beam having a wavelength of 880 nm.

  Anterior eye illumination light sources 221a and 221b having a wavelength of about 780 nm are arranged obliquely in front of the anterior eye part of the eye E to be examined. The luminous flux of the anterior segment image of the eye E illuminated by the anterior segment illumination light sources 221a and 221b passes through the dichroic mirror 107, the lens 211, the dichroic mirror 212, and the central opening 218 of the alignment prism. An image is formed on the light receiving sensor surface. A light source for alignment detection is also used as a measurement light source 101 for measuring eye refractive power. At the time of alignment, a translucent diffusion plate 222 is inserted into the optical path by a diffusion plate driving solenoid.

  The position where the diffusion plate 222 is inserted is a primary image formation position by the projection lens 102 of the measurement light source 201 described above, and is inserted at the focal position of the lens 106. As a result, an image of the measurement light source SLD 101 is once formed on the diffusion plate 222, and this is a secondary light source and is projected from the lens 106 toward the eye E as a thick parallel light beam.

  This parallel light beam is reflected by the eye cornea Ef to be examined to form a bright spot image. A part of the light beam is again reflected by the dichroic mirror 107, reflected by the dichroic mirror 212 through the lens 211, incident from the bifurcated shape of the alignment prism 218, reduced to the lens 219, and imaged on the image sensor 220. The

  Through the opening at the center of the alignment prism 218, a light beam having a wavelength of 780 nm or more of the anterior segment illumination light sources 221a and 221b passes. For this reason, the reflected luminous flux of the anterior segment image illuminated by the anterior segment illumination light sources 221a and 221b follows the observation optical system in the same manner as the path of the reflected luminous flux of the cornea Ef, and through the opening of the alignment prism 218, An image is formed on the image sensor 220 by the imaging lens 219. Further, one of the light beams transmitted through the alignment prism 218 is refracted downward and the other is refracted upward.

  The above is the configuration that realizes refractive power measurement by the eye refractive power measurement optical system, observation of the subject's eye, and cloud detection and alignment detection by a fixation target. These components are controlled by a CPU 233 arranged as a control unit. However, since the measurement light source SLD101 is a light source that emits a coherent light beam, it is diffusely reflected by the fundus Er of the eye E and light waves interfere with each other due to minute unevenness.

  Therefore, by tilting the plane parallel plate 105 arranged substantially orthogonal to the optical axis 01 by vibration, it is possible to shift the position of irradiation to the fundus oculi Er. That is, the plane-parallel plate 105, which is a transmissive optical member, is disposed on the optical axis in the shared optical system, and generates an inclination angle with respect to a substantially orthogonal plane of the optical axis by driving means exemplified by a piezoelectric element or the like described later. Vibrated. In the present embodiment, an example in which interference light is transmitted through the plane-parallel plate 105 is illustrated, but an aspect in which transmitted light is reflected may be employed. Therefore, the member arranged on the optical axis is preferably grasped as an optical member.

FIG. 2 is an optical diagram when the plane parallel plate 105 is tilted. When the plane-parallel plate 105 is tilted at an inclination angle of θ by vibration, the light beam of the measurement light source SLD101 is irradiated to the fundus around the optical axis 01 ′ shifted by δ according to the following two equations.
δ = d / cos (φ) × sin (θ−φ)
n · sin φ = sinθ (where n is the refractive index)

  FIG. 3 shows an optical path to the fundus Er when the optical axis is shifted by δ as described in FIG. Further, the optical members are the same as those shown in FIG. The shift amount at the fundus Er is δ ′, which is obtained by multiplying the shift amount δ generated by the plane parallel plate 105 by the magnification of the refractive power of the objective lens 106 and the eye E to be examined. The shift direction is shifted in a symmetric direction with respect to the optical axis 01. (In FIG. 3, since the plane parallel plate 105 has shifted downward in the figure, the optical axis shifts upward in the fundus Er.)

  The speckle pattern changes when this δ 'is shifted by one speckle pattern or more. If the shift amount for one spot is δ ′ = 50 μm, the magnification of the eye E and the objective lens 106 is 1.5 and δ = 75 μm, and the tilt angle due to the vibration of the parallel flat plate 105 is 2.4. If it is time, it will be good. That is, the parallel plane plate 105 is provided with an inclination of an angle for shifting the optical axis of the coherent light beam on the fundus according to the speckle pattern, that is, the optical axis is shifted more than the interval between the spots of the adjacent speckle pattern. The speckle pattern is removed from the ring image by giving an inclination angle that forms a quantity. Therefore, the speckle pattern is not generated in the picked-up ring image by applying vibration to the plane-parallel plate 105 so as to incline at a maximum of several degrees during the accumulation time of the image pickup device 1/30 seconds. Further, according to the present embodiment, the coherent light beam is transmitted through the plane-parallel plate in a vibrating state, and the state of interference is changed by the vibration, resulting in speckle noise, and thus the speckle pattern itself. The effect of blurring can also be expected. In this embodiment, the plane parallel plate 105 is inclined using a bimorph 302 described later. Specifically, the inclination angle is changed by adjusting the length of the bimorph 302. However, the inclination angle may be adjusted by changing the voltage applied to the bimorph 302, for example. By obtaining an angle for manipulating the shift amount of the optical axis due to the speckle pattern and applying a voltage according to the angle, a suitable optical axis shift of the coherent light beam can be obtained.

(Embodiment of Parallel Plate Driving Device in First Embodiment)
FIG. 4 is a diagram illustrating a technique for vibrating and driving the parallel flat plate 105 around a predetermined axis.
In FIG. 4a, the parallel flat plate 105 is shaken in the left-right direction. A bearing 301 a is joined to the back surface of the plane parallel plate 105 with respect to the axis A orthogonal to the optical axis 01. FIG. 4B is a view of the back surface, and a bearing 301b is joined to the lower part of the plane parallel plate 105 coaxially with the axis A. Also, a bimorph 302 made of a piezoelectric element is joined to the surface to which the bearing is joined. The bearings 301a and 301b correspond to predetermined shafts in the present invention.

The bimorph 302 is obtained by attaching piezoelectric ceramics 302b to both surfaces of a metal plate 302a. That is, the driving means includes a bimorph 302 that is a plate-like member formed by laminating a plate-like metal and plate-like piezoelectric ceramics that are in contact with both sides thereof. By alternately applying an applied voltage to the two piezoelectric ceramics 302b at a frequency of 30 Hz or more, the plate-like bimorph 302 is bent in the thickness direction around the applied voltage portion 302c, and the tip vibrates. By arranging the vibration end in contact with the plane parallel plate 105, the vibration propagates to the plane parallel plate 105 and vibrates. By making the length of the bimorph 302 appropriate, it is possible to generate vibration at an angle necessary to remove the speckle pattern. By applying vibration to the plane-parallel plate 105 with the above configuration, it is possible to remove the speckle pattern regardless of the conventionally used rotation mechanism. Compared with the rotation mechanism, this configuration can reduce the configuration with so-called sliding of bearings and the like, and can reduce the sliding portion or the sliding amount for obtaining the same effect. The effect of improvement is obtained.
Note that the vibration frequency of the plane-parallel plate 105 is preferably set so as to obtain an inclined state in accordance with the timing at which the image sensor 111 captures data, but is not limited to this, and is inclined to any frequency. If the tilting operation is repeated, the effect of reducing the speckle pattern can be obtained.

  Incidentally, although the vibration center axis A (predetermined axis corresponding to the center axis of the bearings 301a and 301b described above) enters the optical path, the stop 108 on the optical axis 02 is as shown in FIG. The diaphragm has a ring-shaped opening. Legs X and Y are arranged on a straight line in order to hold the light shielding member at the center. The legs are made as thin as possible so as not to affect the ring detection. However, it is preferable to arrange them so that the vibration center axis A coincides with the position of the legs that serve as a fixing portion of the light receiving system diaphragm. That is, the central axis A when vibrating the optical member arranged in the shared optical system in the present embodiment is arranged at a position overlapping with the shadow obtained by projecting the fixed portion of the diaphragm plate arranged in the light receiving means. And good.

In addition, although it has been described in FIG. 4 that it vibrates in one direction, another unit is added, and the light source shifted up, down, left and right on the fundus by rotating the vibration center axis A by 90 degrees and arranging two units on the optical axis 01. Can be projected.
In the present embodiment, the parallel plate 105 and the driving device that drives the parallel plate 105 are shown as the configuration that suppresses the speckle pattern. However, from the viewpoint of durability, the configuration operates when acquiring image data. Is preferred. For this reason, in the present embodiment, the control unit 233 is instructed to start vibration in response to receiving an instruction to acquire image data, and is in response to reception of an instruction to end image data acquisition. Is stopped.

Second Embodiment: Other Embodiment of Parallel Plate Driving Device
FIG. 6 shows an embodiment in which a parallel plane plate having a circular diameter is vibrated so as to wave in the circumferential direction. In FIG. 6 a, a cylindrical member 401 and a cylindrical member 402 are arranged coaxially with the optical axis 01, and a coil spring 403 that can expand and contract in the direction of the optical axis 01 is arranged on the inner surface of the cylindrical member 401. A parallel plane plate 404 having a circular diameter has six laminated piezoelectric actuators 406 arranged on the circumference of a donut-shaped substrate 405 as shown in FIG. 6B. When mounted in this manner, the plane parallel plate 404 is brought into close contact with the laminated piezoelectric actuator 406 by the coil spring 403. By sequentially applying voltages applied to the six laminated piezoelectric actuators 406 by a drive circuit (not shown), the parallel flat plate 404 vibrates so as to wave on the circumference. The vibration center portion of the plane parallel plate 404 is guided by the inner diameter of the cylindrical member 401 and is maintained at the approximate center of the optical axis 01.

  That is, the driving means shown here includes a plurality of laminated piezoelectric actuators, a substrate 405 that is a plate-like support member to which each laminated piezoelectric actuator is fixed, and a parallel flat plate 104 that is an optical member. And a coil spring 403 which is an urging member having elasticity for urging so as to be pressed. In addition, although it is set as the laminated piezoelectric actuator here, the general piezoelectric actuator etc. of the aspect from which thickness changes may be used. By applying a voltage to each of these laminated piezoelectric actuators, the optical member is vibrated in the direction of the biasing member. With the vibration driving means having such a configuration, the projection light beam is irradiated so as to draw a circle on the fundus, so that even if the eye to be examined has an astigmatism component, the return light can be obtained evenly and the speckle pattern can be reduced. Can do.

  Although the present invention has been described with reference to the embodiment of the ocular refractive power measuring apparatus, it can be applied to any ophthalmic apparatus that projects a coherent light beam on the fundus and receives an optical image on a two-dimensional light receiving element.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

101 Light source for measurement SLD
DESCRIPTION OF SYMBOLS 102 Lens 103 Diaphragm 104 Perforated mirror 105 Parallel plane plate 106 Objective lens 107 Dichroic mirror 108 Diaphragm 109 Light beam separation prism 110 Lens 111 Image sensor

Claims (11)

Projecting means for projecting a coherent light beam onto the eye to be examined, light receiving means for causing a two-dimensional light receiving element to receive a reflected light beam of the coherent light beam from the eye to be examined, one of optical paths of the projecting means and the light receiving means An optical member disposed on the optical axis of the shared optical system in an ophthalmic apparatus having a shared optical system
Driving means for vibrating the optical member about a predetermined axis so that an inclination angle is generated with respect to a plane orthogonal to the optical axis of the shared optical system;
An ophthalmologic apparatus comprising: A light receiving means for receiving, as a ring image, reflected light from the fundus of the eye to be inspected by projecting the coherent light beam by the projecting means;
Measuring means for measuring eye refractive power of the eye to be examined based on a light reception result of the light receiving means;
The ophthalmic apparatus according to claim 1, comprising:   The predetermined axis when the optical member arranged in the shared optical system is vibrated is an axis at a position overlapping with a shadow obtained by projecting a fixed portion of a diaphragm plate arranged in the light receiving means. The ophthalmic apparatus according to claim 2. The driving means has a piezoelectric element,
The ophthalmologic apparatus according to claim 1, wherein the piezoelectric element is disposed in contact with the optical member at a vibration end.   The driving means has a plate-like member formed by laminating a plate-like metal and plate-like piezoelectric ceramics respectively in contact with both surfaces of the metal, and applies a voltage to each of the piezoelectric ceramics. The ophthalmic apparatus according to claim 1, wherein the plate-like member is bent in the thickness direction.   The drive means includes a plurality of piezoelectric actuators, a plate-like support member to which the plurality of piezoelectric actuators are fixed, and an urging member having an elasticity that urges the optical member to press each of the plurality of piezoelectric actuators. And oscillating the optical member in the direction of the urging member by applying a voltage to each of the piezoelectric actuators. apparatus. And further has control means for instructing start and stop of the operation of the driving means,
The ophthalmologic apparatus according to claim 1, wherein the control unit instructs the start and stop of the operation according to the operation of the projection unit. A projection step of projecting a coherent light beam onto the eye to be examined; and a light receiving step of causing a two-dimensional light receiving element to receive a reflected light beam of the coherent light beam from the eye to be examined. In the method of controlling an ophthalmologic apparatus using a shared optical system that shares a part of the optical path in the process, an optical member is disposed on the optical axis of the shared optical system,
Vibrating the optical member about a predetermined axis so that an inclination angle is generated with respect to a plane orthogonal to the optical axis of the shared optical system;
A method for controlling an ophthalmologic apparatus. Receiving reflected light from the fundus of the subject's eye that has projected the coherent light beam in the projecting step as a ring image;
A measurement step of measuring eye refractive power of the eye to be examined based on a light reception result in the light reception step;
The method for controlling an ophthalmologic apparatus according to claim 8, comprising: A control means for instructing start and stop of vibration of the optical member;
The method for controlling an ophthalmologic apparatus according to claim 8 or 9, wherein the control means instructs the start and stop of the operation according to the projection process.   A program for causing a computer to execute each step of the method for controlling an ophthalmologic apparatus according to any one of claims 8 to 10.

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