Ophthalmic device, method for controlling ophthalmic device, and program

Abstract

To provide an ophthalmic device which adjusts a polarization state of each of signal light and reference light in accordance with a scanning angle at which the signal light has been scanned.SOLUTION: An ophthalmic device comprises: an interference optical system that detects interference light between signal light obtained by scanning a subject's eye with light from a light source, and reference light in which light from the light source is divided; an adjustment unit that is disposed in at least one light path out of the signal light and the reference light and adjusts the polarization state of light propagated through the least one light path such that the polarization state of the signal light and the polarization state of the reference light become the same; and a control unit that controls the adjustment unit in accordance with a scanning angle at which the subject's eye is scanned.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The technology of the present disclosure relates to an ophthalmic device, a control method of the ophthalmic device, and a program.

Background Art

[0002] Conventionally, an optical image measurement device that acquires a fundus tomographic image based on signal light passing through a subject eye and interference light between the signal light is known. Conventionally, it has been required to adjust the polarization states of the signal light and the reference light (see, for example, Japanese Patent Application Laid-Open No. 2015-70919).

Summary of the Invention

[0003] An ophthalmic device according to a first aspect of the technology of the present disclosure includes: an interference optical system that detects interference light between signal light obtained by scanning a subject eye with light from a light source and reference light obtained by splitting the light from the light source; an adjustment unit that is disposed in at least one of the optical paths of the signal light and the reference light and adjusts the polarization state of light propagating through the at least one optical path so that the polarization state of the signal light and the polarization state of the reference light become the same; a control unit that controls the adjustment unit according to a scanning angle at which the subject eye is scanned; and.

[0004] A control method of an ophthalmic device according to a second aspect of the technology of the present disclosure is a control method performed by a processor of the ophthalmic device, and includes: acquiring an adjustment amount corresponding to a scanning angle of OCT signal light of an adjustment unit that is disposed in at least one of the optical paths of the signal light and the reference light and adjusts the polarization state of light propagating through the at least one optical path so that the polarization state of the signal light and the polarization state of the reference light become the same; controlling the adjustment unit based on the adjustment amount; and. including.

[0005] A program according to a third aspect of the technology of the present disclosure causes a computer to: perform: A step of obtaining an adjustment amount corresponding to the scanning angle of the signal light of the OCT, for an adjustment unit that is disposed in at least one of the optical paths of the signal light and the reference light and adjusts the polarization state of the light propagating through the at least one optical path so that the polarization state of the signal light and the polarization state of the reference light are the same; A step of controlling the adjustment unit based on the adjustment amount; To cause to execute.

Brief Description of the Drawings

[0006]

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Embodiments for Carrying Out the Invention

[0007] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For convenience of explanation hereinafter, a Scanning Laser Ophthalmoscope is referred to as "SLO". Also, for convenience of explanation hereinafter, an Optical Coherence Tomography is referred to as "OCT".

[0008] [First Embodiment] With reference to FIG. 1, an example of the configuration of the ophthalmic system 100 will be described. As shown in FIG. 1, the ophthalmic system 100 includes an ophthalmic device 110, an axial length measurement device 120, a server device (hereinafter referred to as "server") 140, and an image display device (hereinafter referred to as "viewer") 150. The ophthalmic device 110 acquires a fundus image and a tomographic image. The axial length measurement device 120 measures the axial length of the subject's eye. The server 140 stores a plurality of fundus images and axial lengths obtained by photographing the fundi of a plurality of subjects by the ophthalmic device 110 in correspondence with the subject IDs. The viewer 150 displays the fundus image acquired by the server 140 and the data obtained by analyzing the fundus image. The fundus image includes an SLO fundus image photographed by SLO, an OCT image (or also referred to as a tomographic image) photographed by OCT, and the like.

[0009] The ophthalmic device 110, the axial length measurement device 120, the server 140, and the viewer 150 are interconnected via the network 130.

[0010] Next, with reference to FIG. 2, the configuration of the ophthalmic device 110 will be described. As shown in FIG. 2, the ophthalmic device 110 includes an imaging device 14 and a control device 16. The imaging device 14 photographs the fundus of the eye to be examined. The control device 16 is realized by a computer including a CPU (Central Processing Unit) 16A, a RAM (Random Access Memory) 16B, a ROM (Read-Only memory) 16C, and an input / output (I / O) port 16D. The ophthalmic device 110 is an example of an ophthalmic device of the technology of the present disclosure.

[0011] A storage device 17 is connected to the input / output (I / O) port 16D. The storage device 17 is composed of, for example, a non-volatile memory (NVM). Also, the input / output (I / O) port 16D is connected to a network 130 via a communication interface (I / F) 15.

[0012] In addition, the control device 16 includes an input / display device 16E connected to the CPU 16A via the I / O port 16D. The input / display device 16E has a graphic user interface for displaying an image obtained by shooting and receiving various instructions including an instruction to shoot. An example of the graphic user interface is a touch panel display.

[0013] A data processing program 17A is stored in the storage device 17. Here, the case where the data processing program 17A is stored in the storage device 17 is described, but the technology of the present disclosure is not limited to this, and the data processing program 17A may be stored in the ROM 16C. The data processing program 17A is an example of the ophthalmic program of the technology of the present disclosure.

[0014] In the following description, when the ophthalmic device 110 is installed on a horizontal plane, the horizontal direction is defined as the "X direction", the vertical direction with respect to the horizontal plane is defined as the "Y direction", and the direction connecting the center 27 of the pupil of the anterior eye part of the eye to be examined 12 and the center O of the eyeball is defined as the "Z direction". Therefore, the X direction, the Y direction, and the Z direction are perpendicular to each other.

[0015] Next, the imaging device 14 will be described. The imaging device 14 operates under the control of the control device 16. The imaging device 14 includes an SLO unit 18, a wide-angle optical system 19, and an OCT unit 20. The wide-angle optical system 19 includes a first optical scanner 22 composed of a polygon mirror or the like that deflects light from the SLO unit 18 in the X direction (horizontal direction), a second scanner 24 composed of a galvanometer mirror or the like that deflects light from the OCT unit 10 in the X direction (horizontal direction), a dichroic mirror 26, and a common optical system 28 including a third scanner 29 composed of a galvanometer mirror or the like that deflects light in the Y direction (vertical direction). The dichroic mirror 26 combines the optical paths of the SLO light and the OCT light, and the SLO light and the OCT light are irradiated onto the photographable region 12A of the fundus through the pupil of the eye to be examined 12 via the common optical system 28. The photographable region 12A is within a range of approximately 200 degrees when converted to the internal irradiation angle from the center O of the eyeball.

[0016] The SLO unit 18 includes a light source 18A, a detection element 18B, a dichroic mirror 18C, etc., and is configured to photograph the fundus of the eye to be examined 12. The light source 18A includes a light source for R light (red light), a light source for G light (green light), a light source for B light (blue light), and a light source for infrared rays (e.g., near-infrared light), and is configured to be switchable between a mode of emitting R light, G light, and / or B light and a mode of emitting infrared rays (e.g., near-infrared light).

[0017] The light from the light source 18A (hereinafter referred to as "SLO light") passes through the dichroic mirror 18C and travels toward the wide-angle optical system 19. The SLO light is deflected in the X direction (horizontal direction) by the first optical scanner 22, passes through the dichroic mirror 26, and is deflected in the Y direction (vertical direction) by the third optical scanner 29 of the common optical system 28. The first optical scanner 22 and the third optical scanner 29 are controlled by the control device 16, and the photographable region 12A of the fundus is scanned. The reflected light from the fundus is reflected by the dichroic mirror 18C via the wide-angle optical system 19 and received by the detection element 18B. An SLO fundus image (hereinafter referred to as "SLO image"), which is a frontal image of the fundus based on the detection signal from the detection element 18B, is generated by the control device 16.

[0018] The OCT unit 20 will be described by taking Fourier domain type OCT as an example. In particular, the ophthalmic device 110 according to the technology of the present disclosure has an OCT unit 20 of swept source type OCT (SS-OCT) using a wavelength-sweeping light source.

[0019] The OCT unit 20 includes a reference optical system 20G including a light source 20A, a sensor 20B, fiber couplers 20C, 20D, and a polarization adjustment unit 20F. The light source 20A is a wavelength-sweeping light source that emits light in the near-infrared wavelength region.

[0020] The light from the light source 20A of the OCT unit 20 (hereinafter referred to as signal light (LS)) is branched by the fiber coupler 20C. One of the signal lights is deflected in the X direction (horizontal direction) by the second optical scanner 24 of the wide-angle optical system 19, reflected by the dichroic mirror 26, and deflected in the Y direction (vertical direction) by the third optical scanner 29 of the common optical system 28. The second optical scanner 24 and the third optical scanner 29 are controlled by the control device 16, and the area for performing OCT imaging in the imaging possible area 12A of the fundus is scanned. The area for performing OCT imaging is specified by the user of the ophthalmic device 110 or the like. There are various scanning patterns for the scanning, such as an A scan which is a scan of a single point on the fundus, a linear B scan for obtaining a tomographic image of the fundus, and a planar C scan for obtaining OCT volume data.

[0021] The signal light reflected from the fundus enters the fiber coupler 20D through the wide-angle optical system 19 and the fiber coupler 20C. Also, the other signal light, that is, the signal light traveling to the light source 20A, the fiber coupler 20C, the polarization adjustment unit 20F, and the sensor 20B is referred to as reference light (LR). The other reference light branched by the fiber coupler 20C has its polarization state adjusted by the polarization adjustment unit 20F and enters the fiber coupler 20D. At the fiber coupler 20D, the reference light with adjusted polarization interferes with the signal light reflected from the fundus, and the interference light enters the sensor 20B. The sensor 20B detects the intensity of the interference light for each wavelength and outputs it to the control device 16 as a detection signal.

[0022] Then, the control device 16 performs processing such as Fourier transform on the detection signal of the sensor 20B to generate an OCT image or a tomographic image (hereinafter referred to as an "OCT image").

[0023] Here, the optical path length of the signal light (LS) is determined by the distance from the light source 20A to the fundus and the distance from the fundus to the sensor 20B. And the optical path length of the reference light is also controlled to be the same as that of the signal light.

[0024] Among the signal lights, the reflected light that is incident on the fiber optic coupler 20D after being reflected from the fundus is particularly referred to as the return light. The OCT unit 20 is an example of the interference optical system of the technology of the present disclosure. Also, the polarization adjustment unit 20F is an example of the adjustment unit of the technology of the present disclosure.

[0025] In the present embodiment, the polarization adjustment unit 20F is connected to the driving unit 20E, and adjusts the incident light to a polarization state corresponding to the driving amount of the driving unit 20E and then emits it. The polarization state is indicated including the azimuth angle. Note that the polarization state may also be indicated by the ratio of the amplitudes of the orthogonal coordinates and the phase difference. In the present embodiment, as an example of the polarization adjustment unit 20F, a half-wave plate that gives a phase difference (λ / 2) is used, and the incident linearly polarized light is rotated and emitted by the half-wave plate. The half-wave plate, which is an example of the polarization adjustment unit 20F, is an example of the optical member of the technology of the present disclosure.

[0026] In the following description, since both the SLO light and the signal light are two-dimensionally scanned lights in the X direction and the Y direction, when there is no need to distinguish between the SLO light and the signal light, the SLO light and the signal light are collectively referred to as "scanning light".

[0027] Next, with reference to FIG. 3, the configuration of the wide-angle optical system 19 included in the ophthalmic device 110 will be described. As shown in FIG. 3, the common optical system 28 includes a slit mirror 30 and an elliptical mirror 32 in addition to the third optical scanner 29. Note that the dichroic mirror 26, the slit mirror 30, and the elliptical mirror 32 are represented by end views in side view. Note that the common optical system 28 may be configured using mirrors such as a concave mirror, a parabolic mirror, and a free-form mirror, or a plurality of lens groups, instead of the slit mirror 30 and the elliptical mirror 32.

[0028] The slit mirror 30 has an elliptical first reflection surface 30A. The first reflection surface 30A has a first focal point P1 and a second focal point P2. The elliptical mirror 32 also has an elliptical second reflection surface 32A. The second reflection surface 32A has a first focal point P3 and a second focal point P4.

[0029] The slit mirror 30, the elliptical mirror 32, and the third optical scanner 29 are arranged such that the first focal point P3 and the second focal point P2 are at the same position with respect to the third optical scanner 29. Also, the slit mirror 30, the elliptical mirror 32, and the third optical scanner 29 are arranged such that the second focal point P4 is located at the center of the pupil of the eye to be examined 12. Further, the first optical scanner 22, the second optical scanner 24, and the slit mirror 30 are arranged such that the first focal point P1 is located at the first optical scanner 22 and the second optical scanner 24.

[0030] That is, the first optical scanner 22, the second optical scanner 24, and the third optical scanner 29 are arranged at positions conjugate to the center of the pupil of the eye to be examined 12.

[0031] In the present embodiment, the wide-angle optical system 19 shown in FIG. 3 makes the viewing angle (FOV: Field of View) of the fundus a large angle, and a wide range of fundus regions can be observed. The wide range of fundus regions will be described separately as an external irradiation angle with respect to the scanning light from the outside by the ophthalmic apparatus 110 and an internal irradiation angle as an irradiation angle inside the eye to be examined irradiated with the scanning light. For example, when the external irradiation angle is 120 degrees, the internal irradiation angle corresponds to about 160 degrees. In the present embodiment, the internal irradiation angle is 200 degrees.

[0032] The external irradiation angle is the light irradiation angle from the side of the ophthalmic device 110, that is, from the outside of the eye to be examined 12. That is, the angle at which the scanning light travels toward the center 27 of the pupil of the eye to be examined 12 (that is, the directly-viewed central point of the pupil (see also FIG. 2)) with respect to the fundus of the eye to be examined 12 is the external irradiation angle. This external irradiation angle is also equal to the angle of the light that is reflected from the fundus and emitted from the center 27 of the pupil to the outside of the eye to be examined 12 and travels toward the ophthalmic device 110.

[0033] On the other hand, the internal irradiation angle represents the light irradiation angle that can be substantially imaged when the fundus of the eye to be examined 12 is irradiated by the scanning light with the center O of the eyeball of the eye to be examined 12 as the reference position. The external irradiation angle A and the internal irradiation angle B are in a corresponding relationship. However, in the following description, since it is an explanation of the ophthalmic device, the external irradiation angle is used as the irradiation angle corresponding to the visual field angle of the fundus.

[0034] The ophthalmic device 110 captures an image within the imageable area 12A (see also FIG. 2), which is the fundus area of the eye to be examined 12 according to the external irradiation angle. This imageable area 12A is, for example, the maximum area that can be scanned by the scanning light using the wide-angle optical system 19.

[0035] The SLO image obtained by the ophthalmic device 110 capturing the imageable area 12A of the eye to be examined 12 is referred to as a UWFSLO image. Note that UWF is an abbreviation for Ultra-Widefield (ultra-wide angle). With a wide-angle optical system 30 having an ultra-wide angle as the visual field angle (FOV) of the fundus, it is possible to capture an image of a region extending from the posterior pole of the fundus of the eye to be examined 12 beyond the equator, and structures existing in the peripheral part of the fundus such as the vortex veins can be imaged.

[0036] Next, with reference to FIG. 4, an example of various functions realized by the CPU 16A of the control device 16 of the ophthalmic device 110 executing the data processing program 17A will be described. The data processing program 17A includes a setting function, an SLO image acquisition function, an OCT image acquisition function (image acquisition function, image processing function, image display function), and a transmission function. By executing the data processing program 17A in which the CPU 16A has these respective functions, the CPU 16A functions as a setting unit 202, an SLO image acquisition unit 204, an OCT image acquisition unit 206 (image acquisition unit 210, image processing unit 212, image display unit 214), and a transmission unit 208, as shown in FIG. 4.

[0037] Also, in the present embodiment, as shown in FIG. 2, the control device 16 of the ophthalmic apparatus 110 includes an input / display device 16E, but the technology of the present disclosure is not limited thereto. For example, the control device 16 of the ophthalmic apparatus 110 may not include the input / display device 16E and may include a separate display device physically independent of the ophthalmic apparatus 110. In this case, the display device includes an image processing processor unit that operates under the control of the CPU 16A of the control device 16, and the image processing processor unit may display an SLO image or the like based on the image signal output-instructed by the image display unit 214.

[0038] (1) Creation of a table showing the correspondence between polarization and scanning angle First, before using the ophthalmic apparatus 110 of the ophthalmic system 100, information for adjusting the polarization state used when acquiring an OCT image is collected. The collected information is stored as a table TB and used when acquiring an OCT image described later. Note that the data of the table TB (hereinafter referred to as table data) may be transmitted to the server 140 and acquired from the server 140. Also, the table data may be derived and stored at the time of setup such as when the device is installed, and may be stored in the server 140 and acquired. Note that the table TB is an example of the table of the technology of the present disclosure.

[0039] Here, as described above, before the OCT imaging process is executed, information for adjusting the polarization state used when acquiring an OCT image is collected. Here, the collected information will be described in detail. The information for adjusting the polarization state is information indicating that the relationship between the polarization state of the signal light and the polarization state of the reference light is adjusted when acquiring an OCT image in a preferable state.

[0040] In OCT, tomography of the interference light obtained by interfering each return light obtained by irradiating the fundus through the pupil of the eye to be examined 12 with the signal light and the reference light is performed. By performing tomography of the interference light in this way, a tomographic region is imaged, and an OCT image indicating the tomographic region is acquired by the image acquisition unit 210.

[0041] For the return light and the reference light to interfere, it is ideal that the polarization state of the signal light is equal to the polarization state of the reference light. However, in OCT, there may be a case where the polarization states (for example, the polarization directions) of the measurement light and the reference light do not match. In a state where the polarization states do not match, the interference effect is suppressed, resulting in a decrease in the contrast of the OCT image. For example, when the signal light with right-handed circular polarization is irradiated onto the fundus of the eye to be examined, assuming that the eye to be examined does not have birefringence, the return light reflected from the fundus of the eye to be examined will be left-handed circular polarization. Also, since the amount of polarization change varies depending on the scanning angle corresponding to the external irradiation angle, the amount of polarization change varies according to the imaging region of the fundus. Further, in the configuration using an elliptical mirror as the wide-angle optical system 19 as shown in FIG. 3, the reflecting surfaces 30A and 32A of the elliptical mirror may not be perfect elliptical surfaces due to the manufacturing accuracy limit. Furthermore, even in each ophthalmic device 110, due to errors in the manufacture of the elliptical mirror, etc., there may be variations in the shape of the elliptical surface of the elliptical mirror among a plurality of ophthalmic devices 110. Due to these variations in the shape during the manufacture of these elliptical mirrors, the polarization states will also be different in each ophthalmic device 110.

[0042] Therefore, when the polarization state of the reference light is maintained at a constant polarization state, the polarization state of the signal light (return light) changes, suppressing the interference between the signal light (return light) and the reference light and deteriorating the image quality of the OCT image captured by OCT. For this reason, it is preferable to make the polarization states of the signal light and the reference light common according to the scanning angle at which the signal light is scanned. Further, it is more preferable to make the polarization states of the signal light and the reference light common according to the fundus position (hereinafter referred to as the scanning position) when the signal light is scanned. This is because the fundus is spherical, and when the signal light is scanned through the center of the pupil away from the center of the eyeball, it is possible to suppress the influence caused by the change in the overall optical path length of the signal light and the return light according to the scanning position.

[0043] The relationship between the scanning angle and the polarization state of the signal light at that scanning angle can be derived in advance. Therefore, based on the relationship between the scanning angle and the polarization state of the signal light at that scanning angle, by performing adjustment to suppress the change in the polarization state of the signal light and the polarization state of the reference light at each scanning angle, the polarization states of the signal light and the reference light are made common. The relationship between this scanning angle and the polarization state of the signal light at that scanning angle is created in advance as a table, and the polarization state is adjusted according to the scanning angle when acquiring the OCT image.

[0044] Next, with reference to FIG. 5, an example of the table creation process of the table TB will be described. The table creation process shown in FIG. 5 is realized by the CPU 16A of the control device 16 of the ophthalmic device 110 executing the table creation process included in the data processing program 17A.

[0045] The table creation process shown in FIG. 5 is performed by the creation unit 200 of the CPU 16A. First, in step S100, the creation unit 200 checks if a model eye is installed in the ophthalmic device 110. In this case, it is checked by the doctor or operator operating the input / display device 16E to instruct the completion of the installation of the model eye. In the next step S102, the scanning range is set. The scanning range is the range in which the signal light is scanned when acquiring an OCT image in the ophthalmic device 110, that is, the range of the scanning angle. Next, in step S104, the scanning angle is set to an initial value. The initial value is predetermined as any scanning angle when scanning within the scanning range set in step S102. For example, the maximum scanning angle is set.

[0046] In step S106, the model eye is scanned at the set scanning angle, and the polarization state of the signal light obtained by the scanning is acquired and stored in step S108. Specifically, the polarization state of the signal light is measured and stored. For measuring the polarization state, a polarization measurement device such as a polarization camera is used, for example. The polarization measurement device is preferably installed in the sensor 20B of the OCT unit 20. Note that the sensor 20B of the OCT unit 20 according to the present embodiment has a polarization measurement function and can operate as a polarization measurement device. A polarization camera, which is an example of the polarization measurement device, has polarizers with different azimuth angles attached to each pixel on the light incident side of the line sensor and the two-dimensional sensor, and only transmits light with a polarization state of a predetermined azimuth angle, so that the azimuth angle (direction of polarization) can be measured as the polarization state of the incident light. Also, as another example of the polarization measurement device, a polarimeter can be used. That is, the polarization state of light is measured by transmitting light through a polarizer and rotating the polarizer.

[0047] Also, a table TBw is set for each ophthalmic device 110 based on a model eye with unified specifications. Therefore, the influence of the change in the polarization state caused by the variation in the shape during the manufacture of the elliptical mirror can be removed. Thus, the influence of the variation in the polarization state in the optical system such as the eye to be examined and the elliptical mirror can be removed regardless of which ophthalmic device 110 is used, and stable OCT imaging can be performed.

[0048] In step S110, the adjustment amount of the polarization adjustment unit 20F corresponding to the polarization state memorized in step S108 is derived. Specifically, the polarization adjustment unit 20F is adjusted to a polarization state according to the driving amount of the driving unit 20E. The relationship between the driving amount of this driving unit 20E and the azimuth angle of polarization is known, and the driving amount of the polarization adjustment unit 20F corresponding to the polarization state is derived as the adjustment amount. For example, based on the scanning angle in the direction along the optical axis passing through the center of the pupil and the center of the eyeball, the driving amount from the polarization state of the signal light in that reference is set as the adjustment amount. Then, in step S112, the scanning angle, the polarization state, and the adjustment amount are memorized in association with each other.

[0049] In step S114, it is determined whether the scanning of the scanning angles covering the scanning range has been completed. If the determination is affirmative, the process proceeds to step S118. If the determination is negative, the process proceeds to step S116. In step S116, the scanning angle is updated and the process returns to step S106. In step S118, the scanning angle, the polarization state, and the adjustment amount associated in step S112 are each created as a table TB and memorized.

[0050] In FIG. 6, a table TBw is shown as an example of the table TB. In the table TBw of the example shown in FIG. 6, the scanning angle θ for determining the scanning position, the polarization state PZ corresponding to the scanning angle, and the adjustment amount W of the polarization adjustment unit 20F are associated with each other. The table TBw is memorized in the storage device 17 of the control device 16 as the table TB. The table TBw of the example shown in FIG. 6 is based on the scanning angle θ (0 degrees) along the optical axis passing through the center of the pupil and the center of the eyeball, and the polarization state PZ of the signal light and the adjustment amount W which is the driving amount for driving the polarization adjustment unit 20F when the scanning angle θ is increased or decreased by 10 degrees are associated with each other.

[0051] In the example shown in FIG. 6, an example with a scanning angle range of ±70 degrees is shown as the table TB, but it is not limited to the scanning angle range shown in FIG. 6. For example, a predetermined range such as a scanning angle range of ±75 degrees and ±80 degrees may be set, or a scanning angle range of ±100 degrees corresponding to the visual field of the eye may be set. Further, the scanning angle range is not limited to being set evenly from the reference (0 degrees). For example, the maximum value on the plus side or and the minimum value on the minus side of the scanning angle may be different, or for example, a partial angle range within a scanning angle range of ±100 degrees may be set.

[0052] Also, in FIG. 6, an example of the table TB associating the scanning angle θ every 10 degrees, the polarization state PZ of the signal light, and the adjustment amount W is shown, but the table TB is not limited to the correspondence relationship of the scanning angle θ every 10 degrees, the polarization state PZ of the signal light, and the adjustment amount W. For example, it may be less than 10 degrees or more than 10 degrees.

[0053] Note that the created table TB may be transmitted to the server 140 and acquired from the server 140. Further, the table data may be derived and stored at the time of setup such as when the device is installed, or may be stored in the server 140 and acquired.

[0054] (2) OCT imaging using the polarization information of the table Next, the imaging process using OCT by the ophthalmic device 110 will be described. The CPU 16A of the control device 16 of the ophthalmic device 110 executes the OCT imaging process included in the data processing program 17A, thereby realizing the OCT imaging process shown in FIG. 7.

[0055] In the OCT imaging process shown in FIG. 7, first, in step S200, the setting unit 202 performs initial settings. Specifically, the initial settings refer to processes such as adjusting the optical system for focus, alignment, etc. in the ophthalmic device 110, performing control such as eye tracking to follow the movement of the eye, and receiving input of the identification information of the subject. Also, in step S200, the reading process of the above-described table TB is also performed.

[0056] In the next step S202, the SLO image acquisition unit 204 acquires an SLO image by performing shooting by SLO, and then transfers the process to step S208. By executing the process of step S202 by the SLO image acquisition unit 204, a live SLO image is displayed on the input / display device 16E. On the input / display device 16E, the SLO image is displayed as a live view image.

[0057] In steps S206 to S224, the OCT image acquisition unit 206 acquires an OCT image. Specifically, first, in step S206, the image acquisition unit 210 receives a designation of a scanning range that is an OCT shooting range. Specifically, the operator views the live SLO image displayed as a live view image on the input / display device 16E, and confirms the location where shooting by OCT is performed based on the data indicating the instruction manual. The operator sets the ophthalmic device 110 so that shooting by OCT is performed on the confirmed location. Specifically, for example, the operator operates the mouse to designate the scanning range 872 that is the OCT shooting range. That is, in step S206, the image acquisition unit 210 receives the designation of the scanning range 872. The scanning range 872 is a line of B-scan. Note that the OCT shooting range may be a rectangular range of C-scan.

[0058] Then, in steps S208 to S220, the scanning range 872 is subjected to OCT shooting with the polarization states of the signal light and the reference light being the same. Specifically, in step S208, the image acquisition unit 210 sets the scanning angle to an initial value. The initial value of the scanning angle is set to, for example, the maximum value or the minimum value of the scanning angles within the scanning range. Next, in step S210, referring to the table TB, the adjustment amount of the polarization corresponding to the scanning angle is acquired, and in step S214, the subject eye is scanned with the polarization state of the reference light adjusted to be the same as the polarization state of the signal light for the set scanning angle.

[0059] In the next step S216, the image acquisition unit 210 determines whether the scanning of the scanning range has been completed. If a negative determination is made in step S216, the scanning angle is incremented or decremented in step S218, and the process returns to step S210 to repeat the above process. If the scanning of the scanning range is completed and an affirmative determination is made in step S216, the process proceeds to step S220. In step S220, the image acquisition unit 210 outputs the detection signal of the interference light obtained by scanning the scanning range to the image processing unit 212.

[0060] In step S222, the image processing unit 212 performs signal processing such as Fourier transform on the detection signal of the interference light to generate OCT data composed of a plurality of A-scan data. Then, image processing such as addition averaging processing and eyeball shape correction processing is performed on the OCT data to generate a tomographic image. After generating the tomographic image, the process proceeds to step S224. In step S224, the image display unit 214 causes the input / display device 16E to display the tomographic image obtained by performing image processing by executing the process of step S222. Then, this process proceeds to step S226.

[0061] FIG. 8 shows the tomographic image displayed on the input / display device 16E. The display screen 800 includes a tomographic image 810 and a navigation image in which an arrow 830 indicating the position information of the tomographic image is superimposed on a reduced SLO image 820 as position information regarding the position where the OCT data was acquired.

[0062] In step S226, the transmission unit 208 transmits the image data indicating the tomographic image obtained by performing image processing by executing the process of step S222 to the server 140 together with the identification information of the subject, and then ends this data processing. Note that the OCT data may be sent to the server 140 together with the image data. The content of the control in step S212 described above is an example of the content of the control by the control unit of the technology of the present disclosure.

[0063] On the one hand, the server 140 transmits image data and the like to the viewer 150 based on a request from the viewer 150. The viewer 150 causes the display 156 to display an SLO image or an OCT image, which is an image of the eye to be examined, based on the image data. The user can diagnose the eye to be examined 12 while viewing the SLO image or the OCT image displayed on the display 156.

[0064] As described above, in the technology of the present disclosure, when scanning the signal light, causing the return light reflected by the retina of the eye to be examined from the signal light to interfere with the reference light branched from the signal light, and photographing the tomographic region in the depth direction of the retina at each scanning position, the polarization state of the reference light is adjusted according to the scanning angle so that interference occurs. As a result, in the technology of the present disclosure, when the tomographic region of the retina is photographed while scanning the signal light, the polarization states of the return light reflected by the retina and the reference light can be kept constant regardless of the scanning angle. Therefore, the influence of polarization different depending on the scanning angle can be removed from the interference light obtained by the return light reflected by the retina and the reference light. From these facts, when performing OCT imaging at a wide angle, the influence of polarization different depending on the scanning angle can be removed, and a high-resolution tomographic image can be obtained.

[0065] [Second Embodiment] Next, a second embodiment will be described. Since the second embodiment has the same configuration as the first embodiment, the same reference numerals are given to the same parts and detailed description thereof is omitted. In the first embodiment, the polarization state of the polarization adjustment unit 20F was measured, the adjustment amount of the polarization adjustment unit 20F was derived from the measurement result, and stored as a table. The second embodiment experimentally obtains the adjustment amount of the polarization adjustment unit 20F at which the polarization state becomes optimal and stores it as a table.

[0066] Next, with reference to FIG. 9, the creation process of the table TB according to the present embodiment will be described. The process of table creation processing shown in FIG. 9 replaces the processing from step S106 to step S112 in the table creation processing shown in FIG. 5 with the processing from step S120 to step S132. The table creation processing shown in FIG. 9 is performed by the creation unit 200.

[0067] First, in the processing from step S100 to step S104, the creation unit 200 sets the scanning range and sets the scanning angle to the initial value.

[0068] Next, in step S120, the adjustment amount of the polarization adjustment unit 20F is set to the initial value. An example of the initial value is setting the azimuth angle of polarization to 0 degrees. In the next step S122, similar to step S106 in FIG. 5, the model eye is scanned at the scanning angle set in step S104. In step S124, the image contrast by the signal light obtained by scanning is acquired and stored as the polarization state of the signal light. Next, in step S126, it is determined whether or not the processing of steps S122 and S124 has been completed for the range in which the polarization state of the polarization adjustment unit 20F can be adjusted. If a negative determination is made in step S126, in step S128, the adjustment amount is updated by driving the polarization adjustment unit 20F by a predetermined adjustment amount. Specifically, the polarization state is adjusted so as to obtain the updated adjustment amount by setting the driving amount of the driving unit 20E to the predetermined driving amount. On the other hand, if an affirmative determination is made in step S126, in step S130, the optimal adjustment amount is derived. Specifically, as shown in FIG. 10, among the plurality of image contrasts stored in step S124, the adjustment amount of the maximum image contrast (shown as the optimal value in FIG. 10) is derived as the adjustment amount of the polarization adjustment unit 20F at the set scanning angle. Then, in step S132, the adjustment amount of the image contrast derived in step S130 and the scanning angle are stored in association with each other.

[0069] Then, in steps S114 to S118, the correspondence relationship between the scanning angles that cover the scanning range and the adjustment amounts is created as a table TB and stored.

[0070] FIG. 11 shows a table TBv as an example of the table TB. In the table TBv of the example shown in FIG. 11, a scanning angle θ for determining a scanning position and an adjustment amount V of the adjustment unit 20F corresponding to the scanning angle are associated with each other. The table TBv is stored in the storage device 17 of the control device 16 as the table TB. In the table TBv of the example shown in FIG. 11, based on the scanning angle θ in the direction along the optical axis passing through the center of the pupil and the center of the eyeball as a reference (0 degrees), the adjustment amount V which is the driving amount for driving the polarization adjustment unit 20F when the scanning angle θ is increased or decreased by 10 degrees is associated with each other.

[0071] Note that, also in the example shown in FIG. 11, similar to the example shown in FIG. 6, it is not limited to setting the range of the scanning angle of ±70 degrees as the table TB.

[0072] As described above, in the technology of the present disclosure, based on the image contrast obtained by driving the polarization adjustment unit 20F, the adjustment amount that gives the maximum contrast is derived, so that the polarization state is adjusted according to the actual machine.

[0073] [First Modification Example] In the above, as an example of the OCT unit 20, the case where the reference optical system 20G including the polarization adjustment unit 20F such as a half-wave plate is provided has been described. The technology of the present disclosure is not limited to this. The first modification example is provided with a depolarizer in the reference optical system 20G that emits light incident in a certain polarization state as non-polarized light instead of the polarization adjustment unit 20F such as a half-wave plate.

[0074] Next, with reference to FIG. 12, the first modification example will be described. As shown in FIG. 12, as an example of the OCT unit 20, the modification example is provided with a mirror-type depolarizer 20M in the reference optical system 20G instead of the polarization adjustment unit 20F such as the half-wave plate shown in FIG. 2. The other signal light branched by the fiber coupler 20C has its polarization state adjusted by reflection in the mirror-type depolarizer 20M and is incident on the sensor 20B via the fiber coupler 20D. As described above, the depolarizer 20M is connected to the drive unit 20E, and adjusts the incident light to a polarization state corresponding to the driving amount of the drive unit 20E and then emits it.

[0075] [Second Modified Example] In the above, as an example of the OCT unit 20, the case where the polarization adjustment unit 20F such as a half-wave plate is provided in the reference optical system 20G in the optical path of the other light split by the fiber coupler 20C has been described. The technology of the present disclosure is not limited to providing the polarization adjustment unit 20F only in the reference optical system 20G. For example, a polarization adjustment unit 20F may be provided between the fiber coupler 20C and the fiber coupler 20D in the optical path of the return light of the signal light, specifically, the optical path in which the return light travels toward the sensor 20B. Further, the polarization adjustment unit 20F may be provided in both the optical path of the other light split by the fiber coupler 20C and the optical path in which the return light travels toward the sensor 20B.

[0076] [Third Modified Example] In the above, an example of using the SLO image (UWFSLO image) to determine the OCT imaging position has been described, but a fundus image obtained by a fundus camera may also be used, and it goes without saying that it can also be applied to fundus images taken by various ophthalmic devices such as an SLO ophthalmic device or a fundus camera with a relatively small field angle (for example, 100° or less for the internal irradiation angle).

[0077] [Fourth Modified Example] In the above description, the case where at least one of the polarization states of the signal light and the reference light is adjusted so that the polarization states of the signal light and the reference light are common according to the scanning angle has been described. The technology of the present disclosure is not limited to adjusting the polarization state according to the scanning angle. For example, according to the scanning position of the fundus of the eye to be examined, the polarization states of the signal light and the reference light may be adjusted so that they are common. For example, in units of A-Scan, at least one of the polarization states of the signal light and the reference light may be adjusted so that the polarization states of the signal light and the reference light are common.

[0078] [Other Modifications] In the above embodiment, the ophthalmic system 100 including the ophthalmic device 110, the axial length measuring device 120, the server 140, and the viewer 150 has been described as an example, but the technology of the present disclosure is not limited thereto. For example, as a first example, the axial length measuring device 120 may be omitted. Further, as a second example, the ophthalmic device 110 may further have at least one function of the server 140 and the viewer 150. Thereby, at least one of the server 140 and the viewer 150 corresponding to the functions provided in the ophthalmic device 110 can be omitted. Furthermore, the server 140 may be omitted, and the viewer 150 may execute the functions of the server 140.

[0079] Note that the ophthalmic device 110 according to the technology of the present disclosure has been described by using an OCT unit using a swept-source type OCT (SS-OCT). However, it is also applicable to an ophthalmic device using a type other than the swept-source type, for example, a spectral domain OCT (SD-OCT). Also, in the technology of the present disclosure, the ophthalmic device 110 having the SLO imaging system function and the OCT imaging system function has been described. However, it is also possible to combine an OCT unit having a configuration according to the technology of the present disclosure with a fundus imaging device such as a fundus camera, a slit lamp, a microscope for ophthalmic surgery, and the like. In addition, the technology of the present disclosure can also be applied to a stand-alone OCT device composed of a control device, an OCT unit, and a wide-angle optical system. The stand-alone OCT device is an ophthalmic instrument specialized for acquiring OCT images of the eye to be examined. In the stand-alone OCT device, when determining the OCT imaging position, a frontal image generated from OCT volume data is used instead of the SLO image.

[0080] The data processing described in the above embodiments is merely an example. Therefore, it goes without saying that unnecessary steps may be deleted, new steps may be added, or the processing order may be changed within the scope not departing from the gist. In the above embodiments, a CPU is used as an example of a general-purpose processor. However, in the above, the processor refers to a processor in a broad sense and includes a general-purpose processor (e.g., CPU: Central Processing Unit, etc.) and a dedicated processor (e.g., GPU (Graphics Processing Unit), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), programmable logic device, etc.). In addition, the operation of the processor in the above-described embodiments may be achieved not only by one processor but also by a plurality of processors cooperating with each other, or by a plurality of physically separated processors cooperating with each other.

[0081] In the above embodiments, a case where data processing is realized by a software configuration using a computer is exemplified. However, the technology of the present disclosure is not limited thereto. For example, instead of a software configuration using a computer, data processing may be executed only by a hardware configuration such as an FPGA or an ASIC. Part of the data processing may be executed by a software configuration, and the remaining processing may be executed by a hardware configuration. Furthermore, in order to cause a computer to execute the processing in the above-described embodiments, a program describing the above-described processing in computer-processable code may be stored in a storage medium such as an optical disk and distributed.

[0082] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. An interference optical system that detects interference light between signal light obtained by scanning an eye to be examined with light from a light source and reference light obtained by splitting the light from the light source; An adjustment unit disposed in at least one of the optical paths of the signal light and the reference light, and that adjusts the polarization state of the light propagating through the at least one optical path; A control unit that controls the adjustment unit so as to suppress a difference between the polarization state of the signal light and the polarization state of the reference light based on the scanning angle at which the eye to be examined is scanned; An ophthalmic apparatus comprising the above components.

2. The control unit performs control to adjust the polarization state of the at least one optical path based on the position at which the eye to be examined is scanned, which corresponds to the scanning angle at which the eye to be examined is scanned. The ophthalmic apparatus according to claim 1.

3. The adjustment unit includes an optical member that adjusts the azimuth angle of polarization. The ophthalmic apparatus according to claim 1.

4. The optical member includes a half-wave plate, and adjusts the azimuth angle of polarization by rotating the half-wave plate. The ophthalmic apparatus according to claim 3.

5. The optical member includes a depolarizer, and adjusts the azimuth angle of polarization by emitting non-polarized light with the depolarizer. The ophthalmic apparatus according to claim 3.

6. The control unit: Detects the scanning angle at which the eye to be examined is scanned; Calculates an adjustment amount based on the detected scanning angle. The ophthalmic apparatus according to claim 1, characterized by the above.

7. The adjustment unit derives the adjustment amount based on a table stored in advance that associates the scanning angle at which the eye to be examined is scanned with the adjustment amount for adjusting the polarization state. The ophthalmic apparatus according to claim 6.

8. A control method performed by a processor of the ophthalmic apparatus according to claim 1, the method including: A step of obtaining an adjustment amount for suppressing a difference between the polarization state of the signal light and the polarization state of the reference light, the adjustment amount corresponding to the scanning angle of the OCT signal light of an adjustment unit disposed in at least one of the optical paths of the signal light and the reference light and that adjusts the polarization state of the light propagating through the at least one optical path; A step of controlling the adjustment unit so as to suppress a difference between the polarization state of the signal light and the polarization state of the reference light based on the adjustment amount. A control method for an ophthalmic apparatus including the above steps.

9. On a computer: A step of obtaining an adjustment amount for suppressing a difference between the polarization state of the signal light and the polarization state of the reference light, the adjustment amount corresponding to the scanning angle of the OCT signal light of an adjustment unit disposed in at least one of the optical paths of the signal light and the reference light and that adjusts the polarization state of the light propagating through the at least one optical path; A step of controlling the adjustment unit based on the adjustment amount. A program that causes [a certain operation] to be executed.

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