Ophthalmic imaging device, method for controlling an ophthalmic imaging device, and program

Abstract

To provide an ophthalmologic imaging apparatus capable of executing accurate measurement by an inexpensive and simple configuration without using an additional optical element in a configuration for disposing an optical path length adjusting mechanism in a measurement optical system.SOLUTION: An ophthalmologic imaging apparatus includes: an interference optical system for detecting multiplexed light acquired by multiplexing return light of measurement light from an eye to be examined obtained by irradiating the eye to be examined with the measurement light, and reference light, and acquiring an interference signal; an optical path length changing part for changing an optical path length of the measurement light; a focus position changing part for changing a focus position of the measurement light; a scanning part for scanning the measurement light with the eye to be examined; and a control part for controlling the optical path length changing part, the focus position changing part, and the scanning part. The control part sets at least one of a scanning angle of the scanning part and the position of the focus position changing part on the basis of the position of the optical path length changing part.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to an ophthalmic imaging apparatus, a control method for an ophthalmic imaging apparatus, and a program. [Background technology]

[0002] As an ophthalmic imaging device, a device (OCT device) that acquires a tomographic image of a test eye using optical coherence tomography (OCT) with low-coherence light has been put into practical use. In an OCT device, since the axial length of the test eye differs from patient to patient, an optical path length adjustment mechanism is provided in one of the optical systems to match the optical path length difference between the measurement optical system and the reference optical system and generate interference light.

[0003] Patent Document 1 discloses a configuration in which an optical path length adjustment mechanism that moves a collimator lens and a fiber end in the optical axis direction is arranged in a measurement optical system. This configuration has the advantage that the reference optical system does not emit reference light into space and can be constructed inexpensively and simply using only fibers without using optical elements such as lenses or mirrors. Furthermore, Patent Document 2 discloses a configuration in which a corner cube arranged in the measurement optical system is moved as an optical path length adjustment mechanism. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-75641 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-140542 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the configuration of Patent Document 1 drives the collimator lens and fiber end, which are part of the measurement optical system, and is therefore subject to linearity accuracy errors and collimation errors in the drive system, which can cause deviations in the imaging position of the measurement light and reduce measurement accuracy. The configuration of Patent Document 2 has the advantage of reducing the effect of linearity accuracy errors by driving a corner cube with retroreflective properties, but the corner cube itself is expensive, and adding a reflection system to the measurement optical system can complicate the device. In addition, in general imaging devices, a method of correcting optical system misalignment through image processing, such as horizontal or rotational movement of the image, is frequently used. However, in tomographic imaging using an OCT device, correction by movement is difficult for axial misalignment that is not included in the plane corresponding to the tomographic image because information about the target area that should be corrected according to the misalignment is not included in the image.

[0006] In view of the above problems, one embodiment of the present disclosure aims to provide an ophthalmic imaging device that can perform highly accurate measurements with an inexpensive and simple configuration, without using any additional optical elements, in a configuration in which an optical path length adjustment mechanism is arranged in the measurement optical system. [Means for solving the problem]

[0007] A fundus observation device according to an embodiment of the present disclosure includes an interference optical system that detects combined light obtained by irradiating a subject's eye with measurement light and combining the return light of the measurement light from the subject's eye with reference light, and acquires an interference signal; and an optical path length changing unit that changes the optical path length of the measurement light. ,before a scanning unit that scans the subject's eye with the measurement light; and an optical path length changing unit. , and and a control unit for controlling the scanning unit, wherein the control unit adjusts the scanning angle of the scanning unit based on the change in the optical path length of the measurement light. degree The control unit calculates a correction angle for the scanning angle using a polynomial that approximates the shift in the irradiation point of the measurement light corresponding to the multiple positions of the optical path length changing unit, and changes the scanning angle of the scanning unit using the calculated correction amount. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, in a configuration in which an optical path length adjustment mechanism is disposed in a measurement optical system, highly accurate measurements can be performed with an inexpensive and simple configuration without using additional optical elements. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a schematic configuration example of an OCT apparatus according to a first embodiment. [Figure 2] 2 illustrates a schematic configuration example of a control unit according to a first embodiment. [Figure 3] 3 shows an example of a screen display according to the first embodiment. [Figure 4] FIG. 4 is a diagram for explaining fundus tracking processing according to the first embodiment. [Figure 5] 3 shows an example of driving the coherence gate according to the first embodiment. [Figure 6] 1 shows an example of an observation result of a spot of measurement light according to Example 1. [Figure 7] FIG. 2 is a diagram for explaining a correction method according to the first embodiment. [Figure 8] 4 is a flowchart of an example of a method for setting a correction coefficient according to the first embodiment. [Figure 9] 4 is a flowchart of an example of a series of imaging processes according to the first embodiment. [Figure 10] FIG. 10 is a diagram for explaining a correction method according to the second embodiment. [Figure 11] 10 is a flowchart illustrating an example of a method for setting a correction coefficient according to the second embodiment. [Figure 12] 10 is a flowchart of an example of a series of imaging processes according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, exemplary embodiments for carrying out the present disclosure will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of components described in the following embodiments are arbitrary and can be changed depending on the configuration of the device to which the present disclosure is applied or various conditions. In addition, the same reference numerals are used in the drawings to indicate identical or functionally similar elements.

[0011] Example 1 An OCT apparatus, which is an example of an ophthalmic imaging apparatus according to a first embodiment of the present disclosure, and a control method for the OCT apparatus will be described below with reference to Figures 1 to 9. The OCT apparatus according to this embodiment corrects the scanning angle of the scanner based on the position of the coherence gate of the OCT optical system.

[0012] <Configuration> The OCT device according to this embodiment is provided with a fundus image capturing unit that captures two-dimensional fundus images and a tomographic image capturing unit that captures three-dimensional tomographic images of the fundus of the subject's eye using information based on optical interference. First, the schematic configuration of the OCT device according to this embodiment will be described with reference to FIG. 1. FIG. 1 shows the schematic configuration of the OCT device according to this embodiment and its optical system. In the following description, the direction that approximately coincides with the line of sight of the subject's eye E is referred to as the Z direction. Furthermore, the plane perpendicular to the Z direction is referred to as the XY plane, the horizontal direction is referred to as the X direction, and the vertical direction is referred to as the Y direction.

[0013] The OCT device is provided with an optical head unit 100, a spectroscope 200, and a control unit 300. The control unit 300 is also provided with a display unit 310 and an input unit 340. The configurations of the optical head unit 100, the spectroscope 200, and the control unit 300 will be described below in order.

[0014] <Configuration of the Optical Head Unit 100 and the Spectrometer 200> The optical head unit 100 is provided with an optical system for capturing two-dimensional images and tomographic images of the anterior segment Ea and fundus Ef of the subject's eye E. Various optical systems arranged in the optical head unit 100 will be described below.

[0015] In the optical head unit 100, an objective lens 101 is disposed facing the subject's eye E. A first dichroic mirror 102 and a second dichroic mirror 103, which function as an optical path branching unit, are disposed on the optical axis L1 of the objective lens 101. The first dichroic mirror 102 and the second dichroic mirror 103 branch the optical path of the anterior eye observation system (optical axis L2), the optical path of the fundus photography system (optical axis L3), and the optical path of the measurement optical system (optical axis L5) for each wavelength band.

[0016] A lens 120, a prism 121, a diaphragm 122, a lens 123, and an image sensor 124 are arranged on an optical axis L2 in the reflection direction of the second dichroic mirror 103. The image sensor 124 is a monochrome sensor sensitive to infrared light. These optical members and the like arranged on the optical axis L2 constitute an anterior eye segment observation system for observing the anterior eye segment Ea.

[0017] The image sensor 124 is connected to the control unit 300. The image sensor 124 sends a signal corresponding to the detected light to the control unit 300. The control unit 300 can generate an anterior eye segment observation image based on the signal received from the image sensor 124 and display the image on the display unit 310. In addition, a light source 125 for anterior eye segment observation, which is arranged near the objective lens 101, illuminates the anterior eye segment Ea of the subject's eye E.

[0018] A perforated mirror 131, a photographing aperture 132, a focus lens 133, an imaging lens 134, a third dichroic mirror 135, and an image sensor 136 are arranged on an optical axis L3 in the transmission direction of the first dichroic mirror 102. The perforated mirror 131 has an opening in the center. The focus lens 133 is held so as to be movable in the optical axis direction indicated by the arrow in the figure by a driving unit such as a motor (not shown) controlled by the control unit 300. The focus of the fundus photography system can be adjusted by moving the focus lens 133 on the optical axis L3. The optical path on the optical axis L3 is branched by the third dichroic mirror 135 into an optical path leading to the image sensor 136 and an optical path leading to the fixation lamp 137, for each wavelength band.

[0019] The image sensor 136 is a fundus image sensor that is sensitive to visible light and infrared light and is capable of both moving image observation and still image capture. The image sensor 136 sends a signal corresponding to the detected light to the control unit 300. The control unit 300 can generate a fundus observation image or a fundus image (frontal fundus image) based on the signal received from the image sensor 136 and display it on the display unit 310. The fixation lamp 137 emits visible light to encourage the subject to fixate. The fixation lamp 137 may also be provided with an aperture (not shown) for cutting off the light beam required for fundus imaging.

[0020] A diopter correction lens 138 can be inserted onto the optical axis L3 using a drive unit such as a motor (not shown). The diopter correction lens 138 can also be removed from the optical axis L3 using the drive unit. The control unit 300 controls the drive unit to insert and remove the diopter correction lens 138, thereby enabling focus adjustment over an even wider diopter range for the fundus photography system.

[0021] A corneal baffle 140, a relay lens 141, a focus target unit 142, a lens 143, and a ring slit 144 are arranged in this order on an optical axis L4 in the reflection direction of the perforated mirror 131. The corneal baffle 140 has a light-blocking point in the center. The ring slit 144 has a ring-shaped slit opening. Also arranged on the optical axis L4 are a crystalline lens baffle 145 as a light-blocking member having a light-blocking point, and a dichroic mirror 146 that transmits infrared light and reflects visible light.

[0022] The focus target unit 142 is an optical element that provides a target for focusing using the focus lens 133, and in this embodiment, a split bright line is projected as an example of the target. The focus target unit 142 according to this embodiment has a split target member that is movable along the optical axis L4 in conjunction with the focus lens 133. The split target member is configured to be inserted into and removed from the optical path of the optical axis L4 by a drive unit such as a motor (not shown) controlled by the control unit 300.

[0023] The split bright lines irradiated by the focus target unit 142 pass through the relay lens 141 and are reflected by the perforated mirror 131 toward the second dichroic mirror 103. The split bright lines reflected by the perforated mirror 131 are projected onto the fundus Ef of the subject's eye E via the second dichroic mirror 103, the first dichroic mirror 102, and the objective lens 101. The control unit 300 can calculate the amount of focus deviation by detecting the positions of the split bright lines from the fundus observation image.

[0024] A condenser lens 147 and a white LED light source 148 are arranged in the reflection direction of the dichroic mirror 146. The white LED light source 148 is a light source for photography in which a plurality of white LEDs that emit visible pulsed light are arranged. A condenser lens 149 and an infrared LED light source 150 are arranged in the transmission direction of the dichroic mirror 146. The infrared LED light source 150 is an observation light source in which a plurality of infrared LEDs that emit constant infrared light are arranged. The driving of the white LED light source 148 and the infrared LED light source 150 is controlled by the control unit 300.

[0025] An illumination optical system for illuminating the fundus Ef is configured by the objective lens 101, the dichroic mirror 146, the optical members therebetween, and the condenser lenses 147 and 149. The fundus Ef of the subject's eye E can be illuminated via the illumination optical system with light from a white LED light source 148 or an infrared LED light source 150. In addition, a fundus photography system is configured by the optical members on the optical axes L3 and L4.

[0026] A measurement optical system including a lens 151, a mirror 152, an XY scanner 153, a focus lens 154, a collimator lens 155-1, and a fiber end 155-2 is arranged on an optical axis L5 in the reflection direction of the first dichroic mirror 102. The XY scanner 153 includes an X scanner 153-1 and a Y scanner 153-2. The X scanner 153-1 and the Y scanner 153-2 are configured with any deflection means such as a galvanometer mirror, and function as a scanning unit that scans the fundus Ef of the subject's eye E with measurement light. The centers of the X scanner 153-1 and the Y scanner 153-2 are optically conjugate with the pupil position of the subject's eye E. Although the optical path between the X scanner 153-1 and the Y scanner 153-2 is shown to be within the plane of the drawing in FIG. 1, it is actually configured in a direction perpendicular to the plane of the drawing. Furthermore, the scanning unit that scans the measurement light may be configured using a MEMS mirror or the like that can deflect light in two-dimensional directions with a single mirror.

[0027] In this embodiment, the X scanner 153-1 can scan the measurement light in the X direction, and the Y scanner 153-2 can scan the measurement light in the Y direction perpendicular to the X direction. In this embodiment, an example is described in which scanning is performed with the X direction as the main scanning direction and the Y direction as the sub-scanning direction, but the scanning directions are not limited to this. The main scanning direction and the sub-scanning direction in such scanning may be directions that intersect with each other. For example, the Y direction may be the main scanning direction and the X direction may be the sub-scanning direction. Alternatively, the main scanning direction and the sub-scanning direction may be oblique directions that intersect with each other and have components in the X and Y directions. The scanning pattern may be, for example, a 3D scan, a radial scan, a cross scan, a Lissajous scan, a circle scan, or a raster scan.

[0028] The measurement light source 157 is a light source that emits light to obtain measurement light to be incident on the measurement optical path. In this embodiment, the measurement light in the OCT optical system is emitted from a fiber end 155-2 of an optical fiber 156-2 as a light source, and the fiber end 155-2 has an optical conjugate relationship with the fundus Ef of the subject's eye E. The fiber end 155-2 is disposed at the focal position of a collimator lens 155-1, and the measurement light is emitted as a parallel beam from the fiber end 155-2 that acts as a light source, passing through the collimator lens 155-1. The collimator lens 155-1 and the fiber end 155-2 form a coherence gate 155.

[0029] The focus lens 154 is a lens for adjusting the focus of the OCT optical system, and is driven in the optical axis direction indicated by the arrow in the figure by a driving unit such as a motor (not shown) controlled by the control unit 300. The focus adjustment is performed so that the measurement light is imaged on the fundus Ef. The focus lens 154 is disposed between the fiber end 155-2, which serves as the measurement light source, and the X scanner 153-1 and Y scanner 153-2, which function as scanning units. By the focus adjustment described above, an image of the measurement light emitted from the fiber end 155-2 can be formed on the fundus Ef of the subject's eye E, and the return light from the fundus Ef can be efficiently returned to the optical fiber 156-2.

[0030] Next, a description will be given of the optical path from measurement light source 157, and the configuration of the reference optical system and spectrometer 200. The OCT optical system is composed of the above-mentioned measurement optical system, optical members included in the optical path from measurement light source 157, the reference optical system, and spectrometer 200. Furthermore, a Michelson interferometer is composed of measurement light source 157, optical coupler 156, optical fibers 156-1 to 156-4, lens 158, dispersion compensation glass 159, reference mirror 160, and spectrometer 200.

[0031] In this embodiment, a super luminescent diode (SLD), a typical low-coherence light source, is used as the measurement light source 157. The light emitted from the measurement light source 157 has a central wavelength of 880 nm and a wavelength width of approximately 60 nm. The wavelength width is an important parameter because it affects the resolution of the resulting tomographic image in the optical axis direction. Although an SLD is selected as the light source type here, any light source capable of emitting low-coherence light, such as an amplified spontaneous emission (ASE), can also be used. Considering the measurement of the eye, a near-infrared wavelength can be used as the central wavelength of the measurement light. Furthermore, the characteristics of the first dichroic mirror 102 and the second dichroic mirror 103 branch into the optical path of the fundus imaging system (optical axis L3), the optical path of the measurement optical system (optical axis L5), and the anterior eye observation optical path (optical axis L2). Therefore, it is necessary to provide a certain degree of wavelength difference between the wavelengths used in each optical path. From these perspectives, the above wavelengths were selected as the SLD wavelengths in this embodiment.

[0032] The optical fibers 156-1 to 156-4 are single-mode optical fibers connected to and integrated with the optical coupler 156. Light emitted from the measurement light source 157 is guided to the optical coupler 156 via the optical fiber 156-1. The light guided to the optical coupler 156 is split by the optical coupler 156 into measurement light directed toward the optical fiber 156-2 side and reference light directed toward the optical fiber 156-3 side. Here, the optical coupler 156 functions as an example of a splitter that splits the light from the measurement light source 157 into the measurement light and the reference light.

[0033] As described above, in this embodiment, the measurement light in the OCT optical system is emitted from the fiber end of the optical fiber 156-2 as a light source. The measurement light travels through the optical path of the measurement optical system described above, is irradiated onto the fundus Ef of the subject's eye E, which is the observation target, and reaches the optical coupler 156 again through the same optical path as returned light due to reflection and scattering by the retina.

[0034] On the other hand, the reference light passes through optical fiber 156-3, lens 158, and dispersion compensation glass 159 inserted to match the dispersion of the measurement light and the reference light, and reaches and is reflected by reference mirror 160. The reference light reflected by reference mirror 160 returns along the same optical path and reaches optical coupler 156 again.

[0035] The reference light and measurement light (return light) that reach the optical coupler 156 again are multiplexed by the optical coupler 156. Here, when the optical path lengths of the measurement light and the reference light become approximately the same, this multiplexing causes interference between the respective lights. A coherence gate 155, consisting of a collimator lens 155-1 and a fiber end 155-2 of the OCT optical system, is held so that its positional relationship can be adjusted as a whole in the optical axis direction indicated by the arrow in the figure by a driving unit such as a motor (not shown). By using the coherence gate 155, it is possible to match the optical path length of the measurement light, which varies depending on the subject's eye E, to the optical path length of the reference light. The obtained interference light is guided to the spectroscope 200 via an optical fiber 156-4.

[0036] The spectrometer 200 is provided with a lens 201, a diffraction grating 202, a lens 203, and a line sensor 204. The interference light emitted from the optical fiber 156-4 becomes approximately parallel light via the lens 201, is then dispersed by the diffraction grating 202, and is imaged on the line sensor 204 by the lens 203. Each element in the line sensor 204 generates an interference signal according to the received light, and the line sensor 204 sends the interference signal to the control unit 300. The control unit 300 samples the interference signal received from the line sensor 204 at a predetermined timing, and performs predetermined signal processing to generate a tomographic image.

[0037] Furthermore, the optical head unit 100 is provided with a head driving unit 170. The head driving unit 170 includes three motors (not shown). The control unit 300 controls the driving of the head driving unit 170 to move the optical head unit 100 in three-dimensional (X, Y, Z) directions relative to the subject's eye E. This allows the control unit 300 to align the optical head unit 100 with the subject's eye E.

[0038] <Configuration of control unit 300> Next, a schematic configuration of the control unit 300 will be described with reference to Fig. 2. The control unit 300 includes an imaging control unit 301, a storage unit 302, an output control unit 303, an acquisition unit 304, and an image processing unit 305.

[0039] The photographing control unit 301 is connected to the storage unit 302, the image processing unit 305, the optical head unit 100, and the input unit 340. The photographing control unit 301 controls each unit of the optical head unit 100 based on an input signal from the input unit 340.

[0040] Here, the control during capture of various images will be described. When capturing an anterior-eye-segment observation image, the capture control unit 301 causes the anterior-eye-segment observation light source 125 to emit light, and the image sensor 124 receives the light returning from the anterior eye segment Ea. The image sensor 124 sends a signal corresponding to the received light to the acquisition unit 304. The image processing unit 305 uses the signal acquired by the acquisition unit 304 to generate an anterior-eye-segment observation image.

[0041] The photographing control unit 301 can also emit light from the infrared LED light source 150 to capture a fundus observation image using the fundus camera. The fundus observation image captured during fundus observation image capture can be used for fundus observation and fundus tracking processing. In fundus observation image capture, the photographing control unit 301 drives the focus target unit 142 to acquire diopter information of the subject's eye E, and then drives the focus lens 133 to match the acquired diopter information. To focus on a wider diopter range, the photographing control unit 301 inserts or removes the diopter correction lens 138 onto the optical axis L3 using a drive unit (not shown). Return light from the fundus Ef is received by the image sensor 136. The image sensor 136 sends a signal corresponding to the received return light to the acquisition unit 304. The image processing unit 305 generates a fundus observation image using the signal acquired by the acquisition unit 304.

[0042] Furthermore, when photographing a fundus image using a fundus camera, the photographing control unit 301 changes the position of the focus lens 133 so that the position matches the diopter position obtained by applying aberration correction due to differences in the wavelength of the light source to diopter information of the subject's eye E acquired using the infrared LED light source 150. Thereafter, the photographing control unit 301 causes the white LED light source 148 to emit visible pulsed light, and receives the returned light from the fundus Ef with the image sensor 136. The image sensor 136 sends a signal corresponding to the received returned light to the acquisition unit 304. The image processing unit 305 generates a fundus image using the signal acquired by the acquisition unit 304.

[0043] In tomographic image capture, the capture control unit 301 drives the focus lens 154 based on diopter information acquired using the focus target unit 142. The capture control unit 301 also sends scan control signals to the X scanner 153-1 and the Y scanner 153-2 to scan the fundus Ef of the subject's eye E in the X and Y directions with measurement light from the measurement light source 157. Return light of the measurement light from the fundus Ef is received by the line sensor 204. The line sensor 204 sends an interference signal corresponding to the received return light to the acquisition unit 304. The image processing unit 305 Fourier transforms the interference signal acquired by the acquisition unit 304 and converts the obtained data into brightness or density information, thereby generating a tomographic image of the subject's eye E in the depth direction (Z direction). This scanning method is called an A-scan, and the obtained tomographic image is called an A-scan image.

[0044] The measurement light for this A-scan is scanned in a predetermined transverse direction on the fundus Ef of the subject's eye E by the XY scanner 153, thereby obtaining multiple A-scan images. The image processing unit 305 can generate a two-dimensional tomographic image based on the multiple A-scan images and scanning information. As a result, for example, scanning in the X direction obtains a tomographic image in the XZ plane, and scanning in the Y direction obtains a tomographic image in the YZ plane. This scanning method of scanning the subject's eye E in a predetermined transverse direction with the measurement light is called a B-scan, and the resulting two-dimensional tomographic image is called a B-scan image.

[0045] By repeatedly scanning a predetermined imaging range on the subject's eye E with the XY scanner 153 in a predetermined direction, multiple B-scan images can be acquired. For example, by repeatedly performing B-scans on the XZ plane while shifting the position in the Y direction, three-dimensional information in the XYZ space can be obtained. This type of scanning method is called a C-scan, and data consisting of the obtained multiple B-scan images is called three-dimensional data. The image processing unit 305 can generate a front image (En-Face image) of the fundus Ef of the subject's eye E by, for example, projecting the three-dimensional data within a predetermined depth range. The front image generated in this manner is called an OCT front image (C-scan image).

[0046] The control unit 300 can capture various images by performing the above-mentioned control using the imaging control unit 301. The imaging control unit 301 can also control each unit of the optical head unit 100 to perform a fundus tracking process (described later) for tracking the movement of the subject's eye E, using the image generated by the image processing unit 305 and the image stored in the storage unit 302. Furthermore, the imaging control unit 301 can correct the optical axis shift of the measurement light caused by driving the coherence gate 155 by setting the scanning angle of the XY scanner based on the position of the coherence gate 155, as described later.

[0047] As described above, the acquisition unit 304 can acquire the signals output from the image sensors 124 and 136 and the interference signal output from the line sensor 204. In addition, the acquisition unit 304 outputs the acquired various signals to the image processing unit 305.

[0048] The image processing unit 305 can generate, for example, an anterior eye observation image, a fundus observation image, a fundus image, a B-scan image which is a tomographic image, three-dimensional data, an OCT front image, and the like, based on the signal output from the acquisition unit 304. Note that any known generation method may be used as a method for generating these images.

[0049] The storage unit 302 stores an anterior segment observation image, a fundus observation image, a fundus image, a B-scan image which is a tomographic image, three-dimensional data, an OCT front image, and the like of the subject's eye E generated by the image processing unit 305. The storage unit 302 also stores, for example, an examination sequence which defines a series of control procedures for performing an examination multiple times, analysis results of various images, photographing conditions when acquiring images, so-called patient information about the subject's eye E, and the like. The storage unit 302 also stores various programs and the like for controlling the above-mentioned anterior segment observation image capturing, fundus observation image capturing and fundus image capturing by a fundus camera, and tomographic image capturing.

[0050] The output control unit 303 is connected to the storage unit 302, the image processing unit 305, and the display unit 310, and can control the display on the display unit 310. The output control unit 303 can display, for example, various images stored in the storage unit 302, such as anterior eye observation images, fundus observation images, fundus images, B-scan images which are tomographic images, 3D data, and OCT front images, as well as patient information, etc. Furthermore, the output control unit 303 can also receive various images generated from the image processing unit 305 and output them to the display unit 310.

[0051] Here, the control unit 300 can be configured by a computer provided with a processor and a memory. The control unit 300 may be configured by a general computer or a computer dedicated to the OCT device. The control unit 300 may also be, for example, a personal computer, such as a desktop PC, a notebook PC, or a tablet PC (portable information terminal). Furthermore, the control unit 300 may be configured as a cloud-based computer in which some of the components are located in an external device.

[0052] Furthermore, each component of the control unit 300 other than the storage unit 302 may be configured by a software module executed by a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The processor may be, for example, a GPU (Graphical Processing Unit) or an FPGA (Field-Programmable Gate Array). Each component may be configured by a circuit that performs a specific function, such as an ASIC. The storage unit 302 may be configured using any memory or storage medium, such as an optical disk.

[0053] The display unit 310 is configured with any display, and displays various information such as patient information, various images, a mouse cursor, etc. in accordance with the operation of the input unit 340, under the control of the output control unit 303. The input unit 340 is an input device that issues instructions to the control unit 300, and specifically includes a keyboard and a mouse. Note that the display unit 310 may be configured with a touch panel display, in which case the display unit 310 can also be used as the input unit 340.

[0054] <Inspection operation flow> Next, the operation flow of the examination in this embodiment will be described with reference to FIG. 3. FIG. 3 shows an example of a measurement screen displayed on the display unit 310. A measurement screen 1000 according to this embodiment displays a right / left eye switching button 1001, a Capture button 1003, a Start button 1004, an anterior eye observation image 1101, a fundus observation image 1201, a tomographic image 1301, and a Scan Mode button 1501. The measurement screen 1000 also displays sliders 1103, 1203, and 1302 for controlling various adjustments, and a frame 1202 for setting the imaging range of the tomographic image. The tomographic image 1301 may be a preview image obtained by roughly scanning the fundus Ef at high speed for various adjustments. The relative positional relationship between the fundus observation image 1201 and the tomographic image 1301 may be stored in the storage unit 302.

[0055] To start the examination according to this embodiment, the operator moves the cursor 1002 on the measurement screen 1000 shown in FIG. 3 via the input unit 340, selects the left or right eye with the left or right eye switch button 1001, and selects a scan mode with the Scan Mode button 1501. Scan modes include, for example, Macula3D, Glaucoma3D, and Disc3D, and switching the scan mode sets the optimal scan pattern and fixation position for each scan mode. Note that the scan mode may also include other scan modes, such as an OCTA (OCT Angiography) mode, a fundus photography mode, and a fundus fluorescence photography mode.

[0056] Furthermore, OCT scanning patterns include, for example, 3D scanning, radial scanning, cross scanning, Lissajous scanning, circle scanning, and raster scanning, etc. In this embodiment, a case where 3D scanning is selected as the scanning pattern will be described.

[0057] Next, when the operator presses the Start button 1004 via the input unit 340, the control unit 300 automatically performs alignment adjustment, focus adjustment, and coherence gate adjustment, and preparations for imaging are made. Here, alignment adjustment is an adjustment to align the optical head unit 100 with respect to the subject's eye E. Focus adjustment is an adjustment to move the focus lenses 133, 154 in the optical axis direction to perform focusing adjustment on the fundus oculi Ef. Furthermore, coherence gate adjustment is an adjustment to move the coherence gate 155 in the optical axis direction so that a tomographic image of the retina, etc., can be observed at a desired position on the tomographic image display screen. Note that focus adjustment, alignment adjustment, and coherence gate adjustment may be performed by any known method.

[0058] For example, the photography control unit 301 may use the anterior eye observation image to determine the amount of misalignment of the optical head unit 100 with respect to the subject's eye E, and adjust the alignment of the optical head unit 100 with respect to the subject's eye E. Note that the photography control unit 301 can detect the distance in the Z-axis direction (optical axis direction) of the optical head unit 100 with respect to the subject's eye E, using an image of the anterior eye segment Ea divided into upper and lower parts based on light that has passed through the prism 121.

[0059] The imaging control unit 301 may also adjust the focus of the fundus imaging system and the OCT optical system using a fundus observation image. For example, the imaging control unit 301 can adjust the focus by moving the focus lenses 133 and 154 so as to eliminate the vertical deviation of the split bright lines in the fundus observation image as targets. In this embodiment, as described above, the split target member of the focus target unit 142 is driven along the optical axis L4 in conjunction with the focus lens 133.

[0060] The imaging control unit 301 may also adjust the coherence gate of the OCT optical system using the acquired tomographic image. For example, the imaging control unit 301 can adjust the coherence gate by moving the coherence gate 155 so that the image of the retinal layer is displayed at a predetermined position on the tomographic image.

[0061] Furthermore, the operator can perform fine adjustments of the alignment, focus, and coherence gate by operating sliders 1103, 1203, 1302, etc. via the input unit 340. When performing fine adjustments of the alignment, the operator can adjust the alignment by operating the slider 1103 or a button (not shown) to move the Z-direction position and XY position of the optical head unit 100 relative to the subject's eye E while viewing the anterior eye observation image 1101. Furthermore, the operator can adjust the focus of the fundus photography system and the OCT optical system by operating the slider 1203 while viewing the brightness, etc., of the fundus observation image 1201 and the tomographic image 1301. Furthermore, the operator can adjust the coherence gate of the OCT optical system by operating the slider 1302 while viewing the tomographic image 1301.

[0062] Furthermore, the operator can adjust the size and position of a frame 1202 on the fundus observation image 1201 to specify the imaging range for the tomographic image. The operator can start imaging by pressing the Capture button 1003. When imaging of the tomographic image starts, the imaging control unit 301 controls the XY scanner 153 based on the specified imaging range to scan the fundus Ef with the measurement light, thereby performing a 3D scan of the subject's eye E.

[0063] The acquisition unit 304 acquires an interference signal obtained by 3D scanning of the subject's eye E. The image processing unit 305 can generate a B-scan image of the subject's eye E, 3D data, an OCT front image, and the like based on the acquired interference signal. The various images generated by the image processing unit 305 are stored in the memory unit 302. The output control unit 303 can display various images stored in the memory unit 302 and various information such as patient information on the display unit 310. Note that while the operation of the OCT scan mode has been described here, in a fundus photography scan mode such as a fundus photography mode, a front image of the fundus may be captured by the fundus photography system in response to operation of the Capture button 1003. In addition, an anterior segment image may be captured depending on the scan mode.

[0064] <Fundus tracking processing> The fundus Ef of the subject's eye E may move during imaging due to movements of the subject's eye E, such as known involuntary eye movement, or movements of the subject. If the fundus Ef moves during imaging, the imaging location will shift, so the imaging control unit 301 can perform fundus tracking to follow the movement of the fundus Ef and correct the imaging location. The fundus tracking process will be described below.

[0065] First, the control unit 300 acquires a reference front fundus image (reference image) for tracking. Specifically, the imaging control unit 301 controls the fundus imaging system of the optical head unit 100 to image the fundus Ef immediately before starting to capture a tomographic image using the OCT optical system. The acquisition unit 304 acquires a signal output from the image sensor 136. The image processing unit 305 generates a front fundus image based on the acquired signal and stores the generated front fundus image in the storage unit 302 as a reference image. Thereafter, the imaging control unit 301 starts capturing a tomographic image and performs subsequent processes in parallel while performing B-scans and C-scans using the OCT optical system.

[0066] The control unit 300 controls the fundus imaging system in the same manner as above, and captures a front image of the target fundus (target image). The control unit 300 also sends the target image generated by the image processing unit 305 and the reference image stored in the storage unit 302 to the imaging control unit 301. The imaging control unit 301 calculates the positional deviation between the target image and the reference image as the amount of movement of the fundus Ef that occurred between the acquisition of these images. The imaging control unit 301 controls the correction of the irradiation position of the measurement light by the XY scanner 153, based on the acquired amount of movement of the fundus Ef.

[0067] Here, an example of a method for calculating the movement amount of the fundus oculi Ef using a reference image and a target image captured at two different times will be described. The imaging control unit 301 according to this embodiment calculates the movement amount of the fundus oculi Ef using a template matching method. Specifically, the imaging control unit 301 sets ROI1 (first region of interest) in the reference image and stores the position of this ROI1 in the reference image. Here, ROI1 can be a region including a feature with strong contrast, such as a blood vessel, present in the reference image. Next, the imaging control unit 301 searches for ROI2 (second region of interest) in the target image that has the highest correlation with ROI1. The imaging control unit 301 calculates the relative difference between the position of ROI1 in the reference image and the position of ROI2 in the target image as the movement amount (displacement amount) of the fundus oculi Ef between two different times.

[0068] The fundus tracking process described above will now be described in detail with reference to FIG. 4. FIG. 4 shows an example of a reference image 401 and a target image 402, which are frontal fundus images of the same subject's eye E captured at different times. The imaging control unit 301 first sets an ROI 403 on the reference image 401. The ROI 403 includes a blood vessel branch as a feature. The imaging control unit 301 then searches the target image 402, captured later, to find an ROI 404 that has the highest correlation with the ROI 403. If the position of the ROI 403 is (x1, y1) and the position of the ROI 404 is (x2, y2) in the fundus image coordinate system, the imaging control unit 301 calculates, from these coordinates, the displacement amount (dx, dy) between the two images, e.g., (x2-x1, y2-y1). The imaging control unit 301 then corrects the scanning position of the measurement light on the fundus Ef by the OCT optical system using the displacement amount (dx, dy).

[0069] In this embodiment, the ROI is set by focusing on contrast, and the ROI is searched for using a correlation function. However, these methods for fundus tracking processing are merely examples, and other methods that can calculate the amount of image movement, such as optical flow methods, can be used. Furthermore, instead of only calculating the amount of parallel movement for the frontal fundus image, for example, two or more ROIs may be set in the reference image, and the amount of rotation of the fundus Ef may also be calculated from the calculation results of the respective movement amounts. Furthermore, various known methods for detecting the movement of the fundus Ef or the subject's eye E can be applied to the fundus tracking processing by the imaging control unit 301.

[0070] Here, the fundus Ef moves not only in the XY directions but also in the Z direction. That is, if the subject's head is not sufficiently fixed and the forehead moves away from the device, the subject's eye E moves, and the optical path length of the measurement light relative to the fundus Ef becomes longer. If the optical path length changes during imaging, the tomographic image of the retina, etc. moves vertically in the tomographic image. For this reason, the control unit 300 controls the OCT optical system to capture a reference tomographic image for tracking immediately before starting to capture the tomographic image and store it in the storage unit 302. Then, while capturing the tomographic image, the control unit 300 calculates the vertical positional deviation between the captured tomographic image and the reference tomographic image, and obtains the amount of movement of the fundus Ef of the subject's eye E in the optical axis direction. Based on the calculated amount of movement of the fundus Ef in the optical axis direction, the imaging control unit 301 can drive the coherence gate 155, which is an optical path length adjustment means, to correct the optical path length of the measurement light.

[0071] The calculation of the amount of movement of the fundus Ef in the optical axis direction may be performed using various known methods, such as a template matching method or an optical flow method. For example, the imaging control unit 301 may set ROIs in each tomographic image as described above and determine the relative difference between the ROIs. One example of such a method of calculating the amount of movement of the fundus Ef in the optical axis direction may include detection of a characteristic part of the retinal layers that has strong contrast, such as the retinal pigment epithelium layer.

[0072] <Coherence Gate> Next, the coherence gate 155 in the OCT optical system will be described in detail with reference to FIGS. 5(a) and 5(b). FIGS. 5(a) and 5(b) show enlarged views of the collimator lens 155-1 and the fiber end 155-2, illustrating an example in which the coherence gate 155 including these elements is driven from position P1 to position P2 by a driving unit such as a motor (not shown). Parallel beams F1 and F2 emitted in parallel from the collimator lens 155-1 at positions P1 and P2 and reaching the fundus Ef are indicated by solid and dashed lines, respectively. For simplicity of explanation, lenses and mirrors disposed in the optical path from the coherence gate 155 to the subject's eye E are omitted. In the example shown in FIGS. 5(a) and 5(b), the XY scanner 153 is directed toward the center of the fundus Ef.

[0073] 5(a) shows an example in which the linearity accuracy of the drive system is ideal. In this example, the optical axis of the coherence gate 155 coincides with the optical axis L5 of the measurement optical system along the entire path from position P1 to position P2. In this case, the emergence angles of both the parallel beams F1 and F2 remain parallel beams, so no change occurs and the conjugate relationship between the fiber end 155-2 and the center of the fundus Ef is maintained.

[0074] However, actual linearity accuracy has a certain error. Figure 5(b) shows an example in which the linearity accuracy of the drive system has an error and the trajectory of the coherence gate 155 is curved. In this example, the angle of the optical axis of the coherence gate 155 continuously changes with respect to the optical axis L5 of the measurement optical system along the path from position P1 to position P2. At the reference position (not shown) of the coherence gate 155, the XY scanner 153 adjusts the conjugate relationship between the fiber end 155-2 and the center of the fundus Ef. However, if the coherence gate 155 moves away from the reference position and the emission angles of the parallel beams F1 and F2 change, the arrival position on the fundus Ef changes, causing a deviation in the conjugate relationship with the fiber end 155-2. Generally, if the emission angle of the light beam is θ, the focal length of the optical system is f, and the image height, which is the arrival position of the light beam on the image plane, is Y = f × tan θ, and therefore there is a positive correlation between the emission angle of the light beam and the arrival position on the fundus Ef.

[0075] If the driving of the coherence gate 155 causes a shift in the conjugate relationship between the fiber end 155-2 and the center of the fundus Ef, problems occur in capturing tomographic images in the operation flow of the examination. First, a shift occurs in the relative positional relationship between the fundus observation image 1201 and the tomographic image 1301 in Figure 3. Therefore, even if the frame 1202 on the fundus observation image 1201 is adjusted and a scan area is specified, it becomes difficult to acquire a tomographic image of the desired position.

[0076] Furthermore, when the coherence gate position is adjusted using the slider 1302 while observing the tomographic image 1301 of the preview image, the imaging target region moves not only in the usual vertical direction but also in the horizontal direction on the display screen of the tomographic image, which is a B-scan image. In particular, if the imaging target region moves in the C-scan direction (sub-scanning direction), the position where the measurement light is scanned deviates from the line to be scanned by the B-scan, and the imaging target region is no longer displayed in the preview image. This makes it difficult to stably adjust the coherence gate.

[0077] Similarly, in fundus tracking processing, when the imaging control unit 301 drives the coherence gate 155 to correct the optical path length of the measurement light in response to a displacement of the subject's eye E in the Z direction, a displacement of the measurement light itself in the X and Y directions occurs, which makes it difficult to perform the desired correction for the movement of the subject's eye E in the X and Y directions.

[0078] A common method for reducing angular misalignment in an optical system is to use a retroreflective mirror (corner cube, retroreflector, etc.). Retroreflective mirrors have the property of reflecting light rays 180 degrees back to their original direction, even if the mirror itself is tilted. Therefore, it is conceivable to reduce optical axis misalignment by driving the retroreflective mirror as a means for adjusting the optical path length. However, retroreflective mirrors are expensive and are dedicated additional parts, so using a retroreflective mirror increases costs. In addition, it is necessary to build a reflective optical system around the coherence gate, which may make the device more complex and larger. The same is true when increasing the precision of the driving system itself.

[0079] Furthermore, methods for correcting misalignment of an optical system by image processing generally involve horizontally shifting or rotating an image. Regarding these methods, when misalignment occurs in the X direction (main scanning direction) of the measurement light, horizontal shifting of the B-scan image is effective. However, when misalignment occurs in the Y direction (sub-scanning direction) of the measurement light, information about the target area is not included in the image, making correction by image shifting difficult.

[0080] <Scanner correction> Next, with reference to FIGS. 6(a) to 7(b), the principle of the method for correcting the optical axis deviation caused by driving the coherence gate 155 using a scanner in this embodiment will be described.

[0081] 6(a) and 6(b) show an example of observing the optical axis shift caused by driving the coherence gate 155 when a model eye (not shown) corresponding to the subject's eye E is placed at the measurement position. FIG. 6(a) illustrates five measurement light spots 602 on a chart 601 placed at a position corresponding to the fundus of the model eye. The intersection of the crosshairs on the chart 601 corresponds to the center of the fundus Ef of the subject's eye E, and the distance from that point represents the amount of optical axis shift. A vertical shift is the Y-direction shift, and a horizontal shift is the X-direction shift. The spot 602 moves between positions S1 and S2 as the coherence gate 155 is driven between positions P1 and P2, and its path depends on the linearity of the drive system incorporated in the device. Note that the amount of shift of the spot 602 and the linearity of the path of the spot 602 are both random for each device.

[0082] FIG. 6(b) is a graph of the coordinates of the spot 602 on the chart 601. The horizontal axis indicates the position P of the coherence gate 155, and the vertical axis indicates the position of the spot 602. FIG. 6(b) also shows the reference position P0 of the coherence gate 155, the position P1 of the drive end of the coherence gate 155 on the optical head unit 100 side, and the position P2 of the drive end of the coherence gate 155 on the subject's eye E side. The X position of the spot 602 corresponding to the position of the coherence gate 155 is indicated by a solid line 603, and the Y position is indicated by a solid line 604. By observing the spot 602 using the model eye in this way, it is possible to obtain position information of the spot 602 corresponding to the position of the coherence gate 155, in other words, information on the deviation of the irradiation point of the measurement light (optical axis deviation).

[0083] In this embodiment, the spot 602 is observed by photographing the chart 601 from the rear side with a camera (not shown), but the method for observing the spot 602 is not limited to this. For example, the chart 601 is photographed by C-scanning and the generated OCT front image (front image) can also be used to obtain information on the optical axis deviation in the XY directions. In this case, for example, C-scans are performed at multiple coherence gate positions to generate multiple front images, and the amount of positional deviation for each front image can be calculated as the amount of optical axis deviation. The amount of positional deviation for each front image can be calculated using a method such as template matching. In this case, the photographing range can be any range, for example, a range that allows the amount of positional deviation of the front image to be calculated by template matching of the front image.

[0084] Furthermore, the method for observing the spot 602 is not limited to the configuration in which a reference chart is placed on the model eye. For example, the position information of the spot 602 can be similarly obtained by placing a chart at a predetermined position outside the optical path of the OCT optical system inside the device and photographing the chart by deflecting the measurement light with a scanner.

[0085] 7(a) and 7(b) show an example of correcting optical axis misalignment using a scanner. FIG. 7(a) shows an enlarged view of the coherence gate 155, the XY scanner 153, and the subject's eye E. For simplicity, other lenses and mirrors included in the OCT optical system are omitted from FIG. 7(a). In the figure, the coherence gate 155 is at position P1, and the emitted parallel beam F1 has an angular misalignment. The light beam passes through the focus lens 154 (not shown) and enters the Y scanner 153-2 while maintaining the angular misalignment. If the Y scanner 153-2 is at a reference angle, the light beam advances to the X scanner 153-1 in the direction indicated by the dashed line, maintaining the angular misalignment. On the other hand, if the Y scanner 153-2 is rotated by a predetermined amount Δθ, the light beam advances along the optical axis of the OCT optical system, as indicated by the solid line, and reaches the center of the fundus Ef of the subject's eye E.

[0086] Figure 7(b) is a graph showing the relationship between the position of coherence gate 155 and the correction angle of Y scanner 153-2. The horizontal axis represents position P of coherence gate 155, and the vertical axis represents correction angle Δθ of Y scanner 153-2. Figure 7(b) also shows the reference position P0 of coherence gate 155, position P1 of the drive end of coherence gate 155 on the optical head unit 100 side, and position P2 of the drive end of coherence gate 155 on the subject's eye E side. Solid line 701 is a function curve showing the correction formula for correction angle Δθ according to position P.

[0087] The correction formula can be obtained, for example, by placing the coherence gate 155 at multiple positions, actually adjusting the scanning angle of the scanner, and interpolating each adjustment amount. Alternatively, the correction formula may be generated from position information of the spot 602 using the correspondence between the scanning angle and the spot position on the fundus Ef, such as the scale relationship between the scanning angle and the fundus Ef, which has been acquired in advance. In either method, the information obtained is discrete, so that a correction formula capable of correcting the optical axis deviation over the entire moving range of the coherence gate 155 can be obtained by fitting using polynomial approximation.

[0088] For example, if the degree of the polynomial is set to 4, the correction formula is expressed as follows using the position P as a variable and coefficients A4 to A0: Δθ=A4×P 4 +A3×P 3 +A2×P 2 +A1×P+A0 The coefficients A4 to A0 are stored in the storage unit 302, and the imaging control unit 301 calculates the correction angle Δθ using the stored coefficients A4 to A0 according to the above correction formula. The imaging control unit 301 then applies the correction angle Δθ to the scanning angle of the Y scanner 153-2 during imaging, thereby correcting the optical axis shift. Note that although the correction method for the Y scanner 153-2 has been described using FIGS. 7(a) and 7(b), the correction method for the X scanner 153-1 can also be performed in a similar manner. Through this processing, the optical axis shift caused by driving the coherence gate 155 can be corrected by the scanner with a simple and inexpensive configuration.

[0089] <How to set the correction coefficient> Next, an example of a method for setting correction coefficients according to this embodiment will be described with reference to Fig. 8. Fig. 8 is a flowchart of an example of a method for setting correction coefficients according to this embodiment. In the method for setting correction coefficients according to this embodiment, first, in step S801, the model eye is placed at a measurement position with respect to the OCT device in order to observe a spot 602 of measurement light on the fundus of the model eye. Note that the model eye may be placed at a position corresponding to the position of the subject's eye E at the time of photographing.

[0090] Next, in step S802, the imaging control unit 301 sets the scanning angles of the X scanner 153-1 and the Y scanner 153-2 to a reference angle. Here, the reference angle of the scanning angle is a scanning angle at which the spot 602 of the measurement light reaches the center of the fundus oculi Ef when the position of the coherence gate 155 is set to the reference position P0.

[0091] In step S803, the imaging control unit 301 sets the position of the coherence gate 155 to the drive end. In this embodiment, the imaging control unit 301 sets the position of the coherence gate 155 to position P1 where the optical path length of the measurement optical system (optical path length of measurement light) is longest.

[0092] Thereafter, a repeat process is performed in steps S804 to S807. In this repeat process, the imaging control unit 301 sequentially performs processes while driving the coherence gate 155 over the entire drive range up to the opposite drive end, in other words, position P2 where the optical path length of the measurement optical system is shortest.

[0093] First, in step S805, the image processing unit 305 acquires the position of the spot 602 on the chart 601. For example, as described above, the image processing unit 305 can acquire the position of the spot 602 by capturing an image of the chart 601 from the back side with a camera. In this case, an image of the spot 602 acquired by a camera (not shown) is sent to the control unit 300, and the image processing unit 305 can acquire the position of the spot 602 based on the image of the spot 602 received from the acquisition unit 304. The image processing unit 305 may also acquire the position of the spot 602 using a front image acquired by a C-scan. In this case, the image processing unit 305 can acquire the position of the spot 602 by, for example, comparing a front image acquired by placing the coherence gate 155 at a reference position P0 with a front image acquired at position P of the coherence gate 155 from which the position of the spot 602 should be acquired. Furthermore, the image processing unit 305 may acquire the position of the spot 602 by capturing an image of a chart placed inside the device.

[0094] Subsequently, in step S806, the image processing unit 305 converts the position information of the spot 602 into a scanning angle. The image processing unit 305 can perform the conversion process by proportional calculation using, for example, previously obtained scanning angle information, in other words, a correspondence relationship between the fundus position and the scanning angle, such as a scale relationship between the fundus position and the scanning angle.

[0095] In step S807, when the coherence gate 155 reaches the drive end on the opposite side, the repetitive process ends. This allows information to be acquired for use in the correction process. Note that, at the drive end on the opposite side, the position information of the spot 602 may also be acquired and the spot position may be converted into a scanning angle.

[0096] In step S808, image processing unit 305 generates a table of the scanning angles of X scanner 153-1 and Y scanner 153-2 corresponding to each position of coherence gate 155. More specifically, image processing unit 305 generates a table that stores each position of coherence gate 155 in the repeated processing in association with the scanning angles of X scanner 153-1 and Y scanner 153-2 converted from positional information of spot 602 at that position.

[0097] Then, in step S809, the image processing unit 305 performs polynomial fitting using the generated table, thereby calculating coefficients A4 to A0, which are fitting coefficients for calculating the correction angle Δθ of the scanning angle corresponding to the position of the coherence gate 155.

[0098] In step S810, the image processing unit 305 stores the calculated fitting coefficients in the memory unit 302, thereby completing the correction coefficient setting process. The correction coefficients can be set, for example, at the time of factory shipment or when drive system components are replaced for repairs or the like. If a chart is placed inside the device, the correction coefficients may be set prior to each inspection, each time an image is captured, or in response to an operator's operation. While the control unit 300 has been described as calculating the correction coefficients here, the correction coefficients may be calculated using a separate device or manually as described above, and the calculated correction coefficients may be stored in the memory unit 302 of the control unit 300. The drive end in step S803 may be the position where the optical path length of the measurement optical system is shortest. In this case, the opposite drive end is the position where the optical path length of the measurement optical system is longest.

[0099] Next, an example of a series of imaging processes including a correction process according to this embodiment will be described with reference to Fig. 9. Fig. 9 is a flowchart of an example of a series of imaging processes according to this embodiment. When the imaging process according to this embodiment is started, alignment adjustment is first performed in step S901. As described above, the imaging control unit 301 can determine the amount of deviation of the optical head unit 100 with respect to the subject's eye E using the anterior eye observation image and adjust the alignment of the optical head unit 100 with respect to the subject's eye E. Note that the operator may move and adjust the Z-direction position and XY position of the optical head unit 100 with respect to the subject's eye E by operating the slider 1103 or the like while viewing the anterior eye observation image.

[0100] In step S902, the imaging control unit 301 adjusts the focus of the fundus imaging system and the OCT optical system using the fundus observation image as described above. Note that the operator may adjust the focus of the fundus imaging optical system and the OCT optical system by operating the slider 1203 or the like while checking the brightness of the fundus observation image and the tomographic image.

[0101] In step S903, the imaging control unit 301 adjusts the coherence gate of the OCT optical system using the acquired tomographic image as described above. Note that the operator may adjust the coherence gate position of the OCT optical system by operating the slider 1302 or the like while viewing the tomographic image.

[0102] Next, in step S904, the imaging control unit 301 calculates a correction angle Δθ based on the position of the coherence gate 155 adjusted in step S903 and the correction coefficient stored in the storage unit 302. Specifically, the imaging control unit 301 substitutes the position of the coherence gate 155 and the correction coefficient stored in the storage unit 302 into the above-mentioned correction formula to calculate the correction angle Δθ.

[0103] In step S905, the imaging control unit 301 performs a C-scan or the like on the set imaging range to capture tomographic images, 3D data, etc. At this time, the imaging control unit 301 applies (adds or subtracts) the correction angle Δθ calculated in step S904 to the scanning angle of the XY scanner 153 corresponding to the set imaging range, thereby correcting the scanning angle of the XY scanner 153. This corrects the optical axis deviation caused by the coherence gate position, making it possible to perform imaging at an appropriate position.

[0104] In step S906, the output control unit 303 displays the various images captured in step S905 on the display unit 310. When the display process in step S906 ends, the series of image capturing processes ends.

[0105] As described above, the fundus Ef of the subject's eye E may move due to involuntary eye movement or movement of the subject during imaging. For this reason, in step S905, the imaging control unit 301 can perform the fundus tracking process described above. In this case, if the coherence gate position moves as a result of the fundus tracking process, the imaging control unit 301 can calculate the correction angle Δθ in the same way as in step S904 according to the coherence position after the movement, and correct the scanning angle of the XY scanner 153.

[0106] As described above, the OCT device according to this embodiment includes an OCT optical system that functions as an example of an interference optical system that detects combined light obtained by irradiating the test eye E with measurement light and combining the return light of the measurement light from the test eye E with reference light, thereby acquiring an interference signal. The OCT device also includes a coherence gate 155, a focus lens 154, an XY scanner 153, and an imaging control unit 301. The coherence gate 155 is disposed in the optical path of the measurement light and functions as an example of an optical path length changer that changes the optical path length of the measurement light. The focus lens 154 functions as an example of a focus position changer that changes the focus position of the measurement light. The XY scanner 153 functions as an example of a scanning unit that scans the test eye E with the measurement light. The imaging control unit 301 functions as an example of a control unit that controls the coherence gate 155, the focus lens 154, and the XY scanner 153. The imaging control unit 301 sets the scanning angle of the XY scanner 153 based on the position of the coherence gate 155. The coherence gate 155 includes a collimator lens 155-1 and a fiber end 155-2.

[0107] The imaging control unit 301 corrects the scanning angle of the XY scanner 153 corresponding to the imaging range based on the position of the coherence gate 155. More specifically, the imaging control unit 301 calculates a correction angle Δθ of the XY scanner 153 using a polynomial that approximates the shift of the irradiation points of the measurement light corresponding to the multiple positions of the coherence gate 155. The imaging control unit 301 sets the scanning angle of the XY scanner 153 by applying the calculated correction angle Δθ to the scanning angle of the XY scanner 153 corresponding to the imaging range.

[0108] With this configuration, the OCT device according to this embodiment can reduce the influence of errors in the position of the measurement light caused by driving the coherence gate 155 by controlling the XY scanner 153, thereby improving the measurement accuracy of the OCT optical system. Therefore, in a configuration in which an optical path length adjustment mechanism is disposed in the measurement optical system, the OCT device can perform highly accurate measurements with an inexpensive and simple configuration without using any additional optical elements.

[0109] The OCT device according to this embodiment also includes an image processing unit 305 that functions as an example of a generating unit that generates a tomographic image of the subject's eye E based on the interference signal. The imaging control unit 301 can perform tracking processing to change the position of the coherence gate 155 based on the tomographic image so as to follow the movement of the subject's eye E. The imaging control unit 301 also sets the scanning angle of the XY scanner 153 based on the position of the coherence gate 155 changed by the tracking processing. This allows the OCT device to change the imaging range so as to follow the movement of the subject's eye E during imaging, and can reduce the influence of errors in the position of the measurement light caused by the movement of the coherence gate 155 when changing the imaging range, thereby improving measurement accuracy.

[0110] Furthermore, the OCT device according to this embodiment further includes a fundus imaging system that functions as an example of an imaging unit that captures a front image of the fundus of the subject's eye E, and an output control unit 303 that functions as an example of a display control unit that displays the front image of the fundus of the subject's eye E on the display unit 310. The output control unit 303 causes a frame 1202 that represents the imaging range of a tomographic image corresponding to the interference signal to be superimposed on the front image of the fundus and displayed on the display unit 310. This allows the operator to set the imaging range of the tomographic image by operating the frame 1202 that is displayed superimposed on the front image of the fundus, and the imaging control unit 301 can obtain information on the scanning angle corresponding to the imaging range.

[0111] Furthermore, the output control unit 303 can display on the display unit 310 a slider 1302 that functions as an example of a display for changing the position of the coherence gate 155. This allows the operator to change the position of the coherence gate 155 in accordance with the desired imaging range while checking the tomographic image 1301 displayed on the display unit 310.

[0112] In this embodiment, the angles of the scanning (main scanning) in the X direction and the scanning (sub-scanning) in the Y direction by the X scanner 153-1 and the Y scanner 153-2 are corrected. On the other hand, the optical axis misalignment in the main scanning direction may be corrected by moving the B-scan image in the left-right direction.

[0113] In this case, the imaging control unit 301 corrects the scanning angle of the Y scanner 153-2 by the above-mentioned correction process. Thereafter, the image processing unit 305 generates a B-scan image based on the acquired interference signal, and performs left-right movement processing on the B-scan image based on the position of the coherence gate 155. Note that, regarding the amount of optical axis deviation to be corrected in the X direction, a table may be created by correlating the spot position acquired in the above-mentioned step S805 with the position of the coherence gate 155, and a correction formula may be found by polynomial fitting or the like.

[0114] As described above, in the OCT device according to the modified example of this embodiment, the image processing unit 305 functions as an example of an image processing unit that processes a tomographic image of the subject's eye E generated based on the interference signal. In this case, the imaging control unit 301 sets the scanning angle of the XY scanner 153 in the sub-scanning direction based on the position of the coherence gate 155, and the image processing unit 305 moves the tomographic image in the main scanning direction based on the position of the coherence gate 155. In this case, too, the OCT device can reduce the influence of errors in the position of the measurement light caused by driving the coherence gate 155 and perform highly accurate measurements with an inexpensive and simple configuration without using additional optical elements.

[0115] Example 2 An OCT device according to a second embodiment of the present disclosure will be described below with reference to FIGS. 10(a) to 12. The OCT device according to this embodiment corrects the drive position of the focus lens based on position information of the coherence gate of the OCT optical system. The configuration of the OCT device according to this embodiment is the same as that of the OCT device according to the first embodiment. Therefore, the components according to this embodiment will be designated by the same reference numerals as those according to the first embodiment, and their description will be omitted. The OCT device according to this embodiment will be described below, focusing on the differences from the OCT device according to the first embodiment.

[0116] <Focus lens correction> The collimated state of the light emitted from the coherence gate 155 is ideally parallel, but in reality, it may not be parallel due to manufacturing errors. In such cases, in this embodiment, the deviation in the focus state (defocus) of the OCT optical system caused by driving the coherence gate 155 is corrected by the focus lens 154. Note that other conditions of the optical system may be the same as in Example 1. However, in this embodiment, for the sake of simplicity, it is assumed that the linearity accuracy of the drive system of the coherence gate 155 is ideal.

[0117] 10(a) and 10(b) show an example in which a deviation in focus state is corrected by a focus lens 154. Fig. 10(a) illustrates a coherence gate 155, a focus lens 154, and an eye E to be examined. Note that, for the sake of simplicity, other lenses and mirrors included in the OCT optical system are omitted from Fig. 10(a).

[0118] 10(a), the position of the coherence gate 155 is indicated by position P, and the position of the focus lens 154 is indicated by position Q. In the example shown in FIG. 10(a), when the coherence gate 155 is disposed at the reference position P0, the focus lens 154 is adjusted to the reference position Q0 indicated by the dashed line so that the light beam F3 is imaged on the fundus Ef of the emmetropic subject's eye E.

[0119] In the example shown in FIG. 10( a), the positional relationship between the collimator lens 155-1 and the fiber end 155-2 is longer than the ideal focal length, and the light beam F3 indicated by the solid line emerging from the coherence gate 155 is a converging light beam. If the light beam F3 is a converging light beam rather than a parallel light beam, the imaging position of the OCT optical system changes depending on the position of the coherence gate 155. In the example shown in FIG. 10( a), when the coherence gate 155 moves from the reference position P0 to position P1 and the optical path length increases, the imaging position shifts toward the optical head unit 100. Therefore, when the coherence gate 155 moves to position P1, the imaging position shifts as indicated by the light beam F4 indicated by the dashed line, causing the measurement light spot on the fundus Ef of the subject's eye E to defocus. The defocusing of the measurement light spot leads to a decrease in the return light from the fundus Ef of the subject's eye E, reducing the sensitivity of OCT imaging.

[0120] In response to this, it is possible to correct the defocus by controlling the position of the focus lens 154. For example, when the focus lens 154 is moved from the reference position Q0 to a position Q1 on the side of the subject's eye E by a correction amount ΔQ, the image formation position of the light beam F4 moves farther toward the subject's eye E than the defocus position, and the light beam F4 can be imaged on the fundus Ef of the subject's eye E.

[0121] The correction amount ΔQ can be obtained using a model eye, as in Example 1. For example, a spot 602 of measurement light is observed on a chart 601 placed at a position corresponding to the fundus of an emmetropic model eye. Then, the focus lens 154 is driven to search for a position of the focus lens 154 where the size of the spot 602 of measurement light is minimized or the peak light intensity is maximized, thereby searching for a position of the focus lens 154 where the imaging state is optimized. By placing the coherence gate 155 at multiple positions and performing this process, the correspondence relationship between the position of the coherence gate 155 and the correction amount ΔQ can be obtained.

[0122] In this embodiment, the spot can be observed by capturing an image from the rear side of the chart 601 using a camera. The control unit 300 may also drive the focus lens 154 to search for a position of the focus lens 154 where the peak or average value of pixel values ​​is maximized for a tomographic image (such as an A-scan image) captured using the measurement light. In this case, too, the position of the focus lens 154 where the imaging state is optimized can be searched for.

[0123] 10(b) is a graph showing the relationship between the position of the coherence gate 155 and the correction position of the focus lens 154. The horizontal axis indicates the position P of the coherence gate 155, and the vertical axis indicates the correction amount ΔQ of the focus lens 154. FIG. 10(b) also shows the reference position P0 of the coherence gate 155, the position P1 of the drive end of the coherence gate 155 on the optical head unit 100 side, and the position P2 of the drive end of the coherence gate 155 on the subject's eye E side. A solid line 901 is a function curve showing the correction formula for the correction amount ΔQ according to the position P.

[0124] To obtain the correction formula, for example, the coherence gate 155 is placed at multiple positions, the position of the focus lens 154 is actually adjusted, and the correction formula can be obtained by interpolating each adjustment amount. However, since the information obtained in this way is discrete, a correction formula that can correct the focus state deviation over the entire movement range of the coherence gate 155 can be obtained by fitting using polynomial approximation, as in the first embodiment.

[0125] Furthermore, similarly to the first embodiment, the coefficients of the obtained polynomial are stored in the storage unit 302, and the imaging control unit 301 calculates a correction amount ΔQ by the above correction formula using the stored coefficients, and applies the correction amount ΔQ to the position of the focus lens 154 during imaging. Specifically, the imaging control unit 301 moves the focus lens 154 to a position obtained by applying the correction amount ΔQ according to the current position of the coherence gate 155 to a reference position Q0 adjusted so that the measurement light is focused on the subject's eye E when the coherence gate 155 is at the reference position P0. Through such processing, the defocus caused by driving the coherence gate 155 can be corrected by the focus lens 154 with a simple and inexpensive configuration without using any additional optical elements.

[0126] <How to set the correction coefficient> Next, a flow of an example of a method for setting correction coefficients in this embodiment will be described with reference to Fig. 11. Fig. 11 is a flowchart of an example of a method for setting correction coefficients according to this embodiment. In the method for setting correction coefficients according to this embodiment, first, in step S1101, the model eye is placed at a measurement position with respect to the OCT device in order to observe a spot 602 of measurement light on the fundus of the model eye. Note that the model eye may be placed at a position corresponding to the position of the subject's eye E at the time of photographing.

[0127] Next, in step S1102, the imaging control unit 301 sets the position of the focus lens 154 to a reference position Q0. Here, the reference position Q0 of the focus lens 154 is the position where the spot 602 of the measurement light is imaged on the fundus Ef when the coherence gate 155 is placed at the reference position P0.

[0128] In step S1103, the imaging control unit 301 sets the position of the coherence gate 155 to the drive end. In this embodiment, the imaging control unit 301 sets the position of the coherence gate 155 to a position where the optical path length of the measurement optical system (optical path length of measurement light) is longest.

[0129] After that, a repeat process is performed in steps S1104 to S1107. In this repeat process, the imaging control unit 301 performs sequential processes while driving the coherence gate 155 over the entire drive range until it reaches the opposite drive end, in other words, the position where the optical path length of the measurement optical system is shortest.

[0130] First, in step S1105, the image processing unit 305 observes the spot 602 on the chart 601 and checks the defocus state of the spot 602. For example, as described above, the image processing unit 305 can photograph the chart 601 from the back side with a camera and check the defocus state of the spot 602 based on the size and peak light intensity of the spot 602. In this case, an image of the spot 602 obtained by a camera (not shown) is sent to the control unit 300, and the image processing unit 305 can check the defocus state of the spot 602 based on the image of the spot 602 received from the acquisition unit 304. Note that the image processing unit 305 may check the defocus state of the spot 602 based on a tomographic image.

[0131] Next, in step S1106, the imaging control unit 301 drives the focus lens 154, and the image processing unit 305 acquires the position of the focus lens 154 when the spot 602 is formed. The search for the position of the focus lens 154 can be performed by searching for the position of the focus lens 154 that satisfies conditions such as the minimum size of the spot 602 or the maximum peak light intensity, as described above. The position of the focus lens 154 that optimizes the imaging state can also be searched for by searching for the position of the focus lens 154 that maximizes the peak or average value of the pixel values ​​for a tomographic image captured using the measurement light.

[0132] In step S1107, when the coherence gate 155 reaches the drive end on the opposite side, the repetitive process ends. This allows information to be acquired for use in the correction process. Note that, at the drive end on the opposite side, the spot 602 may also be observed and the position of the focus lens 154 at which the spot 602 is focused may be acquired.

[0133] In step S1108, the image processing unit 305 generates a table of positions of the focus lens 154 corresponding to each position of the coherence gate 155. More specifically, the image processing unit 305 generates a table that stores each position of the coherence gate 155 in the repeated processing in association with the position of the focus lens 154 at which the spot 602 is imaged.

[0134] Then, in step S1109, the image processing unit 305 performs polynomial fitting using the generated table, thereby calculating fitting coefficients for calculating a correction amount ΔQ for the position of the focus lens 154 corresponding to the position of the coherence gate 155.

[0135] In step S1110, the image processing unit 305 stores the calculated fitting coefficients in the memory unit 302, thereby completing the correction coefficient setting process. The correction coefficients can be set, for example, at the time of factory shipment or when a drive system component is replaced for repair or the like. Although the configuration in which the control unit 300 calculates the correction coefficients has been described here, the correction coefficients may be calculated as described above using a separate device or manually, and the calculated correction coefficients may be stored in the memory unit 302 of the control unit 300. The drive end in step S1103 may be the position where the optical path length of the measurement optical system is shortest, in which case the opposite drive end is the position where the optical path length of the measurement optical system is longest.

[0136] Next, a series of imaging processes including correction processes according to this embodiment will be described with reference to Fig. 12. Fig. 12 is a flowchart of an example of a series of imaging processes according to this embodiment. Note that the imaging processes according to this embodiment are the same as those according to the first embodiment, except for the processes in steps S1204 and S1205. Therefore, to simplify the description, descriptions of steps S1201, S1202, S1203, and S1206 will be omitted.

[0137] In step S1203, once the coherence gate of the OCT optical system has been adjusted, the process proceeds to step S1204. In step S1204, the imaging control unit 301 calculates a correction amount ΔQ based on the position of the coherence gate 155 adjusted in step S1203 and the correction coefficient stored in the storage unit 302. Specifically, the imaging control unit 301 substitutes the position of the coherence gate 155 and the correction coefficient stored in the storage unit 302 into the correction formula described above to calculate the correction amount ΔQ.

[0138] In step S1205, the imaging control unit 301 performs a C-scan or the like on the set imaging range to capture tomographic images, 3D data, and the like. At this time, the imaging control unit 301 applies the correction amount ΔQ calculated in step S1204 to the position of the focus lens 154 adjusted in step S1202, thereby correcting the position of the focus lens 154. Note that the position of the focus lens 154 adjusted in step S1202 may be the position adjusted when the coherence gate 155 is at the reference position P0, and this position is used in processing as the reference position Q0 of the focus lens 154. This makes it possible to correct a shift in the focus state due to the coherence gate position, and to perform imaging in an appropriate focus state. Note that the subsequent processing is the same as in Example 1, and therefore a description thereof will be omitted.

[0139] In this embodiment, too, the imaging control unit 301 can perform the above-described fundus tracking process in step S1205. In this case, if the coherence gate position moves as a result of the fundus tracking process, the imaging control unit 301 can calculate the correction amount ΔQ in the same way as in step S1204 according to the coherence position after the movement, and correct the position of the focus lens 154.

[0140] As described above, the imaging control unit 301 sets the position of the focus lens 154 based on the position of the coherence gate 155. Specifically, the imaging control unit 301 sets the position of the focus lens 154 to a second position obtained by applying a correction amount ΔQ corresponding to the position P of the coherence gate 155 to a first position (reference position Q0) of the focus lens 154, which is adjusted so that the measurement light is focused on the subject's eye E when the coherence gate 155 is at a predetermined position (reference position P0). Here, the imaging control unit 301 calculates the correction amount ΔQ corresponding to the position P of the coherence gate 155 using a polynomial that approximates the defocus amount of the measurement light corresponding to multiple positions of the coherence gate 155 changed from the reference position P0. Here, the defocus amount of the measurement light corresponds to the position of the focus lens 154 adjusted so that the imaging position of the OCT optical system matches the imaging region at each of the multiple positions of the coherence gate 155.

[0141] With this configuration, the OCT device according to this embodiment can reduce the influence of focus errors of the spot 602 caused by driving the coherence gate 155 by controlling the focus lens 154, thereby improving the measurement accuracy of the OCT optical system. Therefore, in a configuration in which an optical path length adjustment mechanism is disposed in the measurement optical system, the OCT device can perform highly accurate measurements with an inexpensive and simple configuration without using any additional optical elements.

[0142] Furthermore, the imaging control unit 301 according to this embodiment can also perform tracking processing to change the position of the coherence gate 155 based on the tomographic image so as to follow the movement of the subject's eye E. Furthermore, the imaging control unit 301 sets the position of the focus lens 154 based on the position of the coherence gate 155 changed by the tracking processing. This allows the OCT device to change the imaging range so as to follow the movement of the subject's eye E during imaging. Furthermore, the OCT device can reduce the influence of focus errors of the measurement light caused by the movement of the coherence gate 155 when changing the imaging range, thereby improving measurement accuracy.

[0143] In the first and second embodiments, examples have been described in which errors in the position and focus of the spot 602 caused by driving the coherence gate 155 are corrected. However, errors in the position and focus of the spot 602 caused by driving the coherence gate 155 may actually occur simultaneously. In this case, by performing both the correction processes of the first and second embodiments, it is possible to reduce the influence of both errors and improve the measurement accuracy of the OCT optical system. The setting of the correction coefficient related to the scanning angle and the setting of the correction coefficient related to the focus lens position may be performed separately or together.

[0144] Furthermore, in the first and second embodiments, the configuration has been described in which the fundus Ef of the subject's eye E is photographed and a front image and a tomographic image of the fundus are acquired. However, the photographed object is not limited to the fundus Ef. For example, the anterior segment Ea of the subject's eye E may be photographed and a front image and a tomographic image of the anterior segment Ea may be acquired. In this case, the above-described fundus tracking process may be performed as a tracking process of the anterior segment Ea.

[0145] Although a Michelson interferometer is used as the interferometer in the above-described first and second embodiments, a Mach-Zehnder interferometer may also be used. Furthermore, although a fiber optics system using a coupler as the splitting means is used, a spatial optical system using a collimator and a beam splitter may also be used. The configuration of the optical head unit 100 is not limited to the above-described configuration, and some of the components included in the optical head unit 100 may be configured separately from the optical head unit 100. Furthermore, the optical systems provided in the reflection and transmission directions of the various dichroic mirrors may be provided in the transmission and reflection directions, respectively. Furthermore, although the various images are configured to be generated by the image processing unit 305, they may also be generated by a calculation unit (not shown) provided in the optical head unit 100 and sent to the control unit 300. In this case, the acquisition unit 304 can acquire an anterior eye observation image, a frontal fundus image, a tomographic image, etc. from the optical head unit 100 and send them to the image processing unit 305.

[0146] Furthermore, in the above-described first and second embodiments, a spectral domain OCT (SD-OCT) device using an SLD as a light source has been described as the OCT device, but the configuration of the OCT device according to the present invention is not limited to this. For example, the present invention can be applied to any other type of OCT device, such as a swept-wavelength OCT (SS-OCT) device using a swept-wavelength light source capable of sweeping the wavelength of emitted light. For example, the present invention can also be applied to an AO-OCT device equipped with adaptive optics. Furthermore, in the above-described first and second embodiments, a fundus camera configuration is used as the fundus observation system, but the configuration for capturing the fundus observation image and the fundus image is not limited to this. For example, a scanning laser ophthalmoscope (SLO) configuration may be used as the configuration for capturing the fundus observation image and the fundus image.

[0147] (Other Examples) The present invention can also be realized by providing a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that implements one or more functions. A computer may have one or more processors or circuits, and may include multiple separate computers or a network of multiple separate processors or circuits to read and execute computer-executable instructions.

[0148] The processor or circuitry may include a central processing unit (CPU), a microprocessing unit (MPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), or a field programmable gateway (FPGA). The processor or circuitry may also include a digital signal processor (DSP), a data flow processor (DFP), or a neural processing unit (NPU).

[0149] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. The present invention also includes inventions that have been modified within the scope of the present invention and inventions equivalent to the present invention. Furthermore, the above-described embodiments and modifications can be combined as appropriate within the scope of the present invention. [Explanation of symbols]

[0150] 153: XY scanner (scanning unit), 154: focus lens (focus position changing unit), 155: coherence gate (optical path length changing unit), 301: imaging control unit (control unit)

Claims

1. an interference optical system that detects combined light obtained by irradiating a measurement light onto the subject's eye and combining the measurement light returned from the subject's eye with a reference light, and acquires an interference signal; an optical path length changing unit that changes the optical path length of the measurement light; a scanning unit that scans the measurement light over the subject's eye; a control unit that controls the optical path length changing unit and the scanning unit; Equipped with the control unit changes the scanning angle of the scanning unit based on the change in the optical path length of the measurement light; The control unit calculates a correction angle for the scanning angle using a polynomial that approximates the shift in the irradiation point of the measurement light corresponding to the multiple positions of the optical path length changing unit, and changes the scanning angle of the scanning unit using the calculated correction amount.

2. The ophthalmologic imaging apparatus according to claim 1 , wherein the optical path length changing unit includes a collimator lens and a fiber end.

3. The ophthalmologic imaging apparatus according to claim 1 , wherein the control unit changes the scanning angle of the scanning unit based on a change in the optical path length of the measurement light and an imaging range.

4. a generating unit that generates a tomographic image of the subject's eye based on the interference signal, The ophthalmologic imaging apparatus according to claim 1 , wherein the control unit changes an optical path length of the measurement light based on the tomographic image so as to follow a movement of the subject's eye.

5. an image processing unit that processes a tomographic image of the subject's eye generated based on the interference signal, the control unit changes a scanning angle of the scanning unit in a sub-scanning direction based on the change in the optical path length of the measurement light; The ophthalmologic imaging apparatus according to claim 1 , wherein the image processing unit moves the tomographic image in a main scanning direction based on a change in the optical path length of the measurement light.

6. an imaging unit that captures a front image of the subject's eye; a display control unit that displays the front image on a display unit, The ophthalmologic imaging apparatus according to claim 1 , wherein the display control unit causes the display unit to display a photographing range of the tomographic image corresponding to the interference signal superimposed on the front image.

7. The ophthalmologic photographing apparatus according to claim 1 , further comprising a display control unit that causes a slider for changing the optical path length of the measurement light to be displayed on a display unit.

8. an interference optical system that detects combined light obtained by irradiating a measurement light onto the subject's eye and combining the measurement light returned from the subject's eye with a reference light, and acquires an interference signal; an optical path length changing unit that changes the optical path length of the measurement light; a focus position changing unit that changes the focus position of the measurement light; a control unit that controls the optical path length changing unit and the focusing position changing unit; Equipped with the control unit changes the position of the focusing position change unit based on the change in the optical path length of the measurement light; The control unit calculates a correction amount corresponding to the position of the optical path length changing unit using a polynomial that approximates the defocus amount of the measurement light corresponding to multiple positions of the optical path length changing unit that have been changed from a first position of the focusing position changing unit, which is adjusted so that the measurement light is focused on the test eye when the optical path length changing unit is in a predetermined position, and changes the position of the focusing position changing unit to a second position using the calculated correction amount.

9. A method for controlling an ophthalmic imaging apparatus, comprising: The ophthalmologic imaging device an interference optical system that detects combined light obtained by irradiating a measurement light onto the subject's eye and combining the measurement light returned from the subject's eye with a reference light, and acquires an interference signal; an optical path length changing unit that changes the optical path length of the measurement light; a scanning unit that scans the measurement light over the subject's eye; Equipped with the control method includes changing a scan angle of the scanner based on a change in the optical path length of the measurement light; A method for controlling an ophthalmic imaging apparatus, wherein changing the scanning angle includes calculating a correction angle for the scanning angle using a polynomial that approximates the shift of the irradiation point of the measurement light corresponding to multiple positions of the optical path length changing unit, and changing the scanning angle of the scanning unit using the calculated correction amount.

10. A method for controlling an ophthalmic imaging apparatus, comprising: The ophthalmologic imaging device an interference optical system that detects combined light obtained by irradiating a measurement light onto the subject's eye and combining the measurement light returned from the subject's eye with a reference light, and acquires an interference signal; an optical path length changing unit that changes the optical path length of the measurement light; a focus position changing unit that changes the focus position of the measurement light; Equipped with The control method includes changing a position of the focus position changing unit based on a change in the optical path length of the measurement light, A method for controlling an ophthalmic imaging apparatus, wherein changing the position includes calculating a correction amount corresponding to the position of the optical path length changing unit using a polynomial that approximates the defocus amount of the measurement light corresponding to multiple positions of the optical path length changing unit changed from a first position of the focus position changing unit, which is adjusted so that the measurement light is focused on the test eye when the optical path length changing unit is in a predetermined position, and changing the position of the focus position changing unit to a second position using the calculated correction amount.

11. A program that, when executed by a computer, causes the computer to execute the method for controlling an ophthalmologic photographing apparatus according to claim 9 or 10.

12. An interference optical system that detects combined light obtained by irradiating a measurement light onto a test eye, combining the return light of the measurement light from the test eye with a reference light, and acquires an interference signal; an optical path length changing unit that changes the optical path length of the measurement light; a scanning unit that scans the measurement light over the subject's eye; a control unit that controls the optical path length changing unit and the scanning unit; Equipped with the control unit changes the scanning angle of the scanning unit based on the change in the optical path length of the measurement light; The control unit changes the scanning angle of the scanning unit using a correction angle calculated using a shift in the irradiation point of the measurement light corresponding to multiple positions of the optical path length changing unit.

Images