Signal processing method for ophthalmologic apparatus, ophthalmologic apparatus, and program

Abstract

According to the present invention, a signal processing method performed by a processor of an ophthalmologic apparatus includes a step for obtaining an interference signal of measurement light and reference light, a step for obtaining a peak value component determined by a distribution of brightness in the interference signal, a step for obtaining a corrected interference signal by subtracting a signal of a magnitude determined by the peak value component from the interference signal, a step for obtaining the peak value component for the interference signal by using the corrected interference signal as the interference signal, a step for obtaining the corrected interference signal, a step for repeatedly executing the above steps until the corrected interference signal that is the subtraction result is no greater than a threshold value that is set in advance, and a step for obtaining OCT data on the basis of the corrected interference signal that is no greater than the threshold value.

Description

Ophthalmic apparatus signal processing method, ophthalmic apparatus, and program

[0001] The technology of the present disclosure relates to a signal processing method for an ophthalmic apparatus, an ophthalmic apparatus, and a program.

[0002] Known devices for observing a subject's eye include optical coherence tomography (OCT) devices that acquire tomographic images of the subject's eye (see, for example, U.S. Patent Application Publication No. 2020 / 0037872). OCT devices are required to acquire tomographic images of the subject's eye over a wider area and with higher accuracy.

[0003] A first aspect of the technology of the present disclosure is an ophthalmic device including a processor, wherein the processor executes processing including the steps of: obtaining an interference signal between measurement light and reference light; obtaining a peak value component determined by a brightness distribution in the interference signal; subtracting a signal having a magnitude determined by the peak value component from the interference signal to obtain a modified interference signal; using the modified interference signal as the interference signal, obtaining the peak value component for the interference signal and obtaining the modified interference signal; repeatedly executing these steps until the modified interference signal resulting from the subtraction becomes equal to or less than a predetermined threshold; and obtaining an OCT signal based on the modified interference signal that is equal to or less than the threshold.

[0004] A second aspect of the technology of the present disclosure is a signal processing method for an ophthalmic device, the signal processing method including: a step of obtaining an interference signal between measurement light and reference light; a step of obtaining a peak value component determined by the brightness distribution in the interference signal; a step of subtracting a signal having a magnitude determined by the peak value component from the interference signal to obtain a modified interference signal; a step of repeatedly executing the steps of obtaining the peak value component for the interference signal using the modified interference signal as the interference signal and obtaining the modified interference signal until the modified interference signal resulting from the subtraction becomes equal to or less than a predetermined threshold; and a step of obtaining an OCT signal based on the modified interference signal that is equal to or less than the threshold.

[0005] A third aspect of the technology of the present disclosure is a program that causes a computer to execute processing including the steps of: obtaining an interference signal between measurement light and reference light; obtaining a peak value component determined by the brightness distribution in the interference signal; subtracting a signal having a magnitude determined by the peak value component from the interference signal to obtain a modified interference signal; using the modified interference signal as the interference signal, obtaining the peak value component for the interference signal and obtaining the modified interference signal; repeatedly executing these steps until the modified interference signal resulting from the subtraction becomes equal to or less than a predetermined threshold; and obtaining an OCT signal based on the modified interference signal that is equal to or less than the threshold.

[0006] 1 is a block diagram showing the configuration of an ophthalmologic system according to an embodiment. FIG. 2 is a block diagram showing the hardware configuration of an ophthalmologic apparatus according to an embodiment. FIG. 3 is a block diagram showing the hardware configuration of an OCT unit according to an embodiment. FIG. 4 is a functional block diagram of an ophthalmologic apparatus according to an embodiment. FIG. 5 is a flowchart showing the flow of signal processing in an ophthalmologic apparatus according to an embodiment. FIG. 6 is a flowchart showing the flow of full-range OCT processing in an ophthalmologic apparatus according to an embodiment. FIG. 7 is a flowchart showing the derivation process of coefficients related to a threshold. FIG. 8 is a diagram showing an example of a tomographic image of a fundus. FIG. 9 is a diagram showing an example of a tomographic image when full-range OCT processing is performed. FIG. 10 is a diagram showing a tomographic image when normal full-range OCT processing is performed. FIG. 11 is a conceptual diagram of an OCT image (tomographic image) obtained by full-range OCT processing. FIG. 12 is a conceptual diagram of an OCT image (tomographic image) that changes depending on the number of times the FR process is repeated. FIG. 13 is a diagram showing a screen displayed on a display.

[0007] Hereinafter, embodiments of the technology of the present disclosure will be described in detail with reference to the drawings. Note that components and processes that perform the same actions and functions are given the same reference numerals throughout the drawings, and redundant explanations may be omitted as appropriate. Also, explanations of configurations that are not directly related to the present disclosure or well-known configurations may be omitted. Also, the dimensional ratios in the drawings are exaggerated for the sake of explanation and may differ from the actual ratios. Furthermore, each drawing is merely a schematic illustration to allow a sufficient understanding of the technology of the present disclosure. Therefore, the technology of the present disclosure is not limited to the illustrated examples.

[0008] The configuration of an ophthalmologic system 100 according to an embodiment of the technique of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the configuration of the ophthalmologic system 100 according to the present embodiment. As shown in Fig. 1, the ophthalmologic system 100 includes an ophthalmologic apparatus 110, a network 130, a management server apparatus (hereinafter referred to as "management server") 140, and an image display apparatus (hereinafter referred to as "image viewer") 150.

[0009] The ophthalmic apparatus 110, the management server 140, and the image viewer 150 are connected to each other via a network 130. The network 130 may be any network such as a LAN, a WAN, the Internet, or a wide area Ethernet. For example, if the ophthalmic system 100 is established in a single hospital, a LAN may be used as the network 130.

[0010] The ophthalmologic apparatus 110 is an apparatus that photographs an eye to be examined and performs at least one of ophthalmologic examination, measurement, and treatment.

[0011] The management server 140 receives, via the network 130, images of the subject's eye obtained by photographing the subject's eye with the ophthalmologic apparatus 110, corresponding to the patient ID, and stores the images in a memory (not shown). Thus, the memory of the management server 140 stores images of the subject's eye corresponding to the patient ID of each patient. The management server 140 also transmits the images of the subject's eye to the image viewer 150 via the network 130.

[0012] The image viewer 150 is a touch panel, a display, or the like, and has a communication function. The image viewer 150 displays the image of the subject's eye acquired by the management server 140.

[0013] In addition, other ophthalmic equipment (examination equipment for visual field measurement, intraocular pressure measurement, etc.) and diagnostic support devices that perform image analysis using artificial intelligence may be connected to the ophthalmic device 110, management server 140, and image viewer 150 via the network 130.

[0014] Next, the configuration of the ophthalmic apparatus 110 will be described with reference to FIG. 2 . FIG. 2 is a block diagram showing the hardware configuration of the ophthalmic apparatus 110 according to this embodiment. As shown in FIG. 2 , the ophthalmic apparatus 110 includes a control device 16, a scanning laser ophthalmoscope (SLO) unit 18, an optical coherence tomography (OCT) unit 20P, and an imaging optical system 19. The control device 16 controls the SLO unit 18, the OCT unit 20P, and the imaging optical system 19. The control device 16 controls the SLO unit 18 and the imaging optical system 19 to acquire an image of the fundus or the anterior segment of the subject's eye 12. The control device 16 controls the OCT unit 20P and the imaging optical system 19 to acquire a tomographic image of the fundus of the subject's eye 12 or the anterior segment.

[0015] When the ophthalmic device 110 is placed on a horizontal plane, the horizontal direction is referred to as the "X direction," the direction perpendicular to the horizontal plane is referred to as the "Y direction," and the direction of the optical axis of the imaging optical system 19 is referred to as the "Z direction." The device is positioned with respect to the subject's eye 12 so that the center of the pupil of the subject's eye is located on the optical axis in the X direction. The X direction, Y direction, and Z direction are perpendicular to each other.

[0016] When acquiring one-dimensional data in the depth direction, one-dimensional OCT data (referred to as "A-scan data") is obtained by scanning one point on the fundus in the depth (optical axis) direction (this scanning is referred to as "A-scan"). When acquiring two-dimensional data, two-dimensional OCT data (referred to as "B-scan data") is obtained by performing A-scans multiple times while moving the scanning position in a direction perpendicular to the depth direction (referred to as "B-scan"). When acquiring three-dimensional data, OCT data (referred to as "volume scan data") is obtained by repeating B-scans while moving the scanning position in a direction perpendicular to the B-scan direction (referred to as "C-scan"). Three-dimensional OCT data is generated from the volume scan data, and two-dimensional en-face images, etc. are generated based on the three-dimensional OCT data.

[0017] The control device 16 includes a computer having a CPU (Central Processing Unit) 16A, a RAM (Random Access Memory) 16B, a ROM (Read-Only Memory) 16C, an input / output (I / O) 16D, an input / display device 16E, and a communication interface (I / F) 16F. Each component of the control device 16 is connected to each other via a bus so that they can communicate with each other.

[0018] The CPU 16A is a central processing unit that executes various programs and controls each component. That is, the CPU 16A reads programs from the ROM 16C and executes the programs using the RAM 16B as a work area. The CPU 16A controls each component and performs various arithmetic processing according to the programs stored in the ROM 16C. In this embodiment, the ROM 16C stores a signal processing program for processing the light intensity distribution (interference spectrum) of the interference light shown in FIG. 5, which will be described later. The CPU 16A is an example of a "processor" of the technology disclosed herein. The RAM 16B and ROM 16C are examples of storage units that store information. The control device 16 is an example of a computer.

[0019] The RAM 16B temporarily stores programs or data as a working area. The ROM 16C stores various programs and various data. The control device 16 may further include a storage device configured with a storage medium such as a hard disk drive (HDD) or a solid state drive (SSD). In this case, the storage device may store various programs including an operating system and various data. The signal processing program shown in FIG. 5 may be stored in the storage device instead of the ROM 16C.

[0020] The input / display device 16E is connected to the CPU 16A via the I / O 16D. The input / display device 16E has a graphical user interface (GUI) that displays an image of the subject's eye 12 and receives various instructions from the user. A touch panel or a display can be used as the GUI.

[0021] The control device 16 connects to the network 130 via a communication interface 16F. The communication interface 16F is an interface for communicating with other devices, and uses standards such as Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark).

[0022] 2, the control device 16 of the ophthalmic apparatus 110 is provided with an input / display device 16E, but the technology of the present disclosure is not limited to this. For example, the control device 16 of the ophthalmic apparatus 110 may not be provided with the input / display device 16E, but may instead be provided with an input / display device that is physically independent from the ophthalmic apparatus 110. In this case, the display device may include an image processing unit that operates under the control of the CPU 16A of the control device 16. The image processing unit may display an acquired image, etc., based on an image signal instructed to be output by the CPU 16A.

[0023] Hereinafter, a front-view image of the retina created based on the SLO data acquired by the SLO unit 18 will be referred to as an SLO image, and a tomographic image or a front image (en-face image) of the retina created based on the OCT data acquired by the OCT unit 20P will be referred to as an OCT image. Note that an SLO image may also be referred to as a two-dimensional fundus image. Furthermore, an OCT image may also be referred to as a fundus tomographic image, a posterior segment tomographic image, or an anterior segment tomographic image depending on the region of the subject's eye 12 that is imaged.

[0024] The angle of view of the ophthalmologic apparatus 110 is preferably wide-angle, and as will be described later, is preferably ultra-wide-angle. In this case, the obtained image may be called a UWF (Ultra Wide Field) fundus image. An image of the fundus captured at an ultra-wide angle will hereinafter be referred to as a UWF fundus image.

[0025] The imaging optical system 19 enables observation of a wide field of view (FOV) at the fundus. The FOV indicates the range that can be imaged by the imaging device. The FOV can be expressed as a field of view angle. In this embodiment, the field of view angle can be defined by an internal illumination angle and an external illumination angle. The external illumination angle is the illumination angle of the light beam irradiated from the ophthalmic device 110 to the subject's eye, defined with the pupil as the reference point. The internal illumination angle is the illumination angle of the light beam irradiated to the fundus, defined with the center of the eyeball as the reference point. The external illumination angle and the internal illumination angle correspond to each other. For example, if the external illumination angle is 120 degrees, the internal illumination angle corresponds to approximately 160 degrees. In this embodiment, the internal illumination angle is 200 degrees.

[0026] Here, an SLO fundus image obtained by photographing at an internal illumination angle with a photographing angle of view of 160 degrees or more is referred to as a UWF-SLO fundus image (UWF fundus image).

[0027] 3 is a block diagram showing the hardware configuration of the OCT unit 20P according to this embodiment. As shown in FIG. 3, the OCT unit 20P includes a light source 52, a first optical coupler 54, a polarization adjuster 56, a delay line 58, a second optical coupler 60, a detector 62, and an analog-to-digital (A / D) converter 64.

[0028] The light source 52 generates light for optical coherence tomography. The light source 52 is a wavelength swept light source that outputs wavelength swept light whose center wavelength changes rapidly by sweeping a predetermined wavelength range at a predetermined wavelength sweep speed. The light source 52 includes, for example, a near-infrared tunable laser. In this way, the OCT unit 20P acquires OCT data of the fundus using the principle of SS-OCT (Swept Source-Optical Coherence Tomography).

[0029] The OCT unit 20P is not limited to SS-OCT, which uses a wavelength swept light source as the light source 52. For example, SD-OCT, which uses a super luminescent diode (SLD), may be adopted.

[0030] The first optical coupler 54 splits the path of the light emitted from the light source 52 into two paths. One path is a path where the light travels toward the polarization adjuster 56, and the other path is a path where the light travels toward the delay line 58.

[0031] Although FIG. 3 shows an example in which the polarization adjuster 56 is disposed in one of the two paths branched by the first optical coupler 54 from the path of light from the light source 52, the present disclosure is not limited thereto. That is, the polarization adjuster 56 may be disposed in at least one of the two paths branched (split) by the first optical coupler 54. This is because any configuration is sufficient if the polarization adjuster 56 can adjust the polarization states of the two lights to the same vibration direction (e.g., maximize the interference state) when the measurement light and the reference light converge and interfere at the optical coupler 60. Also, FIG. 3 shows an example in which the delay line 58 is disposed in the other of the two paths, but the present disclosure is not limited thereto. That is, the delay line 58 may be disposed in at least one of the two paths branched by the first optical coupler 54. This is because any configuration is sufficient if the delay line 58 can adjust the optical path lengths of the two lights to the same optical path length when the measurement light and the reference light converge and interfere at the optical coupler 60.

[0032] The polarization adjuster 56 adjusts the polarization state, which is the direction of vibration of light that is spatially vibrating in a predetermined direction. The light whose polarization state has been adjusted is incident on the photographing optical system 19.

[0033] The light incident on the imaging optical system 19 is scanned in the X and / or Y directions by the imaging optical system 19. The scanning light passes through the pupil of the subject's eye 12 as measurement light and is irradiated onto the fundus. Since the scanning light is scanned, each scanning time corresponds to each scanning position on the fundus. The scanning speed is the speed at which B-scan data can be acquired by B-scan at each scanning position. Note that the scanning speed in the X or Y direction is different from the sweep speed of the light source, and the sweep speed is the A-scan speed at which an A-scan signal is acquired at one point. The measurement light reflected from the fundus is incident on the OCT unit 20P via the imaging optical system 19, and then incident on the second optical coupler 60 via the polarization adjustment unit 56 and the first optical coupler 54.

[0034] The other light beam emitted from the light source 52 and branched by the first optical coupler 54 is incident on a delay line 58 as a reference light beam, and passes through the delay line 58 to be incident on a second optical coupler 60 .

[0035] As described above, the optical path lengths of the reference light and the measurement light are set equal to each other in the delay line 58. These optical path lengths can be adjusted by an operator while viewing a fundus image, for example, before starting the operation of the scanning light, so that the tomographic image is positioned in an appropriate range depending on the axial length of the eye.

[0036] The measurement light (return light) reflected by the subject's eye 12 and the reference light are combined by the second optical coupler 60 to generate interference light. The detector 62 detects the interference light, removes noise, and outputs a detection signal. The detection signal indicates, for example, the distribution of the power of the interference light, such as brightness, i.e., the light intensity distribution of the interference light (hereinafter referred to as the interference spectrum). The A / D converter 64 A / D converts the interference spectrum from the detector 62 and outputs it to the control device 16. The interference spectrum is stored in the RAM 16B of the control device 16.

[0037] When SD-OCT is used in the OCT unit 20P, a spectrometer is placed at the position of the detector 62, and a grabber board is placed at the position of the A / D converter 64, so that the interference light is separated and detected according to its wavelength components.

[0038] The management server 140 and the image viewer 150 each include a computer, an input device, an external storage device, a display device, a communication interface, and the like.

[0039] As shown in FIG. 4, the CPU 16A of the ophthalmologic apparatus 110 of this embodiment functions as an imaging control unit 162, an image processing unit 164, and a display control unit 166.

[0040] The image processing unit 164 is an example of an "interference signal acquisition unit," a "component acquisition unit," a "corrected interference signal acquisition unit," a "repeated execution unit," and an "OCT signal acquisition unit" of the techniques disclosed herein.

[0041] Incidentally, various images (e.g., images called artifacts) appear in fundus images of a test eye acquired by OCT. For example, a complex conjugate component image appears as a mirror image in fundus images acquired using full-range OCT (FR-OCT), which expands the observable depth of OCT. The mirror image is a virtual image that appears on the opposite side of the real image from the position where the optical path length of the measurement light irradiated on the fundus is equal to the optical path length of the reference light. By forming a tomographic image from a real image that appears on one side (e.g., the positive side, in the depth direction of the fundus) from the position where the optical path length of the measurement light is equal to the optical path length of the reference light, it is possible to obtain a tomographic image of a wider range of the test eye. In other words, by forming a tomographic image by removing the mirror image (an image in the opposite direction to the depth direction of the fundus, which is the negative side where the virtual image appears) from the OCT image, a full-range tomographic image of the fundus can be obtained.

[0042] Therefore, in this embodiment, a signal obtained for an OCT image is subjected to signal processing to remove mirror images and the like, thereby obtaining a tomographic image that accurately reflects the contents of the fundus.

[0043] Next, the signal processing for the interference spectrum by the CPU 16A of the ophthalmic apparatus 110 will be described in detail with reference to Fig. 5. The CPU 16A of the ophthalmic apparatus 110 executes a signal processing program to realize the signal processing (signal processing method) shown in the flowchart of Fig. 5.

[0044] The SLO unit 18 and the photographing optical system 19 are controlled to acquire an image of the fundus of the subject's eye 12. The display control unit 166 displays an image of the fundus (also referred to as a UWF-SLO fundus image) SLG on the input / display device 16E, as shown in FIG.

[0045] The operator checks the fundus image SLG displayed on the input / display device 16E and sets the range for acquiring a tomographic image via the input / display device 16E. For example, range L1 is a relatively wide range that includes the center of the fundus including the optic disc (the point where the optical axis of the ophthalmologic apparatus 110 intersects with the fundus (the fundus center)). Ranges L2, L3, and L4 are peripheral ranges around the center of the fundus.

[0046] The setting of the range for acquiring a tomographic image is not limited to using an SLO image. For example, the position for acquiring a tomographic image may be determined using a two-dimensional en-face image based on OCT data, and the tomographic image may be acquired.

[0047] Note that the ranges L1 to L4 are line segments in the horizontal direction (B scan direction) of the fundus, but the range in which a tomographic image is acquired is not limited to line segments in the B scan direction, and may be line segments in a direction intersecting the B scan direction or a rectangular range.

[0048] Furthermore, as will be described in detail later, the user can select in advance whether to execute full-range OCT processing or normal OCT processing, and set which processing to execute in the ophthalmic apparatus 110. Furthermore, the user may wish to execute full-range OCT processing after executing normal OCT processing. In this case, the full-range OCT processing may be selected in chronological order so that it can be executed after executing normal OCT processing.

[0049] In this way, when the operator sets the range for acquiring the tomographic image and the processing to be performed (at least one of normal OCT processing and full-range OCT processing) and issues a start command via the input / display device 16E, the signal processing program starts.

[0050] In step S72, the imaging control unit 162 instructs the OCT unit 20P and the imaging optical system 19 to perform an OCT scan so as to acquire a tomographic image of the set range.

[0051] In step S74, the imaging control unit 162 determines whether or not the tomographic image is set to be output in the full range to the display screen of the input / display device 16E. Here, the full range means that the output range of the image output to the display screen is a range that includes a range in the depth direction of the fundus (positive area) and a range in the opposite direction to the depth direction (negative area) based on a position corresponding to the optical path length of the reference light in the subject's eye 12.

[0052] When the full range is not set, the output range of the tomographic image to be output on the display screen is a range in the depth direction of the fundus based on a position corresponding to the optical path length of the reference light in the subject's eye 12, but does not include the reference position, and the tomographic image is displayed in a certain range where no mirror image is displayed. Fig. 8 shows display examples of tomographic images G1 to G4 corresponding to ranges L1 to L4, respectively, as examples of tomographic images displayed when the full range is not set.

[0053] When the full range is set, the output range of the tomographic image output on the display screen is based on a position corresponding to the optical path length of the reference light in the subject's eye 12, and the tomographic image is displayed in the range in the depth direction of the fundus and the range opposite to the depth direction. Fig. 9 shows an example of a display of a tomographic image G15 corresponding to the range L1 displayed when the full range is set. As shown in Fig. 9, when the full range is set, the output range of the image output on the display screen is based on a position PO corresponding to the optical path length of the reference light in the subject's eye 12, and the tomographic image G15 is displayed in the range NR including a range in the depth direction of the fundus (positive region) PR and a range opposite to the depth direction (negative region). In this way, when the full range is set, a wider tomographic image can be displayed compared to when the full range is not set.

[0054] The full-range OCT process (step S76) performed when the full range is set takes a longer processing time than the normal OCT process (step S78) performed when the full range is not set. The user selects in advance whether to perform the full-range OCT process or the normal OCT process and sets this in the ophthalmic apparatus 110. In step S74, it is determined which process has been set by the user.

[0055] The process of step S74 is not limited to determining whether the process set by the user in the ophthalmologic apparatus 110 is full-range OCT process or normal OCT process.

[0056] When the full range is set as described above, a wider tomographic image can be displayed compared to when the full range is not set. Therefore, in the process of step S74, it may be determined whether the length in the predetermined direction of the range for acquiring tomographic images set by the user is longer than a predetermined length. In this case, if the length in the predetermined direction of the range for acquiring tomographic images set by the user is longer than the predetermined length, a positive determination is made in step S74. If it is not determined that the length in the predetermined direction of the range for acquiring tomographic images set by the user is longer than the predetermined length, a negative determination is made in step S74.

[0057] It may be determined whether at least a portion of the range in which a tomographic image is acquired is located in the peripheral range around the center of the fundus. For example, if at least a portion of the range in which a tomographic image is acquired is located in the peripheral range around the center of the fundus, a positive determination may be made in step S74. On the other hand, if at least a portion of the range in which a tomographic image is acquired is not located in the peripheral range around the center of the fundus, a negative determination may be made in step S74.

[0058] If the determination in step S74 is negative, the image processing unit 164 executes normal OCT processing in step S78. When the processing in step S78 is completed, the signal processing proceeds to step S80. Note that normal OCT processing includes various types of processing, but since these are well-known processing, detailed description thereof will be omitted.

[0059] On the other hand, if the determination in step S74 is affirmative, the image processing unit 164 executes full-range OCT processing in step S76.

[0060] As described above, if full-range OCT processing is to be selectable after normal OCT processing is performed, a judgment process can be provided to determine whether full-range OCT processing should be performed after processing in step S78, and if the judgment is positive, the process can proceed to step S76, and if the judgment is negative, the process can proceed to step S80.

[0061] Next, full-range OCT processing will be described with reference to FIG.

[0062] In step S102, the image processing unit 164 acquires the interference spectrum stored in the RAM 16B of the control device 16. The interference spectra r1, r2, ... rn are data on the light intensity for each wavelength component in the wavelength sweep range at each scanning position corresponding to each scanning time t1, t2, ... tn. In other words, they are data indicating the spectral distribution of the wavelength and light intensity of the interference fringes obtained for each A-scan. The interference spectra r1, r2, ... rn are an example of the "interference signal" of the technology disclosed herein. Note that when SD-OCT is employed in the OCT unit 20P, the interference spectrum stored in the control device 16 is data on the light intensity for each wavelength component obtained by the detector 62, which is a spectroscope, at each scanning position corresponding to each scanning time.

[0063] In step S104, the image processing unit 164 performs preprocessing on each interference spectrum to generate a clearer tomographic image. Examples of preprocessing include resampling, zero padding, and window function processing. Resampling is a process of uniforming the sampling intervals by signal processing, since the sampling intervals when the interference spectrum is obtained are not constant but sparse. Zero padding is a process of increasing the number of data points to improve the resolution of the tomographic image compared to when this process is not performed. Specifically, when the numerical value of data is an integer, this process pads the left side of the numerical value with zeros. For example, when a 10-digit representation is desired, if the numerical value of the data is 12345, it is set to 0000012345. Window function processing is a process of weighting the central data of the interference spectrum more heavily than the surrounding data. Note that zero padding may be omitted.

[0064] In step S106, the image processing unit 164 calculates the average value of the light intensity of the initial interference fringes for all A-scans and calculates a threshold value. The threshold value calculated in step S106 is an example of a threshold value th used to determine whether or not to perform repeated processing in a full-range process (hereinafter referred to as an FR process) executed for each A-scan, which will be described later. The FR process is a process for removing signal components of a complex conjugate component image generated as a mirror image, i.e., a process for removing signal components of the mirror image (hereinafter referred to as a mirror signal) from a signal indicating an interference spectrum. Details will be described later. The processing of step S106 is an example of a process for deriving a "threshold value" of the technology disclosed herein.

[0065] The image processing unit 164 calculates the average value of all data related to the light intensity of the A-scans used in an image formed by the B-scan (for example, a fundus tomographic image), and sets this as the average value of the light intensity of the initial interference fringes (interference spectrum) of all the A-scans. The image processing unit 164 derives the threshold value th from this average value. An example of the threshold value th is shown in the following equation (1) (conditional equation). In the equation, f is the light intensity of the initial interference spectrum (interference fringes or interference signal), and M is the total number of A-scans included in the B-scan. m is a variable, and E is a predetermined coefficient.

[0066]

[0067] In step S108, the image processing unit 164 specifies one of all A-scans (for example, the first A-scan in the B-scan direction) and executes the FR process. In the example shown in Fig. 6, the FR process includes steps S110 to S124.

[0068] In step S110, the image processing unit 164 performs a known dispersion correction process to numerically correct the dispersion of the interference spectrum preprocessed in step S104. This dispersion correction process makes it possible to numerically correct the dispersion of the optical dispersion component caused by the optical system of the OCT unit 20P of the ophthalmic apparatus 110. Note that in the dispersion correction process, a predetermined dispersion correction function is acquired. The process of step S106 is an example of the "dispersion correction process" of the technology disclosed herein.

[0069] In step S112, the image processing unit 164 performs a known inverse Fourier transform (IFFT) on the dispersion-corrected interference spectrum to obtain a first transformed signal.

[0070] In step S114, the image processing unit 164 performs a known multi-peak detection process known as MPD (Multi Peak Detection) on the first converted signal after conversion. In this multi-peak detection process, multiple peaks are detected, and a signal component due to a peak value sequence based on the values ​​(peak values) of the detected multiple peaks is also detected.

[0071] In step S116, the image processing unit 164 stores the detected peaks as a peak value sequence, and also stores the signal components resulting from the peak value sequence. That is, the peak value sequence and data representing the signal components resulting from the peak value sequence are stored in the RAM 16B of the control device 16.

[0072] In step S118, the image processing unit 164 performs a known Fourier transform (FFT) on the stored peak value sequence to obtain a second transformed signal.

[0073] In step S120, the image processing unit 164 performs inverse dispersion correction on the second converted signal based on the peak value sequence after the Fourier transform, to obtain an inverse dispersion corrected signal.

[0074] In step S122, the image processing unit 164 extracts the real part component of the inverse dispersion compensation signal. Note that in step S122, the extracted real part component can be multiplied by a predetermined factor (for example, doubled).

[0075] In step S124, the image processing unit 164 subtracts the extracted real component from the acquired interference spectrum. That is, the image processing unit 164 subtracts the component of the peak value sequence (MPD) from the original interference spectrum. The processing in step S124 is an example of processing to obtain a "corrected interference signal" of the technique of the present disclosure.

[0076] In step S126, the image processing unit 164 calculates the light intensity I (=||ri||) of the interference spectrum after subtraction. ２The determination process in step S126 determines whether the light intensity of the remaining signal, which is the interference spectrum after subtraction, satisfies the following formula (2):

[0077] If the determination in step S126 is negative, the image processing unit 164 sets the interference spectrum after subtraction as the interference spectrum to be subjected to the above-described FR process, and returns the process to step S110. On the other hand, if the determination in step S126 is positive, the image processing unit 164 proceeds to step S128.

[0078] Therefore, the subtraction process of the predetermined value obtained by the FR process described above is repeatedly executed until the interference spectrum by the A-scan becomes equal to or less than the threshold value th. The threshold value th is an example of the “threshold value” of the technology of the present disclosure.

[0079] In step S128, the image processing unit 164 determines whether the above-described FR process has been completed for all A-scans.

[0080] If the determination in step S128 is negative, the image processing unit 164 returns the process to step S108 to execute the above-described FR process for other A-scans, and if the determination is positive, the process routine ends.

[0081] In this manner, step S76 in FIG. 5 is completed, and the signal processing proceeds to step S80.

[0082] In step S80, the display control unit 166 outputs (displays) the OCT data (tomographic image data) to the input / display device 16 E. That is, the data saved in step S116 described above is acquired as OCT data, and output (display) it to the input / display device 16 E.

[0083] As described above, in this embodiment, in full-range OCT processing, the interference spectrum (interference fringes) of each A-scan obtained by each of the multiple A-scans that form a B-scan image is used to extract the peak value of the light intensity indicated by the interference spectrum. Then, an FR process is performed to remove the mirror signal by subtracting the extracted peak value component from the original interference spectrum (interference fringe). This FR process is repeated for each A-scan, and this repetition is performed until the magnitude of the light intensity of the interference spectrum remaining after subtraction of the peak value component falls below a predetermined threshold. The predetermined threshold is a predetermined value derived from the above-mentioned equation (1), i.e., a fixed value determined by the B-scan image, used as the threshold th. As such, in this embodiment, whether to repeat the FR process is determined based on the threshold th, i.e., a fixed value determined from the entire image obtained by the B-scan. Therefore, by using a fixed threshold determined from the B-scan image in common for the FR process of each A-scan, uneven brightness in the image that appears as vertical stripes and shadows can be reduced compared to when different thresholds are used, and a high-quality full-range image can be obtained.

[0084] Furthermore, in an OCT image, brightness variations related to image quality occur when the signal magnitudes of the images obtained by each A-scan are different. For example, if the peak brightness values ​​of the signals of multiple images obtained by each A-scan are different, the magnitude of the noise components in the signals will differ. That is, the magnitude of the noise components will differ between A-scan images of dark areas and A-scan images of bright areas of the fundus. This difference in noise components appears as an image (e.g., vertical stripes), resulting in brightness variations in the obtained OCT image. In contrast, in this embodiment, a fixed threshold th is set for the entire A-scan image obtained by B-scan, making it possible to uniform the brightness of the OCT image.

[0085] As described above, the threshold value th is derived based on the average value of the light intensity of the initial interference fringes (interference spectrum) of all A-scans. Specifically, the threshold value th is a value obtained by multiplying the average value by a coefficient E. The coefficient E is determined in advance.

[0086] Here, an example of derivation of the ratio of light intensities applicable to the removal of the mirror image as described above as the coefficient E of the threshold value th will be described with reference to FIG.

[0087] In step S202, the image processing unit 164 acquires an interference spectrum of the subject's eye that has been photographed by the ophthalmic apparatus 110. It goes without saying that the interference spectrum is not limited to an interference spectrum of the subject's eye that has been photographed, and the subject's eye may be measured by the ophthalmic apparatus 110 and the interference spectrum stored in the RAM 16B of the control device 16 may be acquired.

[0088] In step S204, the image processing unit 164 sets the coefficient E to an initial value (for example, E=0.1).

[0089] In step S206, the image processing unit 164 executes the FR process (steps S110 to S124 in FIG. 6 ) for removing the mirror signal, and in the next step S208, obtains a processed image. The image processing unit 164 also derives a mirror signal removal rate SR using the images before and after processing. The mirror signal removal rate SR can be calculated using the ratio between the signal of the image before processing and the signal of the image after processing. The mirror signal removal rate SR is derived so that the removal rate increases as the amount of mirror signal removed from the original signal increases. While the above description has been given of the case where the image processing unit 164 derives the mirror signal removal rate SR using the images before and after processing, the image processing unit 164 may also derive the mirror signal removal rate SR using only the processed image. In this case, the mirror signal removal rate SR can be calculated using the signal ratio between the real part and the imaginary part of the processed image signal.

[0090] In step S210, the image processing unit 164 determines whether the mirror signal rejection rate SR is equal to or greater than the signal-to-noise ratio SNR (SR≧SNR). The process of step S210 corresponds to determining whether the virtual mirror image has disappeared from the fundus image. The SNR ratio is predetermined before shipment of the ophthalmic device 110, corresponding to the subject to be imaged, such as the anterior segment or posterior segment, of the ophthalmic device 110. For example, an anterior segment image may contain a stronger signal (signal with a higher brightness value) than a posterior segment image. Therefore, a better image can be obtained by setting a higher SNR ratio for anterior segment imagery than for posterior segment imagery. Therefore, the SNR ratio is determined in advance according to the subject to be imaged, and the coefficient E is derived.

[0091] If the determination in step S210 is negative, the image processing unit 164 increases the current value of the coefficient E by a predetermined amount (E=E+ΔE) in step S212, and returns the process to step S206.

[0092] On the other hand, if the determination in step S210 is affirmative, in step S214, the image processing unit 164 determines and stores the current value of the coefficient E as the coefficient E of the ophthalmologic apparatus 110. In this manner, the coefficient E can be determined in advance.

[0093] In the above-described full-range OCT processing, the FR process executed for each A-scan is repeatedly executed until the magnitude of the light intensity of the interference spectrum remaining after subtraction of the peak value component falls below a threshold. The repeated FR process affects, for example, the waiting time between capturing an image of the fundus of the subject's eye and displaying an OCT image. That is, the waiting time increases as the number of repetitions of the FR process executed for each A-scan increases. Furthermore, a longer waiting time reduces usability for operators, such as doctors, who refer to the OCT images. Therefore, it is possible to predetermine an upper limit for the number of repetitions of the FR process so that the process is terminated after a predetermined number of repetitions. For example, the waiting time can be set to a time specified by the operator or a predetermined time determined empirically, and the processing time for the interference spectrum of each A-scan can be determined according to the number of total A-scans so that the processing is stopped after a predetermined time has elapsed since the start of processing. For example, if the waiting time is set to 5 seconds and the total number of A-scans is 100, the processing time for the interference spectrum of each A-scan can be set to 0.05 seconds (= 5 / 100), and the upper limit of the number of repetitive processes described above can be set so as not to exceed 0.05 seconds.

[0094] In this embodiment, the case where the average value of the light intensity of the initial interference fringes of all A-scans is used as an example of the threshold has been described, but the technology of the present disclosure is not limited to this average value. For example, any value between the maximum and minimum values ​​of light intensity may be set as the threshold. Also, a weighted average value such as a weighted average value with respect to wavelength and a weighted average value with respect to the position of the A-scan, i.e., time, may be used. Furthermore, a value calculated based on the frequency of appearance of a light intensity histogram or the like may be derived as the threshold.

[0095] In the above description, the average value of the light intensity of the initial interference fringes of all A-scans is used as the threshold value th, but this is not limiting. For example, the upper limit of the noise component in the obtained signal (interference spectrum) or a predetermined value determined from the noise component may be set as the threshold. The upper limit of the noise component or the predetermined value determined from the noise component can be set as the threshold for a signal containing electrical noise obtained when a dummy eye having a reflective surface on the retina is used instead of the test eye and light is applied to the retina of the dummy eye.

[0096] Alternatively, the threshold may be determined using a previous B-scan image. For example, when imaging is about to be performed, the threshold may be calculated from a previously obtained B-scan image.

[0097] Furthermore, the threshold value th may be a value derived using a learning model that uses the interference spectrum with the mirror image removed as the teacher signal, the interference spectrum including the mirror image as the input signal, and the threshold value as the output signal.

[0098] In the above-described signal processing (full-range OCT processing), the light intensity to be subtracted from the original image to remove signals appearing as mirror images is adjusted for each A-scan by setting the number of repetitions of the FR process based on the light intensities of all A-scans. This makes it possible to remove signal components of mirror images appearing as complex conjugate component images from the tomographic image more efficiently than when the FR process is processed for all A-scans with the same number of repetitions.

[0099] 10 shows an example of an OCT image (tomographic image) obtained by normal full-range OCT processing without performing the above-described signal processing. As shown in FIG. 10, a mirror image Ig15 exists in the tomographic image before the mirror image is removed. Furthermore, if brightness fluctuations occur between adjacent A-scans in the tomographic image, artifacts that appear as vertical stripes may occur in the tomographic image.

[0100] 11 shows a conceptual diagram of an OCT image (tomographic image) obtained by full-range OCT processing, including an OCT image Ga, an OCT image Gb, and a repetition number distribution Gc of the FR process.

[0101] OCT image Ga is an OCT image obtained by normal full-range OCT processing without performing the above-described signal processing. In OCT image Ga, an image G22 showing the fundus is conceptually indicated by a solid line, and a mirror image Ig15 is conceptually indicated by a dotted line. OCT image Gb is an OCT image obtained by full-range OCT processing of this embodiment. The mirror image Ig15 has been removed from OCT image Gb, and only an image G22 showing the fundus is included. Furthermore, the FR process repetition number distribution Gc is a distribution of the number of times the FR process is repeated for each A-scan in the full-range OCT processing of this embodiment. In OCT image Gc, a distribution characteristic G20 of the repetition number is conceptually indicated by a solid line. As shown in the distribution characteristic G20, the number of repetitions of the FR process is changed for each A-scan. This is because a fixed value is used as the threshold th, and this fixed value is used as the criterion for determining whether to repeat the FR process.

[0102] Increasing or decreasing the number of repetitions of the FR process performed to remove the mirror image affects the mirror image that appears in the processed OCT image, as well as the brightness and image quality of the OCT image.

[0103] 12 shows a conceptual diagram of OCT images (tomographic images) obtained by full-range OCT processing, which change depending on the number of times the FR process is repeated. Fig. 12 includes diagrams of OCT images Gd, Gf, Gg, and Gh obtained by signal processing according to this embodiment.

[0104] The OCT image Gd is an image conceptualized from Fig. 10 and is an OCT image obtained by normal full-range OCT processing. The OCT image Gd can also be considered as an OCT image obtained by signal processing without repeating the signal processing of this embodiment.

[0105] OCT images Gf, Gg, and Gh are OCT images obtained by signal processing using different numbers of FR process repetitions. OCT image Gf is an OCT image obtained by full-range OCT processing in which the number of FR process repetitions is set small using a threshold value greater than the threshold value th described above. OCT image Gf contains a mirror image Ig16 that appears as vertical stripes Gfa due to the remaining peak value described above, which increases as the number of FR process repetitions decreases. This causes uneven brightness in the OCT image, reducing image quality.

[0106] OCT image Gg is an OCT image obtained by full-range OCT processing, in which the number of FR process iterations is set to a large number using a threshold smaller than the threshold th. While OCT image Gg is gradually removed as the number of FR process iterations increases, it still contains a shadow image Ig17, in which the light intensity at the corresponding location on the mirror image is reduced, resulting in a continuous vertical stripe Gga with lower light intensity than other areas. As a result, the operator can see image G22 showing the fundus, the background image of image G22, and shadow image Ig17. While the mirror image itself is not visible, the corresponding location and area are identified by the shadow of the mirror image. This results in uneven brightness in the OCT image, reducing image quality.

[0107] In contrast, the OCT image Gh obtained by signal processing according to this embodiment is similar to the OCT image Gb shown in FIG. 11 in that, as described above, vertical stripes and shadows are not generated, the mirror image Ig15 is removed, and only the image G22 showing the fundus is included. That is, in this embodiment, the FR process is repeated an appropriate number of times suited to the signals obtained by each A-scan, using a fixed threshold value th determined by the B-scan image as the criterion. Therefore, it is possible to reduce uneven brightness in the OCT image, and to provide a high-quality OCT image.

[0108] As described above, in this embodiment, the signal processing described above is performed by extracting the peak value of light intensity from the interference spectrum (interference fringes) of each A-scan, and subtracting the extracted peak value component from the original interference spectrum (interference fringes). This makes it possible to remove the signal component of the mirror image that appears as a complex conjugate component image in the tomographic image. Therefore, as shown in FIG. 9, the mirror image can be accurately removed from the tomographic image, making it possible to suppress artifacts that appear in the tomographic image. As described above, in this embodiment, the appearance of artifacts in the tomographic image displayed in the full range can be suppressed, and a tomographic image that accurately reflects the contents of the fundus can be obtained.

[0109] The OCT data (tomographic image data) is transmitted to the management server 140 via the network 130 and stored in the memory of the management server 140 in association with the patient ID of each patient. The management server 140 transmits the OCT data (tomographic image data) together with the patient data via the network 130 in accordance with instructions from the image viewer 150. The image viewer 150 displays the OCT image together with the patient data on the display screen of the display.

[0110] The following describes a display screen for displaying OCT data (tomographic image data) together with patient data on the display screen of the image viewer 150. A display screen 500A is shown in Fig. 13. As shown in Fig. 13, the display screen 500A has an information area 502 and an image display area 504A.

[0111] The information area 502 has a patient ID display field 512, a patient name display field 514, an age display field 516, a visual acuity display field 518, a right eye / left eye display field 520, and an axial length display field 522. In each display area from the patient ID display field 512 to the axial length display field 522, the image viewer 150 displays the respective information based on the information received from the management server 140.

[0112] The image display area 504A is an area for displaying an image of the subject's eye, etc. The image display area 504A is provided with the following display fields, specifically, an OCT image display field 540 and a UWF fundus image display field 542.

[0113] The image display area 504A may be provided with a comment field, which is a remark field in which the user (ophthalmologist) can arbitrarily input the results of his / her observation or diagnosis.

[0114] The UWF fundus image display field 542 displays a UWF-SLO fundus image SLG obtained by photographing the fundus of the subject's eye using the ophthalmologic apparatus 110. A range in which a tomographic image was acquired, for example, a range L1, is superimposed on the UWF-SLO fundus image SLG.

[0115] An OCT image is displayed in the OCT image display field 540. Fig. 13 shows a tomographic image G15 based on OCT data obtained by full-range processing. When the OCT data (tomographic image data) is transmitted to the management server 140 and the image viewer 150, data indicating whether full-range OCT processing or normal OCT processing has been performed is also transmitted. When the tomographic image is displayed, a determination is made based on the data as to whether the tomographic image should be displayed in full range, and the tomographic image is displayed in full range or normal range depending on the determination result.

[0116] In this embodiment, the signal processing program is executed by the CPU 16A of the ophthalmic device 110, but the technology of the present disclosure is not limited to this, and the signal processing program may be executed by the CPU of the management server 140 or the image viewer 150, for example.

[0117] In the present disclosure, each component (device, etc.) may be present in one or more instances, unless a contradiction arises.

[0118] In the examples described above, image processing is realized by a software configuration using a computer, but the technology of the present disclosure is not limited to this. For example, instead of a software configuration using a computer, image processing may be performed only by a hardware configuration such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). Some of the image processing may be performed by a software configuration, and the remaining processing may be performed by a hardware configuration.

[0119] The technology of the present disclosure includes image processing that is realized by a software configuration using a computer, a hardware configuration, or a configuration that combines a software configuration and a hardware configuration. Therefore, the technology of the present disclosure includes the following technologies.

[0120] (First Technology) An ophthalmic device comprising: an interference signal acquisition unit that acquires an interference signal from interference light between measurement light obtained by scanning a test eye with light from a light source and reference light split from the light from the light source; a component acquisition unit that acquires a peak value component determined by the light intensity distribution in the interference signal; a modified interference signal acquisition unit that acquires a modified interference signal by subtracting a signal of a magnitude determined by the peak value component from the interference signal; a repeat execution unit that repeatedly executes the steps of obtaining the peak value component for the interference signal and obtaining the modified interference signal, using the modified interference signal as the interference signal, until the light intensity of the modified interference signal resulting from the subtraction becomes equal to or less than a predetermined threshold; and an OCT signal acquisition unit that acquires OCT data based on the modified interference signal that is equal to or less than the threshold.

[0121] (Second Technology) A signal processing method for an ophthalmologic device, comprising: a step in which an interference signal acquisition unit acquires an interference signal from interference light between measurement light obtained by scanning a test eye with light from a light source and reference light into which the light from the light source is split; a step in which a component acquisition unit acquires a peak value component determined by the light intensity distribution in the interference signal; a step in which a modified interference signal acquisition unit subtracts a signal having a magnitude determined by the peak value component from the interference signal to obtain a modified interference signal; a step in which a repetitive execution unit repeatedly executes the steps of obtaining the peak value component for the interference signal and obtaining the modified interference signal, using the modified interference signal as the interference signal, until the light intensity of the modified interference signal resulting from the subtraction becomes equal to or less than a predetermined threshold; and a step in which an OCT signal acquisition unit acquires OCT data based on the modified interference signal that is equal to or less than the threshold.

[0122] The following technology is proposed from the above disclosure: (Third Technology) A computer program product for obtaining an OCT signal, the computer program product comprising a computer-readable storage medium that is not itself a temporary signal, the computer-readable storage medium storing a program, the program causing a computer to execute processes including: obtaining an interference signal from interference light between measurement light obtained by scanning an eye to be examined with light from a light source and reference light obtained by splitting the light from the light source, obtaining a peak value component determined by the light intensity distribution of the interference signal, subtracting a signal having a magnitude determined by the peak value component from the interference signal to obtain a modified interference signal, using the modified interference signal as the interference signal, repeatedly obtaining the peak value component from the interference signal and obtaining the modified interference signal until the light intensity of the modified interference signal resulting from the subtraction becomes equal to or less than a predetermined threshold, and obtaining OCT data based on the modified interference signal that is equal to or less than the threshold.

[0123] The signal processing described above is merely an example, and it goes without saying that unnecessary steps may be deleted, new steps may be added, or the processing order may be changed, without departing from the spirit of the invention.

[0124] All documents, patent applications, and technical standards described herein are incorporated by reference herein to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference. In addition, the disclosure of Japanese Patent Application No. 2023-159176, filed September 22, 2023, is incorporated by reference in its entirety herein.

Claims

1. An ophthalmic device including a processor, wherein the processor executes processes including the steps of: obtaining an interference signal from interference light between measurement light obtained by scanning a test eye with light from a light source and reference light obtained by dividing the light from the light source; obtaining a peak value component determined by the light intensity distribution in the interference signal; obtaining a modified interference signal by subtracting a signal having a magnitude determined by the peak value component from the interference signal; using the modified interference signal as the interference signal, repeatedly obtaining the peak value component for the interference signal and obtaining the modified interference signal until the light intensity of the modified interference signal resulting from the subtraction becomes equal to or less than a predetermined threshold; and obtaining OCT data based on the modified interference signal that is equal to or less than the threshold.

2. An ophthalmic device as described in claim 1, wherein the threshold value is a value determined based on the light intensity distribution of multiple interference signals when scanning the depth direction of the test eye over a predetermined range in a direction perpendicular to the depth direction.

3. An ophthalmic apparatus according to claim 2, wherein the threshold value is a value determined based on an average value of the light intensity of the interference signal obtained in the step of obtaining an interference signal from the interference light.

4. An ophthalmic device according to claim 2, wherein the threshold value is determined by multiplying a value determined based on the light intensity distribution of the plurality of interference signals by a predetermined ratio.

5. The threshold value is expressed as follows, where f is the initial light intensity in the interference signal obtained by scanning in the depth direction, M is the total number of scans in the depth direction included in a predetermined range of scans in a direction perpendicular to the depth direction, and E is a predetermined coefficient:

3. The ophthalmic apparatus according to claim 2, wherein the value is determined by a conditional expression expressed as follows:

6. The ophthalmic apparatus according to any one of claims 1 to 5, wherein the step of repeatedly executing the step is stopped when a predetermined time has elapsed since the start of the step.

7. An ophthalmic apparatus according to any one of claims 1 to 6, further comprising a step of performing dispersion compensation processing on the interference signal, the signal having undergone the dispersion compensation processing being regarded as the interference signal.

8. An ophthalmic device as claimed in any one of claims 1 to 7, further comprising a step of outputting an image obtained based on the OCT data onto a display screen within an output range of an image in the depth direction of the fundus and in the direction opposite to the depth direction, based on a position corresponding to the optical path length of the reference light.

9. A signal processing method performed by a processor of an ophthalmic device, comprising: a step of obtaining an interference signal from interference light between measurement light obtained by scanning a test eye with light from a light source and reference light obtained by dividing the light from the light source; a step of obtaining a peak value component determined by the light intensity distribution in the interference signal; a step of obtaining a modified interference signal by subtracting a signal having a magnitude determined by the peak value component from the interference signal; a step of repeatedly executing the steps of obtaining the peak value component for the interference signal using the modified interference signal as the interference signal and obtaining the modified interference signal until the light intensity of the modified interference signal resulting from the subtraction becomes equal to or less than a predetermined threshold; and a step of obtaining OCT data based on the modified interference signal equal to or less than the threshold.

10. A program that causes a computer to execute processes including the steps of: obtaining an interference signal from interference light between measurement light obtained by scanning a test eye with light from a light source and reference light divided from the light from the light source; obtaining a peak value component determined by the light intensity distribution in the interference signal; obtaining a modified interference signal by subtracting a signal of a magnitude determined by the peak value component from the interference signal; using the modified interference signal as the interference signal, obtaining the peak value component for the interference signal and obtaining the modified interference signal; repeatedly executing these steps until the light intensity of the modified interference signal resulting from the subtraction becomes equal to or below a predetermined threshold; and obtaining OCT data based on the modified interference signal that is equal to or below the threshold.

Images