Signal processing method for ophthalmic device, ophthalmic device, and program

Abstract

The signal processing method by the processor of the ophthalmic apparatus includes the steps of: obtaining an interference signal of a measurement light and a reference light; obtaining a peak component determined from a distribution of brightness in the interference signal; obtaining a corrected interference signal by subtracting a signal of a size determined from the peak component from the interference signal; setting the corrected interference signal as the interference signal, repeatedly performing the step of obtaining the peak component and the step of obtaining the corrected interference signal until the corrected interference signal after subtraction becomes below a predetermined threshold; and obtaining OCT data based on the corrected interference signal below the threshold.

Description

Technical Field

[0001] The technology disclosed herein relates to signal processing methods, ophthalmic devices, and procedures for ophthalmic devices. Background Technology

[0002] For devices used to examine the eye, OCT (Optical Coherence Tomography) devices are known for acquiring tomographic images of the eye (e.g., U.S. Patent Application Publication No. 2020 / 0037872). In OCT devices, there is a requirement to acquire high-precision tomographic images of the eye over a wider range. Summary of the Invention

[0003] A first aspect of this disclosure is an ophthalmic device comprising a processor,

[0004] The processor performs a process that includes the following steps:

[0005] Obtain the interference signal between the measurement light and the reference light;

[0006] The peak components determined based on the brightness distribution in the interference signal are obtained;

[0007] The corrected interference signal is obtained by subtracting the signal whose magnitude is determined based on the peak component from the interference signal;

[0008] The corrected interference signal is set as the interference signal, and the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal are repeatedly executed until the corrected interference signal after subtracting the result becomes below a predetermined threshold; and

[0009] The OCT signal is obtained based on the modified interference signal below the threshold.

[0010] A second aspect of this disclosure is a signal processing method for an ophthalmic device, which is a signal processing method performed by a processor of the ophthalmic device, comprising the following steps:

[0011] Obtain the interference signal between the measurement light and the reference light;

[0012] The peak components determined based on the brightness distribution in the interference signal are obtained;

[0013] The corrected interference signal is obtained by subtracting the signal whose magnitude is determined based on the peak component from the interference signal;

[0014] The corrected interference signal is set as the interference signal, and the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal are repeatedly executed until the corrected interference signal after subtracting the result becomes below a predetermined threshold; and

[0015] The OCT signal is obtained based on the modified interference signal below the threshold.

[0016] A third aspect of this disclosure is a program that causes a computer to perform processing comprising the following steps:

[0017] Obtain the interference signal between the measurement light and the reference light;

[0018] The peak components determined based on the brightness distribution in the interference signal are obtained;

[0019] The corrected interference signal is obtained by subtracting the signal whose magnitude is determined based on the peak component from the interference signal;

[0020] The corrected interference signal is set as the interference signal, and the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal are repeatedly executed until the corrected interference signal after subtracting the result becomes below a predetermined threshold; and

[0021] The OCT signal is obtained based on the modified interference signal below the threshold. Attached Figure Description

[0022] Figure 1 This is a block diagram illustrating the configuration of an ophthalmic system according to an embodiment.

[0023] Figure 2 This is a block diagram illustrating the hardware configuration of an ophthalmic device according to an embodiment.

[0024] Figure 3 This is a block diagram illustrating the hardware configuration of the OCT unit in an embodiment.

[0025] Figure 4 This is a functional block diagram of the ophthalmic device according to the implementation method.

[0026] Figure 5 This is a flowchart illustrating the signal processing flow in an ophthalmic device according to an embodiment.

[0027] Figure 6 This is a flowchart illustrating the full-coverage OCT processing flow in an ophthalmic device according to an embodiment.

[0028] Figure 7 This is a flowchart illustrating the derivation process of coefficients related to the threshold.

[0029] Figure 8 This is an example of a tomographic image of the fundus.

[0030] Figure 9 This is a diagram illustrating an example of a tomographic image obtained by performing full-coverage OCT processing.

[0031] Figure 10 This is a diagram showing a tomographic image under the condition of performing a typical full-coverage OCT process.

[0032] Figure 11 This is a conceptual diagram of OCT images (tomographic images) processed with full coverage OCT.

[0033] Figure 12 This is a conceptual diagram of an OCT image (tomographic image) that varies depending on the number of repetitions of FR processing.

[0034] Figure 13 It is a diagram showing the screen displayed on the monitor. Detailed Implementation

[0035] The embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that sometimes the same reference numerals are used throughout the drawings for components and processes that perform the same function, and repetitive descriptions are appropriately omitted. Additionally, descriptions of components not directly related to the present disclosure or well-known components are sometimes omitted. Furthermore, the scale of the drawings is sometimes exaggerated and differs from the actual scale. Moreover, the drawings are merely schematic representations to a degree sufficient for a thorough understanding of the present disclosure. Therefore, the technology of the present disclosure is not limited to the examples shown in the drawings.

[0036] Reference Figure 1 The structure of the ophthalmic system 100 according to the technical embodiments of this disclosure is described. Figure 1 This is a block diagram illustrating the configuration of the ophthalmic system 100 according to this embodiment. Figure 1 As shown, the ophthalmology system 100 includes an ophthalmology device 110, a network 130, a management server device (hereinafter referred to as "management server") 140, and an image display device (hereinafter referred to as "image browser") 150.

[0037] The ophthalmic device 110, management server 140, and image viewer 150 are interconnected via network 130. Network 130 can be any network such as LAN, WAN, Internet, or wide area Ethernet. For example, in the case where the ophthalmic system 100 is built in a hospital, network 130 can use a LAN.

[0038] The ophthalmic device 110 is a device for taking pictures of the eye being examined and performing at least one of ophthalmological examinations, measurements and treatments.

[0039] The management server 140 receives images of the examined eye captured by the ophthalmic device 110 via the network 130, corresponding to the patient ID, and stores them in a memory (not shown). Thus, the images of the examined eyes are stored in the memory of the management server 140 corresponding to each patient's patient ID. Furthermore, the management server 140 sends the images of the examined eyes to the image browser 150 via the network 130.

[0040] The image viewer 150 is a touch panel, display, or similar device with communication capabilities. The image viewer 150 displays images of the examined eye acquired through the management server 140.

[0041] It should be noted that other ophthalmic devices (examination equipment such as field measurement and intraocular pressure measurement) and diagnostic support devices that use artificial intelligence for image analysis can also be connected to ophthalmic device 110, management server 140 and image browser 150 via network 130.

[0042] Next, refer to Figure 2 To explain the composition of the ophthalmic device 110. Figure 2 This is a block diagram illustrating the hardware configuration of the ophthalmic device 110 according to this embodiment. Figure 2 As shown, the ophthalmic device 110 includes a control device 16, a scanning laser ophthalmoscope (SLO) unit 18, an optical coherence tomography (OCT) unit 20P, and a photographic optics system 19. The control device 16 controls the SLO unit 18, the OCT unit 20P, and the photographic optics system 19 to acquire images of the fundus or anterior segment of the examined eye 12. The control device 16 also controls the OCT unit 20P and the photographic optics system 19 to acquire tomographic images of the fundus of the examined eye 12 or the anterior segment of the eye.

[0043] It should be noted that, when the ophthalmic device 110 is set on a horizontal plane, the horizontal direction is designated as the "X direction," the vertical direction relative to the horizontal plane is designated as the "Y direction," and the optical axis direction of the photographic optical system 19 is designated as the "Z direction." The device is configured relative to the eye 12 being examined such that the center of the pupil of the examined eye is located on the optical axis of the direction. The X, Y, and Z directions are perpendicular to each other.

[0044] When acquiring one-dimensional data in the depth direction, one-dimensional OCT data ("A-scan data") is obtained by scanning a point in the fundus along the depth (optical axis) direction (denoted as "A-scan"). When acquiring two-dimensional data, two-dimensional OCT data ("B-scan data") is obtained by moving the scanning position in a direction orthogonal to the depth direction and performing multiple A-scans (denoted as "B-scan"). When acquiring three-dimensional data, OCT data ("volume scan data") is obtained by moving the scanning position in a direction orthogonal to the B-scan direction and repeating B-scans (denoted as "C-scan"). Three-dimensional OCT data is generated from the volume scan data, and two-dimensional en-face images are generated based on this three-dimensional OCT data.

[0045] The control device 16 includes a computer having a CPU (Central Processing Unit) 16A, RAM (Random Access Memory) 16B, ROM (Read-Only Memory) 16C, input / output (I / O) 16D, input / display device 16E, and communication interface (I / F) 16F. The components of the control device 16 are communicatively connected to each other via a bus.

[0046] CPU 16A is the central processing unit, executing various programs and controlling various components. Specifically, CPU 16A reads programs from ROM 16C and uses RAM 16B as the working area to execute the programs. CPU 16A performs control and various arithmetic operations on each component according to the programs stored in ROM 16C. In this embodiment, ROM 16C stores data for processing (described later). Figure 5 The signal processing program for the intensity distribution (interference spectrum) of the interference light shown.

[0047] CPU 16A is an example of a "processor" according to the present disclosure. RAM 16B and ROM 16C are examples of storage units for storing information. Control device 16 is an example of a computer.

[0048] RAM 16B serves as the working area for temporary storage of programs or data. ROM 16C stores various programs and data.

[0049] It should be noted that the control device 16 can also be further configured to include a memory composed of storage media such as HDD (Hard Disk Drive) or SSD (Solid State Drive). In this case, various programs including the operating system and various data can also be stored in the memory. Alternatively, the ROM 16C can be replaced by storage in the memory. Figure 5 The signal processing program shown.

[0050] The input / display device 16E is connected to the CPU 16A via I / O 16D. The input / display device 16E has a graphical user interface (GUI) that displays an image of the examined eye 12 or receives various instructions from the user. As the GUI, a touch panel or a display can be used.

[0051] The control device 16 is connected to the network 130 via a communication interface 16F. The communication interface 16F is an interface for communicating with other devices, such as using standards like Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark).

[0052] exist Figure 2 In the ophthalmic device 110, the control device 16 includes an input / display device 16E, but the technology disclosed herein is not limited to this. For example, the control device 16 of the ophthalmic device 110 may not include the input / display device 16E, but may have a separate input / display device physically independent of the ophthalmic device 110. In this case, the display device includes an image processing processor unit that operates under the control of the CPU 16A of the control device 16. The image processing processor unit may also display acquired images based on image signals output by the CPU 16A.

[0053] Hereinafter, the anterior view image of the retina created based on the SLO data acquired through SLO unit 18 will be referred to as an SLO image, and the tomographic image and en-face image of the retina created based on the OCT data acquired through OCT unit 20P will be referred to as OCT images. It should be noted that SLO images are sometimes also called two-dimensional fundus images. Furthermore, corresponding to the imaging site of the examined eye 12, OCT images are sometimes also referred to as fundus tomographic images, posterior ocular tomographic images, and anterior ocular tomographic images.

[0054] The preferred ophthalmic device 110 has a wide-angle view, and more preferably an ultra-wide-angle view, as described below. In this case, the obtained image may also be referred to as a UWF (Ultra Wide Field) fundus image. Images of the fundus taken with an ultra-wide-angle view are hereinafter referred to as UWF fundus images.

[0055] A large field of view (FOV) observation is achieved at the fundus via the photographic optical system 19. FOV represents the range that can be captured by the photographic device. 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 angle of illumination of the light beam emanating from the ophthalmic device 110 to the examined eye, defined with reference to the pupil. The internal illumination angle is the angle of illumination of the light beam emanating from the center of the eyeball to the fundus, defined with reference to the center of the eyeball. The external and internal illumination angles have a corresponding relationship. For example, when the external illumination angle is 120 degrees, the internal illumination angle is approximately 160 degrees. In this embodiment, the internal illumination angle is set to 200 degrees.

[0056] Here, SLO fundus images obtained by shooting from an internal illumination angle of 160 degrees or more are referred to as UWF-SLO fundus images (UWF fundus images).

[0057] Figure 3 This is a block diagram illustrating the hardware configuration of the OCT unit 20P in this embodiment. Figure 3 As shown, the OCT unit 20P includes a light source 52, a first optical coupler 54, a polarization adjustment unit 56, a delay line 58, a second optical coupler 60, a detector 62, and an analog-to-digital (A / D) converter 64.

[0058] Light source 52 generates light for optical coherence tomography (OCT). Light source 52 is a wavelength scanning light source that outputs wavelength scanning light with a rapidly changing center wavelength by scanning a specified wavelength range at a specified wavelength scanning speed. Light source 52 may include, for example, a near-infrared wavelength-variable laser. In this way, OCT unit 20P uses the principle of SS-OCT (Swept Source-Optical Coherence Tomography) to acquire OCT data from the fundus.

[0059] It should be noted that the OCT unit 20P is not limited to an SS-OCT that uses a wavelength scanning light source as the light source 52. For example, an SD-OCT that uses a super luminescent diode (SLD) can also be used.

[0060] The first optical coupler 54 splits the path of the light emitted from the light source 52 into two paths. One path is the path of the light toward the polarization adjustment unit 56, and the other path is the path of the light toward the delay line 58.

[0061] It should be noted that, in Figure 3In the description of the light path from light source 52, an example is shown where a polarization adjustment unit 56 is arranged on one of the two paths branched from the first optical coupler 54, but this disclosure is not limited to this. That is, the polarization adjustment unit 56 can be arranged on at least one of the two paths branched (segmented) from the first optical coupler 54. This is because, when the measurement light and reference light merge and interfere through the optical coupler 60, the polarization adjustment unit 56 can be used to align the polarization states of the two beams with the same vibration direction (e.g., maximize the interference state). Furthermore, in Figure 3 The illustration shows an example where a delay line 58 is configured on one of the two paths described above, but this disclosure is not limited to this. That is, the delay line 58 can be configured on at least one of the two paths branching from the first optical coupler 54. This is because, when the measurement light and the reference light merge and interfere through the optical coupler 60, the delay line 58 can be configured to ensure that the optical path lengths of the two beams are the same.

[0062] The polarization adjustment unit 56 adjusts the direction of light vibration, i.e., the polarization state, which is the light vibrating in a specified direction in space. The light with the polarization state adjusted then enters the photographic optical system 19.

[0063] The light entering the photographic optical system 19 is scanned by the photographic optical system 19 in the X and / or Y directions. The scanning light, as the measurement light, is irradiated onto the fundus through the pupil of the examined eye 12. Because the scanning light scans, each scan time corresponds to each scan position of the fundus. The scanning speed is the speed at which B-scan data can be acquired at each scan position through B-scan. It should be noted that the scanning speed in the X or Y direction is different from the scanning speed of the light source; the scanning speed is the A-scan speed for acquiring the A-scan signal of a point. The measurement light reflected from the fundus enters the OCT unit 20P through the photographic optical system 19, and enters the second optical coupler 60 through the polarization adjustment unit 56 and the first optical coupler 54.

[0064] Another beam of light emitted from the light source 52 and branched from the first optical coupler 54 is used as a reference beam and enters the delay line 58, and then enters the second optical coupler 60 via the delay line 58.

[0065] As described above, the delay line 58 is set to be the same as the optical path length of the reference light, i.e., the optical path length of the measuring light. These optical path lengths can correspond to the axial length of the eye, and the operator can adjust the delay line 58 before the scanning light operation begins, for example, while looking at the fundus image, so that the tomographic image is positioned within the appropriate range.

[0066] The measurement light (return light) reflected by the examined 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 represents, for example, the power distribution 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 performs A / D conversion on 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.

[0067] It should be noted that when the OCT unit 20P adopts SD-OCT, the beam splitter is configured at the detector 62 and the image acquisition card (Grabber board) is configured at the A / D converter 64, thereby detecting the interference light separately according to the wavelength components.

[0068] The management server 140 and image viewer 150 include a computer, input device, external storage device, display device, and communication interface, etc.

[0069] like Figure 4 As shown, the CPU 16A of the ophthalmic device 110 in this embodiment functions as the imaging control unit 162, the image processing unit 164, and the display control unit 166.

[0070] Image processing unit 164 is an example of the "interference signal acquisition unit", "component acquisition unit", "corrected interference signal acquisition unit", "repeated execution unit" and "OCT signal acquisition unit" of the present disclosure.

[0071] However, fundus images of the examined eye acquired via OCT exhibit a variety of images (e.g., images referred to as artifacts). For example, a complex conjugate component image is generated as a mirror image in fundus images acquired using full-coverage OCT (FR-OCT) with extended OCT capable of observing depth. A mirror image is a virtual image that appears on the opposite side of a real image at a position where the optical path length of the measurement light illuminating the fundus is equal to the optical path length of the reference light. By forming a tomographic image from the real image that appears on one side (e.g., the positive side, the depth direction of the fundus) at a position where the optical path length of the measurement light is equal to the optical path length of the reference light, a wider range of tomographic images of the examined eye can be acquired. That is, by removing the mirror image (the negative side that produces the virtual image, i.e., the image in the direction opposite to the depth direction of the fundus) from the OCT image and forming a tomographic image, a full-coverage tomographic image of the fundus can be acquired.

[0072] Therefore, in this embodiment, by performing signal processing on the signal obtained from the OCT image to remove mirror images and the like, a tomographic image that accurately reflects the contents of the fundus is obtained.

[0073] Next, use Figure 5This section details the signal processing for the interference spectrum performed by the CPU 16A of the ophthalmic device 110. The signal processing program is executed by the CPU 16A of the ophthalmic device 110 to achieve… Figure 5 The flowchart illustrates the signal processing (signal processing method).

[0074] The SLO unit 18 and the imaging optical system 19 are controlled to acquire images of the fundus of the examined eye 12. The display control unit 166, as shown... Figure 8 As shown, an image of the fundus (also known as a UWF-SLO fundus image) SLG is displayed on the input / display device 16E.

[0075] The operator confirms the fundus image SLG displayed on the input / display device 16E and sets the range for acquiring the tomographic image via the input / display device 16E. For example, range L1 is a wider range including the central part of the fundus containing the optic nerve head (the point where the optical axis of the ophthalmic device 110 intersects with the fundus (fundus center)). Ranges L2, L3, and L4 are the ranges of the peripheral parts surrounding the central part of the fundus.

[0076] The scope of tomographic image acquisition is not limited to using SLO images. For example, two-dimensional en-face images based on OCT data can also be used to determine the location for acquiring tomographic images.

[0077] It should be noted that the range L1 to L4 is a line segment in the horizontal direction (B-scan direction) of the fundus, but the range for obtaining tomographic images is not limited to the line segment in the B-scan direction. It can also be a line segment in a direction that intersects the B-scan direction, or it can be a rectangular range.

[0078] Additionally, as detailed below, users can pre-select whether to perform full-coverage OCT processing or regular OCT processing, and the ophthalmic device 110 will specify which processing to perform. Furthermore, sometimes users may wish to perform full-coverage OCT processing after regular OCT processing. In this case, full-coverage OCT processing can be performed according to a time sequence after regular OCT processing.

[0079] In this way, the operator sets the range of tomographic images to be acquired and the processing to be performed (at least one of conventional OCT processing and full-coverage OCT processing), and the signal processing program is started when the input / display device 16E indicates that it will be started.

[0080] In step S72, the imaging control unit 162 instructs the OCT unit 20P and the imaging optical system 19 to perform an OCT scan to obtain a tomographic image within a set range.

[0081] In step S74, the imaging control unit 162 determines whether to set the tomographic image to be output to the display screen of the input / display device 16E in a full-coverage manner. Here, full coverage means that the output range of the image output to the display screen includes the range in the depth direction of the fundus (positive region) and the range in the opposite direction of the depth direction (negative region), based on the position in the examined eye 12 corresponding to the optical path length of the reference light.

[0082] Without full coverage, the output range of the tomographic image displayed on the screen is the depth direction of the fundus, based on the position in the examined eye 12 corresponding to the optical path length of the reference light. The tomographic image is displayed within a certain range that does not include this reference position and does not display a mirror image. As an example of a tomographic image displayed without full coverage, Figure 8 Examples of tomographic images G1 to G4 corresponding to ranges L1 to L4 are shown.

[0083] When full coverage is set, the output range of the tomographic image displayed on the screen is within the depth direction of the fundus and the opposite direction, based on the position in the examined eye 12 corresponding to the optical path length of the reference light. Figure 9 The image shown is an example of a tomographic image G15 corresponding to range L1 when full coverage is set. Figure 9 As shown, when full coverage is set, the tomographic image G15 is displayed within the output range of the image output to the display screen, which includes the range (positive region) PR of the fundus in the depth direction (based on the position PO in the examined eye 12 corresponding to the optical path length of the reference light) and the range (negative region) NR in the opposite direction (negative region). In this way, when full coverage is set, a wider range of tomographic images can be displayed compared to when full coverage is not set.

[0084] The full-coverage OCT process performed with full coverage enabled (step S76) takes longer than the normal OCT process performed without full coverage enabled (step S78). The user pre-selects whether to perform full-coverage OCT or normal OCT and sets it on the ophthalmic device 110. In step S74, it is determined which process the user has selected.

[0085] The processing in step S74 is not limited to determining whether the processing set by the user in the ophthalmic device 110 is full-coverage OCT processing or normal OCT processing.

[0086] When full coverage is set as described above, a wider range of tomographic images can be displayed compared to when full coverage is not set. Therefore, in step S74, it can also be determined whether the length of the specified direction of the range of the tomographic image set by the user is longer than a predetermined length. In this case, if the length of the specified direction of the range of the tomographic image set by the user is longer than the predetermined length, step S74 is a positive determination. If it is not determined that the length of the specified direction of the range of the tomographic image set by the user is longer than the predetermined length, step S74 is a negative determination.

[0087] It can also be determined whether at least a portion of the area where the tomographic image is acquired is located within the peripheral region of the central area of ​​the fundus. For example, if at least a portion of the area where the tomographic image is acquired is located within the peripheral region of the central area of ​​the fundus, step S74 can be a positive determination. On the other hand, if at least a portion of the area where the tomographic image is acquired is not located within the peripheral region of the central area of ​​the fundus, step S74 can be a negative determination.

[0088] If the determination in step S74 is negative, the image processing unit 164 performs normal OCT processing in step S78. When the processing in step S78 ends, signal processing proceeds to step S80. It should be noted that there are various types of normal OCT processing, but since these are well-known processes, detailed descriptions are omitted.

[0089] On the other hand, if the determination is positive in step S74, the image processing unit 164 performs full-coverage OCT processing in step S76.

[0090] As described above, when full-coverage OCT processing is set to be selectable after the normal OCT processing is executed, a judgment process is set to determine whether to execute full-coverage OCT processing after the processing in step S78. If the judgment is affirmative, the processing is transferred to step S76; if the judgment is negative, the processing is transferred to step S80.

[0091] Next, refer to Figure 6 Explanation of full-coverage OCT processing.

[0092] In step S102, the image processing unit 164 acquires the interference spectrum stored in the RAM 16B of the control device 16. The interference spectrum r1, r2, ..., rn is the data of the light intensity of each wavelength component of the wavelength scanning range corresponding to each scanning time t1, t2, ..., tn. That is, it is the data representing the spectral distribution of wavelength and light intensity of the interference fringes obtained in each A scan.

[0093] The interference spectra r1, r2, ..., rn are examples of the "interference signals" of the present invention.

[0094] It should be noted that when the OCT unit 20P adopts SD-OCT, the interference spectrum stored in the control device 16 is the light intensity data of each wavelength component obtained by the detector 62, which acts as a spectrometer, at each scanning position corresponding to each scanning time.

[0095] In step S104, the image processing unit 164 performs preprocessing for each interference spectrum to generate a clearer tomographic image. Preprocessing includes, for example, resampling, zero-padding, and window function processing. Resampling is a process that makes the sampling interval uniform during signal processing because the sampling interval is sparse and non-constant when the interference spectrum is obtained. Zero-padding is a process that improves the clarity of the tomographic image compared to the case without this processing by increasing the number of data points. Specifically, when the data value is an integer, the left side of the value is padded with zeros. For example, if it is desired to represent the data with 10 bits, the value 1234 is represented as 0000012345. Window function processing is a process that increases the weight of the data in the center of the interference spectrum compared to the surrounding data. It should be noted that zero-padding can also be omitted.

[0096] In step S106, the image processing unit 164 calculates the average light intensity of the initial interference fringes of all A-scans and calculates a threshold. The threshold calculated in step S106 is an example of a threshold th used to determine whether repeated processing (hereinafter referred to as FR processing) can be performed in each instance of the full-coverage processing of the A-scan described later. FR processing is a process that removes the signal components of the complex conjugate component image generated as a mirror image; that is, it removes the signal components representing the mirror image (hereinafter referred to as error signals) from the signal of the interference spectrum. See below for details.

[0097] The processing in step S106 is an example of the processing that derives the “threshold” of the present disclosure.

[0098] The image processing unit 164 calculates the average value of all data related to the light intensity of the A scan used in the image formed by the B scan (e.g., a fundus tomographic image), and sets it as the average value of the light intensity of the initial interference fringes (interference spectrum) of all A scans. The image processing unit 164 derives a threshold th from this average value. Equation (1) below shows an example of the threshold th (conditional formula). In the formula, f is the light intensity of the initial interference spectrum (interference fringes or interference signal), M is the total number of A scans included in the B scan. m is a variable, and E is a predetermined coefficient.

[0099]

Mathematical Formula 1

[0100]

[0101] In step S108, the image processing unit 164 specifies any one of the A scans (e.g., the initial A scan in the B scan direction) and performs FR processing. Figure 6 In the example shown, as FR processing, the processing from step S110 to step S124 is performed.

[0102] In step S110, the image processing unit 164 performs a known dispersion correction process on the interference spectrum obtained in the preprocessing step S104. This dispersion correction process enables numerical correction of the dispersion components caused by the optical system of the OCT unit 20P of the ophthalmic device 110. It should be noted that a predetermined dispersion correction function is obtained during the dispersion correction process.

[0103] The processing in step S106 is an example of the "dispersion correction processing" of the present disclosure.

[0104] In step S112, the image processing unit 164 performs a known inverse Fourier transform (IFFT) on the interference spectrum obtained by dispersion correction to obtain the first transformed signal.

[0105] In step S114, the image processing unit 164 performs a known multi-peak detection process called MPD (MultiPeak Detection) on the transformed first transformed signal. In this multi-peak detection process, multiple peaks are detected, and signal components based on the values ​​(peak values) of the detected multiple peaks are also detected.

[0106] In step S116, the image processing unit 164 saves the detected multiple peaks as a peak column and saves the signal components of the peak column. That is, the peak column and the data representing the signal components of the peak column are stored in the RAM 16B of the control device 16.

[0107] In step S118, the image processing unit 164 performs a known Fourier transform (FFT) on the stored peak column to obtain the second transformed signal.

[0108] In step S120, the image processing unit 164 performs inverse dispersion correction on the second transform signal of the peak column after Fourier transform to obtain an inverse dispersion corrected signal.

[0109] In step S122, the image processing unit 164 extracts the real component of the inverse dispersion corrected signal. It should be noted that in step S122, the extracted real component can also be set to a predetermined multiple (e.g., 2 times).

[0110] In step S124, the image processing unit 164 subtracts the acquired interference spectrum from the extracted real components. That is, the original interference spectrum is subtracted from the components of the peak column (MPD).

[0111] The process in step S124 is an example of the process of obtaining the "corrected interference signal" of the present disclosure.

[0112] In step S126, the image processing unit 164 determines the light intensity I (=||ri||) of the subtracted interference spectrum. 2 Whether it is below the threshold th mentioned above. The judgment process in step S126 is to determine whether the light intensity of the residual signal of the interference spectrum after subtraction meets the following equation (2).

[0113]

Mathematical Formula 2

[0114]

[0115] If the determination in step S126 is negative, the image processing unit 164 sets the subtracted interference spectrum to the interference spectrum of the object to which the FR processing is performed, and returns the processing to step S110. On the other hand, if the determination in step S126 is positive, the image processing unit 164 transfers the processing to step S128.

[0116] Therefore, the subtraction process obtained by the above FR processing is repeatedly performed until the interference spectrum of the A scan becomes below the threshold th.

[0117] The threshold th is an example of a “threshold” in this disclosure.

[0118] In step S128, the image processing unit 164 determines whether the above-mentioned FR processing has ended for all A scans.

[0119] If the determination in step S128 is negative, the image processing unit 164 returns the processing to step S108 to perform the above-mentioned FR processing for other A scans. If the determination is positive, the processing routine ends.

[0120] As mentioned above, Figure 5 Step S76 ends, and signal processing proceeds to step S80.

[0121] In step S80, the display control unit 166 outputs OCT data (tomographic image data) to (displays on) the input / display device 16E. That is, the data saved in step S116 above is acquired as OCT data and output to (displays on) the input / display device 16E.

[0122] As explained above, in this embodiment, during full-coverage OCT processing, the peak value of the light intensity represented by the interference spectrum is extracted using the interference spectrum (interference fringes) of each A scan obtained by forming a B scan image. Furthermore, FR processing to remove erroneous signals is performed by subtracting the original interference spectrum (interference fringes) from the extracted peak components. This FR processing is repeated for each A scan until the light intensity of the remaining interference spectrum after subtracting the peak components falls below a predetermined threshold. The predetermined threshold is a fixed value determined from the B scan image, derived from equation (1) above. Thus, in this embodiment, the determination of whether to repeatedly perform FR processing is based on the threshold th, i.e., a fixed value determined from the overall image obtained through the B scan. Therefore, by using a fixed threshold determined from the B scan image for the FR processing of each A scan, compared to using different thresholds, the unevenness of image brightness caused by vertical stripes and shadows can be reduced, resulting in a high-quality full-coverage image.

[0123] Furthermore, in OCT images, brightness inhomogeneity related to image quality arises when the signal magnitudes of the images obtained through each A-scan differ. For example, if the peak brightness values ​​differ among the signals of multiple images obtained through each A-scan, the magnitudes of noise components in the signals will also differ. That is, the magnitudes of noise components differ between A-scan images of dark areas and bright areas of the fundus. This difference in noise components appears in the form of images (e.g., vertical stripes), thus causing brightness inhomogeneity in the resulting OCT images. In this embodiment, since a fixed threshold th is set for the entire A-scan images obtained through B-scans, the brightness of the OCT images can be homogenized.

[0124] As mentioned above, the threshold th is derived from the average light intensity of the initial interference fringes (interference spectrum) across the entire A-scan. Specifically, it is the value obtained by multiplying this average by a coefficient E. The coefficient E is predetermined.

[0125] Here, refer to Figure 7 Let's take an example of how the coefficient E, which is the threshold th, is derived from the ratio of light intensity that can be applied to remove the mirrored image described above.

[0126] In step S202, the image processing unit 164 uses the ophthalmic device 110 to acquire the interference spectrum of the examined eye that has been photographed. It should be noted that the interference spectrum is not limited to the photographed interference spectrum of the examined eye; of course, the ophthalmic device 110 can also be used to measure the examined eye and acquire the interference spectrum stored in the RAM 16B of the control device 16.

[0127] In step S204, the image processing unit 164 sets an initial value for the coefficient E (for example, E = 0.1).

[0128] In step S206, the image processing unit 164 performs FR processing to remove the aforementioned error signals. Figure 6 Following steps S110 to S124, in the next step S208, the processed image is acquired. Furthermore, the image processing unit 164 uses the images before and after processing to derive the error signal removal rate SR. This error signal removal rate SR can be calculated using the ratio of the signal from the image before processing to the signal from the image after processing. The error signal removal rate SR is derived such that the greater the amount of error signal removed from the original signal, the higher the removal rate. It should be noted that the above description describes the case where the image processing unit 164 uses the images before and after processing to derive the error signal removal rate SR; however, the image processing unit 164 can also derive the error signal removal rate SR using only the processed image. In this case, the error signal removal rate SR can be calculated using the ratio of the real part to the imaginary part of the processed image signal.

[0129] In step S210, the image processing unit 164 determines whether the error signal removal rate SR is greater than or equal to the signal-to-noise ratio SNR (SR≥SNR). The processing in step S210 corresponds to the determination process for whether the mirror image, which is a virtual image, disappears from the fundus image. The ratio SNR is predetermined before the ophthalmic device 110 is manufactured, corresponding to the imaging subjects such as the anterior and posterior eyes in the ophthalmic device 110. For example, anterior eye images sometimes contain stronger signals (signals with higher brightness values) compared to posterior eye images. By determining a larger ratio SNR during anterior eye imaging than during posterior eye imaging, a better image can be obtained. Therefore, the ratio SNR is predetermined corresponding to the imaging subject, and the coefficient E is derived.

[0130] If the judgment is negative in step S210, the image processing unit 164 increases the value of the current coefficient E by a predetermined amount (E = E + ΔE) in step S212 and returns the processing to step S206.

[0131] On the other hand, if the determination is positive in step S210, the image processing unit 164 determines the current value of coefficient E as the coefficient E of the ophthalmic device 110 and stores it in step S214.

[0132] As mentioned above, the coefficient E can be determined in advance.

[0133] In the aforementioned full-coverage OCT processing, the FR processing performed for each A scan is repeated until the intensity of the residual interference spectrum after subtracting the peak component falls below a threshold. However, repeated FR processing can affect the standby time from the time the fundus of the examined eye is captured until the OCT image is displayed. That is, the more times the FR processing is repeated for each A scan, the longer the standby time. Furthermore, the long standby time reduces the ease of use for operators such as doctors who process OCT images. Therefore, it is possible to predetermine an upper limit for the number of repetitions so that the FR processing is repeated a predetermined number of times. For example, the standby time can be set to a time specified by the operator or an empirically determined time, and the processing time for the interference spectrum of each A scan can be determined corresponding to the total number of A scans, stopping the processing when the predetermined time has elapsed since the start of processing. For example, if the standby 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 is set to 0.05 seconds (=5 / 100), and the upper limit of the number of repeated processing is set to no more than 0.05 seconds.

[0134] It should be noted that, in this embodiment, the average light intensity of the initial interference fringes using all A-scans was described as an example of a threshold, but the technology disclosed herein is not limited to this average value. For example, any value between the maximum and minimum light intensity values ​​can be set as the threshold. Alternatively, a weighted average value related to wavelength and a weighted average value related to the position of the A-scan, i.e., time, can be used. Furthermore, the threshold value can be derived from the calculated value based on the frequency of occurrence of histograms of light intensity, etc.

[0135] The threshold th described above refers to the average light intensity of the initial interference fringes using all A-scans, but is not limited to this. For example, the upper limit of the noise component in the obtained signal (interference spectrum) or a predetermined value determined based on the noise component can also be set as the threshold. This upper limit of the noise component or the predetermined value determined based on the noise component can be used to replace the tested eye with a simulated eye whose retina has a reflective surface, and the signal containing electrical noise obtained when light is irradiated onto the retinal portion of the simulated eye can be determined as the threshold.

[0136] Alternatively, past B-scan images can be used to determine the threshold. For example, the threshold can be calculated based on previously captured B-scan images.

[0137] In addition, the threshold th can also be a value derived by a learning model that uses the interference spectrum of the mirrored image removed as the supervision signal, the interference spectrum containing the mirrored image as the input signal, and the threshold as the output signal.

[0138] In the aforementioned signal processing (full-coverage OCT processing), for each A scan, the number of repetitions of FR processing is set based on the light intensity of all A scans, thereby adjusting the light intensity subtracted from the original image to remove signals appearing as mirror images. Therefore, compared to performing FR processing with the same number of repetitions for all A scans, it is possible to efficiently remove signal components appearing as mirror images from tomographic images.

[0139] Figure 10 An example of a typical full-coverage OCT image (tomographic image) without the signal processing described above is shown. Figure 10 As shown, the tomographic image before the mirror image is removed contains the mirror image Ig15. Additionally, artifacts appearing as vertical stripes can sometimes occur in the tomographic image when there is a change in brightness, for example, between adjacent A scans.

[0140] Figure 11 The diagram shows a concept related to OCT images (tomographic images) processed with full-coverage OCT. Figure 11 The graphs include OCT image Ga, OCT image Gb, and the repetition distribution Gc of FR processing.

[0141] OCT image Ga is a typical full-coverage OCT image without the aforementioned signal processing. In OCT image Ga, the image G22 representing the fundus region is conceptually represented by a solid line, and the mirror image Ig15 is conceptually represented by a dashed line. OCT image Gb is an OCT image with full-coverage OCT processing according to this embodiment. OCT image Gb only includes the image G22 representing the fundus region, while the mirror image Ig15 is removed. Furthermore, in the full-coverage OCT processing of this embodiment, the distribution of the number of repetitions of FR processing Gc is the distribution of the number of repetitions obtained by repeatedly performing FR processing for each A scan. In OCT image Gc, the distribution characteristic G20 of the number of repetitions is conceptually represented by a solid line. As shown by the distribution characteristic G20, the number of repetitions of FR processing 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 FR processing.

[0142] The number of repetitions of the FR process for removing mirror images affects the appearance of mirror images in the processed OCT image, as well as the brightness and image quality of the OCT image.

[0143] Figure 12 A conceptual diagram showing the relationship between OCT images (tomographic images) with full-coverage OCT processing that varies with the number of repetitions corresponding to FR processing. Figure 12The diagram includes OCT images Gd, Gf, Gg, and Gh obtained by performing signal processing according to this embodiment.

[0144] OCT image Gd is a Figure 10 The conceptual image is a typical OCT image obtained through full-coverage OCT processing. The OCT image Gd can also be considered as an OCT image obtained through signal processing without the signal processing described in this embodiment.

[0145] OCT images Gf, Gg, and Gh are OCT images obtained by processing signals with varying numbers of repetitions of FR processing. OCT image Gf is an OCT image based on full-coverage OCT processing, where a threshold larger than the aforementioned threshold th sets a smaller number of FR processing repetitions. OCT image Gf contains a mirror image Ig16 generated in the form of vertical stripes Gfa, retaining the aforementioned peak values ​​that increase as the number of FR processing repetitions decreases. This results in uneven brightness in the OCT image and reduced image quality.

[0146] The OCT image Gg is an OCT image based on a full-coverage OCT process with a large number of FR processing repetitions set to a threshold smaller than the aforementioned threshold th. The OCT image Gg includes a shadow image Ig17. In the shadow image Ig17, although the removal of the mirror image continues as the number of FR processing repetitions increases, only the light intensity at the corresponding location in the mirror image decreases, while the vertical stripes Gga, with lower light intensity than other areas, continue. Thus, Yu Yu indicates that the image G22 of the fundus region, the background image of image 22, and the shadow image Ig17 are identified by the operator. Therefore, although the mirror image itself is not confirmed, its location and region are determined based on the shadow of the mirror image. In this way, uneven brightness is generated in the OCT image, resulting in reduced image quality.

[0147] In response, the OCT image Gh, which underwent signal processing according to this embodiment, and Figure 11 Similarly, as described above, the OCT image Gb shown does not produce vertical stripes or shadows; the mirror image Ig15 is removed, and only the image G22 representing the fundus portion is included. That is, in this embodiment, FR processing is repeated an appropriate number of times, based on a threshold th determined by the B-scan image, to suit the signals obtained from each A-scan. This reduces brightness inhomogeneity in the OCT image, providing a high-quality OCT image.

[0148] In this embodiment, the signal processing described above extracts the peak values ​​of light intensity from the interference spectra (interference fringes) of each A-scan and subtracts the original interference spectra (interference fringes) from the components of the extracted peak values. This allows the removal of signal components from the tomographic images that appear as complex conjugate component images. Thus, as... Figure 9 As shown, it is possible to remove mirror images and known artifacts that appear in tomographic images with high precision. Thus, in this embodiment, artifacts appearing in tomographic images with full coverage can be suppressed, and tomographic images that accurately reflect the contents of the fundus can be obtained.

[0149] OCT data (tomographic image data) is sent to management server 140 via network 130, and stored in the memory of management server 140 according to the patient ID of each patient. Following instructions from image viewer 150, management server 140 sends the OCT data (tomographic image data) along with patient data via network 130. Image viewer 150 displays the OCT images and patient data together on a monitor screen.

[0150] The following describes the display / screen used to display OCT data (tomographic image data) together with patient data on the display screen of the image browser 150. Figure 13 The image shows a monitor / screen 500A. (Example:) Figure 13 As shown, the display / screen 500A has an information area 502 and an image display area 504A.

[0151] Information area 502 includes a patient ID display field 512, a patient name display field 514, an age display field 516, a vision display field 518, a right / 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 browser 150 displays information based on information received from the management server 140.

[0152] Image display area 504A is the area for displaying images of the examined eye, etc. The following display fields are set in image display area 504A, specifically including OCT image display field 540 and UWF fundus image display field 542.

[0153] An annotation field can also be set in the image display area 504A. The annotation field is a comment section where users can freely enter comments based on their ophthalmological observations or diagnoses.

[0154] The UWF fundus image display field 542 displays the UWF-SLO fundus image SLG obtained by taking a picture of the fundus of the examined eye with the ophthalmic device 110. The range of the acquired tomographic image, such as range L1, is overlaid in the UWF-SLO fundus image SLG.

[0155] Display the OCT image in OCT image display field 540. Figure 13 The image displayed is a tomographic image G15 based on OCT data obtained through full-coverage processing. It should be noted that when sending OCT data (tomographic image data) to the management server 140 and image viewer 150, data indicating whether full-coverage OCT processing or normal OCT processing was performed is also sent. When displaying the tomographic image, this data is used to determine whether to display the tomographic image with full coverage; based on the determination result, the tomographic image is displayed within the full-coverage or normal range.

[0156] In this embodiment, the CPU 16A of the ophthalmic device 110 executes a signal processing program, but the technology disclosed herein is not limited to this. For example, it may also be executed by the CPU of the management server 140 or the image browser 150.

[0157] In this disclosure, each constituent element (device, etc.) may exist in only one or more forms, provided that there is no contradiction.

[0158] The examples described above illustrate image processing using computer software, but the technology disclosed herein is not limited to this. For instance, image processing can be performed solely by hardware such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits), instead of using computer software. Alternatively, a portion of the image processing can be performed by software, while the remainder is performed by hardware.

[0159] The technology disclosed herein relates to image processing and includes the following cases: implementation by software using a computer; implementation by hardware; and implementation by a combination of software and hardware. Therefore, the technology disclosed herein includes the following techniques.

[0160] (Technology 1)

[0161] An ophthalmic device comprising:

[0162] The interference signal acquisition unit obtains an interference signal from the interference light obtained by scanning the eye under examination with light from the light source and the reference light obtained by splitting the light from the light source.

[0163] The component acquisition unit obtains the peak components determined based on the light intensity distribution in the interference signal;

[0164] The modified interference signal acquisition unit obtains the modified interference signal by subtracting a signal of magnitude determined based on the peak components from the interference signal;

[0165] The repetitive execution unit sets the corrected interference signal as the interference signal and repeatedly executes the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal until the light intensity of the corrected interference signal after subtracting the result becomes below a predetermined threshold; and

[0166] The OCT signal acquisition unit acquires OCT data based on the modified interference signal below the threshold.

[0167] (Second technology)

[0168] A signal processing method for an ophthalmic device includes the following steps:

[0169] The interference signal acquisition unit obtains the interference signal from the interference light obtained by scanning the eye under examination with light from the light source and the reference light obtained by splitting the light from the light source.

[0170] The component acquisition unit obtains the peak components determined based on the light intensity distribution in the interference signal;

[0171] The corrected interference signal acquisition unit subtracts the signal of magnitude determined based on the peak component from the interference signal to obtain the corrected interference signal;

[0172] The repetitive execution unit sets the corrected interference signal as the interference signal, and repeatedly executes the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal until the light intensity of the corrected interference signal after subtracting the result becomes below a predetermined threshold; and

[0173] The OCT signal acquisition unit obtains OCT data based on the corrected interference signal below the threshold.

[0174] Based on the above publicly available information, the following technologies are proposed.

[0175] (Third technology)

[0176] A computer program product for acquiring OCT signals.

[0177] The computer program product has its own computer-readable storage medium for non-transitory signals.

[0178] The program is stored in the computer-readable storage medium.

[0179] The program causes the computer to perform a process that includes the following steps:

[0180] An interference signal is obtained from the interference of the measurement light obtained by scanning the eye through light from the light source with light from the light source to obtain the reference light obtained by splitting the light from the light source;

[0181] Obtain the peak components determined based on the light intensity distribution in the interference signal;

[0182] The corrected interference signal is obtained by subtracting the signal whose magnitude is determined based on the peak component from the interference signal;

[0183] The corrected interference signal is set as the interference signal, and the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal are repeatedly performed until the light intensity of the corrected interference signal after subtracting the result becomes below a predetermined threshold; and

[0184] OCT data is obtained based on the modified interference signal below the threshold.

[0185] The signal processing described above is just one example. Therefore, it is certainly possible to delete unnecessary steps, add new steps, or change the processing order without departing from the main point.

[0186] All documents, patent applications, and technical standards described in this specification, as well as those specifically and separately described therein, are incorporated herein by reference. Furthermore, the entire disclosure of Japanese Application No. 2023-159176, filed on September 22, 2023, is incorporated herein by reference.

Claims

1. An ophthalmic device, characterized in that, Includes processor, The processor performs a process that includes the following steps: An interference signal is obtained from the interference of the measurement light obtained by scanning the eye through light from the light source with light from the light source to obtain the reference light obtained by splitting the light from the light source; Obtain the peak components determined based on the light intensity distribution in the interference signal; The corrected interference signal is obtained by subtracting the signal of magnitude determined based on the peak components from the interference signal; The corrected interference signal is set as the interference signal, and the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal are repeatedly performed until the light intensity of the corrected interference signal after subtracting the result becomes below a predetermined threshold; and OCT data is obtained based on the modified interference signal below the threshold.

2. The ophthalmic device according to claim 1, characterized in that, The threshold is a value determined based on the light intensity distribution of a plurality of interference signals, which are interference signals used when scanning in the depth direction with respect to a predetermined range of directions orthogonal to the depth direction in the eye under examination.

3. The ophthalmic device according to claim 2, characterized in that, The threshold is a value determined based on the average light intensity of the interference signal obtained in the step of obtaining the interference signal from the interference light.

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

5. The ophthalmic device according to claim 2, characterized in that, Let f be the initial light intensity in the interference signal obtained through scanning in the depth direction, M be the total number of depth direction scans included in a specified range of scans in a direction orthogonal to the depth direction, and E be a specified coefficient. In this case, the threshold is determined by... 【Mathematical Formula 1】 The value determined by the conditional expression shown.

6. The ophthalmic device according to any one of claims 1 to 5, characterized in that, For the repetitive steps, if a predetermined time has elapsed since the start of the step, the step is terminated.

7. The ophthalmic device according to any one of claims 1 to 6, characterized in that, It also includes a step of performing dispersion correction processing on the interference signal. The signal that has undergone the dispersion correction process is designated as the interference signal.

8. The ophthalmic device according to any one of claims 1 to 7, characterized in that, It also includes the following steps: Using the position corresponding to the optical path length of the reference light as a reference, the image obtained based on the OCT data is output to the display screen within the image output range of the fundus in the depth direction and the direction opposite to the depth direction.

9. A signal processing method for an ophthalmic device, wherein the signal processing is performed by a processor of the ophthalmic device, characterized in that it includes the following steps: An interference signal is obtained from the interference of the measurement light obtained by scanning the eye through light from the light source with light from the light source to obtain the reference light obtained by splitting the light from the light source; Obtain the peak components determined based on the light intensity distribution in the interference signal; The corrected interference signal is obtained by subtracting the signal of magnitude determined based on the peak components from the interference signal; The corrected interference signal is set as the interference signal, and the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal are repeatedly performed until the light intensity of the corrected interference signal after subtracting the result becomes below a predetermined threshold; and OCT data is obtained based on the modified interference signal below the threshold.

10. A program, characterized in that, To cause the computer to perform a process that includes the following steps: An interference signal is obtained from the interference of the measurement light obtained by scanning the eye through light from the light source with light from the light source to obtain the reference light obtained by splitting the light from the light source; Obtain the peak components determined based on the light intensity distribution in the interference signal; The corrected interference signal is obtained by subtracting the signal of magnitude determined based on the peak components from the interference signal; The corrected interference signal is set as the interference signal, and the steps of obtaining the peak component of the interference signal and obtaining the corrected interference signal are repeatedly performed until the light intensity of the corrected interference signal after subtracting the result becomes below a predetermined threshold; and OCT data is obtained based on the modified interference signal below the threshold.

Images