OCT Device

Abstract

To provide an OCT apparatus which can suitably acquire OCT data.SOLUTION: An OCT apparatus comprises: an OCT optical system having a wavelength sweeping light source which can change a sweeping frequency and a first detector which detects a spectral interference signal of measurement light and reference light; an image processor which acquires OCT data from the spectral interference signal; an FPN generation optical system which can generate a first FPN and a second FPN at a position apart from a zero delay position with respect to the first FPN; a second detector which detects the first FPN and the second FPN; and a calculation controller which acquires first correction information applied to the calculation processing on the spectral interference signal in a case where the sweeping frequency is the first sweeping frequency on the basis of the first FPN detected in the case of the first sweeping frequency, and acquires second correction information applied to the calculation processing on the spectral interference signal in a case where the sweeping frequency is the second sweeping frequency on the basis of the second FPN generated in a case where the sweeping frequency is the second sweeping frequency.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to an OCT device that obtains OCT data of a test eye. [Background technology]

[0002] In recent years, swept source OCT (SS-OCT) has been increasingly used in the field of ophthalmology. SS-OCT uses a swept source as the OCT light source, and obtains OCT data by sampling and processing at high speed the spectral interference signal between the measurement light and reference light guided to the tissue of the subject's eye.

[0003] In such an apparatus, the mapping state between the spectral interference signal obtained by sampling and the wave number space is affected by the aging of the apparatus and the environmental changes, and changes from the initial state. In response to this, calibration is performed as necessary. For example, Patent Document 1 discloses an apparatus that includes an FPN (Fixed Pattern Noise) generating optical system that includes an optical member that generates an FPN signal, and performs calibration regarding the wave number component by using the FPN signal.

[0004] In the technical field of SS-OCT, a device capable of changing the sweep frequency of a wavelength swept light source has been proposed. For example, Patent Document 2 discloses a device that can change the sweep frequency to drastically change the imaging range in the depth direction from imaging a local part of the subject's eye (anterior eye part or fundus) to imaging the entire eyeball (from the cornea to the fundus). It is also considered that changing the sweep frequency will change the sensitivity and the imaging time of the A-scan. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-124188 A [Patent Document 2] JP 2012-75640 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, as in Patent Document 1, when an FPN generating optical system suitable for calibration at a constant sweep frequency is applied to an apparatus capable of changing the sweep frequency, there are cases where an appropriate FPN signal cannot be obtained. For example, when the sweep frequency is reduced while keeping the optical distance between the position corresponding to the zero delay position and the position of the optical member generating the FPN constant, the envelope of the peak formed when the FPN signal is Fourier transformed may fall into the zero delay region. In such a case, good calibration data cannot be obtained.

[0007] In view of the problems with the conventional techniques described above, a technical object of the present disclosure is to provide an OCT device capable of suitably acquiring OCT data. [Means for solving the problem]

[0008] An OCT device according to a typical embodiment of the present disclosure includes an OCT optical system including a wavelength swept light source capable of changing a sweep frequency between a first sweep frequency and a second sweep frequency, a light splitter that splits light from the wavelength swept light source into a measurement light and a reference light, and a first detector that detects a spectral interference signal between the measurement light and the reference light guided to tissue of a test eye, an image processor that processes the spectral interference signal to obtain OCT data of the test eye, and an FPN generating optical system having at least one optical member that generates a first FPN when the frequency is the first sweep frequency and generates a second FPN at a position away from a zero delay position with respect to the first FPN when the frequency is the second sweep frequency; the first FPN detected when the sweep frequency is the first sweep frequency, and the second FPN detected when the sweep frequency is the second sweep frequency, and the second FPN detected when the sweep frequency is the second sweep frequency, the second FPN detected when the sweep frequency is the first sweep frequency, and the second FPN detected when the sweep frequency is the second sweep frequency, the second FPN detected when the sweep frequency is the second sweep frequency, are used to obtain correction information for correcting a mapping state of each wave number component. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of an OCT apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a flowchart of the control performed by the control unit as a calibration. [Diagram 3] 1 is an example of mapping information of each wave number component obtained based on an FPN signal. [Figure 4] 11A and 11B are diagrams for explaining how the wave number mapping state of each wave number component is corrected based on correction information. [Diagram 5] FIG. 11 is a flowchart of the control performed by the control unit when acquiring correction information. [Figure 6]FIG. 2 is a diagram illustrating an example of an FPN generating optical system. [Figure 7] 1A and 1B are diagrams illustrating an FPN signal generated by an FPN generating optical system. [Figure 8] 10 is a diagram illustrating how the signal frequency at which an FPN signal is detected changes depending on the sweep frequency. FIG. [Figure 9] 13 is a Fourier transform of a second FPN signal when the sweep frequency of the wavelength swept light source is a second sweep frequency. [Figure 10] FIG. 11 is a flowchart of control performed by a control unit to calibrate correction information. [Figure 11] 11A and 11B are diagrams illustrating how a correspondence deviation is corrected by calibrated correction information. [Figure 12] 11A and 11B are diagrams illustrating how a correspondence deviation is corrected by calibrated correction information. [Figure 13] FIG. 2 illustrates a spectral interference signal obtained by a calibration optical system. [Figure 14] 10A and 10B are diagrams illustrating a calibration interference signal acquired by a calibration optical system. [Figure 15] 1A to 1C are diagrams illustrating examples of transformations of the FPN generating optical system. [Figure 16] 1A to 1C are diagrams illustrating examples of modifications of the FPN generating optical system and the reference optical system. [Figure 17] 1A to 1C are diagrams illustrating examples of transformations of the FPN generating optical system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [overview] The following embodiments of the present disclosure will be described. The items grouped in <> below can be used independently or in association with each other. For example, in a certain embodiment, a plurality of items can be appropriately combined. Also, for example, an item described with respect to a certain embodiment can be applied to other embodiments.

[0011] For example, the invention described in the first embodiment and the invention described in the second embodiment may be implemented simultaneously. Also, either one of the invention described in the first embodiment and the invention described in the second embodiment may be implemented.

[0012] <First Embodiment> The OCT device according to the first embodiment is a device capable of changing the sweep frequency into a plurality of values, and calibration data corresponding to each sweep frequency is properly acquired.

[0013] The OCT device according to the first embodiment may include an OCT optical system, and may be capable of obtaining OCT data by performing arithmetic processing on a spectral interference signal output from a first detector of the OCT optical system with an image processor.

[0014] <OCT Optical System> The OCT optical system may be, for example, a Fourier domain OCT optical system. For example, the OCT device may be a wavelength-swept OCT (SS-OCT: Swept Source OCT).

[0015] The OCT optical system may divide the light emitted from a wavelength-swept light source into measurement light and reference light by an optical splitter. Also, the OCT optical system may detect a spectral interference signal between the reflected light of the measurement light from the eye to be examined and the reference light with a first detector.

[0016] For example, the wavelength-sweeping light source may be a wavelength-sweeping light source whose sweeping frequency can be changed between a first sweeping frequency and a second sweeping frequency lower than the first sweeping frequency. In this embodiment, the sweeping frequency indicates the number of sweeps per unit time. For example, by changing between the first sweeping frequency and the second sweeping frequency, the imaging range in the depth direction of the OCT device may be changed. For example, the first sweeping frequency may be the sweeping frequency for acquiring a tomographic image of the fundus of the eye to be examined, and the second sweeping frequency may be the sweeping frequency for acquiring a tomographic image of the entire eyeball of the eye to be examined. Also, by changing the sweeping frequency between the first sweeping frequency and the second sweeping frequency, the imaging time and the measurement sensitivity may be changed. For example, the OCT device may be selectively set to a first imaging mode that images at the first sweeping frequency and a second imaging mode that images at the second sweeping frequency.

[0017] <FPN generation optical system> In the OCT device, an FPN generation optical system is provided. The FPN generation optical system may be, for example, an optical system including an optical member for generating a first FPN and a second FPN, and a second detector capable of detecting the signal of the first FPN and the signal of the second FPN. In the first embodiment, when the sweeping frequencies are the same, the position where the second FPN is generated is a position farther from the zero-delay position than the position of the first FPN. In this embodiment, the zero-delay position is the depth position in the OCT image where the optical path lengths of the measurement light and the reference light coincide.

[0018] Also, some configurations are shared between the FPN generation optical system and the OCT optical system. For example, the second detector of the FPN generation optical system is shared with the first detector of the OCT optical system. That is, the FPN generation optical system guides the light from the light source to the optical member for FPN generation and guides the light passing through the optical member to the first detector.

[0019] In the OCT device, a driving unit may be provided that changes the optical distance between a position corresponding to the zero delay position and the position of the optical member. In this embodiment, the position corresponding to the zero delay position is a position where the optical path length from the light source to the detector via the optical member coincides with the optical path length of the reference light path when the optical member is placed. In other words, the position corresponding to the zero delay is a position where the FPN is generated at the zero delay position when the optical member is placed. In this embodiment, the position corresponding to the zero delay position is called the origin position.

[0020] For example, the actuator changes the optical distance by changing the optical path length of the FPN generating optical system or the optical path length of the reference optical path. For example, the actuator may change the optical distance between a first distance at which a first FPN occurs and a second distance at which a second FPN occurs. For example, the actuator may change the optical distance to the first distance when the swept light source has a first swept frequency and to the second distance when the swept light source has a second swept frequency.

[0021] In addition, the FPN generating optical system may include, for example, a first optical member for generating a first FPN. In addition, the FPN generating optical system may include, for example, a second optical member for generating a second FPN. For example, the first optical member and the second optical member are used together.

[0022] For example, the first optical member and the second optical member may be separate bodies, and in that case, the first optical member and the second optical member may be arranged such that the optical distance from the origin position to the second optical member is longer than the optical distance from the origin position to the first optical member.

[0023] <Mapping status correction> The OCT device may be provided with an arithmetic and control device that obtains correction information for correcting the mapping state of each wave number component. The arithmetic and control device may obtain the first correction information based on the first FPN. For example, the arithmetic and control device performs arithmetic processing on the spectral interference signal using the first correction information in the case of the first sweep frequency. As a result, the mapping state of each wave number component is corrected in the case of the first sweep frequency. For example, the mapping state of each wave number component is corrected so that the correspondence relationship between the sampling point and the wave number of light (2π / λ, λ is the wavelength of light) becomes linear (see FIG. 4).

[0024] Similarly, the arithmetic controller may obtain second correction information according to the second FPN. In addition, the arithmetic controller performs arithmetic processing on the spectral interference signal using the second correction information in the case of the second sweep frequency. Thus, in the case of the second sweep frequency, the mapping state of each wave number component is corrected.

[0025] For example, the arithmetic and control device may acquire the correction information in advance before acquiring the OCT data of the subject's eye.

[0026] Furthermore, for example, the FPN generating optical system may generate a third FPN when the wavelength swept light source has a first sweep frequency, and may generate a fourth FPN when the wavelength swept light source has a second sweep frequency. For example, the third FPN may be generated such that the position of the first FPN differs from the position of the third FPN when the position of the first FPN is compared under the same sweep frequency condition. The same applies to the relationship between the second FPN and the fourth FPN.

[0027] In this case, for example, the arithmetic controller may obtain the first correction information based on the difference information between the mapping information of each wave number component based on the first FPN and the mapping information of each wave number component based on the third FPN. Also, the second correction information may be obtained based on the difference information between the mapping information of each wave number component based on the second FPN and the mapping information of each wave number component based on the fourth FPN. This makes it possible to correct the dispersion components included in the mapping state of each wave number component (see FIG. 3).

[0028] The arithmetic controller may also acquire the correction information in a state where the measurement light is blocked. In this case, for example, the OCT optical system may be provided with a blocking member that can be inserted and removed to block the measurement light. For example, the arithmetic controller acquires the first correction information based on the first FPN detected by the second detector in a state where the blocking member is inserted into the OCT optical system. Similarly, for example, the arithmetic controller acquires the second correction information based on the second FPN detected by the second detector in a state where the blocking member is inserted into the OCT optical system.

[0029] According to the above configuration, even if the wavelength swept light source changes the sweep frequency, the FPN signal can be properly acquired by changing the signal frequency at which the FPN is detected. For example, in this embodiment, an electrical filter that cuts DC components is provided between the detector and the arithmetic controller to protect the arithmetic controller. In this embodiment, the frequency range cut by this electrical filter is called the zero delay range. For example, in this embodiment, the FPN can be generated at a signal frequency such that the envelope of the peak formed when Fourier transforming does not fall within the zero delay range.

[0030] Therefore, it is possible to obtain favorable correction information using the generated FPN, and therefore it is possible to obtain favorable OCT data.

[0031] Furthermore, for example, the FPN generating optical system may include a light intensity adjuster. For example, the light intensity adjuster adjusts the intensity of light emitted from the FPN generating optical system based on the sweep frequency of the wavelength swept light source. For example, the light intensity adjuster adjusts the light intensity so that the FPN signal falls within the dynamic range of the first detector. In this way, even if the sweep frequency is changed and the intensity of light from the wavelength swept light source changes, the first detector can properly detect the FPN signal.

[0032] <Second embodiment> In the OCT device according to the second embodiment, the correspondence discrepancy between time and wavenumber when the wavelength swept light source sweeps the wavelength is appropriately corrected.

[0033] The OCT device according to the second embodiment includes an OCT optical system. The OCT optical system described in the first embodiment is also used in the second embodiment.

[0034] <Calculation controller> The OCT device may include an arithmetic controller that performs arithmetic processing on the detected spectral interference signal to obtain OCT data of the subject's eye. The arithmetic controller may also correct a correspondence deviation between time and wavenumber (hereinafter, referred to as a correspondence deviation) for the light emitted from the swept-wavelength light source. For example, by correcting the correspondence deviation, the inclination of the graph of the mapping state of each wavenumber component is corrected (see FIG. 12(a)). Furthermore, by correcting the correspondence deviation, the shift (parallel movement) of the graph of the mapping state of each wavenumber component is corrected (see FIG. 12(b)).

[0035] <Calibration optical system> The OCT apparatus may be provided with a calibration optical system for correcting the correspondence deviation. The calibration optical system has a wavelength-selective wavelength extraction member that extracts light of a predetermined wavelength from light included in the sweep range of the wavelength swept light source. For example, the calibration optical system detects light of a predetermined wavelength from the light swept by the wavelength swept light source through the wavelength extraction member.

[0036] For example, the wavelength selective wavelength extraction member may be provided removably in the calibration optical system. For example, in this embodiment, the spectral interference signal detected by the arithmetic controller in a state where the wavelength extraction member is inserted in the calibration optical system is used as the calibration interference signal. The arithmetic controller may correct the correspondence deviation based on the detection timing of a predetermined wavelength in the calibration interference signal.

[0037] The wavelength extraction member is retracted from the optical axis except when a correction interference signal is acquired to correct the correspondence deviation.

[0038] For example, the OCT device may be provided with a light guiding optical system that guides measurement light to the subject's eye.

[0039] For example, at least one of the FPN generating optical system and the light guiding optical system and the calibration optical system may share a portion of the optical system. In this case, at least one of the FPN generating optical system and the light guiding optical system is provided with a wavelength extraction member.

[0040] For example, the calibration optical system acquires a calibration interference signal used to correct the correspondence deviation. For example, the calibration interference signal is a spectral interference signal of the light from the wavelength swept light source via the wavelength extraction member and the reference light, which is acquired by the detector from the start of the wavelength swept light source to the end of the sweep. For example, in the calibration interference signal, a spectral interference signal of the light of a predetermined wavelength and the reference light is generated at a sampling point corresponding to the timing when the wavelength swept light source emits light of a predetermined wavelength. Note that, for example, some of the members of the calibration optical system and the OCT optical system may be shared. For example, a detector provided in the calibration optical system may be shared with a detector provided in the OCT optical system. In that case, the calibration optical system guides the light of a predetermined wavelength via the wavelength extraction member to the detector of the OCT optical system.

[0041] <Removal of correspondence deviations (calibration)> In this embodiment, a sampling point at which a spectral interference signal due to light of a predetermined wavelength and a reference light is detected in the calibration interference signal is referred to as a detection timing. For example, the arithmetic controller processes the calibration interference signal to obtain the detection timing. For example, the arithmetic controller calibrates correction information for correcting the mapping state of each wave number component based on the detection timing. For example, the arithmetic controller performs arithmetic processing using the calibrated correction information to correct the mapping state of each wave number component, thereby correcting the correspondence deviation included in the mapping state of each wave number component. In this disclosure, the arithmetic processing for calibrating the correction information is referred to as a calibration processing.

[0042] For example, the wavelength extraction member provided in the calibration optical system for extracting light of a predetermined wavelength may be a wavelength extraction member capable of extracting light of a first predetermined wavelength and light of a second wavelength different from the first wavelength. In this case, the arithmetic controller may calibrate the correction information using the detection timing at which light of the first wavelength is detected and the detection timing at which light of the second wavelength is detected. In this way, when the mapping state of each wave number component is corrected, the correction information can be calibrated so that the correspondence deviation is corrected.

[0043] For example, the calibration of the correction information may be performed before acquiring OCT data of the test eye. In this case, acquisition of the correction information based on the FPN and calibration of the correction information based on the detection timing may be performed before the OCT data of the test eye is acquired.

[0044] For example, the OCT device may include a change means for changing the optical path length difference between a measurement optical path through which the measurement light passes and a reference optical path through which the reference light passes between a predetermined first optical path length difference and a second optical path length difference.

[0045] For example, the change means may change the optical path length of the FPN generating optical system. Also, the change means may change the optical path length of the reference optical system. For example, the change means changes at least one of the optical path length of the FPN generating optical system and the optical path length of the reference optical system to change the optical path length difference.

[0046] For example, the arithmetic controller may correct the corresponding deviation based on the detection timing of a predetermined wavelength when the optical path length difference is the first optical path length difference and the detection timing of the predetermined wavelength when the optical path length difference is the second optical path length difference. For example, the arithmetic controller adds the interference signal obtained when the optical path length difference is the first optical path length difference and the interference signal obtained when the optical path length difference is the second optical path length difference. According to this, the signal intensity of the spectral interference signal generated at the detection timing of the predetermined wavelength increases. Therefore, the arithmetic controller can acquire the detection timing of the predetermined wavelength more accurately.

[0047] That is, the arithmetic controller may correct the corresponding deviation by performing a calibration process using the calibration interference signal detected by the detector when the optical path length difference is the first optical path length difference and the calibration interference signal detected by the detector when the optical path length difference is the second optical path length difference.

[0048] According to the above configuration, for example, regarding the light of the wavelength-swept light source, the deviation in the correspondence between time and wave number can be appropriately corrected, so that the OCT data of the eye to be examined can be suitably acquired.

[0049] [Embodiment] An example of an embodiment of the present disclosure will be described with reference to the drawings. FIGS. 1 to 13 are diagrams related to examples of the first and second embodiments. Note that the items classified in the following <> can be used independently or in combination.

[0050] <OCT optical system> In this embodiment, as the OCT apparatus 1, an optical coherence tomography (OCT) apparatus shown in FIG. 1 is used. The OCT apparatus 1 according to this embodiment is based on, for example, swept source OCT (SS-OCT: SWEPT Source-OCT), and includes a wavelength-swept light source 102, an OCT optical system 100, and an arithmetic controller (arithmetic control unit, hereinafter referred to as control unit) 70. In addition, the OCT apparatus 1 is provided with a memory 72, a display unit 75, a front image observation system (not shown), and a fixation mark projection system. The control unit 70 is connected to the wavelength-swept light source 102, the OCT optical system 100, the memory 72, and the display unit 75.

[0051] The OCT optical system 100 guides the measurement light to the test eye E by the light guide optical system 150. The OCT optical system 100 guides the reference light to the reference optical system 110. The OCT optical system 100 causes a detector (light receiving element) 120 to receive interference signal light obtained by interference between the measurement light reflected by the test eye E and the reference light. Furthermore, the OCT optical system 100 of this embodiment includes an FPN generating optical system 200 (details will be described later). The OCT optical system 100 also includes a calibration optical system 300 (details will be described later). In this embodiment, the FPN generating optical system 200 and the calibration optical system 300 are used together. The OCT optical system 100 may be mounted in a housing (apparatus main body) not shown, and alignment with the test eye E may be performed by three-dimensionally moving the housing with respect to the test eye E by a known alignment movement mechanism via an operating member such as a joystick.

[0052] The OCT optical system 100 employs the SS-OCT method, and uses a wavelength-tunable light source (wavelength scanning light source) that changes the emission wavelength at high speed over time as the wavelength swept light source 102. The wavelength swept light source 102 is composed of, for example, a laser medium, a resonator, and a wavelength selection filter. Examples of the wavelength selection filter include a combination of a diffraction grating and a polygon mirror, and a filter using a Fabry-Perot etalon.

[0053] In this embodiment, the swept light source 102 can change the sweep frequency. In this embodiment, the sweep frequency refers to the number of times a sweep is performed per unit time. For example, the swept light source 102 can change the sweep frequency between a predetermined first sweep frequency H1 (e.g., 200 kHz) and a predetermined second sweep frequency H2 (e.g., 25 kHz). The number of changeable sweep frequencies is not limited to two.

[0054] For example, by changing the sweep frequency of the swept light source 102, the imaging range of the OCT device 1 is changed in the depth direction.

[0055] The coupler (splitter) 104 is used as an optical splitter and splits the light emitted from the swept light source 102 into a measurement optical path and a reference optical path. The coupler 104, for example, guides the light from the swept light source 102 to an optical fiber 105 on the measurement optical path side and also guides the light to a reference optical system 110 on the reference optical path side.

[0056] The coupler (splitter) 130 splits the light (measurement light) from the optical fiber 105 into an optical path for the light guiding optical system 150 and an optical path for the FPN generating optical system 200. That is, the measurement optical path is provided with the light guiding optical system 150 and the FPN generating optical system 200. The coupler (splitter) 130 may be a beam splitter or a circulator.

[0057] <Light guide optical system> The light guiding optical system 150 is provided to guide the measurement light to the subject's eye E. The light guiding optical system 150 may sequentially include, for example, an optical fiber 152, a coupler 153, a collimator lens 154, an optical scanner 156, and an objective lens system 158. In this case, the measurement light passes through the optical fiber 152 and the coupler 153, is converted into a parallel beam by the collimator lens 154, and travels toward the optical scanner 156. The light that has passed through the optical scanner 156 is irradiated onto the subject's eye E via the objective lens system 158. The measurement light is irradiated onto both the anterior and posterior segments of the eye, and is scattered and reflected by each tissue.

[0058] The optical scanner 156 may scan the measurement light in the XY directions (transverse directions) on the subject's eye E. The optical scanner 156 is, for example, two galvanometer mirrors, and the reflection angle is arbitrarily adjusted by a driving mechanism. The light beam emitted from the wavelength swept light source 102 has its reflection (traveling) direction changed, and is scanned in an arbitrary direction on the fundus. As the optical scanner 156, for example, an acousto-optical element (AOM) that changes the traveling (deflection) direction of light, in addition to a reflection mirror (galvanometer mirror, polygon mirror, resonant scanner), may be used.

[0059] In this case, scattered light (reflected light) from the subject's eye E due to the measurement light passes through the objective lens system 158, the optical scanner 156, the collimator lens 154, the coupler 153, the optical fibers 152 to the coupler 130, and the optical fiber 112, and reaches the coupler 350. The scattered light is multiplexed with the reference light in the coupler 350 and interferes with it.

[0060] Also, for example, the light guiding optical system 150 may be provided with a shutter 151 that is insertable into and removable from the optical axis. For example, the shutter 151 is inserted into the optical axis when correction information, which will be described later, is acquired.

[0061] The shutter 151 is an example of a blocking member for blocking light originating from the light-guiding optical system 150, and is not limited thereto. For example, a light-absorbing member may be provided as the blocking means. In that case, for example, the control unit 70 controls the optical scanner 156 to guide the light incident on the light-guiding optical system 150 (or the return light from the subject's eye) to the light-absorbing member, thereby blocking the light originating from the light-guiding optical system 150.

[0062] <Reference optical system> The reference optical system 110 generates a reference light to be combined with reflected light obtained by reflection of the measurement light at the subject's eye E. The reference light passing through the reference optical system 110 is combined with light from the measurement optical path by a coupler 350 and interferes with each other. The reference optical system 110 may be a Michelson type or a Mach-Zehnder type.

[0063] In addition, an optical member for adjusting the optical path length difference between the measurement light and the reference light may be arranged in at least one of the measurement light path and the reference light path. For example, the collimator lens 154 and the coupler 153 may be moved integrally to adjust the optical path length of the measurement light, and as a result, the optical path length difference between the measurement light and the reference light may be adjusted. Of course, the optical member arranged in the reference light path may be moved to adjust the optical path length difference between the measurement light and the reference light.

[0064] <Detector> Detector 120 is provided to detect the interference between the light from the measurement optical path and the light from the reference optical path. As the detector 120, balanced detection may be performed. In this case, the detector 120 includes a plurality of light receiving elements, obtains the difference between the interference signal from the first light receiving element and the interference signal from the second light receiving element, and reduces unnecessary noise included in the interference signal. Each light receiving element is a point sensor having only one light receiving part, and for example, an avalanche photo diode is used.

[0065] <FPN Generation Optical System> The FPN generation optical system 200 generates an FPN signal. The FPN signal is used to correct the mapping information of each frequency component. In this embodiment, the first FPN signal, the second FPN signal, the third FPN signal, and the fourth FPN signal are generated by the FPN generation optical system.

[0066] As shown in FIG. 1, in this embodiment, the FPN generation optical system 200 is disposed at a position branched from the coupler (splitter) 130 to the light guiding optical system 150.

[0067] For example, the FPN generation optical system 200 includes an FPN generation member 204 for generating an FPN, a drive unit 205 for moving the position of the FPN generation member 204 in the optical axis direction, and a detector 121 for detecting the FPN. Note that the FPN generation member 204 is an optical member for generating an FPN, and for example, a gold mirror. Also, the detector 121 for detecting the FPN is shared with the detector 120 provided in the OCT optical system 100.

[0068] For example, the light that enters the FPN generation optical system 200 and passes through the FPN generation member 204 interferes with the reference light, thereby generating an FPN signal. The generated FPN signal is detected by the detector 120. Also, a control unit 70 (also serving as an image processor) described later generates an FPN on the OCT image based on the FPN signal.

[0069] For example, in this embodiment, the FPN generating optical system 200 can change the position in the depth direction at which the FPN is generated on the OCT image.

[0070] For example, the driving unit 205 moves the FPN generating member 204 in a direction parallel to the optical axis. This changes the optical distance from the origin position P0 to the FPN generating member 204. Note that the origin position P0 in this embodiment refers to a position on the optical system where an FPN is generated at the zero delay position on the OCT image when the FPN generating member 204 is disposed.

[0071] The driving unit 205 changes the position of the FPN generating member 204, thereby changing the optical path length of the FPN generating optical system 200, and therefore changing the optical path length difference between the reference optical system 110 and the FPN generating optical system 200. The position in the depth direction where the FPN is generated on the OCT image changes depending on the optical path length difference between the reference optical path and the FPN generating optical system. For this reason, the driving unit 205 can change the position in the depth direction where the FPN is generated by changing the position of the FPN generating member 204.

[0072] In addition, compared to the below-described [Modification Example] (see FIG. 15), the optical path length of the FPN generating optical system 200 can be changed without dividing the optical path, so that each FPN signal may be strong and easy to detect. In addition, since multiple FPN signals do not appear simultaneously on the OCT image, the calculation processing performed by the control unit 70 may be easy.

[0073] For example, in this embodiment, FPN signals can be generated at at least four different depth positions by the FPN generating optical system 200. The FPN signals are used when acquiring correction information for correcting the mapping state of each wave number component, which will be described later.

[0074] <Calibration optical system> In this embodiment, the calibration optical system 300 is used to correct a correspondence deviation between time and the wavelength of the swept light source 102. Note that in this embodiment, the correspondence deviation between the wavenumber of the swept light source 102 and time is referred to as a correspondence deviation.

[0075] 1, for example, the calibration optical system 300 includes a band-pass filter 301 and a notch filter 302 that are detachable from the optical axis. The band-pass filter 301 and the notch filter 302 are examples of wavelength-selective wavelength extraction members that extract light of a predetermined wavelength included in the sweep range of the wavelength swept light source 102.

[0076] For example, the bandpass filter 301 passes light in a wavelength band including the above-mentioned predetermined wavelength. For example, the notch filter 302 attenuates light in a part of the wavelength band passed by the bandpass filter 301. For example, the notch filter 302 attenuates light of wavelengths other than the predetermined wavelength among the light that passes through the bandpass filter 301. Thus, by using the bandpass filter 301 and the notch filter 302 in combination, light of the predetermined wavelength is selectively extracted.

[0077] Moreover, the bandpass filter 301 and the notch filter 302 are examples of wavelength extraction members for extracting light of a predetermined wavelength, and are not limited thereto. For example, a similar effect can be obtained by using a fiber Bragg grating as a wavelength extraction member for extracting light of a predetermined wavelength. In this case, whether or not light of a predetermined wavelength is extracted can be switched by switching between an optical path equipped with a fiber Bragg grating and an optical path not equipped with the fiber Bragg grating.

[0078] For example, in this embodiment, when the wavelength swept light source 102 performs a sweep, the bandpass filter 301 and the notch filter 302 extract light of a predetermined first wavelength and light of a second wavelength different from the light of the first wavelength.

[0079] For example, in this embodiment, the FPN generating optical system 200 and the calibration optical system 300 are used together. Alternatively, the calibration optical system 300 may be used together with the light-guiding optical system 150. In this case, the bandpass filter 301 and the notch filter 302 are provided in the light-guiding optical system 150 so as to be detachable therefrom.

[0080] For example, the band-pass filter 301 and the notch filter 302 are inserted with respect to the optical axis when acquiring a calibration interference signal, which will be described later. For example, the band-pass filter 301 and the notch filter 302 are retracted with respect to the optical axis except when acquiring a calibration interference signal.

[0081] The calibration optical system 300 may be provided in an optical path independent of other optical systems. In that case, the bandpass filter 301 and the notch filter 302 do not necessarily need to be provided so as to be detachable.

[0082] <Control Unit> 1, the control unit 70 may include a CPU (processor), a RAM, a ROM, and the like. For example, the CPU of the control unit 70 may be responsible for controlling the OCT device 1. The RAM temporarily stores various information. The ROM of the control unit 70 may store various programs, initial values, and the like for controlling the operation of the OCT device 1.

[0083] The control unit 70 may be electrically connected to a non-volatile memory (hereinafter, abbreviated to memory) 72, a display unit 75, and the like. The memory 72 may be a non-transient storage medium capable of retaining stored contents even when the power supply is cut off. For example, a hard disk drive, a flash ROM, a USB memory detachably attached to the OCT device 1, and the like may be used as the memory 72. The memory 72 may store a control program for controlling the acquisition of OCT data and the capture of OCT images. The memory 72 may also store various information related to the capture in addition to the OCT images generated from the OCT data. The display unit 75 may display the OCT images generated from the OCT data.

[0084] For example, the control unit 70 may drive a drive unit 205 provided in the FPN generating optical system 200 to control the position of the FPN generating member 204 .

[0085] For example, the control unit 70 may be connected to the swept light source 102. For example, the control unit 70 may change the sweep frequency of the swept light source 102 between a first sweep frequency H1 and a second sweep frequency H2.

[0086] For example, when the sweep frequency is a first sweep frequency H1, a tomographic image of the fundus of the subject's eye E is captured. For example, when the sweep frequency is a second sweep frequency H2, a tomographic image of the entire eyeball of the subject's eye E is captured. Note that, as a method for changing the imaging range in the depth direction according to the sweep frequency, the method described in JP 2012-75640 A can be used.

[0087] For example, a mode in which imaging is performed at a first sweep frequency H1 may be defined as a first imaging mode, and a mode in which imaging is performed at a second sweep frequency H2 may be defined as a second imaging mode. In this case, the control unit 70 may also function as a selection means for selecting an imaging mode. For example, the control unit 70 may select an imaging mode based on a signal input to the control unit 70 by an operator via an input means (e.g., a switch) not shown.

[0088] The imaging mode is not limited to a mode in which the imaging range is changed for each sweep frequency. For example, the imaging time or imaging sensitivity may be changed by changing the sweep frequency of the wavelength swept light source 102. For example, the imaging mode may be a first imaging mode in which imaging is performed at a standard sensitivity and a second imaging mode in which imaging is performed at a higher sensitivity than the first imaging mode. For example, the imaging mode may be a first imaging mode in which imaging is performed for a standard time and a second imaging mode in which imaging is performed for a shorter time than the first imaging mode.

[0089] The control unit 70 may also control the insertion and removal of the shutter 151. Furthermore, the control unit 70 may also control the insertion and removal of the bandpass filter 301 and the notch filter 302.

[0090] The control unit 70 may also be used as an image processor that performs arithmetic processing on the spectral interference signal detected by the detector 120 to obtain OCT data and generate an OCT image.

[0091] For example, the control unit 70 may also function as an arithmetic controller that obtains correction information based on the FPN signal in the OCT data (details will be described in [Operation]). In this case, the memory 72 may store an arithmetic processing program that obtains correction information for correcting the mapping state of each wave number component.

[0092] For example, the control unit 70 may also function as an arithmetic controller that calibrates the correction information based on the calibration interference signal (details will be described in [Operation]). In this case, the memory 72 may store a calibration processing program for calibrating the correction information.

[0093] [Operation] The OCT device 1 having the above-mentioned configuration performs calibration to correct the mapping state of each wave number component and the correspondence deviation. For example, the control of the control unit 70 when the calibration is performed will be described with reference to Fig. 2. Fig. 2 is a flow chart of the control performed by the control unit 70 when the calibration is performed.

[0094] In this embodiment, the calibration involves obtaining correction information using FPN (step S110) and calibrating the correction information using a calibration interference signal (step S120).

[0095] For example, the calibration is performed before acquiring OCT data of the subject's eye E. In this case, correction information obtained by the calibration, which will be described later, may be stored in the memory 72. This can eliminate the time required for performing the calibration during imaging, and therefore allows corrected OCT data to be acquired in a shorter time.

[0096] The calibration in this embodiment will be described in detail below.

[0097] <S110: Acquisition of Correction Information> In this embodiment, the control unit 70 acquires correction information for correcting the mapping state of each frequency component based on the FPN generated by the FPN generation optical system 200. For example, when obtaining OCT data of the eye to be examined E after calibration, by performing arithmetic processing using the correction information, OCT data in which the mapping state of each frequency component is corrected is obtained.

[0098] Note that in this embodiment, the correction of the mapping state of each frequency component includes correcting so that the correspondence between the sampling point and the optical frequency (2π / λ) in the OCT data becomes linear.

[0099] Also, in this embodiment, the correction of the mapping state of each frequency component includes correcting so that the dispersion component included in the OCT data is removed.

[0100] FIG. 3 is an example of the mapping information of each frequency component obtained based on the FPN signal. FIG. 3(a) is the mapping information of each frequency component obtained based on the first FPN signal. FIG. 3(b) is the mapping information of each frequency component obtained based on the third FPN signal. FIG. 4 is a diagram for explaining that the frequency mapping state of each frequency component is corrected based on the correction information.

[0101] For example, when the sweep frequency of the wavelength-sweeping light source 102 changes, the mapping state of each frequency component and the dispersion component included in the signal component may change.

[0102] In this embodiment, in order to appropriately correct the mapping state of each frequency component even when the sweep frequency is changed, the control unit 70 obtains correction information for each sweep frequency. For example, the control unit 70 obtains first correction information to correct the mapping state of each frequency component when the sweep frequency is the first sweep frequency H1, and obtains second correction information to correct the mapping state of each frequency component when the sweep frequency is the second sweep frequency H2.

[0103] The control performed by the control unit 70 when acquiring the first correction information and the second correction information will be described based on the flowchart in FIG. 5. FIG. 5 is a flowchart of the control performed by the control unit 70 as the acquisition of correction information (step S110).

[0104] <S111: Acquisition of the first correction information> For example, the control unit 70 acquires correction information using at least two FPNs among the FPNs generated by the FPN generation optical system 200. Further, the control unit 70 acquires correction information for each sweep frequency of the wavelength sweep light source 102. In the present embodiment, when the sweep frequency of the wavelength sweep light source 102 is the first sweep frequency H1, the control unit 70 performs arithmetic processing based on the first FPN signal and the third FPN signal to acquire the first correction information. The FPN generation optical system 200 and the generated FPN signals in this case will be described with reference to FIGS. 6 and 7. FIG. 6 is a diagram for explaining the arrangement of the FPN generation member 204 of the FPN generation optical system 200. FIG. 7 is a diagram for explaining the FPN signal generated by the FPN generation optical system 200.

[0105] In the present embodiment, the drive unit 205 moves the FPN generation member 204 in the optical axis direction to change the optical distance from the origin position P0 to the FPN generation member 204. For example, when the FPN generation member 204 is arranged at the first distance D1, the first FPN signal is generated. Similarly, when the FPN generation member 204 is arranged at the second distance D2, the second FPN signal is generated; when the FPN generation member 204 is arranged at the third distance D3, the third FPN signal is generated; and when the FPN generation member 204 is arranged at the fourth distance D4, the fourth FPN signal is generated.

[0106] Note that the first distance D1, the second distance D2, the third distance D3, and the fourth distance D4 are positions determined experimentally in advance.

[0107] First, the control unit 70 controls the driving unit 205 to move the position of the FPN generating member 204 so that the distance from the origin position P0 becomes a predetermined first distance D1 (see FIG. 6).

[0108] For example, in this embodiment, the signal frequency of the first FPN signal is set to the first signal frequency f1. The first signal frequency f1 is preferably a low frequency that does not fall within the zero delay position when the first FPN signal is Fourier transformed. This is because, when detecting the FPN signal from the spectral interference signal, the lower the frequency of the FPN signal, the less noise there is and the more accurately it can be analyzed.

[0109] When the FPN generating member 204 is positioned at a first distance D1, the swept light source 102 emits light at a first swept frequency H1, and the detector 120 detects a spectral interference signal that includes a first FPN signal.

[0110] The control unit 70 analyzes the generated OCT image to obtain φ(k) in the spectral interference signal at the position corresponding to the first FPN. k is the wave number, and φ(k) is the change in phase φ of the spectral interference signal according to the swept wavelength (wave number). For example, wave number mapping information is information that indicates the correspondence between k and φ(k).

[0111] φ(k) may be expressed as a function with the horizontal axis being the wave number k and the vertical axis being the phase φ. Polynomial fitting may be performed on φ(k) in the wave number k region where the signal intensity (amplitude) is large, and φ(k) in the wave number k region where the signal intensity is small may be obtained by extrapolation or interpolation. For example, φ(k) may be obtained from the Arc Tangent of the ratio between the real part RealF and the imaginary part ImagF of the Fourier transform value (intensity value) F at the depth position corresponding to FPN. Here, the Arc Tangent process calculates the arc tangent of the ratio between the real part and the imaginary part of the Fourier transform value to obtain φ(k).

[0112] As a method for obtaining φ(k) from the FPN and a method for obtaining mapping information of each wave number component from the FPN, the methods described in JP-A-2013-156229 and JP-A-2015-68775 can be used.

[0113] For example, in this embodiment, the control unit 70 processes the first FPN to obtain the first wave number mapping information φ1(k) (see FIG. 3(a)).

[0114] The control unit 70 then moves the FPN generating member 204 a third distance D3 (see FIG. 6).

[0115] Here, the signal frequency of the third FPN signal generated by the FPN generating member 204 placed at the third distance D3 is set as the third signal frequency f3. The third signal frequency f3 is a signal frequency different from the first signal frequency f1. For example, the third FPN by the third signal frequency f3 is generated at a position deeper in the depth direction than the tomographic image of the test eye E. Therefore, the tomographic image of the test eye E and the third FPN do not overlap, and the FPN signal can be acquired with high accuracy. Note that the third signal frequency f3 is not limited to this. For example, when the return light from the light guiding optical system 150 is blocked by the shutter 151, the tomographic image of the test eye E does not appear on the OCT image. Therefore, it is not necessarily necessary to generate the FPN at a position deeper in the depth direction than the tomographic image of the test eye E.

[0116] For example, the third FPN may be generated at a position that can be distinguished from the first FPN when the control unit 70 obtains mapping information for each wave number component. For example, the third FPN is generated at a position 1 mm or more away from the first FPN in the depth direction.

[0117] When the FPN generating member 204 is disposed at a third distance D3, the swept light source 102 emits light at the first swept frequency H1, and the detector 120 acquires a spectral interference signal including the third FPN signal. The controller 70 then processes the third FPN in the same manner as the first FPN to obtain third wavenumber mapping information φ3(k) (see FIG. 3(b)).

[0118] Next, the control unit 70 obtains difference information Δφ1-3(k) between the first wave number mapping information φ1(k) and the third wave number mapping information φ3(k) as the first correction information (see FIG. 4). Note that the difference information may be obtained as phase difference information for each wave number component. When obtaining the difference information Δφ(k), since the third FPN has a faster phase advance, the difference information may be obtained by Δφ1-3(k)=φ3(k)-φ1(k). By obtaining the difference information, the dispersion component included in the mapping information for each wave number component can be canceled.

[0119] When the wavelength-sweeping light source 102 sweeps the wavelength at the first sweeping frequency H1, the control unit 70 corrects the mapping state of each wave number component based on the first correction information (see FIG. 4). Note that, as a method for correcting the mapping state of each wave number component from the difference information of the mapping information of the wave number component, the method described in Japanese Patent Application Laid-Open No. 2018-124188 can be used.

[0120] <S112: Acquisition of Second Correction Information> As described above, in the present embodiment, the control unit 70 obtains second correction information in order to correct the mapping state of each wave number component when the wavelength-sweeping light source 102 sweeps the wavelength at the second sweeping frequency H2.

[0121] Here, when the wavelength is swept at the second sweeping frequency H2, the first FPN signal may not be appropriately acquired. The reason for this will be described in detail with reference to FIG. 8. FIG. 8 is a diagram for explaining that the signal frequency at which the FPN signal is detected changes for each sweeping frequency. FIG. 8(a) shows the Fourier transform of the first FPN signal in the case of the first sweeping frequency H1. FIG. 8(b) shows the Fourier transform of the first FPN signal in the case of the second sweeping frequency H2.

[0122] For example, when the sweeping frequency changes, the signal frequency at which the FPN is detected also changes.

[0123] For example, when the sweep frequency is a first sweep frequency H1 (for the sake of explanation, it is assumed to be 200 kHz), the first FPN signal is detected as an interference signal with a signal frequency of 100 MHz.

[0124] Here, for example, when the sweep frequency is changed to a second sweep frequency H2 (25 kHz for the sake of explanation), the sweep frequency becomes 25 / 200=1 / 8 times. Therefore, in the case of the second sweep frequency H2, the first FPN signal is detected as an interference signal with a signal frequency of 100 MHz×1 / 8=12.5 MHz. Note that the numerical values ​​used in the calculation are values ​​used for convenience of explanation, and are not limited to these.

[0125] As in the above example, when the sweep frequency is changed from the first sweep frequency H1 to the second sweep frequency H2 which is lower than the first sweep frequency H1, the signal frequency at which FPN is detected becomes lower.

[0126] For example, a first FPN signal detected at a first signal frequency f1 at a first sweep frequency H1 is detected at a second sweep frequency H2 at a signal frequency H2 / H1 times the first signal frequency f1 (see FIG. 7). Similarly, a third FPN signal detected at a third signal frequency f3 at a first sweep frequency H1 is detected at a second sweep frequency H2 at a signal frequency H2 / H1 times the signal frequency corresponding to the third signal frequency f3.

[0127] As described above, when the sweep frequency is the first sweep frequency H1, the lower the first signal frequency f1, the easier the analysis. On the other hand, for example, when the sweep frequency is set to the second sweep frequency H2, the lower the first signal frequency f1, the lower the frequency of the envelope EV1 of the peak of the first FPN signal will be. Therefore, the possibility that the envelope EV1 of the peak of the first FPN signal will fall within the zero delay region increases (see FIG. 8(b)). The zero delay region will be described below.

[0128] In this embodiment, a filter 71 is provided between the detector 120 and the control unit 70. This filter 71 removes electrical DC components to protect the control unit 70. For example, the filter 71 removes signals in a region from zero delay to a predetermined frequency (e.g., 10 MHz). In this embodiment, the region removed by the filter 71 is referred to as the zero delay region.

[0129] For example, in this embodiment, in the case of the second sweep frequency H2, the peak envelope EV1 of the first FPN signal may fall in the zero delay region and be cut by the filter 71. In this case, it is difficult to obtain appropriate correction information from the first FPN signal.

[0130] As described above, when acquiring the second correction information, the first FPN signal may not be properly acquired. Similarly, when acquiring the second correction information, the third FPN signal may not be properly acquired.

[0131] Therefore, in this embodiment, when the sweep frequency of the wavelength swept light source 102 is the second sweep frequency H2, the control unit 70 obtains second correction information by performing arithmetic processing based on the second FPN signal and the fourth FPN signal.

[0132] For example, the control unit 70 changes the position of the FPN generating member 204 to a second distance D2 and generates a second FPN signal. In this embodiment, the second FPN signal is a signal frequency that is not cut by the filter 71 when the sweep frequency is set to the second sweep frequency H2. Fig. 9 shows a Fourier transform of the second FPN signal when the sweep frequency of the wavelength swept light source 102 is the second sweep frequency H2.

[0133] For example, when the sweep frequency is the second sweep frequency H2, the signal frequency at which the second FPN signal is detected is the signal frequency (e.g., 100 MHz) at which the first FPN signal is detected when the sweep frequency is the first sweep frequency H1 (see FIG. 7). Note that the signal frequency at which the second FPN signal is detected is not limited to this, and it is sufficient that the envelope EV2 of the peak formed when the second FPN signal is Fourier transformed is present on the higher frequency side than the zero delay region.

[0134] When the position of FPN generating member 204 is changed to second distance D2, light is emitted from swept light source 102, and detector 120 acquires a spectral interference signal including a second FPN signal. Thereafter, controller 70 processes the second FPN signal in the same manner as in step S111 to obtain second wavenumber mapping information φ2(k).

[0135] Next, the control unit 70 drives the driving unit 205 to move the FPN generating member 204 to a fourth distance D4 so that a fourth FPN is generated. For example, when the sweep frequency is the second sweep frequency H2, the signal frequency at which the fourth FPN signal is detected is the signal frequency at which the third FPN signal is detected when the sweep frequency is the first sweep frequency H1 (see FIG. 7). Note that the signal frequency at which the fourth FPN signal is detected is not limited to this, and it is sufficient that the envelope of the peak formed when the fourth FPN signal is Fourier transformed is present on the high frequency side of the zero delay region.

[0136] Thereafter, the control unit 70 processes the fourth FPN signal in the same manner as in step S111 to obtain the fourth wave number mapping information φ4(k).

[0137] Furthermore, the control unit 70 obtains, as second correction information, difference information Δφ2-4(k) between the second wave number mapping information φ2(k) and the fourth wave number mapping information φ4(k).

[0138] When the wavelength-sweeping light source 102 sweeps the wavelength at the second sweeping frequency H2, the control unit 70 corrects the mapping state of each frequency component based on the second correction information.

[0139] According to the above steps S111 and S112, the first correction information for correcting the mapping state of each frequency component when the sweeping frequency is the first sweeping frequency H1, and the mapping information of each frequency component when the sweeping frequency is the second sweeping frequency H2 are obtained. The second correction information for correction is obtained.

[0140] When the control unit 70 acquires OCT data, by performing arithmetic processing based on the first correction information or the second correction information, the non-linearity and the dispersion component of each frequency component can be corrected for the mapping state of each frequency component (see FIG. 4).

[0141] When acquiring the correction information, the control unit 70 may insert the shutter 151 into the light guiding optical system 150. According to this, since the light derived from the light guiding optical system 150 can be suppressed from affecting the correction information, the correction information can be suitably acquired. The light derived from the light guiding optical system 150 is, for example, scattered light (return light) from the eye E to be examined.

[0142] <S120: Calibration of Correction Information> Next, the control unit 70 corrects the correspondence deviation using the calibration optical system 300. In this embodiment, as described above, the correspondence deviation refers to the deviation of the correspondence between time and frequency with respect to the light emitted during the wavelength sweep of the wavelength-sweeping light source 102. For example, the correspondence deviation may occur due to environmental factors such as aging and temperature.

[0143] For example, the correction information obtained in step S110 may be obtained based on the FPN obtained in a state where this correspondence deviation exists. In this case, in the spectral interference signal acquired by the detector 120, the values of the correction information and the wavelength (or frequency) are shifted, so it is difficult to perform appropriate correction.

[0144] For example, in this embodiment, the control unit 70 performs calibration on the correction information. For example, when acquiring the OCT data of the eye to be examined in this embodiment, the control unit 70 performs arithmetic processing using the calibrated correction information. As a result, the corresponding deviation included in the mapping state of each frequency component is corrected. In the present disclosure, the arithmetic processing for calibrating the correction information is referred to as calibration processing.

[0145] The control of the control unit 70 for calibrating the correction information will be described with reference to FIGS. 10, 11, and 12. FIG. 10 is a flowchart of the control performed by the control unit 70 as calibration of the correction information (step S120). FIG. 11 is a diagram for explaining that the corresponding deviation in the mapping state of each frequency component is corrected by the calibrated correction information. FIG. 11 shows the mapping information of each frequency component when arithmetic processing is performed using the correction information before calibration and the mapping information of each frequency component when arithmetic processing is performed using the correction information after calibration. FIG. 12 is a diagram for explaining that the corresponding deviation included in the frequency mapping state is corrected by performing calibration.

[0146] For example, in this embodiment, due to the corresponding deviation, a change in the slope of the graph occurs between the graph of the mapping information of each frequency component based on the correction information before calibration shown in FIG. 12(a) and the graph of the mapping information of each frequency component based on the correction information after calibration. For example, in this embodiment, due to the corresponding deviation, a shift (parallel movement) of the graph occurs between the graph of the mapping information of each frequency component based on the correction information before calibration shown in FIG. 12(b) and the graph of the mapping information of each frequency component based on the correction information after calibration.

[0147] <S121: Insertion of Band-Pass Filter> First, the control unit 70 inserts the band-pass filter 301 and the notch filter 302 with respect to the optical axis of the calibration optical system 300 (which is also used as the FPN generation optical system 200).

[0148] In this embodiment, the band-pass filter 301 and the notch filter 302 selectively extract light of a predetermined first wavelength included in the sweep range of the wavelength-sweeping light source 102 and light of a second wavelength different from the first wavelength.

[0149] <S122: Acquisition of Calibration Interference Signal> When the wavelength-sweeping light source 102 performs a sweep at the first sweep frequency H1 with the band-pass filter 301 and the notch filter 302 inserted in the calibration optical system 300, the swept light passes through the calibration optical system 300, and light of the first wavelength and light of the second wavelength are extracted.

[0150] The extracted light is combined with the reference light by the coupler 350 and detected by the detector 120 as a spectral interference signal. In this embodiment, the spectral interference signal formed by the extracted light and the reference light is referred to as a calibration interference signal. For example, the spectral interference signal formed by the extracted light and the reference light when the sweep frequency of the wavelength-sweeping light source sweeps at the first sweep frequency H1 is referred to as a first calibration interference signal. For example, the first calibration interference signal includes a calibration interference signal G1 formed by the light of the first wavelength and the reference light and a calibration interference signal G2 formed by the light of the second wavelength and the reference light.

[0151] Note that in this embodiment, the band-pass filter 301 and the notch filter 302 are retracted with respect to the optical axis of the FPN generation optical system 200 except when acquiring the calibration interference signal.

[0152] The calibration interference signal will be described with reference to FIG. 13. Note that FIG. 13 is a diagram showing an example of the first calibration interference signal.

[0153] As the first calibration interference signal, a calibration interference signal G1 formed by the light of the first wavelength and the reference light is detected at a sampling point (first detection timing) T1 corresponding to the timing when the wavelength-sweeping light source 102 emits the light of the first wavelength.

[0154] For example, it is technically difficult to extract only the light of the first wavelength using the bandpass filter 301 and the notch filter 302. For this reason, the calibration interference signal G1 contains a component of an interference signal due to the light of the first wavelength and the reference light, as well as a component of an interference signal due to light of a wavelength other than the first wavelength and the reference light.

[0155] For example, in this embodiment, the closer the wavelength of light is to the first wavelength, the more easily it passes through the bandpass filter 301 and the notch filter 302. Therefore, for example, the calibration interference signal G1 becomes an interference signal with a mountain-shaped waveform whose peak is the interference signal between the light of the first wavelength and the reference light.

[0156] Similarly, at a sampling point (second detection timing) T2 corresponding to the timing at which the wavelength swept light source 102 emits light of the second wavelength, a calibration interference signal G2 due to the light of the second wavelength and the reference light is detected.

[0157] In addition, when acquiring the first calibration interference signal, for example, the FPN generating member 204 of the FPN generating optical system 200 is disposed at a first distance D1. In this embodiment, the optical path length difference between the optical path length of the calibration optical system 300 and the optical path length of the reference optical system 110 when the FPN generating member 204 is disposed at the first distance D1 is set as a first optical path length difference. Furthermore, it should be noted that the first distance D1 is an example of the position of the FPN generating member 204, and is not limited thereto.

[0158] After acquiring the first calibration interference signal, the control unit 70 then acquires the second calibration interference signal. For example, the control unit 70 drives the drive unit 205 to move the FPN generation member 204 from the first distance D1 to another distance. For example, the control unit 70 moves the FPN generation member 204 to the second distance D2.

[0159] For example, in the present embodiment, when the FPN generation member 204 is at the second distance D2, the optical path length difference between the optical path length of the calibration optical system 300 and the optical path length of the reference optical system 110 is defined as the second optical path length difference. Note that the second distance D2 is an example of the distance at which the FPN generation member 204 is disposed, and is not limited thereto.

[0160] For example, in the present embodiment, the driving unit 205 also serves as a changing means for changing the optical path length difference between the reference optical path and the measurement optical path.

[0161] When the position of the FPN generation member 204 is moved to the second distance D2, the wavelength-sweeping light source 102 performs sweeping at the first sweeping frequency H1. As a result, the detector 120 detects a second calibration interference signal in the same manner as the first calibration interference signal.

[0162] Here, when detecting the second calibration interference signal, since the wavelength is swept at the same first sweeping frequency H1 as when obtaining the first calibration interference signal, the timing at which the light of the first wavelength is emitted is also the same. For this reason, on the second calibration interference signal, a calibration interference signal G1 having a waveform different from that of the first calibration interference signal is generated at the same first detection timing T1 as the first calibration interference signal. Similarly, on the second calibration interference signal, a calibration interference signal G2 having a waveform different from that of the first calibration interference signal is generated at the same detection timing as the first calibration interference signal.

[0163] Note that in the present embodiment, when the acquisition of the calibration interference signal is completed, the control unit 70 retracts the band-pass filter 301 and the notch filter 302 from the calibration optical system 300.

[0164] <S123: Acquisition of Detection Timing> A method for acquiring the detection timing will be described with reference to FIG. 14. FIG. 14 is a diagram showing the waveform of the calibration interference signal G1.

[0165] In this embodiment, the swept light source 102 outputs a sweep start signal at the timing of starting the sweep to the controller 70. For example, the controller 70 sets the sampling point of the detector 120 at the timing when the sweep start signal is input from the swept light source 102 as a sweep start sampling point T0.

[0166] In this embodiment, for example, the first detection timing T1 and the second detection timing T2 are determined based on the sampling point T0 at the start of the sweep.

[0167] For example, the control unit 70 determines a sampling point (first detection timing) T1 at which the calibration interference signal G1 is detected based on the first calibration interference signal and the second calibration interference signal. For example, the first detection timing T1 is a sampling point at which a peak of the calibration interference signal G1 exists. For example, the first detection timing T1 is a sampling point at which an interference signal due to the light of the first wavelength and the reference light exists.

[0168] Here, depending on the optical path length difference between the reference optical path and the measurement optical path, the signal intensity of the calibration interference signal G1 may be low. For example, the calibration interference signal G1 in this case is set as the calibration interference signal G1.1 (see FIG. 14). For example, when the signal intensity of the spectral interference signal of the first wavelength light and the reference light is low, it may be difficult to detect the peak. In this case, since the peak cannot be detected appropriately, the control unit 70 may not be able to accurately determine the first detection timing T1.

[0169] For this reason, in this embodiment, the control unit 70 processes a plurality of calibration interference signals to increase the signal intensity of the spectral interference signal produced by the light of the first wavelength and the reference light.

[0170] For example, in this embodiment, for the first calibration interference signal and the second calibration interference signal, the absolute values are taken and then averaged. According to this, the signal intensities of the calibration interference signal G1 are cumulatively added. Therefore, the control unit 70 can accurately detect the peak. Thus, the control unit 70 can accurately obtain the first detection timing T1.

[0171] Note that the calibration interference signal used for the calibration process is not limited to the first calibration interference signal and the second calibration interference signal. For example, the larger the number of calibration interference signals used for the calibration process, the more the signal intensity of the spectral interference signal formed by the light of the first wavelength and the reference light can be increased. Therefore, it becomes easier to detect the peak, and the first detection timing T1 can be accurately obtained.

[0172] For example, the method for obtaining the first detection timing T1 is not limited to this. For example, the sampling point when the signal intensity of the interference signal increases by a predetermined value or more may be used as the first detection timing T1. That is, the sampling point at which the peak rises in the first calibration interference signal may be used as the first detection timing T1. Note that it may also be the sampling point when the signal intensity of the interference signal decreases by a predetermined value or more. That is, the sampling point at which the peak falls in the calibration interference signal may be used as the first detection timing T1.

[0173] Similarly to the first detection timing T1, the control unit 70 detects the sampling point (second detection timing) T2 at which the calibration interference signal G2 is detected.

[0174] <S124: Acquisition of Corresponding Deviation> The control unit 70 detects the corresponding deviation and obtains the number ΔT1-2 of sampling points included between the first detection timing T1 and the second detection timing T2 (see FIG. 13).

[0175] For example, the control unit 70 determines the amount of change between this value of ΔT1-2 and a previously determined value. For example, the previously determined value is the value of ΔT1-2 determined when the OCT device 1 is shipped from the factory. Note that the previously determined value is not limited to this example, and may be any value of ΔT1-2 obtained before this calibration.

[0176] For example, if the value of ΔT1-2 has decreased, the time from when the light of the first wavelength is emitted until when the light of the second wavelength is emitted has become shorter. Therefore, it is considered that the sweep frequency of the wavelength swept light source 102 has increased from the intended sweep frequency. On the other hand, if the value of ΔT1-2 has increased, it is considered that the sweep frequency of the wavelength swept light source 102 has decreased from the intended sweep frequency.

[0177] For example, the control unit 70 can correct the deviation in the sweep frequency of the wavelength swept light source 102 by correcting the value of ΔT1-2. To explain this with reference to a diagram, the slope of the graph of the mapping state of each wave number component is corrected (see FIG. 12(a)).

[0178] Also, for example, after completing correction of the sweep frequency, the control unit 70 calculates the amount of change between the value of the number of sampling points ΔT0-1 between sampling point T0 where the sweep is started and sampling point T1 and a previously calculated value. This allows the sweep frequency to be corrected and the difference in timing at which light of a predetermined wave number is detected to be calculated. This makes it possible to calculate the change in the wavelength (wave number) at which the wavelength swept light source 102 starts sweeping.

[0179] For example, if the value of ΔT0-1 decreases when the sweep speed is corrected, the wavelength at the start of the wavelength sweep is considered to have increased. For example, if the value of ΔT0-1 increases when the sweep speed is corrected, the wavelength (wave number) at the start of the wavelength sweep is considered to have decreased.

[0180] For example, the control unit 70 can correct the wavelength deviation when the wavelength-sweeping light source 102 starts sweeping by correcting the change amount of ΔT0-1. Explaining with reference to a figure, the shift (parallel movement) of the graph of the mapping state of each frequency component is corrected (see Fig. 12(b)). Note that not limited to ΔT0-1, even if calculations are performed using the number of sampling points ΔT0-2 between the sampling point T0 and the sampling point T2, similarly, the change in the wavelength (frequency) at which the wavelength-sweeping light source 102 starts sweeping can be obtained.

[0181] <S125: Correction of corresponding deviation> The control unit 70 corrects the first correction information so that the change amount between the value of ΔT1-2 and the previously obtained value is corrected. According to this, the slope of the graph of the mapping state of each frequency component is corrected (see Fig. 12(a)).

[0182] Also, the control unit 70 corrects the first correction information so that the change amount between the value of ΔT0-1 and the previously obtained value is corrected. According to this, the shift (parallel movement) of the graph of the mapping state of each frequency component is corrected.

[0183] Thereby, in the later-described imaging (S200), the mapping state of each frequency component with the corresponding deviation corrected can be acquired (see Fig. 11).

[0184] Also, the control unit 70 corrects the corresponding deviation by replacing the first sweeping frequency H1 with the second sweeping frequency H2 and executing steps S121 to S125 for the second correction information as well.

[0185] Through the above step S120, the corresponding deviation is corrected for the mapping state of each frequency component (see Fig. 11).

[0186] Also, since the control unit 70 can acquire the change over time of the wavelength sweep of the wavelength-sweeping light source 102 by directly analyzing the spectral interference signal without going through an OCT image or the like, the deviation can be corrected with high accuracy.

[0187] As described above, in this embodiment, the control unit 70 performs calibration by executing steps S110 and S120. As a result, calibrated correction information is acquired for each sweep frequency. The control unit 70 performs arithmetic processing using the calibrated correction information to acquire OCT data of the subject's eye.

[0188] For example, the control unit 70 retracts the shutter 151 with respect to the optical axis and then captures an image of the subject's eye E. For example, as described in [Configuration], the range to be captured is changed for each sweep frequency of the swept light source 102. For example, when light is emitted from the swept light source 102, a spectral interference signal between the reference light and the return light from the subject's eye E is detected by the detector 120.

[0189] For example, the first correction information is used in arithmetic processing of the spectral interference signal obtained when the sweep frequency of the wavelength swept light source 102 is a first sweep frequency H1, and the second correction information is used in arithmetic processing of the spectral interference signal obtained when the sweep frequency of the wavelength swept light source 102 is a second sweep frequency H2.

[0190] Specifically, for example, when the sweep frequency of the swept light source 102 is a first sweep frequency H1, the control unit 70 acquires OCT data based on the first correction information calculated in step S110 and calibrated in step S120. When the sweep frequency of the swept light source 102 is a second sweep frequency H2, the control unit 70 acquires OCT data based on the second correction information calculated in step S110 and calibrated in step S120.

[0191] This makes it possible to appropriately correct the mapping state of each wave number component in accordance with the sweep frequency of the wavelength swept light source 102, thereby making it possible to suitably acquire OCT data.

[0192] In addition, the method described in JP 2018-124188 A can be used as a method for applying correction information to the calculation processing of the spectral interference signal and acquiring OCT data.

[0193] [Variations] For example, in the present embodiment, the bandpass filter 301 and the notch filter 302 are provided in the FPN generating optical system 200, but for example, the bandpass filter 301 and the notch filter 302 may be provided in the light-guiding optical system 150. In this case, the calibration optical system 300 is also used as the light-guiding optical system 150. Furthermore, when obtaining a calibration interference signal with this configuration, the detector 120 detects an interference signal derived from the light originating from the calibration optical system 300 (light-guiding optical system 150), the light of the FPN generating optical system 200, and the reference light. Therefore, the control unit 70 changes the position of the FPN generating member 204 of the FPN generating optical system 200, so that a first calibration interference signal and a second calibration interference signal can be acquired.

[0194] For example, in this embodiment, the first and second calibration interference signals are used to correct the correspondence error in step S120, but the interference signal used to correct the correspondence error may be only the first calibration interference signal, which reduces the time required to correct the correspondence error.

[0195] Furthermore, in order to correct the correspondence deviation, a further calibration interference signal may be used in addition to the first calibration interference signal and the second calibration interference signal. In that case, for example, in step S122, the control unit 70 drives the driving unit 205 to change the position of the FPN generating member 204, and then the wavelength is swept by the wavelength swept light source 102 to obtain a calibration interference signal. Furthermore, by using more calibration interference signals, the position of the peak can be found more accurately in step S124, and therefore the correspondence deviation can be corrected with high accuracy.

[0196] For example, in this embodiment, the correction information is calibrated based on the calibration interference signal to correct the correspondence deviation, but the correspondence deviation may be corrected by performing calibration on the OCT data of the subject's eye E, for example. In this case, for example, the control unit 70 performs a process similar to the calibration process performed on the correction information in step S125. The calibration may also be performed on the OCT data of the subject's eye E. In this case, the calibration may be performed between the acquisition of the OCT data of the subject's eye E and the generation of the OCT image.

[0197] For example, in this embodiment, a case has been described in which the position of the FPN generating member 204 is changed by driving the driving unit 205 in order to generate an FPN at a different position, but the method of generating an FPN at a different position is not limited to this.

[0198] 15, FPN generation optical system 200 may be provided with a plurality of FPN generating members to generate FPNs at different positions. For example, when generating four FPNs, FPN generating member 204a may be disposed at a position corresponding to first distance D1 in this embodiment, FPN generating member 204b may be disposed at a position corresponding to second distance D2, FPN generating member 204c may be disposed at a position corresponding to third distance D3, and FPN generating member 204d may be disposed at a position corresponding to fourth distance D4. In this case, optical path splitting members (e.g., beam splitters) 203a, 203b, and 203c may be provided to guide light to each of the FPN generating members.

[0199] Also, for example, the position where the FPN is generated may be changed by changing the optical path length of the reference optical system 110. FIG. 16 shows an OCT optical system in which a reference mirror 114 is used in the reference optical system 110. In this case, the light emitted from the wavelength swept light source 102 is split into a measurement optical path and a reference optical path by a coupler (splitter) 104. The light incident on the reference optical system 110 is guided to an optical fiber 117 by a circulator 113, reflected by the reference mirror 114, and incident on a coupler 351. The light incident on the measurement optical path passes through a light guiding optical system 150 (and the FPN generating optical system 200) and an optical fiber 112, and then incident on the coupler 351. The light originating from the reference optical path and the light originating from the measurement optical path are combined by the coupler 351, and interference is detected by a detector 120.

[0200] For example, the reference mirror 114 is moved in the optical axis direction by the driver 115, and the optical path length of the reference optical system 110 is changed. This changes the optical path length difference between the optical path length of the reference optical system and the optical path length of the FPN generation optical system 200, and changes the position where the FPN is generated. The driver 115 may have a configuration similar to that of the driver 205 described above.

[0201] For example, in this case, the origin position P0 is the position of the reference mirror where FPN occurs at the zero delay position of the OCT image.

[0202] Also, for example, the optical distance from the origin position P0 to the reference mirror 114 may be changed by the driving unit 115 between a first distance D1 at which a first FPN signal is generated, a second distance D2 at which a second FPN signal is generated, a third distance D3 at which a third FPN signal is generated, and a fourth distance D4 at which a fourth FPN signal is generated. In this way, the optical path length of the reference light is changed.

[0203] The method of changing the optical path length of the reference optical path is not limited to this. For example, the reference optical path may be provided with a plurality of optical fibers having different lengths, and the FPN generated may be changed depending on the length of the optical fibers through which the reference optical path passes.

[0204] In this embodiment, a case has been described in which the first correction information corresponding to the first sweep frequency H1 and the second correction information corresponding to the second sweep frequency are acquired in step S110. However, for example, the first correction information and the second correction information do not necessarily have to be obtained during the same calibration.

[0205] Also, for example, the configuration may be such that first correction information is acquired when a first shooting mode in which shooting is performed at a first sweep frequency is performed, and second correction information is acquired when a second shooting mode in which shooting is performed at a second sweep frequency is performed.

[0206] In addition, in this embodiment, the case has been described in which the acquisition of correction information for each sweep frequency (step S110) and the calibration of the correction information (step S120) are performed as a series of steps as the calibration, but the acquisition of correction information for each sweep frequency and the calibration of the correction information do not necessarily need to be performed during the same calibration. For example, the acquisition of correction information may be performed as the calibration, but the calibration of the correction information may not be performed. Similarly, the calibration may be performed as the calibration, but the acquisition of correction information may not be performed. In this case, the control unit 70 may calibrate the correction information that has been acquired before the calibration (for example, the correction information acquired at the time of shipment from the factory) as the calibration of the correction information.

[0207] Furthermore, for example, when the OCT device 1 is configured to acquire correction information for each sweep frequency but not to calibrate the correction information, the calibration optical system 300 (the bandpass filter 301 and the notch filter 302) may be omitted.

[0208] When acquiring the correction information, the control unit 70 may insert the shutter 151 in the light-guiding optical system 150. This can prevent the light originating from the light-guiding optical system 150 from affecting the correction information, so that the correction information can be acquired suitably. The light originating from the light-guiding optical system 150 is, for example, scattered light (return light) from the subject's eye E.

[0209] Furthermore, in this embodiment, when acquiring the correction information, the band-pass filter 301 and the notch filter 302 are retracted with respect to the optical axis of the FPN generation optical system 200. This allows the FPN signal to be acquired without being affected by the band-pass filter 301 and the notch filter 302, and therefore the correction information can be acquired.

[0210] The intensity of the light emitted from the swept light source 102 varies based on the swept frequency.

[0211] 17, the FPN generation optical system 200 may be provided with a light intensity adjuster 209. The light intensity adjuster 209 adjusts the intensity of the light originating from the FPN generation optical system 200 so that it falls within a predetermined range. For example, the light intensity adjuster 209 adjusts the intensity of the light so that an interference signal (i.e., an FPN signal) due to the light originating from the FPN generation optical system 200 falls within a signal intensity range (dynamic range) in which the detector 120 can detect the signal.

[0212] This allows the detector 120 to properly acquire the FPN signal even if the intensity of the light emitted from the swept light source 102 changes when the sweep frequency is changed.

[0213] For example, the light intensity adjuster 209 is composed of a lens and a drive unit that drives the lens in the optical axis direction. For example, the light intensity adjuster 209 may be composed of a filter that attenuates light and an insertion / removal unit that inserts and removes the filter with respect to the optical axis. Furthermore, for example, the light intensity adjuster may be an attenuator.

[0214] For example, the operation of the optical intensity adjuster 209 is determined in advance for each sweep frequency. Also, the operation of the optical intensity adjuster 209 may be controlled based on the signal intensity of the signal detected by the detector 120.

[0215] In this embodiment, a case has been described in which the bandpass filter 301 and the notch filter 302 are combined to obtain an interference signal including the calibration interference signal G1 and the calibration interference signal G2 as the first calibration interference signal.

[0216] For example, the calibration optical system 300 may be provided with a first bandpass filter for acquiring the calibration interference signal G1 and a second bandpass filter for acquiring the calibration interference signal G2, instead of the bandpass filter 301 and the notch filter 302. The first bandpass filter selectively passes light of a first wavelength. The second bandpass filter selectively passes light of a second wavelength.

[0217] In this case, the wavelength is swept with either the first bandpass filter or the second bandpass filter being selectively inserted with respect to the optical axis, and a calibration interference signal is obtained.

[0218] For example, when the wavelength is swept with a first bandpass filter inserted onto the optical axis and a second bandpass filter removed from the optical axis, an interference signal A with a calibration interference signal G1 generated therein is acquired at a first detection timing T1.

[0219] For example, when the second bandpass filter is inserted onto the optical axis and the wavelength is swept with the first bandpass filter detached from the optical axis, an interference signal B with a calibration interference signal G2 generated therein is acquired at the second detection timing T2.

[0220] For example, the control unit 70 may obtain the first calibration interference signal by superimposing the obtained interference signal A and interference signal B.

[0221] Of course, the second calibration interference signal can be obtained in a similar manner. [Explanation of symbols]

[0222] 1 OCT device 70 Calculation and control device 100 OCT optics 102 Wavelength swept light source 110 Reference optical system 120 Detector 150 Light guiding optical system 200 FPN generation optics 204 FPN generating material 205 Drive unit 300 Calibration Optical System 301 Bandpass Filter 302 Notch Filter

Claims

1. a wavelength swept source capable of changing a sweep frequency between a first sweep frequency and a second sweep frequency; a light splitter that splits the light from the wavelength swept light source into a measurement light and a reference light; an OCT optical system including a first detector that detects a spectral interference signal between the measurement light and the reference light guided to a tissue of a test eye; an image processor that processes the spectral interference signal to obtain OCT data of the subject's eye; an FPN generating optical system having at least one optical member that generates a first FPN when the frequency is the first sweep frequency and generates a second FPN at a position away from a zero delay position with respect to the first FPN when the frequency is the second sweep frequency; a second detector for detecting an FPN including the first FPN and the second FPN; an arithmetic controller that acquires correction information for correcting a mapping state of each wave number component, the arithmetic controller acquiring first correction information to be applied to the arithmetic processing of the spectral interference signal obtained when the sweep frequency is a first sweep frequency, based at least on the first FPN detected when the sweep frequency is the first sweep frequency, and acquiring second correction information to be applied to the arithmetic processing of the spectral interference signal obtained when the sweep frequency is the second sweep frequency lower than the first sweep frequency, based at least on the second FPN generated when the sweep frequency is the second sweep frequency; An OCT apparatus comprising:

2. The OCT device of claim 1, further comprising a driving unit that changes the optical distance between a position corresponding to the zero delay position and a position of the optical element between a first distance generated by the optical element by the first FPN and a second distance generated by the optical element by the second FPN.

3. The OCT device of claim 1, wherein the FPN generating optical system has a first optical element as the optical element that generates the first FPN, and further has a second optical element as the optical element that generates the second FPN, which is separate from the first optical element and is positioned at an optical distance from a position corresponding to the zero delay position farther than the position of the first optical element.

4. the FPN generating optical system further generates a third FPN having a different distance from the zero delay position than the first FPN, and a fourth FPN having a different distance from the zero delay position than the second FPN; The arithmetic controller obtains the first correction information based on the first FPN and the third FPN detected in the case of the first sweep frequency, The OCT apparatus according to claim 1 , wherein the second correction information is acquired based on the second FPN and the fourth FPN detected in the case of the second sweep frequency.

5. a blocking member that blocks irradiation of the measurement light to the subject's eye, An OCT device of any one of claims 1 to 4, wherein the arithmetic controller acquires first correction information and second correction information based on the first FPN and the second FPN detected by the second detector when the blocking member blocks the irradiation of the measurement light to the test eye.

6. In the OCT apparatus, either a first photographing mode for photographing a predetermined range of the subject's eye or a second photographing mode for photographing a range different from the predetermined range is executed; When the first imaging mode is executed, the wavelength swept light source sweeps the wavelength at the first sweep frequency; 6. The OCT apparatus according to claim 1, wherein, when the second imaging mode is executed, the wavelength swept light source sweeps the wavelength at the second sweep frequency.

Images