Optical coherence tomography device, method for controlling optical coherence tomography device, and program

Abstract

This OCT device comprises a wavelength sweeping light source, a splitter, a first interference optical system, a second interference optical system, a combiner, and a wavenumber linear processing unit. The splitter splits light source light emitted from the wavelength sweeping light source into first light source light and second light source light. The first interference optical system detects interference light for measuring an object of interest generated from the first light source light, and generates a first interferogram signal. The second interference optical system detects interference light for calibration generated from the second light source light, and generates a second interferogram signal. The combiner generates a composite signal of the two interferogram signals. The wavenumber linear processing unit performs wavenumber linear processing on the first interferogram signal on the basis of the second interferogram signal included in the composite signal.

Description

Optical coherence tomography apparatus, control method for optical coherence tomography apparatus, and program

[0001] The present disclosure relates to an optical coherence tomography apparatus, a control method for an optical coherence tomography apparatus, and a program.

[0002] In swept source optical coherence tomography (SS-OCT), the higher the sampling rate of the interferogram signal (OCT signal) derived from the object to be measured, the wider the measurable depth range can be. Sampling of the interferogram signal is performed by a DAQ (Data Acquisition board). In SS-OCT, calibration is performed by executing wavenumber linear processing on the OCT signal using an interferogram signal corresponding to the wavelength sweep timing (mainly, since it is often acquired by a Mach-Zehnder Interferometer, it is denoted as an MZI signal).

[0003] After simultaneously capturing the MZI signal and the OCT signal, it is desirable to execute the above-described wavenumber linear processing. At this time, the DAQ has a configuration for two channels for individually inputting the MZI signal and the OCT signal. Also, the DAQ needs to accumulate data for two channels. Therefore, the cost of the DAQ increases.

[0004] Patent Document 1 discloses a technique for synthesizing and outputting a single OCT signal and an MZI signal that are generated simultaneously.

[0005] Japanese Patent No. 6836951

[0006] However, Patent Document 1 does not disclose a specific technique for performing wavenumber linear processing from a singly output signal, focusing on phase stabilization.

[0007] The present invention has been made in view of the above circumstances, and one of its objects is to provide a new technique for performing high-precision wavenumber linear processing on an interferogram signal derived from an object to be measured at low cost in SS-OCT.

[0008] One aspect of several embodiments is an optical coherence tomography apparatus comprising: a wavelength-swept light source; a splitter that divides light emitted from the wavelength-swept light source into a first light source and a second light source; a first interference optical system that divides the first light source into a measurement light and a reference light, guides the measurement light to an object to be measured, and generates a first interferogram signal by detecting interference light for measurement between the reference light and the return light of the measurement light from the object to be measured; a second interference optical system that generates interference light for wavelength linear processing corresponding to a predetermined optical path length difference from the second light source and generates a second interferogram signal by detecting the interference light for wavelength linear processing; a combiner that generates a composite signal of the first interferogram signal and the second interferogram signal; and a wavenumber linear processing unit that performs wavenumber linear processing on at least the first interferogram signal included in the composite signal based on the second interferogram signal included in the composite signal.

[0009] According to the present invention, it is possible to provide a new technology for performing high-precision wavelength-linear processing on interferogram signals originating from the object being measured in SS-OCT at low cost.

[0010] This is a schematic diagram showing an example of the configuration of the optical system of an ophthalmic device according to the embodiment. This is a schematic diagram showing an example of the configuration of the control system of an ophthalmic device according to the embodiment. This is a schematic diagram showing an example of the configuration of the control system of an ophthalmic device according to the embodiment. This is an explanatory diagram for explaining the operation of an ophthalmic device according to the embodiment. This is a schematic diagram showing an example of the configuration of the optical system of an ophthalmic device according to a comparative example of the embodiment. This is a flowchart of an example of the operation of an ophthalmic device according to the embodiment. This is an explanatory diagram for explaining the operation of an ophthalmic device according to the embodiment. This is a flowchart of an example of the operation of an ophthalmic device according to the embodiment. This is an explanatory diagram for explaining the operation of an ophthalmic device according to the embodiment. This is an explanatory diagram for explaining the operation of an ophthalmic device according to the embodiment. This is a schematic diagram showing an example of the configuration of the optical system of an ophthalmic device according to a modified example of the embodiment.

[0011] Examples of embodiments of the optical coherence tomography apparatus (OCT apparatus), control method for the OCT apparatus, and program according to this invention will be described in detail with reference to the drawings. It should be noted that the contents of the documents cited in this specification and any prior art can be incorporated into the following embodiments.

[0012] The OCT apparatus according to this embodiment performs SS-OCT using a wavelength-swept light source on an object under test, acquires an interferogram signal (OCT signal) originating from the object under test, and can perform high-precision wavelength linear processing on the OCT signal. Here, wavelength linear processing means linearization of the wavenumber direction of the OCT signal synchronized with the wavelength sweep timing. At this time, the OCT apparatus uses the light source emitted from the wavelength-swept light source to generate an interferogram signal originating from the object under test (first interferogram signal) and a calibration (adjustment) interferogram signal (second interferogram signal) simultaneously. The OCT apparatus generates a composite signal of the two interferogram signals and sends it to the DAQ as a data acquisition unit. Based on the second interferogram signal included in the composite signal, the OCT apparatus performs wavenumber linear processing (resampling process, rescaling process) on the first interferogram signal included in the composite signal.

[0013] For example, light emitted from a wavelength-swept light source is split into a first light source and a second light source. In this case, the first interferogram signal is generated based on the detection result of interference light originating from the object under test, acquired using a first interference optical system into which the first light source is incident. The second interferogram signal is generated based on the detection result of calibration interference light acquired using a second interference optical system into which the second light source is incident. The second interference optical system may be a Mach-Zehnder interferometer, a Michelson interferometer, or a Fabry-Perot interferometer.

[0014] Examples of combining two interferogram signals include superposition and modulation. Examples of superposition include wavelength division multiplexing (frequency division multiplexing), code division multiplexing, and polarization division multiplexing. Examples of modulation include amplitude modulation, frequency modulation, and phase modulation.

[0015] The two interferogram signals are electrically combined. However, the OCT device may be configured to optically combine the interference light originating from the object under test with the calibration interference light, and send the interferogram signal corresponding to the detection result of the combined interference light to the DAQ.

[0016] This means that the DAQ only needs to have a configuration for one channel. Furthermore, the DAQ only needs to store data (signals) for one channel. Therefore, a low-cost DAQ can be used, which makes it possible to reduce the cost of OCT equipment.

[0017] The control method for the OCT apparatus according to the embodiment includes one or more steps for realizing processing performed by a processor (computer) in the OCT apparatus according to the embodiment. The program (computer program or instruction) according to the embodiment causes the processor to execute each step of the control method for the OCT apparatus according to the embodiment. That is, the program according to the embodiment is a computer program that includes instructions causing the computer to execute the control method for the OCT apparatus according to the embodiment when the program is executed by the computer. The computer program product according to the embodiment includes a computer program or instructions. The computer program product realizes each step of the control method for the OCT apparatus according to the embodiment when the computer program or instructions are executed by the processor. The recording medium (storage medium) according to the embodiment is any non-transitory recording medium that is readable by a computer and on which the program according to the embodiment is recorded (stored). The computer-readable storage medium according to the embodiment stores the computer program or instructions. The computer-readable storage medium realizes each step of the control method for the OCT apparatus according to the embodiment when the computer program or instructions are executed by the processor. The recording medium may be an electronic medium that utilizes magnetism, light, magneto-optical technology, semiconductors, etc. Typically, recording media include magnetic tape, magnetic disks, optical disks, magneto-optical disks, flash memory, and solid-state drives. Examples of magnetic disks include hard disks, floppy disks (registered trademark), and ZIP files. Examples of magneto-optical disks include CD-ROMs, DVD-RAMs, DVD-ROMs, and MOs. It is also possible to send and receive this program via networks such as the internet and LANs.

[0018] In this specification, "processor" means circuits such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), and a programmable logic device (e.g., an SPLD (Simple Programmable Logic Device), a CPLD (Complex Programmable Logic Device), or an FPGA (Field Programmable Gate Array)). The processor realizes the functions according to the embodiment by, for example, reading and executing a program stored in a memory circuit or storage device.

[0019] The following embodiments describe a case where the OCT device is applied to an ophthalmic device capable of performing SS-OCT on the eye being measured and measuring the measurement site in the eye being measured. However, the following embodiments can also be applied when the object being measured is something other than the eye being measured.

[0020] The ophthalmic apparatus according to this embodiment may be an ophthalmic imaging device capable of photographing the measurement site, or an ophthalmic observation device capable of observing the measurement site. In the following description, the measurement site will be assumed to be the fundus, but the measurement site may be a site other than the fundus.

[0021] <Optical System> Figure 1 shows an example of the optical system configuration of an ophthalmic device to which the OCT device according to this embodiment is applied.

[0022] The ophthalmic apparatus 1 includes a wavelength-swept light source 10, a splitter 20, a first interference optical system 30, a second interference optical system 40, a detector 50, a detector 60, an apparatus optical system 70, a frequency filter 80, a combiner 90, and a DAQ 100.

[0023] (Wavelength-swept light source 10) The wavelength-swept light source 10 changes the wavelength of the emitted light (light source) over time in the near-infrared wavelength band, which is invisible to the human eye. For example, the wavelength-swept light source 10 includes a laser light source including a resonator. The light source L0 emitted by the wavelength-swept light source 10 is guided to the splitter 20 through an optical fiber.

[0024] (Splitter 20) The splitter 20 optically splits the light source L0 from the wavelength-swept light source 10, which is guided through the optical fiber, into a first light source L1 and a second light source L2. For example, the splitter 20 may be a fiber coupler. In some embodiments, the splitter 20 splits the light source L0 into a first light source L1 and a second light source L2 with a split ratio of 50:50. In some embodiments, the splitter 20 splits the light source L0 into a first light source L1 and a second light source L2 with a split ratio (e.g., 90:10) such that the optical power of the first light source L1 is greater than the optical power of the second light source L2. The first light source L1 is guided through the optical fiber to a first interference optical system 30. The second light source L2 is guided through the optical fiber to a second interference optical system 40.

[0025] (First Interference Optical System 30) The first interference optical system 30 splits the first light source L1 into a measurement light LS and a reference light LR, guides the measurement light LS to the eye under examination E, and generates an interference light LC (for measurement) between the reference light LR and the return light of the measurement light LS from the eye under examination E. Specifically, the first interference optical system 30 includes fiber couplers 31 and 32. The fiber coupler 31, for example, splits the first light source L1 into a measurement light LS and a reference light LR with a branching ratio of 50:50. The measurement light LS is guided to the device optical system 70 through an optical fiber. As described later, the device optical system 70 deflects the measurement light LS and causes it to enter the eye under examination E to irradiate the measurement site, and guides the return light from the measurement site to the fiber coupler 31.

[0026] The measurement light LS entering the eye is scattered (including reflected) at various depths within the measurement site. The backscattered light of the measurement light LS from the measurement site travels in the reverse direction along the same path as the forward path as the return light of the measurement light LS, and is guided to the fiber coupler 31, and then reaches the fiber coupler 32 via the optical fiber.

[0027] The fiber coupler 32 combines (interferes with) the return light of the measurement light LS from the eye under examination E and the reference light LR that is split by the fiber coupler 31 and passes through the reference optical path to generate interference light LC. In some embodiments, the first interference optical system 30 includes an optical element that can change the optical path length of the reference light LR. An example of such an optical element is a retroreflector. The fiber coupler 32 generates a pair of interference light LC by splitting the measurement light LS and the reference light LR at a predetermined splitting ratio (e.g., 50:50). The pair of interference light LC emitted from the fiber coupler 32 are each led to the detector 50 by optical fibers.

[0028] (Device Optical System 70) The device optical system 70 guides the measurement light LS, which is split by the fiber coupler 31, to the eye under examination E. The device optical system 70 includes, for example, a collimating lens unit, an optical path length difference changing unit, a focusing optical system, an optical scanner, and an objective optical system. The fiber end of the optical fiber that guides the measurement light LS from the fiber coupler 31 is configured to be positioned at a location that is optically approximately conjugate to the measurement site (e.g., the fundus) of the eye under examination E. The measurement light LS emitted from the fiber end is converted into parallel light by the collimating lens unit. The optical path length of the measurement light LS converted into parallel light can be changed by the optical path length difference changing unit. That is, the optical path length difference changing unit can change the difference between the optical path length of the measurement light LS and the optical path length of the reference light LR. The measurement light LS passing through the optical path length difference changing unit is guided to the focusing optical system. The focusing optical system changes the focal position of the measurement light LS to focus it on the measurement site. The measurement light LS, passing through the focusing optical system, is deflected by an optical scanner. The deflected measurement light LS, via the optical scanner, enters the eye through the pupil of the eye E being examined, passing through the objective optical system. The objective optical system includes either a refractive optical system or a reflective optical system. An example of a refractive optical system is one or more lens groups including an objective lens. An example of a reflective optical system is two or more curved mirrors arranged so that their reflective surfaces face each other.

[0029] (Detector 50) The detector 50 is, for example, a balanced photodiode having a pair of photodetectors that detect a pair of interferometric LCs, and outputting the difference between the detection results. The detector 50 sends its detection result (detection signal) to the combiner 90 as an interferogram signal (first interferogram signal). The first interferogram signal is the OCT signal. In some embodiments, the first interferometric optical system 30 includes the detector 50.

[0030] (Second Interferometry Optical System 40) The second interference optics system 40 generates interference light for wavelength linear processing corresponding to a predetermined optical path length difference from the second light source L2. The second interference optics system 40 is, for example, a Mach-Zehnder interferometer. Specifically, the second interference optics system 40 includes a splitter 41 and a fiber coupler 42. The splitter 41 and the fiber coupler 42 are connected by two optical fibers with different optical path lengths. The splitter 41 divides the second light source L2 into two branched beams. For example, the splitter 41 divides the second light source L2 into two branched beams with a splitting ratio of 50:50. The two branched beams are led to the fiber coupler 42 through optical fibers with different optical path lengths. The splitter 41 may be a fiber coupler.

[0031] The fiber coupler 42 generates an interference light by combining (interfering with) two branched light beams that pass through optical fibers with different optical path lengths. In some embodiments, the second interference optical system 40 includes an optical element that can change the difference in optical path lengths between the two optical fibers between the splitter 41 and the fiber coupler 42. In this case, it is possible to change the difference in optical path lengths between the two branched light beams. The fiber coupler 42 generates a pair of interference light beams by splitting the two interference light beams at a predetermined splitting ratio (e.g., 50:50). The pair of interference light beams emitted from the fiber coupler 42 are each led to the detector 60 by optical fibers.

[0032] (Detector 60) The detector 60 is a balanced photodiode that, like the detector 50, has a pair of photodetectors that detect a pair of interference lights and outputs the difference between the detection results. The detector 60 sends its detection result (detection signal) as an interferogram signal (second interferogram signal) to the combiner 90 via the frequency filter 80. The second interferogram signal is the MZI signal. The MZI signal corresponds to an analog k clock signal. In some embodiments, the second interference optical system 40 includes the detector 60.

[0033] (Combiner 90) The combiner 90 electrically superimposes the OCT signal and the MZI signal to generate a superimposed signal as a combined signal. For example, the combiner 90 generates a superimposed signal by sequentially adding two signals at the same time along the time axis.

[0034] (Frequency filter 80) As shown in Figure 1, the frequency filter 80 is placed between the second interference optical system 40 and the combiner 90. The frequency filter 80 is capable of passing MZI signals (second interferogram signals) in a frequency range that does not overlap with the frequency range of the OCT signal (first interferogram signal). Therefore, the combiner 90 is capable of generating a superimposed signal of the OCT signal in the first frequency range and the MZI signal in the second frequency range that does not overlap with the first frequency range.

[0035] The OCT signal contains wavelength information (i.e., frequency information) corresponding to the depth-direction morphology at the measurement site. Therefore, the further the frequency range containing the frequency components of the OCT signal is from the frequency range containing the frequency components of the MZI signal, the easier it becomes to separate the MZI signal included in the superimposed signal, and it becomes possible to perform highly accurate wavenumber linearization of the OCT signal using the components of the MZI signal.

[0036] The frequency filter 80 is, for example, a low-pass filter that allows signals having frequencies lower than a predetermined cutoff frequency to pass through. For example, the passband of the frequency filter 80 includes frequencies less than or equal to 1 / 8 of the maximum sampling frequency of the superimposed signal in the DAQ 100 described later. By providing such a passband, it becomes easier to separate the MZI signal included in the superimposed signal, and it becomes possible to linearize the wavenumber of the OCT signal included in the superimposed signal with high accuracy based on the separated MZI signal, which offers an excellent balance between the cost of the DAQ and the accuracy of wavenumber linearization.

[0037] In some embodiments, the frequency filter 80 is a band-pass filter that allows a signal having a frequency between a predetermined high-frequency cutoff frequency and a low-frequency cutoff frequency to pass through. Even in this case, it becomes possible to perform highly accurate wavenumber linearization of the OCT signal using a superimposed signal including the MZI signal.

[0038] In some embodiments, the ophthalmic device 1 has a configuration in which the MZI signal from the detector 60 is sent to the combiner 90 without passing through the frequency filter 80.

[0039] As described above, the ophthalmic device 1 generates an MZI signal simultaneously with the OCT signal, and superimposes the simultaneously acquired OCT signal and MZI signal in a manner that allows for later separation, thereby acquiring the superimposed signal.

[0040] (DAQ100) The DAQ100 captures the superimposed signal generated by the combiner 90. The DAQ100 then performs A / D conversion on the superimposed signal at a predetermined sampling frequency and captures the superimposed signal after A / D conversion.

[0041] The superimposed signal is sequentially captured by the DAQ 100. Thereafter, the ophthalmic device 1 performs a wavenumber linear process on the OCT signal included in the superimposed signal based on the MZI signal included in the superimposed signal. The ophthalmic device 1 calculates a reflection intensity distribution (reflection intensity profile) by performing, for example, an apodization process, a dispersion compensation process, a fast Fourier transform process, a logarithmic transform process, a luminance conversion process, and a histogram adjustment process on the OCT signal after the wavenumber linear process. The ophthalmic device 1 can form an OCT image by imaging the reflection intensity distribution and arranging it in a one-dimensional direction, a two-dimensional direction, or a three-dimensional direction.

[0042] <Control System> FIGS. 2 and 3 show a configuration example of the control system of the ophthalmic device 1 according to the embodiment. FIG. 2 represents a block diagram of a configuration example of the control system of the ophthalmic device 1 according to the embodiment. FIG. 3 represents a block diagram of a configuration example of the signal processing unit 300 in FIG. 2. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0043] The control system (processing system) of the ophthalmic device 1 is centered around the control unit 200. The control unit 200 controls each part of the ophthalmic device 1.

[0044] The control unit 200 includes a main control unit 210 and a storage unit 220. The function of the main control unit 210 is realized by, for example, one or more processors. A computer program for controlling the ophthalmic device 1 is stored in advance in the storage unit 220. This computer program includes a wavelength sweep light source control program, a detector control program, an apparatus optical system control program, a DAQ control program, a signal processing program, an image formation program, and a user interface program. By operating the main control unit 210 according to such a computer program, the control unit 200 executes control processing.

[0045] (Main Control Unit 210) The main control unit 210 controls the wavelength sweep light source 10, the detectors 50, 60, the apparatus optical system 70, the DAQ 100, the signal processing unit 300, the image formation unit 400, the operation unit 500, and the display unit 600.

[0046] Control of the wavelength-sweeping light source 10 includes control of wavelength-sweeping parameters including at least one of the sweeping start wavelength, sweeping end wavelength, wavelength-sweeping range, wavelength-sweeping speed, or wavelength-sweeping timing. For example, the main control unit 210 can control the wavelength-sweeping light source 10 by setting the wavelength-sweeping parameters.

[0047] Control of the detectors 50 and 60 includes control of the exposure time (charge accumulation time), sensitivity, frame rate, etc.

[0048] Control of the device optical system 70 includes control of the optical path length difference changing unit 71, control of the focus optical system 72, control of the optical scanner 73, etc.

[0049] The main control unit 210 changes the optical path length of the measurement light LS from the first interference optical system 30 by controlling the optical path length difference changing unit 71. As a result, the optical path length difference between the optical path of the measurement light LS and the optical path of the reference light LR is changed. Consequently, it is possible to change the measurement range in the depth direction.

[0050] The main control unit 210 changes the focal position of the measurement light LS so as to converge on the measurement site of the eye to be examined E by controlling the focus optical system 72. For example, the focus optical system 72 includes a focusing lens movable in the optical axis direction, and by moving the focusing lens in the optical axis direction, the focal position of the measurement light LS is changed. This enables measurement with the measurement site in focus.

[0051] The main control unit 210 controls the optical scanner 73. The optical scanner 73 is a uniaxial scanner or a biaxial scanner. The main control unit 210 can control the deflection direction (scan direction) of the measurement light LS by controlling the angle of the deflection plane of the optical scanner 73. Control of the angle of the deflection plane includes control of deflection control parameters including at least one of the deflection start angle, deflection end angle, deflection angle range, or deflection speed. For example, the main control unit 210 can control the scan range (scan start position and scan end position) and scan speed by controlling the deflection control parameters.

[0052] The main control unit 210 controls the optical scanner 73 to deflect the measurement light LS according to a deflection pattern corresponding to a pre-set scan mode. Examples of such scan modes include line scan, cross scan, circle scan, radial scan, concentric circle scan, multi-line cross scan, spiral scan, Lissajous scan, and three-dimensional scan (including scans that combine low-speed and high-speed scans).

[0053] The DAQ100 includes an A / D converter 101. The A / D converter 101 samples the superimposed signal from the combiner 90 at a sampling frequency below a predetermined maximum sampling frequency at which the input analog signal can be sampled, and outputs a digitized superimposed signal. The superimposed signal after A / D conversion is sequentially stored in the storage unit 220 under the control of the main control unit 210.

[0054] (Storage Unit 220) The storage unit 220 stores various types of data (signals). Data stored in the storage unit 220 includes, for example, superimposed signals after A / D conversion sequentially acquired by the DAQ 100, signal processing results by the signal processing unit 300, image data of images formed by the image forming unit 400, and subject eye information. Subject eye information includes information about the subject such as patient ID and name, and information about the subject eye such as left eye / right eye identification information.

[0055] Furthermore, the memory unit 220 stores various programs and data necessary for operating the ophthalmic device 1.

[0056] (Signal Processing Unit 300) The signal processing unit 300 performs predetermined signal processing on the superimposed signal acquired by the DAQ 100. Signal processing includes wavenumber linear processing, (fast) Fourier transform processing, and signal separation processing. The functions of the signal processing unit 300 are realized by, for example, one or more processors. In some embodiments, the functions of the signal processing unit 300 are configured to be realized by one or more processors within the DAQ 100.

[0057] As shown in Figure 3, the signal processing unit 300 includes a wavenumber linear processing unit 310, a Fourier transform processing unit 320, and a signal separation unit 330.

[0058] (Wavenumber linearization processing unit 310) The wavenumber linearization processing unit 310 performs wavenumber linearization on the superimposed signal acquired by the DAQ 100. Wavenumber linearization is a process that linearizes the interferogram signal in the wavenumber direction. The wavenumber linearization processing unit 310 can perform wavenumber linearization on the superimposed signal or the OCT signal (component) contained in the superimposed signal from the DAQ 100 based on the MZI signal (component) contained in the superimposed signal.

[0059] In some embodiments, a background signal (BG signal) is used as the MZI signal as a superimposed signal. The BG signal is an interferogram signal that does not originate from the eye E being measured. For example, the BG signal is a superimposed signal output by the combiner 90 using an interferogram signal (MZI signal) that is acquired at a different timing than the acquisition timing of the OCT signal originating from the eye E, when the eye E being measured is not positioned at the OCT measurement position.

[0060] In this case, the first interference optical system 30 generates a pair of interference lights using the return light of the measurement light LS that does not originate from the eye E by performing OCT when the eye E is not positioned at the measurement location. By detecting the generated pair of interference lights with the detector 50, an OCT signal that does not originate from the eye E is acquired. The combiner 90 acquires a superimposed signal that does not originate from the eye E as a BG signal using the OCT signal that does not originate from the eye E and the MZI signal acquired simultaneously with the OCT signal that does not originate from the eye E.

[0061] Furthermore, at a timing different from the acquisition timing of the OCT signal described above, the first interference optical system 30 performs OCT with the eye under test E positioned at the measurement location, thereby generating a pair of interference lights using the return light of the measurement light LS originating from the eye under test E. By detecting the generated pair of interference lights with the detector 50, the OCT signal originating from the eye under test E is acquired. The combiner 90 acquires a superimposed signal originating from the eye under test E using the OCT signal originating from the eye under test E and the MZI signal acquired simultaneously with the OCT signal originating from the eye under test E.

[0062] The wavenumber linear processing unit 310 performs wavenumber linear processing on the superimposed signal (the OCT signal included in the superimposed signal) that is generated using the return light of the measurement light LS originating from the eye E, based on the BG signal, which is a superimposed signal not originating from the eye E.

[0063] (Fourier Transform Processing Unit 320) The Fourier transform processing unit 320 performs a Fourier transform on the superimposed signal generated by the combiner 90 or the signal after wavenumber linear processing of the superimposed signal. The Fourier transform processing is the process of converting an interferogram signal in time space into an interferogram signal in frequency space. The Fourier transform processing may be a discrete Fourier transform or a fast Fourier transform.

[0064] (Signal separation unit 330) The signal separation unit 330 performs signal separation processing on the signal after Fourier transform processing obtained by the Fourier transform processing unit 320. The signal separation processing is the process of separating the MZI signal and the OCT signal included in the superimposed signal.

[0065] In some embodiments, the signal separation unit 330 separates the OCT signal and the MZI signal by extracting a signal in a predetermined frequency domain for the OCT signal and a signal in a predetermined frequency domain for the MZI signal from the frequency domain signal obtained by the Fourier transform process.

[0066] In some embodiments, the signal separation unit 330 identifies the peaks in the amplitude of the signal obtained by the Fourier transform process, and identifies and separates the OCT signal and the MZI signal based on the position of the identified peaks on the frequency axis.

[0067] Figure 4 shows an explanatory diagram of the operation of the signal separation unit 330. In Figure 4, the horizontal axis represents the A line number (A - scan position), and the vertical axis represents the depth position in the depth direction.

[0068] The OCT signal is a broadband signal with a wide range of frequency components because it is generated based on the reflected light of the measurement beam from the measurement site. In contrast, the MZI signal is a narrowband signal corresponding to the difference in optical path length between the first and second branched beams. Therefore, by adjusting the frequency components of the MZI signal so that they are outside the range of frequency components of the OCT signal, it becomes possible to perform highly accurate wavenumber linearization of the OCT signal without being affected by the MZI signal.

[0069] Specifically, as shown in Figure 4, the OCT signal is concentrated in a frequency range (wavelength range) corresponding to the shape of the depth position in the depth direction (direction of propagation of the measurement light LS) at the measurement site. Therefore, by setting the optical path length difference described above so that the MZI signal has frequency components on the lower frequency side than the frequency range in which the OCT signal is concentrated, the OCT signal and the MZI signal can be separated by utilizing the difference in frequency ranges.

[0070] When the wavelength sweep operation of the wavelength sweep light source 10 is stable, the OCT signal and MZI signal included in the superimposed signal can be identified (separated) with high accuracy. In this case, the BG signal can be used as the MZI signal as described above. That is, the control unit 200 (main control unit 210) controls the wavenumber linear processing unit 310 to perform wavenumber linear processing on the superimposed signal generated by the combiner 90 using the return light of the measurement light LS originating from the eye under examination E, using the BG signal as the MZI signal. At this time, the BG signal can be acquired once, and based on this BG signal, wavenumber linear processing can be performed on each of the multiple superimposed signals originating from the eye under examination E. As a result, the processing load can be reduced and the control can be simplified.

[0071] In contrast, if the wavelength sweep operation of the wavelength sweep light source 10 is unstable, the frequency range of the OCT signal and MZI signal widens, making it difficult to accurately identify (separate) the OCT signal and MZI signal included in the superimposed signal. In this case, the ophthalmic device 1 is configured to separate the MZI signal and the OCT signal from the superimposed signal obtained by applying the rough wavenumber linear processing described later to the superimposed signal, and then apply wavenumber linear processing to the OCT signal using the MZI signal.

[0072] (Image forming unit 400) The image forming unit 400 calculates a reflectance intensity distribution (reflection intensity profile) by applying logarithmic transformation, luminance transformation, and histogram adjustment processing to the signal obtained by the Fourier transform processing unit 320. The image forming unit 400 can calculate the reflectance intensity distribution for signals in a frequency range that includes the frequency range of the OCT signal, excluding the frequency range of the MZI signal from the signal obtained by the Fourier transform processing unit 320. The image forming unit 400 can form an OCT image by imaging the reflectance intensity distribution and arranging it in a one-dimensional, two-dimensional, or three-dimensional direction. Examples of OCT images include A-scan images, B-scan images, and C-scan images.

[0073] Furthermore, the image forming unit 400 can perform known image processing, such as interpolation processing to interpolate pixels between two-dimensional OCT images, to form image data of a three-dimensional image of the eye under examination E. Image data of a three-dimensional image refers to image data in which the position of pixels is defined by a three-dimensional coordinate system. Image data of a three-dimensional image includes image data consisting of voxels arranged in three dimensions. This image data is called volume data or voxel data. The image forming unit 400 can perform rendering processing on the volume data to form image data of a pseudo-three-dimensional image as seen from a specific line of sight direction. Examples of rendering processing include volume rendering and MIP (Maximum Intensity Projection).

[0074] (Operation Unit 500) The operation unit 500 includes an operation device for receiving user operations. The operation unit 500 may also include various buttons and keys provided on the housing or outside of the ophthalmic device 1. The main control unit 210 controls each part of the ophthalmic device 1 based on operation instruction signals corresponding to user operations from the operation unit 500.

[0075] (Display Unit 600) The display unit 600 includes a display device. The display unit 600 receives control from the main control unit 210 and displays various information.

[0076] Furthermore, the operation unit 500 and the display unit 600 do not necessarily need to be configured as separate devices. For example, it is possible to use a device that integrates display and operation functions, such as a touch panel. In that case, the operation unit 500 would consist of this touch panel and a computer program. The operations performed on the operation unit 500 are input to the control unit 200 as electrical signals. Alternatively, operations and information input may be performed using a graphical user interface (GUI) displayed on the display unit 600 and the operation unit 500.

[0077] <Comparative Example> Here, in order to compare it with the ophthalmic device 1 shown in Figure 1, an ophthalmic device according to a comparative example of the embodiment will be described.

[0078] Figure 5 shows an example of the optical system configuration of an ophthalmic device according to a comparative example of the embodiment. In Figure 5, the same reference numerals are used for parts that are the same as in Figure 1, and their descriptions are omitted as appropriate.

[0079] The optical system configuration of the ophthalmic device 1x in this comparative example differs from the optical system configuration of the ophthalmic device 1 according to this embodiment in that the frequency filter 80 and the combiner 90 are omitted, and DAQ100x is provided instead of DAQ100.

[0080] With the configuration shown in Figure 5, wavenumber linear processing can be applied to the OCT signal regardless of the stability of the wavelength sweep operation of the wavelength sweep light source 10. However, the DAQ 100x has a configuration for two channels to input the OCT signal from detector 50 and the MZI signal from detector 60. In contrast, with this embodiment, the configuration of the DAQ can be simplified, making it possible to reduce the cost of the DAQ.

[0081] Furthermore, the DAQ100x, like the DAQ100, sequentially acquires the OCT signal and the MZI signal. That is, as in this embodiment, wavenumber linear processing is sequentially applied to the OCT signal using the MZI signal. According to this embodiment, the capacity required to store interferogram signals such as the OCT signal and the MZI signal can be reduced, making it possible to reduce the cost of the downstream configuration of the DAQ.

[0082] The eye E under examination is an example of the "object under measurement" according to the embodiment. The pair of interference rays LC generated by the first interference optical system 30 is an example of the "interference rays for measurement" according to the embodiment. The pair of interference rays generated by the second interference optical system 40 is an example of the "interference rays for calibration" according to the embodiment. The OCT signal is an example of the "first interferogram signal" according to the embodiment. The MZI signal is an example of the "second interferogram signal" according to the embodiment. The superimposed signal is an example of the "composite signal" according to the embodiment. The ophthalmic device 1 is an example of the "OCT device" according to the embodiment.

[0083] <Operation Examples> Next, an operation example of the ophthalmic device 1 according to the embodiment will be described. Below, a first operation example and a second operation example of the ophthalmic device 1 according to the embodiment will be described. The first operation example is an operation example when the wavelength sweep operation of the wavelength sweep light source 10 is stable. The second operation example is an operation example when the wavelength sweep operation of the wavelength sweep light source 10 is unstable. For example, when the variation in wavelengths swept by the wavelength sweep light source 10 at a predetermined wavelength sweep speed within a predetermined wavelength sweep range is less than or equal to a first threshold, the wavelength sweep operation of the wavelength sweep light source 10 is stable. For example, when the variation in wavelengths swept by the wavelength sweep light source 10 at a predetermined wavelength sweep speed within a predetermined wavelength sweep range is less than a first threshold, the wavelength sweep operation of the wavelength sweep light source 10 is unstable.

[0084] (First Operation Example) Figure 6 shows a flowchart of the first operation example of the ophthalmic device 1 according to the embodiment. Figure 6 represents a flowchart of the first operation example of the ophthalmic device 1 according to the embodiment. The memory unit 220 stores a computer program for realizing the processing shown in Figure 6. The main control unit 210 executes the processing shown in Figure 6 by operating according to this computer program.

[0085] (S1: Performing OCT without placing the eye under examination) First, the main control unit 210 performs OCT by controlling the wavelength sweep light source 10 and the device optical system 70 in a state where the eye under examination E is not placed at the measurement position of the eye under examination in the first interference optical system 30 in Figure 1 (air state). As a result, an OCT signal not originating from the eye under examination E corresponding to the detection result of interference light obtained by the first interference optical system 30 and an MZI signal corresponding to the detection result of interference light obtained by the second interference optical system 40 are acquired simultaneously.

[0086] (S2: Superimposed signal acquired as BG signal) Next, the main control unit 210 acquires the superimposed signal of the OCT signal and MZI signal acquired in step S1 by the combiner 90 as a BG signal and stores it in the storage unit 220.

[0087] Figure 7 shows an example of the BG signal acquired in step S2. For ease of explanation, Figure 7 shows the frequency spectrum of the BG signal obtained by applying a Fourier transform. In Figure 7, the horizontal axis represents the number of pixels corresponding to the depth position, and the vertical axis represents the signal amplitude as a power ratio.

[0088] As shown in Figure 7, the BG signal has a peak at the depth position (frequency component) corresponding to the MZI signal. On the other hand, the BG signal does not have a significant frequency component in the measurement range in the depth direction at the measurement site.

[0089] (S3: Set the BG signal as the MZI signal) Next, the main control unit 210 sets the BG signal acquired in step S2 as the MZI signal.

[0090] (S4: Perform OCT on the eye under examination) Next, the main control unit 210 performs OCT by controlling the wavelength-swept light source 10 and the device optical system 70 while the eye under examination E is positioned at the measurement position of the eye under examination in the first interference optical system 30 in Figure 1. As a result, the OCT signal originating from the eye under examination E corresponding to the detection result of interference light obtained by the first interference optical system 30 and the MZI signal corresponding to the detection result of interference light obtained by the second interference optical system 40 are acquired simultaneously.

[0091] (S5: Superimposed signal acquisition) Next, the main control unit 210 acquires the superimposed signal of the OCT signal and MZI signal acquired in step S4 by the combiner 90 and stores it in the storage unit 220.

[0092] Figure 8 shows an example of the superimposed signal obtained in step S5. For ease of explanation, Figure 8 shows the frequency spectrum of the superimposed signal obtained by applying a Fourier transform. In Figure 8, the horizontal axis represents the number of pixels corresponding to the depth position, and the vertical axis represents the amplitude of the signal as a power ratio.

[0093] As shown in Figure 8, the superimposed signal has a peak at the depth position (frequency component) corresponding to the MZI signal, and has frequency components corresponding to the morphology of the measurement site within the measurement range in the depth direction of the measurement site.

[0094] (S6: Wavenumber linear processing) Next, the main control unit 210 controls the wavenumber linear processing unit 310 to perform wavenumber linear processing on the superimposed signal obtained by executing step S5. That is, the main control unit 210 (control unit 200) controls the wavenumber linear processing unit 310 to perform wavenumber linear processing on the superimposed signal generated by the combiner 90 using the return light of the measurement light LS originating from the eye E, with the BG signal as the MZI signal.

[0095] The wavenumber linear processing unit 310 performs wavenumber linear processing on the superimposed signal (the OCT signal included in the superimposed signal) that is generated using the return light of the measurement light LS originating from the eye E, based on the above MZI signal.

[0096] In some embodiments, the main control unit 210 controls the wavenumber linear processing unit 310 after the completion of OCT execution for all scan positions within a preset scan range, causing it to perform wavenumber linear processing on each of the one or more superimposed signals acquired by repeatedly performing OCT scans.

[0097] (S7: Fourier transform processing) Next, the main control unit 210 controls the Fourier transform processing unit 320 to perform a Fourier transform on the superimposed signal obtained in step S6 after wavenumber linear processing.

[0098] In some embodiments, the main control unit 210 causes the Fourier transform process to be performed on each of the one or more superimposed signals obtained repeatedly in step S6 after wavenumber linear processing.

[0099] (S8: Forming an OCT image) Next, the main control unit 210 controls the image forming unit 400 to form an OCT image based on the signal after the Fourier transform processing obtained in step S7.

[0100] This concludes the first operational example of ophthalmic device 1 (end).

[0101] In some embodiments, the main control unit 210 controls the signal separation unit 330 without acquiring a BG signal to separate the MZI signal from the superimposed signal originating from the eye E under examination and store it in the storage unit 220. The main control unit 210 controls the wavenumber linear processing unit 310 to perform wavenumber linear processing on each of the one or more superimposed signals originating from the eye E under examination using the MZI signal stored in the storage unit 220.

[0102] <Second Operation Example> Figure 9 shows a flowchart of a second operation example of the ophthalmic device 1 according to the embodiment. Figure 9 represents a flowchart of the second operation example of the ophthalmic device 1 according to the embodiment. The memory unit 220 stores a computer program for realizing the process shown in Figure 9. The main control unit 210 executes the process shown in Figure 9 by operating according to this computer program.

[0103] (S11: Perform OCT without placing the eye to be examined) First, the main control unit 210, similar to step S1, performs OCT by controlling the wavelength sweep light source 10 and the device optical system 70 with the eye to be examined E not placed at the measurement position of the eye to be examined in the first interference optical system 30 in Figure 1 (air state). As a result, an OCT signal not originating from the eye to be examined, corresponding to the detection result of interference light obtained by the first interference optical system 30, and an MZI signal corresponding to the detection result of interference light obtained by the second interference optical system 40 are acquired simultaneously.

[0104] (S12: Superimposed signal acquired as BG signal) Next, the main control unit 210, similar to step S2, acquires the superimposed signal of the OCT signal and MZI signal acquired in step S11 by the combiner 90 as a BG signal and stores it in the storage unit 220. In step S12, a BG signal as shown in Figure 7 is acquired.

[0105] (S13: Set the BG signal as the rough MZI signal) Next, the main control unit 210 sets the BG signal acquired in step S12 as the rough MZI signal.

[0106] (S14: Perform OCT on the eye under examination) Next, the main control unit 210, similar to step S4, performs OCT by controlling the wavelength-swept light source 10 and the device optical system 70 with the eye under examination E positioned at the measurement position of the eye under examination in the first interference optical system 30 in Figure 1. As a result, the OCT signal originating from the eye under examination E corresponding to the detection result of interference light obtained by the first interference optical system 30 and the MZI signal corresponding to the detection result of interference light obtained by the second interference optical system 40 are acquired simultaneously.

[0107] (S15: Acquisition of superimposed signal) Next, the main control unit 210 acquires the superimposed signal of the OCT signal and MZI signal acquired in step S14 by the combiner 90 and stores it in the storage unit 220.

[0108] Figure 10 shows an example of the superimposed signal obtained in step S15. For convenience of explanation, Figure 10 shows the frequency spectrum of the superimposed signal obtained by applying a Fourier transform. In Figure 10, the horizontal axis represents the number of pixels corresponding to the depth position, and the vertical axis represents the amplitude of the signal as a power ratio.

[0109] As shown in Figure 10, if the wavelength sweep operation of the wavelength sweep light source 10 is nonlinear, for example, the frequency range of the OCT signal expands to the lower frequency side, and the frequency range of the OCT signal and the frequency range of the MZI signal overlap. In such a state, it is not possible to separate only the MZI signal included in the superimposed signal, and even if wavenumber linear processing is applied to the superimposed signal, it becomes difficult to linearize the OCT signal with high accuracy.

[0110] (S16: Wavenumber linear processing using rough MZI signal) Next, the main control unit 210 controls the wavenumber linear processing unit 310 to perform wavenumber linear processing on the superimposed signal acquired in step S15 using the rough MZI signal set in step S13.

[0111] Figure 11 shows an example of the superimposed signal after wavenumber linear processing obtained in step S16. For convenience of explanation, Figure 11 shows the frequency spectrum of the superimposed signal obtained by applying the Fourier transform. In Figure 11, the horizontal axis represents the number of pixels corresponding to the depth position, and the vertical axis represents the amplitude of the signal as a power ratio.

[0112] As shown in Figure 11, by performing wavenumber linear processing using the rough MZI signal, the frequency components of the MZI signal and the frequency components of the OCT signal included in the superimposed signal can be separated. Therefore, in this embodiment, following step S16, the following processing is performed.

[0113] (S17: Fourier transform processing) Next, the main control unit 210 controls the Fourier transform processing unit 320 to perform a Fourier transform on the superimposed signal obtained in step S16 after wavenumber linear processing.

[0114] (S18: Separation of OCT signal and MZI signal) Next, the main control unit 210 controls the signal separation unit 330 to separate the OCT signal and the MZI signal from the superimposed signal in the frequency space acquired in step S17 (see Figure 11).

[0115] (S19: Wavenumber linear processing is performed on the OCT signal using the MZI signal) Next, the main control unit 210 controls the wavenumber linear processing unit 310 again to perform wavenumber linear processing on the OCT signal separated in step S18 using the MZI signal separated in step S18.

[0116] Specifically, the control unit 200 (main control unit 210) controls the wavenumber linear processing unit 310 to perform wavenumber linear processing on the superimposed signal generated by the combiner 90 using the return light of the measurement light LS originating from the eye E, with the BG signal as the MZI signal (rough MZI signal). Subsequently, the control unit 200 controls the Fourier transform processing unit 320 to perform Fourier transform processing on the superimposed signal after wavenumber linear processing. Subsequently, the control unit 200 controls the wavenumber linear processing unit 310 to perform wavenumber linear processing on the OCT signal included in the superimposed signal after Fourier transform processing, based on the MZI signal separated from the superimposed signal after Fourier transform processing.

[0117] The main control unit 210 executes steps S14 to S19 for each A-scan.

[0118] (S20: Forming an OCT image) Next, the main control unit 210 controls the image forming unit 400 to form an OCT image based on the wavenumber linear processing signal obtained by repeatedly executing steps S14 to S19 for each A-scan.

[0119] This concludes the operation of the second example of ophthalmic device 1 (end).

[0120] Step S6, step S16, or step S19 is an example of a "wavenumber linear processing step" according to the embodiment. Step S1 is an example of an "interferogram signal generation step" according to the embodiment. Step S17 is an example of a "Fourier transform processing step" according to the embodiment. Step S18 is an example of a "signal separation step" according to the embodiment. Steps S11 to S19 are examples of "control steps" according to the embodiment.

[0121] In the above embodiment, steps S15 to S17 describe a case where a Fourier transform is performed on the superimposed signal after wavenumber linear processing, but the embodiment is not limited to this. For example, in step S17, a Fourier transform may be performed on the superimposed signal obtained in step S15, and in step S18, the OCT signal and the MZI signal may be separated from the signal after the Fourier transform processing in step S17.

[0122] As described above, when the wavelength sweep operation of the wavelength sweep light source 10 is stable, according to this embodiment, the configuration of the DAQ is simplified and the BG signal is used as the MZI signal. This makes it possible to perform high-precision wavenumber linear processing on the OCT signal originating from the eye E under examination at low cost with simple control.

[0123] Furthermore, if the wavelength sweep operation of the wavelength sweep light source 10 is unstable, wavenumber linear processing is performed on the OCT signal originating from the eye E using a rough MZI signal. In addition, an MZI signal is extracted from the superimposed signal after wavenumber linear processing, and wavenumber linear processing is performed again on the OCT signal originating from the eye E using the extracted MZI signal. This makes it possible to perform high-precision wavenumber linear processing on the OCT signal originating from the eye E at low cost, even if the wavelength sweep operation of the wavelength sweep light source 10 is unstable.

[0124] <Modification> The configuration of the ophthalmic apparatus according to the embodiment is not limited to the above configuration. For example, the ophthalmic apparatus according to the embodiment may be configured to optically combine interference light for measurement and interference light for calibration originating from the eye E under examination, and to send an interferogram signal corresponding to the detection result of the combined interference light to the DAQ as the superimposed signal according to the above embodiment.

[0125] Figure 12 shows an example of the optical system configuration of an ophthalmic device according to a modified embodiment. In Figure 12, the same reference numerals are used for parts that are the same as in Figure 1, and their descriptions are omitted as appropriate.

[0126] The differences between the optical system configuration of the ophthalmic device 1a according to this modified example and the optical system configuration of the ophthalmic device 1 according to the embodiment are that the splitter 20, the second interference optical system 40, the frequency filter 80, and the combiner 90 are omitted, the first interference optical system 30a is provided in place of the first interference optical system 30, and the DAQ 100a is provided in place of the DAQ 100.

[0127] The first interference optical system 30a includes fiber couplers 31 and 32 and a third interference optical system 35a. The third interference optical system 35a is located in the optical path of the reference light LR. The third interference optical system 35a may be a Mach-Zehnder interferometer, a Michelson interferometer, or a Fabry-Perot interferometer. In Figure 12, the third interference optical system 35a is a Mach-Zehnder interferometer.

[0128] The light source L0 from the wavelength-swept light source 10 is guided through an optical fiber to a fiber coupler 31. The fiber coupler 31 splits the light source L0 from the wavelength-swept light source 10 into a measurement light LS and a reference light LR. The reference light LR is guided through an optical fiber to a third interference optical system 35a.

[0129] The third interference optical system 35a includes a splitter 36a and a fiber coupler 37a. The splitter 36a and the fiber coupler 37a are connected by two optical fibers with different optical path lengths. The splitter 36a splits the reference light LR into two reference lights. For example, the splitter 36a splits the reference light LR into two reference lights with a splitting ratio of 99:1. The two reference lights are led to the fiber coupler 37a through optical fibers with different optical path lengths. The splitter 36a may be a fiber coupler.

[0130] The fiber coupler 37a generates calibration interference light by combining (interfering with) two reference beams traveling through optical fibers with different optical path lengths. In some embodiments, the third interference optical system 35a includes an optical element that can change the difference in optical path lengths between the two optical fibers between the splitter 36a and the fiber coupler 37a. In this case, it is possible to change the difference in optical path lengths between the two reference beams. The calibration interference light emitted from the fiber coupler 37a is guided through the optical fiber to the fiber coupler 32.

[0131] The fiber coupler 32 combines (interferes) the return light of the measurement light LS from the eye E under examination with the reference light from the fiber coupler 37a to generate a pair of interference light LC for measurement. Calibration interference light is superimposed on the interference light LC for measurement. The pair of interference light LC emitted from the fiber coupler 32 are each led to the detector 50 by optical fibers. The detector 50 outputs a superimposed signal (interferogram signal) corresponding to the pair of interference light LC in which calibration interference light is superimposed on the interference light for measurement.

[0132] A configuration in which the third interference optical system 35a is arranged in the optical path of the reference light LR is disclosed in Gangjun Liu, et al., “Postprocessing algorithms to minimize fixed-pattern artifact and reduce trigger jitter in swept source optical coherence tomography” (OPTICS EXPRESS, 9 Apr 2015, Vol. 23, No. 8, pp. 9824-9834).

[0133] DAQ100a, like DAQ100, includes an A / D converter 101 and acquires the superimposed signal from the detector 50. The wavenumber linear processing unit 310 performs wavenumber linear processing on the superimposed signal corresponding to the detection result of the interference light for measurement, based on the calibration interference light contained in the interference light for measurement.

[0134] In this modified example, the wavenumber linear processing of the acquired superimposed signal is the same as in the embodiment described above, so its explanation is omitted.

[0135] According to this modified example, since the superimposed signal is generated optically, only one balanced photodiode is needed, simplifying the configuration compared to the case where the superimposed signal is generated electrically.

[0136] The first interference optical system 30a is an example of an "interference optical system" according to the embodiment.

[0137] <Other Modifications> In the above embodiments or their modifications, a case has been described in which the difference in optical path length for generating calibration interference light is predetermined. However, the configurations according to the embodiments are not limited thereto.

[0138] For example, an ophthalmic apparatus according to the embodiment or a modified thereof may be configured to adjust the optical path length difference for generating calibration interference light so as to improve the image quality of the OCT image based on the signal after wavenumber linear processing of the superimposed signal. Specifically, an ophthalmic apparatus according to the embodiment or a modified thereof is configured to perform an evaluation of the image quality of the OCT image based on the signal after wavenumber linear processing of the superimposed signal. The ophthalmic apparatus then repeatedly performs the above-mentioned adjustment of the optical path length difference based on the evaluation result of the image quality of the OCT image, the execution of wavenumber linear processing of the superimposed signal, the formation of an OCT image based on the signal after wavenumber linear processing, and the evaluation of the image quality of the OCT image in sequence so as to improve the image quality of the OCT image. In this case, high-precision calibration can be performed with uniform control regardless of the stability of the wavelength sweep operation of the wavelength sweep light source 10.

[0139] [Operation] The OCT apparatus, the control method for the OCT apparatus, and the program according to the embodiment will be described.

[0140] The first embodiment is an OCT apparatus (ophthalmic apparatus 1) including a wavelength-swept light source (10), a splitter (20), a first interference optical system (30), a second interference optical system (40), a combiner (90), and a wavenumber linear processing unit (310). The splitter divides the light source light (L0) emitted from the wavelength-swept light source into a first light source light (L1) and a second light source light (L2). The first interference optical system divides the first light source light into a measurement light (LS) and a reference light (LR), and guides the measurement light to the object to be measured (eye to be examined E). Furthermore, the first interference optical system generates a first interferogram signal (OCT signal) by detecting the interference light (LC) for measurement between the reference light and the return light of the measurement light from the object to be measured. The second interference optical system generates interference light for calibration (wavenumber linear processing) corresponding to a predetermined optical path length difference from the second light source, and generates a second interferogram signal (MZI signal) by detecting the calibration interference light. The combiner generates a composite signal (superimposed signal) of the first interferogram signal and the second interferogram signal. The wavenumber linear processing unit performs wavenumber linear processing on at least the first interferogram signal included in the composite signal, based on the second interferogram signal included in the composite signal.

[0141] This configuration allows for high-precision wavenumber linear processing of interferogram signals originating from the object under measurement without reducing accuracy. Furthermore, since the combined signal is supplied to the wavenumber linear processing unit, the wavenumber linear processing unit (or the unit supplying the signal to the wavenumber linear processing unit (e.g., DAQ)) only needs to have a single-channel configuration. Moreover, the amount of signal to be stored in the wavenumber linear processing unit only needs to be for one channel. Consequently, the cost of the OCT device can be reduced.

[0142] In a second embodiment, in the first embodiment, the second interference optical system includes a Mach-Zehnder interferometer, a Michelson interferometer, or a Fabry-Perot interferometer.

[0143] According to this embodiment, it becomes possible to perform high-precision wavenumber linear processing on interferogram signals originating from the object being measured at low cost, using a simple configuration.

[0144] In a third embodiment, in the first or second embodiment, the first interference optical system generates a first interferogram signal using the reflected light of measurement light not originating from the object under measurement. The wavenumber linear processing unit performs wavenumber linear processing on the first interferogram signal generated using the reflected light of measurement light originating from the object under measurement, based on the background signal (BG signal) generated by the combiner using the first interferogram signal.

[0145] In this embodiment, the first interferogram signal generated using the reflected light of the measurement light not originating from the object under measurement, and the second interferogram signal are included in the composite signal in a separable manner. Therefore, once a composite signal containing the second interferogram signal is obtained, wavenumber linear processing using the second interferogram signal can be performed on each of the one or more composite signals containing the first interferogram signal originating from the object under measurement. As a result, it becomes possible to simplify control while reducing the processing load of wavenumber linear processing.

[0146] A fourth aspect of the embodiment includes a control unit (200, main control unit 210) in the third embodiment. The control unit controls the wavenumber linear processing unit to perform wavenumber linear processing on the combined signal generated by the combiner using the reflected light of the measurement light from the object under measurement as a second interferogram signal, with the background signal as the second interferogram signal.

[0147] In this configuration, when the wavelength sweep operation of the wavelength sweep light source is stable, the first interferogram signal generated using the return light of measurement light not originating from the object under measurement and the second interferogram signal are included in the composite signal in a manner that allows for high-precision separation. Consequently, it becomes possible to simplify control while reducing the processing load of wavenumber linear processing.

[0148] A fifth aspect of the embodiment includes, in the first or second embodiment, a Fourier transform processing unit (320) and a signal separation unit (330). The Fourier transform processing unit performs a Fourier transform on the composite signal or the signal after wavenumber linear processing of the composite signal. The signal separation unit separates a first interferogram signal and a second interferogram signal from the signal after the Fourier transform processing.

[0149] According to this configuration, the first interferogram signal and the second interferogram signal can be separated from the combined signal with high precision, and high-precision wavenumber linear processing can be performed at low cost.

[0150] A sixth aspect of the embodiment, in the third embodiment, includes a Fourier transform processing unit (320), a signal separation unit (330), and a control unit (200, main control unit 210). The Fourier transform processing unit performs a Fourier transform on the combined signal or the signal after wavenumber linear processing of the combined signal. The signal separation unit separates the first interferogram signal and the second interferogram signal from the signal after the Fourier transform processing. The control unit controls the wavenumber linear processing unit, the Fourier transform processing unit, and the signal separation unit. The control unit controls the wavenumber linear processing unit so that it performs wavenumber linear processing on the combined signal generated by the combiner using the return light of the measurement light from the object under measurement as the background signal and the second interferogram signal. The control unit also controls the Fourier transform processing unit so that it performs a Fourier transform on the combined signal after wavenumber linear processing. Furthermore, the control unit controls the wavenumber linear processing unit to perform wavenumber linear processing on the first interferogram signal included in the composite signal after the Fourier transform processing, based on the second interferogram signal separated from the composite signal after the Fourier transform processing.

[0151] According to this configuration, even if the wavelength sweep operation of the wavelength-swept light source is unstable and the frequency ranges of the first interferogram signal and the second interferogram signal partially overlap, the MZI signal can be separated from the superimposed signal, and high-precision wavenumber linear processing can be performed at low cost.

[0152] A seventh aspect of the embodiment includes a frequency filter (80) in the first or second embodiment. The frequency filter is positioned between the second interference optical system and the combiner and allows the second interferogram signal to pass through in a frequency range that does not overlap with the frequency range of the first interferogram signal.

[0153] According to this configuration, the first interferogram signal and the second interferogram signal can be included in the composite signal in a manner that allows for high-precision separation, thereby enabling high-precision wavenumber linear processing to be performed at low cost.

[0154] An eighth aspect of the embodiment includes, in the seventh embodiment, an A / D converter (101) for sampling the composite signal. The passband of the frequency filter includes frequencies that are 1 / 8 or less of a predetermined maximum sampling frequency that the A / D converter can sample.

[0155] According to this configuration, high-precision wavenumber linear processing can be performed at low cost using an A / D converter with optimal cost performance.

[0156] The ninth embodiment is an OCT apparatus (ophthalmic apparatus 1a) including a wavelength-swept light source (10), an interference optical system (first interference optical system 30), and a wavenumber linear processing unit (310). The interference optical system splits the light source light (L0) emitted from the wavelength-swept light source into a measurement light (LS) and a reference light (LR), and guides the measurement light to the object to be measured (eye to be examined E). Furthermore, the interference optical system generates two reference lights having a predetermined optical path length difference from the reference light, generates a measurement interference light (LC) between the reference light and the return light of the measurement light from the object to be measured, and a calibration interference light (wavenumber linear processing) between the two reference lights, and also synthesizes the calibration interference light with the measurement interference light. The wavenumber linear processing unit performs wavenumber linear processing on the interferogram signal corresponding to the detection result of the measurement interference light based on the calibration interference light included in the measurement interference light.

[0157] This configuration allows for high-precision wavenumber linear processing of the interferogram signal originating from the object under measurement without reducing accuracy. Furthermore, the wavenumber linear processing unit is configured to optically combine calibration interference light with measurement interference light and supply a signal corresponding to the combined light. Therefore, the wavenumber linear processing unit (or the unit supplying the signal to the wavenumber linear processing unit (e.g., DAQ)) and the balance photodiode only need to have a configuration for one channel. Moreover, the amount of signal to be stored in the wavenumber linear processing unit only needs to be for one channel. Consequently, the cost of the OCT device can be reduced.

[0158] In the tenth embodiment, in the ninth embodiment, the interference optical system includes a Mach-Zehnder interferometer, a Michelson interferometer, or a Fabry-Perot interferometer, which are positioned in the optical path of the reference light.

[0159] According to this embodiment, it becomes possible to perform high-precision wavenumber linear processing on interferogram signals originating from the object being measured at low cost, using a simple configuration.

[0160] In the eleventh embodiment, in the first, second, ninth, or tenth embodiment, the object to be measured is the eye to be examined (E).

[0161] According to this embodiment, it becomes possible to provide an ophthalmic device that can perform high-precision wavenumber linear processing on interferogram signals derived from the eye under examination at low cost.

[0162] A twelfth aspect of the embodiment is a control method for an OCT apparatus (ophthalmic apparatus 1) including a wavelength-swept light source (10), a splitter (20), a first interference optical system (30), a second interference optical system (40), and a combiner (90). The splitter divides the light source light (L0) emitted from the wavelength-swept light source into a first light source light (L1) and a second light source light (L2). The first interference optical system divides the first light source light into a measurement light (LS) and a reference light (LR), and guides the measurement light to the object under test (eye under test E). Furthermore, the first interference optical system generates a first interferogram signal (OCT signal) by detecting the interference light (LC) for measurement between the reference light and the return light of the measurement light from the object under test. The second interference optical system generates interference light for calibration (wavenumber linear processing) corresponding to a predetermined optical path length difference from the second light source, and generates a second interferogram signal (MZI signal) by detecting the calibration interference light. The combiner generates a composite signal (superimposed signal) of the first interferogram signal and the second interferogram signal. The control method of the OCT apparatus includes a wavenumber linear processing step in which wavenumber linear processing is applied to at least the first interferogram signal included in the composite signal, based on the second interferogram signal included in the composite signal.

[0163] This configuration allows for high-precision wavenumber linear processing of interferogram signals originating from the object under measurement without reducing accuracy. Furthermore, since the system is configured to supply a synthesized signal to the wavenumber linear processing execution unit, the wavenumber linear processing execution unit (or the unit supplying signals to the wavenumber linear processing execution unit (e.g., DAQ)) only needs to have a single-channel configuration. Moreover, the amount of signal to be stored and supplied to the wavenumber linear processing execution unit only needs to be for one channel. Consequently, the cost of the OCT device can be reduced.

[0164] In the thirteenth embodiment, in the twelfth embodiment, the first interference optical system includes an interferogram signal generation step in which the first interferogram optical system generates a first interferogram signal using the reflected light of measurement light not originating from the object under measurement. The wavenumber linear processing step applies wavenumber linear processing to the first interferogram signal generated using the reflected light of measurement light originating from the object under measurement, based on a background signal (BG signal) generated by a combiner using the first interferogram signal.

[0165] In this configuration, when the wavelength sweep operation of the wavelength sweep light source is stable, the first interferogram signal generated using the return light of measurement light not originating from the object under measurement and the second interferogram signal are included in the composite signal in a manner that allows for high-precision separation. Consequently, it becomes possible to simplify control while reducing the processing load of wavenumber linear processing.

[0166] A fourteenth aspect of the embodiment includes, in the thirteenth aspect, a Fourier transform processing step and a signal separation step. The Fourier transform processing step applies a Fourier transform to the composite signal or the signal after wavenumber linear processing of the composite signal. The signal separation step separates a first interferogram signal and a second interferogram signal from the signal after the Fourier transform processing.

[0167] According to this configuration, the first interferogram signal and the second interferogram signal can be separated from the combined signal with high precision, and high-precision wavenumber linear processing can be performed at low cost.

[0168] A fifteenth aspect of the embodiment includes a control step. The control step applies wavenumber linear processing to the composite signal generated by the combiner using the reflected light of the measurement light from the object under measurement, with the background signal as the second interferogram signal. The control step also applies a Fourier transform to the composite signal after wavenumber linear processing. Furthermore, the control step applies wavenumber linear processing to the first interferogram signal included in the composite signal after Fourier transform processing, based on the second interferogram signal separated from the composite signal after Fourier transform processing.

[0169] According to this configuration, even if the wavelength sweep operation of the wavelength-swept light source is unstable and the frequency ranges of the first interferogram signal and the second interferogram signal overlap, high-precision wavenumber linear processing can be performed at low cost.

[0170] In the sixteenth embodiment, in any of the twelveth to fifteenth embodiments, the object to be measured is the eye to be examined (E).

[0171] According to this configuration, high-precision wavenumber linear processing can be performed at low cost on interferogram signals derived from the eye being examined.

[0172] A 17th embodiment involves causing a computer to perform each step of the control method for an optical coherence tomography apparatus according to any of the 12th to 15th embodiments.

[0173] This configuration allows for high-precision wavenumber linear processing of interferogram signals originating from the object under measurement without reducing accuracy. Furthermore, since the system is configured to supply a synthesized signal to the wavenumber linear processing execution unit, the wavenumber linear processing execution unit (or the unit supplying signals to the wavenumber linear processing execution unit (e.g., DAQ)) only needs to have a single-channel configuration. Moreover, the amount of signal to be stored and supplied to the wavenumber linear processing execution unit only needs to be for one channel. Consequently, the cost of the OCT device can be reduced.

[0174] <Other> The embodiments described above are merely examples of how to carry out this invention. Anyone intending to carry out this invention may make any modifications, omissions, additions, etc., within the scope of the gist of this invention.

[0175] 1, 1a Ophthalmic apparatus 10 Wavelength-swept light source 20 Splitter 30, 30a First interference optical system 40 Second interference optical system 50, 60 Detector 70 Apparatus optical system 80 Frequency filter 90 Combiner 100, 100a DAQ 101 A / D converter 200 Control unit 210 Main control unit 220 Memory unit 300 Signal processing unit 310 Wavenumber linear processing unit 320 Fourier transform processing unit 330 Signal separation unit E Eye under examination L0 Light source L1 First light source L2 Second light source LC Interference light LR Reference light LS Measurement light

Claims

1. An optical coherence tomography apparatus comprising: a wavelength-swept light source; a splitter that divides light emitted from the wavelength-swept light source into a first light source and a second light source; a first interference optical system that divides the first light source into a measurement light and a reference light, guides the measurement light to an object to be measured, and generates a first interferogram signal by detecting interference light for measurement between the reference light and the return light of the measurement light from the object to be measured; a second interference optical system that generates calibration interference light corresponding to a predetermined optical path length difference from the second light source and generates a second interferogram signal by detecting the calibration interference light; a combiner that generates a composite signal of the first interferogram signal and the second interferogram signal; and a wavenumber linear processing unit that performs wavenumber linear processing on at least the first interferogram signal included in the composite signal based on the second interferogram signal included in the composite signal.

2. The optical coherence tomography apparatus according to claim 1, characterized in that the second interference optical system includes a Mach-Zehnder interferometer, a Michelson interferometer, or a Fabry-Perot interferometer.

3. The optical coherence tomography apparatus according to claim 1 or 2, characterized in that the first interference optical system generates the first interferogram signal using the reflected light not originating from the object under measurement, and the wavenumber linear processing unit performs wavenumber linear processing on the first interferogram signal generated using the reflected light originating from the object under measurement, based on the background signal generated by the combiner using the first interferogram signal.

4. The optical coherence tomography apparatus according to claim 3, further comprising a control unit that controls the wavenumber linear processing unit to perform wavenumber linear processing on the composite signal generated by the combiner using the reflected light from the object under measurement, with the background signal as the second interferogram signal.

5. The optical coherence tomography apparatus according to claim 1 or 2, comprising: a Fourier transform processing unit that performs a Fourier transform on the composite signal or the signal after wavenumber linear processing of the composite signal; and a signal separation unit that separates the first interferogram signal and the second interferogram signal from the signal after the Fourier transform processing.

6. The optical coherence tomography apparatus according to claim 3, comprising: a Fourier transform processing unit that performs a Fourier transform on the composite signal or the signal after wavenumber linear processing of the composite signal; a signal separation unit that separates the first interferogram signal and the second interferogram signal from the signal after the Fourier transform processing; and a control unit that controls the wavenumber linear processing unit, the Fourier transform processing unit, and the signal separation unit, wherein the control unit controls the wavenumber linear processing unit to perform the wavenumber linear processing on the composite signal generated by the combiner using the return light from the object under measurement as the background signal as the second interferogram signal; controls the Fourier transform processing unit to perform the Fourier transform processing on the composite signal after the wavenumber linear processing; and controls the wavenumber linear processing unit to perform the wavenumber linear processing on the first interferogram signal included in the composite signal after the Fourier transform processing, based on the second interferogram signal separated from the composite signal after the Fourier transform processing.

7. The optical coherence tomography apparatus according to claim 1 or 2, characterized in that it includes a frequency filter disposed between the second interference optical system and the combiner, which allows the second interferogram signal to pass through in a frequency range that does not overlap with the frequency range of the first interferogram signal.

8. The optical coherence tomography apparatus according to claim 7, comprising an A / D converter for sampling the composite signal, wherein the passband of the frequency filter includes a frequency of 1 / 8 or less of a predetermined maximum sampling frequency that the A / D converter can sample.

9. An optical coherence tomography apparatus comprising: a wavelength-swept light source; an interference optical system that splits the light source emitted from the wavelength-swept light source into a measurement light and a reference light, guides the measurement light to an object to be measured, generates two reference lights having a predetermined optical path length difference from the reference light, generates interference light for measurement between the reference light and the return light of the measurement light from the object to be measured and interference light for calibration between the two reference lights, and synthesizes the interference light for measurement with the interference light for calibration; and a wavenumber linear processing unit that performs wavenumber linear processing on an interferogram signal corresponding to the detection result of the interference light for measurement based on the interference light for calibration contained in the interference light for measurement.

10. The optical coherence tomography apparatus according to claim 9, characterized in that the interference optical system includes a Mach-Zehnder interferometer, a Michelson interferometer, or a Fabry-Perot interferometer, which is positioned in the optical path of the reference light.

11. The optical coherence tomography apparatus according to claim 1, 2, 9, or 10, characterized in that the object to be measured is an eye to be examined.

12. A method for controlling an optical coherence tomography apparatus, comprising: a wavelength-swept light source; a splitter that divides light emitted from the wavelength-swept light source into a first light source and a second light source; a first interference optical system that divides the first light source into a measurement light and a reference light, guides the measurement light to an object to be measured, and generates a first interferogram signal by detecting interference light for measurement between the reference light and the return light of the measurement light from the object to be measured; a second interference optical system that generates calibration interference light corresponding to a predetermined optical path length difference from the second light source and generates a second interferogram signal by detecting the calibration interference light; and a combiner that generates a composite signal of the first interferogram signal and the second interferogram signal, the method comprising a wavenumber linear processing step of performing wavenumber linear processing on at least the first interferogram signal included in the composite signal based on the second interferogram signal included in the composite signal.

13. The control method for an optical coherence tomography apparatus according to 12, wherein the first interference optical system includes an interferogram signal generation step of generating the first interferogram signal using the return light not originating from the object under measurement, and the wavenumber linear processing step is to perform wavenumber linear processing on the first interferogram signal generated using the return light originating from the object under measurement, based on a background signal generated by the combiner using the first interferogram signal.

14. A control method for an optical coherence tomography apparatus according to 13, comprising: a Fourier transform processing step of applying a Fourier transform to the composite signal or the signal after wavenumber linear processing of the composite signal; and a signal separation step of separating the first interferogram signal and the second interferogram signal from the signal after the Fourier transform processing.

15. A control method for an optical coherence tomography apparatus according to 13, characterized by including a control step of applying the wavenumber linear processing to the composite signal generated by the combiner using the return light from the object to be measured as the background signal as the second interferogram signal, applying a Fourier transform to the composite signal after the wavenumber linear processing, and applying the wavenumber linear processing to the first interferogram signal included in the composite signal after the Fourier transform processing, based on the second interferogram signal separated from the composite signal after the Fourier transform processing.

16. A control method for an optical coherence tomography apparatus according to any one of claims 12 to 15, characterized in that the object to be measured is an eye to be examined.

17. A program characterized by causing a computer to perform each step of the control method for an optical coherence tomography apparatus described in any one of claims 12 to 15.

Images