Imaging Target Movement Correction in a Fourier Domain Optical Coherence Tomography System

Abstract

To compensate for a relative movement between an imaging target and a Fourier-domain optical coherence tomography (FD-OCT) scanner during a scan of the imaging target by the FD-OCT.SOLUTION: A Fourier-domain optical coherence tomography imaging system (10) comprises a Fourier-domain optical coherence tomography scanner (20) arranged to generate complex optical coherence tomography data (25) by performing a scan of an imaging target (30) to acquire samples whose complex values are indicative of an optical property of the imaging target at respective scan locations in the imaging target. The imaging system (10) further comprises a controller (40) arranged to calculate a two-dimensional cross-correlation using phase information of the acquired samples, and controls the scanner (20), based on the calculated cross-correlation, to compensate for relative movement between the imaging target (30) and the scanner (20) during the scan.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Exemplary aspects of the present specification generally relate to the field of Fourier domain optical coherence tomography (FD-OCT) imaging systems, and more particularly, to techniques for correcting relative movement between an imaging target and an FD-OCT scanner during scanning of the imaging target by the FD-OCT scanner.

Background Art

[0002] Optical coherence tomography (OCT) is an imaging technique based on low coherence interferometry and is widely used to obtain high-resolution two-dimensional and three-dimensional images of light-scattering media such as biological tissues.

Summary of the Invention

[0003] As is well known, OCT imaging systems can be classified as time-domain OCT (TD-OCT) or Fourier-domain OCT (FD-OCT) (also called frequency-domain OCT), depending on how depth ranging is achieved. In TD-OCT, the optical path length of the reference arm of the interferometer in the imaging system changes temporally during acquisition of the reflectivity profile of the scattering medium (referred to herein as the “imaging target”) being imaged by the OCT imaging system, and the reflectivity profile is generally referred to as a “depth scan” or “axial scan” (“A-scan”). In FD-OCT, the spectral interference pattern resulting from the interference between the reference arm and the sample arm of the interferometer at the scan position of each A-scan is Fourier-transformed to simultaneously acquire all points along the depth of the A-scan without requiring any variation in the optical path length of the reference arm. Since all backscatter from the sample is measured simultaneously in FD-OCT, it enables imaging at much higher speeds than scanning of the sample arm mirror in the interferometer. Two common types of FD-OCT are spectral-domain OCT (SD-OCT) and swept-source OCT (SS-OCT). In SD-OCT, a broadband light source irradiates the imaging target with a number of wavelengths, and a spectrometer is used as a detector to measure all wavelengths simultaneously. In SS-OCT (also called time-encoded frequency-domain OCT), the light source is swept through a range of wavelengths, and the temporal output of the detector is converted to spectral interference.

[0004] An OCT imaging system can also be classified as a point scan (also known as "point detection" or "scanning point"), line scan, or full field, depending on the method by which the imaging system is configured to acquire OCT data in a lateral direction. A point scan OCT imaging system acquires OCT data by scanning a focused sample beam across the surface of an imaging target. This is typically done by scanning the imaging target along a single line (e.g., which may define a circle or a helix, or alternatively be curved), or along a set of lines (usually substantially parallel) on the surface of the imaging target. Also, by acquiring an axial depth profile (A-scan) for each of a plurality of points along this line (s), an array of one-dimensional or two-dimensional A-scans representing the reflectivity profile of the sample in two or three dimensions (volume) at one point at a time is constructed, including OCT data.

[0005] Despite technological improvements that have enabled OCT imaging systems to acquire sample image data at an ever-increasing rate, involuntary eye movements during imaging (e.g., microsaccades) remain a significant cause of problems in OCT images, even in ultra-fast systems. Post-processing algorithms have been developed to address such eye movement problems, but this approach may not adequately handle large and rapid eye movements and may introduce gaps in the acquired OCT data that cannot be corrected in post-processing. A more effective approach to reducing eye movement problems is to use a second (fast) imaging modality, such as a scanning laser ophthalmoscope (SLO) or fundus camera, to acquire intensity-based retinal images, for example, to monitor movement of the imaged area of the retina during OCT imaging, and to use the eye movement signals obtained therefrom to control the OCT scanning mirror(s) to maintain the OCT scanning grid of the target.

[0006] (Overview) According to a first embodiment of the present specification, a Fourier domain optical coherence tomography (FD-OCT) system is provided, the system generating complex OCT data by scanning an imaging target, the complex values being obtained by acquiring samples indicating the optical characteristics of the imaging target at respective scanning positions of the imaging target, an FD-OCT scanner configured thereby, and performing a cross-correlation calculation using the phase information of the acquired samples, controlling the FD-OCT scanner based on the cross-correlation calculation, and a controller configured to correct a relative movement between the imaging target and the FD-OCT scanner during the scanning.

[0007] In an exemplary embodiment of the FD-OCT imaging system according to the first embodiment, the controller can be configured to perform a cross-correlation calculation by acquiring the first set of samples, where the samples include a first set of samples acquired by the FD-OCT scanner that scans the imaging target along a first scanning line of the imaging target, and acquiring a second set of the samples, where the second set includes samples acquired by the FD-OCT scanner that scans the imaging target along a second scanning line of the imaging target, and the second scanning line at least partially overlaps the first scanning line. Performing the cross-correlation calculation, a third set including at least some of the samples in the first set of samples, a fourth set including at least some of the samples in the second set of samples, and at least some of the samples in the third set of samples. For the common region of the imaging target where the first scanning line and the second scanning line of the fourth set of pre-samples overlap, a cross-correlation calculation is performed based on the phase information in the third set of samples and the phase information in the fourth set of samples. In an exemplary embodiment, the controller further uses the calculated cross-correlation to control the FD-OCT scanner to correct the relative movement between the imaging target and the FD-OCT scanner during scanning, register the first set of samples and the second set of samples with each other, determine the value of an offset index indicating the offset between the scanning position of the first set of samples and the scanning position of the second set of samples, and use the determined value of the offset index to control the FD-OCT scanner to correct the relative movement between the imaging target and the FD-OCT scanner that occurs between the acquisition of the first set of samples and the acquisition of the second set of samples by the FD-OCT scanner during scanning. It can be configured to control the FD-OCT scanner.

[0008] In a first modification of the above-described exemplary embodiment, the FD-OCT scanner can be arranged to generate complex OCT data by performing its scan such that the acquired samples define a repetitive B-scan of the imaging target, repeating a line scan of the imaging target along overlapping scan lines of the imaging target. In the first modification, the controller may be configured to perform a cross-correlation calculation by: obtaining, as a first set of samples, a first B-scan of the repetitive B-scan; obtaining, as a second set of samples, a second B-scan of the repetitive B-scan; and performing a cross-correlation calculation to calculate a cross-correlation between one or more A-scans of the first B-scan and the A-scans of the second B-scan, wherein the A-scans of the second B-scan include A-scans positioned corresponding to the second B-scan relative to one or more A-scans in the first B-scan. In the first modification, the controller may further be configured to control the FD-OCT scanner to correct a relative movement between the imaging target and the FD-OCT scanner that occurred between the acquisition of the first B-scan and the acquisition of the second B-scan by the FD-OCT scanner, by registering the first B-scan as the first set of samples and registering the second sample as the second set of samples, using the cross-correlation calculated to determine a value of an offset index for correcting the relative movement between the imaging target and the FD-OCT scanner.

[0009] In the first modification set as described above, the controller may be configured to execute a cross-correlation calculation that calculates the cross-correlation between a predetermined number of A-scans of the first B-scan and the A-scans of the second B-scan as the cross-correlation calculation. The cross-correlation calculation is based on the phase information in the predetermined number of A-scans of the first B-scan and the phase information in the second B-scan, and the predetermined number is selected such that the variation in the phase information among the predetermined number of A-scans of the first B-scan is less than a predetermined degree of variation. In this case, the controller is further configured to control the FD-OCT scanner so as to correct the relative movement between the imaging target and the FD-OCT scanner during the scanning. During the scanning, a plurality of the cross-correlation calculations are performed to calculate the respective cross-correlations between each set of the predetermined number of A-scans of the first B-scan and each of the A-scans of the second B-scan, and the respective A-scans of the second B-scan including the A-scans located corresponding to the predetermined number of the A-scans of the second B-scan are combined with the calculated cross-correlations to determine, as the offset value, a value indicating the offset between the first B-scan and the second B-scan, and the FD-OCT scanner is controlled to correct the relative movement between the imaging target and the FD-OCT scanner by using the determined offset value indicating the offset between the first B-scan and the second B-scan.

[0010] In the second modification of the FD-OCT imaging system of the above embodiment, the FD-OCT scanner includes, as a scan, an area OCT scan of an imaging target, and as an area OCT scan of the imaging target to generate complex OCT data, an area OCT scan including a sample having a complex value indicating the optical characteristics of the imaging target at each scanning position three-dimensionally distributed on the imaging target. The controller may be arranged to perform a cross-correlation calculation with a set of samples including the samples acquired by the FD-OCT scanner that scans the imaging target along a first scan line as at least a part of the area OCT scan as a first set of samples. The second scan line of the first set of samples obliquely crosses the first scan line.

[0011] In the second modification, the first scan line may be one of a plurality of parallel scan lines of the imaging target. The FD-OCT scanner is configured to perform an area OCT scan by scanning the imaging target along a plurality of parallel scan lines based on the area OCT scan and generate an OCT-C-scan as complex OCT data. The controller may be configured to perform a cross-correlation calculation by acquiring the complex OCT data of the OCT-C-scan as the first set of samples.

[0012] Alternatively, in the second modification, the first scan line may extend along two axial directions of the surface of the imaging target. For example, a square, triangle, rhombus, circle, ellipse, spiral, square spiral, Lissajous figure, epitrochoid, or hypotrochoid may be defined on the surface of the imaging target.

[0013] As a further modification, in the second modification, the first scan line and the second scan line may extend along two axial directions of the surface of the imaging target and be different respective portions of a single scan line that crosses (intersects) itself. The single scan line may define, for example, a Lissajous figure, epitrochoid, or hypotrochoid on the surface of the imaging target.

[0014] According to an aspect of the second example of this specification, a computer-implemented method for controlling an FD-OCT scanner is provided. This method generates complex OCT data by scanning an imaging target, obtains samples whose complex values indicate the optical characteristics of the imaging target at respective scanning positions of the imaging target, and corrects relative movement during scanning between the imaging target and the FD-OCT scanner. This method includes performing a cross-correlation calculation using the phase information of the obtained samples, and based on the cross-correlation calculation, controlling the FD-OCT scanner to correct the relative movement between the imaging target and the FD-OCT scanner during scanning.

[0015] In an exemplary embodiment of the computer-implemented method of the second embodiment, the cross-correlation calculation can be performed by obtaining the first set of samples, wherein the samples among the samples include samples obtained by the FD-OCT scanner that scans the imaging target along a first scanning line of the imaging target, obtaining the first set of the samples among the samples, and obtaining the samples of a second set of the samples, wherein the second set includes samples obtained by the FD-OCT scanner that scans the imaging target along a second scanning line of the imaging target, the second scanning line at least partially overlapping the first scanning line, performing the cross-correlation calculation to calculate a cross-correlation between a third set including at least some of the samples of the first set of samples and a fourth set including at least some of the samples of the second set of samples, and at least some of the samples of the third set being targets where the first scanning line and the second scanning line overlap, and the cross-correlation calculation being based on the phase information of the third set of samples and the phase information of the fourth set of samples. Further, in the computer-implemented method of the second embodiment, the FD-OCT scanner may be controlled to correct a relative movement between the imaging target and the FD-OCT scanner during scanning, which is performed by using the calculated cross-correlation to determine a value of an offset index between the first set of samples and the second set of samples, and using the determined value of the offset index to control the FD-OCT scanner during scanning and correct the relative movement between the imaging target and the FD-OCT scanner that occurred between the acquisition of the first set of samples and the acquisition of the second set of samples by the FD-OCT scanner.

[0016] In a first variant of the embodiment of the computer-implemented method described above, the FD-OCT scanner can generate the complex OCT data by performing the scan, and as the scan, the line scan of the imaging target is repeated along the scan lines overlapping the imaging target, and the acquired samples define the repeated B-scan of the imaging target. The method includes obtaining, as the first set of samples, the first B-scan of the samples of the repeated B-scan, obtaining, as the second set of samples, the second B-scan of the repeated B-scan, and performing, as the cross-correlation calculation, a cross-correlation calculation for calculating the cross-correlation between one or more A-scans of the first B-scan and the A-scans of the second B-scan, wherein the A-scans of the second B-scan include the A-scans located in the second B-scan corresponding to one or more A-scans of the first B-scan. This method includes registering the first B-scan as the first set of samples, and using the calculated cross-correlation as the second set of samples to determine the offset value between the first B-scan and the second B-scan as the value of the offset index, in order to correct the relative movement between the imaging target and the FD-OCT scanner that occurred between the acquisition of the first B-scan and the acquisition of the second B-scan by the FD-OCT scanner using the determined offset value, and controlling the FD-OCT scanner to correct the relative movement between the imaging target and the FD-OCT scanner can be included.

[0017] The method of the first modification example set as described above includes, as a cross-correlation calculation, executing a cross-correlation calculation for calculating a cross-correlation between a predetermined number of A-scans of the first B-scan and A-scans of the second B-scan, the cross-correlation calculation being based on phase information of the predetermined number of A-scans of the first B-scan and phase information of the A-scans of the second B-scan, the predetermined number being selected such that a variation in the phase information among the predetermined number of A-scans of the first B-scan is less than a predetermined degree of variation. The FD-OCT scanner may be controlled to correct a relative movement between the imaging target and the FD-OCT scanner, which includes, during scanning, executing a plurality of cross-correlation calculations for calculating a cross-correlation between each set of a predetermined number of A-scans of the first B-scan and each set of A-scans of the second B-scan, determining, as an offset value of a set of the predetermined number of A-scans, each A-scan of the second B-scan including an A-scan positioned corresponding to the second B-scan, by combining the calculated cross-correlations, and using the determined offset value indicating an offset between the first B-scan and the second B-scan to control the FD-OCT scanner to correct a relative movement between the imaging target and the FD-OCT scanner.

[0018] Alternatively, in the computer-implemented method of the second variant of the above-described example embodiment, the FD-OCT scanner, as the scanning, can generate complex OCT data by obtaining an OCT scan of the region of the imaging target at each of the scanning positions three-dimensionally distributed on the imaging target in order to obtain samples having complex values indicating the optical characteristics of the imaging target. This method can include performing a cross-correlation calculation by obtaining a set of samples including the samples obtained by the FD-OCT scanner that scans the target imaged along the first scan line as at least a part of the region OCT scan as the first set of samples, and the second scan line obliquely crosses the first scan line. The first scan line may be one of a plurality of parallel scan lines of the imaging target, and the FD-OCT scanner performs an OCT scan of the region by scanning the imaging target along the plurality of parallel scan lines, and generates an OCT-C-scan as complex OCT data based on the region OCT scan. In this case, the cross-correlation calculation may include obtaining the complex OCT data of the OCT-C-scan as the first set of samples.

[0019] Alternatively, in the computer-implemented method of the second variant, the first scan line may extend along two axial directions of the surface of the imaging target. For example, a square, triangle, rhombus, circle, ellipse, helix, square helix, Lissajous figure, epitrochoid, or hypotrochoid may be defined on the surface of the imaging target.

[0020] As a further variant, in the computer-implemented method of the second variant, the first scan line and the second scan line may each have different portions of a single scan line, which extends along two axial directions of the surface of the imaging target and crosses itself. The single scan line can define, for example, a Lissajous figure, an epitrochoid, or a hypotrochoid on the surface of the imaging target.

[0021] Also, according to a third exemplary aspect of the present specification, a computer program including computer-readable instructions is provided. When executed by a processor, an FD-OCT scanner generates complex OCT data by scanning an imaging target, and the processor obtains samples where complex values indicate optical characteristics of the imaging target at respective scanning positions of the imaging target. By executing a method according to any of the aspects as the second example, its embodiments, or the modifications described above, the FD-OCT scanner is controlled to correct relative movement between the imaging target and the FD-OCT scanner during scanning. The computer program may be stored in a non-transitory computer-readable storage medium (e.g., a computer hard disk or a CD), or may be carried by a computer-readable signal.

Brief Description of Drawings

[0022] Exemplary embodiments will be described in detail below by way of non-limiting examples with reference to the accompanying drawings described below. Like reference numerals appearing in different figures can indicate the same or functionally similar elements unless otherwise indicated.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

[0023] In view of the above-described background, the inventors have developed a scheme for at least partially avoiding the problem of movement in OCT data acquired during FD-OCT scanning without the need for a post-processing algorithm for solving problems having the above-described drawbacks or a second imaging modality for tracking an imaging target for motion correction. More specifically, the inventors have recognized that the phase information of the complex OCT data acquired by an FD-OCT imaging system can be acquired and used quickly enough to enable operation tracking and real-time control of the OCT data acquisition process to correct for relative movement between the FD-OCT imaging system and the imaging target, providing a detailed and reproducible "fingerprint" of the imaging structure. As a result, the inventors have devised a Fourier domain OCT imaging system, the Fourier domain OCT scanner being an FD-OCT scanner configured to generate complex OCT data, the complex values of which acquire samples indicative of the optical characteristics of the imaging target at respective scan positions of the imaging target by scanning the imaging target, and a controller configured to perform a cross-correlation calculation using the phase information of the acquired samples, and based on the cross-correlation calculation, correct for relative movement between the imaging target and the FD-OCT scanner during the scanning by controlling the FD-OCT scanner.

[0024] The controller can perform a cross-correlation calculation using a first set of samples and a second set of samples that can be obtained, for example, by an FD-OCT scanner that scans a sample light beam along a first scanning line of an imaging target and along a second scanning line that partially overlaps the imaging target along the first scanning line. The scanning line is a virtual line (which may be a curve or a straight line) representing the path of the light beam on the surface of the imaging target that the light beam follows during scanning. The first set of samples and the second set of samples can be obtained from one or more scans taken along the first scanning line and the second scanning line, which can be provided in one of a number of different forms, as described in the following exemplary embodiments. For example, the first and second scanning lines, as in the first embodiment below, can completely overlap and the light beam can continue in each of the different respective scans performed by the FD-OCT scanner, for example, when the FD-OCT scanner acquires repeated B-scans of the imaging portion of the imaging target. Instead, the first and second scanning lines can intersect each other at one or more discrete points of the imaging target, and subsequently, the light beam can continue in separate scans (e.g., a preliminary "reference" scan and a subsequent "measurement" scan) performed by the FD-OCT scanner. As a further alternative, the first and second scanning lines can intersect each other at one or more points on the surface of the imaging target and form part of a single continuous ("self-referencing") scan being performed by the FD-OCT scanner. These alternatives are described in more detail below in connection with the second exemplary embodiment.

[0025] These alternatives are described in more detail below in connection with the second exemplary embodiment.

[0026] Here, an exemplary embodiment of the FD-OCT imaging system will be described in detail with reference to the accompanying drawings.

[0027] (First Embodiment) FIG. 1 is a schematic diagram of an FD-OCT imaging system 10 according to a first exemplary embodiment. The FD-OCT imaging system 10 includes an FD-OCT scanner (OCT scanning and data acquisition system) 20 that generates complex OCT data 25 by scanning an imaging target 30, and the complex values thereof are samples that indicate the optical characteristics (e.g., reflectivity or reflectance) of the imaging target 30 at respective scanning positions of the imaging target 30.

[0028] The FD-OCT scanner 20 may be a frequency-scanning OCT (SS-OCT) system as in the present embodiment. However, the FD-OCT scanner 20 need not be provided in this form and may take an alternative form such as spectral-domain OCT (SD-OCT), for example. More generally, one embodiment may be provided as any form of FD-OCT imaging system capable of generating a Fourier transform of a complex OCT data 25, i.e., each spectral interference diagram (interference spectrum) representing complex A-scan information obtained for each scanning position at which an OCT measurement is performed during scanning. Such complex OCT data 25 encodes phase information from acquired OCT measurement values that can be used by a controller 40 as described herein to correct for relative movement between the FD-OCT scanner 20 and the imaging target 30 while the FD-OCT scanner 20 is performing a scan of the imaging target 30.

[0029] As shown in FIG. 2, the FD-OCT scanner 20 can include well-known components including a scanning system 22, a photodetector 24, OCT data processing hardware 26, and an optical beam generator 28.

[0030] The scanning system 22 may be configured to perform one-dimensional and / or two-dimensional spot scanning of the light beam Lb across the imaging target 30 and collect the light Lc scattered by the imaging target 30 during the spot scanning. Thus, the scanning system 22 is arranged to acquire A-scans at respective scanning positions distributed over the entire surface of the imaging target 30, sequentially irradiate the scanning positions with the light beam Lb, taking one scanning position at a time, and collect at least a part of the light Lc scattered by the imaging target 30 at each scanning position. The scanning system 22 can perform spot scanning using any suitable scanning pattern known in the art, for example, a one-directional scan, a raster scan, or a spiral scan in which a set of (e.g., parallel or overlapping) scan lines follow in a common direction along them. The scanning system 22 is arranged to perform spot scanning in the present exemplary embodiment, but alternatively, in other exemplary embodiments, the scanning system 22 may be arranged to perform line scanning using hardware well known to those skilled in the art.

[0031] In the present embodiment, the FD-OCT imaging system 10 is an ophthalmic FD-OCT imaging system configured to acquire OCT data from the imaging target 30 in the form of the region of the retina of the eye. However, any other part of the eye that can be imaged by OCT, such as a part of the anterior region of the eye, can alternatively or additionally form the imaging target 30. The imaging target 30 is not limited to a part of the eye, but alternatively may be any tissue (e.g., skin), biological sample, or more generally, any scattering medium in which the sub-surface tissue is to be imaged by OCT.

[0032] The light beam generator 28 can include a light source 28-1 and a light source aperture 28-2. In this case, the light source 28-1 is arranged to emit light through the light source aperture 28-2, and the shape and size of the light source aperture 28-2 (for example, the diameter if the light source aperture 28-2 is circular) define the cross-sectional shape and size (for example, the diameter) of the light beam Lb (that is, so that these sizes and shapes are the same), generating the light beam Lb. In some exemplary embodiments, the light beam generating unit 28 may include additional components (not shown in FIG. 2), such as one or more collimating lenses for collimating the light from the light source 28-1, for example.

[0033] The photodetector 24 is configured to generate a detection signal Sd based on the interference light Li resulting from the interference between the reference light Lr and the light Lc collected by the scanning system 22 during scanning. In other words, during point scanning, the reference light and the light collected by the scanning system coincide with each other and interfere, and the resulting interference light Li is guided to and received by a light detection component (not shown) of the photodetector 24. The photodetector 24 photoelectrically converts the received interference light Li to generate the detection signal Sd. The specific form that the photodetector 24 can take depends on the form in which the FD-OCT scanner 20 is implemented. For example, when the FD-OCT scanner 20 is realized as an SD-OCT scanner, the photodetector 24 may include a spectrometer having a diffraction grating, a Fourier transform lens, and a detector array (or a line-scanning camera). When the FD-OCT scanner 20 is realized as an SS-OCT scanner, as in the embodiment of this example, the photodetector 24 can include a balanced photodetector setup with two photodetectors (for example, reverse-biased photodiodes), the output photocurrents of which are subtracted from each other, and the subtracted current signal is converted to a voltage detection signal by a transimpedance amplifier.

[0034] Next, the detection signal Sd is processed by the OCT data processing hardware 26. The OCT data processing hardware 26 is configured to generate complex OCT data of the imaging target 30 based on the detection signal Sd using well-known data processing techniques.

[0035] Referring back to FIG. 1, the FD-OCT imaging system 10 further includes a controller 40 configured to perform a complex cross-correlation calculation to calculate a complex cross-correlation between acquired samples using the phase information of the acquired samples. The controller 40 is further configured to control the FD-OCT scanner 20 based on the result of the cross-correlation calculation to correct the relative movement between the imaging target 30 and the FD-OCT scanner 20 during scanning.

[0036] The FD-OCT scanner 20 may be configured to acquire samples of the complex OCT data 25 by scanning the imaging target 30 along one or more scan lines on the surface of the imaging target 30, as in the case of the present embodiment, and the controller 40 may be configured to perform a cross-correlation calculation by first acquiring a set of samples of the complex OCT data 25. More specifically, the controller 40 can acquire a first set of samples, where the samples of the first set include samples acquired by the FD-OCT scanner 20 scanning the imaging target 30 along a first scan line on the surface of the imaging target 30, and can acquire a second set of samples. Here, the samples of the second set include samples acquired by the FD-OCT scanner 20 scanning the imaging target 30 along a second scan line of the imaging target 30, and the second scan line at least partially overlaps the first scan line. The samples of the first set of samples may include, as in the present embodiment, a first A-scan and respective indications of the scanning positions of the imaging target 30 at which each A-scan of the first A-scan was acquired. Similarly, the samples of the second set of samples may include, as in the present embodiment, a second A-scan and respective indications of the scanning positions of the imaging target 30 at which each A-scan of the second A-scan was acquired.

[0037] The FD-OCT scanner 20 can acquire such first and second sets of samples by scanning the imaging target 30 in one of several different ways. Such first and second sets of samples can be acquired, for example, by being preconfigured to perform a particular type of scan that can acquire the first and second sets of samples, or by being operable in several different operating modes. Here, at least some of these modes cause the FD-OCT scanner 20 to acquire the first and second sets of samples. The first and second scan lines on the surface of the imaging target may, for example, completely overlap and follow the light beam Lb in a separate scan performed by the FD-OCT scanner 20 (e.g., when the FD-OCT scanner 20 acquires repeated B-scans of the imaged portion of the imaging target 30). The first and second scan lines may instead intersect each other at one or more points on the surface of the imaging target 30 and then be performed with the light beam Lb in a separate scan performed by the FD-OCT scanner 20 (e.g., a preliminary "reference" scan and a subsequent "measurement" scan). As a further alternative, the first and second scan lines may intersect each other at one or more points on the surface of the imaging target 30 and form part of a single continuous ("self-referencing") scan being performed by the FD-OCT scanner 20. These alternative scan schemes are described in more detail below.

[0038] Once these sets of samples are acquired, the controller 40 performs a cross-correlation calculation between a third set including at least some of the samples in the first set of samples, a fourth set including at least some of the samples in the second set of samples, and (at least two-dimensional) cross-correlation between the third set of samples. Here, at least some of the samples in the third set of samples and at least some of the samples in the fourth set of samples are acquired from a common area of the imaging target 30 where the first scanning line and the second scanning line overlap. The cross-correlation calculation is based on the phase information of the third set of samples and the phase information of the fourth set of samples, and more specifically, it may be the cross-correlation between the phase information of the third set of samples and the phase information of the fourth set of samples.

[0039] The controller 40 is configured to control the FD-OCT scanner 20 to first correct the relative movement between the imaging target 30 and the FD-OCT scanner 20 during scanning by registering the first set of samples and the second set of samples with each other using the calculated cross-correlation. The controller 40 uses this process to determine the value of an offset indicator (i.e., displacement or translation) that indicates the offset between the scanning position of the first set of samples and the scanning position of the second set of samples, which is caused by the relative movement between the FD-OCT scanner 20 and the imaging target 30 during scanning, between the acquisition of the first set of samples and the acquisition of the second set of samples by the FD-OCT scanner 20. The controller 40 is further configured to control the FD-OCT scanner 20 using the determined value of the offset indicator during scanning to correct the relative movement. The controller 40 can achieve this by adjusting one or more scanning parameters that determine the movement of one or more scanning elements that scan the light beam Lb across the imaging target 30 such that the scanning system 22 of the FD-OCT scanner 20 at least partially accounts for the offset indicated by the offset indicator, resulting in a smaller offset between the scanning position of the set of samples acquired subsequently and the scanning position of the set of samples used in the previous scan along the second scan line, defined by the subsequent repeated scanning parameters defined by the scanning parameters used in the previous scan, as compared to the offset between the scanning position of the first set of samples and the scanning position of the second set of samples.

[0040] The OCT data processing hardware 26 and the controller 40 may be provided in any suitable form. By way of example, both of these components may be implemented in the form of a (single) programmable signal processing hardware 100 of the kind schematically shown in FIG. 3. However, it should be noted that the OCT data processing hardware 26 and the controller 40 may alternatively be implemented in respective (separate) programmable signal processing hardwares 100 of the kind illustrated in FIG. 3. Further, one or both of these components may alternatively be non-programmable hardware such as a dedicated ASIC, FPGA, or other integrated circuit that performs the functions of the OCT data processing hardware 26 and / or the controller 40 (where possible), or a combination of such non-programmable hardware and programmable hardware as described above with reference to FIG. 3.

[0041] The programmable signal processing hardware 100 receives the detection signal Sd from the photodetector 24 and outputs a control signal for controlling the FD-OCT scanner 20 (specifically, its scanning system 22), and includes a communication interface 110 for correcting the relative movement between the imaging target 30 and the FD-OCT scanner 20 during scanning. The signal processing hardware 100 further includes a processor (e.g., a central processing unit, CPU, and / or a graphics processing unit, GPU) 120, a working memory 130 (e.g., a random access memory), and an instruction store 140 that stores a computer program 145 with computer-readable instructions. When these are executed by the processor 120, the processor 120 is caused to perform various functions including the functions of the OCT data processing hardware 26 and the controller 40 described herein. The working memory 130 stores information used by the processor 120 during the execution of the computer program 145. The instruction store 140 may include a ROM (e.g., in the form of an electrically erasable programmable read-only memory (EEPROM) or flash memory) in which computer-readable instructions are pre-loaded. Alternatively, the instruction store 140 may include a RAM or a similar type of memory, and the computer-readable instructions of the computer program 145 may be input from a non-transitory computer-readable storage medium 150 in the form of a CD-ROM, DVD-ROM, etc. or a computer-readable signal 160 that transmits computer-readable instructions. In any case, when the computer program 145 is executed by the processor 120, the processor 120 is caused to execute the functions of the controller 40 as described herein. In other words, the controller 40 of the embodiment may include a computer processor 120 and a memory 140 that stores computer-readable instructions, and when these instructions are executed by the computer's processor 120, the computer's processor 120 is caused to control the FD-OCT scanner 20.This control generates complex OCT data 25 by scanning the imaging target 30, and corrects the relative movement between the imaging target 30 during scanning and the FD-OCT scanner 20 by obtaining samples whose complex values indicate the optical characteristics of the imaging target 30 at respective scanning positions of the imaging target 30.

[0042] FIG. 4 is a flowchart showing a process in which the controller 40 of the embodiment controls the complex OCT scanner 20. This controller generates complex OCT data 25 by scanning the imaging target 30, obtains samples whose complex values indicate the optical characteristics of the imaging target 30 at respective scanning positions of the imaging target 30, and corrects the relative movement between the imaging target 30 during scanning and the FD-OCT scanner 20.

[0043] In process S10 of FIG. 4, the controller 40 performs a cross-correlation calculation using the phase information of the acquired samples. More specifically, in process S10, the controller 40 calculates the cross-correlation between the phase information in the first set of samples and the second set of samples.

[0044] In process S20 of FIG. 4, the controller controls the FD-OCT scanner 20 to correct the relative movement between the imaging target 30 during scanning and the FD-OCT scanner 20 based on the cross-correlation calculation. More specifically, in process S20, the controller 40 uses the result of the cross-correlation calculation to correct the scan being performed by the FD-OCT scanner 20, and after the scan correction, causes the remainder of the scan to be performed with no, or a reduced, influence of the prior relative movement on the samples acquired by the FD-OCT scanner 20 relative to the remainder of the scan (compared to the case where no scan correction is performed).

[0045] FIG. 5 is a flowchart showing a process in which the controller 40 may perform a cross-correlation calculation in process S10 of FIG. 4.

[0046] In the process S12 of FIG. 5, the controller 40 acquires a first set of samples acquired by the FD-OCT scanner 20. The samples of the first set include samples acquired by the FD-OCT scanner 20 that scans the imaging target 30 along a first scanning line of the imaging target 30. The samples of the first set of samples may include, as in the present embodiment, a first A-scan and respective indications of the scanning positions of the imaging target 30 at which each A-scan of the first A-scan is acquired.

[0047] In the process S14 of FIG. 5, the controller 40 acquires a second set of samples. The samples of the second set include samples acquired by the FD-OCT scanner 20, scan the imaging target 30 along a second scanning line of the imaging target 30, and the second scanning line at least partially overlaps the first scanning line. The samples of the second set of samples may include, as in the present embodiment, a second A-scan and respective indications of the scanning positions of the imaging target 30 at which each A-scan of the second A-scan is acquired.

[0048] As described above, the FD-OCT scanner 20 can acquire such first and second sets of samples by scanning the imaging target 30 in one of several different ways. The FD-OCT scanner 20 generates complex OCT data 25, as in the present embodiment, and as its scan, repeatedly performs a line scan of the light beam Lb on the imaging target 30 along overlapping scanning lines of the imaging target 30, so that the acquired samples define repeated B-scans representing respective images of a common cross-section of the imaging target 30. In this way, the FD-OCT scanner 20 can acquire a first B-scan of the repeated B-scans as the first set of samples and a second B-scan of the repeated B-scans as the second set of samples.

[0049] FIG. 6(a) shows an example of a first B-scan (B-scan 1) 610 and an example of a second B-scan (B-scan 2) 620, which is the next B-scan in a sequence of repeated B-scans of an imaging portion of the retina of an eye (as imaging target 30) acquired by the FD-OCT scanner 20 after the first B-scan 610. The second B-scan 620 was acquired 0.02 s after the first B-scan 610, but the interval between B-scans is not so limited. The first B-scan 610 and the second B-scan 620 each include 200 A-scans arranged along the x-axis direction, and as shown in FIG. 6(a), the data elements of each A-scan are arranged along the z-axis direction. The bands extending across each of the first B-scan 610 and the second B-scan 620 in FIG. 6(a) correspond to relatively highly reflective retinal layers. Such retinal layers may include, for example, an outer limiting membrane, an ellipsoid zone (IS / OS junction), an interdigitation zone, and a retinal pigment epithelium.

[0050] FIG. 6(b) shows a plot of how the magnitude of the phase component 630 of the first B-scan 610 and the magnitude of the phase component 640 of the second B-scan 620 vary along the x-axis and z-axis directions. The phase components 630 and 640 appear to be randomly distributed along the x-axis and z-axis directions, and no pattern is apparent in FIG. 6(b).

[0051] However, when the phase component value of the second B-scan 620 is subtracted from the phase component value of the first B-scan 610, the resulting plot 650 of the phase component difference shown in FIG. 6C reveals that the phase information in the two B-scans is strongly correlated and that a vertical band of mostly constant difference values is evident in the plot 650 of FIG. 6C. The fluctuations along the z-axis direction are due to the relative movement between the imaging target 30 and the FD-OCT scanner 20 during the acquisition of the B-scan. The absence of bands in the upper region 660 of the plot 650 and the lower region 670 of the plot 650 results from the absence of retinal structures (and the resulting low signal levels) in the corresponding regions of the first B-scan 610 and the second B-scan 620.

[0052] The inventors recognized that the strong correlation between the phase information in the repeated B-scans 610 and 620 can be used to reliably register the B-scans in a fast and computationally efficient manner. This enables real-time correction of the offsets (along the x-axis and / or z-axis directions) caused by the relative movement of the imaging target 30 and the FD-OCT scanner 20 with respect to each other, and thus effective motion correction can be performed during the scanning executed by the FD-OCT scanner 20 without the need to employ a second imaging modality such as a scanning laser ophthalmoscope or a fundus camera for this purpose. With the techniques described herein, the OCT volume can be accurately registered at the width level with the point spread function.

[0053] Referring again to FIG. 5, in process S16, the controller 40 performs a complex cross-correlation calculation to calculate the two-dimensional cross-correlation between at least some samples of the first B-scan 610 (in this embodiment, the B-scan constitutes the aforementioned first set of samples) and a fourth set of samples including at least some samples of the second B-scan 620 (in this embodiment, the B-scan constitutes the aforementioned second set of samples).

[0054] More specifically, as in this embodiment, the controller 40 can calculate a two-dimensional cross-correlation between a set of a predetermined number N of A-scans of the first B-scan 610 (as a third set of samples) and a set of A-scans of the second B-scan 620 (as a fourth set of samples), where the set of A-scans of the second B-scan 620 includes A-scans positioned corresponding to one or more A-scans in the first B-scan 610, and N is an integer of 1 or more. The cross-correlation calculation is based on the phase information in the third set of samples and the phase information in the fourth set of samples. At least some of the samples in the third set of samples and at least some of the samples in the fourth set of samples are obtained from a common region of the imaging target 30 where the first scanning line and the second scanning line overlap.

[0055] For the third set of samples (denoted as f here) and the fourth set of samples (denoted as g here), the complex cross-correlation between f and g can be expressed as follows: ifftn(fftn(g)*conj(fftn(ff))). Here, "fftn" represents the fast Fourier transform (FFT), "ifftn" represents the inverse FFT, and "conj()" represents the conjugate.

[0056] The complex cross-correlation can be used to identify the phase pattern and perform registration with highly correlated phases when a set of complex OCT data is registered.

[0057] In the process S16 of FIG. 5, the complex cross-correlation between the complex OCT data of the entire first B-scan 610 and the complex OCT data of the entire second B-scan 620 can be calculated by the controller 40. In this case, as shown in FIG. 7(a), a peak is observed in the cross-correlation graph. Also, there is a peak in the plot of the calculated two-dimensional cross-correlation, which is not clearly visible in FIG. 7(b) but is shown in FIG. 7(b).

[0058] However, the inventors have found that the phase fluctuations caused by the relative movement of the imaging target 30 with respect to the FD-OCT scanner 20 during scanning, which cause the appearance of the bands in FIG. 6(c), can deteriorate the result of the cross-correlation calculation when performing this with a relatively large first B-scan 610. The inventors have found that in such cases, it is advantageous to use only a part of the A-scans of the first B-scan 610 in the cross-correlation calculation, in particular, a predetermined number N of adjacent A-scans of the first B-scan 610 (as the third set of samples). Here, N is selected such that the variation in phase information between the N A-scans of the first B-scan 610 is smaller than a predetermined degree of variation.

[0059] The value of N can be determined in one of several different ways. As an example, N calculates the degree of correlation between the i-th A-scan of the first B-scan 610 and the (i + 1)-th A-scan of the first B-scan 610, compares the calculated degree of correlation with a threshold value, calculates the degree of correlation between the i-th A-scan and the (i + 2)-th A-scan, compares the calculated degree of correlation with the threshold value, and when the threshold value is exceeded, calculates the degree of correlation between the i-th A-scan of the sequence of A-scans defining the first B-scan 610 and the next A-scan, and this process is repeated (to calculate the correlation between the i-th A-scan and A-scans further away from the i-th A-scan) until the calculation of the correlation between the i-th A-scan and the correlation between the i-th A-scan is repeated. Then, the (i + N)-th A-scan results in a correlation value that does not exceed the threshold value. The value of N can alternatively be obtained from an examination of the plot 650 of the differences in FIG. 6C, where N may be determined by counting the number of A-scans in a band (e.g., the average or minimum width band) of the vertical bands that are apparent in the plot 650. An example of a set of adjacent A-scans defining an A-scan block 800 with high phase stability is shown in FIG. 8.

[0060] FIG. 9(a) shows an example of a set of 10 adjacent A-scans of a first B-scan 610 that forms a “OCT strip” (as the set of the third sample described above) having a cross-correlation with the entirety of the second B-scan shown in FIG. 9(b) (as the set of the fourth sample described above) to result in the cross-correlation graph shown in FIG. 9(c) and the two-dimensional cross-correlation value plot shown in FIG. 9(d). In this example, the cross-correlation is calculated as ifftn(fftn(second B-scan)*conj(fftn(OCT strip))). Here, “fftn” is the fast Fourier transform (FFT), “ifftn” is the inverse FFT, and “conj()” indicates the conjugate. As shown by the enlarged portion of the plot in FIG. 9D, there are distinct peaks in the calculated two-dimensional cross-correlation.

[0061] For comparison, FIG. 10(a) shows the same set of 10 adjacent A-scans of the first B-scan 610 as in FIG. 9(a), and these sets are cross-correlated with the entirety of the second B-scan shown in FIG. 10(b) (which is the same as FIG. 9(b)) to obtain the cross-correlation graph shown in FIG. 10(c) and the two-dimensional cross-correlation value plot shown in FIG. 10(d). However, the cross-correlation calculation in this case does not involve the phase information in the A-scans of FIGS. 10(a) and 10(b) and is based only on the amplitude of the complex OCT data therein. More specifically, the amplitude-based cross-correlation is calculated as ifftn(fftn(abs(second B-scan))*conj(fftn(abs(OCT strip))), where “abs()” is a function that returns the absolute value of the number on which it operates. As a result, there is no single peak in any of the plots in the figure. In FIGS. 10(c) and 10(d), the B-scans cannot be registered reliably.

[0062] The OCT strip forming part of the first B-scan 610 does not have to be composed of 10 A-scans. Alternatively, it may be composed of a smaller number of adjacent A-scans. It should be noted that across it, the phase information of the complex OCT data changes relatively little. To illustrate with an example, the OCT strip of the first B-scan 610 can have 4 adjacent A-scans, as in the example of Fig. 11(a). This smaller set of A-scans (as the third set of samples above) is cross-correlated with the entire second B-scan shown in Fig. 11(b) (as the fourth set of samples above), and a cross-correlation graph shown in Fig. 11(c) and a two-dimensional cross-correlation value plot shown in Fig. 11(d) are obtained. Similar to the examples of Figs. 9(a) to 9(d), the cross-correlation is calculated as ifftn(fftn(second B-scan)*conj(fftn(OCT strip))). As shown by the enlarged portion of the plot in Fig. 11(d), when N = 4, even though the OCT strip contains only 4 A-scans, there is still a single peak in the calculated two-dimensional cross-correlation.

[0063] Furthermore, as shown in Figs. 12(c) and 12(d), the isolated peak in the calculated cross-correlation can be observed even when the number N of A-scans in the OCT strip is reduced to 2. Fig. 12(a) shows a cross-correlation graph and a two-dimensional cross-correlation value plot obtained by cross-correlating two adjacent A-scans of the first B-scan 610 and the entire second B-scan as shown in Fig. 12(b), respectively. Similar to the examples of Figs. 9(a) to 9(d) and Figs. 11(a) to 11(d), in the examples of Figs. 12(a) to 12(d), the cross-correlation is calculated as ifftn(fftn(second B-scan)*conj(fftn(OCT strip))).

[0064] In fact, even a single A-scan (as an OCT strip) can result in observable peaks in the calculated cross-correlation, as shown in FIGS. 13(c) and (d). FIGS. 13(a) and (b) respectively show a cross-correlation graph and a two-dimensional cross-correlation value plot obtained by cross-correlating a single A-scan of the first B-scan 610 with the entire second B-scan. Also in this example, the cross-correlation is calculated as ifftn(fftn(second B-scan)*conj(fftn(OCT strip))).

[0065] FIG. 14 is a flowchart showing a process in which, in process S20 of FIG. 4, the controller 40 can control the FD-OCT scanner 20 to correct the relative movement between the imaging target 30 and the FD-OCT scanner 20.

[0066] In process S22 of FIG. 14, the controller 40 registers the first set of samples with the second set of samples using the calculated cross-correlation, and determines a value of an offset index indicating an offset between the scanning position of the first set of samples and the scanning position of the second set of samples.

[0067] In process S22 of FIG. 14, the controller 40 can register the first B-scan 601 (as the first set of samples above) with the second B-scan 602 (as the second set of samples above) by using the calculated cross-correlation in order to determine an offset value indicating an offset between the first B-scan 601 and the second B-scan 602 in the x-z plane as the value of the offset index. The controller 40 can execute this registration process by identifying the position of the peak in the calculated two-dimensional cross-correlation, thereby obtaining coordinates in the x-z plane and deriving the value of the offset index therefrom.

[0068] When the controller 40 captures only a subset of the A-scans of the first B-scan 610 as samples for the third set and uses them for cross-correlation calculation, as described above, the controller 40 executes a plurality of cross-correlation calculations in the process S22 of FIG. 14 to perform a plurality of different sets of N adjacent A-scans of the first B-scan 610 (i.e., each of the plurality of A-scan "chunks" into which the first B-scan 610 is divided) and each A-scan of the second B-scan 620. Each two-dimensional cross-correlation therebetween can be calculated, where each A-scan of the second B-scan 620 includes an A-scan located corresponding to the second B-scan 620 for the set of N A-scans (and thus can be cross-correlated with the set of N A-scans). Each chunk n of the plurality of "OCT chunks" (each chunk is defined by a set of N adjacent A-scans of the first B-scan 610, in which the phase information of the complex OCT data does not change by more than a predetermined amount) is the respective cross-correlation, JPEG0007717776000001.jpg1156 To obtain, it may be cross-correlated independently of the second B-scan 620 (at least the overlapping portion). The controller 40 calculates the combined cross-correlation, which is the independently calculated cross-correlation, as shown in Equation 1 below, to register the first B-scan 610 with respect to the second B-scan 620. JPEG0007717776000002.jpg1657 By calculating the sum of the magnitudes of, JPEG0007717776000003.jpg1243 may be calculated.

[0069]

Number

[0070] Smaller OCT chunks tend to be relatively unaffected by movement, but the advantage of using small OCT chunks (which may each be as small as a single A-scan) needs to be weighed against the increased processing burden on the controller 40 caused by their processing. The controller 40 then determines, as an overall offset value (or "composite offset value"), a value indicating the offset between the first B-scan 610 and the second B-scan 620, JPEG0007717776000005.jpg1243 based on.

[0071] In process S24 of FIG. 14, the controller uses the value of the offset index determined in S22 to control the FD-OCT scanner 20 and corrects, during scanning, the relative movement between the imaging target 30 and the FD-OCT scanner 20 that occurs between the acquisition of the first B-scan 601 (as an example of the first set of samples in this embodiment) and the acquisition of the second B-scan (as an example of the second set of samples in this embodiment) by the FD-OCT scanner 20.

[0072] When the controller 40 performs a plurality of cross-correlation calculations in process S22 of FIG. 14 to calculate the respective two-dimensional cross-correlations between each set of a plurality of adjacent N-scans of the first B-scan 610 ("OCT chunk") and each A-scan of the second B-scan 620, as described above, the controller 40 controls the FD-OCT scanner 20 in process S24 of FIG. 14 and uses the above-determined overall (or combined) offset value indicating the offset between the first B-scan 610 and the second B-scan 620 to correct the relative movement between the imaging target 30 and the FD-OCT scanner 20.

[0073] In process S24, the controller 40 uses the determined value of the offset index (or a combination of the determined values of the offset indices described above, as may be the case) to correct the scan being performed by the FD-OCT scanner 20. After the scan is corrected, the remainder of the scan (including acquisition or one or more repeated B-scans) is made to be performed with no prior relative movement effect, or a reduced effect, on the samples acquired by the FD-OCT scanner 20 compared to the case where no scan correction is performed.

[0074] (Second Embodiment) In the first embodiment described above, the FD-OCT scanner 20 is arranged to generate the complex OCT data 25 by repeating the line scan of the light beam Lb on the imaging target 30 along the overlapping scan lines of the imaging target 30 as a scan, such that the acquired samples define repeated B-scans representing respective images of a common cross-section of the imaging target 30. However, as described above, the FD-OCT scanner 20 can alternatively generate the complex OCT data 25 on which motion correction is based in other ways.

[0075] The FD-OCT scanner 20 may be arranged to generate the complex OCT data 25 by performing an area OCT scan of the imaging target 30 as a scan in order to acquire samples having complex values indicating the optical characteristics of the imaging target 30 at each of the scan positions three-dimensionally distributed on the imaging target 30, as in this embodiment. The FD-OCT scanner 20 can perform such an area OCT scan in various different ways.

[0076] To illustrate with an example, the above-described first scanning line may be one of a plurality of parallel scanning lines of the imaging target 30, and along the parallel scanning lines, the FD-OCT scanner 20 of the present embodiment scans the light beam Lb, and thus is arranged to acquire an OCT-C-scan as the complex OCT data 25. These parallel scanning lines collectively define a reference grid of a raster scan that forms a reference scan as shown in FIG. 15(a). The reference grid is sparse enough for the raster scan to be performed quickly (so that the reference scan is substantially stationary at a typical saccade rate), but not so sparse that the reference scan has an inappropriate density and enables the registration process described below to be reliably performed. The size (lateral extent) of the reference scan preferably covers the maximum movement so that the FD-OCT scanner 20 can track the scanning position of the fundus even if it moves away from the imaged area of the fundus in addition to the imaged area of interest of the fundus.

[0077] As shown in FIG. 15(b), the above-described second scanning line intersects the first scanning line at a point on the surface of the imaging target 30 and can intersect one or more additional scanning lines of the parallel scanning lines at one or more intersections (as in the example of FIG. 15(b)). In FIG. 15(b), the scanning line identified by the above-described first scanning line is labeled "L1", and the scanning line identified by the above-described second scanning line is labeled "L2". The light beam Lb is scanned following the scanning lines L1 and L2, and samples are acquired from different scanning positions of the imaging target 30 including the common area of the imaging target 30 where the scanning lines L1 and L2 intersect each other. It should be noted that the scanning line L2 may be one of a set of parallel scanning lines, and along it, the FD-OCT scanner 20 is arranged to scan the light beam Lb to acquire an OCT-C-scan of the imaging target 30.

[0078] The reference scan including the first scan line L1 and the scan lines parallel to the first scan line L1 may be completed by the FD-OCT scanner 20 before the FD-OCT scanner 20 acquires the complex OCT data obtained from the scan along the second scan line L2 and further performs a measurement scan for acquiring an OCT-C-scan including the scan lines parallel to the second scan line L2. However, the eye movement during the measurement scan is corrected by the controller 40 by the technique described herein using the complex OCT data of the reference scan. It should be noted that the scanning method employed by the FD-OCT scanner 20 is not so limited. For example, the FD-OCT scanner 20 may alternatively acquire the reference scan and the measurement scan simultaneously, perform them alternately between the horizontal scan and the vertical scan of the configuration, and use the technique described herein to register the OCT data acquired in each horizontal scan with the OCT data acquired in the preceding vertical scan, for example, to acquire an offset for correcting the scan position of the next horizontal scan. An example of a sequence in which the horizontal and vertical scans are performed alternately is shown in FIG. 16. In the example of FIG. 16, first, a set of vertical (Y) scans labeled "Sequence 1" is performed, followed by a set of horizontal (X) scans, then a set of horizontal (X) scans labeled "Sequence 2" follows, and then another set of vertical (Y) scans labeled "Sequence 3" and displaced along the x-axis with respect to the vertical scans of "Sequence 1" follows. It should be noted that the FD-OCT scanner 20 may scan one or more times along each of the horizontal and / or vertical scan lines shown in FIG. 16, for example, where the FD-OCT scanner 20 is used to acquire OCT data for OCT angiography (OCTA).

[0079] Also, the first scanning line referred to in the description of the first embodiment does not have to be a straight line, and instead of the scanning described with reference to FIGS. 15(a), 15(b), and 16, it should be noted that it may extend along two axial directions of the surface of the imaging target and be curved so as to define a "sparse" reference scan. The sparse reference scan defined by the first scanning line can be, for example, a spiral (as shown in FIG. 17(a)), a Lissajous shape (as shown in FIG. 17(b)), an epitrochoid or hypotrochoid (as shown in FIG. 17(c)), a circle (as shown in FIG. 17(d)), a triangular shape (as shown in FIG. 17(e)), a square shape (as shown in FIG. 17(f)), a rhombus shape (as shown in FIG. 17(g)), a square spiral shape (as shown in FIG. 17(h)), or an ellipse defining the imaging target 30. The reference scan is shown in the figure. The reference scans shown in FIGS. 17(a) to 17(h) are given only as an example, and the first scanning line can define many other shapes extending on the surface of the imaging target 30. Regardless of the formation of the first scanning line, the second scanning line is arranged to cross at least one point, whereby complex OCT data from at least one common region (where the two scanning lines intersect) of the imaging target 30 is obtained from the scan along the scanning line.

[0080] It should also be noted that the first scanning line and the second scanning line do not necessarily have to be different line segments. Alternatively, they may be different respective portions of a single continuous scanning line (line segment) that extends along two axial directions of the imaging target 30 and intersects itself. In this case, the single scanning line can define, for example, a Lissajous figure, an epitrochoid, or a hypotrochoid on the imaging target 30. More generally, the single scanning line may be any type of scanning line that self-intersects when extending into the measurement region of the fundus to cover scanning positions that were not previously covered by scanning (the scanning positions are ultimately densely covered sufficiently to provide the necessary OCT scans). This scanning method can be combined with the use of previously acquired sparse reference scans, as described above, to increase the motion correction ability beyond the measurement region.

[0081] In this embodiment, the controller 40 is configured to obtain, as at least a part of the region OCT scan, a set of samples including the samples acquired by the FD - OCT scanner 20 that scans the imaging target 30 along the first scanning line, as a first set of samples, for the above-described cross - correlation calculation.

[0082] When the first scanning line is one of the plurality of parallel scanning lines of the imaging target 30 described above, the controller 40 may be configured to obtain the complex OCT data of the entire OCT - C - scan as the first set of samples. When the first scanning line takes one of the alternative forms set above, the controller 40 may obtain the complex OCT data of the first scanning line of each form as the first set of samples.

[0083] Next, the controller 40 may calculate the complex cross - correlation between the acquired sets of samples based on the hidden intensity cross - correlation.

[0084] The hidden cross - correlation without normalization is expressed as the following Equation 2.

[0085]

Number

[0086] The hidden cross-correlation is normalized using the signal RMS and can be represented by the following equation (3).

[0087]

Number

[0088] In the above equation, since the signal tends to have an average or zero, there is no need to normalize the average. In the above equation for MC(u, v, w) and MCN (u, v, w), M1(x, y, z) is 1 in the region where the function f1(x, y, z) is defined and 0 otherwise, M2(x, y, z) is 1 in the region where the function f1(x, y, z) is defined and 0 otherwise.

[0089] Instead of the above-mentioned hidden cross-correlation, the region can be divided into smaller sub-regions such that, for example, the functions f1 or f2 maintain coherence (the phase of the complex OCT data is not affected by movement). Otherwise, the complex cross-correlation affected by random movement phases will be averaged to zero in the final result due to destructive interference.

[0090] The sub-regions can be defined in the most general way for either or both of the functions f1 and f2. Each sub-correlation for the sub-regions can be calculated in the same way as the previous equation and then summed in absolute value, M1,i(x, y, z) is 1 for the sub-region i of the complex function f1(x, y, z) and 0 otherwise, M2,j(x, y, z) is 1 for the sub-region j of the complex function f2(x, y, z) and 0 otherwise.

[0091] The hidden cross-correlation without normalization is expressed as the following Equation 4.

[0092]

Equation

[0093] The hidden cross-correlation is normalized using the signal RMS and can be expressed by the following Equation 5.

[0094]

Equation

[0095] The coherent region is defined as the region where the phase of the complex function f1(x, y, z) is not significantly affected by the problem of movement. This condition, although much more restrictive than simply the shape distortion, means that the movement should be much smaller than the center wavelength of the OCT laser.

[0096] The maximum value of the cross-correlation MC(u, v, w) or MCN(u, v, w) can be found by the controller 40 and indicates the most likely position of the scan line defined by the function f2 in the reference scan defined by the function f1. The scan position thus determined is based on the calculated complex cross-correlation between the complex OCT data obtained from each line scan of a set of sequentially executed line scans and the reference scan. Along with information regarding the spatial distribution of the sequentially executed line scans, the controller 40 uses it in real time to move one or more galvanometers (the "galvos") of the FD-OCT scanner 20 or other scan element(s) to correct the relative movement between the imaging target 30 and the FD-OCT scanner 20 during the execution of the line scan. In particular, the controller 40 can use the aforementioned information and the determined scan position to calculate the offset between the predicted scan position and the determined scan position, and also control the FD-OCT scanner 20 based on the calculated offset to correct the relative movement between the imaging target 30 and the FD-OCT scanner 20 during the scan. It should be noted that the result of the complex cross-correlation operation can be used by the controller 40 of the present embodiment not only to correct the relative movement between the imaging target 30 and the FD-OCT scanner 20 in a plane perpendicular to the direction of the OCT optical beam Lb used to acquire the complex OCT data 25, but also to correct for movement along the axis along which the OCT optical beam Lb travels during the scan.

[0097] In the foregoing description, exemplary aspects are described with reference to several exemplary embodiments. Accordingly, the specification should be regarded as illustrative rather than restrictive. Similarly, the figures illustrated in the drawings highlighting the functionality and advantages of the exemplary embodiments are presented for illustrative purposes only. The construction of the exemplary embodiments is sufficiently flexible and configurable such that it can be utilized in ways other than those shown in the accompanying figures.

[0098] Some aspects of the embodiments presented in this specification, for example, the processing of the detection signal Sd for generating complex volume measurement OCT data of the imaging target 30, and the correction algorithm 132, etc., may be provided as software in a computer program, or in one embodiment, one or more programs having instruction sequences included in or stored in a machine-accessible medium or machine-readable medium, an instruction store, or a computer-readable storage device, each of which may be non-transitory. Programs or instructions in a non-transitory machine-accessible medium, machine-readable medium, instruction store, or computer-readable storage device can be used to program a computer system or other electronic device. Machine-readable media, instruction stores, and storage devices can include, but are not limited to, floppy disks, optical disks, and magneto-optical disks, or other types of media / machine-readable media / instruction stores / storage devices suitable for storing or transmitting electronic instructions. The techniques described in this specification are not limited to any particular software configuration. They may find applicability in any computing processing environment. As used herein, the terms "computer-readable," "machine-accessible medium," "machine-readable medium," "instruction store," and "computer-readable storage device" include any medium that can store, encode, or transmit instructions or a sequence of instructions for execution by a machine, computer, or computer processor, and cause the machine / computer / computer processor to perform any one of the methods described herein. Further, in one form or another (e.g., program, procedure, process, application, module, unit, logic, etc.), it is common in the art to speak of software as taking action or causing a result. Such expressions are nothing more than a shorthand way of describing that the execution of software by a processing system causes the processor to perform the actions for generating a result.

[0099] Some or all of the functions of the OCT data processing hardware 26 can also be implemented by preparing application-specific integrated circuits, field programmable gate arrays, or by interconnecting a suitable network of conventional component circuits.

[0100] A computer program product is provided in the form of a storage medium or media, instructions, or a storage device having instructions stored thereon or therein that can be used to control or cause a computer or computer processor to execute any of the exemplary implementation procedures described herein. The storage medium / storage device can include, by way of example and not limitation, optical disks, ROM, RAM, EPROM, EEPROM, DRAM, VRAM, flash memory, flash cards, magnetic cards, optical cards, nanosystems, molecular memory integrated circuits, RAID, remote data storage / archive / warehousing, and / or any other type of device suitable for storing instructions and / or data.

[0101] Some embodiments stored in any of a computer-readable medium or media, an instruction storage device, or a storage device control both the hardware of the system and include software for enabling the system or microprocessor to utilize the results of the example embodiments described herein to interact with a human user or other mechanism. Such software can include, but is not limited to, device drivers, operating systems, and user applications. Ultimately, such a computer-readable medium or storage device further includes software for executing the exemplary aspects of the present invention as described above.

[0102] Included in the programming and / or software of the present system are software modules for implementing the procedures described herein. In some embodiments of the present specification, a module includes software, but in other embodiments of the present specification, a module includes hardware, or a combination of hardware and software.

[0103] Although various exemplary embodiments of the present invention have been described above, it should be understood that they are presented by way of example and not limitation. It will be apparent to those skilled in the art that various forms and details can be changed therein. Therefore, the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0104] Furthermore, the purpose of the abstract is to enable the Patent Office and the general public, particularly scientists, engineers, and practitioners in the technical field who are not proficient in patent or legal terms or terminology, to quickly determine the nature and essence of the technical disclosure of the application from a cursor inspection. The abstract is not intended to limit in any way the scope of the exemplary embodiments presented herein. Also, it should be understood that the procedures recited in the claims need not be performed in the order presented.

[0105] This specification includes details of many specific embodiments, which should not be construed as limitations on the scope of any invention or what may be claimed, but rather as descriptions and interpretations of features specific to the particular embodiments described herein. The specific features described herein in the context of individual embodiments can also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment can also be implemented separately or in any suitable sub-combination in multiple embodiments. Furthermore, features may be described as acting in a particular combination and even as initially claimed as such, but in some cases, one or more features from the claimed combination can be excluded from the combination, and the claimed combination can be directed to a sub-combination or a variation of a sub-combination.

[0106] In certain situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated into a single software product or packaged into multiple software products.

[0107] Next, some exemplary embodiments and implementations have been described, but it is clear that the foregoing embodiments are exemplary and not limiting. In particular, many of the examples presented here involve specific combinations of device or software elements, but those elements may be combined in other ways to achieve the same purpose. The actions, elements, and features discussed only in relation to one embodiment are not intended to be excluded from other embodiments or similar roles in other embodiments.

Claims

【Claim 1】 A Fourier domain optical coherence tomography (FD-OCT) system, an FD-OCT scanner arranged to generate complex OCT data by performing a scan of an imaging target to obtain a sample having a complex value indicative of an optical characteristic of the imaging target at each scan position of the imaging target, the scan system being configured to perform one-dimensional and / or two-dimensional point scanning of an optical beam across the imaging target and to collect light scattered by the imaging target during the point scanning, the FD-OCT scanner including a scan system; a controller configured to perform a cross-correlation calculation using phase information of the acquired sample, control the scan system of the FD-OCT scanner based on the cross-correlation calculation, and correct a relative movement between the imaging target and the FD-OCT scanner during scanning; wherein the controller obtains a first set of samples including samples obtained by the FD-OCT scanner scanning the imaging target along a first scan line of the imaging target; obtains a second set of samples including samples obtained by the FD-OCT scanner scanning the imaging target along a second scan line of the imaging target, the second scan line at least partially overlapping the first scan line; a cross-correlation calculation that calculates a cross-correlation between a third set of samples including at least some of the samples of the first set of samples and a fourth set of samples including at least some of the samples of the second set of samples, wherein at least some of the samples of the third set of samples and at least some of the samples of the fourth set of samples are obtained from a common region of the imaging target where the first scan line and the second scan line overlap, and performs a cross-correlation calculation based on the phase information of the third set of samples and the phase information of the fourth set of samples; thereby performing the cross-correlation calculation; wherein the FD-OCT scanner Using the calculated cross-correlation, the first set of samples and the second set of samples are registered relative to each other to determine a value of an offset index indicating an offset between a scanning position of the first set of samples and a scanning position of the second set of samples. During scanning, the determined value of the offset index is used to control the FD-OCT scanner so as to correct a relative movement between the imaging target and the FD-OCT scanner that occurs between the acquisition of the first set of samples by the FD-OCT scanner and the acquisition of the second set of samples. Thereby, during scanning, the FD-OCT scanner is controlled so as to correct a relative movement between the imaging target and the FD-OCT scanner. It is configured as follows. The FD-OCT scanner is configured to generate the complex OCT data by performing, as the scanning, a repetition of line scanning of the imaging target along overlapping scan lines of the imaging target such that the acquired samples define a repeated B-scan of the imaging target. The controller acquires, as a first set of the samples, a first B-scan of the repeated B-scan. acquires, as a second set of the samples, a second B-scan of the repeated B-scan. As the cross-correlation calculation, the cross-correlation is calculated which is a two-dimensional cross-correlation between one or more A-scans of the first B-scan and A-scans of the second B-scan, and the cross-correlation calculation is executed such that the A-scans of the second B-scan include A-scans positioned in the second B-scan corresponding to one or more of the A-scans in the first B-scan. Thereby, the cross-correlation calculation is executed. The FD-OCT scanner registers the first B-scan with respect to each other as the first set of samples, registers the second B-scan with respect to each other as the second set of samples, and using the calculated cross-correlation, determines, as a value of the offset index, an offset value indicating an offset between the first B-scan and the second B-scan. Correcting the relative movement between the imaging target and the FD-OCT scanner that occurred between the acquisition of the first B-scan and the acquisition of the second B-scan by the FD-OCT scanner, using the determined offset value. Thereby, controlling the FD-OCT scanner so as to correct the relative movement between the imaging target and the FD-OCT scanner during scanning. It is configured as follows. The controller is configured to execute the cross-correlation calculation as the cross-correlation calculation for calculating a two-dimensional cross-correlation between a predetermined number of A-scans of the first B-scan and the A-scans of the second B-scan. The cross-correlation calculation is based on the phase information in the predetermined number of A-scans of the first B-scan and the phase information in the A-scans of the second B-scan. The predetermined number is selected such that the variation in the phase information among the predetermined number of A-scans of the first B-scan is less than a predetermined degree of variation. Fourier domain OCT imaging system. According to claim 2, the controller executes a plurality of the cross-correlation calculations to calculate respective two-dimensional cross-correlations between each set of a plurality of sets of a predetermined number of A-scans of the first B-scan and each A-scan of the second B-scan. Each A-scan of the second B-scan includes an A-scan located in the second B-scan corresponding to the predetermined number of A-scans in the set. Execute a plurality of the cross-correlation calculations. Combining the calculated cross-correlations to determine a value indicating the offset between the first B-scan and the second B-scan as the offset value. By using the determined offset value indicating the offset between the first B-scan and the second B-scan, controlling the FD-OCT scanner to correct the relative movement between the imaging target and the FD-OCT scanner. Thereby, the Fourier domain OCT imaging system according to claim 1, wherein the controller is configured to control the FD-OCT scanner so as to correct the relative movement between the imaging target and the FD-OCT scanner during scanning. Claim 3. A Fourier domain optical coherence tomography (FD-OCT) system, an FD-OCT scanner arranged to generate complex OCT data by performing a scan of an imaging target to obtain a sample having a complex value indicative of an optical characteristic of the imaging target at each scan position of the imaging target, the FD-OCT scanner including a scanning system configured to perform a one-dimensional and / or two-dimensional point scan of an optical beam across the imaging target and to collect light scattered by the imaging target during the point scan; a controller configured to perform a cross-correlation calculation using the phase information of the acquired sample and to control the scanning system of the FD-OCT scanner based on the cross-correlation calculation to correct a relative movement between the imaging target and the FD-OCT scanner during the scan; wherein the controller obtains a first set of samples, including samples obtained by the FD-OCT scanner scanning the imaging target along a first scan line of the imaging target; obtains a second set of samples, including samples obtained by the FD-OCT scanner scanning the imaging target along a second scan line of the imaging target, the second scan line at least partially overlapping the first scan line; a cross-correlation calculation that calculates a cross-correlation between a third set of samples including at least some of the samples of the first set of samples and a fourth set of samples including at least some of the samples of the second set of samples, wherein at least some of the samples of the third set of samples and at least some of the samples of the fourth set of samples are obtained from a common region of the imaging target where the first scan line and the second scan line overlap, and performs a cross-correlation calculation based on the phase information of the third set of samples and the phase information of the fourth set of samples; thereby performing the cross-correlation calculation; wherein the FD-OCT scanner Using the calculated cross-correlation to register the first set of samples and the second set of samples relative to each other to determine a value of an offset indicator indicating an offset between the scanning positions of the first set of samples and the scanning positions of the second set of samples. During scanning, using the determined value of the offset indicator to control the FD-OCT scanner so as to correct a relative movement between the imaging target and the FD-OCT scanner that occurs between the acquisition of the first set of samples by the FD-OCT scanner and the acquisition of the second set of samples. Thereby, during scanning, controlling the FD-OCT scanner so as to correct a relative movement between the imaging target and the FD-OCT scanner. Configured as follows. The FD-OCT scanner is configured to generate the complex OCT data by performing an area OCT scan of the imaging target in order to acquire samples having complex values indicating optical characteristics of the imaging target at respective scanning positions three-dimensionally distributed on the imaging target as the scanning. The controller is configured to perform the cross-correlation calculation by acquiring a set of samples including samples acquired by the FD-OCT scanner that scans the imaging target along the first scan line as at least a part of the area OCT scan, and the second scan line intersects the first scan line. The first scan line and the second scan line extend along two axial directions of the imaging target and are different respective parts of a single scan line that intersects itself, a Fourier area OCT imaging system. **Claim 4**: The Fourier area OCT imaging system according to claim 3, wherein the first scan line is one of a plurality of parallel scan lines of the imaging target, and the FD-OCT scanner is configured to perform the area OCT scan by scanning the imaging target along the plurality of parallel scan lines, and generate an OCT-C-scan as the complex OCT data based on the area OCT scan. **Claim 5**: The Fourier domain OCT imaging system according to claim 4, wherein the controller is configured to perform the cross-correlation calculation by acquiring the complex OCT data of the OCT-C-scan as the first set of samples. **Claim 6**: The Fourier domain OCT imaging system according to claim 3, wherein the first scanning line extends along two axial directions of the imaging target. **Claim 7**: The Fourier domain OCT imaging system according to claim 6, wherein the first scanning line defines one of a square, a triangle, a rhombus, a circle, an ellipse, a helix, a square helix, a Lissajous figure, an epitrochoid, and a hypotrochoid on the imaging target. **Claim 8**: The Fourier domain OCT imaging system according to claim 3, wherein the single scanning line defines one of a Lissajous figure, an epitrochoid, and a hypotrochoid on the imaging target. **Claim 9**: A computer-implemented method for controlling a Fourier domain optical coherence tomography (FD-OCT) scanner, the method comprising: obtaining a sample having a complex value indicative of an optical characteristic of an imaging target at each scanning position of the imaging target; generating complex OCT data by performing a scan of the imaging target to correct for relative movement between the imaging target and the FD-OCT scanner during the scan, the FD-OCT scanner including a scanning system configured to perform one-dimensional and / or two-dimensional point scanning of an optical beam across the imaging target and to collect light scattered by the imaging target during the point scanning, the computer-implemented method comprising: performing a cross-correlation calculation using the phase information of the acquired sample; controlling the scanning system of the FD-OCT scanner to correct the relative movement between the imaging target and the FD-OCT scanner during the scan based on the cross-correlation calculation; wherein the cross-correlation calculation comprises: obtaining a first set of samples including samples acquired by the FD-OCT scanner scanning the imaging target along a first scanning line of the imaging target; A second set of samples, including samples acquired by the FD-OCT scanner that scans the imaging target along a second scan line of the imaging target, wherein the second scan line at least partially overlaps with the first scan line, to obtain the second set of samples, A cross-correlation calculation for calculating a two-dimensional cross-correlation between a third set of samples including at least some of the samples in the first set of samples and a fourth set of samples including at least some of the samples in the second set of samples, wherein at least some of the samples in the third set of samples and at least some of the samples in the fourth set of samples are obtained from a common region of the imaging target where the first scan line and the second scan line overlap, and performing a cross-correlation calculation based on the phase information of the third set of samples and the phase information of the fourth set of samples, which is executed by using the calculated cross-correlation to register the first set of samples and the second set of samples relative to each other so that the FD-OCT scanner determines a value of an offset index indicating an offset between the scan positions of the first set of samples and the second set of samples, using the determined value of the offset index to control the FD-OCT scanner to correct a relative movement between the imaging target and the FD-OCT scanner that occurs during acquisition of the first set of samples and acquisition of the second set of samples by the FD-OCT scanner during scanning, whereby, during scanning, it is controlled to correct a relative movement between the imaging target and the FD-OCT scanner, the FD-OCT scanner is configured to generate the complex OCT data by performing a repetition of line scans of the imaging target along overlapping scan lines of the imaging target such that the acquired samples define a repeated B-scan of the imaging target, acquiring a first B-scan of the repeated B-scan as the first set of samples, acquiring a second B-scan of the repeated B-scan as the second set of samples, As the cross-correlation calculation, perform the cross-correlation calculation for calculating the two-dimensional cross-correlation between one or more A-scans of the first B-scan and the A-scans of the second B-scan, and the A-scans of the second B-scan include A-scans located in the second B-scan corresponding to one or more of the A-scans in the first B-scan, and execute the cross-correlation calculation. Thereby, perform the cross-correlation calculation. The FD-OCT scanner register the first B-scan with respect to each other as a set of the first samples, register the second B-scan with respect to each other as a set of the second samples, and use the calculated cross-correlation to determine, as a value of the offset index, an offset value indicating an offset between the first B-scan and the second B-scan. correct the relative movement between the imaging target and the FD-OCT scanner that occurred during the acquisition of the first B-scan and the acquisition of the second B-scan by the FD-OCT scanner, using the determined offset value. Thereby, control the FD-OCT scanner so as to correct the relative movement between the imaging target and the FD-OCT scanner during scanning. is configured to As the cross-correlation calculation, be configured to execute the cross-correlation calculation for calculating the two-dimensional cross-correlation between a predetermined number of A-scans of the first B-scan and the A-scans of the second B-scan, the cross-correlation calculation is based on the phase information in the predetermined number of A-scans of the first B-scan and the phase information in the A-scans of the second B-scan, and the predetermined number is selected such that the variation of the phase information among the predetermined number of A-scans of the first B-scan is less than a predetermined degree of variation. A computer-implemented method including this. When executed by a processor, by performing the computer-implemented method according to claim 9, the processor controls Fourier domain optical coherence tomography, performs one-dimensional and / or two-dimensional point scanning of a light beam across the imaging target, and includes a scanning system configured to collect light scattered by the imaging target during the point scanning. By performing scanning of the imaging target on the FD-OCT scanner, a sample having a complex value indicating the optical characteristics of the imaging target at each scanning position of the imaging target is obtained to generate complex OCT data, and the processor controls the scanning system of the FD-OCT scanner to correct relative movement between the imaging target and the FD-OCT scanner during scanning. A computer program comprising computer-readable instructions.

Images