OCT data processing device and OCT data processing program

Abstract

According to the present invention, an OCT device comprises an OCT optical system and a focus adjustment unit. The OCT optical system branches light emitted from an OCT light source into measurement light and reference light, and acquires an OCT signal by receiving the measurement light reflected from a tissue and interference light of the reference light. The focus adjustment unit adjusts a focus position of the OCT optical system along an optical axis direction of the OCT optical system. A control unit of this OCT data processing device executes composite steps (S8-S10). In the composite steps, a plurality of OCT images, which are obtained by photographing the same subject's eye tissue while the focus position is adjusted to respective positions corresponding to a plurality of positions on the tissue that are spaced away from each other in a transverse direction intersecting with the optical axis, are aligned and combined to form a composite.

Description

[Technical Field]

[0001] The present disclosure relates to an optical coherence tomography (OCT) data processing device that processes data of OCT images captured based on the principles of OCT, and an OCT data processing program that runs in the OCT data processing device. [Background technology]

[0002] Conventionally, OCT devices are known that capture OCT images, which are tomographic images of tissue, using reflected light from measurement light and reference light. In OCT devices, the quality of captured images is improved by capturing images with the focus position of the OCT optical system adjusted to an appropriate position. For example, the device described in Patent Document 1 acquires the ocular refractive power based on the axial length of the subject's eye and adjusts the focus position to a position corresponding to the ocular refractive power. The focus position is adjusted along the optical axis direction of the measurement light (i.e., the depth direction of the tissue being captured as a tomographic image). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-36717 Summary of the Invention

[0004] In an OCT image, the brightness decreases as the depth position moves farther from the focus position. Furthermore, increasing the focal depth to suppress the brightness difference depending on the distance from the focus position results in a decrease in the brightness of the entire image. Many of the tissues of the subject's eye (e.g., the fundus, cornea, and crystalline lens) that are imaged by an OCT device are curved. Therefore, as the imaging range in the direction intersecting the optical axis (hereinafter sometimes referred to as the "transverse direction") increases, the curvature of the tissue makes it difficult to simultaneously focus on all positions in the transverse direction (e.g., the center and periphery). Therefore, it has been difficult to obtain high-quality OCT images over a wide transverse range using conventional techniques.

[0005] A typical object of the present disclosure is to provide an OCT data processing device and an OCT data processing program for acquiring OCT images with better image quality over a wide range in the transverse direction.

[0006] An OCT data processing device provided by a typical embodiment of the present disclosure is an OCT data processing device that processes data of OCT images of tissue of a subject's eye captured by an OCT device, the OCT device including: an OCT optical system that splits light emitted from an OCT light source into measurement light and reference light, and acquires an OCT signal by receiving interference light between the measurement light reflected by tissue and the reference light; and a focus adjustment unit that adjusts the focus position of the OCT optical system in the optical axis direction of the OCT optical system, and a control unit of the OCT data processing device that processes data of OCT images of tissue of the same subject's eye captured by an OCT device. Identical The tissue is the subject of photography, and In the optical axis direction of the OCT optical system The focus positions correspond to each of a plurality of positions on the tissue spaced apart in a direction intersecting the optical axis. different Adjusted to position and fixed A synthesis step is performed in which multiple OCT images taken in the same state are aligned and synthesized. In the combining step, a focus appropriateness that changes within the image along the optical axis direction is set for each of the plurality of OCT images, and weighting is performed on each of the plurality of pixels that constitute the OCT image according to the set focus appropriateness, and the weighted OCT images are combined. .

[0007] An OCT data processing program provided by a typical embodiment of the present disclosure is an OCT data processing program executed by an OCT data processing device that processes data of OCT images of tissue of a subject's eye captured by an OCT device, the OCT device including: an OCT optical system that splits light emitted from an OCT light source into measurement light and reference light, and acquires an OCT signal by receiving interference light between the measurement light reflected by tissue and the reference light; and a focus adjustment unit that adjusts the focus position of the OCT optical system in the optical axis direction of the OCT optical system, and the OCT data processing program is executed by a control unit of the OCT data processing device to process data of OCT images of tissue of a subject's eye captured by an OCT device. Identical The tissue is the subject of photography, and In the optical axis direction of the OCT optical system The focus positions correspond to each of a plurality of positions on the tissue spaced apart in a direction intersecting the optical axis. different Adjusted to position and fixed a combining step of aligning and combining a plurality of OCT images taken in the same state, In the combining step, a focus appropriateness that changes within the image along the optical axis direction is set for each of the plurality of OCT images, and weighting is performed on each of the plurality of pixels that constitute the OCT images according to the set focus appropriateness, and the weighted OCT images are combined. .

[0008] According to the OCT data processing device and OCT data processing program of the present disclosure, OCT images with better image quality can be acquired over a wide range in the transverse direction.

[0009] The OCT data processing device exemplified in the present disclosure processes data of OCT images of tissues of a subject's eye captured by an OCT device. The OCT device includes an OCT optical system and a focus adjustment unit. The OCT optical system splits light emitted from an OCT light source into measurement light and reference light, and acquires an OCT signal by receiving interference light between the measurement light reflected by the tissue and the reference light. The focus adjustment unit adjusts the focus position of the OCT optical system along the optical axis of the OCT optical system. The control unit of the OCT data processing device executes a synthesis step. In the synthesis step, multiple OCT images are captured using the same tissue of the subject's eye as the imaging target, with the focus position adjusted to correspond to multiple positions on the tissue separated in a direction intersecting the optical axis (transverse direction). The multiple OCT images are aligned and synthesized. In other words, a composite image is generated by combining the multiple OCT images.

[0010] The OCT data processing device according to the present disclosure combines multiple OCT images captured of the same subject at different focus positions in the transverse direction, thereby generating a composite image with good image quality over a wide range in the transverse direction.

[0011] The compositing step may be performed when processing OCT data of curved tissues of a test eye (e.g., fundus, cornea, lens, etc.). As described above, when capturing OCT images of curved tissues, it is difficult to simultaneously focus on all positions in the transverse direction. In contrast, by performing the compositing step on the OCT images of the curved tissues, a composite image of the curved tissues with good image quality can be appropriately obtained.

[0012] The number of OCT images combined in the combining step may be two, or may be three or more. The control unit may further process the data of the combined image. For example, the control unit may cause the display unit to display the combined image. The control unit may also perform an analysis process on the combined image (for example, a process to analyze the thickness of a specific layer) and generate data of the analysis results. The control unit may store the data of the combined image in a storage device.

[0013] Various devices can function as the OCT data processing device. For example, the OCT device itself may function as the OCT data processing device of the present disclosure. In this case, the OCT device can capture multiple OCT images and appropriately combine the captured multiple OCT images. Also, a device (such as a personal computer (PC)) that can exchange data with the OCT device may function as the OCT data processing device. Multiple control units (such as a control unit of the OCT device and a control unit of the PC) may cooperate to perform processing.

[0014] The control unit may further execute a first image acquisition step and a focus setting step. In the first image acquisition step, the control unit acquires a first OCT image captured by the OCT device. In the focus setting step, the control unit sets a second focus position, which is a focus position when capturing a second OCT image to be combined with the first OCT image, based on the position in the optical axis direction of the object captured in the first OCT image and a first focus position, which is the focus position when the first OCT image was captured. The control unit combines the first OCT image with the second OCT image, the second OCT image being captured of the same object as the first OCT image with the focus position adjusted to the second focus position.

[0015] In this case, the second focus position of the second OCT image captured thereafter is appropriately set to a position with low sensitivity in the first OCT image based on the first OCT image that was actually captured, and thus, by combining the first OCT image and the second OCT image, a composite image with better image quality is appropriately generated.

[0016] The specific method for setting the second focus position in the focus setting step can be selected as appropriate. For example, the control unit may set the second focus position at a position different from the first focus position within the range of the optical axis direction (depth direction of tissue) of the imaging target (e.g., tissue such as the fundus or cornea) captured in the first OCT image. The control unit may set the second focus position depending on the number of OCT images to be combined and the depth direction range of the imaging target captured in the first OCT image.

[0017] The control unit may further execute a first determination step. In the first determination step, the control unit determines whether to execute a combining step based on an OCT image captured by the OCT device. When the quality of the already captured OCT image is good, there is little need to generate a composite image. Therefore, by determining whether to execute the combining step based on the already captured OCT image, the control unit can appropriately execute the combining step when there is a high need to generate a composite image.

[0018] A specific method for executing the first determination step can be selected as appropriate. For example, the control unit may execute the combining step when the object shown in the previously captured OCT image does not fall within a predetermined range extending in the optical axis direction from the focus position at the time of capture. Furthermore, the control unit may determine whether to execute the combining step depending on the brightness of the object in the previously captured OCT image.

[0019] The control unit may execute a second determination step. In the second determination step, the control unit determines whether to execute the combining step according to the imaging angle of view when the OCT image is captured by the OCT device. When the tissue to be imaged is curved, the larger the imaging angle of view, the more difficult it becomes to simultaneously focus on each position of the tissue in the transverse direction. As a result, there are more areas away from the focus position in the optical axis direction where sensitivity decreases, so it is desirable to generate a composite image. On the other hand, the smaller the imaging angle of view, the less necessary it is to generate a composite image in many cases. Therefore, by determining whether to execute the combining step according to the imaging angle of view, the control unit can appropriately execute the combining step when there is a high need to generate a composite image.

[0020] A specific method for executing the second determination step can also be selected as appropriate. For example, whether or not to execute the combining step may be determined depending on whether or not the imaging angle of view is greater than a threshold. In this case, the threshold may be predetermined depending on the type of tissue to be imaged, etc.

[0021] In the combining step, the control unit may set a focus appropriateness that varies within the image along the optical axis direction (depth direction) for each of the multiple OCT images. The control unit may weight each of the multiple pixels that make up the OCT image according to the set focus appropriateness. The control unit may combine the weighted OCT images. In this case, the pixel value of each pixel is appropriately reflected in the pixel value of the combined image according to the focus appropriateness. Therefore, the image quality of the combined image is improved. Furthermore, even if the number of OCT images used in the combined image is reduced (for example, even if only two images are used), a combined image with good image quality is more likely to be generated.

[0022] The control unit may set the focus appropriateness of the OCT image based on the focus position when the OCT image was captured. That is, the focus appropriateness may be set so that it decreases as the pixel moves away from the focus position in the optical axis direction. In this case, the focus appropriateness is set appropriately based on the positional relationship of each pixel with respect to the focus position.

[0023] The control unit may set the appropriateness of the focus of the OCT image based on the brightness of multiple pixels that make up the captured OCT image. The closer a pixel is to the focus position, the higher the brightness of the pixel. Therefore, the appropriateness of the focus can be set appropriately by using the brightness of the actually captured OCT image.

[0024] However, the specific method for generating the composite image is not limited to the method using weighting according to the degree of focus appropriateness. For example, the control unit may extract a portion close to the focus position from each of multiple OCT images, and align and paste the extracted portions together to generate a composite image. The control unit may also generate a composite image by aligning multiple OCT images and adding (or averaging) pixel values of pixels at the same position. The control unit may also align multiple OCT images and generate a composite image using a set of pixels with the highest brightness value among pixels at the same position. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of an OCT system 100. [Figure 2] 10 is a flowchart illustrating an example of OCT data processing. [Figure 3] FIG. 10 is a diagram showing an example of a first OCT image 50A when the imaging object width TL falls within the allowable range GL. [Figure 4] FIG. 10 is a diagram showing an example of a first OCT image 50A when the imaging object width TL is not within the allowable range GL. [Figure 5] FIG. 10 is an explanatory diagram for explaining an example of a method for setting a second focus position FB. [Figure 6] FIG. 10 is a diagram showing an example of a second OCT image 50B captured with the focus position adjusted to the second focus position FB. [Figure 7] FIG. 10 is an explanatory diagram illustrating an example of a method for weighting each pixel of an OCT image according to the focus appropriateness. [Figure 8] FIG. 5 is a diagram showing an example of a composite image 50C obtained by combining a first OCT image 50A (see FIG. 5) and a second OCT image 50B (see FIG. 6). DETAILED DESCRIPTION OF THE INVENTION

[0026] A typical embodiment according to the present disclosure will be described below. As an example, the OCT system 100 of this embodiment can capture and process OCT images, which are tomographic images of fundus tissues, using the fundus, one of the curved tissues, of the subject's eye E, as an imaging target (subject). However, at least some of the techniques exemplified in this disclosure can also be applied when processing OCT images of tissues other than the fundus of the subject's eye E. In particular, curved tissues (such as the cornea or lens) in the anterior segment of the subject's eye E are always curved and have a wide depth width. Therefore, when capturing OCT images of the anterior segment using conventional methods, the proportion of areas far from the focus position increases, making it difficult to improve image quality. Therefore, applying at least some of the techniques exemplified in this disclosure is particularly useful when processing OCT images of the anterior segment of the subject's eye E. Furthermore, OCT angiography, which is used to detect motion contrast data of the subject's eye, must capture subtle changes in the tissues, so the focus position has a significant impact. Therefore, applying at least some of the techniques exemplified in this disclosure is also useful when processing OCT angiography data. Furthermore, at least a part of the techniques exemplified in this disclosure can be applied to processing OCT images of a subject (for example, skin, digestive organs, brain, etc.) other than the subject's eye E. Furthermore, the OCT image in this embodiment is a tomographic image acquired based on the principle of optical coherence tomography (OCT).

[0027] The schematic configuration of an OCT system 100 of this embodiment will be described with reference to Fig. 1. The OCT system 100 of this embodiment includes an OCT device 1 and a personal computer (hereinafter referred to as "PC") 40. The OCT device 1 captures an OCT image of a subject's eye E. The PC 40 processes the OCT image captured by the OCT device 1.

[0028] The OCT device 1 includes an OCT optical system 10 and a control unit 30. The OCT optical system 10 includes an OCT light source 11, a coupler (light splitter) 12, a measurement optical system 13, a reference optical system 20, a light receiving element 22, and a front observation optical system 23.

[0029] The OCT light source 11 emits light (OCT light) for capturing an OCT image. The coupler 12 splits the OCT light emitted from the OCT light source 11 into measurement light and reference light. The coupler 12 of this embodiment also combines the measurement light reflected by the subject (the fundus of the subject's eye E in this embodiment) with the reference light generated by the reference optical system 20 to cause interference. That is, the coupler 12 of this embodiment serves both as a branching optical element that branches the OCT light into measurement light and reference light, and as a combining optical element that combines the reflected light of the measurement light with the reference light. Note that the configuration of at least one of the branching optical element and the combining optical element can be changed. For example, an element other than a coupler (e.g., a circulator, a beam splitter, etc.) may be used.

[0030] The measurement optical system 13 guides the measurement light split by the coupler 12 to the subject and returns the measurement light reflected by the subject to the coupler 12. The measurement optical system 13 includes a scanning unit 14, an irradiation optical system 16, and a focus adjustment unit 17. The scanning unit 14 is driven by a driving unit 15 to scan (deflect) the measurement light in a two-dimensional direction intersecting the optical axis of the measurement light. In this embodiment, two galvanometer mirrors capable of deflecting the measurement light in different directions are used as the scanning unit 14. However, another device for deflecting light (e.g., at least one of a polygon mirror, a resonant scanner, an acousto-optical element, etc.) may also be used as the scanning unit 14. The irradiation optical system 16 is provided downstream of the scanning unit 14 in the optical path (i.e., on the subject side) and irradiates the measurement light onto the tissue of the subject. The focus adjustment unit 17 adjusts the focus position of the OCT optical system 10 (the focus position of the irradiation optical system 16) in the optical axis direction (i.e., the depth direction of the tissue) of the measurement light from the OCT optical system 10. As an example, the focus adjustment unit 17 of this embodiment adjusts the focus of the measurement light by moving an optical member (e.g., a lens) included in the irradiation optical system 16 in the direction along the optical axis of the measurement light.

[0031] The reference optical system 20 generates reference light and returns it to the coupler 12. In this embodiment, the reference optical system 20 generates the reference light by reflecting the reference light split by the coupler 12 using a reflective optical system (e.g., a reference mirror). However, the configuration of the reference optical system 20 can also be changed. For example, the reference optical system 20 may transmit the light incident from the coupler 12 without reflecting it and return it to the coupler 12. The reference optical system 20 includes an optical path length difference adjustment unit 21 that changes the optical path length difference between the measurement light and the reference light. In this embodiment, the optical path length difference is changed by moving the reference mirror in the optical axis direction. Note that the configuration for changing the optical path length difference may be provided in the optical path of the measurement optical system 13.

[0032] The light receiving element 22 detects an interference signal by receiving interference light between the measurement light and the reference light generated by the coupler 12. In this embodiment, the principle of Fourier domain OCT is adopted. In Fourier domain OCT, the spectral intensity of the interference light (spectral interference signal) is detected by the light receiving element 22, and a complex OCT signal is acquired by Fourier transforming the spectral intensity data. Examples of Fourier domain OCT that can be adopted include spectral-domain OCT (SD-OCT) and swept-source OCT (SS-OCT). It is also possible to adopt, for example, time-domain OCT (TD-OCT).

[0033] In this embodiment, SD-OCT is employed. In the case of SD-OCT, for example, a low-coherence light source (broadband light source) is used as the OCT light source 11, and a spectroscopic optical system (spectrometer) that separates the interference light into individual frequency components (individual wavelength components) is provided near the light-receiving element 22 in the optical path of the interference light. In the case of SS-OCT, for example, a wavelength-scanning light source (tunable light source) that changes the emission wavelength at high speed over time is used as the OCT light source 11. In this case, the OCT light source 11 may include a light source, a fiber ring resonator, and a wavelength-selective filter. Examples of wavelength-selective filters include a filter that combines a diffraction grating and a polygon mirror, and a filter that uses a Fabry-Perot etalon.

[0034] In this embodiment, a three-dimensional OCT image can also be acquired by scanning a two-dimensional measurement region with a measurement light spot using the scanning unit 14. The principle of capturing an OCT image can also be changed. For example, an OCT image can be captured using the principle of line-field OCT (hereinafter referred to as "LF-OCT"). In LF-OCT, measurement light is simultaneously irradiated onto an irradiation line extending in a one-dimensional direction in tissue, and the reflected light of the measurement light and the interference light of the reference light are received by a one-dimensional light-receiving element (e.g., a line sensor) or a two-dimensional light-receiving element. A three-dimensional OCT image can also be captured by scanning the measurement light in a direction intersecting the irradiation line within the two-dimensional measurement region. A three-dimensional OCT image can also be captured using the principle of full-field OCT (hereinafter referred to as "FF-OCT"). In FF-OCT, measurement light is irradiated onto a two-dimensional measurement region on tissue, and the reflected light of the measurement light and the interference light of the reference light are received by a two-dimensional light-receiving element. In this case, the OCT device 1 does not need to include the scanning unit 14.

[0035] The OCT device 1 of this embodiment can change the imaging angle of view when imaging the tissue of the subject's eye E. The larger the imaging angle of view, the wider the imaging range (imaging range in the transverse direction) when the tissue is viewed from a direction along the optical axis of the measurement light. For example, the imaging angle of view may be changed by attaching or detaching an attachment (not shown) equipped with an optical member for changing the imaging angle of view to or from the OCT optical system 10.

[0036] The front observation optical system 23 is provided to acquire a two-dimensional front image of the tissue of the subject (the fundus of the subject's eye E in this embodiment). The two-dimensional front image in this embodiment is a two-dimensional image of the tissue when viewed from a direction along the optical axis of the OCT measurement light (the front direction). The front observation optical system 23 may be configured with at least one of a scanning laser ophthalmoscope (SLO), a fundus camera, and an infrared camera that captures a front image by irradiating a two-dimensional imaging range with infrared light. The OCT device 1 may also acquire three-dimensional OCT data of the tissue and capture an image of the tissue when viewed from a direction along the optical axis of the measurement light (the front direction) (a so-called "enface image") as the two-dimensional front image. When an enface image is acquired, the front observation optical system 23 may be omitted.

[0037] The control unit 30 is responsible for various controls of the OCT device 1. The control unit 30 includes a CPU 31, a RAM 32, a ROM 33, and a non-volatile memory (NVM) 34. The CPU 31 is a controller that performs various controls. The RAM 32 temporarily stores various information. The ROM 33 stores programs executed by the CPU 31, various initial values, etc. The NVM 34 is a non-transitory storage medium that can retain its contents even if the power supply is cut off. When the OCT device 1 executes OCT data processing (see FIG. 2 ), which will be described later, an OCT data processing program for executing the OCT data processing may be stored in the NVM 34.

[0038] A microphone 36, a monitor 37, and an operation unit 38 are connected to the control unit 30. The microphone 36 inputs sound. The monitor 37 is an example of a display unit that displays various images. The operation unit 38 is operated by a user to input various operation instructions to the OCT device 1. The operation unit 38 may be various devices such as a mouse, a keyboard, a touch panel, or a foot switch. Note that various operation instructions may be input to the OCT device 1 by inputting sound into the microphone 36. In this case, the CPU 31 may determine the type of operation instruction by performing voice recognition processing on the input sound.

[0039] In this embodiment, an integrated OCT device 1 in which the OCT optical system 10 and the control unit 30 are built into a single housing is exemplified. However, it goes without saying that the OCT device 1 may include multiple devices in different housings. For example, the OCT device 1 may include an optical device that incorporates the OCT optical system 10 and a PC that is connected to the optical device via a wired or wireless connection. In this case, the control unit of the optical device and the control unit of the PC may both function as the control unit 30 of the OCT device 1.

[0040] The following describes the schematic configuration of the PC 40. The PC 40 includes a CPU 41, a RAM 42, a ROM 43, and an NVM 44. An OCT data processing program for executing OCT data processing (see FIG. 2), which will be described later, may be stored in the NVM 44. The PC 40 is also connected to a microphone 46, a monitor 47, and an operation unit 48. The microphone 46 inputs sound. The monitor 47 is an example of a display unit that displays various images. The operation unit 48 is operated by a user to input various operation instructions to the PC 40. As with the operation unit 38 of the OCT device 1, various devices such as a mouse, keyboard, or touch panel may be used for the operation unit 48. Furthermore, various operation instructions may be input to the PC 40 by inputting sound into the microphone 46.

[0041] The PC 40 can acquire various data (e.g., data of an OCT image acquired by the OCT device 1) from the OCT device 1. The various data may be acquired, for example, by at least one of wired communication, wireless communication, and a removable storage device (e.g., a USB memory).

[0042] OCT data processing in this embodiment will be described with reference to FIGS. 2 to 8. In this embodiment, the PC 40 acquires data of the OCT image 50 (sometimes simply referred to as the "OCT image 50") from the OCT device 1 and processes the acquired data of the OCT image 50. That is, in this embodiment, the PC 40 functions as an OCT data processing device. However, as described above, another device may also function as the OCT data processing device. For example, the OCT device 1 itself may execute OCT data processing. Furthermore, multiple control units (for example, the CPU 31 of the OCT device 1 and the CPU 41 of the PC 40) may cooperate to execute OCT data processing. In this embodiment, the CPU 41 of the PC 40 executes the OCT data processing shown in FIG. 2 in accordance with an OCT data processing program stored in the NVM 44.

[0043] First, the CPU 41 acquires (S1) a first OCT image 50A (see FIGS. 3 to 5) captured by the OCT device 1. The first OCT image 50A is an image captured with the curved tissue of the subject's eye (for example, the fundus in this embodiment) as the imaging target, and the focus position adjusted to a first focus position FA (see FIGS. 3 to 5) by the focus adjustment unit 17 (see FIG. 1).

[0044] As described above, in the OCT device 1, the focus position is adjusted in the optical axis direction of the OCT measurement light (i.e., the depth direction of the tissue). In FIGS. 3 to 8, the up-down direction on the paper surface corresponds to the optical axis direction (depth direction of the tissue). The direction intersecting the optical axis direction (left-right direction on the paper surface in FIGS. 3 to 8) corresponds to the transverse direction. In the OCT image 50 (first OCT image 50A in FIGS. 3 to 5), the brightness value of a pixel tends to decrease as the position in the optical axis direction (depth direction) moves away from the focus position (first focus position FA in FIGS. 3 to 5). In other words, within the image region of the OCT image 50, the closer the distance from the focus position in the depth direction, the higher the sensitivity, and the farther the distance from the focus position, the lower the sensitivity.

[0045] Next, the CPU 41 acquires information about the imaging angle of view when the first OCT image 50A is captured by the OCT device 1. The CPU 41 determines whether the imaging angle of view when capturing the first OCT image 50A is greater than a threshold (S2). As described above, the larger the imaging angle of view, the wider the imaging range when viewing the tissue from a direction along the optical axis of the measurement light. If the tissue to be imaged is curved, the wider the imaging range, the more difficult it is to simultaneously focus on each position of the tissue in the transverse direction. In other words, the wider the imaging range, the greater the depth direction width (hereinafter referred to as the "imaged object width TL") of the imaging object (in this embodiment, near the surface layer of the fundus) included in the imaging range. For example, because the fundus, cornea, and crystalline lens of the subject's eye are curved, the larger the imaging angle of view, the larger the imaging object width TL included in the imaging range. As illustrated in FIGS. 3 and 4, the larger the imaging target width TL, the greater the area where sensitivity decreases as it moves away from the focus position FA in the depth direction. Therefore, it is desirable to perform the synthesis process (S8 to S10) described below to obtain a high-quality image. On the other hand, the smaller the imaging target width TL, the less need there is for the synthesis process to be performed. Therefore, if the imaging angle of view is equal to or smaller than the threshold (S2: NO), it is determined that the synthesis process (S8 to S10) will not be performed, and the process ends as is. The threshold used in the determination of S2 may be set appropriately. For example, the threshold value may be predetermined depending on the type of tissue to be imaged. Alternatively, the threshold value may be set according to an instruction input by the user via the operation unit 48 or the like.

[0046] If the imaging angle of view is greater than the threshold (S2: YES), the CPU 41 determines (S3) based on the first OCT image 50A whether or not to execute the synthesis process (S8 to S10). If the quality of the already captured first OCT image 50A is good, there is little need to execute the synthesis process. Therefore, if the quality of the first OCT image 50A is good (S3: YES), the CPU 41 determines not to execute the synthesis process and ends the process.

[0047] In S3, a specific method for determining whether to perform the composition process based on the first OCT image 50A can be selected as appropriate. An example of the determination method in S3 will be described with reference to FIGS. 3 and 4. In this embodiment, the CPU 41 determines whether the subject width TL in the first OCT image 50A falls within an allowable range GL extending in the optical axis direction (depth direction of the tissue) from the focus position at the time of imaging (first focus position FA in FIGS. 3 and 4). For example, in the first OCT image 50A illustrated in FIG. 3, the subject has a small degree of curvature, so the subject width TL falls within the allowable range GL. In this case, the portion of the subject in the first OCT image 50A that is far from the focus position FA is small, and image quality is likely to be good. Therefore, the CPU 41 determines not to perform the composition process. On the other hand, in the first OCT image 50A illustrated in FIG. 4, the subject width TL does not fall within the allowable range GL and extends upward in the figure. In this case, a large portion of the object captured in the first OCT image 50A is far from the focus position FA. Therefore, the process proceeds to S5.

[0048] In addition, in S3, whether or not to perform the synthesis process may be determined depending on whether the luminance value of the object in the first OCT image 50A (for example, the average value or maximum value of all luminance values in the object) is greater than a threshold value.

[0049] Next, the CPU 41 sets a second focus position FB for capturing the second OCT image 50B based on the position of the subject in the optical axis direction (depth direction of the tissue) captured in the first OCT image 50A and the first focus position FA when the first OCT image 50A was captured (S5). The second OCT image 50B is an image that is combined with the first OCT image 50A in a combining process (S8 to S10) described below. By performing the process of S5, the second focus position FB of the second OCT image 50B to be captured thereafter is appropriately set to a position with low sensitivity in the already captured first OCT image 50A (i.e., a position where pixel values are likely to be low).

[0050] An example of a method for setting the second focus position FB will be described with reference to FIG. 5. In this embodiment, the CPU 41 sets the second focus position FB at a position different from the first focus position FA within the range of the optical axis direction (depth direction of the tissue) of the subject captured in the first OCT image 50A. For example, when setting one second focus position FB (i.e., when capturing one second OCT image 50B), the CPU 41 may set the second focus position FB so that the first focus position FA and the second focus position FB are symmetrical (vertically symmetrical in FIG. 5) with respect to the center of the subject width TL (the center in the vertical direction in FIG. 5). Alternatively, the CPU 41 may set the second focus position FB at the center between the first focus position FA and an end of the subject width TL (the upper end of the image in FIG. 5).

[0051] Next, the CPU 41 acquires a second OCT image 50B captured with the focus position adjusted to the second focus position FB (S6). In this embodiment, the CPU 41 of the PC 40 notifies the OCT device 1 of the second focus position FB set in S5 and issues an instruction to capture the second OCT image 50B. The OCT device 1 adjusts the focus position to the second focus position FB and captures the second OCT image 50B by capturing the same tissue of the subject's eye as the first OCT image 50A. As illustrated in FIG. 6, the areas with high sensitivity (i.e., areas with high brightness) in the captured second OCT image 50B are different from the areas with high sensitivity in the first OCT image 50A. Furthermore, as shown in FIG. 5, the focus position FA of the first OCT image 50A is adjusted to a position corresponding to the center of the fundus (i.e., a position where the brightness of the center of the fundus is high). 6, the focus position FB of the second OCT image 50B is adjusted to a position corresponding to the peripheral portion of the fundus (i.e., a position where the brightness of the peripheral portion of the fundus is higher than the brightness of the central portion.) In other words, the first OCT image 50A and the second OCT image 50B are each captured with the focus position adjusted to a position corresponding to each of a plurality of positions spaced apart in the transverse direction on the tissue.

[0052] The number of second OCT images 50B captured in S6 (i.e., the number of images to be combined with the first OCT image 50A in the combining process described below) may be one or more. When multiple second OCT images 50B are captured in S6, second focus positions FB, the number of which is equal to the number of second OCT images 50B captured in S6, may be set in different positions in S5.

[0053] Next, the CPU 41 sets a focus adequacy for each of the multiple OCT images 50 (i.e., the first OCT image 50A and the second OCT image 50B) (S8). The focus adequacy is information indicating the quality of the focus state (high sensitivity) within the image region of the OCT image 50. As described above, within the OCT image 50, the closer the distance from the focus position in the optical axis direction (depth direction of the tissue), the better the focus state (sensitivity).

[0054] In this embodiment, the CPU 41 sets the focus adequacy based on the focus positions FA and FB when the OCT image 50 is captured. Specifically, the CPU 41 sets the focus adequacy of a pixel to be lower the farther the pixel's position is from the focus positions FA and FB in the optical axis direction. As a result, the focus adequacy of each pixel is appropriately set based on the positional relationship of each pixel with respect to the focus positions FA and FB.

[0055] The CPU 41 may also set the focus adequacy of the OCT image 50 based on the luminance of multiple pixels that make up the actually captured OCT image 50. As described above, the closer a pixel is to the focus positions FA and FB, the higher the luminance of the pixel. Therefore, by using the luminance of the actually captured OCT image 50, the focus adequacy can be set appropriately.

[0056] Next, the CPU 41 weights each pixel value of the plurality of pixels constituting the OCT image 50 according to the focus adequacy set in S8 (S9). FIG. 7 schematically illustrates a method for weighting the first OCT image 50A shown in FIG. 5 according to the focus adequacy set in S8. In the example shown in FIG. 7, the pixel value of each pixel in the first OCT image 50A is multiplied by a weight 60A configured such that the pixel value decreases as the focus adequacy decreases. As a result, a first OCT image 50AX is generated in which the weighting is reflected in the first OCT image 50A. Similar processing is performed on one or more second OCT images 50B.

[0057] Next, the CPU 41 aligns and combines the multiple OCT images (in this embodiment, the first OCT image 50AX and the second OCT image that have been processed in S9) to generate a composite image 50C (see FIG. 8) (S10). For example, the CPU 41 aligns each of the multiple OCT images 50 using various methods (for example, known image processing using edge detection, etc.). The CPU 41 adds pixel values of pixels at the same position to generate the composite image 50C. As shown in FIG. 8, the composite image 50C has reduced unevenness in pixel brightness due to the focus state compared to the first OCT image 50A (see FIG. 5) and the second OCT image 50B (see FIG. 6), and therefore has improved image quality. The generated composite image 50C may be stored in a storage device such as the NVM 44, or may be displayed on a display device such as the monitor 47.

[0058] The techniques disclosed in the above embodiments are merely examples. Therefore, it is possible to modify the techniques exemplified in the above embodiments. First, it is possible to adopt only some of the techniques exemplified in the above embodiments. For example, it is possible to omit at least one of the process (S2) of determining whether to perform a synthesis process based on the imaging angle of view and the process (S3) of setting whether to perform a synthesis process based on the OCT image 50.

[0059] In the above embodiment, the second focus position FB for capturing the second OCT image 50B is set based on the first OCT image 50A captured previously (S5). Thereafter, the second OCT image 50B is captured with the focus position set to the second focus position FB. However, the focus position for capturing each of the multiple OCT images 50 may be set using a different method. For example, the focus position for capturing each of the multiple OCT images 50 may be set in advance. Furthermore, each focus position may be set according to various measurement results related to the subject's eye (for example, the diopter or axial length of the subject's eye).

[0060] In the above embodiment, weighting according to the focus appropriateness is used when combining multiple OCT images 50 (S8 to S10). However, the specific method of combining processing can be changed. For example, the CPU 41 may extract portions close to the focus position from each of the multiple OCT images 50, align and paste the extracted portions together to generate a combined image. Alternatively, the CPU 41 may align the multiple OCT images 50 and add (or average) the pixel values of pixels at the same position to generate a combined image. Alternatively, the CPU 41 may align the multiple OCT images 50 and generate a combined image using a set of pixels at the same position that have the highest brightness value.

[0061] The process of generating composite image 50C in S8 to S10 in FIG. 2 is an example of a "combining step." The process of acquiring first OCT image 50A in S1 in FIG. 2 is an example of a "first image acquiring step." The process of setting second focus position FB in S5 in FIG. 2 is an example of a "focus setting step." The process of determining whether or not to perform composition processing in S3 in FIG. 2 is an example of a "first decision step." The process of determining whether or not to perform composition processing in S2 in FIG. 2 is an example of a "second decision step."

Claims

1. An OCT data processing device that processes data of an OCT image of tissue of a subject's eye captured by an OCT device, The OCT device is an OCT optical system that splits light emitted from an OCT light source into measurement light and reference light, and acquires an OCT signal by receiving interference light between the measurement light reflected by tissue and the reference light; a focus adjustment unit that adjusts a focus position of the OCT optical system in an optical axis direction of the OCT optical system; Equipped with The control unit of the OCT data processing device a combining step of aligning and combining a plurality of OCT images that are taken while the same tissue of the same subject's eye is being imaged and the focus position in the optical axis direction of the OCT optical system is adjusted and fixed to different positions corresponding to a plurality of positions on the tissue that are spaced apart in a direction intersecting the optical axis; Run In the synthesis step, For each of the plurality of OCT images, a focus appropriateness that changes within the image along the optical axis direction is set; weighting each of a plurality of pixels constituting the OCT image in accordance with the set appropriateness of the focus; An OCT data processing device that synthesizes the weighted OCT images.

2. 2. The OCT data processing device according to claim 1, The control unit a first image acquisition step of acquiring a first OCT image captured by the OCT device; a focus setting step of setting a second focus position, which is a focus position when capturing a second OCT image to be combined with the first OCT image, based on a position in the optical axis direction of the object captured in the first OCT image and a first focus position, which is a focus position when the first OCT image was captured; The OCT data processing device further comprises:

3. 3. The OCT data processing device according to claim 1, The control unit a first determination step of determining whether or not to execute the combining step based on the OCT image captured by the OCT device; The OCT data processing device further comprises:

4. 4. The OCT data processing device according to claim 1, The control unit a second determination step of determining whether or not to execute the combining step depending on an imaging angle of view when the OCT image is captured by the OCT apparatus; The OCT data processing device further comprises:

5. 5. The OCT data processing device according to claim 1, In the combining step, the control unit An OCT data processing apparatus, characterized in that the degree of focus suitability of the OCT image is set based on a focus position when the OCT image was captured.

6. 5. The OCT data processing device according to claim 1, In the combining step, the control unit An OCT data processing apparatus, comprising: an OCT image processing unit configured to set the appropriateness of the focus of the captured OCT image based on the brightness of a plurality of pixels that constitute the captured OCT image.

7. An OCT data processing program executed by an OCT data processing device that processes data of an OCT image of tissue of a subject's eye photographed by an OCT device, The OCT device is an OCT optical system that splits light emitted from an OCT light source into measurement light and reference light, and acquires an OCT signal by receiving interference light between the measurement light reflected by tissue and the reference light; a focus adjustment unit that adjusts a focus position of the OCT optical system in an optical axis direction of the OCT optical system; Equipped with When the OCT data processing program is executed by a control unit of the OCT data processing device, a combining step of aligning and combining a plurality of OCT images that are taken while the same tissue of the same subject's eye is being imaged and the focus position in the optical axis direction of the OCT optical system is adjusted and fixed to different positions corresponding to a plurality of positions on the tissue that are spaced apart in a direction intersecting the optical axis; causing the OCT data processing device to execute In the synthesis step, For each of the plurality of OCT images, a focus appropriateness that changes within the image along the optical axis direction is set; weighting each of a plurality of pixels constituting the OCT image in accordance with the set appropriateness of the focus; An OCT data processing program that synthesizes the weighted OCT images.

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