OCT device and OCT imaging control method

Abstract

To provide an OCT device and an OCT imaging control method for more properly suppressing an affection when stability of a signal acquisition state is reduced.SOLUTION: At a signal set acquisition step, a control part performs processing of scanning measurement light on the same scanning line on a tissue a plurality of times, thereby acquiring a signal set including a plurality of OCT signals. The control part executes, as a quality determination step for determining the quality of a signal set acquisition state, an OCT determination step for determining the quality of an acquisition state of a signal set on the basis of a comparison result of at least two OCT signals which are included in an acquired signal set acquired at the signal set acquisition step. When it is determined that the acquisition state of the signal set is not preferable at the OCT determination step, the control part resets a position of a next scanning line on a position on the same tissue as that of the scanning line at the acquisition of the signal set for which the quality is not preferable.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an OCT device that captures an image of a tissue based on the principle of optical coherence tomography (OCT) by scanning measurement light on the tissue of a subject, and an OCT imaging control method.

Background Art

[0002] While an OCT device guides measurement light split from OCT light to the tissue of a subject (for example, a subject eye), it guides reference light to a reference optical system, and based on an interference signal obtained by combining the measurement light reflected by the tissue and the reference light, it is possible to capture an image (for example, a tomographic image, etc.) of the tissue. The OCT device can be used, for example, when obtaining an image of a living tissue such as an eyeball or skin.

[0003] During imaging by an OCT device, if an event occurs that reduces the stability of the acquisition state of the OCT signal (for example, movement of the tissue during imaging, etc.), an appropriate image may not be obtained. Therefore, techniques for suppressing the influence when the stability of the signal acquisition state decreases have also been proposed. For example, the OCT device described in Patent Document 1 detects misalignment of a plurality of front images of a subject acquired by a front observation optical system. Based on the detection result of the misalignment of the front images, the quality of a plurality of OCT signals acquired for the same scanning region is determined. When it is determined that a plurality of OCT signals are not good, the plurality of OCT signals are reacquired in the same scanning region.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the technology described in Patent Document 1, the stability of the OCT signal acquisition state is detected based on the positional misalignment of multiple frontal images. However, in recent years, it has become possible to increase the OCT signal acquisition rate (i.e., the number of OCT signal acquisitions per unit time, each time the measurement light is scanned through the scanning line) compared to conventional methods. As a result of the increased number of OCT signal acquisitions while a single frontal image is being captured, it has become difficult to accurately detect the stability of the OCT signal acquisition state based on the frontal image. Therefore, a technology is desired that can more appropriately suppress the effects of a decrease in the stability of the signal acquisition state.

[0006] A typical object of this disclosure is to provide an OCT device and an OCT imaging control method that can more appropriately suppress the effects of a decrease in the stability of the signal acquisition state. [Means for solving the problem]

[0007] OCT device provided in a typical embodiment of this disclosure First aspectThe system comprises an OCT light source, a branching optical element that splits light emitted from the OCT light source into measurement light and reference light, an optical scanning unit that scans the measurement light branched by the branching optical element over the tissue of a subject, a photodetector that detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element, and a control unit. The control unit performs a signal set acquisition step of acquiring a signal set containing multiple OCT signals by scanning the measurement light multiple times on the same scanning line on the tissue, or scanning the measurement light on each of multiple adjacent scanning lines, and performs a judgment on the quality of the acquired signal set. The process involves repeatedly performing a pass / fail determination step and a next scan position setting step, which involves setting the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step. The pass / fail determination step involves performing an OCT determination step, which determines whether the acquisition state of the signal set is good or bad based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step. In the next scan position setting step, if the acquisition state of the signal set is determined to be poor in the OCT determination step, the position of the next scanning line is reset to the same position on the tissue as the scanning line at the time of acquisition of the signal set that was determined to be poor. A second aspect of an OCT apparatus provided by a typical embodiment of this disclosure comprises: an OCT light source; a branching optical element that branches light emitted from the OCT light source into measurement light and reference light; an optical scanning unit that scans the measurement light branched by the branching optical element over the tissue of a subject; a photodetector that detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element; a frontal observation optical system that captures a frontal image of the tissue of a subject at a shooting rate lower than the number of times an OCT signal is acquired per unit time; and a control unit, wherein the control unit performs a signal set acquisition step of acquiring a signal set including multiple OCT signals by adjusting the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system and performing a process of scanning the same scanning line on the tissue multiple times, or scanning the measurement light on each of a plurality of adjacent scanning lines; a pass / fail determination step of determining the pass / fail status of the acquired signal set; and the scanning line on which the measurement light will be scanned in the next signal set acquisition step. The next scan position setting step is repeatedly performed to set the position on the tissue, and as the good / bad judgment step, the OCT judgment step is performed to determine the good or bad state of the acquisition of the signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, and the front image judgment step is performed to determine the good or bad state of the acquisition of the signal set based on the comparison result of the latest front image taken by the front observation optical system and a front image taken before the latest front image, and if the good / bad judgment step determines that the acquisition state of the signal set is not good, the judgment result that the acquisition state is not good is continued at least until the acquisition of the next front image by the front observation optical system is completed, and in the next scan position setting step, while the acquisition state of the signal set is determined to be not good in the good / bad judgment step, the position of the next scan line is reset to the same position on the tissue as the scan line at the time of acquisition of any of the signal sets that was determined to be not good, and while the acquisition state of the signal set is determined to be not good,The process of acquiring the signal set in the signal set acquisition step is repeated, and the acquired signal set is excluded from being stored in the memory device. A third aspect of an OCT apparatus provided by a typical embodiment of this disclosure comprises: an OCT light source; a branching optical element that branches light emitted from the OCT light source into measurement light and reference light; an optical scanning unit that scans the measurement light branched by the branching optical element over the tissue of a subject; a photodetector that detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element; and a control unit, wherein the control unit performs a signal set acquisition step of acquiring a signal set including multiple OCT signals by scanning the measurement light multiple times on the same scanning line on the tissue, or scanning the measurement light on each of multiple adjacent scanning lines; a pass / fail determination step of determining whether the acquisition state of the signal set is good or bad; and scanning the measurement light in the next signal set acquisition step. The next scan position setting step is repeatedly performed to set the position of the scan line on the tissue, and as the good / bad determination step, an OCT determination step is performed to determine the good or bad state of the acquisition of the signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, and in the next scan position setting step, if the acquisition state of the signal set is determined to be unsatisfactory in the OCT determination step, the position of the next scan line is reset to the same position on the tissue as the scan line at the time the signal set was acquired which was determined to be unsatisfactory, and in the OCT determination step, the number of pairs of OCT signals to be compared for the good / bad determination from among the multiple OCT signals included in the signal set is changed according to the number of times OCT signals are acquired per unit time when the signal set is acquired. A fourth aspect of an OCT apparatus provided by a typical embodiment of this disclosure comprises: an OCT light source; a branching optical element that branches light emitted from the OCT light source into measurement light and reference light; an optical scanning unit that scans the measurement light branched by the branching optical element over the tissue of a subject; a photodetector that detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element; a frontal observation optical system that captures a frontal image of the tissue of a subject at a shooting rate lower than the number of times an OCT signal is acquired per unit time; and a control unit, wherein the control unit performs a signal set acquisition step of acquiring a signal set including multiple OCT signals by adjusting the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system and scanning the measurement light multiple times on the same scanning line on the tissue, or scanning the measurement light on each of a plurality of adjacent scanning lines; a pass / fail determination step of determining whether the acquisition state of the signal set is good or bad; and scanning the measurement light in the next signal set acquisition step. The next scan position setting step is repeatedly performed to set the position of the scanning line on the tissue, and the good / bad judgment step is performed to perform an OCT judgment step which determines the good or bad state of the acquisition of the signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, and a front image judgment step which determines the good or bad state of the acquisition of the signal set based on the comparison result of the latest front image taken by the front observation optical system and a front image taken before the latest front image, and in the next scan position setting step, while the acquisition state of the signal set is determined to be poor in at least one of the front image judgment step and the OCT judgment step, the position of the next scan line is reset to the same position on the tissue as the scanning line at the time of acquisition of any of the signal sets that was determined to be poorly acquired, and in the front image judgment step, in addition to the latest front image and a first positional displacement amount which is the positional displacement amount of the previous front image taken immediately before the latest front image, the latest front image andIt is possible to acquire a second positional displacement amount, which is the positional displacement amount of a reference frontal image taken before the aforementioned immediately preceding frontal image. If both the first and second positional displacement amounts are acquired, and at least one of the first and second positional displacement amounts exceeds a threshold, it is determined that the acquisition state is not good. Once it is determined that the acquisition state is not good, the reference frontal image is replaced with a newly taken frontal image.

[0008] OCT imaging control method provided by a typical embodiment of this disclosure First aspectThis is an OCT imaging control method performed in an OCT device, the OCT device comprising: an OCT light source; a branching optical element that branches light emitted from the OCT light source into measurement light and reference light; an optical scanning unit that scans the measurement light branched by the branching optical element over the tissue of a subject; and a photodetecting element that detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element, wherein the method involves scanning the measurement light multiple times on the same scanning line on the tissue, or scanning the measurement light on each of a plurality of adjacent scanning lines. The process involves repeatedly performing a signal set acquisition step to acquire a signal set containing multiple OCT signals, a quality determination step to determine whether the acquisition state of the signal set is good or bad, and a next scan position setting step to set the position on the tissue of the scanning line in which the measurement light will be scanned in the next signal set acquisition step. The quality determination step involves performing an OCT determination step to determine whether the acquisition state of the signal set is good or bad based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, and the next scan position setting step involves, When the acquisition of the signal set in the previous signal set acquisition step is completed, regardless of whether the pass / fail determination in the OCT determination step is completed or not, the position of the next scanning line is provisionally set, and in the signal set acquisition step, regardless of whether the pass / fail determination in the OCT determination step is completed or not, scanning of the measurement light to the provisionally set scanning line is started. If, in the OCT determination step, it is determined that the acquisition status of the signal set is not good, In the next scan position setting step, The position of the next scan line is reset to the same location on the tissue as the scan line at the time the signal set was determined to be unsatisfactory was acquired. Furthermore, in the signal set acquisition step, the scanning line on which the measurement light is scanned is changed to the reset scanning line, and if it is determined in the OCT determination step that the signal set acquisition status is good, the signal set acquisition step continues scanning the measurement light on the scanning line with the temporarily set scanning line as the original scanning line. . A second aspect of the OCT imaging control method provided by a typical embodiment of this disclosure is an OCT imaging control method performed in an OCT apparatus, the OCT apparatus comprising: an OCT light source; a branching optical element that branches light emitted from the OCT light source into measurement light and reference light; an optical scanning unit that scans the measurement light branched by the branching optical element over the tissue of a subject; a photodetector that detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element; and a frontal observation optical system that captures a frontal image of the tissue of a subject at an imaging rate lower than the number of times an OCT signal is acquired per unit time, the method comprising: a signal set acquisition step of acquiring a signal set including multiple OCT signals by adjusting the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system and scanning the measurement light multiple times on the same scanning line on the tissue, or scanning the measurement light on each of a plurality of adjacent scanning lines; a pass / fail determination step of determining whether the acquisition state of the signal set is good or bad; and the next signal set The acquisition step repeatedly performs a next scan position setting step in which the scanning line for scanning the measurement light is set on the tissue, and the good / bad judgment step performs an OCT judgment step in which the acquisition status of the signal set is determined to be good or bad based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, and a front image judgment step in which the acquisition status of the signal set is determined to be good or bad based on the comparison result of the latest front image taken by the front observation optical system and a front image taken before the latest front image, and if the good / bad judgment step determines that the acquisition status of the signal set is not good, the determination result that the acquisition status is not good continues at least until the acquisition of the next front image by the front observation optical system is completed, and in the next scan position setting step, while the acquisition status of the signal set is determined to be bad in the good / bad judgment step, the position of the next scan line is reset to the same position on the tissue as the scanning line at the time of acquisition of any of the signal sets that was determined to be in a bad state.While it is determined that the acquisition status of the signal set is not good, the acquisition of the signal set in the signal set acquisition step is repeated, and the acquired signal set is excluded from being stored in the memory device. A third aspect of the OCT imaging control method provided by a typical embodiment of this disclosure is an OCT imaging control method performed in an OCT apparatus, the OCT apparatus comprising: an OCT light source; a branching optical element that branches light emitted from the OCT light source into measurement light and reference light; an optical scanning unit that scans the measurement light branched by the branching optical element over the tissue of a subject; a photodetector that detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element, the method comprising: a signal set acquisition step of acquiring a signal set including multiple OCT signals by scanning the measurement light multiple times on the same scanning line on the tissue, or scanning the measurement light on each of multiple adjacent scanning lines; a pass / fail determination step of determining whether the acquisition state of the signal set is good or bad; and the next signal set acquisition step The next scan position setting step is repeatedly performed, in which the position of the scanning line on the tissue for scanning the measurement light is set, and as the good / bad determination step, an OCT determination step is performed to determine whether the acquisition state of the signal set is good or bad based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, and in the next scan position setting step, if the acquisition state of the signal set is determined to be bad in the OCT determination step, the position of the next scanning line is reset to the same position on the tissue as the scanning line at the time the signal set was acquired which was determined to be bad, and in the OCT determination step, the number of pairs of OCT signals to be compared for the good / bad determination from among the multiple OCT signals included in the signal set is changed according to the number of times OCT signals are acquired per unit time when the signal set is acquired. A fourth aspect of the OCT imaging control method provided by a typical embodiment of this disclosure is an OCT imaging control method performed in an OCT apparatus, the OCT apparatus comprising: an OCT light source; a branching optical element that branches light emitted from the OCT light source into measurement light and reference light; an optical scanning unit that scans the measurement light branched by the branching optical element over the tissue of a subject; a photodetector that detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element; and a frontal observation optical system that captures a frontal image of the tissue of a subject at an imaging rate lower than the number of times an OCT signal is acquired per unit time, the method comprising: a signal set acquisition step of acquiring a signal set including multiple OCT signals by adjusting the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system and scanning the measurement light multiple times on the same scanning line on the tissue, or scanning the measurement light on each of multiple adjacent scanning lines; a pass / fail determination step of determining whether the acquisition state of the signal set is good or bad; and the next signal set acquisition step The next scan position setting step is repeatedly performed, which sets the position on the tissue of the scanning line that scans the measurement light at the top, and the good / bad judgment step is performed, which is an OCT judgment step that determines the good or bad state of the acquisition of the signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, and a front image judgment step that determines the good or bad state of the acquisition of the signal set based on the comparison result of the latest front image taken by the front observation optical system and a front image taken before the latest front image, and in the next scan position setting step, while the acquisition state of the signal set is determined to be poor in at least one of the front image judgment step and the OCT judgment step, the position of the next scan line is reset to the same position on the tissue as the scanning line at the time of acquisition of any of the signal sets that was determined to be poorly acquired, and in the front image judgment step, in addition to the latest front image and the first positional displacement amount which is the positional displacement amount of the previous front image taken immediately before the latest front image, the latest front image andIt is possible to acquire a second positional displacement amount, which is the positional displacement amount of a reference frontal image taken before the aforementioned immediately preceding frontal image. If both the first and second positional displacement amounts are acquired, and at least one of the first and second positional displacement amounts exceeds a threshold, it is determined that the acquisition state is not good. Once it is determined that the acquisition state is not good, the reference frontal image is replaced with a newly taken frontal image.

[0009] According to the OCT device and OCT imaging control method described herein, the effects of a decrease in the stability of the signal acquisition state are more effectively suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing the schematic configuration of OCT device 1. [Figure 2]This figure shows an example of a state in which multiple scanning lines 58 are set on the fundus tissue of the eye E being examined, as captured in a frontal image 40 taken by the frontal observation optical system 23. [Figure 3] This figure shows an example of a two-dimensional tomographic image 41 obtained by processing each OCT signal. [Figure 4] This is a timing chart showing an example of the flow of various processes performed by the OCT device 1 of this embodiment. [Figure 5] This is a flowchart of the OCT imaging process performed by OCT device 1. [Figure 6] This is a flowchart of the frontal image determination process performed during OCT imaging. [Figure 7] This is an explanatory diagram illustrating the processing steps of the front image detection process. [Figure 8] This is an explanatory diagram illustrating the method of OCT signal determination processing according to the acquisition rate of OCT signals. [Modes for carrying out the invention]

[0011] <Overview> The OCT apparatus exemplified in the present disclosure includes an OCT light source, a branching optical element, an irradiation optical system, a light receiving element, and a control unit. The OCT light source emits OCT light. The branching optical element branches the light emitted from the OCT light source into measurement light and reference light. The light receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the tissue and the reference light branched by the branching optical element. The control unit controls the OCT apparatus. The control unit repeatedly executes a signal set acquisition step, a pass / fail determination step, and a next scan position setting step. In the signal set acquisition step, the control unit acquires a signal set including a plurality of OCT signals by performing a process of scanning the measurement light a plurality of times on the same scan line on the tissue or a process of scanning the measurement light on each of a plurality of adjacent scan lines. In the pass / fail determination step, the control unit determines the pass / fail of the acquisition state of the signal set. In the next scan position setting step, the control unit sets the position on the tissue of the scan line for scanning the measurement light in the next signal set acquisition step. As the pass / fail determination step, the control unit executes an OCT determination step of determining the pass / fail of the acquisition state of the signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step. In the next scan position setting step, when it is determined in the OCT determination step that the acquisition state of the signal set is not good, the control unit re-sets the position of the next scan line at the same position on the tissue as the scan line at the time of acquisition of the signal set determined not to be good.

[0012] While measuring light is scanned multiple times on the same scanning line in terms of organization, if there is no event (e.g., movement of the organization, etc.) that inhibits the stability of the signal acquisition state while acquiring a signal set of a plurality of OCT signals, the correlation between the plurality of OCT signals included in the acquired signal set will be high. On the other hand, if the stability of the signal acquisition state decreases while acquiring the signal set, the correlation between the plurality of OCT signals included in the signal set will be low. The same applies when measuring light is scanned on each of a plurality of adjacent (i.e., close) scanning lines to acquire a signal set. Therefore, by comparing the plurality of OCT signals included in the acquired signal set, it is possible to appropriately determine the quality of the signal acquisition state (the quality of the acquired signal set) when the signal set is acquired.

[0013] Here, the time required to acquire an OCT signal for one scanning line is shorter than the time required to capture a two-dimensional front image of the organization once. That is, the acquisition rate of the OCT signal is higher than the imaging rate of the front image. Therefore, based on the comparison result of the plurality of OCT signals included in the acquired signal set, the control unit can finely detect the stability of the signal acquisition state by determining the quality of the signal acquisition state. Thus, according to the technology of the present disclosure, even when the acquisition rate of the OCT signal is increased, it becomes easier to appropriately detect the stability of the signal acquisition state.

[0014] Furthermore, according to the technology of the present disclosure, if it is determined in the OCT determination step that the signal acquisition state is not good, the position of the next scanning line is reset to the same position on the organization as the scanning line at the time of acquiring the signal set for which it is determined that the acquisition state is not good. As a result, it becomes easier to reacquire the signal set for the scanning line for which a good signal set could not be obtained at an early stage. Therefore, the influence when the stability of the signal acquisition state decreases is more appropriately suppressed.

[0015] For example, one might consider improving the overall accuracy of the OCT signal by reacquiring only the signal sets that were determined to have been acquired poorly after the initial acquisition of signal sets for multiple locations. However, in a method where only the signal sets that were acquired poorly are reacquired after the initial acquisition of multiple signal sets, the difference between the conditions for acquiring all signal sets (e.g., tissue position and angle) and the conditions for reacquiring some signal sets becomes large, making it easy for the overall quality of the signal to deteriorate (for example, in the image obtained based on the acquired OCT signal, the reacquired portion of the signal set becomes more noticeable). In contrast, according to the technology of this disclosure, the signal sets for scan lines where good signal sets were not obtained are reacquired at an earlier stage. Therefore, the entire OCT signal is more easily acquired with high accuracy.

[0016] Furthermore, if tissue movement during imaging is detected due to positional misalignment between multiple two-dimensional frontal images, it is conceivable to improve the overall accuracy of the OCT signal by reacquiring the OCT signal acquired during the acquisition of the frontal image. However, as mentioned above, the time required to acquire each frontal image is often longer than the time required to acquire each OCT signal. In particular, in recent years, it has become possible to increase the OCT signal acquisition rate compared to conventional methods. As a result, the frontal image acquisition rate tends to be even lower than conventional methods compared to the OCT signal acquisition rate. In methods for reacquiring OCT signals when positional misalignment occurs between multiple frontal images, the lower the frontal image acquisition rate is compared to the OCT signal acquisition rate, the more positions there tend to require reacquisition of the OCT signal. In contrast, according to the technology disclosed herein, the quality of the signal acquisition state (quality of the signal set) is determined by the OCT signal that can be acquired in a short time, and the signal set for scanning lines where a good signal set was not obtained is reacquired at an early stage. As a result, the number of positions where reacquisition of the signal set is necessary is reduced compared to the method described above. Furthermore, the technology disclosed herein offers the advantage of making it easier to accurately identify poor signal sets from among a series of acquired signal sets.

[0017] In the next scan position setting step, if the control unit determines in the pass / fail judgment that the signal set acquisition status is good, it may set the position of the next scan line to the tissue location where the signal set is scheduled to be acquired after the location where the signal set was previously acquired (i.e., a new location where the measurement light has not yet been scanned). In this case, if the signal acquisition status is good, the acquisition of signal sets at the planned multiple locations will be repeated smoothly.

[0018] The specific method for determining the quality of the signal acquisition state (signal set) based on multiple OCT signals can be selected as appropriate. For example, the control unit may acquire tomographic images by processing each of at least two OCT signals included in the signal set, and then determine the quality of the signal acquisition state (signal set) based on the correlation values ​​of the acquired tomographic images. In this case, the control unit may determine that the signal acquisition state is good if the correlation value is above a threshold, and that the signal acquisition state is not good if the correlation value is below the threshold. Using the correlation values ​​of the tomographic images makes it easier to determine the quality with higher accuracy. Alternatively, the control unit may determine the quality of the signal acquisition state by comparing at least two OCT signals themselves included in the signal set. Known methods may be used to compare OCT signals (for example, between tomographic images generated based on OCT signals), such as using the correlation value (similarity) obtained by the Phase Only Correlation method.

[0019] In the next scan position setting step, once the acquisition of the signal set in the previous signal set acquisition step is complete, the control unit may tentatively set the position of the next scan line, regardless of whether the pass / fail judgment of the signal set in the OCT judgment step is complete. In the signal acquisition step, the control unit may start scanning the measurement light to the tentatively set scan line, regardless of whether the pass / fail judgment in the OCT judgment step is complete. Furthermore, if the position of the scan line is reset to a different position after the control unit has started scanning the measurement light to the tentatively set scan line, the control unit may change the scan line to which the measurement light is scanned to the reset scan line. If the scanning of the measurement light is stopped until the pass / fail judgment of the signal acquisition state based on the OCT signal is completed, it becomes difficult to shorten the acquisition time of the entire set of multiple OCT signals. Also, if the drive of the optical scanning unit is stopped, it takes even more time to restart the drive. In contrast, the control unit can appropriately shorten the acquisition time of multiple OCT signals by tentatively setting the next scan line and starting the scanning of the measurement light, regardless of whether the pass / fail judgment based on the OCT signal is complete.

[0020] Furthermore, if the temporarily set scanning line remains unchanged and is maintained, the control unit may continue scanning the measurement light along the scanning line, treating the temporarily set scanning line as the original scanning line. In this case, the acquisition time for multiple OCT signals is appropriately shortened.

[0021] Furthermore, if the control unit resets the scan line position to a position different from the temporarily set position, it may exclude the signals (such as OCT signals) acquired for the temporarily set scan line from being stored in the memory. In this case, the problem of inappropriate signals being adopted is suppressed.

[0022] In the OCT judgment step, the control unit may change the number of pairs of OCT signals compared to determine the quality of the signal acquisition state from among the multiple OCT signals included in the signal set, according to the number of OCT signal acquisitions per unit time when the signal set is acquired (i.e., the number of OCT signal acquisitions per unit time each time the measurement light is scanned along the scanning line). The more pairs of OCT signals compared from among the multiple OCT signals included in the signal set, the higher the accuracy of the quality determination of the signal acquisition state (signal set). On the other hand, the more pairs of OCT signals compared to determine quality, the longer the time required for quality determination. If the time required for quality determination of the signal acquisition state becomes too long, it may lead to a decrease in the quality of the acquired OCT signal. Therefore, when increasing the number of OCT signal acquisitions per unit time each time the measurement light is scanned along the scanning line (which can also be expressed as the "OCT signal acquisition rate"), the acquisition time of the signal set is shortened, and it is desirable that the time required for quality determination of the signal acquisition state is also shortened. Therefore, by changing the number of OCT signal pairs used to determine the quality of the signal acquisition status according to the OCT signal acquisition rate, it becomes easier to perform a proper quality determination according to the OCT signal acquisition rate.

[0023] Furthermore, the specific method for changing the number of OCT signal pairs used to determine the quality of the signal acquisition status according to the OCT signal acquisition rate can be appropriately selected. For example, the control unit may reduce the number of OCT signal pairs used for quality determination when the OCT signal acquisition rate is above a threshold, compared to when the acquisition rate is below a threshold.

[0024] In the OCT judgment step, the control unit may, regardless of the OCT signal acquisition rate, always include the pair of the first and last acquired OCT signals from among the multiple OCT signals included in the signal set as the pair used for determining the quality of the signal acquisition state. Among the multiple OCT signals included in the signal set, the stability of the signal acquisition state during the acquisition of the signal set (e.g., whether or not there is tissue movement) tends to have an effect on the pair of the first and last acquired OCT signals. Therefore, including the pair of the first and last OCT signals in the pair used for determining quality tends to improve the accuracy of the quality determination.

[0025] However, it is also possible to exclude the first and last OCT signal pairs from the pair used for pass / fail determination among the multiple OCT signals included in the signal set. In this case, the control unit can perform pass / fail determination without waiting for the acquisition of the last OCT signal in the signal set to be completed. Furthermore, even if the number of OCT signal pairs used for pass / fail determination is constant regardless of the OCT signal acquisition rate, the impact of a decrease in the stability of the signal acquisition state is appropriately suppressed.

[0026] The OCT device may further include a frontal observation optical system that captures frontal images of the subject's tissue at a lower imaging rate (i.e., the number of frontal images captured per unit time) than the number of OCT signal acquisitions per unit time (i.e., the OCT signal acquisition rate mentioned above). In the signal set acquisition step, the control unit may adjust the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system, thereby causing the measurement light to scan along a scanning line set on the tissue. In this case, even if the tissue moves, the measurement light is more likely to scan along an appropriate scanning line on the tissue based on the latest frontal image. Therefore, the accuracy of the acquired OCT signal is more likely to improve.

[0027] Furthermore, specific methods for adjusting the scanning position of the measurement light based on the latest front image can be selected as appropriate. For example, the control unit may detect the positional misalignment between the latest front image and a front image (reference image) taken before the latest front image, and adjust the scanning position of the measurement light to scan the next scanning line based on the detected positional misalignment (e.g., the amount and direction of the misalignment).

[0028] The control unit may further perform a front image determination step as a quality determination step, in which it determines the quality of the signal set acquisition status based on a comparison result between the most recent front image taken by the front observation optical system and a front image taken before the most recent front image (for example, a front image taken immediately before the most recent front image). In the next scan position setting step, while the control unit has determined that the signal set acquisition status is not good in at least one of the front image determination step and the OCT determination step, it may reset the position of the next scan line to the same tissue position as the scan line at the time of any signal set acquisition where the acquisition status was determined to be poor. In this case, the position of the next scan line is set after considering the signal acquisition status determination result based on the front image in addition to the signal acquisition status determination result based on the OCT signal. Therefore, the effects of a decrease in the stability of the signal acquisition status are further suppressed.

[0029] However, the control unit can also set the position of the next scan line by referring only to the judgment result of the signal acquisition result in the OCT judgment step, without performing the front image judgment step. Even in this case, the signal set for the scan line from which a good signal set was not obtained is more likely to be reacquired at an earlier stage.

[0030] In the frontal image determination step, the control unit may acquire, in addition to the latest frontal image and a first positional displacement amount which is the positional displacement amount of the previous frontal image taken immediately before the latest frontal image, a second positional displacement amount which is the positional displacement amount of the latest frontal image and a reference frontal image taken before the previous frontal image. If both the first and second positional displacement amounts are acquired, the control unit may determine that the acquisition state is not good if at least one of the first and second positional displacement amounts exceeds a threshold. If the control unit has determined that the acquisition state is not good, it may replace the reference frontal image with a newly taken frontal image. In this case, even if the tissue is moving slowly, by referring to both the first and second positional displacement amounts, it is possible to detect with higher accuracy that the signal acquisition state is deteriorating due to the movement of the tissue.

[0031] If the control unit determines that the signal set acquisition status is not good, it may continue to maintain this determination until at least the acquisition of the next frontal image by the frontal observation optical system is completed. While the control unit is determined to be in a state where the signal set acquisition status is not good, it may repeat the signal set acquisition step and exclude the acquired signal set from being stored in the memory device. If the signal acquisition status is determined to be unsatisfactory, it is highly likely that the tissue has already moved. Therefore, even if the signal set acquisition status recovers before the acquisition of the next frontal image is completed, the acquired signal set may be a signal set at a different location than intended. Therefore, by excluding the acquired signal set from being stored until at least the acquisition of the next frontal image is completed after it is determined that the signal acquisition status is not good, the possibility of OCT signals acquired at an inappropriate location being used is appropriately reduced.

[0032] Furthermore, as mentioned above, once the optical scanning unit is stopped, it takes time to restart the drive, making it difficult to shorten the acquisition time for multiple OCT signals. In contrast, the control unit can suppress the prolonged acquisition time for multiple OCT signals by repeating the signal set acquisition step even while it is determined that the acquisition status of the signal set is not good.

[0033] In the next scan position setting step, the control unit may, after initially resetting the position of the next scan line to the same tissue location as the scan line used when acquiring a signal set where the signal acquisition status was determined to be unsatisfactory, repeatedly set the position of the next scan line to the same location as before, at least until the acquisition of the next frontal image is completed. In this case, when the signal acquisition status recovers, the signal set acquisition process is more likely to resume from the location where the signal acquisition status became unsatisfactory. As a result, the acquisition time for multiple OCT signals is more likely to be further shortened.

[0034] The control unit may repeat the OCT determination step to check the quality of the signal set acquisition status, even while it has determined that the signal set acquisition status is not good. In this case, the stability of the signal acquisition status is detected in detail, regardless of whether the acquired signal set is adopted or not. Therefore, the stability of the signal acquisition status is detected with high accuracy.

[0035] However, if the control unit determines that the signal set acquisition status is not good, it may suspend the OCT judgment step for determining the quality of the signal set acquisition status until at least the acquisition of the front image by the next front observation optical system is completed. In this case, the processing load on the control unit can be easily reduced.

[0036] Furthermore, if the control unit determines that the signal set acquisition status is not good, it may simply repeat scanning of the measurement light to the set scanning line instead of performing the signal set acquisition process in the signal set acquisition step, at least until the acquisition of the front image by the next front observation optical system is completed. In this case, when the signal acquisition status recovers, the normal signal set acquisition process can be easily resumed immediately. As a result, the acquisition time for multiple OCT signals can be further shortened.

[0037] The control unit may, while it determines that the signal set acquisition status is not good, reduce the number of OCT signals acquired as a signal set in the signal set acquisition step compared to when the acquisition status is determined to be good. In this case, the acquisition time for each signal set is shortened while the signal acquisition status is determined to be poor. Therefore, the stability of the signal acquisition status can be detected with greater precision.

[0038] The control unit may also acquire motion contrast data (OCT angio data) in the subject's tissue by processing multiple OCT signals (signal sets) acquired by scanning the same scanning line on the tissue multiple times with the measurement light. Motion contrast data is data generated by processing at least two OCT signals acquired at different times for the same location in the subject's tissue. Since motion contrast data includes perfusion information of the vascular network in the tissue, it is useful for diagnosis, etc. The motion contrast data acquired for each scanning line generates an OCT angio image showing the two-dimensional distribution of perfusion information of the vascular network when the tissue is viewed from the front (in the direction along the optical axis of the OCT measurement light). By using the technology in this disclosure, motion contrast data with the effects of unstable signal acquisition conditions suppressed can be acquired appropriately.

[0039] <Embodiment> The following describes one typical embodiment of the present disclosure. As an example, the OCT device 1 of this embodiment can use the fundus of the eye E as the subject and acquire and process OCT signals from the fundus tissue. Based on the acquired OCT signals, it is possible to generate OCT angiography images, two-dimensional tomography images, and three-dimensional tomography images. However, even when processing OCT signals from tissues other than the fundus of the eye E (e.g., the anterior segment of the eye E), or from subjects other than the eye E (e.g., skin, digestive organs, brain, blood vessels (including cardiovascular vessels), or teeth), at least some of the techniques illustrated in this disclosure can be applied. An OCT signal is a signal acquired based on the principle of optical coherence tomography (OCT).

[0040] Referring to Figure 1, the schematic configuration of the OCT apparatus 1 of this embodiment will be described. The OCT apparatus 1 comprises an OCT unit 10 and a control unit 30. The OCT unit 10 comprises an OCT light source 11, a coupler (optical splitter) 12, a measurement optical system 13, a reference optical system 20, a light-receiving element 22, and a front observation optical system 23.

[0041] The OCT light source 11 emits light (OCT light) for acquiring an OCT signal. The coupler 12 splits the OCT light emitted from the OCT light source 11 into measurement light and reference light. In addition, the coupler 12 in this embodiment combines and interferes the measurement light reflected by the subject's tissue (fundus of the eye E in this embodiment) with the reference light generated by the reference optical system 20. In other words, the coupler 12 in this embodiment serves as both a branching optical element that splits the OCT light into measurement light and reference light, and a multiplexing optical element that combines the reflected measurement light with the reference light. It is also possible to change the configuration of at least one of the branching optical element and the multiplexing optical element. For example, elements other than the coupler (e.g., a circulator, beam splitter, etc.) may be used.

[0042] 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 back to the coupler 12. The measurement optical system 13 comprises an optical scanning unit 14, an illumination optical system 16, and a focus adjustment unit 17. The optical scanning unit 14 is driven by a drive unit 15, which allows the measurement light to be scanned (blinded) 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 optical scanning unit 14. However, another device that deflects light (e.g., at least one of a polygon mirror, resonant scanner, or acousto-optic element) may be used as the optical scanning unit 14. The illumination optical system 16 is located downstream of the optical path (i.e., on the subject side) from the optical scanning unit 14 and irradiates the subject's tissue with the measurement light. The focus adjustment unit 17 adjusts the focus of the measurement light by moving the optical elements (e.g., lenses) of the illumination optical system 16 in a direction along the optical axis of the measurement light.

[0043] The reference optical system 20 generates reference light and returns it to the coupler 12. In this embodiment, the reference optical system 20 generates 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 reflection 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. The configuration for changing the optical path length difference may be provided in the optical path of the measurement optical system 13.

[0044] The photodetector 22 detects the interference signal for acquiring the OCT signal by receiving the interference light, which is the composite light of the measurement light and the reference light generated by the coupler 12. In this embodiment, the principle of Fourier domain OCT is employed. In Fourier domain OCT, the spectral intensity of the interference light (spectral interference signal) is detected by the photodetector 22, and a complex OCT signal is acquired by performing a Fourier transform on the spectral intensity data. The OCT signal is acquired by processing the complex OCT signal (for example, processing to calculate the absolute value of the amplitude in the complex OCT signal). Examples of Fourier domain OCT include Spectral-domain-OCT (SD-OCT) and Swept-source-OCT (SS-OCT). It is also possible to employ, for example, Time-domain-OCT (TD-OCT).

[0045] In this embodiment, SD-OCT is employed. In the case of SD-OCT, for example, a low-coherent light source (broadband light source) is used as the OCT light source 11, and a spectroscopic optical system (spectrometer) that spectrally separates the interference light into each frequency component (each wavelength component) is provided near the photodetector 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 output wavelength rapidly 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 filters that combine a diffraction grating and a polygon mirror, and filters that use a Fabry-Perot etalon.

[0046] The frontal observation optical system 23 is provided to capture a frontal image (for example, the frontal image 40 shown in Figure 2) of the subject's tissue (in this embodiment, the fundus of the eye E under examination) in real time. In this embodiment, the frontal image is a two-dimensional image of the tissue viewed from a direction along the optical axis of the OCT measurement light (frontal direction). In this embodiment, a scanning laser ophthalmoscope (SLO) is used as the frontal observation optical system 23. The SLO scans the subject's tissue with laser light and captures a frontal image of the tissue by receiving the reflected laser light from the tissue. For example, the SLO may be a so-called line scan type device. In this case, a line-shaped beam of light is scanned on the observation surface. The frontal observation optical system 23 in this embodiment repeatedly captures frontal images of the tissue at a shooting rate lower than the OCT signal acquisition rate. The OCT signal acquisition rate is the number of OCT signals acquired per unit time, each time the OCT measurement light is scanned along the scanning line. The shooting rate of the frontal observation optical system 23 is the number of times a two-dimensional frontal image is captured per unit time. In recent years, it has become possible to increase the acquisition rate of OCT signals compared to conventional methods. In this embodiment, if the acquisition rate of OCT signals is increased as much as possible, the acquisition rate of OCT signals becomes approximately eight times the imaging rate of the front observation optical system 23. Note that the configuration of the front observation optical system 23 may also employ a configuration other than SLO (for example, an infrared camera that captures a front image by illuminating a two-dimensional imaging range with infrared light all at once).

[0047] The control unit 30 is responsible for various controls of the OCT device 1. The control unit 30 includes a CPU 31, RAM 32, ROM 33, and 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, as well as various initial values. The NVM 34 is a non-transient storage medium that can retain its contents even if the power supply is cut off. The OCT imaging control program for executing the OCT imaging process (see Figure 3), which will be described later, may also be stored in the NVM 34.

[0048] The control unit 30 is connected to a microphone 36, a monitor 37, and an operation unit 38. 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 the user to input various operation instructions to the OCT device 1. Various devices such as a mouse, keyboard, touch panel, and foot switch can be used for the operation unit 38. Alternatively, 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 speech recognition processing on the input sound.

[0049] In this embodiment, an integrated OCT device 1 is illustrated, in which the OCT unit 10 and the control unit 30 are housed in a single housing. However, it goes without saying that the OCT device 1 may comprise multiple devices with different housings. For example, the OCT device 1 may comprise an optical device housing the OCT unit 10 and a PC connected to the optical device by wire or wireless. 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.

[0050] (An example of how to acquire OCT signals) Referring to Figures 2 and 3, an example of the method for acquiring (imaging) the OCT signal in this embodiment will be described. Figure 2 shows an example in which multiple scanning lines 58 are set on the fundus tissue of the eye E being examined, as captured in a frontal image 40 taken by the frontal observation optical system 23. In this embodiment, the spot of the measurement light is scanned within a two-dimensional target area 55 on the tissue by the optical scanning unit 14, thereby acquiring the OCT signal in the target area 55. More specifically, in this embodiment, motion contrast data (OCT angio data) in the target area 55 is acquired (imaging). Motion contrast data is generated by processing at least two OCT signals acquired at different times for the same position on the subject. Since the motion contrast data includes perfusion information of the vascular network in the tissue, it is useful for diagnosis, etc.

[0051] As shown in Figure 2, the OCT device 1 of this embodiment sets up multiple scan lines 58 at equal intervals within a two-dimensional target area 55 that extends in a direction intersecting the optical axis of the measurement light, for scanning the spot of the measurement light. In the example shown in Figure 2, the scan lines 58 are arranged at equal intervals in the order of the first scan line 581, the second scan line 582, the third scan line 583, and the fourth scan line 584, with the last scan line being the Kth scan line 58K. The OCT device 1 scans the spot of the measurement light multiple times (for example, four times each in this embodiment) on each scan line 58 on the tissue, thereby acquiring multiple (four in this embodiment) sets of OCT signals for each scan line 58. Motion contrast data for each scan line 58 is acquired by processing the multiple OCT signals included in the signal set for each scan line 58.

[0052] As shown in Figure 3, the OCT device 1 can acquire a two-dimensional tomographic image 41 extending in the depth direction of the tissue from the scanning line 58 by processing each OCT signal acquired when measurement light is passed through the scanning line 58 once. As will be described in detail later, when the OCT device 1 performs a judgment on the quality of the OCT signal acquisition state (hereinafter sometimes simply referred to as "signal acquisition state") based on multiple OCT signals, it uses the correlation value between the two-dimensional tomographic images 41 acquired by processing each OCT signal. The signal acquisition state deteriorates in particular when tissue movement occurs while the OCT signal is being acquired.

[0053] The processes performed by the OCT device 1 of this embodiment will be described in detail below. As mentioned above, the processes illustrated in this embodiment are those used when acquiring motion contrast data of the fundus of the eye E to be examined using the method illustrated in Figure 2. However, at least a part of the processes described below can also be applied when acquiring data other than motion contrast data (for example, data from three-dimensional tomography images, or data from an averaged image obtained by adding and averaging multiple two-dimensional tomography images).

[0054] (Summary of the process) First, with reference to Figure 4, the flow of various processes performed by the OCT device 1 of this embodiment will be briefly explained. Figure 4 is a timing chart showing an example of the flow of various processes performed by the OCT device 1 of this embodiment. In the example shown in Figure 4, "Front Image Acquisition" indicates the timing when front images 40 of the tissue are continuously acquired by the front observation optical system 23. "Front Image Judgment Result" indicates the timing when a judgment is made on whether the signal acquisition state is good or bad based on the acquired front images 40. "Signal Set Acquisition" indicates the timing when multiple OCT signal sets are continuously acquired for each scanning line 58. "OCT Signal Judgment Result" indicates the timing when a judgment is made on whether the signal acquisition state is good or bad based on the OCT signals included in the acquired signal sets. "Signal Acquisition State" indicates the timing when the good or bad state of the signal acquisition state switches, as determined by the state deterioration flag described later. In "Front Image Judgment Result" and "OCT Signal Judgment Result," "○" indicates that the judgment result of the signal acquisition state was good, and "×" indicates that it was not good. In "Signal Set Acquisition," a "○" indicates that the actual signal acquisition status when the signal set was acquired was good, and a "×" indicates that it was not good. Furthermore, the period during which the signal acquisition status, as determined by the status deterioration flag, was good is indicated by a "○," and the period during which it was not good is indicated by a "×."

[0055] The OCT device 1 of this embodiment repeatedly performs the following processes: signal set acquisition processing, signal acquisition state quality determination processing, and next scan position setting processing (omitted in Figure 4). In the signal set acquisition processing, multiple OCT signal sets are acquired by scanning the same scan line 58 set at that time multiple times (in this embodiment, generally four times) with the OCT measurement light. In the signal acquisition state quality determination processing, basically, each time the acquisition of a signal set is completed, the quality of the signal acquisition state is determined based on the OCT signals included in the acquired signal set. The stability of the signal acquisition state is detected in detail by the quality determination of the signal acquisition state based on the OCT signals. Furthermore, in the signal acquisition state quality determination processing of this embodiment, quality determination is also performed based on the comparison result between the latest front image 40 and front images 40 taken before the latest front image 40. In the next scan position setting processing, the position on the tissue of the scan line 58 to which the OCT measurement light will be scanned next is set.

[0056] The OCT device 1 adjusts the scanning position of the OCT measurement light based on the most recently captured frontal image 40, thereby scanning the OCT measurement light along the set scanning line 58 on the tissue. As a result, even if the tissue moves, the OCT measurement light is more likely to scan along the appropriate scanning line 58 on the tissue based on the most recently captured frontal image 40.

[0057] When the OCT device 1 determines that the signal acquisition status based on the OCT signal is poor, it sets the status deterioration flag, which indicates the quality of the signal acquisition status, to "ON," indicating that the status is not good. In the example shown in Figure 4, the status deterioration flag is set to "ON" because the acquisition status of the fifth acquired signal set was determined to be poor. In addition, the OCT device 1 of this embodiment also sets the status deterioration flag to "ON" if the signal acquisition status based on the front image is poor. In the example shown in Figure 4, the signal acquisition status based on the third and fourth front images is poor, but the status deterioration flag remains "ON" and is not changed.

[0058] When the OCT device 1 determines that the signal acquisition status is good, it stores the acquired signal sets in a memory device (e.g., NVM34). In the example shown in Figure 4, when acquiring the 1st to 4th signal sets and when acquiring the 12th to 14th signal sets, both the signal acquisition status determination based on the OCT signal and the signal acquisition status as determined by the status deterioration flag are good. Therefore, the signal sets acquired from the 1st to 4th and the 12th to 14th are stored in the memory device. Furthermore, when the OCT device 1 determines that the signal acquisition status is good, it sets the position of the next scan line to the tissue location where it plans to acquire a signal set after the position where the signal set was previously acquired (scan line 58). As a result, signal sets for each of the multiple scan lines are acquired and stored sequentially.

[0059] On the other hand, if the OCT device 1 determines that the signal acquisition status based on the OCT signal is unsatisfactory, it resets the position of the next scan line 58 to the same tissue location as the scan line 58 at the time the signal set was acquired under the unsatisfactory conditions. (In Figure 7, after the acquisition of the fifth signal set, the position of the next scan line 58 is reset to the same location as the previous time.) As a result, signal sets for scan lines 58 from which good signal sets were not obtained are more likely to be reacquired at an earlier stage. Furthermore, if the OCT device 1 determines that the signal acquisition status based on the OCT signal is unsatisfactory, it excludes the signal set that was determined to be unsatisfactory from being stored in the memory device. As a result, the possibility of poor quality signal sets being adopted is reduced. In the example shown in Figure 7, the OCT device 1 determines that the signal acquisition status based on the OCT signal is unsatisfactory when the fifth signal set is acquired. Therefore, the fifth signal set is excluded from being stored in the memory device.

[0060] Furthermore, while the OCT device 1 determines that the signal acquisition state is not good (i.e., while the state deterioration flag is set to "ON"), it repeatedly acquires signal sets and excludes the acquired signal sets from being stored in the memory device. As a result, the possibility of poor quality signal sets being selected is reduced. In the example shown in Figure 7, when the 6th to 11th signal sets were acquired, the signal acquisition state was determined to be not good (i.e., the state deterioration flag was set to "ON"). Therefore, the 6th to 11th signal sets were excluded from being stored in the memory device. Note that even while the signal acquisition state is determined to be not good, the repeated acquisition of signal sets shortens the time required to restart the optical scanning unit 14. As a result, the acquisition time for multiple OCT signals is more easily shortened. In addition, once the OCT device 1 resets the position of the next scanning line 28 to the same position as the previous time, it repeatedly sets the position of the next scanning line 58 to the same position as the previous time until the signal set for the reset scanning line 58 is acquired under good signal acquisition conditions. As a result, after the signal acquisition state is restored, the signal set acquisition process is more likely to resume from the appropriate position. In the example shown in Figure 7, the setting position of the next scan line 58, which was reset after the acquisition of the 5th signal set, remains the same until the acquisition of the 12th signal set is completed.

[0061] Furthermore, in this embodiment, if the OCT device 1 determines that the signal acquisition state is not good, it keeps the status deterioration flag "ON" until at least the next front image 40 has been captured, thereby maintaining the determination that the signal acquisition state is not good. When the signal acquisition state is determined to be not good, there is a high probability that the tissue has already moved. Therefore, even if the signal set acquisition state recovers before the next front image 40 is captured, it becomes difficult to adjust the scanning position of the measurement light based on the latest front image 40. In other words, the signal set acquired after the initial determination that the signal acquisition state is not good, at least until the next front image 40 is captured, may be a signal set at a different position than intended. Therefore, by maintaining the determination that the signal acquisition state is not good until at least the next front image 40 is captured, the possibility of using a signal set of poor quality is reduced.

[0062] In detail, the OCT device 1 of this embodiment, once it determines that the signal acquisition state is not good, continues to maintain the determination that the signal acquisition state is not good until the result of the signal acquisition state quality judgment based on the front image becomes good (i.e., it maintains the state deterioration flag "ON"). As a result, it becomes easier for signal sets of poor quality to be appropriately reacquired. In the example shown in Figure 7, the signal acquisition state is determined to be poor when acquiring the 5th signal set, but for the 8th and subsequent signal sets, the result of the signal acquisition state quality judgment based on the OCT signal has recovered. However, the OCT device 1 continues to maintain the determination that the signal acquisition state is not good even when acquiring the 8th to 11th signal sets, thereby reducing the possibility that signal sets of poor quality may be adopted.

[0063] As shown in Figure 7, the OCT device 1 of this embodiment repeatedly performs a judgment on the quality of the signal acquisition state based on the OCT signal, even while it is determined that the signal set acquisition state is not good (i.e., while the acquired signal set is excluded from being stored in the memory device). Therefore, the stability of the signal acquisition state is detected in detail, regardless of whether the acquired signal set is adopted or not.

[0064] (OCT imaging processing) Referring to Figures 5 to 8, the OCT imaging process performed by the OCT device 1 of this embodiment will be described. The CPU 31 of the OCT device 1 executes the OCT imaging process shown in Figure 5 according to the OCT imaging control program stored in the NVM 34.

[0065] As shown in Figure 5, in the OCT imaging process of this embodiment, processing related to the front image 40 (S1 to S4) and processing related to the OCT signal (S21 to S38) are executed in parallel. First, the processing related to the front image 40 (S1 to S4) will be described. When the OCT imaging process starts, the CPU 31 performs continuous imaging of the front image 40 using the front observation optical system 23.

[0066] The CPU 31 determines whether or not the capture of one front image 40 has been completed (S1). The determination in S1 is repeated until the capture of the front image 40 is completed (S1: NO), and the system remains in a waiting state. Once the capture of the front image 40 is complete (S1: YES), the CPU 31 executes the front image determination process (S2). In the front image determination process, the CPU 31 determines whether the signal acquisition status is good or bad based on the comparison result between the latest front image 40 captured in S1 and the front images 40 captured before the latest front image 40.

[0067] As shown in Figure 6, in the front image determination process, the CPU 31 obtains a first positional displacement amount, which is the positional displacement amount between the latest front image 40, which was captured in S1 (see Figure 5), and the previous front image 40, which was captured immediately before the latest front image 40 (S11). Next, the CPU 31 determines whether the latest front image 40 is the reference front image 40 (S12). The reference front image 40 is one or more front images 40 that were captured before the aforementioned previous front image 40, and which are the images from which the positional displacement amount between the latest front image 40 and the reference front image 40 is to be obtained. If the latest front image 40 is the reference front image 40 (S12: YES), the process proceeds directly to S15. On the other hand, if an image different from the latest front image 40 is designated as the reference front image 40 (S12: NO), the CPU 31 obtains a second positional displacement amount, which is the positional displacement amount between the latest front image 40 and the reference front image 40 (S13), and the process proceeds to S15. In addition, known image processing methods may be used to obtain the amount of positional displacement between the front images in S11 and S13.

[0068] The CPU 31 determines whether the signal acquisition status is good or bad based on the positional displacement amounts acquired in S11 to S13 (S15). Specifically, if only the first positional displacement amount is acquired, the CPU 31 determines that the signal acquisition status is good if the acquired first positional displacement amount is less than the threshold. If both the first and second positional displacement amounts are acquired, the CPU 31 determines that the signal acquisition status is good if both the first and second positional displacement amounts are less than the threshold. On the other hand, if at least one of the first and second positional displacement amounts exceeds the threshold, the CPU 31 determines that the signal acquisition status is not good.

[0069] If CPU31 determines that the signal acquisition status is not good (faulty) (S15:NO), it sets the status deterioration flag, which indicates whether the OCT signal acquisition status is good or not at that time, to "ON" (S17), indicating that the signal acquisition status is not good. Note that in S17, if the status deterioration flag is already set to "ON", the "ON" state is maintained.

[0070] Furthermore, if the CPU 31 determines that the signal acquisition state is good (S15:YES), it determines whether the state deterioration flag is set to "OFF," which indicates that the signal acquisition state is good (S17). If the state deterioration flag is "OFF" (S17:YES), the process returns to the OCT imaging process (see Figure 5). If the state deterioration flag is "ON" (S17:NO), the signal acquisition state has returned from a poor state to a good state. Therefore, the CPU 31 changes the state deterioration flag from "ON" to "OFF" (see timing T2 in Figure 4). As a result, the process of acquiring the signal set and storing it in the memory device is resumed. In addition, the CPU 31 replaces the reference front image 40 with either the latest front image or the previous front image (for example, the previous front image in this embodiment) from which the first positional displacement amount was acquired in S11 (S19).

[0071] Referring to Figure 7, the front image determination process in this embodiment will be explained based on a specific example. In Figure 7, six front images S1 to S6 are arranged in order of the time they were captured. Furthermore, for each of the front images from S2 onward, the front image that will be compared when determining the quality of the signal acquisition state is indicated by an arrow. The arrow indicating the target for acquiring the first positional displacement amount is labeled "1", and the arrow indicating the target for acquiring the second positional displacement amount is labeled "2". In the example shown in Figure 7, a positional displacement between the front images occurs due to tissue movement between the completion of capturing the third front image S3 and the completion of capturing the fourth front image S4.

[0072] In the example shown in Figure 7, the first frontal image S1 is designated as the reference frontal image. When the second frontal image S2 is taken, only the first positional displacement between S2 and the immediately preceding frontal image S1 is acquired. Since no tissue movement occurs during the acquisition of S1 and S2, no positional displacement is detected when the acquisition of S2 is complete, and the reference frontal image remains S1.

[0073] When the third frontal image S3 is captured, the first positional displacement between S3 and the immediately preceding frontal image S2 is obtained. Furthermore, the second positional displacement between S3 and the reference frontal image S1 is obtained. Since no tissue movement occurs during the capture of S2 and S3, no positional displacement is detected when the capture of S3 is completed, and the reference frontal image remains S1.

[0074] When the fourth frontal image S4 is captured, the first positional displacement between S4 and the previous frontal image S3 is acquired. Furthermore, the second positional displacement between S4 and the reference frontal image S1 is acquired. Since tissue movement occurs during the capture of S3 and S4, a positional displacement between the frontal images is detected when the capture of S4 is completed, and the signal acquisition status is determined to be poor. After the signal acquisition status is determined to be poor when the capture of S4 is completed, the reference frontal image is replaced from S1 to the newly captured frontal image. In detail, when the fifth frontal image S5 is captured, the first positional displacement between S5 and the previous frontal image S4 is acquired. Since no tissue movement occurs during the capture of S4 and S5, the signal acquisition status returns from a poor state to a good state (i.e., the status deterioration flag is changed from "ON" to "OFF"). At this point, the reference frontal image is replaced from S1 to the previous frontal image S4. The same process is repeated thereafter.

[0075] As described above, according to the front image determination process of this embodiment, for example, if the tissue is moving slowly during imaging in S1 to S4, even if the positional displacement between S3 and S4 is less than the threshold, if the positional displacement between S1 and S4 is greater than or equal to the threshold, the poor signal acquisition state due to tissue movement is appropriately detected. Therefore, the deterioration of the signal acquisition state due to tissue movement is detected with higher accuracy.

[0076] Returning to the explanation of Figure 5, once the frontal image determination process (S2) is completed, the CPU 31 adjusts the scanning position of the OCT measurement light controlled in S21 to S38 based on the latest frontal image 40 acquired in S1, causing the measurement light to scan the scanning line 58 set on the tissue (S3). Therefore, even if the tissue moves, the measurement light is more likely to scan the appropriate scanning line on the tissue based on the latest frontal image 40. In S3 of this embodiment, the CPU 31 detects the positional displacement between the latest frontal image 40 and a frontal image 40 (reference image) acquired before the latest frontal image, and adjusts the scanning position of the measurement light to scan the next scanning line 58 based on the detected positional displacement (e.g., the amount and direction of the positional displacement).

[0077] The CPU 31 determines whether the acquisition of signal sets for all planned scan lines 58 has been completed in the parallel processing of S21 to S38 (S4). If it has not yet been completed (S4: NO), the process returns to S1. Once the acquisition of signal sets for all scan lines 58 is complete (S4: YES), the OCT imaging process ends.

[0078] Next, the processing related to the OCT signal (S21-S38) will be explained. When the CPU 31 starts the OCT imaging process, it sets the scanning line 58 on the tissue where the signal set is to be acquired first from among the multiple scanning lines 58 on the tissue where the signal set is to be acquired as the scanning line 58 on which the OCT measurement light will be scanned next, and starts scanning the measurement light.

[0079] The CPU 31 determines whether the acquisition of a signal set of multiple OCT signals for the configured scan line 58 has been completed (S21). If it has not been completed (S21: NO), the determination in S21 is repeated and the system enters a waiting state. If the acquisition of the signal set is completed (S21: YES), the CPU 31 starts the OCT signal determination process (S22). The CPU 31 may also start the OCT signal determination process when the acquisition of at least two of the multiple (in this embodiment, generally four) OCT signals included in the signal set has been completed. In this case, the determination of the quality of the signal acquisition status based on the OCT signals can be performed in a shorter time.

[0080] In the OCT signal determination process, the CPU 31 determines the quality of the signal acquisition state based on the comparison result of at least two OCT signals included in the acquired signal set. If no events that disrupt the stability of the signal acquisition state (e.g., tissue movement) occur while scanning the same scanning line 58 on the tissue multiple times to acquire multiple OCT signal sets, the correlation between the multiple OCT signals included in the acquired signal set will be high. On the other hand, if the stability of the signal acquisition state decreases while acquiring the signal set, the correlation between the multiple OCT signals included in the signal set will be low. Therefore, by comparing the multiple OCT signals included in the acquired signal set, the quality of the signal acquisition state at the time the signal set was acquired (the quality of the acquired signal set) is appropriately determined. Also, as mentioned above, the OCT signal acquisition rate (i.e., the number of OCT signals acquired per unit time each time the OCT measurement light is scanned on the scanning line 58) is higher than the frontal image 40 acquisition rate by the frontal observation optical system 23 (i.e., the number of frontal images 40 taken per unit time). Therefore, the OCT signal determination process makes it possible to precisely detect the stability of the signal acquisition state.

[0081] In detail, in the OCT signal determination process of this embodiment, the CPU 31 changes the number of pairs of OCT signals to compare in order to determine the quality of the signal acquisition state from among the multiple OCT signals included in the signal set, according to the OCT signal acquisition rate (i.e., the number of acquisitions per unit time of the OCT signal acquired each time the OCT measurement light is scanned once on the scanning line 58) when the signal set is acquired. The more pairs of OCT signals compared from among the multiple OCT signals included in the signal set, the higher the accuracy of the determination of the quality of the signal acquisition state (signal set). On the other hand, the more pairs of OCT signals to compare in order to determine quality, the longer the time required for the determination. If the time required for determining the quality of the signal acquisition state becomes too long, it may lead to a decrease in the quality of the acquired OCT signal. Therefore, when increasing the OCT signal acquisition rate, it is desirable that the time required for the OCT signal determination process is also shortened, as the acquisition time of the signal set is shortened. Therefore, the CPU 31 appropriately determines the quality of the OCT signals according to the acquisition rate of the OCT signals by changing the number of pairs of OCT signals used to determine the quality of the signal acquisition state.

[0082] Referring to Figure 8, an example of an OCT signal judgment processing method according to the OCT signal acquisition rate will be described. In Figure 8, the four OCT signals O1 to O4 included in the signal set are arranged in order of acquisition time. Also, pairs of OCT signals that are compared in the OCT signal judgment processing are connected by arrows. In this embodiment, the CPU 31 reduces the number of OCT signal pairs used to determine the quality of the signal acquisition state as the OCT signal acquisition rate increases. In the example shown in Figure 8, at the lowest OCT signal acquisition rate, three pairs—the first and second OCT signals, the first and third OCT signals, and the first and fourth OCT signals—are used to determine the quality of the signal acquisition state. In this case, the accuracy of the quality determination tends to improve. Furthermore, at a medium OCT signal acquisition rate, two pairs—the first and second OCT signals, and the first and fourth OCT signals—are used to determine the quality of the signal acquisition state. If the OCT signal acquisition rate is at its highest level, only the first and fourth OCT signal pairs are used to determine the quality of the signal acquisition. In this case, the time required for OCT signal judgment processing is reduced. As shown in Figure 8, the CPU 31 always includes the pair of the first (1st) acquired OCT signal and the last (4th) acquired OCT signal from among the multiple OCT signals included in the signal set as the pair used to determine the quality of the signal acquisition. The stability of the signal acquisition state during the acquisition of the signal set (e.g., whether or not there is tissue movement) tends to have an effect on the pair of the first and last acquired OCT signals. Therefore, including the first and last OCT signal pairs in the pair used for quality determination tends to improve the accuracy of the quality determination.

[0083] In the OCT signal determination process of this embodiment, the CPU 31 acquires a tomographic image 41 (see Figure 3) by processing each of at least two OCT signals included in the signal set, and determines the quality of the signal acquisition state (signal set) based on the correlation value of the acquired tomographic images 41. The CPU 31 determines that the signal acquisition state is good if the correlation value is above a threshold, and that the signal acquisition state is not good if the correlation value is below the threshold. By using the correlation value of the tomographic images 41, the quality determination can be made with greater accuracy. Alternatively, the CPU 31 may also determine the quality of the signal acquisition state by comparing at least two OCT signals themselves included in the signal set. For comparing OCT signals (for example, between tomographic images 41 generated based on OCT signals), the correlation value (similarity) obtained by the Phase Only Correlation method can be used.

[0084] Returning to the explanation of Figure 5, the OCT signal determination process takes a certain amount of time. Regardless of whether the OCT signal determination process based on the signal set acquired in S21 is completed, the CPU 31 determines whether the signal acquisition state at that time is good or not based on the state deterioration flag (S23).

[0085] If the status deterioration flag is set to "OFF" and it is determined that the OCT signal acquisition status at that time is good (S23:YES), the CPU 31, regardless of whether the OCT signal judgment process is completed or not, provisionally sets the position of the next scanning line 58 to acquire the signal set to the tissue position where the signal set is scheduled to be acquired after the position where the signal set was previously acquired (S25). Furthermore, regardless of whether the OCT signal judgment process is completed or not, the CPU 31 starts scanning the OCT measurement light to the provisionally set scanning line 58 (S26). As a result, if the signal acquisition status remains good, the signal set at the next scheduled position will be acquired smoothly. Also, if the scanning of the OCT measurement light is stopped until the judgment of the quality of the signal acquisition status based on the OCT signal (OCT signal judgment process) is completed, it becomes difficult to shorten the acquisition time for the entire set of OCT signals. In addition, if the drive of the optical scanning unit 14 is stopped, it takes even more time to restart the drive. In contrast, in this embodiment, regardless of whether the pass / fail judgment based on the OCT signal is completed or not, the next scanning line 58 is provisionally set and scanning of the OCT measurement light is started. Therefore, the acquisition time of multiple OCT signals is appropriately shortened. If the acquisition status of the OCT signals at that time is good, the CPU 31 sets the number of OCT signals to be acquired as a signal set for the next scanning line 58 set in S25 to the normal number N1 (4 in this embodiment).

[0086] Next, the CPU 31 determines whether the result of the signal acquisition status determination (OCT signal determination process) based on the OCT signal was good or bad (S28). If the result of the OCT signal determination process is good (S28: YES), the CPU 31 stores the signal set acquired in S21 in the memory device (S29). Furthermore, the CPU 31 maintains the next scan line 58 that was provisionally set in S25 as the actual scan line 58 and continues scanning the OCT measurement light to the set scan line 58 as is (S30). As a result, the acquisition time of multiple OCT signals (signal sets) is appropriately shortened. The CPU 31 determines whether the acquisition of signal sets for all planned scan lines 58 has been completed (S31). If the acquisition of signal sets for all scan lines 58 is completed (S31: YES), the OCT imaging process ends. On the other hand, if the acquisition of signal sets for all scan lines 58 has not yet been completed (S31: NO), the process returns to S21.

[0087] Furthermore, if the result of the OCT signal judgment process is not good (S28:NO), the CPU 31 changes the status deterioration flag, which indicates whether the OCT signal acquisition state at that time is good or not, to "ON" to indicate that it is not good (S33). (See timing T1 in Figure 4). After that, the process moves to S35. As mentioned above, once the CPU 31 determines that the signal acquisition state is not good (S28:NO, S33), it maintains the status deterioration flag as "ON" at least until the next front image 40 is captured (in this embodiment, until the judgment result of the signal acquisition state based on the front image 40 becomes good), thereby continuing the determination that the signal acquisition state is not good. As a result, the possibility of adopting a low-accuracy signal set is reduced. Next, the CPU 31 resets the position of the next scan line 58 to the same tissue location (i.e., the same location as last time) as the scan line 58 at which the signal set acquired in S21 (i.e., the signal set determined to have an unsatisfactory signal acquisition state) was acquired (S35). As a result, the signal set for the scan line 58 from which a good signal set was not obtained is more likely to be reacquired at an earlier stage. Note that in S35, the position of the scan line 58 is reset to a different location than the position temporarily set in S26. In this case, the CPU 31 excludes (discards) the signal set acquired in S21 from being stored in the memory device (S36). The CPU 31 starts scanning the scan line 58 that was reset in S35 with OCT measurement light (S37). Furthermore, the CPU 31 sets the number of OCT signals to be acquired for the next scan line 58, which was reset in S35, to N2 (2 in this embodiment), which is less than N1 (4 in this embodiment) when the signal acquisition state is determined to be good (S38), and the process returns to S21. As a result, the signal set acquisition time is shortened while the determination result that the signal acquisition state is not good persists (i.e., while the state deterioration flag is set to "ON"). Therefore, the stability of the signal acquisition state is detected in more detail.

[0088] Also, in the determination of S23, if it is determined that the state deterioration flag is "ON" and the acquisition state of the OCT signal at that time is poor (S23: NO), the CPU 31 repeatedly resets the position of the next scanning line 58 on the tissue to the same position as the previous time (S35). Therefore, when the signal acquisition state recovers, the acquisition process of the signal set is likely to resume from the position where the signal acquisition state has become poor. As a result, the acquisition time of a plurality of OCT signals is more likely to be further shortened. Next, the CPU 31 excludes (discards) the signal set acquired in S21 from the target to be stored in the storage device while the signal acquisition state is determined to be poor (S36). The CPU 31 starts scanning the OCT measurement light on the scanning line 58 reset in S35 (S37). That is, the acquisition of the signal set is repeated even while the signal acquisition state is poor. As a result, compared with the case where the operation of the optical scanning unit 14 is temporarily stopped, the acquisition time of a plurality of OCT signals is suppressed from being prolonged. The CPU 31 sets the number of OCT signals to be acquired for the next scanning line 58 reset in S35 to N2 (<N1) (S38), and the process returns to S21. Note that the CPU 31 repeatedly determines whether the signal acquisition state is good or bad based on the OCT signal even while the acquisition state of the signal set is poor (that is, while the signal set is discarded). As a result, regardless of whether the signal set acquired in S21 is adopted, the stability of the signal acquisition state is detected in detail. Therefore, the stability of the signal acquisition state is detected with high accuracy.

[0089] The technologies disclosed in the above embodiments are merely examples. Therefore, it is possible to modify the technologies exemplified in the above embodiments. It is also possible to implement only some of the technologies exemplified in the above embodiments. For example, in the above embodiments, in addition to the determination of the quality of the signal acquisition state based on the OCT signal (S22), a determination of the quality of the signal acquisition state based on the front image (S2, see Figure 6) is also performed. However, the determination of the quality of the signal acquisition state based on the front image may be omitted. In this case, if the CPU 31 determines that the signal acquisition state is not good based on the determination of the quality of the signal acquisition state based on the OCT signal, it may continue to maintain the determination that the signal acquisition state is not good until the acquisition of the next front image 40 is completed (S1:YES). In other words, the CPU 31 may change the state deterioration flag from "ON" to "OFF" when the acquisition of the next front image 40 is completed (S1:YES). In this case, if the signal acquisition state has recovered, the signal set acquisition process will smoothly resume when the acquisition of the next front image 40 is completed. [Explanation of Symbols]

[0090] 1 OCT device 11 OCT light source 12 Couplers 14 Optical scanning unit 16 Irradiation optical system 20 Reference optical system 22 Photodetector 23 Frontal observation optical system 31 CPU 34 NVM 40 Front view 58 scanning lines

Claims

1. OCT light source and A branching optical element that splits the light emitted from the OCT light source into measurement light and reference light, An optical scanning unit that scans the measurement light branched by the branched optical element over the tissue of the subject, A light-receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the aforementioned structure and the reference light branched by the branched optical element. Control unit and Equipped with, The control unit, A signal set acquisition step involves obtaining a signal set containing multiple OCT signals by performing a process to scan the same scanning line on the tissue multiple times with the measurement light, or by performing a process to scan each of multiple adjacent scanning lines with the measurement light, A pass / fail determination step for determining whether the acquisition status of the signal set is good or bad, A next scan position setting step in which the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step is set, Repeated execution, As the aforementioned pass / fail determination step, an OCT determination step is performed to determine the pass / fail status of the acquired signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step. In the next scan position setting step, Once the acquisition of the signal set in the previous signal set acquisition step is complete, regardless of whether the pass / fail determination in the OCT determination step is complete or not, the position of the next scan line is provisionally set. In the aforementioned signal set acquisition step, Regardless of whether the pass / fail determination in the OCT determination step is completed or not, the scanning of the measurement light to the provisionally set scanning line is started. If the OCT determination step determines that the acquisition state of the signal set is not good, the next scan position setting step resets the position of the next scan line to the same position on the tissue as the scan line at the time the signal set was acquired and determined to be unsatisfactory, and the signal set acquisition step changes the scan line on which the measurement light is scanned to the reset scan line. In the OCT determination step, if it is determined that the acquisition state of the signal set is good, the OCT apparatus is characterized in that, in the signal set acquisition step, the provisionally set scanning line is used as the original scanning line and the scanning of the measurement light on the scanning line is continued as is.

2. OCT light source and A branching optical element that splits the light emitted from the OCT light source into measurement light and reference light, An optical scanning unit that scans the measurement light branched by the branched optical element over the tissue of the subject, A light-receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the aforementioned structure and the reference light branched by the branched optical element. A frontal observation optical system that captures frontal images of the subject's tissue at a scanning rate lower than the number of OCT signal acquisitions per unit time, Control unit and Equipped with, The control unit, A signal set acquisition step involves adjusting the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system, and performing a process to scan the same scanning line on the tissue multiple times, or a process to scan each of multiple adjacent scanning lines, thereby acquiring a signal set containing multiple OCT signals. A pass / fail determination step for determining whether the acquisition status of the signal set is good or bad, A next scan position setting step in which the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step is set, Repeated execution, As the aforementioned pass / fail determination step, An OCT determination step is performed to determine whether the acquisition status of the signal set is good or bad based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, A front image determination step that determines the quality of the signal set acquisition status based on a comparison result between the latest front image captured by the front observation optical system and a front image captured before the latest front image, Execute, In the aforementioned quality determination step, if it is determined that the acquisition state of the signal set is not good, the determination result that the acquisition state is not good will be maintained at least until the next acquisition of the front image by the front observation optical system is completed. In the next scan position setting step, while the acquisition status of the signal set is determined to be unsatisfactory in the good / bad judgment step, the position of the next scan line is reset to the same position on the tissue as the scan line at the time of acquisition of any of the signal sets that was determined to be unsatisfactory. An OCT device characterized in that, while it is determined that the acquisition status of the signal set is not good, the acquisition of the signal set in the signal set acquisition step is repeated, and the acquired signal set is excluded from being stored in the storage device.

3. OCT light source and A branching optical element that splits the light emitted from the OCT light source into measurement light and reference light, An optical scanning unit that scans the measurement light branched by the branched optical element over the tissue of the subject, A light-receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the aforementioned structure and the reference light branched by the branched optical element. Control unit and Equipped with, The control unit, A signal set acquisition step involves obtaining a signal set containing multiple OCT signals by performing a process to scan the same scanning line on the tissue multiple times with the measurement light, or by performing a process to scan each of multiple adjacent scanning lines with the measurement light, A pass / fail determination step for determining whether the acquisition status of the signal set is good or bad, A next scan position setting step in which the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step is set, Repeated execution, As the aforementioned pass / fail determination step, an OCT determination step is performed to determine the pass / fail status of the acquired signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step. In the next scan position setting step, if the acquisition state of the signal set is determined to be unsatisfactory in the OCT determination step, the position of the next scan line is reset to the same position on the tissue as the scan line at the time the signal set was acquired which was determined to be unsatisfactory. An OCT apparatus characterized in that, in the OCT determination step, the number of pairs of OCT signals to be compared for the pass / fail determination from among the plurality of OCT signals included in the signal set is changed according to the number of times OCT signals are acquired per unit time when the signal set is acquired.

4. OCT light source and A branching optical element that splits the light emitted from the OCT light source into measurement light and reference light, An optical scanning unit that scans the measurement light branched by the branched optical element over the tissue of the subject, A light-receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the aforementioned structure and the reference light branched by the branched optical element. A frontal observation optical system that captures frontal images of the subject's tissue at a scanning rate lower than the number of OCT signal acquisitions per unit time, Control unit and Equipped with, The control unit, A signal set acquisition step involves adjusting the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system, and performing a process to scan the same scanning line on the tissue multiple times, or a process to scan each of multiple adjacent scanning lines, thereby acquiring a signal set containing multiple OCT signals. A pass / fail determination step for determining whether the acquisition status of the signal set is good or bad, A next scan position setting step in which the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step is set, Repeated execution, As the aforementioned pass / fail determination step, An OCT determination step is performed to determine whether the acquisition status of the signal set is good or bad based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, A front image determination step that determines the quality of the signal set acquisition status based on a comparison result between the latest front image captured by the front observation optical system and a front image captured before the latest front image, Execute, In the next scan position setting step, while it is determined in at least one of the front image determination step and the OCT determination step that the acquisition state of the signal set is not good, the position of the next scan line is reset to the same position on the tissue as the scan line at the time of acquisition of any of the signal sets that was determined to be in a poor state. In the aforementioned front image determination step, In addition to the latest frontal image and the first positional displacement amount, which is the positional displacement amount of the previous frontal image taken immediately before the latest frontal image, It is possible to obtain the latest frontal image and a second positional displacement amount, which is the positional displacement amount of a reference frontal image taken before the previous frontal image. If both the first positional displacement amount and the second positional displacement amount are acquired, and at least one of the first positional displacement amount and the second positional displacement amount exceeds a threshold, it is determined that the acquisition state is not good. An OCT device characterized by replacing the reference front image with a newly captured front image once it is determined that the acquisition status is not good.

5. An OCT imaging control method performed in an OCT device, The OCT device is OCT light source and A branching optical element that splits the light emitted from the OCT light source into measurement light and reference light, An optical scanning unit that scans the measurement light branched by the branched optical element over the tissue of the subject, A light-receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the aforementioned structure and the reference light branched by the branched optical element. Equipped with, A signal set acquisition step involves obtaining a signal set containing multiple OCT signals by performing a process to scan the same scanning line on the tissue multiple times with the measurement light, or by performing a process to scan each of multiple adjacent scanning lines with the measurement light, A pass / fail determination step for determining whether the acquisition status of the signal set is good or bad, A next scan position setting step in which the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step is set, Repeated execution, As the aforementioned pass / fail determination step, an OCT determination step is performed to determine the pass / fail status of the acquired signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step. In the next scan position setting step, Once the acquisition of the signal set in the previous signal set acquisition step is complete, regardless of whether the pass / fail determination in the OCT determination step is complete or not, the position of the next scan line is provisionally set. In the aforementioned signal set acquisition step, Regardless of whether the pass / fail determination in the OCT determination step is completed or not, the scanning of the measurement light to the provisionally set scanning line is started. If the OCT determination step determines that the acquisition state of the signal set is not good, the next scan position setting step resets the position of the next scan line to the same position on the tissue as the scan line at the time the signal set was acquired and determined to be unsatisfactory, and the signal set acquisition step changes the scan line on which the measurement light is scanned to the reset scan line. An OCT imaging control method characterized in that, if it is determined in the OCT determination step that the acquisition state of the signal set is good, the signal set acquisition step continues scanning the measurement light onto the scan line with the provisionally set scan line as the original scan line.

6. An OCT imaging control method performed in an OCT device, The OCT device is OCT light source and A branching optical element that splits the light emitted from the OCT light source into measurement light and reference light, An optical scanning unit that scans the measurement light branched by the branched optical element over the tissue of the subject, A light-receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the aforementioned structure and the reference light branched by the branched optical element. A frontal observation optical system that captures frontal images of the subject's tissue at a scanning rate lower than the number of OCT signal acquisitions per unit time, Equipped with, A signal set acquisition step involves adjusting the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system, and performing a process to scan the same scanning line on the tissue multiple times, or a process to scan each of multiple adjacent scanning lines, thereby acquiring a signal set containing multiple OCT signals. A pass / fail determination step for determining whether the acquisition status of the signal set is good or bad, A next scan position setting step in which the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step is set, Repeated execution, As the aforementioned pass / fail determination step, An OCT determination step is performed to determine whether the acquisition status of the signal set is good or bad based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, A front image determination step that determines the quality of the signal set acquisition status based on a comparison result between the latest front image captured by the front observation optical system and a front image captured before the latest front image, Execute, In the aforementioned quality determination step, if it is determined that the acquisition state of the signal set is not good, the determination result that the acquisition state is not good will be maintained at least until the next acquisition of the front image by the front observation optical system is completed. In the next scan position setting step, while the acquisition status of the signal set is determined to be unsatisfactory in the good / bad judgment step, the position of the next scan line is reset to the same position on the tissue as the scan line at the time of acquisition of any of the signal sets that was determined to be unsatisfactory. An OCT imaging control method characterized by repeating the acquisition of the signal set in the signal set acquisition step while it is determined that the acquisition state of the signal set is not good, and excluding the acquired signal set from the items to be stored in the storage device.

7. An OCT imaging control method performed in an OCT device, The OCT device is OCT light source and A branching optical element that splits the light emitted from the OCT light source into measurement light and reference light, An optical scanning unit that scans the measurement light branched by the branched optical element over the tissue of the subject, A light-receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the aforementioned structure and the reference light branched by the branched optical element. Equipped with, A signal set acquisition step involves obtaining a signal set containing multiple OCT signals by performing a process to scan the same scanning line on the tissue multiple times with the measurement light, or by performing a process to scan each of multiple adjacent scanning lines with the measurement light, A pass / fail determination step for determining whether the acquisition status of the signal set is good or bad, A next scan position setting step in which the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step is set, Repeated execution, As the aforementioned pass / fail determination step, an OCT determination step is performed to determine the pass / fail status of the acquired signal set based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step. In the next scan position setting step, if the acquisition state of the signal set is determined to be unsatisfactory in the OCT determination step, the position of the next scan line is reset to the same position on the tissue as the scan line at the time the signal set was acquired which was determined to be unsatisfactory. An OCT imaging control method characterized in that, in the OCT judgment step, the number of pairs of OCT signals to be compared for good or bad judgment from among a plurality of OCT signals included in the signal set is changed according to the number of times OCT signals are acquired per unit time when the signal set is acquired.

8. An OCT imaging control method performed in an OCT device, The OCT device is OCT light source and A branching optical element that splits the light emitted from the OCT light source into measurement light and reference light, An optical scanning unit that scans the measurement light branched by the branched optical element over the tissue of the subject, A light-receiving element detects an interference signal for acquiring an OCT signal by receiving the combined light of the measurement light reflected by the aforementioned structure and the reference light branched by the branched optical element. A frontal observation optical system that captures frontal images of the subject's tissue at a scanning rate lower than the number of OCT signal acquisitions per unit time, Equipped with, A signal set acquisition step involves adjusting the scanning position of the measurement light based on the latest frontal image captured by the frontal observation optical system, and performing a process to scan the same scanning line on the tissue multiple times, or a process to scan each of multiple adjacent scanning lines, thereby acquiring a signal set containing multiple OCT signals. A pass / fail determination step for determining whether the acquisition status of the signal set is good or bad, A next scan position setting step in which the position on the tissue of the scanning line that will scan the measurement light in the next signal set acquisition step is set, Repeated execution, As the aforementioned pass / fail determination step, An OCT determination step is performed to determine whether the acquisition status of the signal set is good or bad based on the comparison result of at least two OCT signals included in the signal set acquired in the signal set acquisition step, A front image determination step that determines the quality of the signal set acquisition status based on a comparison result between the latest front image captured by the front observation optical system and a front image captured before the latest front image, Execute, In the next scan position setting step, while it is determined in at least one of the front image determination step and the OCT determination step that the acquisition state of the signal set is not good, the position of the next scan line is reset to the same position on the tissue as the scan line at the time of acquisition of any of the signal sets that was determined to be in a poor state. In the aforementioned front image determination step, In addition to the latest frontal image and the first positional displacement amount, which is the positional displacement amount of the previous frontal image taken immediately before the latest frontal image, It is possible to obtain the latest frontal image and a second positional displacement amount, which is the positional displacement amount of a reference frontal image taken before the previous frontal image. If both the first positional displacement amount and the second positional displacement amount are acquired, and at least one of the first positional displacement amount and the second positional displacement amount exceeds a threshold, it is determined that the acquisition state is not good. An OCT imaging control method characterized by replacing the reference frontal image with a newly captured frontal image once it is determined that the acquisition status is not good.

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