Ophthalmic imaging equipment and ophthalmic imaging control programs

Abstract

To provide an ophthalmology imaging apparatus and an ophthalmology imaging control program which can properly shorten the time required for imaging of a subject eye by scanning of light.SOLUTION: A control unit repeatedly executes a scan position setting step and a partial image data acquisition step. In the scan position setting step, the control unit sets the scan position of light by an optical scanning unit in order to acquire partial image data being a portion of image data. In the partial image data acquisition step, the control unit acquires the partial image data while driving the optical scanning unit by applying a drive signal that causes the light to scan the set scan position to the optical scanning unit. The control unit causes the optical scanning unit to execute the operation different from the time of image acquisition by applying a continuation drive signal that continues drive of the optical scanning unit until the next partial image data acquisition step is started to the optical scanning unit during the partial image data acquisition step that is executed in plural times.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to an ophthalmic imaging device that captures an image of tissue by scanning light on the tissue of an eye to be examined, and an ophthalmic imaging control program executed in the ophthalmic imaging device.

Background Art

[0002] Conventionally, an ophthalmic imaging device that captures an image of tissue by scanning light on the tissue of an eye to be examined is known. During the imaging operation of one image, the ophthalmic imaging device may repeatedly execute setting of the light scanning position and drive control of the light scanning unit for scanning light at the set scanning position. For example, the ophthalmic imaging device described in Patent Document 1 corrects the light scanning position based on the positional deviation between the live image of the tissue of the eye to be examined and the frontal image where the acquisition position of the tomographic image is set. The ophthalmic imaging device controls the drive of the light scanning unit so as to scan light at the corrected scanning position, thereby tracking the measurement light to the acquisition position on the eye to be examined set in advance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the imaging time of an image is prolonged, the burden on the subject and the risk of image quality degradation due to movement of the eye to be examined during imaging increase. Therefore, in an ophthalmic imaging device, it is desirable to shorten the imaging time of an image as much as possible. The inventor of the present application newly found a method of shortening the imaging time of an image by shortening the time from the end of the drive of the light scanning unit for scanning light at one scanning position until the drive of the light scanning unit for scanning light at the next scanning position is actually started during the imaging operation of one image.

[0005] A typical object of this disclosure is to provide an ophthalmic imaging device and an ophthalmic imaging control program that can appropriately reduce the time required to image the eye of a subject by scanning it with light. [Means for solving the problem]

[0006] Ophthalmic imaging device provided by a typical embodiment in this disclosure First aspect The ophthalmic imaging device for capturing images of tissue of an eye under examination comprises a light source that emits light, a deflection unit that deflects the light emitted by the light source, a light scanning unit that scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue, a light receiving element that receives light from the tissue irradiated by the light scanned by the light scanning unit, and a control unit, wherein the control unit performs a scanning position setting step to set the scanning position of the light by the light scanning unit for acquiring partial image data, which is a part of the image data, between the start and end of a single image data acquisition process, and the scanning position setting step The process involves repeatedly performing a partial image data acquisition step, which involves applying a drive signal to the optical scanning unit to scan light at the scanning position set in the step, thereby driving the optical scanning unit and acquiring the partial image data via the light-receiving element. In between the multiple partial image data acquisition steps performed to acquire the image data, a continuous drive signal is applied to the optical scanning unit to continue driving it until the next partial image data acquisition step begins, thereby performing a continuous drive step that causes the optical scanning unit to perform an operation separate from the operation to acquire the image data. In the continuous drive step, the control unit applies the continuous drive signal to the optical scanning unit, which causes light to scan over the scanning position in the previously executed partial image data acquisition step, until the next partial image data acquisition step is started. . A second aspect of an ophthalmic imaging apparatus provided by a typical embodiment of the present disclosure is an ophthalmic imaging apparatus for capturing images of tissue of an eye under examination, comprising: a light source that emits light; a deflection unit that deflects the light emitted by the light source; a light scanning unit that scans the light over the tissue in a manner that allows control of the irradiation position and speed of the light over the tissue; a light receiving element that receives light from the tissue irradiated by the light scanned by the light scanning unit; and a control unit, wherein the control unit performs a scanning position setting step to set the scanning position of the light by the light scanning unit for acquiring partial image data, which is a part of the image data, between the start and end of a single image data acquisition process; and applies a drive signal to the light scanning unit to cause the light to scan the scanning position set in the scanning position setting step. In this way, the control unit repeatedly performs a partial image data acquisition step in which it acquires the partial image data via the light receiving element while driving the optical scanning unit, and in between the partial image data acquisition steps which are performed multiple times to acquire the image data, it applies a continuous drive signal to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step is started, thereby performing a continuous drive step in which the optical scanning unit performs an operation separate from the operation to acquire the image data, and in the continuous drive step, the control unit applies the continuous drive signal to the optical scanning unit to scan light over a part of the scanning position in the previously executed partial image data acquisition step until the next partial image data acquisition step is started. A third aspect of an ophthalmic imaging apparatus provided by a typical embodiment of the present disclosure is an ophthalmic imaging apparatus for capturing images of tissue of an eye under examination, comprising: a light source that emits light; a deflection unit that deflects the light emitted by the light source; a light scanning unit that scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue; a light receiving element that receives light from the tissue irradiated by the light scanned by the light scanning unit; a frontal observation optical system that captures a frontal image of the tissue of the eye under examination; and a control unit, wherein the control unit, during the period from the start to the end of a single image data acquisition process, detects a positional shift between the frontal image captured in real time by the frontal observation optical system and the frontal image captured in the past, and sets the scanning position of the light by the light scanning unit for acquiring partial image data which is a part of the image data based on the detected positional shift, and the scanning position setting step The control unit repeatedly performs a partial image data acquisition step in which a drive signal is applied to the optical scanning unit to drive the optical scanning unit and acquire the partial image data via the light receiving element, and in between the partial image data acquisition steps which are performed multiple times to acquire the image data, a continuous drive step is performed in which the optical scanning unit is driven by applying a continuous drive signal to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step is started, thereby causing the optical scanning unit to perform an operation separate from the operation to acquire the image data, and in the continuous drive step, the control unit applies the continuous drive signal to the optical scanning unit to repeatedly scan light at least a part of the next scanning position which is set in the scanning position setting step if no positional misalignment has occurred, until the next partial image data acquisition step is started. A fourth aspect of an ophthalmic imaging apparatus provided by a typical embodiment of the present disclosure is an ophthalmic imaging apparatus for capturing images of tissue of an eye under examination, comprising: a light source that emits light; a deflection unit that deflects the light emitted by the light source; a light scanning unit that scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue; a light receiving element that receives light from the tissue irradiated by the light scanned by the light scanning unit; and a control unit, wherein the control unit performs a scanning position setting step to set the scanning position of the light by the light scanning unit for acquiring partial image data, which is a part of the image data, between the start and end of a single image data acquisition process; and applies a drive signal to the light scanning unit to cause the light to scan the scanning position set in the scanning position setting step, thereby driving the light scanning unit and acquiring the partial image data via the light receiving element. The process of acquiring partial image data is repeatedly performed, and in between the multiple partial image data acquisition steps performed to acquire the image data, a continuous drive signal is applied to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step is started, thereby performing a continuous drive step that causes the optical scanning unit to perform an operation separate from the operation for acquiring the image data. When the unit continuous drive process, which is a single drive of the optical scanning unit by the continuous drive signal, is completed, if the setting of the next scan position in the scan position setting step has not been completed, the unit continuous drive of the optical scanning unit by the continuous drive signal is repeated. When the unit continuous drive process is completed, if the setting of the next scan position in the scan position setting step has been completed, the process proceeds to the next partial image data acquisition step.

[0007] Ophthalmic imaging control program provided by a typical embodiment in this disclosure First aspectThis is an ophthalmic imaging control program executed in an ophthalmic imaging device for capturing images of tissue of an eye under examination, wherein the ophthalmic imaging device comprises a light source that emits light, a deflection unit that deflects the light emitted by the light source, a light scanning unit that scans the tissue with the light in a state that can control the irradiation position and speed of the light on the tissue, a light receiving element that receives light from the tissue irradiated by the light scanned by the light scanning unit, and a control unit, and the ophthalmic imaging control program is executed by the control unit of the ophthalmic imaging device, so that during the period from the start to the end of one image data acquisition process, the scanning position of the light by the light scanning unit for acquiring partial image data which is a part of the image data The ophthalmic imaging device repeatedly performs the following steps: a scanning position setting step, and a partial image data acquisition step, which involves applying a drive signal to the optical scanning unit to scan light at the scanning position set in the scanning position setting step, thereby driving the optical scanning unit and acquiring the partial image data via the light-receiving element; and, in between the multiple partial image data acquisition steps performed to acquire the image data, a continuous drive step is applied to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step begins, thereby causing the optical scanning unit to perform an operation separate from the operation to acquire the image data. Scientific photography Executed by the shadow device In the continuous drive step, the control unit applies the continuous drive signal to the optical scanning unit, which causes light to scan a portion of the scanning position in the previously executed partial image data acquisition step, until the next partial image data acquisition step is started. . A second aspect of the ophthalmic imaging control program provided by a typical embodiment of this disclosure is an ophthalmic imaging control program executed in an ophthalmic imaging apparatus for capturing images of tissue of an eye under examination, wherein the ophthalmic imaging apparatus comprises a light source that emits light, a deflection unit that deflects the light emitted by the light source, an optical scanning unit that scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue, a light receiving element that receives light from the tissue irradiated by the light scanned by the optical scanning unit, and a control unit, wherein the ophthalmic imaging control program is executed by the control unit of the ophthalmic imaging apparatus, and during the period from the start to the end of a single image data acquisition process, a scanning position setting step is performed to set the scanning position of the optical scanning unit for acquiring partial image data which is a part of the image data, and a drive signal is applied to the optical scanning unit to drive the optical scanning unit so as to scan the light at the scanning position set in the scanning position setting step. The ophthalmic imaging device is repeatedly made to perform a partial image data acquisition step, in which the partial image data is acquired via the light-receiving element. Between the partial image data acquisition steps, which are performed multiple times to acquire the image data, a continuous drive signal is applied to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step begins. This causes the ophthalmic imaging device to perform a continuous drive step, which is an operation separate from the operation to acquire the image data. When the unit continuous drive process, which is a single drive of the optical scanning unit by the continuous drive signal, is completed, if the setting of the next scanning position in the scanning position setting step has not been completed, the unit continuous drive of the optical scanning unit by the continuous drive signal is repeated. When the unit continuous drive process is completed, if the setting of the next scanning position in the scanning position setting step has been completed, the device proceeds to the next partial image data acquisition step.

[0008] According to the ophthalmic imaging device and ophthalmic imaging control program described herein, the time required to image the eye of the subject by scanning with light is appropriately reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing the schematic configuration of ophthalmic imaging device 1. [Figure 2] This is a perspective view of the optical scanning unit 14. [Figure 3] This is an explanatory diagram illustrating one example of how to take an image. [Figure 4] This is a flowchart of the ophthalmic imaging process performed by ophthalmic imaging device 1. [Figure 5] This is an example of a graph showing the magnitude of the drive signal applied to the first optical scanning unit 14X over time when the first and third embodiments of the method for generating a continuous drive signal are employed. [Figure 6] This is an example of a graph showing the magnitude of the drive signal applied to the first optical scanning unit 14X over time when the second and third embodiments of the method for generating the continuous drive signal are employed. [Modes for carrying out the invention]

[0010] <Overview> The ophthalmic imaging device illustrated in this disclosure captures images of tissue of an eye under examination. The ophthalmic imaging device comprises a light source, an optical scanning unit, a photodetector, and a control unit. The light source emits light. The optical scanning unit has a deflection unit that deflects the light emitted by the light source, and scans the light over the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue. The photodetector receives light from the tissue irradiated by the light scanned by the optical scanning unit. The control unit repeatedly executes a scanning position setting step and a partial image data acquisition step during the acquisition process of one image data (acquisition of image data according to a scanning pattern (e.g., a scanning pattern such as a map scan) that includes multiple scanning positions) from start to finish. In the scanning position setting step, the control unit sets the scanning position of the light by the optical scanning unit for acquiring partial image data, which is a part of the image data. In the partial image data acquisition step, the control unit is driven by applying a drive signal to the optical scanning unit to cause it to scan the light at the scanning position set in the scanning position setting step, and the partial image data is acquired via the photodetector. Furthermore, the control unit performs a continuous drive step in which, between partial image data acquisition steps that are performed multiple times to acquire image data, the control unit applies a continuous drive signal to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step begins, thereby causing the optical scanning unit to perform an operation separate from the operation to acquire image data.

[0011] Conventional ophthalmic imaging devices would temporarily stop the optical scanning unit once it had finished driving the optical scanning unit corresponding to one scanning position (i.e., for scanning light to one scanning position) until it was ready to start driving the optical scanning unit corresponding to a newly set scanning position. However, the optical scanning unit has a characteristic that once its driving is stopped, it takes time from the start of applying the drive signal until the driving actually resumes. One possible reason for the delay in restarting the optical scanning unit after it has stopped is the time it takes from the start of applying the drive signal to the optical scanning unit by the control unit until the driver receives the feedback signal from the optical scanning unit. In this case, the driver cannot start the next drive until it receives the feedback signal, so it takes time to restart the optical scanning unit. In addition, the delay in restarting the driving may also be caused by insufficient tracking ability of the deflection unit of the optical scanning unit. Furthermore, in conventional ophthalmic devices, when the scanning of the optical scanning unit was temporarily stopped, the deflection unit was sometimes driven so that the light illumination position was outside the imaging field of view in order to prevent continuous light illumination on the same position on the tissue. In this case, the time required to scan the light to the next scanning position becomes even longer.

[0012] In contrast, in the ophthalmic imaging apparatus of this disclosure, a continuous drive signal is applied to the optical scanning unit between the multiple partial image data acquisition steps performed to acquire image data, so as to continue driving the optical scanning unit until the next partial image data acquisition step begins. In other words, the optical scanning unit is made to perform an operation separate from the operation for acquiring image data between the repeatedly performed partial image data acquisition steps, thereby continuing to drive the optical scanning unit. As a result, the drive state of the optical scanning unit transitions from the state of drive due to the continuous drive signal (hereinafter referred to as "continuous drive") to the drive state for the next partial image data acquisition step without stopping the drive. Therefore, the time from when the drive of the optical scanning unit corresponding to one scanning position ends until the drive of the optical scanning unit corresponding to the next scanning position actually begins is appropriately shortened.

[0013] That is, in the ophthalmic imaging apparatus of the present disclosure, although there may be cases where intervals between each of the partial image acquisition steps executed multiple times occur frequently, the intervals are shortened by applying a continuous drive signal to the optical scanning unit. By accumulating the shortening of each interval, the imaging time itself is appropriately shortened as a result.

[0014] In the embodiments exemplified below, in the intervals between the partial image data acquisition steps (that is, the intervals between the optical scans for each of the plurality of scanning positions) that are executed multiple times to acquire one image data, a continuous drive signal is applied to the optical scanning unit so that the driving of the optical scanning unit is always continued. That is, in the embodiments exemplified below, the optical scanning unit never stops even once after the driving corresponding to one scanning position ends until the driving corresponding to the next scanning position starts (in other words, in the embodiments exemplified below, the application of the drive signal to the optical scanning unit does not stop during the intervals between the optical scans for each of the plurality of scanning positions). However, the driving of the optical scanning unit by the continuous drive signal only needs to be executed at least when the driving corresponding to the next scanning position starts. Therefore, for example, even when the control unit temporarily stops the application of the drive signal to the optical scanning unit after the driving corresponding to one scanning position ends and then immediately applies the continuous drive signal, the imaging time is appropriately shortened compared to the conventional case.

[0015] Further, the control unit may temporarily stop or block the irradiation of light from the light source toward the tissue during continuous driving, or may continue the irradiation of light even during continuous driving. The scanning position indicates the position on the tissue where the light is scanned (in the embodiments described below, the position on the tissue of the scanning line where the light is scanned).

[0016] In the embodiments described below, an OCT device that captures an image of the fundus of an eye is exemplified as an ophthalmic imaging device that captures an image of the tissue of an examined eye by scanning light. However, the ophthalmic imaging devices to which the technology exemplified in the present disclosure can be applied are not limited to OCT devices that capture images of the fundus. For example, the technology exemplified in the present disclosure can be applied to various ophthalmic imaging devices that capture tissue images by non-resonantly driving an optical scanning unit, such as a laser scanning ophthalmoscope (SLO) that captures a two-dimensional frontal image of the fundus and an OCT device that captures an anterior segment image of an examined eye.

[0017] In the embodiments described below, two galvanoscanners are used as the optical scanning unit. However, the optical scanning unit driven by the above-described drive signal (including the continuous drive signal) may be any optical scanning unit that scans light on tissue in a state where the irradiation position and speed of the light can be controlled, and is not limited to a galvanoscanner. For example, as the optical scanning unit, it is possible to use an optical scanning unit that swings a deflection unit (such as a mirror) in a non-resonant manner. The optical scanning unit swung by non-resonant driving may be a piezo scanner, a MEMS scanner, or the like. Further, the ophthalmic imaging device may be provided with a plurality of optical scanning units (for example, an optical scanning unit swung by non-resonant driving) that can control the irradiation position and speed, or may be provided with only one. When the ophthalmic imaging device includes a plurality of the above-described optical scanning units, the continuous drive signal may be applied to each of the plurality of optical scanning units, or may be applied only to some of the optical scanning units. Further, the ophthalmic imaging device may include both an optical scanning unit swung by non-resonant driving and other scanning units (for example, an optical scanning unit driven resonantly, or an optical scanning unit that continuously rotates a deflection unit). In this case, the continuous drive signal may be applied to at least any one of the optical scanning units swung by non-resonant driving. Note that, unlike an optical scanning unit driven resonantly, an optical scanning unit swung by non-resonant driving has the characteristic that the deflection angle of the light by the deflection unit can be precisely controlled according to the magnitude of the drive signal.

[0018] In the continuous drive step, the control unit may apply a continuous drive signal to the optical scanning unit to cause light to scan over the scanning position from the previously executed partial image data acquisition step until the next partial image data acquisition step begins. In this case, the control unit can simply use the drive signal used in the previous partial image data acquisition step as the continuous drive signal, eliminating the need to generate a new continuous drive signal. Therefore, the acquisition time can be shortened appropriately with simpler control.

[0019] In the continuous drive step, the control unit may apply a continuous drive signal to the optical scanning unit to scan a portion of the scanning position in the previously executed partial image data acquisition step until the next partial image data acquisition step begins. In this case, the control unit can generate the continuous drive signal using the drive signal from when the light was scanned to the previous scanning position, thus making the control less complex. Furthermore, it becomes easier to shorten the time required for one continuous drive compared to using a continuous drive signal that scans the entire previous scanning position with light. Consequently, if the setting of the next scanning position is completed while the optical scanning unit is continuously driving, the average time from the end of continuous driving to the transition to the driving state of the optical scanning unit corresponding to the next scanning position can be further shortened.

[0020] The ophthalmic imaging device may further include a frontal observation optical system for capturing a frontal image of the tissue of the eye under examination. In the scanning position setting step, the control unit may detect the positional misalignment between the frontal image captured in real time by the frontal observation optical system and a previously captured frontal image, and set the next scanning position based on the detected misalignment. In this case, even if the tissue of the eye under examination moves during imaging, the ophthalmic imaging device can set multiple scanning positions in appropriate locations on the tissue each time by setting the next scanning position according to the positional misalignment caused by the tissue movement. In other words, the ophthalmic imaging device can perform tracking processing to make the optical scanning position follow the tissue movement. Furthermore, by applying a continuous drive signal to the optical scanning unit, the time from when the optical scanning unit corresponding to one scanning position ends until when the optical scanning unit corresponding to the next scanning position actually starts is appropriately shortened. Therefore, the time required to acquire high-quality images using tracking is appropriately shortened.

[0021] The ophthalmic imaging device may be an OCT device that splits light emitted from an OCT light source into measurement light and reference light, and acquires an OCT signal by receiving the interference light between the measurement light reflected by the tissue and the reference light. The ophthalmic imaging device may perform a scan position setting step, a partial image data acquisition step, and a continuous drive step while acquiring (imaging) OCT angiodata. OCT angiodata is motion contrast data generated by processing at least two OCT signals acquired at different times for the same position in the eye under examination. In other words, when acquiring OCT angiodata, the ophthalmic imaging device needs to scan the light multiple times over the same scanning position. Therefore, it has been difficult to shorten the imaging time with conventional techniques. However, by applying the technique illustrated in this application, the imaging time for OCT angiodata can be appropriately shortened. Furthermore, the ophthalmic imaging device may perform the scan position setting step, the partial image data acquisition step, and the continuous drive step while acquiring (imaging) OCT angiodata while performing the tracking process described above. In this case, the imaging time for acquiring high-quality OCT angiodata using tracking can be appropriately shortened.

[0022] However, the techniques exemplified in this disclosure can also be used when acquiring image data other than OCT angio data. For example, an ophthalmic imaging device (OCT device) may perform a scan position setting step, a partial image data acquisition step, and a continuous drive step when performing an averaging process on multiple tomographic images acquired by scanning light multiple times on the same scanning line. In this case as well, the ophthalmic imaging device may perform a tracking process. Furthermore, as mentioned above, the techniques exemplified in this disclosure can also be applied to ophthalmic imaging devices other than OCT devices.

[0023] In the continuous drive step, the control unit may apply a continuous drive signal to the optical scanning unit until the next partial image data acquisition step begins, causing the optical scanning unit to repeatedly scan light over at least a portion of the next scanning position, which is set in the scanning position setting step if no positional misalignment occurs between frontal images. During image acquisition, the eye under examination is fixed, so the eye under examination often does not move during acquisition, and even if the eye under examination does move, the amount of movement is often small. Therefore, the distance between the next scanning position assuming no positional misalignment occurs between frontal images (i.e., positional misalignment of the tissue of the eye under examination) (hereinafter sometimes referred to as the "expected scanning position") and the next scanning position actually set based on the detected positional misalignment is often short. Thus, by causing the optical scanning unit to repeatedly scan light over at least a portion of the expected scanning position during the continuous drive of the optical scanning unit, the average time until the optical scanning unit is driven based on the next scanning position that is actually set can be further shortened.

[0024] In the scanning position setting step, the control unit may set the next scanning position based on the front image captured in real time by the front observation optical system and the positional shift of the front image captured when the previous scanning position was set (i.e., the positional shift of the tissue at the time of the previous scanning position setting and the current tissue). In this case, in the continuous drive step, the control unit may set the expected scanning position based on the front image captured when the previous scanning position was set, and then generate a continuous drive signal. In this case, the continuous drive of the optical scanning unit is performed under the assumption that there has been no positional shift of the tissue since the previous scanning position was set. Therefore, the accuracy of the continuous drive is more easily improved. In addition, during continuous drive, the control unit may repeatedly scan the entire expected scanning position with light, or repeatedly scan a part of the expected scanning position with light.

[0025] Furthermore, the control unit may generate a continuation drive signal based on at least the position of the scanning start point among the next scanning positions set in the scanning position setting step, provided that no positional misalignment occurs between the front images. Specifically, the control unit may generate a continuation drive signal so that the optical scanning continues near the next scanning start point. The control unit may also generate a continuation drive signal so that the next scanning start point is included in a portion of the scanning position during continuous driving. In this case, the average time until transitioning to the driving state of the optical scanning unit based on the actually set next scanning position becomes even easier to shorten.

[0026] Here, the technique of continuously driving the optical scanning unit before starting to drive the optical scanning unit corresponding to the next scanning position is also useful even when the aforementioned tracking process is not performed. For example, when setting multiple scanning positions that differ from each other in at least one aspect, such as shape, length, or angle, between the start and end of a single image data acquisition process (for example, when performing a radial scan in which light is scanned at each of multiple concentrically arranged annular scanning positions, or when performing a scan that switches from annular scanning positions to linear scanning positions), the acquisition time can be appropriately shortened by continuously driving the optical scanning unit. Furthermore, when there is a time lag between the completion of light scanning for one scanning position and the start of light scanning for the next scanning position due to the inertial force of the deflection unit, etc. (for example, when the scanning angle for one scanning position and the scanning angle for the next scanning position are significantly different), the acquisition time can be appropriately shortened by continuously driving the optical scanning unit.

[0027] The control unit may repeat the unit continuous drive of the optical scanning unit using the continuous drive signal if the setting of the next scanning position in the scanning position setting step has not been completed when the unit continuous drive process, which is a single drive of the optical scanning unit using the continuous drive signal, is completed. The control unit may proceed to the next partial image data acquisition step if the setting of the next scanning position in the scanning position setting step has been completed when the unit continuous drive process is completed. In this case, regardless of the timing of the completion of the setting of the next scanning position, the drive state of the optical scanning unit smoothly transitions from the continuous drive state to the drive state based on the next scanning position.

[0028] <Embodiment> The following describes one typical embodiment of the present disclosure. As an example, the ophthalmic imaging device 1 of this embodiment is an OCT device capable of capturing at least one of the following: a two-dimensional tomographic image, a three-dimensional tomographic image, OCT angiography (OCT angiodata), or a two-dimensional frontal image (for example, an Enface image generated based on a three-dimensional tomographic image of the tissue when the tissue is viewed from a frontal direction along the optical axis of the measurement light), using the fundus tissue of the eye E as the imaging target (subject). However, as mentioned above, the ophthalmic imaging device to which the technology exemplified in this disclosure can be applied is not limited to an OCT device that images fundus tissue. Furthermore, the technology exemplified in this disclosure can also be applied to imaging devices that image biological tissues other than the eye E (for example, skin, digestive organs, brain, etc.). Note that an OCT image is an image captured based on the principle of optical coherence tomography (OCT).

[0029] (Outline configuration of an ophthalmic imaging system) Referring to Figure 1, the schematic configuration of the ophthalmic imaging device 1 of this embodiment will be described. The ophthalmic imaging device 1 of this embodiment captures an OCT image of the eye E under examination. The ophthalmic imaging device 1 comprises an OCT optical system 10 and a control unit 30. The OCT optical system 10 comprises a light source (OCT light source) 11, a coupler (optical divider) 12, a measurement optical system 13, a reference optical system 20, a photodetector 22, and a frontal observation optical system 23.

[0030] The light source 11 emits light for capturing an image (OCT light in this embodiment). The coupler 12 splits the light emitted from the 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 (fundus tissue 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.

[0031] The measurement optical system 13 guides the measurement light, which has been split by the coupler 12, to the subject, and returns the measurement light reflected by the subject to the coupler 12. The measurement optical system 13 comprises an optical scanning unit 14, an illumination optical system 17, and a focus adjustment unit 18. The optical scanning unit 14 is driven by a drive unit 15, which allows the measurement light to be deflected (scanned) 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. Details of the optical scanning unit 14 will be described later with reference to Figure 2. The illumination optical system 17 is located downstream of the optical path from the optical scanning unit 14 (i.e., on the subject eye E side), and irradiates the tissue of the subject eye E with the measurement light. The focus adjustment unit 18 adjusts the focus position of the OCT optical system 10 in the direction of the optical axis of the measurement light of the OCT optical system 10 (i.e., in the depth direction of the tissue). As an example, the focus adjustment unit 18 of this embodiment adjusts the focus of the measurement light by moving the optical element (e.g., a lens) of the illumination optical system 17 in a direction along the optical axis of the measurement light.

[0032] 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.

[0033] The photodetector 22 receives light from the tissue irradiated by the light scanned by the optical scanning unit 14. More specifically, the photodetector 22 in this embodiment detects an interference signal by receiving the interference light between the measurement light and the reference light generated by the coupler 12. In this embodiment, the principle of Fourier domain OCT is 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 obtained by performing a Fourier transform on the spectral intensity data. 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).

[0034] 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 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 at high speed over time is used as the light source 11. In this case, the light source 11 may include 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.

[0035] The frontal observation optical system 23 is provided for capturing a frontal image of the subject's tissue (in this embodiment, the fundus of the eye E under examination). 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). The configuration of the frontal observation optical system 23 can employ at least one of the following: a scanning laser ophthalmoscope (SLO), a fundus camera, and an infrared camera that captures a frontal image by simultaneously irradiating a two-dimensional imaging range with infrared light. Alternatively, the ophthalmic imaging device 1 in this embodiment may acquire three-dimensional OCT data of the tissue and acquire an image of the tissue viewed from a direction along the optical axis of the measurement light (frontal direction) (a so-called "Enface image") as the frontal image. If an Enface image is acquired, the frontal observation optical system 23 may be omitted. In other words, the OCT optical system 10 may also serve as the frontal observation optical system.

[0036] The control unit 30 is responsible for various controls of the ophthalmic imaging 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 (control unit) 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 ophthalmic imaging control program for executing the ophthalmic imaging process (see Figure 4), which will be described later, may also be stored in the NVM 34.

[0037] 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 ophthalmic imaging 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 ophthalmic imaging 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.

[0038] In this embodiment, an integrated ophthalmic imaging device 1 is illustrated, in which the OCT optical system 10 and the control unit 30 are housed in a single housing. However, it goes without saying that the ophthalmic imaging device 1 may comprise multiple devices with different housings. For example, the ophthalmic imaging device 1 may comprise an optical device that houses the OCT optical system 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 ophthalmic imaging device 1.

[0039] (Optical scanning unit) Referring to Figure 2, the optical scanning unit 14 of this embodiment will be described in detail. The ophthalmic imaging apparatus 1 of this embodiment comprises a first optical scanning unit 14X and a second optical scanning unit 14Y. Both the first optical scanning unit 14X and the second optical scanning unit 14Y scan light on tissue by oscillating rotation of the deflection unit 4 (4X, 4Y) by non-resonant drive. Unlike optical scanning units that are resonantly driven, the non-resonant driven optical scanning unit 14 has the advantage of being able to precisely control the deflection angle of the light by the deflection unit according to the magnitude of the drive signal. In other words, the optical scanning unit 14 of this embodiment can scan light on tissue while controlling the irradiation position and speed of the light. As an example, both the first optical scanning unit 14X and the second optical scanning unit 14Y of this embodiment use galvanometer scanners. However, devices other than galvanometer scanners (e.g., piezo scanners or MEMS scanners, etc.) may be used as the optical scanning unit.

[0040] In this embodiment, the pivot axis of the deflection section 4X of the first optical scanning section 14X extends in the Y direction, and the deflection section 4X scans light in the X direction intersecting the Y direction (perpendicularly in this embodiment). The pivot axis of the deflection section 4Y of the second optical scanning section 14Y extends in the X direction, and the deflection section 4Y scans light in the Y direction. As a result, the light that has passed through the first optical scanning section 14X and the second optical scanning section 14Y is scanned in two dimensions on the tissue of the eye E under examination.

[0041] A drive unit 15X is connected to the deflection unit 4X of the first optical scanning unit 14X via a pivot axis. The drive unit 15X incorporates an actuator (e.g., a motor) that rotates (oscillates) the deflection unit 4X and a potentiometer that detects the position (angle) of the deflection unit 4X. Similarly, a drive unit 15Y is connected to the deflection unit 4Y of the second optical scanning unit 14Y via a pivot axis. The drive unit 15Y incorporates an actuator that rotates (oscillates) the deflection unit 4Y and a potentiometer that detects the position (angle) of the deflection unit 4Y. Each of the drive units 15X and 15Y includes a driver that actually controls the driving of the deflection units 4X and 4Y by the actuators. The driver controls the driving of the actuators according to the drive signals applied from the CPU 31.

[0042] The CPU 31 applies drive signals to the drive unit 15X of the first optical scanning unit 14X and the drive unit 15Y of the second optical scanning unit 14Y, respectively. The drive units 15(15X,15Y) precisely control the angle of deflection of light by the deflection unit 4(4X,4Y) (i.e., the angle of the deflection units 4X,4Y) according to the magnitude of the applied drive signal. Furthermore, the drivers of the drive units 15X and 15Y control the driving of the deflection units 4X,4Y based on feedback signals indicating the position (angle) of the deflection units 4X,4Y acquired by the potentiometer, thereby enabling more accurate driving of the first optical scanning unit 14X and the second optical scanning unit 14Y.

[0043] Here, when the optical scanning units 14X and 14Y are started to be driven, a certain amount of time is required between the start of application of the drive signal to the optical scanning units 14Y and 14Y and the driver receiving the feedback signal from the optical scanning units 14X and 14Y. The driver cannot control the drive of the next optical scanning unit 14X and 14Y until it receives the feedback signal. Therefore, it takes a certain amount of time to restart the drive of the optical scanning units 14X and 14Y from a stopped state. In addition, it may take time to restart the drive due to insufficient tracking ability of the deflection units 4X and 4Y provided by the optical scanning units 14X and 14Y. If it takes a long time to restart the drive of the optical scanning units 14X and 14Y, it becomes difficult to shorten the image acquisition time. Therefore, the ophthalmic imaging device 1 of this embodiment aims to shorten the image acquisition time by performing the ophthalmic imaging process described later.

[0044] (An example of how to take an image) Referring to Figure 3, an example of the image acquisition method in this embodiment will be described. In this embodiment, the spot of measurement light is scanned within a two-dimensional imaging area 55 by the optical scanning unit 14, thereby acquiring (capturing) OCT angiodata in the imaging area 55. OCT angiodata is motion contrast data generated by processing at least two OCT signals acquired at different times for the same position in the eye under examination. Since OCT angiodata includes perfusion information of the vascular network in the tissue, it is useful for diagnosis and other purposes.

[0045] As shown in Figure 3, the ophthalmic imaging device 1 of this embodiment sets multiple scanning positions (scanning lines) 58 at equal intervals within a two-dimensional imaging 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 3, the scanning positions 58 are arranged at equal intervals in the order of the 1st scanning position 581, the 2nd scanning position 582, the 3rd scanning position 583, the 4th scanning position 584, and so on, with the last scanning position being the Kth scanning position 58K. The ophthalmic imaging device 1 scans the spot of the measurement light multiple times (for example, twice each in this embodiment) on each scanning position 58 to capture OCT angio data in the two-dimensional imaging area 55.

[0046] In this embodiment, for the sake of simplicity, the direction in which each of the multiple scanning positions 58 extends is defined as the X direction, the depth direction of the tissue (i.e., the direction along the optical axis of the measurement light) is defined as the Z direction, and the direction perpendicular to both the X and Z directions is defined as the Y direction. In this case, the drive amount and drive time of the second optical scanning unit 14Y, which scans light in the Y direction, are significantly smaller than those of the first optical scanning unit 14X, which scans light in the X direction. Therefore, the technology relating to this disclosure will be explained below by illustrating the driving method of the first optical scanning unit 14X, which has a large drive amount and drive time. However, it goes without saying that the driving method of the second optical scanning unit 14Y may also be the same as the driving method of the first optical scanning unit 14X.

[0047] (Ophthalmic imaging processing) Referring to Figures 4 to 6, the ophthalmic imaging process performed by the ophthalmic imaging device 1 of this embodiment will be described. As mentioned above, the ophthalmic imaging process 1 illustrated in Figure 4 is the process when OCT angiodata of the fundus of the eye under examination E is acquired using the imaging method illustrated in Figure 3. However, at least a part of the process illustrated in Figure 4 can also be applied when acquiring images other than OCT angiodata (for example, two-dimensional tomographic images, three-dimensional tomographic images, averaged images, two-dimensional frontal images, etc.). The CPU 31 of the ophthalmic imaging device 1 executes the ophthalmic imaging process shown in Figure 4 according to the ophthalmic imaging control program stored in the NVM 34.

[0048] First, the CPU 31 acquires an initial reference frontal image of the tissue (in this embodiment, the fundus of the eye E under examination). The initial reference frontal image is the first reference image for setting multiple scanning positions 58. In this embodiment, a two-dimensional frontal image of the tissue of the eye E under examination, captured by the frontal observation optical system 23, is acquired as the initial reference frontal image.

[0049] The CPU 31 sets an imaging area 55 (see Figure 3) for acquiring image data on the initial reference frontal image acquired in S1, and also sets multiple provisional scanning positions within the set imaging area 55 (S2). A provisional scanning position is the scanning position of the light (measurement light) assuming that no displacement (movement) occurs in the tissue of the eye E during imaging. In other words, if the tissue of the eye E does not move at all during imaging, the optical scanning unit 14 is driven so that the light is scanned to the provisional scanning positions set in S2, and the acquisition of all images within the imaging area 55 is completed. After that, the process in S4 is repeated and the system enters a standby state until a trigger is input to instruct the start of image acquisition (S4:NO).

[0050] When a trigger is received to instruct the start of image capture, the CPU 31 sets the value of counter N, which identifies the order of the multiple scan positions 58 to be set later, to its initial value of "1" (S5).

[0051] Next, the CPU 31 generates a continuous drive signal at the start of shooting and begins applying the generated continuous drive signal to the optical scanning unit 14 (S6). The continuous drive signal at the start of shooting is a drive signal that continues to drive the optical scanning unit 14 until the optical scanning unit 14 starts driving to scan light to the first scanning position 581. As mentioned above, a certain amount of time is required between the application of a drive signal to the stopped optical scanning unit 14 and the actual start of the optical scanning unit 14's operation. However, if the drive signal is switched while the optical scanning unit 14 is being driven, the time until the optical scanning unit 14 starts driving based on the newly switched drive signal is likely to be shortened. Therefore, by applying the continuous drive signal at the start of shooting to the optical scanning unit 14, the operation of the optical scanning unit 14 corresponding to the first scanning position 581 is more likely to start in a shorter time compared to when the optical scanning unit 14 is switched from a stopped state to a driven state.

[0052] The method for generating the continuous drive signal at the start of image acquisition can be selected as appropriate. For example, in this embodiment, the CPU 31 assumes that no positional displacement has occurred due to tissue movement of the eye E under examination, and generates a drive signal as the continuous drive signal at the start of image acquisition that causes the light to scan to at least a part of the first provisional scan position set in S2, or to any position including the scanning start point of the provisional scan position. Since the eye E under examination is fixed during image acquisition, the eye E under examination often does not move during acquisition, and even if the eye E under examination does move, the amount of movement is often small. Therefore, by generating the continuous drive signal at the start of image acquisition so that the light is operated to the first provisional scan position or its vicinity, the time it takes for the drive state of the optical scanning unit 14 to transition from the drive state based on the continuous drive signal at the start of image acquisition to the drive state corresponding to the first scan position 581 set later can be further shortened.

[0053] Next, the CPU 31 executes the process of setting the Nth scanning position 58 (S8-S10) and the process of continuing to drive the optical scanning unit 14 (S11-S13) in parallel.

[0054] First, the process of setting the Nth scanning position 58 (S8-S10) will be explained. The CPU 31 acquires a frontal image of the tissue (fundus) captured in real time by the frontal observation optical system 23 (hereinafter referred to as the "real-time frontal image") (S8). The CPU 31 detects the positional displacement due to tissue movement by detecting the positional displacement between the real-time frontal image and a reference frontal image, which is a frontal image previously captured by the frontal observation optical system 23 (i.e., captured before the real-time frontal image was captured) (S9). As an example, in this embodiment, when setting the N-1th scanning position 58, the frontal image captured by the frontal observation optical system 23 (if N=1, the initial reference frontal image acquired in S1) is used as the reference frontal image. However, it is also possible to change the reference frontal image. For example, in S9, the initial reference frontal image acquired in S1 may always be used as the reference frontal image.

[0055] Furthermore, specific methods for detecting the positional misalignment between the real-time frontal image and the reference frontal image can be selected as appropriate. For example, the CPU 31 may detect feature positions (e.g., feature points) by performing known image processing on each of the real-time frontal image and the reference frontal image, and then detect the positional misalignment by comparing the detected feature positions. Note that the detection of positional misalignment may be performed by a control unit of a device other than the ophthalmic image acquisition device 1 (a device connected to the ophthalmic image acquisition device 1).

[0056] The CPU 31 sets the Nth scanning position 58, which is corrected for the positional misalignment detected in S9. In this embodiment, the CPU 31 sets the Nth scanning position 58 by correcting the position and angle of the Nth provisional scanning position set in S2 according to the direction, distance, and rotation angle of the positional misalignment detected in S9. As a result, tracking processing is appropriately performed to make the scanning position 58 follow the movement of the tissue. After that, the process moves to S12, and then to the acquisition of partial image data (S15) based on the Nth scanning position 58. Partial image data is a part of the tissue image data acquired by ophthalmic imaging processing.

[0057] Next, the processing related to the continuous driving of the optical scanning unit 14 (S11 to S13) will be described. The CPU 31 determines whether the processing of driving the optical scanning unit 14 with a single continuous driving signal (hereinafter referred to as "unit continuous driving") has been completed, out of the continuous driving signals that may be repeatedly applied to the optical scanning unit 14 (S11). As an example, in S11 of this embodiment, it is determined whether the application of a single continuous driving signal to the optical scanning unit 14 has been completed. If the unit continuous driving processing has not been completed (S11: NO), the processing in S11 is repeated and the system enters a standby state.

[0058] When the unit continuous drive process is completed (S11:YES), the CPU 31 determines whether the setting of the next scan position 58 (i.e., the setting of the Nth scan position 58, which is performed in S8 to S10) has been completed (S12). If the setting of the Nth scan position 58 has not been completed (S12:NO), the acquisition process of partial image data based on the Nth scan position 58 cannot be performed yet. Therefore, the CPU 31 applies the continuous drive signal to the optical scanning unit 14 again (S13), and the process returns to S11. In other words, the unit continuous drive of the optical scanning unit 14 is repeated until the setting of the next scan position 58 is completed.

[0059] If the continuous unit drive process is completed (S11:YES) and the setting of the next scan position 58 is completed (S12:YES), the CPU 31 applies a drive signal to the continuously driven optical scanning unit 14 to scan light to the next (Nth) scan position 58, and acquires partial image data corresponding to the Nth scan position 58 based on the light received signal from the photodetector 22 (S15). In other words, the drive state of the optical scanning unit 14 transitions from a continuous drive state to a drive state for scanning light to the next scan position 58 without stopping the drive. As a result, the drive of the optical scanning unit 14 to scan light to the Nth scan position 58 is started in a short time, so the shooting time is appropriately shortened.

[0060] When the acquisition process of partial image data based on the Nth scanning position 58 is completed (S16:YES), the CPU 31 determines whether the acquisition process of all image data (i.e., the acquisition process of image data based on all of the multiple scanning positions 58) has been completed (S18). If the acquisition process of all image data has not been completed (S18:NO), the CPU 31 generates a continuous drive signal to continue driving the optical scanning unit 14 until the next partial image data acquisition process based on the scanning position 58 (S15) is started, and begins applying the generated continuous drive signal to the optical scanning unit 14 (S19). The specific method for generating the continuous drive signal will be described later with reference to Figures 5 and 6.

[0061] Next, the CPU 31 adds "1" to the value of counter N, which identifies the order of the scanning positions 58 (S20). After that, the process of setting the Nth scanning position 58 (S8-S10) and the process related to the continued operation of the optical scanning unit 14 (S11-S13) are executed again in parallel. Once the acquisition of all image data is complete (S18: YES), the ophthalmic imaging process ends.

[0062] (Method for generating continuous drive signals) Referring to Figures 5 and 6, an example of a specific method for generating a continuous drive signal (S19) will be described. Figures 5 and 6 are graphs showing the magnitude of the drive signal (voltage value of the drive voltage in this embodiment) applied to the optical scanning unit 14 over time. In Figures 5 and 6, the horizontal axis represents time, and the vertical axis represents the magnitude of the drive signal. The graph shown by the solid line represents the magnitude of the drive signal applied to the optical scanning unit 14. For reference, the actual angle of the optical scanning unit 14 driven according to the applied drive signal is shown by the dotted line. The actual angle of the optical scanning unit 14 changes with a slight delay relative to the applied drive signal.

[0063] In this embodiment, a continuous drive signal is applied to both the first optical scanning unit 14X and the second optical scanning unit 14Y. However, as mentioned above, the explanation will be simplified by illustrating and describing only the driving method for the first optical scanning unit 14X, which has a large drive amount and drive time.

[0064] Furthermore, in the examples shown in Figures 5 and 6, so-called tracking processing (see S8 to 10 in Figure 4) is performed, resulting in the generation of drive signals to scan light at each scanning position 58 so that the X-direction displacement of the tissue of the eye E being examined is appropriately corrected (see C1, C2, and C3 in the figures).

[0065] A first embodiment of the method for generating a continuous drive signal will be described. In this first embodiment, the CPU 31 generates a continuous drive signal that repeatedly scans the entire previous scan position 58 with light until the drive processing of the optical scanning unit 14 corresponding to the next scan position 58 and the acquisition processing of partial image data begin. As a result, as shown in Figure 5, according to the first embodiment, the drive signal used in the drive processing corresponding to the previous scan position 58 (the drive signal for "driving the Nth scan position" shown in Figure 5) is used as the continuous drive signal. Therefore, the CPU 31 does not need to generate a new continuous drive signal. Thus, the shooting time can be appropriately shortened with simpler control. (Note that in the example shown in Figure 5, the setting of the next scan position 58 is completed during the processing of one unit continuous drive. As a result, the drive processing corresponding to the next scan position is started without the continuous drive being repeated multiple times.)

[0066] A second embodiment of the method for generating a continuous drive signal will be described. In the second embodiment, the CPU 31 generates a continuous drive signal that repeatedly scans a portion of the previous scan position 58 (in the example shown in Figure 6, a portion including the scanning start point at scan position 58) until the drive processing of the optical scanning unit 14 corresponding to the next scan position 58 and the acquisition processing of partial image data are started. As a result, as shown in Figure 6, according to the second embodiment, the continuous drive signal can be generated using the drive signal when the light was scanned at the previous scan position 58, so the signal generation process is less likely to become complicated. In addition, it becomes easier to shorten the time required for one unit of continuous drive compared to the first embodiment. Therefore, if the setting of the next scan position 58 is completed while the optical scanning unit 14 is being continuously driven, the average time from the end of the continuous drive processing to the transition to the drive state of the optical scanning unit 14 corresponding to the next scan position 58 can be further shortened.

[0067] In the example shown in Figure 6, the drive amount (drive cycle) in one unit of continuous drive is represented as larger than the actual drive amount in order to facilitate understanding of the operation of the optical scanning unit 14 based on the continuous drive signal. As a result, in the example shown in Figure 6, the operation waveform of the optical scanning unit 14 based on the continuous drive signal appears jagged. However, it is desirable to make the drive amount in one unit of continuous drive as small as possible. In this embodiment, a continuous drive signal (for example, a drive signal with a control waveform of the minimum table size allowed as per the specifications of the optical scanning unit 14) is applied to the optical scanning unit 14 to perform unit continuous drive with the smallest drive amount within the range in which it can be driven in a stable state. As a result, the average time from the end of the continuous drive process to the transition to the drive state of the optical scanning unit 14 corresponding to the next scan position 58 is further shortened.

[0068] Furthermore, the waveform of the continuous drive signal is not limited to the jagged waveform shown in Figure 6. In other words, as long as the scanning unit 14 does not stop, the waveform of the continuous drive signal can be any waveform.

[0069] Furthermore, even if light is not scanned over at least a portion of the previous scanning position 58, the imaging time can be appropriately shortened by applying a process that continuously drives the optical scanning unit 14 in units with the minimum drive amount within the range that can be driven in a stable state. For example, a continuous drive signal may be generated to continuously drive the optical scanning unit 14 in units with the minimum drive amount within the range that can be driven in a stable state in the vicinity of the next scanning start point (for example, a position including the scanning start point at the next expected scanning position described later). In this case, the imaging time can be shortened even further.

[0070] A third embodiment of the method for generating a continuous drive signal will be described. In the third embodiment, the CPU 31 generates a continuous drive signal that causes light to repeatedly scan at least a portion of the next scan position 58 (expected scan position) (in this embodiment, the position including the scanning start point in the expected scan position), which is set assuming that no positional misalignment has occurred in the detection process of positional misalignment between frontal images for setting the next scan position 58 (see S8 and S9 in Figure 4). Since the eye under examination E is fixed during image acquisition, the eye under examination E often does not move during acquisition, and even if the eye under examination E does move, the amount of movement is often small. Therefore, the distance between the next expected scan position assuming that no positional misalignment has occurred in the tissue of the eye under examination and the next scan position 58 actually set based on the detected positional misalignment is often short. Thus, according to the third embodiment, the average time until transitioning to the driving state of the optical scanning unit 14 corresponding to the next scan position 58 that has actually been set can be further shortened.

[0071] For example, when the CPU 31 finishes driving the optical scanning unit 14 corresponding to the Nth scanning position 58, it may set the (N+1)th scanning position 58 (expected scanning position) assuming no positional shift occurs, based on the front image acquired in S8 when setting the Nth scanning position 58. The CPU 31 may also generate a continuous drive signal to drive the light to the set expected scanning position. In this case, the continuous drive of the optical scanning unit 14 is performed under the assumption that no positional shift of the tissue has occurred since the previous setting of the scanning position 58. Therefore, the accuracy of the continuous drive can be further improved.

[0072] The CPU 31 may repeatedly scan the entire predicted scanning position with light during continuous operation, or it may repeatedly scan a part of the predicted scanning position with light. Furthermore, the CPU 31 may repeatedly scan an arbitrary scanning position, including the scanning start point of the predicted scanning position, during continuous operation. For example, in the example shown in Figure 3, the range in the X direction of the multiple scanning positions 58 set on the tissue is constant, and only the position in the Y direction differs. That is, in the example shown in Figure 3, if there is no tissue displacement, the drive signal to the first optical scanning unit 14X corresponding to the Nth scanning position 58 and the drive signal to the first optical scanning unit 14X corresponding to the N+1th scanning position 58 will be the same. Therefore, in the third embodiment, when light is scanned across the entire predicted scanning position during continuous operation, the graph of the drive signal applied to the first optical scanning unit 14X will be the same as in Figure 5. Also, in the third embodiment, when light is scanned only over a part of the predicted scanning position during continuous operation, the graph of the drive signal applied to the first optical scanning unit 14X will be the same as in Figure 6. In the example shown in Figure 3, if no tissue displacement occurs, the drive signal to the second optical scanning unit 14Y corresponding to the Nth scanning position 58 and the drive signal to the second optical scanning unit 14Y corresponding to the (N+1)th scanning position 58 are slightly different.

[0073] 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 adopt only some of the technologies exemplified in the above embodiments. For example, the process of applying a continuous drive signal at the start of shooting (S6) may be omitted. Furthermore, the process of applying a continuous drive signal to the optical scanning unit 14 is also useful even when tracking processing (S8, S9) is not performed. For example, even when setting the scanning position 58 multiple times between the start and end of a single image data acquisition process (for example, when performing a radial scan in which light is scanned at each of multiple annular scanning positions arranged concentrically), the shooting time can be appropriately shortened by continuously driving the optical scanning unit 14. Moreover, the method of generating the continuous drive signal is not limited to the first to third embodiments described above. In other words, even when the specific content of the continuous drive signal (such as the position in which light is scanned by the application of the continuous drive signal) is changed, the shooting time can be appropriately shortened by transitioning the drive state of the optical scanning unit 14 from a continuous drive state to a drive state corresponding to the next scanning position 58 without stopping the drive.

[0074] Note that the process of setting the next scanning position 58 in S8 to S10 in Figure 4 is an example of a "scanning position setting step". The process of acquiring partial image data based on the scanning position 58 in S15 in Figure 4 is an example of a "partial image data acquisition step". The process of applying a continuous drive signal to the optical scanning unit 14 in S6, S11 to S13, and S19 in Figure 4 is an example of a "continuous drive step". [Explanation of symbols]

[0075] 1. Ophthalmic imaging equipment 4(4X,4Y) Deflection part 11 Light source 14(14X,14Y) Optical scanning unit 15 (15X, 15Y) Drive Unit 22 Photodetector 23 Frontal observation optical system 31 CPU 34 NVM 55 Shooting area 58 Scanning position

Claims

1. An ophthalmic imaging device that takes images of the tissue of the eye being examined, A light source that emits light, A light scanning unit has a deflection unit that deflects the light emitted by the light source, and scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue, A light-receiving element that receives light from the tissue irradiated with light scanned by the optical scanning unit, Control unit and Equipped with, The control unit, During the entire process from the start to the end of one image data acquisition cycle, A scanning position setting step for setting the scanning position of light by the optical scanning unit in order to acquire partial image data which is a part of the aforementioned image data, A partial image data acquisition step involves applying a drive signal to the optical scanning unit to scan light at the scanning position set in the scanning position setting step, thereby driving the optical scanning unit and acquiring the partial image data via the light receiving element. Repeated execution, Between the multiple partial image data acquisition steps performed to acquire the aforementioned image data, a continuous drive signal is applied to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step begins, thereby executing a continuous drive step that causes the optical scanning unit to perform an operation separate from the operation for acquiring the aforementioned image data. In the continuous drive step, the control unit applies the continuous drive signal to the optical scanning unit, which causes light to scan over the scanning position in the previously executed partial image data acquisition step, until the next partial image data acquisition step is started.

2. An ophthalmic imaging device that takes images of the tissue of the eye being examined, A light source that emits light, A light scanning unit has a deflection unit that deflects the light emitted by the light source, and scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue, A light-receiving element that receives light from the tissue irradiated with light scanned by the optical scanning unit, Control unit and Equipped with, The control unit, During the entire process from the start to the end of one image data acquisition cycle, A scanning position setting step for setting the scanning position of light by the optical scanning unit in order to acquire partial image data which is a part of the aforementioned image data, A partial image data acquisition step involves applying a drive signal to the optical scanning unit to scan light at the scanning position set in the scanning position setting step, thereby driving the optical scanning unit and acquiring the partial image data via the light receiving element. Repeated execution, Between the multiple partial image data acquisition steps performed to acquire the aforementioned image data, a continuous drive signal is applied to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step begins, thereby executing a continuous drive step that causes the optical scanning unit to perform an operation separate from the operation for acquiring the aforementioned image data. In the continuous drive step, the control unit applies the continuous drive signal to the optical scanning unit, which causes light to scan a portion of the scanning position in the previously executed partial image data acquisition step, until the next partial image data acquisition step is started.

3. An ophthalmic imaging device that takes images of the tissue of the eye being examined, A light source that emits light, A light scanning unit has a deflection unit that deflects the light emitted by the light source, and scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue, A light-receiving element that receives light from the tissue irradiated with light scanned by the optical scanning unit, A frontal observation optical system for capturing a frontal image of the tissue of the eye under examination, Control unit and Equipped with, The control unit, During the entire process from the start to the end of one image data acquisition cycle, A scanning position setting step involves detecting a positional shift between the front image captured in real time by the front observation optical system and the front image captured in the past, and setting the scanning position of the light by the optical scanning unit to acquire partial image data, which is a part of the image data, based on the detected positional shift. A partial image data acquisition step involves applying a drive signal to the optical scanning unit to scan light at the scanning position set in the scanning position setting step, thereby driving the optical scanning unit and acquiring the partial image data via the light receiving element. Repeated execution, Between the multiple partial image data acquisition steps performed to acquire the aforementioned image data, a continuous drive signal is applied to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step begins, thereby executing a continuous drive step that causes the optical scanning unit to perform an operation separate from the operation for acquiring the aforementioned image data. In the continuous drive step, the control unit applies the continuous drive signal to the optical scanning unit, which causes light to be repeatedly scanned over at least a portion of the next scanning position set in the scanning position setting step if no positional misalignment has occurred, until the next partial image data acquisition step is started.

4. An ophthalmic imaging device that takes images of the tissue of the eye being examined, A light source that emits light, A light scanning unit has a deflection unit that deflects the light emitted by the light source, and scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue, A light-receiving element that receives light from the tissue irradiated with light scanned by the optical scanning unit, Control unit and Equipped with, The control unit, During the entire process from the start to the end of one image data acquisition cycle, A scanning position setting step for setting the scanning position of light by the optical scanning unit in order to acquire partial image data which is a part of the aforementioned image data, A partial image data acquisition step involves applying a drive signal to the optical scanning unit to scan light at the scanning position set in the scanning position setting step, thereby driving the optical scanning unit and acquiring the partial image data via the light receiving element. Repeated execution, Between the multiple partial image data acquisition steps performed to acquire the aforementioned image data, a continuous drive signal is applied to the optical scanning unit to continue driving the optical scanning unit until the next partial image data acquisition step begins, thereby executing a continuous drive step that causes the optical scanning unit to perform an operation separate from the operation for acquiring the aforementioned image data. When the unit continuous drive process, which is one drive of the optical scanning unit by the continuous drive signal, is completed, if the setting of the next scanning position in the scanning position setting step has not been completed, the unit continuous drive of the optical scanning unit by the continuous drive signal is repeated. An ophthalmic imaging apparatus characterized in that, when the unit continuous drive process is completed, if the setting of the next scan position in the scan position setting step is completed, the apparatus proceeds to the next partial image data acquisition step.

5. An ophthalmic imaging device according to claim 1, 2, or 4, The system further comprises a frontal observation optical system for capturing a frontal image of the tissue of the eye under examination, In the scanning position setting step, the control unit detects a positional misalignment between the frontal image captured in real time by the frontal observation optical system and a frontal image captured in the past, and sets the next scanning position based on the detected positional misalignment.

6. An ophthalmic imaging control program executed in an ophthalmic imaging device that captures images of tissue of the eye under examination, The aforementioned ophthalmic imaging device is A light source that emits light, A light scanning unit has a deflection unit that deflects the light emitted by the light source, and scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue, A light-receiving element that receives light from the tissue irradiated with light scanned by the optical scanning unit, Control unit and Equipped with, The ophthalmic imaging control program is executed by the control unit of the ophthalmic imaging device, During the entire process from the start to the end of one image data acquisition cycle, A scanning position setting step for setting the scanning position of light by the optical scanning unit in order to acquire partial image data which is a part of the aforementioned image data, A partial image data acquisition step involves applying a drive signal to the optical scanning unit to scan light at the scanning position set in the scanning position setting step, thereby driving the optical scanning unit and acquiring the partial image data via the light receiving element. The above ophthalmic imaging device is used to repeatedly perform this operation, A continuous drive step is performed in between the multiple partial image data acquisition steps performed to acquire the aforementioned image data, by applying a continuous drive signal to the optical scanning unit to keep it running until the next partial image data acquisition step begins, thereby causing the optical scanning unit to perform an operation separate from the operation for acquiring the aforementioned image data. The ophthalmic imaging device is instructed to perform the following: An ophthalmic imaging control program characterized in that, in the continuous drive step, the control unit applies the continuous drive signal to the optical scanning unit, which causes light to scan a portion of the scanning position in the previously executed partial image data acquisition step, until the next partial image data acquisition step is started.

7. An ophthalmic imaging control program executed in an ophthalmic imaging device that captures images of tissue of the eye under examination, The aforementioned ophthalmic imaging device is A light source that emits light, A light scanning unit has a deflection unit that deflects the light emitted by the light source, and scans the light on the tissue in a manner that allows control of the irradiation position and speed of the light on the tissue, A light-receiving element that receives light from the tissue irradiated with light scanned by the optical scanning unit, Control unit and Equipped with, The ophthalmic imaging control program is executed by the control unit of the ophthalmic imaging device, During the entire process from the start to the end of one image data acquisition cycle, A scanning position setting step for setting the scanning position of light by the optical scanning unit in order to acquire partial image data which is a part of the aforementioned image data, A partial image data acquisition step involves applying a drive signal to the optical scanning unit to scan light at the scanning position set in the scanning position setting step, thereby driving the optical scanning unit and acquiring the partial image data via the light receiving element. The above ophthalmic imaging device is used to repeatedly perform this operation, A continuous drive step is performed in between the multiple partial image data acquisition steps performed to acquire the aforementioned image data, by applying a continuous drive signal to the optical scanning unit to keep it running until the next partial image data acquisition step begins, thereby causing the optical scanning unit to perform an operation separate from the operation for acquiring the aforementioned image data. The ophthalmic imaging device is instructed to perform the following: When the unit continuous drive process, which is one drive of the optical scanning unit by the continuous drive signal, is completed, if the setting of the next scanning position in the scanning position setting step has not been completed, the unit continuous drive of the optical scanning unit by the continuous drive signal is repeated. An ophthalmic imaging control program characterized in that, when the unit continuous drive process is completed, if the setting of the next scan position in the scan position setting step is completed, the program proceeds to the next partial image data acquisition step.

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