OCT device

Abstract

This OCT device 1 is provided with an OCT optical system 100 and a control unit 70 which also serves as an image processor. The control unit 70 acquires OCT data of ocular fundus by processing a spectral interference signal outputted from the OCT optical system. Further, the control unit 70 makes an adjustment to the position of a high-accuracy region, which is a depth region where OCT data of relatively higher accuracy can be obtained, by controlling the OCT optical system 100 according to the level of curvature of an image of the ocular fundus within the imaging range of the OCT data. As a result, it becomes possible to acquire favorable OCT data regardless of the level of curvature of the ocular fundus.

Description

Technical Field

[0001] The present disclosure relates to an OCT apparatus that acquires (images) OCT data of an eye to be examined.

Background Art

[0002] An OCT apparatus for obtaining OCT data of an eye to be examined is known. In the OCT apparatus, various adjustments such as optical path length adjustment for adjusting the optical path lengths of the measurement light and the reference light, focus adjustment for adjusting the focus on the subject, and polarization adjustment for adjusting the polarization states of the measurement light and the reference light are performed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] When adjustments are made based on the same criteria between cases where the curvature of the fundus image is small and cases where it is large within the imaging range of the OCT data, it has been difficult to obtain OCT data with good image quality in at least one of the cases.

[0005] On the other hand, it is considered that it is cumbersome for an examiner to manually perform adjustment operations according to each eye to be examined, and the examination time becomes longer due to the cumbersome nature, which also places a burden on the subject.

[0006] In view of the problems of the prior art, an object of the present disclosure is to provide an OCT apparatus capable of acquiring good OCT data regardless of the curvature level of the fundus image.

[0007] The OCT device according to the first aspect of the present disclosure includes an optical splitter for splitting the light from the OCT light source into a measurement optical path and a reference optical path, and an optical path length changing means for changing the optical path length of at least one of the measurement optical path and the reference optical path. The OCT device further includes an OCT optical system for detecting a spectral interference signal between the measurement light guided to the fundus of the eye to be examined via the measurement optical path and the reference light from the reference optical path. image processing means for processing the spectral interference signal output from the OCT optical system to obtain OCT data of the fundus, and adjusting the zero-delay position where the optical path lengths of the measurement optical path and the reference optical path match by controlling the optical path length changing means according to the curvature level of the fundus image in the imaging range of the OCT data. When the curvature level is at the first level, and when the curvature level is at the second level where the curvature is larger than the first level, control means for displacing the zero-delay position to the shallower layer side is provided. No. 1 level and when the curvature level is at the second level where the curvature is larger than the first level, control means for displacing the zero-delay position to the shallower layer side is provided. This The first 2 The OCT device according to the aspect of the disclosure includes an optical splitter for splitting the light from the OCT light source into a measurement optical path and a reference optical path, and an optical path length changing means for changing the optical path length of at least one of the measurement optical path and the reference optical path. The OCT device further includes an OCT optical system for detecting a spectral interference signal between the measurement light guided to the fundus of the eye to be examined via the measurement optical path and the reference light from the reference optical path, an axial length information acquisition means for acquiring axial length information regarding the axial length value in the eye to be examined, image processing means for processing the spectral interference signal output from the OCT optical system to obtain OCT data of the fundus, and control means for adjusting the zero-delay position where the optical path lengths of the measurement optical path and the reference optical path match by controlling the optical path length changing means according to the curvature level of the fundus image in the imaging range of the OCT data, which is the curvature level considering the axial length information.

[0008] According to the present disclosure, good OCT data can be obtained regardless of the curvature level of the fundus image.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3A

Figure 3B

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Figure 7

Best Mode for Carrying Out the Invention

[0010] An example of an embodiment of the present disclosure will be described with reference to the drawings. FIGS. 1 to 7 are diagrams related to the examples of this embodiment. Note that the items classified in the following <> can be used independently or in combination.

[0011] The OCT apparatus according to this embodiment includes an OCT optical system (see FIG. 1), an image processor (image processing means in this embodiment), and a control unit (control means in this embodiment, see FIG. 2).

[0012] <OCT Optical System> The OCT optical system may be, for example, a Fourier domain OCT optical system (SS-OCT optical system, SD-OCT optical system). The OCT optical system has an optical splitter for splitting the light from the OCT light source into a measurement optical path and a reference optical path, and may detect a spectral interference signal between the measurement light guided to the object to be examined through the measurement optical path and the reference light from the reference optical path by a detector.

[0013] The optical scanner may be provided to scan the measurement light guided to the eye to be examined in a transverse direction (a direction intersecting the depth direction) on the eye to be examined. The OCT optical system is not limited to a configuration including an optical scanner, and a full-field OCT optical system may be used.

[0014] Further, the OCT optical system may have at least any one of an optical path length adjustment unit (optical path length adjustment means in the present embodiment), a focus adjustment unit (focus adjustment means in the present embodiment), and a polarization adjustment unit (polarization adjustment means in the present embodiment).

[0015] <Optical path length adjustment unit> The optical path length adjustment unit changes the optical path length of at least any one of the measurement optical path and the reference optical path. The optical path length adjustment unit may change the optical path length by moving an optical member disposed in at least any one of the measurement optical path and the reference optical path by a driving unit, or may change the optical path length by adjusting the operating distance between the eye to be examined and the apparatus.

[0016] <Focus adjustment unit> The focus adjustment unit is used to adjust the focus position (focusing position) of the measurement light. The focus adjustment unit may include, for example, a moving lens, or may include a variable focus lens such as a liquid crystal lens, or may include an optical system capable of changing the optical path length. The optical system capable of changing the optical path length may be, for example, one or a plurality of lenses, mirrors, or a combination thereof.

[0017] <Polarization adjustment unit> The polarization adjustment unit adjusts the polarization of at least any one of the measurement light and the reference light. The polarization adjustment unit may be a polarizer and may be disposed in at least any one of the measurement optical path and the reference optical path.

[0018] <Image processor> The image processor may be capable of processing the spectral interference signal output from the OCT optical system to obtain OCT data.

[0019] Here, referring to FIGS. 3A and 3B, the fundus image in the OCT data will be described. FIGS. 3A and 3B show image data G of a tomographic image, which is an example of OCT data. The image data G consists of first image data G1 corresponding to the back side (deeper side) of the zero-delay position Z and second image data G2 corresponding to the front side (shallower side) of the zero-delay position Z, and the images are symmetric with respect to the zero-delay position Z. Specifically, the real image and the virtual image of the fundus image are formed symmetrically with respect to the zero-delay position Z.

[0020] In FIG. 3A, the optical path length is adjusted so that the zero-delay position Z is formed on the front side (shallower side) of the retinal surface. In this case, a positive image is obtained as the real image. The retinal surfaces face each other between the first image data G1 and the second image data G2. In this case, a real image is obtained in the first image data G1, and a virtual image (mirror image) is obtained in the second image data G2.

[0021] On the other hand, when the optical path length is adjusted so that the zero-delay position Z is formed on the back side of the retinal surface, as shown in FIG. 3B, an inverted image is obtained as the real image. In this case, the retinal surfaces face in opposite directions between the first image data G1 and the second image data G2. In this case, a real image is obtained in the second image data G2, and a virtual image (mirror image) is obtained in the first image data G1.

[0022] One of the real image and the virtual image formed in this way may be extracted as a tomographic image to be displayed on the monitor.

[0023] <Application of the full-range technology> By the way, if the curvature of the fundus image is large, each of the real image and the virtual image is likely to be formed so as to straddle the zero-delay position Z (see FIG. 4). In this case, an overlapping region OL of the real image and the virtual image is formed in the vicinity of the zero-delay position Z.

[0024] In response to this, various methods for removing virtual images, called full-range techniques, have been proposed. In this embodiment, any of the full-range techniques may be applied, which may enable acquisition of wide-range OCT data from which virtual images have been selectively removed. When using wide-range OCT data from which virtual images have been removed by the full-range technique, it is possible to obtain good OCT data by not only adjusting the zero-delay position Z to a position that does not overlap with the fundus image as shown in Figures 3A and 3B, but also setting the zero-delay position Z to a position that overlaps with the fundus image.

[0025] Examples of full-range technologies include a technology that uses additional hardware to remove virtual images (also called mirror images) (see, for example, Non-Patent Document 1), and a technology that uses software to perform correction without using additional hardware (see, for example, Patent Document 2). [Non-Patent Document 1] Wojtkowski, M. et al. (2002) Full range complex spectral optical coherence tomography technique in eye imaging, Optics Letters, 27(16), p. 1415. [Patent Document 2] Patent Literature 1: JP 2015-506772 A Furthermore, in an application filed by the present applicant (Patent Application No. 2019-014771), still another full-range technology is proposed in which, based on a plurality of OCT data having different optical path lengths when detecting a spectral interference signal, at least an interpolation process is performed on an overlapping region between a real image and a virtual image in the OCT data, and OCT data that has been subjected to the interpolation process is generated. This technology may be applied to the present embodiment.

[0026] <Control Unit> The control unit (control means in this embodiment, see FIG. 2) is a processor that controls various operations of the OCT device. The control unit may be configured with, for example, a CPU, a RAM, and a ROM. The control unit may also function as an image processor.

[0027] The control unit can change the position of the depth region (hereinafter referred to as the high-precision region) where relatively high-precision OCT data can be obtained by controlling the OCT optical system.

[0028] The accuracy in OCT data is not necessarily uniform in the depth direction. The accuracy here may be represented, for example, by the level of interference sensitivity. For example, the closer the depth region is to the zero-delay position Z on the OCT data, the higher the sensitivity, and the sensitivity decreases as the distance from the zero-delay position Z increases. That is, it can be said that the OCT data is relatively highly accurate in the depth region close to the zero-delay position Z. For example, in the tomographic image shown in FIG. 3A, the accuracy of the retinal surface side portion is higher than that of the choroid side portion, and in the tomographic image shown in FIG. 3B, this relationship is reversed. However, if the curvature of the fundus image in the imaging range is small enough as in the tomographic images shown in FIGS. 3A and 3B, the difference in accuracy in each depth region is considered to be easily tolerated during observation.

[0029] However, it is considered that the larger the curvature of the fundus image in the OCT data imaging range (that is, the larger the height difference of the subject's image), the more difficult it is to tolerate the difference in accuracy in each depth region.

[0030] In contrast, the control unit adjusts the position of the high-precision region according to the curvature level (magnitude of curvature) of the fundus image in the imaging range. As an example, in the following description, the position of the high-precision region is adjusted by driving and controlling at least the optical path length adjustment unit of the OCT optical system. As a result of adjusting the position of the high-precision region according to the curvature level, as will be described later, OCT data that can be more favorably observed can be obtained. In this case, in each figure, the high-precision region is regarded as the zero-delay position Z and its vicinity region.

[0031] For example, the position of the high-precision region with respect to the reference position of the fundus image in each OCT data (which may be a predetermined layer of the retina at the center of the image, for example) may be set to different positions for each OCT data according to the curvature level of the fundus image. As an example, in the case where the curvature level is roughly classified into a first level and a second level (where the curvature is greater than that of the first level), for example, the position of the high-precision region with respect to the reference position of the fundus image may be set to different positions between the case where the curvature level is the first level and the case where it is the second level.

[0032] In this case, the control unit may adjust the position of the high-precision region to a shallower layer side for the case of the first level than for the case of the second level. Also, the curvature level may be divided into three or more levels, and the position of the high-precision region may be adjusted to a position corresponding to each level.

[0033] At this time, in the case where the OCT data is after full-range processing, for example, the position of the high-precision region corresponding to at least the first level may be set to be shallower than the retinal surface in the central region (the region near the fovea) and deeper than the choroid in the peripheral region.

[0034] Also, when a plurality of scan lines are included as the imaging range, the control unit may adjust the position of the high-precision region according to the curvature level of the fundus image for each scan line (for each scan of each scan line). Thereby, good OCT data can be acquired for each scan line.

[0035] Also, not necessarily limited to this, the position of the high-precision region may be controlled to be constant among a plurality of scan lines.

[0036] For example, the curvature of the fundus image increases towards the more peripheral parts of the fundus, and the peripheral parts are depicted on the shallower side. Also, currently, in the peripheral part of the fundus, clinically, the need to observe deep information such as the choroid is not necessarily high compared to the central part of the fundus. Therefore, when the peripheral part of the fundus is included in the imaging range, by automatically adjusting the position of the high-precision area to the shallower side, it smoothly transitions to a state suitable for the retinal surface side, which is relatively emphasized in the observation and diagnosis of the peripheral part of the fundus.

[0037] Also, for example, the curvature of the fundus image naturally depends on individual differences. Examples of cases where the curvature due to individual differences becomes a problem include diseased eyes with an elongated axial length, such as in cases of axial myopia. When such a significant curvature occurs, thinning may be considered to occur in the central part of the fundus. Due to the occurrence of thinning, the fundus itself is in a state where it is easy to accurately obtain deep information such as the choroid in the central part of the fundus. Therefore, by adjusting the position of the high-precision area to the shallower side, it becomes easier to obtain good images of the fundus tissue at each position.

[0038] The curvature of the fundus image increases towards the more peripheral side. That is, the curvature of the fundus image depends on the size and position of the OCT data imaging range on the fundus. Therefore, if the examiner is required to set the OCT data imaging range, the curvature level in the fundus image will correspond to the set imaging range as a result of the operation. Therefore, the position of the high-precision area may be adjusted by controlling the OCT optical system (here, the optical path length adjustment unit) according to the imaging range set as a result of the operation. The operation for setting the imaging range may be, for example, an operation for specifying the acquisition range of volume data, a selection operation for selecting any one from a plurality of predetermined scan patterns, an operation for setting the scan line at an arbitrary position and length on the fundus, or others.

[0039] In this case, for example, the curvature level when the central part of the fundus is the imaging range may be the first level, and the curvature level when the peripheral part of the fundus is included in the imaging range may be the second level.

[0040] In this case, the OCT device may have an operation detection unit that detects (accepts) the setting operation of the imaging range. The operation detection unit may be realized by, for example, a control unit and an input interface.

[0041] Also, the imaging range of the OCT data is restricted by the field angle in the OCT optical system. The OCT device may have a field angle switching unit that optically changes the field angle in the OCT optical system. The field angle switching unit may be able to switch the field angle between a first field angle corresponding to the central part of the fundus and a second field angle corresponding to a wide-angle region including the central part and the peripheral part of the fundus. In this case, a larger curvature may occur in the image of the fundus at the second field angle compared to the first field angle. Therefore, the control unit may adjust the position of the high-precision region by controlling the OCT optical system according to the curvature level within the imaging range considering the field angle. In this case, for example, the curvature level corresponding to the first field angle may be the first level, and the curvature level corresponding to the second field angle may be the second level.

[0042] The field angle switching unit may be, for example, a mechanism that inserts and removes optical elements such as lenses into and from the measurement optical path from the optical splitter to the eye to be examined. Also, for example, it may be a mechanism that displaces the position of the objective optical system in the OCT optical system.

[0043] In addition, the curvature of the fundus image naturally depends on the curvature of the fundus itself. Examples of cases where the curvature of the fundus becomes a problem include diseased eyes accompanied by an elongation of the axial length, such as in cases of axial myopia. Therefore, in the present embodiment, the control unit may adjust the position of the high-precision region by controlling the OCT optical system according to the curvature level considering the axial length information of the eye to be examined. In this case, for example, the curvature level when the axial length is within the first range (e.g., normal range) may be set as the first level, and the curvature level when the axial length is within the second range (e.g., long axial length eye) may be set as the second level.

[0044] The axial length information is information regarding the axial length value. The axial length value may be measured via the OCT optical system, and the measured value may be acquired as the axial length information. For example, it can be calculated based on the working distance and the depth position information of the retinal surface acquired via the OCT optical system. The depth position information of the retinal surface (preferably, the depth position information of the fovea) can be acquired based on the optical path length difference between the measurement light and the reference light and one or both of the spectral interference signals. In this case, the working distance may be the value at the completion of alignment, and the optical path length difference may be the value when the zero-delay position Z is arranged on the retinal surface. Also, the axial length information may be acquired as the measurement result by an axial length measuring device separate from the OCT device.

[0045] In addition, the control unit may adjust the position of the high-precision region based on information more directly indicating the curvature level of the fundus image. In this case, for example, information indicating the curvature level may be acquired as the processing result for the OCT data.

[0046] Information regarding the curvature level may be acquired based on the OCT data obtained when the optical path length is adjusted in the optimization control of the imaging conditions (referred to as Optimize). For example, information regarding the curvature level may be acquired as the processing result of the image processing for the OCT data.

[0047] In optimization control (referred to as "Optimize"), the zero-delay position Z in the OCT data is adjusted so as to be arranged at a predetermined position with respect to the fundus image (for example, always in front of the retinal surface). For example, further, the zero-delay position Z may be adjusted so that an evaluation value regarding the signal intensity of the fundus image is maximized.

[0048] In the OCT data obtained after adjustment, the magnitude of the curvature of the fundus image can be grasped according to the ratio of the fundus image included in each of a range A within a predetermined distance from the zero-delay position Z toward the back side and a range B farther than the predetermined distance. That is, the greater the curvature, the more the fundus image is formed up to the deeper layer side, and thus it is considered that the ratio of the fundus image included in the range A becomes larger.

[0049] Also, curve fitting may be performed on the fundus image in the OCT data, and a curvature level may be obtained based on the curvature of the fitting curve. During curve fitting, segmentation processing for the fundus image may be appropriately performed.

[0050] Also, the polarization of the measurement light and the reference light is also correlated with the interference sensitivity in each depth region. For example, the polarization state of the reflected / scattered light is different for each tissue of the eye to be examined (for each layer in the fundus). Therefore, when the polarization of the measurement light and the reference light is adjusted so that the sensitivity (interference sensitivity) is optimized for a certain tissue, this adjustment does not necessarily result in good sensitivity for tissues in other depth regions.

[0051] Also, for example, the above accuracy may be caused by focusing. That is, the depth region closer to the focus position of the measurement light has higher-contrast data, but the contrast decreases as the distance from the focus position increases. Therefore, when paying attention to the resolution as an index indicating the accuracy, it can be said that the OCT data is relatively highly accurate in the depth region close to the focus position.

[0052] Therefore, in this embodiment, for example, at least one of the focus position and the polarization may be adjusted in conjunction with the adjustment of the optical path length. In this case, the focus position may be adjusted so that the contrast in the area near the zero delay position Z is optimized. Also, the polarization may be adjusted so that the interference sensitivity in the tissue near the zero delay position Z is optimized. For example, refer to JP 2018-102789 A by the present applicant for a method of adjusting the polarization so that the interference sensitivity in a specific tissue is optimized.

[0053] However, in this embodiment, the high-precision area in this embodiment is changed at least according to the optical path length, but this is not necessarily limited to this, and may be changed at least according to at least one of the focus position and the polarization.

[0054] Furthermore, in conjunction with the control of the high-precision region, the amount of dispersion of the optical system between the measurement light path and the reference light may be changed, thereby obtaining better OCT data.

[0055] Furthermore, in this embodiment, the image processor may correct the layer thickness of the OCT data according to the change in the optical path length of the measurement light to the retinal surface between each scanning position, and display the corrected layer thickness. That is, in an area where the influence of the curvature is large, such as the peripheral area of the fundus, the layer thickness is depicted as if it were thinner (see FIG. 4). Therefore, an image in which the influence of the curvature has been corrected may be displayed by performing image conversion such as deforming the image and adjusting the aspect ratio, taking into account the influence of the curvature.

[0056] "Example" Hereinafter, an optical coherence tomography (OCT) device shown in Figures 1 and 2 will be described as an embodiment. The OCT device according to this embodiment has, for example, a basic configuration of a spectral domain OCT (SD-OCT).

[0057] The OCT device 1 includes a light source 102, an OCT optical system 100, and an arithmetic controller (arithmetic control unit) 70 (see FIG. 2). In addition, the OCT device may be provided with a memory 72, a display unit 75, a front image observation system (not shown), and a fixation target projection system. The arithmetic controller (hereinafter referred to as the control unit) 70 is connected to the light source 102, the OCT optical system 100, the memory 72, and the display unit 75.

[0058] The OCT optical system 100 guides the measurement light to the eye E by the light guiding optical system 150. The OCT optical system 100 guides the reference light to the reference optical system 110. The OCT optical system 100 causes the detector (light receiving element) 120 to receive the interference signal light obtained by the interference between the measurement light reflected by the eye E and the reference light. Note that the OCT optical system 100 is mounted in a housing (device main body) (not shown), and alignment with respect to the eye to be examined may be performed by three-dimensionally moving the housing with respect to the eye E by a well-known alignment movement mechanism via an operation member such as a joystick.

[0059] The SD-OCT method is used for the OCT optical system 100. As the light source 102, one that emits a light beam with a low coherence length is used, and as the detector 120, a spectral detector that spectrally detects the spectral interference signal for each wavelength component is used.

[0060] The coupler (splitter) 104 is used as a first optical splitter and splits the light emitted from the light source 102 into a measurement optical path and a reference optical path. The coupler 104 guides the light from the light source 102 to the optical fiber 152 on the measurement optical path side and also guides it to the reference optical system 110 on the reference optical path side.

[0061] <Light guiding optical system> The light guiding optical system 150 is provided to guide the measurement light to the eye E. The light guiding optical system 150 may be sequentially provided with, for example, an optical fiber 152, a collimator lens 153, a variable beam expander 154, a focusing lens 155, an optical scanner 156, and an objective lens system 158 (the objective optical system in this embodiment). In this case, the measurement light is emitted from the emission end of the optical fiber 152 and becomes a parallel beam by the collimator lens 153. Then, after being adjusted to a desired light beam diameter by the variable beam expander 154, it travels toward the optical scanner 156 via the focusing lens 155. The focusing lens 155 is displaceable along the optical axis by a driving unit (not shown) and is used to adjust the light condensing state on the fundus. The light that has passed through the optical scanner 156 is irradiated onto the eye E via the objective lens system 158. A first turning point P1 is formed at a position conjugate with the optical scanner 156 with respect to the objective lens system 158. When the anterior eye part is located at this turning point P1, the measurement light reaches the fundus without being scattered. Also, the measurement light is scanned on the fundus according to the operation of the optical scanner 156. At this time, the measurement light is scattered and reflected by the tissues of the fundus.

[0062] The optical scanner 156 may scan the measurement light in the XY directions (transverse directions) on the eye E. The optical scanner 156 is, for example, two galvanometer mirrors, and their reflection angles are arbitrarily adjusted by a driving mechanism. The light beam emitted from the light source 102 has its reflection (travel) direction changed and is scanned in an arbitrary direction on the fundus. As the optical scanner 156, for example, in addition to a reflection mirror (galvanometer mirror, polygon mirror, resonant scanner), an acousto-optic element (AOM) that changes the traveling (deflecting) direction of light may also be used.

[0063] The scattered light (reflected light) from the eye E by the measurement light is incident on the optical fiber 152 along the path during light projection and reaches the coupler 104. The coupler 104 guides the light from the optical fiber 152 to the optical path toward the detector 120.

[0064] <Attachment Optical System> In the OCT apparatus of the embodiment, the attachment optical system 160 (an example of the "field angle switching unit") is inserted and removed between the objective optical system 158 in the light guiding optical system 150 and the eye to be examined E. By attaching and detaching the lens barrel including the attachment optical system to a housing surface (not shown), the attachment optical system 160 is inserted and removed between the objective optical system 158 and the eye to be examined E.

[0065] The attachment optical system 160 may include a plurality of lenses 161 to 164. Here, in the attachment optical system 160 shown in FIG. 1, the lens having the main positive power is the lens 164 placed in front of the eye to be examined. At least the insertion and removal position of the lens 164 is between the first turning point P1 formed by the objective optical system 158 and the eye to be examined E. By bending at least the measurement light passing through the first turning point P1 toward the optical axis L by the lens 164, a second turning point P2 is formed at a position conjugate with the light scanner 156 with respect to the attachment optical system 160 and the objective optical system 158. That is, the attachment optical system 160 is an optical system that relays the turning point P1 to the turning point P2.

[0066] In this embodiment, the solid angle of the measurement light at the second turning point P2 is larger than the solid angle at the first turning point P1. For example, the solid angle at the second turning point P2 is increased to more than twice the solid angle at the first turning point P1. In this embodiment, in the retracted state, it is possible to scan with a field angle of about φ60°, and in the inserted state, it is possible to scan with a field angle of about φ100°.

[0067] The variable beam expander 154 is a light beam diameter adjustment unit in the embodiment. As an example, the variable beam expander 154 may have a plurality of lenses forming a bilateral telecentric optical system, and the beam diameter may be switched by changing the lens interval by an actuator. The variable beam expander 154 adjusts the beam diameter of the measurement light based on an instruction from the control unit 70.

[0068] If the beam diameter of the measurement light guided from the variable beam expander 154 to the optical scanner 156 is constant between the inserted state and the retracted state, the spot size of the measurement light on the fundus is proportional to the angular field of view. Therefore, the resolution in the inserted state is lower than that in the retracted state. Thus, in this embodiment, the control unit 70 drives the variable beam expander 154 in accordance with the insertion / removal of the attachment optical system, and reduces the beam diameter in the inserted state with respect to the retracted state. The ratio of the beam diameters (the beam diameter in the variable beam expander 154) between the inserted state and the retracted state is the inverse ratio of the angular fields of view between the inserted state and the retracted state, so that the change in resolution based on the insertion / removal of the attachment optical system 160 can be suppressed.

[0069] Incidentally, in order to ensure a sufficient working distance, the measurement light needs to be bent from a position with a sufficient ray height toward the optical axis L by the attachment optical system 160. Further, in order to suppress the aberration generated in the attachment optical system 160 within an allowable range, there are limitations on the power of each lens included in the attachment optical system 160. Therefore, it is difficult to shorten the optical path length of the attachment optical system 160.

[0070] In a conventional OCT apparatus, although there is a configuration for adjusting the optical path length difference between the reference light and the measurement light, there is no configuration having an adjustment range applicable to the insertion / removal of the attachment optical system 160. For example, conventionally, there is known an apparatus that enables anterior eye segment imaging by attaching an optical adapter to fundus imaging OCT (see, for example, "Japanese Patent Application Laid-Open No. 2011-147612" by the present applicant). However, this optical adapter does not relay the pivot point formed by the optical system of the apparatus main body, and since there is no requirement to widen the scanning range, it can be formed with a relatively short optical path length. Further, as the optical adapter is inserted, the position of the image plane shifts from the fundus to the anterior eye segment. Therefore, it has not been necessary to greatly adjust the optical path length difference as the optical adapter is inserted.

[0071] <Reference optical system> The reference optical system 110 generates reference light that is combined with the fundus reflected light of the measurement light. The reference light passing through the reference optical system 110 is combined with the light from the measurement optical path at the coupler 148 and interferes. The reference optical system 110 may be of the Michelson type or the Mach-Zehnder type.

[0072] The reference optical system 110 shown in FIG. 1 is formed by a transmission optical system. In this case, the reference optical system 110 guides the light from the coupler 104 to the detector 120 by transmitting it without returning it. Not limited to this, the reference optical system 110 may be formed by, for example, a reflection optical system, and the light from the coupler 104 may be guided to the detector 120 by reflecting it with the reflection optical system.

[0073] In this embodiment, the reference optical system 110 may be provided with a plurality of reference optical paths. For example, in FIG. 1, the reference optical path is branched by the coupler 140 into an optical path passing through the fiber 141 (the first branched optical path in this embodiment) and an optical path passing through the fiber 142 (the second branched optical path in this embodiment). The fiber 141 and the fiber 142 are connected to the coupler 143, whereby the two branched optical paths are combined and incident on the coupler 148 via the optical path length adjustment unit 145 and the polarization adjustment unit 147.

[0074] In this embodiment, the reference light from the coupler 104 is simultaneously guided to the fiber 141 and the fiber 142 by the coupler 143. The light passing through either the fiber 141 or the fiber 142 is combined with the measurement light (fundus reflected light) at the coupler 148.

[0075] The optical path length difference between the fiber 141 and the fiber 142, that is, the optical path length difference between the first branched optical path and the second branched optical path, may be a fixed value. In this embodiment, it has an optical path length difference substantially the same as the optical path length of the attachment optical system 160.

[0076] Note that an optical member for adjusting the optical path length difference between the measurement light path and the reference light path may be disposed in at least one of the measurement light path and the reference light path. As an example, in the optical system shown in FIG. 1, a reference light path adjustment unit 145 is provided, and at this location, a mirror 145a having two orthogonal surfaces is provided to adjust the optical path length difference between the measurement light and the reference light. By moving this mirror 145a in the direction of the arrow by an actuator 145b, the optical path length of the reference light path can be increased or decreased. Of course, the configuration for adjusting the optical path length difference between the measurement light and the reference light is not limited to this. For example, in the light guiding optical system 150, when the collimator lens 153 and the coupler are integrally moved, the optical path length of the measurement light is adjusted, and as a result, the optical path length difference between the measurement light and the reference light may be adjusted.

[0077] Here, in this embodiment, since the reference light path adjustment unit 145 is provided on the optical path between the coupler 143 and the coupler 148, that is, on the common optical path of the first branched optical path and the second branched optical path, the adjustment of the optical path length difference between the measurement light path and the reference light path, specifically, the adjustment related to the individual differences in the axial length of the eye, can be performed collectively for both the first branched optical path and the second branched optical path.

[0078] Note that the adjustment range of the optical path length in the reference light path adjustment unit 145 is preferably set to be sufficiently short with respect to the optical path length difference between the fiber 141 and the fiber 142 (in other words, the optical path length difference between the first branched optical path and the second branched optical path).

[0079] <Photodetector> The detector 120 is provided for detecting the interference between the light from the measurement light path and the light from the reference light path. In this embodiment, the detector 120 is a spectroscopic detector, and includes, for example, a spectroscope and a line sensor. The measurement light and the reference light multiplexed by the coupler 148 are spectroscopically separated by the spectroscope and received by different regions (pixels) of the line sensor for each wavelength. Thereby, the output for each pixel is acquired as a spectral interference signal.

[0080] The curvature of the fundus and the imaging plane (condensing plane) of the measurement light do not necessarily coincide. In the inserted state of the attachment optical system 150, the deviation between the two increases at least in either the central part or the peripheral part of the fundus. Therefore, in the photodetector, it is preferable that a sufficient effective Depth range considering the deviation is ensured. For example, in SD-OCT, it is preferable to employ a line camera with a sufficient number of pixels for the expected effective Depth range. Further, a configuration described later as a <modification example> may be further employed.

[0081] <Acquisition of depth information> The control unit 70 processes (Fourier analyzes) the spectral signal detected by the detector 120 to obtain OCT data of the eye to be examined.

[0082] The spectral signal (spectral data) may be rewritten as a function of the wavelength λ and converted into a function I(k) that is equally spaced with respect to the wave number k (=2π / λ). Alternatively, it may be acquired from the beginning as a function I(k) that is equally spaced with respect to the wave number k (K-CLOCK technology). The arithmetic controller may obtain OCT data in the depth (Z) region by Fourier-transforming the spectral signal in the wave number k space.

[0083] Furthermore, the information after Fourier transform may be represented as a signal including a real component and an imaginary component in the Z space. The control unit 70 may obtain OCT data by obtaining the absolute values of the real component and the imaginary component in the signal in the Z space.

[0084] Here, in the coupler 148, the reference light passing through the first branched optical path and the reference light passing through the second branched optical path are simultaneously guided, and each is multiplexed with the measurement light. Since there is a large optical path length difference, about the same as the optical path length of the attachment optical system 160, between the first branched optical path and the second branched optical path, among the reference light passing through the first branched optical path and the reference light passing through the second branched optical path, although interference with the measurement light is likely to occur in one of them, interference is less likely to occur in the other. Although the spectral interference signal from the detector 120 includes a component due to the reference light passing through the first branched optical path and a component due to the reference light passing through the second branched optical path, among the two types of components, one corresponding to the state of the light guiding optical system 150 is obtained as a significantly stronger signal than the other. As a result, good OCT data can be obtained regardless of the state of the light guiding optical system 150. That is, by having a plurality of reference optical paths having an optical path length difference corresponding to the attachment optical system 160, the OCT apparatus according to the embodiment compensates for the amount of change in the optical path length difference between the measurement optical path and the reference optical path, which is the amount of change associated with the insertion and removal of the attachment optical system 160, regardless of the state of the light guiding optical system 150.

[0085] Note that it is necessary to control the reference optical path adjustment unit 145 and pre-adjust the optical path length difference between the measurement optical path and the reference optical path, which is the optical path length difference related to the axial length of the eye E to be examined. In this embodiment, for example, the mirror 145a may be moved within a predetermined adjustment range, the interference signal may be acquired at each position, and the position of the mirror 145a may be determined based on the position where the intensity of the interference signal becomes the highest. When the adjustment range of the optical path length in the reference optical path adjustment unit 145 is sufficiently small with respect to the optical path length difference between the first branched optical path and the second branched optical path), within the adjustment range of the reference optical path adjustment unit 145, the position where the intensity peak of the interference signal occurs can be uniquely specified.

[0086] In the inserted state, since the fundus reflected light of the measurement light from the peripheral fundus part becomes weaker than the reflected light from the fundus central part, the optical path length difference between the measurement optical path and the reference optical path may be adjusted by the reference optical path adjustment unit 145 so that the zero delay position between the measurement optical path and the reference optical path overlaps with the desired fundus tissue (for example, retina, choroid, sclera, etc.) or transparent tissue (vitreous body, etc.) in the peripheral fundus part.

[0087] <Dispersion correction by software> In this embodiment, the control unit 70 may perform dispersion correction processing by software on the spectral data output from the detector 120. The control unit 70 obtains OCT data based on the spectral data after dispersion correction. For this reason, a difference in image quality occurs between the real image and the virtual image.

[0088] That is, in this embodiment, the difference in the dispersion amount of the optical system between the measurement optical path and the reference optical path is corrected signal - processing - wise. Specifically, it is performed by applying the correction value stored in the memory 72 in advance to the processing of the above - mentioned spectral signal.

[0089] The control unit 70 acquires the spectral intensity of light based on the received light signal output from the detector 120 and rewrites it as a function of the wavelength λ. Next, the spectral intensity I(λ) is converted into an equally - spaced function I(k) with respect to the wave number k(=2π / λ).

[0090] The influence of the dispersion mismatch between the measurement light and the reference light shifts the phase of the interference component, lowers the peak of the combined wave signal at each wavelength, and gives the signal a spread (the resolution decreases). Therefore, in dispersion correction, by returning the phase shifted for each wavelength, the decrease in resolution due to the decrease in the interference signal is corrected. In this case, the amount of phase shift φ(k) as a function of the wave number k is obtained in advance, and the phase shift is returned for each value of k by I(k)·exp - iφ(k). Here The phase φ(k) to be dispersion-corrected can be obtained in advance by calibration, or the phase φ(k) corresponding to the acquired tomographic image may be obtained. Then, parameters for dispersion correction (for example, the phase φ(k)) are stored in the memory 72.

[0091] Thereafter, the control unit 70 performs Fourier transform on the spectrum intensity I(k) after dispersion correction corrected by the set dispersion correction data, thereby obtaining OCT data.

[0092] For example, a first dispersion correction value (for positive image) is acquired from the memory 72 as a dispersion correction value for correcting the influence of dispersion on the real image, the spectrum data output from the detector 120 is corrected using the first dispersion correction value, and the corrected spectrum intensity data is Fourier-transformed to form OCT data. The real image R is acquired as a high-sensitivity and high-resolution image, and the virtual image M (mirror image) is acquired as a low-resolution blurred image due to the difference in dispersion correction values.

[0093] Thereby, when the real image is acquired in the first image region G1, the real image is acquired as a high-sensitivity and high-resolution image, and the virtual image (mirror image) thereof is acquired as a low-resolution blurred image in the second image region G2 due to the difference in dispersion correction values. On the other hand, when the real image is acquired in the second image region G2, the virtual image thereof is acquired as a low-resolution blurred image in the first image region G1 due to the difference in dispersion correction values.

[0094] Of course, it is not limited to this, and software dispersion correction for the virtual image M may be performed. In this case, the virtual image M is acquired as a high-sensitivity and high-resolution image, and the real image R is acquired as a low-resolution blurred image.

[0095] For details of the method of performing dispersion correction by software as described above, refer to U.S. Patent No. 6,980,299, Japanese Patent Publication No. 2008-501118, etc. Also, refer to Japanese Patent Application Laid-Open No. 2010-29648.

[0096] When software-based dispersion correction processing is performed and OCT data at the center of the fundus is obtained, for example, the control unit 70 may extract the image data with higher sensitivity and resolution from among the real image and virtual image data.

[0097] In this embodiment, a first correction value corresponding to the retracted state and a second correction value different from the first correction value and corresponding to the inserted state are stored in advance in the memory 72, and the correction value to be applied is switched according to the state of the light guiding optical system. As a result, in the OCT apparatus according to the embodiment, the change amount of the dispersion amount between the measurement optical path and the reference optical path, that is, the change amount accompanying the insertion / removal of the attachment optical system 160, is compensated in each state of the light guiding optical system 150.

[0098] Furthermore, in this embodiment, a plurality of second correction values corresponding to the inserted state are set according to the scanning position of the measurement light. Specifically, a correction value for the center of the fundus and a correction value for the peripheral part of the fundus are set as different values as the second correction value. For example, the first correction value may be applied to a region within φ60° of the fundus, and the second correction value may be set as a value to be applied to a region farther than φ60°. Since the attachment optical system 160 has a large power as a whole, it is considered that a significant difference in the dispersion amount occurs between the light beam passing through the center of the fundus and the light beam passing through the peripheral part of the fundus. In contrast, in this embodiment, since the correction value of the dispersion amount is changed according to the irradiation position of the measurement light on the fundus, good OCT data can be obtained in a wide-angle region of the fundus.

[0099] Of course, the second correction value may be further subdivided. For example, the entire fundus may be divided into the center of the fundus, a first peripheral part of the fundus outside the center of the fundus, and a second peripheral part of the fundus outside the first peripheral part of the fundus, and a correction value corresponding to the center of the fundus, a correction value corresponding to the first peripheral part of the fundus, and a correction value corresponding to the second peripheral part of the fundus may be set as different values as the second correction value.

[0100] <Control system> The control unit 70 may include a CPU (processor), a RAM, a ROM, etc. (see Fig. 2). For example, the CPU of the control unit 70 may control the OCT device. The RAM temporarily stores various information. Various programs for controlling the operation of the OCT device, initial values, etc. may be stored in the ROM of the control unit 70.

[0101] A non-volatile memory (hereinafter abbreviated as memory) 72 as a storage unit, a display unit 75, etc. may be electrically connected to the control unit 70. As the memory 72, a non-transitory storage medium that can retain the stored content even when the power supply is cut off may be used. For example, a hard disk drive, a flash ROM, and a USB memory detachably attached to the OCT device can be used as the memory 72. A control program for controlling the acquisition of OCT data and the shooting of OCT images may be stored in the memory 72. In addition, various information related to shooting, in addition to the OCT images generated from the OCT data, may be stored in the memory 72. The display unit 75 may display the OCT images generated from the OCT data.

[0102] Note that a plug-in / detachment detection unit that automatically detects whether or not the attachment optical system 160 is inserted into the light guiding optical system may be provided. Based on the detection signal from the detection unit, the control unit 70 may execute the control and processing of each part in the OCT optical system 100. For example, the switching control of the light beam diameter by the variable beam expander 154, the setting control of the zero delay position by the reference optical path adjustment unit 145, the change process of the dispersion amount of the optical system between the measurement optical path and the reference light, etc. may be appropriately executed. The insertion detection unit may be a sensor disposed near the objective optical system 158.

[0103] Of course, the examiner may input information specifying the state of the light guiding optical system (the insertion state / retraction state of the attachment optical system 160) to the UI (user interface) of the OCT device, and based on this information, the control unit may execute the control and processing of each part in the OCT optical system 100.

[0104] <Operation Explanation> Next, the operation of the device in this embodiment will be described according to the flowchart of FIG. 5. The flowchart of FIG. 5 shows the flow from various settings to shooting.

[0105] <Setting of the shooting angle> In the flowchart of FIG. 5, first, based on the insertion / retraction of the attachment optical system 160, the shooting angle is set (S1). The operation of setting the shooting angle is part of the operation of setting the shooting range in this embodiment.

[0106] <Alignment> Next, alignment of the device with respect to the eye to be examined is performed (S2). After having the subject fixate on a fixation target in advance, based on the anterior eye observation image captured by a front-eye observation camera (not shown), the positional relationship between the eye to be examined and the measurement optical axis is adjusted. For example, it is adjusted so that the pupil center of the eye to be examined coincides with the measurement optical axis. The alignment may be adjusted manually or automatically. At the position where the alignment adjustment is completed, a frontal image of the fundus may be acquired as an observation image through an observation optical system (not shown), and display on the monitor 75 may be started (see FIG. 6).

[0107] <Setting of the scan range> Next, the scan range is set (S3). For example, as shown in FIG. 6, the scan line may be set based on an operation input through the observation image displayed on the screen. The operation input at this time may be to set at least the start point and the end point of the scan line on the observation image. Further, the control unit 70 may set the scan range by selecting any one from a plurality of predetermined scan patterns. In this case, the selection operation of the scan pattern is input through the input interface 80. Examples of the scan pattern include raster scan, multi-scan that scans a plurality of scan lines spaced apart from each other, cross-scan in which a plurality of scan lines intersect each other, radial scan in which a plurality of scan lines are formed radially, and the like.

[0108] <Optimization control> Next, optimization control is executed (S4). The optimization control may be started, for example, by operating the Optimize button 501. By the optimization control, high-precision (for example, high-sensitivity and high-resolution) OCT data can be acquired at a desired fundus site. Note that by the optimization control (S4) of the present embodiment, the optical path length, focus, and polarization state are adjusted.

[0109] In the present embodiment, the optimization control is started using the optimization start operation on the input interface 80 as a trigger. Hereinafter, the optimization control in the present embodiment will be described as an example with reference to the flowchart of FIG. 7.

[0110] <Initialization> First, the control unit 70 initializes the optical path length and the focus position (S10). For example, the control unit 70 moves each of the focusing lens 155 and the position of the mirror 145a to a predetermined initial position (movement start position). In the present embodiment, each initial position may be either the upper limit or the lower limit of the movable range.

[0111] <Axial length measurement> After initialization, the axial length of the eye to be examined is measured (S12). The control unit 70 adjusts the optical path length of the reference light so that the zero-delay position Z is arranged on the retinal surface. After the adjustment, the control unit 70 acquires the spectral interference signal between the measurement light irradiated along the optical axis L and the reference light.

[0112] Although details are omitted, the axial length of the eye to be examined is calculated and acquired by the control unit 70 based on the working distance and the depth position information of the retinal surface acquired through the OCT optical system. At this time, the distance between the irradiation position of the measurement light, that is, the irradiation position on the cornea and the irradiation position on the retina, can be obtained as the axial length.

[0113] Note that the working distance is the distance between the device and the eye to be examined in the front-rear direction. In this embodiment, it is assumed that the working distance is a fixed value. However, the working distance may be an actually measured value. In this case, the working distance may be obtained from the driving amount of the driving unit for adjusting the positional relationship in the Z direction between the OCT optical system 100 and the eye to be examined.

[0114] <Determine the curvature level of the fundus image> Next, the control unit 70 executes a determination process for the curvature level. In the determination process, the curvature level of the fundus image in the imaging range set in the processes of S1 and S3 is determined. The depth region (high-precision region) where relatively high-precision OCT data can be obtained is adjusted according to the determination result of the curvature level.

[0115] In the flowchart of FIG. 7, S13, S14, S15, and S16 are shown as an example of the determination process in this embodiment.

[0116] The flowchart of FIG. 7 includes two types of determination processes.

[0117] In the first determination process (S13, S14), the curvature level is determined in consideration of the axial length of the eye and the scan length. For example, regarding the axial length of the eye, a threshold value for determining the axial length of the eye as a long axial length assuming that the fundus is greatly curved is compared with the axial length of the eye to be examined obtained in the process of S12 (S13). As an example, 28 mm is set as the threshold value. If the axial length of the eye to be examined is less than the threshold value (S13: No), the process proceeds to the second determination process (S15, S16).

[0118] On the other hand, when the axial length of the eye to be examined is less than the threshold value (S13: Yes), it is determined whether the scan length set in the process of S3 is equal to or greater than the threshold value (here, 9 mm as an example) (S14). Here, even if the fundus itself is greatly curved due to a long axial length, if the scan length is sufficiently short, the influence of the curvature (height difference) on the image of the fundus is small. On the contrary, the greater the scan length, the greater the influence of the curvature (height difference) on the image of the fundus. The threshold value may be the scan length at which the accuracy of the OCT data between each depth position where the fundus image exists begins to be a problem in the case of a long axial length eye with a greatly curved fundus for a normal eye. This threshold value may be empirically obtained through experiments or the like.

[0119] When the scan length is equal to or greater than the threshold value (S14: No), the control unit 70 optimizes various conditions assuming that the curvature level is the second level (S18). In the present embodiment, the optical path length is adjusted so that the zero-delay position Z is arranged on the shallower layer side than the retinal surface in the central region of the fundus image. Further, the focus position may be adjusted so that the contrast of the region on the retinal surface side of the fundus image is maximized. In addition, the polarizer may be driven so that the interference sensitivity in the region on the retinal surface side of the fundus image is maximized. When the curvature level is the second level (relatively large curvature), these adjustments make it easier to acquire (photograph) OCT data with a brighter peripheral side. Therefore, when photographing the peripheral part of the fundus, it becomes easier to favorably observe the lesions in the peripheral part. In addition, in a long axial length eye, it becomes easier to acquire overall bright OCT data due to the influence of thinning in the central part.

[0120] On the other hand, when the scan length is less than the threshold value (S14: No), the process proceeds to the second determination process (S15, S16).

[0121] In the second determination process (S15, S16), the curvature level is determined in consideration of the angle of view and the scan range.

[0122] In this case, first, it is determined whether the angular field of view of the OCT optical system 100 is the first angular field of view or the second angular field of view (S15). When it is the second angular field of view, a wide-angle region including the central part and the peripheral part of the fundus can be scanned. Particularly when the peripheral part of the fundus is scanned, the accuracy of the OCT data between the depth positions where the fundus images exist can be a problem. Therefore, in this embodiment, when it is the second angular field of view (S15: Yes), it is determined whether the scan range set in the process of S3 includes the peripheral part of the fundus (S16). And when the peripheral part of the fundus is included in the scan range (S16: Yes), the control unit 70 optimizes various conditions assuming that the curvature level is the second level (S18).

[0123] Also, in the process of S14, when the angular field of view is the first angular field of view (S14: Yes), it is considered that the curvature of the fundus image is small throughout the imaging range. In this case, the control unit 70 optimizes various conditions assuming that the curvature level is the first level (S17). Also, even when the angular field of view is the second angular field of view (S14: No), and when the scan range set in the process of S3 is only the central part of the fundus (S16: No), the control unit 70 optimizes various conditions assuming that the curvature level is the first level (S17).

[0124] In this case, in this embodiment, the optical path length is adjusted so that the zero-delay position Z is arranged deeper than the choroid in the central region of the fundus image. Also, the focus position may be adjusted so that the contrast of the region on the choroid side of the fundus image is maximized. Additionally, the polarizer may be driven so that the interference sensitivity in the region on the choroid side of the fundus image is maximized. When the curvature level is the first level (relatively small curvature), with these adjustments, overall brighter OCT data is likely to be acquired (captured).

[0125] <Imaging process> Returning to the flowchart of FIG. 5, the description will be continued. In this embodiment, after the optimization control (S4), the imaging process is executed (S5). As a result, OCT data (tomographic image) in which a high-precision region is set at a depth position corresponding to the curvature level is captured as a captured image. The captured image is stored in the memory 72. It may also be displayed on the confirmation screen.

[0126] In addition, information regarding the depth position of the high-precision region in the captured OCT data may also be stored in the memory 72. This information may be, for example, the parameters at the time of imaging of each adjustment unit (for example, at least any one of an optical path length adjustment unit, a focus adjustment unit, and a polarization adjustment unit) regarding the position of the depth region. This information may be stored in association with the identification information of the subject. When re-imaging (follow-up imaging) is performed at a later date, the control unit 70 may reproduce the adjustment state of each adjustment unit based on the above information and perform imaging. In this case, by making the adjustment states of each adjustment unit coincide for each imaging, it is easy to appropriately compare the OCT data captured on different days.

[0127] Also, at the time of follow-up imaging, it is conceivable that eye characteristics such as the axial length of the eye and the refractive error of the eye to be examined have changed since the previous imaging. In this case, after estimating the change in the curvature level according to the change amount of the eye characteristics, the depth position of the high-precision region may be adjusted according to the estimated curvature level. "Modification example" As described above, the present disclosure has been described based on the embodiments and examples, but the present disclosure is not necessarily limited thereto.

[0128] For example, in the imaging process of the above embodiment, unambiguously, OCT data in which the control unit 70 has set a high-precision area at a depth position corresponding to the curvature level is imaged. However, it is not necessarily limited to this, and before and after the optimization control (S4), the position of the high-precision area may be adjustable to a position according to an operation from the examiner. For example, it may be possible to manually set which side, the retina side or the choroid side, to image with higher sensitivity based on the operation input. For example, each time the switching button 502 shown in FIG. 6 is selected, the depth position of the high-precision area may be switched between the retina side and the choroid side.

[0129] Also, on the OCT image, by designating an area to be observed with high precision, the position of the high-precision area may be changed with reference to the designated position. For example, when the upper part is designated in the image of the fundus, the zero-delay position Z may be moved to the front side of the retinal surface, etc., and when the lower part is designated, the zero-delay position Z may be moved to the back side of the choroid, etc.

[0130] Also, for example, in the above description, an embodiment of an apparatus for imaging OCT data of the fundus has been described, but it is not necessarily limited to this, and the above technology can also be applied to an apparatus for imaging OCT data of the anterior segment of the eye. That is, when a plurality of tissues are included in the imaging range, it may be used to automatically determine the tissue to be depicted with high precision according to the imaging settings.

[0131] In this case, for example, the position of the high-precision area may be adjusted according to various scan settings (imaging settings) such as the angle of view and the scan pattern. Also, different positions of the high-precision area may be associated in advance for each part of the anterior segment of the eye (front side of the cornea, back side of the cornea, front side of the lens, back side of the lens, etc.), and the position of the high-precision area may be controlled by specifying the part to be imaged based on the setting operation.

Claims

1. An optical splitter for splitting light from an OCT light source into a measurement optical path and a reference optical path, and an optical path length changing means for changing the optical path length of at least one of the measurement optical path and the reference optical path, having an OCT optical system for detecting a spectral interference signal between the measurement light guided to the fundus of an eye to be examined through the measurement optical path and the reference light from the reference optical path, image processing means for processing the spectral interference signal output from the OCT optical system to obtain OCT data of the fundus, a control means for adjusting the zero-delay position where the optical path lengths of the measurement optical path and the reference optical path coincide by controlling the optical path length changing means according to the curvature level of the image of the fundus in the imaging range of the OCT data, and for displacing the zero-delay position to a shallower layer when the curvature level is a second level with a greater curvature than the first level when the curvature level is the first level. An OCT apparatus comprising the same.

2. An optical splitter for splitting light from an OCT light source into a measurement optical path and a reference optical path, and an optical path length changing means for changing the optical path length of at least one of the measurement optical path and the reference optical path, having an OCT optical system for detecting a spectral interference signal between the measurement light guided to the fundus of an eye to be examined through the measurement optical path and the reference light from the reference optical path, axial length information acquisition means for acquiring axial length information regarding the axial length value of the eye to be examined, image processing means for processing the spectral interference signal output from the OCT optical system to obtain OCT data of the fundus, control means for adjusting the zero-delay position where the optical path lengths of the measurement optical path and the reference optical path coincide by controlling the optical path length changing means according to the curvature level of the image of the fundus in the imaging range of the OCT data, taking into account the axial length information, An OCT apparatus comprising the same.

3. The OCT apparatus according to claim 2, wherein the control means displaces the zero-delay position to a shallower layer when the curvature level is a second level with a greater curvature than the first level when the curvature level is the first level.

Images