Ophthalmic imaging equipment

Abstract

To acquire a high-quality OCT image while performing a wide-angle OCT scan at a high speed.SOLUTION: An ophthalmological imaging device according to an embodiment applies a preparatory OCT scan to the subject's eye, which passes through both a central region and a peripheral region of the OCT scan application area, to acquire data. From this data, a preparatory image is constructed, and focus control parameters are set on the basis of the preparatory image. Thereafter, the ophthalmological imaging device performs an OCT scan according to a scan pattern including a continuous first partial pattern for the central region and a continuous second partial pattern for the peripheral region, while controlling the focal position in the optical path of measurement light according to the set focus control parameters.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This invention relates to an ophthalmic imaging device. [Background technology]

[0002] In ophthalmology, the importance of diagnostic imaging and image analysis is increasing. The application of optical coherence tomography (OCT) to ophthalmology is particularly accelerating this trend. OCT enables three-dimensional imaging of the eye under examination, as well as three-dimensional structural and functional analysis, proving invaluable for obtaining the distribution of various measured values, for example.

[0003] In recent years, efforts have been made to expand the OCT scanning range, that is, to widen the field of view of OCT. For example, in order to scan a wide area from the center to the periphery of the fundus, devices have been developed that feature an increased deflection angle of the optical scanner (such as a galvanometer mirror) and corresponding optimization of structure, control, and imaging (see, for example, Patent Documents 1 and 2).

[0004] When OCT scans (generally raster scans) are applied to a wide area of ​​the fundus, image quality deteriorates, particularly in areas far from the center of the fundus (referred to as the peripheral region), due to the effects of aberrations in the ocular optical system. This is because the aberrations of the ocular ball are greater in the peripheral region than in the central region of the fundus (see, for example, Non-Patent Document 1).

[0005] One possible solution to this image degradation is to perform focus control. However, since the speed of focus control is considerably slower than the speed of OCT scanning (for example, the repetition rate of A-scans), it is not practical to perform focus control while applying high-speed raster scanning to a wide area of ​​the fundus. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-086311 [Patent Document 2] Japanese Patent Publication No. 2017-047113 [Non-patent literature]

[0007] [Non-Patent Document 1] JAMES POLANS, 4 others, "Wide-field optical model of the human eye with asymmetrically tilted and decentered lens that reproduces measured ocular aberrations", Optica, February 2015, Vol. 2, No. 2, p. 124-134 [Overview of the project] [Problems that the invention aims to solve]

[0008] The objective of this invention is to acquire high-quality OCT images while performing wide-angle OCT scans at high speed. [Means for solving the problem]

[0009] A first aspect of an exemplary embodiment is an ophthalmic imaging apparatus including: a data acquisition unit that applies an optical coherence tomography (OCT) scan to an eye under examination to collect data; an image construction unit that constructs an image from the data collected by the data acquisition unit; a focal position changing unit provided in the optical path of the measurement light projected onto the eye under examination by the data acquisition unit; a scan control unit that controls the data acquisition unit according to a scan pattern including a continuous first partial pattern for the central region of the OCT scan application area and a continuous second partial pattern for the peripheral region; and a focus control unit that controls the focal position changing unit to apply a first focal position in parallel with the application of the OCT scan to at least a portion of the first partial pattern, and to apply a second focal position different from the first focal position in parallel with the application of the OCT scan to at least a portion of the second partial pattern.

[0010] A second aspect of the exemplary embodiment is the ophthalmic imaging apparatus of the first aspect, wherein the scan pattern includes a curved scan pattern defined in a polar coordinate system with the center of the OCT scan application area as the origin.

[0011] A third embodiment of the exemplary embodiment is an ophthalmic imaging apparatus of the second embodiment, wherein the curved scan pattern is either a spiral scan pattern extending from the center to the outer edge of the OCT scan application area, or a spiral scan pattern extending from the outer edge to the center of the OCT scan application area.

[0012] A fourth aspect of the exemplary embodiment is an ophthalmic imaging apparatus of the second or third embodiment, wherein the image construction unit forms an image defined in polar coordinates from data collected by an OCT scan applied to the eye under examination according to the curved scan pattern, and converts the image defined in polar coordinates into an image defined in a three-dimensional Cartesian coordinate system.

[0013] A fifth embodiment of the exemplary embodiment is an ophthalmic imaging apparatus according to any of the first to fourth embodiments, wherein the first focal length corresponding to the first focal position is longer than the second focal length corresponding to the second focal position.

[0014] A sixth aspect of the exemplary embodiment is an ophthalmic imaging apparatus according to any of the first to fifth aspects, wherein, prior to an OCT scan according to the scan pattern, the data acquisition unit applies a preliminary OCT scan to the eye under examination, the image construction unit constructs a preliminary image from the data acquired by the preliminary OCT scan, and further includes a parameter setting unit that sets one or more focus control parameters based on the preliminary image constructed by the image construction unit, and the focus control unit performs control of the focus position change unit according to the one or more focus control parameters set by the parameter setting unit.

[0015] A seventh aspect of the exemplary embodiment is the ophthalmic imaging apparatus of the sixth aspect, wherein the one or more focus control parameters include a focus position change range including the first focal position and the second focal position.

[0016] An eighth aspect of the exemplary embodiment is an ophthalmic imaging apparatus of the sixth or seventh aspect, wherein the one or more focus control parameters include at least one of the movement speed and movement acceleration of the focal position.

[0017] A ninth aspect of the exemplary embodiment is an ophthalmic imaging apparatus according to any of the first to eighth aspects, further comprising: an imaging unit for repeatedly imaging the eye under examination; and a movement detection unit for detecting movement of the eye under examination by analyzing time-series images acquired by the imaging unit, wherein the data acquisition unit includes an optical scanner for deflecting light for OCT scanning; and the scan control unit controls the optical scanner based on the output from the movement detection unit while controlling the data acquisition unit according to the scan pattern.

[0018] A tenth aspect of an exemplary embodiment is a method for controlling an ophthalmic imaging apparatus, which includes a data acquisition unit that applies an optical coherence tomography (OCT) scan to an eye under examination to collect data; an image construction unit that constructs an image from the data collected by the data acquisition unit; and a focal position changing unit provided in the optical path of a measurement light projected onto the eye under examination by the data acquisition unit, the method comprising: a scan control step of controlling the data acquisition unit according to a scan pattern including a continuous first partial pattern for the central region of the OCT scan application area and a continuous second partial pattern for the peripheral region; and a focus control step of controlling the focal position changing unit to apply a first focal position in parallel with the application of the OCT scan to at least a portion of the first partial pattern, and to apply a second focal position different from the first focal position in parallel with the application of the OCT scan to at least a portion of the second partial pattern.

[0019] An eleventh aspect of the exemplary embodiment is a program that causes a computer to execute the control method of the tenth aspect.

[0020] A twelfth aspect of the exemplary embodiment is a computer-readable non-temporary recording medium that stores the program of the eleventh aspect. [Effects of the Invention]

[0021] According to an exemplary embodiment, it is possible to perform wide-angle OCT scans at high speed while acquiring high-quality OCT images. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic diagram illustrating an example of the configuration of an ophthalmic imaging device according to an exemplary embodiment. [Figure 2] This is a schematic diagram illustrating an example of the configuration of an ophthalmic imaging device according to an exemplary embodiment. [Figure 3] This is a schematic diagram illustrating an example of the configuration of an ophthalmic imaging device according to an exemplary embodiment. [Figure 4] This is a schematic diagram illustrating an example of the configuration of an ophthalmic imaging device according to an exemplary embodiment. [Figure 5A] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 5B] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 6A] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 6B] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 6C] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 7] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 8A] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 8B] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 9A] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 9B] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 9C] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 9D] This is a schematic diagram illustrating an example of a process performed by an ophthalmic imaging device according to an exemplary embodiment. [Figure 10] This is a flowchart illustrating an example of the operation of an ophthalmic imaging device according to an exemplary embodiment. [Figure 11] This is a schematic diagram illustrating an example of the operation of an ophthalmic imaging device according to an exemplary embodiment. [Figure 12] This is a schematic diagram illustrating an example of the operation of an ophthalmic imaging device according to an exemplary embodiment. [Modes for carrying out the invention]

[0023] An exemplary embodiment of an ophthalmic imaging apparatus, its control method, program, and recording medium will be described in detail with reference to the drawings. The disclosures of the literature cited herein and any other publicly known technology can be incorporated into the embodiments. Furthermore, unless otherwise specified, there is no distinction between "image data" and the "image" derived therefrom. Similarly, unless otherwise specified, there is no distinction between the "part" of the eye being examined and its "image."

[0024] The ophthalmic imaging device according to the exemplary embodiment is capable of measuring the fundus of a living eye using Fourier domain OCT (e.g., swept-source OCT). The type of OCT applicable to the embodiment is not limited to swept-source OCT, but may be spectral domain OCT or time domain OCT, for example. Furthermore, the application of OCT is not limited to the fundus, but may be any part of the eye, such as the anterior segment or vitreous humor.

[0025] The exemplary embodiment may be capable of processing images acquired by modalities other than OCT. For example, the exemplary embodiment may be capable of processing images acquired by any of a fundus camera, SLO, slit lamp microscope, and ophthalmic surgical microscope. The ophthalmic imaging device according to the exemplary embodiment may include any of a fundus camera, SLO, slit lamp microscope, and ophthalmic surgical microscope.

[0026] Images of the eye to be processed by the exemplary embodiment may include images obtained by analyzing images acquired by any modality. Examples of such analyzed images include pseudo-colored images (e.g., segmented pseudo-color images), images consisting of only a part of the original image (e.g., segmented images), images representing the thickness distribution of tissue obtained by analyzing OCT images (e.g., thickness maps, thickness graphs), images representing the shape of tissue (e.g., curvature maps), and images representing the distribution of lesions (e.g., lesion maps).

[0027] <composition> The ophthalmic imaging device 1 in the exemplary embodiment shown in Figure 1 includes a fundus camera unit 2, an OCT unit 100, and a calculation and control unit 200. The fundus camera unit 2 is provided with an optical system and mechanism for acquiring a frontal image of the eye under examination. The OCT unit 100 is provided with part of the optical system and mechanism for performing OCT. Other parts of the optical system and mechanism for performing OCT are provided in the fundus camera unit 2. The calculation and control unit 200 includes one or more processors that perform various calculations and controls. In addition to these, optional elements and units such as members for supporting the patient's face (chin rest, forehead rest, etc.) and lens units for switching the target area of ​​OCT (e.g., anterior segment OCT attachment) may be provided in the ophthalmic imaging device 1.

[0028] In this specification, "processor" means, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), a programmable logic device (e.g., SPLD (Simple Programmable Logic Device), CPLD (Complex Programmable Logic Device), FPGA (Field Programmable Gate Array)), or other circuit. The processor realizes the functions according to the embodiment by, for example, reading and executing a program stored in a memory circuit or memory device.

[0029] <Fundus Camera Unit 2> The fundus camera unit 2 is equipped with an optical system for capturing the fundus effusion (Ef) of the eye under examination (E). The acquired fundus effusion images (referred to as fundus images, fundus photographs, etc.) are frontal images such as observation images and captured images. Observation images are obtained, for example, by video recording using near-infrared light and are used for alignment, focusing, tracking, etc. Captured images are still images obtained, for example, using flash light in the visible or infrared region.

[0030] The fundus camera unit 2 includes an illumination optical system 10 and an imaging optical system 30. The illumination optical system 10 irradiates the eye E under examination with illumination light. The imaging optical system 30 detects the reflected light from the illumination light from the eye E under examination. Measurement light from the OCT unit 100 is guided to the eye E under examination through an optical path within the fundus camera unit 2, and its reflected light is guided back to the OCT unit 100 through the same optical path.

[0031] The light (observation illumination light) output from the observation light source 11 of the illumination optical system 10 is reflected by the concave mirror 12, passes through the focusing lens 13, and is transmitted through the visible cut filter 14 to become near-infrared light. Furthermore, the observation illumination light is focused near the imaging light source 15, reflected by the mirror 16, and passes through the relay lens system 17, relay lens 18, aperture 19, and relay lens system 20. The observation illumination light is then reflected at the peripheral part of the perforated mirror 21 (the area around the hole), passes through the dichroic mirror 46, is refracted by the objective lens 22, and illuminates the eye E (fundus Ef) under examination. The light of the observation illumination light returned from the eye E under examination is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the hole formed in the central region of the perforated mirror 21, passes through the dichroic mirror 55, passes through the imaging focusing lens 31, and is reflected by the mirror 32. Furthermore, this reflected light passes through the half mirror 33A, is reflected by the dichroic mirror 33, and is imaged onto the light-receiving surface of the image sensor 35 by the imaging lens 34. The image sensor 35 detects the reflected light at a predetermined frame rate. The focus (focal position) of the imaging optical system 30 is adjusted to match the fundus Ef or the anterior segment of the eye.

[0032] Light (imaging illumination light) output from the imaging light source 15 is irradiated onto the fundus Ef via the same path as the observation illumination light. The reflected light from the examination eye E is guided to the dichroic mirror 33 via the same path as the reflected light of the observation illumination light, passes through the dichroic mirror 33, is reflected by the mirror 36, and is imaged onto the light-receiving surface of the image sensor 38 by the imaging lens 37.

[0033] The liquid crystal display (LCD) 39 displays a fixation target (fixation target image). A portion of the light beam output from the LCD 39 is reflected by the half mirror 33A, then by the mirror 32, passes through the imaging focusing lens 31 and the dichroic mirror 55, and then passes through the hole in the perforated mirror 21. The light beam that has passed through the hole in the perforated mirror 21 passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus Ef.

[0034] The fixation position of the eye E under examination by the fixation target can be changed by changing the display position of the fixation target image on the LCD39 screen. Examples of fixation positions include a fixation position for acquiring an image centered on the macula, a fixation position for acquiring an image centered on the optic nerve head, a fixation position for acquiring an image centered on the area between the macula and the optic nerve head, and a fixation position for acquiring an image of an area far from the macula (periphery of the fundus). A graphical user interface (GUI) can be provided to specify at least one of these typical fixation positions. A GUI can also be provided to manually move the fixation position (display position of the fixation target).

[0035] The configuration for presenting a fixation target with a changeable fixation position to the eye under examination E is not limited to a display device such as an LCD. For example, a fixation matrix in which multiple light-emitting units (such as light-emitting diodes) are arranged in a matrix (array) can be used instead of a display device. In this case, the fixation position of the eye under examination E can be changed by selectively lighting up the multiple light-emitting units. As another example, a fixation target with a changeable fixation position can be generated by one or more movable light-emitting units.

[0036] The alignment optical system 50 generates alignment indicators used for aligning the optical system with respect to the eye E under examination. Alignment light output from the light-emitting diode (LED) 51 passes through the aperture 52, aperture 53, and relay lens 54, is reflected by the dichroic mirror 55, passes through the opening of the perforated mirror 21, is transmitted through the dichroic mirror 46, and is projected onto the eye E under examination via the objective lens 22. The reflected light from the eye E under examination (corneal reflection, etc.) is guided to the image sensor 35 via the same path as the reflected light of the observation illumination light. Based on the received image (alignment indicator image), manual alignment or auto-alignment can be performed.

[0037] As in conventional methods, the alignment indicator image in this example consists of two bright spot images whose positions change depending on the alignment state. When the relative position between the eye E and the optical system changes in the xy direction, the two bright spot images are displaced together in the xy direction. When the relative position between the eye E and the optical system changes in the z direction, the relative position (distance) between the two bright spot images changes. When the distance between the eye E and the optical system in the z direction matches a predetermined working distance, the two bright spot images overlap. When the position of the eye E and the optical system coincide in the xy direction, the two bright spot images are presented within or near a predetermined alignment target. When the distance between the eye E and the optical system in the z direction matches the working distance, AND the position of the eye E and the optical system coincide in the xy direction, the two bright spot images overlap and are presented within the alignment target.

[0038] In auto-alignment, the data processing unit 230 detects the positions of the two bright spot images, and the main control unit 211 controls the movement mechanism 150 (described later) based on the positional relationship between the two bright spot images and the alignment target. In manual alignment, the main control unit 211 displays the two bright spot images on the display unit 241 along with the observation image of the eye under examination E, and the user operates the movement mechanism 150 using the operation unit 242 while referring to the two displayed bright spot images.

[0039] The focusing optical system 60 generates a split indicator used for focusing on the eye E under examination. In conjunction with the movement of the imaging focusing lens 31 along the optical path (imaging optical path) of the imaging optical system 30, the focusing optical system 60 moves along the optical path (illumination optical path) of the illumination optical system 10. The reflecting rod 67 is inserted into and removed from the illumination optical path. When adjusting the focus, the reflective surface of the reflecting rod 67 is tilted in the illumination optical path. The focusing light output from the LED 61 passes through the relay lens 62, is separated into two beams by the split indicator plate 63, passes through the double-hole diaphragm 64, is reflected by the mirror 65, and is first imaged onto the reflective surface of the reflecting rod 67 by the converging lens 66 before being reflected again. Furthermore, the focusing light passes through the relay lens 20, is reflected by the perforated mirror 21, passes through the dichroic mirror 46, and is projected onto the eye E under examination via the objective lens 22. The light reflected from the eye E under examination (such as the retinal reflection) of the focused light is guided to the image sensor 35 via the same path as the light reflected from the alignment light. Based on the received image (split index image), manual focusing or autofocus can be performed.

[0040] Diopter correction lenses 70 and 71 can be selectively inserted into the photographic light path between the perforated mirror 21 and the dichroic mirror 55. Diopter correction lens 70 is a positive lens (convex lens) for correcting high hyperopia. Diopter correction lens 71 is a negative lens (concave lens) for correcting high myopia.

[0041] The dichroic mirror 46 combines the optical path for fundus photography and the optical path for OCT (measuring arm). The dichroic mirror 46 reflects light in the wavelength range used for OCT and transmits light for fundus photography. The measuring arm is equipped with, in order from the OCT unit 100 side, a collimator lens unit 40, a retroreflector 41, a dispersion compensation member 42, an OCT focusing lens 43, an optical scanner 44, and a relay lens 45.

[0042] The retroreflector 41 is movable in the direction of the arrow shown in Figure 1, thereby changing the length of the measuring arm. Changing the length of the measuring arm is used, for example, to correct the optical path length according to the axial length of the eye, or to adjust the interference state.

[0043] The dispersion compensation member 42, together with the dispersion compensation member 113 (described later) located on the reference arm, works to match the dispersion characteristics of the measurement light LS with those of the reference light LR.

[0044] The OCT focusing lens 43 is moved along the measuring arm to adjust the focus of the measuring arm. The movement of the imaging focusing lens 31, the movement of the focusing optical system 60, and the movement of the OCT focusing lens 43 can be controlled in a coordinated manner.

[0045] The optical scanner 44 is positioned substantially optically conjugate to the pupil of the eye E under examination. The optical scanner 44 deflects the measurement light LS guided by the measurement arm. The optical scanner 44 is a 2D scanning galvanoscanner, for example, including a galvanoscanner for scanning in the x-direction and a galvanoscanner for scanning in the y-direction.

[0046] <OCT Unit 100> As illustrated in Figure 2, the OCT unit 100 is equipped with an optical system for applying swept-source OCT. This optical system includes an interference optical system. This interference optical system splits light from a tunable light source (wavelength-swept light source) into measurement light and reference light, and generates interference light by superimposing the return light of the measurement light from the eye E under examination with the reference light that has passed through the reference optical path, and detects this interference light. The detection result (detection signal) obtained by the interference optical system is a signal representing the spectrum of the interference light and is sent to the arithmetic control unit 200.

[0047] The light source unit 101 includes, for example, a near-infrared tunable laser that rapidly changes the wavelength of the emitted light. The light L0 output from the light source unit 101 is guided by an optical fiber 102 to a polarization controller 103 where its polarization state is adjusted. Furthermore, the light L0 is guided by an optical fiber 104 to a fiber coupler 105 where it is split into a measurement light LS and a reference light LR. The optical path of the measurement light LS is called a measurement arm, and the optical path of the reference light LR is called a reference arm, etc.

[0048] The reference light LR is guided by the optical fiber 110 to the collimator 111, converted into a parallel beam, and then guided to the retroreflector 114 via the optical path length correction member 112 and the dispersion compensation member 113. The optical path length correction member 112 acts to match the optical path length of the reference light LR with that of the measurement light LS. The dispersion compensation member 113, together with the dispersion compensation member 42 located on the measurement arm, acts to match the dispersion characteristics between the reference light LR and the measurement light LS. The retroreflector 114 is movable along the optical path of the reference light LR incident on it, thereby changing the length of the reference arm. Changing the length of the reference arm is used, for example, to correct the optical path length according to the axial length of the eye or to adjust the interference state.

[0049] The reference light LR, passing through the retroreflector 114, is converted from a parallel beam to a focused beam by the collimator 116 via the dispersion compensation member 113 and the optical path length correction member 112, and then incident on the optical fiber 117. The reference light LR incident on the optical fiber 117 is guided to the polarization controller 118 to adjust its polarization state, then guided to the attenuator 120 via the optical fiber 119 to adjust its light intensity, and finally guided to the fiber coupler 122 via the optical fiber 121.

[0050] Meanwhile, the measurement light LS generated by the fiber coupler 105 is guided by the optical fiber 127, converted into a parallel beam by the collimator lens unit 40, and passes through the retroreflector 41, dispersion compensation member 42, OCT focusing lens 43, optical scanner 44 and relay lens 45, reflected by the dichroic mirror 46, refracted by the objective lens 22, and projected onto the eye under examination E. The measurement light LS is scattered and reflected at various depth positions in the eye under examination E. The return light of the measurement light LS from the eye under examination E travels in the reverse direction along the same path as the outward journey and is guided to the fiber coupler 105, and reaches the fiber coupler 122 via the optical fiber 128.

[0051] The fiber coupler 122 generates interference light by superimposing the measurement light LS incident via the optical fiber 128 and the reference light LR incident via the optical fiber 121. The fiber coupler 122 generates a pair of interference light LC by splitting the generated interference light at a predetermined splitting ratio (e.g., 1:1). The pair of interference light LC are led to the detector 125 through optical fibers 123 and 124, respectively.

[0052] The detector 125 includes, for example, a balanced photodiode. The balanced photodiode has a pair of photodetectors, each detecting a pair of interfering LCs, and outputs the difference between the pair of detection results obtained from these. The detector 125 sends this output (detection signal) to the data acquisition system (DAQ) 130.

[0053] The data acquisition system 130 is supplied with a clock KC from the light source unit 101. The clock KC is generated in the light source unit 101 in synchronization with the output timing of each wavelength swept within a predetermined wavelength range by the tunable light source. For example, the light source unit 101 splits the light L0 of each output wavelength to generate two branched beams, optically delays one of these branched beams, combines these branched beams, detects the resulting combined beam, and generates the clock KC based on the detection result. The data acquisition system 130 performs sampling of the detection signal input from the detector 125 based on the clock KC. The data acquisition system 130 sends the results of this sampling to the arithmetic control unit 200.

[0054] In this example, both an element for changing the measuring arm length (e.g., retroreflector 41) and an element for changing the reference arm length (e.g., retroreflector 114 or reference mirror) are provided, but only one of these elements may be provided. Furthermore, the elements for changing the difference between the measuring arm length and the reference arm length (optical path length difference) are not limited to these and may be any element (optical member, mechanism, etc.).

[0055] <Control Systems / Processing Systems> Figures 3 and 4 show examples of the configuration of the control and processing systems of the ophthalmic imaging device 1. The control unit 210, image construction unit 220, and data processing unit 230 are provided, for example, in the arithmetic control unit 200. The ophthalmic imaging device 1 may include a communication device for data communication with external devices. The ophthalmic imaging device 1 may also include a drive device (reader / writer) for processing data to be read from a recording medium and processing data to be written to a recording medium.

[0056] <Control Unit 210> The control unit 210 performs various controls. The control unit 210 includes a main control unit 211 and a storage unit 212. Furthermore, as shown in Figure 4, the control unit 210 in this embodiment includes a scan control unit 213 and a focus control unit 214.

[0057] <Main control unit 211> The main control unit 211 includes a processor and controls each element of the ophthalmic imaging device 1 (including the elements shown in Figures 1 to 4). The main control unit 211 is realized through the cooperation of hardware, including a processor, and control software.

[0058] The main control unit 211 can operate the scan control unit 213 and the focus control unit 214 in a coordinated (synchronous) manner. This allows the OCT scan and focus adjustment to be performed in a coordinated (synchronous) manner.

[0059] The imaging focus drive unit 31A moves the imaging focus lens 31 located in the imaging light path and the focus optical system 60 located in the illumination light path under the control of the main control unit 211. The retroreflector (RR) drive unit 41A moves the retroreflector 41 provided on the measuring arm under the control of the main control unit 211. The OCT focus drive unit 43A moves the OCT focus lens 43 located on the measuring arm under the control of the main control unit 211. The optical scanner 44 provided on the measuring arm operates under the control of the main control unit 211. The retroreflector (RR) drive unit 114A moves the retroreflector 114 located on the reference arm under the control of the main control unit 211. Each of the above drive units includes an actuator such as a pulse motor that operates under the control of the main control unit 211.

[0060] The moving mechanism 150 moves, for example, the fundus camera unit 2 in at least three dimensions. In a typical example, the moving mechanism 150 includes an x-stage that can move in the ±x directions (left and right directions), an x-movement mechanism that moves the x-stage, a y-stage that can move in the ±y directions (up and down directions), a y-movement mechanism that moves the y-stage, a z-stage that can move in the ±z directions (depth directions), and a z-movement mechanism that moves the z-stage. Each of these moving mechanisms includes an actuator such as a pulse motor that operates under the control of the main control unit 211.

[0061] <Storage section 212> The memory unit 212 stores various types of data. These include OCT images, fundus images, subject eye information, and control parameters.

[0062] The eye examination information includes patient information such as patient ID and name, left / right eye identification information, and electronic medical record information.

[0063] Control parameters include, for example, parameters used to control OCT scanning (scan control parameters) and parameters used to control focus (focus position) (focus control parameters).

[0064] Scan control parameters are parameters that indicate the content of control over the optical scanner 44. Examples of scan control parameters include parameters that indicate the scan pattern, parameters that indicate the scan speed, and parameters that indicate the scan interval. The scan speed is defined, for example, as the repetition rate of A scans. The scan interval is defined, for example, as the interval between adjacent A scans, i.e., the spacing between scan points. The scan pattern will be described later.

[0065] The focus control parameters are parameters that indicate the control content for the OCT focusing drive unit 43A. Examples of focus control parameters include parameters indicating the focal position of the measuring arm, parameters indicating the movement speed of the focal position, and parameters indicating the movement acceleration of the focal position. The parameter indicating the focal position is, for example, a parameter indicating the position of the OCT focusing lens 43. The parameter indicating the movement speed of the focal position is, for example, a parameter indicating the movement speed of the OCT focusing lens 43. The parameter indicating the movement acceleration of the focal position is, for example, a parameter indicating the movement acceleration of the OCT focusing lens 43. The movement speed may be constant or not. The same applies to the movement acceleration.

[0066] <Scan control unit 213> The scan control unit 213 controls the optical scanner 44 based on scan control parameters. The scan control unit 213 may further control the light source unit 101. The details of the processing performed by the scan control unit 213 will be described later. The scan control unit 213 is included in the main control unit 211. The scan control unit 213 is realized through the cooperation of hardware, including a processor, and scan control software.

[0067] <Focus control unit 214> The focus control unit 214 controls the OCT focusing drive unit 43A based on focus control parameters. The details of the processing performed by the focus control unit 214 will be described later. The focus control unit 214 is included in the main control unit 211. The focus control unit 214 is realized through the cooperation of hardware, including a processor, and focus control software.

[0068] <Image construction unit 220> The image reconstruction unit 220 includes a processor and forms OCT image data of the fundus Ef based on signals (sampling data) input from the data acquisition system 130. The OCT image data is, for example, B-scan image data (two-dimensional tomographic image data).

[0069] The process for forming OCT image data includes noise reduction, filtering, and fast Fourier transform (FFT), similar to conventional Fourier domain OCT. In the case of other types of OCT devices, the image reconstruction unit 220 performs known processing appropriate to that type.

[0070] The image reconstruction unit 220 forms three-dimensional data of the fundus Ef based on signals input from the data acquisition system 130. This three-dimensional data is three-dimensional image data that represents the three-dimensional region (volume) of the fundus Ef. This three-dimensional image data means image data in which the position of pixels is defined by a three-dimensional coordinate system. Examples of three-dimensional image data include stacked data and volume data.

[0071] Stacked data is image data obtained by arranging multiple tomographic images acquired along multiple scan lines in a three-dimensional manner based on the positional relationship of these scan lines. In other words, stacked data is image data obtained by representing multiple tomographic images, originally defined by separate two-dimensional coordinate systems, using a single three-dimensional coordinate system (i.e., embedding them in a single three-dimensional space). Alternatively, stacked data is image data obtained by arranging multiple A-scan data acquired for multiple scan points (scan point arrays) arranged in a two-dimensional manner in a three-dimensional manner based on the positional relationship of these scan points.

[0072] Volume data is image data in which pixels are voxels arranged in a three-dimensional array, and is also called voxel data. Volume data is formed by applying interpolation and voxelization processes to stack data.

[0073] The image reconstruction unit 220 renders the 3D image data to form a display image. Examples of applicable rendering methods include volume rendering, surface rendering, maximum projection (MIP), minimum projection (MinIP), and multi-sectional reconstruction (MPR).

[0074] The image reconstruction unit 220 is capable of forming an OCT frontal image (OCT en-face image) based on 3D image data. For example, the image reconstruction unit 220 can construct projection data by projecting 3D image data in the z direction (A-line direction, depth direction). Furthermore, the image reconstruction unit 220 can construct a shadowgram by projecting a portion of the 3D image data in the z direction.

[0075] The partial three-dimensional image data projected to construct the shadowgram is set up, for example, using segmentation. Segmentation is the process of identifying a sub-region within an image. Typically, segmentation is used to identify an image region corresponding to a given tissue in the fundus Ef. Segmentation is performed, for example, by the image construction unit 220 or the data processing unit 230.

[0076] The ophthalmic imaging device 1 may be capable of performing OCT angiography. OCT angiography is an imaging technique that constructs images with enhanced retinal and choroidal blood vessels (see, for example, Japanese Patent Publication No. 2015-515894). Generally, fundus tissue (structure) does not change over time, but the blood flow portion inside the blood vessels does. OCT angiography generates images by enhancing the parts where such temporal changes exist (blood flow signals). OCT angiography is also called OCT motion contrast imaging. Images obtained by OCT angiography are called angiographic images, angiograms, or motion contrast images.

[0077] When OCT angiography is performed, the ophthalmic imaging device 1 repeatedly scans the same area of ​​the fundus Ef a predetermined number of times. For example, repeated scans can be performed along a trajectory between two points on a predetermined scan pattern (e.g., a spiral scan pattern). The image reconstruction unit 220 can construct a motion contrast image from the dataset collected by the data acquisition system 130 during repeated scans. This motion contrast image is an angiographic image that emphasizes the temporal changes in interference signals caused by blood flow in the fundus Ef. Typically, OCT angiography is applied to a three-dimensional region of the fundus Ef to obtain an image representing the three-dimensional distribution of blood vessels in the fundus Ef.

[0078] When OCT angiography is performed, the image reconstruction unit 220 can construct arbitrary two-dimensional angiography image data and / or arbitrary pseudo-three-dimensional angiography image data from three-dimensional angiography image data. For example, the image reconstruction unit 220 can construct two-dimensional angiography image data representing any cross-section of the fundus Ef by applying multi-planar reconstruction to the three-dimensional angiography image data.

[0079] The image reconstruction unit 220 is realized through the collaboration of hardware, including a processor, and image reconstruction software.

[0080] <Data Processing Unit 230> The data processing unit 230 includes a processor and applies various data processing to the image of the eye E being examined. For example, the data processing unit 230 is realized through the cooperation of hardware including a processor and data processing software.

[0081] The data processing unit 230 can perform registration between two images acquired for the fundus Ef. For example, the data processing unit 230 can perform registration between three-dimensional image data acquired by OCT and a frontal image acquired by the fundus camera unit 2. The data processing unit 230 can also perform registration between two OCT images acquired by OCT. Furthermore, the data processing unit 230 can perform registration between two frontal images acquired by the fundus camera unit 2. It is also possible to apply registration to the analysis results of OCT images and the analysis results of frontal images. Registration can be performed using known methods, including, for example, feature point extraction and affine transformation.

[0082] As illustrated in Figure 4, the data processing unit 230 of this embodiment includes a parameter setting unit 231 and a movement detection unit 232.

[0083] <Parameter setting unit 231> The parameter setting unit 231 sets focus control parameters based on previously acquired OCT images of the fundus Ef. These OCT images (preparatory images) are used to detect the general shape of the application area of ​​the wide-angle OCT scan, and the focus control parameters are set based on the shape detected.

[0084] The ophthalmic imaging device 1 can acquire OCT images used to set focus control parameters. For example, the ophthalmic imaging device 1 can apply a preparatory OCT scan to the eye E before applying a wide-angle OCT scan to the eye E.

[0085] A preparatory OCT scan is performed to pass through both the central and peripheral regions of the wide-angle OCT scan application area. For example, in a preparatory OCT scan for a wide-angle OCT scan of the fundus Ef, the macular region (and its vicinity) can be set as the central region of the fundus Ef, and the region located at a predetermined distance or more from the macula can be set as the peripheral region. Similarly, in a preparatory OCT scan for a wide-angle OCT scan of the anterior segment, the corneal apex and its vicinity can be set as the central region of the anterior segment, and the region located at a predetermined distance or more from the corneal apex can be set as the peripheral region. More generally, the axial length of the eye E under examination and its vicinity can be set as the central region, and the region located at a predetermined distance or more from the axial length can be set as the peripheral region.

[0086] The pattern for a preparatory OCT scan may be a scan pattern containing many scan points, such as a 3D scan (raster scan). However, considering that the purpose of a preparatory OCT scan is to grasp the general shape of the area to be applied to the wide-angle OCT scan, a relatively simple scan pattern such as a B-scan (line scan), cross scan, or radial scan is sufficient.

[0087] The image reconstruction unit 220 constructs a preliminary image from the data collected by the preliminary OCT scan. The preliminary image typically includes one or more B-scan images representing one or more cross-sections of the central region and one or more cross-sections of the peripheral region of the wide-angle OCT scan application area.

[0088] In the following examples, the outer edges of the central region and the outer and inner edges of the peripheral region are both circular, but the shapes of the central region and the peripheral region are not limited to these. For example, the outer edge of the central region and the outer and inner edges of the peripheral region may be rectangular, or they may be of any shape. Also, the outer and inner edges of the peripheral region may be the same, or they may be different.

[0089] The example of a preparatory OCT scan shown in Figure 5A is a single B-scan 330 that passes through the central region 310 containing the macula Em of the fundus Ef and the peripheral region 320 (indicated by diagonal lines) away from the macula Em. The symbol Ed indicates the optic nerve head. In this example, a single B-scan image is obtained representing the cross-section to which the B-scan 330 was applied. The B-scan image in this example shows the relative relationship between the depth position (z position) of the central region 310 and the depth position of the peripheral region 320. In this example, the relative depth position relationship between the central region 310 and the peripheral region 320 is obtained only in the direction to which the B-scan 330 was applied.

[0090] The example of a preparatory OCT scan shown in Figure 5B consists of two B-scans 341 and 342, which pass through the central region 310 and the peripheral region 320, respectively. The two B-scans 341 and 342 are orthogonal to each other. In other words, the preparatory OCT scan in this example is a cross-scan. In this example, a B-scan image representing the cross-section to which B-scan 341 is applied and a B-scan image representing the cross-section to which B-scan 342 is applied are obtained. Each of the two B-scan images in this example represents the relative relationship between the depth position (z position) of the central region 310 and the depth position of the peripheral region 320. In this example, the relative depth position relationship between the central region 310 and the peripheral region 320 is obtained for the direction in which B-scan 341 is applied and the direction in which B-scan 342 is applied, that is, for two mutually orthogonal directions.

[0091] Although not shown in the diagram, when a radial scan (multiple B scans arranged at equal angular intervals) is applied as a preparatory OCT scan, the relative depth position relationship between the central region and the peripheral region is obtained for multiple directions arranged at equal angular intervals from each other. Similarly, although not shown in the diagram, when a 3D scan (e.g., a raster scan) is applied as a preparatory OCT scan, the relative depth position relationship between the central region and the peripheral region is obtained for any direction in the xy plane. Even when other scan patterns are applied, the relative depth position relationship between the central region and the peripheral region is obtained for one or more directions corresponding to that scan pattern.

[0092] Thus, the pattern of the preparatory OCT scan determines the content (direction, etc.) and quantity (angle interval, etc.) of information acquired as relative depth-position relationships. Conversely, the pattern of the preparatory OCT scan can be determined according to the content and quantity of information to be acquired as relative depth-position relationships. The determination of the preparatory OCT scan pattern is performed, for example, in advance or before each examination.

[0093] The data collected by the preparatory OCT scan is sent to the image reconstruction unit 220, where a preparatory image is constructed. The parameter setting unit 231 sets one or more focus control parameters based on this preparatory image. As mentioned above, the focus control parameters are parameters that indicate the content of the control to the OCT focusing drive unit 43A, and examples of such parameters include a parameter indicating the focal position of the measuring arm, a parameter indicating the movement speed of the focal position, and a parameter indicating the movement acceleration of the focal position.

[0094] An example of the processing performed by the parameter setting unit 231 is described below. An example of a preparatory image is shown in Figure 6A. Preparatory image G is an image constructed from data collected by, for example, the B scan 330 shown in Figure 5A (or the B scan 341 or a similar B scan shown in Figure 5B). The area outlined by the dotted line labeled with code 310 corresponds to the intersection area (common area) of the central area 310 and the B scan 330 shown in Figure 5A. The area indicated by the diagonal line labeled with code 320 corresponds to the intersection area (common area) of the peripheral area 320 and the B scan 330 shown in Figure 5A. Note that there are two peripheral areas 320 in preparatory image G. Also, code Em is the image area of ​​the macula, and code Ed is the image area of ​​the optic nerve head.

[0095] The parameter setting unit 231 analyzes the central region 310 of the preliminary image G to detect the macular region Em and determine its depth position (z-coordinate). To this end, the parameter setting unit 231 includes, for example, segmentation to identify the image region of the internal limiting membrane (ILM), shape analysis to detect the macular region Em from the shape (indentation) of the identified internal limiting membrane region, and processing to determine the z-coordinate of the pixel of a representative point of the detected macular region Em. The representative point of the macular region Em may be, for example, the center of the macula (fovea, the deepest part of the indentation). Let the z-coordinate of the macular center obtained in this example be z1 (see Figure 6B). Note that the location where the z-coordinate is determined is not limited to the center of the macula, but may be any representative point within the central region 310.

[0096] Furthermore, the parameter setting unit 231 analyzes the peripheral region 320 of the preliminary image G to detect the image region of a predetermined tissue (e.g., the internal boundary membrane) and identifies its depth position (z-coordinate). To this end, the parameter setting unit 231 includes, for example, segmentation to identify the image region of the predetermined tissue and a process to determine the z-coordinate of the pixel of the representative point of the identified image region. The representative point of the image region of the predetermined tissue may be, for example, the center position of the peripheral region 320 in the B-scan direction, or the endpoint of the peripheral region 320. When the center positions of each of the two peripheral regions 320 of the preliminary image G are the representative points, the z-coordinate of the internal boundary membrane obtained in this example is z 21 and z 22 (See Figure 6C).

[0097] Furthermore, the parameter setting unit 231 sets the z-coordinate (z1) of the representative point of the central region 310 and the z-coordinate (z) of the representative point of the peripheral region 320. 21 , z 22 The focus control parameters are set based on the following.

[0098] For example, the parameter setting unit 231 sets the position of the OCT focusing lens 43 corresponding to the z-coordinate (z1) of a representative point in the central region 310, and the z-coordinate (z1) of a representative point in the peripheral region 320. 21 and z 22 The position of the OCT focusing lens 43 corresponding to each of the following can be determined. The position of the OCT focusing lens 43 corresponds to the focal position of the measurement arm. This example can be described as a process for determining the absolute position of the OCT focusing lens 43. The process in this example is performed based, for example, on the coherence gate position (arm length, position of retroreflector 41, position of retroreflector 114) and the z-axis scale (for example, distance per pixel) when the preliminary image G is acquired.

[0099] The parameter setting unit 231 sets the position (focal position) of the OCT focusing lens 43 corresponding to the z-coordinate (z1) of a representative point in the central region 310, and the z-coordinate (z1) of a representative point in the peripheral region 320. 21 and z 22It is possible to obtain the difference from the position (focal position) of the OCT focusing lens 43 corresponding to each of ) In other words, this example can be said to be a process of obtaining the relative position of the OCT focusing lens 43. The process of this example is executed based on, for example, the scale of the z-axis.

[0100] The parameter setting unit 231 calculates the position (focal position) of the OCT focusing lens 43 corresponding to the z coordinate (z1) of the representative point in the central region 310, and the z coordinate (z 21 and z 22 It is possible to obtain a focal position change range including the position (focal position) of the OCT focusing lens 43 corresponding to each of ). The focal position change range is the range of the focal position changed by the focus control, and is defined as, for example, the movement range of the OCT focusing lens 43. The process of this example is executed based on, for example, the coherence gate position when the preparatory image G is acquired and the scale of the z-axis.

[0101] The parameter setting unit 231 can set the speed at which the focal position of the measurement arm moves. The process of this example is executed based on, for example, the absolute position or relative position of the OCT focusing lens 43 described above, or based on the movement range of the OCT focusing lens 43.

[0102] The parameter setting unit 231 can set the acceleration at which the focal position of the measurement arm moves. The process of this example is executed based on, for example, the absolute position or relative position of the OCT focusing lens 43, or based on the movement range of the OCT focusing lens 43, or based on the movement speed of the OCT focusing lens 43.

[0103] When the preparatory image G is obtained, for example, as shown in FIG. 7, the parameter setting unit 231 sets the focus control parameters so that the focal position moves in the +z direction as it goes from the left peripheral region 320 side to the central region 310 side, and the focal position moves in the -z direction as it goes from the central region 310 side to the right peripheral region 320 side.

[0104] The parameter setting unit 231 can set information representing the relationship between the scan control parameter and the focus control parameter, for example, based on one of the examples of focus control parameters described above.

[0105] As a prerequisite, a scan pattern for wide-angle OCT scanning is set. The wide-angle OCT scan pattern is set, for example, in advance or for each examination.

[0106] In this embodiment, the wide-angle OCT scan pattern includes a scan pattern comprising a continuous first partial pattern for the central region of the wide-angle OCT scan application area and a continuous second partial pattern for the peripheral region. The first partial pattern is a pattern for continuously scanning at least a portion of the central region, and the second partial pattern is a pattern for continuously scanning at least a portion of the peripheral region. Here, "continuously scanning" means, for example, sequentially scanning a plurality of scan points arranged in a predetermined pattern according to their arrangement order.

[0107] The wide-angle OCT scan pattern may include a curved scan pattern defined in a polar coordinate system with the center of the wide-angle OCT scan application area as the origin. The center of the wide-angle OCT scan application area may be, for example, the center of the macula, or another part of the fundus. While the center of the wide-angle OCT scan application area may be defined based on a part or tissue of the eye being examined, it is also possible to define it based on the ophthalmic imaging device 1. For example, the center of the wide-angle OCT scan application area may be defined as the neutral position (neutral orientation) of the directional mirror (galvanometer mirror, etc.) of the optical scanner 44, or as the position of the optical axis of the measuring arm (optical axis of the objective lens 22). Examples of curved wide-angle OCT scan patterns defined in a polar coordinate system with the center of the wide-angle OCT scan application area as the origin include spiral patterns and concentric circle patterns.

[0108] If the wide-angle OCT scan pattern is the curved scan pattern described above, this wide-angle OCT scan pattern may be a spiral scan pattern extending from the center to the outer edge of the wide-angle OCT scan application area (see spiral scan pattern 510 shown in Figure 8A), or a spiral scan pattern extending from the outer edge to the center of the wide-angle OCT scan application area (see spiral scan pattern 520 shown in Figure 8B).

[0109] The spiral scan pattern 510 shown in Figure 8A starts with the macula center within the central region (not shown) as the scanning starting point, and passes through the peripheral region (not shown) while increasing the radial movement as the angle of deviation changes, reaching the scanning ending point near the outer edge.

[0110] The spiral scan pattern 520 shown in Figure 8B starts at the outer edge (or nearby) as the scan begins, passes through the peripheral region (not shown) while decreasing the radial velocity as the angle of deviation changes, and reaches the scan end point set at the macula center within the central region (not shown).

[0111] Note that in the spiral scan patterns 510 and 520, the spacing between the spirals is depicted more coarsely than it actually is for illustrative purposes. In reality, the spacing between the spirals can be dense enough, for example, to allow for the construction of three-dimensional image data.

[0112] When the wide-angle OCT scan pattern is the aforementioned curved scan pattern (for example, a spiral scan pattern), some examples of focus control parameters that can be set by the parameter setting unit 231 will be explained with reference to Figures 9A to 9D.

[0113] Note that the focus control parameters that can be set by the parameter setting unit 231 are not limited to these examples, and may be any focus control parameters that satisfy the required conditions in this embodiment.

[0114] In the example shown in Figure 9A, the horizontal axis of the coordinate system represents the scan position, and the vertical axis represents the focal position. The scan position on the horizontal axis is defined as the number n (n=0,1,2,...,N-1) of N scan points ordered according to the applied scan pattern. The focal position on the vertical axis is defined as the z-coordinate. The focus control parameters in Figure 9A are applicable when a spiral scan pattern is adopted, such as the spiral scan pattern 510 shown in Figure 8A, which extends from the center to the outer edge of the wide-angle OCT scan application area. The spiral scan pattern 510 will be explained below as an example.

[0115] In Figure 9A, the initial scan position n=0 corresponds to the scan start point (macula center) in the spiral scan pattern 510, and the final scan position n=N-1 corresponds to the scan end point (position on or near the outer edge) in the spiral scan pattern 510.

[0116] Focal position ζ assigned to scan start position n=0 11 This is set based on the z-coordinate z1 of the central region 310 (e.g., the macula) shown in Figure 6B, for example. 11 is set to be equal to z1, or ζ 11 It is set to a value approximately equal to z1.

[0117] Focal position ζ assigned to scan end position n=N-1 12 For example, the z coordinate of the peripheral region 320 shown in Figure 6C is z 21 and z 22 It is set based on at least one of the following. For example, ζ 12 is z 21 Set to equal to ζ 12 is z 21 It is set to a value approximately equal to ζ 12 is z 22 Set to equal to ζ 12 is z 22 It is set to a value that is approximately equal to ζ 12 is z 21 and z 22The value is set to the value obtained from both of the following. 21 and z 22 From both sides ζ 12 As an example of how to find z 21 and z 22 Calculating the average of, z 21 and z 22 Calculating a weighted average with z 21 and z 22 It is possible to use any statistical processing, such as selecting the larger or smaller value between the two.

[0118] The focus control parameters shown in Figure 9A correspond to the coordinates (0, ζ) of the scan start point in the 2D coordinate system (n, z). 11 ) and coordinates (N-1, ζ) corresponding to the scan end point 12 It can be set as a smooth curve (e.g., a spline curve, a Bézier curve) connecting the two points.

[0119] The two-dimensional coordinate system (n,z) in the example shown in Figure 9B is the same as that in the example shown in Figure 9A. The focus control parameters in Figure 9B are applicable when a spiral scan pattern is adopted, such as the spiral scan pattern 520 shown in Figure 8B, which moves from the outer edge to the center of the wide-angle OCT scan application area. The spiral scan pattern 520 will be explained below as an example.

[0120] In Figure 9B, the initial scan position n=0 corresponds to the scan start point (position on or near the outer edge) in the spiral scan pattern 520, and the final scan position n=N-1 corresponds to the scan end point (center of the macula) in the spiral scan pattern 520.

[0121] Focal position ζ assigned to scan start position n=0 21 For example, the focal position ζ in Figure 9A. 12 It can be set in the same manner. Also, the focal position ζ is assigned to the scan end position n=N-1. 22 For example, the focal position ζ in Figure 9A. 11 It can be configured in the same manner as before.

[0122] The focus control parameters shown in Figure 9B correspond to the coordinates (0, ζ) of the scan start point in the 2D coordinate system (n, z). 21 ) and coordinates (N-1, ζ) corresponding to the scan end point 22 It can be set as a smooth curve (e.g., a spline curve, a Bézier curve) connecting the two points.

[0123] The two-dimensional coordinate system (n,z) in the example shown in Figure 9C is the same as that in the example shown in Figure 9A. The focus control parameters in Figure 9C are applicable when a spiral scan pattern is adopted, such as the spiral scan pattern 510 shown in Figure 8A, which extends from the center to the outer edge of the wide-angle OCT scan application area. The spiral scan pattern 510 will be explained below as an example.

[0124] In Figure 9C, the initial scan position n=0 corresponds to the scan start point (macula center) in the spiral scan pattern 510, and the final scan position n=N-1 corresponds to the scan end point (position on the outer edge or near the outer edge) in the spiral scan pattern 510.

[0125] Scan position interval n = [0, n 31 ] assigned focal position ζ 31 For example, the focal position ζ in Figure 9A. 11 It can be set in the same manner. Also, the scan position interval n = [n 32 Focal position ζ assigned to [N-1] 33 For example, the focal position ζ in Figure 9A. 12 It can be set in the same manner. Furthermore, the scan position interval n = (n 31 ,n 32 )=[n 31 +1,n 32 Focal position ζ assigned to -1] 32 For example, the focal position ζ 31 and ζ 33 It can be set based on the following. Typically, the focal position ζ 32This can be obtained, for example, by any statistical process. An example of a statistical value that can be obtained is ζ 31 and ζ 33 The average of, ζ 31 and ζ 33 A weighted average of ζ 31 and ζ 33 The larger of the two values, ζ 31 and ζ 33 There are values ​​such as the smaller of the two.

[0126] Similar to the relationship between the focus control parameters shown in Figure 9A and Figure 9B, the stepped focus control parameters shown in Figure 9C can be inverted. The focus control parameters obtained by inversion can be applied when a spiral scan pattern is adopted, such as the spiral scan pattern 520 shown in Figure 8B, which moves from the outer edge to the center of the wide-angle OCT scan application area.

[0127] Furthermore, it is possible to modify the focus control parameters shown in Figure 9C. For example, the scan position interval n = [0, n 31 ], coordinates (0, ζ 31 ) and coordinates (n 31 ,ζ 32 A smooth curve (e.g., a spline curve, a Bézier curve) can be assigned to connect the scan position interval n=[n 32 In [N-1], coordinate (n 32 ,ζ 32 ) and coordinates (N-1, ζ 33 A smooth curve (e.g., a spline curve, a Bézier curve) can be assigned to connect the two points. For example, when a spiral scan pattern is adopted, such as the spiral scan pattern 520 shown in Figure 8B, which moves from the outer edge to the center of the wide-angle OCT scan application area, it is possible to invert the focus control parameters that have been partially replaced by curves in this way.

[0128] Alternatively, the scan position interval n = [0, n 31 ], coordinates (0, ζ 31 ) and coordinates (n 31 ,ζ 32A straight line (diagonal line) connecting them can be assigned. Also, in the section n = [n 32 , N - 1] of the scan position, a straight line (diagonal line) connecting the coordinates (n 32 , ζ 32 ) and the coordinates (N - 1, ζ 33 ) can be assigned. For example, when a spiral scan pattern like the spiral scan pattern 520 shown in FIG. 8B is adopted, which is a spiral scan pattern from the outer edge to the center of the wide-angle OCT scan application area, it is possible to invert the focus control parameter partially replaced with a diagonal line in this way.

[0129] The two-dimensional coordinate system (n, z) in the example shown in FIG. 9D is the same as that in the example shown in FIG. 9A. The focus control parameter in FIG. 9D is applicable when a spiral scan pattern from the center to the outer edge of the wide-angle OCT scan application area is adopted, such as the spiral scan pattern 510 shown in FIG. 8A. Hereinafter, as an example, it will be described together with the spiral scan pattern 510.

[0130] The first scan position n = 0 in FIG. 9D corresponds to the scan start point (macular center) in the spiral scan pattern 510, and the last scan position n = N - 1 corresponds to the scan end point (a position on the outer edge or a position near the outer edge) in the spiral scan pattern 510.

[0131] The focal position ζ 41 assigned to the section n = [0, n 41 of the scan position can be set in the same manner as, for example, the focal position ζ 11 in FIG. 9A. Also, the focal position ζ 42 assigned to the section n = [n 42 , N - 1] of the scan position can be set in the same manner as, for example, the focal position ζ 12 in FIG. 9A. Further, in the section n = (n 41 , n 42 ) = [n 41 + 1, n 42 - 1], there are the coordinates (n 41 , ζ 41 ) and the coordinates (n 42, ζ 42 A straight line connecting ( ) is assigned.

[0132] Similar to the relationship between the focus control parameters shown in FIG. 9A and the focus control parameters shown in FIG. 9B, the focus control parameters shown in FIG. 9D can be inverted. The focus control parameters obtained by inversion are applicable when an involute scan pattern that goes from the outer edge to the center of the wide-angle OCT scan application area, such as the involute scan pattern 520 shown in FIG. 8B, is adopted.

[0133] Also, it is possible to modify the focus control parameters shown in FIG. 9D. For example, for the scan position interval n = (n 41 , n 42 ) = [n 41 +1, n 42 −1], a smooth curve (e.g., a spline curve, a Bézier curve) connecting the coordinates (n <00​​​​​​​​​​​​​​For example, in the example shown in Figure 6B, the depth position (z-coordinate) of one representative point (macula center) within the central region 310 is determined and used as the depth position of the central region 310. Alternatively, it is possible to determine the depth position of two or more points within the central region and then determine the depth position of the central region from these two or more depth positions. For example, the depth position of the central region can be determined by applying statistical processing to two or more depth positions. The statistical values ​​obtained from two or more depth positions may be, for example, the mean, weighted mean, median, mode, maximum, and minimum. The same processing can be applied when determining the depth position of the peripheral region.

[0136] When determining two or more depth positions within a central region, instead of calculating a single statistical value from these depth positions and using it as the depth position of the central region, as described above, it is possible to obtain information representing the change in depth position within the central region from these depth positions. For example, based on these depth positions, a graph (focus control parameter) representing the curvilinear, linear, or stepwise change in depth position within the central region can be obtained. Figures 9A and 9B show examples of curvilinear change. Although not illustrated, as an example of linear change in depth position within the central region, in the two-dimensional coordinate system shown in Figure 9C, the coordinates (0, ζ 31 ) and coordinates (n 31 ,ζ 32 It is possible to find a straight line connecting ). Also, although not shown in the diagram, as an example of a stepwise change in depth position in the central region, in the two-dimensional coordinate system shown in Figure 9C, the scan position interval n = [0, n 31 ] The value of the focal position is ζ 31 From ζ 32 It is possible to set focus control parameters that change in stages. The same process can be applied when determining focus control parameters for peripheral regions.

[0137] As described above, the process of determining two or more depth positions within the central region and setting focus control parameters is considered effective, for example, when the width of the central region (length in the direction perpendicular to the z direction) is relatively wide, or when there is a large change in depth position within the central region (for example, when there is a large difference between the maximum depth position and the minimum depth position within the central region). The parameter setting unit 231 may be configured to determine the number (and positions) of points within the central region for which depth regions can be determined, according to the width of the central region and / or according to the magnitude of the change in depth position within the central region. The same process can also be applied when determining focus control parameters for peripheral regions.

[0138] In the example described above, the central region (310) and the peripheral region (320) are separated from each other. In other words, in the example described above, an annular intermediate region exists between the outer edge of the central region and the inner edge of the peripheral region. In other examples, the outer edge of the central region and the inner edge of the peripheral region may coincide.

[0139] More generally, in this embodiment, the central and peripheral regions can be arbitrarily defined. For example, the central and peripheral regions may be defined according to the location of the fundus. Specifically, the central region can be defined as the region centered on a predetermined location of the fundus (e.g., the center of the macula) and within a predetermined first distance from this center. Furthermore, the peripheral region can be defined as the region at or beyond a predetermined second distance (a distance greater than or equal to the first distance) from this center. Here, a third distance representing the outer edge of the peripheral region may be further defined, or the outer edge of the wide-angle OCT scan application area may be defined as the outer edge of the peripheral region. The distance in this example may be a distance in the fundus, an optically calculated distance, or a standard distance obtained from a model eye or clinical data.

[0140] Another definition of the central and peripheral regions is one that depends on the OCT scan. For example, it is possible to set a predetermined first region in the wide-angle OCT scan application area as the central region, and a predetermined second region, different from the second region, as the peripheral region. Typically, the first region, which includes the center of the wide-angle OCT scan application area, is set as the central region, and the second region, which is located outside this first region, is set as the peripheral region.

[0141] The examples described above primarily focused on scan patterns consisting of curves, such as spiral scan patterns. However, it is also possible to employ scan patterns that consist of at least some straight lines. For example, a spiral scan pattern consisting of multiple straight lines can be applied by alternately combining line scans in the x-direction and line scans in the y-direction.

[0142] The settings for the wide-angle OCT scan pattern and focus control parameters (and scan speed) exemplified above include the setting of the movement speed and / or movement acceleration of the focal position. For example, in the focus control parameters exemplified in Figures 9A to 9D, the slope of the graph showing the focus control parameters corresponds to the movement speed, and the rate of change of the graph slope corresponds to the movement acceleration. Conversely, it is possible to set the focus control parameters by setting the movement speed and / or movement acceleration of the focal position.

[0143] In the focus control parameters illustrated in Figures 9A to 9D, the focal position applied to the central region (first focal position) is located on the +z side of the focal position applied to the peripheral region (second focal position). In other words, the focal length corresponding to the first focal position (first focal length) is set to be longer than the focal length corresponding to the second focal position (second focal length). This is in accordance with the shape of the eye (fundus) being examined. However, the first focal length does not necessarily need to be longer than the second focal length.

[0144] The parameter setting unit 231, capable of performing the above-described processes, is realized through the cooperation of hardware, including a processor, and parameter setting software.

[0145] <Movement detection unit 232> The ophthalmic imaging device 1 includes a fundus camera unit 2 that repeatedly photographs the eye E under examination to acquire time-series images. The time-series images acquired by the fundus camera unit 2 are, for example, the observation images described above.

[0146] The motion detection unit 232 analyzes the observation images acquired by the fundus camera unit 2 to detect the movement of the eye under examination E. For example, the motion detection unit 232 analyzes each image included in the observation images to detect feature points and determines the time-series changes in the position of the feature points. Feature points may be, for example, the center, centroid, and contour of the pupil, or the center, centroid, and contour of the iris.

[0147] The scan control unit 213 controls the optical scanner 44 and the OCT unit 100 according to the wide-angle OCT scan pattern, and can also control the optical scanner 44 based on the output from the motion detection unit 213. The control of the optical scanner 44 based on the output from the motion detection unit 213 is what is known as tracking control.

[0148] Tracking is performed by the following series of processes, for example, disclosed in Japanese Patent Publication No. 2017-153543. First, the movement detection unit 232 registers one of the frames (front view image) of the observation images acquired by the fundus camera unit 2 as a reference image.

[0149] Furthermore, the motion detection unit 232 determines the change in the position of the feature points in other frames relative to the position of the feature points in the reference image. This corresponds to determining the time-series change in the position of the feature points, that is, determining the displacement between the reference image and other frames. If the displacement exceeds a threshold due to blinking or fixation shift, or if displacement detection becomes impossible, the motion detection unit 232 can register the frame acquired thereafter as a new reference image. Moreover, the method for determining the time-series change in the position of the feature points is not limited to this; for example, the displacement of the feature points between two consecutive frames may be determined sequentially.

[0150] The motion detection unit 232 sends control information to the scan control unit 213 to cancel the time-series change in the position of the feature point each time such a change is detected. The scan control unit 213 corrects the orientation of the optical scanner 44 based on the control information that is input sequentially.

[0151] The motion detection unit 232 is realized through the cooperation of hardware, including a processor, and motion detection software.

[0152] <User Interface 240> The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes a display device 3. The operation unit 242 includes various operating devices and input devices. The user interface 240 may also include a device that integrates display and operation functions, such as a touch panel. It is also possible to construct embodiments that do not include at least a part of the user interface 240. For example, the display device may be an external device connected to an ophthalmic imaging device.

[0153] <Operation> The operation of ophthalmic imaging device 1 will be explained. It is assumed that preparatory processes such as patient ID input, fixation target presentation, fixation position adjustment, alignment, focus adjustment, and OCT optical path length adjustment have already been performed, as in conventional procedures.

[0154] An example of the operation of the ophthalmic imaging device 1 will be explained with reference to Figure 10.

[0155] (S1: Preparatory OCT scan applied to the fundus to acquire preliminary images) First, the ophthalmic imaging device 1 applies a preliminary OCT scan to the fundus Ef using the optical scanner 44 and the OCT unit 100. The image reconstruction unit 220 constructs a preliminary image from the data collected by the preliminary OCT scan. The preliminary image is sent to the parameter setting unit 231.

[0156] (S2: Set control parameters) The parameter setting unit 231 sets focus control parameters based on the preliminary image obtained in step S1. The set control parameters are stored, for example, in the storage unit 212.

[0157] In step S2 or earlier, the ophthalmic imaging device 1 may set the wide-angle OCT scan application area, the central region, the peripheral region, and the scan control parameters. Any of these conditions may be fixed, selected from multiple options, or manually set by the user. The parameter setting unit 231 may set the focus control parameters based on the results of these settings and the preliminary image.

[0158] In this example, the central region 310 and peripheral region 320 shown in Figure 5A, the spiral scan pattern 510 shown in Figure 8A, and the focus control parameters shown in Figure 9A are applied. Furthermore, the outer edge of the peripheral region 320 is assumed to define the outer edge of the wide-angle OCT scan application area.

[0159] (S3: Control the optical scanner based on the scan start position) The scan control unit 213 identifies the scan start position based on the scan control parameters set in step S2 or an earlier step, and controls the optical scanner 44 based on this scan start position. As a result, each galvanometer mirror included in the optical scanner 44 is positioned in the orientation corresponding to the scan start position.

[0160] In this example, typically, a fixation target corresponding to the fixation position for acquiring a macula-centered image is displayed on the LCD 39, and the center of the wide-angle OCT scan application area is set to the center of the macula. Assuming that the alignment and fixation state of the eye E under examination are favorable, the center of the macula is positioned on the optical axis of the measurement arm. Therefore, in this example, each galvanometer mirror of the optical scanner 44 is positioned in the neutral position.

[0161] (S4: Move the OCT focusing lens based on the initial focal position) The focus control unit 214 identifies the initial focal position in focus control based on the focus control parameters set in step S2, and controls the OCT focusing drive unit 43A to move the OCT focusing lens 43 based on this initial focal position.

[0162] In this example, the focal position ζ corresponds to the scan start position n=0 shown in Figure 9A. 11 This is identified as the initial focal position, and this initial focal position ζ 11 The OCT focusing drive unit 43A is controlled to position the OCT focusing lens 43 at the corresponding location.

[0163] Furthermore, the control related to step S4 may be executed before the control related to step S3. Also, the control related to step S3 and the control related to step S4 may be performed in parallel.

[0164] (S5: Command to start wide-angle OCT scan) After the control related to step S3 and the control related to step S4 are completed, a command to start a wide-angle OCT scan is input to the scan control unit 213 and the focus control unit 214. This command may be given manually by the user, or it may be given automatically by the main control unit 211 after a predetermined condition has been met (for example, the control related to step S3 and the control related to step S4 has been completed).

[0165] (S6: Start of coordinated execution of scan control and focus control) Upon receiving the start instruction in step S5, the scan control unit 213 and the focus control unit 214 begin coordinated control, thereby initiating a wide-angle OCT scan.

[0166] In this example, scan control by the scan control unit 213 and focus control by the focus control unit 214 are performed based on the focus control parameters shown in Figure 9A (a graph representing the relationship between scan position n and focal position z).

[0167] More specifically, the scan control unit 213 controls the optical scanner 44 and the OCT unit 100 to sequentially apply A-scan to a plurality of scan points (scan positions n=0 to N-1 shown in Figure 9A) arranged along the spiral scan pattern 510 shown in Figure 8A.

[0168] In parallel with this, the focus control unit 214 controls the OCT focusing drive unit 43A so that when an A scan is applied to each scan position n shown in Figure 9A, the OCT focusing lens 43 is positioned at a position corresponding to the focal position z=ζ(n) that corresponds to the scan position n.

[0169] This allows the fundus Ef to be scanned according to the spiral scan pattern 510 shown in Figure 8A, while the focal position is moved according to the focus control parameters shown in Figure 9A.

[0170] (S7: Tracking started) Following the commencement of coordinated control in step S6, or at any time before the commencement of this coordinated control, tracking is initiated to correct the projection position of the measurement light LS (the application position of the A scan) in accordance with the movement of the eye E under examination. Tracking is performed by the fundus camera unit 2, the movement detection unit 232, the scan control unit 213, etc., in the manner described above. As a result, even if the eye E under examination moves during the execution of the wide-angle OCT scan, it is possible to apply the spiral scan pattern 510 shown in Figure 8A.

[0171] (S8: Wide-angle OCT scan complete) The wide-angle OCT scan initiated in step S6 is terminated after an OCT scan has been performed along the spiral scan pattern 510 shown in Figure 8A, for example.

[0172] Note that OCT scans along the wide-angle OCT scan pattern are performed only once or a predetermined number of times. For example, OCT scans along the spiral scan pattern 510 can be performed two or more times. In this case, in the next step S9, two or more OCT images can be constructed from two or more datasets collected by these two or more OCT scans, and these two or more OCT images can be combined (averaged).

[0173] (S9: Constructs an OCT image according to the wide-angle OCT scan pattern) The image reconstruction unit 220 constructs an OCT image from the data collected by the wide-angle OCT scan performed in steps S6 to S8.

[0174] The spiral scan pattern 510 shown in Figure 8A is typically defined using a two-dimensional polar coordinate system (r,θ). Using a two-dimensional polar coordinate system (r,θ), the spiral scan pattern 510 can be defined, for example, by the following equations: x = cosθ - θ × sinθ, y = sinθ + θ × cosθ.

[0175] In this case, the OCT image constructed in step S9 is also defined using a two-dimensional polar coordinate system (r,θ). In other words, the positions of the multiple A-scan images that make up the OCT image constructed in step S9 are defined using a two-dimensional polar coordinate system (r,θ).

[0176] In this example, the positions of the multiple A scans that constitute the spiral scan pattern 510 shown in Figure 8A each correspond to the multiple scan positions n=0 to N-1 shown in Figure 9A. Therefore, the positions of the multiple A scan images constructed in step S9 also each correspond to the multiple scan positions n=0 to N-1. For example, step S9 constructs the OCT image H1 shown in Figure 11. The OCT image H1 consists of scan positions n=n p A scan image A(n) assigned to p It is composed of the following. Note that each scan position n=n p It is defined using a two-dimensional polar coordinate system (r,θ).

[0177] Note that the definition formula for the spiral scan pattern is not limited to this example, and the coordinate system used to define the wide-angle OCT scan pattern and OCT image is not limited to a two-dimensional polar coordinate system.

[0178] (S10: Apply coordinate transformation to OCT image) The image reconstruction unit 220 applies a coordinate transformation to the OCT image constructed in step S9.

[0179] For example, when a wide-angle OCT scan pattern is applied that includes a curved scan pattern defined in a polar coordinate system with the center of the OCT scan application area as the origin, the image reconstruction unit 220 forms an OCT image defined in a polar coordinate system from the data collected by the OCT scan applied to the eye E according to this curved scan pattern (S9), and converts this OCT image into an image defined in a three-dimensional Cartesian coordinate system (S10).

[0180] If the OCT image H1 shown in Figure 11 is constructed in step S9, the image construction unit 220 constructs each scan position n=n defined in the two-dimensional polar coordinate system (r,θ) according to the coordinate transformation formula between the two-dimensional polar coordinate system (r,θ) and the two-dimensional Cartesian coordinate system (x,y). p The coordinates are transformed into coordinates defined in a two-dimensional Cartesian coordinate system (x, y). This coordinate transformation formula is, for example, the aforementioned (x = cosθ - θ × sinθ, y = sinθ + θ × cosθ).

[0181] Through such coordinate transformations, for example, a group of OCT images H2(m) (m=1,2,···,M) shown in Figure 12 can be obtained. Each OCT image H2(m) is a B-scan image along the x-direction and is defined using a two-dimensional Cartesian coordinate system (x,z). Furthermore, the M OCT images H2(1) to H2(M) are arranged along the y-direction. Thus, the M OCT images H2(1) to H2(M) are defined using a three-dimensional Cartesian coordinate system (x,y,z).

[0182] (S11: Construct a 3D image from coordinate-transformed OCT images) The image reconstruction unit 220 can construct a three-dimensional image from the OCT image obtained in step S10 after coordinate transformation.

[0183] In this example, step S10 yields, for example, M stacked OCT images H2(1) to H2(M). The image construction unit 220 can voxelize the M OCT images H2(1) to H2(M) to construct volume data.

[0184] (S12: Displays a rendered image of a 3D image) The image construction unit 220 can render the 3D image constructed in step S11. The main control unit 211 can then display the resulting rendered image on the display unit 241.

[0185] <Mechanism of Action / Effect> The operation and effects of exemplary embodiments will be described.

[0186] An ophthalmic imaging apparatus (1) according to an exemplary embodiment includes a data acquisition unit, an image reconstruction unit, a focal position changing unit, a scan control unit, and a focus control unit.

[0187] The data acquisition unit collects data by applying an OCT scan to the eye under examination (E). In the above example, the data acquisition unit includes an OCT unit 100 and elements within the fundus camera unit 2 that constitute the measurement arm (retroreflector 41, OCT focusing lens 43, optical scanner 44, objective lens 22, etc.).

[0188] The image construction unit constructs an image from the data collected by the data acquisition unit. In the example above, the image construction unit includes an image construction unit 220.

[0189] The focal position changing unit is provided in the optical path (measuring arm) of the measurement light projected onto the eye (E) under examination by the data acquisition unit, and changes the focal position of the measuring arm. In the above example, the focal position changing unit includes an OCT focusing lens 43 and an OCT focusing drive unit 43A.

[0190] The scan control unit controls the data acquisition unit according to a scan pattern (wide-angle OCT scan pattern) which includes a continuous first partial pattern for the central region (310) and a continuous second partial pattern for the peripheral region (320) of the OCT scan application area (wide-angle OCT scan application area). In the above example, the scan control unit includes a scan control unit 213.

[0191] The focus control unit controls the focus position change unit to apply a first focal position in parallel with the application of an OCT scan to at least a portion of the first partial pattern. Furthermore, the focus control unit controls the focus position change unit to apply a second focal position different from the first focal position in parallel with the application of an OCT scan to at least a portion of the second partial pattern. In the above example, the focus control unit includes a focus control unit 214. Also in the above example, at least a portion of the first partial pattern corresponds to at least a portion of the central region 310, and the first focal position is, for example, the z-coordinate ζ in Figure 9A. 11 This corresponds to the following. Furthermore, in the above example, at least a portion of the second partial pattern corresponds to at least a portion of the peripheral region 320, and the second focal position corresponds to, for example, the z coordinate ζ in Figure 9A. 12 It corresponds to.

[0192] According to this embodiment, a scan pattern can be applied that includes a continuous first partial pattern for the central region and a continuous second partial pattern for the peripheral region. Considering the shape of the eyeball (the concave curvature of the fundus), the central region is located at a relatively deep position in the eyeball, and the peripheral region is located at a relatively shallow position. Therefore, the optimal focal position for the central region is different from the optimal focal position for the peripheral region. In addition to scan control according to the above scan pattern, this embodiment makes it possible to apply a first focal position to the central region (first partial pattern) and a second focal position to the peripheral region (second partial pattern). This makes it possible to perform wide-angle OCT scanning while moving the focal position at a practical speed. Therefore, according to this embodiment, it is possible to acquire high-quality OCT images while performing wide-angle OCT scanning at high speed.

[0193] Furthermore, when applying raster scanning to wide-angle OCT scanning as in the conventional method, several B-scans pass through both the central and peripheral regions. It is practically impossible to perform such B-scans at high speed while simultaneously switching between and applying two or more focal positions, including the first and second focal positions.

[0194] In this embodiment, the scan pattern may include a curved scan pattern defined in a polar coordinate system with the center of the OCT scan application area as the origin.

[0195] When setting the curved scan pattern, for example, the structural characteristics and control characteristics of the optical scanner (44), the required scan speed, and the required scan density can be taken into consideration.

[0196] In this embodiment, the curved scan pattern may be a spiral scan pattern (510) that extends from the center to the outer edge of the OCT scan application area. Alternatively, the curved scan pattern may be a spiral scan pattern that extends from the outer edge to the center of the OCT scan application area (520).

[0197] Another example of a curved scan pattern is a concentric circle scan pattern.

[0198] In this embodiment, the image reconstruction unit (220) can form an image defined in a polar coordinate system (OCT image H1) from data collected by an OCT scan applied to the eye (E) according to a curved scan pattern. Furthermore, the image reconstruction unit (220) can convert this image defined in a polar coordinate system (OCT image H1) into an image defined in a three-dimensional Cartesian coordinate system (OCT image H2(m)).

[0199] With this configuration, it is possible to construct an OCT image defined in a three-dimensional orthogonal coordinate system, which allows for easy image processing and analysis, from an OCT image obtained using a curved scan pattern.

[0200] In this embodiment, the first focal length corresponding to the first focal position applied to the central region (first partial pattern) may be set to be longer than the second focal length corresponding to the second focal position applied to the peripheral region (second partial pattern).

[0201] With this configuration, wide-angle OCT scans can be performed at high speed while changing the focal point to match the shape of the eyeball, making it possible to acquire high-quality OCT images.

[0202] In this embodiment, the ophthalmic imaging device (1) may apply a preparatory OCT scan to the eye under examination (E) by the data acquisition unit before performing a wide-angle OCT scan according to a wide-angle OCT scan pattern. If a preparatory OCT scan is performed, the image reconstruction unit (220) can construct a preparatory image (G) from the data collected by the preparatory OCT scan. Furthermore, the parameter setting unit (231) of the ophthalmic imaging device (1) in this embodiment can set one or more focus control parameters based on the preparatory image (G) constructed by the image reconstruction unit (220). In addition, the focus control unit (214) can control the focus position change unit according to the one or more focus control parameters set by the parameter setting unit (231).

[0203] Here, the focus control parameter may be a graph like the one shown in Figure 9A, or it may be a numerical value greater than or equal to 1. As an example of the latter, a numerical value indicating the focal position (for example, the z-coordinate ζ) 11 and ζ 12 ) is acceptable.

[0204] With this configuration, focus control parameters can be set based on the actual shape of the eye being examined (e.g., the fundus). This makes it possible to further improve the quality of the acquired OCT images.

[0205] In this embodiment, one or more focus control parameters constructed from the preparatory image may include a focus position change range that includes a first focal position and a second focal position. In the above example, for example, the focus control parameter in Figure 9A is the focus position change range [ζ 12 ,ζ 11 It contains ] as information.

[0206] With this configuration, it is possible to set the range in which the focal point is changed based on the preparatory image (i.e., based on the actual shape of the eye being examined).

[0207] In this embodiment, one or more focus control parameters constructed from the preparatory image may include at least one of the movement speed and movement acceleration of the focal position. In the above example, for example, the focus control parameter consisting of a smooth curve shown in Figure 9A includes the movement speed and movement acceleration of the focal position of the measuring arm as information.

[0208] With this configuration, it is possible to set the movement speed and acceleration of the focal point based on the preparatory image (i.e., based on the actual shape of the eye being examined).

[0209] The ophthalmic imaging device (1) according to this embodiment may further include an imaging unit (fundus camera unit 2) that repeatedly images the eye under examination (E), and a movement detection unit (232) that analyzes time-series images acquired by the imaging unit to detect movement of the eye under examination. The data acquisition unit may also include an optical scanner (44) that deflects light for OCT scanning. Furthermore, the scan control unit (213) can control the data acquisition unit according to a wide-angle OCT scan pattern and control the optical scanner (44) based on the output from the movement detection unit (232).

[0210] With this configuration, it is possible to perform a wide-angle OCT scan while tracking to correct the projection position of the measurement light in accordance with the movement of the eye being examined. As a result, even if the eye being examined moves during the wide-angle OCT scan, the scan can be performed appropriately according to the wide-angle OCT scan pattern. In addition, interruptions or retakes of the scan can be avoided.

[0211] The above example describes the application of OCT scanning to the fundus (Ef), but embodiments can be constructed that can achieve similar effects and behaviors on the anterior segment of the eye (cornea, lens, iris, iridocorneal angle, etc.). The focus control parameters are set according to the shape of the area being scanned by the OCT scanner.

[0212] An exemplary embodiment provides a method for controlling an ophthalmic imaging device. The ophthalmic imaging device to which this control method is applied includes a data acquisition unit that applies an OCT scan to the eye under examination to collect data, an image construction unit that constructs an image from the collected data, and a focal position changing unit provided in the optical path of the measurement light projected onto the eye under examination by the data acquisition unit.

[0213] This control method includes a scan control step and a focus control step. The scan control step controls the data acquisition unit according to a scan pattern that includes a continuous first partial pattern for the central region of the OCT scan application area and a continuous second partial pattern for the peripheral region. The focus control step controls the focus position changing unit to apply a first focal position in parallel with the application of the OCT scan to at least a portion of the first partial pattern, and to apply a second focal position different from the first focal position in parallel with the application of the OCT scan to at least a portion of the second partial pattern.

[0214] It is possible to combine any of the matters described in the exemplary embodiment with the control method for such an ophthalmic imaging device.

[0215] An exemplary embodiment provides a program that causes an ophthalmic imaging device to perform such a control method. Any of the matters described in the exemplary embodiment can be combined with this program.

[0216] Furthermore, it is possible to create a computer-readable non-temporary recording medium on which such a program is recorded. Any of the matters described in the exemplary embodiments can be combined with this recording medium. Also, this non-temporary recording medium may take any form, such as magnetic disks, optical disks, magneto-optical disks, and semiconductor memory.

[0217] According to the exemplary embodiment of the method, program, or recording medium, it is possible to acquire high-quality OCT images while performing wide-angle OCT scans at high speed. Furthermore, the exemplary embodiment of the method, program, or recording medium will produce effects and benefits depending on the items that are combined with it.

[0218] The configuration described above is merely an example of an embodiment of this invention. Therefore, any modifications (omissions, substitutions, additions, etc.) within the scope of the gist of this invention are possible. [Explanation of symbols]

[0219] 1. Ophthalmic imaging equipment 100 OCT units 210 Control Unit 211 Main Control Unit 212 Storage section 213 Scan Control Unit 214 Focus Control Unit 220 Image Construction Section 230 Data Processing Unit 231 Parameter setting section 232 Movement detection unit 240 User Interfaces 241 Display section 242 Operation section

Claims

1. A data acquisition unit that collects data by applying optical coherence tomography (OCT) scans to the eye under examination, An image construction unit constructs an image from the data collected by the data acquisition unit, A focal position changing unit is provided in the optical path of the measurement light projected onto the eye under examination by the data acquisition unit, A scan control unit controls the data acquisition unit according to a scan pattern that includes a continuous first partial pattern for the central region of the OCT scan application area and a continuous second partial pattern for the peripheral region. A focus control unit controls the focus position changing unit to apply a first focal position in parallel with applying an OCT scan to at least a portion of the first partial pattern, and to apply a second focal position different from the first focal position in parallel with applying an OCT scan to at least a portion of the second partial pattern, A parameter setting unit for setting focus control parameters provided to the focus control unit, Includes, Prior to the OCT scan according to the scan pattern, the data acquisition unit applies a preparatory OCT scan that passes through both the central region and the peripheral region to the eye under examination. The image reconstruction unit constructs a preliminary image from the data collected by the preliminary OCT scan. The parameter setting unit sets one or more focus control parameters based on the preparatory image constructed by the image construction unit. After the parameter setting unit sets one or more focus control parameters, the scan control unit causes the data acquisition unit to perform the OCT scan according to the scan pattern. In parallel with the OCT scan according to the scan pattern, the focus control unit controls the focus position change unit according to the one or more focus control parameters set by the parameter setting unit. An ophthalmic imaging device characterized by the following features.

2. The preparatory OCT scan includes two B-scans that are orthogonal to each other. The ophthalmic imaging device according to feature 1.

3. The one or more focus control parameters include a focus position change range that includes the first focus position and the second focus position. The ophthalmic imaging device according to claim 1 or 2.

4. The one or more focus control parameters include at least one of the movement speed and movement acceleration of the focal position. An ophthalmic imaging device according to any one of the features 1 to 3.

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