Ophthalmic photography device and ophthalmic photography program

Abstract

To provide an ophthalmologic imaging device and an ophthalmologic imaging program capable of acquiring appropriate OCT data on an eye to be examined.SOLUTION: An ophthalmologic imaging device for imaging an eye to be examined includes: an OCT optical system for dividing light from a light source into a measurement light path and a reference light path, and detecting, by a detector, a spectral interference signal of return light of the measurement light guided to the eye to be examined through an objective lens and the reference light corresponding to the measurement light; OCT data acquisition means for acquiring OCT data based on the spectral interference signal without using a saturation signal based on the reflection light generated when the measurement light is reflected by the objective lens, the saturation signal being generated in part of the spectral interference signal; and output means for outputting the OCT data.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to an ophthalmic imaging apparatus and an ophthalmic imaging program for imaging an eye to be examined. [Background technology]

[0002] In order to obtain OCT data of the subject's eye, an ophthalmic imaging apparatus is known that includes an OCT optical system that detects an interference signal between measurement light reflected from the subject's eye and reference light using a detector. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-195874 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned device, the measurement light may be reflected by the objective lens and received by the detector. In such cases, the interference signal may become saturated, causing noise in the OCT data and preventing proper OCT data from being obtained.

[0005] In view of the above problems, the present disclosure has as its technical object to provide an ophthalmic imaging apparatus and an ophthalmic imaging program that can acquire appropriate OCT data of a subject's eye. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention is characterized by having the following configuration.

[0007] (1) An ophthalmologic imaging apparatus according to a first aspect of the present disclosure includes an OCT optical system that splits light from a light source into a measurement optical path and a reference optical path, and detects, by a detector, a spectral interference signal between return light of the measurement light guided to the subject's eye via an objective lens and a reference light corresponding to the measurement light;One A-scan and the corresponding A portion of the spectral interference signal 、 A saturation signal based on the reflected light of the measurement light reflected by the objective lens occurs, the saturation signal is removed from the spectral interference signal corresponding to the A-scan, and a signal is calculated based on a signal different from the saturation signal in the spectral interference signal corresponding to the same A-scan. The apparatus includes an OCT data acquisition means for acquiring OCT data, and an output means for outputting the OCT data. (2) An ophthalmic imaging program according to a second aspect of the present disclosure is an ophthalmic imaging device for imaging an eye to be examined, the ophthalmic imaging device having an OCT optical system that splits light from a light source into a measurement optical path and a reference optical path, and detects, by a detector, a spectral interference signal between return light of the measurement light guided to the eye to be examined via an objective lens and reference light corresponding to the measurement light, the ophthalmic imaging program being used in the ophthalmic imaging device, when executed by a processor of the ophthalmic imaging device: One A-scan and the corresponding A portion of the spectral interference signal 、 A saturation signal based on the reflected light of the measurement light reflected by the objective lens occurs, the saturation signal is removed from the spectral interference signal corresponding to the A-scan, and a signal is calculated based on a signal different from the saturation signal in the spectral interference signal corresponding to the same A-scan. The ophthalmologic imaging apparatus is caused to execute an OCT data acquisition step of acquiring OCT data and an output step of outputting the OCT data. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an optical system and a control system of an ophthalmologic photographing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 4 is a diagram illustrating an example of a screen displayed on a display unit according to the present embodiment. [Figure 3] FIG. 10 is a diagram showing an example of a fundus image in which noise occurs due to reflection from an objective lens. [Figure 4] 10A and 10B are diagrams for explaining a method for suppressing reflection of light of a predetermined wavelength by coating. [Figure 5] FIG. 4 is a flowchart of a control operation executed by the ophthalmologic imaging apparatus of the present embodiment. [Figure 6] FIG. 10 is a diagram for explaining a method for setting scan lines. [Figure 7] FIG. 10 is a flowchart of a control operation when acquiring a tomographic image. [Figure 8] FIG. 10 is a diagram for explaining a saturated signal. [Figure 9] It is a diagram showing an example of a spectral interference signal from which a DC component has been removed. [Figure 10] It is a diagram showing an example of a spectral interference signal in which a saturation signal has been interpolated. [Figure 11] It is a diagram showing an example of a fundus image acquired by the ophthalmic imaging device according to the present embodiment.

Embodiments for Carrying Out the Invention

[0009] [Overview] Embodiments of an ophthalmic imaging device according to the present disclosure will be described. The items classified in the following <> can be used independently or in combination.

[0010] The ophthalmic imaging device of the present embodiment (for example, the ophthalmic imaging device 1) is a device for imaging an eye to be examined. The ophthalmic imaging device includes an OCT optical system (for example, the OCT optical system 200). Further, the ophthalmic imaging device includes OCT data acquisition means (for example, the control unit 70). Furthermore, the ophthalmic imaging device includes output means (for example, the display unit 75) for outputting OCT data.

[0011] <OCT Optical System> The OCT optical system splits the light from a light source (for example, the OCT light source 102) into a measurement optical path and a reference optical path, and detects, by a detector (for example, the detector 120), a spectral interference signal between the return light of the measurement light guided to the eye to be examined through an objective lens (for example, the objective lens 25) and the reference light corresponding to the measurement light. Note that the objective lens may be an objective lens group composed of a plurality of lenses.

[0012] For example, the OCT optical system may have a Fourier domain OCT optical system as its basic configuration. The Fourier domain OCT optical system may be a spectral domain OCT (SD-OCT) optical system. In this case, a broadband light source may be used as the light source, and a spectroscope (spectrometer) may be used as the detector. Also, for example, the Fourier domain OCT optical system may be a wavelength swept OCT (SS-OCT) optical system. In this case, a wavelength tunable light source may be used as the light source, and a balanced detector may be used as the detector.

[0013] In addition, the technology of this embodiment can also be applied to intensity OCT for detecting the reflection intensity of the eye to be examined, OCT angiography (e.g., Doppler OCT) for detecting motion contrast data of the eye to be examined, polarization sensitive OCT (PS-OCT), multi-functional OCT in which intensity OCT and PS-OCT are combined, and the like.

[0014] The OCT data may be data generated from a spectral interference signal. For example, the OCT data may be at least any one of A-scan data (e.g., A-scan tomographic image data, etc.), B-scan data (e.g., B-scan tomographic image data, two-dimensional OCT angiography data, etc.), three-dimensional data (e.g., three-dimensional tomographic image data, three-dimensional OCT angiography data, etc.), and the like. Note that the B-scan tomographic image data may be tomographic image data obtained by scanning the measurement light in any direction in the XY direction along a scanning line (transverse position). This may include two-dimensional OCT angiography data and the like. The three-dimensional tomographic image data may be tomographic image data obtained by two-dimensionally scanning the measurement light. This may include three-dimensional OCT angiography data. Also, for example, the tomographic image data of the eye to be examined may be en face image data based on such tomographic image data. This may include OCT en face image data, en face motion contrast data, and the like.

[0015] <OCT Data Acquisition Means> The OCT data acquisition means acquires OCT data based on the spectral interference signal without using a saturation signal, which is a saturation signal generated in part of the spectral interference signal and is based on the reflected light of the measurement light reflected by the objective lens. For example, a saturation signal can be generated when the reflected light of the measurement light reflected by the objective lens is detected by a detector. More specifically, a saturation signal can be generated when a signal due to the reflected light of the measurement light is detected in addition to the spectral interference signal, and a part of the spectral interference signal reaches the detection limit (dynamic range) of the detector. In other words, a saturation signal can be generated when the total intensity of the spectral interference signal and the reflected light exceeds the detection limit of the detector. Note that if the spectral interference signal includes a saturation signal, noise may be introduced into the OCT data. However, by not using the saturation signal, appropriate OCT data with reduced noise can be acquired.

[0016] When a saturation signal is detected in the spectral interference signal by the detection means described below, the OCT data acquisition means may acquire OCT data without using the saturation signal of the spectral interference signal. For example, when a saturation signal is detected in the spectral interference signal, the OCT data acquisition means may appropriately remove the saturation signal and acquire OCT data based on a signal different from the saturation signal. As an example, instead of obtaining a spectral interference signal that does not contain a saturation signal separately from the initially obtained spectral interference signal by adjusting the gain of the detection means, OCT data may be acquired by using a signal in a wavelength band different from that of the saturation signal of the initially obtained spectral interference signal. This allows for the acquisition of good OCT data.

[0017] The OCT data acquisition means may acquire OCT data based on a spectral interference signal obtained by interpolating a saturation signal using an interpolation means (described later). For example, the OCT data acquisition means can acquire good OCT data by estimating the signal strength that the saturation signal may have and using the estimated signal instead of the saturation signal.

[0018] The OCT data acquisition means can also acquire OCT data without using the saturation signal by discarding the saturation signal in the spectral interference signal. This also reduces noise caused by the saturation signal. However, for example, interpolating the saturation signal may improve the depth resolution in the noise-reduced portion compared to discarding the saturation signal. Therefore, interpolating the saturation signal in the spectral interference signal can acquire better OCT data.

[0019] Furthermore, the OCT data acquisition means can acquire better OCT data if a saturation signal is detected by a detection means (described later) and then interpolated by an interpolation means (described later). For example, if a position (e.g., wavelength band, frequency, etc.) to be treated as a saturation signal is set in advance based on experiments, simulations, etc., and a different position is used for the interpolation calculation, signals that are not actually saturation signals may be treated as saturation signals and interpolated. In other words, there is a possibility that even signals that do not affect noise may be removed and interpolated. For this reason, for example, by detecting and interpolating saturation signals, only the saturation signals may be appropriately replaced.

[0020] The OCT data acquisition means may acquire OCT data without using a saturation signal of the spectral interference signal when the focus adjustment unit is positioned at a predetermined position by a focus control unit (described later). For example, the predetermined position of the focus adjustment unit may be a position where the reflected light of the measurement light reflected by the objective lens is easily detected by the detector. As an example, it may be a position where the lens surface of the objective lens and the fiber end of the OCT optical system are conjugate with each other. As another example, it may be a position where the center of curvature of the objective lens and the fiber end of the OCT optical system are conjugate with each other. Note that these predetermined positions may be set in advance through experiments, simulations, etc. This allows the focus position to be adjusted according to the diopter of the test eye, and even if the reflected light of the measurement light from the objective lens is detected, it is possible to acquire OCT data with reduced noise due to the saturation signal. Furthermore, this allows the execution of calculations, etc. for interpolating the saturation signal to be omitted when the reflected light of the measurement light from the objective lens is difficult to detect (i.e., when a saturation signal is unlikely to occur).

[0021] The OCT data acquisition unit may acquire OCT data without using a saturation signal of the spectral interference signal when the measurement light passes through a predetermined position on the objective lens. For example, the predetermined position on the objective lens may be a position on the objective lens where the measurement light is likely to be reflected by the objective lens. As an example, the predetermined position may be the center position of the lens surface of the objective lens or a position near the center. Note that the position where the measurement light is likely to be reflected by the objective lens exists in a wider range from the center of the lens surface as the radius of curvature of the objective lens increases. In other words, the predetermined position on the objective lens may change depending on the shape of the lens surface. Furthermore, whether the measurement light passes through the predetermined position on the objective lens may change depending on the scanning conditions of the measurement light (scanning position, scanning pattern, etc.). Therefore, the predetermined position on the objective lens may be set in advance through experiments, simulations, etc. based on at least one of the shape of the lens surface of the objective lens and the scanning conditions of the measurement light. This makes it possible to acquire OCT data with reduced noise based on the saturation signal, even if the scanning conditions of the measurement light cause reflected light of the measurement light by the objective lens to be detected. Furthermore, this makes it possible to omit the execution of calculation processes for interpolating the saturation signal when it is difficult to detect the reflected light of the measurement light from the objective lens.

[0022] <Detection method> In this embodiment, the ophthalmologic imaging apparatus may include a detection unit (e.g., the control unit 70). The detection unit detects a saturation signal in the spectral interference signal. The detection unit may detect whether or not a saturation signal exists in the spectral interference signal. For example, in this case, the detection unit may detect whether or not the signal intensity of the spectral interference signal includes the detection limit value of the detector, and if the signal intensity includes the detection limit value, it may be determined that a saturation signal exists. The detection unit may also detect the position where the saturation signal exists in the spectral interference signal. For example, in this case, the detection unit may detect the wavelength band or frequency range where the signal intensity of the spectral interference signal is the detection limit value of the detector. Of course, the detection unit may also detect whether or not a saturation signal exists in the spectral interference signal and the position of the saturation signal in the spectral interference signal.

[0023] The detection means may perform detection on the spectral interference signal, or may perform detection on the interference signal obtained by applying noise removal processing (for example, DC subtraction) to the spectral interference signal.

[0024] <Interpolation method> In this embodiment, the ophthalmologic imaging apparatus may include an interpolation unit (e.g., the control unit 70). The interpolation unit interpolates the saturation signal of the spectral interference signal based on a signal different from the saturation signal. The interpolation unit may supplement the saturation signal of the spectral interference signal based on a signal different from the saturation signal and calculate the possible signal intensities of the spectral interference signal. For example, the possible signal intensities of the spectral interference signal may be calculated based on a signal of the spectral interference signal that has a wavelength band different from that of the saturation signal.

[0025] The interpolation means may interpolate the saturation signal using regression analysis of the spectral interference signal. For example, the regression analysis may be used to estimate a signal intensity that corresponds to the saturation signal of the spectral interference signal and that could be assumed if there were no detection limit for the detector. The spectral interference signal may be interpolated by replacing the saturation signal with the estimated signal. As an example of the regression analysis, an autoregressive model may be applied. As another example of the regression analysis, the GAPES (gapped amplitude and phase estimation) method may be applied.

[0026] The interpolation means may perform interpolation on the saturated signal of the spectral interference signal, or may perform interpolation on the saturated signal included in the interference signal obtained by applying noise removal processing (for example, DC subtraction) to the spectral interference signal.

[0027] <Focus adjustment section> In this embodiment, the ophthalmologic imaging apparatus may include a focus adjustment unit (e.g., the control unit 70). The focus adjustment unit adjusts the focus position of the measurement light in the OCT optical system. For example, the focus adjustment unit may be a lens (e.g., the focusing lens 124) that moves along the optical axis. Alternatively, the focus adjustment unit may be a lens that is inserted and removed on the optical axis. Alternatively, the focus adjustment unit may be a variable-focus lens that is arranged on the optical axis.

[0028] <Focus control means> In this embodiment, the ophthalmologic imaging apparatus may include a focus control unit (e.g., a control unit 70). The focus control unit positions the focus adjustment unit at a focus position corresponding to the diopter of the subject's eye. For example, the focus control unit may be configured to adjust the focus position by controlling a drive unit that moves or inserts / removes the focus adjustment unit (lens) along the optical axis. Also, for example, the focus adjustment control unit may be configured to adjust the focus position by changing the refractive index of the focus adjustment unit (variable focus lens).

[0029] The focus control means may be configured to appropriately correct the diopter even when the refractive error of the subject's eye is large. For example, the focus position may be adjustable so that the diopter can be corrected even for refractive errors of -10D or less and +10D or more, which are considered to be high diopter eyes. As an example, the focus position may be adjustable to accommodate at least -15D.

[0030] When the focus control means adjusts the focus position according to the diopter, the reflected light of the measurement light reflected by the objective lens may be more easily detected by the detector of the OCT optical system. For example, when the focus control means adjusts the focus position and the focus adjustment unit is positioned at a predetermined first position, the lens surface of the objective lens and the fiber end of the measurement optical system are conjugate with each other, and the reflected light is focused at the fiber end, making it easier for the detector to detect it. Also, when the focus adjustment unit is positioned at a predetermined second position and the center of curvature of the objective lens and the fiber end are conjugate with each other, the reflected light is also more easily detected by the detector. Note that the first position and the second position are not necessarily the same position.

[0031] <Photographing optical system> In this embodiment, the ophthalmologic imaging apparatus may include an imaging optical system (e.g., a fundus camera optical system 100). The imaging optical system irradiates the subject's eye with visible light via an objective lens and captures a color fundus image of the subject's eye. Additionally, the imaging optical system may also be capable of capturing a monochrome fundus image. By including such a configuration, the ophthalmologic imaging apparatus can acquire a color fundus image of the subject's eye by the imaging optical system while acquiring OCT data of the subject's eye by the OCT optical system.

[0032] In this embodiment, the measurement light of the OCT optical system is infrared light, and the objective lens may be coated to suppress reflection of visible light from the imaging optical system. For example, as described above, reflection of the measurement light by the objective lens may result in a saturation signal. Furthermore, for example, visible light from the imaging optical system reflected by the objective lens may be detected by an imaging element, resulting in noise (white spots) on the color fundus image. However, it is difficult to sufficiently suppress reflection by coating the objective lens for a wide wavelength range including visible and infrared light. Therefore, in this embodiment, the reflection of infrared light by the objective lens is removed by saturation signal processing, and the reflection of visible light by the objective lens is removed by coating. This allows for the appropriate acquisition of both OCT data in which noise caused by reflected measurement light (infrared light) is suppressed, and color fundus images in which noise caused by reflected visible light is suppressed.

[0033] If a color fundus image is captured using visible light, adjusting the capturing conditions (e.g., exposure time, gain of the image sensor, etc.) based on the acquired color fundus image to suppress noise caused by reflected visible light from the objective lens may result in changes in color and brightness of the color fundus image. In this embodiment, by suppressing reflected visible light using a coating, it is possible to acquire a color fundus image that is less affected by noise (white spots) while suppressing changes in color and brightness of the color fundus image.

[0034] <Output method> The output means outputs OCT data based on the spectral interference signal. The output means may output the OCT data to a display means (e.g., a monitor 75) to display the OCT data. The output means may also output the OCT data to a printing means to print the OCT data. The output means may also output the OCT data to a storage means (e.g., memory 74, a server, a cloud, etc.) to store the OCT data. The output means may output the OCT data by at least one of the above means of display, printing, storage, etc.

[0035] Note that the present disclosure is not limited to the devices described in this embodiment. For example, terminal control software (program) that performs the functions of the above embodiment can be supplied to a system or device via a network or various storage media, etc., and a control device (e.g., CPU, etc.) of the system or device can read and execute the program.

[0036] [Example] FIG. 1 is a schematic configuration diagram for explaining the configuration of an ophthalmic imaging device according to this example. In the following description, as an ophthalmic imaging device, an ophthalmic imaging device that captures a tomographic image of the fundus of an eye to be examined using infrared light and also captures a frontal image of the fundus of the eye to be examined using visible light will be described as an example.

[0037] The ophthalmic imaging device 1 of this example mainly includes an illumination optical system 10, a fundus imaging optical system 30, and an interference optical system 200 (hereinafter also referred to as an OCT optical system). Further, the optical system may include a focus index projection optical system 40, an alignment index projection optical system 50, and an anterior eye observation optical system 60. The illumination optical system 10 and the fundus imaging optical system 30 are used as a fundus camera optical system 100 for obtaining a color fundus image by imaging the fundus with visible light (e.g., in a non-dilated state). The fundus imaging optical system 30 captures an image of the fundus of the eye to be examined. The OCT optical system 200 non-invasively obtains a tomographic image of the fundus of the eye to be examined using the technique of optical interference.

[0038] <OCT Optical System> The OCT optical system 200 has the device configuration of a so-called ophthalmic optical coherence tomography (OCT) system and captures a tomographic image of the eye E. The OCT optical system 200 splits light emitted from an OCT light source 102 into measurement light (sample light) and reference light using a coupler (light splitter) 104. The OCT optical system 200 then guides the measurement light to the fundus Ef of the eye E and guides the reference light to the reference optical system 110. The measurement light passes through a collimator lens 123 and a focus lens 124 and reaches the scanning unit 108, where the reflection direction is changed by, for example, driving two galvanometer mirrors. The measurement light reflected by the scanning unit 108 is then reflected by a dichroic mirror 24 and then focused on the fundus of the subject's eye via an objective lens 25. Thereafter, the detector (light receiving element) 120 receives interference light resulting from the synthesis of the measurement light reflected by the fundus oculi Ef and the reference light.

[0039] The detector 120 detects the interference state between the measurement light and the reference light. In this embodiment, the spectral intensity of the interference light (hereinafter referred to as a spectral interference signal) is detected by the detector 120, and a depth profile (A-scan signal) in a predetermined range is acquired by Fourier transform of the spectral intensity data. In this embodiment, a broadband light source is used as the OCT light source 102, and a spectroscope (spectrometer) is used as the detector 120.

[0040] The scanning unit 108 scans the light emitted from the measurement light source on the fundus of the subject's eye. For example, the scanning unit 108 scans the measurement light two-dimensionally (in the X and Y directions (transverse directions)) on the fundus. The scanning unit 108 is disposed at a position approximately conjugate with the pupil. The scanning unit 108 is, for example, two galvanometer mirrors, and the reflection angles thereof are arbitrarily adjusted by the driving unit 151.

[0041] As a result, the reflection (traveling) direction of the light beam emitted from the OCT light source 102 is changed, and the light beam is scanned in any direction on the fundus Ef. This changes the imaging position on the fundus Ef. The scanning unit 108 may be configured to deflect light. For example, a reflecting mirror (galvanometer mirror, polygon mirror, resonant scanner) or an acousto-optic element (AOM) that changes the traveling (deflection) direction of light may be used.

[0042] The reference optical system 110 generates reference light to be combined with reflected light obtained by reflection of the measurement light on the fundus oculi Ef. The reference optical system 110 may be of a Michelson type or a Mach-Zehnder type.

[0043] The reference optical system 110 may change the optical path length difference between the measurement light and the reference light by moving an optical member in the reference light path. For example, the reference mirror 131 is moved in the optical axis direction. A configuration for changing the optical path length difference may be disposed in the measurement light path of the measurement optical system.

[0044] More specifically, the reference optical system 110 mainly includes, for example, a collimator lens 129, a reference mirror 131, and a reference mirror driver 150. The reference mirror driver 150 is disposed in the reference light path and is configured to be movable in the optical axis direction to change the optical path length of the reference light. The light is reflected by the reference mirror 131 and returned to the coupler 104, from which it is guided to the detector 120. As another example, the reference optical system 110 is formed by a transmission optical system (for example, an optical fiber), and the light from the coupler 104 is transmitted rather than returned, thereby guiding it to the detector 120.

[0045] <Fundus camera optical system> Next, an example of the optical arrangement of the fundus camera optical system 100 will be shown.

[0046] <Illumination optical system> The illumination optical system 10 includes, for example, an observation illumination optical system and a photographic illumination optical system. The photographic illumination optical system mainly includes a photographic light source 14, a condenser lens 15, a ring slit 17, a relay lens 18, a mirror 19, a black spot plate 20, a relay lens 21, a perforated mirror 22, and an objective lens 25. The photographic light source 14 may be a flash lamp, an LED, or the like. The black spot plate 20 has a black spot in the center. The photographic light source 14 is used, for example, to photograph the fundus of the subject's eye using light in the visible range.

[0047] The observation illumination optical system mainly includes an observation light source 11, an infrared filter 12, a condenser lens 13, a dichroic mirror 16, and an optical system ranging from a ring slit 17 to an objective lens 25. The observation light source 11 may be a halogen lamp, an LED, or the like. The observation light source 11 is used, for example, to observe the fundus of the subject's eye using light in the near-infrared range. The infrared filter 12 is provided to transmit near-infrared light with a wavelength of 750 nm or more and to cut light in a wavelength band shorter than 750 nm. The dichroic mirror 16 is disposed between the condenser lens 13 and the ring slit 17. The dichroic mirror 16 has the property of reflecting light from the observation light source 11 and transmitting light from the imaging light source 14. The observation light source 11 and the imaging light source 14 may be configured to be arranged in series on the same optical axis.

[0048] <Photographing optical system> The fundus photography optical system 30 mainly comprises, for example, an objective lens 25, a photographing aperture 31, a focusing lens 32, an imaging lens 33, and an image sensor 35. The photographing aperture 31 is located near the opening of the perforated mirror 22. The focusing lens 32 is movable in the optical axis direction. The image sensor 35 can be used for photography sensitive to the visible range. The photographing aperture 31 is located at a position approximately conjugate with the pupil of the subject's eye E relative to the objective lens 25. The focusing lens 32 is moved in the optical axis direction by a movement mechanism 49 equipped with a motor.

[0049] A dichroic mirror 37, which has the property of reflecting a portion of infrared light and visible light and transmitting most of visible light, is disposed between the imaging lens 33 and the image sensor 35. An observation image sensor 38, which is sensitive to the infrared region, is disposed in the direction of reflection from the dichroic mirror 37. Note that a bounce mirror may be used instead of the dichroic mirror 34. The bounce mirror is inserted into the optical path when observing the fundus and is retracted from the optical path when photographing the fundus, for example.

[0050] A removable dichroic mirror (wavelength-selective mirror) 24 is obliquely disposed between the objective lens 25 and the perforated mirror 22 as an optical path branching member. The dichroic mirror 24 reflects the wavelength light of the OCT measurement light and the wavelength light (e.g., central wavelength 940 nm) of the alignment target projection optical system 50 and the anterior eye illumination light source 58. The dichroic mirror 24 also has the property of transmitting wavelengths of 800 nm or less, including the light source wavelength (e.g., central wavelength 780 nm) of the wavelength light for fundus observation illumination. During photography, the dichroic mirror 24 is flipped up in conjunction with an insertion / removal mechanism 66 and retracted out of the optical path. The insertion / removal mechanism 66 can be configured with a solenoid, a cam, or the like.

[0051] Furthermore, an optical path compensation glass 28 is disposed on the imaging element 35 side of the dichroic mirror 24 so that it can be flipped up by driving an insertion / removal mechanism 66. When inserted into the optical path, the optical path compensation glass 28 serves to correct the position of the optical axis L1 that has been shifted by the dichroic mirror 24.

[0052] The light beam emitted from the observation light source 11 is converted into an infrared light beam by the infrared filter 12, reflected by the condenser lens 13 and the dichroic mirror 16, and illuminates the ring slit 17. The light that passes through the ring slit 17 passes through the relay lens 18, the mirror 19, the black dot plate 20, and the relay lens 21 and reaches the perforated mirror 22. The light reflected by the perforated mirror 22 passes through the correction glass 28 and the dichroic mirror 24, and is once converged near the pupil of the subject's eye E by the objective lens 25, and then diffuses to illuminate the fundus of the subject's eye.

[0053] Furthermore, light reflected from the fundus passes through the objective lens 25, the dichroic mirror 24, the correction glass 28, the opening of the perforated mirror 22, the photographing diaphragm 31, the focusing lens 32, the imaging lens 33, and the dichroic mirror 37 to form an image on the image sensor 38. The image sensor 38 is disposed at a position conjugate with the fundus. The output of the image sensor 38 is input to the control unit 70, which then displays on the display unit 75 a fundus observation image (frontal fundus observation image) 82 of the subject's eye captured by the image sensor 38.

[0054] The light beam emitted from the imaging light source 14 passes through a condenser lens 15 and a dichroic mirror 16. Thereafter, the light travels along the same optical path as the illumination light for fundus observation, and the fundus is illuminated with visible light. The light reflected from the fundus then travels through the objective lens 25, the opening of the perforated mirror 22, the imaging diaphragm 31, the focusing lens 32, and the imaging lens 33, and forms an image on the imaging element 35. In this way, a color fundus image of the subject's eye is captured by the imaging element 35.

[0055] In this embodiment, the objective lens 25 is coated to suppress reflection of visible light from the imaging light source 14. This prevents the reflected light from the objective lens from being received by the image sensor 35, thereby suppressing noise from appearing on the color fundus image (details will be described later).

[0056] <Focus index projection optical system> The focus target projection optical system 40 mainly comprises an infrared light source 41, a slit target plate 42, two deflection prisms 43, a projection lens 47, and a spot mirror 44 disposed obliquely in the optical path of the illumination optical system 10. The two deflection prisms 43 are attached to the slit target plate 42. The spot mirror 44 is disposed obliquely in the optical path of the illumination optical system 10. The spot mirror 44 is also fixed to the tip of a lever 45. The spot mirror 44 is normally disposed obliquely in the optical axis, but is retracted out of the optical path by rotation of the shaft of a rotary solenoid 46 at a predetermined timing before photography.

[0057] The spot mirror 44 is disposed at a position conjugate with the fundus of the subject's eye E. The light source 41, slit index plate 42, deflection prism 43, projection lens 47, spot mirror 44, and lever 45 are moved in the optical axis direction by a movement mechanism 49 in conjunction with the focusing lens 32. The light beam from the slit index plate 42 of the focus index projection optical system 40 passes through the deflection prism 43 and projection lens 47 and is reflected by the spot mirror 44, and then passes through the relay lens 21, the aperture mirror 22, the dichroic mirror 24, and the objective lens 25 to be projected onto the fundus of the subject's eye E. The focus index image projected onto the fundus of the subject's eye is then captured by the imaging element 38 together with the fundus image.

[0058] <Alignment target projection optical system> As shown within the dotted line in the upper left of FIG. 1 , the alignment target projection optical system 50, which projects the alignment target light beam, has multiple infrared light sources arranged at 45-degree intervals on a concentric circle centered on the imaging optical axis L1. The ophthalmologic imaging apparatus in this embodiment mainly includes a first target projection optical system (0 degrees and 180 degrees) and a second target projection optical system. The first target projection optical system has an infrared light source 51 and a collimating lens 52. The second target projection optical system is located at a different position from the first target projection optical system and has six infrared light sources 53. The infrared light sources 51 are arranged symmetrically across a vertical plane passing through the imaging optical axis L1. In this case, the first target projection optical system projects an infinitely distant target onto the cornea of ​​the subject's eye E from the left and right. The second target projection optical system is configured to project a finitely distant target onto the cornea of ​​the subject's eye E from the top, bottom, or oblique direction. For convenience, FIG. 1 shows only the first target projection optical system (0 degrees and 180 degrees) and a part of the second target projection optical system (45 degrees, 135 degrees).

[0059] <Anterior segment observation optical system> The anterior-segment observation (photography) optical system 60, which images the anterior segment of the subject's eye, mainly includes a dichroic mirror 61, an aperture 63, a relay lens 64, and a two-dimensional image sensor (light-receiving element: hereinafter, sometimes abbreviated as image sensor 65) 65 on the reflecting side of the dichroic mirror 24. The image sensor 65 has sensitivity in the infrared range. The image sensor 65 also serves as an imaging means for detecting an alignment index, and images of the anterior segment and alignment index illuminated by an anterior-segment illumination light source 58 that emits infrared light are captured by the image sensor 65. The anterior segment illuminated by the anterior-segment illumination light source 58 is received by the image sensor 65 via the objective lens 25, the dichroic mirror 24, and the dichroic mirror 61 through the optical system of the relay lens 64. An alignment light beam emitted from a light source included in the alignment index projection optical system 50 is projected onto the cornea of ​​the subject's eye. The corneal reflection image is received (projected) onto the image pickup element 65 via the objective lens 25 to the relay lens 64 .

[0060] The output of the two-dimensional image sensor 65 is input to the control unit 70, and as shown in Fig. 2, the anterior eye image captured by the two-dimensional image sensor 65 is displayed on the display unit 75 as an anterior eye observation image 81. The anterior eye observation optical system 60 also serves as a detection optical system for detecting the alignment state of the device main body with respect to the subject's eye.

[0061] Infrared light sources (two in this embodiment, but not limited to this) 55 are arranged around the hole in the perforated mirror 22 to form optical alignment indicators (working dots W) on the cornea of ​​the subject's eye. The light sources 55 may be configured to guide infrared light to an optical fiber whose end face is located near the perforated mirror 22. The corneal reflected light from the light sources 55 is formed on the imaging surface of the imaging element 38 when the working distance between the subject's eye E and the imaging unit 3 (device main body) becomes appropriate. This allows the examiner to fine-tune the alignment using the working dots formed by the light sources 55 while the fundus image is displayed on the monitor 75.

[0062] <Control unit> The control unit 70 includes a CPU (processor), RAM, ROM, etc. The CPU controls the ophthalmic imaging apparatus 1. The RAM temporarily stores various types of information. The ROM stores various programs, initial values, etc. for controlling the operation of the ophthalmic imaging apparatus 1.

[0063] The control unit 70 is electrically connected to a nonvolatile memory (hereinafter simply referred to as memory) 74, an operation unit 76, the device drive unit 6, a display unit 75, and the like. The memory 72 is a non-transitory storage medium that can retain its stored contents even when the power supply is cut off. For example, a hard disk drive, a flash ROM, or a USB memory that is detachably attached to the ophthalmic imaging apparatus 1 can be used as the memory 72. The memory 72 also stores an imaging control program for controlling the imaging of tomographic images and color fundus images by the ophthalmic imaging apparatus 1. The memory 72 also stores various information related to imaging, such as tomographic images (OCT data) on the scan line, three-dimensional tomographic images (three-dimensional OCT data), color fundus images, and information on the imaging position of the tomographic images.

[0064] Various operation instructions are input by the examiner to the operation unit 76. The operation unit 76 outputs a signal according to the input operation instructions to the CPU 71. The operation unit 76 may be, for example, at least one user interface such as a mouse, a joystick, a keyboard, or a touch panel.

[0065] The device driving unit 6 moves the ophthalmic photographing device 1 in the left-right, up-down, and front-back directions relative to the subject's eye E. The control unit 70 controls the device driving unit 6 to change the positional relationship between the ophthalmic photographing device 1 and the subject's eye E. For example, the control unit 70 may control the device driving unit 6 based on input from the operation unit 76.

[0066] The display unit 75 may be a display mounted on the device main body, or may be a display connected to the main body. A display of a personal computer (hereinafter referred to as "PC") may be used. Multiple displays may be used in combination. The display unit 75 may also be a touch panel. When the display unit 75 is a touch panel, the display unit 75 functions as the operation unit 76. For example, the display unit 75 displays image data obtained by processing a spectral interference signal acquired by the OCT optical system 100.

[0067] The control unit 70 may be configured with multiple control units (i.e., multiple processors). For example, the control unit 70 of the ophthalmic imaging apparatus 10 may be configured with a setting control unit provided in a PC and an operation control unit that controls the operation of the OCT optical system 100, etc. In this case, for example, the setting control unit of the PC may set the imaging position of the tomographic image, etc. based on the operation of an operation unit connected to the PC, and instruct the operation control unit about the set content. The operation control unit may control the imaging operation of each component of the ophthalmic imaging apparatus 10 in accordance with the instructions from the setting control unit. Furthermore, the process of generating (acquiring) an image based on the spectral interference signal may be performed by either the operation control unit or the setting control unit.

[0068] The control unit 70 controls each component of the fundus camera optical system 100, the OCT optical system 200, the focus target projection optical system 40, the alignment target projection optical system 50, and the anterior segment observation optical system 60 based on an operation signal output from the operation unit 76.

[0069] For example, the control unit 70 acquires a tomographic image by image processing based on the spectral interference signal output from the detector 120 of the OCT optical system 200, and also acquires a fundus image (frontal fundus image) based on a light-receiving signal output from a light-receiving element (two-dimensional light-receiving element 35 or observation image sensor 38) of the fundus camera optical system 100. Furthermore, for example, the control unit 70 acquires an anterior eye image based on a light-receiving signal output from the image sensor 65. The acquired tomographic image, fundus image, and anterior eye image are output to the display unit 75 as a still image or a moving image, and are also stored in the memory 72.

[0070] <Reflection of measurement light and imaging light by the objective lens> Here, when the measurement light in the OCT optical system 200 irradiated toward the subject's eye is reflected by the objective lens 25 and the reflected light of the measurement light is detected by the detector 120, noise N may occur in the tomographic image as shown in Fig. 3. Furthermore, when the visible light in the fundus camera optical system 100 irradiated toward the subject's eye is reflected by the objective lens 25 and the reflected light of the visible light is captured by the image sensor 35, noise (such as blown-out highlights in the color fundus image) may occur in the color fundus image.

[0071] To reduce these noises, it is conceivable to apply a coating to the objective lens 25 to suppress reflection of the measurement light (infrared light) of the OCT optical system and the visible light of the fundus camera optical system 100. Specifically, as shown in FIG. 4, a coating is applied so that the measurement light and imaging light reflected by the coating film are in opposite phase to the measurement light and imaging light reflected by the objective lens. In this way, reflected light R1 by the objective lens and reflected light R2 by the coating film interfere with each other and weaken each other, resulting in a reduction in reflected light R1 by the objective lens 25. Note that, for example, reflection of multiple light beams with different wavelengths can also be suppressed by stacking multiple anti-reflection films as coating films.

[0072] However, the wider the wavelength band in which reflection is suppressed by the coating film, the more complex the structure of the anti-reflection film becomes. For example, if an anti-reflection film is applied to suppress the reflection of light of a specific wavelength, the phase of light of other wavelengths may be shifted by the thickness of the anti-reflection film. As a result, problems may arise, such as the reflection of light of unintended wavelengths or a decrease in the amount of reflected light reduction.

[0073] Furthermore, the more layers of coating film are layered on an objective lens, the more difficult the coating process itself becomes. For example, when applying one layer of anti-reflection film, a manufacturing error (tolerance) of -0.01 to +0.01 mm (these values ​​are merely examples) occurs. In this case, if ten layers of anti-reflection film are layered, the overall thickness error of the laminated anti-reflection film will be -0.1 to +0.1 mm. In other words, thickness variations of 0.2 mm will occur between individual lenses produced. This can lead to problems such as differences in the wavelengths at which reflection can be suppressed and differences in the amount of reflected light reduced between lenses. For this reason, the more layers of anti-reflection film are layered, the more stringent the conditions under which the coating must be applied.

[0074] In this embodiment, for the reasons described above, it is difficult to coat the objective lens with an anti-reflection film that suppresses the reflection of measurement light by the objective lens to an extent that noise does not occur in the tomographic image and suppresses the reflection of visible light by the objective lens to an extent that noise does not occur in the color fundus image in an apparatus that combines the OCT optical system 200 and the fundus camera optical system 100. Note that even if the reflection of both measurement light and visible light can be suppressed to some extent by coating the objective lens, if the amount of reflected light reduction is insufficient, noise may occur in at least one of the tomographic image and the color fundus image.

[0075] For example, in the ophthalmologic imaging apparatus 1 of this embodiment, a coating is applied to the objective lens so that reflection suppression in the visible light band takes priority over reflection suppression in the infrared light band. This removes reflected light from the imaging light of the fundus camera optical system 100, allowing a color fundus image with reduced noise to be acquired. Furthermore, reflected light from the measurement light of the OCT optical system 200 that was not removed by the coating is removed by processing a saturation signal included in part of the spectral interference signal, allowing a tomographic image with reduced noise to be acquired (details will be described later). In other words, the ophthalmologic apparatus 1 of this embodiment can acquire both color fundus images and tomographic images with reduced noise.

[0076] It should be noted that it is not always necessary to suppress reflection in the infrared light band by using a coating.

[0077] [Operation] The control operation of the ophthalmologic photographing apparatus 1 will be described with reference to the flowchart of Fig. 5. In this embodiment, a case where a tomographic image and a color fundus image of the fundus Ef of the subject's eye are acquired will be described.

[0078] 2, the control unit 70 may display an anterior eye observation image 81 from the imaging element 65, a fundus observation image 82 from the imaging element 38, and a tomographic image 83 from the control unit 70 as an observation screen on the screen of the display unit 75. For example, the anterior eye observation image 81, the fundus observation image 82, and the tomographic image 83 may each be a live image that is updated in real time, or may be a still image.

[0079] <S1:アライメント> The examiner supports the examinee's face on a face support unit (not shown). The examiner then instructs the examinee to gaze at a fixation target (not shown). At this time, the dichroic mirror 24 is inserted in the optical path of the fundus imaging optical system 30, and the anterior eye image captured by the image sensor 65 is displayed on the display unit 75. While observing the anterior eye image, the examiner controls the operation unit 76 to change the positional relationship between the ophthalmologic imaging device 1 and the examinee's eye E, thereby performing alignment. For example, the examiner performs alignment in the left-right, up-down, and front-to-back directions based on the image height of the alignment target image projected onto the anterior eye of the examinee's eye by the alignment target projection optical system 50. For example, the control unit 70 may perform automatic alignment by detecting the alignment target image through image analysis of the anterior eye image. For details of the alignment method, see Japanese Patent Application Laid-Open No. 2015-195874.

[0080] After the alignment is completed, the control unit 70 may determine whether the pupil state of the subject's eye is appropriate based on the pupil edge detected from the anterior eye image. For details of the method for determining whether the pupil state is appropriate, the method described in Japanese Patent Application Laid-Open No. 2005-160549 may be referred to.

[0081] After the alignment is completed, the control unit 70 may adjust the focus of the fundus camera optical system 100 (auto focus). For example, the control unit 70 acquires a fundus image of the subject eye from the imaging device 38. Then, the control unit 70 detects the focus state based on the focus index projected by the focus index projection optical system 40. Then, the control unit 70 may control the drive of the moving mechanism 49 to move the focusing lens 32 along the optical axis to adjust the focus on the fundus. For details of the auto focus method, reference may be made to the method described in Japanese Patent Laid-Open No. 2015-195874.

[0082] <S2: Setting of Scan Position> When the alignment is completed, the examiner sets the position where the tomographic image is to be acquired. For example, the examiner may set the position where the tomographic image is to be acquired with respect to the fundus observation image 82 on the display unit 75. As an example in that case, as shown in FIG. 6, the examiner uses the touch panel type display unit 75 and performs a drag operation to move the line 85 with respect to the fundus observation image 82 to set the scan position. FIG. 6(a) is a diagram showing the scan position before the drag operation, and FIG. 6(b) is a diagram showing the scan position after the drag operation.

[0083] <S3: Optimization of Imaging Conditions> When the setting of the scan position is completed, the control unit 70 optimizes the imaging conditions of the OCT optical system 200. The control unit 70 issues a trigger signal for starting the optimization of the imaging conditions and starts the control operation of the optimization. In this embodiment, the control of the optimization is the control of the optical path length adjustment, the focus adjustment, and the adjustment of the polarization state (polarizer adjustment). In the control of the optimization, it is only necessary to satisfy a certain allowable condition for the fundus, and it is not always necessary to adjust to the most appropriate state.

[0084] In the optimization control, as initialization control, the control unit 70 sets the positions of the reference mirror 131 and the focusing lens 124 to their initial positions. After the initialization is completed, the control unit 70 moves the reference mirror 131 in one direction by a predetermined step from the set initial position to perform the first optical path length adjustment (the first automatic optical path length adjustment). Also, in parallel with the first optical path length adjustment, the control unit 70 acquires focus position information (for example, the movement amount of the lens 32) with respect to the fundus of the eye to be examined based on the focusing result of the fundus camera optical system with respect to the fundus of the eye to be examined. When the focus position information is acquired, the control unit 70 controls the drive unit 12ba to move the focusing lens 124 to the focus position to perform autofocus adjustment (focus adjustment). Note that the focus position may be any position where the contrast of the tomographic image that can be tolerated as an observation image can be obtained, and it is not necessarily the optimal position in the focused state.

[0085] After the focus adjustment is completed, the control unit 70 moves the reference mirror 131 again in the optical axis direction to perform a second optical path length adjustment for readjusting the optical path length (fine adjustment of the optical path length). After the second optical path length adjustment is completed, the control unit 70 drives the polarizer 133 for adjusting the polarization state of the reference light to adjust the polarization state of the measurement light (for details, refer to Japanese Patent Application No. 2012-56292). <0OO0327>

[0086] As described above, when the optimization control operation is completed, the fundus part desired by the examiner can be observed with high sensitivity and high resolution.

[0087] <S4: Acquisition of Tomographic Image> When the optimization of the shooting conditions is completed, the examiner inputs an imaging signal to the control unit 70 via the operation unit 76. Thereby, the acquisition of the tomographic image is started. The detailed control operation for acquiring the tomographic image will be described using the flowchart of FIG. 7.

[0088] <S401: Acquisition of Spectral Interference Signal> First, the control unit 70 acquires a tomographic image by B-scan based on the set scanning position. The control unit 70 drives the scanning unit 108 to scan the measurement light so that a tomographic image of the fundus corresponding to the display position of the line 85 set on the fundus observation image 82 can be obtained.

[0089] An interference light obtained by combining the return light of the measurement light reflected by the test eye and the reference light is received by the detector (light receiving element) 120, and a spectral interference signal is acquired. The spectral interference signal (spectral data) is represented as the signal intensity for each wavelength. Also, the spectral interference signal may be rewritten as a function of the wavelength λ and converted into a function with equal intervals with respect to the wave number k (= 2π / λ).

[0090] Here, as shown in FIG. 8, when the reflected light of the measurement light reflected by the objective lens 25 is received by the detector 120, for the detected spectral interference signal Sp0, the signal intensity increases compared to the original spectral interference signal Sp1, and as a result, a part of the spectral interference signal may exceed the detection range Ra of the detector 120. In this case, the part exceeding the detection range (Sp2 in FIG. 8) is saturated, and this part is output as a signal with a signal intensity at the detection limit value (for example, signal intensity Ia). In the present embodiment, the part (Sp3 in FIG. 8) where the signal intensity is output as the detection limit value is treated as a saturation signal.

[0091] <S_{402}: Detect saturation signal on spectral interference signal> When acquiring a tomographic image using the saturation signal, it may not be possible to appropriately acquire the tomographic image. As an example, as shown in FIG. 3, noise N may occur on the tomographic image. Therefore, the control unit 70 detects the saturation signal on the spectral interference signal and performs interpolation processing. Thereby, a tomographic image with the noise N suppressed is acquired.

[0092] The control unit 70 detects whether the acquired spectral interference signal contains a saturation signal by analyzing the spectral interference signal. When it is detected that the spectral interference signal contains a saturation signal, the control unit 70 detects where the saturation signal appears in terms of frequency. As an example, when there is a portion on the spectral interference signal that takes a predetermined signal intensity Ia, the control unit 70 detects that portion as the saturation signal.

[0093] After detecting the saturation signal, the control unit 70 performs DC subtraction to remove the DC component. FIG. 9 is a diagram showing the spectral interference signal from which the DC component has been removed. For example, even when the DC component is removed, the portion corresponding to the saturation signal is not removed. For example, the control unit 70 may perform arithmetic processing to remove noise components such as compensation for group velocity dispersion.

[0094] Note that when the saturation signal is not detected, there is no saturated portion on the interference signal and no noise occurs on the fundus image, so the interpolation process described below may not be performed.

[0095] <S403: Interpolation Process> When a saturation signal is detected on the spectral interference signal, the control unit 70 performs the interpolation process described below to interpolate the saturation signal (that is, the portion detected as the signal intensity Ia because the signal intensity exceeded the detection limit of the detector 120).

[0096] As the interpolation process, the control unit 70 interpolates the saturation signal by performing arithmetic processing on the spectral interference signal from which the DC component has been removed using the portion other than the saturation signal. An example of the arithmetic processing using the portion other than the saturation signal will be described below.

[0097] First, the control unit 70 performs regression analysis on the spectral interference signal to estimate the signal of the missing part on the spectral interference signal. As an example of regression analysis, the control unit 70 applies an autoregressive model to the spectral interference signal to estimate the signal of the missing part on the spectral interference signal. Then, the control unit 70 interpolates the saturation signal for the spectral interference signal by replacing the estimated signal with the saturation signal. FIG. 10 shows an example of the spectral interference signal after interpolation. For example, by performing arithmetic processing on the spectral interference signal from which the DC component has been removed, the spectral interference signal can be interpolated more accurately.

[0098] In this way, by performing regression analysis, the missing interference signal can be interpolated more accurately. Of course, the application of the autoregressive model is an example of a method for estimating the waveform of the missing part on the spectral interference signal, and is not limited thereto. For example, any arithmetic processing that uses the part of the spectral interference signal other than the saturation signal, such as the application of the autoregressive model, can interpolate the waveform of the missing part more accurately.

[0099] <S404: Fourier transform> The control unit 70 obtains a tomographic image as information in the depth region (Z space) by performing a Fourier transform on the interpolated spectral interference signal. Further, the information after the Fourier transform may be represented as a signal including a real component and an imaginary component in the Z space. The control unit 70 may obtain a tomographic image by obtaining the absolute values of the real component and the imaginary component in the signal in the Z space.

[0100] According to the above, a tomographic image with reduced noise N due to reflection of the objective lens 25 is obtained. FIG. 11 shows an example of a tomographic image with reduced noise due to reflection of the objective lens 25.

[0101] <S5: Acquisition of color fundus image> Once the tomographic image is obtained, the control unit 70 acquires a color fundus image 82 using the fundus camera optical system 100. While observing the fundus observation image 82 displayed on the display unit 75, the examiner operates the operation unit 76 to fine-tune the alignment and focus so that the image can be captured in the desired state. Then, when the examiner inputs a command to start capturing, the image is captured. The control unit 70 drives the insertion / removal mechanism 66 based on a trigger signal from an image capture start switch (not shown), thereby removing the dichroic mirror 24 from the optical path and causing the image capture light source 14 to emit light.

[0102] The fundus of the subject's eye is illuminated with visible light when the imaging light source 14 is turned on. Light reflected from the fundus passes through the objective lens 25, the opening of the perforated mirror 22, the imaging diaphragm 31, the focusing lens 32, the imaging lens 33, and the dichroic mirror 37, and is focused on the two-dimensional light-receiving element 35. The color fundus image captured by the two-dimensional light-receiving element 35 is stored in the memory 72.

[0103] As described above, the objective lens 25 is coated to suppress reflection of light from the imaging light source 14. This prevents noise from being generated in the frontal fundus image due to reflection from the objective lens 25. This allows a color fundus image to be suitably acquired.

[0104] As described above, for example, the ophthalmologic imaging apparatus of this embodiment acquires OCT data based on the spectral interference signals without using the saturation signal that is generated in part of the spectral interference signals and is based on the reflected light of the measurement light reflected by the objective lens, thereby obtaining OCT data with reduced noise due to the reflection of the objective lens.

[0105] Furthermore, for example, the ophthalmologic imaging apparatus of this embodiment detects a saturation signal that occurs in a portion of the spectral coherence signal, and if the saturation signal is detected, acquires OCT data without using the saturation signal of the spectral coherence signal. In this way, since the saturation signal is detected, the saturation signal can be appropriately removed from the spectral coherence signal to acquire OCT data.

[0106] Furthermore, for example, the ophthalmologic imaging apparatus of this embodiment interpolates the saturation signal of the spectral interference signal based on a signal different from the saturation signal, and acquires OCT data based on the interpolated spectral interference signal. This allows for better acquisition of OCT data compared to when the saturation signal is discarded without interpolation. For example, when interpolation is performed, the depth resolution may be higher in the noise-reduced portion compared to when interpolation is not performed.

[0107] Furthermore, for example, the ophthalmologic imaging apparatus of this embodiment interpolates the saturated signal by using regression analysis of the spectral coherence signal. By using regression analysis, it is possible to estimate the signal of the saturated signal portion (the portion missing due to saturation) in the spectral coherence signal. For example, by replacing the saturated signal with the estimated signal, it is possible to more appropriately interpolate the spectral coherence signal.

[0108] Furthermore, for example, the ophthalmologic photographing apparatus of this embodiment includes a fundus camera optical system 100 that irradiates visible light through an objective lens to capture a color fundus image of the subject's eye, thereby enabling a color fundus image of the subject's eye to be acquired while acquiring OCT data of the subject's eye.

[0109] Furthermore, in the ophthalmic imaging apparatus of this embodiment, for example, the measurement light of the OCT optical system 200 is infrared light, and a coating is applied to the objective lens 25 to suppress reflection of visible light in the fundus camera optical system 100. Furthermore, the ophthalmic imaging apparatus of this embodiment removes infrared light reflected by the objective lens by processing a saturation signal, and removes visible light reflected by the objective lens by a coating. This makes it possible to acquire both a color fundus image in which noise due to reflection from the objective lens is suppressed, and OCT data in which noise due to reflection from the objective lens is suppressed.

[0110] [Example of transformation] Although the present disclosure has been described above based on the examples, the present disclosure is not necessarily limited to these.

[0111] For example, in the OCT optical system 200, when the position of the fiber end 125 (see FIG. 1) on the measurement optical path and the lens surface (either the front surface or the back surface) of the objective lens 25 is in a conjugate relationship, or when the position of the fiber end 125 and the center of curvature of the objective lens 25 is in a conjugate positional relationship, the reflected light of the measurement light by the objective lens is likely to be received by the detector 120. Therefore, when the position of the fiber end 125 and the position of the lens surface or the center of curvature of the objective lens 25 is in a conjugate positional relationship, the control unit 70 may perform the above <S402: Detection of saturation signal> and <S403: Interpolation processing>. As an example, when the focusing lens 124 is arranged at a position corresponding to a predetermined diopter (for example, -15D) as a result of the optimization of the imaging conditions, the control unit 70 may perform <S402: Detection of saturation signal> and <S403: Interpolation processing>. Of course, the numerical value of the diopter is just an example.

[0112] According to this, even when reflection of the objective lens in the measurement light is likely to occur, the ophthalmic imaging device can acquire OCT data with reduced noise caused thereby. Also, according to this, when the reflected light of the objective lens in the measurement light is difficult to be received (that is, a saturation signal is unlikely to occur), arithmetic processing such as interpolation processing can be omitted. That is, it is possible to suppress adding arithmetic processing to the spectral interference signal when no noise occurs.

[0113] Also, for example, depending on the shape of the objective lens 25, there may be an area that is more likely to reflect the measurement light. As an example, in the vicinity of the center of the curved surface of the lens, the measurement light may be more likely to be reflected than in other areas. Therefore, when the measurement light passes through a predetermined area of the objective lens 25, the control unit 70 may perform the above <S402: Detection of saturation signal> and <S403: Interpolation processing>. As an example, when the examiner sets the scan line 85, the control unit 70 may determine whether the measurement light passes through a predetermined area of the objective lens 25. Alternatively, when the control unit 70 controls the scanning unit 108 to scan the measurement light, the control unit 70 may determine whether the measurement light has passed through a predetermined area of the objective lens 25 based on the operation of the scanning unit 108. When the measurement light passes through a predetermined area of the objective lens 25, the control unit 70 may perform the above <S402: Detection of saturation signal> and <S403: Interpolation processing>.

[0114] According to this, when reflection is unlikely to occur due to the objective lens, calculations such as interpolation processing can be omitted. Therefore, when the saturation signal is not included in the spectral interference signal, execution of the interpolation processing can be suppressed.

[0115] Also, for example, the fundus camera optical system 100 may be a slit scan type optical system. In that case, the fundus camera optical system 100 may be an optical system that scans slit-shaped light on the fundus of the subject eye and acquires a frontal image of the fundus based on the reflected light from the fundus.For example, for the configuration of the slit scan type optical system, the configuration described in JP-A-2021-104229 may be referred to.

[0116] In the above embodiment, the spectral interference signal detected by the detector 120 is rewritten as a function of wavelength λ and converted into an equally spaced function with respect to wavenumber k (=2π / λ), and then saturation signal detection is performed. However, this is not limiting. For example, saturation signal detection may be performed on raw data of the spectral interference signal acquired by the detector 120. In this case, a portion where the intensity of light detected by the detector 120 reaches a predetermined value (e.g., 4096) may be detected as a saturation signal. Even in this case, a tomographic image with suitably reduced noise can be obtained by similarly performing calculation processing such as interpolation.

[0117] In the above embodiment, the saturated signal is interpolated by performing interpolation processing on the spectral interference signal from which the DC component has been removed, but this is not limiting. For example, the interpolation processing may be performed on the spectral interference signal before the DC component has been removed (i.e., the raw data of the spectral interference signal acquired by the detector 120). In this case, the interpolation processing may be the same as that in the above embodiment.

[0118] In the above embodiment, the control unit 70 detects whether the spectral coherence signal contains a saturated signal, but the detection of a saturated signal is not necessarily required. For example, the interpolation process may be performed regardless of whether the spectral coherence signal contains a saturated signal. In this case, the portion of the spectral coherence signal that is likely to saturate may be acquired in advance through experiments, simulations, or the like, and the spectral coherence signal acquired by actually measuring the subject's eye may be interpolated for the portion that is likely to saturate.

[0119] It is also possible to detect whether or not a saturated signal exists on the spectral interference signal, and if it is determined that a saturated signal exists, to perform interpolation processing on the portion that is likely to be saturated and that has been acquired in advance as described above.

[0120] In the above-described embodiment, as an example of the case where a tomographic image is acquired, the case where <S402: Detection of saturation signal> and <S403: Interpolation processing> are performed on the spectral interference signal acquired after the imaging signal is input to the control unit 70 has been described as an example. However, for example, <S402: Detection of saturation signal> and <S403: Interpolation processing> may also be performed on the OCT data acquired as a live image in the control operation.

[0121] In the above-described embodiment, the case where the objective lens 25 is constituted by a single lens has been described as an example, but it is not limited thereto. The objective lens 25 may be constituted as an objective lens unit including a plurality of lenses. For example, even when measurement light is reflected in the objective lens unit and a saturation signal is generated, OCT data with suppressed noise can be acquired by processing the saturation signal in the same manner as in the above-described embodiment. When the objective lens unit is coated, the coating may be applied to at least any one of the lenses in the objective lens unit.

[0122] In the above-described embodiment, the case of suppressing the reflection caused by the objective lens 25 has been described as an example, but it is not limited thereto. For example, in the OCT optical system 200, even when measurement light is reflected by an optical member (for example, a lens, a mirror, etc.) other than the objective lens 25 and a saturation signal is generated, OCT data with suppressed noise can be acquired by processing the saturation signal in the same manner as in the above-described embodiment.

[0123] The ophthalmic apparatus of this embodiment may be capable of acquiring OCT data without performing interpolation processing on the spectral coherence signal. In this case, it may be possible to switch between performing interpolation processing on the saturation signal of the spectral coherence signal and not performing interpolation processing. That is, the ophthalmic imaging apparatus may include a switching unit that switches between a first mode in which OCT data is acquired without using the saturation signal of the spectral coherence signal and a second mode in which OCT data is acquired using the saturation signal of the spectral coherence signal. In this case, the OCT data acquisition unit acquires OCT data based on the mode set by the switching unit. Note that the OCT data acquisition unit may acquire OCT data based on both the first mode and the second mode.

[0124] The switching means may set each mode based on a switching signal for switching modes. For example, the switching signal may be output by the examiner operating the operation unit 76. For example, a button for switching modes may be displayed on the display unit 75, and the examiner may operate the button to output the signal. Note that such a button is merely an example, and the present invention is not limited to this.

[0125] The ophthalmic imaging apparatus of this embodiment may notify the examiner that interpolation processing will be performed on the saturated signal of the spectral interference signal. That is, the ophthalmic imaging apparatus may include a notifying means for notifying that interpolation of the saturated signal will be performed by the interpolation means. Note that such a notifying means may at least notify that interpolation will be performed, and may also notify that interpolation will not be performed. For example, the notifying means may display an icon or a message on the display unit 75 indicating that interpolation processing will be performed (or has been performed). Alternatively, a similar message may be generated by a speaker or the like. Alternatively, a similar indication may be indicated by a change in the color or blinking of a lamp, etc. [Explanation of symbols]

[0126] 1. Ophthalmic imaging equipment 25 objective lenses 70 Control Unit 75 monitors 102 OCT light source 120 detectors

Claims

1. An ophthalmic imaging device for photographing an eye to be examined, an OCT optical system that splits light from a light source into a measurement optical path and a reference optical path, and detects, by a detector, a spectral interference signal between return light of the measurement light guided to the subject's eye via an objective lens and a reference light corresponding to the measurement light; an OCT data acquisition means for, when a saturation signal based on reflected light of the measurement light reflected by the objective lens occurs in a part of the spectral interference signal corresponding to one A-scan, removing the saturation signal from the spectral interference signal corresponding to the A-scan, and acquiring OCT data based on a signal different from the saturation signal in the spectral interference signal corresponding to the same A-scan; an output means for outputting the OCT data; An ophthalmic imaging apparatus comprising:

2. 2. The ophthalmologic photographing apparatus according to claim 1, detecting means for detecting the saturation signal of the spectral interference signal; The ophthalmologic imaging apparatus is characterized in that, when the saturation signal is detected by the detection means, the OCT data acquisition means acquires the OCT data without using the saturation signal of the spectral interference signal.

3. 3. The ophthalmologic photographing apparatus according to claim 1, an interpolation means for interpolating the saturation signal of the spectral interference signal based on a signal different from the saturation signal; The ophthalmologic imaging apparatus is characterized in that the OCT data acquisition means acquires OCT data based on the spectral interference signal interpolated by the interpolation means.

4. An ophthalmic imaging program for use in an ophthalmic imaging apparatus for imaging an eye to be examined, the ophthalmic imaging apparatus having an OCT optical system that splits light from a light source into a measurement optical path and a reference optical path, and detects, by a detector, a spectral interference signal between return light of the measurement light guided to the eye to be examined via an objective lens and a reference light corresponding to the measurement light, the program comprising: When executed by a processor of the ophthalmologic imaging device, an OCT data acquisition step of, when a saturation signal based on reflected light of the measurement light reflected by the objective lens occurs in a part of the spectral interference signal corresponding to one A-scan, removing the saturation signal from the spectral interference signal corresponding to the A-scan, and acquiring OCT data based on a signal different from the saturation signal in the spectral interference signal corresponding to the same A-scan; an output step of outputting the OCT data; an ophthalmic photography program for causing the ophthalmic photography apparatus to execute the above steps;

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