Ophthalmologic device, method for determining eye fundus imaging distance, and recording medium

Abstract

An imaging unit 2 of an ophthalmologic device 1 according to an embodiment projects illumination light onto an eye fundus Ef via an optical scanner 30, and detects return light by using an image sensor 51 capable of being operated in a rolling shutter mode. An image analysis unit 421 analyzes an image of the eye fundus Ef so as to obtain a luminance parameter value. A pupil diameter data acquisition unit 422 acquires pupil diameter data pertaining to a to-be-examined eye E. A control amount determination unit 423 determines a control amount for the distance between the to-be-examined eye E and the imaging unit 2 on the basis of the luminance parameter value obtained by the image analysis unit 421 and the pupil diameter data acquired by the pupil diameter data acquisition unit 422. A movement control unit 424 controls a movement mechanism 3 on the basis of said control amount. As a result, the distance between the to-be-examined eye E and the imaging unit 2 is adjusted.

Description

Ophthalmic apparatus, method for determining fundus photographing distance, and recording medium

[0001] The present disclosure relates to an ophthalmologic apparatus, a method for determining a fundus photographing distance, and a recording medium.

[0002] Fundus photography is a powerful and common technique for ophthalmologic diagnosis and is performed using a fundus camera or a scanning laser ophthalmoscope (SLO). The fundus photography modality disclosed in Patent Document 1 is configured to generate a fundus image by illuminating the fundus with slit light and detecting the returned light with a rolling shutter-type imaging device (e.g., a rolling shutter-type CMOS image sensor). This fundus photography modality synchronously repeats the movement of the projection position of the slit light on the fundus and the detection (photography) of the returned light by the imaging device to collect multiple images, and then combines these images, thereby enabling the acquisition of a fundus image with a simple configuration. This type of fundus photography modality is also called slit scanning.

[0003] It is known that flare may occur in images generated by slit scanning, and that reducing the illumination light intensity is generally effective in eliminating or reducing flare. Furthermore, in slit scanning, there is a trade-off between the illumination light intensity and the imaging time. Therefore, it is known that extending the imaging time due to a reduction in the illumination light intensity increases the likelihood of involuntary eye movements, and conversely, increasing the illumination light intensity due to a reduction in the imaging time increases the likelihood of flare. Furthermore, it is known that the likelihood of flare occurrence varies for each subject's eye, and therefore, it is necessary to address each subject's eye individually. Note that flare is an image of unwanted light generated by the reflection and scattering of light returning from the subject's eye (e.g., corneal reflection light) by an optical element.

[0004] In addition to explaining these matters, Patent Document 2 discloses an ophthalmologic apparatus configured to determine the presence or absence of flare based on an infrared fundus image of the subject's eye and control conditions for slit scanning. This condition control includes control of a light flux limiting member (slit, iris diaphragm) provided in the illumination optical system, control of a light flux limiting member (photography diaphragm) provided in the photographing optical system, control of the illumination light intensity, and control of the photographing time (exposure time of the image sensor).

[0005] Many ophthalmic devices used for fundus photography are configured to automatically align (auto-align) the optical system with the subject's eye before photography. For example, the ophthalmic device described in Patent Document 3 performs auto-alignment of the subject's eye and auto-focusing of the fundus before fundus photography. This conventional auto-alignment is characterized by adjusting the alignment target positions in the up / down and left / right directions (X and Y directions) based on the size of the subject's pupil. Meanwhile, alignment in the anterior-posterior direction (near-to-far direction, Z direction) is performed using a well-known method that references a split image of the anterior segment. Patent Document 3 also discloses that if the subject's pupil is determined to be small based on the size of the flare area in the fundus image, adjustment of the alignment target positions in the X and Y directions is automatically initiated.

[0006] US Patent No. 7,831,106 JP 2021-145896 A JP 2016-185192 A

[0007] One object of the present disclosure is to provide a novel technique for acquiring flare-free images in slit-scan fundus photography.

[0008] One aspect of an embodiment according to the present disclosure is an ophthalmologic apparatus including an imaging unit, a movement mechanism, an image analysis unit, a pupil diameter data acquisition unit, a control amount determination unit, and a movement control unit. The imaging unit includes an illumination optical system that projects illumination light from a light source onto the fundus of the subject's eye via an optical scanner, and an imaging optical system that detects return light of the illumination light with a first image sensor operable in a rolling shutter mode. The movement mechanism is configured to move the imaging unit. The image analysis unit is configured to analyze an image of the fundus of the subject's eye to determine a value of a predetermined luminance parameter. The pupil diameter data acquisition unit is configured to acquire pupil diameter data of the subject's eye. The control amount determination unit is configured to determine a control amount for a distance between the subject's eye and the imaging unit based on the luminance parameter value determined by the image analysis unit and the pupil diameter data acquired by the pupil diameter data acquisition unit. The movement control unit is configured to control the movement mechanism based on the control amount determined by the control amount determination unit.

[0009] Another aspect of an embodiment according to the present disclosure is a method for determining a distance between a subject's eye and an imaging unit for fundus photography. The fundus photography is performed using an ophthalmologic apparatus including an imaging unit configured to project illumination light from a light source onto the fundus of the subject's eye via an optical scanner and detect returned light of the illumination light with an image sensor operable in a rolling shutter mode. The method of this aspect includes a first step of acquiring an image of the fundus of the subject's eye, a second step of analyzing the image acquired in the first step to determine a value of a predetermined luminance parameter, a third step of acquiring pupil diameter data of the subject's eye, and a fourth step of determining the distance between the subject's eye and the imaging unit based on the value of the luminance parameter determined in the second step and the pupil diameter data acquired in the third step.

[0010] Yet another aspect of the embodiment of the present disclosure is a program that causes a computer to execute a method according to the embodiment.

[0011] Yet another aspect of an embodiment according to the present disclosure is a computer-readable non-transitory recording medium on which a program according to an embodiment is recorded.

[0012] According to some aspects of the embodiments of the present disclosure, a novel technique for acquiring a flare-free image in slit-scan fundus photography can be provided.

[0013] FIG. 1 is a schematic diagram for describing one non-limiting example of the configuration of an ophthalmic apparatus according to an embodiment. FIG. 2 is a schematic diagram for describing one non-limiting example of the configuration of an ophthalmic apparatus according to an embodiment. FIG. 3 is a schematic diagram for describing one non-limiting example of the configuration of an ophthalmic apparatus according to an embodiment. FIG. 4 is a schematic diagram for describing one non-limiting example of the configuration of an ophthalmic apparatus according to an embodiment. FIG. 5 is a schematic diagram for describing one non-limiting example of the operation of an ophthalmic apparatus according to an embodiment. FIG. 6 is a schematic diagram for describing one non-limiting example of the operation of an ophthalmic apparatus according to an embodiment. FIG. 7 is a schematic diagram for describing one non-limiting example of the configuration of an ophthalmic apparatus according to an embodiment. FIG. 8 is a schematic diagram for describing one non-limiting example of a fundus image acquired by slit scanning using a rolling shutter method, in which flare is mixed. FIG. 9 is a schematic diagram for describing one non-limiting example of a fundus image acquired by imaging using a global shutter method, in which flare is mixed. FIG. 10 is a schematic diagram for describing one non-limiting example of the operation of an ophthalmic apparatus according to an embodiment. FIG. 1 is a schematic diagram for explaining one non-limiting example of the configuration of an ophthalmic apparatus according to an embodiment; FIG. 2 is a schematic diagram for explaining one non-limiting example of the operation of an ophthalmic apparatus according to an embodiment; FIG. 3 is a schematic diagram for explaining one non-limiting example of the operation of an ophthalmic apparatus according to an embodiment; FIG. 4 is a flowchart for explaining one non-limiting example of the operation performed by the ophthalmic apparatus according to an embodiment; and FIG. 5 is a flowchart for explaining one non-limiting example of the operation performed by the ophthalmic apparatus according to an embodiment.

[0014] Certain non-limiting aspects of embodiments of the present disclosure will now be described in detail with reference to the drawings.

[0015] Any known technology can be combined with any aspect of the present disclosure. For example, any matter disclosed in a document cited in this specification can be combined with any aspect of the present disclosure. Furthermore, any known technology in the technical field related to the present disclosure can be combined with any aspect of the present disclosure. For example, any technical matter disclosed by the applicant of the present application (matters disclosed in patent applications, papers, etc.) regarding technology related to the present disclosure or technology applicable to the technology can be incorporated by reference into any aspect of the present disclosure.

[0016] Any two or more of the various aspects described in this disclosure may be combined, at least in part.

[0017] At least a portion of the functionality of the elements described in this disclosure is implemented using circuitry or processing circuitry. The circuitry or processing circuitry may be a general-purpose processor, a special-purpose processor, an integrated circuit, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), an Application Specific Integrated Circuit (ASIC), a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), a Field Programmable Gate Array (FPGA)), or a combination of these devices configured and / or programmed to perform at least some of the disclosed functions. Array), conventional circuitry, and any combination thereof. A processor is considered to be processing circuitry or circuitry, including transistors and / or other circuitry. In this disclosure, circuitry, unit, means, or similar terms refers to hardware that performs at least a portion of the disclosed functions or hardware that is programmed to perform at least a portion of the disclosed functions. The hardware may be hardware disclosed herein or known hardware that is programmed and / or configured to perform at least a portion of the described functions. In the case of a processor, where the hardware can be considered to be a type of circuitry, circuitry, unit, means, or similar terms refers to a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0018] A first aspect of an ophthalmologic apparatus according to a non-limiting embodiment includes an imaging unit, a movement mechanism, an image analysis unit, a pupil diameter data acquisition unit, a control amount determination unit, and a movement control unit.

[0019] The photographing unit is an element for photographing the fundus of the subject's eye, and includes an illumination optical system and a photographing optical system.

[0020] The illumination optical system is an element for illuminating the fundus of the subject's eye, and is configured to project illumination light from a light source onto the fundus of the subject's eye via an optical scanner.

[0021] The light source may be an element of the imaging unit (illumination optics) or an external light source, in which case the light generated by the external light source is input to the illumination optics through a light guide (e.g., fiber optics and / or bulk optics).

[0022] The optical scanner is an element of the illumination optical system and is configured to change the traveling direction of the illumination light.

[0023] The imaging optical system detects, with a first image sensor operable in a rolling shutter mode, return light of illumination light projected onto the fundus of the subject's eye by the illumination optical system.

[0024] The return light of the illumination light includes reflected light and scattered light of the illumination light applied to the subject's eye, and is light that enters the imaging unit (imaging optical system).

[0025] The first image sensor is an element of the imaging section (imaging optical system). The operation mode (control mode) of the first image sensor may be only the rolling shutter mode, or may be the rolling shutter mode and another mode. An example of the other mode is a global reset release shutter mode. The rolling shutter mode and the global reset release shutter mode will be described later. In another example, the first image sensor may be an imaging unit that combines a global shutter type image sensor and a slit diaphragm. The slit diaphragm may be configured mechanically and / or electronically.

[0026] The moving mechanism is configured to move the imaging unit. The portion of the imaging unit moved by the moving mechanism may be the entire imaging unit or only a part of the imaging unit.

[0027] The image analysis unit is configured to analyze an image of the fundus of the subject's eye to determine the value of a predetermined brightness parameter. The function of the image analysis unit is realized, for example, by cooperation between hardware including a processor and software including a program for causing the processor to execute image analysis processing.

[0028] In some examples, the image analyzed by the image analysis unit may be an image acquired using a photographing method other than the rolling shutter method, and specific examples thereof include an image acquired by applying a slit scan in global reset release shutter mode to the fundus of the test eye, or an image acquired by applying photographing using a global shutter type image sensor to the fundus of the test eye.

[0029] If the first image sensor of the photographing optical system is operable in global reset release shutter mode, an image of the fundus of the subject's eye acquired by slit scanning in global reset release shutter mode using the first image sensor may be provided to the image analysis unit, or an image of the fundus of the subject's eye acquired by slit scanning in global reset release shutter mode using another rolling shutter type image sensor or an image of the fundus of the subject's eye acquired by photographing using another global shutter type image sensor may be provided to the image analysis unit.

[0030] On the other hand, if the first image sensor of the photographing optical system cannot operate in the global reset release shutter mode, an image of the fundus of the subject's eye acquired by slit scanning in the global reset release shutter mode using another rolling shutter type image sensor, or an image of the fundus of the subject's eye acquired by photographing using another global shutter type image sensor, is provided to the image analysis unit.

[0031] The luminance parameter (type of parameter) calculated by the image analysis unit is, for example, determined in advance. In some aspects, the luminance parameter may be a parameter related to the corneal reflection of illumination light projected onto the subject's eye (corneal reflection parameter).

[0032] Examples of corneal reflection parameters that can be obtained from an image of the fundus of the test eye include parameters obtained from brightness information of the image (e.g., brightness histogram) (e.g., maximum brightness, brightness distribution, number of pixels having brightness values ​​equal to or greater than a threshold, etc.), parameters obtained from brightness information of a partial region of the image (e.g., brightness histogram) (e.g., maximum brightness, brightness distribution, number of pixels having brightness values ​​equal to or greater than a threshold, etc.), and parameters that indicate the appearance of a partial region of the image (e.g., shape, dimensions, position, etc.).

[0033] The partial region may be, for example, a high-brightness region in the image. The high-brightness region is, for example, an image region that is estimated to be an image of corneal reflection light, and is identified by a predetermined segmentation method (for example, threshold processing on brightness).

[0034] Although some examples of brightness parameters are described in this disclosure, applicable brightness parameters are not limited to these and may be any brightness parameter that can be used to determine the value (control amount) of a parameter for controlling the distance between the test eye and the imaging unit.

[0035] The pupil diameter data acquisition unit is configured to acquire measurement data (pupil diameter data) of the pupil diameter of the subject's eye.

[0036] The method for acquiring pupil diameter data of the subject's eye may be any predetermined method. In some examples, the pupil diameter data acquisition unit may include a pupil diameter calculation unit that calculates the pupil diameter by analyzing an anterior segment image generated by photographing the anterior segment of the subject's eye using the ophthalmic device. In some examples, the pupil diameter data acquisition unit may include a pupil diameter calculation unit that calculates the pupil diameter by analyzing an anterior segment image generated by photographing the anterior segment of the subject's eye using another ophthalmic device.

[0037] The functions of these pupil diameter calculation units are realized, for example, by cooperation between hardware including a processor and software including a program for causing the processor to execute the pupil diameter calculation process.

[0038] Note that various methods are known for calculating pupil diameter from an anterior eye image, including, for example, methods that utilize threshold processing, edge detection, pattern matching, segmentation, and the like.

[0039] Another method for acquiring pupil diameter data of the subject's eye is to input the pupil diameter data acquired by another ophthalmic apparatus into the ophthalmic apparatus by accepting the pupil diameter data. In this case, the pupil diameter data acquisition unit includes a data accepting unit configured to accept the pupil diameter data. In some examples, the data accepting unit may include a communication device that accepts the pupil diameter data of the subject's eye via a communication line.

[0040] In addition, in some examples, the data receiving unit may include a data reader device that reads out the pupil diameter data of the subject's eye recorded on a recording medium from the recording medium.

[0041] In a typical example, the pupil diameter data acquisition unit acquires actual measurement data of the pupil diameter of the subject's eye. However, if it can be assumed that the pupil diameter of the subject's eye and the pupil diameter of the fellow eye are substantially equal, pupil diameter data of the fellow eye of the subject's eye may be acquired and used as the pupil diameter data of the subject's eye.

[0042] The control amount determination unit is configured to determine a control amount of the distance between the subject's eye and the imaging unit based on the value of the luminance parameter calculated from the image of the fundus of the subject's eye by the image analysis unit and the pupil diameter data of the subject's eye acquired by the pupil diameter data acquisition unit. The function of the control amount determination unit is realized, for example, by cooperation between hardware including a processor and software including a program for causing the processor to execute the control amount determination process.

[0043] The distance between the subject's eye and the imaging unit is typically defined as the distance between the subject's eye and a specific component located at the front (closest to the subject's eye) of the optical system included in the imaging unit. In a typical example, this specific component is an objective lens, and the distance between the subject's eye and the imaging unit is defined as the distance between the front surface of the objective lens (the surface closest to the subject's eye) and the subject's eye. Note that the distance corresponding to the control amount determined by the control amount determination unit is not limited to this typical example distance and may be any distance representing the distance between the subject's eye and the imaging unit.

[0044] A well-known parameter representing the distance between the subject's eye and an imaging unit is the working distance (WD). The working distance is the distance between the subject's eye and the ophthalmic device (optical system) that must be achieved in order for the ophthalmic device to acquire data (photograph, measure, etc.) of the subject's eye, and is preset as a value specific to each ophthalmic device (preset value, default value). The working distance is determined based on the configuration of the optical system, the part of the subject's eye from which data is to be acquired, and other factors. In general, the operation of aligning the subject's eye and the ophthalmic device is called alignment, and in particular, the operation of matching the distance between the subject's eye and the ophthalmic device to the working distance is called Z alignment.

[0045] The control amount determined by the control amount determination unit may be the value (quantity) of any parameter that can be used to control the distance between the subject's eye and the imaging unit. In some examples, the control amount may be a physical distance value (a distance value in real space). This physical distance value may be the distance between the subject's eye and the imaging unit, or may be a change from the current distance between the subject's eye and the imaging unit (a movement distance from the current position). In some examples, the control amount may be a parameter value (such as a voltage value, a current value, or a pulse count) of a control signal applied to an element (in this embodiment, a movement mechanism) for changing the distance between the subject's eye and the imaging unit. The control amount may be a scalar value or a vector value.

[0046] In some examples, the control amount may include position information. For example, the control amount may include information indicating the position of the image capture unit corresponding to the physical distance in addition to or instead of the physical distance value.

[0047] The movement control unit is configured to control the movement mechanism based on the control amount determined by the control amount determination unit. This makes it possible to move the imaging unit according to the control amount, and in particular, to change (adjust) the distance between the subject's eye and the imaging unit according to the control amount. The function of the movement control unit is realized, for example, by cooperation between hardware including a processor and software including a program for causing the processor to execute movement control processing.

[0048] In some examples, the control amount includes a value of the distance between the subject's eye and the imaging unit (target distance value), and the movement control unit controls the movement mechanism so that the distance between the subject's eye and the imaging unit matches this target distance value. In some examples, the control amount includes a movement distance from a current position between the subject's eye and the imaging unit, and the movement control unit controls the movement mechanism so as to move the imaging unit by this movement distance. In some examples, the control amount includes a parameter value of a control signal to be applied to the movement mechanism, and the movement control unit controls the movement mechanism by generating a control signal corresponding to this parameter value and applying it to the movement mechanism.

[0049] Flare is an artifact that occurs in an image due to light returning from the subject's eye (especially light reflected from the cornea, which has a relatively high brightness). Conditions that affect the occurrence and extent of flare include the intensity of the illumination light and the distance between the subject's eye and the imaging unit.

[0050] According to the first aspect, the distance between the subject's eye and the imaging unit can be automatically adjusted based on the brightness parameter value calculated from the fundus image of the subject's eye and pupil diameter data of the subject's eye. After this automatic adjustment, the fundus of the subject's eye can be photographed using the rolling shutter mode. This makes it possible to provide flare-free images by slit-scan fundus photography.

[0051] The expression "image without flare" includes not only an image that is completely free of flare, but also an image that contains a low level of flare, an image in which the level of flare has been reduced, and an image in which the impact of flare is small from the perspective of image diagnosis.

[0052] Conventional techniques for eliminating or reducing flare typically involve controlling the amount of illumination light (illumination intensity). In contrast, the first aspect achieves this goal by controlling the distance between the subject's eye and the imaging unit. This makes it possible to generate a flare-free image of the subject's eye without extending the light-receiving time (exposure time, imaging time) of the image sensor, and therefore without increasing the likelihood of involuntary eye movements occurring during imaging of the subject's eye.

[0053] Furthermore, according to the first aspect, since the device is configured to control the distance between the subject's eye and the imaging unit, there is no need to perform the condition control described in Patent Document 2 (specifically, control of the beam limiting member of the illumination optical system, control of the beam limiting member of the imaging optical system, control of the illumination light intensity, and control of the imaging time). Therefore, there are no problems associated with controlling the beam limiting member (e.g., a reduction in the intensity of the illumination light projected onto the fundus, a reduction in the intensity of the return light projected onto the image sensor, etc.), problems associated with a reduction in the illumination light intensity (e.g., an extension of the imaging time), or problems associated with an extension of the imaging time (e.g., a reduction in image quality due to fixational eye movement, etc.).

[0054] Furthermore, the technology described in Patent Document 3 is characterized in that when the eye to be examined is determined to have a small pupil based on the flare dimension, the target positions of the alignment in the X and Y directions are automatically adjusted, while the alignment in the Z direction is performed by a well-known method that references a split image of the anterior segment image. In contrast, the first aspect is configured to automatically perform alignment in the Z direction based on the value of the luminance parameter and pupil diameter data, which is clearly different from the technology described in Patent Document 3.

[0055] Although the first aspect is characterized by controlling the distance between the subject's eye and the imaging unit, it is not intended to prohibit the execution of other controls. Some examples may be configured to execute other controls (e.g., control of a beam limiting member of an illumination optical system, control of a beam limiting member of an imaging optical system, control of an illumination light intensity, control of imaging time, and one or more other controls) in addition to control of the distance between the subject's eye and the imaging unit.

[0056] In addition, some examples may be configured to selectively execute control of the distance between the subject's eye and the imaging unit and another control, and the selection of the control may be performed by a user or automatically based on the state of the subject's eye or the state of the image.

[0057] A second aspect of the ophthalmic apparatus according to a non-limiting embodiment may include the following features in addition to the first aspect described above.

[0058] The illumination optical system of this aspect is configured to project infrared illumination light onto the fundus of the subject's eye. Some examples of the illumination optical system include a light source that emits light in the infrared range (infrared light source). Some examples of the illumination optical system also include a light source that emits light in a wavelength range that includes the infrared range (e.g., a white light source) and a filter that transmits the infrared component of the light.

[0059] The first image sensor of this aspect is configured to be able to operate in a global reset release shutter mode in addition to the rolling shutter mode. In some examples, the first image sensor is a rolling shutter camera with a global reset release shutter function.

[0060] The photographing unit of this embodiment is configured to acquire an infrared image (first infrared image) of the fundus of the test eye using infrared illumination light projected onto the fundus of the test eye by an illumination optical system and slit scanning in global reset release shutter mode using a first image sensor.

[0061] The image analysis unit of this embodiment is configured to analyze a first infrared image of the fundus of the subject's eye acquired by slit scanning in global reset release shutter mode, and determine the value of a predetermined brightness parameter.

[0062] According to the second aspect, both fundus photography for determining the value of the brightness parameter (slit scanning in the global reset release shutter mode) and photography for obtaining fundus images used for diagnosis, etc. (slit scanning in the rolling shutter mode) can be performed using a single image sensor (first image sensor). This makes it possible to simplify the configuration of the optical system. Typically, slit scanning in the global reset release shutter mode is performed using infrared illumination light, and slit scanning in the rolling shutter mode is performed using visible illumination light. Therefore, the first image sensor has sensitivity in both the infrared wavelength range and the visible wavelength range.

[0063] A third aspect of the ophthalmic apparatus according to a non-limiting embodiment may include the following features in addition to the second aspect described above.

[0064] The optical scanner of this embodiment is configured to move the projection position of infrared illumination light projected onto the fundus of the subject's eye by an illumination optical system. That is, the optical scanner of this embodiment is one of the elements for realizing slit scanning of the fundus using infrared illumination light, and may be any type of optical deflection device, such as a galvanometer scanner, a MEMS scanner, or a resonant scanner.

[0065] It is known that an image obtained by slit scanning in the global reset release shutter mode may have flare in (at least) two locations, similar to the flare that occurs in an image obtained by a global shutter camera. When the illumination light is moved in the vertical direction (Y direction) during slit scanning in the global reset release shutter mode, flare typically occurs in the upper and lower regions of the obtained image. Also, when the illumination light is moved in the horizontal direction (X direction) during slit scanning in the global reset release shutter mode, flare typically occurs in the left and right regions of the obtained image.

[0066] Thus, in a typical image obtained by slit scanning in the global reset release shutter mode, a first flare occurs on the starting point side (movement starting point side) of the moving illumination light, and a second flare occurs on the ending point side (movement ending point side). The positional relationship between the first flare and the second flare is relative. The first flare occurs closer to the starting point of movement than the second flare, and conversely, the second flare occurs closer to the ending point of movement than the first flare. Furthermore, the first flare occurs at a position closer to the starting point of movement than the center position of the movement range, and the second flare occurs at a position closer to the ending point of movement than the center position of the movement range.

[0067] The image capturing unit of this embodiment is configured to perform slit scanning in the global reset release shutter mode at the timing when a first infrared image is acquired, in which both a first flare (first high-luminance area) occurring at the start point of movement of the infrared illumination light and a second flare (second high-luminance area) occurring at the end point of movement of the infrared illumination light are depicted. An example of a method for determining this timing will be described later.

[0068] According to the third aspect, an image depicting both types of flares can be acquired by a single slit scan in the global reset release shutter mode, making it possible to obtain abundant and rapid information about the flares occurring in the image.

[0069] A fourth aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to any of the first to third aspects described above.

[0070] As in the second and third aspects, the illumination optical system of this aspect is configured to be able to project infrared illumination light onto the fundus of the subject's eye.

[0071] The photographic optical system of this embodiment includes a first image sensor operable in a rolling shutter mode, as well as a second image sensor of a global shutter type.

[0072] In some examples, the imaging optical system includes an optical path splitting element (beam splitter) that splits the optical path of the returned light into a first branched optical path and a second branched optical path, and the first image sensor is disposed in the first branched optical path and the second image sensor is disposed in the second branched optical path.

[0073] Typically, the slit scan in the global reset release shutter mode is performed using infrared illumination light, and the slit scan in the rolling shutter mode is performed using visible illumination light, so that the first image sensor has sensitivity in the visible wavelength range and the second image sensor has sensitivity in the infrared wavelength range.

[0074] The optical path splitting element is configured to guide light in the visible wavelength range to the first optical path and light in the infrared wavelength range to the second optical path. This optical path splitting element is, for example, a dichroic mirror. If a reduction in the amount of light is acceptable, a half mirror can be used as this optical path splitting element. In some examples, a polarizing beam splitter can be used that utilizes the polarization characteristics of the returning light to separate light in the infrared wavelength range from light in the visible wavelength range.

[0075] The imaging unit of this embodiment is configured to acquire an infrared image (second infrared image) of the fundus of the subject's eye using infrared illumination light projected onto the fundus of the subject's eye by an illumination optical system and a second image sensor of a global shutter type. The imaging method for acquiring the second infrared image is the same as that used for infrared fundus imaging using a general fundus camera (including a global shutter type camera).

[0076] The image analysis unit of this embodiment is configured to analyze the second infrared image acquired by photographing using the second global shutter image sensor, and to determine the value of a predetermined brightness parameter.

[0077] The fourth aspect is configured to perform fundus photography (slit scanning in global reset release shutter mode) to obtain the brightness parameter value and fundus slit scanning (slit scanning in rolling shutter mode) using separate image sensors, thereby enabling switching between these two types of photography methods by simple control (e.g., switching the wavelength range of the illumination light).

[0078] A fifth aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to any of the first to fourth aspects described above.

[0079] The image analysis unit of this embodiment is configured to determine, as the value of a predetermined brightness parameter, the maximum brightness value in the image of the fundus of the test eye and / or the value of a parameter indicating the appearance of a high-brightness area in the image of the fundus of the test eye.

[0080] The fifth aspect provides some examples of brightness parameter values ​​determined by the image analysis unit. Examples of the types of brightness parameters provided by this aspect include the value of the brightest pixel in the image (the brightness of the brightest position in the flare), the shape, size, and position of the image region identified as a flare (high-brightness region), etc.

[0081] By using the brightness parameters according to this aspect, it is possible to grasp the features and characteristics of the flare depicted in the image of the subject's eye, and it is possible to appropriately control the distance between the subject's eye and the imaging unit. Note that the types of brightness parameters provided by this aspect are not limited to the examples given here.

[0082] A sixth aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to any of the first to fifth aspects described above.

[0083] The control amount determination unit of this embodiment is configured to compare the value of the brightness parameter determined by the image analysis unit with a predetermined first threshold value (brightness threshold value), and determine the control amount of the distance between the test eye and the imaging unit based on the result of this comparison.

[0084] The luminance threshold may be a predetermined value (default value). In some examples, multiple luminance thresholds are prepared in advance and selectively used in each process. The multiple luminance thresholds may be determined based on, for example, attributes of the subject (e.g., age, sex, race, medical history, etc.) or attributes of the subject's eye (e.g., pupil size, iris color, medical history, etc.).

[0085] In some examples, the brightness threshold is determined when photographing the fundus. This brightness threshold may be determined based on, for example, attributes of the subject, attributes of the subject's eye, the state of the image of the fundus of the subject's eye, etc. The state of the image of the fundus of the subject's eye may be, for example, the state of brightness in the entire image (brightness statistics, brightness distribution, noise, etc.) or the state of brightness in a specific region of the image.

[0086] According to the sixth aspect, it is possible to change the control of the distance between the subject's eye and the imaging unit based on a specific criterion (a brightness threshold). Some examples of this are described below.

[0087] A seventh aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to the sixth aspect described above.

[0088] The movement control unit of this aspect is configured to control the movement mechanism for adjusting the relative position of the imaging unit with respect to the subject's eye before the image of the fundus of the subject's eye to be provided to the image analysis unit is acquired. That is, in this aspect, after the imaging unit is aligned with the subject's eye, the image of the fundus of the subject's eye to be analyzed by the image analysis unit is acquired.

[0089] The positioning performed before acquiring an image of the fundus of the subject's eye includes at least alignment and may further include tracking. This alignment is typically three-dimensional alignment (XY alignment and Z alignment). Tracking is a combined operation of detecting the positional relationship between the fundus of the subject's eye and the imaging unit and adjusting the relative position based on the result of this detection, which is performed to maintain the relative position (appropriate alignment state) between the fundus of the subject's eye and the imaging unit achieved by the alignment.

[0090] The control amount determination unit of this embodiment is configured to compare the value of the brightness parameter determined by the image analysis unit with a brightness threshold, and to execute a process of determining the control amount only if the value of the brightness parameter is greater than or equal to the brightness threshold.

[0091] In the seventh aspect having such a configuration, only when it is determined that the flare depicted in the image of the fundus of the test eye is strong (i.e., the flare intensity is outside the allowable range), the control amount is determined and the distance between the test eye and the imaging unit is controlled based on this control amount. According to this aspect, when it is required to remove or reduce the flare, the distance between the test eye and the imaging unit is adjusted for the purpose of removing or reducing the flare. As a result, it is possible to obtain a flare-free image by performing fundus photography using the slit scan method after this distance adjustment.

[0092] On the other hand, if the value of the brightness parameter is less than the brightness threshold, in other words, if it is determined that the flare depicted in the image of the fundus of the test eye is not strong (i.e., the flare strength is within the allowable range), the control amount is not determined, and therefore, the distance adjustment between the test eye and the imaging unit for the purpose of removing or reducing the flare is not performed. As a result, if it is considered that removing or reducing the flare is not important from the perspective of image diagnosis, this distance adjustment is skipped and the system moves on to fundus imaging using the slit scan method. This makes it possible to speed up and shorten the examination time.

[0093] As described above, according to the seventh aspect, it is possible to improve the quality of the examination by eliminating or reducing flare, and also to reduce the labor required for the examination and improve the throughput by speeding up or shortening the time required for the examination. These effects achieved by this aspect are useful in actual medical settings.

[0094] An eighth aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to the sixth or seventh aspect described above.

[0095] The ophthalmologic apparatus of this aspect further includes a luminance threshold determination unit. The luminance threshold determination unit has a function of determining a luminance threshold to be compared with the value of the luminance parameter determined by the image analysis unit. The luminance threshold determined by the luminance threshold determination unit is provided to the control amount determination unit and used in the comparison process with the value of the luminance parameter.

[0096] In the series of processes executed in this embodiment to determine the brightness threshold, first, a fundus image data set is prepared. The fundus image data set is a data set including a plurality of fundus images.

[0097] The fundus image dataset may include any type of fundus image. In some examples, the fundus image dataset may include images obtained by photographing the fundus of a living eye (living fundus images). The living fundus images may be anonymized. In some examples, the fundus image dataset may include processed fundus images obtained by processing the living fundus images. The processed fundus images may be anonymized. In some examples, the fundus image dataset may include fundus images generated using computer techniques such as computer graphics and generative artificial intelligence (virtual fundus images).

[0098] The fundus image dataset may include fundus images having specific attributes. For example, the fundus image dataset may include fundus images of eyes diagnosed (by a doctor and / or a computer) as normal eyes (healthy eyes), fundus images of eyes diagnosed as not having a specific disease, fundus images of eyes diagnosed as having a specific disease, and fundus images of eyes diagnosed as having some disease. The attributes of the fundus images may also include attributes of the subject (e.g., age, gender, race, medical history, etc.) or attributes of the subject's eye (e.g., pupil size, iris color, medical history, etc.). When the fundus image dataset includes two or more sub-datasets corresponding to two or more attributes, respectively, the brightness threshold determiner may be configured to determine two or more brightness thresholds corresponding to the two or more sub-datasets, respectively.

[0099] The fundus image data set thus prepared is provided to a brightness threshold determination unit. The brightness threshold determination unit is configured to obtain a maximum brightness value distribution of the fundus image data set and determine a brightness threshold based on the maximum brightness value distribution. The maximum brightness value distribution is distribution information generated based on the maximum brightness values ​​of the multiple fundus images included in the fundus image data set.

[0100] In some examples, the brightness threshold determiner identifies a maximum brightness value in each of the plurality of fundus images included in the fundus image dataset, thereby obtaining a plurality of maximum brightness values ​​respectively corresponding to the plurality of fundus images included in the fundus image dataset.

[0101] Next, the brightness threshold determination unit of this example obtains a statistical representation of the obtained maximum brightness values. This statistical representation may take any form, such as a histogram, graph, map, etc. The obtained statistical representation is the maximum brightness value distribution.

[0102] The brightness threshold determination unit of this example determines the brightness threshold based on the determined maximum brightness value distribution. Any method may be used to determine the brightness threshold from the maximum brightness value distribution. For example, a predetermined calculation process (e.g., statistical calculation) may be applied to the maximum brightness value distribution. This calculation process may include a process of comparing a group of maximum brightness values ​​of fundus images with flare (or strong flare) with a group of maximum brightness values ​​of fundus images without flare (or weak flare). An example of the process of determining the brightness threshold will be described later.

[0103] The control amount determination unit of this embodiment is configured to compare the brightness threshold value determined in this manner with the value of the brightness parameter obtained by the image analysis unit, and to determine the control amount based on the result of this comparison.

[0104] According to the eighth aspect, an example for determining the brightness threshold can be provided, and a good quality brightness threshold can be provided by a statistical method based on a fundus image dataset.

[0105] In addition, by preparing multiple brightness thresholds corresponding to multiple attributes, selecting a brightness threshold according to the state of the subject's eye, and using the selected brightness threshold, it is possible to improve the quality of the control amount determination process.

[0106] A ninth aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to the eighth aspect described above.

[0107] The brightness threshold determination unit of this embodiment is configured to calculate a weighted F value (Fβ score) of the maximum brightness value distribution obtained from the fundus image data set, and determine a brightness threshold based on this Fβ score. An example of the processing content executed in this embodiment will be described later.

[0108] The ninth aspect provides a preferred example of a statistical method for determining the luminance threshold.

[0109] A tenth aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to the eighth or ninth aspect described above.

[0110] The brightness threshold determination unit of this aspect is configured to determine at least two brightness thresholds based on the maximum brightness value distribution obtained from the fundus image data set.

[0111] In some examples, the brightness threshold determiner may be configured to determine at least two brightness thresholds corresponding to at least two attributes, respectively, as described above.

[0112] In some examples, the luminance threshold determiner may be configured to determine at least two luminance thresholds according to flare detection levels. For example, when three levels of sensitivity for flare detection (flare detection sensitivity) are set, the luminance threshold determiner may determine a luminance threshold for high-sensitivity detection, a luminance threshold for medium-sensitivity detection, and a luminance threshold for low-sensitivity detection based on a maximum luminance value distribution obtained from the fundus image dataset.

[0113] The control amount determination unit of this embodiment is configured to select one brightness threshold from at least two brightness thresholds determined by the brightness threshold determination unit, compare the value of the brightness parameter determined by the image analysis unit with the selected brightness threshold, and determine the control amount based on the result of this comparison.

[0114] According to the tenth aspect, a desired brightness threshold can be selected and used from a plurality of prepared brightness thresholds, so that flare removal or flare reduction can be performed in accordance with the user's requests or the requirements of the examination content. Note that examples of the processing content executed in this aspect will be described later.

[0115] An eleventh aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to any of the first to tenth aspects described above.

[0116] The control amount determination unit of this aspect is configured to determine the control amount based on the magnitude of the pupil diameter data value acquired by the pupil diameter data acquisition unit. That is, in this aspect, the content of control of the distance between the subject's eye and the imaging unit is determined based on at least the size of the subject's pupil. The configuration of this aspect is made taking into consideration that the presence or absence and degree of flare are affected by the size of the pupil.

[0117] Non-limiting examples of such an eleventh aspect include the twelfth aspect and the thirteenth to fifteenth aspects.

[0118] In a twelfth aspect, the control amount determiner is configured to determine the control amount based on the magnitude of the pupil diameter data value acquired by the pupil diameter data acquirer so that a decrease in the peripheral light intensity of the illumination light projected onto the fundus of the subject's eye by the illumination optical system is equal to or less than a predetermined second threshold (peripheral light intensity threshold). The configuration of the twelfth aspect is made in consideration of the fact that a change in the peripheral light intensity of the illumination light accompanying a change in the distance between the subject's eye and the imaging unit depends on the pupil diameter of the subject's eye.

[0119] The quantity representing the reduction in peripheral light intensity evaluated by the control amount determination unit of this embodiment may be any physical quantity, such as the reduction amount or reduction rate. The reduction amount is the amount of change in peripheral light intensity relative to a reference value. The reduction rate is the ratio of the reduction amount to the reference value of peripheral light intensity. The reference value of peripheral light intensity may be, for example, the value of peripheral light intensity in an image of the fundus of the test eye provided to the image analysis unit, and is calculated by the control amount determination unit (or the image analysis unit or another element) analyzing the image. The change in peripheral light intensity is, for example, the amount of change from the value of peripheral light intensity in an image of the fundus of the test eye.

[0120] According to the twelfth aspect, it is possible to control the distance between the test eye and the imaging unit so that an image of acceptable brightness can be obtained by slit scanning performed after controlling the distance between the test eye and the imaging unit.

[0121] In a thirteenth aspect, control amount information is prepared in advance. The control amount information includes a correspondence relationship between a pupil diameter value and a control amount. This correspondence relationship may be, for example, a correspondence relationship between a range (a numerical range) of pupil diameter values ​​and a control amount.

[0122] In some examples of the control amount information, a control amount value is assigned to each of two or more ranges of pupil diameter values. In this control amount information, for example, first to Kth control amounts are assigned to first to Kth pupil diameter value ranges, respectively (K is an integer equal to or greater than 2). Such control amount information defines a discrete correspondence between pupil diameter values ​​and control amounts. The form of the discrete correspondence may be any form, and may be, for example, a table or a graph.

[0123] In some examples, the control amount information defines a continuous correspondence between the pupil diameter value and the control amount, and may be, for example, a graph or a mathematical formula that represents the relationship between the pupil diameter value and the control amount.

[0124] The control amount determination unit, for example, selects a value corresponding to a value indicated by the pupil diameter data of the subject's eye (pupil diameter value) from among a plurality of control amount values ​​included in the control amount information. More generally, the control amount determination unit determines a control amount corresponding to the subject's eye by applying the value indicated by the pupil diameter data of the subject's eye (pupil diameter value) to the control amount information. The process of applying the pupil diameter value to the control amount information may include, for example, a process of calculating a control amount by substituting the pupil diameter value into a formula, a process of determining a control amount corresponding to the pupil diameter value from a table or graph, etc.

[0125] The movement control unit of this embodiment controls the movement mechanism to adjust the distance between the subject's eye and the imaging unit based on the value of the control amount obtained by the control amount determination unit from the control amount information, for example, by any of the above-mentioned processes.

[0126] According to the thirteenth aspect, it is possible to provide an example of a process for determining a control amount for adjusting the distance between the subject's eye and the imaging unit. By improving the quality of the control amount information, it is possible to improve the quality (accuracy, precision, reproducibility, etc.) of the distance adjustment between the subject's eye and the imaging unit according to the pupil size.

[0127] The control amount information used in the thirteenth aspect may be generated by a device or system other than the ophthalmic apparatus according to the embodiment, but the ophthalmic apparatus according to the embodiment may have a function for generating the control amount information. The fourteenth aspect provides an example of an ophthalmic apparatus having a function for generating the control amount information.

[0128] An ophthalmologic apparatus according to a fourteenth aspect includes a control amount information generating unit. The control amount information generating unit is configured to generate control amount information based on, for example, one or more of the following information (1) to (4): (1) a distance between the eye and the imaging unit; (2) a reduction in the peripheral light intensity of illumination light (for example, an amount or rate of reduction); (3) a probability of a high-brightness area occurring in a fundus image; and (4) a pupil diameter value.

[0129] This disclosure will later describe in detail a case in which control amount information is generated based on the relationships among these four pieces of information (1) to (4). The relationships among the pieces of information (1) to (4) can be determined by actual measurements and / or calculations (computer simulations such as ray tracing). Note that a person skilled in the art will understand from the description of this case that the embodiment is not limited to this case.

[0130] According to the fourteenth aspect, it is possible to provide an example of a process for generating control amount information, and to provide good quality control amount information based on any of the four pieces of information (1) to (4).

[0131] The fifteenth aspect provides an example of the above case in which control amount information is generated based on the relationship between the four pieces of information (1) to (4). In this aspect, the control amount information is generated in which values ​​of the control amount corresponding to each of two or more ranges of pupil diameter values ​​are recorded.

[0132] First, two or more ranges of pupil diameter values ​​are set. These ranges may be set based on standard classifications of pupil diameters or may be set based on clinical data, etc. The control amount information generator of this aspect is configured to determine, for each of the two or more ranges of pupil diameter values, a control amount value to be assigned to this range so that the reduction in peripheral light intensity of the illumination light is equal to or less than a predetermined second threshold (peripheral light intensity threshold).

[0133] As with the twelfth aspect, the configuration of the fifteenth aspect is designed in consideration of the fact that a change in the peripheral light amount of illumination light accompanying a change in the distance between the subject's eye and the imaging unit depends on the pupil diameter of the subject's eye. Any feature related to the twelfth aspect can be applied to the fifteenth aspect. An example of this aspect will be described later.

[0134] According to the fifteenth aspect, it is possible to control the distance between the test eye and the imaging unit so that an image of acceptable brightness can be obtained by slit scanning performed after controlling the distance between the test eye and the imaging unit.

[0135] A sixteenth aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to any of the first to fifteenth aspects described above.

[0136] The control amount determination unit of this aspect is configured to determine whether or not to execute a process for determining a control amount for adjusting the distance between the subject's eye and the imaging unit, based on the value of the luminance parameter determined by the image analysis unit. For example, similar to the seventh aspect, the control amount determination unit of this aspect may be configured to compare the value of the luminance parameter determined by the image analysis unit with a predetermined threshold, and determine to execute the process for determining the control amount if the value of the luminance parameter is equal to or greater than the threshold, and determine not to execute the process for determining the control amount if the value of the luminance parameter is less than the threshold.

[0137] When it is determined that the process for determining the control amount is to be executed, the control amount determiner of this aspect is configured to determine the control amount based on the pupil diameter data acquired by the pupil diameter data acquirer. The method for determining the control amount based on the pupil diameter data may be, for example, any of the methods described in the eleventh to fifteenth aspects, another method described in the present disclosure, or a method other than these.

[0138] According to the sixteenth aspect, an example of the operation of the first to fifteenth aspects can be provided. This example of operation determines whether or not to adjust the distance between the subject's eye and the imaging unit based on the value of the luminance parameter determined by the image analysis unit. If it is determined that the distance adjustment is not to be performed, the system proceeds to a slit scan of the fundus of the subject's eye. If it is determined that the distance adjustment is to be performed, the system determines a control amount based on pupil diameter data acquired by the pupil diameter data acquisition unit, and controls the movement mechanism based on this control amount to adjust the distance between the subject's eye and the imaging unit, after which a slit scan of the fundus of the subject's eye is performed.

[0139] A seventeenth aspect of the ophthalmologic apparatus according to a non-limiting embodiment may include the following features in addition to any of the first to sixteenth aspects described above.

[0140] In this aspect, the movement control unit controls the movement mechanism based on the control amount determined by the control amount determination unit to increase the distance between the test eye and the imaging unit. This allows for the elimination or reduction of flare contained in the image of the fundus of the test eye (first image) analyzed by the image analysis unit to determine the control amount. In other words, no flare occurs in the image (second image) acquired by the slit scan performed after the distance is increased, or the flare that occurs in the second image is weaker (e.g., lower in brightness and / or smaller in size) than the flare in the first image. On the other hand, increasing the distance between the test eye and the imaging unit to eliminate or reduce flare can reduce the brightness of the image, resulting in a second image that is darker than the acceptable range. This aspect was developed to address these problems and has the following configuration.

[0141] The image analysis unit of this embodiment is configured to determine a new value of the brightness parameter by analyzing a new image of the fundus of the test eye obtained after the distance between the test eye and the imaging unit is increased by the movement control unit.

[0142] The brightness parameters may be the same as or different from the brightness parameters determined from the first image, and the new image may be a slit-scan image or an image acquired with another modality (e.g., a slit-scan image in global reset release shutter mode, a global shutter camera, etc.).

[0143] The control amount determination unit of this embodiment is configured to determine a new control amount for controlling the distance between the test eye and the imaging unit based on the new value of the brightness parameter obtained by analyzing this new image.

[0144] For example, the control amount determiner determines the new control amount by comparing the new value of the brightness parameter with a predetermined value, which may be a predetermined threshold value, the brightness parameter value determined from the first image, or another value.

[0145] This comparison process determines whether the new image has sufficient brightness. If it is determined that the new image has sufficient brightness, the operation according to this aspect ends. In other words, the process of determining a new control amount is not executed. On the other hand, if it is determined that the new image does not have sufficient brightness, the control amount determination unit determines a new control amount for acquiring an image brighter than the new image. This new control amount is a value for reducing the distance between the subject's eye and the imaging unit. The movement control unit according to this aspect controls the movement mechanism based on this new control amount.

[0146] According to the seventeenth aspect, when the brightness of an image obtained after the distance between the subject's eye and the imaging unit is increased for the purpose of eliminating or reducing flare is insufficient, the distance between the subject's eye and the imaging unit can be shortened so as to obtain a brighter image. There is a trade-off between image brightness and the occurrence of flare. The configuration and operation of the seventeenth aspect are designed in consideration of this trade-off so as to obtain a brighter image with a lower degree of flare.

[0147] Any feature of the present disclosure and / or any feature of the publicly known art can be combined with aspects 1 to 17. An ophthalmic device obtained by such a combination further exhibits the actions and effects of the combined features, as well as synergistic actions and effects of the combination of features.

[0148] Another aspect of the embodiment provides a method for determining a distance between an ophthalmic apparatus performing slit scanning and an eye to be examined, the ophthalmic apparatus including an imaging unit configured to project illumination light from a light source onto a fundus of the eye to be examined via an optical scanner and detect return light of the illumination light with an image sensor operable in a rolling shutter mode.

[0149] The method of this aspect is a method for determining the distance between the subject's eye and the imaging unit for fundus photography using this ophthalmologic apparatus, and includes the following steps: In a first step, a computer acquires an image of the fundus of the subject's eye; In a second step, the computer analyzes the image of the fundus of the subject's eye acquired in the first step to determine a value of a predetermined brightness parameter; In a third step, the computer acquires pupil diameter data of the subject's eye; In a fourth step, the computer determines the distance between the subject's eye and the imaging unit based on the value of the brightness parameter determined in the second step and the pupil diameter data acquired in the third step; The ophthalmologic apparatus can move the imaging unit so that the distance between the subject's eye and the imaging unit matches the distance determined in the fourth step.

[0150] The computer that executes the first to fourth steps may be a processor (and memory) included in the ophthalmic apparatus, or may be a device separate from the ophthalmic apparatus.

[0151] The first to fourth steps and the movement of the photographing unit based on the distance determined thereby correspond to the elements of the ophthalmologic apparatus of the first aspect described above. Specifically, the first step corresponds to an element that acquires the fundus of the subject's eye to be analyzed by the image analysis unit, the second step corresponds to the image analysis unit, the third step corresponds to the pupil diameter data acquisition unit, the fourth step corresponds to the control amount determination unit, and the movement of the photographing unit corresponds to the movement control unit.

[0152] According to the method of this aspect, like the ophthalmologic apparatus of the first aspect, it is possible to provide a flare-free image by slit-scan fundus photography.

[0153] Any feature of the present disclosure (e.g., any feature related to the ophthalmic device according to the embodiment) and / or any feature related to the publicly known art can be combined with the method according to the embodiment, and the method obtained by such a combination further exhibits the functions and effects of the combined features and the synergistic functions and effects of the combination of the features.

[0154] Another aspect of the embodiment provides a program for causing a computer to execute a method according to the embodiment. Another aspect of the embodiment provides a computer-readable non-transitory recording medium having a program according to the embodiment recorded thereon. These aspects also achieve similar effects. The recording medium according to the embodiment may be a recording medium in any form, and may be, for example, a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.

[0155] The aspects of the embodiments of the present disclosure are not limited to ophthalmic apparatuses, methods for determining a fundus photographing distance, programs, and storage media. For example, it will be understood by those skilled in the art that the present disclosure provides embodiments of a method for controlling an ophthalmic apparatus, an embodiment of a method for photographing an eye to be examined, an embodiment of a method for processing ophthalmic information, and similar embodiments in fields other than ophthalmology.

[0156] <Exemplary Embodiment> A non-limiting example of the configuration of an ophthalmic apparatus according to an embodiment is shown in Fig. 1. The ophthalmic apparatus 1 of this example functions as an ophthalmic imaging apparatus capable of imaging the fundus of a living eye using a slit-scan modality.

[0157] The ophthalmic apparatus 1 includes an imaging unit 2, a moving mechanism 3, a processor 4, a memory 5, and a user interface 6. Unless otherwise specified, the hardware elements included in the ophthalmic apparatus 1 may be similar to the hardware elements of an existing slit-scan type ophthalmic imaging apparatus.

[0158] The photographing unit 2 is configured to be able to perform slit scanning by photographing with a rolling shutter type image sensor (image capturing device) while moving the projection position of the slit light on the fundus of the subject's eye. In other words, the photographing unit 2 is configured to illuminate the fundus of the subject's eye while moving the irradiation position (irradiation range) of the slit-shaped illumination light (slit light), and to receive the returning light from the fundus with an image sensor in which light receiving elements are arranged one-dimensionally or two-dimensionally.

[0159] The signal readout from the image sensor that detects the returning light is executed under the control of the processor 4, and in synchronization with the timing of the movement of the slit light irradiation position, signals are sequentially readout from the light receiving elements at the returning light receiving positions corresponding to each slit light irradiation position. This signal readout is performed using a rolling shutter system. A non-limiting example of the specific configuration of the imaging unit 2 will be described later.

[0160] The image sensor provided in the ophthalmologic apparatus 1 is operable at least in the rolling shutter mode. Some image sensors may be operable in the rolling shutter mode and the global reset release shutter mode.

[0161] In some embodiments, an imaging unit (imaging device) that combines a global shutter image sensor with a mechanically or electronically configured slit diaphragm instead of a rolling shutter image sensor can be used to perform a similar imaging operation to that of a rolling shutter image sensor. The imaging operation of this embodiment is an example of slit scanning in rolling shutter mode.

[0162] The imaging unit 2 includes a hardware element (focus adjustment unit) for performing focus adjustment (focusing) of the optical system provided in the imaging unit 2. Any method of focus adjustment may be used. For example, focus adjustment may be performed using a configuration that changes the focal length (position of the focal point) of a lens disposed between the subject (fundus of the subject's eye) and the image sensor, or may be performed using a configuration that changes the distance between the lens and the image sensor.

[0163] The movement mechanism 3 is configured to move the imaging unit 2. The movement mechanism 3 is configured to move the imaging unit 2 three-dimensionally under the control of the processor 4, and includes, for example, a mechanism for moving a stage on which the imaging unit 2 is mounted in the X direction, a mechanism for moving it in the Y direction, and a mechanism for moving it in the Z direction. Each mechanism includes an actuator (for example, a stepping motor) that operates under the control of the processor 4.

[0164] The processor 4 realizes the functions according to this embodiment by executing processes in accordance with programs stored in the memory 5 and / or other storage devices.

[0165] The memory 5 stores various computer programs and various data. In a typical embodiment, the memory 5 includes a non-volatile memory and a volatile memory.

[0166] The memory 5 stores control programs and / or control data for causing the ophthalmic device 1 to perform predetermined operations, and calculation programs and / or calculation data for causing the ophthalmic device 1 to perform predetermined calculation processing.

[0167] The memory 5 also stores data acquired by the ophthalmic apparatus 1. For example, data generated by the ophthalmic apparatus 1 and data acquired by the ophthalmic apparatus 1 from an external source are stored in the memory 5. The programs and data stored in the memory 5 are not limited to those exemplified here.

[0168] The user interface 6 is an element (hardware element, software element, protocol) for exchanging information between the ophthalmic apparatus 1 and its user. The user interface 6 includes, for example, an input unit (operation unit) that is a means for providing information from the user to the ophthalmic apparatus 1, and an output unit that is a means for providing information from the ophthalmic apparatus 1 to the user. Non-limiting examples of hardware elements of the input unit include an operation panel, a mouse, a keyboard, a trackball, a switch, a button, a dial, a scanner, an optical character recognition (OCR) device, a microphone, a camera (video camera), etc. Non-limiting examples of hardware elements of the output unit include a display, a printer, a speaker, etc. The user interface 6 may include a device that integrates input and output functions, such as a touch screen.

[0169] Although not shown in the drawings, the ophthalmic apparatus 1, like existing ophthalmic apparatuses of the same type, includes elements for aligning (positioning) the imaging unit 2 with the subject's eye E. The alignment method performed by the ophthalmic apparatus 1 may be any method, and may be, for example, stereo alignment described in Japanese Patent Application Laid-Open No. 2013-248376, which uses two or more anterior segment cameras to determine the position of the subject's eye E, a method for determining the position of the subject's eye E by analyzing a front image of the subject's eye E (e.g., an observation image of the anterior segment Ea), or a method for determining the position of the subject's eye E by projecting an alignment index onto the anterior segment Ea. The ophthalmic apparatus 1 includes hardware elements and software elements according to the alignment method.

[0170] A non-limiting example of the configuration of the imaging unit 2 is shown in Fig. 2, which is a side view. In Fig. 2, the direction along the optical axis of the optical system (the optical axis of the objective lens 46) is defined as the Z direction (front-back direction, working distance direction), one direction perpendicular to the Z direction (left-right direction, horizontal direction in this example) is defined as the X direction, and the direction perpendicular to both the Z direction and the Y direction (up-down direction, vertical direction in this example) is defined as the Y direction.

[0171] The photographing unit 2 in this example includes a light source 10, an illumination optical system 20, an optical scanner 30, a photographing optical system 40, and an imaging device 50. The illumination optical system 20 projects illumination light from the light source 10 onto the fundus Ef of the subject's eye E via the optical scanner 30. The light source 10 may be considered an element of the illumination optical system 20. The optical scanner 30 moves the position (projection position) of the slit light projected onto the fundus Ef by the illumination optical system 20. The optical scanner 30 may be considered an element of the illumination optical system 20. The photographing optical system 40 guides the return light of the slit light projected onto the fundus Ef by the illumination optical system 20 to the imaging device 50. The imaging device 50 may be considered an element of the photographing optical system 40. Each element of the photographing unit 2 will be described below.

[0172] The light source 10 generates light (illumination light) for illuminating the subject's eye E. The light source 10 may include a visible light source that generates light in the visible region (e.g., a white light source that generates white light). The light source 10 may also include an infrared light source (near-infrared light source) that generates light in the infrared region (near-infrared region).

[0173] The light source 10 may be capable of switching between and outputting light in two or more different wavelength ranges. In this case, the light source 10 may include a single light source (tunable light source) capable of outputting light in two or more different wavelength ranges, a light source device that combines a broadband light source such as a white light source with a wavelength selection element such as a bandpass filter, or a light source device that combines two or more light sources that output light in different wavelength ranges with an optical path coupling element (a dichroic mirror, a half mirror, or the like).

[0174] The light source 10 may include any type of light source, such as one or more of a light emitting diode (LED), a laser diode (LD), a halogen lamp, and a xenon lamp.

[0175] When the imaging unit 2 is properly aligned with the subject's eye E, the light source 10 is placed at a position optically non-conjugate with respect to the fundus Ef and the iris.

[0176] In some embodiments, under the control of processor 4, light source 10 outputs visible light when performing slit scanning in rolling shutter mode and outputs infrared light for other purposes, such as slit scanning in global reset release shutter mode, alignment, and focus adjustment. Note that focus adjustment may also be performed using visible light.

[0177] The illumination optical system 20 generates slit-shaped illumination light (slit light) from the light emitted by the light source 10 and projects it onto the fundus Ef of the subject's eye E. In this example, the illumination optical system 20 includes an iris diaphragm 21, a slit aperture diaphragm (slit) 22, a relay lens 23, an optical scanner 30, a relay lens 31, a hole mirror 45, and an objective lens 46. The relay lens 23 includes one or more lenses, the relay lens 31 includes one or more lenses, and the objective lens 46 includes one or more lenses.

[0178] The photographing optical system 40 guides the return light of the illumination light (slit light) projected onto the fundus Ef of the subject's eye E by the illumination optical system 20 (and the optical scanner 30) to the imaging device 50. In this example, the photographing optical system 40 includes an objective lens 46, a hole mirror 45, a focus lens 47, and an imaging lens 48. The focus lens 47 includes one or more lenses, and the imaging lens 48 includes one or more lenses. A relay lens may be provided between the focus lens 47 and the imaging lens 48. This relay lens includes one or more lenses.

[0179] The light output from the light source 10 (specifically, a portion of this light) passes through an opening formed in the iris diaphragm 21, an opening formed in the slit aperture diaphragm 22, and a relay lens 23, and is guided to the optical scanner 30.

[0180] When the alignment of the photographing unit 2 with respect to the subject's eye E is appropriate, the iris diaphragm 21 (specifically, the opening formed in the iris diaphragm 21) is positioned at a position that is approximately optically conjugate with the iris (pupil) of the subject's eye E.

[0181] The iris diaphragm 21 has one or more openings formed at positions spaced apart from the optical axis of the illumination optical system 20. For example, in the iris diaphragm 21 according to the non-limiting example shown in Fig. 3, two openings 21A and 21B having predetermined dimensions (a predetermined length and a predetermined width) are formed along a circle centered on the optical axis O of the illumination optical system 20.

[0182] The opening of the iris diaphragm 21 defines the incidence state (incident position, incident shape) of the illumination light on the pupil of the subject's eye E. For example, when the iris diaphragm 21 having the openings 21A and 21B formed therein is used, in a state in which the optical axis O of the illumination optical system 20 (the optical axis of the objective lens 46) is positioned so as to substantially coincide with the center of the pupil of the subject's eye E (that is, in a state in which alignment in the X and Y directions is appropriate), the illumination light (slit light) can be guided to the fundus Ef through positions spaced apart from the center of the pupil (specifically, two positions arranged point-symmetrically with respect to the center of the pupil).

[0183] In some embodiments, an optical element that deflects light from light source 10 may be provided between light source 10 and iris diaphragm 21 to optimize the light intensity distribution in the direction connecting the opening of iris diaphragm 21 and the opening (slit) of slit aperture diaphragm 22. Furthermore, by configuring the relative position between light source 10 and the opening of iris diaphragm 21 to be changeable, the light intensity distribution of light passing through the opening of iris diaphragm 21 may be made variable.

[0184] When the imaging unit 2 is properly aligned with the subject's eye E, the slit aperture stop 22 (specifically, the opening formed in the slit aperture stop 22) is positioned at a position that is approximately optically conjugate with the fundus Ef of the subject's eye E.

[0185] The slit aperture stop 22 has an opening formed therein whose longitudinal direction corresponds to the direction along the line (row direction) along which signals are read out by the rolling shutter method from the image sensor 51, which will be described later. For example, the slit aperture stop 22 according to the non-limiting example shown in Figure 4 has an opening 22A having predetermined dimensions (a predetermined length and a predetermined width) formed in a region including the optical axis O of the illumination optical system 20.

[0186] The opening formed in the slit aperture diaphragm 22 defines the shape of the projected image of the slit light on the fundus Ef of the subject's eye E. The longitudinal direction of the slit formed in the slit aperture diaphragm 22 may be referred to as the slit length direction. Also, the lateral direction of the slit formed in the slit aperture diaphragm 22 may be referred to as the slit width direction.

[0187] The slit aperture stop 22 can be moved in a direction along the optical axis of the illumination optical system 20 by a moving mechanism 22M (see FIG. 2). The moving mechanism 22M operates under the control of the processor 4. The processor 4 may be configured to control the moving mechanism 22M depending on the state of the subject's eye E (e.g., refractive power (refractive power, diopter), fundus shape, etc.).

[0188] The light that has passed through the opening of the iris diaphragm 21 is converted into slit-shaped illumination light (slit light) by passing through the opening of the slit aperture diaphragm 22. The slit light is guided to the optical scanner 30 via the relay lens 23, deflected by the optical scanner 30, and guided to the hole mirror 45 via the relay lens 31.

[0189] The hole mirror 45 is an optical component used in existing fundus cameras and functions as an optical path coupling component that couples the optical path of the illumination optical system 20 with the optical path of the photographing optical system 40. An opening (or a light-transmitting portion) is formed at the center of the hole mirror 45. For example, the outer edge of this opening is circular. The optical axes of the illumination optical system 20 and the photographing optical system 40 intersect at the opening of the hole mirror 45. A reflecting portion (mirror portion) is formed around the opening of the hole mirror 45.

[0190] The slit light guided to the hole mirror 45 via the relay lens 31 is reflected by the reflecting portion, refracted by the objective lens 46, and enters the subject's eye E. The slit light entering the subject's eye E is projected onto the fundus Ef.

[0191] In some aspects, the shape of the projected image (projection area) of the slit light on the fundus Ef is approximately slit-shaped, and the longitudinal direction of this slit-shaped projected image approximately coincides with the X direction. In this case, the optical scanner 30 deflects the slit light generated by the iris diaphragm 21 and the slit aperture diaphragm 22 so as to move the projected image of the slit light on the fundus Ef in the Y direction.

[0192] The longitudinal direction of the projected image of the slit light on the fundus Er is not limited to the X direction, and the moving direction of the projected image by the optical scanner 30 is not limited to the Y direction. For example, the longitudinal direction of the projected image of the slit light can be set to the Y direction, and the moving direction of the projected image by the optical scanner 30 can be set to the X direction. Furthermore, at least one of the direction and moving direction of the projected image of the slit light may be variable.

[0193] When the imaging unit 2 is properly aligned with the subject's eye E, the optical scanner 30 is positioned at a position that is approximately optically conjugate with the iris of the subject's eye E. This makes it possible to deflect the slit light in a predetermined direction (in a typical aspect of this embodiment, the Y direction) using a position within the pupil of the subject's eye E (or a position near the pupil) as a pivot (scan axis, deflection center axis), and to project the slit light sequentially onto multiple slit-shaped partial regions formed by virtually dividing a predetermined scan range of the fundus Ef. In other words, it becomes possible to perform a slit scan of the fundus Ef.

[0194] The reflected light of the slit light projected onto the fundus Ef exits the subject's eye E through the pupil of the subject's eye Ef and enters the photographing unit 2. The light (returned light) that enters the photographing unit 2 from the subject's eye E is guided to the hole mirror 45 via the objective lens 46. This returned light passes through the opening of the hole mirror 45 (or passes through the light-transmitting portion), and is guided to the imaging device 50 via the focus lens 47 and the imaging lens 48, where it is detected.

[0195] The optical scanner 30 is capable of deflecting the slit light one-dimensionally or two-dimensionally, for example. The optical scanner 30 for one-dimensional deflection deflects the slit light within a predetermined deflection angle range based on a predetermined direction. This deflection angle range is defined in a direction corresponding to the movement direction of the slit light at the fundus Ef (e.g., the Y direction). The optical scanner 30 capable of two-dimensional deflection is, for example, a combination of two optical scanners that provide different deflection directions. The type of optical deflection device used in the optical scanner 30 may be any type, and may be, for example, a galvanometer scanner.

[0196] The focus lens 47 can be moved in a direction along the optical axis of the imaging optical system 40 by a moving mechanism 47M (see FIG. 2). The moving mechanism 47M operates under the control of the processor 4. The processor 4 may be configured to control the moving mechanism 47M depending on the state of the subject's eye E (e.g., refractive power, fundus shape, etc.).

[0197] The imaging device 50 includes an image sensor 51 that detects the returning light guided by the imaging optical system 40. Under the control of the processor 4, the imaging device 50 can read out a signal from the image sensor 51 that detects the returning light.

[0198] The image sensor 51 functions as a pixelated light receiver. When the imaging unit 2 is properly aligned with the subject's eye E, the light receiving surface (detection surface, imaging surface) of the image sensor 51 is positioned at a position that is approximately optically conjugate with the fundus Ef of the subject's eye E. The signal generated by the image sensor 51 through photoelectric conversion is read out by a rolling shutter method under the control of the processor 4.

[0199] In some embodiments, the image sensor 51 includes a CMOS image sensor. In this case, the image sensor 51 includes a plurality of pixel groups arranged in a row direction, and these pixel groups are arranged in a column direction. More specifically, the image sensor 51 includes a plurality of two-dimensionally arranged pixels, a plurality of vertical signal lines, and a horizontal signal line. Each pixel includes a photodiode and a capacitor. A vertical signal line is provided for each pixel group arranged in a column direction (vertical direction) perpendicular to the row direction (horizontal direction). Each vertical signal line is selectively electrically connected to a pixel group that accumulates charge corresponding to the detection result of the returned light. The horizontal signal line is selectively electrically connected to multiple vertical signal lines. Each pixel accumulates charge corresponding to the detection result of the returned light, and the accumulated charge is read out, for example, sequentially for each pixel group in the row direction. For example, a voltage corresponding to the charge accumulated in each pixel is supplied to the vertical signal line for each line in the row direction. The multiple vertical signal lines are selectively electrically connected to the horizontal signal line. By sequentially performing the above-described readout operation for each line in the row direction in the vertical direction, it is possible to read out detection results from a plurality of pixels arranged two-dimensionally.

[0200] A received light image corresponding to a desired virtual aperture shape extending in the row direction is acquired by using a rolling shutter method to read out the detection results from the image sensor 51. This control is well known and is disclosed in, for example, U.S. Pat. No. 7,831,106.

[0201] The slit scan performed by the ophthalmologic apparatus 1 will be described with reference to Fig. 5. In Fig. 5, the symbol IP indicates the position (projection range) of the projected image of the slit light on the fundus oculi Ef, and the symbol OP indicates the position (opening range) of the virtual opening on the light receiving surface SR of the image sensor 51.

[0202] The ophthalmologic device 1 deflects the slit light using the optical scanner 30, thereby moving the projection range IP of the slit light on the fundus Ef in the slit width direction (e.g., Y direction, column direction, vertical direction) perpendicular to the slit length direction (e.g., X direction, row direction, horizontal direction).

[0203] When reading out signals from the image sensor 51 under the control of the processor 4, the pixel group from which signals are to be read out is switched sequentially in units of lines, thereby sequentially setting the aperture range OP.

[0204] The opening range OP corresponding to the projection range IP is set so as to include a range IP' where the return light of the slit light projected onto the projection range IP is projected onto the light-receiving surface SR. In other words, the opening range OP of the light-receiving surface SR corresponding to the projection range IP of the slit light is set as a light-receiving area that coincides with the projection range IP', or as a wider light-receiving area that includes the projection range IP'.

[0205] The processor 4 executes control for moving the projection range IP of the slit light and control for moving the opening range OP in parallel with each other. For example, the processor 4 executes these two controls (and one or more additional controls) synchronously (in cooperation with each other).

[0206] By performing slit scanning in this manner, the imaging target range of the fundus oculi Ef can be scanned while the projection range IP of the slit light and the aperture range OP of the image sensor 51 are moved in coordination. This makes it possible to acquire high-quality fundus images with high contrast without being affected by unnecessary scattered light. Moreover, this effect can be achieved with a simple configuration.

[0207] As described above, there are several operation modes (operation methods) for slit scanning. In this embodiment, the rolling shutter mode and the global reset release shutter mode will be described.

[0208] Slit scanning in the rolling shutter mode will now be described. An example of a control mode for slit scanning in the rolling shutter mode is shown in FIG.

[0209] 6, the horizontal axis represents time [t] and the vertical axis represents the line number. The intersection of the vertical and horizontal axes corresponds to the start time of the slit scan.

[0210] The line number is an identifier of a plurality of pixel lines included in a light receiving element array (pixel array) arranged on the light receiving surface of the image sensor 51. In some aspects, the line number is an identifier of a plurality of pixel lines arranged in a row direction, and each pixel line is made up of a group of pixels arranged in a column direction. In other aspects, the line number is an identifier of a plurality of pixel lines arranged in a column direction, and each pixel line is made up of a group of pixels arranged in the row direction.

[0211] Each pixel line may be a group of pixels arranged in one column, or two or more columns. Furthermore, two pixel lines with consecutive line numbers may be adjacent pixel lines in the pixel array of the image sensor 51, or may be non-adjacent pixel lines with one or more intervening pixel lines in the pixel array of the image sensor 51.

[0212] The number of pixel lines used for the slit scan in the rolling shutter mode may be any number. In the example shown in Figure 6, 1920 pixel lines are used. Each pixel line in Figure 6 is denoted by L(n) (n = 1, 2, ..., 1920).

[0213] In each pixel line L(n), the period indicated by diagonal lines indicates the period during which scanning is performed (scan period), and the period indicated by solid lines indicates the period during which signals are read out (read period). In the rolling shutter mode of FIG. 6, the length of the scan period (scan time) RSt is set equal for all pixel lines L(1) to L(1920), but the embodiment is not limited to this setting. The read period may be set arbitrarily.

[0214] 6, the difference between the scan start time of the n-th pixel line L(n) and the scan start time of the next (n+1)-th pixel line L(n+1) is a constant value ΔRSt (n=1 to 1919). Note that the difference in scan start time does not have to be constant.

[0215] 6, RRt indicates the time required to read out signals from 1920 pixel lines L(1) to L(1920) (total readout time), and RTt indicates the time required for slit scanning (scan time).

[0216] In this way, in the slit scan of the rolling shutter mode of Figure 6, control is performed so that scanning and signal readout corresponding to multiple pixel lines L(1) to L(1920) are performed sequentially with a certain time difference ΔRSt in the order of line number n = 1 to 1920.

[0217] Slit scanning in the global reset release shutter mode will now be described. An example of the control mode for slit scanning in the global reset release shutter mode is shown in Fig. 7. As in Fig. 6, the horizontal axis indicates time [t], the vertical axis indicates the line number, and the intersection of the vertical and horizontal axes corresponds to the start time of the slit scan.

[0218] The number of pixel lines used for slit scanning in the global reset release shutter mode may be any number. In the example shown in Fig. 7, 1920 pixel lines L(n) (n = 1, 2, ..., 1920) are used, similar to Fig. 6.

[0219] Unlike the rolling shutter mode of Fig. 6, in the global reset release shutter mode of Fig. 7, the scan start times of all pixel lines L(1) to L(1920) are the same, and the scan times of all pixel lines L(1) to L(1920) are different from each other. If the scan time of each pixel line L(n) is denoted by GSt(n), then for any different line numbers n1 and n2 (n1 ≠ n2), GSt(n1) and GSt(n2) are different (GSt(n1) ≠ GSt(n2)).

[0220] 7, the difference between the scan time GSt(n) of the n-th pixel line L(n) and the scan time GSt(n+1) of the next n+1-th pixel line L(n+1) is a constant value ΔGSt (n=1 to 1919). Note that the difference in scan time does not have to be constant.

[0221] GRt indicates the time required to read out signals from 1920 pixel lines L(1) to L(1920) (total readout time), and GTt indicates the time required for slit scanning (scan time).

[0222] In this way, in the slit scan of the global reset release shutter mode of Figure 7, scans corresponding to all pixel lines L(1) to L(1920) start simultaneously, and control is performed so that scans of pixel lines L(1) to L(1920) are completed sequentially with a certain time difference ΔGSt in the order of line number n = 1 to 1920, and signal readout is performed.

[0223] In such a slit scan in the global reset release shutter mode, a common exposure period (common exposure time Ct) is set for all pixel lines L(1) to L(1920). This common exposure time Ct corresponds to the exposure time in image capture using a global shutter image sensor.

[0224] In some embodiments, a black spot for eliminating harmful reflected light can be provided between the optical scanner 30 and the hole mirror 45. The black spot is placed at a position that is approximately optically conjugate with the position of the central ghost caused by reflection of the slit light by the objective lens 46.

[0225] In some embodiments, a focus index projection optical system that generates a focus adjustment index (split index) to be projected onto the fundus oculi Ef is provided between the optical scanner and the hole mirror, and a mechanism for moving the focus index projection optical system is provided. Note that the configuration for focus adjustment is not limited to this.

[0226] The processor 4 executes various control processes and various arithmetic processes. The processor 4 is configured to execute, for example, control for causing the imaging unit 2 to execute the slit scan described with reference to Figures 5 to 7 (slit scan control), and position adjustment of the imaging unit 2 to acquire a flare-free image (alignment process). The processes executed by the processor 4 are not limited to these, and it is possible to execute, for example, focus adjustment and display control.

[0227] The slit scan control may be performed by a known method. In contrast, the alignment process of this embodiment is a novel technique. Several examples of the alignment process will be described below.

[0228] In order to perform a novel alignment process, the ophthalmologic apparatus 1 of this embodiment is configured to execute a series of processes including analyzing a fundus image, acquiring pupil diameter data, determining an alignment control amount, and moving the imaging unit 2. By executing this novel series of processes (i.e., by employing a configuration including novel software elements), the ophthalmologic apparatus 1 makes it possible to acquire a flare-free image in fundus photography using the slit scan method.

[0229] 8 shows a non-limiting example of the configuration of the processor 4. The processor 4 in this example includes an imaging control unit 410 and an alignment processing unit 420. The alignment processing unit 420 includes an image analysis unit 421, a pupil diameter data acquisition unit 422, a control amount determination unit 423, and a movement control unit 424.

[0230] The imaging control unit 410 controls the imaging unit 2 to capture an image of the subject's eye E. Under the control of the imaging control unit 410, the imaging unit 2 is capable of capturing an image of the fundus Ef of the subject's eye E, and may also be capable of capturing an image of the anterior segment Ea.

[0231] The imaging control unit 410 causes the imaging unit 2 to perform, for example, the slit scan shown in Fig. 5. The imaging control unit 410 is configured to cause the imaging unit 2 to perform, for example, the slit scan in rolling shutter mode shown in Fig. 6. The slit scan in rolling shutter mode in this example is performed using visible light and / or infrared light. The visible image and / or infrared image acquired by this slit scan is provided, for example, for diagnosing the subject's eye E.

[0232] The imaging control unit 410 may be configured to cause the imaging unit 2 to perform, for example, a slit scan in the global reset release shutter mode shown in FIG. 7 . In this example, the slit scan in the global reset release shutter mode is performed using, for example, infrared light. The infrared image acquired by this slit scan is provided to, for example, an alignment process performed in preparation for a slit scan in the rolling shutter mode. By using the infrared image for alignment, it is possible to avoid miosis of the subject's eye E.

[0233] When the photographing unit 2 includes the optical system of a general fundus camera (i.e., an optical system including a global shutter camera), the photographing control unit 410 is configured to perform photographing control similar to that of a processor of a general fundus camera.

[0234] The alignment processing unit 420 executes processing for aligning the photographing unit 2 (the illumination optical system 20 and the photographing optical system 40) with the subject's eye E.

[0235] The alignment in this embodiment is an operation for providing an effect different from general alignment (i.e., XY alignment for aligning the axis of the test eye with the optical axis of the device optical system, and Z alignment for matching the distance between the test eye and the device optical system to the working distance), and specifically, it is a position adjustment between the test eye and the device optical system with one of the purposes being to obtain a flare-free fundus image by slit scanning.

[0236] 9A is an image obtained by photographing the fundus of a subject's eye using a rolling shutter slit scan. This slit scan was performed using visible illumination light, and the fundus image 101 is a color image. Flare 101A occurs in this color fundus image 101.

[0237] 9B is an image acquired by applying global shutter photography to the fundus of the same subject's eye. This photography was performed using infrared illumination light, and the fundus image 102 is a grayscale image. This photography was performed using, for example, a slit scan with a global reset release shutter or a global shutter camera. Two flares 102A and 102B are generated in this infrared fundus image 102.

[0238] The flare 101A and the flares 102A and 102B are all caused by the corneal reflection of illumination light. Therefore, it is believed possible to estimate the state of the flare 101A from the states of the flares 102A and 102B. For example, before performing a rolling shutter slit scan to acquire a color fundus image used in image diagnosis, it is believed possible to estimate the state of flare in the image acquired by the slit scan by performing infrared photography using a global shutter and analyzing the state of flare in the acquired infrared fundus image. More specifically, it is possible to estimate whether or not a flare is included in the slit scan image based on whether or not a flare is included in the infrared fundus image. Furthermore, it is possible to estimate the state of flare that may occur in the slit scan image based on the state of flare in the infrared fundus image (e.g., brightness, size, position, etc.). These matters are the findings of the inventors.

[0239] The likelihood of flare occurrence varies from eye to eye. For example, the amount of corneal reflection (corneal reflectance) and ocular tissue structure (tissue shape, tissue arrangement, etc.) vary from eye to eye. Therefore, whether or not the corneal reflection of illumination light enters the device optical system varies from eye to eye, and the intensity and direction of the corneal reflection entering the device optical system also vary from eye to eye. Therefore, it is very difficult to estimate the state of flare in an image obtained by rolling shutter slit scanning without performing preliminary imaging and processing. In this embodiment, the preliminary imaging and processing involves performing global shutter infrared imaging and analyzing infrared fundus images, thereby making it possible to estimate the state of flare in an image obtained by rolling shutter slit scanning.

[0240] As described above, the alignment processing unit 420 includes the image analysis unit 421 , the pupil diameter data acquisition unit 422 , the control amount determination unit 423 , and the movement control unit 424 .

[0241] The image analysis part 421 is configured to analyze an image of the fundus Ef of the subject's eye E and obtain the value of a predetermined brightness parameter.

[0242] The image provided to the image analysis unit 421 may be any image acquired by photographing the fundus Ef of the subject's eye E. In some examples, an image generated by the ophthalmic apparatus 1 is provided to the image analysis unit 421. In some examples, an image generated by an ophthalmic imaging device other than the ophthalmic apparatus 1 is provided to the image analysis unit 421.

[0243] In some examples, an image generated by imaging using a rolling shutter camera (i.e., an image generated by slit scanning) is provided to the image analysis unit 421. Here, imaging using a rolling shutter camera may be slit scanning in rolling shutter mode or slit scanning in global reset release shutter mode.

[0244] In some examples, an image generated by imaging using a global shutter camera is provided to the image analysis unit 421. This image may be, for example, an image generated by imaging using a general fundus camera optical system.

[0245] As illustrated above, there are various modes for the process of providing an image to the image analysis unit 421, and the following three modes are typical examples.

[0246] In the first aspect, the imaging unit 2 applies a slit scan in a global reset release shutter mode using infrared illumination light to the fundus Ef of the subject's eye E. An image (first infrared image) generated by this slit scan is provided to the image analysis unit 421. This aspect can be implemented using the optical system of FIG.

[0247] In this embodiment, a typical image provided to the image analysis unit 421 contains two flares as shown in FIG. 9B . In this embodiment, in order to obtain abundant and rapid information about the flares in such an image, shooting control may be performed so that an image depicting both flares is acquired by a single slit scan in the global reset release shutter mode. An example of this shooting control will be described with reference to FIG. 10 .

[0248] 10, the horizontal axis represents time [t], and the vertical axis represents the direction of movement (scanning direction) of the projection position of the slit light. In this example, the scanning direction is the Y direction, and the vertical axis represents the Y coordinate. The symbols FU and FL represent two flares mixed into the image.

[0249] In this example, slit scanning is performed from above downward. The symbol SP indicates the scan start position, and the symbol EP indicates the scan end position. When slit scanning is started from the upper scan start position SP toward the lower scan end position EP, a downward flare FL (a flare FL on the scan end position EP side) occurs first, followed by an upper flare FU (a flare FU on the scan start position SP side). Hereinafter, the former will be referred to as a lower flare FL, and the latter will be referred to as an upper flare FU.

[0250] In order to generate a single image depicting both the lower flare FL and the upper flare FU, the imaging control unit 410 of this example executes exposure control of the image sensor 51 so as to include periods during which both the flares FL and FU are occurring. In Fig. 10 , exposure is performed during the period from time t1 to time t2.

[0251] Photography control including such exposure control is performed, for example, as follows after XY alignment and Z alignment performed under the control of the processor 4. At the completion of XY alignment and Z alignment, the optical axis of the photography unit 2 (the optical axis of the objective lens 46) and the axis of the subject's eye E are substantially aligned, and the distance between the photography unit 2 (objective lens 46) and the subject's eye E is substantially aligned with a predetermined working distance. In addition, the operating mode (shutter mode) of the image sensor 51 is set to the global reset release shutter mode.

[0252] Upon receiving a predetermined imaging trigger (e.g., a signal indicating that XY alignment and Z alignment have been completed), the imaging control unit 410 starts moving the infrared illumination light (slit light) from the scan start position SP (time t0). The intensity of the infrared illumination light used is set to, for example, the minimum possible setting value.

[0253] The shooting control unit 410 starts exposure of the image sensor 51 when a predetermined delay time has elapsed from time t0 (time t1). This delay time is a preset time, and is determined, for example, by measuring the timing of flare occurrence in advance, or by theoretical calculation and / or simulation based on the moving speed of the slit light, the configuration of the optical system, etc.

[0254] When a predetermined exposure time has elapsed since the start of exposure (time t1), the shooting control unit 410 ends (time t2) the exposure of the image sensor 51. This exposure time is a preset time, and is determined, for example, in the same manner as the delay time described above.

[0255] When the projection position of the slit light reaches the scan end position EP, the imaging control unit 410 ends the slit scan in this example (time t3).

[0256] By performing such imaging control, a single image depicting both the upper flare FU and the lower flare FL can be generated by slit scanning in the global reset release shutter mode. In this example, the image generated in this manner is provided to the image analysis unit 421.

[0257] In the second embodiment, the photographing unit 2 includes a global shutter image sensor in addition to the rolling shutter image sensor 51. An image (second infrared image) generated using this global shutter camera is provided to the image analysis unit 421.

[0258] This aspect can be implemented, for example, by using an imaging device 50A shown in Fig. 11 instead of the imaging device 50 in Fig. 2. The imaging device 50A in Fig. 11 includes an image sensor 52 in addition to the image sensor 51 similar to that of the imaging device 50 in Fig. 2. The image sensor 51 is of a rolling shutter type, and the image sensor 52 is of a global shutter type.

[0259] The imaging device 50A further includes an optical path splitting element (beam splitter) 53. The optical path splitting element 53 splits the optical path of the light that has passed through the imaging lens 48 into an optical path that reaches the image sensor 51 and an optical path that reaches the image sensor 52. The optical path splitting element 53 may be any optical element that has an optical path splitting function, and may be, for example, any of a half mirror, a dichroic mirror, and a polarizing beam splitter.

[0260] The optical system applicable to this embodiment is not limited to the configuration shown in Fig. 11. Some example optical systems include an optical path splitting element that splits the optical path that has passed through focus lens 47 in Fig. 2 into a first optical path and a second optical path, a first imaging lens and a rolling shutter type image sensor disposed in the first optical path, and a second imaging lens and a global shutter type image sensor disposed in the second optical path.

[0261] In the third embodiment, an image of the fundus Ef of the subject's eye E generated by another ophthalmic imaging device is provided to the image analysis unit 421. The modality of this other ophthalmic imaging device may be any.

[0262] Although not shown in the drawings, this embodiment includes a data receiving unit that receives images generated by another ophthalmic imaging device. The data receiving unit includes, for example, either a communication device that receives images via a communication line or a data reader device that reads images from a recording medium.

[0263] Next, a description will be given of examples of the brightness parameter calculated by the image analysis unit 421. The brightness parameter may be any type of parameter related to flare occurring in a fundus image, for example, any type of parameter related to corneal reflection light of illumination light (corneal reflection parameter), or any brightness parameter that can be used to determine a control amount for adjusting the distance between the subject's eye E and the imaging unit 2.

[0264] In this embodiment, a case where the image analysis unit 421 determines the maximum brightness value will be described, but it will be understood by those skilled in the art that similar processing can be performed when determining the value of another type of brightness parameter, some examples of which have been described above.

[0265] The image analysis unit 421 identifies the maximum value among the values ​​(brightness values) of multiple pixels that make up the input image. This maximum brightness value may be a value identified from all pixels that make up the image, or a value identified from some of the pixels. In the former case, the image analysis unit 421 can identify the maximum brightness value by comparing the magnitude of the brightness values ​​of all pixels in the image.

[0266] An example of determining a maximum luminance value from some pixels of an input image will be described. The image analysis unit 421 of this example first identifies a partial region of the input image. This partial region is a high-luminance region. The high-luminance region is identified based on, for example, the pixel position (coordinates), the magnitude of the luminance value (e.g., comparison with a threshold), the region configuration (e.g., position, shape, dimensions), etc. Furthermore, the image analysis unit 421 of this example identifies the maximum value of the luminance values ​​of all pixels included in the identified high-luminance region. The luminance value identified in this way is used as the maximum luminance value of this image. According to this example, for example, two high-luminance regions corresponding to the upper flare FU and the lower flare FL in FIG. 10 are identified, and the maximum luminance values ​​in these high-luminance regions are identified.

[0267] The pupil diameter data acquisition unit 422 is configured to acquire pupil diameter data of the subject's eye E.

[0268] In some examples, an image (anterior eye image) generated by the imaging unit 2 by imaging the anterior eye portion Ea of the subject's eye E is provided to the pupil diameter data acquisition unit 422. The pupil diameter data acquisition unit 422 in this example is configured to execute, for example, a process of specifying a pupil region by applying predetermined image processing (e.g., threshold processing, edge detection, pattern matching, segmentation, etc.) to the anterior eye image, and a process of determining the dimensions of the specified pupil region (pupil diameter).

[0269] In some examples, another ophthalmic imaging device captures an image of the anterior segment Ea of the subject's eye E to generate an anterior segment image. The pupil diameter data acquisition unit 422 of the present example includes a data accepting unit (such as a communication device or a data reader device) that accepts the anterior segment image generated by the other ophthalmic imaging device. Furthermore, the pupil diameter data acquisition unit 422 of the present example is configured to execute, for example, a process of specifying a pupil region by applying predetermined image processing to the anterior segment image, and a process of determining the dimensions of the specified pupil region (pupil diameter).

[0270] The control amount determination unit 423 is configured to determine the control amount of the distance between the test eye E and the photographing unit 2 based on the brightness parameter value obtained by the image analysis unit 421 and the pupil diameter data acquired by the pupil diameter data acquisition unit 422.

[0271] The control amount determined by the control amount determination unit 423 may be the value (quantity) of any parameter that can be used to control the distance between the test eye E and the photographing unit 2, for example, the distance between the test eye E and the photographing unit 2 (objective lens 46), the amount of change from the current distance between the test eye E and the photographing unit 2 (objective lens 46), and the parameter value of the control signal provided to the moving mechanism 3.

[0272] In some examples, the control amount determination unit 423 may be configured to compare the brightness parameter value determined by the image analysis unit 421 with a threshold value (brightness threshold value) and determine the control amount based on the result of this comparison.

[0273] The luminance threshold value applied to the comparison with the luminance parameter value may be, for example, one preset value (default value), one or more values ​​selected from a plurality of preset luminance threshold values ​​(a plurality of default values), or one or more values ​​determined when photographing the subject's eye E. Any method for determining the luminance threshold value may be used, and some non-limiting examples will be described later.

[0274] In this example, before the photographing unit 2 acquires an image of the fundus Ef of the subject's eye E to be processed by the alignment processing unit 420, it is possible to perform position adjustment of the photographing unit 2 relative to the subject's eye E (for example, only XY alignment and Z alignment, or XY alignment, Z alignment and tracking). This makes it possible to provide the alignment processing unit 420 with a better fundus image than when fundus photography is performed without performing position adjustment. This position adjustment before fundus photography may be performed by the movement control unit 424 controlling the movement mechanism 3 according to a known method.

[0275] When an image of the fundus Ef of the subject's eye E acquired by fundus photography after position adjustment is input to the alignment processing unit 420, the image analysis unit 421 calculates a brightness parameter value from this image, and the control amount determination unit 423 compares this brightness parameter value with a brightness threshold. The control amount determination unit 423 of this example executes control amount determination processing when the brightness parameter value is equal to or greater than the brightness threshold, and does not execute control amount determination processing when the brightness parameter value is less than the brightness threshold.

[0276] In this way, in this example, when a strong flare occurs, the control amount is determined and the distance between the subject's eye E and the imaging unit 2 is adjusted, but when a strong flare does not occur (when no flare occurs or when only a weak flare occurs), these processes are not performed. Here, a strong flare and a weak flare are distinguished based on a brightness threshold value.

[0277] When tracking is performed in addition to XY alignment and Z alignment before fundus photography, even if eye movement or the like occurs between alignment and fundus photography, the positional deviation can be canceled by tracking, so that fundus photography can always be performed with a good relative position between the subject's eye E and the photography unit 2. Therefore, the processing according to this example (i.e., comparison of the brightness parameter value with the brightness threshold value, determination of the control amount based on the comparison result, and movement control of the photography unit 2 based on the control amount) can be performed effectively.

[0278] In contrast, if only XY alignment and Z alignment are performed before fundus photography, that is, if fundus photography is performed without performing tracking after XY alignment and Z alignment, there is a possibility that an image obtained from fundus photography performed when there is a positional misalignment between the subject's eye E and the photography unit 2 will be input to the alignment processing unit 420.

[0279] In such a case, the ophthalmologic apparatus 1 may be configured to perform, for example, any of the following operation examples (1) to (3): (1) perform the processing according to this example; (2) determine a control amount and control the movement of the imaging unit 2 based on this control amount regardless of the magnitude relationship between the brightness parameter value and the brightness threshold; (3) if the brightness parameter value is equal to or greater than the brightness threshold, determine a control amount and control the movement of the imaging unit 2 based on this control amount, and if the brightness parameter value is less than the brightness threshold, perform another alignment (auto-alignment and / or manual alignment).

[0280] Next, several examples of determining the brightness threshold will be described. The processor that executes the process of determining the brightness threshold may be provided in the ophthalmologic apparatus 1, or may be provided in another device (e.g., an ophthalmologic apparatus or an information processing device). An example configuration for the former case is shown in Fig. 12. An illustration of the latter case is omitted.

[0281] 12 is an element that can be applied to the ophthalmologic apparatus 1 in place of the processor 4 in FIG. 8 , and has the same configuration as the processor 4, except that it includes a luminance threshold determination unit 430. Note that when the luminance threshold determination processor is provided in a separate device, this luminance threshold determination processor may have the same function and configuration as the luminance threshold determination unit 430.

[0282] The brightness threshold determination unit 430 may be configured to, for example, perform a process of determining a maximum brightness value distribution of a fundus image data set acquired in advance, and a process of determining a brightness threshold based on this maximum brightness value distribution. This brightness threshold determination process can be performed in the manner described above, but an exemplary process performed by the inventors will be described below.

[0283] The inventors used three ophthalmologic imaging devices to photograph the left and right eyes of 10 subjects twice each. For each fundus photograph, global shutter photography was performed three times using infrared illumination light. This resulted in a fundus image data set consisting of 360 infrared fundus images.

[0284] The inventors identified the maximum luminance value of each infrared fundus image and created a histogram showing the relationship between the maximum luminance value and the number of images. This histogram is a statistical representation showing the distribution of the maximum luminance values ​​in this fundus image data set, and can also be considered as a statistical representation showing the relationship between the flare state (presence or absence of flare and its intensity) and the maximum luminance value.

[0285] The inventors determined the brightness threshold by applying a statistical operation to such a maximum brightness distribution. This statistical operation is a weighted F-value (Fβ score). The Fβ score is one of the evaluation indices for binary classification problems, and is defined as a weighted harmonic mean of precision and recall, which are in a trade-off relationship with each other. Specifically, the Fβ score is defined by the following formula: Fβ = [(1 + β ２ ) × precision × recall] / [β ２ × precision rate + recall rate].

[0286] Here, precision indicates the proportion of predicted positive results that were actually positive, and recall indicates the proportion of predicted positive results that were actually positive. β is a positive real number and is a coefficient that indicates how much more importance is attached to recall compared to precision. The minimum value of the Fβ score is 0, and the maximum value is 1.

[0287] The larger the value of coefficient β, the higher the sensitivity of flare detection (flare detection sensitivity, flare detection capability). That is, the larger the value of coefficient β, the smaller the luminance value determined to be a flare (i.e., the smaller the luminance threshold). On the other hand, there is a higher possibility that an image in which no flare actually occurs will be erroneously determined to contain a flare.

[0288] By using such a maximum luminance value distribution and statistical calculation, the inventors determined the following luminance threshold set, which includes three luminance thresholds with different flare detection sensitivities: the luminance threshold having high flare detection sensitivity (the luminance threshold for high-sensitivity detection) was set to a luminance value of 40, the luminance threshold having medium flare detection sensitivity (the luminance threshold for medium-sensitivity detection) was set to a luminance value of 66, and the luminance threshold having low flare detection sensitivity (the luminance threshold for low-sensitivity detection) was set to a luminance value of 88.

[0289] When a luminance threshold for high-sensitivity detection is used, it has the advantage of being able to detect low-luminance flares, but the disadvantage of increasing the possibility of erroneously determining that a non-flare region is a flare. When a luminance threshold for low-sensitivity detection is used, it has the advantage of reducing the possibility of such erroneous detection, but the disadvantage of being unable to detect low-luminance flares. The luminance threshold for medium-sensitivity detection has properties intermediate between the luminance threshold for high-sensitivity detection and the luminance threshold for low-sensitivity detection. The number of luminance thresholds to be determined is not limited to three, and may be any number equal to or greater than one.

[0290] When multiple brightness thresholds are prepared, the brightness threshold to be used can be selected taking into consideration the properties of each brightness threshold. Furthermore, two or more brightness thresholds may be used in alignment processing based on one fundus image. In this case, the control amount can be determined based on two or more flare detection results obtained using two or more brightness thresholds. For example, it is possible to determine the control amount by selecting one of two or more flare detection results, or to determine the control amount by integrating two or more flare detection results.

[0291] In some examples, the control amount determination unit 423 compares the brightness parameter value determined by the image analysis unit 421 with the brightness threshold determined in the above manner. If the brightness parameter value is equal to or greater than the brightness threshold, the process proceeds to the next step of the control amount determination process. If the brightness parameter value is less than the brightness threshold, the control amount determination process (and therefore the alignment process) ends. In other words, if it is determined that the fundus image contains flare, the process proceeds to the next step of the control amount determination process. If it is determined that the fundus image does not contain flare, the control amount determination process (and therefore the alignment process) ends.

[0292] As described above, the control amount determination process is performed based on the brightness parameter value and pupil diameter data. In some examples, when the brightness parameter value is equal to or greater than the brightness threshold, the control amount determiner 423 proceeds to a process of determining the control amount based on the pupil diameter data. Some examples of this process are described below.

[0293] The pupil diameter data includes measurement data of the pupil diameter of the subject's eye E. This measurement data may be, for example, a measurement value of the pupil diameter of the subject's eye E and / or an evaluation result of the measurement value of the pupil diameter of the subject's eye E. This evaluation result may be, for example, a result of comparing the measurement value with a brightness threshold, a numerical range to which the measurement value belongs, etc. In these cases, the control amount is determined based on the magnitude of the value of the pupil diameter data.

[0294] In some examples of the aspect of determining the control amount based on the magnitude of the pupil diameter data value, the control amount is determined with attention paid to the peripheral light amount during fundus photography. More specifically, the control amount is determined so that the reduction in peripheral light amount during fundus photography is not large, in other words, so that fundus photography is performed with an allowable peripheral light amount.

[0295] The control amount determination unit 423 in this example may be configured to determine a control amount based on the magnitude of the pupil diameter data value so that the reduction in the peripheral light amount of the illumination light projected onto the fundus Ef of the subject's eye E by the illumination optical system 20 is equal to or less than a threshold value (peripheral light amount threshold value). Here, the reduction in peripheral light amount may be, for example, any of the reduction rate, the reduction amount, the evaluation result of the reduction rate, and the evaluation result of the reduction amount.

[0296] The peripheral light intensity threshold used to determine the control amount may be, for example, one preset value (default value), one or more values ​​selected from a plurality of preset peripheral light intensity thresholds (a plurality of default values), or one or more values ​​determined when photographing the subject's eye E. Any method may be used to determine the peripheral light intensity threshold, and some non-limiting examples will be described later.

[0297] In some examples of aspects in which a control amount is determined based on the magnitude of the pupil diameter data value, prepared control amount information is used. The control amount information is information indicating a correspondence relationship between the pupil diameter value and the control amount. For example, the control amount information defines two or more ranges of pupil diameter values ​​(two or more sections of pupil diameter values), and a control amount value is assigned to each range.

[0298] The control amount determination unit 423 of this example acquires, from the control amount information, a control amount value corresponding to the pupil diameter data value (i.e., the measured value of the pupil diameter of the subject's eye E) acquired by the pupil diameter data acquisition unit 422. Then, the movement control unit 424 of this example adjusts the position of the imaging unit 2 by controlling the movement mechanism 3 based on the acquired control amount value.

[0299] Next, several examples of generation of control amount information will be described. The processor that executes the process of generating the control amount information may be provided in the ophthalmologic apparatus 1, or may be provided in another apparatus (e.g., an ophthalmologic apparatus or an information processing apparatus). An example of the configuration in the former case is shown in Fig. 13. An illustration of the latter case is omitted.

[0300] 13 is an element that can be applied to the ophthalmologic apparatus 1 in place of the processor 4 in FIG. 8 , and has the same configuration as the processor 4, except that it includes a control amount information generation unit 440. Note that when the control amount information generation processor is provided in another device, this control amount information generation processor may have the same function and configuration as the control amount information generation unit 440.

[0301] The control amount information generating unit 440 may be configured to generate control amount information based on the relationship between, for example, the following four factors: (1) the distance between the eye and the imaging unit 2; (2) the reduction in peripheral light intensity of the illumination light; (3) the probability that a high-brightness area will occur in the fundus image; and (4) the pupil diameter value of the eye.

[0302] Under the assumption that the alignment state in the X and Y directions is good (i.e., the axis of the eye and the optical axis of the imaging unit 2 are aligned), the "distance" of the first factor (1) may be defined as the distance in the Z direction. The "decrease" of the second factor (2) may be defined as the rate or amount of decrease. The "high-brightness area" of the third factor (3) may be defined as an image area that is estimated to be a flare.

[0303] An example of the relationship between these four factors is shown in Figure 14. In Figure 14, four graphs are shown: F, P(2.5), P(3.0), and P(3.5).

[0304] The horizontal axis of the coordinate system in which these graphs are defined indicates the offset from the predetermined working distance, i.e., the offset from the reference position corresponding to the working distance. The unit of the offset is millimeters. An offset of "0" indicates the reference position corresponding to the working distance of the ophthalmic apparatus 1 (the illumination optical system 20 and the photographing optical system 40 of the photographing unit 2). A negative offset indicates a position closer to the eye than the reference position, and a positive offset indicates a position farther from the eye than the reference position. Meanwhile, the vertical axis of this coordinate system indicates the probability of flare occurrence and the rate of reduction in peripheral light intensity.

[0305] Graph F shows the relationship between the offset from the working distance and the probability of flare occurrence. Graph P(2.5) shows the relationship between the offset from the working distance and the rate of reduction in peripheral light intensity when an eye with a pupil diameter value of 2.5 millimeters is being photographed. Graph P(3.0) shows the relationship between the offset from the working distance and the rate of reduction in peripheral light intensity when an eye with a pupil diameter value of 3.0 millimeters is being photographed. Graph P(3.5) shows the relationship between the offset from the working distance and the rate of reduction in peripheral light intensity when an eye with a pupil diameter value of 3.5 millimeters is being photographed.

[0306] The relationships shown by these four graphs F, P(2.5), P(3.0), and P(3.5) were discovered by the inventor. To obtain these graphs, the following two conditions were assumed: (1) no flare occurs when the offset from the working distance is +1.0 millimeter or more; and (2) the allowable range of the rate of reduction in peripheral illumination is from 0 percent to 40 percent. Graph L(40) in Fig. 14 indicates 40 percent, which is the maximum allowable rate of reduction in peripheral illumination.

[0307] By considering the four graphs F, P(2.5), P(3.0), and P(3.5) derived under these preconditions, the following three points become clear.

[0308] First, when the pupil diameter value is 2.5 mm or less, if the offset from the working distance is a positive value, the reduction rate of peripheral illumination exceeds 40%. In other words, when the pupil diameter value is 2.5 mm or less, if the imaging unit 2 is positioned farther from the eye than the reference position corresponding to the working distance, the brightness of the resulting image will be insufficient. Therefore, when the pupil diameter value of the subject's eye is 2.5 mm or less, fundus photography should not be performed with the imaging unit 2 positioned farther from the eye than the reference position corresponding to the working distance. In other words, fundus photography of an eye with a pupil diameter value of 2.5 mm or less should be performed with the imaging unit 2 positioned at the reference position corresponding to the working distance (or at a position closer to the eye than the reference position).

[0309] Second, if the pupil diameter value is greater than 2.5 millimeters and less than 3.5 millimeters, the offset from the working distance can be determined, for example, as follows.

[0310] If the pupil diameter value in this example is φ, then a graph P(φ) corresponding to this pupil diameter value φ can be obtained in a manner similar to that of graph P(2.5) in FIG. 14 . The offset amount in this example can be determined based on at least graph P(φ) and graph L(40). For example, the offset amount corresponding to the pupil diameter value φ can be set to an offset amount corresponding to any point on a line segment (which is part of graph P(φ)) having a first end defined as the intersection of graph P(φ) and graph L(40) and a second end defined as the intersection of graph P(φ) and a line indicating an offset amount of "zero."

[0311] As a specific example, when the pupil diameter value φ is 3.0 millimeters, the graph P(3.0) in Fig. 14 is considered. In this example, as shown in Fig. 15, the offset amount corresponding to an arbitrary point on a line segment Q (which is part of graph P(3.0)) having a first end at an intersection Q1 between graph P(3.0) and graph L(40) and a second end at an intersection Q2 between graph P(3.0) and line M(0) indicating an offset amount of "zero" is set as the offset amount corresponding to the pupil diameter value φ=3.0 millimeters in this example.

[0312] For example, the difference between a reference pupil diameter value φ0 = 2.5 mm and the pupil diameter value φ = 3.0 mm in this example (φ - φ0 = +0.5 mm) is set as the offset amount Δ(3.0) corresponding to the pupil diameter value φ = 3.0 mm in this example. Here, the offset amount Δ(3.0) = +0.5 mm corresponding to the pupil diameter value φ = 3.0 mm in this example corresponds to point Q0 on line segment Q. In other words, the offset amount Δ(3.0) = +0.5 mm corresponding to the pupil diameter value φ = 3.0 mm in this example corresponds to point Q0 of intersection between line segment Q and the line indicating the offset amount "+0.5".

[0313] In this way, when the pupil diameter value φ is greater than 2.5 millimeters and less than 3.5 millimeters (i.e., when 2.5<φ<3.5), by subtracting 2.5 (millimeters) from the pupil diameter value φ (millimeters) and setting the difference value (φ-2.5) as the offset amount Δ(φ) corresponding to the pupil diameter value φ, the offset amount Δ(φ) when the pupil diameter value φ belongs to the interval (2.5, 3.5) can be expressed as a continuous function.

[0314] The offset amount for the range of pupil diameter values ​​in this example may be defined as a continuous function, a discrete function, or another function, even when another range of pupil diameter values ​​is applied.

[0315] Third, when the pupil diameter value is 3.5 millimeters or greater, flare does not occur if the offset from the working distance is +1.0 millimeters or greater, as can be seen from the above precondition (1) and the relationship between graph P(3.5) and graph F. Therefore, the offset Δ(φ) corresponding to a pupil diameter value φ of 3.5 millimeters or greater is set to +1.0 millimeter. Note that, if the offset is greater than +1.0 millimeter, not only will there be no effect in reducing flare, but the reduction in peripheral light intensity will also be significant, and therefore it is considered advantageous to set the offset Δ(φ) to +1.0 millimeter.

[0316] Based on the first to third considerations described above, in this example, the offset amount Δ(φ) corresponding to the pupil diameter value φ is defined as follows: Δ(φ) = 0 (when φ≦2.5), Δ(φ) = φ − 2.5 (when 2.5 < φ < 3.5), Δ(φ) = 1 (when Δ≧3.5).

[0317] In this example, the two pupil diameter values ​​"2.5" and "3.5" are used as thresholds for evaluating the size of the pupil diameter of the subject's eye, that is, for determining the amount of offset from the working distance. Note that the pupil diameter values ​​used as thresholds are not limited to the values ​​in this example, and may be determined arbitrarily depending on the design concept for control of the ophthalmic apparatus, the conditions to be considered, and the like.

[0318] The control amount information generator 440 generates control amount information including a control amount indicating the offset amount Δ(φ) determined as described above. The control amount indicating the offset amount Δ(φ) may be, for example, the offset amount Δ(φ) itself (i.e., the value of the physical distance), or may be a parameter value of a control signal applied to the movement mechanism 3 (such as a voltage value, a current value, or the number of pulses calculated from the offset amount Δ(φ)). The generated control amount information is stored in the memory 5, for example.

[0319] The movement control unit 424 is configured to adjust the distance between the subject's eye E and the imaging unit 2 by controlling the movement mechanism 3 based on the control amount determined by the control amount determination unit 423. Some non-limiting examples of the processing executed by the movement control unit 424 will be described later.

[0320] A non-limiting example of the operation of the ophthalmologic apparatus 1 according to this embodiment will be described with reference to Fig. 16 and Fig. 17. Fig. 16 is a flowchart showing the entire operation example (steps S1 to S5), and Fig. 17 is a flowchart showing the details of step S3 in the flowchart of Fig. 16.

[0321] In this operation example, the ophthalmologic apparatus 1 first executes auto-alignment (S1) and auto-focus (S2). Steps S1 and S2 are at least a part of a preparatory operation for photographing the fundus Ef of the subject's eye E.

[0322] The auto-alignment in step S1 includes XY alignment and Z alignment of the imaging unit 2 with respect to the subject's eye E. The auto-alignment is performed under the control of the processor 4. Instead of or in addition to the auto-alignment, manual alignment may be performed. Completion of the auto-alignment may be used as a trigger to cause the ophthalmologic apparatus 1 to start tracking. The tracking is performed under the control of the processor 4.

[0323] The autofocus in step S2 is an operation for focusing the imaging unit 2 on the fundus Ef of the subject's eye E. The autofocus is performed under the control of the processor 4. The autofocus may be performed in parallel with tracking. Instead of or in addition to the autofocus, manual focusing may be performed.

[0324] Triggered by the completion of autofocus in step S2, the ophthalmologic apparatus 1 performs adjustment of the offset of the working distance of the photographing unit 2, that is, the distance between the subject's eye E and the photographing unit 2 (S3).

[0325] In this operation example, since alignment (particularly Z alignment) is performed in step S1, the distance between the subject's eye E and the imaging unit 2 at the start of step S3 can be considered to be substantially equal to the predetermined working distance. Generally, the time required for autofocusing in step S2 is sufficiently short, so step S3 can be considered to start while the alignment state achieved in step S1 is almost maintained. Furthermore, when tracking is performed, the ability to maintain the alignment state achieved in step S1 is improved.

[0326] In conventional ophthalmic devices, image capture is triggered by the completion of auto-alignment and auto-focus (auto-shoot function), so it is not possible to avoid situations where images containing flare or images with insufficient brightness are obtained (at least, it is difficult to avoid such situations). In contrast, this embodiment aims to obtain a flare-free, sufficiently bright image by performing a working distance offset step (S3) between auto-focus (S2) and auto-shoot (S4). Step S3 will be described in detail later.

[0327] Triggered by the completion of the offset of the working distance of the photographing unit 2 (S3), the ophthalmologic apparatus 1 applies a slit scan of the rolling shutter method (rolling shutter mode) to the fundus Ef of the subject's eye E (S4).

[0328] The fundus image generated in step S4 is stored in, for example, the memory 5 or another storage device (S5). This fundus image may also be displayed on the display device of the user interface 6, output by another device, transmitted to another device, and processed by the processor 4 or another processor. This completes the processing of this operation example (END).

[0329] Next, a non-limiting example of a series of steps for performing step S3 (offsetting the working distance) will be described with reference to Fig. 17. Triggered by the completion of autofocus (S2), the ophthalmologic apparatus 1 (imaging unit 2) applies global shutter infrared fundus photography to the fundus Ef of the subject's eye E (S11).

[0330] The infrared fundus photography in step S11 is performed under the control of the processor 4 (photography control unit 410). This infrared fundus photography is, for example, photography using a slit scan in a global reset release shutter mode or a global shutter image sensor. By performing step S11, an infrared fundus image of the fundus Ef of the subject's eye E is acquired (see, for example, FIG. 9B ).

[0331] Next, the ophthalmologic apparatus 1 (image analysis unit 421) analyzes the infrared fundus image acquired in step S11 and calculates the brightness parameter value (S12). This step is performed according to any of the examples described above.

[0332] Next, the ophthalmic apparatus 1 (control amount determination unit 423) compares the brightness parameter value calculated in step S12 with a threshold value (S13). This threshold value is determined in advance by, for example, the ophthalmic apparatus 1 (brightness threshold value determination unit 430 in FIG. 12 ) or another device, and is stored in the control amount determination unit 423 or the memory 5.

[0333] If the brightness parameter value calculated in step S12 is equal to or greater than the threshold value (S13: Yes), the operation of this example proceeds to step S14. On the other hand, if the brightness parameter value calculated in step S12 is less than the threshold value (S13: No), the operation of this example proceeds to step S15c.

[0334] If the luminance parameter value calculated in step S12 is equal to or greater than the threshold value (S13: Yes), the ophthalmologic apparatus 1 (control amount determination unit 423) evaluates the size of the pupil diameter value φ of the subject's eye E (S14).

[0335] The pupil diameter value φ of the subject's eye E is acquired at any stage before step S14. For example, during the period from immediately after the completion of step S2 to immediately before the start of step S14, the ophthalmic apparatus 1 can acquire an anterior segment image of the subject's eye E using the imaging unit 2, and determine the pupil diameter value φ from this anterior segment image using the pupil diameter data acquisition unit 422. Alternatively, before the start of step S14, the ophthalmic apparatus 1 can acquire the pupil diameter value φ of the subject's eye E from another device using the pupil diameter data acquisition unit 422.

[0336] The evaluation in step S14 uses control amount information generated in advance. The control amount information records the relationship between the pupil diameter value φ and the control amount, and more specifically, records two or more values ​​of the control amount assigned to two or more ranges of the pupil diameter value φ. The control amount information is generated in advance, for example, by the ophthalmic apparatus 1 (the control amount information generation unit 440 in FIG. 13 ) or another device, and is stored in the control amount determination unit 423 or the memory 5.

[0337] The control amount information in this operation example records the following information: (1) offset amount Δ(φ) = +1.0 (millimeters) for the first range of pupil diameter value φ (φ≧3.5); (2) offset amount Δ(φ) = φ-2.5 (millimeters) (0 < Δ(φ) < +1.0) for the second range of pupil diameter value φ (2.5<φ<3.5); (3) offset amount Δ(φ) = 0 (millimeters) for the third range of pupil diameter value φ (φ≦2.5).

[0338] In other words, the control amount information in this operation example records the following information: (1) if the pupil diameter value φ is 3.5 millimeters or more, the photographing unit 2 is moved back by 1.0 millimeter from the reference position corresponding to the working distance (i.e., the distance between the subject's eye E and the photographing unit 2 is set to "working distance + 1.0 (millimeters)"); (2) if the pupil diameter value φ is greater than 2.5 millimeters and less than 3.5 millimeters, the photographing unit 2 is moved back by "φ-2.5 (millimeters)" from the reference position corresponding to the working distance (i.e., the distance between the subject's eye E and the photographing unit 2 is set to "working distance + φ-2.5 (millimeters)"); (3) if the pupil diameter value φ is 2.5 millimeters or less, the photographing unit 2 is not moved from the reference position corresponding to the working distance (i.e., the distance between the subject's eye E and the photographing unit 2 is maintained at the working distance).

[0339] In step S14, if it is determined that the pupil diameter value φ belongs to the first range indicated in the control amount information (S14: φ≧3.5), the ophthalmic device 1 (control amount determination unit 423) sets the value of the offset amount Δ(φ) to “+1.0 (millimeters)” (S15a).

[0340] Furthermore, if it is determined that the pupil diameter value φ falls within the second range (S14: 2.5 < φ < 3.5), the ophthalmic device 1 (control amount determination unit 423) sets the value of the offset amount Δ(φ) to "φ-2.5 (millimeters)" (S15b).

[0341] Furthermore, if it is determined that the pupil diameter value φ falls within the third range (S14: φ≦2.5), the ophthalmologic apparatus 1 (control amount determination unit 423) sets the value of the offset amount Δ(φ) to "0 (millimeters)" (S15c). In this case, the process of step S3 is terminated (S3: End) without moving the photographing unit 2, and the process proceeds to step S4 (auto shoot).

[0342] After the offset amount Δ(φ) is set in step S15a or S15b, the ophthalmic apparatus 1 (movement control unit 424) controls the movement mechanism 3 to move the imaging unit 2 by this offset amount Δ(φ) (S16).

[0343] This completes the process of step S3 (offsetting the working distance of the imaging unit 2) (S3: End). Triggered by the completion of the process of step S3, the ophthalmologic apparatus 1 applies a rolling shutter slit scan to the fundus Ef of the subject's eye E to generate a fundus image (S4), and stores this fundus image (S5). This completes the process of this operation example (End).

[0344] A variation of the above-described operational example will now be described. In the above operational example, when the pupil diameter value φ exceeds 2.5, fundus photography is performed by placing the photography unit 2 at a distance farther than the default working distance. The brightness of the image acquired under these conditions may be lower than the brightness predicted based on, for example, FIGS. 14 and 15 (i.e., a darker image than predicted may be obtained). To address this issue, the following optional processing may be performed.

[0345] After the distance between the test eye E and the photographing unit 2 is increased in step S16 of Figure 17, the ophthalmic device 1 again applies global shutter infrared fundus photography to the fundus Ef of the test eye E to obtain a new image of the fundus Ef.

[0346] Next, the image analysis unit 421 analyzes this new image to determine a new brightness parameter value (second brightness parameter value).

[0347] Next, the control amount determination unit 423 compares the second brightness parameter value with the brightness parameter value calculated in step S12 (first brightness parameter value), and determines a new control amount based on the result of this comparison.

[0348] For example, when any of the following comparison results is obtained, the control amount determination unit 423 can set a negative offset amount: (1) when the second luminance parameter value is smaller than the first luminance parameter value; (2) when the decrease (decrease rate, decrease amount) of the second luminance parameter value relative to the first luminance parameter value is larger than a predetermined threshold; or (3) when the second luminance parameter value is smaller than a predetermined threshold. Here, the negative offset amount corresponds to control to reduce the distance between the subject's eye E and the imaging unit 2. The magnitude (absolute value) of the negative offset amount may be a default value or may be a value determined based on the result of the above comparison.

[0349] The movement control unit 424 controls the movement mechanism 3 based on the new control amount (negative offset amount) set by the control amount determination unit 423. This reduces the distance between the subject's eye E and the imaging unit 2, thereby increasing the brightness of the image.

[0350] As described above, there is a trade-off between image brightness and the occurrence of flare. This modified example is designed taking this trade-off into consideration. For example, any of the steps or parameters of this modified example can be designed to satisfy both the conditions related to image brightness and the conditions related to flare, and a series of steps of this modified example can be configured to be repeated.

[0351] It will be understood by those skilled in the art that the ophthalmic apparatus 1 according to the present embodiment provides embodiments in categories other than ophthalmic apparatuses. For example, the ophthalmic apparatus 1 according to the present embodiment can provide an embodiment of a method for determining a fundus photographing distance, an embodiment of a method for controlling an ophthalmic apparatus, an embodiment of a method for photographing an eye to be examined, an embodiment of a method for processing ophthalmic information, an embodiment of a program for causing a computer to execute any of the methods, an embodiment of a storage medium on which any of the programs is recorded, and the like.

[0352] This disclosure presents several embodiments and several aspects thereof. These embodiments and aspects are merely non-limiting examples of the present invention. Therefore, any modifications (omissions, substitutions, additions, etc.) within the scope of the spirit of the present invention can be made to the embodiments and aspects presented in this disclosure.

[0353] REFERENCE SIGNS LIST 1 Ophthalmic apparatus 2 Photography unit 3 Movement mechanism 4 Processor 5 Memory 6 User interface 410 Photography control unit 420 Alignment processing unit 421 Image analysis unit 422 Pupil diameter data acquisition unit 423 Control amount determination unit 424 Movement control unit 430 Brightness threshold determination unit 440 Control amount information generation unit

Claims

1. An ophthalmic device comprising: an imaging unit including an illumination optical system that projects illumination light from a light source onto the fundus of a test eye via an optical scanner, and an imaging optical system that detects return light of the illumination light with a first image sensor capable of operating in a rolling shutter mode; a movement mechanism that moves the imaging unit; an image analysis unit that analyzes an image of the fundus to determine a value of a predetermined brightness parameter; a pupil diameter data acquisition unit that acquires pupil diameter data of the test eye; a control amount determination unit that determines a control amount of a distance between the test eye and the imaging unit based on the value of the brightness parameter determined by the image analysis unit and the pupil diameter data acquired by the pupil diameter data acquisition unit; and a movement control unit that controls the movement mechanism based on the control amount determined by the control amount determination unit.

2. The ophthalmic device of claim 1, wherein the illumination optical system is capable of projecting infrared illumination light onto the fundus; the first image sensor is further capable of operating in a global reset release shutter mode; the photographing unit obtains a first infrared image of the fundus using the infrared illumination light and photographing in the global reset release shutter mode; and the image analysis unit analyzes the first infrared image to determine the value of the brightness parameter.

3. An ophthalmic device according to claim 2, wherein the optical scanner moves the projection position of the infrared illumination light, and the photographing unit performs the photographing at a timing when the first infrared image is acquired, in which both a first high-luminance area generated on the starting point side of the movement of the infrared illumination light and a second high-luminance area generated on the end point side of the movement are depicted.

4. An ophthalmic device as claimed in claim 1, wherein the illumination optical system is capable of projecting infrared illumination light onto the fundus, the photographing optical system further includes a second image sensor of a global shutter type, the photographing unit obtains a second infrared image of the fundus using the infrared illumination light and the second image sensor, and the image analysis unit analyzes the second infrared image to determine the value of the brightness parameter.

5. The ophthalmologic apparatus according to claim 1, wherein the brightness parameters include at least one of a maximum brightness in the image of the fundus and a parameter indicating an aspect of a high brightness area in the image of the fundus.

6. The ophthalmologic apparatus according to claim 1, wherein the control amount determination section determines the control amount based on a result of comparison between the value of the luminance parameter obtained by the image analysis section and a first predetermined threshold value.

7. An ophthalmic device as claimed in claim 6, wherein the movement control unit controls the movement mechanism to adjust the relative position of the imaging unit with respect to the subject's eye at least prior to acquisition of the image of the fundus, and the control amount determination unit determines the control amount only when the value of the brightness parameter is equal to or greater than the first threshold value.

8. An ophthalmic device according to claim 6, further comprising a brightness threshold determination unit which determines a maximum brightness value distribution of a fundus image data set acquired in advance and determines the first threshold based on the maximum brightness value distribution, and the control amount determination unit determines the control amount based on a result of comparing the value of the brightness parameter with the first threshold determined by the brightness threshold determination unit.

9. The ophthalmologic apparatus according to claim 8, wherein the luminance threshold value determination unit calculates a weighted F-number of the maximum luminance value distribution, and determines the first threshold value based on the weighted F-number.

10. The ophthalmic device of claim 8, wherein the luminance threshold determination unit determines at least two first thresholds based on the maximum luminance value distribution, and the control amount determination unit selects one first threshold from the at least two first thresholds and determines the control amount based on a result of comparing the value of the luminance parameter with the one first threshold.

11. The ophthalmic apparatus according to claim 1, wherein the control amount determination unit determines the control amount based on the magnitude of the value of the pupil diameter data.

12. The ophthalmic device of claim 11, wherein the control amount determination unit determines the control amount based on the magnitude of the value of the pupil diameter data so that a reduction in the peripheral light amount of the illumination light projected onto the fundus by the illumination optical system is equal to or less than a predetermined second threshold.

13. The ophthalmic device of claim 11, wherein the control amount determination unit obtains a control amount value corresponding to the magnitude of the value of the pupil diameter data from pre-defined control amount information in which a control amount value is assigned to each of two or more ranges of pupil diameter values, and the movement control unit controls the movement mechanism based on the control amount value obtained from the control amount information.

14. The ophthalmologic device of claim 13, further comprising a control amount information generating unit that generates the control amount information based on the relationship between the distance between the eye and the imaging unit, the reduction in peripheral light intensity of the illumination light, the probability of a high-luminance area occurring in a fundus image, and a pupil diameter value.

15. The ophthalmic device of claim 14, wherein the control amount information generation unit determines a control amount value to be assigned to each of the two or more ranges of pupil diameter values ​​such that the reduction in the peripheral light amount of the illumination light is equal to or less than a second predetermined threshold value.

16. The ophthalmic device of claim 1, wherein the control amount determination unit determines whether or not to execute the determination of the control amount based on the value of the luminance parameter, and determines the control amount based on the pupil diameter data when it is determined that the determination of the control amount is to be executed.

17. An ophthalmic device as claimed in claim 1, wherein the image analysis unit analyzes a new image of the fundus acquired after the distance between the test eye and the photographing unit is increased by the movement control unit to determine a new value of the brightness parameter, the control amount determination unit determines a new control amount based on a result of comparing the value of the brightness parameter with the new value, and the movement control unit controls the movement mechanism based on the new control amount.

18. A method for determining a distance between a test eye and an imaging unit for fundus photography using an ophthalmic device including an imaging unit configured to project illumination light from a light source onto the fundus of the test eye via an optical scanner and detect the return light of the illumination light with an image sensor capable of operating in rolling shutter mode, comprising the steps of: acquiring an image of the fundus; analyzing the image of the fundus to determine a value of a predetermined brightness parameter; acquiring pupil diameter data of the test eye; and determining the distance based on the value of the brightness parameter and the pupil diameter data.

19. A non-transitory computer-readable recording medium having a program recorded thereon that causes a computer to execute the method of claim 18.

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