Fundus imaging device

Abstract

To more reliably guide the subject's gaze toward the fixation target during the adjustment of the OCT optical system. [Solution] The fundus imaging apparatus comprises a fixation optical system, an OCT optical system, an imaging optical system, and a control means. The control means acquires a focus evaluation value based on the slit image formed on the two-dimensional image sensor of the imaging optical system by the slit-shaped illumination light when the optical scanner is deflected in a predetermined direction, and performs diopter correction control of the OCT optical system by driving the first focus adjustment unit of the OCT optical system based on the focus evaluation value.

Description

Technical Field

[0001] The present disclosure relates to a fundus imaging device.

Background Art

[0002] Fundus imaging devices such as fundus cameras and OCT devices are widely used in the field of ophthalmology.

[0003] For example, the fundus imaging device described in Patent Document 1 includes an OCT optical system for obtaining a tomographic image of the fundus of an eye to be examined, and a front imaging optical system for imaging a front image of the fundus. The front imaging optical system in the fundus imaging device described in Patent Document 1 is a slit-scan type optical system.

[0004] In the fundus imaging device described in Patent Document 1, an optical system for projecting a focus adjustment index (hereinafter referred to as "focus index") onto the fundus is arranged in the front imaging optical system separately from the illumination light.The focus index described in Patent Document 1 is also called a split index. The focus index is an index composed of, for example, two light beams separated by a deflection prism or the like, and is reflected in the observation image obtained through the front imaging optical system. By changing the focus position of the front imaging optical system so that the two index images in the observation image coincide, the focus of the front imaging optical system is appropriately adjusted. In this case, by changing the focus position of the OCT optical system in联动 with the front imaging optical system, the focus index is also used for the focus adjustment of the OCT optical system.

[0005] Further, for example, the fundus imaging device described in Patent Document 2 includes a configuration in which a plurality of fixation lights (fixation marks) having different positions with respect to the optical axis are selectively lit in order to change the imaging range in the fundus.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] While the optical system is being adjusted, such as focusing, a fixation target is presented to the eye under examination. If the focus indicator is within the wavelength range visible to the subject, both the fixation target and the focus indicator are formed as points, which can be confusing. This could lead to the subject's gaze being guided to the focus indicator instead of the fixation target. As a result, the optical system adjustment or imaging could fail or be prolonged.

[0008] In response to this, the inventors considered forming the focus indicator with light in the invisible wavelength range, but found that it was sometimes difficult to separate the wavelength band of the focus indicator from the wavelength band of the measurement light in the OCT optical system. In this case, there was a possibility that noise based on the focus indicator would be generated when adjusting the OCT optical system.

[0009] This disclosure is based on at least one of the problems of the prior art, and aims to provide a fundus imaging device that can more reliably guide the subject's gaze toward a fixation target when adjusting the OCT optical system. [Means for solving the problem]

[0010] A fundus imaging apparatus according to a first aspect of the present disclosure is a fundus imaging apparatus comprising a fixation optical system, an OCT optical system, an imaging optical system, and a control means, wherein the fixation optical system presents a fixation target to the fundus of the eye under examination; the OCT optical system comprises an OCT light source, a branching optical element that branches light from the OCT light source into measurement light and reference light, a detector that detects a spectral interference signal between the measurement light and the reference light reflected from the fundus of the eye under examination, and a first focus adjustment unit that adjusts the focus position of the measurement light with respect to the fundus of the eye under examination; and the imaging optical system has a light source capable of emitting infrared light as illumination light, and forms two light projection regions on the pupil of the eye under examination through which the illumination light passes in a first direction, and is formed to be elongated along a second direction intersecting the first direction. The OCT optical system comprises an illumination optical system that projects a slit-shaped illumination light onto the fundus of the eye under examination, an optical scanner that deflects the illumination light in the first direction on the fundus, and a light-receiving optical system that forms a light-receiving area on the pupil of the eye under examination, sandwiched between the two light-emitting areas, where the fundus reflected light of the illumination light is extracted, and includes a two-dimensional image sensor that receives the fundus reflected light of the illumination light. The control means acquires a focus evaluation value based on the slit image formed by the slit-shaped illumination light on the two-dimensional image sensor of the imaging optical system when the optical scanner is deflected in a predetermined direction, and performs diopter correction control of the OCT optical system by driving the first focus adjustment unit of the OCT optical system based on the focus evaluation value.

[0011] According to this disclosure, the subject's gaze can be more reliably guided toward the fixation target when adjusting the OCT optical system. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a schematic configuration of the fundus imaging device used in the embodiment. [Figure 2] This figure shows an overview of the optical system of the apparatus in the embodiment. [Figure 3] This is a diagram illustrating the shape of the light source in the imaging optical system. [Figure 4] This is a diagram illustrating pupil division in the imaging optical system. [Figure 5] It is a diagram for explaining slit light irradiated from an imaging optical system to the fundus of an eye to be examined. [Figure 6] It is a diagram for explaining the arrangement of a fixation lamp in a first fixation optical system. [Figure 7] It is a diagram for explaining the arrangement of a fixation lamp in a second fixation optical system. [Figure 8A] It is a diagram for explaining fixation guidance and alignment when imaging the peripheral part of the fundus. When the eye to be examined is at a position farther from the proper operating distance, it is shown that fixation is induced by a fixation target presented by the second fixation optical system. [Figure 8B] It is a diagram for explaining fixation guidance and alignment when imaging the peripheral part of the fundus. When the proper operating distance is reached, it is shown that fixation is induced by a fixation target presented by the first fixation optical system. [Figure 9] It is a flowchart showing the operation flow of the device in an embodiment. [Figure 10A] It is a diagram showing slit light irradiated to the eye to be examined from two light projection regions when the slit part is arranged at the movement limit position on the minus diopter side. [Figure 10B] It is a diagram showing slit light irradiated to the eye to be examined from two light projection regions when appropriate diopter correction is performed on the eye to be examined. [Figure 10C] It is a diagram showing slit light irradiated to the eye to be examined from two light projection regions when the slit part is arranged at the movement limit position on the plus diopter side. [Figure 11] It is a slit image formed on an imaging element, showing a slit image corresponding to FIG. 10A. [Figure 12] It is a slit image formed on an imaging element, showing a slit image corresponding to FIG. 10B.

Mode for Carrying Out the Invention

[0013] [Summary] The fundus imaging device according to the present disclosure includes a fixation optical system, an OCT optical system, an imaging optical system, and a control unit.

[0014] The fixation optical system presents a fixation target on the fundus of the subject eye. The line-of-sight direction of the subject eye is induced by the fixation target. The fixation target is projected as a fixation light beam using visible light. The fixation target may be projected at a position eccentric with respect to the optical axes of the OCT optical system and the imaging optical system. The OCT optical system includes an OCT light source, a branching optical element that branches the light from the OCT light source into measurement light and reference light, a detector that detects a spectral interference signal between the measurement light reflected from the fundus of the subject eye and the reference light, and a first focus adjustment unit that adjusts the focus position of the measurement light with respect to the fundus of the subject eye. The imaging optical system includes an irradiation optical system, an optical scanner, and a light receiving optical system. The irradiation optical system has a light source capable of emitting infrared light as illumination light. The irradiation optical system forms two light projection regions through which the illumination light passes on the pupil of the subject eye side by side in a first direction, and irradiates the fundus of the subject eye with slit-shaped illumination light elongated along a second direction intersecting the first direction. The optical scanner deflects the illumination light in the first direction on the fundus. The light receiving optical system forms a light receiving region from which the fundus reflected light of the illumination light is extracted on the pupil of the subject eye so as to be sandwiched between the two light projection regions, and includes a two-dimensional imaging element that receives the fundus reflected light of the illumination light.

[0015] The control unit obtains a focus evaluation value based on a slit image formed by the slit-shaped illumination light on the two-dimensional imaging element of the imaging optical system when the optical scanner is deflected in a predetermined direction. The control unit executes diopter correction control of the OCT optical system by driving the first focus adjustment unit of the OCT optical system based on the focus evaluation value.

[0016] The focus evaluation value is obtained based on information correlated with the focus state in the slit image. For example, the focus evaluation value may be obtained based on the position information of the slit image. However, it is not necessarily limited to this. Edge contrast, brightness information, etc., of the slit image can be used. Furthermore, when using edge contrast, brightness information, etc., adjustments may be made so that the number of pixels exceeding a threshold is minimized.

[0017] The fundus imaging device disclosed herein does not project a point-shaped focus indicator, allowing for appropriate guidance of the subject's gaze direction relative to the fixation target, and enabling the acquisition of OCT images. Furthermore, even when acquiring OCT images during focus adjustment, noise is less likely to occur in the OCT images.

[0018] Furthermore, the imaging optical system can be used as an optical system for observing the fundus. In this case, the control means may further acquire an observational image of the fundus of the eye under examination based on the light signal received from the two-dimensional image sensor when the optical scanner is scanned.

[0019] In this disclosure, the imaging optical system may be capable of selectively irradiating with visible light for imaging and infrared light for observation as illumination light. Visible light is used for capturing color fundus images. Infrared light is used for capturing (acquiring) fundus observation images. In focus adjustment, the control means may acquire a slit image by irradiating with infrared light as a slit-shaped illumination light. In this case, the visible light may be broadband light from λ=400nm to 750nm. The infrared light may have a central wavelength between λ=750nm and 800nm ​​(more preferably λ=770nm to 790nm).

[0020] In this disclosure, the OCT optical system may be an SD-OCT optical system. In this case, the OCT light source may emit low-coherence light with a central wavelength in the range of 820 nm to 880 nm. The detector may be a spectrometer. Generally, with an SS-OCT optical system that uses measurement light with a central wavelength of around 1050 nm, the wavelength band between the measurement light and the visible region is wide, making it easy to project the split indicator in the invisible wavelength band. However, in an SD-OCT optical system that emits measurement light with a central wavelength of 820 nm to 880 nm, wavelength separation is difficult when attempting to project the split indicator in the invisible wavelength band. Therefore, focusing based on the positional information of the slit image from a slit-shaped illumination light is particularly useful.

[0021] In this disclosure, it is not necessarily required to continuously maintain the direction of the slit light when acquiring focus evaluation values. In this case, for example, the direction of the optical scanner may be fixed to capture a slit image when acquiring focus evaluation values ​​during focus adjustment, and the slit light may be scanned to acquire observation images at other times. Since the slit light is not continuously irradiated for a long period of time while its direction is kept constant, fixation is less likely to be mistakenly guided to the slit-shaped illumination light. Also, while the line of sight is easily guided because the fixation target is point-shaped, the line of sight is less likely to be guided because the slit light is linear and the illuminated area is relatively wide.

[0022] Furthermore, the fixation optical system may share a portion of its optical system with the OCT optical system and the imaging optical system, and may be capable of presenting a peripheral fixation target for positioning the optic disc of the eye under examination in the center of the imaging range. In addition, the fundus imaging device may have an external fixation target corresponding to the peripheral fixation target around the objective lens in the OCT optical system and the imaging optical system. The external fixation target may guide the direction of the subject's gaze toward the direction corresponding to the peripheral fixation target from a stage when the eye under examination is located beyond the appropriate working distance, in order to guide the subject's gaze direction so that the optics of the eye under examination are positioned in the center of the imaging range. It is desirable that the optical system be smoothly guided toward the peripheral fixation target when the optical system is brought closer to the eye under examination at the working distance while the subject is fixated on the external fixation target. Even if the slit light is in a visible wavelength range, it becomes easier to appropriately guide the gaze of the eye under examination toward the fixation target without being affected by the slit light.

[0023] [Examples] Next, with reference to the drawings, the fundus imaging device 1 according to the embodiment will be described. The fundus imaging device 1 is a composite device comprising an OCT device and a slit-scan type fundus imaging device.

[0024] The fundus imaging device 1 captures an OCT image of the eye E under examination. Furthermore, it captures at least a color fundus image as a two-dimensional reflection image of the fundus Er.

[0025] Figure 1 is an external view of the fundus imaging device 1. In this embodiment, the fundus imaging device 1 includes an imaging unit 3, a base 5, a drive unit 6, a face support unit 7, a control unit 100, and a touch panel display 8 (hereinafter referred to as "touch panel 8"). For convenience, in the following description, the unit on which the imaging unit 3 is installed will be referred to as the main device body. In this embodiment, the base 5, drive unit 6, face support unit 7, control unit 100, and touch panel 8 are part of the main device body. However, the control unit 100 and touch panel 8 may be separate units from the main device body. The base 5, drive unit 6, and face support unit 7 can be omitted from the main device body as appropriate.

[0026] In this embodiment, the driving unit 6 moves the imaging unit 3 in the XYZ directions with respect to the eye E to be examined on the driving unit 6. The driving unit 6 has an actuator for moving the imaging unit 3 in each movable direction and is driven based on a control signal from the control unit 100. The face support unit 7 supports the face of the subject. The face support unit 7 is fixed to the base 5. The face support unit 7 has a jaw base 7a. The jaw base 7a is movable in the vertical direction, thereby adjusting the height of the eye E to be examined according to the eye level of the device.

[0027] Next, FIG. 2 shows the optical system of the fundus imaging device 1. The fundus imaging device 1 at least includes a front imaging optical system 10, an OCT optical system 30, an anterior eye observation optical system 60, a first fixation mark projection optical system 70, and a second fixation mark projection optical system 80. As shown in FIG. 2, the front imaging optical system 10, the OCT optical system 30, and the first fixation mark projection optical system 70 share an objective optical system and are coaxial by a beam splitter / combiner (for example, a half mirror and a dichroic mirror, etc.).

[0028] <OCT optical system> The OCT optical system 3 is a SD-OCT (Spectral Domain OCT) optical system. The OCT optical system 30 is used to capture OCT data of the fundus Er. The OCT optical system 30 includes an OCT light source 31, a coupler (optical splitter) 32, a measurement optical system 40, a reference optical system 50, and a detector 33.

[0029] In SD-OCT, a broadband light source is used for the OCT light source 31. As an example, the OCT light source 31 of this embodiment emits light having a central wavelength of λ = 880 nm and a bandwidth of ±40 nm with respect to the central wavelength. However, it is not necessarily limited to this. For example, in a typical SD-OCT, light having a central wavelength between λ = 800 nm and 900 nm is emitted from the OCT light source. Also, the bandwidth can be, for example, about ±30 to 60 nm with respect to the central wavelength. For example, within such a range, the wavelength band of the light emitted from the OCT light source 31 may be changed.

[0030] Light from the OCT light source 31 is split into measurement light (sample light) and reference light by the coupler 32. The measurement light is guided to the fundus Er via the measurement optical system 40. The reference light is guided to the reference optical system 50.

[0031] In this embodiment, the measuring optical system 40 includes a collimator lens 41, a focusing lens 42, a scanning unit 43, a lens 44, and an objective lens 18.

[0032] The measurement light is guided to the scanning unit 43 via the collimator lens 41 and the focus lens 42. The scanning unit 43 scans the measurement light two-dimensionally over the fundus Er. The scanning unit 43 is positioned approximately conjugate to the pupil of the eye being examined E. As a result, the measurement light is rotated around the pupil of the eye being examined E. In this embodiment, for example, two galvanometer mirrors are used for the scanning unit 33. The measurement light that has passed through the scanning unit 43 is irradiated onto the fundus Er via the objective lens 18. The measurement light from the fundus Er is then guided to the detector 33 after retracing its path through the measurement optical system 40.

[0033] In this embodiment, the reference optical system 50 is a reflective optical system mainly comprising a reference mirror (not shown). The reference light makes one round trip between the coupler 32 and the reference mirror. The reference light that has made one round trip and entered the coupler 32 is guided to the detector 33. The reference mirror is movable in the optical axis direction. The optical path length of the reference optical system 50 is changed according to the position of the reference mirror (not shown). As a result, the difference in optical path length between the measurement light and the reference light is adjusted.

[0034] In this embodiment, the reference optical system 50 is shown to be formed by a reflective optical system, but the reference optical system 50 may also be formed by a transmissive optical system (for example, an optical fiber).

[0035] In this embodiment, the polarization state of the reference light is adjusted by a polarizer (not shown) placed between the coupler 32 and the reference optical system 50. The polarizer may also be placed in a position that adjusts the polarization state of the measurement light.

[0036] Detector 33 receives interference light from the reflected light of the measurement light from the fundus Er and the reference light. In SD-OCT, a spectrometer is used as the detector 33. Based on the spectral interference signal from detector 33, OCT data of the fundus Er is generated.

[0037] <Frontal imaging optical system> The frontal imaging optical system 10 acquires a two-dimensional reflected image of the fundus based on the reflected light from the fundus. The frontal imaging optical system 10 is a slit-scan type optical system. The frontal imaging optical system 10 scans a slit-shaped illumination light over the fundus of the eye being examined and acquires a frontal image of the fundus based on the reflected light from the fundus.

[0038] The front imaging optical system 10 includes an illumination optical system 10a and a light-receiving optical system 10b. The illumination optical system 10a includes a light source unit 11, a slit-shaped member 12, a lens 13, an optical scanner 14, a lens 15, a perforated mirror 16, a half mirror 17, an objective lens 18, etc. The light-receiving optical system 10b includes an objective lens 18, a half mirror 17, a perforated mirror 16, lenses 19 and 20, an image sensor 21, etc.

[0039] The light source unit 11 has multiple types of light sources with different wavelength bands. For example, the light source unit 11 has visible light sources 11a and 11b and infrared light sources 11c and 11d. In this embodiment, the visible light emitted from the visible light sources 11a and 11b is used to capture color fundus images. The visible light may be, for example, white light. In this embodiment, the visible light sources 11a and 11b emit light in the band from λ=400nm to 750nm. However, the visible light sources 11a and 11b may emit multiple monochromatic visible lights. For example, they may emit monochromatic lights of three colors: R (red), G (green), and B (blue). In this case, IR (infrared) light may be emitted to the fundus in addition to, or as a substitute for, the R light. This is not necessarily the case, and two colors of visible light may be combined, or five or more colors may be combined.

[0040] The infrared light emitted from the infrared light sources 11c and 11d is used at least for acquiring (capturing) fundus observation images. In this embodiment, the infrared light sources 11c and 11d emit light that extends in the band from λ=750nm to 800nm. However, it is not necessarily limited to this, and the wavelength band of the light from the infrared light sources 11c and 11d may be appropriately changed within a range that is longer wavelength than the visible light emitted from the visible light sources 11a and 11b, and shorter wavelength than the visible light emitted from the visible light sources 11a and 11b. For example, the infrared light sources 11c and 11d may emit light with a central wavelength (more preferably, λ=770nm to 790nm) between λ=750nm and 800nm.

[0041] As described above, the light source unit 11 of this embodiment is provided with two light sources for each wavelength. The two light sources of the same wavelength are arranged on the pupil conjugate plane, away from the optical axis L. The two light sources are arranged side by side along the X direction, which is the scanning direction in Figure 3, and are arranged axially symmetric with respect to the optical axis L. As shown in Figure 3, the outer shape of the two light sources may be a rectangular shape in which the direction intersecting the scanning direction is longer than the scanning direction.

[0042] Light from the two light sources passes through the lens and is irradiated onto the slit-shaped member 12. In this embodiment, the slit-shaped member 12 has a slit that is elongated along the Y direction. This causes the illumination light to be formed in a slit shape on the fundus of the eye.

[0043] The optical scanner 14 scans the illumination light over the fundus of the eye. In this embodiment, the illumination light is scanned in the X direction. For example, the optical scanner 14 in this embodiment is a galvanometer scanner. However, it is not necessarily limited to this.

[0044] In the illumination optical system 10a, the images from the two light sources are relayed by the optical system from lens 13 to objective lens 18 and formed on the pupil of the eye being examined. In other words, two pupil images are formed in the pupil of the eye being examined, with light incident toward the fundus at positions separated with respect to the scanning direction.

[0045] Furthermore, the illumination light is relayed by the optical system from lens 17a to objective lens 18 and imaged onto the fundus Er. This creates a slit-shaped illumination light on the fundus Er. The illumination light is reflected from the fundus Er and extracted through the pupil Ep.

[0046] The perforated mirror 16 is an optical path coupling unit that connects the optical paths of the illumination optical system 10a and the light-receiving optical system 10b. The perforated mirror 16 reflects the illumination light from the light source unit 11 toward the eye E under examination, and allows a portion of the fundus reflected light from the eye E under examination, after passing through the aperture, to pass toward the image sensor 21. Various beam splitters other than the perforated mirror 16 can be used as the optical path coupling unit.

[0047] Since the aperture of the perforated mirror 16 is conjugate to the pupil of the eye being examined, the fundus reflected light used for imaging is limited to a portion that passes through the image of the perforated mirror aperture (pupil image) on the pupil of the eye being examined. For this reason, the image of the aperture on the pupil of the eye being examined becomes the light-receiving region R in this embodiment. As shown in Figure 4, the light-receiving region R is formed sandwiched between two light-emitting regions P1 and P2 (images of two light sources). Furthermore, as a result of appropriately setting the imaging magnification of each image, the diameter of the aperture, and the spacing between the two light sources, the light-receiving region R and the two light-emitting regions P1 and P2 are formed so that they do not overlap on the pupil.

[0048] The retinal reflected light that has passed through the apertures of the objective lens 18 and the perforated mirror 16 forms a slit-shaped image Sr at the conjugate position of the retina via lenses 25a and 25b (see Figure 5).

[0049] The image sensor 21 is positioned at a conjugate location in the fundus. The image sensor 21 is sensitive to both infrared and visible light. In this embodiment, a CMOS sensor with a two-dimensional light-receiving surface is used as the image sensor 21. An image Sr of a slit-shaped region of the fundus Er is projected onto the image sensor 21. In this embodiment, as the slit-shaped illumination light scans over the fundus Er, images of the scanning positions on the fundus Er (slit-shaped images Sr) are projected sequentially. In this way, the entire image of the scanning range is projected onto the image sensor 21 in a time-division manner. As a result, a frontal image (two-dimensional reflection image) of the fundus is acquired as the entire image of the scanning range.

[0050] In this embodiment, harmful light is removed by using the rolling shutter function of the CMOS sensor to displace the area exposed on the imaging surface in synchronization with the scanning unit in the illumination optical system 10a. Instead of the rolling shutter function, a liquid crystal shutter or the like can be used as the scanning unit that electronically scans the slit. In this case, an image sensor in which exposure and readout are performed by a global shutter can be used. It is desirable that the width of the area exposed on the imaging surface is wider than the width corresponding to the slit light projected onto the fundus of the eye.

[0051] The front imaging optical system 10 has a diopter correction unit. In this embodiment, focus adjustment is performed in both the illumination optical system 10a and the light-receiving optical system 10b. The focus adjustment unit in the illumination optical system 10a includes a slit member 12 and a drive unit 12a. The drive unit 12a changes the position of the slit member 12 along the optical axis L1. By adjusting the position of the slit member 12 so that the aperture of the slit member 12 becomes conjugate to the fundus, proper focus adjustment is performed. The focus adjustment unit in the light-receiving optical system 10b includes a lens 19 and a drive unit 19a. The drive unit 19a changes the position of the lens 19 along the optical axis L2. By adjusting the position of the lens 19 so that the image sensor 21 becomes conjugate to the fundus, proper focus adjustment is performed. The slit member 12 and the lens 19 are driven in conjunction. In the following explanation, when describing the positions of the slit member 12 and the lens 19, the position corresponding to the nearsighted eye will be referred to as the negative diopter position, and the position corresponding to the farsighted eye will be referred to as the positive diopter position, with the position corresponding to the 0D eye of each member as the reference point.

[0052] <Anterior segment observation optical system> The anterior segment observation optical system 60 images the anterior segment of the eye E under examination and acquires it as an anterior segment observation image. In this embodiment, the anterior segment observation optical system 60 illuminates the anterior segment with infrared light from an infrared light source (not shown) as observation light. The reflected light from the anterior segment is also received by the image sensor 61. Based on the signal from the image sensor 61, a frontal image of the anterior segment is acquired as an anterior segment observation image. The anterior segment observation image is used for alignment and tracking control of the imaging unit 3 relative to the eye E under examination during fundus photography.

[0053] <First fixation optical system> The first fixation optical system 70 is provided to project a fixation target onto the fundus of the eye being examined. The subject's line of sight is guided toward the fixation target. In this embodiment, the first fixation optical system 70 can change the presentation position of the fixation target.

[0054] The first fixation optical system 70 includes, for example, a fixation target unit 71 and a relay lens 72. The first fixation optical system 70 also shares the optical path from the dichroic mirror 73 to the objective lens 18 with the front imaging optical system 10. The optical axis L3 passing through the center of the fixation target unit 71 is made coaxial with the optical axis L2 by the dichroic mirror 73.

[0055] Figure 6 shows the fixation target unit 71 as viewed from the front. The fixation target unit 71 is equipped with a plurality of fixation light sources 71a to 71k that emit visible light. For example, LEDs may be used as the fixation light sources 71a to 71k. The presentation positions of the fixation targets are predetermined, and the fixation light sources 71a to 71k are positioned at positions corresponding to each presentation position. In this embodiment, the presentation position of the fixation target is changed by selectively lighting one of the fixation light sources 71a to 71k. However, the configuration of the fixation target unit 71 is not necessarily limited to this, and it may be a dot matrix display (e.g., a dot matrix LED) in which the fixation light sources are arranged two-dimensionally on a substrate, or a liquid crystal display. Alternatively, it may be a configuration in which the fixation light beam is deflected by an optical scanner to present the target at any position in a stepless manner.

[0056] In the fixation target unit 71, the fixation light source 71a is positioned on the optical axis L2, while the fixation light sources 71b to 71k are positioned away from the optical axis L2. The fixation light source 71a, positioned on the optical axis L2, is used, for example, when the macula is the center of the imaging range. The fixation light sources 71b and 71c are used when the area between the macula and the optic nerve head is the center of the imaging range. The other fixation light sources 71d to 71k are used when imaging the peripheral part of the fundus. For example, the fixation light sources 71d and 71e are used when the optic nerve head is the center of the imaging range. The fixation light sources 71b and 71d are used when imaging the right eye, and the fixation light sources 71c and 71e are used when imaging the left eye. The fixation light sources 71f to 71k are used in panoramic imaging, etc.

[0057] <Second fixation target projection optical system> The second fixation optical system 80 is used to guide the direction of the subject's gaze when photographing the peripheral part of the fundus, starting from the stage when the eye E being examined is located further away from the imaging unit 3 than the appropriate working distance WD2. Figure 7 shows the second fixation optical system 80 as seen from the front. As shown in Figure 7, the second fixation optical system 80 includes at least a plurality of fixation light sources 81f to 81k. Each of the fixation light sources 81f to 81k is positioned around the objective lens 18, corresponding to the fixation light sources 71d to 71k for peripheral imaging in the fixation target unit 71.

[0058] As shown in Figure 8A, when guiding the line of sight of the eye under examination towards a fixation target formed by the fixation light source 71d or 71f of the fixation target unit 71, the fixation light source 81f of the second fixation optical system 80 is turned on. The fixation light source 81f can be seen when the line of sight is tilted by θ1 with respect to the optical axis L2 when the working distance is WD1, which is greater than the appropriate value WD2. By moving the imaging unit 3 closer to the eye under examination E from there, as shown in Figure 8B, when the working distance becomes the appropriate value WD2, the line of sight of the eye under examination is smoothly guided towards the fixation target formed by the fixation light source 71d or 71f of the fixation target unit 71. It is desirable that the tilt of the line of sight θ2 with respect to the fixation target formed by the fixation light source 81f is approximately equal to θ1.

[0059] <Department Head> The control unit 100 is a processing unit (processor) that performs control processing for each part and calculation processing. The control unit 100 includes a CPU, RAM, ROM, etc. Furthermore, for convenience, the control unit 100 is assumed to perform image processing on various images obtained by the fundus imaging device 1. In other words, the control unit 100 also serves as the image processing unit.

[0060] The control unit 100 is electrically connected to the OCT optical system 30, the drive unit 12a, the drive unit 19a, the drive unit 41a, the frontal imaging optical system 10, the anterior segment observation optical system 60, the memory unit 101, the touch panel 8, and other components.

[0061] The memory unit 101 may be a non-transient storage medium that can retain its contents even if the power supply is interrupted. For example, the memory unit 101 may store various control programs, fixed data, etc. Also, for example, the memory unit 101 may store images captured by the fundus imaging device 1. The captured images may be transferred to an external storage device (for example, a storage device connected to the control unit 100 via LAN and WAN).

[0062] Furthermore, the memory unit 51 stores the shooting control program. The operations described later are executed according to the shooting control program.

[0063] <Operation Description> Next, the operation of the fundus imaging device 1 in this embodiment will be explained with reference to the flowchart in Figure 9. For convenience, the following explanation will describe the case in which OCT data of the fundus is acquired using one type of scan pattern in the fundus imaging device 1.

[0064] Prior to the examination, the examiner places the subject's face on the face support unit 7. First, the scan pattern and the fixation target presentation position are determined by the control unit 100 (S1). Examples of scan pattern types include line scan, cross scan, multi scan, radial scan, and raster scan (also called map scan). In this embodiment, the fixation target presentation position is used as the reference (center) of the scan pattern on the fundus. In this embodiment, the fixation target presentation position can be selected from positions corresponding to the fovea, optic disc, and the center of the fundus (between the fovea and optic disc). The combination of scan pattern and fixation target presentation position is selected and further determined, for example, based on the examiner's input. At this stage, either the right eye, left eye, or both eyes are selected as the target eye for imaging.

[0065] Once the scan pattern and the presentation position of the fixation target are determined, the control unit 100 starts acquiring observation images (S3). Acquisition of anterior segment observation and fundus observation images is initiated as observation images. The OCT optical system 30 is also controlled to start acquiring adjustment OCT images. In this embodiment, a typical example of an adjustment OCT image is acquired: an image of the XZ cross-section passing through the optical axis L. Adjustment OCT images are acquired repeatedly. Furthermore, the fixation light source in the first fixation optical system 70 is turned on according to the determined presentation position. If a fixation light source 71d or 71e corresponding to the optic disc is selected, the corresponding fixation light source 81f or 81j in the second fixation optical system 80 is also turned on.

[0066] Next, alignment adjustment is performed (S4). Based on the observed image, the control unit 100 adjusts the position of the imaging unit 3 relative to the eye E so that the eye E can be photographed. In this embodiment, the position of the imaging unit 3 is adjusted from a predetermined initial position until the optical axis of the imaging unit 3 coincides with the eye E and the appropriate working distance is achieved. Based on the anterior segment observation image, the position of the imaging unit 3 is automatically moved relative to the eye E. In this embodiment, after projecting alignment indicators (not shown) and adjusting the positional relationships in the XYZ directions, the imaging optical axis is further adjusted in the XY direction so that it coincides with the pupil center.

[0067] <Adjusting shooting conditions> After the alignment is complete, the control unit 100 performs adjustment processing on the OCT optical system 30 and the front imaging optical system 10. In this embodiment, as an example, the OPL, focus, and polarization of the OCT optical system 30, and the focus of the front imaging optical system 10 are adjusted to at least a predetermined state.

[0068] <Focus adjustment> Here, we will explain focus adjustment in detail.

[0069] First, the control unit 100 moves the slit portion 12 and focusing lens 19 in the front imaging optical system 10, and the focusing lens 41 in the OCT optical system 30 to their initial positions. In this embodiment, the initial position is the limit of movement on the negative diopter side. However, it is not necessarily limited to this, and the initial position may be the limit of movement on the positive diopter side, or an intermediate position between those limit positions (for example, a position corresponding to 0D). Also, the direction of deflection of the slit light by the optical scanner 14 of the front imaging optical system 10 is fixed to a predetermined direction. As an example, it is fixed to the 0° direction. In this case, the centers of the two slit beams guided from the optical scanner 14 to the eye E under examination coincide with the optical axis L2.

[0070] The control unit 100 lights up the infrared light sources 11c and 11d while maintaining a constant direction of the slit light. The retinal reflected light from the slit light incident on the eye under examination in a predetermined direction is projected onto the image sensor 21 via the frontal imaging optical system 10. Hereinafter, the slit-shaped image based on the retinal reflected light projected onto the image sensor 21 will be referred to as the "slit image". The control unit 100 controls the image sensor 21 to capture at least one frame and detects the slit image based on the captured image. In this embodiment, at least the position of the slit image is detected.

[0071] Figures 10A to 10C schematically show the slit light rays directed at the eye under examination. As described above, in this embodiment, the images P1 and P2 (projection areas P1 and P2) of the two light sources are formed axially symmetric with respect to the optical axis L2 in the anterior segment of the eye under examination. The aperture image Si of the slit portion 12 is formed downstream of the images P1 and P2 of the light sources. The slit light is irradiated onto the fundus of the eye as two rays, one from the images P1 and P2 of the two light sources toward the aperture image Si.

[0072] Figure 10A shows the light rays when the direction of the slit light is kept constant and the slit portion 12 is positioned at its initial position (the limit of movement on the negative diopter side). In this case, the position of the aperture image Si of the slit portion 12 is behind the fundus of the eye E being examined on the optical axis L2, so the illumination position of the slit light on the fundus is spaced away from the optical axis L2. As a result, as shown in Figure 11, the slit image is detected on the image sensor 21 at a position away from the optical axis L2 (the center of the image in Figures 11 and 12).

[0073] For example, the control unit 100 moves the slit unit 12 from its initial position to the opposite limit position and obtains the distance D between the slit image and the optical axis L2 at each position. In this case, the light rays irradiated onto the fundus change in the order of Figure 10B → Figure 10C. Figure 10B shows the light rays when the direction of the slit light is kept constant and diopter correction is performed appropriately. In this case, the position of the aperture image Si of the slit unit 12 approximately coincides with the fundus. Therefore, the irradiation position of the slit light on the fundus, irradiated from the images P1 and P2 of the two light sources, coincides as shown in Figure 5. Figure 10C shows the light rays when the direction of the slit light is kept constant and the slit unit 12 is positioned at the limit position on the positive diopter side. In this case, the position of the aperture image Si of the slit unit 12 is in front of the fundus of the eye E being examined on the optical axis L2. In this case as well, as shown in Figure 12, the irradiation position of the slit light on the fundus is spaced away from the optical axis L2.

[0074] Therefore, the control unit 100 determines the position of the slit portion 12 where the distance D from the optical axis L2 to the slit image is minimized, and performs focus adjustment by moving the slit portion 12 in the imaging optical system 10, the focusing lens 19, and the focusing lens 41 in the OCT optical system 30 to the position corresponding to that position. However, in this case, it is assumed that the correspondence between the slit portion 12 in the front imaging optical system 10, the focusing lens 19, and the focusing lens 41 in the OCT optical system 30 is known.

[0075] Additionally, in the OCT optical system 30, fine adjustment of focus may be performed. For example, the position of the focusing lens 41 may be adjusted so that the focus position matches a predetermined layer. The fine adjustment of focus in the OCT optical system 30 is preferably performed at a stage when adjustments such as OPL and polarization are completed.

[0076] Note that the method of diopter correction in this embodiment is not necessarily limited to this. For example, the distance D from the optical axis L2 to the slit image corresponds to the diopter of the eye to be examined. Also, the appropriate positions of the optical elements (slit portion 12, focusing lens 19, focusing lens 41) for each diopter are known. Therefore, for example, the control unit 100 obtains the diopter (an example of a focus evaluation value) of the eye to be examined E from the distance D from the optical axis L2 to the slit image at the initial position, and further moves each optical element (slit portion 12 in the front imaging optical system 10, focusing lens 19, focusing lens 41 in the OCT optical system 30) to the appropriate position corresponding to the diopter, thereby performing focus adjustment. A look-up table that stores in advance the correspondence between the diopter of the eye to be examined and the distance D from the optical axis L2 to the slit image at the initial position may be used to obtain the diopter. The look-up table can be created, for example, by measuring the distance D from the optical axis L2 to the slit image at the initial position for a plurality of eyes to be examined or model eyes with known diopters.

[0077] <OPL adjustment> Next, the control unit 100 adjusts the OPL and polarization in the OCT optical system 30. In this embodiment, the optical path length adjustment is performed by changing the optical path length in the reference optical system. However, it is not necessarily limited to this, and it may be performed by changing the optical path length in the measurement optical system 40. The control unit 100 changes the optical path length step by step (for example, by several millimeters in terms of air conversion). Based on the output signal output from the detector 33 at each step, the optical path length at which the tomographic image of the fundus is acquired is specified. After adjusting the optical path length so that the tomographic image of the fundus is acquired, the control unit 100 finely adjusts the OPL. For example, the optical path length may be adjusted so that the fundus image is arranged at a predetermined target position with respect to the imaging range in the depth direction. Note that a real image and a virtual image are generated at positions symmetric with respect to zero delay in the tomographic image of the fundus. Since either the real image or the virtual image can be appropriately selected, one of the real image and the virtual image determined in advance can be arranged at the target position.

[0078] <Polarizer adjustment> In this embodiment, the control unit 100 drives the polarizer to adjust the polarization state between the measurement light and the reference light. When the polarization states match between the measurement light and the reference light, a stronger interference signal can be obtained. Therefore, the polarizer is driven and controlled based on the signal intensity so that the signal intensity output from the detector 33 of the OCT optical system 30 is maximized.

[0079] <Taking an OCT image> By receiving an operation input serving as a trigger for imaging, the imaging scan is executed in a predetermined scan pattern (S6). The captured OCT image may be stored in the storage unit 101, for example. The captured OCT image may be displayed on the screen (S7). Also, a report may be generated based on the captured OCT image.

[0080] <Regarding the visibility of the fixation mark> In the above description, it is desirable that the subject's gaze direction be appropriately guided toward the fixation target presented to the eye under examination from alignment to the completion of OCT image acquisition. In this embodiment, however, since no point-shaped focus indicator is projected, the subject's gaze direction can be appropriately guided toward the fixation target, and OCT images can be acquired.

[0081] Furthermore, in this embodiment, even if the wavelength band of infrared light used for fundus observation is visible to the eye under examination, it is unlikely to affect fixation. First, the scanning of the slit light, which is repeated between alignment and OCT image acquisition, is fast, and from the perspective of the eye under examination, the observation light appears to be irradiated almost simultaneously across the acquisition range of the observation image, making it difficult for the line of sight to follow the moving slit light. Second, during focus adjustment, the direction of the slit light is fixed in a certain direction in order to acquire focus evaluation values, but since the acquisition time of one frame of the slit image is generally sufficiently short (around several tens of milliseconds), there is no need to continuously irradiate the slit light for a long time while keeping the direction constant in order to acquire focus evaluation values. In this case, for example, during focus adjustment, the direction of the slit light may be fixed to acquire the slit image at the timing of acquiring focus evaluation values, and the slit light may be scanned to acquire observation images at other times. Also, since the fixation target is point-shaped, the line of sight is easily guided, whereas the slit light is linear and the irradiated area is relatively wide, making it difficult for the line of sight to be guided. Thus, according to this embodiment, the subject's gaze direction can be appropriately guided toward the fixation target presented to the eye under examination, and an OCT image can be acquired.

[0082] Furthermore, in this embodiment, when photographing the peripheral portion of the fundus, the subject's gaze direction is guided by the second fixation optical system 80 from the stage when the subject eye E is located further away from the imaging unit 3 than the appropriate working distance WD2. This smoothly guides the subject's gaze toward the fixation target formed by the fixation light sources 71d~71k of the fixation target unit 71. Therefore, the subject's gaze direction can be appropriately guided without being affected by the slit light, and OCT images can be acquired.

[0083] Furthermore, because the subject's gaze direction is easily guided appropriately towards the fixation target, the frequency of examiner intervention, such as assisting with the examination, can be reduced from the start of alignment until the completion of OCT image acquisition.

[0084] <Variation> For example, in the above embodiment, in order to obtain a focus evaluation value of the eye under examination based on the slit image, slit light was simultaneously irradiated onto the fundus from two projection areas P1 and P2 formed in the anterior segment of the eye under examination. However, this is not necessarily limited to this. For example, slit light may be selectively irradiated from either of the two projection areas P1 and P2. In this case, the focus evaluation value may be obtained based on the position of the slit image based on the selectively irradiated slit light. Alternatively, slit images based on slit light alternately irradiated from the two projection areas P1 and P2 may be captured as separate frames. The focus evaluation value may be obtained based on the position of the slit image in each frame. When slit light is selectively or alternately irradiated onto the fundus from the two projection areas P1 and P2, it is easy to determine the sign (plus or minus) of the diopter correction amount required in the optical system from the position of the slit image. Therefore, for example, it is not necessary to set the initial position of the slit portion 12 to the movement limit position, and readjusting the focus based on the slit image becomes easier. In the configuration of the above embodiment, selective or alternating illumination of the fundus of the eye with slit light from two light-emitting regions P1 and P2 can be achieved by controlling the lighting of light sources 10c and 10d. However, this is not necessarily the only option, and light-limiting members such as shutters that correspond to the light-emitting regions P1 and P2 and can be selectively opened and closed may be placed in the optical path of the illumination light at a position conjugate to the anterior portion of the eye. [Explanation of Symbols]

[0085] 1. Fundus imaging device 10. Imaging optical system 10a Irradiation optical system 10b Receiving optical system 14 Optical Scanners 21 Two-dimensional image sensor 30 OCT optics 31 OCT light source 32 branched optical elements 33 Detectors 41 Focusing Lens 70 Fixation optical system 100 Control Unit

Claims

1. A fundus imaging apparatus comprising a fixation optical system, an OCT optical system, an imaging optical system, and a control means, The fixation optical system presents a fixation target to the fundus of the eye being examined. The OCT optical system is, An OCT light source, a branching optical element that splits the light from the OCT light source into a measurement light and a reference light, and a detector that detects the spectral interference signal of the measurement light and the reference light reflected from the fundus of the eye under examination, It has a first focus adjustment unit that adjusts the focus position of the measurement light with respect to the fundus of the eye being examined, The aforementioned imaging optical system is An illumination optical system having a light source capable of emitting infrared light as illumination light, forming two light-emitting regions on the pupil of the eye to which the illumination light passes in a first direction, and irradiating the fundus of the eye to be examined with an elongated slit-shaped illumination light formed along a second direction intersecting the first direction, An optical scanner that deflects the illumination light in the first direction on the fundus of the eye, The optical system includes a light-receiving region formed on the pupil of the eye under examination, sandwiched between the two light-emitting regions, from which the light reflected from the retina of the illumination light is extracted, and a light-receiving optical system equipped with a two-dimensional image sensor for receiving the light reflected from the retina of the illumination light. The control means is When the optical scanner is deflected in a predetermined direction, a focus evaluation value is obtained based on the slit image formed on the two-dimensional image sensor of the imaging optical system by the slit-shaped illumination light. The diopter correction control of the OCT optical system is performed by driving the first focus adjustment unit of the OCT optical system based on the focus evaluation value.

2. The fundus imaging device according to claim 1, The OCT light source emits low-coherence light with a central wavelength in the range of 820 nm to 880 nm, and the detector is a spectrometer.

3. A fundus imaging device according to claim 1 or 2, The control means is At the timing when the focus evaluation value is acquired, the orientation of the optical scanner is fixed and the slit image is captured. At other times, the optical scanner is driven to scan the illumination light and acquire the observation image based on the light received signal from the two-dimensional image sensor.

4. A fundus imaging device according to any one of claims 1 to 3, The fixation optical system shares a portion of its optical system with the OCT optical system and the imaging optical system, and is capable of presenting a peripheral fixation target for positioning the optic disc of the eye under examination in the center of the imaging range. Furthermore, The OCT optical system and the imaging optical system have external fixation targets around the objective lenses, which correspond to the peripheral fixation targets and guide the direction of the subject's gaze to the direction corresponding to the peripheral fixation targets, even when the subject's eye is located at a position further than the appropriate working distance.

Images