Fundus imaging device

Abstract

To provide a fundus imaging device that can properly capture a fundus image of a subject's eye.SOLUTION: A fundus imaging device includes: a radiation optical system which emits light to the eyeground of a subject's eye via an objective optical system, the radiation optical system having scanning means for scanning the light on the eyeground; a light receiving optical system having a light receiving element for receiving the light reflected on the eyeground; image generation means for generating a two-dimensional reflective image of the eyeground on the basis of a light receiving signal from the light receiving element; and control means for capturing two-dimensional reflective images with different imaging conditions including image angle and resolution by controlling the scanning means to change an amount of driving of the scanning means and scanning density.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a fundus imaging apparatus that captures a fundus image of a subject's eye. [Background technology]

[0002] In recent years, in the field of ophthalmology, wide-angle fundus photography devices capable of photographing the peripheral part of the fundus have been attracting attention. As one type of device, a device that expands the angle of view of the device by attaching a lens attachment (see Patent Document 1), a device that switches the angle of view by changing the lens arrangement of the objective lens (see Patent Document 2), etc. have been proposed. In the technology described in these documents, the resolution is changed according to the angle of view, and an image photographed with a narrower angle of view can obtain a high-resolution, more detailed image than an image photographed with a wider angle of view. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-123467 A [Patent Document 2] JP 2018-99631 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the methods of Patent Documents 1 and 2, it is necessary to attach and detach the lens attachment or change the lens arrangement every time the angle of view is changed, which takes time to prepare for shooting.Furthermore, there is a problem that the optical system configuration tends to become large-scale and complicated.

[0005] The present disclosure has been made in consideration of the problems of the conventional technology, and has an object to provide a fundus imaging device capable of capturing a good fundus image of a subject's eye. [Means for solving the problem]

[0006] A fundus imaging device according to a first aspect of the present disclosure comprises an illumination optical system which irradiates light onto the fundus of a test eye via an objective optical system, the illumination optical system having a scanning means which scans the light on the fundus, a light receiving optical system having a light receiving element which receives fundus reflected light, an image generating means which generates a two-dimensional reflected image of the fundus based on a light receiving signal from the light receiving element, and a control means which controls the scanning means to change the drive amount and scan density of the scanning means, thereby capturing the two-dimensional reflected images with different imaging conditions including angle of view and resolution. Effect of the Invention

[0007] According to the present disclosure, a fundus image of a subject's eye can be captured satisfactorily. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an apparatus configuration according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing an optical system in the apparatus of the embodiment. [Diagram 3] 4 is a flowchart showing the operation of the device according to the embodiment. [Figure 4] FIG. 11 is a diagram for explaining a shooting method in a second mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] "overview" Hereinafter, the present disclosure will be described based on the embodiments. In this disclosure, "conjugate" is not necessarily limited to a perfect conjugate relationship. An error from a perfect conjugate relationship may be allowed within a range that is allowed in relation to the purpose of use of the fundus image (e.g., observation, analysis, etc.). In addition, the numerical value of the angle of view (deg) is represented by the center of the pupil of the subject's eye.

[0010] The fundus imaging device of the present disclosure is a scanning type device that captures a fundus image by scanning light onto the fundus. The scanning method may be a spot scan method (flying spot method) or a line scan method.

[0011] The fundus imaging device of the present disclosure has at least an irradiation optical system, a light receiving optical system, an image generator, and a control unit. The irradiation optical system irradiates light onto the fundus of the subject's eye via an objective optical system. The irradiation optical system also has a scanning unit (optical scanner) that scans the fundus with the light irradiated onto the fundus. The light receiving optical system has a light receiving element, which receives fundus reflected light of the light irradiated onto the fundus. The image generator generates a two-dimensional reflection image of the fundus based on a light receiving signal from the light receiving element. The control unit controls at least the scanning unit. The control unit controls the scanning unit to change the driving amount and scan density of the scanning unit, thereby acquiring two-dimensional reflection images with different imaging conditions including angle of view and resolution.

[0012] Therefore, the fundus photographing device of the present embodiment can photograph fundus images with different angles of view and resolutions without the need to attach or detach an attachment to the objective optical system or change the arrangement of optical elements (e.g., lenses, etc.) in the objective optical system. This makes it possible to prevent the optical system from becoming complicated when photographing fundus images with different angles of view and resolutions. In addition, the required working distance between the subject's eye and the device can be kept substantially constant before and after changing the angle of view, allowing smooth photography when the angle of view is changed.

[0013] The irradiation optical system may be capable of irradiating light at an angle of view of 90° or more, and the control unit may at least change the shooting conditions between a first shooting condition where a two-dimensional reflection image is acquired at an angle of view of 90° or more and a second shooting condition where a two-dimensional reflection image is acquired at an angle of view of 30° or more and 60° or less (more preferably, 40° or more and 55° or less). However, the angle of view may be changeable in multiple steps of three or more steps.

[0014] In the present embodiment, the control unit may change the angle of view and the resolution at least in the sub-scanning direction by changing the drive amount and the scan density of the scanning unit at least in the sub-scanning direction. In the main scanning direction, the angle of view and the resolution may be constant, or the control unit may have an optical element for changing the angle of view and the resolution in the main scanning direction in conjunction with the angle of view and the resolution in the sub-scanning direction.

[0015] The irradiation optical system may have a light source unit that selectively emits observation light by infrared light and photographing light by visible light. In addition, in the irradiation optical system, a scanning unit that scans the observation light and the photographing light may be the same. The control unit may acquire two-dimensional reflection images based on the observation light as observation images and sequentially display them, and may photograph photographed images that are two-dimensional reflection images based on the photographing light based on a photographing trigger. In this case, the control unit may switch between a first mode in which the observation image and the photographed image are both acquired under a first photographing condition, and a second mode in which the observation image is acquired under the first photographing condition, and the photographed image is acquired under a second photographing condition with a narrower angle of view and a higher resolution than the first photographing condition. In other words, in any mode, the observation image is acquired under the first photographing condition, and the angle of view and resolution of the photographed image photographed based on the photographing trigger are changed according to the mode.

[0016] In this case, the control unit may accept an operation input to specify a shooting range of a captured image acquired under the second shooting condition on an observation image under the first shooting condition that is sequentially displayed on the screen in the second mode. The control unit executes shooting of a captured image for the specified shooting range. Thus, a captured image in which a desired shooting range confirmed by the examiner on the observation image is depicted in detail under the second shooting condition can be easily captured.

[0017] In this case, the photographing range may be specified at a position eccentric to the image center of the observation image. The fundus photographing device may have a fixation optical system that presents a fixation light, and in the second mode, photographing is performed with the presentation position of the fixation light fixed in each of the cases where the photographing range is specified so that the center of the photographing range coincides with the image center of the observation image and where the photographing range is specified at a position eccentric to the image center of the observation image. When an attachment is attached or detached from the objective optical system, or the arrangement of an optical element (e.g., a lens, etc.) in the objective optical system is changed, it is necessary to adjust the presentation position of the fixation light to a position corresponding to the peripheral part when photographing the peripheral part of the fundus at high resolution. In contrast, in this embodiment, the presentation position of the fixation light does not change even when photographing the peripheral part of the fundus at high resolution from when photographing the central part of the fundus, so that fixation guidance is easy even for subjects who have difficulty in fixating.

[0018] Furthermore, when the shooting range is specified on the observation image, the control unit may track the shooting range of the captured image based on the observation image acquired at any time. That is, the observation image at the timing when the shooting range is specified is used as a template, and the amount of positional deviation between the observation image acquired at the timing of capture and the template is calculated, and the driving amount of the scanning unit may be controlled so that the specified shooting range is captured based on the position information and the amount of positional deviation of the shooting range in the template.

[0019] The control unit may take an image under a first photographing condition with a low resolution and a wide angle of view, and then enlarge and display a part of the image. In this case, the image taken under the first photographing condition may be super-resolution processed and enlarged. The super-resolution process may be a known method such as single-frame super-resolution or multiple-frame super-resolution. The single-frame super-resolution may be a process using machine learning such as Sin GAN, In GAN, or Infinity GAN. In an ophthalmic facility that operates a fundus photographing device that can switch between a wide-angle and a normal angle of view, it is time-consuming and difficult to take the same type of image with a wide-angle and a normal angle of view in a single examination. In this embodiment, when an examiner wants to check in detail a part of the image taken under the first photographing condition with a lower resolution, the super-resolution process is performed and the image is enlarged, so that the examiner can check the details well without changing the angle of view and the resolution and retaking the image.

[0020] In addition, when machine learning is used in the super-resolution processing, the machine learning model may convert unclear tissue in a part of a fundus image captured under a first photographing condition into clear tissue. For example, the machine learning model may be trained in advance to perform a process of converting a part of a fundus image captured under a first photographing condition into a fundus image captured under a second photographing condition when the part of the fundus image captured under the first photographing condition is input, using as training data a part of the fundus image captured under a first photographing condition and a fundus image captured under a second photographing condition at the same site as the part of the fundus image.

[0021] Additionally, the fundus imaging device may perform at least one of fluorescence imaging and dark-field imaging (retro mode imaging). Fluorescence imaging may be contrast imaging (FA, IA, etc.) or autofluorescence imaging. Dark-field imaging is an imaging method in which, for example, an optical restriction member is used at the position of a confocal aperture in a confocal optical system to block the confocal position while allowing peripheral scattered light to enter a light receiving element.

[0022] In addition, in the case of contrast imaging (FA, IA, etc.), video imaging may be performed. That is, imaging light may be continuously irradiated to continuously obtain multiple fluorescent contrast images. Since contrast imaging is highly invasive and difficult to retake, it is desirable to be able to capture at least under the second imaging condition that can obtain a high-resolution image.

[0023] "Example" An SLO device 1 according to an embodiment of the present disclosure will be described below with reference to Figs. 1 to 3. Fig. 1 shows a schematic configuration of the SLO device 1. The SLO device 1 is a confocal fundus imaging device used to capture a fundus image (frontal fundus image). The SLO device 1 is an apparatus integrated with other modalities such as an optical coherence tomography (OCT) or a perimeter, and the frontal fundus image captured by the SLO may be used as an observation image in the other modality or as an image for alignment.

[0024] The SLO device 1 scans the fundus with laser light (photographing light in this embodiment) and receives the fundus reflection light of the laser light to obtain a front image of the fundus. In this embodiment, the SLO device 1 obtains a fundus image by two-dimensionally scanning the laser light, which is focused on a spot on the observation surface, based on the operation of a scanning unit (optical scanner).

[0025] 1, the SLO device 1 includes an imaging unit 1A and an arithmetic and control unit 1B (hereinafter simply referred to as a "control unit"). As shown in FIG. 1, the imaging unit 1A includes an optical system of the SLO device 1.

[0026] The optical system of the SLO device 1 will be described with reference to FIG. 2. The SLO device 1 has imaging optical systems 10 and 20. The imaging optical systems 10 and 20 are confocal optical systems. The SLO device 1 captures fundus images via the imaging optical systems 10 and 20. In this embodiment, the imaging optical systems 10 and 20 are broadly divided into an irradiation optical system 10 and a light receiving optical system 20. The irradiation optical system 10 is used to irradiate the subject's eye E with laser light. The light receiving optical system 20 is used to guide the fundus irradiation light of the laser light to a light receiving element. As will be described later, the irradiation optical system 10 and the light receiving optical system 20 share some components.

[0027] In this embodiment, the irradiation optical system 10 includes at least a scanning unit 16 and an objective lens system 17. Additionally, the irradiation optical system 10 in this embodiment further includes a laser light source 11, a collimating lens 12, a perforated mirror 13, a lens 14 (part of the diopter adjustment unit 40 in this embodiment), and a lens 15.

[0028] The laser light source 11 is a light source of the irradiation optical system 10. In this embodiment, the laser light from the laser light source 11 is used as illumination light for fundus photography. As an example, the laser light source 11 may include a plurality of LDs (laser diodes) that emit three colors of visible light, red, green, and blue, and infrared light. In this embodiment, the infrared light is used at least to obtain an observation image of the fundus. The three colors of red, green, and blue are used at least to photograph a color fundus image. In addition, light in a corresponding wavelength range may be used as appropriate for red-free photography and various types of fluorescent photography (e.g., FA, IA, FAF).

[0029] In this embodiment, the laser light is guided to the fundus Er through the light path shown in Fig. 2. That is, the laser light from the laser light source 11 passes through the collimating lens 12, an opening formed in the perforated mirror 13, and lenses 14 and 15 before heading toward the scanning unit 16. The laser light reflected by the scanning unit 16 passes through an objective lens system 17 and is then irradiated onto the fundus Er of the subject's eye E. The laser light is reflected and scattered by the fundus Er. This light (i.e., reflected and scattered light) is emitted from the pupil as return light.

[0030] The scanning unit 16 is a two-dimensional optical scanner that two-dimensionally scans the fundus with laser light emitted from a light source (laser light source 11). In this embodiment, the scanning unit 16 includes an optical scanner 16a for main scanning (for example, for scanning in the X direction) and an optical scanner 16b for sub-scanning (for example, for scanning in the Y direction). As an example, the optical scanner 16a for main scanning may be a resonant scanner, and the optical scanner 16b for sub-scanning may be a galvanometer mirror. However, other optical scanners may be applied to each of the optical scanners 16a and 16b. For example, an acousto-optical element (AOM) that changes the traveling (deflection) direction of light may be applied to each of the optical scanners 16a and 16b in addition to other reflection mirrors (galvanometer mirrors, polygon mirrors, resonant scanners, MEMS, etc.).

[0031] The objective lens system 17 is an objective optical system of the SLO device 1. The objective lens system 17 is used to guide the laser light scanned by the scanning unit 16 to the fundus Er. The objective lens system 17 forms a rotation point P of the laser light in the pupil of the subject's eye. In detail, the position of the rotation point P is on the optical axis L1 of the irradiation optical system 10, and is a position optically conjugate with the scanning unit 16 with respect to the objective lens system 17. At the rotation point P, the laser light that has passed through the scanning unit 16 is rotated.

[0032] The laser light that has passed through the scanning unit 16 passes through the objective lens system 17 and passes through the rotation point P, and is then irradiated onto the fundus Er. The laser light is rotated around the rotation point P, causing the laser light to scan the fundus Er two-dimensionally. The objective lens 17 focuses the laser light onto the fundus (the light beam is focused on the fundus). The laser light irradiated onto the fundus Er is reflected by the retina.

[0033] Next, the light receiving optical system 20 will be described. In this embodiment, the light receiving optical system 20 shares each member arranged from the objective lens system 17 to the perforated mirror 13 with the irradiation optical system 10. In this case, light from the fundus is guided to the perforated mirror 13 by tracing back the optical path during irradiation. The perforated mirror 13 guides the fundus reflected light to an independent optical path of the light receiving optical system 20 while removing at least a part of the noise light caused by reflection at the cornea of ​​the subject eye and the optical system inside the device (for example, the lens surface of the objective lens system, etc.). Note that the optical path branching member that branches the irradiation optical system 10 and the light receiving optical system 20 is not limited to the perforated mirror 13, and other beam splitters may be used.

[0034] The light receiving optical system 20 of this embodiment has a lens 21, a pinhole aperture 23, and a light separating section (light separating unit) 30 in the reflected light path of the holed mirror 13. In addition, lenses 24, 26, and 28 are provided between the light separating section 30 and each of the light receiving elements 25, 27, and 29.

[0035] The pinhole aperture 23 is disposed on the fundus conjugate plane and functions as a confocal diaphragm in the SLO device 1. The pinhole aperture 23 restricts the area through which the return light guided to the light receiving element passes (hereinafter referred to as the passing area). That is, when the diopter is properly corrected, the light from the fundus Er that passes through the lens 21 is focused at the opening of the pinhole aperture 23. The pinhole aperture 23 removes light from positions other than the light collecting point (or focal plane) of the fundus Er, and the remaining light (light from the light collecting point) is guided to the light receiving elements 25, 27, and 29.

[0036] The light separating unit 30 separates light from the fundus Er. In this embodiment, the light separating unit 30 selectively separates the light from the fundus Er. The light separating unit 30 may also serve as a light branching unit that branches the optical path of the light receiving optical system 20. For example, as shown in FIG. 2, the light separating unit 30 may include two dichroic mirrors (dichroic filters) 31 and 32 having different optical separation characteristics (wavelength separation characteristics). The optical path of the light receiving optical system 20 is branched into three by the two dichroic mirrors 31 and 32. At the end of each branched optical path, one of the light receiving elements 25, 27, and 29 is disposed.

[0037] For example, the light separation unit 30 separates the wavelengths of light from the fundus Er and causes the three light receiving elements 25, 27, and 29 to receive light in different wavelength ranges. For example, the light receiving elements 25, 27, and 29 may receive three colors of light, blue, green, and red, one color each. In this case, a color image may be obtained from the light receiving results of the light receiving elements 25, 27, and 29. The light separation unit 30 also causes one of the light receiving elements to receive fundus reflected light in the infrared range. An infrared image is obtained based on the signal from this light receiving element.

[0038] In addition, in the case of fluorescence photography, it is necessary to separate the fundus reflection light due to the excitation light from the fluorescence from the fundus. In this embodiment, the light separation unit 30 is used to separate the fundus reflection light and the fluorescence during the fluorescence photography. In addition, the SLO device 1 may additionally have a wavelength-selective filter.

[0039] <Fixation optical system> The SLO device 1 may also have a fixation optical system. In the example of Fig. 2, the fixation optical system is also used as the irradiation optical system 10. Visible light intermittently emitted from the laser light source 11 is used as a fixation light beam (in other words, a fixation target). The presentation position of the fixation target can be changed by controlling the operation of the scanning unit 16 and the lighting timing of the fixation light beam.

[0040] Each part of the SLO device 1 is controlled by a control unit 1B. The control unit 1B includes a processing device (processor) having electronic circuits that perform control processing of each part of the SLO device 1 and arithmetic processing. The control unit 1B is realized by a CPU, a ROM, a RAM, etc. A non-volatile storage medium (e.g., a hard disk, a flash memory, etc.) for storing captured images, an input interface 75 (e.g., a mouse, a keyboard, a touch panel, etc.), a monitor 80 for displaying captured images, etc. are connected to the control unit 1B.

[0041] In this embodiment, the control unit 1B serves as an image processing unit, and forms, for example, a fundus image based on a light receiving signal output from the light receiving element 29. For example, the control unit 70 may form one frame of a fundus image for each raster scan.

[0042] The control unit 70 causes the laser light source 11 to emit infrared light, and also causes the fundus image based on the infrared light to be acquired as an observation image at any time and displayed in real time on the monitor 80. Also, based on a predetermined photographing trigger, the control unit 70 causes the laser light source 11 to emit visible light (in this embodiment, three colors: red, green, and blue), and also acquires (captures) a color fundus image based on the visible light as a photographed image. The photographed image is stored in a storage medium.

[0043] <Operation description> The flow of operations in the SLO device 1 of this embodiment will be described with reference to FIGS.

[0044] First, the eye E to be examined and the device are aligned (S1). At that time, a fixation target is presented to the eye E to be examined, and an observation image is acquired at any time and displayed on the screen. Unless otherwise specified, the observation image is a low-resolution image with a field angle of 90°. The fixation target may be presented, for example, along the optical axis of the irradiation optical system 10. Based on the observation image, the positional relationship between the eye E to be examined and the device is adjusted.

[0045] Next, a selection operation of the photographing mode is accepted (S2). The angle of view and resolution of the photographed fundus image are changed according to the photographing mode. In the first mode, a fundus image is photographed at a low resolution with an angle of view of 90°, and in the second mode, a fundus image is photographed at a high resolution with an angle of view of 45°. The angle of view of 45° is equivalent to the angle of view of a general fundus camera.

[0046] When the first mode is selected (S3: first mode), after focus adjustment based on the observed image, a shooting trigger is issued based on a release operation, etc., and a fundus image is captured at a low resolution with a 90° angle of view (S4).

[0047] After photographing, the fundus image is displayed on the screen (S5). In this embodiment, any range can be enlarged for display. When enlarging the image, the control unit 70 performs super-resolution processing on the fundus image (S7). This allows the fundus tissue to be confirmed with good image quality even when the image is enlarged.

[0048] When the second mode is selected (S3: second mode), like the first mode, acquisition of an observation image with a low resolution and a 90° angle of view continues and is displayed. An operation to specify the shooting range of the captured image is accepted on the observation image (S8). For example, as shown in FIG. 4, the shooting range is set by moving a window W indicating the shooting range on the observation image. This sets the drive amount for the scanning unit 16 during shooting and the cropping range of the image.

[0049] That is, in this embodiment, since a galvano scanner is used as the optical scanner 16b for the sub-scanning, the scan width and scan speed are controlled for the main scanning, and the designated shooting range is scanned more densely (with higher resolution) than in the first mode. On the other hand, since the optical scanner 16a for the main scanning is a resonant scanner, it is difficult to control the scan width and scan speed for the main scanning. Therefore, in the main scanning direction, a range with a field angle of 90° is scanned as in the first mode, but a portion corresponding to the designated shooting range is cut out from the acquired image to generate a shooting image. When shooting, the sampling period of the received light signal may be increased compared to the first mode, so that scanning with higher resolution can be performed in the main scanning direction as well.

[0050] When a shooting trigger is issued based on a release operation or the like, a high-resolution fundus image with a 45° angle of view is shot (S9), and the shooting result is displayed on the screen (S10). Even if the center of the specified shooting range is decentered from the center of the observed image, the drive amount of the scanning unit 16 and the image cut-out range are controlled without changing the presentation position of the fixation target, so that a fundus image in the desired shooting range can be obtained. For example, even when shooting the peripheral part of the fundus, the presentation position of the fixation light does not change from when shooting the central part of the fundus, so fixation guidance is easy even for subjects who have difficulty in fixating.

[0051] In the second mode, at least in the sub-scanning direction, only the designated photographing range is scanned, which tends to prevent the photographing time from being prolonged. In a scanning fundus photographing device, image distortion and motion artifacts occur due to eye movement during photographing, but in this embodiment, even if photographing is performed more densely, image distortion and motion artifacts are unlikely to occur because photographing is performed in a short time.

[0052] Although the present disclosure has been described above based on the embodiments and examples, it should be understood that the present disclosure is not limited to the above-described embodiments and may be modified in various ways.

Claims

1. an illumination optical system that illuminates a fundus of a subject's eye with light via an objective optical system, the illumination optical system having a scanning means that scans the fundus with the light; a light receiving optical system having a light receiving element for receiving fundus reflected light; an image generating means for generating a two-dimensional reflection image of the fundus based on a light receiving signal from the light receiving element; and a control means for controlling the scanning means to change the drive amount and scan density of the scanning means, thereby capturing the two-dimensional reflection images with different capturing conditions including an angle of view and a resolution.

2. the irradiation optical system has a light source unit that selectively emits observation light using infrared light and photographing light using visible light as the light, and the scanning means that scans the observation light and the photographing light is the same; the control means acquires the two-dimensional reflection image based on the observation light as an observation image and sequentially displays it, and captures a captured image, which is the two-dimensional reflection image based on the photographing light, based on a photographing trigger; Furthermore, The fundus photographing device of claim 1, wherein the control means switches between a first mode in which the observation image and the photographed image are both acquired under first photographing conditions, and a second mode in which the observation image is acquired under the first photographing conditions and the photographed image is acquired under second photographing conditions which have a narrower angle of view and higher resolution than the first photographing conditions.

3. A fundus photography device as described in claim 2, in which, in the second mode, an operation input is accepted to specify a shooting range of the photographed image obtained under the second photographing conditions on the observation image under the first photographing conditions that is displayed sequentially on the screen, and the photographed image is photographed for the specified shooting range.

4. the irradiation optical system is capable of irradiating the light at an angle of view of 90° or more; A fundus imaging device as described in any one of claims 1 to 3, wherein the control means at least changes the imaging condition between a first imaging condition in which the two-dimensional reflection image is acquired at an angle of view of 90° or more and a second imaging condition in which the two-dimensional reflection image is acquired at an angle of view of 30° or more and 60° or less.

5. 5. The fundus imaging apparatus according to claim 2, wherein the control means performs super-resolution processing to enlarge and display a portion of the photographed image photographed under the first photographing condition.

Images