Optical system, fundus imaging device, and fundus imaging system

Abstract

To provide a technology capable of suppressing generation of artifact in fundus observation.SOLUTION: A fundus imaging apparatus (10) has luminaire (11) having a light source (111) and an illumination optical system (112), and an imaging device (12) having an image pickup device (121) and an imaging optical system (122). The illumination optical system (112) radiates light from the light source (111) to the fundus. The imaging optical system (122) forms an image of the fundus on the image pickup device (121). The optical axis of the illumination optical system (112) does not agree with the optical axis of the imaging optical system (122), or the illumination optical system (112) does not have a specific optical axis.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical system, a fundus imaging device, and a fundus imaging system. [Background technology]

[0002] There are three known major causes of blindness in Japanese people: diabetic retinopathy, age-related macular degeneration, and glaucoma. Fundus examinations are effective for early detection of these diseases. Fundus cameras used in fundus examinations use a coaxial epi-illumination optical system in which the optical axis of the light entering the eye coincides with the optical axis of the light reflected from the fundus.

[0003] Known methods for such optical systems include a method of preventing overlap of the optical paths of the irradiated light and the reflected light by separating the irradiated light (see, for example, Patent Documents 1 and 2), a method of imaging and blocking unnecessary light (see, for example, Patent Document 3), and a method of blocking unnecessary light using a linear polarization element (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-28677 [Patent Document 2] Japanese Patent Application Publication No. 5-337087 [Patent Document 3] Japanese Patent Application Publication No. 9-28675 [Non-patent literature]

[0005] [Non-Patent Document 1] Nara Institute of Science and Technology, Japan Science and Technology Agency, "Development of a compact fundus camera system that can take selfies without blurring or glare," [online], June 18, 2018, JST Joint Announcement, [Retrieved January 14, 2020], Internet (URL: https: / / www.jst.go.jp / pr / announce / 20180618 / index.html) Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above-mentioned conventional technology, a coaxial epi-illumination optical system is used in which the optical axis of the light incident on the eye coincides with the optical axis of the light reflected from the fundus, and such conventional technology has a problem in that unnecessary light reflected at places other than the fundus of the eye is mixed with the light forming the fundus image, resulting in artifacts such as ghosts and flares.

[0007] For example, in the methods described in Patent Documents 1 and 2, when the angle of the irradiated light is wide, the optical paths of the irradiated light and the reflected light overlap in large part, and the occurrence of ghost flare cannot be prevented. In the method described in Patent Document 3, when the angle of the irradiated light is wide, the image of the unnecessary light becomes large, and the necessary light is also blocked. In the method described in Non-Patent Document 1, when the angle of the irradiated light is wide, a four-leaf ghost may remain due to the rotation of the polarized light caused by reflection. For this reason, in the technical field of fundus observation, a technology capable of suppressing the occurrence of artifacts is required.

[0008] An object of one aspect of the present invention is to provide a technique capable of suppressing the occurrence of artifacts in fundus imaging. [Means for solving the problem]

[0009] In order to solve the above problems, an optical system according to one embodiment of the present invention has an illumination optical system that irradiates light from a light source onto the fundus of a subject's eyeball, and an imaging optical system that forms an image of the fundus on an imaging element, wherein the optical axis of the illumination optical system does not coincide with the optical axis of the imaging optical system, or the illumination optical system does not have a specific optical axis.

[0010] In addition, in order to solve the above problem, a fundus imaging device according to one embodiment of the present invention has an illumination device having a light source and the above-mentioned illumination optical system, and an imaging device having an imaging element and the above-mentioned imaging optical system.

[0011] Furthermore, in order to solve the above-mentioned problems, a fundus imaging system according to one aspect of the present invention includes the above-mentioned fundus imaging device. Effect of the Invention

[0012] According to one aspect of the present invention, it is possible to provide a technique capable of suppressing the occurrence of artifacts in fundus imaging. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing an example of the configuration and usage of a fundus imaging apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing a schematic diagram of a suitable location on an eyeball to which light from a light source is irradiated in an embodiment of the present invention. [Diagram 3] 1 is a diagram showing an example of a suitable location on a subject's face to be irradiated with light from a light source in an embodiment of the present invention. FIG. [Figure 4] 10A to 10C are diagrams illustrating other examples of suitable locations on the subject's face that are suitable for irradiating with light from a light source in an embodiment of the present invention. [Diagram 5] 1 is a block diagram showing an example of a functional configuration of a fundus imaging system according to a first embodiment of the present invention. [Figure 6] 1 is a diagram illustrating a schematic configuration of a fundus imaging apparatus according to a first embodiment of the present invention. [Figure 7] 1A and 1B are diagrams for explaining differences between an embodiment of the present invention and a conventional embodiment. [Figure 8] FIG. 11 is a diagram illustrating a schematic configuration of a fundus imaging apparatus according to a second embodiment of the present invention. [Figure 9] FIG. 13 is a diagram illustrating a schematic configuration of a fundus imaging apparatus according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 〔overview〕 1 is a diagram showing a schematic configuration and a usage form of a fundus imaging system according to an embodiment of the present invention. The fundus imaging system according to an embodiment of the present invention has a fundus imaging device 10. The fundus imaging device 10 has an illumination device 11 and an imaging device 12.

[0015] [Lighting equipment] The illumination device 11 has a light source 111 and an illumination optical system 112. The light source 111 may be any light source that can be used for fundus observation, and may be an intermittent light source 111 such as a strobe, or may be a continuous light source, and is preferably a continuous light source. Examples of continuous light sources include a thermoelectric lamp, a laser diode (LD), and a light-emitting diode (LED). The wavelength of the light from the light source 111 is preferably 600 nm or more from the viewpoint of suppressing miosis reaction due to irradiation of light from the light source 111. Moreover, the wavelength of the light from the light source 111 is preferably 1600 nm or less from the viewpoint of suppressing attenuation of the irradiated light due to absorption by water in a living body.

[0016] From the viewpoint of suppressing attenuation of the light in a living body, the wavelength of the light from the light source 111 is preferably 650 to 1000 nm, which is also called the biological window, and more preferably 800 to 900 nm. Note that in this specification, the symbol "to" means a range of "greater than or equal to", including both the numerical values ​​at both ends.

[0017] The illumination optical system 112 is an optical system that irradiates the fundus of the eyeball E of the subject H. The illumination optical system 112 collects, refracts, and reflects the light from the light source 111 as necessary. The illumination optical system 112 can be configured with known optical elements such as lenses, prisms, beam splitters, polarizers, reflecting members, light flux control members, solid-state semiconductor elements, and thermal light sources. Examples of solid-state semiconductor elements include light-emitting diodes (LEDs), semiconductor lasers (LDs), lasers (LASERs), and EL (electroluminescent) elements. These optical elements are supported in a desired positional relationship with respect to the light source 111 or between multiple optical elements by an appropriate member such as a tube or casing. The optical elements may be supported so as to be movable along their optical axes.

[0018] [Imaging device] The imaging device 12 has an imaging element 121 and an imaging optical system 122. The imaging element 121 may be a known solid-state imaging element that can be used for fundus imaging, examples of which include a CCD image sensor and a CMOS image sensor. These image sensors may be color sensors or monochrome sensors, but monochrome sensors are more preferable from the viewpoint of high image quality.

[0019] The imaging optical system 122 is an optical system that forms an image of the fundus on the imaging element 121. The imaging optical system 122 collects light from the fundus to form an image, refracts or reflects the image as necessary, and forms the image on the imaging element 121. The imaging optical system 122 can be configured using known optical elements, similar to the illumination optical system 112, and the optical elements are supported in a desired positional relationship with respect to the light source 111 or between multiple optical elements by an appropriate member such as a tube or a casing. The optical elements of the imaging optical system 122 may also be supported so as to be movable along their optical axes.

[0020] [Explanation of optical system] In the embodiment of the present invention, the optical axis of the illumination optical system 112 that irradiates the fundus with light from the light source 111 does not coincide with the optical axis of the imaging optical system 122. In the embodiment of the present invention, "the optical axis of the illumination optical system does not coincide with the optical axis of the imaging optical system" means that a part or all of the optical axis of the illumination optical system does not substantially coincide with the optical axis of the imaging optical system. For example, in the above-mentioned coaxial epi-illumination, a part of the optical axis of the illumination optical system usually substantially coincides with the optical axis of the imaging optical system between the outside of the front of the eyeball and the fundus, and is shown overlapping when illustrated. In the embodiment of the present invention, the optical axis of the illumination optical system 112 does not include a part that coincides (overlaps) with the optical axis of the imaging optical system 122.

[0021] Alternatively, in the embodiment of the present invention, the illumination optical system 112 does not have a specific optical axis. "The illumination optical system does not have a specific optical axis" means that the illumination optical system is an asymmetric or non-imaging system that does not have an optical axis. Examples of such illumination systems include LEDs that are directly used to illuminate the eyeball, and optical systems with diffusion of light from a light source such as car headlights. Such illumination systems can also be the illumination optical system in the embodiment of the present invention.

[0022] In the embodiment of the present invention, light from the fundus is usually extracted to the outside through the pupil. For this reason, the imaging optical system 122 is located in front of the eyeball E. The illumination optical system 112 is usually disposed at a position where its optical axis is aligned in a direction intersecting with the optical axis of the imaging optical system 122. From such a position, the illumination device 11 irradiates the fundus with light from the light source 111 via the illumination optical system 112.

[0023] [Explanation about the eye as the target of irradiation] In the embodiment of the present invention, the fundus refers to a portion of the eyeball E that is inside the crystalline lens. The fundus may be the entire portion of the eyeball E, or a portion of the portion. For example, the fundus may be the retina. Here, an embodiment in which the retina is imaged as the fundus will be described as an example.

[0024] Fig. 2 is a diagram showing a schematic diagram of a portion of an eyeball E suitable for irradiation with light from a light source 111 in an embodiment of the present invention. As shown in Fig. 2, the eyeball E has, from the front, a cornea 21, an iris 22, a lens 23, a Zonula 24, a vitreous body 25, and a retina 26. The vitreous body 25 and the retina 26 correspond to the above-mentioned fundus.

[0025] The eyeball E also has a trans-pars-plana region 27 and an iris-Zinn zonule region 28. The trans-pars-plana region 27 is a region from the tip of the retina 26 to the Zinn zonule 24. The trans-pars-plana region 27 is a region where the retina 26 is not interposed between the vitreous body 25 and the surface of the eyeball E. The iris-Zinn zonule region 28 is a region where the iris 22 and the Zinn zonule 24 overlap. The iris-Zinn zonule region 28 is a region where the crystalline lens 23 is not interposed between the iris 22 and the vitreous body 25. Although not shown, adipose tissue called orbital fat is present around the eyeball E.

[0026] [Explanation about light irradiation] The illumination optical system 112 may be an optical system that directly irradiates the fundus of the eyeball E of the subject H. Here, "direct irradiation" means that the light from the light source 111 is irradiated toward the fundus to be imaged and by passing through the anterior eye tissue on the optical path. In this case, the illumination optical system 112 is preferably configured to directly irradiate the fundus with the light from the light source 111 without passing through the crystalline lens. The illumination optical system 112 directly irradiates the fundus with light, thereby obtaining an image of the reflected light at the fundus. It is preferable that the illumination optical system 112 is an optical system that directly irradiates the fundus from the viewpoint of preventing the occurrence of artifacts or illuminating the fundus more brightly. It is also preferable that the illumination optical system 112 is an optical system that directly irradiates the fundus without passing through the crystalline lens from the viewpoint of preventing the subject H from feeling dazzled.

[0027] The illumination optical system 112 is preferably an optical system that irradiates the fundus with light from the light source 111 via the trans-pars-plana region 27 of the eyeball E. Illuminating the fundus via the trans-pars-plana region 27 is preferable from the viewpoints of preventing the subject H from feeling glare, since the light from the illumination optical system 112 reaches the vitreous body 25 or the retina 26 without passing through the retina 26, and of illuminating the fundus more brightly.

[0028] Moreover, the illumination optical system 112 is preferably an optical system that irradiates the fundus with light from the light source 111 via the iris-Zinn zonule region 28 of the eyeball E. Illuminating the fundus via the iris-Zinn zonule region 28 is preferable from the viewpoints of preventing the subject H from feeling glare, and of illuminating the fundus more brightly, since the light from the illumination optical system 112 reaches the vitreous body 25 or the retina 26 without passing through the crystalline lens 23.

[0029] The illumination optical system 112 may be an optical system that indirectly irradiates the fundus of the eyeball E of the subject H. The term "indirectly irradiates" here means that the light from the light source 111 is irradiated to the tissues surrounding the eyeball E, and the fundus is illuminated by the light scattered by the orbital fat. Examples of the surrounding tissue include orbital fat, sclera, muscle tissue, and nerve tissue. In the following description, the orbital fat is taken as an example of the surrounding tissue. In this case, the illumination optical system 112 may be an optical system that irradiates the light from the light source 111 to the orbital fat around the eyeball E via, for example, the biological tissue of the subject H. By irradiating the orbital fat with light, the eyeball E is illuminated from behind the crystalline lens by the scattered light from the orbital fat, and an image of the light transmitted through the fundus from behind is obtained. It is preferable that the illumination optical system 112 illuminates the fundus via the orbital fat from the viewpoint of more reliably preventing the subject H from feeling dazzled and the occurrence of artifacts.

[0030] More specifically, the illumination optical system 112 that indirectly irradiates the fundus of the eyeball E of the subject H may be an optical system that irradiates the light from the light source onto the fatty tissue around the eyeball E through the skull of the subject H. In this case, the illumination optical system may be arranged to irradiate the light from the light source onto the frontal or parietal part of the subject H as indicated by the arrow A in Fig. 1, or may be arranged to irradiate the light from the light source onto the temporal or occipital part of the subject H as indicated by the arrow B in Fig. 1. In the above case, it is preferable that the illumination optical system is an optical system that irradiates the light from the light source onto the fatty tissue around the eyeball E through multiple points on the skull of the subject H, from the viewpoint of illuminating the fundus more brightly.

[0031] Alternatively, the illumination optical system that indirectly irradiates the fundus of the eyeball E of the subject H may be an optical system that irradiates the light from a light source to the fatty tissue around the eyeball E through the ethmoid bone of the subject H as indicated by the arrow C in FIG. 1. The light from the light source is irradiated toward the ethmoid bone of the subject H, so that the fundus is irradiated from the nasal cavity side through the ethmoid sinus and orbital fat. Such an illumination device can be configured by an optical system including an optical element such as an optical fiber that can be inserted into the nasal cavity of the subject H, or an optical system including a small light source and an optical element such as a light flux control member that directs the light from the light source toward the ethmoid bone. It is preferable for the illumination optical system to illuminate the fundus through the ethmoid bone from the viewpoint of brightly illuminating the fundus from below or behind, and from the viewpoint of easily stabilizing the conditions for illuminating the eyeball, such as the conditions of the position of the light source.

[0032] When the illumination optical system 112 illuminates the fundus of the subject H, it is preferable that the area of ​​the illuminated portion of the subject H is larger in terms of illuminating the fundus more brightly. In this case, the illumination optical system 112 may be an optical system that illuminates light from the light source 111 to specific areas scattered around the eye of the subject H, but it is preferable that the illumination optical system 112 is an optical system that illuminates a specific area having a sufficient area in terms of illuminating the fundus more brightly.

[0033] 3 is a diagram showing an example of a suitable location on the face of the subject H to be irradiated with light from the light source 111 in the embodiment of the present invention. As shown in FIG. 3, the illumination optical system 112 may be an optical system that illuminates an arc-shaped region 31 including the upper eyelid of the subject H with light from the light source 111.

[0034] 4 is a diagram showing another example of a suitable location on the face of the subject H suitable for irradiation with light from the light source 111 in the embodiment of the present invention. As shown in FIG. 4, the illumination optical system 112 may be an optical system that illuminates an annular region 41 including the upper eyelid and the lower eyelid of the subject H with light from the light source 111.

[0035] In this way, the illumination optical system 112 may be an optical system that irradiates light from the light source 111 onto the fundus E through an arc-shaped region 31 or an annular region 41 around the eye on the face of the subject H. Such an optical system can be configured using a reflecting member or a light flux control member, a light blocking member that blocks light in a specific direction, or the like.

[0036] When irradiating a specific area on the surface of the subject H with light from the light source 111 as described above, it is preferable that the area of ​​the area irradiated with light is large in order to illuminate the fundus more brightly. From this perspective, the area of ​​the area irradiated with light is set to 1 cm 2 It is preferable that the length is 2cm or more. 2 It is more preferable that the area of ​​the region is 700 cm2 or more, assuming that the skull is a 15 cm2 sphere, in order to illuminate the fundus sufficiently brightly. 2 It may be the following:

[0037] Hereinafter, the embodiments of the present invention will be described more specifically.

[0038] [First embodiment] [Fundus Imaging System] Fig. 5 is a block diagram showing an example of a functional configuration of a fundus imaging system according to a first embodiment of the present invention. As shown in Fig. 5, the fundus imaging system 50 includes an illumination device 61, an imaging device 62, and a control unit 51. The fundus imaging system 50 further includes a storage unit 52, an input device 53, and an output device 54.

[0039] The lighting device 61 and the imaging device 62 have the same configurations as the above-mentioned lighting device 11 and imaging device 12, respectively. The configurations of the lighting device 61 and the imaging device 62 will be described in more detail later.

[0040] The control unit 51 controls the operation of various devices related to fundus imaging in response to input signals from the various devices as necessary. The storage unit 52 stores information for controlling fundus imaging by the control unit 51, and also stores information related to fundus imaging as necessary. The storage unit 52 is configured with a non-volatile recording medium such as an HDD, SSD, or DVD-RAM.

[0041] The input device 53 is a device for allowing the subject H or an operator of the fundus imaging system to input information relating to fundus imaging to the control unit 51. The input device 53 is, for example, a keyboard, a touch panel, a voice input device, or a receiving device.

[0042] The output device 54 is a device for outputting fundus image data or information related to fundus imaging from the control unit 52. The output device 54 is, for example, a display, an audio output device, or a transmission device.

[0043] [Fundus Imaging Device] <Device configuration> Fig. 6 is a diagram showing a schematic configuration of a fundus imaging device 60 according to a first embodiment of the present invention. As shown in Fig. 6, the fundus imaging device 60 includes an illumination device 61, an imaging device 62, and a monitor 63. In the fundus imaging device 60, the optical axis of the emitted light from the illumination device 61 and the optical axis of the received light from the imaging device 62 are independent of each other and do not share a common portion. Thus, the fundus imaging device 60 has a structure that does not include an optical system for coaxial epi-illumination.

[0044] The illumination device 61 has a light emitting diode (LED) 611 and a lens 612. The LED 611 and the lens 612 are integrally held in an appropriate positional relationship by, for example, a tube or a casing. The LED 611 outputs light with a wavelength of 600 to 1600 nm. The LED 611 corresponds to the above-mentioned light source. The lens 612 receives the light from the LED 611 and focuses it on the fundus (retina) of the eyeball E of the subject H from a direction oblique to the front of the eyeball E. The lens 612 corresponds to the above-mentioned illumination optical system. The illumination device 61 does not include an eyepiece that comes into contact with the periphery of the eye of the subject H, and is disposed away from the subject H. In addition, the illumination device 61 is not fixed relative to the imaging device 62, and its position can be adjusted around the eyeball E of the subject H.

[0045] The imaging device 62 has a lens 621 and a CMOS image sensor 622. The lens 621 and the CMOS image sensor 622 are integrally held in an appropriate positional relationship by, for example, an eyepiece casing or a tube. The lens 621 receives light from the fundus (retina) from the front of the eyeball E and focuses the light on the CMOS image sensor 622. The lens 621 corresponds to the imaging optical system described above. The CMOS image sensor 622 corresponds to the imaging element described above.

[0046] The monitor 63 is a liquid crystal display device, and displays information input from the input device 53 or information relating to fundus imaging, such as image data of the captured fundus. The monitor 63 corresponds to the output device 54 described above.

[0047] [Explanation of fundus imaging] An example of a processing flow for imaging a fundus by the fundus imaging system of this embodiment will be described. The control unit 51 operates the illumination device 61 and the imaging device 62 in response to information instructing the start of fundus imaging from the input device 53. Alternatively, the control unit 51 operates the illumination device 61 in response to image data from the imaging device 62 indicating that the eyeball E of the subject H is at a specific position.

[0048] The illumination device 61 outputs light from the LED 611 in response to a signal from the control unit 51 instructing the operation. Furthermore, the illumination device 61 adjusts the distance between the LED 611 and the lens 612 in the optical axis direction in response to the signal, as necessary, to adjust the focusing of light on the surface or fundus of the subject H. The lens 612 receives the light from the LED 611 and directly irradiates it onto the fundus of the eyeball E of the subject H. The light irradiated onto the fundus is reflected by the fundus.

[0049] Alternatively, the lens 612 receives light from the LED 611 and irradiates it onto the orbital fat around the eyeball E of the subject H. The light scattered by the orbital fat passes through the fundus from behind.

[0050] The imaging device 62 adjusts the focusing of light from the eyeball E of the subject H and the formation of an image on the CMOS image sensor 622 in response to a signal from the control unit 51 instructing the operation. At this time, the imaging device 62 adjusts the distance between the CMOS image sensor 622 and the lens 612 in the optical axis direction in response to the signal, as necessary. The lens 612 receives light (reflected light or transmitted light) from the fundus to form an image of the fundus and focuses it on the CMOS image sensor 622. The CMOS image sensor 622 detects the light from the lens 612 and transmits the detected signal to the control unit 51. The control unit 51 outputs information on the image of the fundus to the monitor 63 in response to the signal from the imaging device 62, and causes the monitor 63 to display the image of the fundus.

[0051] In this embodiment, a good image of the fundus is formed that is substantially free from the influence of reflected light on the surface of the eyeball E. Fig. 7 is a diagram for explaining the difference between the embodiment of the present invention and the conventional embodiment. The solid arrow in the figure represents the optical axis of light in the embodiment of the present invention. The dashed arrow in the figure represents the optical axis of light in the conventional embodiment.

[0052] As described above, the embodiment of the present invention does not include a coaxial epi-illumination optical system. Therefore, as shown in FIG. 7, the light from the LED 611 is irradiated onto the fundus so that the optical axis LA1 of the light from the lens 621 extends in a direction other than the front of the eyeball E, for example, in a diagonal direction with respect to the front of the eyeball E. Then, the reflected light from the fundus is taken out to the front of the eyeball E through the pupil. That is, the optical axis LA2 of the light from the fundus extends in the direction of the front of the eyeball E. Thus, in this embodiment, the optical axis of the illumination optical system that irradiates the fundus with light from the light source does not coincide with the optical axis of the imaging optical system. Therefore, the CMOS image sensor 622 does not substantially detect the reflected light from the surface of the eyeball E, and a good image of the fundus that does not substantially include the image of the reflected light is formed.

[0053] On the other hand, in the case of including a conventional coaxial epi-illumination optical system, light from a light source is irradiated onto the fundus from the front of the eyeball E, and the reflected light from the fundus is extracted from the front of the eyeball E. Therefore, the optical axis LA3 of the light from the conventional light source and the optical axis LA2 of the light from the fundus both extend in the direction of the front of the eyeball E and substantially coincide with each other. Furthermore, a part of the light from the light source is reflected on the surface of the cornea. The optical axis LA4 of the reflected light from this surface also extends in the direction of the front of the eyeball E and substantially coincides with the optical axes LA2 and LA3. For this reason, in the conventional case, the image sensor detects the reflected light from the surface of the eyeball E as well as the light from the eyeball E, so that the image of the fundus contains artifacts caused by the reflected light from the surface of the eyeball E. If the reflected light from the surface of the eyeball E toward the image sensor is blocked, the image of the fundus of the part overlapping with the artifact is not formed, and an image of the fundus lacking the part of the artifact is formed.

[0054] In addition, in the past, in a time-division fundus imaging device using a light source that irradiates intermittently, such as a flash or a scanning laser ophthalmoscope (SLO), the illumination is set to be within the range of safety standards. In addition, the light reflectance of the retina in the fundus is not particularly high. For this reason, it is not possible to obtain many photon statistics in imaging the retina, which is disadvantageous for spectroscopic observation of the fundus (retina). In this embodiment, it is easy to obtain a sufficiently large number of photon statistics.

[0055] In addition, in this embodiment, since the fundus can be illuminated with a constant irradiation light from the illumination optical system, it is more advantageous in terms of illuminating the fundus uniformly than SLO. Therefore, in this embodiment, the fundus can be imaged under more stable imaging conditions than SLO, and imaging data of better quality can be obtained.

[0056] As described above, conventional fundus imaging devices have a tendency to have difficulty photographing the fundus due to the influence of artifacts. This tendency becomes more pronounced as the angle becomes wider. For this reason, the image of the artifacts contained in the fundus image may degrade the image quality of the fundus image, making diagnosis based on the fundus image more difficult.

[0057] In the embodiment of the present invention, the image of the fundus does not substantially include an image of the artifact. Therefore, the above-mentioned problems do not occur, and it is possible to take a good-quality image of the fundus even for a subject H with a small pupil diameter. In addition, by the above-mentioned indirect irradiation, it is also possible to take a transmission image of the fundus by performing backlight irradiation that illuminates the eyeball E from the surroundings from a part having an area other than the pupil of the subject H, and thereby it is possible to easily obtain a high-precision image of the fundus.

[0058] In addition, in this embodiment, the imaging optical system is composed of a lens 612 that realizes light collection and imaging. Therefore, the configuration of the imaging optical system in the fundus imaging device is simplified compared to a configuration having a primary imaging optical system that receives light from the fundus and forms an image of the fundus, and a secondary imaging optical system that re-images the image on the imaging element. As a result, in this embodiment, the entire fundus imaging device can be configured more compactly.

[0059] Second Embodiment Another embodiment of the present invention will be described below. For convenience of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the explanations thereof will not be repeated. Fig. 8 is a diagram showing a schematic configuration of a fundus imaging device according to a second embodiment of the present invention. The fundus imaging device of this embodiment has the same configuration as the first embodiment described above, except for the imaging optical system.

[0060] 8, the imaging optical system in this embodiment is composed of two lenses 821 and 822. These lenses 821 and 822 are supported in a casing or a cylinder through which the subject H can place his / her eye. The lens 821 receives light from the fundus and forms an image of the fundus. The lens 822 re-images the image of the fundus formed by the lens 821 on the CMOS image sensor 622. Thus, in this embodiment, the imaging optical system includes both optical elements constituting the primary imaging optical system and optical elements constituting the secondary imaging optical system.

[0061] As described above, in this embodiment, the imaging optical system is a typical secondary imaging optical system, and this embodiment is advantageous from the viewpoint of forming a high-quality image of the fundus even in the case of a wide angle, as compared with the first embodiment described above.

[0062] Third Embodiment Other embodiments of the present invention will be described below. For convenience of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiments, and the explanations thereof will not be repeated. Fig. 9 is a diagram showing a schematic configuration of a fundus imaging device according to a third embodiment of the present invention. The fundus imaging device of this embodiment has the same configuration as the second embodiment described above, except for the illumination device.

[0063] 9, an illumination device 91 in this embodiment has a light source 911 and a reflecting member 912. A plurality of light sources 911 are arranged around and in the vicinity of an eyeball E of a subject H. For example, a plurality of light sources 911 are arranged around a lens 621 in an imaging optical system near the eyelid of the subject H. The light sources 911 may be arranged at equal intervals on a circle, or may be arranged at appropriate intervals on an asymmetric shape that matches the shape of the human body.

[0064] The reflecting member 912 is a member for reflecting the light from the light source 911 toward the periphery of the eyeball E (e.g., the eyelid, the trans-pars-plana region, etc.), and is, for example, a reflecting mirror that totally reflects the light from the light source 911. The reflecting mirror is also disposed, for example, at a position farther away from the eyeball E than the light source 911, in the periphery or periphery of the lens 621 in the imaging optical system. The illumination device 91 in this embodiment irradiates the light from the light source 911 onto an area having a given shape and area around the pupil. The area is set to 1 cm from the viewpoint of forming a sufficiently clear image of the fundus. 2 It is preferable that the length is 2cm or more. 2 It is more preferable that the above is satisfied. Moreover, it is preferable that the region includes the peripheral portion of the cornea of ​​the eye E to be examined (for example, the iris-Zonule region).

[0065] This embodiment is more advantageous than the above-described embodiment of the present invention in terms of more uniform illumination of the periphery and surroundings of the eyeball E of the subject H. In addition, in this embodiment, the area irradiated with the light from the light source 911 is wide, so the luminance of the light can be reduced. Therefore, this embodiment is more advantageous than the above-described embodiment of the present invention in terms of further reducing the load on the subject H and the eyeball E or preventing the load from occurring even when the light from the light source reaches the fundus through the pupil.

[0066] In this embodiment, instead of the reflecting member, the illumination optical system may be configured using an optical element that refracts the light from the light source 911 to illuminate a desired position around the eyeball E. Alternatively, in this embodiment, the illumination optical system may be configured by combining an optical element that refracts the light from the light source 911 with a reflecting member. Examples of optical elements that refract the light from the light source 911 include a prism and a light flux control member. This configuration also achieves the effects of this embodiment described above.

[0067] Other embodiments The fundus imaging system, fundus imaging device, and optical system according to the embodiments of the present invention may include configurations other than those described above, as long as the effects of the embodiments of the present invention can be obtained.

[0068] For example, the illumination device may be disposed in contact with the subject. Such an illumination device may be composed only of a light source that is in contact with the subject to irradiate light. Alternatively, the illumination device may be configured such that an object side end face of the illumination optical system is in contact with the subject during use. Alternatively, the illumination device may be configured such that a frame supporting the illumination optical system determines the position of the subject's head relative to the illumination optical system during use. This configuration is advantageous from the viewpoint of increasing the stability of the conditions for fundus imaging and from the viewpoint of simplifying the configuration of the fundus imaging device.

[0069] Moreover, the imaging device may not include an eyepiece and may be disposed away from the subject H. This configuration is preferable from the viewpoint of realizing imaging of the fundus without contacting the subject H. Realizing imaging of the fundus without contact allows for simpler examination.

[0070] In addition, in an embodiment of the present invention, the illumination device may be of one type or more, and the fundus imaging device may be configured to be capable of performing either or both of direct illumination and indirect illumination at the same time.

[0071] In addition, in the embodiment of the present invention, the fundus imaging system may further include an addition processing unit that performs processing to add up the light signals detected by the imaging elements and synthesize an image, in addition to controlling fundus imaging. This configuration is advantageous from the viewpoint of obtaining many photon statistics and thus forming a clear fundus image even when the fundus is illuminated with a small amount of light.

[0072] In addition, in an embodiment of the present invention, the fundus imaging system may further include an internal imaging processing unit that performs processing to image the internal structure of the subject H from the light signal detected by the imaging element. Such further processing may be performed by a technique that realizes diffuse optical tomography (DOT). Diffuse optical tomography is a technique that detects diffuse light in a living body and images optical property values ​​in living tissue. As a result, information on the structure and metabolism in a specific area of ​​the living body can be quantitatively detected. In the case where the fundus imaging system further includes the above-mentioned internal imaging processing unit, it is preferable that the fundus imaging device has an illumination device having a plurality of light sources and an illumination optical system. An example of a suitable illumination device includes a configuration in which a plurality of light sources and an illumination optical system are arranged in an instrument that is worn on the head, such as a headband.

[0073] In the embodiments of the present invention, the fundus imaging apparatus may be installed in conjunction with other eye examination equipment such as a visual acuity examination apparatus, and may share some of its configurations. This configuration is advantageous from the viewpoint of further popularizing the fundus imaging apparatus of the embodiments of the present invention.

[0074] Alternatively, in the embodiments of the present invention, the lighting device and the imaging device may be configured to be attachable as accessories to an information device capable of implementing information processing, such as a smartphone. When the information device includes a light and a camera, the camera of the information device may be used as the lighting device in the embodiments of the present invention, as long as the effects of the embodiments of the present invention can be obtained. Also, the camera of the information device may be used as the imaging device in the embodiments of the present invention, as long as the effects of the embodiments of the present invention can be obtained.

[0075] In addition, in the embodiment of the present invention, the fundus imaging system may further include a simple diagnosis processing unit that performs processing to output simple diagnosis information according to the acquired fundus image. Such processing can be realized, for example, by a process of determining abnormality in the eyeball E based on the characteristics of the acquired fundus image, and outputting information recommending a medical examination or a possible disease name according to the determination result. The determination of abnormality and the determination of the disease name can be realized, for example, by machine learning based on image data of a fundus having a specific abnormality. In addition, the determination of abnormality in the eyeball E can be realized, for example, by a process of referring to information on the user's past fundus images and detecting the characteristics of the fundus moving toward an abnormal state and the degree of it.

[0076] The functions of the control unit of the fundus imaging system in an embodiment of the present invention can be realized by a program for causing a computer to function as the control unit, and a program for causing a computer to function as each control block of the control unit (in particular, each of the above-mentioned units that may be included in the control unit).

[0077] In this case, the control unit includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program to realize each function described in each of the above embodiments.

[0078] The program may be non-transitory and may be recorded in one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be provided to the device via any wired or wireless transmission medium.

[0079] In addition, some or all of the functions of each of the control blocks can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention.

[0080] Furthermore, each process described in each of the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may be executed by the control device or another device (for example, an edge computer or a cloud server).

[0081] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the different embodiments are also included in the technical scope of the present invention.

[0082] 〔summary〕 As is clear from the above description, the optical system in the embodiment of the present invention includes an illumination optical system (112) that irradiates light from a light source (111) onto the fundus of the eyeball (E) of a subject (H), and an imaging optical system (122) that forms an image of the fundus on an imaging element (121), and the optical axis of the illumination optical system does not coincide with the optical axis of the imaging optical system, or the illumination optical system does not have a specific optical axis. In addition, the fundus imaging device (10) in the embodiment of the present invention includes an illumination device (11) having a light source and the illumination optical system, and an imaging device (12) having an imaging element and the imaging optical system. Furthermore, the fundus imaging system (50) in the embodiment of the present invention includes the fundus imaging device. Therefore, the embodiment of the present invention can suppress the occurrence of artifacts in fundus observation.

[0083] The illumination optical system may irradiate the fundus with light from the light source through the trans-pars-plana region of the eye (27). This configuration is more effective in preventing the subject from feeling dazzled and in illuminating the fundus more brightly.

[0084] The illumination optical system may also irradiate the fundus with light from the light source through the iris-Zonule region 28 of the eyeball. This configuration is more effective in terms of preventing the subject from feeling dazzled and in terms of illuminating the fundus more brightly.

[0085] The illumination optical system may irradiate the light from the light source onto the tissue surrounding the eyeball of the subject through the eyelids of the subject, which is more effective in preventing the subject from feeling glare and the occurrence of artifacts more reliably.

[0086] The illumination optical system may irradiate the light from the light source onto the tissue surrounding the eyeball through the skull of the subject, which is more effective in terms of brightly illuminating the fundus.

[0087] The illumination optical system may irradiate the light from the light source onto the tissue surrounding the eyeball through a plurality of points on the skull of the subject, which is more effective in terms of brightly illuminating the fundus.

[0088] The illumination optical system may irradiate light from the light source onto the tissue surrounding the eyeball through the ethmoid bone of the subject, which is more effective in terms of brightly illuminating the fundus from below or behind the eyeball.

[0089] The illumination optical system may irradiate the fundus with light from the light source through an arc-shaped area 31 or an annular area 41 around the eye on the face of the subject, which is more effective in terms of brightly illuminating the fundus.

[0090] The wavelength of the light from the light source may be 600 to 1600 nm. This configuration is more effective from the viewpoint of suppressing the miosis reaction caused by the irradiation of light from the light source and from the viewpoint of suppressing the attenuation of the irradiated light due to absorption by water in the living body.

[0091] The illumination device may be disposed in contact with the subject, which is more effective from the viewpoint of improving the stability of the conditions for fundus imaging and from the viewpoint of simplifying the configuration of the fundus imaging apparatus.

[0092] The imaging device may be located away from the subject, which is even more effective in terms of realizing non-contact imaging of the fundus with respect to the subject.

[0093] The fundus imaging system according to the embodiment of the present invention may further include a process for synthesizing an image by adding up the light signals detected by the imaging elements. This configuration is even more effective in terms of obtaining a large number of photon statistics.

[0094] The fundus imaging system according to the embodiment of the present invention may further include a process for imaging an internal structure of the subject from the optical signal detected by the imaging element, which is even more effective in terms of enabling measurement by diffuse optical tomography to be performed. [Explanation of symbols]

[0095] 10, 60 Fundus imaging device 11, 61, 91 Lighting equipment 12, 62 Imaging device 21 Cornea 22 Iris 23 crystalline lens 24 Frenulum of the Chin 25 Vitreous Humor 26 Retina 27 trans-pars-plana region 28 Iris-Zonule Region 31 Arc-shaped area 41 Circular Region 50 Fundus Imaging System 51 Control section 52 Storage section 53 Input Devices 54 Output Device 63 Monitor 111, 911 light source 112 Illumination optical system 121 Image sensor 122 Imaging Optical System 611 LED 612, 621, 821, 822 Lenses 622 CMOS Image Sensor 912 Reflective material E Eyeball H. Subject LA1~LA5 Arrows showing optical axis

Claims

1. an illumination optical system that irradiates light from a light source onto a fundus of an eye of a subject; an imaging optical system that forms an image of the fundus on an imaging element; the optical axis of the illumination optical system does not coincide with the optical axis of the imaging optical system, or the illumination optical system is asymmetric or non-imaging and does not have a specific optical axis; The illumination optical system is an optical system that irradiates the fundus with light from the light source via one or more regions selected from the group consisting of the iris-Zinn's zonule region of the eyeball, multiple locations on the subject's skull, the subject's ethmoid bone, an arc-shaped or annular region in the iris-Zinn's zonule region of the eyeball, an arc-shaped or annular region on the subject's eyelid, and a region with an area irradiated with light of 2 cm2 or more.

2. An illumination optical system that irradiates light from a light source onto the fundus of a subject's eye; an imaging optical system that forms an image of the fundus on an imaging element; the optical axis of the illumination optical system does not coincide with the optical axis of the imaging optical system, or the illumination optical system is asymmetric or non-imaging and does not have a specific optical axis; The illumination optical system is an optical system that irradiates the fundus through an arc-shaped or annular region in the trans-pars-planar region of the eyeball, the area of ​​which is irradiated with light having an area of ​​2 cm 2 or more.

3. 3. The optical system according to claim 1, wherein the wavelength of the light from the light source is 600 to 1600 nm.

4. An illumination device having a light source and an illumination optical system according to any one of claims 1 to 3; A fundus imaging apparatus comprising: an imaging device having an imaging element and the imaging optical system according to any one of claims 1 to 3.

5. The fundus imaging apparatus according to claim 4 , wherein the illumination device is disposed in contact with the subject.

6. The fundus imaging apparatus according to claim 4 , wherein the imaging device is disposed away from the subject.

7. A fundus imaging system comprising the fundus imaging device according to any one of claims 4 to 6.

8. The fundus imaging system according to claim 7 , further comprising a process for synthesizing an image by adding up the light signals detected by the imaging elements.

9. The fundus imaging system according to claim 7 or 8, further comprising a process for imaging an internal structure of the subject from a light signal detected by the imaging element.

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