Fundus photography device

Abstract

A fundus photography device comprises: a light source; a scanning unit that performs two-dimensional scanning on light emitted from the light source by driving a reflecting mirror in two axes in the horizontal direction and the vertical direction; an optical system that allows the light reflected by the reflecting mirror of the scanning unit to enter the eye of a subject; and a light detector that detects the light reflected by the retina of the subject, wherein the outer diameter of the reflecting mirror of the scanning unit is greater than 1.7 mm and less than 2.0 mm.

Description

Technical Field

[0001] The invention relates to a fundus photography device. Background Art

[0002] A scanning laser ophthalmoscope (SLO) is known, which scans light at high speed to illuminate the retina of a subject and acquires a fundus image by detecting reflected light from the retina using a photodetector. Conventionally, a combination of a polygon mirror and a galvano-mirror is used for scanning light. In addition, for miniaturization and cost reduction, a MEMS (Micro Electro Mechanical System) that uses a 2-axis drive to perform two-dimensional scanning of light is proposed to replace the polygon mirror and the galvanomirror (for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application No. 2016-510628 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, it is known that it is difficult to obtain a high-quality fundus image simply by replacing the polygon mirror and the galvano mirror with a scanning unit such as a two-axis driven MEMS.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a fundus imaging device capable of acquiring a high-quality fundus image.

[0009] Means for solving problems

[0010] The fundus photography device of the present invention comprises: a light source; a scanning unit, which performs two-dimensional scanning on the light emitted from the light source by driving a reflecting mirror in two axes in the horizontal direction and the vertical direction; an optical system, which makes the light reflected by the reflecting mirror of the scanning unit incident on the eye of the subject; and a light detector, which detects the light reflected by the retina of the subject, and the outer diameter of the reflecting mirror of the scanning unit is greater than 1.7 mm and less than 2.0 mm.

[0011] In the above configuration, the optical system may have an optical magnification of 0.8 times or more and 1.2 times or less.

[0012] In the above configuration, the scanning unit may have a horizontal resonance frequency of 6 kHz or more and 12 kHz or less.

[0013] In the above configuration, a mechanical deflection angle of at least one of a horizontal direction and a vertical direction of the scanning unit may be set to a half angle of not less than 13 degrees and not more than 16 degrees.

[0014] In the above configuration, the scanning unit may be a MEMS.

[0015] In the above structure, it can be set as follows: the scanning unit is MEMS, the optical magnification of the optical system is greater than 0.8 times and less than 1.2 times, the resonant frequency of the scanning unit in the horizontal direction is greater than 6 kHz and less than 12 kHz, and the mechanical deflection angle of at least one of the horizontal and vertical directions of the scanning unit is greater than 13 degrees and less than 16 degrees at half angle.

[0016] In the above structure, it can be set as follows: the optical system includes an optical element, which converts the incident light rays whose optical axes diffuse with each other and each light ray is diffused light into light rays whose optical axes converge with each other and each light ray is approximately parallel light, and the light rays reflected by the reflector of the scanning unit become diffused light after being converged between the scanning unit and the optical element and are incident on the optical element, and are converted into approximately parallel light by the optical element and are incident on the eye of the subject.

[0017] In the above structure, it can be set as follows: the optical system includes: a first optical element, which converts the incident light whose optical axes diffuse and each light is approximately parallel light into a light whose optical axes are approximately parallel and each light is converging light; and a second optical element, which converts the light emitted from the first optical element into a light whose optical axes converge and each light is approximately parallel light, the light reflected by the reflector of the scanning unit is incident on the first optical element as approximately parallel light, and after being focused between the first optical element and the second optical element, it becomes diffuse light and is incident on the second optical element, and is converted into approximately parallel light by the second optical element and is incident on the eye of the subject.

[0018] The above configuration may include: a signal processing unit that processes an output signal from the photodetector; and an image generating unit that generates a fundus image of the subject based on the signal processed by the signal processing unit.

[0019] Effects of the Invention

[0020] According to the present invention, a fundus image with high image quality can be acquired. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a block diagram of the fundus imaging device of the first embodiment.

[0022] Figure 2 1 is a diagram showing an optical system of the fundus imaging device according to Example 1.

[0023] Figure 3 This is a diagram illustrating the scanning of light rays.

[0024] Figure 4 (a) is a three-dimensional diagram of the scanning unit. Figure 4 (b) is a magnified stereoscopic image of the vicinity of the reflector.

[0025] Figure 5 1 is a diagram showing an optical system of a fundus imaging device according to a comparative example.

[0026] Figure 6 This is a diagram showing the relationship between the diameter of a light ray incident on the cornea and the diameter of the light ray on the retina.

[0027] Figure 7 : is a graph which shows the relationship between the outer diameter of the reflection mirror of the scanning part and the horizontal resonance frequency of the scanning part.

[0028] Figure 8 (a) to Figure 8 (d) is a diagram showing simulation results regarding deformation of the reflection mirror of the scanning unit.

[0029] Fig. 9 1 is a diagram showing an optical system of a fundus imaging device according to Example 2.

[0030] Fig.10 1 is a diagram showing an optical system of a fundus imaging device according to a third embodiment. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0032] Example 1

[0033] Figure 1 1 is a block diagram of a fundus imaging device according to Embodiment 1. Figure 1 The fundus imaging device 100 includes a projection unit 10, a control unit 30, a photodetector 40, and a display unit 50. The projection unit 10 includes a light source 11, an adjustment mechanism 12, a scanning unit 13, an optical system 14, and a driving circuit 15. The control unit 30 includes a driving control unit 31, a signal processing unit 32, and an image generating unit 33.

[0034] The drive control unit 31 generates a control signal for controlling the light beam irradiated to the retina of the subject. The drive circuit 15 drives the light source 11 and the scanning unit 13 based on the control signal of the drive control unit 31 .

[0035] The light source 11 emits invisible light such as infrared laser light with a wavelength of about 785 nm to 1.4 μm. The light source 11 may also emit visible light such as red laser light (wavelength: about 610 nm to 660 nm), green laser light (wavelength: about 515 nm to 540 nm) and / or blue laser light (wavelength: about 440 nm to 480 nm).

[0036] The adjustment mechanism 12 includes a collimating lens, a toric lens and / or an aperture, etc., and shapes the light 60 emitted from the light source 11. The light 60 is, for example, an infrared laser, a red laser, a green laser or a blue laser.

[0037] The scanning unit 13 is a scanner that performs two-dimensional scanning of the light 60 by driving a reflection mirror in a two-axis swing. The light 60 is scanned in the horizontal direction (main scanning direction) and the vertical direction (sub-scanning direction) by the scanning unit 13. The scanning unit 13 is, for example, a MEMS (Micro Electro Mechanical System).

[0038] The optical system 14 irradiates the light beam 60 scanned by being reflected by the reflection mirror of the scanning unit 13 to the eye 70 of the subject.

[0039] The photodetector 40 is a photodetector such as an avalanche photodiode, and detects the reflected light 61 that is reflected by the retina of the subject's eye 70 and passes through the optical system 14, the scanning unit 13, and the adjustment mechanism 12. The photodetector 40 starts detection at the time when the light source 11 emits the light 60 based on the synchronization signal from the drive circuit 15.

[0040] The signal processing unit 32 processes the output signal of the photodetector 40 based on the control signal from the drive control unit 31. The signal processing unit 32 starts processing based on the synchronization signal from the drive circuit 15 at the time when the light source 11 emits the light beam 60.

[0041] The image generation unit 33 generates a fundus image based on the signal processed by the signal processing unit 32. The display unit 50 is, for example, a liquid crystal display, and displays the fundus image generated by the image generation unit 33.

[0042] The drive control unit 31, the signal processing unit 32, and the image generation unit 33 may be processed by a processor such as a CPU (Central Processing Unit) in cooperation with a program. The drive control unit 31, the signal processing unit 32, and the image generation unit 33 may also be specially designed circuits. The drive control unit 31, the signal processing unit 32, and the image generation unit 33 may be one circuit or different circuits.

[0043] Figure 2 2 is a diagram showing an optical system of a fundus imaging device according to Embodiment 1. Figure 2 The light 60 emitted from the light source 11 is converted from diffuse light to substantially parallel light by the collimating lens 20, and then passes through the semi-transparent mirror 21, the diopter adjustment lens 22, and the diopter adjustment lens 23 to enter the reflector 24. The light 60 becomes convergent light and enters the reflector 24. The light 60 is reflected by the reflector 24 and enters the scanning unit 13, and is reflected by the scanning unit 13, thereby being two-dimensionally scanned.

[0044] The light 60 that has been two-dimensionally scanned by the reflection of the scanning unit 13 passes through the projection lens 25 and enters the eye 70 of the subject. The optical axes of the light 60 scanned by the scanning unit 13 are mutually diffused, and each light 60 is a converging light until the focus 62. Each light 60 enters the projection lens 25 as diffused light. The projection lens 25 converts the light 60 whose optical axes are mutually diffused by the reflection of the scanning unit 13 in different directions into the light 60 whose optical axes are mutually converging, and converts each light 60 from diffused light into approximately parallel light, and makes it enter the eye 70 of the subject. The light 60 passes through the pupil 71 and converges in the lens 72 or near the lens 72, and passes through the vitreous body 73 and is approximately focused on the retina 74. That is, the light 60 is irradiated to the retina 74 of the subject using Maxwell vision. The so-called approximately parallel means that the light 60 is approximately parallel to the extent that it can be approximately focused on the retina 74 (the same applies below). The projection lens 25 is a convex lens, and the optical magnification is 0.8 times or more and 1.2 times or less, which will be described later. The optical magnification is a value expressed by the ratio of the distance between the projection lens 25 and the reflector of the scanning unit 13 to the distance between the projection lens 25 and the lens 72 of the subject or the convergence position of the light 60 near the lens 72.

[0045] The light 60 is reflected by the retina 74 of the subject. The reflected light 61 reflected by the retina 74 returns in the order of the projection lens 25, the scanning unit 13, the reflector 24, the diopter adjustment lens 23, and the diopter adjustment lens 22 in the optical path of the light 60 toward the retina 74, is reflected by the half mirror 21, passes through the condenser lens 26, and enters the photodetector 40. The photodetector 40 detects the reflected light 61 reflected by the retina 74. The image generation unit 33 generates a fundus image based on the signal processed by the signal processing unit 32 on the detection result of the brightness change of the reflected light 61 of the photodetector 40.

[0046] The collimating lens 20, the diopter adjustment lens 22 and the diopter adjustment lens 23 are equivalent to Figure 1 The projection lens 25 is equivalent to the adjustment mechanism 12 in FIG. Figure 1 The optical system 14 in.

[0047] Figure 3 This is a diagram illustrating the scanning of light rays. Figure 3 , the scanning unit 13 performs raster scanning of the light 60 from the upper left to the lower right as shown by arrow 65. In raster scanning, the horizontal direction is the main scanning direction and the vertical direction is the sub-scanning direction. For example, the number of scanning lines is 640. If the light source 11 does not emit the light 60 even if the reflector of the scanning unit 13 is driven by two-axis swing, the light 60 will not irradiate the retina 74. For example, in Figure 3 The light 60 is not emitted at the dotted arrow 65. The drive circuit 15 synchronizes the emission of the light 60 from the light source 11 with the two-axis oscillation drive of the scanning unit 13. Thus, the light source 11 emits the light 60 at the solid arrow 65.

[0048] Figure 4 (a) is a three-dimensional diagram of the scanning unit. Figure 4 (b) is a perspective view of the vicinity of the reflector of the scanning unit, which is enlarged. Figure 4 (a) and Figure 4 (b), the scanning unit 13 is, for example, a MEMS, and includes an outer frame 80, a suspension 81, an inner frame 82, a piezoelectric unit 83, and a reflector 84. The inner frame 82 is fixed to the outer frame 80 via the suspension 81. The piezoelectric unit 83 is formed in a structure in which a piezoelectric film such as a PZT film is sandwiched by upper and lower electrodes, and is fixed to the inner frame 82 by four first torsion bars 85 arranged at intervals of 90 degrees. The reflector 84 is fixed to the piezoelectric unit 83 by two second torsion bars 86 arranged at intervals of 180 degrees.

[0049] The scanning unit 13 transmits the warping motion generated by applying voltage to the piezoelectric unit 83 to the reflector 84 through the second torsion bar 86, thereby driving the reflector 84 in a two-axis swing. As a result, the light 60 is incident on the reflector 84, and the light 60 is scanned in two-dimensional directions. Figure 4 (a) and Figure 4 In (b), a piezoelectric MEMS is shown as an example, but the scanning unit 13 may be a capacitive MEMS or other types.

[0050] The peripheral area of ​​the reflector 84 is curved (collapsed) for manufacturing reasons. Therefore, if the light 60 is reflected in the entire area including the peripheral area of ​​the reflector 84, it is difficult to reflect the light 60 only in the desired direction. Therefore, in order to reflect the light 60 well, the light 60 is reflected in the area closer to the inner side than the curved peripheral area of ​​the reflector 84. That is, the area other than the curved peripheral area in the reflector 84 becomes an effective area that can reflect the light 60 well. Therefore, the effective diameter as the length of the effective area of ​​the reflector 84 becomes the size obtained by subtracting the length of the curved peripheral area from the length of the reflector 84. For example, when the reflector 84 is circular and the bend is generated within a range of 0.1mm from the end of the reflector 84, the effective diameter of the reflector 84 becomes the size obtained by subtracting 0.2mm from the diameter as the outer diameter of the reflector 84. In addition, when the reflector 84 is elliptical, the effective diameter of the reflector 84 becomes the size obtained by subtracting the length of the curved peripheral area from the short diameter as the outer diameter. The outer diameter of the reflector 84 is greater than or equal to 1.7 mm and less than or equal to 2.0 mm, and the effective diameter is greater than or equal to 1.5 mm and less than or equal to 1.8 mm, which will be described later.

[0051] Figure 5 2 is a diagram showing an optical system of a fundus imaging device according to a comparative example. Figure 5 In the fundus photographing device 500 of the comparative example, a combination of a polygon mirror 513a and a galvano mirror 513b is used to perform two-dimensional scanning of the light 60. The polygon mirror 513a scans the light 60 in the horizontal direction (main scanning direction), for example, and the galvano mirror 513b scans the light 60 in the vertical direction (sub-scanning direction), for example. In the fundus photographing device 500, the optical magnification of the projection lens 525 is 2.5 times. The optical magnification is a value expressed by the ratio of the distance between the projection lens 525 and the polygon mirror 513a and the galvano mirror 513b to the distance between the projection lens 525 and the lens 72 of the subject or the convergence position of the light 60 near the lens 72. The other structures are the same as those of the fundus photographing device 100 of Example 1, and therefore the description thereof is omitted.

[0052] In the comparative example fundus photography device 500, the optical magnification of the projection lens 525 is 2.5 times for the following reason. When the retina 74 is irradiated with light 60 to obtain a fundus image, in order to find the peripheral diseased part, a field of view of a full angle of 60 degrees or more is required. That is, the angle θ at which the light 60 converges at the convergence point in the eye 70 is required to be 60 degrees or more. However, when the polygon mirror 513a and the galvanometer mirror 513b are used, it is difficult for the galvanometer mirror 513b in particular to scan the light 60 at a large angle. Therefore, in the comparative example fundus photography device 500 using the polygon mirror 513a and the galvanometer mirror 513b, the optical magnification of the projection lens 525 is 2.5 times, so that the field of view when the fundus image is obtained is about 60 degrees.

[0053] The fundus photographing device 500 using the polygon mirror 513a and the galvano mirror 513b is large and expensive. Therefore, it is considered to use a scanning unit 13 that performs two-dimensional scanning of the light 60 by a two-axis swing drive instead of the polygon mirror 513a and the galvano mirror 513b, but the inventors have found that it is difficult to obtain a high-quality fundus image simply by directly arranging the scanning unit 13 at the position of the polygon mirror 513a and the galvano mirror 513b. This is described below.

[0054] In the fundus photography device, in order to ensure the resolution on the retina and the SN ratio of the fundus image, it is necessary to irradiate about 450 light beams 60 without interference in the entire width of about 11 mm on the retina corresponding to a field angle of 45 degrees (full angle). In other words, it is required to set the spot diameter (diameter) of the light beam 60 on the retina 74 to 25 μm or less. Figure 6 : is a diagram showing the relationship between the diameter of a light ray incident on the cornea and the diameter of the light ray on the retina. Figure 6 , the larger the diameter of the light 60 when incident on the cornea, the smaller the diameter of the light 60 on the retina 74. It can be seen that by making the diameter of the light 60 when incident on the cornea be 1.25 mm or more, the diameter of the light 60 on the retina 74 (spot diameter) can be made less than 25 μm. The larger the diameter of the light 60 when incident on the cornea, the smaller the diameter of the light 60 on the retina 74. This is because there is a lens 72 on the retina side of the cornea, and the cornea and the lens 72 act as a convex lens and have the optical characteristics of positive focusing power. This is because, if the diameter of the light 60 incident here is larger, the focusing power becomes larger, and the spot diameter on the retina 74 becomes smaller. On the contrary, if the diameter of the incident light 60 is smaller, the focusing power becomes smaller, it is difficult to focus, and the spot diameter on the retina 74 cannot be completely reduced.

[0055] In the fundus photography device 500 of the comparative example, the optical magnification of the projection lens 525 is 2.5 times, so when the scanning unit 13 is directly arranged at the position of the polygon mirror 513a and the galvano mirror 513b, in order to make the diameter of the light 60 incident on the cornea be 1.25 mm or more, it is necessary to make the effective diameter of the mirror 84 of the scanning unit 13 be 3.2 mm or more. However, it is not realistic to set the effective diameter of the mirror 84 of the scanning unit 13 to be 3.2 mm or more. This is due to the following reasons.

[0056] Figure 7 : is a graph showing the relationship between the outer diameter of the reflective mirror of the scanning unit and the horizontal resonance frequency of the scanning unit. Figure 7 , the larger the outer diameter of the reflector 84 of the scanning unit 13, the lower the horizontal resonance frequency of the scanning unit 13. This is because the larger the outer diameter of the reflector 84 of the scanning unit 13, the greater the inertia, the greater the deformation of the reflector 84, and therefore the horizontal resonance frequency cannot be increased. In the case where the difference between the outer diameter and the effective diameter of the reflector 84 is 0.2 mm, when the outer diameter of the reflector 84 is 1.6 mm, the horizontal resonance frequency can be about 12 kHz, when it is 1.7 mm, the horizontal resonance frequency can be about 10 kHz, when it is 1.8 mm, the horizontal resonance frequency can be about 9 kHz, and when it is 2.0 mm, the horizontal resonance frequency can be about 6 kHz. Assuming that the scanning unit 13 is a circular MEMS, the value of the difference between the outer diameter and the effective diameter of the reflector 84 is set to 0.2 mm, but this value may be different depending on the characteristics of the MEMS.

[0057] When acquiring a fundus image by irradiating light 60 to the retina 74 through raster scanning, in order to obtain a high-quality fundus image, it is required to set the number of scanning lines to 640 or more and the frame rate to 15fps or more. In order to set the frame rate to 15fps in raster scanning with 640 scanning lines, it is necessary to set the horizontal resonance frequency of the scanning unit 13 to 6kHz or more. Figure 7 In order to make the horizontal resonance frequency of the scanning unit 13 be 6 kHz or more, the outer diameter of the reflector 84 of the scanning unit 13 needs to be 2.0 mm or less (the effective diameter of the reflector 84 is 1.8 mm or less). Therefore, it is not realistic to set the effective diameter of the reflector 84 of the scanning unit 13 to be 3.2 mm or more in order to obtain the resonance frequency required by the fundus photography device.

[0058] The deformation of the reflection mirror 84 of the scanning unit 13 was simulated when the outer diameter of the reflection mirror 84 of the scanning unit 13 was 1.6 mm, the mechanical deflection angle was 14.6 degrees at a half angle, and the horizontal resonance frequency was 12 kHz. Figure 8 (a) to Figure 8 (d) is a diagram showing simulation results regarding deformation of the reflection mirror of the scanning unit. Figure 8 (a) is a diagram showing the reflector 84 as viewed from above. Figure 8 (b) is a diagram showing the reflector 84 as viewed from the front. Figure 8 (c) is a diagram showing the reflecting mirror 84 as viewed from an oblique direction. Figure 8 (d) means Figure 8 (a) is a diagram of the deformation between AA. Figure 8 (a) to Figure 8 In (c), the portions with small deformation amounts are indicated by thick hatching, and the portions with large deformation amounts in the positive and negative directions are indicated by dense hatching.

[0059] like Figure 8 (a) to Figure 8 As shown in (d), when the outer diameter of the reflector 84 is 1.6 mm, the mechanical deflection angle is 14.6 degrees, and the horizontal resonance frequency is 12 kHz, a high-order deformation mode is generated in the reflector 84, and the maximum deformation amount is about ±100 nm. It is believed that such a high-order deformation mode is larger as the outer diameter of the reflector 84 is larger. Therefore, if the effective diameter of the reflector 84 is set to more than 3.2 mm, it is believed that the optical performance is hindered by the high-order deformation mode generated in the reflector 84, and it is unrealistic to set the effective diameter of the reflector 84 to more than 3.2 mm. In addition, if the effective diameter of the reflector 84 is set to more than 3.2 mm, it is considered that a large deflection angle cannot be obtained due to the increase in air resistance. Therefore, in this regard, it is also unrealistic to set the effective diameter of the reflector 84 to more than 3.2 mm.

[0060] When the scanning unit 13 that performs two-dimensional scanning of the light 60 by two-axis swing driving is used as in the fundus imaging device 100 of the first embodiment, the scanning angle θ1 of the light 60 can be increased compared with the case of using the polygon mirror 513a and the galvano mirror 513b (see Figure 2 In this case, even when the optical magnification of the projection lens 25 is 0.8 or more and 1.2 or less, the convergence angle θ2 of the light 60 at the convergence point in the eye 70 (see Figure 2 ) also becomes larger, so that the field of view angle when acquiring the fundus image can be about 60 degrees. In this case, by making the effective diameter of the reflector 84 of the scanning unit 13 larger than 1.5 mm (the outer diameter is larger than 1.7 mm), the spot diameter of the light 60 on the retina 74 can be made smaller than 25 μm.

[0061] According to Embodiment 1, the outer diameter of the reflector 84 of the scanning unit 13 is greater than or equal to 1.7 mm and less than or equal to 2.0 mm. By making the outer diameter of the reflector 84 greater than or equal to 1.7 mm (the effective diameter is, for example, greater than or equal to 1.5 mm), the spot diameter of the light 60 on the retina 74 can be made less than or equal to 25 μm, and the resolution on the retina 74 and the SN ratio of the fundus image can be ensured. By setting the outer diameter of the reflector 84 to less than or equal to 2.0 mm (the effective diameter is, for example, less than or equal to 1.8 mm), a raster scan with more than 640 scanning lines and a frame rate of more than 15 fps can be performed. Therefore, a high-quality fundus image can be obtained. In addition, since the diameter of the light 60 when incident on the cornea is less than or equal to 2.5 mm, and the pupil diameter of a person is generally about 2 mm to 8 mm, even if there is no mydriasis, it is almost not blocked by the iris, and a fundus image can be obtained. The outer diameter of the reflector 84 can be 1.8 mm to 2.0 mm, 1.7 mm to 1.9 mm, or 1.8 mm to 1.9 mm. That is, the effective diameter of the reflector 84 can be 1.6 mm to 1.8 mm, 1.5 mm to 1.7 mm, or 1.6 mm to 1.7 mm.

[0062] Since the scanning unit 13 can increase the scanning angle θ1, even if the optical magnification of the projection lens 25 (optical system) is 0.8 times or more and 1.2 times or less, the field of view angle of about 60 degrees can be achieved when acquiring the fundus image. In this case, by making the outer diameter of the reflector 84 of the scanning unit 13 greater than 1.7 mm (the effective diameter is, for example, greater than 1.5 mm), the spot diameter of the light 60 on the retina 74 can be less than 25 μm. The optical magnification of the projection lens 25 (optical system) can be greater than 0.8 times and less than 1.1 times, or greater than 0.9 times and less than 1.2 times, or greater than 0.9 times and less than 1.1 times, or 1.0 times.

[0063] When the light 60 two-dimensionally scanned by the scanning unit 13 is irradiated onto the retina 74 to acquire a fundus image, in order to obtain a high-quality fundus image, the horizontal resonance frequency (the resonance frequency in the main scanning direction) of the reflector 84 of the scanning unit 13 is preferably 6 kHz or more, more preferably 7 kHz or more, and even more preferably 8 kHz or more. In order to prevent the high-order deformation mode generated in the reflector 84 from becoming larger and causing an obstacle to the optical performance, the horizontal resonance frequency of the reflector 84 of the scanning unit 13 is preferably 12 kHz or less, more preferably 10 kHz or less, and even more preferably 9 kHz or less.

[0064] In order to achieve a field of view of about 60 degrees when acquiring a fundus image, the mechanical deflection angle of at least one of the horizontal and vertical directions, preferably both directions, of the reflector 84 of the scanning unit 13 is preferably 13 degrees or more at a half angle, more preferably 13.5 degrees or more, and even more preferably 14 degrees or more. Taking into account air resistance and deformation of the reflector 84, etc., the mechanical deflection angle of at least one of the horizontal and vertical directions, preferably both directions, of the reflector 84 of the scanning unit 13 is preferably 16 degrees or less at a half angle, more preferably 15.5 degrees or less, and even more preferably 15 degrees or less.

[0065] The projection lens 25 (optical element) converts the light 60 reflected in different directions by the scanning unit 13 and having mutually diffused optical axes into the light 60 having mutually converged optical axes, and converts each light 60 from diffused light into substantially parallel light. The light 60 is concentrated between the scanning unit 13 and the projection lens 25 to become diffuse light and enter the projection lens 25, and is converted into substantially parallel light by the projection lens 25 and enters the eye 70 of the subject. When the optical system 14 is composed of such a projection lens 25, the fundus photography device 100 can be miniaturized.

[0066] Example 2

[0067] Fig. 9 2 is a diagram showing an optical system of a fundus imaging device according to Embodiment 2. Fig. 9 In the fundus photography device 200 of Example 2, the optical system 14 that irradiates the light 60 reflected by the scanning unit 13 to the eye 70 of the subject includes a projection lens 27a (first optical element) and a projection lens 27b (second optical element). The projection lens 27a converts the light 60 reflected by the scanning unit 13 in different directions and whose optical axes diffuse to each other into light 60 whose optical axes are approximately parallel to each other, and converts each light 60 from approximately parallel light to convergent light. That is, the multiple light rays 60 reflected by the scanning unit 13 in multiple different directions become approximately parallel to each other through the projection lens 27a. The projection lens 27b converts the light 60 emitted from the projection lens 27a into light 60 whose optical axes converge to each other, and converts each light 60 from diffuse light to approximately parallel light. The light 60 enters the projection lens 27a as substantially parallel light, is focused between the projection lens 27a and the projection lens 27b, becomes diffuse light, and enters the projection lens 27b, is converted into substantially parallel light by the projection lens 27b, and enters the subject's eye 70. The other structures are the same as those of the fundus photography device 100 of the first embodiment, and therefore the description thereof is omitted.

[0068] When the optical system 14 includes the projection lens 27a (first optical element) and the projection lens 27b (second optical element) as in the fundus photography device 200 of Example 2, the optical magnification of the optical system 14 can be easily achieved to be greater than 0.8 times and less than 1.2 times.

[0069] Example 3

[0070] Fig.10 2 is a diagram showing an optical system of a fundus imaging device according to Embodiment 3. Fig.10 In the fundus photographing device 300 of the third embodiment, in the optical system 14 for irradiating the light 60 reflected by the scanning unit 13 to the eye 70 of the subject, in addition to the projection lens 525, a converter lens 28 is included between the scanning unit 13 and the projection lens 525, and the scanning unit 13 as a MEMS is used instead of Figure 5 The other structures are the same as those of the fundus imaging device 500 of the comparative example, and thus the description thereof is omitted.

[0071] In the structure of the third embodiment, by providing the converter lens 28 between the scanning unit 13 and the projection lens 525, even when the polygon mirror 513a and the galvano mirror 513b are replaced by the scanning unit 13 which is a MEMS, it is possible to configure the fundus imaging device without replacing the projection lens 525. The projection lens 525 is Figure 5 The projection lens used in the comparative example is used in scanning based on a polygon mirror and a galvano mirror.

[0072] In the first to third embodiments, the scanning unit 13 that performs two-axis driving to two-dimensionally scan the light beam 60 is exemplified as a MEMS, but the scanning unit 13 may be other than a MEMS.

[0073] As mentioned above, although the embodiment of the present invention is described in detail, the present invention is not limited to this specific embodiment, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. A fundus photography device, comprising: light source; A scanning unit, the scanning unit is a MEMS that performs two-dimensional scanning of the light emitted from the light source by driving a reflection mirror in two axes in the horizontal direction and the vertical direction; an optical system that causes the light reflected by the reflective mirror of the scanning unit to enter an eye of a subject; as well as a light detector that detects the light reflected by the retina of the subject, The outer diameter of the reflective mirror of the scanning unit is greater than or equal to 1.7 mm and less than or equal to 2.0 mm, The effective diameter of the reflector of the scanning unit is greater than 1.5 mm. The optical magnification of the optical system is 0.8 times or more and 1.2 times or less, The resonant frequency of the scanning unit in the horizontal direction is greater than or equal to 6 kHz and less than or equal to 12 kHz.

2. The fundus photography device according to claim 1, wherein: A mechanical deflection angle of at least one of a horizontal direction and a vertical direction of the scanning unit has a half angle of not less than 13 degrees and not more than 16 degrees.

3. The fundus photography device according to claim 1 or 2, wherein: The diameter of the light beam when incident on the eye of the subject is 1.25 mm or more.

4. The fundus photography device according to claim 1 or 2, wherein: The fundus photography device comprises: a signal processing unit that processes an output signal from the photodetector; and An image generating unit generates a fundus image of the subject based on the signal processed by the signal processing unit.

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