JP6720653B2 - Ophthalmic imaging device - Google Patents

Description

The present disclosure relates to ophthalmic imaging equipment for obtaining a front image of the eye.

2. Description of the Related Art Conventionally, an ophthalmologic photographing apparatus that photographs a front image of an eye to be inspected has been known. For example, as in Patent Document 1, a lens system (refractive system) is applied to an objective optical system of a fundus imaging apparatus, which is a type of ophthalmologic imaging apparatus, and illumination light is applied to the fundus and reception of fundus reflected light is performed. In both of these cases, there is known a device for taking an image through an objective optical system including a lens system.

JP, 2016-28687, A

Here, in an apparatus in which a lens system is applied to the objective optical system, when an attempt is made to obtain a front image of the eye to be inspected, a reflected image due to reflection on the lens surface of the objective optical system may be included in the captured image. It is possible.

The present disclosure has been made in view of the problems of the prior art, and an object to provide an ophthalmic photographing equipment can be obtained satisfactorily front image of the eye.

An ophthalmologic imaging apparatus according to a first aspect of the present disclosure, an objective lens system including at least one lens, an irradiation optical system that illuminates illumination light emitted from a light source to an eye to be inspected through the objective lens system, A light-receiving optical system including a light-receiving element that receives reflected light of the illumination light from the eye to be inspected through the objective lens system; An ophthalmologic imaging device to generate, front image capturing means for obtaining a front image of the subject's eye as the captured image, and a background image for the front image of the subject's eye acquired by the front image capturing means, at least the A background image acquisition unit that acquires a background image including a reflection image by the objective lens system, performs a background difference based on the front image of the eye to be examined and the background image, and as a difference image, the reflection in the front image of the eye to be examined. Image processing means for generating an image in which the influence of an image is suppressed , wherein the front image capturing means is a first illumination light which is an illumination light of a first wavelength, and a second illumination light different from the first wavelength. Second illumination light having a wavelength is irradiated from the irradiation optical system onto the eye to be inspected, and a first front image of the eye to be inspected based on reflected light of the first illumination light and reflection of the second illumination light. A second front image of the eye to be inspected based on light is photographed, and the background image acquisition unit is configured to generate a first background image based on the first illumination light and a background image based on the second illumination light. A certain second background image, and the image processing means obtains a first difference image based on the first front image and the first background image, and the second front image and the second background image. And a second difference image based on the above are combined to obtain a combined difference image.
An ophthalmologic imaging apparatus according to a second aspect of the present disclosure, an objective lens system including at least one lens, an irradiation optical system for irradiating illumination light emitted from a light source to an eye to be inspected through the objective lens system, A light-receiving optical system including a light-receiving element that receives reflected light of the illumination light from the eye to be inspected through the objective lens system; An ophthalmologic imaging device to generate, front image capturing means for obtaining a front image of the subject's eye as the captured image, and a background image for the front image of the subject's eye acquired by the front image capturing means, at least the A background image acquisition unit that acquires a background image including a reflection image by the objective lens system, performs a background difference based on the front image of the eye to be examined and the background image, and as a difference image, the reflection in the front image of the eye to be examined. Image processing means for generating an image in which the influence of an image is suppressed, wherein the front image capturing means is a first illumination light which is an illumination light of a first wavelength, and a second illumination light different from the first wavelength. Second illumination light having a wavelength is irradiated onto the eye to be inspected from the irradiation optical system, and a first front image based on the reflected light of the first illumination light and a reflected light of the second illumination light are used. A second front image is photographed, and the background image acquisition means includes a first background image that is a background image based on the first illumination light and a second background image that is a background image based on the second illumination light. And a background image based on a first combined image of the first front image and the second front image, and a combined image of the first background image and the second background image. A synthetic difference image is obtained by the difference.
An ophthalmologic imaging apparatus according to a third aspect of the present disclosure, an objective lens system including at least one lens, an irradiation optical system that irradiates illumination light emitted from a light source to an eye to be inspected through the objective lens system, A light-receiving optical system including a light-receiving element that receives reflected light of the illumination light from the eye to be inspected through the objective lens system; An ophthalmologic imaging device to generate, a fundus image capturing means for obtaining a fundus image which is a front image of the fundus of the eye to be examined as the captured image, and a background image for the fundus image of the eye to be examined acquired by the fundus image capturing means A background image acquisition unit that acquires a background image including at least a reflection image by the objective lens system, performs a background difference based on the fundus image and the background image of the eye to be inspected, and as a difference image, the eye to be inspected Image processing means for generating an image in which the influence of the reflected image is suppressed in the fundus image, a first shooting mode for shooting the fundus image by the fundus reflected light, and a fundus image by fluorescence emitted from the fundus A second photographing mode for controlling the light source, and a switching control unit for controlling and switching the light source. The image processing unit includes the background for the fundus image photographed in the first photographing mode. The subtraction is performed, and the background subtraction is not performed on the fundus image captured in the second capturing mode.
An ophthalmologic imaging apparatus according to a fourth aspect of the present disclosure, an objective lens system including at least one lens, an irradiation optical system that irradiates illumination light emitted from a light source to an eye to be inspected through the objective lens system, A light-receiving optical system including a light-receiving element that receives reflected light of the illumination light from the eye to be inspected through the objective lens system; An ophthalmologic imaging device to generate, front image capturing means for obtaining a front image of the subject's eye as the captured image, and a background image for the front image of the subject's eye acquired by the front image capturing means, at least the A background image acquisition unit that acquires a background image including a reflection image by an objective lens system, performs a background difference based on the front image of the eye to be examined and the background image, and as a difference image, the reflection in the front image of the eye to be examined. An image processing unit for generating an image in which the influence of an image is suppressed, wherein the photographing optical system includes a first photographing mode for photographing the photographed image at a first angle of view, and the photographed image. It is possible to switch to a second shooting mode for shooting at an angle of view narrower than the first angle of view, and the image processing means is for the front image of the subject's eye taken in the first shooting mode. The background subtraction is performed, and the background subtraction is not performed on the front image of the eye to be inspected captured in the second capturing mode.
An ophthalmologic imaging apparatus according to a fifth aspect of the present disclosure, an objective lens system including at least one lens, an irradiation optical system for irradiating illumination light emitted from a light source to an eye to be inspected through the objective lens system, A light-receiving optical system including a light-receiving element that receives reflected light of the illumination light from the eye to be inspected through the objective lens system; An ophthalmologic imaging device to generate, front image capturing means for obtaining a front image of the subject's eye as the captured image, and a background image for the front image of the subject's eye acquired by the front image capturing means, at least the A background image acquisition unit that acquires a background image including a reflection image by the objective lens system, performs a background difference based on the front image of the eye to be examined and the background image, and as a difference image, the reflection in the front image of the eye to be examined. An image processing unit that generates an image in which the influence of an image is suppressed, wherein the front image capturing unit and the background image acquiring unit are a front image of the eye to be examined represented by a first gradation number; Each of the background images is acquired, and the image processing unit performs a background difference between the front image of the eye to be inspected represented by the first gradation number and the background image to obtain the first gradation number. The difference image represented by the second gradation number that is smaller than the above is generated.

According to the present disclosure, a front image of an eye to be inspected can be favorably obtained.

It is a figure which shows the external appearance of SLO in this embodiment. It is a figure which shows the optical system in the main-body part of SLO. It is the figure which showed an example of the aperture unit applicable instead of the confocal diaphragm shown in FIG. It is the figure which showed typically the luminous flux of the laser beam in the periphery of a scanning part. It is the figure which showed the objective lens system which concerns on a comparative example. It is a figure which shows the optical system in the state which mounted the lens attachment. It is a figure which shows the detailed structure of a light-shielding member. FIG. 3 is a diagram for explaining noise light blocked by a light blocking member in the optical system shown in FIG. 2. It is a figure which shows an example of the control system in SLO. 7 is a flowchart showing an outline of a photographing operation in SLO. It is the figure which showed the picked-up image (reflection image) of the fundus by SLO. FIG. 12 is a diagram showing a background image corresponding to FIG. 11. FIG. 13 is a diagram showing a difference image between the fundus image of FIG. 11 and the background image of FIG. 12. It is a figure for demonstrating a partial background image, and has shown the area|region extracted as a partial background image from the background image of FIG. It is the figure which showed the difference image of the fundus image of FIG. 11 and the partial background image of FIG.

Hereinafter, a scanning laser ophthalmoscope (SLO) according to an exemplary embodiment of the present disclosure will be described with reference to the drawings. A scanning laser ophthalmoscope (hereinafter referred to as “SLO”) 1 according to the present disclosure is a device that scans a laser beam on a fundus and receives a return light of the laser beam from the fundus to acquire a front image of the fundus. Is. As an imaging method of SLO1, in addition to an imaging method using fundus reflected light, for example, an imaging method of fluorescence imaging is known. The scanning laser ophthalmoscope according to the present disclosure may be a device integrated with another ophthalmologic device such as an optical coherence tomography (OCT) or perimeter.

In the embodiments described below, unless otherwise specified, the SLO 1 scans the laser light focused on the spot on the observation surface two-dimensionally based on the operation of the scanning unit. Shall be obtained. However, it is not necessarily limited to this. For example, the technology of the present disclosure may be applied to so-called line scan SLO. In this case, the linear laser beam is one-dimensionally scanned on the observation surface based on the operation of the scanning unit.

<Appearance of device>
First, with reference to FIG. 1, a schematic configuration of a scanning laser ophthalmoscope (SLO) 1 according to the present embodiment will be described. As shown in FIG. 1, the SLO 1 includes a main body (apparatus main body) 2 and a wide-angle lens attachment 3 (hereinafter, abbreviated as “lens attachment 3”). In the present embodiment, the main body portion 2 has an optical system (see FIG. 2) and a control system (see FIG. 9) that are main for the SLO 1 to capture a fundus image. In addition, in this embodiment, the lens attachment 3 is configured to be attachable to and detachable from the housing 2 a of the main body 2. More specifically, the lens attachment 3 is attached to and detached from the casing surface on the subject side. The SLO 1 can perform fundus imaging in each of the mounted state and the non-mounted state of the lens attachment 3. When the lens attachment 3 is attached to the housing 2a, the lens attachment 3 widens the angle of view of the fundus image obtained by the main body 2.

In the present embodiment, the main body 2 has a measuring unit 4, a positioning mechanism 5, a base 6, a face support unit 7, and a sensor 8. The measuring unit 4 stores an optical system for capturing an image of the eye E to be inspected. This optical system will be described later with reference to FIG.

The alignment mechanism 5 is used to align the device with the eye E to be inspected. The positioning mechanism 5 of the present embodiment moves the measuring unit 4 three-dimensionally with respect to the base 6. That is, it is moved in each of the Y direction (vertical direction), the X direction (horizontal direction:), and the Z direction (front-back direction).

As shown in FIG. 1, the face support unit 7 supports the subject's face with the eye E to be examined facing the measurement unit 4. In the present embodiment, the face support unit 7 is provided on the base 6.

The sensor 8 is a detection unit that detects attachment of the lens attachment 3. The sensor 8 outputs an electric signal according to the mounting state of the lens attachment 3. For example, the sensor 8 continuously outputs electric signals having different voltage values depending on whether the lens attachment 3 is attached to the main body 2 or the lens attachment 3 is not attached to the main body 2. It may be. Such a sensor 3 may be a contact sensor such as a micro switch, or may be a non-contact sensor such as a photoelectric sensor or a magnetic sensor.

<Optical configuration of the main unit>
Next, the optical system provided in the main body 2 of the SLO 1 will be described. As shown in FIG. 2, the SLO 1 has an irradiation optical system 10 and a light receiving optical system 20 (collectively referred to as “imaging optical system”). That is, the irradiation optical system 10 and the light receiving optical system 20 are housed in the same housing 2a. The SLO 1 captures a fundus image using these optical systems 10 and 20.

The irradiation optical system 10 includes at least a scanning unit 16 and an objective lens system 17. Further, as shown in FIG. 2, the irradiation optical system 10 further includes a laser light emitting unit 11, a collimating lens 12, a perforated mirror 13, a lens 14 (a part of the diopter adjusting unit 40 in the present embodiment. ), and the lens 15.

The laser light emitting unit 11 is a light source of the irradiation optical system 10. The laser light emitting unit 11 may include, for example, a laser diode (LD) and a super luminescent diode (SLD). Although the description of the specific structure is omitted, the laser light emitting unit 11 emits light in at least one kind of wavelength range. In the present embodiment, it is assumed that lights of a plurality of colors are emitted from the laser light emitting section 11 simultaneously or selectively. For example, in the present embodiment, a total of four colors of light are emitted from the laser light emitting unit 11 including three colors in the visible range of blue, green and red and one color in the infrared range. The three colors in the visible range of blue, green, and red are used for color photography, for example. For example, color photography is performed by emitting three colors of blue, green, and red from the light source 11 substantially at the same time. Further, any one of the three colors in the visible range may be used for visible fluorescence imaging. For example, blue light may be used for FAG imaging (fluorescein fluorescence contrast imaging), which is a type of visible fluorescence imaging. Further, for example, the light in the infrared region may be used for infrared fluorescence imaging as well as infrared imaging using the fundus reflection light in the infrared region. For example, ICG imaging (indocyanine green fluorescence imaging) is known as infrared fluorescence imaging. In this case, it is preferable that the infrared light emitted from the laser light source 11 is set in a wavelength range different from the fluorescence wavelength of indocyanine green used in ICG imaging.

The laser light is guided to the fundus Er through the path of the light beam shown in FIG. That is, the laser light from the laser light emitting unit 11 passes through the collimating lens 12, the opening formed in the perforated mirror 13, passes through the lens 14 and the lens 15, and then goes to the scanning unit 16. The laser light reflected by the scanning unit 16 passes through the objective lens system 17, and then is applied to the fundus Er of the eye E to be inspected. As a result, the laser light is reflected and scattered by the fundus Er. Alternatively, a fluorescent substance existing in the fundus is excited to cause fluorescence from the fundus. These lights (that is, reflected/scattered light, fluorescence, etc.) are emitted from the pupil as return light.

In the present embodiment, the lens 14 shown in FIG. 2 is a part of the diopter adjustment unit 40. The diopter adjustment unit 40 is used to correct (reduce) an error in diopter of the eye E to be inspected. For example, the lens 14 can be moved in the optical axis direction of the irradiation optical system 10 by the drive mechanism 14a. The diopters of the irradiation optical system 10 and the light receiving optical system 20 change depending on the position of the lens 14. Therefore, by adjusting the position of the lens 14, the error of the diopter of the eye E is reduced, and as a result, the focus position of the laser light is on the observation site (for example, the retina surface) of the fundus Er. It can be set. Note that the diopter adjustment unit 40 may be applied with an optical system different from that in FIG. 2, such as a Badard optical system.

The scanning unit 16 (also referred to as “optical scanner”) is a unit for scanning the laser light emitted from the light source (laser light emitting unit 11) on the fundus. In the following description, unless otherwise specified, the scanning unit 16 includes two optical scanners having different laser beam scanning directions. The two optical scanners are arranged at different positions. That is, it includes an optical scanner 16a for main scanning (for example, scanning in the X direction) and an optical scanner 16b for sub-scanning (for scanning in the Y direction). The main scanning optical scanner 16a and the sub-scanning optical scanner 16b may be a resonant scanner and a galvanometer mirror, respectively. However, the present invention is not necessarily limited to this, and for each of the optical scanners 16a and 16b, in addition to other reflection mirrors (galvano mirrors, polygon mirrors, resonant scanners, MEMS, etc.), the traveling (deflection) direction of light is changed. An acousto-optic device (AOM) or the like may be applied. The scanning unit 16 does not necessarily have to be a plurality of optical scanners, and may be a single optical scanner. As a single optical scanner that two-dimensionally scans a laser beam, for example, a scanner using one of a MEMS device, an acousto-optic device (AOM), and the like has been proposed.

The objective lens system 17 is an objective optical system of SLO1. The objective lens system 17 is used to guide the laser light scanned by the scanning unit 16 to the fundus Er. Therefore, the objective lens system 17 forms a turning point P at which the laser light passing through the scanning unit 16 is turned. The turning point P is formed on the optical axis L1 of the irradiation optical system 10 and at a position optically conjugate with the scanning unit 16 with respect to the objective lens system 17. The detailed configuration of the objective lens system 17 will be described later. It should be noted that in the present disclosure, “conjugate” is not necessarily limited to a complete conjugate relationship and includes “substantially conjugate”. That is, a case where the fundus image is arranged with a deviation from the complete conjugate position within the range permitted in relation to the purpose of use (for example, observation, analysis, etc.) of the fundus image is also included in the “conjugate” in the present disclosure.

The laser beam that has passed through the scanning unit 16 passes through the objective lens system 17, passes through the turning point P, and is applied to the fundus Er. Therefore, the laser light that has passed through the objective lens system 17 is swung around the turning point P as the scanning unit 16 operates. As a result, in the present embodiment, the laser light is two-dimensionally scanned on the fundus Er. The laser light applied to the fundus Er is reflected at the focus position (for example, the retina surface). Further, the laser light is scattered by the tissues before and after the converging position. The reflected light and the scattered light are emitted from the pupil as parallel light.

Next, the light receiving optical system 20 will be described. The light receiving optical system 20 shares the objective lens system 17 with the irradiation optical system 10 and has at least one light receiving element. For example, as shown in FIG. 2, a plurality of light receiving elements 25, 27, 29 may be included. In this case, the light emitted from the fundus Er by the laser light emitted by the irradiation optical system 10 is received by the light receiving elements 25, 27, 29.

As shown in FIG. 2, in the light receiving optical system 20 in the present embodiment, each member arranged from the objective lens system 17 to the perforated mirror 13 may be shared with the irradiation optical system 10. In this case, the light from the fundus goes back to the optical path of the irradiation optical system 10 and is guided to the perforated mirror (optical path branching member in the present embodiment) 13. Further, the perforated mirror 13 branches the irradiation optical system 10 and the light receiving optical system 20. In the present embodiment, the light from the fundus Er is guided by the reflecting surface of the perforated mirror 13 to the independent optical path of the light receiving optical system 20 (the optical path on the side of the light receiving elements 25, 27, 29). Light traveling from the common optical path of the irradiation optical system 10 and the light receiving optical system 20 toward the perforated mirror is likely to include noise light in a region near the optical axis L2 of the principal ray of the laser light. It should be noted that the noise light referred to here mainly refers to light from other than the target of photographing and observation, such as the condensing position of the fundus Er (for example, the retina surface). Specific examples include reflected light from the cornea and reflected light from the optical system inside the device. The perforated mirror 13 guides the light from the fundus Er to the independent optical path of the light receiving optical system 20 while removing at least a part of such noise light. In this embodiment, the perforated mirror 13 is arranged at a conjugate position with the anterior segment. Therefore, the reflected light from the cornea and the reflected light from the optical system inside the device are removed by the aperture of the perforated mirror 13. On the other hand, of the light from the fundus Er, the light passing through the periphery of the pupil is reflected by the reflecting surface of the perforated mirror 13 and guided to the independent optical path.

The optical path branching member for branching the irradiation optical system 10 and the light receiving optical system 20 is not limited to the perforated mirror 13. For example, instead of the perforated mirror 13, a member in which the opening and the reflection surface of the perforated mirror 13 are replaced with each other can be used as the optical path branching portion. However, for example, when applied to FIG. 2, an independent optical path of the irradiation optical system 10 (from the light source 11 to the perforated mirror 13) and an independent optical path of the light receiving optical system 20 (from the perforated mirror 13 to the light receiving element 25, 27, up to 29) must be replaced with each other. The optical path branching member may be another beam splitter.

The light receiving optical system 20 includes a lens 21, a light blocking portion 22, a pinhole plate 23, and a light separating portion (light separating unit) 30 in the reflected light path of the perforated mirror 13. Further, lenses 24, 26, 28 are provided between the light separating section 30 and the respective light receiving elements 25, 27, 29.

Although the details will be described later, the light blocking portion 22 blocks light in the vicinity of the optical axis L2 of the light receiving optical system 20. The light from the fundus conjugate surface passes through the light blocking portion 22, and at least a part of the noise light is blocked by the light blocking portion 22.

The pinhole plate 23 is arranged on the fundus conjugate plane and functions as a confocal diaphragm in SLO1. That is, when the diopter is properly corrected by the diopter adjusting unit 40, the light from the fundus Er that has passed through the lens 21 is focused at the opening of the pinhole plate 23. The pinhole plate 23 removes light from positions other than the condensing point (or focal plane) of the fundus Er, and the rest (light from the condensing point) is mainly guided to the light receiving elements 25, 27, 29. ..

Note that, unless otherwise specified, the pinhole plate 23 (confocal diaphragm) is placed at the fundus conjugate position between the light receiving elements 25, 27, 29 and the perforated mirror 13. Instead of the pinhole plate 23, an aperture unit 230 as shown in FIG. 3 may be arranged. The aperture unit 230 has a confocal diaphragm 231 having an opening at a position conjugate with the light condensing point on the observation surface (fundus), and a light-shielding portion at a position conjugate with the light converging point on the observation surface (fundus). Among the light scattered before and after, the apertures 232 and 232 having openings for passing the light in the region apart from the optical axis L2 to the light receiving elements 25, 27 and 29 are switched. Deploy. When the apertures 232 and 232 are arranged, fundus images based on scattered light from before and after the converging point are acquired. In this case, it is possible to image a minute biological substance in the fundus that cannot be confirmed in the fundus image (for example, a reflection image) captured when the confocal diaphragm 231 is arranged.

The light separating unit 30 separates the light from the fundus Er. In the present embodiment, the light separating section 30 wavelength-selectively separates the light from the fundus Er. Further, the light splitting unit 30 may also serve as a light splitting unit that splits the optical path of the light receiving optical system 20. For example, as shown in FIG. 2, the light separation unit 30 may include two dichroic mirrors (dichroic filters) 31 and 32 having different light 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. Further, one of the light receiving elements 25, 27, 29 is arranged at the tip of each branched optical path.

For example, the light splitting unit 30 splits the wavelength 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, light of three colors of blue, green, and red may be received by the light receiving elements 25, 27, 29 one by one. In this case, a color image can be easily obtained from the light receiving results of the light receiving elements 25, 27, 29.

Further, the light separating section 30 may cause at least one of the light receiving elements 25, 27, 29 to receive light in the infrared region used in infrared imaging. In this case, for example, the fluorescence used in fluorescence imaging and the light in the infrared region used in infrared imaging may be received by different light receiving elements.

The wavelength bands in which the respective light receiving elements 25, 27, 29 have sensitivity may be different from each other. Further, at least two of the light receiving elements 25, 27, 29 may have sensitivity in a common wavelength range. Each of the light receiving elements 25, 27, 29 outputs a signal (hereinafter referred to as a light receiving signal) corresponding to the intensity of the received light. In the present embodiment, the received light signal is processed separately for each light receiving element to generate an image. That is, in this embodiment, a maximum of three types of fundus images are generated in parallel.

In SLO1 (here, the optical system of the main body 2), the anterior ocular segment conjugate position between the perforated mirror 13 and the objective lens system 17 is the position of the scanning unit 16 and the position of the perforated mirror 13. It is formed only in places. As a result, an optical system having a short overall length is realized.

<Conditions for optical scanner placement intervals>
When the laser beam applied to the fundus is vignetted by the pupil, a fundus image with a dark surrounding is obtained. On the other hand, vignetting can be suppressed by setting the distance a between the optical scanner 16a and the optical scanner 16b so as to satisfy the following mathematical expression (1).

a ≤ {sin(θ/2) / sin(θo/2)} ・(k-1)・φ/tan(θo/2) ・・・(1)
Here, θ is an angle representing the field-of-view diameter, θo is the full angle of the optical swing angle in the scanning unit 16 (optical scanners 16a and 16b), and φ is the aperture of the perforated mirror 13 in the anterior segment. The diameter of the image. Further, k is a constant obtained as a result of examination by the inventor. k is a value greater than 1. As a result of the study by the inventor, it was confirmed that vignetting is unlikely to occur even if other parameters are changed when the constant k is a value of about “1.5”.

For example, in the case of θ=60°, θo=16°, φ=1.4 mm, k=1.5, if a is within 18 mm, the laser light passes nearer to the turning point P. While being rotated, the laser light is less likely to be vignetted even for an eye with a small pupil diameter of about φ2.5 mm.

Formula (1) will be described with reference to FIG. FIG. 4 is a diagram schematically showing the periphery of the scanning unit 16. FIG. 4 schematically shows the luminous flux when projecting through the perforated mirror 13. G is an intermediate point between the optical scanners 16a and 16b and is formed at a position anterior ocular segment conjugate (pupil conjugate). The thickness of the light flux (actual thickness of the light flux) when the optical scanners 16a and 16b are stationary is shown as Do. Further, the apparent thickness of the laser light at the intermediate point C (intermediate surface) during the operation of the optical scanners 16a and 16b is shown as D.

Here, “sin(θ/2)/sin(θo/2)” in Expression (1) is considered to be a term representing the magnification in the objective lens system 17 under the assumption of the sine condition. Therefore, “sin(θ/2)/sin(θo/2)·φ” included in the mathematical expression (1) has the same meaning as the actual thickness Do of the light beam. Here, the equation (1) is rewritten using Do and is shown as the following equation (2).

a ≤ Do・(k-1) / tan(θo/2)
a・tan(θo/2) ≤ Do ・(k-1) ・・・(2)
As is clear from FIG. 4, the relation of “D=Do+a·tan(θo/2)” is established. Then, by substituting and rearranging (2), the mathematical expression (3) can be derived.

D = Do+a・tan(θo/2) ≤ Do・k ・・・(3)
As described above, the mathematical expression (1) is a condition that determines that the apparent thickness D of the light flux at the intermediate point C that is the anterior segment conjugate position is within k times the actual thickness Do of the light flux. Become. Setting the constant k as a value of about “1.5” has been confirmed by the inventor as a value in which vignetting is unlikely to occur in consideration of this relationship.

<Optical configuration that contributes to noise suppression>
As described above, the SLO 1 of the present embodiment can suppress the noise light from being incident on the light receiving elements 25, 27, 29 by the confocal diaphragm (pinhole plate 23) and the perforated mirror 13.

However, in general, in an SLO having an objective lens system, it is difficult to secure a focal length of the objective lens system with a margin when trying to secure a shooting field angle of several tens of degrees or more. At this time, by arranging the light source side lens surface of the lens that largely bends the laser light in the objective lens system near the fundus conjugate plane (also called the intermediate image plane) related to the objective lens system, the confocal diaphragm and the aperture are opened. Noise light that cannot be completely removed by a mirror or the like is likely to occur. In a lens that bends laser light greatly, the radius of curvature of the lens surface on the light source side tends to be small. Therefore, even if this lens is tilted, it is difficult to let the noise light escape to the outside of the light receiving optical path. The fundus conjugate plane related to the objective lens system is a primary magnified image formed by the objective lens system and mainly indicates an inverted image. However, it does not necessarily have to be a primary enlarged image.

In addition, diopter correction may be performed in order to properly focus the laser light on the fundus. At this time, the fundus conjugate surface formed via the objective lens system moves according to the diopter correction amount. For example, the stronger the myopia of the eye to be inspected, the closer the fundus conjugate plane with respect to the objective lens system is to the eye E to be inspected as a result of diopter correction. Therefore, it is conceivable that noise light that cannot be completely removed by the confocal diaphragm, the perforated mirror, etc. may be generated due to the influence of diopter correction.

On the other hand, the SLO 1 of this embodiment may have the configuration described below. It should be noted that when implementing the technology according to the present disclosure, all of the configurations described below do not necessarily have to be implemented, and some of them may be selectively implemented.

<Objective lens system>
As shown in FIG. 2, the objective lens system 17 has a first lens system 17a and a second lens system 17b. Each lens system 17a, 17b includes at least one or more lenses. The first lens system 17a is a main lens system for bending the laser light toward the turning point in the objective lens system 17. For example, the first lens system 17a shown in FIG. 2 bends the laser light toward the turning point P at the position where the chief ray height of the laser light in the objective lens system 17 is the highest. In addition, the first lens system 17a is disposed closest to the eye to be examined in the objective lens system 17.

In this embodiment, the single lens 171 forms the first lens system 17 a. As shown in FIG. 2, an aspherical lens may be used as the lens 171.

By the way, in order to realize fundus imaging at an angle of view of several tens of degrees or more while securing a sufficient working distance between the device and the eye E to be inspected, as shown in FIG. Must be provided in the first lens system 17a to bend the laser light. Therefore, in the objective lens system 17 (in particular, the first lens system 17a), aberrations (for example, spherical aberration, coma aberration, etc.) depending on the lens aperture are likely to occur. On the other hand, it is desirable that the lens 171 has a lens surface formed in an aspherical shape so as to reduce the aberration depending on the aperture of the lens. For example, the lens 171 is formed with an aspherical lens surface so as to reduce spherical aberration of image formation at the turning point P. For example, the light source side lens surface 171a of the lens 171 may be an aspherical surface. For example, the lens surface 171a may be formed by a curved surface such that the radius of curvature becomes larger at a position farther from the optical axis (lens axis) of the lens 171. On the other hand, the lens surface 171b of the lens 171 on the side of the eye to be examined may be a spherical surface, a flat surface, or an aspherical surface.

The lens 171 (or the first lens system 17a) is preferably arranged such that its optical axis is along the optical axis L1 of the irradiation optical system 10. For example, since the lens 171 is a lens having a large refracting power, the distortion in the fundus image can be suppressed by disposing the lens 171 so that the optical axis thereof is along the optical axis L1. Here, the optical axis of the lens 171 may be completely coaxial with the optical axis L1 of the irradiation optical system 10, or may be slightly inclined with respect to the optical axis L1. For example, the optical axis L1 of the lens 171 may be arranged with a slight inclination within a range in which distortion of the fundus image is allowed. By arranging the optical axis of the lens 171 so as to be inclined with respect to the optical axis L1, the inclination of the image plane due to a “tilted lens” described later may be reduced.

The second lens system 17b is arranged between the first lens system 17a and the scanning unit 16. The second lens system 17b has at least one lens whose lens surface on the light source side is tilted with respect to the optical axis L1 of the irradiation optical system 10 (hereinafter, referred to as “tilted lens” for convenience). When the second lens system 17b includes a plurality of lenses, two or more lenses may be tilted lenses, or all may be tilted lenses as shown in FIG.

For example, in the present embodiment, each of the cemented lens 172 and the convex meniscus lens 173 is an inclined lens in the second lens system 17b. As shown in FIG. 2, in each of the inclined lenses 172 and 173, the light source side lens surfaces 172a and 173a are formed to have a larger radius of curvature than the light source side lens surface 171a in the first lens system 17. There is. Each of the tilted lenses 172 and 173 shown in FIG. 2 is a spherical lens. Further, both the tilt lenses 172 and 173 have positive power. However, the present invention is not necessarily limited to this, and an aspherical lens and/or a lens having negative power may be applied to some or all of the lenses included in the second lens system 17b. ..

The second lens system 17b may include a lens for correcting the aberration caused by the first lens system 17a. For example, the cemented lens 172 of this embodiment corrects chromatic aberration. The chromatic aberration to be corrected may be one or both of the axial chromatic aberration and the chromatic aberration of magnification. More specifically, the cemented lens 172 may be an achromatic lens formed by bonding at least two lenses having different light dispersions (Abbe numbers). It should be noted that there is a possibility that noise light may occur due to the reflection of the laser light on the cemented surface 172b of the cemented lens 172. On the other hand, the refractive index of each lens (concave lens and convex lens in FIG. 2) included in the cemented lens 172 and the adhesive for bonding the lenses are the same (including substantially the same). Good. Thereby, the reflection of the laser light on the bonding surface 172b is suppressed. As a result, noise light due to reflection on the bonding surface 172b is less likely to occur. Here, when the refractive index difference between each lens included in the cemented lens 172 and the adhesive is 0.01 or less, the effect of suppressing noise light can be more suitably obtained.

The cemented surface 172b of the cemented lens 171 is preferably convex toward the eye to be examined. This is because the joining surface 172b and the fundus conjugation surface H are separated from each other, so that generation of noise light is appropriately suppressed.

Further, the higher the refractive index of each of the lenses included in the cemented lens 172 and the adhesive, the easier it is to increase the radius of curvature of the cemented surface, and the light reflected by the cemented surface 172b becomes light receiving elements 25, 27,. It becomes difficult to be reflected at the angle of incidence on 29. As a result, the influence of noise light on the fundus image is further suppressed. Further, since the radius of curvature of the cemented surface 172b is increased, the manufacturing cost of the cemented lens 172 can be suppressed. For example, a concave lens and a convex lens and an adhesive for bonding the lenses may be selected so that the refractive indexes are 1.63 and are substantially the same.

The number of lenses forming the cemented lens 172 may be determined according to the number of colors included in the laser light. For example, the cemented lens 172 having a two-lens configuration can align the light-condensing positions of the two colors of the three colors included in the laser light with the other one-color condensing positions. As described above, in the SLO 1 of the present embodiment, the laser light emitting unit 11 emits a total of four colors of three colors of red, green, and blue and one color in the infrared region. In the case of the two-element cemented lens 172 as shown in FIG. 2, the condensing position of the blue light having the shortest wavelength and the condensing position of the light in the infrared region are set to light of an intermediate wavelength ( The “intermediate wavelength” here does not necessarily have to match the wavelength of the laser light emitted from the laser light emitting unit 11.) so as to match (including substantially match) with the converging position. It may be designed. By providing the cemented lens 172, the position of the turning point in the laser light of each color is less likely to shift. As a result, fundus photography performed by projecting light of a plurality of colors is likely to be favorably performed for an eye with a smaller pupil or with a larger angle of view.

Each lens included in the cemented lens 172 may be selected so that the power of the cemented lens 172 becomes zero. In this case, the cemented lens 172 is unlikely to affect the inclination and height of the light beam. Therefore, the presence or absence of the cemented lens 172 is unlikely to influence the design of the lens (for example, the first lens system 17a) that bends the laser light in the objective lens system 17.

The convex meniscus lens 173 has a positive power. Therefore, it contributes to bending the laser light to the turning point P. However, the bending amount is sufficiently smaller than that of the first lens system 17a.

By the way, in order to secure the same angle of view as that of the present embodiment, a design solution in which a plurality of lenses included in the objective lens system as described above are formed as one cemented lens 500 is also conceivable. (See Comparative Example 5). However, when the objective lens system is formed by one cemented lens 500, the lens surface 500a is likely to be arranged near the fundus conjugate plane (intermediate image I). As a result, noise light is likely to occur due to the reflection of the laser light on the lens surface 500a. Further, since the radius of curvature of the lens surface 500a on the light source side becomes small, it is difficult to escape the reflected light at the lens surface 500a from the light receiving optical path even if the lens 500 is tilted.

In contrast to such a comparative example, the objective lens system 17 of this embodiment is divided into a first lens system 17a and a second lens system 17b. Since the second lens system 17b is provided between the scanning unit 16 and the first lens system 17a, which is a main lens system for bending the laser light toward the turning point, the objective lens system 17 is compared. It becomes easy to dispose the lens surface 171a of the first lens system having a relatively small radius of curvature away from the fundus conjugate plane (intermediate image H) of the objective lens system 17. As a result, the light reflected by the lens surface 171a is less likely to enter the light receiving elements 25, 27, 29 as noise light. Further, in the inclined lenses 172 and 173 of the second lens system 17b, the lens surfaces 172a and 173a that reflect the laser light are inclined with respect to the optical axis L1, and further, the lens surfaces 172a and 173a are the first lens system. Since the radius of curvature is larger than that of the lens surface 171a of 17a, even if the position of any of the lens surfaces 172a and 173a is near the fundus conjugate plane (intermediate image H), the lens surfaces 172a and 173a are The reflected light is less likely to enter the light receiving elements 25, 27, 29 as noise light. As a result, according to the objective lens system 17 of the present embodiment, noise light incident on the light receiving elements 25, 27, 29 is less likely to occur.

By the way, as shown in FIG. 2, the fact that the main scanning optical scanner 16a and the sub-scanning optical scanner 16b are separate bodies means that in the image position of the scanning unit 16 in the pupil of the eye E to be examined, It can be a factor that causes a point difference. That is, it may cause a deviation in the direction along the optical axis L1 between the position of the turning point of the laser beam in the main scanning direction and the position of the turning point of the laser beam in the sub scanning direction. If there is an astigmatic difference, there is a high possibility that the laser light will be vignetted in the pupil, and thus unevenness in which the brightness in the peripheral part of the fundus image becomes darker than the central part is likely to occur.

On the other hand, the tilting lenses 172 and 173 included in the second lens system 17b are tilted with respect to the optical axis L1 so as to cancel (reduce) the astigmatic difference caused by the two optical scanners 16a and 16b. It may be arranged. In this case, the astigmatism caused by the inclination of the tilting lens and the astigmatism caused by the two optical scanners 16a and 16b cancel each other, so that the astigmatism remaining at the turning point P is suppressed. For example, as shown in FIG. 2, when the sub-scanning optical scanner 16b and the main-scanning optical scanner 16a are arranged in this order from the light source side, the tilting lens is appropriately arranged in the yz plane (in the paper plane). The astigmatism can reduce the astigmatic difference. As a result, it becomes easy to obtain a fundus image with uniform brightness.

<Wide-angle lens attachment>
A lens attachment 3 is attached to the SLO 1. The optical system in the state where the lens attachment 3 is attached will be described with reference to FIG.

The lens attachment 3 is attached to the subject-side housing surface of the SLO 1 so that a second objective lens system 50 described later is arranged in the optical path of the laser light. For example, it is arranged near the first turning point P.

As shown in FIG. 6, the lens attachment 3 mainly has a second objective lens system 50. The lens attachment 3 may also have a lens system and a mirror system in addition to the above. For example, the lens attachment 3 shown in FIG. 6 has a diopter correction lens 57 (diopter correction lens optical system). By mounting the lens attachment 3 on the SLO 1, the above optical system included in the lens attachment 3 is arranged between the objective lens system 17 of the SLO 1 and the eye E to be inspected.

The diopter correction lens 57 cancels the diopter change due to the second objective lens system 50 (that is, cancels a part or all of the diopter change). More specifically, the diopter correction lens 57 suppresses the difference in diopter of the light incident on the eye E to be inspected between when the lens attachment 3 is attached and when the lens attachment 3 is not attached. As shown in FIG. 6, the diopter correction lens 57 may be a lens having a positive power (more specifically, a plano-convex lens having a convex surface facing the eye E side). When it is attempted to realize fundus imaging in a wide angle (for example, an angle of view of φ90° or more) by mounting the lens attachment 3, it is assumed that the second objective lens system 50 has a refractive power of several tens of diopters or more. .. In this case, it is possible that the body of the SLO 1 (for example, the irradiation optical system 10) cannot completely correct the change in diopter. On the other hand, by applying a lens having a power corresponding to the second objective lens system 50 as the diopter correction lens 57, the diopter change due to the second objective lens system 50 is offset. As a result, a wide-angle fundus image can be captured well. Further, according to the diopter correction lens 57, the difference in diopter of the light incident on the eye E to be inspected between the mounted state and the non-mounted state of the lens attachment 3 is reduced, so that the lens attachment 3 can be attached to and detached from the SLO 1. The adjustment of the diopter that accompanies it is simplified or unnecessary.

Further, as shown in FIG. 6, the diopter correction lens 57 is arranged on the light source side with respect to the second objective lens system 50. More specifically, the diopter correction lens 57 is arranged at the position of the turning point P. As a result, the laser light passes near the center of the diopter correction lens 57. Therefore, a lens having a small diameter can be used as the diopter correction lens 57. Further, since the laser light passes near the center of the diopter correction lens 57, the inclination of the principal ray of the laser light is less likely to be affected by the power of the diopter correction lens 57. As a result, the setting of the diopter can be changed only by changing the diopter correction lens 57. As a result, the number of design steps in the second objective lens system 50 is reduced. The diopter correction lens 57 does not necessarily have to be located at the turning point P. However, the arrangement on the fundus conjugate plane (that is, the intermediate image L, in other words, the primary magnified image by the second objective lens system 50) inside the lens attachment 3 should be avoided.

The second objective lens system 50 forms a turning point Q (second turning point Q) in the mounted state of the lens attachment 3. The turning point Q is a point at which the laser light that has passed through the turning point P (more specifically, the principal ray of the laser light) is further turned along with the operation of the scanning unit 16. The turning point Q is formed at a position optically conjugate with the scanning unit 16 with respect to the second objective lens system 50. The turning point Q is formed on the optical axis L3 of the second objective lens system 50. As shown in FIG. 6, the optical axis L3 of the second objective lens system 50 may be coaxial with the optical axis L1 of the irradiation optical system 10.

The second objective lens system 50 has a first lens system 50a and a second lens system 50b. The first lens system 50a in the second objective lens system 50 may have at least some of the features described above with respect to the first lens system 17a in the first objective lens system 17, and the second objective lens system 50. The second lens system 50b in 1 may have at least a part of the features described above regarding the second lens system 17b in the first objective lens system 17.

That is, the first lens system 50a is a main lens system for bending the laser light toward the turning point Q in the second objective lens system 50. That is, the first lens system 50a bends the laser light toward the turning point Q at the position where the chief ray height of the laser light in the second objective lens system 50 is the highest. Further, the first lens system 50a is arranged closest to the eye to be examined in the second objective lens system 50.

The first lens system 50a may be formed by one lens 51. Further, an aspherical lens that suppresses spherical aberration of image formation at the turning point Q may be applied to the lens 51. In order to reduce spherical aberration, the lens surface 51a on the light source side is formed by a curved surface such that the radius of curvature becomes larger at a position farther from the optical axis L3 of the second objective lens system 50.

Here, the angle of view of the fundus image and the working distance have a trade-off relationship. In order to secure a larger working distance while realizing an angle of view of φ90° or more, for example, in the lens 51, the radius of curvature of the lens surface 51b on the eye side to be inspected is smaller than the radius of curvature of the lens surface 51a on the light source side. It is formed to be large. It has been confirmed that the larger the radius of curvature of the lens surface 51b on the eye side to be inspected, the easier it is to secure the distance w between the lens surface 51b (however, the position on the eye surface 51b closest to the eye to be inspected) and the turning point Q. .. In the example of FIG. 6, the lens surface 51b is a flat surface and its radius of curvature is infinite. Therefore, it becomes easy to design an optical system in which a sufficient distance w can be obtained. As a result of forming the lens surface 51b with a surface having a sufficiently large radius of curvature as described above, the working distance is easily secured. This facilitates, for example, the eyelid opening work (the work of lifting the upper eyelid with a finger or the like) of the subject by the examiner or the like. In addition, in one design solution of the optical system of FIG. 6 by the inventor, it was possible to secure the interval w of about 13 mm while securing the angle of view of 100° or more. Here, assuming that the lens surface 51b also serves as an inspection window, and assuming that the working distance is a value obtained by subtracting about 3 mm, which is a typical distance from the corneal apex of the human eye to the pupil, the working distance is 10 mm. The degree can be secured. The lens surface 51b may be a curved surface such as a spherical surface. In this case, the radius of curvature of the lens surface 51b is preferably a value that is, for example, 10 times or more the desired working distance.

The second lens system 50b is arranged between the first lens system 50a and the scanning unit 16 (more specifically, between the first objective lens system 17). The second lens system 50b has at least one tilt lens. When the second lens system 50b includes a plurality of lenses, two or more lenses may be tilted lenses, or all may be tilted lenses as shown in FIG.

The second lens system 50 shown in FIG. 6 includes a cemented lens 52 and convex meniscus lenses 53, 54, 55 as tilt lenses. As shown in FIG. 6, in each of the tilted lenses 52, 53, 54, 55, the lens surface on the light source side is larger than the lens surface 51a on the light source side in the first lens system (more specifically, the lens 51). It is formed to have a radius of curvature. Each of the tilt lenses may be a spherical lens. Further, each of the tilt lenses 52, 53, 54, 55 has a positive power. However, the present invention is not limited to this, and an aspherical lens and/or a lens having negative power may be applied to some or all of the lenses included in the second lens system 50b. .. Also in the second objective lens system 50, the tilting lenses 52, 53, 54, 55 are arranged between the first lens system 50a and the scanning unit 16 as in the first objective lens system 17, so that Light reflected by the lens surface of the one-lens system 50a is suppressed from entering the light-receiving elements 25, 27, and 29.

The second lens system 50b may include a lens for correcting the aberration caused by the first lens system 50a. For example, the cemented lens 52 corrects chromatic aberration. More specifically, the cemented lens 52 may be an achromatic lens formed by bonding at least two lenses having different light dispersion (Abbe number). In addition, in order to suppress reflection at the cemented surface of the cemented lens 52, in the cemented lens 52, the refractive index of each lens and the adhesive for bonding the lenses are matched (including substantially matched) with each other. You may have. Further, each lens included in the cemented lens 52 may be selected so that the power of the cemented lens 52 becomes zero.

Note that it is not necessary for the cemented lens 52 to correct all the chromatic aberration that occurs when the lens attachment 3 is mounted. The lens attachment 3 may further include a non-tilted chromatic aberration correction lens 59 (achromatic lens). These may be used together to correct chromatic aberration. In this case, the power of the lens 59 is preferably 0 (that is, the sum of the powers of the concave lens and the convex lens is 0).

The convex meniscus lenses 53, 54, 55 have positive power. Therefore, it contributes to bending the laser light to the turning point Q. However, the bending amount is sufficiently smaller than that of the first lens system 50a.

In the present embodiment, the astigmatic difference due to the optical scanners 16a and 16b (the astigmatic difference at the turning point P) is the tilting lens 172 provided in the first objective lens system 17 arranged in the housing of the SLO1. It is corrected (reduced) by 173. Here, it is possible that the astigmatic difference due to the optical scanners 16a and 16b remains via the first objective lens system 17. When the laser beam incident on the second objective lens system 50 has the above-mentioned astigmatic difference, the tilted lens included in the second lens system 50b is lighted so as to be in a direction to cancel (reduce) the astigmatic difference. It may be inclined with respect to the axis L1. For example, as shown in FIG. 6, the tilt amounts of the tilt lenses 52, 53, 54, 55 in the second objective lens system 50 are tilted so as to further reduce the remaining astigmatic difference.

Further, as shown in FIG. 6, when the second lens system 50b includes a plurality of tilted lenses, some of the tilted lenses and some of the remaining tilted lenses have the optical axis L3 (of the lens attachment). Alternatively, they may be arranged in mutually opposite phases with respect to the optical axis L1) of the irradiation optical system 10. As a specific example, in the second objective lens system 50b of FIG. 6, the tilt lenses 52 and 53 and the tilt lenses 54 and 55 are arranged so as to be tilted in opposite phases with respect to the optical axis L3. As a result, the tilts of the image planes generated by the tilt lenses 52 and 53 and the tilt lenses 54 and 55 can be canceled out. The tilt of the image plane does not necessarily have to be corrected inside the second lens system 50b. For example, the tilt of the image plane caused by the tilted lens of the second lens system 50b may be corrected by tilting the lenses included in the first lens system 50a. In this case, at least one lens included in the first lens system 50a is arranged in an opposite phase to at least one tilted lens included in the second lens system 50b with respect to the optical axis L3.

<Arrangement of perforated mirror>
In the above description, the perforated mirror 13 has been described as being arranged at a position conjugate with the anterior segment. In order to suppress the noise light more preferably, the perforated mirror 13 may be arranged at the corneal conjugate position when the working distance is appropriate. When the SLO 1 has an aperture unit 230 as shown in FIG. 3 and one of the apertures 232 and 233 for capturing scattered light is arranged in the optical path of the light receiving optical system 20, the apertures of the apertures 232 and 233 are large. Therefore, it may be possible that the apertures 232 and 233 cannot sufficiently remove the noise light. In particular, noise light due to corneal reflection is likely to be guided to the light receiving elements 25, 27, 29. On the other hand, when the working distance is appropriate, the perforated mirror 13 is arranged so as to be at the corneal conjugate position, so that the corneal reflection is satisfactorily removed in the perforated mirror 13.

<Light-shielding member>
The light shielding portion 22 is provided at a position deviating from the fundus conjugate plane in the optical path between the perforated mirror 13 and the light receiving elements 25, 27, 29. The light blocking unit 22 allows light from the fundus conjugate plane to pass therethrough and blocks at least a part of the reflected light from the lens surfaces of the objective lens systems 17 and 50. In the present embodiment, the light blocking portion 22 blocks light near the optical axis L2 of the light receiving optical system 20.

In the present embodiment, the light blocking portion 22 is a black dot plate having a black dot 22a forming a light blocking region and a translucent plate 22b having a ring-shaped opening (see FIG. 7). The black spot 22a is disposed on the optical axis L2, for example, and is provided to block light near the optical axis L2. The translucent plate 22b is formed in a region away from the optical axis L2 and is provided to transmit light from the fundus conjugate plane. The vicinity of the optical axis L2 may be a region close to the optical axis L2 with respect to the outer edge of the passage region of the light from the fundus reflected by the perforated mirror 13. As will be described later, it is more preferable that the black spot 22a is formed in a region near the optical axis L2 with respect to the inner edge of the passage region. The preferred installation range of the black dots 22a will be described later.

The installation position of the light shielding portion 22 (that is, the position deviated from the fundus conjugate plane) can be defined under the condition that it is deviated from at least the substantially conjugate position of the fundus. That is, the light blocking portion 22 blocks light near the optical axis L2 (mainly including light from the lens surface) of the light traveling toward the light receiving elements 25, 27, 29, and at a region distant from the optical axis L2. Passes light (mainly light from the fundus conjugate plane). In this case, the light shielding portion 22 is configured to allow light from the substantially conjugate surface (front and rear surfaces with respect to the light collecting surface of the fundus) to pass therethrough.

Further, the installation position of the light shielding unit 22 may be a position between the pupil conjugate position and the fundus conjugate position, and may be a position deviating from both the pupil conjugate position and the fundus conjugate position. For example, as shown in FIG. 2 and FIG. 8, the installation position of the light shield 22 may be between the perforated mirror 13 and the pinhole plate 23. As described above, in the present embodiment, in the lenses 51 and 171, in which the bending amount of the laser light is relatively large, the reflection on the lens surface on the light source side becomes a problem. Therefore, the light shielding portion 22 may be arranged at a position conjugate with the light source side lens surfaces 51a and 171a of the lens 51 or the lens 171. For the sake of convenience, in FIG. 8, it is assumed that the light shielding portion 22 is arranged at a position conjugate with the lens surface 171a. However, as compared with the lens 171, the lens 51 that bends the laser light more greatly allows the light reflected by the lens surface on the light source side to be guided to the light receiving elements 25, 27, and 29. For this reason, it is more preferable that the light shielding portion 22 is arranged at a conjugate position with the light source side lens surface 51a of the lens 51 (a ray diagram in this case is omitted). Further, one light shielding portion 22 may be arranged at each of the conjugate position of the lens surface 171a and the conjugate position of the lens surface 51.

The light blocking unit 22 blocks the vicinity of the optical axis of the light receiving optical system 20 to remove the reflected light from the lens surfaces 51a and 171a, for example. The image of the laser light irradiation area A on the lens surfaces 51a and 171a is formed in the area B near the optical axis of the light receiving optical system 20 at the position of the light shielding portion 22. Here, the irradiation area A is sequentially displaced by the scanning of the laser light. However, the displacement of the reflected light from the lens surfaces 51a and 171a is canceled by passing through the scanning unit 16. As a result, the image of the irradiation area A is formed in a certain area (specifically, in the area near the optical axis L2) at the installation position of the light shielding member 23 conjugated with the lens surface 171a or the lens surface 51a. To be done. That is, when the reflected light from the lens surface 171a or the lens surface 51a is reflected by the perforated mirror 13, the reflected light is incident inside the region B due to the conjugate relationship. Therefore, the light shielded by the black dots 22b is formed in the region B, so that the reflected light from the lens surface 17a is removed.

Even if there is some error between the installation position of the light blocking portion 22 and the conjugate position of the lens surface 171a or the lens surface 51a, the light blocking portion 22 favorably suppresses the reflected light from the lens surface 171a or the lens surface 51a. The inventor has confirmed that this can be done by a simulation calculation using a ray tracing method. Therefore, the installation position of the light shielding unit 22 may be separated from the front and the rear with respect to the conjugate position of the lens surface 171a or the lens surface 51a within a range suitable for the purpose of the present disclosure. When the diopter of the optical system is adjusted by the diopter adjusting unit 40, a deviation may occur between the light shielding unit 22 and the conjugate position of the lens surface 171a or the lens surface 51a, but this deviation may be allowed.

The light-shielding region (black dot 22) is formed in the range where the viewing angle (apparent size) with reference to the pinhole 23a at the installation position of the light-shielding portion 22 is equal to the viewing angle of the opening 13a of the perforated mirror 13. Good.

For example, the light-shielding region may be such that the viewing angle at the installation position of the light-shielding portion 22 with respect to the pinhole 23a completely matches that of the opening 13a. In this case, the reflected light from the lens surface 171a or the lens surface 51a may enter the light receiving elements 25, 27, 29 while suppressing a decrease in the amount of light from the fundus Er guided to the light receiving elements 25, 27, 29. Suppressed. Further, the light-shielding region may be formed such that the viewing angle with respect to the pinhole 23a is larger than the viewing angle of the opening 13a within a range where the fundus reflected light is not completely blocked.

In the following description, the light blocking portion 22a is described as blocking light in all wavelength bands emitted from the laser light emitting portion 11, but the light blocking portion 22a is not necessarily limited to this. For example, it may be a filter that transmits fluorescence (mainly a part of visible region) from the fundus and blocks observation light (mainly infrared light). In this case, by irradiating the excitation light and the observation light from the laser light emitting unit 11, it becomes possible to satisfactorily observe the fluorescent fundus image while suppressing noise light in the observation image. A light blocking member having a light blocking portion 22a formed of such a filter and a light blocking member blocking the light of all wavelength bands emitted from the laser light emitting portion 11 are arranged by switching with respect to the optical axis L2. The unit may be provided in SLO1.

<Polarizing plate>
Further, as shown in FIG. 2, the SLO 1 may include the polarization unit 45 in the light receiving optical system 20. The polarization unit 45 has a polarizing plate 46 (deflecting unit) and a drive mechanism 46a. The polarizing plate 46 is inserted/removed in the optical path between the perforated mirror 13 and the light receiving elements 25, 27, 29 by the drive control of the drive mechanism 46a. It is preferable that the direction of linearly polarized light that can be transmitted through the polarizing plate 46 be adjusted so that the reflected light from the objective lens system 17 and the second objective lens system 51 is blocked by the deflecting plate 46, and the light from the fundus is transmitted. .. The polarization direction of the reflected light from the objective lens system 17 and the second objective lens system 51 is constant. On the other hand, in the retina of the fundus, since the photoreceptor cells and the like have anisotropy, the fundus reflected light has a different polarization direction from the reflected light from the objective lens system 17 and the second objective lens system 51. Therefore, by appropriately rotating (spinning) the polarizing plate 46 around the optical axis L2, the deflecting plate 46 can be adjusted to meet the above conditions. Such adjustment work may be performed, for example, when the product is shipped.

<Other Embodiments Regarding Objective Lens System>
As described above, in the present embodiment, the shooting angle of view is switched by attaching and detaching the lens attachment 3. That is, in the present embodiment, only the objective lens system 17 of the objective lens system 17 provided in the main body portion 2 and the second objective lens system 50 provided in the lens attachment 3 in advance is used as the first objective lens system 17. Fundus imaging is performed at the shooting angle of view of. In addition, fundus imaging is performed through both the objective lens system 17 and the second objective lens system 50 at a second imaging field angle different from the first imaging field angle. However, the configuration for switching the shooting angle of view is not necessarily limited to the method of this embodiment. For example, in the objective lens system provided in the main body of the SLO, the photographing field angle may be switched by switching the positional relationship of the lenses. In this case, for example, the positional relationship between the lenses included in the objective lens system may be switched along the optical axis of the irradiation optical system, and the shooting angle of view may be switched accordingly. Further, the imaging angle of view may be switched by exchanging the lens attachment mounted on the body surface of the subject on the subject side. In this case, the main body of the SLO does not necessarily have to have the objective lens system. In any of these cases, at least some of the features described above regarding the objective lens system 17 or the second objective lens system 50 in the present embodiment can be applied. In this case, in any of the embodiments, at least a part of the irradiation optical system 10 and at least a part of the light receiving optical system 20 are housed in the same housing.

<Control system configuration>
Next, the control system of the SLO1 will be described with reference to FIG. The control unit 70 controls each unit of the SLO1. The control unit 70 is a processing device (processor) having an electronic circuit that performs control processing of each unit of the SLO 1 and arithmetic processing. The control unit 70 is realized by a CPU (Central Processing Unit), a memory, and the like. The control unit 70 is electrically connected to the storage unit 71 via a bus or the like. The control unit 70 is also electrically connected to the laser light emitting unit 11, the light receiving elements 25, 27 and 29, the driving mechanisms 14a and 46a, the scanning unit 16, the input interface 75, the monitor 80, and the like.

The storage unit 71 stores various control programs, fixed data, and the like. Further, the storage unit 71 may store temporary data and the like. The captured image by SLO1 may be stored in the storage unit 71 as shown in FIG. However, the present invention is not limited to this, and the captured image may be stored in an external storage device (for example, a storage device connected to the control unit 70 by LAN and WAN).

For the sake of convenience, in the present embodiment, the control unit 70 also serves as the image processing unit. For example, the control unit 70 forms a fundus image based on the light receiving signals output from the light receiving elements 25, 27, and 29. Further, the image processing (image processing, analysis, etc.) on the fundus image is also performed by the control unit 70. Of course, the image processing unit may be a device separate from the control unit 70. Note that, as shown in FIG. 9, the control unit 70 displays a maximum of three types of images based on the signals from the respective light receiving elements 25, 27, 29 based on the signals from the respective light receiving elements 25, 27, 29. They are generated almost at the same time.

Further, the control unit 70 controls each of the above-mentioned members based on an operation signal output from the input interface 75 (operation input unit). The input interface 75 is an operation input unit that receives an operation of an examiner. For example, a mouse and a keyboard may be used.

<Operation explanation>
Due to the characteristics of the optical system described above, it is possible to reduce the reflection of the reflected image due to the reflected light from the objective lens system 17 and the second objective lens system 50 on the fundus image. However, since the effect of suppressing glare and the amount of light from the fundus Er guided to the light receiving elements 25, 27, 29 have a trade-off relationship, the objective lens system 17 and the second objective lens system 50 Design solutions and shooting conditions that allow reflection of reflected images are also conceivable. Therefore, in the present embodiment, the reflection of the reflection image described above is also reduced by image processing.

First, an outline of processing performed by the control unit 70 of the present disclosure will be described. The control unit 70 performs a photographing process of the fundus image and photographs the fundus Er to acquire the fundus image as a photographed image. The control unit 70 also acquires a background image (also referred to as a “mask image”) for the captured image (fundus image). The “background image” includes at least a reflection image by the objective lens system. The background image is an image in which at least a reflection image by the objective lens system is captured so that the subject's eye to be examined is not captured. In addition, the background image is used in comparison with an observation image (a fundus image in the present embodiment) with a background difference that is a type of image processing (see FIG. 12 ). In addition to the reflection image of the objective lens system, the background image includes artifacts that hinder observation and analysis of the fundus image.

Such a background image may be acquired based on shooting by the shooting optical system in the “light-shielded state”. The “light-shielded state” is realized by shielding the eye to be inspected of the lens that produces a reflected image in the objective lens system. In an objective lens system having a plurality of lenses, it is desirable that light is shielded at a position on the eye to be examined side of the lens that produces a desired reflected image. For example, light may be shielded at the position of the front end of the lens barrel of the objective lens system. In this case, the reflected image resulting from all the lenses of the objective optical system may be included in the background image. The timing of capturing the background image may be before or after the capturing of the fundus image that is the target of the background difference (details will be described later).

In the objective lens system, light may be shielded by disposing a “light-shielding member” on the side of the eye to be inspected with respect to the lens that produces a reflected image. The light shielding member is arranged on the optical path of the illumination light and shields the illumination light guided to the subject's eye. The light shielding member may be a member separate from the device body, or may be provided in the device body in advance. Specifically, a lens cap, a shutter, a dark curtain, or the like can be applied as the light blocking member. In the case of a shutter, the drive mechanism (shutter mechanism) for inserting and removing the shutter (light blocking member) with respect to the optical path of the illumination light is the device body or the lens barrel of the objective lens system (for example, the lens barrel of the lens attachment may be used). May be provided. The shutter mechanism is in a closed state in which the eye to be inspected of the lens that produces a reflected image is shielded by the light shielding member in response to the insertion and removal of the light shielding member, and the eye to be inspected of the lens that produces the reflected image is shielded by the light shielding member. Switch between open state, not. Note that the shutter mechanism may be a mechanism that switches between a state in which the light-shielding member covers the front end of the lens barrel of the objective lens system and a state in which the cover is removed. It is preferable that the surface of the light shielding member that is irradiated with the illumination light is formed of a material having a high absorption rate of the illumination light. For example, black flocked paper may be used. In addition, for example, a new material using carbon nanotubes has been attracting attention in recent years, and this may be applied.

Further, the light blocking state of the light blocking member may be detected by a sensor or the like. Then, the background image may be captured (acquired) based on the detection result of the light shielding state. For example, when the shutter mechanism is provided, the background image may be captured based on the switching of the shutter mechanism from the open state to the closed state.

In the present embodiment, the background difference based on the fundus image (see FIG. 11) and the background image (see FIG. 12) is performed by the control unit 70, so that the influence of the reflection image of the objective lens system on the fundus image is suppressed. The generated image is generated as a difference image (see FIG. 13). That is, the reflection of the reflection image on the fundus image by the objective lens system is post-reduced by the image processing. The difference image in the present embodiment may be a difference image generated by directly taking the difference between the fundus image and the background image. Further, it may be a difference image generated by correcting at least one of the fundus image and the background image and taking the difference between the corrected images.

Here, the difference image obtained as a result of the background difference may have more random noise than the original fundus image. Therefore, for example, the control unit 70 may acquire a difference image for each of a plurality of fundus images obtained by photographing the same region at different timings, and generate an averaged image by each difference image. As a result, a front image of the fundus in which random noise is suppressed can be obtained together with the reflected image of the objective lens system.

Further, for example, a case where a resonant scanner is applied to the scanning unit of the irradiation optical system can be considered. In the resonant scanner, the scanning of the laser light may become unstable due to disturbance or the like. Therefore, the magnification in the scanning direction may differ between at least a part of the image between the fundus image and the background image. As a result, it is considered that the appearance position of the artifact is deviated between the fundus image and the background image. When the position of minute artifacts due to dust or the like attached to the optical system of SLO1 is deviated between the fundus image and the background image, the background difference of the minute artifacts is increased, and rather increases. It is possible.

On the other hand, the control unit 70 extracts, from the background image, the portion including the reflection image of the objective lens system, and extracts the extracted image (for convenience, referred to as “partial background image”, for example, the region U in FIG. 14). Alternatively, the difference image may be acquired by performing background difference based on the fundus image. That is, the difference image is generated by subtracting the brightness value in the partial background image for each pixel from the region in the fundus image whose position corresponds to the position of the partial background image. As a result, minute artifacts are suppressed to the same extent as the original fundus image, and a front image of the fundus in which the influence of the reflected image from the objective lens system is suppressed is generated as a difference image (see, for example, FIG. 15). .. Further, the processing time in the image processing can be shortened as compared with the case where the background difference is performed using the entire background image.

Here, in the fundus image and the background image, the position of the region where the reflection image by the objective lens system occurs is substantially constant. For example, it occurs at the center of the image. Therefore, the partial background image may be an image in which a region at a predetermined position is extracted in the background image. Further, the control unit 70 may detect the area of the reflection image by the objective lens system from the background image and extract the partial background image from the detected area.

By the way, in order to satisfactorily reduce the reflected image from the objective lens system, it is preferable that the fundus image and the background image have the same shooting conditions. Alternatively, it is preferable to suppress the influence of a difference in shooting conditions by performing image correction on one or both of the fundus image and the background image. The photographing condition is a condition (for example, a set value) relating to at least one of the output of the illumination light, the gain of the received light signal, and the diopter in the photographing optical system.

In order to match the shooting conditions with each other, for example, the control unit 70 may shoot the background image without changing (not accepting) the shooting condition after shooting the fundus image that is the target of the background difference. .. In this case, the fundus image and the background image are acquired in a series of shooting operations.

Further, the control unit 70 may store the information indicating the shooting condition when the fundus image is shot in the storage unit in association with the fundus image. Then, the control unit 70 may reproduce the shooting conditions stored in the storage unit and shoot the background image. In this case, even after the photographing condition is once reset or changed after the photographing of the fundus image, it is possible to obtain a good background image for performing the background difference from the fundus image.

Further, the control unit 70 switches the shooting conditions relating to at least one of the output of the illumination light, the gain of the received light signal, and the diopter of the shooting optical system while blocking the plurality of background images having different shooting conditions from each other. It may be acquired in advance by repeating the shooting in. In this case, the background image that is the background difference from the fundus image is selected from the plurality of background images acquired in advance. For example, the control unit 70 may select a background image acquired under the shooting condition that is the same as or closer to the shooting condition of the fundus image. The background difference between the selected background image and the fundus image is performed, and a difference image is obtained. In this case, the difference image in which the reflection image by the objective lens system is well suppressed can be obtained immediately after capturing the fundus image (for example, with a slight time lag from the capturing of the fundus image). In this method, for example, a real-time moving image can be displayed by sequentially acquiring observation images of fundus images and sequentially generating and displaying difference images based on the respective fundus images.

Here, the output characteristics of the light source and the gain characteristics of the light receiving element may change gradually over time. The background image is preferably updated as appropriate. For example, the background image may be updated every few days (including every few weeks, every few months, etc.). Further, the update time may be managed, and the control unit 70 may display guide information for notifying the update of the background image on the monitor when the update time approaches a predetermined update time.

Next, an example of a method of performing image correction on one or both of the fundus image and the background image will be described. For example, the control unit 70 may acquire at least one background image in advance when the shooting condition regarding at least one of the output of the illumination light and the gain of the received light signal is the first shooting condition. .. When the shooting condition (second shooting condition) in the fundus image that is the target of the background difference is different from the first shooting condition in the background image, the control unit 70 controls the contrast in at least one of the fundus image and the background image or The brightness may be corrected, and the background difference may be performed based on the corrected image. In this case, the correction amount in the image correction (that is, matching) regarding the contrast or the brightness may be acquired according to the information indicating the first photographing condition and the information indicating the second photographing condition. For example, the correction value may be acquired by a calculation result of a predetermined calculation formula that is a function of the information indicating the first shooting condition and the information indicating the second shooting condition. Further, the correction value may be acquired by referring to a lookup table in which the correction value is associated with each combination of the information indicating the first shooting condition and the information indicating the second shooting condition. Good. For example, the correction amounts of contrast and brightness for correcting the background image under the first shooting condition into the background image under the second shooting condition are as follows. It may be obtained from the difference from the background image. In this case, the correction value stored in the look-up table can be obtained, for example, based on a plurality of background images with different shooting conditions. In this method, many background images do not have to be stored in the storage unit in advance. Further, with this method, a good difference image can be obtained immediately after the fundus image is captured. Therefore, for example, a real-time moving image based on the difference image can be displayed.

In this method, a plurality of images having different shooting conditions (second shooting conditions) regarding at least one of the output of the illumination light and the gain of the received light signal may be used as the background image acquired in advance. .. A background image photographed under a second photographing condition that is closer to the photographing condition (first photographing condition) of the fundus image is selected from among a plurality of backgrounds having mutually different photographing conditions. Then, the contrast or brightness in at least one of the fundus image and the background image is corrected with a correction value according to the information indicating the first shooting condition and the information indicating the second shooting condition, and the corrected image The background difference may be calculated based on In this case, the correction value may be used to interpolate the difference in the shooting conditions between the plurality of background images. As a result, the number of background images acquired in advance can be suppressed. In addition, since the output characteristics of the light source and the gain characteristics of the light receiving element change over time, the correction value and the background image may be updated as appropriate.

A fundus image (referred to as a “first fundus image”) captured by the fundus reflection light of the first illumination light and a fundus reflection light of the second illumination light (having a different wavelength range from the first illumination light). Even when at least two images of the fundus image (referred to as “second fundus image”) are combined, the background difference can be applied. “Combining” may be a process of mixing colors corresponding to each image for each corresponding pixel in at least two images to generate one image.

For example, a background image in the first wavelength range (referred to as “first background image”) and a background image in the second wavelength range (referred to as “second background image”) may be acquired. Then, the background difference between the first fundus image and the first background image and the background difference between the second fundus image and the second difference image are performed to generate a first difference image and a second difference image, respectively. A combined difference image may be obtained by combining the image and the second difference image. It is considered that the reflected image in the objective lens system has different intensity distribution and range for each wavelength range. Therefore, by performing the background difference for each fundus image in each wavelength range, the reflection image of the objective lens system is appropriately suppressed in the first difference image and the second difference image. Since such images are combined, a good combined difference image can be obtained.

However, it is not always necessary to perform the background difference for each fundus image in each wavelength range. For example, the combined difference image may be obtained by a background difference based on the first combined image of the first fundus image and the second fundus image and the second combined image of the first background image and the second background image. Good. Further, a difference image may be generated by the fundus image and the background image in which the wavelength regions of the illumination light are different from each other, or a combined image using such difference images may be generated.

Next, a specific operation in SLO1 will be described with reference to the flowchart shown in FIG. After the alignment between the eye to be inspected and the apparatus (S1) is completed, the imaging mode is selected by the control unit 70 (S2). For example, a plurality of shooting modes may be prepared in advance depending on the shooting method and the angle of view. For example, in the present embodiment, the shooting modes are roughly classified into a “normal mode”, which is a shooting mode when the lens attachment 3 is not attached, and a “wide-angle mode” which is a shooting mode when the lens attachment 3 is attached. To be done. That is, the "wide-angle mode" has a larger shooting angle of view than the "normal mode". Each of the “normal mode” and the “wide-angle mode” further includes, as a shooting mode, a mode for shooting a fundus image by fundus reflection light (more specifically, an “IR mode” for infrared shooting). , And a “color mode” for color photography, and a mode for photographing a fundus image by fluorescence emitted from the fundus (more specifically, “ICG mode” for ICG photography, FAG photography “FA mode” for automatic fluorescence imaging, “FAF mode” for spontaneous fluorescence imaging, etc.) may be prepared. These shooting modes may be selected, for example, according to a shooting mode selection operation performed on the input interface 75. Further, the control unit 70 may automatically select the shooting mode based on the detection result of the state of the device and/or according to a predetermined shooting order. In this case, for example, the control unit 70 selects the “normal mode” or the “wide-angle mode” according to a signal from the sensor 8 (see FIG. 1) indicating whether or not the lens attachment 3 is attached. May be.

In accordance with the selected photographing mode, the control unit 70 controls the light receiving element used for observing and photographing the fundus image among at least the wavelength region of the laser light from the laser light emitting unit 11 and the three light receiving elements 25, 27, 29. The setting of the photographing optical system (irradiation optical system 10 and light receiving optical system 20) is switched (S3).

Next, the control unit 70 determines whether or not a specific shooting mode is selected (S4). The specific shooting mode mentioned here is a mode in which shooting is performed by utilizing the fundus reflected light. For example, "IR mode", "color mode", and the like. In the present embodiment, a filter (for example, dichroic mirrors 31 and 32. Other filters (not shown) or the like may be used) provided in the light separating unit 30 or the like may be used for fluorescence imaging in a wavelength range of excitation light (that is, an objective light). Light in the wavelength range of the reflected light from the lens system 17 and the second objective lens system 50 is less likely to enter the light receiving element for obtaining the fluorescence image. For this reason, the above-mentioned glare is unlikely to be a problem in a captured image. However, even in the fluorescence image, a reflected image may occur due to the reflection by the objective lens system 17 and the second objective lens system 50. Therefore, the background difference may be performed on the fluorescence image as well. In this case, it is preferable to perform the background difference with the background image taken under the same imaging conditions as when the fundus is fluorescently imaged. For example, in the configuration in which the exciter filter and the barrier filter are inserted into the optical path of the photographing optical system during fluorescence photographing, the background image may be acquired by photographing under the condition that the filters are similarly arranged. Further, for example, if the above-mentioned reflection is a problem only in the “wide-angle mode” of the “normal mode” and the “wide-angle mode”, the “wide-angle mode” is set as the condition of the specific shooting mode. May be done.

In the case of the specific shooting mode (S4: Yes), the control unit 70 limits the adjustment range of at least one of the light amount and the gain (S5). For example, the adjustment range is such that, in the fundus image and the background image to be described later, the brightness value of a region (for example, the central portion of the fundus image) where the reflection image of the objective lens system 17 and the second objective lens system 50 is reflected is saturated ( It is limited to the range that does not. This is because when the luminance value is saturated, the area does not include information indicating the structure of the fundus. Such an adjustment range may be set in advance, for example, based on the results of experiments or the like, or may be set based on an observation image. The “limitation of the adjustment range” means that the adjustment range is narrower than the shooting modes other than the specific shooting mode in the shooting modes of SLO1. It includes switching at least one of the light amount and the gain to a certain value (fixed value).

Next, the fundus image is photographed (S6). For example, in the “color mode”, a color fundus image is captured. The laser light emitting section 11 simultaneously emits light in the red, green, and blue wavelength ranges (may be emitted sequentially at different timings), and based on the signals from the respective light receiving elements 25, 27, 29, red, A reflection image based on light in the green and blue wavelength ranges is formed. Then, a color fundus image is formed by combining these reflection images (see FIG. 11). The color fundus image thus obtained may be stored in the storage unit 71.

Next, in this embodiment, a background image is captured (S7). The background image includes artifacts that hinder observation and analysis in the fundus image. In the present embodiment, a typical artifact is the reflected image S from the objective lens systems 17a and 51a. Images such as dust adhering to the optical system, scratches, stains on the optical system, and flare may be included in the background image as artifacts. Further, in the SLO, it is considered that the reflection of the edge of an optical scanner such as a galvanometer mirror also occurs as an artifact. FIG. 12 shows an image D of dust as an example.

The background image may be, for example, an SLO image captured while being shielded from light at the positions of the eye E to be inspected and the lens surfaces (for example, the lens surface 51a and the lens surface 171a) arranged closest to the eye E to be inspected. .. “Shading” means that a shading member is arranged between the lens surface 51a (or the lens surface 171a) closest to the eye E to be inspected and the eye E so that the fundus does not appear in the SLO image captured as the background image. Therefore, it may be realized. The light blocking member does not necessarily have to be provided in the device in advance. For example, a lens cap, a shutter, a dark curtain, or the like can be applied as the light blocking member. The shutter mechanism may be provided in the main body of the SLO 1 or the lens attachment 3, and in this case, the shutter mechanism lowers the shutter at the rear stage (the side away from the light source) of the lens 51 and the lens 171, and shields light.

Further, it is not always necessary to realize the light shielding by disposing the light shielding member at the position of the lens surface 51a (or the lens surface 171a). For example, by closing the eyelids of the eye E to be examined, the fundus Er does not appear in the SLO image. Therefore, it can be considered that the light is shielded by closing the eyelid of the subject. In this case, for example, the control unit 70 may detect the blink of the eye to be inspected and capture the background image while the eyelid is closed by the blink.

The background image may be captured by detecting that the light is shielded and using the detection as a trigger (in other words, based on the detection signal). Specifically, for example, the body of the lens attachment 3, and/or SLO 1 may be provided with a sensor for detecting that the position of the lens surface closest to the subject's eye is shielded. Based on the signal from the sensor, the control unit 70 may identify whether or not the light is shielded. Further, if it is a blink, it may be detected based on a result of photographing the anterior segment by an anterior segment camera (not shown), or based on a histogram of an observed image or the like. However, when the light blocking state is detected, the background image may not be automatically captured. For example, when the examiner confirms the light blocking and inputs a predetermined operation to the input interface 75, The background image may be captured based on the input.

In the process of S7, after the fundus image of S6 is captured, the output of the light source (light amount), the gains of the light receiving elements 25, 27, 29, and the imaging conditions regarding the diopter of the optical system are acquired in S6. From time to time, shooting is performed in a light-shielded state without changing. As a result of such shooting, a background image is acquired.

Next, the control unit 70 acquires a difference image by the background difference based on the fundus image and the background image (S8). In the difference image, the influence of artifacts on the fundus image is suppressed. For example, as shown in FIG. 13, an image in which the reflection image S by the objective lens systems 17a and 51a and the image D such as dust are removed from the fundus image of FIG. 11 is acquired as a difference image. The acquired difference image may be stored in the storage unit 71. It may also be displayed on the monitor 75. In this way, the reflection of the reflection image by the objective lens system in the fundus image is reduced after the fact by the image processing.

In the process of S8, the contrast of the difference image may be adjusted together with the background difference. For example, the correction process of adjusting the contrast is included in the process of S8 so that the histogram of the intermediate image (a kind of difference image) obtained by the background difference is expanded in the predetermined gradation range. Good.

Here, the difference image after the contrast adjustment is represented by the first gradation number (for example, 8 bits). The first number of gradations may be the number of gradations displayed on the monitor 75. On the other hand, SLO1 may acquire an image represented by a second gradation number (for example, 12 bits) larger than the first gradation number by the processes of S6 and S7. That is, both the fundus image and the background image that are the targets of the background difference may be represented by the second gradation number. Then, the control unit 70 performs background difference between the images represented by the second gradation number to obtain an intermediate image (a kind of difference image). Then, after the contrast adjustment is performed on the intermediate image, the image after the contrast adjustment may be compressed to obtain the difference image represented by the first gradation number. By doing so, the artifact can be removed more accurately.

In the present embodiment, in order to obtain the difference image, the background image and the fundus have the same imaging conditions (that is, the output of the light source, the gains of the light receiving elements 25, 27, 29, and the imaging conditions regarding the diopter of the optical system). Background subtraction is performed based on the image. Since the shooting conditions are the same, it is difficult for the background image and the fundus image to show different artifact components in the respective images. Therefore, the influence of artifacts on the difference image is easily suppressed.

The image processing such as the background difference described above can be appropriately applied to the SLO having a refraction system (lens system) in the objective optical system. However, as described above, when the luminance value of the reflection image S is saturated in the fundus image, as a result of removing the artifacts by the background difference, information on the fundus at the position of the reflection image S is obtained in the difference image. It is possible that it does not exist. In order to suppress the saturation of the brightness value in the reflected image S, the characteristic for suppressing the reflection of the reflected light from the objective lens system 17 and the second objective lens system 50 shown in the present embodiment. At least one of them may be appropriately used together with the image processing.

Further, the image processing such as the background difference described above is not limited to the application to the SLO, and other than that, “the objective lens system including at least one lens and the illumination light emitted from the light source are described above. An imaging optical system including an irradiation optical system that irradiates the eye to be inspected through the objective lens system, and a light receiving optical system including a light receiving element that receives reflected light of illumination light from the eye to be inspected through the objective lens system. The present invention may also be applied to an ophthalmologic image capturing apparatus that includes a light emitting element and generates a captured image based on a signal from the light receiving element. Such an ophthalmologic photographing apparatus may be a fundus photographing apparatus. In this case, the irradiation light system irradiates the fundus of the subject's eye with the illumination light, and the light receiving optical system receives the fundus reflected light of the illumination light by the light receiving element. As a fundus imaging apparatus other than SLO, for example, a fundus camera or the like can be considered. Further, the ophthalmologic imaging apparatus may be an anterior segment imaging apparatus.

Although the description has been given above based on the embodiment, the content of the embodiment can be appropriately changed in implementing the present disclosure.

1 SLO
10 Irradiation Optical System 11 Laser Light Emitting Unit 17 Objective Lens System 20 Light Receiving Optical System 50 Second Objective Lens System 70 Control Unit 71 Storage Unit

Claims (5)

An objective lens system including at least one lens, an irradiation optical system for irradiating illumination light emitted from a light source to an eye to be inspected through the objective lens system, and reflected light of the illumination light by the eye to be inspected A light receiving optical system including a light receiving element that receives light via a system, and a photographing optical system including: a ophthalmic photographing apparatus that generates a photographed image based on a signal from the light receiving element,
Front image capturing means for obtaining a front image of the eye to be inspected as the captured image,
Background image acquisition means for acquiring a background image for the front image of the eye to be inspected acquired by the front image capturing means, the background image including at least a reflection image by the objective lens system,
A background difference is performed based on the front image of the eye to be examined and the background image, and as a difference image, image processing means for generating an image in which the influence of the reflection image is suppressed in the front image of the eye to be inspected ,
The front image capturing means includes, from the irradiation optical system, each of the first illumination light having the first wavelength and the second illumination light having a second wavelength different from the first wavelength from the illumination optical system. The first front image of the eye to be inspected based on the reflected light of the first illumination light, and the second front image of the eye to be inspected based on the reflected light of the second illumination light,
The background image acquisition means acquires a first background image that is a background image based on the first illumination light and a second background image that is a background image based on the second illumination light.
The image processing means synthesizes a first difference image based on the first front image and the first background image, and a second difference image based on the second front image and the second background image. An ophthalmologic imaging device that obtains a synthetic difference image . An objective lens system including at least one lens, an irradiation optical system for irradiating illumination light emitted from a light source to an eye to be inspected through the objective lens system, and reflected light of the illumination light by the eye to be inspected A light receiving optical system including a light receiving element that receives light via a system, and a photographing optical system including: a ophthalmic photographing apparatus that generates a photographed image based on a signal from the light receiving element,
Front image capturing means for obtaining a front image of the eye to be inspected as the captured image,
Background image acquisition means for acquiring a background image for the front image of the eye to be inspected acquired by the front image capturing means, the background image including at least a reflection image by the objective lens system,
A background difference is performed based on the front image of the eye to be examined and the background image, and as a difference image, image processing means for generating an image in which the influence of the reflection image is suppressed in the front image of the eye to be inspected,

The front image capturing means includes, from the irradiation optical system, each of the first illumination light having the first wavelength and the second illumination light having a second wavelength different from the first wavelength from the illumination optical system. The first front image based on the reflected light of the first illumination light and the second front image based on the reflected light of the second illumination light.
The background image acquisition means acquires a first background image that is a background image based on the first illumination light and a second background image that is a background image based on the second illumination light.
The image processing means is a synthetic difference image based on a background difference based on a first combined image of the first front image and the second front image, and a combined image of the first background image and the second background image. obtained Ru eye School shooting device. An objective lens system including at least one lens, an irradiation optical system for irradiating illumination light emitted from a light source to an eye to be inspected through the objective lens system, and reflected light of the illumination light by the eye to be inspected A light receiving optical system including a light receiving element that receives light via a system, and a photographing optical system including: a ophthalmic photographing apparatus that generates a photographed image based on a signal from the light receiving element,
A fundus image photographing means for obtaining a fundus image which is a front image of the fundus of the eye to be examined as the photographed image,
Background image acquisition means for acquiring a background image for a fundus image of the eye to be inspected acquired by the fundus image capturing means, the background image including at least a reflection image by the objective lens system,
Performing a background difference based on the fundus image of the eye to be examined and the background image, as a difference image, an image processing unit that generates an image in which the influence of the reflection image is suppressed in the fundus image of the eye to be examined,
A first photographing mode to photograph a fundus image by the fundus reflection light, and a second switching control means for switching a photographing mode, the controls at least the light source for photographing a fundus image by the fluorescence emitted from the fundus ,,
The image processing means performs the background subtraction on the fundus image captured in the first capturing mode, and does not perform the background subtraction on the fundus image captured in the second capturing mode. There ophthalmology imaging apparatus. An objective lens system including at least one lens, an irradiation optical system for irradiating illumination light emitted from a light source to an eye to be inspected through the objective lens system, and reflected light of the illumination light by the eye to be inspected A light receiving optical system including a light receiving element that receives light via a system, and a photographing optical system including: a ophthalmic photographing apparatus that generates a photographed image based on a signal from the light receiving element,
Front image capturing means for obtaining a front image of the eye to be inspected as the captured image,
Background image acquisition means for acquiring a background image for the front image of the eye to be inspected acquired by the front image capturing means, the background image including at least a reflection image by the objective lens system,
A background difference is performed based on the front image of the eye to be examined and the background image, and as a difference image, image processing means for generating an image in which the influence of the reflection image is suppressed in the front image of the eye to be inspected,
The photographing optical system has a first photographing mode for photographing the photographed image at a first angle of view and a second photographing mode for photographing the photographed image at an angle of view narrower than the first angle of view. And can be switched to
The image processing means performs the background subtraction on a front image of the eye to be inspected captured in the first imaging mode, and for the front image of the eye to be inspected captured in the second imaging mode. the background difference has ophthalmology imaging apparatus, such carried out. An objective lens system including at least one lens, an irradiation optical system for irradiating illumination light emitted from a light source to an eye to be inspected through the objective lens system, and reflected light of the illumination light by the eye to be inspected A light receiving optical system including a light receiving element that receives light via a system, and a photographing optical system including: a ophthalmic photographing apparatus that generates a photographed image based on a signal from the light receiving element,
Front image capturing means for obtaining a front image of the eye to be inspected as the captured image,
Background image acquisition means for acquiring a background image for the front image of the eye to be inspected acquired by the front image capturing means, the background image including at least a reflection image by the objective lens system,
A background difference is performed based on the front image of the eye to be examined and the background image, and as a difference image, image processing means for generating an image in which the influence of the reflection image is suppressed in the front image of the eye to be inspected,
The front image capturing unit and the background image acquisition unit respectively acquire a front image of the eye to be inspected and a background image represented by a first gradation number,
The image processing means performs a background difference between the front image of the eye to be inspected represented by the first gradation number and the background image, and a second gradation number smaller than the first gradation number. in ophthalmology imaging apparatus that generates a difference image to be represented.