JP7593864B2 - Ophthalmic device and control method thereof - Google Patents

Description

The present invention relates to an ophthalmic device and a control method capable of deflecting illumination light that illuminates a part of an area to be examined of a subject's eye.

A slit-scan type fundus camera (ophthalmic device) that photographs the fundus of a subject's eye is known (see Patent Document 1). The fundus camera described in Patent Document 1 uses an optical scanner to deflect slit light (illumination light) that is irradiated onto the fundus, while capturing the return light from the illumination area of the slit light that moves within the fundus with a CMOS (Complementary Metal Oxide Semiconductor) type imaging element that has a rolling shutter function. This makes it possible to obtain a fundus image in which the effects of scattered light are suppressed.

With such a fundus camera, it is necessary to evaluate the focusing state (also called the focusing situation) of the fundus camera relative to the fundus before starting to photograph the fundus, and to perform focusing control (focus adjustment) to focus the fundus camera on the fundus based on the evaluation results.

For example, in the fundus camera described in Patent Document 2, split index light is irradiated onto the fundus, and the return light of the split index light from the fundus is detected by a detector. Based on the detection result, the focus state of the fundus camera is evaluated and focus control is performed.

In the ophthalmic device (auto-refractor keratometer) described in Patent Document 3, a ring illumination light is irradiated onto the fundus, and the return light of the ring illumination light from the fundus is detected by a detector, and based on the detection result, the focus state of the ophthalmic device is evaluated and focus control is performed. Furthermore, in the ophthalmic device (auto-refractor keratometer) described in Patent Document 4, the contrast of the fundus image is used as an index to evaluate the focus state of the ophthalmic device relative to the fundus and focus control is performed.

Patent No. 5735211 Patent No. 6518054 JP 2014-108310 A JP 2016-159071 A

However, when applying the method described in Patent Document 2 or Patent Document 3 to a slit-scan type fundus camera to evaluate the focusing state of the fundus camera, it is necessary to provide a separate illumination system that emits split index light or ring illumination light to the fundus camera, which increases costs.

In addition, when the method described in Patent Document 4 is applied to a slit-scan fundus camera, there is no need to provide a separate illumination system. However, fundus cameras generally use infrared light (near-infrared light), to which the eye has low sensitivity, as illumination light for evaluating the focus state, which reduces the contrast of the fundus image used for evaluating the focus state. As a result, when evaluating the focus state using the contrast of the fundus image as an index, there is a risk that the accuracy will decrease or the evaluation will fail.

The present invention has been made in consideration of these circumstances, and aims to provide an ophthalmic device and a control method thereof that can evaluate the focusing state of the ophthalmic device with respect to the observed area at low cost and with high accuracy.

The ophthalmic apparatus for achieving the object of the present invention includes an illumination system that irradiates illumination light onto a part of an observed area of a subject's eye, an optical scanner that deflects the illumination light irradiated from the illumination system onto the observed area to move the illumination area of the illumination light within the observed area, a light receiving system having a detector that detects return light from the illumination area that moves within the observed area in response to the deflection of the illumination light while the optical scanner is deflecting the illumination light, and a focus confirmation control unit that controls the optical scanner to perform focus confirmation control to cause the detector to detect the return light from the illumination area while the illumination area is fixed within the observed area. The return light referred to here is light that returns from the illumination area of the observed area or an area nearby, and includes reflected light of the illumination light, scattered light of the illumination light, and fluorescence excited by the illumination light and its scattered light.

An ophthalmic device according to another aspect of the present invention includes a focus optical system provided in the optical path of the return light, and a focus control unit that performs focus control of the focus optical system based on a detection signal of the return light detected by the detector during focus confirmation control.

An ophthalmologic apparatus according to another aspect of the present invention includes an image generating unit that generates a focus evaluation image indicating the focus state of the illumination system and the light receiving system for the observed area based on the detection signal, and a focus control unit performs focus control based on the focus evaluation image generated by the image generating unit.

In an ophthalmic device according to another aspect of the present invention, the focus optical system has a focus lens, and is provided with a repeat control unit that repeatedly operates the focus confirmation control unit and the image generation unit for each of a plurality of different lens positions of the focus lens, and the focus control unit performs focus control based on the focus evaluation image for each lens position generated by the image generation unit.

In another aspect of the ophthalmic device of the present invention, the detector has a light receiving surface on which the returning light is incident, and has a first operation mode in which the detector continuously detects the returning light in the light receiving area while tracking a local light receiving area that detects the returning light within the light receiving surface with the incident area of the returning light that moves within the light receiving surface in response to the movement of the illumination area, and a second operation mode in which the light receiving area is moved along a predetermined movement path within the light receiving surface, and the returning light from the illumination area fixed by the optical scanner in the focus confirmation control is incident on the middle of the movement path of the light receiving area, and the focus confirmation control unit drives the detector in the second operation mode.

In another aspect of the ophthalmic device of the present invention, the detector has a light receiving surface on which the returning light is incident, and has a first operation mode in which the detector continuously detects the returning light in the light receiving area while tracking a local light receiving area that detects the returning light within the light receiving surface with the incident area of the returning light that moves within the light receiving surface in response to the movement of the illumination area, and a third operation mode in which the light receiving area is fixed at a position within the light receiving surface where the returning light from the illumination area fixed by the optical scanner can be detected, and a focus confirmation control unit drives the detector in the third operation mode.

In an ophthalmic device according to another aspect of the present invention, when directions perpendicular to the optical axis of the illumination system and perpendicular to each other are defined as a first direction and a second direction, the illumination system irradiates the observed area with a slit light parallel to the first direction as illumination light, and the optical scanner deflects the slit light in the second direction.

An ophthalmic apparatus according to another aspect of the present invention includes an aperture provided in an illumination system, which is optically conjugate with the anterior segment of the subject's eye and has multiple apertures at positions eccentric to the illumination optical axis of the illumination system.

To achieve the object of the present invention, a control method for an ophthalmic device including an illumination system that irradiates illumination light onto a part of an observed area of a subject's eye, an optical scanner that deflects the illumination light irradiated from the illumination system onto the observed area to move the illumination area of the illumination light within the observed area, and a light receiving system having a detector that detects return light from the illumination area that moves within the observed area in response to the deflection of the illumination light while the optical scanner is deflecting the illumination light, includes a focus confirmation control step that controls the optical scanner to fix the illumination area within the observed area and causes the detector to detect the return light from the illumination area.

The present invention can evaluate the focusing state of an ophthalmic device for the area being observed at low cost and with high accuracy.

FIG. 1 is a schematic diagram of a fundus camera. FIG. 2 is a functional block diagram of a control device. 3A is an explanatory diagram comparing the fundus (see symbol 3A) and the light receiving surface of the imaging element (see symbol 3B) during slit scan photography. FIG. FIG. 4 is an explanatory diagram showing an example of a fundus image generated by an image generating unit. 5A is a ray diagram of a light beam incident on a subject's eye when focused (see symbol 5A), and a front view of a light beam incident on an anterior segment (see symbol 5B). FIG. Reference numerals 6A and 6B are explanatory diagrams showing ray diagrams of light beams incident on the subject's eye when out of focus. 7A and 7B are explanatory diagrams comparing the fundus (see symbol 7A) and the light receiving surface of the imaging element (see symbol 7B) when focus confirmation control is executed during focusing. 8A is an explanatory diagram comparing the fundus (see symbol 8A) and the light receiving surface of the imaging element (see symbol 8B) when focus confirmation control is executed during out-of-focus. FIG. 5 is an explanatory diagram showing an example of a focus evaluation image generated by an image generating unit when focusing; FIG. 11 is an explanatory diagram showing an example of a focus evaluation image generated by an image generating unit when the image is out of focus; FIG. 11 is a flowchart showing a flow of fundus photographing processing of a slit scan type using a fundus camera, in particular, a flow of focus confirmation control. 13 is an explanatory diagram for explaining a modified example of driving the image sensor by the focus confirmation control unit during focus confirmation control. FIG. 11 is an explanatory diagram showing a modified example of the irradiation position of illumination light on the fundus during focus confirmation control (see reference symbol XIIIA) and the correspondence relationship between the focus evaluation image (see reference symbol XIIIB). FIG. 13 is a front view of another example of light beams incident on the anterior segment of the subject's eye from the illumination system through two paths. FIG.

[Overall configuration of fundus camera]
1 is a schematic diagram of a fundus camera 10 corresponding to an ophthalmologic apparatus of the present invention. In the mutually orthogonal XYZ directions in the figure, the X direction is a left-right direction based on the subject (the interpupillary direction of the subject's eye E), the Y direction is a top-bottom direction, and the Z direction is a front-back direction (also called a working distance direction) parallel to the front direction approaching the subject and the rear direction away from the subject.

As shown in FIG. 1, the fundus camera 10 corresponds to the ophthalmic device of the present invention, and photographs the fundus Ef of the subject eye E using a slit scan method (hereinafter, abbreviated as slit scan photography). This fundus camera 10 is roughly divided into a camera head 12 (also called the device body), an operation unit 14, a display unit 16, and a control device 18.

The camera head 12 is provided with various optical systems and the like necessary for slit scan photography, which will be described in detail later. In addition, although not shown, the camera head 12 is held so as to be movable relative to the subject's eye E in the XYZ directions by a drive mechanism (not shown). This allows the camera head 12 to move relative to the subject's eye E in the XYZ directions, making it possible to align the camera head 12 with the subject's eye E.

The operation unit 14 accepts inputs for various operations of the fundus camera 10, such as starting slit scan photography, moving the camera head 12 in the XYZ directions, and setting the fundus camera 10.

The display unit 16 may be any of a variety of known displays, such as an LCD (Liquid Crystal Display). The display unit 16 displays a fundus image D, which is an observation image (frontal image) of the fundus Ef generated by the control device 18 (described below), as well as various setting screens, etc.

The control device 18 is a processing device such as a computer that executes various types of calculation processing and control processing. The camera head 12, the operation unit 14, and the display unit 16 are connected to this control device 18. The control device 18 controls the operation of each part of the camera head 12 and the display unit 16 based on the operation instructions input to the operation unit 14. The control device 18 executes various controls and processes including alignment of the camera head 12, focus confirmation control for capturing a focus evaluation image DS (see FIG. 9) showing the focus state of the illumination system 20 and the light receiving system 40 on the fundus Ef, focus control of the focus optical system 36, slit scan photography of the fundus Ef by the camera head 12, and generation and display of a fundus image D.

[Camera head configuration]
The camera head 12 includes an illumination system 20 , an optical scanner 30 , and a light receiving system 40 .

The illumination system 20 irradiates a portion of the fundus Ef with illumination light LS (slit light) via an optical scanner 30 described below. This illumination system 20 includes a light source 22, an aperture 24, a slit aperture 26, an illumination system lens 28, a lens 31, an optical path splitting member 34, and an objective lens 38. The aperture 24, the optical scanner 30, the optical path splitting member 34, and the anterior segment Ea of the subject's eye E are in an optically conjugate relationship.

The light source 22 emits illumination light L. Visible light is used as this illumination light L when slit scan photography of the fundus Ef is performed, and infrared light, which is light in the infrared region (including the near-infrared region) to which the subject's eye E has low sensitivity, is used during focus confirmation control, which will be described later. Visible light may also be used during focus confirmation control. The light source 22 may be, but is not limited to, a laser light source, an LED (Light Emitting Diode) light source, a white LED light source, a laser-excited white light source, or the like.

The diaphragm 24 includes, but is not limited to, a diaphragm (such as an iris diaphragm or a front lens diaphragm) that is optically conjugate or nearly optically conjugate with the anterior segment Ea (cornea and iris) of the subject's eye E. The diaphragm 24 is a light-shielding member having a pair of openings 24a that are symmetrical about the central axis of the light source 22. The number and arrangement of the openings 24a are not particularly limited as long as multiple openings 24a are provided at positions eccentric to the central axis of the light source 22. The illumination light L that passes through the diaphragm 24 is incident on the slit aperture diaphragm 26.

The slit aperture diaphragm 26 generates illumination light LS parallel to the X direction (corresponding to the first direction of the present invention) from the illumination light L incident from the diaphragm 24, and emits this illumination light LS toward the illumination system lens 28. When focused, the illumination light LS becomes a slit shape (slit light) parallel to the X direction at the fundus position and the fundus conjugate position. Note that the illumination light LS (slit light) is not particularly limited as long as it is perpendicular to the optical axis of the objective lens 38 (illumination system 20). In addition, the slit aperture diaphragm 26 is provided so as to be freely movable along the optical path of the illumination light LS by an actuator (not shown). By moving this slit aperture diaphragm 26, the illumination system 20 can be focused on the fundus Ef.

The illumination system lens 28 is composed of one or more lenses, and emits the illumination light LS incident from the slit aperture diaphragm 26 toward the optical scanner 30. The lens 31 emits the illumination light LS reflected by the optical scanner 30 toward the optical path splitting material 34. The lens 31 makes the optical scanner 30 and the optical path splitting material 34 optically conjugate. The optical path splitting material 34 and the objective lens 38 will be described later.

The illumination system 20 may be a projector capable of emitting illumination light LS. Examples of such projectors include LCD projectors, LCOS (Liquid crystal on silicon) projectors using a reflective liquid crystal panel, and projectors using a DMD (Digital Mirror Device). In this case, the optical scanner 30 may be replaced by a fixed mirror, and the optical scanning performed by the optical scanner 30 may be simulated by changing the pattern of the projector.

The optical scanner 30 is a deflection mechanism capable of one-dimensionally deflecting (scanning) the illumination light LS, such as a galvanometer mirror, a resonant mirror, a polygon mirror, or a MEMS (Micro Electro Mechanical Systems), and is disposed at the intersection of the optical axis of the illumination system lens 28 and the optical axis of the lens 31. The optical scanner 30 reflects the illumination light LS incident from the illumination system lens 28 toward the lens 31, and is capable of deflecting the illumination light LS.

The polarization direction and deflection angle of the illumination light LS by the optical scanner 30 are controlled by the control device 18. During slit scan photography, the optical scanner 30 deflects the illumination light LS in a direction perpendicular to both the optical axis of the objective lens 38 and the slit light, in this case the Y direction (corresponding to the second direction of the present invention).

The optical path splitting material 34 reflects the illumination light LS incident from the lens 31 and emits it toward the objective lens 38, and also passes the return light LB incident from the objective lens 38, which will be described later, and emits it toward the focus optical system 36. Note that various splitters can be used as the optical path splitting material 34 as long as it is capable of splitting the illumination light LS and the return light LB, reflecting the illumination light LS toward the objective lens 38, and emitting the return light LB toward the focus optical system 36.

The objective lens 38 irradiates the illumination light LS reflected by the optical path splitting material 34 onto a part of the fundus Ef through the anterior segment Ea (pupil) of the subject's eye E. At this time, the illumination light LS is deflected in the Y direction by the optical scanner 30 described above, and the fundus Ef is scanned in the Y direction with the illumination light LS (slit light) parallel to the X direction. While the illumination light LS is being deflected in the Y direction, the return light LB from the fundus Ef of the subject's eye E irradiated with the illumination light LS enters the focus optical system 36 through the objective lens 38 and the optical path splitting material 34.

The light receiving system 40 includes an objective lens 38, an optical path splitter 34, a focusing optical system 36, a light receiving system lens 42, and a CMOS type image sensor 44 which corresponds to the detector of the present invention.

The focus optical system 36 includes one or more lenses (focus lenses) that can move along the optical path of the return light LB, and adjusts the focus of the fundus camera 10 (light-receiving system 40) under the control of the control device 18. The focusing of the light-receiving system 40 by the focus optical system 36 and the focusing of the illumination system 20 by the slit aperture diaphragm 26 move in conjunction with each other according to the diopter (visual acuity) of the subject's eye E. The return light LB that enters the focus optical system 36 from the optical path splitter 34 enters the light-receiving system lens 42. Note that instead of providing one or more movable focus lenses in the focus optical system 36, one or more variable focus lenses may be provided, and the method of focus adjustment is not particularly limited.

The light receiving lens 42 is composed of one or more lenses, and focuses the return light LB incident from the focus optical system 36 onto the image sensor 44.

The image sensor 44 has a light receiving surface 44a on which the return light LB from the light receiving lens 42 is incident, and has a rolling shutter function that captures (receives, detects) the return light LB while shifting the timing of the start and end of exposure for each area (including each pixel and each line) within this light receiving surface 44a. During slit scan photography, this image sensor 44 is driven by the control device 18 as a rolling shutter to capture the return light LB of the illumination light LS that moves within the fundus Ef in response to the deflection of the illumination light LS by the optical scanner 30, and outputs an image signal of the return light LB to the control device 18.

[Control device functions]
Fig. 2 is a functional block diagram of the control device 18. As shown in Fig. 2, the functions of the control device 18 are realized by using various processors. The various processors include a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and a programmable logic device (e.g., simple programmable logic devices (SPLD), complex programmable logic devices (CPLD), and field programmable gate arrays (FPGA)). The various functions of the control device 18 may be realized by one processor, or may be realized by multiple processors of the same type or different types.

The control device 18 executes a control program (not shown) to function as an illumination control unit 50, a deflection control unit 52, an imaging control unit 54, a signal acquisition unit 56, an image generation unit 58, a focus confirmation control unit 59, a repetition control unit 61, a focus control unit 62, and a display control unit 64. Note that what is described as a "unit" of the control device 18 may also be a "circuit", a "device", or a "equipment". In other words, what is described as a "unit" may be composed of firmware, software, and hardware, or a combination of these.

(Slit scan photography)
First, a description will be given of functions related to slit scan photography of the control device 18. During slit scan photography, the illumination control unit 50, the deflection control unit 52, the imaging control unit 54, the signal acquisition unit 56, the image generation unit 58, and the display control unit 64 of the control device 18 function.

The illumination control unit 50 controls the emission of illumination light L from the light source 22, i.e., the emission of illumination light LS from the illumination system 20. This illumination control unit 50 causes the illumination light L (visible light) to be emitted from the light source 22 during slit scan photography.

Figure 3 is an explanatory diagram comparing the fundus Ef (see symbol 3A) and the light receiving surface 44a (see symbol 3B) of the image sensor 44 during slit scan photography. Symbol R1A in Figure 3 indicates the illumination area R1A of the illumination light LS in the fundus Ef, and symbol R1B indicates the incidence area R1B of the return light LB that enters the light receiving surface 44a. Also, symbol R2B in Figure 3 indicates the light receiving area R2B (active exposure area) in the light receiving surface 44a, and symbol R2A indicates the imaging range R2A imaged by the light receiving area R2B in the fundus Ef.

In the figure, the width of the imaging range R2A is larger than the width of the illumination area R1A, and the width of the light receiving area R2B is larger than the width of the entrance area R1B, but this is not limited to the above. In other words, the individual positional shapes of the illumination area R1A and imaging range R2A within the fundus Ef, and the individual positional shapes of the entrance area R1B and light receiving area R2B within the light receiving surface 44a are not limited to the example shown in FIG. 3, and may be changed as appropriate (the same applies to other figures).

As shown in FIG. 3 and the above-mentioned FIG. 2, the deflection control unit 52 controls the deflection angle of the illumination light LS by the optical scanner 30. During slit scan photography, the deflection control unit 52 controls the optical scanner 30 to deflect the illumination light LS in the Y direction, thereby scanning the fundus Ef in the Y direction with the illumination light LS (slit light).

In response to the deflection of the illumination light LS in the Y direction, the illumination area R1A of the illumination light LS in the fundus Ef moves in the Y direction (see reference symbol 3A in FIG. 3). In response to the movement of the illumination area R1A, the incidence area R1B of the return light LB moves in the Y direction in the light receiving surface 44a (see reference symbol 3B in FIG. 3). The control of the optical scanner 30 during focus confirmation control by the deflection control unit 52 will be described later.

The imaging control unit 54 controls the driving of the imaging element 44. During slit scan photography, the imaging control unit 54 performs rolling shutter driving of the imaging element 44 (driving in the first operating mode of the present invention) while the illumination light LS is being deflected in the Y direction by the optical scanner 30, i.e., while the illumination area R1A is moving in the Y direction within the fundus Ef.

Specifically, the imaging control unit 54 continuously captures images of the return light LB by the local light receiving area R2B at a position corresponding to the entrance area R1B on the light receiving surface 44a in response to (synchronization with) the movement of the entrance area R1B in the Y direction on the light receiving surface 44a. As a result, the imaging control unit 54 continuously captures images of the return light LB by the light receiving area R2B while making the light receiving area R2B follow the entrance area R1B moving in the Y direction on the light receiving surface 44a (see symbol 3B).

In other words, within the fundus Ef, the imaging element 44 continuously captures an image of the local imaging range R2A while tracking the illumination area R1A moving in the Y direction (see symbol 3A). This type of rolling shutter drive is a known technique, so a detailed description will be omitted (see Patent Document 1 above).

The signal acquisition unit 56 is connected to the image sensor 44 by wire or wirelessly via a communication interface (not shown). During slit scan photography, the signal acquisition unit 56 sequentially acquires an image signal (also called a detection signal or a light receiving signal) from the light receiving region R2B of the image sensor 44 while the illumination light LS is being deflected by the optical scanner 30.

Figure 4 is an explanatory diagram showing an example of a fundus image D generated by the image generating unit 58. As shown in Figure 4 and the above-mentioned Figure 2, during slit scan photography, the image generating unit 58 generates a fundus image D based on the imaging signal acquired by the signal acquiring unit 56 while the illumination light LS is being deflected by the optical scanner 30.

The display control unit 64 controls the display by the display unit 16. During slit scan photography, the display control unit 64 causes the display unit 16 to display the fundus image D generated by the image generation unit 58.

(Focus confirmation control and focus control)
Next, the functions of the control device 18 relating to focus confirmation control and focus control will be described. In this embodiment, before slit scan photography of the fundus Ef by the fundus camera 10, the focus state of the illumination system 20 and the light receiving system 40 with respect to the fundus Ef (hereinafter simply abbreviated as "focus state") is evaluated using the existing configuration of the fundus camera 10. In this case, in this embodiment, attention is paid to the fact that the incidence state of the illumination light LS with respect to the fundus Ef changes between a state in which the illumination system 20 and the light receiving system 40 are focused on the fundus Ef (hereinafter referred to as in-focus) and a state in which the illumination system 20 and the light receiving system 40 are not focused on the fundus Ef (hereinafter referred to as out-of-focus).

Figure 5 is an explanatory diagram showing a ray diagram of a light beam incident on the subject's eye E when in focus (see reference symbol 5A), and a front view of a light beam incident on the anterior segment Ea (see reference symbol 5B). Reference symbols 6A and 6B in Figure 6 are explanatory diagrams showing ray diagrams of a light beam incident on the subject's eye E when not in focus.

As shown in Figures 5 and 6, in this embodiment, the aperture 24 (see Figure 1) is in an optically conjugate relationship with the anterior eye segment Ea, so that light beams enter the anterior eye segment Ea from the illumination system 20 through two different paths corresponding to a pair of openings 24a of the aperture 24 (see reference numeral 5B in Figure 5).

As shown by reference numeral 5A in FIG. 5, when in focus, the focusing position of each light beam coincides (including approximately coincides) with the fundus Ef, so that each light beam is incident on one area on the fundus Ef. Conversely, as shown by reference numerals 6A and 6B in FIG. 6, when out of focus, the focusing position of each light beam shifts forward or backward with respect to the fundus Ef, so that each light beam is split and incident on two areas on the fundus Ef. Therefore, the focusing state can be evaluated based on the incidence state of the illumination light LS on the fundus Ef.

The control device 18 then performs focus confirmation control to capture the return light LB from the fundus Ef irradiated with the illumination light LS by the optical scanner 30 with the image sensor 44 while fixing the deflection angle of the illumination light LS, thereby acquiring a focus evaluation image DS (see FIG. 9) indicating the focus state. The control device 18 then performs focus control of the focus optical system 36 based on the focus evaluation image DS acquired by the focus confirmation control.

Returning to FIG. 2, during focus confirmation control and focus control, the illumination control unit 50, deflection control unit 52, imaging control unit 54, signal acquisition unit 56, image generation unit 58, focus confirmation control unit 59, repetition control unit 61, and focus control unit 62 of the control device 18 function.

The illumination control unit 50 emits illumination light L (infrared light) from the illumination system 20 during focus confirmation control.

The focus confirmation control unit 59 controls the optical scanner 30 via the illumination control unit 50, and also controls the image sensor 44 via the imaging control unit 54 to perform focus confirmation control, i.e., capture the focus evaluation image DS (see FIG. 9).

Figure 7 is an explanatory diagram comparing the fundus Ef (see symbol 7A) and the light receiving surface 44a (see symbol 7B) of the image sensor 44 when focus confirmation control is executed during focusing. Figure 8 is an explanatory diagram comparing the fundus Ef (see symbol 8A) and the light receiving surface 44a (see symbol 8B) of the image sensor 44 when focus confirmation control is executed during defocusing.

As shown in Figures 7 and 8, the focus confirmation control unit 59 controls the optical scanner 30 via the deflection control unit 52 to fix the deflection angle of the illumination light LS by the optical scanner 30, thereby irradiating the illumination light LS to the fundus Ef without scanning. The deflection angle of the illumination light LS at this time is set to an angle at which the return light LB can be incident on the middle of the movement path of the light receiving area R2B within the light receiving surface 44a. For example, when the scanning direction of the illumination light LS within the fundus Ef is the Y direction, the focus confirmation control unit 59 controls the deflection angle of the illumination light LS so that the illumination light LS is incident on the central area (including the approximately central area) of the fundus Ef in the Y direction.

By fixing the deflection angle of the illumination light LS in this manner, the position of the illumination region R1A within the fundus Ef is fixed, as shown by reference numeral 7A in FIG. 7 and reference numeral 8A in FIG. 8. In addition, in response to the fixing of the position of the illumination region R1A, the position of the incidence region R1B within the light receiving surface 44a, i.e., the position of the pattern image Pi of the return light LB on the light receiving surface 44a, is also fixed, as shown by reference numeral 7B in FIG. 7 and reference numeral 8B in FIG. 8.

In this case, as shown in FIG. 5, when in focus, each light beam of the illumination light LS is incident on one area on the fundus Ef, so the number of incident areas R1B and pattern images Pi on the light receiving surface 44a is one (see symbol 7B). On the other hand, as shown in FIG. 6, when out of focus, each light beam of the illumination light LS is incident on two areas on the fundus Ef, so the incident areas R1B and pattern images Pi on the light receiving surface 44a expand, and when the degree of out of focus is large, they are divided into two (see symbol 8B).

The focus confirmation control unit 59 also drives the image sensor 44 in a rolling shutter manner (driving in the second operating mode) via the imaging control unit 54, moving the light receiving area R2B within the light receiving surface 44a along a predetermined movement path (movement pattern) (see symbols 7B and 8B).

In this embodiment, the second operation mode is set to be the same as the first operation mode during slit scan photography, so the movement path of the light receiving area R2B during focus confirmation control is set to the same path as the movement path during slit scan photography, but is not particularly limited as long as it includes the incident area R1B along the way. For example, the second operation mode may be made different from the first operation mode by setting the movement path of the light receiving area R2B during focus confirmation control to be narrower than the movement path during slit scan photography, or to a path different from the movement path during slit scan photography. This allows the return light LB incident on the light receiving surface 44a to be reliably imaged by the light receiving area R2B.

During focus confirmation control, the signal acquisition unit 56 sequentially acquires the image signal (corresponding to the detection signal of the present invention) output from the light receiving region R2B of the image sensor 44 while the rolling shutter drive of the image sensor 44 is being performed.

Figure 9 is an explanatory diagram showing an example of a focus evaluation image DS generated by the image generation unit 58 when in focus. Figure 10 is an explanatory diagram showing an example of a focus evaluation image DS generated by the image generation unit 58 when out of focus. As shown in Figures 9 and 10 and the already-described Figure 2, the image generation unit 58 generates a focus evaluation image DS indicating the focus state based on the imaging signal acquired by the signal acquisition unit 56 while the rolling shutter drive of the image sensor 44 is being performed during focus confirmation control.

As shown in Figures 9 and 10, the focus evaluation image DS includes a pattern image Pi of the return light LB whose brightness value is relatively high within the image. The focus evaluation image DS generated when in focus (see Figure 9) includes one pattern image Pi, while the focus evaluation image DS generated when out of focus (see Figure 10) includes a spread pattern image Pi or, if the degree of out of focus is large, two pattern images Pi.

Returning to FIG. 2, the repeat control unit 61 executes repeat control to repeatedly operate the focus confirmation control unit 59, the signal acquisition unit 56, and the image generation unit 58 for each of a plurality of different lens positions while changing the lens position of the focus lens of the focus optical system 36. This generates a focus evaluation image DS for each of the plurality of lens positions. Note that if the focus optical system 36 includes a variable focus lens instead of a focus lens, the repeat control unit 61 executes repeat control for each of a plurality of different focus positions of the variable focus lens.

The focusing control unit 62 performs focusing control of the focus optical system 36 to focus the illumination system 20 and the light receiving system 40 on the fundus Ef. As described above, the focusing of the light receiving system 40 by the focus optical system 36 and the focusing of the illumination system 20 by the slit aperture diaphragm 26 move in conjunction with each other according to the diopter (visual acuity) of the subject's eye E. First, the focusing control unit 62 determines the focusing evaluation image DS taken when the illumination system 20 and the light receiving system 40 are most focused on the fundus Ef from the focusing evaluation images DS for each lens position of the focus lens (including each variable focus lens focal position, the same applies below) generated by the repeated control. For example, the focusing control unit 62 performs the above-mentioned determination by comparing the number of pattern images Pi, luminance value, luminance distribution, etc. contained in the focusing evaluation images DS for each lens position. Next, the focusing control unit 62 controls the focus optical system 36 to move the focus lens to the lens position corresponding to the determined focusing evaluation image DS.

In addition, instead of performing focusing control by the focusing control unit 62 based on the focusing evaluation images DS for each of multiple lens positions, focusing control by the focusing control unit 62 may be performed based on the focusing evaluation image DS generated in one focusing confirmation control or the imaging signal on which it is based. In this case, the focusing control unit 62 drives the focusing optical system 36 so that the illumination system 20 and the light receiving system 40 are focused on the fundus Ef based on the number of pattern images Pi, the luminance value, and the luminance distribution (peak, spread), etc.

[Operation of this embodiment]
FIG. 11 is a flow chart showing a slit-scan type fundus photographing process using the fundus camera 10 having the above-mentioned configuration, in particular, a flow of focus confirmation control corresponding to a control method for an ophthalmologic apparatus of the present invention.

As shown in FIG. 11, after the subject's face is supported by a face support unit (not shown), the examiner operates the operation unit 14 to start shooting, and the alignment of the camera head 12 with the subject's eye E is performed by a known method (step S1). In addition, the illumination control unit 50 starts emitting illumination light L (infrared light) from the light source 22, so that illumination light LS is irradiated from the illumination system 20 to the fundus Ef. Then, the focus confirmation control unit 59 starts focus confirmation control (step S2).

As shown in Figures 7 and 8, the focus confirmation control unit 59 controls the optical scanner 30 via the deflection control unit 52 to fix the deflection angle of the illumination light LS by the optical scanner 30, thereby fixing the position of the illumination region R1A within the fundus Ef (step S3). In addition, the focus confirmation control unit 59 drives the image sensor 44 in a rolling shutter manner (drives it in the second operation mode) via the imaging control unit 54 to move the light receiving region R2B within the light receiving surface 44a along a predetermined movement path (step S4). Note that steps S3 and S4 correspond to the focus confirmation control steps of the present invention.

In addition, at the same time that the rolling shutter drive of the image sensor 44 starts, the signal acquisition unit 56 starts acquiring an image signal from the image sensor 44 (step S5).

Then, the processes of steps S4 and S5 are repeatedly executed until the rolling shutter drive of the image sensor 44 is stopped, that is, until the movement of the light receiving area R2B along the movement path within the light receiving surface 44a described above is completed (NO in step S6). As a result, the light receiving area R2B overlaps with the incident area R1B (pattern image Pi) as it moves within the light receiving surface 44a, imaging of the return light LB is performed by the light receiving area R2B, and the signal acquisition unit 56 acquires an imaging signal of the return light LB from the image sensor 44.

When the rolling shutter drive of the image sensor 44, i.e., the movement of the light receiving area R2B within the light receiving surface 44a, is completed (YES in step S6), the image generating unit 58 generates a focus evaluation image DS as shown in Figures 9 and 10 described above based on the image signal acquired by the signal acquiring unit 56 during the rolling shutter drive of the image sensor 44 (step S7).

When the focus evaluation image DS is generated by the image generation unit 58, the repeat control unit 61 moves the lens position of the focus lens of the focus optical system 36 and then repeats the processes from step S4 to step S7 (YES in step S8). This generates focus evaluation images DS corresponding to different lens positions of the focus lens.

The repeat control unit 61 similarly performs repeat control to repeatedly execute the processes from step S4 to step S7 described above for each lens position while moving the lens position of the focus lens of the focus optical system 36. This generates a focus evaluation image DS for each lens position.

When the generation of focus evaluation images DS at all lens positions is completed (NO in step S8), the focus control unit 62 determines the focus evaluation image DS taken when the illumination system 20 and the light receiving system 40 are most focused on the fundus Ef, based on the focus evaluation image DS for each lens position. The focus control unit 62 then performs focus control to move the focus lens of the focus optical system 36 to the lens position corresponding to the determined focus evaluation image DS (step S9). As described above, the focus control unit 62 may perform focus control based on the focus evaluation image DS generated in one focus confirmation control, in which case step S8 is omitted.

When the focusing control by the focusing control unit 62 is completed, the illumination control unit 50, the deflection control unit 52, the imaging control unit 54, the signal acquisition unit 56, the image generation unit 58, and the display control unit 64 of the control device 18 are operated to perform slit scan photography of the fundus Ef shown in FIG. 3 (step S10). The fundus image D photographed by this slit scan photography is displayed on the display unit 16 by the display control unit 64.

[Effects of this embodiment]
As described above, in the fundus camera 10 of the present embodiment, by performing focus confirmation control to photograph the fundus Ef with the deflection angle of the illumination light LS fixed, a focus evaluation image DS showing the focus state or an image signal on which the focus evaluation image DS is based can be obtained, and the focus state can be evaluated with high accuracy. Moreover, this focus confirmation control can be performed using the existing slit scan photographing function of the fundus camera 10, and no additional configuration is required, as it is only necessary to change the control program of the fundus camera 10. As a result, the focus state can be evaluated with high accuracy at low cost.

[Modification of driving of image sensor during focus confirmation control]
12 is an explanatory diagram for explaining a modified example of driving the image sensor 44 by the focus confirmation control unit 59 during focus confirmation control. In addition, in FIG. 12, reference character XIIA indicates the fundus oculi Ef, and reference character XIIB indicates the light receiving surface 44a of the image sensor 44.

In the above embodiment, the light receiving area R2B is moved along a predetermined movement path within the light receiving surface 44a during focus confirmation control, but the light receiving area R2B does not have to be moved. For example, as shown in FIG. 12, the focus confirmation control unit 59 may drive the image sensor 44 in an operation mode (the third operation mode of the present invention) different from the above embodiment via the imaging control unit 54 to fix the position of the light receiving area R2B within the light receiving surface 44a. In this case, the fixed position of the light receiving area R2B is a position where the return light LB (pattern image Pi) from the illumination area R1A fixed within the fundus Ef by the optical scanner 30 can be detected.

When the position of the light receiving region R2B is fixed within the light receiving surface 44a, the width of the light receiving region R2B in the Y direction may be made wider than in the above embodiment, taking into consideration that the incident region R1B (pattern image Pi) within the light receiving surface 44a expands when out of focus, or is divided into two when the degree of out of focus is large (see Figure 8).

Even if the position of the light receiving area R2B within the light receiving surface 44a is fixed during focus confirmation control in this way, the focus evaluation image DS or the image signal on which it is based as shown in Figures 9 and 10 can be obtained, so the same effect as in the above embodiment can be obtained.

[Modification of the irradiation position of illumination light during focus confirmation control]
Fig. 13 is an explanatory diagram showing a modified example of the irradiation position of the illumination light LS on the fundus Ef during focus confirmation control (see symbol XIIIA) and the correspondence relationship between the focus evaluation image DS (see symbol XIIIB). In the above embodiment, the illumination light LS is irradiated to the central region of the fundus Ef during focus confirmation control, but as shown by symbol XIIIA in Fig. 13, the irradiation position of the illumination light LS on the fundus Ef may be set to a region other than the central region of the fundus Ef. Even in this case, as shown by symbol XIIIB in Fig. 13, a focus evaluation image DS including a pattern image Pi is obtained, and therefore the same effect as in the above embodiment can be obtained.

[others]
Fig. 14 is a front view of another example of light beams incident from the illumination system 20 through two paths onto the anterior segment Ea of the subject's eye E. In the above embodiment, an example of light beams incident on the anterior segment Ea through two paths is shown by reference numeral 5A in Fig. 5, but the shapes of these light beams are not particularly limited, and may be changed to, for example, the shape shown in Fig. 14, or may be changed to another shape.

In the above embodiment, the light beam enters the anterior segment Ea from the illumination system 20 via two paths, but the number of light beams entering the anterior segment Ea and the paths of incidence may be changed as appropriate depending on the number and positions of the openings 24a (including ring-shaped openings 24a) formed in the aperture 24.

In each of the above embodiments, a CMOS-type image sensor 44 having a rolling shutter function has been described as an example of a detector of the present invention, but various other well-known detectors may also be used.

In each of the above embodiments, the illumination light LS is irradiated onto the fundus Ef, but light of any shape, such as line light, spot light, or dot light, may be irradiated. When spot light or dot light is irradiated onto the fundus Ef from the fundus camera 10, the fundus Ef may be scanned two-dimensionally with the spot light, etc., using an optical scanner 30 capable of two-dimensionally deflecting the spot light, etc.

In the above embodiment, an example of the arrangement of the illumination system 20, the optical scanner 30, and the light receiving system 40 of the fundus camera 10 is shown in FIG. 1, but the arrangement of each of these parts can be changed as appropriate.

In each of the above embodiments, a fundus camera 10 that photographs the fundus Ef of the subject's eye E has been described as an example, but the present invention can be applied to various ophthalmic devices that observe other observed areas of the subject's eye E (e.g., the anterior segment Ea) and that are capable of deflecting illumination light (including excitation light) that is irradiated to a portion of the observed area.

10 Fundus camera 12 Camera head 14 Operation unit 16 Display unit 18 Control device 20 Illumination system 22 Light source 24 Aperture 24a Aperture 26 Slit aperture diaphragm 28 Illumination system lens 30 Optical scanner 31 Lens 34 Optical path splitting material 36 Focus optical system 38 Objective lens 40 Light receiving system 42 Light receiving system lens 44 Image sensor 44a Light receiving surface 50 Illumination control unit 52 Deflection control unit 54 Imaging control unit 56 Signal acquisition unit 58 Image generation unit 59 Focus confirmation control unit 61 Repetition control unit 62 Focus control unit 64 Display control unit D Fundus image DS Focus evaluation image E Eye to be examined Ea Anterior eye portion Ef Fundus L Illumination light LB Return light LS Illumination light Pi Pattern image R1A Illumination area R1B Incident area R2A Imaging range R2B Light receiving area

Claims (8)

an illumination system for irradiating a part of an observation site of a subject's eye with illumination light;
a diaphragm provided in the illumination system, the diaphragm being in an optically conjugate relationship with an anterior segment of the subject's eye, and having a plurality of apertures at positions eccentric to an illumination optical axis of the illumination system;
an optical scanner that deflects the illumination light irradiated from the illumination system onto the observation site to move an illumination area of the illumination light within the observation site;
a light receiving system having a detector for detecting return light from the illumination area that moves within the observation site in response to the deflection of the illumination light while the optical scanner is deflecting the illumination light;
a focus confirmation control unit that controls the optical scanner to execute focus confirmation control for causing the detector to detect the return light from the illumination area while the illumination area is fixed within the observation site;
An ophthalmic apparatus comprising: a focusing optical system provided in an optical path of the return light;
a focus control unit that performs focus control of the focus optical system based on a detection signal of the return light detected by the detector during the focus confirmation control;
The ophthalmic device of claim 1 . an image generating unit that generates a focus evaluation image indicating a focus state of the illumination system and the light receiving system with respect to the observation site based on the detection signal,
The ophthalmologic apparatus according to claim 2 , wherein the focus control unit performs the focus control based on the focus evaluation image generated by the image generation unit. the focusing optical system has a focusing lens,
a repeat control unit that repeatedly operates the focus confirmation control unit and the image generation unit for each of a plurality of different lens positions of the focus lens,
The ophthalmologic apparatus according to claim 3 , wherein the focus control unit performs the focus control based on the focus evaluation image for each of the lens positions generated by the image generation unit. the detector has a light receiving surface on which the return light is incident, and has a first operation mode in which the detector continuously detects the return light in the light receiving area while making a local light receiving area that detects the return light within the light receiving surface follow an incident area of the return light that moves within the light receiving surface in response to the movement of the illumination area, and a second operation mode in which the light receiving area is moved within the light receiving surface along a predetermined movement path,
the return light from the illumination area fixed by the optical scanner in the focus confirmation control is incident on a part of the movement path of the light receiving area,
The ophthalmologic apparatus according to claim 1 , wherein the focus confirmation control unit drives the detector in the second operation mode. the detector has a light receiving surface on which the return light is incident, and has a first operation mode in which the detector continuously detects the return light in the light receiving area while making a local light receiving area that detects the return light within the light receiving surface follow an incident area of the return light that moves within the light receiving surface in response to the movement of the illumination area, and a third operation mode in which the light receiving area is fixed at a position within the light receiving surface where the return light from the illumination area fixed by the optical scanner can be detected;
The ophthalmologic apparatus according to claim 1 , wherein the focus confirmation control unit drives the detector in the third operation mode. When directions perpendicular to an optical axis of the illumination system and perpendicular to each other are defined as a first direction and a second direction, the illumination system irradiates the observation site with a slit light parallel to the first direction as the illumination light,
The ophthalmic apparatus according to claim 1 , wherein the optical scanner deflects the slit light in the second direction. an illumination system for irradiating a part of an observation site of a subject's eye with illumination light;
a diaphragm provided in the illumination system, the diaphragm being in an optically conjugate relationship with an anterior segment of the subject's eye, and having a plurality of apertures at positions eccentric to an illumination optical axis of the illumination system;
an optical scanner that deflects the illumination light irradiated from the illumination system onto the observation site to move an illumination area of the illumination light within the observation site;
a light receiving system having a detector for detecting return light from the illumination area that moves within the observation site in response to the deflection of the illumination light while the optical scanner is deflecting the illumination light;
A method for controlling an ophthalmic apparatus comprising:
A control method for an ophthalmic apparatus comprising a focus confirmation control step of controlling the optical scanner to cause the detector to detect the return light from the illumination area while the illumination area is fixed within the region to be observed.

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