JP7268357B2 - Scanning ophthalmic imaging device and ophthalmic imaging program - Google Patents

Description

BACKGROUND 1. Technical Field The present disclosure relates to a scanning ophthalmic photographing apparatus that photographs an eye to be examined by scanning light, and an ophthalmic photographing program.

A scanning ophthalmic imaging apparatus (for example, a scanning laser ophthalmoscope (SLO) that scans a laser beam) that captures an image of an eye to be examined by scanning light with a scanning unit (scanner, etc.) is known (Patent Document 1). ). A scanning laser ophthalmoscope obtains an image of a subject's eye by scanning a spot, line, or slit-shaped light flux and receiving light from the subject's eye.

JP 2017-46939 A

By the way, in a scanning ophthalmologic imaging apparatus, when an eye to be inspected is photographed while being scanned with imaging light, an image may blur. In order to suppress this, it is conceivable to stop driving the scanning unit only while each frame is being exposed. .

A technical problem of the present disclosure is to provide a scanning ophthalmic imaging apparatus and an ophthalmologic imaging program capable of obtaining good images in view of the problems of the prior art.

In order to solve the above problems, the present disclosure is characterized by having the following configurations.

(1) A scanning ophthalmologic imaging apparatus comprising: a light source that emits imaging light; a projection optical system that projects the imaging light emitted from the light source onto an eye to be examined in a slit shape having a width; a light-receiving optical system for receiving the reflected light of the photographing light reflected from the light-receiving optical system; scanning means for scanning the photographing light projected by the light projecting optical system in the width direction of the eye; a detector for detecting the reflected light received by the optical system at a detection cycle corresponding to scanning by the scanning means; and a control means for changing the light amount of the photographing light.
(2) An ophthalmic imaging program to be executed in a scanning ophthalmic imaging apparatus, which is executed by a processor of the scanning ophthalmic imaging apparatus so that imaging light emitted from a light source is formed into a wide slit of the eye to be examined. a light receiving step of receiving the reflected light of the photographing light reflected from the eye to be inspected; a detecting step of detecting the reflected light received in the light receiving step at a detection cycle corresponding to the scanning in the scanning step; and controlling the light source so that the photographing light is directed in the width direction and a control step of changing the light amount of the photographing light in synchronization with the detection period when the scanning is performed by the scanning ophthalmic photographing apparatus.

According to the present disclosure, a good image of the subject's eye can be obtained.

1 is a schematic diagram showing an example of an imaging optical system of a scanning ophthalmologic imaging apparatus; FIG. It is a figure for demonstrating the imaging|photography method. 4A and 4B are diagrams for explaining the operation of a scanning unit, exposure timing, and the amount of photographing light; FIG. FIG. 11 is a diagram illustrating an example different from the present embodiment; It is a figure for demonstrating how to change light quantity. It is a figure for demonstrating the modification of a present Example. It is a figure which shows about the scanning of imaging|photography light.

<Embodiment>
Embodiments of the present disclosure will be described below based on the drawings. The scanning ophthalmologic imaging apparatus (eg, scanning ophthalmologic imaging apparatus 1) of the present embodiment includes a light source (eg, light source 2), a projection optical system (eg, projection optical system 10), and a light receiving optical system (eg, , a light receiving optical system 40), a scanning unit (for example, scanning unit 20), a detector (for example, detector 30), and a control unit (for example, control unit 60). The light source emits imaging light. The projection optical system projects imaging light emitted from the light source onto the subject's eye. The light receiving optical system receives the reflected light of the photographing light reflected from the eye to be examined. The scanning unit scans the subject's eye with imaging light projected by the projection optical system. The detector detects reflected light received by the light receiving optical system. The control unit changes the light amount of the photographing light. With the configuration described above, the scanning ophthalmologic imaging apparatus of the present embodiment can capture good images without blurring while suppressing mechanical blurring of the scanning unit.

The detector may detect the reflected light received by the light receiving optical system at a detection cycle corresponding to scanning by the scanning unit. In this case, the control unit may control the light source and change the light amount of the photographing light in synchronization with the detection period.

The controller may adjust the exposure time of the detector by changing the amount of light. Here, the term "exposure" refers to, for example, a state in which the detector is exposed to photographing light. For example, the controller may adjust the length of time during which the detector receives the imaging light by blinking the amount of light.

Note that the control unit may adjust the exposure time for each cycle of the detector. Here, the term "exposure" means, for example, a state in which the detector can detect light regardless of whether or not the light is actually applied. The projection optical system may project, for example, wide slit-shaped photographing light onto the subject's eye. Further, the scanning unit may scan the photographing light in the width direction of the slit-shaped photographing light. In this case, the control section may make the exposure time of the detector shorter than the scanning time when the photographing light scans a distance half the width.

Note that the processor (eg, CPU 61) of the scanning ophthalmic imaging apparatus may cause the scanning ophthalmologic imaging apparatus to execute an ophthalmologic imaging program stored in the storage unit (eg, storage unit 62). The ophthalmologic imaging program includes, for example, a projecting step, a receiving step, a scanning step, and a controlling step. The projecting step is, for example, a step of projecting photographing light emitted from a light source onto the subject's eye. The light receiving step is, for example, a step of receiving reflected light of imaging light reflected from the subject's eye. The scanning step is a step of scanning the subject's eye with the photographing light projected in the projection step. The detection step is, for example, a step of detecting the reflected light received in the light receiving step at a detection cycle according to the scanning in the scanning step. The control step is, for example, a step of controlling the light source and changing the light amount of the photographing light in synchronization with the detection period.

<Example>
One exemplary embodiment of the present disclosure is described below. As an example, in the present embodiment, a scanning ophthalmologic imaging apparatus (hereinafter also referred to as "SLO apparatus") 1 having a laser treatment unit 70 will be described. That is, the scanning ophthalmologic imaging apparatus of this embodiment has a configuration for scanning light to capture an image of the tissue of the eye to be inspected E, and a configuration for irradiating the tissue with therapeutic laser light based on the captured image. together with the configuration. However, it is also possible to change the configuration of the SLO device 1 . For example, the SLO device 1 does not have to include the laser treatment section 70 . In addition, the configuration for capturing an image of the tissue of the subject's eye by scanning light and the configuration for irradiating the tissue with the treatment laser light may be provided in separate housings. Also, instead of the laser treatment unit, a fixation projection optical system that projects a fixation target may be provided, or an OCT optical system that acquires OCT data of the fundus may be provided.

In addition, in the present embodiment, the SLO device 1 that photographs the fundus of the eye E to be examined is illustrated. However, at least part of the technique illustrated in this embodiment can also be used when imaging tissues other than the fundus (for example, the anterior segment of the eye).

A schematic configuration of the SLO device 1 of the present embodiment will be described with reference to FIG. The SLO device 1 includes a light source 2, a light projecting optical system 10, a scanning section 20, a detector 30, a light receiving optical system 40, an optical path branching section 50, a control section 60, a laser treatment section 70, and the like.

The light source 2 emits light for capturing an image of the tissue (hereinafter referred to as “imaging light”). For example, at least one of a laser light source, an SLD (super luminescent diode) light source, and an LED can be used as the light source 2 . A point light source may be used for the light source 2 . The light source 2 of this embodiment is arranged at a position conjugate with the tissue of the subject's eye E (in this embodiment, the fundus). The light source 2 may be a light source that emits at least one of infrared light and visible light. When the light source 2 that emits infrared light is used, photographing can be easily performed in a non-mydriatic state. When the light source 2 that emits white light is used, color photography is easily performed. In this embodiment, the light source 2 is a laser light source. In other words, the SLO apparatus (scanning laser optometric apparatus) 1 of this embodiment is a type of scanning ophthalmic imaging apparatus that scans light to capture an image of tissue of an eye to be examined.

The projection optical system 10 projects the photographing light emitted from the light source 2 onto the fundus of the eye E to be examined. The projection optical system 10 includes a slit plate 11, an imaging lens 15, and an objective lens 18 in order from the upstream side of the optical path of photographing light (that is, the light source 2 side). In this embodiment, the imaging lens 15 and the objective lens 18 are shared between the light projecting optical system 10 and the light receiving optical system 40 . An optical path branching section 50 is provided on the optical path between the slit plate 11 and the imaging lens 15 . A scanning unit 20 and a half mirror 17 are provided on the optical path between the imaging lens 15 and the objective lens 18 . The optical path branching section 50 and the scanning section 20 can also be regarded as part of the projection optical system 10 .

The slit plate 11 shields part of the photographing light emitted from the light source 2, thereby converting the photographing light into a slit-like light flux. That is, the slit plate 11 functions as a light flux conversion element that converts the photographing light into a slit light flux. The slit plate 11 is arranged, for example, on the fundus conjugate position. The slit plate 11 of this embodiment has a slit extending in a direction intersecting (perpendicular to in this embodiment) the scanning direction of the slit-like light flux by the scanning unit 20, and has a slit width in the scanning direction. Light from the slit plate 11 passes through the optical path branching portion 50 and the imaging lens 15 and enters the scanning portion 20 .

Note that an optical element other than the slit plate 11 can be employed as the light beam conversion element. For example, a cylindrical lens disposed between the light source 2 and the conjugate position of the fundus may be employed as the light flux conversion element, and the photographing light may be condensed into a line at the conjugate position of the fundus. As a result, the illumination light is shaped into a line on the fundus Er.

The imaging lens 15 once forms an image of the photographing light emitted from the light source 2 at the front focal position of the objective lens 18 . The imaging lens 15 forms an image on the detector 30 of the photographing light reflected by the fundus of the eye E to be inspected. The imaging lens 15 may be composed of one lens, or may be composed of a group of lenses. The imaging lens 15 of this embodiment is arranged downstream of the slit plate 11 (more specifically, downstream of the optical path branching section 50) and upstream of the scanning section 20 in the optical path of the photographing light. ing.

The objective lens 18 guides the photographing light incident from the scanning unit 20 to the fundus of the eye E to be examined. Further, the objective lens 18 returns the reflected light of the photographing light reflected by the fundus of the eye E to be examined to the scanning unit 20 . The objective lens 18 may be composed of one lens or may be composed of a group of lenses. In this embodiment, the scanning unit 20 is arranged at a position conjugate with the pupil of the eye E to be inspected by the objective lens 18 . The objective lens 18 is arranged downstream of the scanning unit 20 (more specifically, downstream of the half mirror 17) and upstream of the subject's eye E in the optical path of the photographing light.

The scanning unit 20 scans the imaging light projected by the light projecting optical system 10 on the tissue of the subject's eye E (in this embodiment, the fundus). As described above, the scanning unit 20 is arranged on the common optical path of the light projecting optical system 10 and the light receiving optical system 40 . The scanning unit of the present embodiment scans the slit-shaped light flux of photographing light in a direction intersecting (perpendicular to in the present embodiment) the slit direction. The scanning direction may be, for example, the vertical direction or the horizontal direction. At least one of a reflecting mirror (for example, a galvanomirror, a polygon mirror, or a resonant scanner) or an acousto-optical element that changes the traveling direction of light can be used as an element constituting the scanning unit 20 . Further, the scanning unit 20 may include a plurality of elements (for example, an element that scans the imaging light in the X direction and an element that scans the imaging light in the Y direction).

The detector 30 detects reflected light of photographing light projected by the projection optical system 10 and reflected by the fundus, and outputs a detection signal. The detector 30 is arranged at a position conjugate with the fundus of the eye E to be examined. A two-dimensional light-receiving element (for example, a CCD camera or the like) that receives slit-like reflected light is used for the detector 30 of this embodiment. Note that it is also possible to change the configuration of the detector 30 . For example, in the case of a scanning ophthalmologic imaging apparatus that two-dimensionally scans a spot of imaging light, a point-shaped light receiving element may be used. Further, for example, in the case of a scanning ophthalmologic imaging apparatus that one-dimensionally scans a line of imaging light, a one-dimensional light receiving element (for example, a line camera or the like) may be used.

The light receiving optical system 40 guides the reflected light of the imaging light reflected by the fundus to the detector 30 . The light-receiving optical system 40 of this embodiment includes an objective lens 18, an imaging lens 15, and a plane mirror 41 in order from the downstream side of the optical path of imaging light (that is, the subject's eye E side). As described above, in this embodiment, the imaging lens 15 and the objective lens 18 are shared between the light projecting optical system 10 and the light receiving optical system 40 . An optical path splitter 50 is provided on the optical path between the imaging lens 15 and the plane mirror 41 . A half mirror 17 and a scanning unit 20 are provided on the optical path between the objective lens 18 and the imaging lens 15 . The optical path branching section 50 and the scanning section 20 can also be regarded as part of the light receiving optical system 40 . In addition, it is also possible to change the configuration of the light receiving optical system 40 . For example, the reflected light from the optical path branching section 50 may be directly guided to the detector 30 without providing the plane mirror 41 .

After being deflected by the scanning unit 20 , the photographing light is applied to the subject's eye E via the objective lens 18 . The objective lens 18 guides photographing light to the fundus through an exit pupil formed in the anterior segment of the eye. The objective lens 18 shown in FIG. 2 is a lens system, but it may be a mirror system. The imaging light is rotated at the position of the exit pupil according to the driving of the scanning unit 20 . The imaging light is reflected or scattered by the fundus. As a result, return light (scattered/reflected light) from the fundus is emitted from the pupil as parallel light.

The optical path branching unit 50 passes (or transmits) photographing light (slit-shaped light flux in this embodiment) emitted from the light source 2 and projected onto the fundus by the projection optical system 10 . Further, the optical path branching unit 50 reflects the reflected light of the photographing light reflected by the fundus (a slit-like light flux in this embodiment), and guides the reflected light to the independent optical path of the light receiving optical system 40 . After that, the reflected light reflected by the plane mirror 41 is applied to the detector 30 . The light is directed towards detector 30 . The optical path splitter 50 may be any one of various beam splitters such as a perforated mirror and a half mirror.

Note that it is also possible to change the configuration of the optical path branching unit 50 . For example, the optical path branching unit 50 reflects photographing light projected onto the fundus by the projection optical system 10 , transmits reflected light of the photographing light reflected by the fundus, and guides the light toward the detector 30 . good too.

The control unit 60 performs various control processes in the SLO apparatus (ophthalmic apparatus) 1 . The control unit 60 includes a CPU 61, which is a controller for control, and a storage unit 62 capable of storing programs, data, and the like. The storage unit 62 stores an ophthalmologic imaging program and the like for executing imaging of an eye to be examined. Note that the number of control units and controllers is not limited to one. For example, a control unit for controlling image capturing and a control unit for controlling laser treatment by the laser treatment unit 70 may cooperate to perform processing.

The laser treatment section 70 includes a treatment light source 71 , an aiming light source 72 , a focus adjustment section 73 and a treatment light scanning section 74 . The therapeutic light source 71 emits therapeutic laser light. The aiming light source 72 emits aiming light that indicates the irradiation state of the treatment laser beam applied to the fundus (for example, the spot size and focus of the treatment laser beam). The optical axis of the therapeutic laser beam and the optical axis of the aiming beam are coaxial. The focus adjustment unit 73 adjusts the focus of the treatment laser light and the aiming light on the tissue of the subject's eye E (in this embodiment, the fundus). For the focus adjustment unit 73, for example, a configuration that moves the focusing lens in the optical axis direction can be adopted. The therapeutic light scanning unit 74 scans the fundus with therapeutic laser light and aiming light. In this embodiment, the treatment laser beam and the aiming beam are reflected by the half mirror 17 and applied to the fundus. Part of the aiming light reflected by the fundus is transmitted through the half mirror 17 and guided to the detector 30 .

<Shooting operation>
A photographing operation of the SLO device 1 will be described. The SLO device 1 causes the scanning unit 20 to scan the fundus Er with a slit-shaped photographing light, and the detector 30 detects the reflected light of the photographing light reflected by the fundus Er. Thereby, the SLO device 1 obtains a slit-shaped two-dimensional image. The detector 30 acquires a plurality of frames of images of different imaging regions by detecting the reflected light at a cycle corresponding to scanning by the scanning unit 20 (see FIG. 2). The SLO device 1 creates one full-size image of the fundus by arranging the images of the plurality of frames.

FIG. 3 is a diagram showing the operation of the scanning unit 20, the light amount of the photographing light, and the exposure timing of the detector 30 when the SLO device 1 performs photographing. The control unit 60 of this embodiment continuously changes the scanning angle of the scanning unit 20 over time. That is, the scanning unit 20 is driven smoothly. As a result, the occurrence of mechanical blurring of the scanning unit 20 is suppressed.

Also, the control unit 60 controls the exposure time of the detector 30 at a predetermined cycle according to scanning by the scanning unit 20 . For example, as shown in FIG. 3 , the control unit 60 causes the detector 30 to repeat the exposure time required to acquire one frame of image at a predetermined cycle according to the scanning speed of the scanning unit 20 . As a result, the detector 30 acquires a plurality of frames of images with different imaging regions.

In addition, as shown in FIG. 3, the control unit 60 changes the light amount of the light source 2 . For example, the control unit 60 causes the light source 2 to blink in synchronization with the exposure timing of the detector 30 . For example, the control unit 60 turns on the light source 2 only momentarily during the exposure time of the detector 30 in each frame. For example, the control unit 60 turns on the power of the light source 2 after the exposure is started, and immediately (before the end of the exposure) turns off the power of the light source 2 to blink the photographing light.

In this way, the controller 60 blinks the light source 2 to prevent the image from blurring due to the movement of the scanning unit 20 during the exposure of the detector 30 . In other words, the control unit 60 reduces the amount of change in the imaging area while the detector 30 actually detects the imaging light by shortening the lighting time of the imaging light, thereby suppressing blurring of the image.

In general, the longer the exposure time per frame in the detector 30, the more light that can be captured per frame and the brighter the image. However, in this case, since the scanning unit 20 continues to drive even while one frame is being exposed, the photographing area moves and the image becomes blurred, resulting in a decrease in resolution. This is because even in the case of creating one full-size image by photographing and arranging a plurality of frames of two-dimensional images as in this embodiment, the angle of view per frame is increased (one full-size image As the number of frames per frame is reduced, the scanning distance scanned by the scanning unit 20 during exposure for each frame becomes longer, resulting in noticeable blurring of the image.

In such a case, as shown in FIG. 4, it is conceivable to keep the scanning unit 20 stationary only while each frame is exposed while continuously irradiating the photographing light. As a result, mechanical blurring of the scanning unit 20 occurs, and the control of the scanning unit 20 becomes complicated. On the other hand, the SLO device 1 of the present embodiment blinks the light source 2 to smoothly drive the scanning unit 20 and obtain a clear image with less blurring.

It should be noted that when the photographing light is blinked, by shortening only the lighting time without changing the blinking period of the light source 2, the influence of the image blur caused by the movement of the scanning unit 20 during the exposure of the detector 30 can be further suppressed. can. At this time, if the lighting time is shortened, the amount of light will be insufficient, resulting in a dark image. Therefore, it is preferable to increase the amount of light within a range that satisfies the optical safety of the eyes and use a continuous pulse light source with a high amount of light and a short emission time.

The method of blinking the photographing light is not limited to turning on/off the light source 2 as described above. For example, the control unit 60 may blink the photographing light emitted from the continuously lit light source by repeatedly shielding it with a mechanical shutter or the like. Further, the photographing light irradiated to the subject's eye E may blink by repeatedly deflecting the photographing light emitted from the continuously lit light source out of the optical path of the projection optical system 10 by an optical element.

Note that the control unit 60 does not have to turn off the imaging light completely, and may limit the imaging light received by the detector 30 by reducing the amount of light. Thereby, the control unit 60 may suppress blurring of the image.

In the above embodiment, as shown in FIG. 3, the amount of light is changed in a rectangular wave pulse shape (steeply), but the present invention is not limited to this. For example, as shown in FIG. 5A, the controller 60 may change the amount of light in a sinusoidal pulse (slowly). Also, the control unit 60 may change the amount of light between each frame, as shown in FIG. 5(b).

<transformation example>
A modified example of this embodiment will be described. The SLO apparatus 1 of the modified example differs from the above embodiment in the amount of light at the time of photographing and the exposure time of the detector 30 . Specifically, as shown in FIG. 6, the controller 60 keeps the light intensity of the light source 2 constant and sets the exposure time of the detector 30 to be sufficiently short. As a result, it is possible to suppress blurring of the photographed image due to scanning by the scanning unit 20 during exposure of the detector 30 . Moreover, since the SLO apparatus 1 of the modified example does not need to periodically change the light intensity of the light source 2, the apparatus configuration can be simplified. As a method of shortening the exposure time of the detector 30, a mechanical shutter may be used to shield light, or an electronic shutter of the detector may be used to limit the exposure.

The exposure time is preferably shorter than the time required to scan the distance A (see FIG. 7) that is half the slit width. As a result, the SLO device 1 can capture good images with less blurring. More preferably, the exposure time should be shorter than the time it takes to scan the distance of one pixel of the detector.

1 scanning ophthalmic imaging apparatus 2 light source 10 light projecting optical system 20 scanning unit 30 detector 40 light receiving optical system 50 optical path branching unit

Claims (3)

A scanning ophthalmic imaging device comprising:
a light source that emits imaging light;
a projection optical system for projecting imaging light emitted from the light source in a wide slit shape onto the subject's eye;
a light receiving optical system for receiving reflected light of the imaging light reflected from the eye to be inspected;
scanning means for scanning the photographing light projected by the projection optical system in the width direction of the eye to be inspected;
a detector that detects the reflected light received by the light receiving optical system at a detection cycle corresponding to scanning by the scanning means;
a control means for changing the light amount of the photographing light in synchronization with the detection period when the photographing light is scanned in the width direction ;
A scanning ophthalmic imaging apparatus comprising: 2. A scanning ophthalmic photographing apparatus according to claim 1, wherein said control means makes the exposure time of said detector shorter than the scanning time when said photographing light scans a distance half of said width. An ophthalmic imaging program executed in a scanning ophthalmic imaging apparatus, the program being executed by a processor of the scanning ophthalmic imaging apparatus,
a projecting step of projecting photographing light emitted from a light source in a wide slit shape onto an eye to be inspected;
a light receiving step of receiving reflected light of the imaging light reflected from the eye to be inspected;
a scanning step of scanning the eye to be inspected with the photographing light projected in the light projecting step in the width direction ;
a detection step of detecting the reflected light received in the light receiving step at a detection cycle corresponding to scanning in the scanning step;
and a control step of controlling the light source and changing the light amount of the imaging light in synchronization with the detection period while the imaging light is being scanned in the width direction. An ophthalmic imaging program characterized by:

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