JP2023002782A - Fundus imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently image a subject eye with a small pupil.

SOLUTION: A fundus imaging apparatus comprises: an irradiation optical system in which two light projection regions that allow illumination light to pass therethrough on a pupil of a subject eye are formed so as to be arrayed in a first direction and which emits slit-like illumination light formed to be slender along a second direction intersecting the first direction onto a fundus of the subject eye; a scanning unit which scans the illumination light on the fundus in the first direction; and a light reception optical system in which a light reception region from which the fundus reflection light of the illumination light is taken out is formed on the pupil of the subject eye so as to be held between the two light projection regions and which includes an image pick-up device that receives the fundus reflection light of the illumination light. The fundus imaging apparatus acquires a fundus image being a front image of the fundus on the basis of a light reception signal from the image pick-up device, and also comprises control means which changes a clearance in the first direction among the two light projection regions and the light reception region on the pupil of the subject eye.

SELECTED DRAWING: Figure 9

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present disclosure relates to a fundus imaging device for obtaining a front image of the fundus.

A fundus photographing apparatus for photographing a front image of the fundus of an eye to be examined is widely used in the field of ophthalmology. Examples of the fundus imaging device include a fundus camera, a scanning laser ophthalmoscope, and the following devices. For example, in Patent Document 1, a slit-shaped illumination light is scanned on the fundus, and an image of the illuminated slit-shaped region on the fundus is sequentially projected onto a two-dimensional imaging surface according to the scanning, thereby performing the scanning of the fundus. An apparatus for obtaining frontal images is disclosed.

Japanese Patent Publication No. 61-48940

When capturing a front image based on reflected light from the fundus, the narrower the slit-shaped region, the less likely an artifact will occur on the front image. On the other hand, the narrower the slit-like region, the lower the efficiency of light projection and reception, making it difficult to obtain a bright front image.

The present disclosure has been made in view of at least one of the problems of the conventional technology, and a technical object thereof is to provide a fundus imaging apparatus that facilitates capturing of bright and excellent fundus images.

A fundus imaging device according to a first aspect of the present disclosure forms two light projection regions arranged side by side in a first direction on a pupil of an eye to be inspected, through which illumination light passes, and a second light projection region intersecting the first direction. an irradiation optical system that irradiates a slit-shaped illumination light elongated along the direction of the eye to be examined onto the fundus of the subject's eye, a scanning unit that scans the illumination light on the fundus in the first direction, and the illumination light a light-receiving optical system that forms a light-receiving region on the pupil of the subject's eye so as to be sandwiched between the two light-projecting regions from which the fundus-reflected light is extracted, and includes an imaging device that receives the fundus-reflected light of the illumination light; and acquiring a fundus image, which is a front image of the fundus, based on a light reception signal from the imaging element, the two light projection areas and the light reception area on the pupil of the subject's eye. and control means for changing the clearance in the first direction.

According to the present disclosure, it is easy to capture a bright and favorable fundus image.

It is a figure showing the appearance composition of the device concerning one example. It is the figure which showed the optical system accommodated in the imaging|photography unit of an Example. 3 is a block diagram showing a control system of the device according to the embodiment; FIG. FIG. 3 is a diagram showing an optical chopper applicable as a scanning unit in the optical system of FIG. 2; FIG. 4 is a diagram showing area division in an optical chopper; 4 is a timing chart for explaining light emission/reception control for each area; It is a flow chart showing the operation of the device. FIG. 10 is a diagram showing area division when obtaining an observation image in a modified example; FIG. 5 is a diagram for explaining a switching operation between a normal shooting mode and a small-pupil shooting mode;

"overview"
An embodiment of a fundus imaging apparatus according to the present disclosure will be described below with reference to the drawings. The fundus imaging device captures a fundus image. In addition, in the present disclosure, the front image of the fundus is referred to as a “fundus image”.

The fundus imaging device (see FIG. 1) has at least an imaging optical system (see FIG. 2, for example) and a controller (see FIG. 3, for example).

<Control part>
The control unit is a processing device (processor) that performs control processing of each unit in the fundus imaging apparatus and arithmetic processing. For example, the control unit is implemented by a CPU (Central Processing Unit), a memory, and the like. In this embodiment, the control section may also serve as the image processing section. The image processing unit generates a fundus image and executes at least one of various image processing on the fundus image.

<Photography optical system>
The imaging optical system includes an irradiation optical system and a light receiving optical system. The illumination optical system illuminates the fundus of the subject's eye with illumination light. The light receiving optical system has at least an imaging device. In addition, the light receiving optical system receives return light of the illumination light from the fundus by the imaging device. The fundus photographing device obtains a fundus image, which is a front image of the fundus, based on the received light signal from the imaging device.

The irradiation optical system and the light receiving optical system share at least an objective optical system (for example, an objective lens). In addition, the irradiation optical system and the light receiving optical system may share an optical path coupling section. The optical path coupling unit couples and separates the projection optical path of the illumination light and the reception optical path of the fundus reflected light. In this case, the objective optical system is arranged on the common optical path of the light-projecting optical path and the light-receiving optical path formed by the optical path coupling section.

The imaging element receives return light from the illumination area. In this embodiment, the fundus reflected light with respect to the illumination light and the fluorescence from the fundus are collectively referred to as "returned light". In this embodiment, the imaging element may be a two-dimensional light receiving element arranged at the fundus conjugate position.

The imaging device may be, for example, CMOS and two-dimensional CCD. The imaging element receives return light from the illumination area. A signal from the imaging device is input to the image processing section. The image processing unit acquires (generates) a fundus image of the subject's eye based on the signal from the imaging device.

In the following description, the fundus image acquired by the fundus imaging device is broadly classified into a photographed image and an observed image. The photographed image is a fundus image photographed (captured) based on the release signal. A typical example of a captured image is a still image. The observation image is a moving image used for observing the fundus when adjusting the imaging conditions of the device. For example, it is used when adjusting conditions such as focus and alignment. Also, an observation image is acquired by infrared light.

In this embodiment, the imaging optical system is a scanning optical system. The imaging optical system includes an optical element and a scanning section.

The optical element is used to form a slit-like imaging area on the fundus. Further, the scanning unit scans a slit-shaped photographing area with respect to the fundus. For example, the imaging region may be linearly scanned on the fundus or may be rotationally scanned on the fundus. In the case of rotational scanning, the center of rotation may be the optical axis of the imaging optical system.

Additionally, the imaging optics may have at least one of a light source and a barrier filter. The light source emits illumination light. The illumination light may be, for example, visible light or infrared light. Also, a plurality of light sources may be provided for each wavelength.

<Optical element>
The optical element is arranged on the optical path of at least one of the illumination light and return light, thereby forming a slit-shaped imaging area on the fundus. The optical element may have, for example, a slit aperture positioned conjugate with the fundus. It is preferable that the optical element is arranged in each of the optical path of the illumination light (that is, the optical path of the irradiation optical system) and the optical path of the return light (that is, the optical path of the light receiving optical system). By arranging an optical element in each of the optical path of the illumination light and the optical path of the return light, it becomes difficult to capture stray light that causes artifacts.

In the present disclosure, "conjugated" is not necessarily limited to a perfect conjugated relationship, but includes "substantially conjugated". That is, the "conjugated" in the present disclosure also includes the case where the parts are displaced from the perfectly conjugated position within the allowable range in relation to the technical significance of each part.

In this embodiment, the width of the imaging area can be switched between a first width and a second width wider than the first width by the optical element. In this case, the optical element may have at least two types of slit apertures, a first slit aperture corresponding to the first width and a second slit aperture corresponding to the second width.

However, it is not necessarily limited to this. For example, the optical element may have a slit aperture of variable width.

Also, the photographing area may be switchable to a plurality of widths of three or more. For example, the width of the imaging region may be switchable to a third width different from both the first width and the second width.

In addition, in the present disclosure, "width" means "length from end to end on the short side of a vertically long one". In other words, it is the length from end to end in the short direction.

The imaging device may also serve as an optical device arranged on the optical path of the return light. In this case, the imaging device may be a line sensor having a slit-like shape. Also, a CMOS that performs line exposure on a two-dimensional imaging surface (in other words, has a rolling shutter function) may be used.

<Scanning part>
The scanning unit scans a slit-shaped imaging region with respect to the fundus.

<First Scan Method: Method for Driving the Slit Forming Unit>
The optical element may be part of the scanning portion. In this case, the optical element may be driven to scan the slit-shaped imaging area on the fundus.

A specific example of the scanning unit is an optical chopper (eg, see FIG. 4). In the optical chopper, the optical element is a body of revolution in which a plurality of slit openings are arranged side by side on one circumference. In the optical chopper, the rotating body is rotationally driven. Thereby, a plurality of slit apertures are continuously traversed with respect to the optical path of illumination light or return light. The shape of the rotating body may be, for example, disk-like or cylindrical. A plurality of slits are formed in the cylindrical side surface of the cylindrical rotating body. Note that the rotating body may be driven at a constant speed.

Also, one rotator may be used both as an optical element arranged on the optical path of the illumination light and an optical element arranged on the optical path of the return light. In this case, the optical elements can be driven in good synchronization on the optical path of the illumination light and on the optical path of the return light.

The rotating body has a first area in which one or more first slit openings corresponding to the first width are continuously arranged, and one or two second slit openings corresponding to the second width. A second area arranged continuously as described above may be provided (see, for example, FIG. 5). In this case, the controller switches the width of the imaging region on the fundus between a first period during which the first area passes through the optical path and a second period during which the second area passes through the optical path.

If the scanning unit is an optical chopper, it may have a sensor that detects the rotational position of the rotating body.

Also, the optical element arranged on the optical path of the illumination light and the optical element arranged on the optical path of the return light may be separate bodies. When a CMOS is used as the imaging element, the CMOS may also be used as an optical element arranged on the optical path of the return light. That is, the line exposure by the rolling shutter function may be controlled in synchronization with the displacement of the optical element on the illumination light side. Thereby, the number of parts of the optical system can be suppressed.

<Second Scan Method: Method for Driving Deflection Device>
The scanning unit may be separate from the optical element. For example, the scanning unit may be a device that deflects the traveling direction of light (hereinafter referred to as "deflection device"). A deflection device deflects the illumination light and the returned light in a direction according to the control signal. The deflection device may be any of a variety of devices such as, for example, galvanomirrors, MEMS, and AODs (Acousto-Optic Deflectors). The deflection device is preferably arranged at a position conjugate with the anterior segment of the eye to be examined.

In this method, the return light from the fundus is descanned by the deflecting device, so that the optical element arranged on the optical path of the return light does not need to be moved along with the scanning. Thus, for example, the optical element may have a slit aperture fixedly positioned at the fundus conjugate position.

As described above, the scanning method in the present embodiment is roughly divided into at least two methods, ie, the method of driving the slit forming section and the method of driving the deflection device.

<Switching shooting modes>
The controller switches the imaging mode of the device between a first imaging mode and a second imaging mode. Here, in the first imaging mode, the controller captures the first fundus image by scanning the imaging region with the first width. In the second imaging mode, the controller captures the second fundus image by scanning the imaging region with the second width. As a result, fundus images can be captured by changing the amount of light projected and received. In the first imaging mode, the width of the imaging area is narrower than in the second imaging mode, so artifacts due to reflection from the objective lens or the like are less likely to occur. On the other hand, in the second photographing mode, the photographing area is wider than in the first photographing mode, so that the efficiency of light projection and reception is improved with respect to the amount of light.

When the scanning unit is an optical chopper provided with a rotator divided into the first area and the second area as described above, photographing in each mode is performed as follows.

In this case, in the first photographing mode, the control unit photographs the first fundus image based on the signal from the imaging device exposed during the first period during which the first area passes through the optical path. Also, in the second photographing mode, a second fundus image is acquired based on the signal from the imaging element exposed during the second period in which the second area passes through the optical path.

<Observation Image Acquisition Operation Using Optical Chopper>
In this case, the controller may control the optical chopper to continuously rotate the rotator, and obtain observation images at a constant frame rate based on the signal from the imaging element.

In this case, the control unit may alternately acquire the first observation image and the second observation image each time the first period and the second period are switched. Here, the first observation image is generated based on the signal from the imaging device exposed in the first period. Also, the second observation image is generated based on the signal from the image sensor exposed in the second period. At this time, the control unit may reduce either the light amount of the illumination light or the gain of the received light signal from the imaging element in the second period compared to the first period (see FIG. 6). Thereby, the brightness is uniformed between the first observation image and the second observation image. Therefore, screen flickering is suppressed when the first observation image and the second observation image are displayed as moving images.

Alternatively, the control unit acquires each frame of the observed image based on the signal from the imaging element exposed during at least part of the first period and at least part of the second period. (see, eg, FIG. 8). As a result, when generating each frame, the amount of light that exposes the imaging element is likely to be uniform. As a result, it becomes easier to obtain an observation image with uniform brightness.

Further, the control unit may acquire the observed image by exposing the imaging element during only one of the first period and the second period. Although the frame rate is slower than the above method, it is useful for displaying observation images with uniform brightness.

<First Aspect of Mode Switching>
For example, the first imaging mode may be set to capture a color image of the fundus as the first fundus image. Also, the second imaging mode may be set to capture a fluorescence image of the fundus as the second fundus image. In this case, the control unit changes the width of the imaging region used for imaging the fundus image according to the imaging mode, and at least changes the wavelength of the illumination light according to the imaging mode. For example, the control unit controls the light source according to the imaging mode, such that visible light such as white light is emitted from the light source in the first imaging mode, and excitation light corresponding to the fluorescent material is emitted in the second imaging mode. You can irradiate. Also, in the second imaging mode, the controller may further insert a barrier filter on the optical path of the return light. The barrier filter has a spectral characteristic of blocking reflected light from the fundus and allowing fluorescence from the fundus to pass through to the imaging element side. Reflection from the objective lens or the like is also shielded by the barrier filter, so artifacts are less likely to occur in the fluorescence image of the fundus.

In this way, when capturing a color image of the fundus, the width of the imaging region on the fundus is relatively narrow, thereby suppressing artifacts due to reflection from the objective lens or the like. In addition, when capturing a fluorescence image of the fundus, the width of the imaging region on the fundus is relatively wide, so that excitation light and fluorescence are emitted and received efficiently, making it easier to obtain a fluorescence image with high brightness. Become.

<Second Aspect of Mode Switching>
By the way, in order to reduce flare, the exit pupil and the entrance pupil are separated in the photographing optical system. In this embodiment, the spacing between the exit pupil and the entrance pupil may be variable. When the distance between the exit pupil and the entrance pupil is reduced, even an eye with a smaller pupil can be photographed. On the other hand, by shortening the distance between the exit pupil and the entrance pupil, artifacts due to reflection at the objective lens and the like tend to occur.

Therefore, for example, the control unit may selectively set either the first imaging mode or the second imaging mode according to the pupil diameter of the subject's eye. The first imaging mode may be set when imaging an eye with a smaller pupil diameter. Also, the second imaging mode may be set when imaging an eye with a larger pupil diameter.

In addition, in the first imaging mode, the control unit not only narrows the width of the imaging region as described above, but also controls the imaging optical system (more specifically, the irradiation optical system ) to reduce the distance between the exit pupil and the entrance pupil. According to this, even an eye with a small pupil can be satisfactorily imaged while suppressing the occurrence of artifacts.

In this case, the fundus imaging device may have a pupil information acquisition unit that is information about the size of the pupil of the subject's eye. The information about the pupil size may be the pupil diameter or information correlated with the pupil diameter. The pupil information acquisition unit may include, for example, an anterior segment observation optical system that captures an image of the anterior segment of the subject's eye. For example, the control unit compares the size of the pupil detected from the image of the anterior segment obtained through the anterior segment observation optical system with a threshold value, and selects an imaging mode according to the comparison result. good too. Also, the pupil information acquisition unit may acquire information about the size of the pupil of the subject's eye measured by another ophthalmologic apparatus. Also, information about the size of the pupil may be input to the examiner via the operation unit.

<Third Aspect of Mode Switching>
The imaging optical system may have a diopter correction unit for correcting diopter errors in the subject's eye. The dioptric correction unit may be arranged, for example, on the common optical path of the irradiation optical system and the light receiving optical system, or may be arranged on each of the independent optical paths of the irradiation optical system and the light receiving optical system.

The occurrence of artifacts due to reflection on the objective lens and the like changes according to the state of diopter correction. The fundus conjugate plane formed closest to the objective lens is displaced according to the diopter correction amount. For example, artifacts are more likely to occur as the fundus conjugate plane approaches the lens surface of the objective lens. On the other hand, artifacts may not be a problem within a certain diopter correction amount range. However, it is considered that this range differs for each optical system.

Therefore, the control section may selectively set either the first shooting mode or the second shooting mode according to the visibility correction amount in the visibility correction section. The control unit selects the first imaging mode in a first range of the first diopter correction amount in which artifacts are likely to occur, and selects the second imaging mode in a second range in which artifacts are less likely to occur than in the first range. You may choose.

"Example"
Next, embodiments will be described with reference to FIGS. 1 to 7. FIG.

A fundus imaging device 1 (hereinafter simply referred to as "imaging device 1") according to the embodiment forms illumination light in a slit shape on the fundus of an eye to be inspected, and a region formed in the slit on the fundus is captured. A front image of the fundus is captured by scanning and receiving the fundus reflected light of the illumination light.

<Appearance of device>
Referring to FIG. 1, the external configuration of the photographing device 1 will be described. The imaging device 1 has an imaging unit 3 . The imaging unit 3 mainly includes an optical system shown in FIG. The photographing apparatus 1 has a base 7 , a drive section 8 , a face support unit 9 , and a face photographing camera 110 , and uses these to adjust the positional relationship between the subject's eye E and the photographing unit 3 .

The drive unit 8 can move in the left-right direction (X direction) and front-rear direction (Z direction, in other words, working distance direction) with respect to the base 7 . Further, the driving section 8 moves the photographing unit 3 on the driving section 8 with respect to the subject's eye E in three-dimensional directions. The driving section 8 has an actuator for moving the driving section 8 or the photographing unit 3 in each predetermined movable direction, and is driven based on a control signal from the control section 80 . A face support unit 9 supports the subject's face. A face support unit 9 is fixed to the base 7 .

The face photographing camera 110 is fixed to the housing 6 so that the positional relationship with respect to the photographing unit 3 is constant. A face photographing camera 110 photographs the subject's face. The control unit 100 specifies the position of the subject's eye E from the photographed face image, and drives and controls the driving section 8 to align the photographing unit 3 with the specified position of the subject's eye E. A detailed configuration of the control system will be described later with reference to FIG.

In addition, the photographing device 1 further has a monitor 120 . The monitor 120 displays a fundus observation image, a photographed fundus image, an anterior segment observation image, and the like.

<Optical System of Example>
The optical system of the imaging device 1 will be described with reference to FIG. The photographing device 1 has a photographing optical system (fundus photographing optical system) 10 and an anterior segment observation optical system 40 . These optical systems are provided in the photographing unit 3 .

In FIG. 2, positions conjugated to the pupil of the subject's eye are indicated by "Δ" on the photographing optical axis, and positions conjugate to the fundus are indicated by "x" on the photographing optical axis.

The imaging optical system 10 has an irradiation optical system 10a and a light receiving optical system 10b. In the embodiment, the illumination optical system 10a has a light source unit 11, a lens 13, a slit member 15a, lenses 17a and 17, a mirror 18, a perforated mirror 20, and an objective lens 22. The light receiving optical system 10b has an objective lens 22, a perforated mirror 20, lenses 25a and 25b, a slit-shaped member 15b, and an imaging device . Note that the perforated mirror 20 is an optical path coupling portion that couples the optical paths of the irradiation optical system 10a and the light receiving optical system 10b. The perforated mirror 20 reflects the illumination light from the light source toward the eye to be inspected E, and allows a part of the fundus reflected light from the eye to be inspected E that has passed through the aperture to pass through to the imaging element side. Various beam splitters other than the apertured mirror 20 can be used. For example, instead of the perforated mirror 20, a mirror in which the perforated mirror 20, the transmissive portion and the reflective portion are reversed may be used as the optical path coupling portion. However, in this case, the independent optical path of the light receiving optical system 10b is placed on the reflection side of the mirror, and the independent optical path of the irradiation optical system 10a is placed on the transmission side of the mirror. Also, the perforated mirror and its alternative mirror can be further replaced by a combination of a half mirror and a light blocking section.

In this embodiment, the light source unit 11 has multiple types of light sources with different wavelength bands. For example, the light source unit 11 has visible light sources 11a and 11b and infrared light sources 11c and 11d. Two light sources having the same wavelength range are arranged apart from the imaging optical axis L on the pupil conjugate plane. The two light sources are arranged along the X direction, which is the scanning direction in FIG. As shown in FIG. 2, the outer peripheral shapes of the two light sources may be rectangular shapes in which the direction intersecting the scanning direction is longer than the scanning direction.

Although two visible light sources 11a and 11b are shown in FIG. 2, each light source 11a and 11b includes a plurality of visible light sources for each wavelength. For example, light sources corresponding to three colors of R (red), G (green), and B (blue) may be included in the visible light sources 11a and 11b, respectively. Thus, in this embodiment, any one of the three colors of R (red), G (green), and B (blue) can be irradiated in any combination. For example, when capturing a color fundus image, three colors of R (red), G (green), and B (blue) may be emitted. In addition, when performing autofluorescence photography, which is a type of fluorescence photography, light with a wavelength of G (green) or B (blue) may be irradiated.

Light from the light source passes through the lens 13 and irradiates the slit-shaped member 15 . In this embodiment, the slit-shaped member 15a has a translucent portion (aperture) elongated along the Y direction. As a result, the illumination light is formed in a slit shape on the fundus conjugate plane (the region illuminated in a slit shape on the fundus is illustrated as B).

In FIG. 2, the slit-shaped member 15a is displaced by the drive section 15c so that the translucent section crosses the photographing optical axis L in the X direction. Thereby, the scanning of the illumination light in this embodiment is realized. In this embodiment, scanning is also performed by the slit member 15b on the light receiving system side. In this embodiment, the slit-shaped members on the light-projecting side and the light-receiving side are driven in conjunction with one driving section (driver).

In the irradiation optical system 10a, the image of each light source is relayed by the optical system from the lens 13 to the objective lens 22 and formed on the pupil conjugate plane. That is, images of the two light sources are formed at positions separated in the scanning direction on the pupil conjugate plane. In this way, in this embodiment, the two projection areas P1 and P2 (exit pupil in this embodiment) on the pupil conjugate plane are formed as images of the two light sources.

Also, the slit-shaped light that has passed through the slit-shaped member 15a is relayed by the optical system from the lens 17a to the objective lens 22 and forms an image on the fundus Er. Thereby, the illumination light is formed in a slit shape on the fundus Er. The illumination light is reflected on the fundus Er and extracted from the pupil Ep.

Here, since the aperture of the perforated mirror 20 is conjugate with the pupil of the eye to be inspected, the fundus reflected light used for photographing the fundus image passes through the image of the aperture of the perforated mirror (pupil image) on the pupil of the eye to be inspected. limited to some Thus, the image of the aperture on the pupil of the subject's eye is the light-receiving region R (entrance pupil in this embodiment) in this embodiment. The light receiving region R is formed between two light projecting regions P1 and P2. Further, as a result of appropriately setting the imaging magnification of each image, the diameter of the aperture, and the arrangement interval of the two light sources, the light receiving region R and the two light projecting regions P1 and P2 are arranged so as not to overlap each other on the pupil. formed in That is, the exit pupil and the entrance pupil are separated. As a result, the occurrence of flare is favorably reduced.

The fundus reflected light that has passed through the apertures of the objective lens 22 and the perforated mirror 20 forms an image of the slit-like region of the fundus Er at the fundus conjugate position via the lenses 25a and 25b. At this time, harmful light is removed by arranging the translucent portion of the slit-shaped member 15b at the image forming position.

The imaging device 28 is arranged at a fundus conjugate position. In this embodiment, a relay system 27 is provided between the slit-shaped member 15b and the imaging device 28, whereby both the slit-shaped member 15b and the imaging device 28 are arranged at the fundus conjugate position. As a result, both harmful light rejection and imaging are performed well. Alternatively, the relay system 27 between the imaging element 28 and the slit member 15b may be omitted and the two may be arranged close to each other. In this embodiment, a device having a two-dimensional light receiving surface is used as the imaging device 28 . For example, it may be CMOS, two-dimensional CCD, or the like. An image of the slit-shaped region of the fundus Er formed on the light-transmitting portion of the slit-shaped member 15b is projected onto the imaging device 28 . The imaging device 28 has sensitivity to both infrared light and visible light.

In this embodiment, as the slit-shaped illumination light scans the fundus Er, images (slit-shaped images) of scanning positions on the fundus Er are sequentially projected for each scanning line of the imaging element 28 . In this manner, the entire image of the scanning range is projected onto the imaging device in a time division manner. As a result, a front image of the fundus Er is captured as an entire image of the scanning range.

In the embodiments, the scanning unit in the light receiving system is a device that mechanically scans the slit, but it is not necessarily limited to this. For example, the scanning unit on the light receiving optical system side may be a device that electronically scans the slit. As an example, if the imaging device 28 is a CMOS, slit scanning may be realized by the CMOS rolling shutter function. In this case, by displacing the exposed area on the imaging surface in synchronization with the scanning unit in the light projecting system, it is possible to remove harmful light and efficiently perform imaging. A liquid crystal shutter or the like can also be used as a scanning unit that electronically scans the slit.

The imaging optical system 10 has a dioptric correction section. In this embodiment, the independent optical path of the irradiation optical system 10a and the independent optical path of the light receiving optical system 10b are each provided with a dioptric correction unit (dioptric correction optical systems 17 and 25). Hereinafter, for convenience, the dioptric correction optical system on the irradiation side will be referred to as the dioptric correction optical system 17 on the irradiation side, and the dioptric correction optical system on the light receiving side will be referred to as the dioptric correction optical system 25 on the light receiving side. The irradiation-side diopter correction optical system 17 of this embodiment includes lenses 17a, 17b, and a driving section 17c (see FIG. 3). The light-receiving side dioptric correction optical system 25 of this embodiment includes a lens 25a, a lens 25b, and a driving section 25c (see FIG. 3). In the dioptric correction optical system 17 on the irradiation side, the distance between the lenses 17a and 17b is changed, and in the dioptric correction optical system 25 on the reception side, the distance between the lenses 25a and 25b is changed. Accordingly, diopter correction is performed in each of the irradiation optical system 10a and the light receiving optical system 10b.

<Split target projection optical system>
As shown in FIG. 2, the imaging optical system 10 further has a split index projection optical system 50 as an example of the focus index projection optical system. A split index projection optical system 50 projects two split indices onto the fundus. A split index is used to detect the focus state. Further, in the present embodiment, the refractive power of the subject's eye E is obtained from the detection result of the focus state.

The split target projection optical system 50 may have at least a light source 51 (infrared light source), a target plate 52, and a deviation prism 53, for example. In this embodiment, the index plate 52 is arranged at a position corresponding to the imaging plane in the light receiving optical system 50 . Similarly, the slit-shaped members 15a and 15b are also arranged at corresponding positions. Specifically, when the diopter correction amount on the irradiation side and the light receiving side is 0D, the optotype plate 52 is arranged at a position substantially conjugate with the fundus of the emmetropic eye (0D eye). The deflection prism 53 is arranged closer to the index plate 52 on the subject's eye side than the index plate 52 .

The indicator plate 52 is formed using, for example, slit light as an indicator. A deflection prism 53 splits the index light beam passing through the optotype plate 52 to form a split index. The separated split index is projected onto the fundus of the subject's eye via the irradiation-side dioptric correction optical system 17 and the objective lens 22 . Therefore, the split index is reflected in the fundus image (for example, the fundus observation image).

When the index plate 52 is displaced from the fundus conjugate position, the two split indices are separated on the fundus, and when the index plate 52 is placed at the fundus conjugate position, the two split indices are aligned. The conjugate relationship is adjusted by the irradiation-side dioptric correction optical system 17 arranged between the deviation prism 53 and the subject's eye Er. Therefore, in this embodiment, defocusing is performed while matching the diopter correction amount on the irradiation side and the dioptric correction amount on the light receiving side. At this time, the separation state of the split indicator indicates the focus state. By adjusting the dioptric correction amounts on the irradiation side and the light receiving side so that the two split indices match each other, the imaging surface and the slit-shaped members 15a and 15b each have a conjugate positional relationship with the fundus. becomes.

<Detailed description of the optical chopper>
The scanner may be, for example, an optical chopper 150 as shown in FIG. The optical chopper 150 has a wheel 151 having a plurality of slit openings formed on its outer periphery, and by rotating the wheel 151, the slits can be scanned at high speed. The wheel 151 is an example of a disk-shaped rotating body.

In this case, the wheel 151 corresponds to the slit-shaped members 15a and 15b shown in FIG. 2, and the body portion 152 includes the driving portion 15c (see FIG. 3).

In this embodiment, the imaging device 1 may include a sensor (not shown) that detects the amount of rotation of the wheel 151 . Thereby, the control unit 100 can detect the rotational position of the wheel 151 .

Here, in FIG. 2, the light source unit 11 to the mirror 18 of the irradiation optical system 10a and the perforated mirror 20 to the imaging device 28 of the light receiving optical system 10b are arranged in parallel in the X direction. By rotating the directions of the aperture mirror 20 and the mirror 18 by 90° from the illustrated state and arranging them in parallel in the Y direction, the optical chopper can be applied as a scanning unit. In this case, the optical axis of the irradiation optical system 10a and the optical axis of the light receiving optical system 10b are made to cross each other at two points, the upper end and the lower end of the wheel 151, so that the single optical chopper 150 can be used for the projection system and the light reception system. The scanning of the light receiving system can be easily synchronized.

The wheel 151 of this embodiment is divided into four areas, two first areas and two second areas, as shown in FIG. Each area has four slit openings evenly distributed.

A first slit aperture corresponding to an imaging region having a first width is arranged in the first area. Also, in the second area, a second slit opening corresponding to the imaging area having the second width is arranged. In order to make the second width wider than the first width, the second slit opening is formed wider than the first slit opening.

The two first areas are arranged diagonally (symmetrically with respect to the axis of rotation) on the wheel 151 , and the two second areas are also arranged diagonally on the wheel 151 . As a result, slit openings of the same width are always arranged at diagonal positions on the wheel 151 . In this embodiment, the wheel 151 intersects the optical axis of the irradiation optical system 10a and the optical axis of the light receiving optical system 10b at two diagonal locations. As a result, the relationship between the width of the slit opening that traverses the optical path of the irradiation optical system 10a and the width of the slit opening that traverses the optical path of the light receiving optical system 10b can always be kept constant.

By using such an optical chopper 150, in the present embodiment, the imaging on the fundus can be performed between the first period during which the first area passes through the optical path and the second period during which the second area passes through the optical path. The width of the region switches between a first width and a second width.

As an example, in this embodiment, one frame of fundus image is acquired for each area. That is, during one rotation of the wheel 151, a maximum of four frames of fundus images are acquired. Specifically, four slit openings arranged in one area cross the optical path, and the return light is scanned four times on the imaging element 28 . During that time, the imaging device 28 is continuously exposed, and one frame of fundus image is formed based on the signals accumulated during that time. However, the invention is not necessarily limited to this, and one frame of fundus image may be acquired each time an arbitrary number of slit apertures are crossed.

<Barrier filter>
Returning to FIG. 2, the explanation of the optical system is continued. The imaging device 1 further has a barrier filter 61 . At the time of fluorescence imaging, the fluorescence from the fundus based on the excitation light is guided to the imaging device 28 in the light receiving optical system 10b. A barrier filter 61 can be arranged on the independent optical path of the receiving optical system. The barrier filter 61 has a spectral characteristic that blocks light in the same wavelength range as the excitation light and allows fluorescence to pass through. As an example, in this embodiment, the barrier filter 61 has spectral characteristics suitable for autofluorescence photography. For example, green or blue light, which is the excitation light, is blocked, and light on the longer wavelength side is allowed to pass through to the imaging device 28 side. As a result, spontaneous fluorescence is selectively received by the imaging element 28 . As a result, a good autofluorescence image of the fundus can be obtained. The photographing device 1 may have a driving section 61a for inserting and removing the barrier filter 61. As shown in FIG. Also, the insertion and removal of the barrier filter is controlled by the controller 100, for example.

<Anterior segment observation optical system>
Next, the anterior segment observation optical system 40 will be described. The anterior segment observation optical system 40 shares the objective lens 22 and the dichroic mirror 43 with the imaging optical system 10 . The anterior segment observation optical system 40 further includes a light source 41, a half mirror 45, an imaging device 47, and the like. The imaging device 47 is a two-dimensional imaging device, and is arranged at a position optically conjugate with the pupil Ep, for example. The anterior segment observation optical system 40 illuminates the anterior segment with infrared light and captures a front image of the anterior segment.

Note that the anterior segment observation optical system 40 shown in FIG. 2 is merely an example, and the anterior segment may be imaged through an optical path independent of other optical systems.

<Control system of the embodiment>
Next, referring to FIG. 3, the control system of the imaging device 1 will be described. In this embodiment, the control unit 100 controls each unit of the photographing apparatus 1 . Further, for the sake of convenience, it is assumed that image processing of various images obtained by the photographing device 1 is also performed by the control unit 100 . In other words, in this embodiment, the control section 100 also serves as an image processing section.

The control unit 100 is a processing device (processor) having an electronic circuit that performs control processing of each unit and arithmetic processing. The control unit 100 is implemented by a CPU (Central Processing Unit), a memory, and the like. The control unit 100 is electrically connected to the storage unit 101 via a bus or the like.

The storage unit 101 stores various control programs, fixed data, and the like. Temporary data or the like may be stored in the storage unit 101 .

Images captured by the imaging device 1 may be stored in the storage unit 101 . However, the captured image is not necessarily 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 100 via LAN and WAN).

The control unit 100 is also electrically connected to each unit such as the driving unit 8, the light sources 11a to 11d, the imaging element 28, the light source 41, the imaging element 47, the light source 51, the input interface 110, the monitor 120, and the like.

Further, the control unit 100 controls each of the above members based on operation signals output from the input interface 110 (operation input unit). The input interface 110 is an operation input unit that receives operations of the examiner. For example, it may be a mouse and keyboard.

<Description of operation>
Next, the photographing operation will be described with reference to the flowchart of FIG.

<Alignment>
The photographing device 1 may automatically start the photographing operation when the subject's face is placed on the face support section 9 and included in the photographing range of the face detection camera 110 .

First, photographing by the face detection camera 110 and the anterior segment observation optical system 40 is performed in parallel, and alignment adjustment is performed using the photographing results of both.

Specifically, the control unit 100 detects the position of one of the left and right eyes included in the face image, and drives the driving unit 8 based on the position information. Thereby, the position of the photographing unit 4 is adjusted to a position where the anterior segment can be observed.

Next, an alignment reference position is set based on the front image of the anterior segment, and alignment is guided to the set alignment reference position. In this embodiment, the control unit 100 adjusts the positional relationship between the subject's eye E and the photographing unit 3 based on the front image of the anterior segment. In this embodiment, the control unit 100 controls the position where the center of the pupil in the observed image of the anterior eye and the center of the image (in this embodiment, the position of the imaging optical axis L) substantially match based on the signal from the imaging element 47. A first reference position targeting relationship is established. Then, an alignment deviation from the first reference position is detected, and the photographing unit 4 is moved up, down, left and right in a direction in which the alignment deviation is eliminated. At this time, for example, misalignment with the first reference position may be detected based on the amount of misalignment between the center of the pupil on the anterior segment observed image and the imaging optical axis. Further, if the fundus imaging apparatus 1 has, for example, an alignment projection optical system that projects an alignment index onto the corneal vertex, misalignment may be detected based on the amount of deviation between the alignment index and the imaging optical axis. .

Further, the control section 100 moves the photographing unit 4 in the front-rear direction so that the pupil Ep is focused on the pupil Ep. Thereby, the distance from the device to the eye to be examined is adjusted to a predetermined working distance.

As described above, in this embodiment, as a result of the alignment adjustment, the positional relationship between the subject's eye and the imaging unit 4 is such that the center of the light receiving region R on the pupil of the subject's eye (that is, the imaging optical axis) coincides with the pupil center. is adjusted to a position (first reference position in the present embodiment) where

<Acquisition and Display of Fundus Observation Image>
Subsequently, the control unit 100 starts acquisition and display of the fundus observation image. Specifically, the control unit 100 turns on the light sources 11c and 11d at the same time and starts driving the driving unit 15c so that a predetermined range on the fundus Er is repeatedly scanned with the slit-shaped illumination light.

Each time an area of the wheel 151 passes through the optical path, a one-frame fundus image is generated as the fundus observation image based on the signal output from the imaging device 28 . The control unit 100 causes the monitor 120 to display the fundus observation image as a substantially real-time moving image.

At this time, the efficiency of light emission and reception differs greatly between when the first area passes through the optical path and when the second area passes through the optical path. Therefore, the control unit 100 switches at least one of the light intensity of the light sources 11c and 11d and the gain of the received light signal according to the rotational position of the wheel 151 detected by the sensor. Specifically, when the first area passes through the optical path (first period in this embodiment), the light sources 11c, Either the light amount of 11d or the gain of the received light signal is increased (see FIG. 6). Thus, in this embodiment, an observed image is obtained each time each area passes through the optical path, so that the observed image can be displayed at a higher frame rate.

Note that when LEDs are used as the light sources 11c and 11d, the control section 100 preferably performs the above control by controlling the light sources 11c and 11d because the time response to the control signal is rapid.

<Dioptric correction>
Next, based on the fundus observation image, the focus states of the irradiation optical system and the light receiving optical system are adjusted. In this embodiment, after the alignment is completed, the dioptric correction optical system is driven to adjust the focus. At this time, in this embodiment, both the irradiation side dioptric correction optical system 17 and the light receiving side dioptric correction optical system 25 are driven.

In the focus adjustment process, the control unit 100 first turns on the light source 51 to start projecting the split index onto the fundus. The control unit 100 performs defocusing by changing the correction amount while matching the diopter correction amount on the irradiation side and the dioptric correction amount on the light receiving side. In addition, the control unit 100 detects the separation state of the split index from the fundus observation image each time the correction amount changes, and adjusts the irradiation-side dioptric correction amount and the light-receiving side dioptric correction amount until the split indices match. adjust. As a result of such adjustment, each of the imaging surface and the slit-shaped members 15a and 15b has a conjugate positional relationship with the fundus.

Here, during the focus adjustment process, the control unit 100 may switch the light amount of the light source 51 between when the first area passes through the optical path and when the second area passes through the optical path ( See Figure 6). For example, when the first area passes through the optical path, the amount of light from the light source 51 may be increased compared to when the second area passes through the optical path. As a result, for example, even if the brightness of the observed image varies from frame to frame, it is easy to detect the separation state of the split indicators.

<Selecting a shooting mode and shooting>
Subsequently, the control unit 100 selects an imaging mode and adjusts imaging conditions according to the imaging mode. The imaging mode is selected, for example, according to an instruction from the examiner. The control unit 100 may select an imaging mode between the normal imaging mode and the fluorescence imaging mode. The normal imaging mode is set to capture a fundus image based on fundus reflected light. The fluorescence imaging mode is set to capture a fluorescence fundus image.

In this embodiment, the control unit 100 adjusts at least the wavelength conditions of the light emitted from the light sources 11a and 11b according to the imaging mode, and also adjusts the insertion/removal of the barrier filter 61 with respect to the optical path of the light receiving optical system 10b. Adjust conditions. Furthermore, in the present embodiment, the control unit 100 also adjusts the conditions regarding the exposure period of the imaging device 28 when acquiring the fundus image.

Specifically, in the normal photographing mode, three colors of R (red), G (green), and B (blue) are simultaneously emitted from the light sources 11a and 11b for photographing. Also, the barrier filter 61 is retracted from the optical path of the light receiving optical system 10b. Furthermore, a fundus image is generated based on the exposure of the imaging device 28 while the first area passes through the optical path. By setting the width of the slit-shaped photographing area on the fundus to be relatively narrow, it is possible to photograph a photographed image in which artifacts due to reflection at the objective lens 22 or the like are suppressed.

Further, in the fluorescence photographing mode of this embodiment, photographing is performed by emitting one color of B (blue) from the light sources 11a and 11b. Also, a barrier filter 61 is inserted into the optical path of the light receiving optical system 10b. As a result of the barrier filter 61 being inserted, the aforementioned artifacts need not be considered. Therefore, a fundus image is generated based on the exposure of the imaging device 28 while the second area passes through the optical path. That is, shooting is performed with the width of the slit-shaped shooting area widened compared to the normal shooting mode.

It should be noted that the control section 100 may stop the light emission from the light sources 11c and 11d for observation and then turn on the light sources 11a and 11b for photography. In this case, a photographed image of the fundus is obtained as a photographing result based on the visible light emitted from the light sources 11a and 11b.

<transformation example>
Although the above has been described based on the embodiments, the contents of the embodiments can be changed as appropriate in carrying out the present disclosure.

<small pupil shooting mode>
For example, in the above embodiment, the photographing mode is selected between the normal photographing mode and the fluorescence photographing mode, but it is not necessarily limited to this. For example, the shooting mode may be switched between normal shooting mode and small pupil shooting mode. In both the normal imaging mode and the small-pupil imaging mode, a captured image is obtained based on reflected light from the fundus.

In this case, the photographing device 1 may acquire the pupil diameter from the anterior segment observed image as the information about the size of the pupil of the subject's eye. The controller 100 compares the pupil diameter of the subject's eye with a predetermined threshold value. As an example, a value of approximately φ4 mm may be used as the threshold. When the pupil diameter of the subject's eye E is larger than the threshold, the normal imaging mode is set. Also, when the pupil diameter is smaller than the threshold, the small pupil photographing mode is set.

In this case, the intervals between the light sources 11a to 11d and the optical axis L may be changeable. By changing the distance between each light source 11a to 11d and the optical axis L, it may be possible to change the clearance between the entrance pupil and the exit pupil. The larger the clearance, the less likely the objective lens 22 will produce artifacts. A small clearance is advantageous for photographing eyes with small pupils.

In this case, for example, when the exit pupil is formed on the pupil of the subject's eye by arranging the light sources on the pupil conjugate plane at a position away from the imaging optical axis, a pair of light sources are shown in FIG. Two sets may be arranged as shown. The two sets may have different distances from the imaging optical axis to the light source. Also, all the light sources are arranged side by side in the scanning direction. FIG. 9 shows two sets of light source images formed on the pupil of the subject's eye and an aperture image of the diaphragm. In this case, the two sets of light source images form the exit pupil on the pupil, and the aperture image of the stop forms the entrance pupil.

Which one of the two sets is used for imaging may be selected according to the pupil diameter of the subject's eye. In other words, the control section 100 may select a light source from one set arranged further outside in the normal shooting mode. In this case, the reflected image is likely to be reduced. Further, in the small pupil photographing mode, the control unit 100 may select a light source from among a set of light sources arranged further inside. In the small-pupil photography mode, artifacts are more likely to occur due to the reduced clearance between the entrance and exit pupils. Therefore, the captured image may be captured using the period during which the first area passes through the optical path as the exposure period. On the other hand, in the normal photographing mode, since the clearance between the entrance pupil and the exit pupil is wide, the photographed image may be photographed using the period during which the second area passes through the optical path as the exposure period.

1 fundus photographing device 10 photographing optical system 10a irradiation optical system 10b light receiving optical system 22 objective lens 100 control unit 150 optical chopper E eye to be examined Er fundus

Claims (5)

A slit-shaped illuminator formed by arranging two light projection areas on the pupil of the eye to be inspected, through which the illumination light passes, in a first direction, and forming an elongated slit along a second direction intersecting the first direction. an irradiation optical system that irradiates light onto the fundus of the eye to be examined;
a scanning unit that scans the illumination light on the fundus in the first direction;
A light receiving device comprising: a light receiving area from which the fundus reflected light of the illumination light is extracted is formed on the pupil of the subject's eye so as to be sandwiched between the two light projecting areas, and an imaging device that receives the fundus reflected light of the illumination light. an optical system;
A fundus photographing device that obtains a fundus image, which is a front image of the fundus, based on a received light signal from the imaging device,
A fundus photographing apparatus comprising control means for changing a clearance in the first direction between the two light projecting areas and the light receiving area on the pupil of the subject's eye. 2. The fundus imaging apparatus according to claim 1, wherein said light receiving element is a CMOS having a rolling shutter function, and line exposure by said rolling shutter function is controlled in synchronization with displacement of said scanning unit. 2. The fundus imaging apparatus according to claim 1, wherein said control means changes said clearance according to a pupil diameter of an eye to be examined. 4. The control unit according to claim 3, wherein said control means acquires pupillary information, which is information relating to the size of the pupil of said eye to be examined, based on an anterior ocular segment observed image of said eye to be examined, and changes said clearance based on said pupillary information. fundus imaging device. 4. The fundus imaging apparatus according to claim 3, wherein said control means selects one of a first imaging mode and a second imaging mode having different clearances according to an instruction from an examiner.

Images