JP7543790B2 - Fundus photography device - Google Patents

Description

This disclosure relates to a fundus imaging device for obtaining a frontal image of the fundus.

Fundus imaging devices that capture a front image of the fundus of a subject's eye are widely used in the field of ophthalmology. Examples of fundus imaging devices include fundus cameras, scanning laser ophthalmoscopes, and the following devices. For example, Patent Document 1 discloses a device that obtains a front image of the fundus by driving a slit placed in the optical path to scan a slit-shaped illumination light on the fundus and sequentially projecting an image of the illuminated slit-shaped area on the fundus onto a two-dimensional imaging surface as the light is scanned.

Special Publication No. 61-48940

By the way, various imaging methods, such as color imaging and fluorescent imaging, are used to capture frontal images of the fundus. As a result of the inventor's investigation, it is believed that in a device that scans slit-shaped illumination light as described above, it is difficult to capture images effectively using each imaging method with a slit of a single width.

This disclosure has been made in consideration of at least one of the problems with the conventional technology, and has as its technical objective the provision of a fundus imaging device that can easily capture bright, high-quality fundus images.

A fundus imaging device according to a first aspect of the present disclosure is a fundus imaging device that includes an imaging optical system including an illumination optical system that illuminates an illumination light onto the fundus of a subject's eye, and a light receiving optical system including an imaging element that receives return light of the illumination light from the fundus, and acquires a fundus image, which is a front image of the fundus, based on a light receiving signal from the imaging element, wherein the imaging optical system includes a slit forming section that includes a slit opening and a light blocking section for forming a slit-shaped imaging area on the fundus, a drive section that rotates and moves the slit forming section in a direction in which the long side of the slit opening crosses at least one of the light beams of the illumination light and the return light, and a switching mechanism , and the slit forming section has two types of slits with different widths. A slit plate in which the slit openings are arranged alternately, and a mask which selectively opens one of the two types of slit openings are stacked along the optical axis, the drive unit is capable of reversing the direction of rotational movement in the slit forming unit, and the switching mechanism has a delay generating mechanism which delays the transmission of power from the drive unit to the slit plate and the mask by a predetermined amount of movement between the slit plate and the mask when the direction of movement is switched between forward and reverse, in order to change the positional relationship between the slit plate and the mask depending on whether the direction of movement is forward or reverse, and mechanically switch the area ratio between the light-shielding portion and the slit opening in the slit forming unit.

This disclosure makes it easy to capture bright, high-quality fundus images.

FIG. 1 is a diagram showing the external configuration of an apparatus according to an embodiment. FIG. 2 is a diagram showing an optical system housed in the photographing unit of the embodiment. FIG. 2 is a block diagram showing a control system of the apparatus according to the embodiment. FIG. 3 is a diagram showing an optical chopper that can be used as a scanning unit in the optical system of FIG. 2. FIG. 4 is a diagram showing a slit plate which is a part of a slit forming portion in the embodiment. FIG. 13 is a diagram showing a mask that is a part of a slit forming portion in the embodiment. The slit plate and the mask are shown connected and rotated counterclockwise. This shows the slit plate and the mask connected together and rotated clockwise. 4 is a flowchart showing the operation of the device.

"overview"
Hereinafter, an embodiment of a fundus imaging device according to the present disclosure will be described with reference to the drawings. The fundus imaging device captures a fundus image. In the present disclosure, a 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, for example, FIG. 2). The fundus imaging device of this embodiment may additionally have a control unit (see, for example, FIG. 3).

<Photographic optical system>
The photographing optical system includes an illumination optical system and a light receiving optical system. The illumination optical system irradiates illumination light onto the fundus of the subject's eye. The light receiving optical system has at least an imaging element. The light receiving optical system receives return light of the illumination light from the fundus by the imaging element. The fundus photographing device obtains a fundus image, which is a front image of the fundus, based on a light receiving signal from the imaging element.

The illumination optical system and the light receiving optical system share at least the objective optical system (e.g., an objective lens). Alternatively, the illumination optical system and the light receiving optical system may share an optical path coupling section. The optical path coupling section couples and separates the projection optical path of the illumination light and the receiving optical path of the fundus reflected light. In this case, the objective optical system is disposed on a common optical path formed by the projection optical path and the receiving optical path by the optical path coupling section.

The image sensor receives return light from the illumination area. In this embodiment, the fundus reflection light in response to the illumination light and the fluorescence from the fundus are collectively referred to as "return light." In this embodiment, the image sensor may be a two-dimensional light receiving element arranged at a fundus conjugate position.

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

In the following description, fundus images acquired by a fundus imaging device are broadly divided into photographed images and observed images. Photographed images are fundus images that are photographed (captured) based on a release signal. A typical example of a photographed image is a still image. Observation images are videos that are used to observe the fundus when adjusting the imaging conditions of the device. For example, they are used when adjusting conditions such as focus and alignment. Observation images are acquired using infrared light.

In this embodiment, the imaging optical system is a scanning optical system. The imaging optical system includes a slit forming unit, a drive unit, and a switching mechanism.

The slit forming section has a slit opening and a light blocking section for forming a slit-shaped photographing area on the fundus. A driving force is transmitted from the driving section to the slit forming section. The driving section moves the slit forming section in a direction in which the long side of the slit opening crosses the optical axis. This causes the slit-shaped photographing area to be scanned over the fundus.

Additionally, the imaging optical system 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. In addition, the imaging optical system may have multiple light sources for each wavelength.

<Slit forming section>
The slit forming unit is disposed on at least one of the optical paths of the illumination light and the return light, thereby forming a slit-shaped photographing area on the fundus. The slit opening of the slit forming unit is disposed, for example, at a position conjugate with the fundus. It is preferable that the slit forming unit is disposed on each of the optical path of the illumination light (i.e., the optical path of the irradiation optical system) and the optical path of the return light (i.e., the optical path of the light receiving optical system). By disposing the slit forming unit on each of the optical paths of the illumination light and the return light, stray light that causes artifacts is less likely to be captured.

In this disclosure, "conjugation" is not necessarily limited to a perfect conjugate relationship, but includes "approximate conjugation." In other words, "conjugation" in this disclosure also includes cases where the positions are shifted from a perfect conjugate position within the range permitted in relation to the technical significance of each part.

One specific example of the slit forming unit is an optical chopper (see, for example, FIG. 4). In an optical chopper, the slit forming unit is a rotating body in which multiple slit openings and light blocking units are arranged alternately on one circumference. In an optical chopper, the rotating body is driven to rotate by a driving unit. This causes multiple slit openings to continuously cross the optical path of the illumination light or return light. The shape of the rotating body may be, for example, disk-shaped or cylindrical. In a cylindrical rotating body, multiple slits are formed on the cylinder side. The rotating body may be driven at a constant speed. Alternatively, the slit forming unit and the driving unit may be configured to drive the slit openings back and forth. Alternatively, the rotating body may be a mechanical shutter that can change the light beam passing position.

<Switching mechanism>
The switching mechanism mechanically switches the area ratio between the slit opening and the light blocking portion by acting on the slit forming portion. The area ratio may be changed by switching the width of the slit opening. It may also be changed by changing the number of slit openings. In this disclosure, "width" means "the length from one end to the other of the shorter side of something that is vertically long." In other words, it is the length of the short side of the slit opening.

For example, the switching mechanism may change the positional relationship between the slit plate and the mask depending on whether the direction of movement is forward or reverse, thereby switching the area ratio. In this case, the drive unit may be capable of reversing the direction of movement of the slit forming unit.

An example of such a configuration will be described. In the slit forming section, a slit plate and a mask may be arranged overlapping along the optical axis. The mask partially or selectively blocks the opening formed in the slit plate. In this case, the area through which light passes through the slit plate and the mask arranged in the optical path is formed as a slit opening in the slit forming section. For example, in the above example of the optical chopper, the rotating body in which the slit opening is formed is formed by the slit plate and the mask referred to here. The positional relationship between the slit plate and the mask is switched by the switching mechanism acting on the slit forming section depending on the forward and reverse movement direction. As a result, the area ratio between the slit opening and the light blocking section is changed depending on the forward and reverse movement direction. At this time, the area ratio is switched between a first area ratio and a second area ratio in which the proportion of slit openings is higher than the first area ratio.

At this time, the switching mechanism may be a delay generating mechanism. That is, the switching mechanism, which is a delay generating mechanism, may delay the power transmission from the drive unit to the slit plate and the mask by a predetermined movement amount between the slit plate and the mask when the moving direction is switched between forward and reverse. For example, when the slit forming part is moved in the forward direction, one of the slit plate and the mask is arranged to be shifted in the reverse direction by a predetermined movement amount with respect to the other, and when the slit forming part is moved in the reverse direction, the other of the slit plate and the mask is arranged to be shifted in the forward direction by a predetermined movement amount with respect to the other. At this time, the switching mechanism, which is a delay generating mechanism, switches the positional relationship between the slit plate and the mask by utilizing the momentum when the slit forming part is moved from a stopped state or when the moving direction is reversed. No actuator other than the drive unit is required for switching, and the area ratio between the slit opening and the light blocking part can be switched with a simple configuration in which the positional relationship between the slit plate and the mask arranged overlapping along the optical axis is simply switched.

When the power from the drive unit is directly transmitted to both the slit plate and the mask, the delay generating mechanism is provided between the drive unit and one of the slit plate and the mask. When the power from the drive unit is directly transmitted to only one of the slit plate and the mask, and indirectly transmitted to the other via the other, the delay generating mechanism may be provided between the slit plate and the mask. Please refer to the examples for a specific example of applying the slit forming unit to an optical chopper.

The switching mechanism is not necessarily limited to the above. For example, when the device has two or more slit forming sections with different area ratios between the slit opening and the light blocking section, the switching mechanism may be a mechanism that selectively places one of the slit forming sections on the optical path. In this case, a separate drive unit may be provided for each of the two or more slit forming sections, and the slit forming sections may be selectively placed on the optical path by moving the paired slit forming section and drive unit together.

In addition, in a configuration in which the slit plate and the mask are stacked along the optical axis in the slit forming section, the switching mechanism may change the positional relationship between the slit plate and the mask by transmitting power from an actuator separate from the drive section to one of the slit plate and the mask.

<Control Unit>
The control unit is a processing device (processor) that controls each unit in the fundus imaging apparatus and performs calculation processing. For example, the control unit is realized by a CPU (Central Processing Unit), a memory, and the like.

<Switching the shooting mode>
In this embodiment, the control unit controls the drive direction of the drive unit to switch the imaging mode between a first imaging mode and a second imaging mode. In the first imaging mode, a first fundus image based on scanning at a first area ratio is obtained as a captured image. In the second imaging mode, a second fundus image based on scanning at a second area ratio is obtained as a captured image.

In the first shooting mode, the area ratio between the slit opening and the light blocking portion is a first area ratio in which the proportion of the slit opening is lower than in the second shooting mode, so artifacts due to reflection from the objective lens, etc. are less likely to occur. On the other hand, in the second shooting mode, the proportion of the slit opening is higher than in the first shooting mode, so the efficiency of light projection and reception in terms of the amount of light is improved.

In this embodiment, the control unit changes at least the wavelength of the illumination light depending on the shooting mode. As a result, in the first shooting mode, a color image of the fundus may be acquired as the first fundus image, and in the second shooting mode, a fluorescent image of the fundus may be acquired as the second fundus image. In the second shooting mode, the control unit may further insert a barrier filter on the optical path of the return light. The barrier filter has spectral characteristics that block fundus reflected light and allow fluorescence from the fundus to pass to the image sensor side. Reflections from the objective lens, etc. are also blocked by the barrier filter.

In this way, when capturing a color image of the fundus, by setting the area ratio between the slit opening and the light-shielding portion to a first area ratio in which the proportion of the slit opening is lower, it is possible to suppress artifacts due to reflection from the objective lens, etc. Furthermore, when capturing a fluorescent image of the fundus, by setting the area ratio between the slit opening and the light-shielding portion to a second area ratio in which the proportion of the slit opening is higher, it is possible to efficiently project and receive excitation light and fluorescent light, making it easier to obtain a fluorescent image with high brightness.
"Example"
Next, an embodiment will be described with reference to FIGS.

The fundus imaging device 1 according to the embodiment (hereinafter, simply referred to as "imaging device 1") forms illumination light in a slit shape on the fundus of the subject's eye, scans the slit-shaped area on the fundus, and receives the fundus reflection of the illumination light to capture a frontal image of the fundus.

<Appearance of the device>
The external configuration of the photographing device 1 will be described with reference to Fig. 1. The photographing device 1 has a photographing unit 3. The photographing unit 3 mainly includes an optical system shown in Fig. 2. The photographing device 1 has a base 7, a drive unit 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 left and right (X direction) and front and rear (Z direction, in other words, working distance direction) relative to the base 7. The drive unit 8 also moves the photographing unit 3 on the drive unit 8 in three-dimensional directions relative to the subject's eye E. The drive unit 8 has an actuator for moving the drive unit 8 or the photographing unit 3 in each of the predetermined movable directions, and is driven based on a control signal from the control unit 80. The face support unit 9 supports the subject's face. The face support unit 9 is fixed to the base 7.

The face photographing camera 110 is fixed to the housing 6 so that its positional relationship with the photographing unit 3 is constant. The face photographing camera 110 photographs the subject's face. The control unit 100 identifies the position of the subject's eye E from the photographed face image, and aligns the photographing unit 3 with the identified position of the subject's eye E by controlling the drive unit 8. The detailed configuration of the control system will be described later with reference to FIG. 3.

The imaging device 1 also has a monitor 120. The monitor 120 displays fundus observation images, fundus photographed images, anterior segment observation images, etc.

Optical System of the Example
2, the optical system of the photographing device 1 will be described. The photographing device 1 has a photographing optical system (fundus photographing optical system) 10 and an anterior eye observation optical system 40. These optical systems are provided in the photographing unit 3.

In Figure 2, the position conjugate with the pupil of the test eye is indicated by a "△" on the imaging optical axis, and the position conjugate with the fundus is indicated by an "X" on the imaging optical axis.

The photographing optical system 10 has an irradiation optical system 10a and a light receiving optical system 10b. In the embodiment, the irradiation optical system 10a has a light source unit 11, a lens 13, a slit forming section 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 forming section 15b, and an image sensor 28. The perforated mirror 20 is an optical path coupling section that couples the optical paths of the irradiation optical system 10a and the light receiving optical system 10b. The perforated mirror 20 reflects illumination light from the light source to the subject's eye E, and transmits a portion of the fundus reflected light from the subject's eye E that passes through the opening to the image sensor. Various beam splitters other than the perforated mirror 20 can be used. For example, instead of the perforated mirror 20, a mirror in which the light-transmitting portion and the light-reflecting portion are reversed may be used as the light path coupling portion. In this case, however, the independent light path of the light-receiving optical system 10b is placed on the reflecting side of the mirror, and the independent light path of the irradiation optical system 10a is placed on the transmitting side of the mirror. In addition, the perforated mirror and the mirror as an alternative means can each be further replaced with a combination of a half mirror and a light-shielding portion.

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. The two light sources with the same wavelength band are arranged away 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. 2, and are arranged axially symmetrically with respect to the imaging optical axis L. As shown in FIG. 2, the outer peripheral shape of the two light sources may be a rectangle whose length in the direction intersecting the scanning direction is longer than that in the scanning direction.

In FIG. 2, two visible light sources are shown, denoted by reference numerals 11a and 11b, but each of the light sources 11a and 11b includes multiple visible light sources for each wavelength. For example, light sources corresponding to the three colors R (red), G (green), and B (blue) may be included in each of the visible light sources 11a and 11b. As a result, in this embodiment, any combination of the three colors R (red), G (green), and B (blue) may be irradiated. For example, when taking a color fundus image, the three colors R (red), G (green), and B (blue) may be irradiated. Also, 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 is irradiated onto the slit forming section 15a. In this embodiment, the slit forming section 15a has a light transmitting section (opening) formed in an elongated shape along the Y direction. This causes the illumination light to be formed in a slit shape on the fundus conjugate plane (the area illuminated in a slit shape on the fundus is illustrated as symbol B).

In FIG. 2, the slit forming section 15a is displaced by the driving section 15c so that the light transmitting section crosses the imaging optical axis L in the X direction. This realizes the scanning of the illumination light in this embodiment. Note that in this embodiment, scanning is also performed by the slit forming section 15b on the light receiving system side. In this embodiment, the slit forming sections 15a, 15b on the light projecting side and the light receiving side are driven in conjunction with each other by a single driving section (driver).

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

The slit-shaped light that passes through the slit forming section 15a is relayed by the optical system from the lens 17a to the objective lens 22, and is imaged on the fundus Er. This forms a slit-shaped illumination light on the fundus Er. The illumination light is reflected on the fundus Er and extracted through the pupil Ep.

Here, the opening of the perforated mirror 20 is conjugate with the pupil of the subject's eye, so the fundus reflected light used to capture the fundus image is limited to a portion that passes through the image of the perforated mirror opening (pupil image) on the pupil of the subject's eye. In this way, the image of the opening on the pupil of the subject's eye becomes the light receiving area R in this embodiment (entrance pupil in this embodiment). The light receiving area R is formed between two light projection areas P1 and P2. In addition, as a result of appropriately setting the imaging magnification of each image, the diameter of the opening, and the arrangement interval of the two light sources, the light receiving area R and the two light projection areas P1 and P2 are formed so as not to overlap each other on the pupil. In other words, the exit pupil and the entrance pupil are separated. As a result, the occurrence of flare is effectively reduced.

The fundus reflected light that passes through the objective lens 22 and the aperture of the perforated mirror 20 forms an image of a slit-shaped region of the fundus Er at the fundus conjugate position via lenses 25a and 25b. At this time, harmful light is removed by placing the light-transmitting portion of the slit forming portion 15b at the position of image formation.

The image sensor 28 is disposed at a fundus conjugate position. In this embodiment, a relay system 27 is provided between the slit forming section 15b and the image sensor 28, and thus both the slit forming section 15b and the image sensor 28 are disposed at a fundus conjugate position. As a result, both the removal of harmful light and the formation of an image are performed well. Alternatively, the relay system 27 between the image sensor 28 and the slit forming section 15b may be omitted, and the two may be disposed in close proximity. In this embodiment, a device having a two-dimensional light receiving surface is used as the image sensor 28. For example, it may be a CMOS, a two-dimensional CCD, or the like. An image of the slit-shaped area of the fundus Er formed at the light transmitting section of the slit forming section 15b is projected onto the image sensor 28. The image sensor 28 is sensitive to both infrared light and visible light.

In this embodiment, as the slit-shaped illumination light is scanned on the fundus Er, an image (slit-shaped image) of the scanning position on the fundus Er is projected sequentially for each scanning line of the image sensor 28. In this way, the entire image of the scanning range is projected onto the image sensor in a time-division manner. As a result, a front image of the fundus Er is captured as the entire image of the scanning range.

The photographing optical system 10 has a diopter correction section. In this embodiment, a diopter correction section (diopter correction optical system 17, 25) is provided in each of the independent optical paths of the irradiation optical system 10a and the receiving optical system 10b. Hereinafter, for convenience, the diopter correction optical system on the irradiation side is referred to as the irradiation side diopter correction optical system 17, and the diopter correction optical system on the receiving side is referred to as the receiving side diopter correction optical system 25. The irradiation side diopter correction optical system 17 in this embodiment includes a lens 17a, a lens 17b, and a drive unit 17c (see FIG. 3). The receiving side diopter correction optical system 25 in this embodiment includes a lens 25a, a lens 25b, and a drive unit 25c (see FIG. 3). In the irradiation side diopter correction optical system 17, the distance between the lens 17a and the lens 17b is changed, and in the receiving side diopter correction optical system 25, the distance between the lens 25a and the lens 25b is changed. This allows diopter correction to be performed in both the irradiation optical system 10a and the light receiving optical system 10b.

<Split target projection optical system>
2, the photographing optical system 10 further includes a split index projection optical system 50 as an example of a focus index projection optical system. The split index projection optical system 50 projects two split indexes onto the fundus. The split indexes are used to detect the focus state. In this 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 deflection prism 53, for example. In this embodiment, the target plate 52 is arranged at a position corresponding to the imaging surface in the light receiving optical system 50. Similarly, the target plate 52 is arranged at a position corresponding to each of the slit forming portions 15a and 15b. In detail, when the diopter correction amount on the irradiation side and the light receiving side is 0D, the target plate 52 is arranged at a position approximately conjugate with the fundus of the emmetropic eye (0D eye). The deflection prism 53 is arranged closer to the target plate 52 and closer to the target eye.

The index plate 52 forms, for example, a slit light as an index. The deflection prism 53 splits the index light beam that passes through the target plate 52 to form a split index. The split index is projected onto the fundus of the subject's eye via the illumination-side diopter correction optical system 17 and the objective lens 22. Therefore, the split index is reflected in a fundus image (for example, a 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 illumination side diopter correction optical system 17 placed between the deflection prism 53 and the subject's eye Er. In this embodiment, therefore, defocusing is performed while matching the illumination side diopter correction amount and the light receiving side diopter correction amount. At this time, the separation state of the split indices indicates the focus state. The illumination side and light receiving side diopter correction amounts are each adjusted so that the two split indices are aligned, and the imaging surface and the slit forming sections 15a and 15b each have a positional relationship conjugate with the fundus.

<Details of the Optical Chopper>
In this embodiment, an optical chopper 150 as shown in FIG. 4 is used as the slit forming units 15a, 15b and the driving unit 15c (see FIG. 3). The optical chopper 150 has a wheel 151 with a plurality of slit openings formed on its outer circumference, and can scan the slits at high speed by rotating the wheel 151. The wheel 151 is an example of a rotating body. The wheel 151 corresponds to the slit-shaped members 15a, 15b shown in FIG. 2. The main body 152 also includes a driving unit 15c (see FIG. 3). The driving unit 15c is, for example, a motor capable of switching the direction of rotation between forward and reverse.

2, the light source unit 11 to the mirror 18 of the irradiation optical system 10a and the perforated mirror 20 to the image sensor 28 of the light receiving optical system 10b are arranged in parallel in the X direction, but for example, by rotating the perforated mirror 20 and the mirror 18 by 90 degrees from the state shown in the figure and arranging them in parallel in the Y direction, the optical chopper can be used as a scanning unit. In this case, by intersecting the optical axis of the irradiation optical system 10a and the optical axis of the light receiving optical system 10b at two points, the upper and lower ends of the wheel 151, the single optical chopper 150 can easily synchronize the scanning of the light projection system and the light receiving system.

In this embodiment, as shown in Figures 5 to 8, the wheel 151 is formed by a slit plate 160 and a mask 165. Both are arranged overlapping in the optical axis direction with their rotation axes aligned. Power is transmitted from the drive unit 15c to each of the slit plate 160 and the mask 165, causing them to rotate around their respective rotation axes.

Figure 5 shows the slit plate 160. In this embodiment, the slit plate 160 has two types of slit openings 161, 162 with different widths, each of which is formed in equal numbers and arranged alternately. In this embodiment, 16 slit openings each of 161, 162 are arranged at regular intervals.

Figure 6 shows the mask 165. The mask 165 is a member for blocking one of the two types of slit openings 161, 162 formed in the slit plate 160 and opening the other. In this embodiment, the mask 165 has 16 slit openings 166 arranged at regular intervals in such a way that a light blocking portion is formed between adjacent slit openings when the mask 165 is overlapped with the slit plate 160. The slit openings 166 are formed to be wider than either of the slit openings 161, 162.

In this embodiment, the slit plate 160 is directly connected to the rotating shaft. In other words, the power from the driving unit 15c is transmitted without delay. The mask 165 is attached to the slit plate 160 so as to be slidable in the direction of rotation by a predetermined amount. As shown in Figs. 5 and 6, the slit plate 160 has a pin 163 disposed at a position a certain distance away from the rotating shaft, and the mask 165 has a connecting hole 167 formed at a similar position, and the slit plate 160 and the mask 165 are connected via the pin 163 and the connecting hole 167 (see Figs. 7 and 8). The connecting hole 167 is an elongated hole extending in the direction of rotation. The length of the connecting hole 167 in the circumferential direction corresponds to the interval between the two types of adjacent slit openings 161 and 162 in the slit plate 165 (1/32 of the circumference in this embodiment).

In this way, by connecting the pin 163 and the connecting hole 167 to each other, the mask 165 rotates with a delay of a predetermined movement amount (in this embodiment, approximately 1/32 of a rotation) relative to the slit plate 160.

As shown in FIG. 7, when the driving unit 15c rotates the slit plate 160 counterclockwise, the slit plate 160 and the mask 165 rotate together with the pin 163 in contact with the left side of the connecting hole 167. At this time, the slit opening 161 is exposed and the slit opening 162 is shielded from light.

On the other hand, as shown in FIG. 8, when the driving unit 15c rotates the slit plate 160 clockwise, the slit plate 160 and the mask 165 rotate together with the pin 163 in contact with the right side of the connecting hole 167. In this way, the driving unit 15c drives the slit plate 160 counterclockwise/clockwise, so that one of the two types of slit openings 161, 162, which have different widths, can be selectively exposed. As a result, the area ratio between the slit openings and the light-shielding portion can be switched.

When the rotation direction of the wheel 151 is reversed, the mask 165 rotates unstably as the pin 163 repeatedly comes into contact with and separates from the left or right side of the connecting hole 167 several times, and then the slit plate 160 and the mask 165 begin to rotate in perfect synchronization. In order to shorten the time until synchronization, a biasing member (not shown) may be further provided to bias the slit plate 160 and the mask 165 so that they slightly press against each other. The friction generated between the slit plate 160 and the mask 165 shortens the time until the rotation direction is reversed and the slit plate 160 and the mask 165 rotate in perfect synchronization.

In this embodiment, as described above, the width of the slit opening passing through the optical path is constant as long as the lens rotates in one direction, so that fundus images can be captured more efficiently than, for example, when the width of the slit opening changes while the lens rotates in one direction. In other words, scanning with an inappropriate amount of light is more likely to be suppressed, and a frame rate is more likely to be ensured in continuous shooting such as video shooting. Alternatively, the shooting time per image can be more easily shortened, so distortion caused by eye movement can be more easily suppressed.

<Barrier filter>
Returning to FIG. 2, the optical system will be described. The photographing device 1 further includes a barrier filter 61. During fluorescence photographing, the light receiving optical system 10b guides the fluorescence from the fundus based on the excitation light to the image sensor 28. The barrier filter 61 may be disposed on an independent optical path of the light receiving optical system. The barrier filter 61 has a spectral characteristic that blocks light in the same wavelength range as the excitation light and passes the fluorescence. As an example, in this embodiment, the barrier filter 61 has a spectral characteristic suitable for spontaneous fluorescence photographing. For example, it blocks green or blue light, which is the excitation light, and passes light on the longer wavelength side to the image sensor 28 side. This allows the spontaneous fluorescence to be selectively received by the image sensor 28. As a result, a satisfactory spontaneous fluorescence image of the fundus is obtained. The photographing device 1 may include a drive unit 61a that inserts and removes the barrier filter 61. The insertion and removal of the barrier filter is controlled by, for example, the control unit 100.

<Anterior segment observation optical system>
Next, the anterior eye observation optical system 40 will be described. The anterior eye observation optical system 40 shares the objective lens 22 and the dichroic mirror 43 with the photographing optical system 10. The anterior eye observation optical system 40 further includes The anterior segment observation optical system 40 includes a light source 41, a half mirror 45, and an image sensor 47. The image sensor 47 is a two-dimensional image sensor, and is arranged at a position optically conjugate with the pupil Ep. The anterior segment is illuminated with infrared light and a frontal image of the anterior segment is taken.

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

<Control system of the embodiment>
Next, a control system of the photographing device 1 will be described with reference to Fig. 3. In this embodiment, the control unit 100 controls each unit of the photographing device 1. For convenience, it is also assumed that the image processing of various images obtained by the photographing device 1 is performed by the control unit 100. In other words, in this embodiment, the control unit 100 also functions as an image processing unit.

The control unit 100 is a processing device (processor) having electronic circuits that perform control processing of each unit and arithmetic processing. The control unit 100 is realized by a CPU (Central Processing Unit) and memory, etc. The control unit 100 is electrically connected to the storage unit 101 via a bus, etc.

The memory unit 101 stores various control programs, fixed data, etc. The memory unit 101 may also store temporary data, etc.

The images captured by the imaging device 1 may be stored in the storage unit 101. However, this is not necessarily limited to this, and the captured images may also be stored in an external storage device (for example, a storage device connected to the control unit 100 via a LAN or WAN).

The control unit 100 is also electrically connected to each of the components, such as the drive unit 8, light sources 11a to 11d, image sensor 28, light source 41, image sensor 47, light source 51, input interface 110, and monitor 120.

The control unit 100 also controls the above-mentioned components based on operation signals output from an input interface 110 (operation input unit). The input interface 110 is an operation input unit that accepts operations by the examiner. For example, it may be a mouse and a keyboard, etc.

<Operation description>
Next, the photographing operation will be described with reference to the flow chart of FIG.

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

First, images are captured by the face detection camera 110 and the anterior eye observation optical system 40 in parallel, and alignment adjustment is performed using the captured images from both cameras.

In detail, the control unit 100 detects the position of one of the left and right eyes contained in the face image, and drives the drive unit 8 based on the position information. This adjusts the position of the photographing unit 4 to a position where the anterior segment can be observed.

Next, an alignment reference position is set based on the anterior eye front image, and alignment is guided to the set alignment reference position. In this embodiment, the positional relationship between the subject's eye E and the photographing unit 3 is adjusted by the control unit 100 based on the anterior eye front image. In this embodiment, the control unit 100 sets a first reference position that targets a positional relationship in which the pupil center in the anterior eye observation image and the image center (in this embodiment, the position of the photographing optical axis L) approximately coincide with each other based on a signal from the image sensor 47. Then, the control unit 100 detects an alignment deviation from the first reference position and moves the photographing unit 4 up, down, left, and right in a direction in which the alignment deviation is eliminated. At this time, for example, the alignment deviation from the first reference position may be detected based on the amount of deviation between the pupil center and the photographing optical axis on the anterior eye observation image. In addition, if the fundus photographing device 1 has an alignment projection optical system that projects an alignment index onto the corneal apex, for example, the alignment deviation may be detected based on the amount of deviation between the alignment index and the photographing optical axis.

The control unit 100 also moves the photographing unit 4 back and forth so that the anterior eye observation image is focused on the pupil Ep. This adjusts the distance from the device to the subject's eye to a predetermined working distance.

In this manner, in this embodiment, as a result of the alignment adjustment, the positional relationship between the test eye and the photographing unit 4 is adjusted to a position (first reference position in this embodiment) where the center of the light receiving area R on the pupil of the test eye (i.e., the photographing optical axis) coincides with the center of the pupil.

<Acquisition and display of fundus observation images>
Next, the control unit 100 starts acquiring and displaying the fundus observation image. In detail, the control unit 100 simultaneously turns on the light sources 11c and 11d and starts driving the driving unit 15c, so that the slit-shaped illumination light is repeatedly scanned in a predetermined range on the fundus Er. In this embodiment, the fundus observation image is acquired using the first slit opening 161 by rotating the wheel 151 counterclockwise. The fundus observation image is generated at any time based on the signal output from the image sensor 28 every time the first slit opening 161 passes through the optical path. The control unit 100 causes the monitor 120 to display the fundus observation image as a moving image in approximately real time.

<Diopter correction>
Next, the focus states of the irradiating optical system and the receiving optical system are adjusted based on the fundus observation image. In this embodiment, after the alignment is completed, the diopter correction optical system is driven to perform focus adjustment. At this time, in this embodiment, both the irradiating diopter correction optical system 17 and the receiving diopter 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 a split index onto the fundus. The control unit 100 performs defocusing by changing the amount of diopter correction on the illumination side and the amount of diopter correction on the reception side while matching them. In addition, the control unit 100 detects the separation state of the split index from the fundus observation image each time the amount of correction changes, and adjusts the amount of diopter correction on the illumination side and the amount of diopter correction on the reception side until the split indexes match. As a result of such adjustments, the imaging surface and the slit-shaped members 15a and 15b each have a positional relationship conjugate with the fundus.

<Selecting the shooting mode and taking pictures>
Next, 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 the imaging mode between a normal imaging mode and a fluorescent imaging mode. The normal imaging mode is set to capture a fundus image based on fundus reflection light. The fluorescent imaging mode is set to capture a fluorescent fundus image.

In this embodiment, the control unit 100 adjusts at least the wavelength-related conditions for the light emitted from the light sources 11a and 11b according to the shooting mode, and also adjusts the conditions for inserting and removing the barrier filter 61 into and from the optical path of the light receiving optical system 10b.

In detail, in the normal shooting mode, the light sources 11a and 11b simultaneously emit the three colors R (red), G (green), and B (blue) to capture images. The barrier filter 61 is also retracted from the optical path of the light receiving optical system 10b. Furthermore, a fundus image is generated based on the exposure of the image sensor 28 while the first area passes through the optical path. By setting the width of the slit-shaped shooting area on the fundus to be relatively narrow, an image can be captured in which artifacts caused by reflections on the objective lens 22, etc. are suppressed.

In addition, in the fluorescence photography mode of this embodiment, photography is performed by emitting one color, G (green), 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 inserting the barrier filter 61, it becomes unnecessary to consider the above-mentioned artifacts. Therefore, in this embodiment, a fundus fluorescence image is photographed using the second slit opening 162 by rotating the wheel 151 clockwise based on the photography trigger signal. In other words, photography is performed with a wider width of the slit opening than in the normal photography mode.

In this embodiment, when a fundus fluorescent image is captured, the rotation direction of the wheel 151 is reversed from the previous direction (when a fundus observation image was being acquired). There is a time lag between when the rotation is reversed and when the desired rotation speed is reached. Therefore, when a fundus fluorescent image is captured, the fundus fluorescent image is captured after a sufficient amount of time has elapsed since the release signal was output.

During photography, the control unit 100 may stop the light emission from the observation light sources 11c and 11d, and then turn on the photography light sources 11a and 11b. In this case, a photographed image of the fundus is obtained as a result of photography based on the visible light irradiated from the light sources 11a and 11b.

<Example of transformation>
Although the above description has been given based on the embodiments, the contents of the embodiments can be appropriately modified in implementing the present disclosure.

Reference Signs List 1 Fundus imaging device 10 Imaging optical system 10a Irradiation optical system 10b Light receiving optical system 22 Objective lens 100 Control unit 150 Optical choppers 161, 162 Slit opening E Test eye Er Fundus

Claims (3)

A fundus photographing apparatus comprising an imaging optical system including an illumination optical system that illuminates an illumination light onto a fundus of a subject's eye, and a light receiving optical system including an image sensor that receives return light of the illumination light from the fundus, the apparatus acquiring a fundus image, which is a front image of the fundus, based on a light receiving signal from the image sensor, the apparatus comprising:
The photographing optical system includes:
a slit forming unit including a slit opening for forming a slit-shaped photographing area on the fundus and a light blocking unit; and a drive unit for rotating and moving the slit forming unit in a direction in which a long side of the slit opening crosses at least one of the illuminating light and the return light;
A switching mechanism ,
the slit forming section includes a slit plate in which two types of slit openings having different widths are alternately arranged, and a mask that selectively opens one of the two types of slit openings, the slit plate being overlapped along an optical axis,
The drive unit is capable of reversing a direction of rotational movement in the slit forming unit,
The switching mechanism changes the positional relationship between the slit plate and the mask depending on whether the movement direction is forward or reverse, thereby mechanically switching the area ratio between the light-shielding portion and the slit opening in the slit forming portion, and has a delay generating mechanism that delays the transmission of power from the driving unit to the slit plate and the mask by a predetermined amount of movement between the slit plate and the mask when the movement direction is switched between forward and reverse.A fundus photography device. the area ratio of the slit opening is switchable between a first area ratio and a second area ratio in which the ratio of the slit opening is higher than the first area ratio;
The fundus photographing device of claim 1, further comprising a control means for switching the photographing mode between at least two of a first photographing mode in which a first fundus image based on scanning at the first area ratio is obtained as a photographed image by controlling the moving direction, and a second photographing mode in which a second fundus image based on scanning at the second area ratio is obtained as a photographed image. The fundus imaging device according to claim 2, wherein the control means changes at least the wavelength of the illumination light depending on the imaging mode, thereby obtaining a color image of the fundus as the first fundus image in the first imaging mode, and obtaining a fluorescent image of the fundus as the second fundus image in the second imaging mode.

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