JP7375323B2 - fundus imaging device - Google Patents

Description

The present disclosure relates to a fundus photographing device for obtaining a frontal image of the fundus.

Fundus photographing devices that photograph a frontal image of the fundus of an eye to be examined are widely used in the field of ophthalmology. Fundus imaging devices include fundus cameras, scanning laser ophthalmoscopes, and the following devices. For example, in Patent Document 1, a frontal image of the fundus is obtained by scanning a slit-shaped illumination light on the fundus and sequentially projecting an image of the illuminated fundus region onto a two-dimensional imaging plane according to the scanning. An apparatus is disclosed. In many fundus imaging devices, illumination light is projected and received through an objective lens.

Special Publication No. 61-48940

In an apparatus having an objective lens, under at least some imaging conditions, reflected light generated on the front or back surface of the objective lens may appear as an artifact in the fundus image. The artifact appears as a bright spot image (reflected image) near the center of the fundus image. Bright spot images can be an obstacle to diagnosis and observation.

The present disclosure has been made in view of at least one of the problems of the prior art, and a technical problem is to provide a fundus imaging device that can obtain a fundus image with suppressed artifacts.

A fundus photographing apparatus according to a first aspect of the present disclosure includes an irradiation optical system that irradiates illumination light to the fundus of an eye to be examined through an objective lens, the objective lens being used in common with the irradiation optical system, and further comprising: a light-receiving optical system having a light-receiving element that receives the fundus-reflected light; and a photographing optical system including a light-receiving optical system, and controlling one or both of the irradiation optical system and the light-receiving optical system to vary the photographing conditions. A photographing control means that acquires two fundus images based on a signal from the light receiving element, and an image processing means that obtains a composite image by combining at least two fundus images having different photographing conditions. , the photographing optical system includes a diopter correction optical system, and the photographing control means sets the diopter correction optical system as the photographing condition when photographing at least two fundus images that are the basis of the composite image. The amount of diopter correction in is made different for each photograph by controlling the diopter correction optical system.

According to the present disclosure, a fundus image with suppressed artifacts can be obtained.

1 is a diagram showing an external configuration of an apparatus according to one embodiment. FIG. 3 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 an apparatus according to an embodiment. FIG. 3 is a diagram for explaining the operation of the diopter correction optical system according to the refractive power of the subject's eye, and is a diagram showing the state of diopter correction when the refractive power is in the first range. FIG. 6 is a diagram for explaining the operation of the diopter correction optical system according to the refractive power of the subject's eye, and is a diagram showing the state of diopter correction when the refractive power is in the second range. FIG. 7 is a diagram for explaining an overview of second artifact suppression processing. FIG. 7 is a diagram for explaining an overview of third artifact suppression processing. FIG. 3 is a diagram illustrating how the optical system of FIG. 2 irradiates and scans the fundus with illumination light. FIG. 3 is a diagram illustrating how the optical system of FIG. 2 irradiates and scans the fundus with illumination light. FIG. 7 is a diagram for explaining the outline of the fourth artifact suppression process, and shows a fundus image obtained when illumination light is irradiated from two light projection areas simultaneously. FIG. 4 is a diagram for explaining the outline of the fourth artifact suppression process, and shows a fundus image obtained when illumination light is selectively irradiated from one of the two light projection areas. FIG. 7 is a diagram for explaining an overview of a fifth artifact suppression process. 3 is a diagram showing an optical chopper that can be used as a scanning section in the optical system of FIG. 2. FIG. It is a figure for explaining the outline of the 6th artifact suppression processing, and especially shows an example using an optical chopper in which a plurality of slits with different widths are formed. 3 is a flowchart showing the photographing operation of the device.

"overview"
Hereinafter, embodiments of a fundus photographing apparatus according to the present disclosure will be described with reference to the drawings. Below, in each of the first and second embodiments, an apparatus will be disclosed in which artifacts caused by reflection and scattering within the subject's eye or the apparatus are suppressed. Each embodiment can utilize part or all of other embodiments as appropriate.

<First embodiment>
First, a first embodiment will be described. In the first embodiment, the fundus photographing device (see FIG. 1) includes at least a photographing optical system (see, for example, FIG. 2) and a control section (see, for example, FIG. 3). The ophthalmologic imaging device may additionally include a refractive power information acquisition section.

<Control unit>
The control section is a processing device (processor) that performs control processing for each section of the fundus photographing device 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 an image processing section. The image processing unit executes at least one of generating a fundus image and performing various types of image processing on the fundus image.

<Photography optical system>
The photographing optical system is used to project and receive illumination light to the fundus of an eye to be examined through an objective lens, and to photograph a fundus image. In the first embodiment, the photographing optical system includes an irradiation optical system, a light receiving optical system, and a diopter correction optical system (see FIGS. 2, 4A, and 4B).

The irradiation optical system irradiates illumination light to the fundus of the eye to be examined through the objective lens. Additionally, the illumination optical system may include a light source that emits illumination light (illumination light source). The light-receiving optical system includes a light-receiving element that receives the fundus-reflected light of the illumination light. The signal from the light receiving element is input to the image processing section. The image processing unit acquires (generates) a fundus image of the eye to be examined based on the signal from the light receiving element. Note that in this disclosure, a front image of the fundus is referred to as a "fundus image."

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

The photographing optical system may be a scanning optical system that performs photographing by scanning illumination light on the fundus of the eye. Further, the photographing optical system may be a non-scanning optical system. Examples of scanning optical systems include spot scan type optical systems and line scan type optical systems. In a spot scan type optical system, a spot of illumination light is scanned two-dimensionally on the fundus of the eye. In a line scan type optical system, a line of illumination light is scanned in one direction. For example, the linear illumination light may be linearly scanned on the fundus of the eye, or may be rotationally scanned on the fundus of the eye. In the case of rotational scanning, the rotation center may be the optical axis of the photographing optical system. In a scanning optical system, any one of a point light receiving element, a line sensor, a two-dimensional light receiving element (photographing element), etc. can be appropriately employed as a light receiving element. Furthermore, an example of a non-scanning optical system is an optical system of a general fundus camera.

<Diopter correction optical system>
The diopter correction optical system (see FIGS. 2, 4A, and 4B) is used to correct the diopter of the imaging optical system according to the refractive power of the eye to be examined. The refractive power of the eye to be examined is also referred to as refractive error and diopter value. In this embodiment, the diopter correction optical system includes a diopter correction amount in the irradiation optical system (hereinafter referred to as "irradiation side correction amount") and a diopter correction amount in the light receiving optical system (hereinafter referred to as "light receiving side correction amount"). ) are adjusted independently.

The diopter correction optical system may be arranged at two or more separate locations in the photographing optical system. In this case, the diopter correction optical system may include a first diopter correction optical system and a second diopter correction optical system. The diopter correction amount in the first diopter correction optical system and the diopter correction amount in the second diopter correction optical system are set independently. For example, the first diopter correction optical system may be arranged on the optical path of one of the irradiation optical system and the light receiving optical system, and in this case, the second diopter correction optical system is arranged on the optical path of one of the irradiation optical system and the light receiving optical system. Alternatively, the irradiation optical system and the light receiving optical system may be placed on a common optical path.

In this embodiment, it may have a 1st drive part (1st driver) and a 2nd drive part (2nd driver). The first drive section and the second drive section are each independently controlled by a control section. The first driver drives at least one optical element included in the first diopter correction optical system. Further, the second driving section drives at least one optical element included in the second diopter correction optical system.

Note that when the second diopter correction optical system is arranged in the common optical path, the diopter correction amount in the other optical system is the same as the diopter correction amount in the first diopter correction optical system and the second diopter correction optical system. It is determined by the sum of the diopter correction amount and the diopter correction amount. For convenience of explanation, one or both of the first diopter correction optical system and the second diopter correction optical system that affect the diopter of the irradiation optical system will be referred to as the "irradiation side diopter correction optical system", and One or both of the optical systems that affect the diopter may be referred to as a "receiving side diopter correction optical system."

By the way, the position of the objective lens that is conjugate with the fundus (that is, the position of the intermediate image plane of the fundus) is displaced according to the refractive power (mainly the spherical power) of the eye to be examined. Note that in FIGS. 4A and 4B, the position of the intermediate image plane is indicated by the symbol J. In this embodiment, the diopter correction optical system disposed between the objective lens and the light receiving surface is driven so that the intermediate image plane and the light receiving surface of the light receiving optical system are in a conjugate relationship. image is well formed on the light receiving surface.

Note that in the present disclosure, "conjugate" is not necessarily limited to a perfect conjugate relationship, but includes "substantially conjugate". That is, the term "conjugate" in the present disclosure also includes a case where the arrangement is shifted from a perfect conjugate position within the allowable range in relation to the technical significance of each part.

Furthermore, if diopter correction is performed in the irradiation optical system, it is considered that, for example, errors in the illumination range are suppressed and the light amount distribution of illumination light in the fundus becomes more uniform. However, the light focusing position in the irradiation optical system is displaced along the optical axis depending on the irradiation side correction amount. Specifically, it is considered that as the irradiation side correction amount shifts to the minus diopter side, the light condensing position approaches the objective lens. In addition, in FIG. 4A and FIG. 4B, the light condensing position is shown as K. When the light condensing position approaches the surface of the objective lens, reflection of illumination light by the objective lens may easily appear as an artifact in the fundus image. In other words, if the irradiation side correction amount is adjusted according to the refractive power, the more the refractive power of the subject's eye is on the minus diopter side (for example, the higher the myopic eye is), Artifacts are more likely to occur.

<Suppression of artifacts by making the irradiation side correction amount and the light receiving side correction amount inconsistent>
On the other hand, the control unit may adjust the irradiation side correction amount and the light receiving side correction amount to different values by controlling the diopter correction optical system (see FIG. 4B). For example, the control unit may adjust the light-receiving side correction amount according to the refractive power of the eye to be examined. More specifically, the light-receiving side correction amount may be adjusted to approximately the same diopter as the refractive power.

At this time, the control unit may further adjust the condensing position of the illumination light via the diopter correction optical system with reference to the intermediate image of the fundus formed via the objective lens (see FIG. 4B). More specifically, the irradiation side correction amount may be adjusted so that the condensing position is located further away from the objective lens with respect to the intermediate image. As a result, the image of the fundus is well formed on the imaging surface of the light-receiving optical system, and the generation of artifacts due to reflection from the objective lens is suppressed. As a result, a good fundus image is captured.

At this time, the irradiation side correction amount may be adjusted so that its absolute value is smaller than the light receiving side correction amount. The larger the difference between the irradiation-side correction amount and the light-receiving-side correction amount, the more likely various effects such as a decrease in the amount of received light occur. Therefore, by limiting each correction amount so that a large difference does not occur between the irradiation side correction amount and the light receiving side correction amount, it is possible to obtain a fundus image with good image quality while suppressing the occurrence of artifacts. I can do it.

When adjusting the irradiation side correction amount and the light receiving side correction amount to different values, the control unit may adjust the irradiation side correction amount to a constant value regardless of the light receiving side correction amount. However, it is not necessarily limited to this, and in the same case, the irradiation side correction amount may be adjusted to a different value for each light receiving side correction amount.

However, it is not necessary to always adjust the irradiating side correction amount and the light receiving side correction amount in each photographing so that they have different values. For example, under predetermined imaging conditions, the irradiation-side correction amount and the light-receiving-side correction amount may be made equal to each other. Here, imaging conditions in which artifacts do not become a problem can be investigated in advance through experiments, optical simulations, and the like. For example, a range of diopter correction amounts in which artifacts do not occur when the irradiation-side correction amount and the light-receiving-side correction amount are matched may be predetermined as the imaging condition. In the case where the irradiation side correction amount and the light receiving side correction amount match each other, each of the irradiation side correction amount and the light receiving side correction amount may be adjusted to a diopter that is substantially the same as the refractive power.

<Switching the shooting mode according to the refractive power>
In the present embodiment, the control unit operates in a first shooting mode (see FIG. 4A) in which shooting is performed with the irradiation-side correction amount and the light-receiving-side correction amount made to match each other, and in a first shooting mode (see FIG. 4A) in which the irradiation-side correction amount and the light-receiving-side correction amount are made to be different from each other. The imaging mode of the apparatus may be switched between a second imaging mode (see FIG. 4B) in which imaging is performed in a state where the subject's eye is tilted, depending on the refractive power of the subject's eye. The refractive power may be roughly divided into a first range and a second range on the minus diopter side with respect to the first range. In other words, the second range is the intermediate image plane of the fundus reflected light formed through the objective lens (mainly, the intermediate image plane formed closest to the objective lens) with respect to the first range. is a range that approaches the rear surface of the objective lens. In addition, in FIGS. 4A and 4B, the range of the diopter correction amount corresponding to the first range is the range indicated by the symbol A1, and the range of the diopter correction amount corresponding to the second range is indicated by the symbol A2. This is the range shown in the figure. The photographing mode may be switched between a case where the refractive power is in the first range and a case where the refractive power is in the second range. The control unit may switch to the first imaging mode when the refractive power is in the first range. In this case, the control unit may photograph the fundus in a state where the irradiation side correction amount and the light receiving side correction amount are made to match each other. At this time, both the irradiation side correction amount and the light receiving side correction amount may be adjusted to values according to the refractive power. Moreover, the control unit may switch to the second photographing mode when the refractive power is in the second range. In this case, the control unit may adjust the light-receiving side correction amount according to the refractive power of the eye to be examined, and may also set the irradiation-side correction amount to a smaller absolute value than the light-receiving side correction amount.

The value of the refractive power that becomes the threshold value between the first range and the second range can be determined in advance by, for example, experiments, optical simulations, and the like. For example, when changing the diopter correction amount in the diopter correction optical system from the plus diopter side to the minus diopter side while keeping the emission side correction amount and the light receiving side correction amount the same, the A value at which artifacts begin to occur may be determined as a threshold value.

<Scanning type photographic optical system>
By the way, as a scanning type photographing optical system, an apparatus having a harmful light removing section and a scanning section is known. In a scanning type photographing optical system, the illumination optical system forms a local illumination area in a part of the photographing range in the fundus of the eye. As a typical example, a device is known in which an illumination area is formed in the shape of a slit or a spot.

For example, the harmful light removing section is arranged on the optical path of the light receiving optical system, with the diopter correction optical system interposed between the harmful light removing section and the objective lens. In this case, the harmful light removing section may be arranged at a position conjugate with the fundus with respect to at least the objective lens and the diopter correction optical system, with the light receiving side correction amount being set according to the refractive power of the eye to be examined.

The harmful light removing unit causes the light receiving element to receive fundus reflected light from a local imaging area (hereinafter referred to as "effective area") that is a part of the imaging range. Further, the harmful light removing section is used to remove light from areas other than the effective area. The harmful light removing section may be, for example, a diaphragm. A typical aperture in a spot scan type device is a pinhole, and a typical aperture in a slit scan type device is a slit. In this case, light reflected from the fundus from an effective area corresponding to the aperture of the diaphragm out of the entire imaging range of the fundus is selectively guided to the light receiving element and acquired as an effective image. Further, particularly in a slit scan type device, the light receiving element itself may be used as a harmful light removing section. In this case, a line sensor formed in the shape of a slit may be used as the light receiving element, or line exposure is performed on a two-dimensional imaging surface (in other words, it has a rolling shutter function). CMOS may also be used. In this case, within the entire imaging range of the fundus, the fundus reflected light from the effective area corresponding to the line-shaped effective pixels is selectively guided to the light receiving element and acquired as an effective image.

The scanning unit scans the local illumination area and the effective area (local imaging area) on the fundus of the eye in synchronization. The scanning unit may be, for example, an optical scanner shared between the irradiation optical system and the light receiving optical system. In this case, the optical scanner is placed on a common optical path between the irradiation optical system and the light receiving optical system.

Further, the scanning section may include a first scanning section provided in the irradiation optical system, and a second scanning section, which is separate from the first scanning section and provided in the light receiving optical system. In this case, in an example of a slit scan type device, a first slit-shaped member may be placed on the optical path of the irradiation optical system in order to form a local illumination area in a slit-shape. The first scanning section may include a first slit-like member and a drive section that moves the first slit-like member in a direction intersecting the optical axis. Furthermore, when the second slit-like member is used as the harmful light removing section, the second scanning section includes the second slit-like member and a drive section that moves the second slit-like member in a direction intersecting the optical axis. You may do so. The driving section of the first scanning section and the driving section of the second scanning section may be separate devices or may be a common device.

Further, in a slit scan type device, when a CMOS is used as a light receiving element, the CMOS can also serve as the second scanning section. That is, the line exposure using the rolling shutter function described above may be controlled in synchronization with the first scanning section. In this case, the CMOS which is the light receiving element serves both as a harmful light removing section and a second scanning section. This reduces the number of parts in the optical system.

<Suppression of image height changes due to diopter correction>
In the above-mentioned scanning type photographic optical system, if the position of the area on the fundus where the illumination light is irradiated and the position of the effective area are misaligned, the amount of light received may decrease or the image may not be obtained at all. It is possible that you will no longer be able to do so.

On the other hand, the diopter correction optical system performs diopter correction in each of the irradiation optical system and the light reception optical system between when the irradiation side correction amount and the light reception side correction amount match and when they are different from each other. The optical system may include a telecentric optical system that maintains the image height in a region on the image side of the optical system. (However, here, in both the irradiation optical system and the light receiving optical system, the side of the eye to be examined is referred to as the object side, and the side opposite to the eye to be examined with the diopter correction optical system in between is referred to as the image side.) Irradiation Even if the side correction amount and the light-receiving side correction amount do not match, the position of the area on the fundus of the eye that is irradiated with illumination light and the position of the effective area are unlikely to occur. Therefore, the above-mentioned telecentric optical system has the effect that, in an apparatus having a scanning type photographing optical system, a fundus image can be taken satisfactorily when the generation of artifacts is suppressed. However, the telecentric optical system may be a substantially telecentric optical system within the range of permissible accuracy.

Note that, more specifically, the telecentric optical system may include a first telecentric optical system and a second telecentric optical system. The first telecentric optical system maintains the image height in a region closer to the image side than the diopter correction optical system, regardless of changes in the light-receiving side correction amount. The second telecentric optical system maintains the ray height of the principal ray of the illumination light on the fundus regardless of changes in the irradiation side correction amount.

Further, the above telecentric optical system is also useful in non-scanning type photographing optical systems. That is, the telecentric optical system suppresses changes in magnification of the fundus image and changes in illumination unevenness due to diopter correction.

<Adjustment of shooting conditions according to diopter correction amount>
In order to suppress the occurrence of artifacts, the irradiating side correction amount is adjusted to a value different from the receiving side correction amount, resulting in the outer edge of the area on the fundus that is irradiated with illumination light becoming blurred or the illumination light being irradiated. There may be cases where the position of the area is shifted from the position of the effective area. In these cases, the amount of received light tends to decrease compared to the case where the irradiation-side correction amount and the light-receiving-side correction amount match.

On the other hand, in the present embodiment, there is a case where the irradiation side correction amount and the light receiving side correction amount are the same, and a case where the irradiation side correction amount and the light receiving side correction amount are different values. The control unit may perform switching control to switch at least one of the amount of illumination light irradiated to the fundus, the gain of the light receiving element, and the exposure time. More specifically, in contrast to the case where the irradiation-side correction amount and the light-receiving-side correction amount are the same, when the irradiation-side correction amount and the light-receiving-side correction amount are different values, the light intensity of the illumination light, At least one of the gain and exposure time of the light receiving element is increased. This makes it possible to obtain a fundus image with a wide dynamic range even if the irradiation-side correction amount and the light-receiving-side correction amount do not match. This switching control may be linked to switching of the shooting mode. Note that in order to increase the exposure time, the control unit may slow down the scanning speed. In addition, in a device that takes multiple fundus images continuously and adds up the multiple images to create a single image, increasing the number of fundus images used for addition can increase the exposure time. can be substantially increased.

<Refraction power acquisition unit>
The refractive power information acquisition unit acquires refractive power information as information regarding the refractive power of the eye to be examined. For example, the refractive power information acquisition unit may be a measurement unit that acquires refractive power information by measuring the eye to be examined. In this case, at least a part of the photographing optical system may be used as the measurement section which is the refractive power information acquisition section. For example, the refractive power information acquisition unit may detect the focus state in the light receiving optical system and acquire the refractive power information based on the detection result of the focus state. More specifically, the focus state is detected while changing the light-receiving side correction amount, which is the diopter correction amount in the light-receiving optical system, and the value of the light-receiving side correction amount when the best focus state is achieved is the value of the refraction side correction amount. It may also be acquired as frequency information. However, this is not limited to the light-receiving side correction amount, but also the amount of drive in the drive section that is driven to change the light-receiving side correction amount (or the irradiation side correction amount), and the position information of the optical element displaced by the drive section. , etc. may be acquired as refractive power information. The focus state may be detected based on a fundus image obtained via a photographing optical system. In this case, the focus state may be detected as contrast information of the fundus image. Further, the focus state may be detected based on the fundus image in which the index image of the focus index is reflected. A split index is known as an example of a focus index (see FIG. 2). The split index is projected onto the fundus as two index images separated by a prism. The focus state may be detected based on the positional relationship between the two index images. In this case, the refractive power information acquisition section includes an index projection section that projects the focus index.

Note that the refractive power information acquisition section is not necessarily limited to the measurement section. For example, the refractive power information acquisition unit may be configured to receive refractive power information measured in advance with a device separate from the fundus photographing device, and thereby acquire the refractive power information. In this case, the refractive power information acquisition section may include a control section and a port for connecting the ophthalmological measuring device to any one of a separate device, an external storage medium, a user interface, etc. . Examples of the separate device include a subjective or objective refraction testing device. Refraction power information may be stored in the external storage medium in advance, and the control unit may acquire the refraction power information by reading the refraction power information from the storage medium. The user interface may also be utilized to manually enter refractive power information. In this case, the refractive power information may be acquired as an input result by the examiner.

<Second embodiment>
Next, a second embodiment will be described.

In the fundus photographing apparatus according to the second embodiment, processing for suppressing artifacts due to reflection of the objective lens (hereinafter referred to as artifact suppression processing) is executed. In the second embodiment, the artifact suppression process is automatically executed when the refractive power of the subject's eye is within a predetermined range, and is not executed when it is outside the range. In other words, the shooting mode can be changed by the control unit between a first mode in which artifact suppression processing is not executed when capturing a fundus image and a second mode in which artifact suppression processing is executed when capturing a fundus image. , switched based on the refractive power.

As explained in the first embodiment, when diopter correction is performed according to the refractive power in both the irradiation optical system and the light receiving optical system, artifacts are more likely to occur as the refractive power is on the minus diopter side. . Therefore, in the second embodiment, when the refractive power is included in the first range and when the refractive power is included in the second range, the first mode is set in the former case, and the second mode is set in the latter case. In some cases, the second mode may be set. As a result, a fundus image with suppressed artifacts can be obtained regardless of the refractive power of the eye to be examined. In addition, when photographing the subject's eye whose refractive power is relatively on the plus diopter side and where artifacts are less likely to occur, it is important to consider the effects on the fundus image based on artifact suppression processing, the burden on the subject due to photography, etc. At least one of these is prevented.

Note that the diopter correction optical system in the first embodiment sets the irradiation side correction amount (the diopter correction amount in the irradiation optical system) and the light receiving side correction amount (the diopter correction amount in the light receiving optical system) to a mismatched state. Driving the system corresponds to one of various artifact suppression processes. However, the artifact suppression process in the second embodiment is not necessarily limited to this. For example, in the artifact suppression process, a plurality of fundus images having different positions of artifacts with respect to the tissue of the subject's eye may be photographed, and a composite image may be generated by combining the plurality of fundus images (for example, the following second and fifth artifact suppression processing). Further, various operations illustrated in the following description may be employed.

The detailed configuration of the second embodiment will be described below, focusing on the differences from the first embodiment. The fundus photographing device according to the second embodiment includes at least a photographing optical system, an image processing section, a refractive power acquisition section, and a control section. Regarding each of these configurations, the items of <control unit>, <image processing unit>, <imaging optical system>, and <refraction power acquisition unit> in the description of the first embodiment can be appropriately referred to.

<Second artifact suppression processing>
In the second artifact suppression process, the fundus image is photographed at least twice by switching the positional relationship between the optical axis of the photographing optical system and the visual axis of the eye to be examined. Further, a plurality of fundus images obtained through at least two imaging operations are combined by an image processing section. As a result, the device obtains a composite image that is a fundus image with suppressed artifacts (see FIG. 5). Note that in FIGS. 5 to 10, artifacts are indicated by the symbol N or symbols N1 and N2. The image processing unit selects an area containing an artifact in at least one of the plurality of fundus images (referred to as a first fundus image), which is an image area that has the same positional relationship with the fundus tissue as that area and is in another fundus image. A composite image is generated by complementing the image area. More specifically, a region containing an artifact in at least one of the plurality of fundus images may be replaced with a corresponding image region in another image. Further, a region including an artifact may be complemented by adding up a plurality of fundus images.

In order to perform the second artifact suppression process, the fundus imaging device may include a position adjustment section. The position adjustment unit adjusts the position of occurrence of the artifact with respect to the fundus tissue in the fundus image by changing the positional relationship between the optical axis of the imaging optical system and the visual axis of the eye to be examined. The position adjustment section may include a fixation optical system. The fixation optical system presents a fixation target to the subject's eye. The fixation optical system may be capable of switching the presentation position of the fixation target to a plurality of positions in a direction intersecting the optical axis of the photographing optical system. Further, the position adjustment section may include a drive section that moves the imaging optical system relative to the eye to be examined. For example, the drive unit may change the positional relationship between the optical axis of the imaging optical system and the visual axis of the eye to be examined by rotating the imaging optical system around the anterior segment of the eye to be examined. Of course, the position adjustment section may include both the fixation optical system and the drive section.

For more detailed content regarding the second artifact suppression process, please refer to, for example, Japanese Patent Laid-Open No. 2017-184787 by the present applicant.

<Third artifact suppression processing>
In the third artifact suppression process, the image processing unit executes a background difference based on the fundus image and the background image, and as a result, a fundus image in which artifacts are suppressed is generated (see FIG. 6). The background image here is a background image relative to the fundus image, and includes at least artifacts caused by the objective lens. The background image may be an image taken with the front side of the objective lens covered with a lens cover or the like.

For more detailed content regarding the third artifact suppression process, please refer to, for example, Japanese Patent Application Publication No. 2017-217076 by the present applicant.

<Device configuration as a premise for the fourth and fifth artifact suppression processes>
The fourth and fifth artifact suppression processes are both based on the assumption that the photographing optical system has the following configuration. That is, the photographing optical system is a slit scan type optical system. For example, the optical system shown in FIG. 2 may be used. The photographing optical system includes at least a slit forming section, a scanning section, and a light emitting/receiving separating section. Additionally, the photographing optical system may include a light source, an image sensor, an optical path branching section, and the like.

The slit forming section forms illumination light into a slit shape on the fundus of the eye to be examined. The slit forming part may be, for example, a slit-shaped light-transmitting part (for example, an opening) arranged in a plane conjugate with the fundus of the eye.

The scanning unit scans illumination light formed in a slit shape on the fundus in a direction intersecting the slit. As shown in FIGS. 2 and 7, the scanning unit scans illumination light formed in a slit shape on the fundus in a direction intersecting the slit (specifically, in a direction intersecting the longitudinal direction of the slit). . The scanning section may scan the illumination light by moving the slit forming section in a direction intersecting the slit. Examples of this type of scanning unit include a mechanical shutter, a liquid crystal shutter, an optical chopper (see FIG. 11), a drum reel, and the like.

The scanning direction of the slit is preferably a direction perpendicular to the slit. However, the direction may be oblique to the direction orthogonal to the slit.

Further, the scanning section may be a member that changes the direction of the light that has passed through the slit forming section. For example, various optical scanners such as a galvano scanner may be used as the scanning unit. A scanning unit that performs scanning by rotating light may be placed at a position conjugate with the pupil of the eye to be examined.

The photographing optical system may further include an optical path coupling section and an objective lens.

The optical path coupling unit couples and separates the light projection optical path of the illumination light and the reception optical path of the fundus reflected light. The objective lens is arranged on a common optical path of the light emitting optical path and the light receiving optical path, which is formed by the optical path coupling section. At this time, it is desirable that the optical axis of the photographing optical system (hereinafter also referred to as "photographing optical axis") and the optical axis of the objective lens coincide.

Various beam splitters can be used as optical path combiners. In this case, the optical path coupling part may be a mirror with a hole, a simple mirror, a half mirror, or some other beam splitter.

The light emitting/receiving separation section separates, on the pupil of the subject's eye, an area onto which illumination light is projected (light emitting area) and an area where fundus reflected light from the illumination light is extracted (light receiving area).

Specifically, as shown in FIGS. 2 and 8, the light projection/reception separation section forms light projection regions at two positions separated from each other in the scanning direction of the illumination light. The two light projection areas may be formed to sandwich the photographing optical axis. In the first embodiment, the light emitting/receiving separation section may form at least two light emitting areas, and may form three or more light emitting areas. The illumination light that has passed through each light projection area illuminates the same slit-shaped area on the fundus of the eye. Then, as the scanning section is driven, the slit-shaped area is scanned.

As shown in FIG. 8, the light emitting and receiving area is formed so as to be sandwiched between the two light emitting areas by the light emitting/receiving separating section. That is, each area is formed in a line in the order of one light projection area, one light reception area, and the other light projection area. Further, the light receiving area may be formed on the photographing optical axis. The light projecting area and the light receiving area may be arranged so as not to overlap each other. In this case, part of the illumination light is reflected and scattered by the cornea or the intermediate light-transmitting body, which reduces flare in the fundus image.

The light emitting/receiving separation section may include a plurality of members respectively arranged in the light emitting optical path of the illumination light and the light receiving optical path.

A part of the projection/reception light separation section sets illumination light irradiation positions at at least two positions separated from each other with respect to the scanning direction of the illumination light, for example, on the pupil conjugate plane in the projection optical path of the illumination light. There may be. In this case, a light source that emits illumination light may be arranged at each of the two irradiation positions, or an opening through which the illumination light passes may be arranged at each of the two irradiation positions.

In other words, the light emitting and receiving light separating unit includes at least two illumination light sources or two apparent illumination light sources that are arranged at different positions in the scanning direction at a position conjugate with the pupil of the eye to be examined. There may be. Thereby, the light projection areas are formed at two positions separated from each other in the scanning direction of the illumination light. More preferably, the two illumination light sources or the two apparent illumination light sources may be arranged symmetrically with respect to the imaging optical axis. Thereby, the two light projection areas can be formed symmetrically with respect to the photographing optical axis. The state of light projection from the two light sources or the two apparent light sources may be controllable for each light source by a control unit described below. As a result of controlling the light projection state for each light source, whether or not to allow illumination light to pass through is individually set for each light projection region. Of course, the light emitting and receiving light separating section may include three or more illumination light sources or three or more apparent illumination light sources.

Note that there can be at least two types of light projection states: a state in which illumination light from a light source or an apparent light source reaches the subject's eye, and a state in which it does not reach the eye. Switching of the light projection state may be realized by lighting control of the light source. Furthermore, the light projection state may be switched by driving and controlling a shutter that selectively blocks the light beam from the light source or the apparent light source toward the subject's eye.

In addition, a part of the light emitting/receiving separation section allows the fundus reflected light from the light receiving area, which is the area sandwiched between the two light emitting areas, to pass to the imaging surface side on the pupil conjugate plane in the light receiving optical path of the illumination light. , the other light may be prevented from passing to the imaging surface side. For example, the light emitting/receiving separation section may include a light blocking member that allows the fundus reflected light from the light receiving area to pass through to the imaging surface side and blocks other light. For example, the light shielding member may be arranged on the pupil conjugate plane in the light receiving optical path. For example, when a diaphragm having an aperture centered on the photographing optical axis is provided as a light shielding member, a light receiving area is formed by an aperture image of the diaphragm.

When a light shielding member is included in the light emitting/receiving separation section, the light shielding member may be used in common with the above-mentioned optical path coupling section, or may be a separate body.

<Fourth artifact suppression process>
In the above device configuration, the control unit may individually set whether or not to allow the illumination light to pass through the two light projection areas on the pupil of the eye to be examined. In this case, the control unit may photograph the fundus image based on the illumination light selectively projected from one (either) of the two light projection areas.

Incidentally, a reflected image (a bright spot image, a type of artifact) may occur at a position near the imaging optical axis in a fundus image due to illumination light being reflected at the center of the lens surface of the objective lens. Since the light projection area is far from the photographing optical axis, the reflected image tends to appear at a position slightly shifted from the position of the photographing optical axis in the fundus image. As an example, FIG. 9A shows a fundus image taken by simultaneously projecting illumination light from both of the two light projection areas. As shown in FIG. 9A, reflected images (indicated by symbols N1 and N2) may occur at two locations across the imaging optical axis in the center of the fundus image, corresponding to the two light projection areas. The two reflected images appear side by side in the scanning direction (that is, at different positions with respect to the scanning direction).

In contrast, in this embodiment, illumination light is selectively projected onto the fundus from one of the two light projection areas, and a fundus image is captured. As a result, the number of locations in the objective lens where a reflected image is generated is reduced by half compared to the above case. As a result, as shown in FIG. 9B, the reflected image in the fundus image can be reduced by half. In this way, selectively projecting illumination light to the fundus from one of the two light projecting areas on the pupil of the subject's eye and photographing the fundus image is advantageous in reducing artifacts. be.

<Fifth artifact suppression process>
After selectively projecting illumination light onto the fundus from one of the two light projection areas and photographing the first fundus image, the control unit further selects the light projection area from which the illumination light is projected from the other one. Alternatively, the second fundus image may be taken by selectively projecting illumination light from the other side. Through such two imaging operations, two fundus images are obtained in which the appearance positions of artifacts such as images reflected by the objective lens differ from each other depending on the light projection area used for imaging. Photographing may be performed without changing the positional relationship between the eye to be examined and the photographing optical system between the first photographing and the second photographing. Furthermore, it is desirable that the second fundus image be photographed continuously and automatically from the first fundus image.

In this embodiment, when taking two fundus images, there is no need to change the positional relationship between the eye to be examined and the photographing optical system, and moreover, it is relatively easy to change the positional relationship between the eye to be examined and the photographing optical system. The light projection area on the pupil of the eye to be examined can be switched in a short time. Therefore, two fundus images can be captured in a short time. As a result, even if the first fundus image and the second fundus image are taken consecutively, the burden on the subject is suppressed. In addition, even if the illumination light is visible light, the second image is taken immediately after the first image is taken, so the miosis caused by the first image is caused in the second image. The impact can be suppressed.

Here, an example of the effect of miosis is that the illumination light and the fundus reflected light are vignetted by the iris, resulting in a dark fundus image. The effect of vignetting (change in brightness) between the center of the image and the periphery of the image is not necessarily uniform. For example, the peripheral area of an image may be more susceptible to vignetting as the shooting angle of view becomes larger.

In the fifth artifact suppression process, one fundus image (hereinafter referred to as a "composite image") may be generated by performing a synthesis process on these two fundus images. The compositing process is executed by the image processing section. In this embodiment, compositing processing is performed to obtain an image in which the influence of artifacts is suppressed. There can be various synthetic methods, as exemplified below.

For example, a composite image may be generated by replacing an area containing an artifact in one of two fundus images with a corresponding part of the other fundus image (see FIG. 10). ). At this time, replacement may be performed in units of scanning lines. For example, when the aforementioned reflected image occurs as an artifact, a composite image may be generated by replacing the reflected image occurring at the center of one fundus image with a corresponding area in the other fundus image.

Alternatively, a composite image may be generated as an average image of two fundus images. In this case, the averaging process may be performed by giving different addition ratios between the reflected image and other areas.

Note that the area where the reflected image occurs is a substantially constant range based on the photographing optical axis, although there is some variation depending on the diopter. Therefore, in the two fundus images, the area to be combined with the other image in the combining process may be determined in advance. However, the present invention is not necessarily limited to this, and a reflection image detection process may be performed on the fundus image, and areas to be combined may be individually set based on the results of the detection process. Further, the area to be synthesized may be set according to the diopter.

The control unit captures the first fundus image based on scanning only a part of the scanning range corresponding to the composite image, switches the light projection area, and then captures the second fundus image based on scanning the remaining part. A composite image may be generated by capturing a second fundus image and combining (collage) the fundus images. In this case, it is preferable that the scanning range is divided into two parts around the photographing optical axis, and fundus images are photographed in each of the two divided scanning ranges. Note that in this case, the compositing process is not necessarily limited to image processing. For example, a composite image can be formed on the imaging surface by switching the light projection area on which the illumination light is projected at the timing when the illumination light arrives at the divided position of the scanning range.

In this case, between the two fundus images, it is preferable that the relationship between the scanning range on the fundus and the projection area where the illumination light is projected intersect between the two fundus images. For example, when two light projection areas are placed side by side in the vertical direction and the illumination light is scanned vertically on the fundus, when passing the illumination light from the upper light projection area, the lower half of the fundus is When the first fundus image is taken based on the scan and the illumination light is passed from the lower light projection area, the second fundus image is taken based on the scan of the upper half of the fundus, and both A composite image may also be generated. In this case, in relation to each light projection area, the reflected image of the objective lens and images taken of portions that are unlikely to contain artifacts such as flare are combined. Therefore, a composite image with suppressed artifacts can be obtained.

Instead of this compositing process, the following photography control may be performed. That is, the light projection area may be switched by the control unit at the timing when the illumination light scanning the fundus during imaging reaches the boundary position of the two divisions. A composite image with suppressed reflected images is generated without the need for composition processing.

<Sixth artifact suppression process>
In the sixth artifact suppression process, the fundus image is photographed twice (at least twice) without changing the positional relationship between the optical axis of the photographing optical system and the visual axis of the eye to be examined. Between the two shootings, the control unit switches the shooting conditions other than the positional relationship. As a result, a first fundus image in which artifacts are suppressed and a second fundus image in which image quality is given priority over the first fundus image are captured, and the area containing the artifact in the second fundus image is captured. , synthesize corresponding regions in the first fundus image. As a result, the device obtains a composite image that is a fundus image with suppressed artifacts.

In the sixth artifact suppression process, the positional relationship between the optical axis of the imaging optical system and the visual axis of the subject's eye is not changed between the two image captures, so it is completed in a shorter time compared to the second artifact suppression process. A composite image can be obtained by photographing twice.

Various conditions that make a trade-off between image quality and the difficulty of producing artifacts can be the imaging conditions that are changed between two imaging operations.

For example, the control unit may change the imaging conditions regarding the diopter correction amount between two imaging operations. In this case, the first fundus image may be, for example, a fundus image obtained by performing the artifact suppression process in the first embodiment described above. That is, the fundus image may be photographed with the irradiation-side correction amount adjusted to a value different from the light-receiving-side correction amount. In this case, the second fundus image may be a fundus image photographed with the irradiation side correction amount and the light receiving side correction amount matched.

Further, for example, the control unit may change the conditions regarding the state of separation of the fundus reflected light and the harmful light between two imaging sessions. In this case, the first fundus image may be photographed under photographing conditions such that the brightness is lower than that of the second fundus image.

For example, when photographing the first fundus image, the aperture of the diaphragm disposed in at least one of the light emitting optical system and the light receiving optical system is reduced compared to when photographing the second fundus image. Good too. For example, in the above-mentioned slit scan type optical system, the size of the transparent part (e.g., aperture) in the slit forming section is different when the first fundus image is taken, and when the second fundus image is taken. may be reduced compared to In addition, when photographing the first fundus image, the passage area of the fundus reflected light in the harmful light removing unit (for example, a diaphragm) provided in the light receiving optical system is different from that when photographing the second fundus image. may be restricted. Thereby, harmful light reflected by the objective lens or the like is suitably separated from the fundus reflected light guided onto the imaging surface. As a result, it becomes easier to obtain a fundus image with suppressed artifacts.

In the case of a slit scan type optical system, one or both of the slit forming section and the harmful light removing section may be a variable slit. That is, the width of the irradiation area, the effective area (imaging area), or both may be switchable between a first width and a second width wider than the first width. In this case, one or both of the slit forming section and the harmful light removing section has at least two types of slit openings: a first slit opening corresponding to the first width and a second slit opening corresponding to the second width. It may have.

In this case, as shown in FIG. 12, the apparatus may include an optical chopper equipped with a rotating body (for example, a wheel) as a scanning section. In an optical chopper, a rotating body in which a plurality of slit openings are arranged side by side on one circumference serves as one or both of a slit forming section and a harmful light removing section. In an optical chopper, a rotating body is rotationally driven. Thereby, a plurality of slit openings are successively traversed with respect to the optical path of the illumination light or return light. The shape of the rotating body may be, for example, a disk shape (wheel shape) as shown in FIG. 12, or a cylindrical shape. In a cylindrical rotating body, a plurality of slits are formed on the cylindrical side surface. Note that the rotating body may be driven at a constant speed.

In the example of FIG. 12, the rotating body has a first area in which one or more first slit openings corresponding to a first width are consecutively arranged, and a second slit opening corresponding to a second width. a second area in which one or more are consecutively arranged. In this case, the control unit controls the illumination area or effective area (imaging area) on the fundus between the first period in which the first area passes through the optical path and the second period in which the second area passes through the optical path. Width changes. The control unit obtains a fundus image obtained in the first period as a first fundus image, obtains a fundus image obtained in the second period as a second fundus image, and generates a composite image of both. Good too.

Note that when the illumination light is visible light, it is preferable that of the two fundus images, the second fundus image with priority given to image quality is photographed first, and the first fundus image is photographed later. . Therefore, the control unit may perform a continuous shooting operation (continuous shooting process) of shooting two fundus images at a predetermined interval in the order of the second fundus image and the first fundus image. It is preferable that the predetermined interval is a sufficiently short interval from the time (about several tens of seconds) taken from photographing with visible light until miosis disappears.

When two fundus images are taken in a short period of time using visible light, miosis occurs, and in images taken later, the periphery tends to become dark due to vignetting of illumination light at the pupil. On the other hand, by first photographing the second fundus image with priority on image quality and photographing the first fundus image later, it is easy to obtain a good fundus image up to the periphery in the composite image.

When the scanning unit is an optical chopper, the device may further include a sensor that detects the rotational position of the rotating body. Exposure of the image sensor and sweeping of the image may be controlled based on the signal from the sensor.

"Example"
Next, with reference to FIGS. 1 to 4, FIG. 11, and FIG. 13, examples of the fundus photographing apparatus according to the first embodiment and the second embodiment will be described.

A fundus photographing device 1 (hereinafter simply abbreviated as "photographing device 1") forms illumination light in the form of a slit on the fundus of the eye to be examined, scans the area formed in the slit shape on the fundus, and performs illumination. By receiving the light reflected from the fundus, a frontal image of the fundus is captured.

<Appearance of the device>
The external configuration of the photographing device 1 will be described with reference to FIG. 1. The photographing device 1 includes a photographing unit 3. The photographing unit 3 mainly includes an optical system shown in FIG. The photographing device 1 includes 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 eye E and the photographing unit 3.

The drive unit 8 can move in the left-right direction (X direction) and the front-back direction (Z direction, in other words, the working distance direction) with respect to the base 7. Further, the drive unit 8 further moves the photographing unit 3 on the drive unit 8 in a three-dimensional direction with respect to the eye E to be examined. The drive unit 8 includes an actuator for moving the drive unit 8 or the photographing unit 3 in each predetermined movable direction, 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 the positional relationship with respect to 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 eye E to be examined from the photographed facial image, and controls the driving unit 8 to align the imaging unit 3 with the identified position of the eye E to be examined.

Further, the photographing device 1 further includes a monitor 120. The monitor 120 displays a fundus observation image, a fundus photography image, an anterior segment observation image, and the like.

<Optical system of example>
Next, the optical system of the photographing device 1 will be explained with reference to FIG. The photographing device 1 includes 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 conjugate to the pupil of the subject's eye are indicated with a ``△'' on the photographing optical axis, and positions conjugate to the fundus are indicated with an ``x'' on the photographing optical axis, respectively.

The photographing optical system 10 includes an irradiation optical system 10a and a light receiving optical system 10b. In the embodiment, the irradiation optical system 10a includes a light source unit 11, a lens 13, a slit-like member 15a, lenses 17a, 17, a mirror 18, a perforated mirror 20, and an objective lens 22. The light receiving optical system 10b includes an objective lens 22, a perforated mirror 20, lenses 25a and 25b, a slit-like member 15b, and an image sensor 28. 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 subject's eye E, and allows a portion of the fundus reflected light from the subject's eye E to pass through the aperture toward the imaging device. 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 transparent part, and the reflective part are reversed may be used as the optical path coupling part. 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. Furthermore, the hole-opening mirror and the mirror as an alternative thereof can each be further replaced with a combination of a half mirror and a light shielding part.

In this embodiment, the light source unit 11 includes multiple types of light sources with different wavelength bands. For example, the light source unit 11 includes visible light sources 11a and 11b and infrared light sources 11c and 11d. In this way, the light source unit 11 of this embodiment is provided with two light sources for each wavelength. The two light sources having the same wavelength are placed 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. 2, and are arranged axially symmetrically with respect to the photographing optical axis L. As shown in FIG. 2, the outer peripheral shapes of the two light sources may be rectangular shapes that are longer in the direction intersecting the scanning direction than in the scanning direction.

Light from the two light sources passes through the lens 13 and is irradiated onto the slit-shaped member 15 . In the present embodiment, the slit-like member 15a has a light-transmitting portion (opening) that is 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 unit 15c so that the transparent part crosses the photographing optical axis L in the X direction. Thereby, scanning of the illumination light in this embodiment is realized. Note that in this embodiment, scanning by the slit-shaped member 15b is also performed on the light receiving system side. In this embodiment, the slit-shaped members on the light emitting side and the light receiving side are driven in conjunction with each other by one driving section (actuator).

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 are imaged on the pupil conjugate plane. That is, on the pupil conjugate plane, images of the two light sources are formed at positions separated in the scanning direction. In this manner, in this embodiment, the two light projection areas P1 and P2 on the pupil conjugate plane are formed as images of two light sources.

Further, 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 is imaged on the fundus Er. Thereby, the illumination light is formed into a slit shape on the fundus Er. The illumination light is reflected on the fundus Er and taken out from the pupil Ep.

Here, since the aperture of the perforated mirror 20 is conjugate with the pupil of the subject's eye, the fundus reflected light used for photographing the fundus image passes through the image of the perforated mirror aperture (pupil image) on the pupil of the subject's eye. Limited to some. In this way, the image of the aperture on the pupil of the eye to be examined becomes the light receiving area R in this example. The light receiving area R is formed between two light projecting areas P1 and P2 (images of two light sources). In addition, 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 area R and the two light emitting areas P1 and P2 do not overlap each other on the pupil. is formed. This effectively reduces the occurrence of flare.

The fundus reflected light that has passed 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 a conjugate position of the fundus via lenses 25a and 25b. At this time, harmful light is removed by disposing the light-transmitting portion of the slit-like member 15b at the image formation position.

The image sensor 28 is placed at a position conjugate to the fundus. In this embodiment, a relay system 27 is provided between the slit-like member 15b and the image sensor 28, so that both the slit-like member 15b and the image sensor 28 are arranged at conjugate positions of the fundus. As a result, both the removal of harmful light and the imaging are performed satisfactorily. Alternatively, the relay system 27 between the image sensor 28 and the slit-shaped 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 image sensor 28. For example, CMOS, two-dimensional CCD, etc. may be used. An image of the slit-shaped region of the fundus Er, which is imaged by the transparent portion of the slit-shaped member 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 scans the fundus Er, an image (slit-shaped image) of the scanning position on the fundus Er is sequentially projected 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 scanning range.

In addition, although the scanning unit in the light receiving system in the embodiment is a device that mechanically scans the slit, it is not necessarily limited to this. For example, the scanning section on the light receiving optical system side may be a device that electronically scans the slit. As an example, when the image sensor 28 is a CMOS, scanning of the slit may be realized by a rolling shutter function of the CMOS. In this case, by displacing the exposed area on the imaging surface in synchronization with the scanning section in the light projection system, it is possible to efficiently image while removing harmful light. Further, a liquid crystal shutter or the like can also be used as a scanning unit that electronically scans the slit.

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

The driving section 17c of the irradiation optical system 10a and the driving section 25c of the light receiving optical system 10b can be driven independently. As a result, in this embodiment, as shown in FIG. 4B, the irradiation side correction amount, which is the diopter correction amount in the irradiation optical system 10a, and the light receiving side correction amount, which is the diopter correction amount in the light receiving optical system 10b, are Each can be set independently.

In this embodiment, each of the irradiation side diopter correction optical system 17 and the light receiving side diopter correction optical system 25 includes a telecentric optical system. Each telecentric optical system maintains the image height in the image side region even if the diopter correction amount changes. Thereby, the positional relationship between the slit opening of the irradiation optical system and the slit opening of the light receiving optical system on the fundus can be kept constant regardless of the balance between the irradiation side correction amount and the light receiving side correction amount. Therefore, the slit aperture of the irradiation optical system and the slit aperture of the light-receiving optical system on the fundus can always be matched regardless of the balance between the irradiation-side correction amount and the light-receiving-side correction amount. Further, it is possible to suppress a change in image size in response to a change in the diopter correction amount.

As shown in FIG. 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 of the eye. The split index is used to detect the focus state. Further, in this embodiment, the refractive power of the eye E to be examined is acquired from the detection result of the focus state.

The split index projection optical system 50 may include at least a light source 51 (infrared light source), an index plate 52, and a deflection prism 53, for example. In this embodiment, the index plate 52 is arranged at a position corresponding to the imaging surface of the light receiving optical system 50. Similarly, each of the slit-shaped members 15a and 15b are also arranged at corresponding positions. Specifically, when the diopter correction amounts on the irradiation side and the light receiving side are 0D, the optotype plate 52 is placed at a position that is substantially conjugate with the fundus of the emmetropic eye (0D eye). The deflection prism 53 is disposed closer to the index plate 52 on the eye to be examined side than the index plate 52 is.

The indicator plate 52 is formed using, for example, slit light as an indicator. The deflection prism 53 separates the index light beam that has passed 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 diopter correction optical system 17 to the objective lens 22. Therefore, the split index is reflected in the fundus image (eg, fundus observation image).

When the index board 52 is deviated from the fundus conjugate position, the two split indices are separated on the fundus, and when the index board 52 is placed at the fundus conjugate position, the two split indices are matched. The conjugate relationship is adjusted by the irradiation-side diopter correction optical system 17 disposed between the deflection prism 53 and the eye to be examined Er. Therefore, in this embodiment, defocusing is performed while making the irradiation side diopter correction amount and the light receiving side diopter correction amount match. At this time, the separated state of the split index indicates the focus state. By adjusting the diopter correction amounts on the irradiation side and the light receiving side so that the two split indicators match, the imaging surface and each of the slit-like members 15a and 15b are in a conjugate positional relationship with the fundus. becomes.

The refractive power of the eye E to be examined can be derived from the diopter correction amount when the imaging surface and each of the slit-like members 15a and 15b are in a conjugate positional relationship with the fundus. Therefore, this embodiment may further include an encoder (not shown) that reads either the distance between the lens 17a and the lens 17b or the distance between the lens 25a and the lens 25b. The refractive power of the eye E may be acquired based on the signal from the .

Note that the scanning section may be, for example, an optical chopper as shown in FIG. 11. An optical chopper has a wheel with multiple slits formed around its outer circumference, and by rotating the wheel, it can scan the slits at high speed.

Here, in FIG. 2, from the light source unit 11 to the mirror 18 of the irradiation optical system 10a and from the perforated mirror 20 to the image sensor 28 of the light receiving optical system 10b are arranged in parallel in the X direction. By rotating the orientations of the mirror 20 and the mirror 18 by 90 degrees from the illustrated state and arranging them in parallel in the Y direction, the optical chopper can be used as a scanning section. In this case, as shown in FIG. 11, by making the optical axis of the irradiation optical system 10a and the optical axis of the light receiving optical system 10b cross each other at the upper and lower ends of the wheel, a single optical chopper can be used. , the scanning of the light projecting system and the light receiving system can be easily synchronized.

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

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

<Control system of example>
Next, the control system of the photographing device 1 will be explained with reference to FIG. In this embodiment, the control section 100 controls each section of the photographing device 1. Further, for 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. Further, temporary data and 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 present invention 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 also includes a drive unit 8, light sources 11a to 11d, a drive unit 15c, a drive unit 17c, a drive unit 25c, an image sensor 28, a light source 41, an image sensor 47, a light source 51, an input interface 110, a monitor 120, etc. All parts are electrically connected.

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

<Explanation of operation of embodiment>
Next, the photographing operation will be explained based on the flowchart of FIG. 13.

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

First, the face detection camera 110 and the anterior eye segment observation optical system 40 begin to take pictures in parallel (S1), and alignment adjustment is performed using the results of both shots (S2).

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

Next, an alignment reference position is set based on the anterior segment front image, and alignment is guided to the set alignment reference position. In this embodiment, the positional relationship between the eye E to be examined and the photographing unit 3 is adjusted by the control unit 100 based on the anterior segment front image. In this embodiment, the control unit 100 determines the position at which the center of the pupil in the anterior eye segment observation image and the image center (in this embodiment, the position of the imaging optical axis L) substantially coincides, based on the signal from the image sensor 47. A first reference position is established that targets the relationship. Then, an alignment shift from the first reference position is detected, and the photographing unit 4 is moved vertically and horizontally in a direction in which the alignment shift is eliminated. At this time, the alignment deviation with the first reference position may be detected, for example, based on the amount of deviation between the pupil center and the imaging optical axis on the anterior segment observation image. Furthermore, if the fundus imaging device 1 includes, for example, an alignment projection optical system that projects an alignment index onto the corneal vertex, an alignment shift may be detected based on the amount of shift between the alignment index and the imaging optical axis. .

Further, the control unit 100 moves the photographing unit 4 in the front-back direction so that the anterior segment observation image 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 in S2, the positional relationship between the eye to be examined and the photographing unit 4 is such that the center of the light receiving area R on the pupil of the eye to be examined (that is, the photographing optical axis) is the center of the pupil. (the first reference position in this embodiment).

After the first photographing mode is set, the control unit 100 starts photographing and displaying a fundus observation image (S3). Specifically, the control unit 100 turns on the light sources 11c and 11d simultaneously, and starts driving the drive unit 15c, so that the slit-shaped illumination light repeatedly scans a predetermined range on the fundus Er. A fundus image photographed in substantially real time is generated at any time as a fundus observation image based on a signal output from the image sensor 28 every predetermined number of scans (at least once). The control unit 100 may display the fundus observation image on the monitor 120 as a substantially real-time moving image.

Next, the focus states of the irradiation optical system and the light receiving optical system are adjusted based on the fundus observation image (S4). In this embodiment, after alignment is completed, focus adjustment is performed by driving the diopter correction optical system. At this time, in this embodiment, both the irradiation side diopter correction optical system 17 and the light receiving side 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 the split index onto the fundus. The control unit 100 performs defocusing by changing the correction amount while making the irradiation side diopter correction amount match the light receiving side diopter correction amount. In addition, the control unit 100 detects the separation state of the split index from the fundus observation image every time the correction amount changes, and adjusts the irradiation side diopter correction amount and the receiving side diopter correction amount until the split index matches. adjust. As a result of such adjustment, the imaging surface and each of the slit-like members 15a and 15b have a conjugate positional relationship with the fundus.

Further, in this embodiment, the diopter correction amount when the split indexes match is acquired by the control unit 100 as refraction power information (S5).

Next, the control unit 100 sets the photographing mode based on the refraction power information. First, the diopter correction amount, which is refractive power information, is compared with a predetermined threshold (S6). In this example, it is assumed that artifacts occur when the emitting side correction amount and the receiving side correction amount are each on the minus diopter side with respect to -12D, and "-12D" is set as the threshold value of the refractive power. It has been adopted. That is, the first range indicated by the symbol A1 in FIG. 4B is a range on the plus diopter side of "-12D" in this embodiment. Further, the second range indicated by the symbol A2 is "-12D" in this embodiment and a range on the minus diopter side. However, since the diopter range in which artifacts due to reflection of the objective lens 22 occur differs depending on the optical design of the apparatus, a value depending on the optical design of the apparatus may be adopted as the threshold value.

In this embodiment, if the refractive power of the eye to be examined is a value on the plus diopter side than "-12D", the first imaging mode is set (S6: No). On the other hand, if the refractive power of the eye to be examined is "-12D" or a value on the minus diopter side, the second imaging mode is set (S6: Yes).

In the first photographing mode, the process proceeds to S8, and photographing conditions other than the diopter correction amount are adjusted according to the photographing mode (S8). After the adjustment, a fundus image is photographed (S9). At this time, the observation light sources 11c and 11d may stop emitting light, and then the photographing light sources 11a and 11b may be turned on. In this case, a photographed image of the fundus is obtained as a result of photographing based on visible light emitted from the light sources 11a and 11b.

In this embodiment, in the first photographing mode, a fundus image is photographed in a state where the irradiation side correction amount and the light receiving side correction amount are matched (see FIG. 4A). When photographing, the irradiation side correction amount and the light receiving side correction amount are the values immediately after adjustment in the focus adjustment process (S5). Therefore, the diopter correction amount is within a range where artifacts do not become a problem, and the fundus is photographed with the imaging plane and the slit-like members 15a and 15b each in a conjugate positional relationship with the fundus. Therefore, a good fundus image is taken.

On the other hand, in the second imaging mode, the irradiation side correction amount is shifted to the plus diopter side with respect to the value when the split index matches (see FIG. 4B). As a result, the condensing position of the illumination light moves away from the objective lens, so that artifacts due to reflection from the objective lens 22 are less likely to occur. In this embodiment, the value of the irradiation-side correction amount after the change may be a fixed value, or may vary according to the light-receiving-side correction amount within a range that does not match the light-receiving-side correction amount. In this embodiment, the irradiation side correction amount is shifted to "-10D", which is a value on the plus diopter side of the threshold value. However, it is not necessarily limited to this, and may be shifted to a threshold value.

Next, photographing conditions other than the diopter correction amount are adjusted according to the second photographing mode. At this time, since the diopter correction amount in the irradiation optical system deviates from the best focus, the slit light irradiated as illumination light becomes blurred on the fundus of the eye. This reduces the amount of light reflected from the fundus that passes through the opening of the slit 15b in the light receiving optical system, leading to a decrease in the amount of light received.

Therefore, the control unit 100 sets any one of the amount of illumination light outputted from the light sources 11a and 11b or the light sources 11c and 11d, the gain of the image sensor 28, and the exposure time to the second shooting mode. Increase in shooting mode. This suppresses deterioration in image quality due to the slit light emitted as illumination light becoming blurred on the fundus as a result of the process in S7.

After adjusting the photographing conditions, the control unit 100 photographs a fundus image (S9). In the second photographing mode, a fundus image is photographed in a state where the irradiation side correction amount and the light receiving side correction amount do not match each other. As a result, in this embodiment, even when photographing a myopic eye, the occurrence of artifacts is suppressed. When photographing, the diopter correction amount in the light receiving optical system 10b is the value immediately after adjustment in the focus adjustment process (S5). Therefore, since the fundus of the eye and the imaging surface are conjugate, out-of-focus in the fundus image is suppressed. Furthermore, in the second photographing mode, the slit 15a is arranged in a non-conjugate positional relationship with the fundus Er, so the slit light emitted as illumination light becomes blurred on the fundus. However, since any one of the photographing conditions among the amount of illumination light, the gain of the image sensor 28, and the exposure time is increased compared to the first photographing mode, it is easy to obtain a fundus image with an appropriate dynamic range.

In a method of suppressing artifacts on a fundus image by image processing, traces of the image processing may remain in the image. In contrast, in this embodiment, image processing for suppressing artifacts is not necessarily required, so the tissue of the fundus is depicted more naturally in the fundus image.

Furthermore, in the second mode, the burden on the subject is considered to be greater than in the first mode because the amount of illumination light or the exposure time is increased. However, since the time from the start of imaging (start of irradiation of illumination light for imaging) to completion is relatively short, the amount of increase in burden is considered to be relatively small. Therefore, even when photographing a subject's eye with a high degree of myopia, a fundus image with suppressed artifacts can be photographed without placing a large burden on the subject.

Although the description has been made above based on the embodiments, the content of the embodiments can be changed as appropriate when implementing the present disclosure.

<Example of transformation of diopter correction optical system>
For example, in the above embodiment, an optical system in which the amount of diopter correction is set according to the distance between lenses is shown as an example of the diopter correction optical systems 17 and 25. However, the diopter correction optical system is not necessarily limited to this, and various optical systems can be employed. For example, in the case of the optical system shown in FIG. 2, diopter correction in the irradiation optical system 10a becomes possible by displacing the slit-like member 15a in the optical axis direction instead of the lens 17a. Slit-shaped member 15a
By displacing in the optical axis direction, the position of the condensing point K is displaced in the optical axis direction. Similarly, by displacing the slit-like member 15b in the optical axis direction instead of the lens 25b, diopter correction in the light-receiving optical system 10b becomes possible. In this case, both the lens 27 and the image sensor 28 may be moved in conjunction with the slit-shaped member 25b. Furthermore, in this case, it becomes difficult for one drive unit to perform scanning by the slit-shaped member 15a and scanning by the slit-shaped member 15b, so the slit-shaped member 15a and the slit-shaped member 15b are , each may have a drive unit.

<Photography control during fluorescence photography>
For example, in each of the embodiments described above, the fundus imaging device not only captures a fundus image based on light reflected from the fundus, but also captures a fluorescent fundus image, which is a fundus image based on fluorescence emitted from the fundus. good.

In this case, illumination light is emitted from the irradiation optical system as excitation light. The wavelength range of the illumination light can be appropriately set depending on the intended fluorescent substance. The fluorescent substance may be a contrast agent (eg, indocyanine green, fluorescein, etc.) or an autofluorescent substance accumulated in the fundus of the eye (eg, lipofuscin).

In the light receiving optical system, fluorescence from the fundus of the eye based on excitation light is guided to a light receiving element. When fluorescence photography is performed, a barrier filter is placed on an independent optical path of the light receiving optical system. The barrier filter has spectral characteristics that block light in the same wavelength range as the excitation light and allow fluorescence to pass through. As a result, of the fundus reflected light of the excitation light and the fluorescence from the fundus, the fluorescence is selectively received by the light receiving element. As a result, a good fundus fluorescence image can be obtained. The fundus imaging device may include a drive unit that inserts and removes the barrier filter. Furthermore, insertion and removal of the barrier filter may be controlled by a control section.

The control unit may switch the imaging mode between a normal imaging mode and a fluorescence imaging mode. The normal photographing mode is set to photograph a fundus image based on fundus reflected light. The fluorescence photography mode is set to capture a fluorescence fundus image. The control unit may control insertion and removal of the barrier filter depending on the imaging mode. In this case, the control unit retracts the barrier filter in the normal shooting mode. Further, the control unit causes a barrier filter to be inserted in the fluorescence imaging mode. Here, in the fluorescence photography mode, the barrier filter blocks not only the light reflected from the fundus of the excitation light but also the light reflected by the objective lens. Therefore, there is no need to perform the various artifact suppression processes shown in the above embodiments in the fluorescence imaging mode. Therefore, in the fluorescence imaging mode, the control unit does not need to execute the artifact suppression process regardless of the refractive error of the eye to be examined. For example, in a device that suppresses the occurrence of artifacts by making the diopter correction amount in the irradiation optical system (irradiation side correction amount) and the diopter correction amount in the light receiving optical system (light receiving side correction amount) inconsistent, In the fluorescence imaging mode, each value is adjusted according to the refractive error so that the irradiation side correction amount and the light receiving side correction amount match.

1 Fundus photographing device 10 Photographic optical system 10a Irradiation optical system 10b Light receiving optical system 17, 25 Diopter correction optical system 22 Objective lens 100 Control section 150 Optical chopper E Examine eye Er Fundus

Claims (1)

An irradiation optical system that irradiates illumination light to the fundus of the eye to be examined through an objective lens, and a light receiving optical system that shares the objective lens with the irradiation optical system and further includes a light receiving element that receives the fundus reflected light of the illumination light. a photographing optical system including a system;
a photographing control means that controls one or both of the irradiation optical system and the light receiving optical system to obtain at least two fundus images based on signals from the light receiving element under different photographing conditions;
an image processing means for obtaining a composite image by combining at least two fundus images having different photographing conditions;
The photographing optical system includes a diopter correction optical system,
The photographing control means controls the diopter correction optical system so as to set a diopter correction amount in the diopter correction optical system as the photographing condition when photographing at least two fundus images that are the basis of the composite image. A fundus photographing device that allows the fundus to be different for each photograph.