JP7651339B2 - Ophthalmic device and method for controlling the device - Google Patents

Description

The disclosed technology relates to an ophthalmic device and a method for controlling the ophthalmic device.

As ophthalmic devices, devices for obtaining two-dimensional images of the fundus of the examinee's eye (hereinafter referred to as fundus camera devices) and devices for obtaining tomographic images of the examinee's eye using optical coherence tomography (OCT) with low-coherence light (hereinafter referred to as OCT devices) are in practical use.

Some of these devices are equipped with a fully automatic function that automatically performs various adjustments and then automatically captures images without the examiner having to operate them during the process. Patent Document 1 discloses an optical image measurement device that determines whether each state of the fully automatic functions, such as alignment, focus, and position adjustment of the measurement image, is suitable, and captures images only when all are determined to be suitable.

JP 2010-191172 A

Here, depending on the subject's posture, failure may occur repeatedly no matter how many times the image is taken. In such cases, for example, the subject may be in a posture where the head is away from the forehead rest, which can cause the eye movements to become unstable.

One of the objectives of the disclosed technology is to reduce the possibility of failure to photograph the subject's eye.

In addition to the above objective, the present invention also has another objective to achieve effects that cannot be obtained by conventional techniques, which are derived from the configurations shown in the detailed description of the invention described below.

One of the disclosed ophthalmic devices includes:
a driving means for driving an optical head unit including an optical system for imaging an image of a subject's eye to be examined so as to move the optical head unit;
a control unit that controls the driving unit so as to reduce a first positional deviation amount between the eye to be examined and the optical head unit;
and an alarm means for notifying information regarding the posture of the subject associated with the detection of movement of the subject's eye when it is determined that a difference between the second positional deviation amount acquired under the control of the driving means and the first positional deviation amount is different from the time when the first positional deviation amount was acquired, the difference being a second positional deviation amount acquired at a time later than the time when the first positional deviation amount was acquired, and the amount by which the optical head unit was driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired is different.

One of the disclosed techniques can reduce the possibility of failing to photograph the subject's eye.

1 shows a schematic configuration example of an apparatus according to an embodiment. 1 shows a flowchart of a method for controlling automatic alignment according to an embodiment. 1 shows a flowchart of a control method for detecting movement of an eye to be examined according to an embodiment. 1 shows a flowchart of a control method for automatic coherence gate adjustment according to an embodiment. 1 shows a schematic configuration example of an optical head unit and a face receiving unit of an apparatus according to an embodiment. FIG. 1 is a schematic diagram showing a change in position of an optical head unit and a test eye over time according to an embodiment; 13 shows an example of display of notification content on a monitor according to an embodiment.

Each embodiment of the present invention will be described in detail below with reference to the drawings.

The device according to this embodiment detects the movement of the subject's eye in the control flow for automatic alignment and automatic coherence gate adjustment, and notifies the examiner of information regarding the subject's posture.

<Configuration>
The ophthalmic apparatus of this embodiment includes a fundus image capturing unit that captures a two-dimensional fundus image and a tomographic image capturing unit that captures a three-dimensional tomographic image of the fundus of a subject's eye using information based on optical interference. The present embodiment will be described below with reference to Fig. 1, which shows a schematic configuration of the ophthalmic apparatus of this embodiment and its optical system. The ophthalmic apparatus includes an optical head unit 100, a spectroscope 200, and a control unit 300. The configurations of the optical head unit 100, the spectroscope 200, and the control unit 300 will be described below in order.

<Configuration of Optical Head Unit 100 and Spectrometer 200>
The optical head unit 100, which is an inspection unit, is configured with a measurement optical system for capturing two-dimensional images and tomographic images of the anterior part Ea of the subject's eye E and the fundus Ef of the subject's eye. Various optical systems arranged in the optical head unit 100 will be described below. In the optical head unit 100, an objective lens 101 is installed facing the subject's eye E. That is, the optical head unit 100 may be configured to include, for example, an optical system for capturing an image of the subject's subject's eye. The optical system included in the optical head unit 100 may include, for example, a measurement optical system having an OCT measurement optical path including an objective optical system. In this case, the optical system included in the optical head unit 100 may or may not include various optical systems described later. The various optical systems described later may be configured to be included, for example, in a stage unit not shown, and in this case, the optical system inside the optical head unit 100 and the optical system inside the stage unit may be connected by an optical fiber or the like.

A first dichroic mirror 102 and a second dichroic mirror 103 that function as an optical path separation section are arranged on the optical axis L1 of the objective lens 101. These dichroic mirrors split the optical path of the anterior eye observation system (optical axis L2), the optical path of the fundus photography system (optical axis L3), and the optical path of the OCT interference system (optical axis L5) into separate optical paths for each wavelength band.

<Anterior eye observation system>
A lens 120, a diaphragm 121, a prism 122, a lens 123, and an image sensor 124 are arranged on an optical axis L2 in the reflection direction of the dichroic mirror 103. The image sensor 124 is a monochrome sensor having sensitivity in the infrared range. An anterior eye observation optical system for observing the anterior eye is configured by the optical members and the like arranged on the optical axis L2. The CMOS sensor 124 is connected to a control unit 300. Each pixel value acquired by the image sensor 124 is output to a monitor 301 via the control unit 300. In addition, an anterior eye observation light source 125 arranged near the objective lens 101 illuminates the anterior eye of the subject's eye E.

<Fundus photography system and fixation light>
On the optical axis L3 in the transmission direction of the dichroic mirror 103, a perforated mirror 131, a photographing aperture 132, a focus lens 133, an imaging lens 134, a third dichroic mirror 135, and an image sensor 136 are arranged. An optical system for observing and photographing the fundus is configured. The perforated mirror 131 has an opening in the center. The focus lens 133 adjusts the focus by moving its position on the optical axis L3. The optical path on the optical axis L3 is branched by the third dichroic mirror 135 into an optical path leading to the image sensor 136 and an optical path leading to the fixation lamp 137 for each wavelength band. The image sensor 136 is a sensor that is sensitive to visible light and infrared light and is used for both moving image observation and still image capture. The fixation lamp 137 generates visible light to encourage the subject to fixate.

<Fundus illumination system>
A corneal baffle 140, a relay lens 141, a focus index unit 142, a lens 143, and a ring slit 144 are arranged in this order on an optical axis L4 in the reflection direction of the perforated mirror 131. The corneal baffle 140 has a light-shielding point at the center. The ring slit 144 has a ring-shaped slit opening. Also arranged on the optical axis L4 are a crystalline lens baffle 145 as a light-shielding member having a light-shielding point, and a dichroic mirror 146 having the property of transmitting infrared light and reflecting visible light. The focus index unit 142 is movable along the optical axis L4 and can be inserted into and removed from the optical axis L4.

A condenser lens 147 and a white LED light source 148 are arranged in the reflection direction of the dichroic mirror 146. The white LED light source 148 is a light source for photography in which multiple white LEDs that emit visible pulsed light are arranged. A condenser lens 149 and an infrared LED light source 150 are arranged in the transmission direction of the dichroic mirror 146. The infrared LED light source 150 is an observation light source in which multiple infrared LEDs that emit constant infrared light are arranged. The objective lens 101, the dichroic mirror 146, the optical members between them, and the condenser lens 147 and the condenser lens 149 constitute an illumination optical system that illuminates the fundus. The light from the white LED light source 148 or the infrared LED light source 150 illuminates the fundus of the subject's eye via this illumination optical system.

<OCT optical system>
On the optical axis L5 in the reflection direction of the dichroic mirror 102, the lens 151, the mirror 152, the OCTX scanner 153-1, the OCTY scanner 153-2, and the lenses 154 and 155 are arranged. The OCTX scanner 153-1 and the OCTY scanner 153-2 are, for example, dichroic mirrors, and function as a scanning unit that scans the fundus Ef of the subject's eye with the measurement light. Furthermore, the OCTX scanner 153-1 and the OCTY scanner 153-2 are arranged so that the vicinity of their center positions is the focal position of the lens 151. In addition, the vicinity of this center position is optically conjugate with the position of the pupil of the subject's eye E. With this configuration, the optical path with the scanning unit as the object point is approximately parallel between the objective lens 101 and the lens 151. As a result, even if the fundus Ef is scanned with measurement light by the OCTX scanner 153-1 and the OCTY scanner 153-2, the angle of incidence of the measurement light incident on the dichroic mirror disposed between them can be made the same. Note that the OCTX scanner 153-1 and the OCTY scanner 153-2 each scan with the measurement light in a main scanning direction and a sub-scanning direction perpendicular to the main scanning direction, but the scanning direction is not limited to this.

The measurement light source 157 is a light source that emits light to obtain measurement light that is incident on the measurement optical path.

In the present embodiment, the measurement light in the OCT optical system is emitted from the fiber end as a light source, and the fiber end has an optically conjugate relationship with the fundus Ef of the test eye E. The lens 154 is a lens for focus adjustment, and is driven in the optical axis direction indicated by the arrow in the figure by a motor (not shown). The focus adjustment of the measurement light is performed so that the measurement light emitted from the fiber end acting as a light source is imaged on the fundus Ef. The lens 154 functioning as a focus adjustment unit is disposed between the fiber end serving as the measurement light source and the OCTX scanner 153-1 and OCTY scanner 153-2 functioning as a scanning unit. By the focus adjustment described above, the image of the measurement light emitted from the fiber end can be imaged on the fundus Ef of the test eye E, and the return light from the fundus Ef can be efficiently returned to the optical fiber 156-2.

In FIG. 1, the optical path between the OCTX scanner 153-1 and the OCTY scanner 153-2 is configured within the plane of the paper, but in reality it is configured in a direction perpendicular to the plane of the paper.

Next, the configuration of the optical path from the measurement light source 157, the reference optical system, and the spectrometer 200 will be described. The measurement light source 157, the optical coupler 156, the optical fibers 156-1 to 156-4, the lens 158, the dispersion compensation glass 159, the reference mirror 160, and the spectrometer 200 constitute a Michelson interference system. The optical fibers 156-1 to 156-4 are single-mode optical fibers that are connected to the optical coupler 156 and integrated. The light emitted from the measurement light source 204 is guided to the optical coupler 156 via the optical fiber 156-1. The light guided to the optical coupler 156 is split by the optical coupler 156 into measurement light on the optical fiber 156-2 side and reference light on the optical fiber 156-3 side. The measurement light is irradiated to the fundus Ef of the subject's eye E, which is the object of observation, through the optical path of the OCT optical system described above, and reaches the optical coupler 156 again through the same optical path due to reflection and scattering by the retina.

On the other hand, the reference light reaches the reference mirror 160 through the optical fiber 156-3, the lens 158, and the dispersion compensation glass 159 inserted to adjust the dispersion of the measurement light and the reference light, and is reflected. The reference light reflected by the reference mirror 160 returns along the same optical path and reaches the optical coupler 156 again. The reference light and the measurement light (return light) that reach the optical coupler 156 again are combined by the optical coupler 156. Here, when the optical path length of the measurement light and the optical path length of the reference light become almost the same, this combination causes interference between the respective lights. The reference mirror 160 is held in an adjustable position in the optical axis direction indicated by the arrow in the figure by a motor and a drive mechanism (not shown). The drive mechanism is an example of a drive means for driving an optical member to change the optical path length difference between the measurement light and the reference light, and is composed of a stepping motor, a feed screw, and a linear guide (not shown). By using this motor or the like, the optical path length of the reference light can be adjusted to the optical path length of the measurement light, which changes depending on the eye E to be examined. The resulting interference light is guided to the spectrometer 200 via optical fiber 156-4.

The spectrometer 200 includes a lens 201, a diffraction grating 202, a lens 203, and a line sensor 204. The interference light emitted from the optical fiber 156-4 becomes approximately parallel light via the lens 201, is then dispersed by the diffraction grating 202, and is imaged on the line sensor 204 by the lens 203. Each element in the line sensor 204 outputs a signal corresponding to the received light. The control unit 300 samples this signal at a predetermined timing using the image acquisition and generation unit 304 described later, and performs predetermined signal processing to generate a tomographic image.

Next, the surroundings of the measurement light source 157 will be described. In this embodiment, the measurement light source 157 uses an SLD (Super Luminescent Diode), which is a typical low-coherent light source. The central wavelength of the light emitted from the measurement light source 157 is 855 nm, and the wavelength bandwidth is about 100 nm. Here, the bandwidth is an important parameter because it affects the resolution in the optical axis direction of the obtained tomographic image. In addition, an SLD is selected as the type of light source here, but as long as it can emit low-coherent light, ASE (Amplified Spontaneous Emission) and the like can also be used. Considering that the central wavelength of the measurement light is to measure the eye, near-infrared light is appropriate. In addition, since the central wavelength affects the lateral resolution of the obtained tomographic image, it is desirable that the wavelength be as short as possible. For both reasons, in this embodiment, light with a central wavelength of 855 nm is used.

In this embodiment, a Michelson interferometer is used as the interferometer, but a Mach-Zehnder interferometer may also be used. It is preferable to use a Mach-Zehnder interferometer when the light intensity difference between the measurement light and the reference light is large, and to use a Michelson interferometer when the light intensity difference is relatively small.

Furthermore, the optical head unit 100 includes a head drive unit 170. The head drive unit 170 is an example of a drive means for driving the optical head unit 100, and is composed of a linear motion mechanism in three dimensions (X, Y, Z). The linear motion mechanism in each direction is composed of a stepping motor, a feed screw, and a linear motion guide (not shown), and is configured to be able to move the optical head unit 100 in three dimensions (X, Y, Z) relative to the subject's eye E. This allows alignment of the optical head unit 100 with respect to the subject's eye E. The configuration of the drive unit is not limited to this. Here, the optical head unit 100 may be configured to be movable relative to the stage unit 180 in FIG. 5, for example. In addition, a face support unit 181 for receiving the subject's face may be provided on the stage unit, and the face support unit 181 may be provided with a forehead support unit 182 for supporting the subject's forehead and a chin support unit 183 for receiving the subject's chin. The chin rest 183 is connected to the control unit 300 and is configured to be movable up and down relative to the face rest 181. This makes it possible to roughly adjust the height of the subject's eye E relative to the optical head unit 100 by adjusting the elevation of the chin rest 183 according to the size of the subject's face, etc. At this time, for example, the optical head unit 100 can be moved relative to the stage unit to perform alignment with the subject's eye.

<Configuration of control unit 300>
The control unit 300 is connected to each unit of the optical head unit 100 and the spectroscope 200. Specifically, the control unit 300 is connected to the infrared CCD 142 in the optical head unit 100, and is configured to be capable of generating an observation image of the anterior segment Ea of the subject's eye E. The control unit 300 is also connected to the APD 115 in the optical head unit 100, and is configured to be capable of generating an observation image of the fundus Er of the subject's eye E. Furthermore, the control unit 300 is also connected to the head drive unit 170 in the optical head unit 100, and is configured to be capable of driving the optical head unit 100 three-dimensionally with respect to the subject's eye E.

The control unit 300 is also connected to the line sensor 204 of the spectrometer 200. This makes it possible to acquire measurement signals that have been wavelength-resolved by the spectrometer 200, and further to generate a tomographic image of the subject's eye E based on the measurement signals.

The generated anterior segment observation image, fundus observation image, and tomographic image of the subject's eye E can be displayed on a monitor 301 connected to the control unit 300.

<Method of Aligning Eye E>
Fig. 2 is a flowchart showing a control method of the fundus imaging apparatus according to the present embodiment. A method of automatic alignment of the subject's eye E using the optical coherence tomography imaging apparatus according to the present embodiment will be described with reference to the flowchart of Fig. 2. Prior to imaging, the examiner first has the subject sit in front of the apparatus.

The control unit 300 starts automatic alignment upon receiving a switch operation (not shown) by the examiner. When automatic alignment starts, in step S201, the control unit 300 functions as an anterior eye image acquisition unit, and periodically acquires an anterior eye image from the infrared CCD 142 and analyzes it. Specifically, the control unit 300 detects the pupil area in the input anterior eye image. The control unit 300 calculates the center position of the detected pupil area. The center position of the pupil area is an example of a predetermined position of the anterior eye to be examined. The control unit 300, as a deviation amount calculation means, calculates the amount of displacement (positional deviation amount) between the center position of the detected pupil area and the center position of the anterior eye image. The optical coherence tomography imaging device of this embodiment is configured so that the center of the anterior eye image and the optical axis of the objective lens 101-1 coincide with each other, and the amount of displacement calculated in step S201 represents the amount of positional deviation between the test eye E and the measurement optical axis. Note that the above displacement amount (positional deviation amount) is an example of the positional deviation amount between the test eye E and the optical head unit 100.

In step S202, the control unit 300 determines whether the positional deviation amount calculated in step S201 is less than a predetermined value. If it is determined that the positional deviation amount is equal to or greater than the predetermined value (S202; No), the process proceeds to step S203. On the other hand, if it is determined that the positional deviation amount is less than the predetermined value (S202; Yes), the automatic alignment process ends.

If the process of step S203 is the first time, the control unit 300 proceeds to step S205.

In step S205, the control unit 300 instructs the head drive unit 170 to move the optical head unit 100 according to the amount of positional deviation calculated in step S201 in order to reduce the amount of positional deviation. The head drive unit 170 drives three motors (not shown) to move the position of the optical head unit 100 in three-dimensional (X, Y, Z) directions relative to the subject's eye E. More specifically, the control unit 300 instructs the number of rotations of each of the three motors (not shown). As a result, the position of the optical axis of the objective lens 101-1 mounted on the optical head unit 100 is corrected so as to approach the pupil center position of the anterior segment Ea of the subject's eye E. The control unit 300 is an example of a control means that controls the head drive unit 170 so as to reduce the first amount of positional deviation between the subject's eye E and the optical head unit 100.

Then, the process returns to step S201. In step S201, the control unit 300 functions as an anterior eye image acquisition unit, acquires multiple anterior eye images of the subject's eye E at different times, and repeats the above process. In step S205, the control unit 300 functions as a tracking unit, and tracks the subject's eye using the head driving unit 170 based on the multiple anterior eye images.

This series of automatic alignment operations causes the optical axis position of the objective lens 101-1 to match the pupil center position of the anterior segment Ea of the test eye E, making it possible to capture a tomographic image of the test eye in a properly aligned state. Note that the positional relationship between the test eye E and the optical head unit 100 in this alignment state is an example of a predetermined positional relationship.

The process of step S201 is performed at a predetermined time interval. Therefore, depending on the relationship between the rotation speed of the motor and the magnitude of the positional deviation, the process may proceed to the next step of S201 before the positional deviation falls below the predetermined value.

In step S202, if the positional deviation amount is repeatedly determined to be equal to or greater than the predetermined value (S202; No) even after the reduction of the positional deviation amount in step S205 is performed, it is considered that the movement of the subject's eye continues to be in a state in which the movement amount is greater than the predetermined value in S202 and the movement speed is faster than the movement speed of the optical head 100. The subject's posture that causes this state may be such that the head is away from the forehead rest 182, causing the movement of the subject's eye to be unstable.

Therefore, if the process of step S203 is the second or subsequent times, the control unit 300 proceeds to step S204, detects the movement of the subject's eye, and, if necessary, notifies the examiner of information regarding the subject's posture.

<Method for detecting movement of subject's eye E based on anterior eye observation image>
FIG. 3 is a flowchart showing a control method for detecting the movement of the subject's eye E in step S204.

In step S301, the control unit 300 calculates the difference between the positional deviation amount (second positional deviation amount) calculated in the immediately preceding processing of S201 and the positional deviation amount (first positional deviation amount) calculated in the processing of S201 one step before that. This difference is called the change in positional deviation. Note that the second positional deviation amount is a positional deviation amount acquired at a time later than the time when the first positional deviation amount was acquired, and is an example of a positional deviation amount acquired under the control of the head driving unit 170, which is an example of a driving means. Note that "under the control of the head driving unit 170" does not strictly specify that the head driving unit 170 is actually being driven, but is a concept that also includes, for example, a timing when the head driving unit 170 is not being driven temporarily in preparation for the next drive.

In step S302, the control unit 300 calculates the reduction in the positional deviation of the subject's eye E in the immediately preceding processing of S205. The reduction in the positional deviation is the amount of movement of the optical head unit 100 in the immediately preceding processing of S205. The amount of movement of the optical head unit 100 can be calculated from the number of rotations of the motor and the pitch of the feed screw, etc. Note that the method of calculating the amount of movement of the optical head unit 100 is not limited to this. It may also be calculated using an encoder or a displacement meter, for example. In this case, the reduction in the positional deviation is an example of the amount by which the optical head unit 100 is driven between the time when the first positional deviation amount is obtained and the time when the second positional deviation amount is obtained.

In step S303, the control unit 300 calculates the difference between the amount of change in positional deviation calculated in S301 and the amount of reduction in positional deviation calculated in S302.

In step S304, the control unit 300 determines whether the difference between the amount of change in positional deviation calculated in S303 and the amount of reduction in positional deviation is less than a predetermined value. If it is determined that the difference is equal to or greater than the predetermined value (S304; No), the process proceeds to step S305. On the other hand, if it is determined that the difference is less than the predetermined value (S304; Yes), the process proceeds to step S306.

If there is no movement of the subject's eye E, the reduction in positional deviation will be approximately the same as the change in positional deviation. On the other hand, if it is determined that the reduction in positional deviation and the change in positional deviation are different, it is understood that the subject's eye E has moved over time, and the movement of the subject's eye E can be detected. If it is determined that the change in positional deviation is greater than the reduction in positional deviation, it is considered that the subject's forehead has moved away from the forehead support unit 182, for example, and the subject's eye has moved away from the optical head unit 100. On the other hand, if it is determined that the change in positional deviation is smaller than the reduction in positional deviation, it is considered that the subject's forehead, which was away from the forehead support unit 182, has moved away, for example, and the subject's eye has moved closer to the optical head unit 100.

Figure 6 is a schematic diagram showing the positional change over time of the optical head unit 100 and the test eye E during automatic alignment according to this embodiment. At time t1, the position of the optical head unit 100 is Zhead(t1), and the position of the test eye E is Zeye(t1). As described above, the first positional deviation amount at time t1 is calculated by the control unit 300 as ΔZwd(t1) (=Zhead(t1)-Zeye(t1)) based on the anterior eye observation image (processing of step S201). The shaded area in Figure 6(b) indicates a certain range in which the positional deviation amount is less than a predetermined value. If the positional deviation amount ΔZwd(t1) is outside the range of predetermined values, the control unit 300 drives the optical head unit 100 by a motor (not shown) to move it to position Zeye(t1) in order to reduce the positional deviation amount ΔZwd(t1). The gradient Vz in FIG. 6(a) indicates the moving speed of the optical head unit 100, and is determined by, for example, the number of rotations of a motor (not shown) and the pitch of a feed screw. At time t, only ΔZwd(t) is detectable, and the position Zhead(t) of the optical head unit 1000 and the position Zeye(t) of the subject's eye E are values that cannot be directly detected. At time t2, the control unit 300 calculates a second positional deviation amount ΔZwd(t2) (=Zhead(t2)-Zeye(t2)) between the optical head unit 1000 and the subject's eye E based on the anterior eye observation image. Furthermore, the control unit 300 calculates the reduction amount of the positional deviation (step S302). The reduction amount of the positional deviation is calculated as Zhead(t2)-Zhead(t1)=Vz×(t2-t1). In the case of FIG. 6, the amount of change in positional shift ΔZwd(t2)-ΔZwd(t1) is smaller than the amount of reduction in positional shift Zhead(t2)-Zhead(t1), so it is determined that the amount of reduction in positional shift and the amount of change in positional shift are different. As a result, it is found that the subject's eye has come closer to the optical head unit 100, for example, due to the forehead, which was away from the forehead support unit 182, moving.

In step S305, the control unit 300 notifies the monitor 301 that the movement of the subject's eye has been detected as a notification means. FIG. 7 shows an example of the notification content displayed on the monitor 301. The notification method may include displaying a text message on the monitor 301. Examples of the text message to be displayed include "Please check the subject's posture" and "The head may be separated from the forehead support" as shown in FIG. 7(a). An illustration expressing the notification content may also be displayed. An example of the illustration to be displayed is one that calls attention to the posture of the subject and the state of the forehead support of the subject's head as shown in FIG. 7(b). In addition, when the anterior eye observation image is displayed on the monitor 301, the outer frame of the anterior eye observation image may be displayed in red as shown in FIG. 7(c). When the notification is displayed on the monitor 301, the control unit 300 continues the notification until the notification cancellation process is performed. The various notification methods described above are examples of methods for notifying information regarding the posture of the subject. Also, different messages may be notified as information regarding the subject's posture depending on the magnitude relationship between the amount of change in positional deviation and the amount of reduction in positional deviation. After step S305, the control unit 300 ends the detection of the movement of the subject's eye and proceeds to step S205.

In step S306, the control unit 300 determines whether or not a notification is being displayed on the monitor 301. If a notification is not being displayed (S306: No), the control unit 300 ends the detection of the movement of the subject's eye and proceeds to step S205. If a notification is being displayed (S306: Yes), the control unit 300 proceeds to step S307.

In step S307, the control unit 300 cancels the notification on the monitor 301. The control unit 300 removes the display of information related to the subject's posture from the monitor 301.

In this embodiment, automatic alignment of the optical system with respect to the subject's eye is performed based on an anterior segment image taken using an infrared CCD, but this may be performed using other methods. For example, automatic alignment in three dimensions (X, Y, Z) can be performed by projecting an alignment indicator onto the anterior segment of the subject's eye and detecting the reflected light.

<Anterior eye tracking during preparation for shooting>
Next, the examiner performs preparation for photographing to obtain a tomographic image for photographing. Here, the preparation for photographing includes at least one of focus adjustment, polarization adjustment, light amount adjustment, and optical path length difference adjustment, for example. In addition, the preparation for photographing includes at least one of focus adjustment, polarization adjustment, light amount adjustment, and optical path length difference adjustment, for example. The examiner performs these preparations for photographing while viewing the anterior eye observation image, fundus observation image, and tomographic image displayed on the monitor 301, but if the alignment state of the subject's eye is not good, the preparation for photographing may take a long time.

Focus adjustments, polarization adjustments, etc. are generally made while observing the brightness of the acquired image, but if the alignment of the test eye is poor, part of the light beam may be blocked by the pupil edge, causing the image to become dark. In addition, the optical path length difference is generally adjusted while observing the position of the retina in the tomographic image, but if the alignment of the test eye is unstable, the position of the retina in the tomographic image may continue to move and become unstable.

Therefore, the optical coherence tomography imaging apparatus of this embodiment is equipped with an anterior eye tracking function that continuously performs automatic alignment operations to prevent deterioration of the alignment state of the subject's eye. By using anterior eye tracking during preparation for imaging, the alignment state can be maintained as much as possible, and imaging preparation can be completed in a relatively short time.

When starting anterior eye tracking during preparation for imaging, it is desirable to continue anterior eye tracking as is after the completion of the automatic alignment described above. When the automatic alignment is completed, the positional relationship between the optical axis position of the objective lens 101-1 and the anterior eye portion Ea of the subject's eye E is appropriately adjusted. Therefore, by repeating the automatic alignment operation, anterior eye tracking can maintain the positional relationship between the optical axis position of the objective lens 101-1 and the anterior eye portion Ea of the subject's eye E at the time of completion of the first automatic alignment. In addition, the optical coherence tomography imaging device of this embodiment continues to perform a movement detection operation of the subject's eye E to detect the movement of the subject's eye, and notifies the examiner of information regarding the subject's posture.

<Focus adjustment of fundus observation image>
After the automatic alignment is completed, the control unit 300 adjusts the focus of the fundus observation image. The control unit 300 drives the focus lens 133 by a motor (not shown) using the focus index unit 142 as an index. After adjusting the focus of the fundus observation image, the control unit 300 acquires a tomographic image and adjusts the coherence gate.

<Method of capturing tomographic images>
A method for capturing a tomographic image using the optical coherence tomographic imaging apparatus of this embodiment will be described. The examiner starts capturing images by operating a switch (not shown) on the control unit 300. In response to an instruction to start capturing images, the control unit 300 periodically starts generating a tomographic image for recording based on the interference light output from the line sensor 204. Note that "for recording" is also expressed as "for capturing images."

Here, the interference light output from the line sensor 204 is a signal for each frequency dispersed by the diffraction grating 202. The control unit 300 performs FFT (Fast Fourier Transform) processing on the signal from the line sensor 204 to generate depth information at a certain point on the fundus Er. This generation of depth information at a certain point on the fundus Er is called an A-scan.

The measurement light irradiated onto the fundus Er can be arbitrarily scanned over the fundus Er by controlling the driving of at least one of the X scanner 153-1 and the Y scanner 153-2. The measurement light can be scanned over the subject's eye by the X scanner 153-1 and the Y scanner 153-2.

The control unit 300 generates a tomographic image of the arbitrary trajectory on the fundus Er by bundling a series of multiple A-scans acquired during one scan along this arbitrary trajectory into a single two-dimensional image.

Furthermore, the control unit 300 repeats the above-mentioned scanning along the arbitrary trajectory multiple times by controlling the driving of at least one of the X scanner 153-1 and the Y scanner 153-2. When the same trajectory operation is performed multiple times, multiple tomographic images can be obtained along the arbitrary trajectory on the fundus Er. For example, the control unit 300 drives only the X scanner 153-1 to repeatedly perform scanning in the X direction and generate multiple tomographic images on the same scanning line of the fundus Er. The control unit 300 can also drive the X scanner 153-1 and the Y scanner 153-2 simultaneously to repeatedly perform a circular operation and generate multiple tomographic images on the same circle of the fundus Er. The control unit 300 then performs averaging processing on the multiple tomographic images to generate a single high-quality tomographic image and display it on the monitor 301.

On the other hand, the control unit 300 can also perform multiple scans while shifting the scan along the arbitrary trajectory described above in the XY directions by driving and controlling at least one of the X scanner 153-1 and the Y scanner 153-2. For example, multiple scans in the X direction are performed multiple times while shifting the scan in the Y direction at regular intervals, thereby generating multiple tomographic images that cover the entire rectangular area on the fundus Er. The control unit 300 then synthesizes the multiple tomographic images to generate three-dimensional information of the fundus Er and displays it on the monitor 301.

The scanning patterns of the X scanner 153-1 and the Y scanner 153-2 can be arbitrarily switched by pressing a scan pattern selection button (not shown).

The control unit 300 functions as a tomographic image acquisition unit, and acquires a tomographic image of the test eye E based on interference light produced by interference between return light from the test eye E irradiated with measurement light and reference light corresponding to the measurement light.

Automatic coherence gate adjustment
FIG. 4 is a flowchart showing a method for controlling the fundus imaging apparatus according to the present embodiment. With reference to the flowchart of FIG. 4, a method for automatic coherence gate adjustment of the subject's eye E using the optical coherence tomography imaging apparatus according to the present embodiment will be described. The coherence gate is, for example, a position corresponding to the optical path length of the reference light in the measurement optical path. The coherence gate adjustment can be performed by changing the optical path length difference between the measurement light and the reference light. At this time, the reference mirror 160 is an example of an optical member for changing the optical path length difference between the measurement light and the reference light, and is also an example of an optical member for changing the optical path length of the reference light. The optical member for changing the optical path length difference may be an optical member for changing the optical path length of the measurement light.

In step S401, the control unit 300 functions as a tomographic image acquisition unit, and periodically generates and analyzes an "adjustment" tomographic image based on the interference light output from the line sensor 204. Specifically, the control unit 300 detects the retina in the generated tomographic image. The control unit 300 calculates the detected retinal position. As a deviation amount calculation means, the control unit 300 calculates the amount of displacement (Z deviation amount) between the detected retinal position (Z direction) and a predetermined position (Z direction) of the tomographic image.

In step S402, the control unit 300 determines whether the Z deviation amount calculated in step S401 is less than a predetermined value. If it is determined that the Z deviation amount is equal to or greater than the predetermined value (S401; No), the process proceeds to step S403. On the other hand, if it is determined that the Z deviation amount is less than the predetermined value (S402; Yes), the automatic coherence gate adjustment is terminated.

If the process of step S403 is being performed for the first time, the control unit 300 proceeds to step S405.

In step S405, the control unit 300 instructs the driving mechanism (not shown) to move the reference mirror 160 according to the Z shift amount calculated in step 401 in order to reduce the Z shift amount. The driving mechanism drives a motor (not shown) to move the position of the reference mirror 160 in the optical axis direction. More specifically, the control unit 300 instructs the number of rotations of the motor (not shown). As a result, the reference mirror 160 moves, so that the optical path length of the reference system is corrected to approximately match the optical path length of the OCT optical system, and the retina of the test eye is displayed at a suitable position in the tomographic image. Note that the positional relationship between the test eye E and the OCT optical system in this state is an example of a predetermined positional relationship. At this time, the control unit 300 is an example of a control means for controlling the driving mechanism so as to reduce the first positional shift amount between the test eye and an optical member (e.g., the reference mirror 160) for changing the optical path length difference between the measurement light and the reference light. For example, even during automatic coherence gate adjustment, a function (anterior eye tracking) for driving the optical head unit 100 using an anterior eye observation image may be executed, while a method for detecting the movement of the subject's eye E based on the anterior eye observation image may also be executed. In this case, the positional deviation amount (Z deviation amount) between the subject's eye and an optical member (e.g., the reference mirror 160) for changing the optical path length difference between the measurement light and the reference light may be calculated as a third positional deviation amount. The driving mechanism may be an example of a second driving means. The positional deviation amount (Z deviation amount) acquired at a time later than the time when the third positional deviation amount was acquired may be calculated as a fourth positional deviation amount acquired under the control of the second driving means.

In step S402, if the Z deviation amount is repeatedly determined to be equal to or greater than the predetermined value (S402; No) even after the reduction of the Z deviation amount in step S405 is performed, it is considered that the movement of the subject's eye continues to be in a state in which the movement amount is greater than the predetermined value in S402 and the movement speed is faster than the movement speed of the reference mirror 160. The subject's posture that causes this state may be such that the head is away from the forehead rest 182, causing the movement of the subject's eye to be unstable.

Therefore, if the process of step S403 is the second or subsequent times, the control unit 300 proceeds to step S404. In step S404, the control unit 300 detects the movement of the subject's eye, and, in some cases, notifies the examiner of information regarding the subject's posture.

<Method for detecting movement of subject's eye E based on tomographic images>
The control method for detecting the movement of the subject's eye E in step S404 can also be explained using the flowchart in FIG.

In step S301, the control unit 300 calculates the difference between the Z shift amount (second positional shift amount) calculated in the immediately preceding processing of S201 and the Z shift amount (first positional shift amount) calculated in the processing of S201 one step before that. This difference is called the change in Z shift. The second positional shift amount is a positional shift amount (Z shift amount) acquired at a time later than the time when the first positional shift amount was acquired, and is an example of a positional shift amount acquired under the control of the drive mechanism, which is an example of a drive means. Note that "under the control of the drive mechanism" does not strictly specify that the drive mechanism is actually being driven, but is a concept that also includes, for example, a timing when the drive mechanism is not being driven temporarily in preparation for the next drive.

In step S302, the control unit 300 calculates the amount of reduction in the Z-shift of the test eye E in the immediately preceding process of S405. The amount of reduction in the Z-shift is the amount of movement of the reference mirror 160 in the immediately preceding process of S405. The amount of movement of the reference mirror 160 can be calculated from the number of rotations of the motor and the pitch of the feed screw, etc. Note that the method of calculating the amount of movement of the reference mirror 160 is not limited to this. It may also be calculated using an encoder or a displacement meter, for example. In this case, the amount of reduction in the Z-shift is an example of the amount by which the reference mirror 160 is driven between the time when the first positional shift amount is obtained and the time when the second positional shift amount is obtained.

In step S303, the control unit 300 calculates the difference between the amount of change in Z shift calculated in S301 and the amount of reduction in Z shift calculated in S302.

In step S304, the control unit 300 determines whether the difference between the amount of change in Z shift calculated in S303 and the amount of reduction in Z shift is less than a predetermined value. If it is determined that it is equal to or greater than the predetermined value (S304; No), the process proceeds to step S305. On the other hand, if it is determined that the amount of displacement is less than the predetermined value (S304; Yes), the process proceeds to step S306. If there is no movement of the subject's eye E, the amount of reduction in Z shift will be approximately the same as the amount of change in Z shift. On the other hand, if it is determined that the amount of reduction in Z shift and the change in Z shift are different, it is found that the subject's eye E has moved over time, and the movement of the subject's eye E can be detected.

In step S305, the control unit 300 notifies the monitor 301 that the movement of the subject's eye has been detected as a notification means. FIG. 7 shows an example of the notification content displayed on the monitor 301. The notification method may include displaying a text message on the monitor 301. Examples of the text message to be displayed include "Please check the subject's posture" and "The head may be separated from the forehead support 182" as shown in FIG. 7(a). An illustration expressing the notification content may also be displayed. An example of the illustration to be displayed is one that calls attention to the posture of the subject and the state of the forehead support of the subject's head as shown in FIG. 7(b). In addition, when a tomographic image is displayed on the monitor 301, the outer frame of the tomographic image may be displayed in red as shown in FIG. 7(d). When a notification is displayed on the monitor 301, the control unit 300 continues the notification until the notification cancellation process is performed. The various notification methods described above are examples of methods for notifying information regarding the posture of the subject. After step S305, the control unit 300 ends the detection of the movement of the subject's eye and proceeds to step S205.

In step S306, the control unit 300 determines whether or not a notification is being displayed on the monitor 301. If a notification is not being displayed (S306: No), the control unit 300 ends the detection of the movement of the subject's eye and proceeds to step S205. If a notification is being displayed (S306: Yes), the control unit 300 proceeds to step S307.

In step S307, the control unit 300 cancels the notification on the monitor 301. The control unit 300 removes the display of information related to the subject's posture from the monitor 301.

<Focus lens adjustment for tomographic images>
After the automatic coherence gate adjustment is completed, the control unit 300 adjusts the focus of the tomographic image. The lens 154 is driven by a motor (not shown) so that the tomographic image is in a suitable state. After the above adjustments are completed, the control unit 300 captures a tomographic image for storage and a fundus observation image.

<Anterior eye tracking during shooting>
When multiple scans are performed as described above to capture multiple tomographic images, the time required for the multiple scans is longer than that required for one scan. For example, the optical coherence tomographic imaging apparatus according to this embodiment can set 696 scanning positions on the fundus Er by shifting the scan of 10 mm in the X direction by 0.014 mm in the Y direction. The optical coherence tomographic imaging apparatus performs four operations at the same position for each of the 696 scanning positions to obtain a total of 2784 tomographic images (696 x 4 times), and can generate three-dimensional information of a range of 10 mm x 10 mm on the fundus Er. In the optical coherence tomographic imaging apparatus according to this embodiment, one tomographic image is composed of a total of 696 A-scans, and the time required for one A-scan is 14.3 microseconds. Therefore, 696 x 14.3 microseconds = 10.0 milliseconds are required to obtain one tomographic image, and at least 10.0 milliseconds/image x 2784 images = 27.8 seconds are required to obtain a total of 128 tomographic images.

On the other hand, human eye movements are a type of involuntary movement, and it is difficult to completely suppress them, even if the subject is gazing at a fixation light or the like. In addition, the period in which they occur is significantly shorter than the aforementioned 27.8-second shooting period, and it is highly likely that these eye movements will occur multiple times while all 2,784 tomographic images are acquired.

Therefore, to prevent the alignment of the subject's eye from deteriorating even during imaging, the system is equipped with an anterior eye tracking function that continues automatic alignment operations. In addition, to detect the movement of the subject's eye, the system continues to perform a movement detection operation of the subject's eye E, and notifies the examiner of information regarding the subject's posture.

According to this embodiment, the movement of the subject's eye E is detected from a fundus observation image or a tomographic image, and the examiner is notified of information regarding the subject's posture, thereby reducing the possibility of imaging failure.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims.

Other Embodiments
The present invention can also be realized by executing the following process. That is, the present invention can also be realized by supplying software (programs) that realize one or more functions of the various embodiments described above to a system or device via a network or a storage medium, and having a computer (or a CPU, MPU, etc.) of the system or device read and execute the programs. The computer has one or more processors or circuits, and may include multiple separate computers or a network of multiple separate processors or circuits to read and execute computer-executable instructions.

In this case, the processor or circuitry may include a central processing unit (CPU), a microprocessing unit (MPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), or a field programmable gate array (FPGA). The processor or circuitry may also include a digital signal processor (DSP), a data flow processor (DFP), or a neural processing unit (NPU).

Claims (8)

a driving means for driving an optical head unit including an optical system for imaging an image of a subject's eye to be examined so as to move the optical head unit;
a control unit that controls the driving unit so as to reduce a first positional deviation amount between the eye to be examined and the optical head unit;
a notification means for notifying information on the posture of the subject associated with the detection of the movement of the subject's eye when it is determined that a difference between the second positional deviation amount acquired under the control of the drive means and the first positional deviation amount is different from an amount by which the optical head unit is driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired, the difference being a second positional deviation amount acquired at a time later than the time when the first positional deviation amount was acquired, and a difference between an amount by which the optical head unit is driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired, is different;
An ophthalmic apparatus comprising: The ophthalmic device according to claim 1, further comprising an acquisition means for acquiring the first positional deviation amount and the second positional deviation amount using information related to the result of detecting the anterior segment of the subject's eye. a second driving means for driving an optical member included in the optical system to move the optical member for changing the optical path length difference between the measurement light and the reference light;
the control means controls the second driving means so as to reduce a third positional deviation amount between the eye to be examined and the optical member; and
The ophthalmic device of claim 1 or 2, wherein the notification means notifies information regarding the posture of the subject associated with the detection of movement of the subject's eye when it is determined that a fourth positional deviation amount is acquired at a time later than the time when the third positional deviation amount is acquired, and that a difference between the fourth positional deviation amount acquired under the control of the second driving means and the third positional deviation amount is different from an amount by which the optical element is driven between the time when the third positional deviation amount was acquired and the time when the fourth positional deviation amount was acquired. a driving means for driving an optical member included in an optical system for imaging an eye of a subject, the optical member being for changing an optical path length difference between the measurement light and the reference light, so as to move the optical member;
a control unit that controls the driving unit so as to reduce a first positional deviation amount between the eye to be examined and the optical member;
a notification means for notifying information on the posture of the subject associated with the detection of a movement of the subject's eye when it is determined that a difference between the second positional deviation amount acquired under the control of the driving means and the first positional deviation amount is different from an amount by which the optical member is driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired, the difference being a second positional deviation amount acquired at a time later than the time when the first positional deviation amount was acquired, and a difference between an amount by which the optical member is driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired is different;
An ophthalmic apparatus comprising: The ophthalmic device according to claim 4, further comprising an acquisition means for acquiring the first positional deviation amount and the second positional deviation amount using information on a tomographic image of the test eye obtained using interference light between the return light from the test eye irradiated with the measurement light and the reference light. A method for controlling an ophthalmic apparatus including a driving unit that drives an optical head unit including an optical system for imaging an eye to be examined of a subject, comprising the steps of:
controlling the driving means so as to reduce a first positional deviation amount between the eye to be examined and the optical head unit;
a step of notifying information on the posture of the subject associated with the detection of the movement of the subject's eye when it is determined that a difference between the second positional deviation amount acquired under the control of the driving means and the first positional deviation amount is different from an amount by which the optical head unit is driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired is different from an amount by which the optical head unit is driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired is different;
A method for controlling an ophthalmic apparatus comprising: 1. A method for controlling an ophthalmic apparatus including a driving unit that drives an optical member included in an optical system for imaging an eye of a subject, the optical member being for changing an optical path length difference between a measurement light and a reference light, the method comprising the steps of:
controlling the driving means so as to reduce a first positional deviation amount between the eye to be examined and the optical member;
a step of notifying information on the posture of the subject associated with the detection of the movement of the subject's eye when it is determined that a difference between the second positional deviation amount acquired under the control of the driving means and the first positional deviation amount is different from an amount by which the optical member is driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired, the difference being a second positional deviation amount acquired at a time later than the time when the first positional deviation amount was acquired, and a difference between an amount by which the optical member is driven between the time when the first positional deviation amount was acquired and the time when the second positional deviation amount was acquired, is different;
A method for controlling an ophthalmic apparatus comprising: A program for causing a computer to execute the control method for an ophthalmic device according to claim 6 or 7.

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