JP2017127578A - Imaging method, imaging apparatus, and program for executing the imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire an image of an imaging position intended by an imaging person, eliminating involuntary movements of the eye.SOLUTION: Provided is a control method for an examination apparatus, comprising the steps of: acquiring an image of a given imaging range of an object to be examined as a reference image for measuring the movement of the object to be examined; detecting a positional deviation between the reference image and plural detected images acquired in a period of time different from that for the step of acquiring the reference image; calculating a center position of the positional deviation by applying statistical processing to the positional deviation detected in the step of detecting the positional deviation; and correcting the image acquisition position for the object to be examined, based on the center position and detected images acquired after the center position calculation step.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an imaging method, an imaging apparatus, and a program for executing the imaging method for imaging an object to be inspected exemplified by the fundus.

  In recent years, SLO (Scanning Laser Ophthalmoscope) and OCT (Optical Coherence Tomography) are used as an ophthalmic imaging apparatus. In SLO, for example, laser light irradiated to the fundus is scanned two-dimensionally, the reflected light is received and imaged to obtain an image of the fundus. The OCT is an imaging apparatus that generates a tomographic image of the retina, for example, in the fundus using the interference of low-coherence light. These apparatuses are used particularly for the purpose of obtaining a fundus image or a tomographic image near the fundus.

  In recent years, such an ophthalmic imaging apparatus has been improved in resolution by increasing the NA of an irradiation laser.

  However, when imaging the fundus, the image must be captured through the optical tissue of the eye such as the cornea or the crystalline lens. For this reason, as the resolution increases, the influence on the image quality of the picked-up image due to the aberration of the cornea and the crystalline lens has become remarkable.

  Therefore, research on AO-SLO and AO-OCT in which an adaptive optics (AO) function for measuring aberrations of an eye and correcting the aberrations is incorporated in an optical system has been underway. In the measurement of aberration, generally, a wavefront distribution expressing the aberration of the eye is measured by a Shack-Hartmann wavefront sensor. In the Shack-Hartmann method, illumination light is incident on the eye, the reflected light is dispersed and condensed through a microlens array, received by a CCD camera, and the wavefront distribution of the reflected light is measured from a plurality of condensing positions. is there. For the measured wavefront distribution, a wavefront correction device such as a deformable mirror or a spatial phase modulator for correcting the wavefront distribution is arranged on the optical path to correct it. By performing imaging of the fundus through such an adaptive optical system, AO-SLO and AO-OCT enable high-resolution imaging with reduced effects of eye aberrations.

  Further, in these ophthalmologic imaging apparatuses, there is a problem that the imaging position of the fundus is not an intended position due to the movement of the eyes. It is common practice to reduce the movement of the eye by presenting an index called a fixation target so that the subject's line of sight is fixed during fundus imaging, and letting the subject gaze at this index. It has been broken. However, even in such a state, eye movement called fixation fixation micromotion always occurs. This involuntary eye movement is a minute movement of the eyeball that is involuntarily repeated in order to maintain vision. Also, it is difficult to keep a close eye on the fixation target because of problems such as maintenance of concentration and fatigue. Furthermore, in a subject having a disease in the eye, there is a decrease in visual acuity, narrowing of the visual field, and the movement of the eye becomes large.

  As a response to such eye movement, there is a fundus tracking technique that measures the movement of the eye and changes the irradiation position of the laser light to the fundus in real time so as to track the movement (also referred to as tracking).

  Patent Document 1 discloses an example of this tracking technique. In this tracking technique, a reference image (hereinafter referred to as a reference image) is first set as a reference image. Thereafter, a relative positional deviation between a target image (hereinafter referred to as a detected image) obtained every moment by imaging and a reference image is calculated. The scanning position of the laser light as illumination light on the eye to be examined is changed by a scanner, and a planar image is obtained by scanning with the laser light. By inputting the calculated relative positional deviation and correcting the operation position of the scanner that scans the laser beam on the fundus, it is possible to track the movement of the eye.

US2015 / 0077710A1

  The imager uses the apparatus with the intention to image the fundus position corresponding to the position of the fixation target. However, among the eye movements described above, there is a large movement that is called a saccade and occurs involuntarily. For example, in the case where the tracking technique described above is used, consider a case where an image acquired when this saccade occurs is used as a reference image. In this case, an image centered on a position that is temporarily deviated from the temporarily intended position is set as a reference image, and the tracking function is activated with the center position as a target position for tracking. As a result, an appropriate relative positional shift cannot be obtained, and a position that is significantly different from the position intended by the photographer is captured.

  The present invention has been made in view of such a situation, and an imaging method, an imaging apparatus, and the imaging method capable of obtaining an image at an imaging position intended by an imager without depending on involuntary eye movements. Provide a program to execute

In order to solve the above problems, a photographing method according to one embodiment of the present invention includes:
Obtaining an image of a predetermined imaging range of the inspection object as a reference image when measuring the movement of the inspection object;
Detecting a positional deviation between a plurality of detected images acquired at a time different from the step of acquiring the reference image and the reference image;
Calculating the center position of the positional deviation by performing statistical processing on the positional deviation detected by the step of detecting the positional deviation;
Correcting the acquisition position of the image of the inspection object based on the center position and the detected image obtained after the step of calculating the center position.

  According to the present invention, it is possible to obtain an image at an imaging position intended by an imager, regardless of involuntary eye movement.

1 is a schematic diagram illustrating a configuration of a fundus imaging apparatus according to Embodiment 1 of the present invention. It is a figure explaining the relationship between the reference | standard image in a WF-SLO image, and a to-be-detected image. It is a flowchart which shows the process sequence at the time of operating the conventional tracking function. It is the figure which represented typically the relationship of the eye movement, the range which can image AO-SLO, and the imaging field angle of AO-SLO. It is a flowchart which shows the process sequence at the time of operating the tracking function which concerns on Example 1 of this invention. It is a flowchart which shows the process sequence at the time of operating the tracking function which concerns on Example 2 of this invention. It is the figure which represented typically the angle of view of the image of AO-SLO in Example 3 of this invention. It is a flowchart which shows the process sequence at the time of operating the tracking function which concerns on Example 3 of this invention. It is a flowchart which shows the process sequence at the time of operating the tracking function which concerns on Example 4 of this invention. It is a figure which shows the example of a display of the operation screen in the fundus imaging apparatus which concerns on one Example of this invention. It is a flowchart of the whole process in the fundus imaging apparatus which concerns on one Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below do not limit the present invention related to the scope of claims, and all combinations of features described in the present embodiments are essential for the solution means of the present invention. Not exclusively.

  The present invention relates to a fundus imaging method that corrects an imaging position by measuring a movement of an eye to be examined, and a fundus imaging apparatus. More specifically, in the present invention, the illumination light irradiation position is detected by the movement of the eye, and the illumination light irradiation direction is changed so as to correct the influence of the eye movement. A tracking function for correcting the imaging position is provided in the fundus imaging method and apparatus.

[Example 1]
Hereinafter, a scanning laser ophthalmoscope (SLO) equipped with a fundus imaging method according to Embodiment 1 of the present invention will be described with reference to FIG. 1 which is a schematic diagram showing the configuration thereof.

  In FIG. 1, there are two imaging configurations. One is an AO-SLO (Adaptive Optics-SLO) of a scanning laser ophthalmoscope for obtaining a high-definition image using an adaptive optical system. The other is a WF-SLO (Wide Field-SLO) of a scanning laser ophthalmoscope that does not use an adaptive optical system. Although WF-SLO is inferior in image quality to AO-SLO, it has a feature that the imaging angle of view is wide.

Here, the main configuration of the AO-SLO will be described in more detail with reference to FIG.
In this embodiment, an SLD light source (Super Luminescent Diode) having a wavelength of 840 nm was used as the light source 101. Although the wavelength of the light source 101 is not particularly limited, about 800 to 1500 nm is preferably used for fundus imaging in order to reduce the glare of the subject and maintain the resolution. In this embodiment, an SLD light source is used as the light source 101, but other light sources may be used.

  The light emitted from the light source 101 passes through the single mode optical fiber 102 and is irradiated as a parallel light (illumination light 105) by the collimator lens 103.

  The irradiated illumination light 105 passes through the light splitting unit 104 formed of a beam splitter and is guided to the compensation optical system for performing aberration correction. The adaptive optics system includes a light splitting unit 106, a wavefront measuring device 115, a wavefront correcting device 108, and reflecting mirrors 107-1 to 107-4 for guiding them. Here, the reflection mirrors 107-1 to 107-4 are arranged so that at least the pupil of the eye 111 to be examined and the wavefront measuring device 115 and the pupil and the wavefront correcting device 108 are optically conjugate. Further, as the light splitting unit 106, a beam splitter is used in this embodiment.

  The illumination light 105 transmitted through the light splitting unit 106 is reflected by the reflection mirrors 107-1 and 107-2 and enters the wavefront correction device 108. The illumination light 105 reflected by the wavefront correction device 108 is emitted toward the reflection mirror 107-3.

  In this embodiment, a reflective liquid crystal spatial phase modulator using a liquid crystal element is used as the wavefront correction device 108 having wavefront correction means. However, as the wavefront correction device, a deformable mirror (also referred to as a deformable mirror) having a variable mirror shape may be used, and any wavefront correction device can be used as long as the wavefront can be corrected. Good.

  In FIG. 1, the illumination light 105 reflected by the reflection mirrors 107-3 and 4 is scanned on the fundus of the eye 111 to be examined one-dimensionally or two-dimensionally by the scanning optical system 109. In this embodiment, two scanners 109-1 and 109-2 (galvano scanner in this embodiment) are used for the scanning optical system 109 for main scanning (horizontal direction of the fundus) and sub-scanning (vertical direction of the fundus). As the scanning optical system 109, a resonant scanner may be used for main scanning for higher-speed imaging. In addition, in order to make each scanner in the scanning optical system 109 optically conjugate, optical elements such as mirrors and lenses may be arranged between the scanners. Each of the scanners of the scanning optical system 109 is connected to the tracking control unit 202. In addition to the normal illumination light scanning, the scanning position of the illumination light is changed so that the influence of the eye movement is corrected in the acquired image. Accept instructions.

  The illumination light 105 scanned by the scanning optical system 109 is irradiated to the eye 111 through the eyepieces 110-1 and 110-2. The illumination light 105 irradiated to the eye 111 is reflected or scattered by the fundus. By adjusting the positions of the eyepieces 110-1 and 110-2, it is possible to optimally irradiate the illumination light 105 in accordance with the diopter of the eye 111 to be examined. In this embodiment, the eyepieces 110-1 and 110-2 are used as the eyepiece, but these may be constituted by a spherical mirror or the like.

  Reflected light reflected or scattered from the retina of the fundus of the eye 111 to be examined travels in the opposite direction along the incident path, and part of the reflected light is reflected by the light splitting unit 106 to the wavefront measuring device 115, and the wavefront distribution of the light beam is determined. Used to measure. In this embodiment, a Shack-Hartmann sensor is used as the wavefront measuring device 115 having wavefront measuring means. However, the wavefront measuring apparatus is not limited to this, and other wavefront measuring means such as a curvature sensor or an apparatus to which a method for obtaining wavefront aberration by inverse calculation from an imaged point image is used. Also good.

  In FIG. 1, the reflected light transmitted through the light splitting unit 106 is reflected by the light splitting unit 104 and guided to the light intensity sensor 114 through the collimator 112 and the optical fiber 113. The reflected light is converted into an electric signal by the light intensity sensor 114, and the intensity of the light detected by the control unit 117 is arranged, and an image is formed based on the intensity. The constructed image is displayed on the display 118 as a fundus image.

  The wavefront measuring device 115 is connected to the adaptive optics controller 116 and transmits the measured wavefront distribution of the light to the adaptive optics controller 116. The wavefront correction device 108 is also connected to the adaptive optics control unit 116, and performs spatial phase modulation instructed by the adaptive optics control unit 116 on the light passing through the adaptive optical control unit 116. More specifically, the adaptive optics control unit 116 calculates a correction amount for correcting to a wavefront distribution having no aberration based on the wavefront distribution measured by the wavefront measuring device 115, and sets a correction condition in the wavefront correcting device 108. Command.

  In AO-SLO, the optical system is indeterminate because the eye to be examined is included in a part of the optical system. For this reason, it is generally difficult to reach a wavefront distribution with small aberrations by measuring and correcting the wavefront distribution once. Therefore, the measurement and correction of the wavefront distribution are repeatedly performed, and this repetition is continued until the aberration that can be imaged is converged. Thereby, the aberration of the optical path from the illumination light to the fundus can be reduced, the size of the spot condensed on the fundus can be reduced, and an image with high spatial resolution can be obtained.

  Next, WF-SLO will be described. The configuration of WF-SLO is basically the same as AO-SLO described so far. WF-SLO differs from AO-SLO in that there is no wavefront measuring device, wavefront correcting device, or adaptive optics control unit. In addition, the angle of view of an image captured by WF-SLO is wider than that of AO-SLO. Further, the resolution of an image captured with WF-SLO is inferior to that of AO-SLO. That is, the WF-SLO can obtain a low-resolution and wide-angle image, and the AO-SLO can obtain a high-resolution and narrow-angle image. In addition, the involuntary eye movement described above may exceed the angle of view of AO-SLO, and in order to obtain information for tracking, a WF-SLO image having a wide angle of view is usually used.

  The wavelength of the light source used in the WF-SLO 201 in the configuration shown in FIG. 1 is 900 nm. There is a dichroic mirror 200 in the AO-SLO, and the illumination light from the WF-SLO 201 and the illumination light 105 of the AO-SLO are combined and applied to the eye 111 to be examined. The light irradiated to the eye 111 is collected on the fundus by a crystalline lens that is an eye lens. This condensed light is reflected by the fundus and returns to the apparatus. The light returned from the eye 111 to be examined is separated into WF-SLO 201 light and AO-SLO light by the dichroic mirror 200 according to the wavelength band of light, and is guided to each optical system.

  An example of an image (referred to as a WF image) acquired by the WF-SLO 201 is shown in FIG. As shown in the figure, in the fundus image, the optic disc 300, the blood vessel 301, and the region 303 where the fovea exists are simultaneously imaged.

  In addition, a fixation target that causes the subject to gaze to reduce eye movement is displayed on the subject's eye. The fixation target is displayed using, for example, an organic EL display (not shown). The shape of the fixation target is generally a cross shape, but may be a round shape or a ring shape. It is preferable that the position and size of the fixation target can be changed. By changing the display position of the fixation target, the direction in which the subject gazes, that is, the direction of the eyes is changed. As a result, the location where the light of WF-SLO 201 and AO-SLO is collected on the fundus can be changed, and the imaging position can be changed.

  Here, with reference to FIG. 10, detailed contents such as an image displayed on the display 118 will be described. Further, accompanying the display contents, the imaging procedure of the photographer and the behavior of the fundus imaging apparatus such as a scanning laser ophthalmoscope (SLO) corresponding thereto will be described.

  The display 118 displays an image 700 of the entire display including various images to be described later. When capturing an actual fundus image or the like, an image of the anterior segment of the eye 111 to be examined is captured using an anterior segment camera (not shown). This image is displayed on the anterior segment display screen 701 as an anterior segment image.

  The fixation target position screen 702 displays the display position of the fixation target. In addition, marks 702-1 and 702-2 displayed on the fixation target position screen 702 indicate the positions of the fixation target actually presented to the eye to be examined. When the photographer moves the index displayed at an arbitrary position on the fixation target position screen 702 using a mouse or the like connected to the control unit 117 and performs a click operation, the position on the organic EL display described above The fixation target moves to the location corresponding to. When the subject gazes at the fixation target, the eye to be examined can be directed in a desired direction, and the fundus imaging position can be changed.

  On the WF-SLO real-time display screen 703, an image captured by the WF-SLO 201 is displayed in real time. An arrow in the WF-SLO real-time display screen 703 indicates the direction and amount of movement of the fundus due to the eye movement of the subject at a certain moment. The circle in the display simulates a nipple, and the two curves extending from it simulate an arcade blood vessel. These also move in response to eye movements. In addition, frames 900 (900-1 and 2) superimposed on the WF-SLO real-time display screen 703 are AO-SLO imaging frames that are areas to be imaged by AO-SLO.

  In this embodiment, the movement of the eye to be examined is detected by a tracking function described later, and the same position of the fundus can always be captured with AO-SLO. Therefore, the AO-SLO imaging frame 900 has also moved from 900-1 to 900-2 in response to this tracking operation. The imager can arbitrarily switch tracking ON / OFF by clicking the tracking ON button 710 or tracking OFF button 711.

  The activation button 708 is a button for activating an autofocus function that focuses illumination light on the fundus in the imaging of the WF-SLO 201. When the imaging of the WF-SLO 201 is started, the imager can click the activation button 708 to autofocus on the fundus and obtain a good WF-SLO image. In the actual autofocus operation in this embodiment, the position of the focus lens (not shown) is changed so that the contrast of the image reaches a peak.

Here, recording of still images by WF-SLO will be described.
On the WF-SLO still image display screen 705, a WF-SLO still image created based on a WF-SLO moving image for a predetermined time is displayed. This predetermined time is specified by inputting a numerical value to the WF-SLO recording time instruction unit 707. When the WF-SLO recording start button 709 is clicked, recording of a WF-SLO moving image is started, and moving images for the instructed time are recorded. The WF-SLO still image is created by superimposing the frames of the moving image, and the random noise contained in each frame is canceled out to reduce the random noise. This superimposed image becomes a still image by WF-SLO and is displayed on the WF-SLO still image display screen 705 on the image 700.

  On the AO-SLO real-time display screen 704, an image captured by AO-SLO is displayed in real time.

  AO-SLO has a function called steering for adjusting the imaging position on the fundus. The steering is a function of arbitrarily adjusting the imaging position by superimposing an offset value on the scanning position of the illumination light 105 by the scanners 109-1 and 109-2. If steering is used when a plurality of positions to be imaged are determined in advance, it is not necessary for the subject to intentionally move his eyes. Specifically, by changing the scanning position of the illumination light 105 by the scanners 109-1 and 109-2 based on the information on the scheduled imaging positions, it is possible to automatically perform imaging at a plurality of positions. Further, even when a position different from the photographer's intention is captured, the imaging position can be adjusted using the steering function.

  In this embodiment, this steering operation is executed using the steering operation button 714. The imager can change the imaging position in two directions such as XY on a plane orthogonal to the eye axis of the eye 111 by clicking this button (arrow part). This change in the imaging position is reflected in the position of the AO-SLO imaging frame 900 (900-1, 3) in the WF-SLO still image display screen 705. That is, by this steering operation, the AO-SLO imaging frame 900 is changed from the position of the frame 900-1 to the position of the frame 900-3, for example.

  The AO-SLO focus adjustment buttons 712 and 713 are buttons for adjusting the focus of the AO-SLO. By clicking this button, the focus position of the illumination light 105 on the fundus can be changed. In this embodiment, an offset is given to the focus component of the wavefront correction device 108 in accordance with this operation. Thereby, it is possible to image a layer intended by the imager, such as a layer of photoreceptor cells in the fundus or a layer of blood vessels. In this embodiment, the wavefront correction device 108 is mainly used for focus adjustment. However, the position adjustment of the eyepiece 110 may be performed by these buttons, and focus adjustment may be performed by this. Moreover, you may combine these structures.

  On the AO-SLO still image display screen 706, an AO-SLO still image created based on the AO-SLO moving image for a predetermined time is displayed. This predetermined time is designated by inputting a numerical value to the AO-SLO recording time instruction unit 715. When the AO-SLO recording start button 716 is clicked, this recording is started and a moving image for the instructed time is recorded. The AO-SLO still image is created by superimposing the frames of the moving image, and the random noise contained in each frame is canceled out, thereby reducing the random noise. This superimposed image becomes a still image by AO-SLO and is displayed on the AO-SLO still image display screen 706 on the image 700.

  Next, the flow of the photographer's operation, apparatus processing, and screen display will be described with reference to FIG. 11 showing a flowchart of the entire processing in the fundus imaging apparatus according to the present embodiment. In the figure, the left column indicates the operation of the photographer, the middle column indicates the processing of the apparatus, and the right column indicates the screen display.

  First, in step S1301, the imaging program is activated by the control unit 117 after the photographer turns on the power of the apparatus. Next, in step S1302, the control unit 117 performs operations of starting up the apparatus, displaying a fixation target, starting WF-SLO imaging, and starting AO-SLO imaging. Note that the start-up process includes an operation of starting imaging of an anterior ocular segment image using a fundus camera (not shown) described above.

  Immediately after these processes, in step S1303, each of the images on the anterior segment display screen 701, fixation target position screen 702, WF-SLO real time display screen 703, and AO-SLO real time display screen 704 on the display 118 is displayed. Display is executed. In each of these screens, the image update is continued until step S1320, which is the final step in the flowchart.

  In step S1304 after step S1303, the photographer can refer to the eyepiece unit of the apparatus enabled by a position adjustment mechanism (not shown) while referring to the anterior segment image displayed on the anterior segment display screen 701. Adjust the position with the eye to be examined. The position adjustment mechanism is exemplified by a joystick, for example, but other known means may be used. In subsequent step S1305, when the photographer clicks an activation button 708 that activates the autofocus function, in step S1306, the fundus imaging apparatus starts WF-SLO autofocus.

  After autofocusing is completed, the photographer clicks the WF-SLO recording start button 709 in step S1307. In response to this operation, in step S1308, the fundus imaging apparatus again performs WF-SLO autofocus, and after the operation ends, a WF-SLO still image is acquired. This WF-SLO still image is displayed on the WF-SLO still image display screen 705.

  At the same time, a tracking operation (tracking) described later is started. In step S1309, the WF-SLO still image is displayed on the WF-SLO still image display screen 705. In addition, the tracking ON button 710 lights up along with this display operation to notify the operator that tracking is ON.

  In step S1310, the position on the fundus to be imaged by AO-SLO by moving and clicking the index on the fixation target position screen 702 by the photographer or by moving and clicking the index on the WF-SLO still image display screen 705. Is specified. In step S1311, the fundus imaging apparatus changes the fixation target presentation position corresponding to this position designation. At this time, the auto focus in the WF-SLO 201 is performed again so that the focus follows the desired layer, and the focus state is also tracked.

  In step S1312, the photographer operates the steering operation button 714 while viewing the display image on the WF-SLO still image display screen 705, the AO-SLO imaging frame 900 superimposed on the display image, and the AO-SLO real-time display screen 704. Click. By this click, the AO-SLO imaging position is adjusted. In accordance with this operation, the AO-SLO focus adjustment buttons 712 and 713 are clicked to adjust the focus position of the AO-SLO. Further, in response to these operations, in step S1313, the fundus imaging apparatus changes and adjusts the AO-SLO imaging position and focus state.

  After these adjustments, when the photographer clicks the AO-SLO recording start button 716 in step S1314, the fundus imaging apparatus reduces the angle of view and narrows the pixel pitch to obtain a high-definition image in step S1315. . Thereafter, the operations of changing the AO-SLO imaging position, acquiring the AO-SLO image, aligning the AO-SLO image, and displaying the AO-SLO still image in steps S1316 to S1319 are repeated. As described above, the change of the imaging position using the steering operation, the still image recording by AO-SLO, the alignment of the captured images, the combination of the images after alignment, and the display of the still image by AO-SLO are repeated. When the repetition of these imaging operations is completed, a series of imaging is completed in step S1320.

  Next, a change in the position of the imaging region in the fundus that moves continuously with the movement of the eye is detected, the direction of the illumination light is changed so as to correct this change in position, and the imaging position (the illumination light A tracking function for correcting (scanning position) will be described.

  First, the processing procedure when the conventional tracking function is operated will be described with reference to the flowchart shown in FIG. The processing described here is controlled and executed by the tracking control unit 202.

  In step S100, a fundus tracking program for operating the tracking function is started. In subsequent step S101, a reference image 305 obtained by imaging the entire WF-SLO image shown in FIG. 2 is acquired using the WF-SLO 201. In step S102, the detected image 306-1 is acquired using the WF-SLO 201. In this example, the detected image 306-1 is a partial region of the WF-SLO image (reference image 305). After obtaining the detected image 306-1, in step S103, a relative displacement between the reference image 305 and the detected image 306-1 is detected. The detection algorithm uses a phase only correlation method.

  In this example, the phase only correlation method is used, but any other detection algorithm may be used. The detection result of the relative displacement is obtained as a detection value ΔX in the X direction (horizontal direction of the fundus) and a detection value ΔY in the Y direction (vertical direction of the fundus) in FIG. In the tracking operation in the AO-SLO, these detection values are used not for correcting the measurement light irradiation position in the WF-SLO but for correcting the measurement light irradiation position in the AO-SLO. In step S104, the detected ΔX is commanded as a correction value for position correction when the AO-SLO scanner 109-1 irradiates the illumination light 105 to the fundus, and ΔY is used for position correction of the AO-SLO scanner 109-2. Command as a correction value. Thereby, the imaging position of the AO-SLO is corrected in both the X direction (horizontal direction of the fundus) and the Y direction (vertical direction of the fundus) with respect to the eye movement, and the imaging position can be tracked.

  When the process in step S104 ends, the flow moves to step S102, and this tracking operation is repeated. In this repetition, the detected images are successively changed in the order indicated by the detected images 306-2, 306-3, 306-4, and 306-5. When the processing on the detected image 306-5 is completed, the image acquisition position is returned to the base so that the image corresponding to the detected image 306-1 becomes a new detected image. Thereafter, image acquisition at positions corresponding to the detected images 306-2, 3, 4, and 5 and subsequent processing are sequentially executed. That is, the operation of changing the position of the detected image 306 is sequentially repeated for each of the detected images 306-1 to 306-5.

  In the example described here, when the frame update period of the WF-SLO image is T, the detection of the shift of the imaging position and the position correction command for the irradiation position of the illumination light 105 in the AO-SLO are transmitted during the update period T. Can be done 5 times. Rather than using an image in the same imaging range as that of the reference image 305 as the detected image, the detected image 306 is made a part of the WF-SLO image in this way, so that a misalignment detection and position correction command can be issued. The frequency per unit time of output can be increased. As a result, the effect of shortening the time delay when tracking the eye movement is obtained, and the effect of reducing the tracking residual with respect to the eye movement is obtained.

  In parallel with the repetition of the operations from step S102 to S104, an AO-SLO image using AO-SLO is acquired. If the tracking function described above operates normally and the irradiation position of the illumination light 105 by the scanners 109-1 and 10-2 follows the movement of the eye, an AO-SLO image is acquired using ΔX and ΔY. The irradiation position is corrected as appropriate. Therefore, a good AO-SLO image can be obtained. The above-described repetition is performed until an AO-SLO image is acquired, and the fundus tracking program is terminated in step S105.

Here, the conventional tracking function will be described in detail.
FIG. 4 is a diagram schematically illustrating the relationship between the eye movement 400, the AO-SLO image capturing range 500, and the AO-SLO image capturing angle of view 501. In the figure, the locus of the eye movement 400 is schematically represented by an arrow. Actually, the point at the position A in the fundus of the eye to be examined (the center of the imaging angle of view 501A) moves on the observation screen along this arrow. On the other hand, the AO-SLO imaging optical system or the like does not move with respect to the eye to be examined, and thus the imageable range 500 does not move.

  Here, the involuntary eye movement 400 includes a trema 401, a drift 402, a flick 403, and a saccade 404. The trema 401 is a high-frequency movement of a very small amplitude of the eye to be examined. The drift 402 is a small smooth movement of the eye to be examined. The flick 403 is a small jumping movement of the eye to be examined. The saccade 404 is also referred to as a jumping movement, and is a large jumping movement of the eye to be examined.

  A range 500 that can be imaged by AO-SLO is L × L on the fundus in FIG. When an image outside this range 500 is obtained by the configuration of the optical system, the image information of the reflected light from the fundus is partially lost, so-called vignetting occurs, or based on light that has passed through a portion where the aberration of the optical system is large. Imaging occurs. As a result, significant image quality degradation can occur in the generated image. In the example shown here, the imaging field angle 501 in AO-SLO has a size of M × M on the fundus.

  In the conventional tracking function, when the fundus tracking program in step S100 is started, the WF-SLO image acquired in step S101 immediately after that becomes the reference image 305. At that time, fixation of the eye to be examined is prompted by the presentation of a fixation target (not shown), and the reference image 305 is obtained as an image of a substantially central portion in a desired range on the fundus. The imaging position where the image is to be obtained by AO-SLO at the time of acquiring the reference image is a point within the imaging angle of view 501A by presentation of the same fixation target, more ideally the position where the center of the imaging position is the point A. The following tracking program is executed on the assumption that the reference image 305 is acquired and the AO-SLO imaging position is the angle of view 501A.

  However, in reality, the position of the eye movement 400 at the moment of acquiring the reference image is indefinite. That is, when the reference image 305 is acquired, there is a possibility that the imaging angle of view to be imaged in the AO-SLO may deviate from the position of the intended angle of view 501A due to involuntary movement. Specifically, the imaging center is not the position of the point A, but the position of the point B (view angle 501B), the position of the point C (view angle 501C), or the position of the point D (view angle) shown in FIG. 501D). That is, the WF-SLO image obtained in the state where the imaging angle of view 501 from which an image is to be obtained exists at the position of point B or point C may be set as the target position of the tracking program as a reference image. It can actually happen.

  In this case, the photographing frame determined on the WF-SLO 201 and AO-SLO apparatus side does not move, but the fundus region existing in the frame moves due to saccade or the like. Therefore, when the saccade is generated, the center of the imaging field angle captured by the AO-SLO is an imageable range 500 that is determined based on the WF-SLO image acquired with respect to the region of the fundus that is not originally intended due to the occurrence of the saccade. The position of the point A at. As a result, the fundus region corresponding to the angle of view 501A originally intended to be obtained protrudes outside the range 500 that can be imaged by AO-SLO, and good tracking is not performed. In addition, since an image is generated based on the obtained image information in the protruding area, the image quality is significantly deteriorated. Here, when tracking is to be performed with high accuracy, the value of L, which is the size of the imageable range 500, is made relatively small with respect to M of the size of the imaging angle of view 501 in order to perform finer position correction. Is also possible. However, when the ratio of the dimension M of the imaging angle of view 501 to the dimension L of the imageable range 500 is large, the frequency of occurrence of the problem of the projection of the angle of view described here increases.

  Further, as described above, the AO-SLO has a function called steering for adjusting the imaging location. As described above, the steering is a function of arbitrarily adjusting the imaging position by superimposing an offset value on the irradiation position of the illumination light 105 by the scanners 109-1 and 109-2. When the imaging positions of a plurality of positions to be imaged are determined in advance, the irradiation position of the illumination light 105 by the scanners 109-1 and 109-2 can be changed by steering based on the information on the imaging positions. Therefore, it is possible to automatically perform imaging at a plurality of imaging positions by changing the positions of the scanners 109-1 and 109-2 without intentionally moving the eyes of the subject. Further, even when a position different from the photographer's intention is captured, the imaging position can be adjusted using the steering function.

  However, for example, when the reference image 305 of the WF-SLO image is set at the position of the point D in the eye movement 400, an allowable amount of irradiation position adjustment that can be performed in combination with steering in the Y direction and tracking in the figure. Is limited to the amount of H in the figure. Here, assuming that the position in the Y direction in the figure at the position of the point D is J, the equation H = (LM) / 2−J is established.

  For example, it is assumed that the dimension M in the Y direction of the imaging angle of view is 50% of the dimension L and the dimension J in the Y direction is 20% of the dimension L with respect to the dimension L in the Y direction of the imageable range. In this case, the allowable amount H of correction of the illumination light irradiation position combining the steering and tracking is as small as 5% of the dimension L in the Y direction in the imageable range.

  The tracking function used in the present embodiment in consideration of the above will be described next. FIG. 5 is a flowchart illustrating a processing procedure during operation of the tracking function according to the present embodiment. The series of processes shown in the figure is controlled and executed by the tracking control unit 202.

  Here, the characteristic part of the present embodiment is the processing executed in steps S202 to S206. Specifically, the feature of this embodiment is that the eye movement is detected and stored as data, the approximate center position of the eye movement is calculated, and this center position is set as the target position during the operation of the tracking function. There is.

  Hereinafter, each process in the flowchart will be described. In step S200, a fundus tracking program for operating the tracking function is started. In subsequent step S201, a reference image 305 obtained by imaging the entire WF-SLO image shown in FIG. 2 is acquired using WF-SLO201. In step S202, the detected image 306-1 is acquired. In this embodiment, the detected image 306-1 is a partial region of the WF-SLO image (reference image). After obtaining the detected image 306-1, in step S203, a relative positional shift between the reference image 305 and the detected image 306-1 is detected. The detection algorithm uses a phase only correlation method.

  That is, in step S201, an image in a predetermined imaging range corresponding to the reference image 305 on the fundus oculi to be examined is acquired as a reference image for measuring the movement of the fundus. This operation is executed by various configurations that function as acquisition means including the WF-SLO 201 and the control unit 117. In step S202, a plurality of detected images 306-1 to 306-5, which are acquired at different times, are acquired as regions included in a predetermined imaging range. This operation is also executed by various configurations including the WF-SLO 201 and the control unit 117. Here, the detected image is obtained by dividing the reference image 305 into a plurality of strips arranged in the Y direction, but the extraction pattern of the detected image is not limited to this. The detected image is extracted and acquired from the region of the predetermined imaging range in a time-sharing manner, and images in the same region may not be obtained continuously at that time. In step S203, a positional deviation between the reference image 305 and each of the detected images is detected. This operation is executed by a configuration that functions as a deviation detection unit in the control unit 117.

  In the present embodiment, the phase only correlation method is used, but any other detection algorithm may be used. The detection result of the relative displacement is obtained as a detection value ΔX in the X direction (horizontal direction of the fundus) and a detection value ΔY in the Y direction (vertical direction of the fundus) in FIG. In step S204, the detected values ΔX and ΔY are stored in a predetermined data storage area of the tracking control unit 202. After the storage, the flow returns to S202, and the next detected image 306-2 is acquired. Thereafter, in steps S203 and S204, the same operation as that of the detected image 306-1 is executed. That is, the operations of steps S202 to S204 are repeated while changing the range of the detected image 306, and eye movement data is accumulated in the data storage area. The accumulation period and number of times may be arbitrary, for example, 1 second or 100 sampling.

  After storing an arbitrary number of data, in step S205, the approximate center position in the X direction and the Y direction in FIG. 4 is calculated from the data of the relative displacement. That is, the center position of the shift in the reference image 305 is calculated by performing statistical processing, which will be described in detail later, on the position shift detected in step S204. This operation is executed in a configuration that functions as a calculation unit in the control unit 117 and the tracking control unit 202.

  Note that the calculation algorithm in the statistical processing used when calculating the coordinates of the substantially center position in the present embodiment is an averaging process. However, although the averaging process is used in the present embodiment, any arithmetic algorithm may be used as long as the approximate center position is obtained. For example, the median value may be calculated, the mode value may be calculated, the median rank may be adopted, and the root mean square may be used. The position may be integrated by the staying time and averaged. Further, any filter may be applied in each calculation. Insert spatial filter processing, temporal filter processing, absolute value of the detected value, cut-off filter processing, bandpass filter processing, and moving average processing for frequency components. May be. That is, by performing these calculations based on statistical processing on the accumulated relative position or relative positional deviation data, the position of the point A in the eye to be examined as the approximate center of the eye movement in FIG. Can be specified.

  After specifying the position of the point A, in step S206, the target position in the tracking operation is set to X0 for the X coordinate and Y0 for the Y coordinate. That is, the reference image in the subsequent tracking operation is set to the entire WF-SLO image centered on X0 and Y0. Thereby, the target position of the tracking function is set to the approximate center of eye movement. A range 500 where the fundus of the AO-SLO image can be captured is specified in the XY coordinate system based on the coordinate center (X0, Y0) in the reference image. At that time, the designated coordinate is designated as the position of the point A that is the center of the imageable range 500 and the center of the imaging angle of view 501A. Therefore, the initial image acquisition position in the case of correcting the position as needed when an image is acquired in AO-SLO is an image obtained at the imaging angle of view 501A.

  Thereafter, the detected image 306 is acquired in step S207, and the relative position between the reference image 305 and the detected image 306 generated around the target position is calculated in step S208. This calculation method uses a phase-only correlation method. The detection algorithm may be any other method. In other words, after step S207, after the center position is obtained by calculation, the image acquisition position (illumination light irradiation position) is corrected based on the detected image 306 obtained thereafter and the center position. This operation is executed by a configuration that functions as an acquisition position correction unit in the tracking control unit 202. The detection result of the relative position is a detection value ΔX in the X direction (horizontal direction of the fundus) in FIG. 2 and a detection value ΔY in the Y direction (vertical direction of the fundus).

  In step S209, ΔX + X0 is commanded as the irradiation position of the illumination light 105 by the corrected scanner 109-1, and ΔY + Y0 is commanded as the irradiation position of the illumination light 105 by the scanner 109-2. As a result, the tracking position of the AO-SLO imaging position can be executed in both the X direction (horizontal direction of the fundus) and the Y direction (vertical direction of the fundus) with respect to the eye movement. When step S209 ends, the flow returns to step S207, and the operations of steps S207 to S209 are repeated. At this time, the position of the detected image 306 is changed in 306-1 to 306-5, and the tracking operation is repeated according to each image acquisition.

  This operation is the same as the conventional tracking function. In this embodiment, the image used as the reference image is different from the conventional one. Thus, the effect obtained by the operation obtained by finely dividing the detected image in the reference image is the same as the conventional tracking function. That is, the effect of shortening the time delay when tracking the eye movement and reducing the tracking residual with respect to the eye movement can be obtained.

  In parallel with the repetition of the operations from step S207 to S209, an image is acquired using AO-SLO. According to the present embodiment, the tracking function works after setting the imaging angle of view 501 to be imaged at substantially the center position of the photographic range 500 in which an AO-SLO image with good image quality can be stably obtained. The tracking function works effectively on the movement of the eye, and a good AO-SLO image is obtained.

  After acquiring the desired AO-SLO image, it is not necessary to perform tracking, and the fundus tracking program is terminated in step S210.

Here, the effect of the tracking function used in the present embodiment will be described.
As described above, in the conventional tracking function, the WF-SLO image obtained at the position of the point D in the eye movement 400 may be set as the reference image 305. In this case, the allowable amount of position correction combining the steering and tracking in the Y direction in FIG. 4 is limited to the amount of H in the figure. With the tracking function used in the present embodiment, an image for determining the target position in WF-SLO is obtained when the eye movement is at the position of point A in FIG. Is possible.

  In this case, the allowable amount for correcting the irradiation position of the illumination light 105 combining the steering and tracking in the Y direction in FIG. 4 can be expanded to the amount I in the drawing. That is, the formula of I = (LM) / 2 is established. In the conventional tracking function, H = (LM) / 2−J. Therefore, according to the tracking function according to the present embodiment, the above-described allowable amount including the steering and the tracking is J (= I−H). Just expanding.

  For example, it is assumed that the dimension M in the Y direction of the imaging field angle is 50% and the dimension J that is the allowable amount in the Y direction is 20% of the dimension L in the Y direction of the imageable range 500. In this case, with the conventional tracking function, the allowable amount H of position correction combined with steering and tracking is as small as 5% of the dimension L. On the other hand, when the tracking function of the present invention is applied, the position correction allowable amount I that combines the steering and the tracking can secure 25% of the dimension L. In AO-SLO, the above-described offset amount is added to the calculated center position of the WF-SLO reference image to set the position of the image to be acquired within the reference image in a predetermined range. In this case, according to the present embodiment, it is possible to execute the tracking and offset operations with sufficient room.

  In the above-described effects, only the effects in the Y direction in FIG. 4 are described. However, in this embodiment, the target position of the tracking function can be set to the approximate center of the eye movement in the X direction. Accordingly, it is possible to increase the allowable amount of position correction of the irradiation position of the illumination light combined with steering and tracking in the X direction, and the same effect as in the Y direction can be obtained.

  Here, the imaging range is limited depending on the configuration of the optical system of the apparatus. If this range is exceeded, the image information of the reflected light from the fundus will be lost, or the image will be imaged based on the light that has passed through the part where the aberration of the optical system is large. End up. As an object of the present invention, when an image when the eye moves greatly is set as a reference image, and a target position for tracking is set for the image, the target position is out of the imageable range. End up. When the target position is set in such a limited range that can be imaged by the apparatus, vignetting is larger than expected, information with large aberrations is extremely increased, and the like is naturally good. No image can be obtained.

  On the other hand, as described above, in this embodiment, information on the position of the approximate center of fixation fixation is obtained, the position of the approximate center is set as the tracking target position, and an image of the intended imaging position is thereby obtained. It is possible to get. Therefore, the image capturing range can be surely kept within the image capturing range of the apparatus, and as a result, problems such as vignetting and image quality degradation can be avoided. That is, with the configuration according to the present embodiment, it is possible to suppress image quality degradation that may occur when the tracking target position is set based on the position when the eye moves greatly.

  In the embodiment described above, the acquisition of the fundus image, the detection of the positional deviation from the detected image, and the calculation of the center position are executed based on the image acquired by the WF-SLO 201. Further, the correction of the image acquisition position in the AO-SLO as the second image acquisition means is performed using the center position and the detected image obtained after the calculation of the center position.

[Example 2]
The second embodiment is the same as the first embodiment, and detects the position change of the imaging region in the fundus that moves continuously with the eye movement, and changes the direction of the illumination light so as to correct this position change. A tracking function for correcting the imaging position on the fundus is provided in the fundus imaging method and apparatus.

  Hereinafter, the difference between the second embodiment of the present invention and the first embodiment will be mainly described. In this embodiment, when obtaining the coordinates (X0, Y0) for the reference image originally obtained in Embodiment 1, the image quality of the reference image used for obtaining the relative position after setting the target position is simultaneously improved. It is different in the point to keep. The configuration of the fundus imaging apparatus according to the second embodiment is the same as the apparatus configuration of the first embodiment, and a description thereof is omitted here. Hereinafter, the present embodiment will be described with reference to FIG. 6 which is a flowchart showing a processing procedure when the tracking function is operated.

  In step S300, a fundus tracking program for operating the tracking function is started. In subsequent step S301, a reference original image equivalent to the reference image 305 obtained by imaging the entire WF-SLO image shown in FIG. 2 is acquired using the WF-SLO 201. In the present embodiment, since the reference image of the first embodiment is determined based on these images after the acquisition of the original image as the reference image is repeated, the image acquired in step S301 is referred to as the reference original image below. Called.

  In step S302, it is determined whether or not the image quality of the acquired reference original image is good. If the image quality is poor, the flow returns to step S301 because the acquired image is not suitable for the reference original image, and the reference original image is reacquired. The operations in steps S301 and S302 are repeated until a good reference original image is obtained. In step S305, which will be described later, the relative position is calculated. If the image quality of the reference original image is defective at that time, the accuracy of the relative position calculation is poor. In the present embodiment, in order to prevent the occurrence of this accuracy failure, an image having an appropriate image quality is selected and extracted using an image quality index.

  In this embodiment, the image quality is determined based on whether or not the average luminance of the reference original image is equal to or higher than a predetermined value. However, the determination of image quality is not based on this method, and in addition to this, it may be determined whether the amount of contrast, histogram or noise is good, or other image quality index may be used.

  When a reference original image having an image quality higher than the reference is obtained, the flow proceeds to step S303, and this reference original image is stored. In subsequent step S304, the detected image 306-1 is acquired in the same manner as in step S202 of the first embodiment. In step S305, the relative displacement of the detected image 306-1 with respect to the reference original image is calculated. The relative displacement is obtained as a detected value ΔX in the X direction (horizontal direction of the fundus) and a detected value ΔY in the Y direction (vertical direction of the fundus) in FIG. In step S <b> 306, ΔX and ΔY, which are the calculated relative displacement amounts, are stored in a predetermined data storage area of the tracking control unit 202.

  After the deviation amount is stored, it is determined in step S307 whether or not the relative positional deviation has been sufficiently calculated. In this embodiment, the determination is made based on whether or not the number of calculations is equal to or greater than a predetermined amount.

  Note that the criterion for determination is not limited to the number of calculations, and may be another criterion. For example, it may be determined based on whether or not a predetermined time calculation has been performed, or may be determined based on whether the time frequency of the relative position covers a predetermined range of time frequencies. Alternatively, another criterion for better capturing eye movement may be used.

  If it is determined in step S307 that the relative displacement calculation is still insufficient, the flow returns to step S304, and the operations in steps S304 to S307 are repeated. At this time, as in the first embodiment, the detected image 306-1 is changed to an image at the position of the detected image 306-2.

  If it is determined in step S307 that the relative displacement has been sufficiently calculated, the flow proceeds to step S308. In step S308, it is determined whether the number of reference original images stored is sufficient. In steps S310 and S311, which will be described later, the relative positions of the plurality of reference original images are corrected, and a group of these reference original images is superimposed. At this time, the reference original image to be used needs to have a number enough to reduce random noise. In this embodiment, when the number of reference original images stored satisfies the condition of 16 or more, the flow proceeds to step S309. If the condition is not satisfied, the flow returns to step S301, and the operations of steps S301 to S308 are repeated until the condition is satisfied.

  In step S309, the relative positional deviation between the stored reference original images is calculated. In step S310, based on the calculation result in step S309, the relative positional deviation between the reference original images is corrected, and an overlay process is performed. Thereby, the random noise which each reference | standard original image has cancels, and noise reduction is realizable. In step S311, an image obtained by performing the overlay process is set as a reference image.

  As a result, it is possible to use a reference image in which noise is reduced and image quality is improved when calculating a relative positional shift between a reference image and a detected image performed in step S315 described later. Therefore, the accuracy of calculation of relative positional deviation is improved.

  Subsequent operations performed in steps S314 to S317 are the same as the operations performed in steps S207 to S210 in the first embodiment. Therefore, the description thereof is omitted here.

  In this embodiment, the reference original image is aligned and then superimposed to reduce random noise. As a result, a reference image is obtained. However, even if the alignment is omitted, the effect of improving the image quality of the reference image can be obtained although the effect of reducing random noise is reduced by performing the overlapping process.

[Example 3]
The third embodiment is the same as the first embodiment, and detects the position change of the imaging region in the fundus that moves continuously with the eye movement, and changes the direction of the illumination light so as to correct this position change. A tracking function for correcting the imaging position on the fundus is provided in the fundus imaging method and apparatus. In the third embodiment, these tracking functions are utilized to efficiently acquire a plurality of AO-SLO images, thereby obtaining a composite image in a relatively short time.

  Embodiment 3 of the present invention will be described below. The present embodiment is characterized by the imaging procedure at the steering described in the first embodiment and the reference image setting method in the fundus tracking program related thereto. The configuration of the fundus imaging apparatus according to the third embodiment is the same as the apparatus configuration of the first embodiment, and a description thereof is omitted here.

FIG. 7 schematically shows the angle of view of the AO-SLO image obtained in this embodiment.
With respect to the angle of view 600 for one AO-SLO imaging, the imaging region is moved using the steering to perform imaging at four locations (imaging at angles of view 600-1 to 600-4). The angles of view 600-1 to 600-4 overlap in a region 602 in the drawing. The combined image 601 is obtained by aligning the angles of view 600-1 to 600-4 using the image in the region 602 and combining the images. The combined image 601 is presented on the display 118. By combining such images, an AO-SLO image having a wider angle of view can be obtained. In the present embodiment, a fundus tracking program that operates the tracking function described in the first embodiment is used when each field angle 600 is imaged. More specifically, every time the imaging position is switched, a reference image and a target position used in the tracking operation are sequentially set.

  Hereinafter, the present embodiment will be described with reference to FIG. 8 which is a flowchart showing a processing procedure when the tracking function is operated. In addition, about the step similar to each step of the tracking process in Example 1 shown in FIG. 5, the same reference number is attached and detailed description here is abbreviate | omitted.

  The operations performed in steps S200 to S209 in the present embodiment are the same as the operations in the first embodiment. While the operations in steps S207 to S209 are repeated, the irradiation position of the illumination light 105 for acquiring the AO-SLO image by the scanners 109-1 and 109-2 is corrected with the position of the point A in FIG. Has been done.

  In this state, the shooting position (view angle 600) is set in step S211. In step S212, for example, the offset amounts of the scanners 109-1 and 109-2 are calculated so as to correspond to the angle of view 600-1 that is the set photographing position, and the calculation result is reflected in the position command for each. The In the calculation at this time, it is preferable to reflect the change in the photographing position due to the aberration of the optical system.

  After the scanners 109-1 and 109-2 change the irradiation position of the illumination light 105 according to the position command, the fundus image is captured at the set imaging angle of view 600-1 in step S213. In step S214, it is determined whether imaging at all imaging positions has been completed. In the case of the present embodiment, it is determined whether or not the imaging at all the imaging positions shown in FIG. 7 (imaging angle of view 600-1 to 600-4) has been completed. If not completed, the process returns to step S211, the imaging position is changed to the next position, and then the operations in steps S211 to S213 are repeated. If it is determined in step S214 that all the imaging positions (view angle 600) have been imaged, the flow proceeds to step S215.

  In step S215, all the acquired images (view angles 600-1 to 4) are subjected to image processing and combined to generate a combined image 601. After the combined image 601 is generated, the flow moves to step S210 and ends the tracking program.

  According to the present embodiment, images at four imaging positions are captured, and the setting of the reference image and the setting of the target position of the tracking function are performed once. Therefore, the processing cost is lower and the total imaging time is shorter than the method of performing these for every four locations. Thereby, the restraint time concerning imaging of a subject can be made small.

[Example 4]
As in the third embodiment, the fourth embodiment also utilizes the tracking function to efficiently acquire a plurality of AO-SLO images, thereby obtaining a composite image in a relatively short time. The present embodiment differs from the third embodiment in that the reference image and the target position determined in the tracking operation are reset every time the imaging position (view angle 600) is changed.

  Hereinafter, the present embodiment will be described with reference to FIG. 9 which is a flowchart showing a processing procedure when the tracking function is operated. In addition, about the step similar to each step of the tracking process in Example 3 shown in FIG. 8, the same reference number is attached and detailed description here is abbreviate | omitted.

  In this embodiment, after the AO-SLO image is captured at a predetermined position (corresponding to the view angle 600-1) in step S213, all the image capture positions (view angles 600-1 to 600-4) are captured in step S214. It is determined whether the imaging of () is completed. If not completed, the flow returns to step S211, changes the imaging position to a position corresponding to the next angle of view, and repeats the operations after step S211. At this time, the reference image is acquired and the target position is reset by the tracking function by the operations in steps S201 to S206.

  If the time elapses after setting the reference image, the image quality of the WF-SLO image changes, and the influence of the influence may decrease the position detection accuracy. In this embodiment, compared to the case of the third embodiment, an effect of improving the accuracy of position detection is obtained by using a temporally recent reference image at the timing of capturing an AO-SLO image. Similarly, it is possible to obtain recent information on eye movement, and the effect of shortening the time required for the tracking operation can be expected.

[Other Examples]
In the above-described embodiment, two galvano scanners 109-1 and 109-2 are used for the main scanning and the sub-scanning as scanners operated by the tracking function, and the irradiation position of the illumination light 105 by these is changed.

  In contrast, there is an example in which a resonance scanner is used as a main scanning scanner. While the resonant scanner has a high scanning speed, it can only reciprocate with a predetermined period and cannot move according to various frequencies of eye movement (including DC components). For this reason, there is an example in which a galvano scanner operating in the main scanning direction is added for the tracking function. Also in this configuration, the same effect can be obtained by applying the configuration and method of the above-described embodiment.

  In addition, there is an example in which alignment (also referred to as registration) is performed by image processing after acquiring an image in order to correct an eye movement component that could not be removed by the tracking function. As a result, the relative position shift between the images can be reduced, and a phenomenon such as blurring of the image due to the position shift when the images are superimposed can be prevented.

  In the embodiment described above, the acquisition of the fundus image, the detection of the positional deviation from the detected image, and the calculation of the center position are executed based on the image acquired by the WF-SLO 201. Further, the correction of the image acquisition position in the AO-SLO as the second image acquisition means is performed using the center position and the detected image obtained after the calculation. However, acquisition of a reference image or the like can be performed by an apparatus that obtains various fundus images regardless of WF-SLO, and the second image acquisition unit is not limited to AO-SLO. In addition, although an example has been given as AO-SLO of a scanning laser ophthalmoscope that scans illumination (measurement) light, the present invention can also be applied to OCT that can acquire an optical coherence tomographic image. That is, the same effect can be obtained by additionally providing the OCT with a WF-SLO to provide the tracking function of the present invention.

  The present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the case where the object to be inspected is the fundus of the eye to be inspected is described. In addition, even for an inspected object such as skin or organ other than the eye to be examined, it may be configured to acquire a high-definition, narrow-angle image for acquisition and tracking. The present invention can be applied. In this case, the present invention has an aspect as a medical device such as an endoscope other than the ophthalmologic apparatus. Therefore, it is desirable that the present invention is grasped as an inspection apparatus exemplified by an ophthalmologic apparatus, and the eye to be examined is grasped as one aspect of the object to be examined.

  In addition, the present invention provides a program code of software that realizes the functions of the above-described embodiments (for example, processing shown by a flowchart in which the processing of each unit described above is associated with each process), or a storage medium that records the program code. This can also be realized by supplying the system or apparatus. In this case, the above-described functions can be realized by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium so that the computer can read it. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

101: light source 108: wavefront correction device 109: scanning optical system 111: eye to be examined 114: light intensity sensor 115: wavefront measuring device 116: adaptive optics control unit 117: control unit 201: WF-SLO
202: Tracking control unit 305: Reference image 306: Image to be detected

Claims (11)

Obtaining an image of a predetermined imaging range of the inspection object as a reference image for measuring the movement of the inspection object;
Detecting a positional deviation between a plurality of detected images acquired at a time different from the step of acquiring the reference image and the reference image;
Calculating the center position of the positional deviation by performing statistical processing on the positional deviation detected by the step of detecting the positional deviation;
And a step of correcting an acquisition position of an image of the inspection object based on the center position and the detected image obtained after the step of calculating the center position.   The imaging method according to claim 1, further comprising a step of superimposing a group of images of the inspection object to obtain the reference image.   3. The method according to claim 2, further comprising: calculating a deviation amount of each relative position in the group of images to correct the deviation amount, wherein the superimposing step is performed after the correcting step. Imaging method.   The imaging method according to claim 2 or 3, wherein the group of images includes images extracted from a plurality of images of the inspection object using an image quality index.   The imaging according to claim 1, further comprising: adding an offset amount to the center position to set a position of an image to be acquired within the predetermined imaging range. Method.   The step of obtaining an image of the inspection object includes a step of scanning illumination light on the inspection object, a step of detecting the intensity of reflected light of the illumination light from the inspection object, and the intensity based on the intensity. 6. The imaging method according to claim 1, further comprising: generating an image.   The imaging method according to claim 6, comprising: detecting a wavefront distribution of the reflected light; and correcting the wavefront distribution.   A program for causing a computer to execute each step of the imaging method according to any one of claims 1 to 7. Image acquisition means for acquiring an image of a predetermined imaging range of the inspection object as a reference image for measuring the movement of the inspection object;
A plurality of detected images acquired at a time different from the acquisition unit acquired as the reference image, and a shift detection unit that detects a positional shift between the reference image,
Arithmetic means for performing a statistical process on the positional deviation detected by the deviation detecting means to calculate the center position of the positional deviation;
An imaging apparatus comprising: an acquisition position correction unit that corrects an acquisition position of an image of the inspection object based on the center position and the detected image obtained after the calculation unit. A second image acquisition means for acquiring a second image different from the image acquisition means;
The acquisition position correction unit corrects the acquisition position of the second image based on the center position and the detected image obtained after the calculation of the center position. Imaging device. The object to be examined is the fundus of the eye,
The image acquisition means acquires the reference image of the predetermined imaging range on the fundus and a detected image that is an image of an area obtained by dividing the predetermined imaging range into a predetermined number;
11. The second image acquisition unit according to claim 10, wherein the second image acquisition unit scans illumination light on the fundus to obtain a higher-definition image than the reference image with an angle of view narrower than the predetermined imaging range. Imaging device.

Images