JP2019187798A - Image processing apparatus and control method thereof - Google Patents

Abstract

To allow for efficient generation of a high-resolution motion contrast images corresponding to various blood flow velocities.SOLUTION: An image processing apparatus is provided that acquires a motion contrast image using a plurality of images of an object to be measured which are generated on the basis of a return light of measurement light obtained by irradiating the object to be measured with measurement light. The image processing apparatus comprises: setting means setting an interval between a plurality of images; generating means generating a motion contrast image using images which are based on the set interval; and control means outputting the generated motion contrast image to output means.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image processing apparatus and a control method therefor, and more particularly, to an image processing apparatus that processes a fundus image of a subject eye and a control method therefor.

  In recent years, as an ophthalmologic photographing apparatus, scanning laser opthalmoscope (SLO) that irradiates laser light two-dimensionally on the fundus and receives the return light to form an image, and interference of low coherence light. Utilized imaging devices have been developed. An imaging device using low-coherence light interference is called OCT (Optical Coherence Tomography), and is used particularly for the purpose of obtaining a tomographic image of the fundus or its vicinity. Various types of OCT have been developed, including TD-OCT (Time Domain OCT: Time Domain Method) and SD-OCT (Spectral Domain OCT: Spectral Domain Method).

  In particular, in such an ophthalmologic photographing apparatus, in recent years, higher resolution has been promoted by increasing the NA of an irradiation laser. However, when photographing the fundus, the photograph must be taken through the optical tissue of the eye such as the cornea and the crystalline lens. For this reason, as the resolution increases, the aberration of the cornea and the crystalline lens has greatly influenced the image quality of the captured image. Therefore, research on AOSLO and AOOCT in which an adaptive optics (AO) function for measuring aberration of the eye and correcting the aberration is incorporated in the optical system is underway. For example, Non-Patent Document 1 shows an example of AOOCT. These AOSLO and AOOCT generally measure the wavefront of the eye using the Shack-Hartmann wavefront sensor method. The Shack-Hartmann wavefront sensor system measures the wavefront by making measurement light incident on the eye and receiving the return light through a microlens array to a CCD camera. AOSLO and AOOCT can be imaged with high resolution by driving a deformable mirror and a spatial phase modulator to correct the measured wavefront and imaging the fundus oculi through them.

  Recently, an angiographic method (OCT Angiography: OCTA) using OCT has been used as a method for imaging structures such as blood vessels of the retina without using a contrast agent. In OCTA, a blood vessel image (hereinafter referred to as an OCTA image) is generated by projecting three-dimensional motion contrast data acquired by OCT onto a two-dimensional plane. Here, the motion contrast data is data obtained by repeatedly photographing the same position of the measurement object and detecting a temporal change of the measurement object during the photographing. The motion contrast data is obtained, for example, by calculating a temporal change in the phase, vector, and intensity of the complex OCT signal from a difference, a ratio, or a correlation (for example, Patent Document 1).

  Similarly, also in the above-described SLO and AOSLO, a method of generating an image of a blood vessel or the like (hereinafter referred to as a motion contrast image) from the motion contrast data of the planar image has been studied. Similar to the OCTA motion contrast data, the SLO motion contrast data is data obtained by detecting temporal changes at the same imaging position of the measurement target. However, since the SLO image is a continuous moving image of a specific plane, there is no need for a process such as cutting out a specific slice or projecting onto a plane like OCTA. In particular, since the depth of focus is shallow in AOSLO, the layer range to be imaged is limited to several tens of μm, and only a thin slice of the retina can be imaged.

JP, 2015-131107, A JP 2017-143994 A

Y. Zhang et al, Optics Express, Vol. 14, no. 10, 2006, 4380

  In the case of an eye disease in which the blood flow of the retinal blood vessel is impaired, the change that can be depicted is limited depending on the performance of the OCT obtained by capturing the OCT image as the original data in the OCTA, where the meandering of the blood vessel and the thickening of the blood vessel wall occur. . For example, in general OCT, since there is only an in-plane direction resolution (lateral resolution) of about 20 μm, structures and changes on an image below that resolution cannot be captured. In addition, since OCTA needs to acquire three-dimensional data of the retina, there is a substantial limit on the number of repeated imaging at the same position due to the limitation of the OCT imaging speed. In general, the image is repeatedly shot about three times within several milliseconds to several tens of milliseconds. This is a problem that events that do not occur very often and very slow events cannot be captured. In order to cope with this problem, a method of changing the combination of imaging data and a method of changing a scan pattern (Patent Document 2) have been proposed as a method of capturing a low-speed phenomenon in OCT, but this is also effective from the limitation of the imaging speed of OCT. Was limited.

  On the other hand, AOSLO and SLO capture only a planar image, and a plane moving image can be captured at a very high speed. Therefore, hundreds of plane images can be acquired by shooting for a few seconds, and when a motion contrast image is created by AOSLO, it is possible to capture events that occur less frequently or at low speeds. For example, the presence of a blood vessel called Leukocyte Preferred Path (LPP) through which leukocytes frequently pass in the blood vessels of the retina is also known. In such a blood vessel, other blood cells (red blood cells, etc.) are relatively less likely to pass through and there are few changes in the image in a short time. Is expensive. Furthermore, AOSLO has a very high lateral resolution and can capture very minute changes in the cell level. If it is a blood vessel, it can also capture changes in the internal blood cell level. However, even in AOSLO and SLO, blood flow is considered to be stationary, and there is a problem that blood vessels with different flow velocities cannot be drawn only by performing a single process on a series of images.

  In view of the above problems, an object of the present invention is to efficiently generate motion contrast images corresponding to various blood flow velocities.

  In order to solve the above problems, the image processing apparatus of the present invention uses a plurality of images of the measurement object generated based on the return light of the measurement light obtained by irradiating the measurement object with the measurement light. An image processing apparatus for acquiring a motion contrast image, wherein a setting unit that sets intervals between a plurality of images, a generation unit that generates a motion contrast image using a plurality of images based on the set intervals, Control means for outputting the generated motion contrast image to the output means.

  According to the present invention, motion contrast images corresponding to various blood flow velocities can be generated.

1 is a functional configuration diagram of an ophthalmologic photographing apparatus according to an embodiment of the present invention. 1 is a side view of an ophthalmologic photographing apparatus according to an embodiment of the present invention. It is a block diagram of the optical system in one Embodiment of this invention. It is an image of AOSLO in one embodiment of the present invention. It is a figure for demonstrating the imaging | photography order of the AOSLO image in one Embodiment of this invention. It is a flowchart which produces | generates the motion contrast image in one Embodiment of this invention. It is a schematic diagram for demonstrating the frame interval in one Embodiment of this invention. It is a figure for demonstrating the display screen by the display control part in one Embodiment of this invention. It is a flowchart which produces | generates the motion contrast image in one Embodiment of this invention. It is a flowchart which produces | generates the motion contrast image in one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The following description is merely illustrative and exemplary in nature and is not intended to limit the present disclosure and its application or uses in any way. The relative configurations of components shown in the embodiments, and the steps, numerical expressions, and numerical values do not limit the scope of the present disclosure unless specifically indicated otherwise. Techniques, methods and devices well known by those skilled in the art may not have been discussed in detail because those skilled in the art do not need to know these details to enable the embodiments discussed below.

[Embodiment 1]
[Overall configuration of the device]
FIG. 1 is a functional block diagram of an ophthalmologic apparatus as an embodiment of an image processing apparatus according to the present invention. In FIG. 1, the optical system 200 controlled by the control unit 300 irradiates the measurement target T with measurement light and detects return light from the measurement target T. The image generation unit 400 processes the signal S that is the output of the optical system 200 to generate an image IM and outputs the image IM to the display control unit 500. The display control unit 500 includes a display device such as a liquid crystal display, and displays an input image or the like. The generated image is stored in the storage unit 600 in association with information for specifying the measurement target T.

  The ophthalmologic apparatus shown in FIG. 1 can be realized by a PC (personal computer) connected to hardware having a specific function. For example, the optical system 200 can be realized by hardware, and the control unit 300, the image generation unit 400, and the display control unit 500 can be realized by software modules that can be mounted on a PC connected to the hardware.

  A schematic configuration of the ophthalmologic apparatus according to the present embodiment will be described with reference to FIG. 2 which is a side view of the ophthalmologic apparatus. The optical head 101 is an ophthalmic apparatus housing including the optical system 200, and can be moved with respect to the base unit 151 by using a stage unit 150 that is moved in the XYZ directions by a motor or the like. The control device 125 is a PC equipped with a software module, and also serves as the control unit 300, the image generation unit 400, and the display control unit 500. The storage device 126 is a hard disk that also serves as a subject information storage unit and stores a program for tomography. Further, in accordance with an instruction from the control device 125, the acquired image or the like is displayed on the display device 128 such as a monitor. The input unit 129 is an input unit that gives instructions to the PC (control device 125), and specifically includes a keyboard, a mouse, and the like. The face receiver 105 fixes the subject's face 190.

  In the following embodiment, the arithmetic processing unit CPU (not shown) of the control device 125 implements the function by executing the software module, but the present invention is not limited to such a method. The image generation unit 400 may be realized by dedicated hardware such as an ASIC, for example, and the display control unit may be a dedicated processor such as a GPU different from the CPU. Further, the connection between the optical system and the PC can be realized by changing the configuration via a network without changing the gist of the present invention.

  FIG. 3 is a diagram illustrating an optical configuration when the measurement target T in FIG. The configuration of the optical system 200 will be described below with reference to FIG.

  Although not shown in FIG. 3, a wide-angle fundus photographing unit for confirming the photographing position of the fundus, an anterior eye observation unit for facilitating alignment, and a fixation point for presenting the fixation position to the eye to be examined. It has a visual lamp optical system. However, this can be done by a known configuration and is not a central part of the present invention, so the explanation is omitted.

  The AOSLO of this embodiment has both a confocal imaging function that is almost limited to only reflected and scattered light from the focal position of the irradiation beam and a dark field imaging function that also images reflected and scattered light due to multiple scattering other than that. It was set as the structure which has.

  In FIG. 3, 201 is a light source, and an SLD light source (Super Luminescent Diode) having a wavelength of 760 nm was used. Although the wavelength of the light source 201 is not particularly limited, about 750 to 1500 nm is preferably used for fundus imaging in order to reduce the glare of the subject and maintain resolution. In this embodiment, an SLD light source is used, but a laser or the like is also used. In the present embodiment, light sources for fundus photographing and wavefront measurement are shared, but each may be a separate light source and combined in the middle of the optical path.

  The light emitted from the light source 201 passes through the single mode optical fiber 202 and is irradiated as a parallel light beam (measurement light 205) by the collimator 203. The polarization of the irradiated light is adjusted by a polarization adjuster (not shown) provided in the path of the single mode optical fiber 202. As another configuration, there is a configuration in which an optical component for adjusting polarization is arranged in the optical path after being emitted from the collimator 203.

  The irradiated measurement light 205 passes through the light splitting unit 204 formed of a beam splitter and is guided to the adaptive optics optical system.

  The compensation optical system includes a light splitting unit 206, a wavefront sensor 215, a wavefront correction device 208, and reflection mirrors 207-1 to 207-4 for guiding them.

  Here, the reflection mirrors 207-1 to 207-4 are installed so that at least the pupil of the eye 211, the wavefront sensor 215, and the wavefront correction device 208 are optically conjugate. In addition, a beam splitter is used as the light dividing unit 206 in the present embodiment.

  The measurement light 205 transmitted through the light splitting unit 206 is reflected by the reflection mirrors 207-1 and 207-2 and enters the wavefront correction device 208. The measurement light 205 reflected by the wavefront correction device 208 is further reflected by the reflection mirrors 207-3 and 207-4 and guided to the scanning optical system.

  In the present embodiment, a deformable mirror is used as the wavefront correction device 208. The deformable mirror is a mirror in which the reflection surface is divided into a plurality of regions, and the wavefront of the return light can be changed by changing the angle of each region. As the wavefront correction device, a spatial phase modulator using a liquid crystal element instead of the deformable mirror can be used. In that case, two spatial phase modulators may be used to correct both polarizations of light from the eye to be examined.

  In FIG. 3, the light reflected by the reflection mirrors 207-3 and 4 is scanned one-dimensionally or two-dimensionally by the scanning optical system 209-1. In this embodiment, one resonance scanner and one galvano scanner are used for the main scanning (horizontal direction of the fundus) and the sub-scanning (vertical direction of the fundus) in the scanning optical system 209-1. In another configuration, two galvano scanners may be used for the scanning optical system 209-1. In order to bring each scanner in the scanning optical system 209-1 into an optically conjugate state, there may be an apparatus configuration that uses an optical element such as a mirror or a lens between the scanners. In this example, the scanning optical system further includes a tracking mirror 209-2. The tracking mirror 209-2 is composed of two galvano scanners, and can further move the imaging region in two directions. In another configuration, the scanning optical system 209-1 also serves as the tracking mirror 209-2, the tracking mirror 209-2 is configured only in the resonance scanner direction of the scanning optical system 209-1, and the tracking mirror 209-2 is a two-dimensional mirror. There is also the structure which is. Also, in order to optically conjugate 209-1 and 209-2, a relay optical system (not shown) is often used.

  The measurement light 205 scanned by the scanning optical systems 209-1 and 209-2 is irradiated to the eye 211 through the eyepiece lenses 210-1 and 210-2. The measurement light applied to the eye 211 is reflected or scattered by the fundus. By adjusting the positions of the eyepieces 210-1 and 210-2, it is possible to perform optimal irradiation according to the diopter of the eye 211. Here, a lens is used for the eyepiece, but a spherical mirror or the like may be used.

  The return light reflected or scattered from the retina of the eye 211 travels in the opposite direction along the incident path, and is partially reflected by the light splitting unit 206 to the wavefront sensor 215 and used to measure the wavefront of the light beam. It is done. The light beam reflected by the light splitting unit 206 toward the wavefront sensor 215 passes through the relay optical systems 219-1 and 219-2 and enters the wavefront sensor 215. An aperture 220 is installed between the relay optical systems 219-1 and 219-2 so that unnecessary reflected and scattered light from a lens or the like is not incident on the wavefront sensor. In this embodiment, a Shack-Hartmann sensor is used as the wavefront sensor 215.

  The wavefront sensor 215 is connected to the control unit 300 and transmits the received wavefront to the control unit 300. The wavefront correction device 208 is also connected to the control unit 300 and performs modulation instructed by the control unit 300. Based on the wavefront information acquired from the measurement result of the wavefront sensor 215, the control unit 300 calculates a modulation amount (correction amount) for each pixel of the wavefront correction device that corrects the wavefront without aberration, and the wavefront correction device. 208 is instructed to do so. The measurement of the wavefront and the instruction to the wavefront correction device are repeatedly processed, and feedback control is performed so that the optimum wavefront is always obtained.

  In FIG. 3, a part of the return light transmitted through the light splitting unit 206 is reflected by the light splitting unit 204, and is condensed near the hole of the perforated mirror 213 by the condenser lens 212. The hole of the perforated mirror 213 is often adjusted to a diameter in the vicinity of the diffraction limit of the measurement light 205 in order to obtain a confocal effect. When the diameter is large, the sensitivity is improved but the resolution is lowered. When the diameter is small, the resolution is high but the sensitivity tends to be lowered. The light that has passed through the hole of the perforated mirror 213 enters the optical sensor 214-1 and is converted into an electric signal S corresponding to the light intensity.

  The optical sensor 214-1 is connected to the image generation unit 400, and the image generation unit 400 constructs an image IM based on the obtained signal S and the position of optical scanning, and transmits the image IM to the display control unit 500. The display control unit 500 displays the image on the display device 128 as a confocal image.

  The light reflected by the mirror part other than the hole of the perforated mirror 213 is condensed again near the edge of the knife edge 216 through the relay optical system 221, and is divided into approximately half by the knife edge 216. The divided light is incident on the optical sensors 214-2 and 214-3. The optical sensors 214-2 and 214-3 are converted into electrical signals corresponding to the light intensity, communicated to the image generation unit 400, and imaged as dark field captured images. The knife edge 216 may divide the condensed light in any way, and the division direction in the horizontal direction and the vertical direction with respect to the paper surface and the division ratio are not half and non-uniform division such as 40:60 is also possible. . Further, it is possible to divide into more components instead of two. It is also possible to dynamically change such a division method during shooting.

  The tracking mirror 209-2 is controlled by a tracking control unit (not shown). The tracking control unit acquires the image signal of the photographing part from the control unit 300, calculates the amount of deviation from the desired photographing position, and moves the tracking mirror 209-2 so as to always keep the photographing position at a predetermined position. To control.

  An example of an image taken with AOSLO is shown in FIG. FIG. 4A shows a confocal image. Since the blood vessel layer is focused, only blood cells in the blood vessel are partially observed with high brightness. 4B and 4C are dark field captured images. Each is an image generated based on signals detected on the right and left sides of the knife edge. These dark-field captured images simultaneously acquire return light from the fundus and are images constructed from signals at the same imaging position. In AOSLO, such images are continuously acquired to form a moving image.

  FIG. 5 shows the shooting order of each frame of a moving image shot with AOSLO. The abscissa represents the shooting order n, and represents a total of N images starting from n = 1 to n = N. In the present embodiment, the image generation unit 400 generates a motion contrast image using the dark field captured image. The blood vessels 511, 512, and 513 represent blood vessels with different blood flow velocities. The blood vessel 511 has a fast blood flow, the blood vessel 513 has a slow blood flow due to the presence of an aneurysm, and rarely a blood cell 521. A blood vessel 512 passing therethrough. By using AOSLO, blood vessels with a relatively slow blood flow rate, such as capillaries and LPP, can be depicted.

  Dark field photographed images 501-1 and 501-2 are images photographed while the blood cell 521 does not pass through the blood vessel 512, and dark field photographed images 502-1, 502-2, and 502-3 are blood vessels. This is an image taken while the blood cell 521 passes through 512. The images 502-1, 502-2, and 502-3 are represented by n = k, k + 1, and k + 2 in the shooting order.

  A method of acquiring an AOSLO motion contrast image will be described with reference to the flowchart shown in FIG.

  In step S600, the control unit 300 acquires the AOSLO image generated by the image generation unit 400. In the present embodiment, N dark-field captured images that are continuously captured are used.

  In step S601, the control unit 300 aligns N dark-field captured images. In this embodiment, the image having the highest average luminance value is used as a reference image, and the alignment is performed by calculating the correlation with the reference image. Note that the alignment method is not limited to this method. For example, alignment may be performed using a confocal image acquired at the same time as the dark-field captured image, and the result may be used. Further, as a reference for selecting a reference image, alignment may be performed based on contrast and edge sharpness in addition to the average luminance value of the image. Further, a phase only correlation method or the like can be used.

  In step S602, the control unit 300 sets a frame interval Δn. Here, the frame interval Δn is a value indicating the interval (number of frames, etc.) of the combined images when calculating the motion contrast, and indicates a combination of images that are separated in shooting order and time as the value of Δn increases. For example, Δn = 1 represents a combination of continuously acquired images, and Δn = 2 represents a combination of every other image. As an example, FIG. 7A shows a case where Δn = 1. Note that a plurality of frame intervals Δn may be defined in advance or may be set based on a user instruction.

  Based on the set frame interval Δn, a motion contrast image is created in the image generation unit 400 under the control of the control unit 300 in step S603. To generate a motion contrast image, the difference in luminance value for each pixel is squared between the combined images, and maximum value projection is performed. For the calculation of motion contrast, various calculation methods that can emphasize changes in luminance values, such as calculating the ratio of luminance values for each pixel between combined images, can be used. The motion contrast can also be calculated from the correlation or the like as described in the explanation of the background art.

  By changing the frame interval, motion contrast images corresponding to various time intervals can be generated. FIG. 7B shows the case where the frame intervals are Δn = 1, 2, and 3, respectively. In this embodiment, AOSLO imaging is performed at 64 fps, and motion contrast images are generated at intervals of 16 milliseconds, 31 milliseconds, and 47 milliseconds, respectively. In other words, an image corresponding to the blood flow velocity whose luminance value changes at each time interval can be acquired.

  FIG. 8 shows a screen display example of motion contrast images acquired at different frame intervals Δn. The image display units 802-1 to 802-3 are displayed side by side in the window 801, and the user can select parameters of images to be displayed on the respective display units by using pull-down menus 810-1 to 810-3. In the present embodiment, a frame interval Δn and a time interval corresponding to each frame interval are displayed in a selectable manner. In this embodiment, the time and the number of frames are displayed. However, only the selectable time or the selectable number of frames may be displayed. Here, the image displayed on any one of the image display units 802-1 to 802-3 may be a moving image displayed by switching the motion contrast image, and the difference in luminance value at different frame intervals is presented to the user in an easily understandable manner. Is possible. Furthermore, a translucent image may be displayed in a superimposed manner, and the user can easily check the change site by adjusting the transparency using a slider bar or the like (not shown). Furthermore, a composite image in which a blood vessel with a slow blood flow velocity and a blood vessel with a fast blood flow are color-coded (which may be hatched) may be generated from motion contrast images at different frame intervals and presented to the user. By this method, it is not necessary for the user to switch images, and the blood flow velocity distribution can be easily confirmed.

  Thus, by changing the frame interval with AOSLO and acquiring motion contrast images, it becomes possible to easily compare motion contrast images of various blood flow velocities.

  Note that when an invalid frame in which AOSLO imaging has failed due to blinking or the like is included, it is desirable to select a combination that maintains the frame interval at a specified value. This makes it possible to exclude a mixture of motion contrasts with different blood flow velocities.

  In this embodiment, the dark-field captured image 501 is used. However, when the AOSLO confocal image has high brightness, a confocal image can be used, and a higher-contrast AOSLO motion contrast image can be created. It is.

[Embodiment 2]
An example of a method for controlling the fundus imaging apparatus having a different form from the first embodiment to which the present invention is applied will be described with reference to the flowchart of FIG. In the present embodiment, the basic apparatus configuration and the basic flow of photographing are the same as those in the first embodiment, but when the process of motion contrast image generation of the image generation unit 400 is different and blood flow is not steady. Especially effective.

  Steps S900 to S901 are the same as those in the first embodiment. In step S902, the control unit 300 extracts a blood vessel region by performing known image processing from a series of aligned images. For extraction of the blood vessel region, it is desirable to use edge detection of a confocal image or a dark-field image. In step S903, the control unit 300 performs a mask process that excludes the extracted blood vessel region from the image processing target.

  In step S904, a target region ROI for image processing is set. In this embodiment, a region along one branch of a blood vessel is selected as the ROI. In step S905 and subsequent steps, under the control of the control unit 300, the image generation unit 400 generates a motion contrast image by sequentially changing the frame intervals in the selected ROI. First, a frame interval is set in step S905, then a motion contrast image is generated in step S906, and the motion contrast image is stored in the storage unit in step S907. Although the case where the ROI is automatically set has been described, the ROI may be set based on an instruction from the user.

  In step S908, the control unit 300 determines whether all frame interval conditions have been completed. If not, the control unit 300 selects the next interval condition in step S921, and returns to step S905. On the other hand, when all the frame interval conditions are completed, a series of motion contrast images stored in the storage unit is evaluated in S909, and the best motion contrast image is obtained in step S910 based on the evaluation result in step S909. Remember. Here, the best motion contrast image is a motion contrast image with the highest contrast. At this time, the best motion contrast image and the frame interval associated with the image are stored in the storage unit.

  In step S911, the control unit 300 determines whether all ROIs are completed. If not, the control unit 300 selects the next ROI in step S922 and returns to step S904. On the other hand, when all the ROIs are completed, the image generation unit 400 synthesizes the best motion contrast image under the control of the control unit 300 in step S912.

  The synthesized best motion contrast image is color-coded so as to be identifiable based on the frame interval associated therewith, and then sent to the display control unit 500 to be presented on a screen or the like. By this method, it is possible to efficiently generate a motion contrast image from an AOSLO image in which blood vessels with different blood flow rates are mixed and present it to the user.

  Note that in a blood vessel 513 having different blood flow velocities along the branch of the blood vessel, the ROI selection method for generating a motion contrast image can be divided into a blood vessel aneurysm and other regions. The vascular flow may be selected by the user using an input device, or may be automatically selected by comparing motion contrast images at different frame intervals.

[Embodiment 3]
An example of a method for controlling the fundus imaging apparatus having a different form from the first and second embodiments to which the present invention is applied will be described using the flowchart of FIG. In the present embodiment, the basic apparatus configuration and the basic flow of photographing are the same as those in the first embodiment, but when the process of motion contrast image generation of the image generation unit 400 is different and blood flow is not steady. Especially effective.

  In FIG. 10, steps S900 to S903 are the same as those in the second embodiment. In the present embodiment, the extraction of the blood vessel region in step S902 may be changed to a method of extracting the blood vessel region based on the region specified by the user using the input device, for example. In the following, it is assumed that the frame interval Δn = 1 is set.

  In step S1004, under the control of the control unit 300, the image generation unit 400 generates a motion contrast image using the nth and n + 1th images. Next, in step S1005, the control unit 300 calculates the contrast value of the motion contrast image, and compares it with a threshold value set in advance and stored in the storage unit. When it is determined that the contrast value of the motion contrast image is higher than the threshold value, that is, a good motion contrast image is generated, the motion contrast image and the imaging order n are stored in the storage unit in step S1006. After that, in step S1007, the control unit 300 determines whether the imaging order n has reached the maximum number. On the other hand, if the contrast value of the motion contrast image is lower than the threshold value in step S1005, it is determined in step S1007 whether the imaging order n has reached the maximum number.

  In step S1007, from n = 1 to a value of N-2, n is incremented in step S1010 and the process returns to S1004. When n = N-1, the process proceeds to step S1008.

  FIG. 7C schematically shows the imaging order n stored when the blood vessel 512 is an ROI. The imaging order including the imaging order n = k, k + 1, k + 2 in which the blood cell 521 appears in the AOSLO image and the imaging order before and after that is stored. In step S1008, the image generation unit 400 synthesizes the motion contrast image under the control of the control unit 300 based on the motion contrast image stored in step S1006 and the shooting order n.

  By using this method, it becomes possible to efficiently visualize the blood flow velocity in a blood vessel through which blood cells intermittently pass, such as LPP.

[Embodiment 4]
With reference to the schematic diagram of FIG. 7D, an example of a method for controlling the fundus imaging apparatus having a different form from the first embodiment to which the present invention is applied will be described. In this embodiment, the basic apparatus configuration and the basic flow of imaging are the same as those in the first embodiment, but the combination method of AOSLO images is different, and the image quality of motion contrast images is particularly great when blood flow is steady. Effective for improvement.

  When the frame interval Δn is larger than 1, an image out of the combination may occur in a series of images acquired by AOSLO. In general, in order to prevent motion contrast images with different blood flow velocities from being mixed, it is desirable to select a combination that maintains the frame interval at a specified value. However, when the blood flow rate is fast with respect to the frame rate and the blood flow can be determined to be steady, the image quality of the motion contrast image can be improved by the method schematically shown in FIG.

  FIG. 7D schematically shows a situation where N consecutive images acquired by AOSLO are arranged in order of photographing until n = N, and then arranged again from the image of n = 1. . For convenience, the imaging order of these virtual images is represented as n = N + 1, N + 2,. When the frame interval Δn is larger than 1 and it can be determined that the blood flow is steady, it is possible to improve the image quality by generating a motion contrast image with a combination including an image where n> N.

[Other Embodiments]
In the above-described embodiment, the motion contrast by AOSLO has been described, but the application of the present invention is not limited to this. For example, the present invention can be similarly applied to a fundus camera using AO or a blood flow measuring device from which the influence of aberration is removed by software.

  In the above-described embodiments, the case where the measurement target is the eye is described. However, the present invention can also be applied to an inspection object such as a skin or an organ other than the eye. In this case, the present invention has an aspect as a medical device such as an endoscope other than the ophthalmologic photographing apparatus. Therefore, it is preferable that the present invention is grasped as an image processing apparatus exemplified by an ophthalmologic photographing apparatus, and the eye to be examined is grasped as one aspect of the measurement object.

Claims (12)

An image processing apparatus that acquires a motion contrast image using a plurality of images of the measurement target generated based on return light of the measurement light obtained by irradiating the measurement target with measurement light,
Setting means for setting the interval between a plurality of images;
Generating means for generating a motion contrast image using a plurality of images based on the set interval;
An image processing apparatus comprising: control means for outputting the generated motion contrast image to output means. The setting means sets a plurality of intervals;
2. The generation unit according to claim 1, wherein the generation unit generates a plurality of motion contrast images respectively corresponding to the plurality of intervals using a plurality of images based on the plurality of set intervals. Image processing device. The output means is a display means;
The image processing apparatus according to claim 2, wherein the display unit displays a plurality of motion contrast images respectively corresponding to the plurality of intervals generated by the generation unit.   The image processing apparatus according to claim 2, further comprising an evaluation unit that evaluates a plurality of motion contrast images respectively corresponding to the plurality of intervals. Extracting means for extracting a blood vessel region from the motion contrast image;
The image processing apparatus according to claim 2, further comprising a synthesizing unit that synthesizes blood vessel regions extracted from a plurality of motion contrast images respectively corresponding to the plurality of intervals.   The image processing apparatus according to claim 2, wherein the interval includes at least one of a time interval and a frame number.   The image processing apparatus according to claim 5, wherein the synthesizing unit synthesizes the extracted blood vessel region in a form in which an interval at which the blood vessel region is extracted can be identified. Means for setting a target area for generating a motion contrast image;
The image processing apparatus according to claim 1, wherein the generation unit generates a motion contrast image of the set target area.   The image processing apparatus according to claim 1, wherein the plurality of images are AOSLO images.   The image processing apparatus according to claim 2, wherein the plurality of intervals set by the setting unit are set with different numbers of frames and / or different times.   11. The apparatus according to claim 1, further comprising means for extracting a plurality of images used when the motion contrast image is generated by the generation means from a plurality of images acquired at predetermined intervals. The image processing apparatus according to item 1. A control method for an image processing apparatus that acquires a motion contrast image using a plurality of images of the measurement target generated based on return light of the measurement light obtained by irradiating the measurement target with measurement light. ,
A setting step for setting the interval between a plurality of images;
Generating a motion contrast image using a plurality of images based on the set interval;
And a control step of outputting the generated motion contrast image to an output unit.