JP2022133399A - Image processing apparatus and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently generate a motion contrast image corresponding to various blood velocities.

SOLUTION: An image processing apparatus for acquiring a motion contrast image on the basis of return light of measurement light comprises: setting means which sets a time interval for acquiring a plurality of images; generation means which generates a motion contrast image using the plurality of images on the basis of the set time interval; and control means which displays the motion contrast image on display means. The generation means generates the first motion contrast image using the plurality of images of the first time interval and the second motion contrast image using the plurality of images of the second time interval different from the first time interval. The control means displays a composite image obtained by combining the first motion contrast image and the second motion contrast image in an identifiable manner on the display means.

SELECTED DRAWING: Figure 5

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to an image processing apparatus and its control method, and more particularly to an image processing apparatus for processing a fundus image of an eye to be examined and its control method.

In recent years, as imaging devices for ophthalmology, SLOs (scanning laser ophthalmoscopes) that two-dimensionally irradiate the fundus of the eye with laser light and receive the returned light to form an image, and interference of low-coherence light have been used. An imaging device has been developed that utilizes An imaging apparatus using interference of low-coherence light 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) and SD-OCT (Spectral Domain OCT).

In particular, in recent years, such an ophthalmic imaging apparatus has been further improved in resolution by increasing the NA of the irradiation laser. However, when photographing the fundus, the photograph must be taken through the optical tissues of the eye such as the cornea and the lens. Therefore, as the resolution becomes higher, the aberrations of the cornea and the crystalline lens come to greatly affect the image quality of the photographed image. Therefore, AOSLO and AOOCT, in which an optical system incorporates an adaptive optics (AO) function for measuring eye aberrations and correcting the aberrations, is being studied. For example, Non-Patent Document 1 shows an example of AOOCT. These AOSLO and AOOCT generally measure the wavefront of the eye by 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 returned light by a CCD camera through a microlens array. AOSLO and AOOCT enable high-resolution imaging by driving the deformable mirror and the spatial phase modulator so as to correct the measured wavefront and imaging the fundus through them.

Recently, OCT angiography (OCTA) is used as a method for imaging structures such as blood vessels in 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 between the photographing. Motion contrast data can be obtained, for example, by calculating phases, vectors, and temporal changes in intensity of complex OCT signals from differences, ratios, correlations, or the like (eg, Patent Document 1).

Similarly, 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 is also being researched. Like the OCTA motion contrast data, the SLO motion contrast data is data obtained by detecting changes over time at the same imaging position of the object to be measured. However, since an SLO image is a continuous moving image of a specific plane, processing such as cutting out a specific slice like OCTA and projection onto a plane is not necessary. In particular, since AOSLO has a shallow depth of focus, the layer range to be imaged is limited to several tens of μm, and only thin slices 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 eye diseases in which retinal blood flow is disturbed, vascular meandering and vascular wall thickening can be observed with OCTA. . For example, since general OCT has an in-plane resolution (horizontal resolution) of only about 20 μm, it is not possible to capture structures and changes on images with a resolution lower than that resolution. In addition, since OCTA requires acquisition of three-dimensional data of the retina, there is a practical limit to the number of repetitions of imaging at the same position due to the limitations of the imaging speed of OCT. In general, the shooting is repeated about three times within several milliseconds to several tens of milliseconds. This poses a problem that it is impossible to capture events that occur infrequently or events that occur very slowly. In order to deal with this problem, a method of changing the combination of imaging data and a method of changing the scan pattern (Patent Document 2) have been proposed as methods of capturing low-speed phenomena in OCT. was limited.

On the other hand, AOSLO and SLO are for photographing only planar images, and are capable of photographing planar moving images at extremely high speeds. Therefore, hundreds of planar images can be acquired in a few seconds of imaging, and when creating a motion contrast image with AOSLO, it is possible to capture events that occur infrequently or at low speed. For example, it is known that there is a blood vessel called Leukocyte Preferred Path (LPP) through which leukocytes pass frequently in the retina. In such blood vessels, other blood cells (red blood cells, etc.) pass through relatively little and there is little change in the image in a short period of time. is high. Furthermore, AOSLO has a very high horizontal resolution and can detect very minute changes at the cell level. However, even in AOSLO and SLO, there is a problem that blood vessels with different flow velocities cannot be visualized simply by applying a single process to a series of images, assuming that the blood flow is stationary.

SUMMARY OF THE INVENTION 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 motion contrast images, comprising setting means for setting time intervals for acquiring a plurality of images, and generating motion contrast images using the plurality of images based on the set time intervals. and control means for displaying the generated motion contrast image on display means, the generating means generating a first motion contrast image using a plurality of images at a first time interval; generating a second motion contrast image using a plurality of images at a second time interval different from the first time interval, the control means controlling the first motion contrast image and the second motion contrast image; The display means is caused to display a composite image that is identifiably combined with the contrast image.

Further, the image processing apparatus of the present invention acquires a motion contrast image using 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 that includes setting means for setting a time interval for acquiring a plurality of images, generation means for generating a motion contrast image using a plurality of images based on the set time interval, a control means for displaying the generated motion contrast image on a display means, wherein the generation means generates a plurality of motion contrasts respectively corresponding to a plurality of time intervals; A plurality of generated motion contrast images respectively corresponding to the plurality of time intervals are displayed side by side on the display 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 imaging apparatus according to one embodiment of the present invention; FIG. 1 is a side view of an ophthalmologic imaging apparatus according to one embodiment of the present invention; FIG. 1 is a configuration diagram of an optical system in one embodiment of the present invention; FIG. 1 is an image of AOSLO in one embodiment of the present invention; FIG. 4 is a diagram for explaining the order in which AOSLO images are captured in one embodiment of the present invention; Figure 4 is a flow chart for generating a motion contrast image in one embodiment of the present invention; FIG. 4 is a schematic diagram for explaining frame intervals in one embodiment of the present invention; FIG. 4 is a diagram for explaining a display screen by a display control unit according to an embodiment of the present invention; FIG. Figure 4 is a flow chart for generating a motion contrast image in one embodiment of the present invention; Figure 4 is a flow chart for generating a motion contrast image in one embodiment of the present invention;

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

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

The ophthalmologic apparatus shown in FIG. 1 can be realized by a PC (personal computer) connected to hardware having specific functions. For example, the optical system 200 can be implemented by hardware, and the controller 300, image generator 400, and display controller 500 can be implemented by software modules that can be installed in a PC connected to the hardware.

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

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

FIG. 3 is a diagram showing an optical configuration when the measurement object T in FIG. 1 is the eye 211. As shown 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 imaging unit for confirming the imaging position of the fundus, an anterior segment observation unit for facilitating alignment, and a fixation position for presenting a fixation position to the eye to be examined. It has a sighting optical system. However, this can be based on a known configuration and is not a central part of the present invention, so the description is omitted.

The AOSLO of this embodiment has both a confocal imaging function, which is almost limited to reflected and scattered light from the focal position of the irradiation beam, and a dark-field imaging function, which also images reflected and scattered light due to other factors such as multiple scattering. It is configured to have

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

Light emitted from a light source 201 passes through a single-mode optical fiber 202 and is emitted by a collimator 203 as parallel rays (measurement light 205). The polarization of the irradiated light is adjusted by a polarization adjuster (not shown) provided in the path of 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 is transmitted through a light splitting section 204 consisting of a beam splitter and guided to an optical system of adaptive optics.

The adaptive optics system is composed of a light splitting section 206, a wavefront sensor 215, a wavefront correction device 208, and reflection mirrors 207-1 to 207-4 for guiding light to them.

Here, the reflecting 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 in an optically conjugate relationship. A beam splitter is used as the light splitting unit 206 in this embodiment.

The measurement light 205 transmitted through the light splitting section 206 is reflected by reflecting 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 reflecting mirrors 207-3 and 207-4 and guided to the scanning optical system.

In this embodiment, a deformable mirror is used as the wavefront correction device 208 . A deformable mirror has a reflecting surface divided into a plurality of areas, and is a mirror that can change the wavefront of return light by changing the angle of each area. As the wavefront correction device, a spatial phase modulator using a liquid crystal element can be used instead of the deformable mirror. In that case, two spatial phase modulators may be used to correct for both polarizations of light from the subject's eye.

In FIG. 3, the light reflected by reflecting mirrors 207-3 and 4 is scanned one-dimensionally or two-dimensionally by scanning optical system 209-1. In this embodiment, the scanning optical system 209-1 uses one resonance scanner and one galvanometer scanner for main scanning (in the horizontal direction of the fundus) and for sub-scanning (in the vertical direction of the fundus). In another configuration, two galvo scanners may be used in scanning optics 209-1. In order to make each scanner in the scanning optical system 209-1 optically conjugate, there is a device configuration using an optical element such as a mirror or a lens between each scanner. In this example, the scanning optical system further has a tracking mirror 209-2. The tracking mirror 209-2 is composed of two galvanometer scanners and can move the imaging area 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 resonant scanner direction of the scanning optical system 209-1, and the tracking mirror 209-2 is a two-dimensional mirror. There is also a configuration that is A relay optical system (not shown) is often used to optically conjugate 209-1 and 209-2.

Measurement light 205 scanned by scanning optical systems 209-1 and 209-2 is irradiated to eye 211 through eyepieces 210-1 and 210-2. The measurement light irradiated 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 optimum irradiation according to the diopter of the eye 211. FIG. 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 section 206 to the wavefront sensor 215, which is used to measure the wavefront of the light. be done. The light rays reflected toward the wavefront sensor 215 by the light splitting section 206 pass through the relay optical systems 219-1 and 219-2 and enter the wavefront sensor 215. FIG. An aperture 220 is provided between the relay optical systems 219-1 and 219-2 to prevent unnecessary reflected and scattered light from lenses or the like from entering 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 section 300 and performs modulation instructed by the control section 300 . Based on the wavefront information obtained from the measurement result of the wavefront sensor 215, the control unit 300 calculates the modulation amount (correction amount) for each pixel of the wavefront correction device that corrects the wavefront to a wavefront without aberration, 208 to modulate accordingly. Wavefront measurement and instructions to the wavefront correction device are repeatedly processed, and feedback control is performed so that the optimum wavefront is always obtained.

In FIG. 3 , the return light transmitted through the light splitting section 206 is partly reflected by the light splitting section 204 and condensed near the hole of the perforated mirror 213 by the condensing lens 212 . The holes in the perforated mirror 213 are often adjusted to a diameter near the diffraction limit of the measurement light 205 to obtain a confocal effect. If the diameter is large, the sensitivity is improved but the resolution is lowered, and if the diameter is small, the resolution is high but the sensitivity tends to be lowered. The light passing through the hole of the perforated mirror 213 is incident on the optical sensor 214-1 and converted into an electrical 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 optical scanning position, and transmits the image IM to the display control unit 500 . The display control unit 500 displays it on the display device 128 as a confocal image.

The light reflected by the mirror portion other than the hole of the perforated mirror 213 passes through the relay optical system 221 and converges near the edge of the knife edge 216 again, and is split into approximately half by the knife edge 216 . The split light enters photosensors 214-2 and 214-3. At the optical sensors 214-2 and 214-3, the signals are converted into electrical signals corresponding to the light intensity, communicated to the image generation unit 400, and imaged as a dark field photographed image. The knife edge 216 may divide the condensed light in any way, and it is also possible to divide the condensed light in a non-uniform manner such as 40:60 instead of 50:60 in terms of the division direction in the horizontal direction or the vertical direction with respect to the paper surface and the division ratio. . Furthermore, it is also possible to divide into more components instead of dividing into 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 photographed part from the control unit 300, calculates the amount of deviation from the desired photographing position, and moves the tracking mirror 209-2 so that the photographing position is always kept at a predetermined position. to control.

An example of an image taken with AOSLO is shown in FIG. FIG. 4(a) is a confocal image. Because the focus is on the vascular layer, only blood cells inside the blood vessels are observed with high brightness. FIGS. 4B and 4C are dark-field photographed images. These are images generated based on signals detected on the right and left sides of the knife edge, respectively. These dark-field photographed images simultaneously acquire the return light from the fundus, and are images constructed from signals at the same photographing 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 by AOSLO. The horizontal axis represents the shooting order n, and represents a total of N images starting from n=1 to n=N. In this embodiment, the image generation unit 400 generates the motion contrast image using the dark field captured image. Blood vessels 511, 512, and 513 represent vessels with different blood flow velocities, and a blood vessel 511 with fast blood flow, a blood vessel 513 with slow blood flow due to an aneurysm or the like, and blood cells 521 in rare cases are shown. A blood vessel 512 passes through. By using AOSLO, it is possible to visualize blood vessels such as capillaries and LPPs, in which the blood flow velocity is relatively slow.

Dark field images 501-1 and 501-2 are images captured while blood cells 521 are not passing through the blood vessel 512, and dark field images 502-1, 502-2 and 502-3 are images of the blood vessel. The image is taken while blood cells 521 are passing through 512 . The images 502-1, 502-2, and 502-3 are represented by n=k, k+1, and k+2 in the imaging order, respectively.

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

In step S<b>600 , control unit 300 acquires the AOSLO image generated by image generation unit 400 . In this embodiment, N consecutively captured dark-field images are used.

In step S601, the control unit 300 aligns N dark-field captured images. In this embodiment, an image having the highest average luminance value of the image is used as a reference image, and alignment is performed by calculating the correlation with the reference image. 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 photographed image, and the results may be used. Further, as a criterion for selecting a reference image, alignment may be performed based on the contrast or edge sharpness in addition to the average luminance value of the image. Furthermore, it is also possible to use a phase-only correlation method or the like.

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

Based on the set frame interval Δn, a motion contrast image is created in the image generator 400 under the control of the controller 300 in step S603. Motion contrast images are generated by squaring the difference in pixel-by-pixel luminance values between the combined images and performing maximum intensity projection. Note that various calculation methods capable of emphasizing changes in luminance values, such as calculating the ratio of luminance values for each pixel between combined images, can be used to calculate the motion contrast. In addition, motion contrast can also be calculated from correlation, etc., as described in the description of the background art.

By changing the frame interval, it is possible to generate motion contrast images corresponding to various time intervals. FIG. 7B shows the case where the frame intervals are Δn=1, 2, 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. This means that it is possible to obtain an image corresponding to the blood flow velocity such that the brightness value changes at each time interval.

FIG. 8 shows screen display examples of motion contrast images acquired at different frame intervals Δn. Image display portions 802-1 to 802-3 are displayed side by side in a window 801, and the user can select parameters of images to be displayed on the respective display portions from pull-down menus 810-1 to 810-3. In this embodiment, frame intervals Δn and time intervals corresponding to the respective frame intervals are displayed in a selectable manner. Although the time and the number of frames are displayed in this embodiment, only the selectable time or only the selectable number of frames may be displayed. Here, the display on any one of the image display units 802-1 to 802-3 may be a moving image in which motion contrast images are switched and displayed, and the difference in luminance values at different frame intervals can be presented to the user in an easy-to-understand manner. is possible. Furthermore, a translucent image may be superimposed and displayed so that the user can easily check the changed part by adjusting the transparency using a slider bar or the like (not shown). Furthermore, from motion contrast images of different frame intervals, a composite image may be generated in which blood vessels with slow blood flow and blood vessels with fast blood flow are color-coded (hatching or the like may be used) so as to be distinguishable, and presented to the user. This method eliminates the need for the user to switch images and allows the user to easily check the blood flow velocity distribution.

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

Note that if there are invalid frames for which AOSLO imaging has failed due to blinking or the like, it is desirable to select a combination that keeps the frame interval at a designated value. This makes it possible to exclude the mixture of motion contrasts of different blood flow velocities.

In addition, although the dark field image 501 is used in the present embodiment, the confocal image can also be used when the AOSLO confocal image has high brightness, and a higher contrast AOSLO motion contrast image can be created. is.

[Embodiment 2]
An example of a control method for a fundus imaging apparatus that is different from the first embodiment to which the present invention is applied will be described with reference to the flowchart of FIG. In this embodiment, the basic device configuration and the basic flow of imaging are the same as in Embodiment 1, but the motion contrast image generation processing of the image generation unit 400 is different. Especially effective.

Steps S900 to S901 are the same as in the first embodiment. In step S902, the control unit 300 performs known image processing from the registered series of images to extract a blood vessel region. It is desirable to use edge detection or the like of a confocal image or a dark-field photographed image for extraction of the blood vessel region. In step S903, the control unit 300 performs mask processing to exclude areas other than the extracted blood vessel area from image processing.

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. After step S905, the image generation unit 400 under the control of the control unit 300 sequentially changes the frame interval in the selected ROI to generate a motion contrast image. 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 of automatically setting the ROI has been described, the configuration may be such that the ROI is set based on an instruction from the user.

In step S908, the control unit 300 determines whether or not all frame interval conditions have been completed. If not yet completed, the next interval condition is selected in S921, and the process returns to step S905. On the other hand, if the conditions for all frame intervals are completed, the series of motion contrast images stored in the storage unit are evaluated in step S909, and the best motion contrast image is selected in step S910 based on the evaluation results of step S909. Remember. Here, the best motion contrast image is the motion contrast image with the highest contrast. At this time, the best motion contrast image and the frame interval associated with that image are stored in the memory.

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

The synthesized best motion contrast images are identifiably color-coded based on the frame intervals associated with each, and then sent to the display control unit 500 and presented on a screen or the like. With this method, it is possible to efficiently generate a motion contrast image from an AOSLO image in which blood vessels with different blood flow velocities coexist, and present it to the user.

In the blood vessel 513 with different blood flow velocities along the branches of the blood vessel, it is also possible to divide the ROI selection method for generating the motion contrast image into the aneurysm and other regions. The selection of vascular flow may be user selectable using an input device, or may be automatically selected by comparing motion contrast images at different frame intervals.

[Embodiment 3]
An example of a control method for a fundus imaging apparatus that is different from the first and second embodiments to which the present invention is applied will be described with reference to the flowchart of FIG. In this embodiment, the basic device configuration and the basic flow of imaging are the same as in Embodiment 1, but the motion contrast image generation processing of the image generation unit 400 is different. Especially effective.

In FIG. 10, steps S900 to S903 are the same as in the second embodiment. Note that, in this 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. Also, in the following, it is assumed that the frame interval Δn is set to 1.

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 preset threshold value stored in the storage unit. If the contrast value of the motion contrast image is higher than the threshold value, that is, if it is determined that a good motion contrast image has been generated, the motion contrast image and the shooting order n are stored in the storage unit in step S1006. After that, in step S1007, the control unit 300 determines whether the shooting 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 in step S1005, it is determined in step S1007 whether the shooting order n has reached the maximum number.

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

FIG. 7C schematically shows the imaging order n stored when the blood vessel 512 is the 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 motion contrast images under the control of the control unit 300 based on the motion contrast images and the imaging order n stored in step S1006.

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

[Embodiment 4]
An example of a control method for a fundus imaging apparatus having a configuration different from that of Embodiment 1 to which the present invention is applied will be described with reference to the schematic diagram of FIG. 7(d). In this embodiment, the basic device configuration and the basic flow of imaging are the same as in Embodiment 1, but the method of combining AOSLO images is different. Effective for improvement.

If the frame interval Δn is greater than 1, out-of-combine images may occur in the sequence of images acquired with AOSLO. In general, it is desirable to select a combination that keeps the frame interval at a specified value in order to prevent motion contrast images of different blood flow velocities from being mixed. However, when the blood flow velocity is high relative to the frame rate and it can be determined that the blood flow is steady, the image quality of the motion contrast image can be improved by the method schematically shown in FIG. 7(d).

FIG. 7(d) schematically shows a situation in which, for N consecutive images acquired by AOSLO, the images are arranged in order of photography up to n=N, and then arranged again from the image of n=1. . For convenience, the shooting order of these virtual images is expressed as n=N+1, N+2, . When the frame interval Δn is greater than 1 and the blood flow can be determined to be steady, the image quality can be improved by generating a motion contrast image with a combination including images where n>N.

[Other embodiments]
Although the motion contrast by AOSLO has been described in the above embodiment, 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 that eliminates the effects of aberrations using software.

In addition, in the above-described embodiments, the case where the measurement object is the eye is described, but the present invention can also be applied to objects other than the eye, such as skin and organs. In this case, the present invention has an aspect as a medical device such as an endoscope other than an ophthalmic photographing device. Therefore, it is preferable that the present invention be grasped as an image processing apparatus exemplified by an ophthalmic photographing apparatus, and that an eye to be examined be grasped as one mode of an object to be measured.

Claims (15)

An image processing apparatus for acquiring a motion contrast image using 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,
setting means for setting a time interval when acquiring a plurality of images;
generating means for generating a motion contrast image using a plurality of images based on the set time interval;
and a control means for displaying the generated motion contrast image on a display means,
The generating means generates a first motion contrast image using a plurality of images of a first time interval and a second motion contrast image using a plurality of images of a second time interval different from the first time interval. and generate a motion contrast image of
The image processing apparatus, wherein the control means causes the display means to display a synthesized image in which the first motion contrast image and the second motion contrast image are synthesized so as to be identifiable. The plurality of images are images taken in succession,
The setting means sets first and second time intervals,
The generating means uses a plurality of images based on each of the set first and second time intervals to generate first and second motion contrast images respectively corresponding to the first and second time intervals. 2. The image processing apparatus according to claim 1, wherein the image processing apparatus generates: An image processing apparatus for acquiring a motion contrast image using 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,
setting means for setting a time interval for acquiring a plurality of images;
generating means for generating a motion contrast image using a plurality of images based on the set time interval;
and a control means for displaying the generated motion contrast image on a display means,
The generating means generates a plurality of motion contrast images respectively corresponding to a plurality of time intervals;
The image processing apparatus, wherein the control means causes the display means to display the plurality of motion contrast images respectively corresponding to the plurality of time intervals generated by the generation means side by side. 4. The image processing apparatus according to claim 3, further comprising evaluation means for evaluating a plurality of motion contrast images respectively corresponding to said plurality of time intervals. extraction means for extracting a plurality of blood vessel regions from the motion contrast image;
4. The image processing apparatus according to claim 3, further comprising synthesizing means for synthesizing a motion contrast image selected for each blood vessel region from a plurality of motion contrast images respectively corresponding to said plurality of time intervals. . 6. The image processing apparatus according to claim 3, wherein said time interval includes at least one of a frame interval and a number of frames. 6. The image processing apparatus according to claim 5, wherein said synthesizing means synthesizes said selected motion contrast images in such a manner that time intervals at which said motion contrast images are extracted can be identified. further comprising means for setting a region of interest for generating the motion contrast image;
8. The image processing apparatus according to any one of claims 1 to 7, wherein said generating means generates a motion contrast image of said set target area. 9. The image processing apparatus according to claim 1, wherein said plurality of images are AOSLO images. 4. The image processing apparatus according to claim 3, wherein the plurality of time intervals set by said setting means are set with different numbers of frames and/or different times. 11. The apparatus according to any one of claims 1 to 10, further comprising means for extracting a plurality of images used when said motion contrast image is generated by said generating means from a plurality of images acquired at predetermined time intervals. 1. The image processing apparatus according to claim 1. A control method for an image processing device that acquires a motion contrast image using a plurality of images of a measurement object generated based on return light of the measurement light obtained by irradiating the measurement object with the measurement light, the method comprising: ,
a setting step of setting a time interval for acquiring a plurality of images;
generating a motion contrast image using a plurality of images based on the set time interval;
a control step of displaying the generated motion contrast image on display means;
In the generating step, a first motion contrast image is generated using a plurality of images of a first time interval and a second motion contrast image is generated using a plurality of images of a second time interval different from the first time interval. produces a motion contrast image of
A control method for an image processing apparatus, wherein in the control step, the first motion contrast image and the second motion contrast image are synthesized so as to be identifiable and displayed on the display means. 2. The image processing apparatus according to claim 1, wherein said synthesized image is an image in which blood vessels with slow blood flow and blood vessels with fast blood flow can be identified by color. 7. The image processing apparatus according to claim 6, wherein said setting means sets a plurality of time intervals by changing said frame interval. A control method for an image processing device that acquires a motion contrast image using a plurality of images of a measurement object generated based on return light of the measurement light obtained by irradiating the measurement object with the measurement light, the method comprising: ,
a setting step of setting a time interval for acquiring a plurality of images;
generating a motion contrast image using a plurality of images based on the set time interval;
a control step of displaying the generated motion contrast image on display means;
A control method for an image processing apparatus, wherein in the control step, a plurality of motion contrast images respectively corresponding to the plurality of time intervals generated in the generating step are arranged and displayed on the display means.

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