JP7677411B2 - IMAGE PROCESSING METHOD, IMAGE PROCESSING APPARATUS, AND PROGRAM - Google Patents

Description

The technology disclosed herein relates to an image processing method, an image processing device, and a program.

U.S. Publication No. 2020/0214557 discloses a technology for acquiring a tomographic image of a subject's eye. It is desirable to acquire a tomographic image at a wide angle.

The image processing method of the first aspect of the technology disclosed herein is image processing performed by a processor, and includes the steps of acquiring OCT data of the fundus of the test eye based on interference light between return light obtained by scanning signal light and reference light, and correcting contrast differences between multiple A-scan data included in the OCT data to generate corrected OCT data.

The image processing device of the second aspect of the technology disclosed herein is an image processing device equipped with a processor, which executes the steps of acquiring OCT data of the fundus of the test eye based on interference light between return light obtained by scanning signal light and reference light, and correcting contrast differences between multiple A-scan data included in the OCT data to generate corrected OCT data.

The program of the third aspect of the technology disclosed herein causes a computer to execute the steps of acquiring OCT data of the fundus of the test eye based on interference light between return light obtained by scanning a signal light and a reference light, and correcting contrast differences between multiple A-scan data included in the OCT data to generate corrected OCT data.

FIG. 1 is a block diagram of an ophthalmology system 100. 1 is a block diagram showing an overall configuration of an ophthalmic apparatus 110. FIG. 10 is an explanatory diagram of functions realized by an image processing program executed by a CPU 16A of the ophthalmic apparatus 110. FIG. 10 is a flowchart showing image processing performed by a CPU 16A. FIG. 13 is a diagram showing the relationship between the scan angle and the polarization and A-scan. FIG. 11 is a diagram showing each A-scan data. FIG. 6B is a diagram showing an OCT image based on each A-scan data of FIG. 6A. FIG. 13 is a diagram showing the calculated contrast of A1 scan data. FIG. 13 is a diagram showing the calculated contrast of A2 scan data. FIG. 13 is a diagram showing the calculated contrast of A2 scan data. FIG. 13 is a diagram showing each A-scan data after correction. FIG. 8B is a diagram showing an OCT image based on each A-scan data after correction in FIG. 8A. FIG. 7B is a diagram in which the contrast of the A1 scan data of FIG. 7A is corrected. FIG. 7C is a diagram showing the A2 scan data of FIG. 7B after contrast correction. FIG. 5 is a diagram showing a screen 500 displayed on the viewer 150.

[First embodiment]
An ophthalmic system 100 according to an embodiment of the technique of the present disclosure will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of the ophthalmic system 100. As shown in FIG. 1, the ophthalmic system 100 includes an ophthalmic device 110, a server device (hereinafter referred to as a "server") 140, and a display device (hereinafter referred to as a "viewer") 150. The ophthalmic device 110 acquires fundus images. The server 140 stores a plurality of fundus images obtained by photographing the fundus of a plurality of patients by the ophthalmic device 110 and an axial length measured by an axial length measuring device (not shown) in association with a patient ID. The viewer 150 displays the fundus images acquired by the server 140 and analysis results.

The ophthalmic device 110 is an example of an "image processing device" of the technology disclosed herein.

The ophthalmic device 110, the server 140, and the viewer 150 are connected to each other via the network 130. The network 130 is any network such as a LAN, a WAN, the Internet, or a wide area Ethernet network. For example, when the ophthalmic system 100 is constructed in a single hospital, a LAN can be adopted for the network 130.

The viewer 150 is a client in a client-server system, and multiple units are connected via a network. In addition, multiple servers 140 may also be connected via a network to ensure system redundancy. Alternatively, if the ophthalmic device 110 has an image processing function and an image viewing function of the viewer 150, fundus image acquisition, image processing, and image viewing are possible when the ophthalmic device 110 is in a stand-alone state. Also, if the server 140 has an image viewing function of the viewer 150, the configuration of the ophthalmic device 110 and the server 140 allows fundus image acquisition, image processing, and image viewing.

In addition, other ophthalmic equipment (examination equipment for visual field measurement, intraocular pressure measurement, etc.) and a diagnostic support device that performs image analysis using AI (Artificial Intelligence) may be connected to the ophthalmic device 110, server 140, and viewer 150 via network 130.

Next, the configuration of the ophthalmic device 110 will be described with reference to Figure 2.

For ease of explanation, Scanning Laser Ophthalmoscope is referred to as "SLO" and Optical Coherence Tomography is referred to as "OCT."

When the ophthalmic device 110 is placed on a horizontal plane, the horizontal direction is the "X direction", the vertical direction to the horizontal plane is the "Y direction", and the direction connecting the center of the pupil of the anterior part of the subject's eye 12 and the center of the eyeball is the "Z direction". Therefore, the X direction, Y direction, and Z direction are perpendicular to each other.

The ophthalmic device 110 includes an imaging device 14 and a control device 16. The imaging device 14 is equipped with an SLO unit 18 and an OCT unit 20, and acquires a fundus image of the fundus of the subject's eye 12. Hereinafter, the two-dimensional fundus image acquired by the SLO unit 18 will be referred to as an SLO image. In addition, a tomographic image or an en-face image of the retina created based on the OCT data acquired by the OCT unit 20 will be referred to as an OCT image.

The control device 16 comprises a computer having a Central Processing Unit (CPU) 16A, a Random Access Memory (RAM) 16B, a Read-Only Memory (ROM) 16C, and an Input/Output (I/O) port 16D.
In this embodiment, the ROM 16C stores an image processing program shown in FIG. 4, which will be described later.
The CPU 16A is an example of a "processor" of the technology disclosed herein. The ROM 16C is an example of a "storage unit" of the technology disclosed herein. The control device 16 is an example of a "computer program product."

The control device 16 includes an input/display device 16E connected to the CPU 16A via an I/O port 16D. The input/display device 16E has a graphic user interface that displays an image of the subject's eye 12 and receives various instructions from the user. An example of the graphic user interface is a touch panel display.

The control device 16 also includes an image processor 17 connected to the I/O port 16D. The image processor 17 generates an image of the subject's eye 12 based on the data obtained by the photographing device 14. The control device 16 is connected to the network 130 via a communication interface 16F.

As described above, in FIG. 2, the control device 16 of the ophthalmic device 110 is provided with an input/display device 16E, but the technology of the present disclosure is not limited to this. For example, the control device 16 of the ophthalmic device 110 may not be provided with the input/display device 16E, but may be provided with a separate input/display device that is physically independent from the ophthalmic device 110. In this case, the display device includes an image processing processor unit that operates under the control of the display control unit 204 of the CPU 16A of the control device 16. The image processing processor unit may display an SLO image, etc., based on an image signal that the display control unit 204 instructs to output.

The imaging device 14 operates under the control of the CPU 16A of the control device 16. The imaging device 14 includes an SLO unit 18, an imaging optical system 19, and an OCT unit 20. The imaging optical system 19 includes an optical scanner 22 and a wide-angle optical system 30.

The optical scanner 22 performs two-dimensional scanning in the X and Y directions with the light emitted from the SLO unit 18. The optical scanner 22 may be any optical element capable of deflecting a light beam, such as a polygon mirror or a galvanometer mirror. It may also be a combination of these.

The optical scanner 22 combines the light from the SLO unit 18 and the light from the OCT unit 20.

The wide-angle optical system 30 may be a reflective optical system using a concave mirror such as an elliptical mirror, a refractive optical system using a wide-angle lens, or a catadioptric system combining concave mirrors and lenses. By using a wide-angle optical system using an elliptical mirror or a wide-angle lens, it is possible to photograph the retina not only in the center of the fundus but also in the peripheral part of the fundus.

When a system including an elliptical mirror is used, the system using the elliptical mirror described in International Publication WO2016/103484 or International Publication WO2016/103489 may be used. The disclosures of International Publication WO2016/103484 and International Publication WO2016/103489 are each incorporated herein by reference in their entirety.

The wide-angle optical system 30 realizes observation of the fundus with a wide field of view (FOV) 12A. The FOV 12A indicates the range that can be photographed by the photographing device 14. The FOV 12A can be expressed as a field of view. In this embodiment, the field of view can be defined by an internal irradiation angle and an external irradiation angle. The external irradiation angle is the irradiation angle of the light beam irradiated from the ophthalmic device 110 to the subject's eye 12, which is defined based on the pupil 27. The internal irradiation angle is the irradiation angle of the light beam irradiated to the fundus F, which is defined based on the center O of the eyeball. The external irradiation angle and the internal irradiation angle are in a corresponding relationship. For example, when the external irradiation angle is 120 degrees, the internal irradiation angle corresponds to approximately 160 degrees. In this embodiment, the internal irradiation angle is 200 degrees.

Here, an SLO fundus image captured at an internal illumination angle of 160 degrees or more is referred to as a UWF-SLO fundus image. UWF is an abbreviation for Ultra Wide Field. The wide-angle optical system 30, which sets the fundus field of view (FOV) to an ultra-wide angle, can capture an image of the area from the posterior pole of the fundus of the subject eye 12 beyond the equator, and structures present in the peripheral area of the fundus, such as vortex veins, can be captured.

The ophthalmologic device 110 can capture an image of the area 12A with an internal irradiation angle of 200° with the eyeball center O of the subject's eye 12 as the reference position. The internal irradiation angle of 200° is 110° in terms of the external irradiation angle based on the pupil of the subject's eye 12. In other words, the wide-angle optical system 30 irradiates laser light from the pupil with an angle of view of an external irradiation angle of 110°, and captures an image of the fundus area of 200° with an internal irradiation angle.

The SLO system is realized by the control device 16, the SLO unit 18, and the imaging optical system 19 shown in Figure 2. The SLO system is equipped with a wide-angle optical system 30, which enables fundus imaging with a wide FOV 12A.

The SLO unit 18 includes a light source 40 of B light (blue light), a light source 42 of G light (green light), a light source 44 of R light (red light), and a light source 46 of IR light (infrared light (e.g., near-infrared light)), and optical systems 48, 50, 52, 54, and 56 that reflect or transmit the light from the light sources 40, 42, 44, and 46 and guide them to one optical path. The optical systems 48 and 56 are mirrors, and the optical systems 50, 52, and 54 are beam splitters. The B light is reflected by the optical system 48, transmits through the optical system 50, and is reflected by the optical system 54, the G light is reflected by the optical systems 50 and 54, the R light is transmitted through the optical systems 52 and 54, and the IR light is reflected by the optical systems 52 and 56, and each is guided to one optical path.

The SLO unit 18 is configured to be able to switch between a light source that emits laser light of different wavelengths or a combination of light sources that emit light, such as a mode that emits R light and G light and a mode that emits infrared light. In the example shown in FIG. 2, four light sources are provided: a light source 40 of B light, a light source 42 of G light, a light source 44 of R light, and a light source 46 of IR light, but the technology of the present disclosure is not limited to this. For example, the SLO unit 18 may further include a light source of white light and emit light in various modes, such as a mode that emits G light, R light, and B light, or a mode that emits only white light.

Light incident on the imaging optical system 19 from the SLO unit 18 is scanned in the X and Y directions by the optical scanner 22. The scanning light passes through the wide-angle optical system 30 and the pupil 27 and is irradiated onto the fundus. The light reflected by the fundus passes through the wide-angle optical system 30 and the optical scanner 22 and is incident on the SLO unit 18.

The SLO unit 18 includes a beam splitter 64 that reflects B light and transmits light other than B light from the posterior segment (fundus) of the subject's eye 12, and a beam splitter 58 that reflects G light and transmits light other than G light from the light that has passed through the beam splitter 64. The SLO unit 18 includes a beam splitter 60 that reflects R light and transmits light other than R light from the light that has passed through the beam splitter 58. The SLO unit 18 includes a beam splitter 62 that reflects IR light from the light that has passed through the beam splitter 60. The SLO unit 18 includes a B light detection element 70 that detects B light reflected by the beam splitter 64, a G light detection element 72 that detects G light reflected by the beam splitter 58, an R light detection element 74 that detects R light reflected by the beam splitter 60, and an IR light detection element 76 that detects IR light reflected by the beam splitter 62.

The light (reflected light reflected by the fundus) incident on the SLO unit 18 via the wide-angle optical system 30 and the optical scanner 22 is reflected by the beam splitter 64 and received by the B light detection element 70 in the case of B light, and is reflected by the beam splitter 58 and received by the G light detection element 72 in the case of G light. The incident light passes through the beam splitter 58 in the case of R light, is reflected by the beam splitter 60, and is received by the R light detection element 74. The incident light passes through the beam splitters 58 and 60 in the case of IR light, is reflected by the beam splitter 62, and is received by the IR light detection element 76. The image processor 17, which operates under the control of the CPU 16A, generates a UWF-SLO image using signals detected by the B light detection element 70, the G light detection element 72, the R light detection element 74, and the IR light detection element 76.

A UWF-SLO image generated using a signal detected by the B light detection element 70 is called a B-UWF-SLO image (B-color fundus image). A UWF-SLO image generated using a signal detected by the G light detection element 72 is called a G-UWF-SLO image (G-color fundus image). A UWF-SLO image generated using a signal detected by the R light detection element 74 is called an R-UWF-SLO image (R-color fundus image). A UWF-SLO image generated using a signal detected by the IR light detection element 76 is called an IR-UWF-SLO image (IR fundus image). UWF-SLO images include R-color fundus images, G-color fundus images, B-color fundus images, and even IR fundus images. They also include fluorescent UWF-SLO images captured using fluorescence.

The control device 16 also controls the light sources 40, 42, 44 to emit light simultaneously. The fundus of the test eye 12 is photographed simultaneously with B light, G light, and R light, thereby obtaining a G-color fundus image, an R-color fundus image, and a B-color fundus image, each of which corresponds to each other. An RGB color fundus image is obtained from the G-color fundus image, the R-color fundus image, and the B-color fundus image. The control device 16 controls the light sources 42, 44 to emit light simultaneously, and the fundus of the test eye 12 is photographed simultaneously with G light and R light, thereby obtaining a G-color fundus image and an R-color fundus image, each of which corresponds to each other. An RG color fundus image is obtained from the G-color fundus image and the R-color fundus image. A full-color fundus image may also be generated using the G-color fundus image, the R-color fundus image, and the B-color fundus image.

The wide-angle optical system 30 makes the field of view (FOV) of the fundus an ultra-wide angle, making it possible to capture images of the area from the posterior pole of the fundus of the test eye 12 beyond the equator.

The OCT system is realized by the control device 16, OCT unit 20, and imaging optical system 19 shown in FIG. 2. The OCT system includes a wide-angle optical system 30, and thus enables OCT imaging of the peripheral part of the fundus, similar to the above-mentioned SLO fundus image. In other words, the wide-angle optical system 30, which has an ultra-wide fundus field of view (FOV), can image the fundus of the subject eye 12 at a wide angle, specifically, OCT imaging of the area from the posterior pole of the fundus of the subject eye 12 beyond the equator can be performed. OCT data of structures present in the peripheral part of the fundus, such as vortex veins, can be obtained, and a tomographic image of the vortex vein and a 3D structure of the vortex vein can be obtained by image processing the OCT data.

The OCT unit 20 includes a light source 20A, a sensor (detection element) 20B, a first optical coupler 20C, a reference optical system 20D, a collimating lens 20E, and a second optical coupler 20F.

Light emitted from the light source 20A is branched by the first optical coupler 20C. One of the branched lights is collimated by the collimating lens 20E as signal light and then enters the imaging optical system 19. The signal light passes through the wide-angle optical system 30 and the pupil 27 and is irradiated onto the fundus. The signal light reflected by the fundus is also passed through the wide-angle optical system 30 and enters the OCT unit 20, and enters the second optical coupler 20F via the collimating lens 20E and the first optical coupler 20C.

The other light emitted from the light source 20A and branched by the first optical coupler 20C is incident on the reference optical system 20D as reference light, and passes through the reference optical system 20D to be incident on the second optical coupler 20F.

These lights incident on the second optical coupler 20F, i.e., the signal light reflected from the fundus and the reference light, are interfered with by the second optical coupler 20F to generate interference light. The interference light is received by the sensor 20B. The image processor 17, which operates under the control of the image processing unit 206, performs processing such as Fourier transform on the detection signal detected by the sensor 20B to generate OCT data. It is also possible for the image processor 17 to generate OCT images such as tomographic images and en-face images based on the OCT data.

Here, the OCT unit 20 can scan a predetermined range (for example, a rectangular range of 6 mm x 6 mm) in one OCT imaging. The predetermined range is not limited to 6 mm x 6 mm, but may be a square range of 12 mm x 12 mm or 23 mm x 23 mm, or a rectangular range such as 14 mm x 9 mm or 6 mm x 3.5 mm, and can be any rectangular range. It may also be a circular range with a diameter of 6 mm, 12 mm, or 23 mm.

By using the wide-angle optical system 30, the ophthalmic device 110 can scan the area 12A with an internal irradiation angle of 200°. In other words, by controlling the optical scanner 22, OCT imaging of a predetermined range including the vortex vein is performed. The ophthalmic device 110 can generate OCT data by the OCT imaging.

Therefore, the ophthalmologic device 110 can generate OCT images, such as tomographic images (B-scan images) of the fundus including vortex veins, OCT volume data including vortex veins, and en-face images (frontal images generated based on the OCT volume data) that are cross sections of the OCT volume data. It goes without saying that the OCT images include OCT images of the center of the fundus (the posterior pole of the eyeball where the macula, optic disc, etc. are present).

The OCT data (or image data of the OCT image) is sent from the ophthalmic device 110 to the server 140 via the communication interface 16F and stored in a storage device not shown.

In this embodiment, the light source 20A is exemplified as a wavelength-swept type SS-OCT (Swept-Source OCT), but various types of OCT systems may also be used, such as SD-OCT (Spectral-Domain OCT) and TD-OCT (Time-Domain OCT).

Next, various functions realized by the CPU 16A of the ophthalmic apparatus 110 executing the image processing program will be described with reference to Fig. 3. The image processing program has an imaging control function, a display control function, an image processing function, and a processing function. By the CPU 16A executing the image processing program having these functions, the CPU 16A functions as an imaging control unit 202, a display control unit 204, an image processing unit 206, and a processing unit 208 as shown in Fig. 3.
The image processing unit 206 is an example of the “acquisition unit” and the “generation unit” of the technology of the present disclosure.

Next, the image processing of the ophthalmic device 110 will be described in detail with reference to Figure 4. The image processing shown in the flowchart of Figure 4 is realized by the CPU 16A of the control device 16 of the ophthalmic device 110 executing an image processing program.

The processing shown in the flowchart of Figure 4 is an example of an "image processing method" of the technology disclosed herein.

When patient information (patient ID, name, sex, age, and information on whether the eye to be examined is the right eye or the left eye) is entered via the display screen of the input/display device 16E and a start button provided on the display screen is operated, the image processing process shown in FIG. 4 is started.
In step 300, the display control unit 204 and the imaging control unit 202 control the OCT unit 20 and the imaging optical system 19 to capture an image of the desired imaging range of the fundus of the subject's eye 12 specified by the user. Specifically, the display control unit 204 first displays a display screen for OCT imaging on the input/display device 16E. A UWF fundus image and an OCT imaging start button are displayed on the display screen. The user specifies the desired imaging range on the UWF fundus image and operates the OCT imaging start button.

When the image capture start button is pressed, the image capture control unit 202 controls the OCT unit 20 and the image capture optical system 19 to scan the range specified by the user. Then, the image processing unit 206 generates OCT data based on the detection signal of the sensor 20B and stores it in the RAM 16B. The OCT data is composed of multiple A-scan data. The A-scan data refers to data obtained by scanning the fundus of the subject eye 12 in the depth (optical axis) direction (this scanning is called "A-scan"). FIG. 5 is a diagram showing the relationship between the scanning positions _A1 to _A5 on the fundus corresponding to five A-scan data of the A1 scan data to the A5 scan data and the polarization state. As shown in FIG. 5, each of the multiple A-scan data is A-scan data at a different scanning position. FIG. 6A shows A-scan data with scanning positions A1 to A5. The _A3 scan data is A-scan data at a position of the fundus where the signal light is incident along the optical axis passing through the center of the eyeball. The _A2 scan data is A-scan data at a scanning position located lower than the scanning position of the _A3 scan data. The _A1 scan data is A-scan data at a scanning position located lower than the scanning position of the _A2 scan data. The _A4 scan data is A-scan data at a scanning position located lower than the scanning position of the _A3 scan data. The _A5 scan data is A-scan data at a scanning position located higher than the scanning position of the _A4 scan data.

In step 302, the image processing unit 206 acquires the OCT data of the fundus of the test eye 12 from the RAM 16B, and acquires each A-scan data of the multiple A-scan data included in the OCT data. The image processing unit 206 also assigns the position of the A-scan data on the test eye (for example, the position on the fundus in the case of the fundus) to each A-scan data. Here, the position on the test eye is calculated from the scanning position when scanning the desired photographing range (predetermined area) of the fundus. Alternatively, the position on the test eye may be calculated based on the control signal of the optical scanner 22. In this way, the image processing unit 206 assigns the position on the test eye to all A-scans included in the OCT data. The position on the test eye is coordinate data, and may be the fundus or the anterior part of the eye such as the cornea.

In step 304, the image processor 206 calculates the contrast of each A-scan data. Here, contrast refers to the difference between the approximate maximum luminance (luminance greater than a threshold) and the approximate minimum luminance (luminance less than a threshold) of a pixel in the A-scan data. Also, luminance refers to the brightness of the pixels constituting the A-scan data.

Specifically, the image processing unit 206 calculates the contrast of the _A1 scan data from the pixel values of each pixel in the _A1 scan data in Fig. 6A as shown in Fig. 7A, assuming that the maximum brightness value is _D40 and the minimum brightness value is _D20 . Note that P1 to Pn are positions in the depth direction of the fundus where return light that interferes with the reference light is generated. The image processing unit 206 calculates the contrast of the _A2 scan data from the pixel values of each pixel in the _A2 scan data in Fig. 6A as shown in Fig. 7B, assuming that the maximum brightness value is _D45 and the minimum brightness value is _D15 .

From the pixel values of each pixel in the _A3 scan data, the contrast of the A3 scan data is calculated as shown in Fig. 7C, assuming that the maximum brightness value is D ₅₀ and the minimum brightness value is D _10. Similarly, the image processing unit 206 calculates the contrast for the _A4 scan data and the _A5 scan data, and calculates the contrast for all A-scan data included in the OCT data.

As shown in Figure 5, the angle of incidence of the signal light on the fundus varies depending on the scanning position on the fundus. Therefore, the degree of polarization of the reflected light also varies depending on the angle of incidence of the signal light on the fundus. On the other hand, the polarization state of the reference light is always the same. Therefore, the degree to which the polarization states of the signal light and the reference light match changes depending on the scanning position.

The greater the difference in polarization state between the signal light and the reference light, the smaller the intensity of the interference light becomes. Thus, the intensity of the interference light changes depending on the scanning position. In other words, the intensity of the interference light changes depending on the scanning position, and the change in the intensity of the interference light is particularly large in OCT data captured at a wide angle. The change in the intensity of the interference light is then manifested as a change in the contrast of each A-scan data that makes up the OCT data.

6A shows the brightness values of each A-scan data ( _A1 , _A2 , _A3 , _A4 , _A5 ) when the OCT data is composed of five A-scan data. FIG. 6B shows an OCT image generated by the five A-scan data of FIG. 6A. As shown in FIG. 6A and FIG. 6B, the contrast of the A-scan data at each scanning position is different from the contrast of the A-scan data at other scanning positions. For example, the contrast of the A _- scan data is larger than that of the A _- scan data at the A- ₃ scanning position.

Therefore, when the scanning position is different, the contrast of each A-scan data will be different. Therefore, when an OCT image is displayed based on each A-scan data with different contrast, the OCT image shown in Figure 6B will have different brightness values even though it is the same layer. Therefore, it is necessary to correct the contrast of each A-scan data.

In the next step 306, the image processing unit 206 corrects the contrast difference between each A-scan data calculated in step 304 and generates corrected OCT data.

As a correction target, a histogram of pixel values in specific A-scan data or predetermined A-scan data ( _A3 scan data in this embodiment) can be used as a model histogram to correct each of the other multiple A-scan data ( _A1 scan data, _A2 scan data, _A4 scan data, and _A5 scan data).

The contrast of the _A3 scan data at the position of the fundus where the signal light is incident along the optical axis passing through the center of the eyeball, i.e., the maximum brightness value is D50 and the minimum brightness value is D10, is set as the reference contrast. The image processing unit 206 corrects the brightness value of each pixel of the other A-scan data ( _A1 , _A2 , _A4 , _A5 ) so that the contrast of each of the other A-scan data becomes the reference contrast.

Specifically, the image processing unit 206 corrects the maximum brightness value _D40 and the minimum brightness value _D20 of the _A1 scan data in Fig. 7A to the maximum brightness value _D50 and the minimum brightness value _D10 as shown in Fig. 9A. Similarly, for the pixel values of the other pixels in the _A1 scan data, pixel values greater than the median value are increased at the increase rate of the maximum brightness value, and pixel values smaller than the median value are decreased at the decrease rate of the minimum brightness value. In this way, the image processing unit 206 corrects the _A1 scan data in Fig. 6A and outputs f(A1), which is the corrected _A1 scan data shown in Fig. 8A.

Furthermore, the maximum luminance value _D45 and the minimum luminance value _D15 of the _A2 scan data in Fig. 7B are corrected to maximum luminance value _D50 and minimum luminance value _D10 as shown in Fig. 9B. The pixel values of the other pixels of the _A2 scan data are also corrected in the same manner as the _A1 scan data. In this manner, the image processing unit 206 corrects the _A2 scan data in Fig. 6A, and outputs f(A2), which is the corrected A-scan data shown in Fig. 8A.

The image processing unit 206 performs the correction in the same manner to generate corrected A-scan data f( _A4 ,) and f( _A5 ), and since the A3 scan data is the reference contrast, the _A3 scan data is directly set as the corrected A-scan data f( _A3 ). In this manner, the image processing unit 206 corrects the contrast of the A-scan data ( _A1 , _A2 , _A4 , _A5 ) shown in Fig. 6A to generate corrected scan data (f( _A1 ), f( _A2 ), f( _A4 ), f( _A5 )) shown in Fig. 8A. This correction makes it possible to correct the difference in contrast between the A-scans.

The contrast correction of this embodiment is particularly effective when capturing an OCT image at a wide angle of view or when capturing an OCT image of the peripheral part of the fundus, where the curvature of the fundus changes significantly. When capturing an OCT image at a wide angle of view or the peripheral part of the fundus, the polarization state changes more significantly than when capturing an OCT image at a narrow angle of view in the center of the fundus. Therefore, the contrast difference between the A-scans in the OCT data tends to be large. In this embodiment, OCT data and OCT images with uniform contrast can be generated, whether the OCT image is captured over a wide range or the peripheral part of the fundus. An OCT image can be formed in which the brightness value of each pixel in the same layer is the same.

Next, in step 308, the image processing unit 206 uses the A-scan data whose contrast difference has been corrected in step 306 to create an OCT image (tomographic image/B-scan image) as shown in FIG. 8B.

In step 310, the display control unit 204 displays the generated OCT image on the input/display device 16E. In addition, the processing unit 208 stores the OCT data consisting of the image data of the OCT image created in step 308 and the corrected A-scan data in the RAM 16B. The processing unit 208 transmits the UWF fundus image, the desired shooting range on the UWF fundus image, the image data of the OCT image, and the corrected A-scan data together with the patient ID to the server 140. The server 140 stores the OCT data consisting of the UWF fundus image, the desired shooting range on the UWF fundus image, the image data of the OCT image, and the corrected A-scan data in a storage device (not shown) corresponding to the patient ID. Furthermore, in response to a request from the viewer 150, the server 140 transmits to the viewer 150 the OCT data consisting of the UWF fundus image, the desired imaging range on the UWF fundus image, image data of the OCT image, and corrected A-scan data, together with patient information (patient ID, name, sex, age, and information on whether the examined eye is right or left eye). The viewer 150 displays the patient information, the UWF fundus image, the desired imaging range on the UWF fundus image, and the OCT image on a display (not shown).

Figure 10 shows the display contents of a screen 500 displayed on the display of the viewer 150. The screen 500 has a patient information display area 502, a UWFSLO image display area 504, and an OCT image display area 506.

The patient information display area 502 has a patient ID display field 502A, a patient name display field 502B, a gender display field 502C, an age display field 502D, and a right eye/left eye display field 502E. Each piece of information is displayed in these fields (502A to 502E).
On the screen 500, a UWFSLO image 404 of the right eye is displayed in a UWFSLO image display area 504. The position of the OCT image 702 on the fundus (desired imaging range) is superimposed and displayed as an arrow mark 402 on the UWFSLO image 404. The OCT image 702 with the contrast corrected is displayed in an OCT image display area 506.

In this way, the user can check the position of the OCT image 702 on the fundus using the viewer 150. Furthermore, the contrast-corrected OCT image can be used to perform diagnosis, etc.

(Modification)
<First Modification>
In the first embodiment, the contrast of each A-scan data is corrected to be the same as the contrast (reference contrast) of other A-scan data. However, the technology of the present disclosure is not limited to this. Only the specific luminance value (e.g., maximum value, minimum value, or median value) may be corrected so that the difference between the specific luminance value, e.g., maximum value, minimum value, or median value, is within a predetermined value in each A-scan data.
In this way, in the first modified example, it is possible to calculate the contrast for at least the unique luminance value. Also, in the first modified example, it is possible to correct the contrast for at least the unique luminance value. Furthermore, in the first modified example, it is possible to correct the influence of polarization for at least the pixels with the unique luminance value, and to obtain an OCT image without unevenness.

<Second Modification>
In the above first embodiment, a luminance value representing lightness is used as the pixel value, but the technology of the present disclosure is not limited to this, and a value representing at least one of saturation and hue may be used instead of or together with the luminance value.

<Third Modification>
In the first embodiment described above, the contrast of the A-scan data at the center of the eyeball was used as the reference, but in the technology disclosed herein, the contrast of the A-scan data at a specific position, not limited to the center of the eyeball, may be used as the reference, and the correction rate may be changed depending on the scanning position.

<Fourth Modification>
In the first embodiment, the contrast of the A-scan data at the center of the eyeball is used as a reference. However, in the technology disclosed herein, the contrast may be corrected using a correction coefficient table including a scanning position and a correction coefficient (a parameter dependent on the number of bright pixels) for correcting each pixel value of the A-scan data at that scanning position. In this case, the processing unit 208 reads out the correction coefficient table from the RAM 16B or the server 140 prior to step 300 in FIG. 4. The image processing unit 206 corrects each pixel value of the A-scan data with the read correction coefficient.
<Fourth Modification>
In the first embodiment, the contrast difference between each A-scan data is corrected by the CPU 16A of the ophthalmic device 110. However, the technology disclosed herein is not limited to this, and OCT data acquired by the ophthalmic device 110 may be transmitted to the server 140, and the contrast difference between each A-scan data included in the OCT data may be corrected by the CPU of the server 140. Furthermore, the correction may be performed by a CPU of a computer other than the viewer 150 or the ophthalmic device 110, instead of the server 140.

The data processing described in the above embodiment is merely an example. It goes without saying that unnecessary steps may be deleted, new steps may be added, or the processing order may be changed without departing from the spirit of the invention.

In this disclosure, each component (device, etc.) may be present in one or more instances, provided no contradiction arises.

In addition, in the above embodiment, a case where data processing is realized by a software configuration using a computer is exemplified, but the technology of the present disclosure is not limited to this. For example, instead of a software configuration using a computer, data processing may be performed only by a hardware configuration such as an FPGA or an ASIC. A part of the data processing may be performed by a software configuration, and the remaining processing may be performed by a hardware configuration.

As such, the technology disclosed herein includes both cases in which image processing is achieved by a software configuration using a computer and cases in which it is not achieved, and therefore includes the following technologies.

(First Technology)
an acquisition unit that acquires OCT data of the fundus of the subject's eye based on interference light between return light obtained by scanning the signal light and the reference light;
A generating unit that corrects a difference in contrast between a plurality of A-scan data included in the OCT data and generates corrected OCT data;
An image processing device comprising:

(Second Technology)
An acquisition unit acquires OCT data of the fundus of the test eye based on interference light between return light obtained by scanning the signal light and the reference light;
A generating unit corrects contrast differences between a plurality of A-scan data included in the OCT data, and generates corrected OCT data;
An image processing method comprising:

Based on the above disclosure, the following techniques are proposed.
(Third Technology)
1. A computer program product for obtaining an OCT signal, comprising:
The computer program product comprises a computer-readable storage medium that is not itself a transitory signal;
The computer-readable storage medium stores a program,
The program is
On the computer,
acquiring OCT data of the fundus of the subject's eye based on interference light between return light obtained by scanning the signal light and the reference light;
correcting a contrast difference between a plurality of A-scan data included in the OCT data to generate corrected OCT data;
Execute a process including
Computer program products.

All publications, patent applications, and technical standards described in this specification are incorporated by reference into this specification to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

The disclosure of Japanese Patent Application No. 2021-087903 is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims (8)

Image processing performed by a processor,
acquiring OCT data of the fundus of the subject's eye based on interference light between return light obtained by scanning the signal light and the reference light;
Calculating contrast of each of a plurality of A-scan data included in the OCT data;
selecting reference A-scan data from the plurality of A-scan data;
correcting contrasts of a plurality of A-scan data included in the OCT data to match contrasts of the reference A-scan data , thereby generating corrected OCT data;
An image processing method comprising: The image processing method according to claim 1 , wherein the step of selecting the reference A-scan data comprises selecting A-scan data of a central portion of the fundus of the subject's eye. The image processing method of claim 1 , further comprising generating an OCT image using the corrected OCT data.
The image processing method according to claim 1 , further comprising: The image processing method according to claim 1, characterized in that the contrast is calculated by determining the difference between the maximum and minimum brightness of a pixel in the A-scan data. The image processing method according to claim 1, characterized in that each of the plurality of A-scan data is A-scan data of a different scanning position of the fundus of the subject eye. The image processing method according to any one of claims 1 to 5, characterized in that the OCT data is obtained by photographing the fundus of the subject's eye at a wide angle. An image processing device including a processor,
The processor,
acquiring OCT data of the fundus of the subject's eye based on interference light between return light obtained by scanning the signal light and the reference light;
Calculating contrast of each of a plurality of A-scan data included in the OCT data;
selecting reference A-scan data from the plurality of A-scan data;
correcting contrasts of a plurality of A-scan data included in the OCT data to match contrasts of the reference A-scan data , thereby generating corrected OCT data;
An image processing device that performs the above. On the computer,
acquiring OCT data of the fundus of the subject's eye based on interference light between return light obtained by scanning the signal light and the reference light;
Calculating contrast of each of a plurality of A-scan data included in the OCT data;
selecting reference A-scan data from the plurality of A-scan data;
correcting contrasts of a plurality of A-scan data included in the OCT data to match contrasts of the reference A-scan data , thereby generating corrected OCT data;
A program that executes the following.