JP6437055B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing method for processing an image of a subject.

  Optical coherence tomography (hereinafter referred to as OCT) using multiwavelength lightwave interference can obtain a tomographic image of a sample (particularly the fundus) with high resolution.

  In recent years, in Ophthalmic OCT, in addition to normal OCT for imaging the shape of the fundus tissue, development of polarized OCT for imaging using polarization parameters (retardation and orientation), which are one of the optical characteristics of the fundus tissue, has progressed. It is out.

  Polarization OCT can construct a polarization OCT image using polarization parameters, and can perform fundus tissue discrimination and segmentation (processing for calculating the boundary of each layer from tomographic image data). Therefore, pathological diagnosis such as glaucoma diagnosis can be supported by distinguishing tissues that are difficult to diagnose with luminance information.

  Polarization OCT uses light modulated into circularly polarized light as measurement light for observing a sample, divides and detects interference light as two orthogonal linearly polarized lights, and generates a polarized OCT image (see Patent Document 1).

WO2010 / 122118A1

However, Patent Document 1 does not disclose any device or method for performing disease follow-up or the like using the acquired OCT image.
One of the objects of the present invention is to assist the user in effectively performing the disease follow-up and the like based on the polarization information obtained from the polarization OCT.

One of the image processing apparatuses according to the present invention is
A tomographic luminance image and a polarized tomographic image of the subject obtained by processing a common OCT signal by the return light and the reference light from the subject irradiated with the measurement light , the subjects being photographed at different times A tomographic image acquisition means for acquiring a plurality of obtained tomographic luminance images and a plurality of polarized tomographic images corresponding to the plurality of tomographic luminance images;
Alignment means for aligning the plurality of acquired polarization tomographic images using the positional deviation information of the acquired plurality of tomographic luminance images.
One of the image processing methods according to the present invention is as follows.
A tomographic luminance image and a polarized tomographic image of the subject obtained by processing a common OCT signal by the return light and the reference light from the subject irradiated with the measurement light , the subjects being photographed at different times Obtaining a plurality of tomographic luminance images obtained and a plurality of polarization tomographic images corresponding to the plurality of tomographic luminance images;
And using the positional deviation information of the acquired plurality of tomographic luminance images to align the acquired plurality of polarized tomographic images.

  According to one aspect of the present invention, registration of a plurality of polarization tomographic images corresponding to the plurality of tomographic luminance images is performed using positional deviation information of the plurality of tomographic luminance images obtained by imaging the subject at different times. I do. Thereby, based on the polarization information obtained from the polarization OCT, it is possible to assist the user in effectively observing the progress of the disease.

1 is a schematic diagram of an overall configuration of an image processing apparatus according to a first embodiment. An example of an image generated by the signal processing unit 190 according to the first embodiment. The processing flow in 1st Embodiment. 4 is a display example on a display screen of a display unit of the image processing apparatus according to the first embodiment. Explanatory drawing of the alignment of the OCT scan position in 1st Embodiment. Explanatory drawing of the alignment at the time of the tomographic luminance image superimposition in 1st Embodiment. FIG. 5 is a conceptual diagram of tomographic luminance image superposition in the first embodiment. 4 is a display example on a display screen of a display unit of the image processing apparatus according to the first embodiment. 4 is a display example on a display screen of a display unit of the image processing apparatus according to the first embodiment. The conceptual diagram of the 3D tomographic luminance image comprised from the superimposition image in 2nd Embodiment. The processing flow in 2nd Embodiment.

  The imaging apparatus according to the present invention can be applied to subjects such as eyes, skin, and internal organs. In addition, examples of the photographing apparatus according to the present invention include an ophthalmologic apparatus and an endoscope. Hereinafter, as an example of the present invention, an ophthalmologic apparatus according to the present embodiment will be described in detail with reference to the drawings.

(First embodiment)
[Overall system configuration]
FIG. 1 is a schematic diagram of the overall configuration of an “ophthalmologic apparatus” that is an example of an imaging apparatus according to the present embodiment. Note that at least a part of the signal processing unit 190 described later can be regarded as an “image processing apparatus”. In this case, the entire “ophthalmic apparatus” is the “ophthalmic system” or the entire “imaging apparatus” is the “imaging system”. Can also be considered.

  This apparatus includes a polarization OCT (Polarization Sensitive OCT; hereinafter referred to as PS-OCT) 100, a polarization-sensitive scanning ophthalmoscope (hereinafter referred to as PS-SLO) 140, an anterior eye imaging unit 160, and an internal part. A fixation lamp 170 and a control unit 200 are included.

  The apparatus is aligned using an image of the anterior segment of the subject's eye observed by the anterior segment imaging unit 160 in a state where the internal fixation lamp 170 is turned on and the subject's eye is gazed. After the alignment is completed, the fundus is imaged by PS-OCT 100 and PS-SLO 140.

<Configuration of PS-OCT100>
A configuration of the PS-OCT 100 will be described.

  The light source 101 is an SLD light source (Super Luminescent Diode) that is a low-coherent light source, and emits light having a center wavelength of 850 nm and a bandwidth of 50 nm, for example. Although an SLD is used as the light source 101, any light source capable of emitting low-coherent light, such as an ASE light source (Amplified Spontaneous Emission), may be used.

  Light emitted from the light source 101 is guided to a fiber coupler 104 having a polarization maintaining function via an SM (Single Mode) fiber 134, a polarization controller 103, a connector 135, and a PM (Polarization Maintaining) fiber 102, and is measured light. (Hereinafter also referred to as “measurement light for tomographic image” or “OCT measurement light”) and a reference light corresponding to the measurement light.

  The polarization controller 103 adjusts the polarization state of the light emitted from the light source 101 and is adjusted to linearly polarized light. The branching ratio of the fiber coupler 104 is 90 (reference light): 10 (measurement light).

  The measurement light is emitted as parallel light from the collimator 106 via the PM fiber 105. The emitted measurement light is composed of an X scanner 107 configured by a galvanometer mirror that scans the measurement light in the horizontal direction on the fundus Er, lenses 108 and 109, and a galvanometer mirror that scans the measurement light in the vertical direction on the fundus Er. It reaches the dichroic mirror 111 via the Y scanner 110. The X scanner 107 and the Y scanner 110 are controlled by the drive control unit 180, and can scan the measurement light in a desired range of the fundus Er. The range on the fundus where the measurement light is scanned can be regarded as a tomographic image acquisition range, a tomographic image acquisition position, and a measurement light irradiation position. The X scanner 107 and the Y scanner 110 are examples of PS-OCT scanning means, and may be configured as a common XY scanner. The dichroic mirror 111 has a characteristic of reflecting light of 800 nm to 900 nm and transmitting other light.

  The measurement light reflected by the dichroic mirror 111 passes through the lens 112 and passes through a λ / 4 polarizing plate 113 installed at an angle of 45 ° with respect to the S-polarized light from the P-polarized light with the optical axis as the rotation axis. Is shifted by 90 °, and the polarization is controlled by circularly polarized light. The P-polarized light referred to in the present embodiment is light that oscillates horizontally with respect to the incident surface when the polarization splitting surface of the polarizing beam splitter is used as a reflecting surface, and the S-polarized light is relative to the incident surface. Light that vibrates vertically. The λ / 4 polarizing plate 113 is an example of a measurement light polarization adjusting member that adjusts the polarization state of the measurement light. Here, when a PS-SLO optical system to be described later is applied, the λ / 4 polarizing plate 113 can be provided in a common optical path of a part of the PS-OCT optical system and a part of the PS-SLO optical system. Thereby, the dispersion | variation in the polarization state which arises in the image acquired with the PS-SLO optical system and the image acquired with the PS-OCT optical system can be suppressed. At this time, the scanning means for PS-SLO and the scanning means for PS-OCT are provided at a position conjugate with each other, and can be provided at a position conjugate with the pupil of the eye to be examined. The inclination of the λ / 4 polarizing plate 113 is an example of the state of the λ / 4 polarizing plate 113. For example, the inclination of the optical axis of the polarization splitting surface of the fiber coupler 123 incorporating the polarizing beam splitter is a predetermined axis. The angle from the position.

  Further, the λ / 4 polarizing plate 113 can be configured to be detachable from the optical path. For example, a mechanical configuration in which the λ / 4 polarizing plate 113 is rotated about an optical axis or an axis parallel to the optical axis as a rotation axis is conceivable. Thereby, it is possible to realize a small apparatus capable of easily switching between the SLO optical system and the PS-SLO optical system. Further, it is possible to realize a small apparatus that can easily switch between the OCT optical system and the PS-OCT optical system.

  Here, the light incident on the eye to be examined is controlled to be circularly polarized light by tilting the λ / 4 polarizing plate by 45 °, but is not circularly polarized on the fundus Er due to the characteristics of the eye to be examined. There is. Therefore, the tilt of the λ / 4 polarizing plate 113 can be finely adjusted by the control of the drive control unit 180.

  The measurement light whose polarization is controlled to be circularly polarized is focused on the retinal layer of the fundus Er by the focus lens 114 mounted on the stage 116 via the anterior segment Ea of the subject eye. The measurement light irradiated on the fundus Er is reflected and scattered by each retinal layer and returns to the fiber coupler 104 through the optical path described above.

  On the other hand, the reference light branched by the fiber coupler 104 is emitted as collimated light from the collimator 118 via the PM fiber 117. Like the measurement light, the emitted reference light is polarization-controlled by a λ / 4 polarizing plate 119 installed with an optical axis as a rotation axis and inclined by 22.5 ° from P-polarized light to S-polarized light. The λ / 4 polarizing plate 119 is an example of a reference light polarization adjusting member that adjusts the polarization state of the reference light. The reference light is reflected by the mirror 122 on the coherence gate stage 121 through the dispersion compensation glass 120 and returns to the fiber coupler 104. The reference light passes through the λ / 4 polarizing plate 119 twice, so that the linearly polarized light returns to the fiber coupler 104.

  The coherence gate stage 121 is controlled by the drive control unit 180 in order to cope with a difference in the axial length of the subject. The coherence gate is a position corresponding to the optical path length of the reference light in the optical path of the measurement light. In the present embodiment, the optical path length of the reference light is changed, but it is sufficient that the optical path length difference between the optical path of the measurement light and the optical path of the reference light can be changed.

  The return light that has returned to the fiber coupler 104 and the reference light are combined to form interference light (hereinafter also referred to as “combined light”), which is incident on the fiber coupler 123 with a built-in polarization beam splitter, and has different polarization directions. The light is divided into certain P-polarized light and S-polarized light at a branching ratio of 50:50.

  P-polarized light is split by the grating 131 through the PM fiber 124 and the collimator 130 and received by the lens 132 and the line camera 133. Similarly, the S-polarized light is split by the grating 127 through the PM fiber 125 and the collimator 126 and received by the lens 128 and the line camera 129. Note that the gratings 127 and 131 and the line cameras 129 and 133 are arranged according to the direction of each polarization.

  The light received by the line cameras 129 and 133 is output as an electrical signal corresponding to the intensity of the light and received by the signal processing unit 190.

  The inclination of the λ / 4 polarizing plates 113 and 119 can be automatically adjusted based on the inclination of the polarization splitting surface of the polarizing beam splitter 123. At this time, it is preferable to have an inclination detector (not shown) that detects the inclination of the λ / 4 polarizing plates 113 and 119. This inclination detection unit can detect whether the current inclination matches a predetermined inclination. Of course, the inclination of the λ / 4 polarizing plates 113 and 119 may be detected based on the intensity of the received light, and the inclination may be adjusted so as to have a predetermined intensity. As will be described later, an object indicating inclination may be displayed on the GUI, and the user may adjust using a mouse. The same effect can be obtained by adjusting the polarization beam splitter and the λ / 4 polarizing plates 113 and 119 with respect to the vertical direction as the polarization reference.

<Configuration of PS-SLO 140>
The configuration of the PS-SLO 140 will be described.

  The light source 141 is a semiconductor laser, and emits light having a central wavelength of 780 nm, for example, in the present embodiment. The measurement light emitted from the light source 141 (hereinafter also referred to as “fundus image measurement light” or “SLO measurement light”) is polarization-controlled by the polarization controller 145 via the PM fiber 142 to be a collimator. 143 is emitted as parallel light. The emitted measurement light passes through the perforated part of the perforated mirror 144, passes through the lens 155, and scans the measurement light in the horizontal direction on the fundus Er. The X scanner 146, the lenses 147, 148, the fundus The light reaches a dichroic mirror 154 via a Y scanner 149 configured by a galvanometer mirror that scans measurement light in the vertical direction at Er. The X scanner 146 and the Y scanner 149 are controlled by the drive control unit 180 and can scan a desired range on the fundus with measurement light. Note that the X scanner 146 and the Y scanner 149 are examples of PS-SLO scanning means, and may be configured as a common XY scanner. The dichroic mirror 154 has a characteristic of reflecting 760 nm to 800 nm and transmitting other light.

  The linearly polarized measurement light reflected by the dichroic mirror 154 passes through the same optical path as the PS-OCT 100 and reaches the fundus Er.

  The measurement light applied to the fundus Er is reflected and scattered by the fundus Er and reaches the mirror 144 with a hole following the optical path described above. The light reflected by the perforated mirror 144 is split into light of different polarization directions (in this embodiment, P-polarized light and S-polarized light) via the lens 150 by the polarizing beam splitter 151, and an avalanche photodiode is obtained. Light received by (APD) 152 and 153, converted into an electric signal, and received by the signal processing unit 190.

  Here, the position of the perforated mirror 144 is conjugate with the pupil position of the eye to be examined, and the light passing through the periphery of the pupil out of the light reflected and scattered from the measurement light irradiated to the fundus Er is Reflected by the perforated mirror 144.

  In the present embodiment, the PM fiber is used for both PS-OCT and PS-SLO, but the same configuration and effect can be obtained by controlling the polarization using a polarization controller even with a single mode fiber (SMF).

<Anterior Eye Imaging Unit 160>
The anterior segment imaging unit 160 will be described.

  The anterior segment imaging unit 160 irradiates the anterior segment Ea with an illumination light source 115 including LEDs 115-a and 115-b that emit illumination light having a wavelength of 1000 nm. The light reflected by the anterior segment Ea reaches the dichroic mirror 161 via the lens 114, the polarizing plate 113, the lens 112, and the dichroic mirrors 111 and 154. The dichroic mirror 161 has a characteristic of reflecting light of 980 nm to 1100 nm and transmitting other light. The light reflected by the dichroic mirror 161 is received by the anterior eye camera 165 via the lenses 162, 163, and 164. The light received by the anterior eye camera 165 is converted into an electrical signal and received by the signal processing unit 190.

<Internal fixation lamp 170>
The internal fixation lamp 170 will be described.

  The internal fixation lamp 170 includes an internal fixation lamp display unit 171 and a lens 172. As the internal fixation lamp display unit 171, a plurality of light emitting diodes (LDs) arranged in a matrix is used. The lighting position of the light emitting diode is changed according to the part to be photographed under the control of the drive control unit 180. Light from the internal fixation lamp display unit 171 is guided to the eye to be examined through the lens 172. The light emitted from the internal fixation lamp display unit 171 is 520 nm, and a desired pattern is displayed by the control unit 180.

<Control unit 200>
A control unit 200 for controlling the entire apparatus will be described.

  The control unit 200 includes a drive control unit 180, a signal processing unit 190, a display control unit 191, and a display unit 192.

  The drive control unit 180 controls each unit as described above.

  The signal processing unit 190 includes an image generation unit 193, an image analysis unit 194, an image overlay unit 195, and a comparison unit 196. The signal processing unit 190 generates an image, analyzes the generated image, and generates visualization information of the analysis result based on signals output from the line cameras 129 and 133, the APDs 152 and 153, and the anterior eye camera 165, respectively. . Details of image generation and analysis will be described later.

  The display control unit 191 displays the fundus image, the fundus tomographic image, and the like generated by the signal processing unit 190 on the display screen of the display unit 192. Here, the display unit 192 is a display such as a liquid crystal display, for example. Note that the image data generated by the signal processing unit 190 may be transmitted to the display control unit 191 by wire or may be transmitted wirelessly. In this case, the display control unit 191 can be regarded as an image processing device, and it is only necessary that the image processing device and the imaging device (ophthalmic device) are connected to be communicable. The imaging system may be configured such that the fundus image acquisition unit includes an SLO optical system and the tomographic image acquisition unit includes an OCT optical system. In this specification, in the case of a subject other than the subject's eye, “fundus image (fundus luminance image)” can be rephrased as “flat image (flat luminance image)”, and “fundus image acquisition unit” Can be rephrased as a “planar image acquisition unit”.

  The display unit 192 displays a display form indicating various information as described later under the control of the display control unit 191. Note that the image data from the display control unit 191 may be transmitted to the display unit 192 by wire or wirelessly. In addition, the display unit 192 and the like are included in the control unit 200, but the present invention is not limited thereto, and may be provided separately from the control unit 200. Moreover, the tablet which is an example of the apparatus which the display control part 191 and the display part 192 integrated, and the user can carry may be sufficient. In this case, it is preferable that a touch panel function is mounted on the display unit so that operations such as movement, enlargement / reduction, and change of the displayed image can be performed on the touch panel.

[Image processing]
Next, image generation in the image generation unit 193 constituting the signal processing unit 190 will be described.

  The image generation unit 193 performs a reconstruction process used for general SD-OCT (Spectral Domain OCT) on each interference signal output from the line cameras 129 and 133, and thereby based on each polarization component. The tomographic luminance image corresponding to the first polarized light that is the two tomographic images and the tomographic luminance image corresponding to the second polarized light are generated.

  First, the image generation unit 193 performs fixed pattern noise removal from the interference signal. Fixed pattern noise removal is performed by extracting fixed pattern noise by averaging a plurality of detected A-scan signals and subtracting this from the input interference signal.

  Next, the image generation unit 193 generates a tomographic signal indicating a polarization state by converting the interference signal from a wavelength to a wave number and performing a Fourier transform.

  By performing the above processing on the interference signals of the two polarization components, two tomographic luminance images are generated.

  In addition, the image generation unit 193 aligns the signals output from the APDs 152 and 153 in synchronization with the driving of the X scanner 146 and the Y scanner 149, thereby providing two first fundus images based on the respective polarization components. A fundus image corresponding to the second polarized light and a fundus image corresponding to the second polarized light are generated.

<Generation of tomographic luminance image or fundus luminance image>
The image generation unit 193 generates a tomographic luminance image from the two tomographic signals described above.

Tomographic luminance image is calculated prior basically the same as the tomographic image at OCT, the pixel value r from the fault signals A _H and A _V obtained from the line sensors 129 and 133 by (Equation 1) .

  Similarly, a fundus luminance image is generated from two fundus images.

  FIG. 2A shows an example of a luminance image of the optic nerve head.

  When the λ / 4 polarizing plate 113 is removed from the optical path, the display control unit 191 may display the tomographic luminance image acquired by the conventional OCT technique on the display unit 192, or the conventional SLO. The fundus luminance image acquired by the technique may be displayed on the display unit 192.

<Generation of retardation image>
The image generation unit 193 generates a retardation image from the tomographic images of polarization components orthogonal to each other.

The litter value of each pixel of the retardation image [delta], at the position of each pixel constituting the tomographic image is a value indicating the ratio of the effect of the vertical polarization component and the horizontal polarization component is subjected in the subject's eye, the tomographic signals A _H and It is calculated from A _V by (equation 2).

  FIG. 2B shows an example of the retardation image of the optic nerve head generated in this way, and can be obtained by calculating (Equation 2) for each B-scan image. Here, as described above, the retardation image is a tomographic image showing the difference in the influence of two polarized light on the eye to be examined. In FIG. 2B, the value indicating the above ratio is displayed in color as a tomographic image, and the value indicating the above ratio is small in a dark and light place, and the value indicating the above ratio is large in a light and dark place. Represents. Therefore, it is possible to grasp a birefringent layer by generating a retardation image. The details are as described in “E. Gotzinger et al., Opt. Express 13, 10217, 2005”.

  Similarly, the image generation unit 193 can also generate a retardation image in the planar direction of the fundus based on the outputs from the APDs 152 and 153.

<Generation of retardation map>
The image generation unit 193 generates a retardation map from the retardation images obtained for a plurality of B scan images.

  First, the image generation unit 193 detects a retinal pigment epithelium (hereinafter also referred to as “RPE”) in each B-scan image. Since RPE has the property of depolarizing, each A scan is examined for the retardation distribution in the range not including RPE from the inner boundary film (hereinafter also referred to as “ILM”) along the depth direction. The value is a representative value of retardation in the A scan.

  The image generation unit 193 generates a retardation map by performing the above processing on all the retardation images.

  FIG. 2C shows an example of a retardation map of the optic nerve head. A dark and light place indicates that the value indicating the ratio is small, and a dark and light place indicates that the value indicating the ratio is large. In the optic papilla, the birefringent layer is the retinal nerve fiber phase (hereinafter also referred to as “RNFL”), and the retardation map receives two polarizations with RNFL birefringence and RNFL thickness. It is an image which shows the difference in influence. Therefore, when the density of the retinal nerve fibers is uniform, the value indicating the ratio becomes large at a location where the RNFL is thick, and the value indicating the ratio becomes small at a location where the RNFL is thin.

<Generation of birefringence map>
The image generation unit 193 linearly approximates the value of the retardation δ in the range of ILM to RNFL in each A scan image of the previously generated retardation image, and the inclination thereof at the position on the retina of the A scan image. Determined as birefringence. That is, since the retardation is a product of the distance, birefringence, and product in RNFL, a linear relationship is obtained by plotting the depth and the retardation value in each A-scan image. Therefore, if this plot is linearly approximated by the method of least squares or the like and the slope is obtained, it becomes the value of the birefringence of the RNFL in the A-scan image. A map representing birefringence is generated by performing this process on all the retardation images acquired.

  FIG. 2D shows an example of a birefringence map of the optic nerve head. Since the birefringence map directly maps the birefringence value, even if the RNFL thickness does not change, it can be visualized as a change in birefringence when the fiber structure changes.

<Generation of DOPU images>
Image generating unit 193 calculates the acquired tomographic signals A _H, the phase difference ΔΦ between them and A _V, the Stokes vector S for each pixel (equation 3).

However, ΔΦ is calculated as ΔΦ = Φ _V −Φ _H from the phases Φ _H and Φ _{V of} each signal obtained when calculating two tomographic images.

  Next, the image generation unit 193 sets a window having a size of about 70 μm in the main scanning direction of the measurement light and a size of about 18 μm in the depth direction for each B-scan image, and the Stokes vector calculated for each pixel in each window. Each element is averaged, and the polarization uniformity DOPU (Degree Of Polarization Uniformity) in the window is calculated by (Expression 4) according to (Expression 4).

However, Q _m , U _m , and V _m are values obtained by averaging the Stokes vector elements Q, U, and V in each window. By performing this process on all the windows in the B-scan image, the DOPU image of the optic papilla shown in FIG. 2 (e) is generated. Here, as described above, the DOPU image is a tomographic image showing the uniformity of two polarizations.

  DOPU is a numerical value indicating the uniformity of polarization, and is a value close to 1 at a portion where polarization is maintained, and is a value smaller than 1 at a portion where polarization is not maintained. In the structure in the retina, the RPE has a property of canceling the polarization state. Therefore, the value of the portion corresponding to the RPE in the DOPU image is smaller than that in other regions. In the figure, a lightly shaded area 210 indicates RPE, and a darkly shaded area 220 indicates a retinal layer region where polarization is maintained. Since the DOPU image is an image of a layer that eliminates polarization, such as RPE, even when the RPE is deformed due to a disease or the like, the RPE can be imaged more reliably than a change in luminance.

  Similarly, the image generation unit 193 can also generate a DOPU image in the planar direction of the fundus based on the outputs from the APDs 152 and 153.

  In the present specification, the above-described tomographic luminance image, retardation image, DOPU image and the like corresponding to the first and second polarized light are also referred to as a tomographic image or a polarized tomographic image indicating a polarization state. In the present specification, the retardation map, birefringence map, and the like described above are also referred to as a fundus image or a polarized fundus image indicating a polarization state.

  The image analysis unit 194, which is an example of an extraction unit, extracts (detects) a region (location) from which polarization is removed, for example, a layer such as RNFL, from a tomographic image indicating a polarization state such as a DOPU image or a retardation image. be able to. In addition, the image analysis unit 194, which is an example of the specifying unit, specifies a predetermined shape as a lesioned part in the region where the polarization is eliminated. In addition, the area | region from which polarization | polarized-light was canceled is an area | region where the difference of the influence which two polarized light receives with a to-be-tested eye is comparatively large, for example.

[Processing operation]
Next, a processing operation by the image processing apparatus will be described.

  FIG. 3 is a flowchart showing the processing operation of the image processing apparatus.

<Adjustment>
First, in step S101, the apparatus and the eye to be examined are aligned with the eye to be examined being placed on the apparatus. Regarding the description of the alignment, processing unique to the present embodiment will be described, and alignment in the XYZ directions such as working distance, focus, adjustment of the coherence gate, and the like are common, and description thereof will be omitted.

(Adjustment of PS-OCT imaging position)
FIG. 4 shows a window 400 displayed on the display unit 192 during adjustment. In a display area 410 that is an example of the first display area, a fundus image 411 that is captured by the PS-SLO 140 and generated by the image generation unit 193 is displayed, and the imaging position of the PS-OCT 100 is displayed on the fundus image 411. A guide 412 shown is superimposed and displayed.

  A method in which an operator uses a pointing device (not shown) such as a mouse to perform an instruction by performing a click operation or a drag operation from a cursor displayed on the window 400, or a numerical input frame is provided in the window 400 and designated directly. By using the method, the shooting range is set under the control of the drive control unit 180. Thereby, the drive control unit 180 sets an imaging range for controlling the drive angle of the scanner. The mouse of this embodiment includes, for example, a sensor that detects a movement signal when the mouse body is moved two-dimensionally by the user's hand, and a left and right for detecting that the mouse is pressed by the user's hand. Two mouse buttons and a wheel mechanism that can rotate back and forth and right and left are provided between the two left and right mouse buttons. In addition, the pointing device may include a touch panel function on the display unit and specify an acquisition position on the touch panel.

(Adjustment of λ / 4 polarizing plate)
Adjustment of the λ / 4 polarizing plate 113 will be described.

  In FIG. 4, instruction units 413 and 414 are displays for adjusting the angle of the λ / 4 polarizing plate 113, and are controlled by the drive control unit 180 by an operator using an instruction device. The angle of the λ / 4 polarizing plate 113 is adjusted. The instruction unit 413 is a display for instructing counterclockwise adjustment, and the instruction unit 414 is an instruction for instructing clockwise adjustment. The numerical value displayed beside the instruction units 413 and 414 represents the current angle of the λ / 4 polarizing plate 113. The display control unit 191 may display an instruction unit for adjusting the angle of the λ / 4 polarizing plate 119 along with the instruction unit 413 on the display unit 192 or may be displayed instead of the instruction unit 413. .

  The operator makes the luminance of the tomographic luminance images of the respective polarizations displayed in the display area 430, which is an example of the third display area, and the display area 440, which is an example of the fourth display area, the same. Point with the cursor using the mouse. A configuration may be adopted in which the peak luminance value is displayed together with the tomographic luminance images 431 and 441 of each polarized light, or the waveform of each interference signal itself is displayed and the adjustment is performed while viewing the waveform. Here, the tomographic luminance images 431 and 441 of each polarization are examples of a tomographic luminance image corresponding to the first polarized light and a tomographic luminance image corresponding to the second polarized light. In addition, in the tomographic luminance images 431 and 441 of each polarization, a display form indicating the type of each image, for example, a letter “P” indicating P polarization or a letter “S” indicating S polarization is superimposed on the image. Are preferably displayed. Thereby, it can prevent that a user recognizes an image accidentally. Of course, the image may be displayed on the upper side or the side of the image without being superimposed on the image, or may be displayed so as to correspond to the image.

  In addition, in the display area 420 as an example of the second display area, nothing may be displayed at this stage, and in the case of auto adjustment or the like, a display form indicating the current adjustment state, for example, “λ A message such as “Adjusting the / 4 polarizing plate” may be displayed. The window 400 may display a display form indicating patient information such as the left and right eyes of the eye to be examined and a display form indicating imaging information such as an imaging mode. Note that it is desirable to repeatedly insert and remove the λ / 4 polarizing plate 113 with respect to the optical path so that the fundus luminance image and the tomographic luminance image indicating the polarization state are alternately acquired. Thereby, in the ophthalmologic apparatus as small as possible, for example, the display control unit 191 can display a fundus luminance image on the display area 410 and can display a tomographic luminance image indicating a polarization state on the display area 420. Here, the order of adjustment includes alignment adjustment using the anterior ocular segment image and corneal bright spot, focus adjustment using the fundus image indicating the polarization state, coherence gate adjustment using the tomographic luminance image indicating the polarization state, λ / The order of adjustment of the four polarizing plates 113 is preferable. Note that the determination of the acquisition position of the tomographic luminance image indicating the polarization state is preferably performed before the coherence gate adjustment using the tomographic luminance image indicating the polarization state, but the initial setting is to acquire the central region of the fundus image indicating the polarization state. You may make it decide with. Accordingly, it is possible to easily adjust the tomographic luminance image indicating the polarization state that covers a narrower range that is finer and narrower than the fundus image indicating the polarization state so that the tomographic luminance image can be accurately acquired. At this time, the λ / 4 polarizing plate 113 may be automatically adjusted according to the completion of the coherence gate adjustment, or the λ / 4 polarizing plate 113 according to the input of a signal for obtaining an image indicating the polarization state. May be adjusted automatically. Of course, the λ / 4 polarizing plate 113 may be adjusted in advance on the initial setting screen or the like when the ophthalmologic apparatus is started up, and may not be adjusted for each photographing.

  Further, when the λ / 4 polarizing plate 113 is configured to be detachable from the optical path, the adjustment order is alignment adjustment using an anterior segment image or corneal bright spot, and focus adjustment using an SLO fundus image. The order of coherence gate adjustment using the OCT tomographic luminance image, insertion of the λ / 4 polarizing plate 113 into the optical path, and adjustment of the λ / 4 polarizing plate 113 is preferable. Thereby, the adjustment before acquisition of the image indicating the polarization state can be performed using the normal SLO fundus image and the OCT tomographic luminance image that the user is intuitively accustomed to. However, after the focus adjustment, the coherence gate adjustment using the tomographic luminance image indicating the polarization state of PS-OCT may be performed after the λ / 4 polarizing plate 113 is inserted. At this time, the λ / 4 polarizing plate 113 may be automatically inserted into the optical path in accordance with completion of coherence gate adjustment or focus adjustment, or in response to input of a signal for obtaining an image indicating a polarization state. Then, the λ / 4 polarizing plate 113 may be automatically inserted into the optical path.

  In the focus adjustment, fine focus adjustment using an OCT tomographic luminance image may be performed after coarse focus adjustment using an SLO fundus image.

  These adjustments may all be automatically performed in the above order, or the cursor may be placed on a slider corresponding to each adjustment displayed on the display unit and a drag operation may be performed. When the λ / 4 polarizing plate 113 is inserted / removed, an icon for instructing to insert / remove the λ / 4 polarizing plate 113 into / from the optical path may be displayed on the display unit.

<Fundus photography> to <fundus image generation>
In steps S102 to S103, the measurement light is emitted from the light source 141, the return light from the retina Er is received by the APDs 152 and 153, and the fundus image is generated by the image generation unit 193 as described above. The comparison unit 196 records the acquired fundus data.

<OCT scan position setting>
In step S104, the fundus image captured in steps S102 to S103 is compared with the fundus image acquired in the past and acquired, and the scan position of the PS-OCT 100 is set.

  First, the comparison unit 196 extracts position information of feature points in the fundus image acquired and recorded in the past. In the case of extracting feature points, it is desirable that the number of extracted points is two or more because the scanning direction cannot be matched when only one point is extracted. Here, the feature points are tissues such as the optic disc, the macula, and the capillaries. Next, the relative position information of the OCT scan position acquired and recorded in the past is calculated for the position information of the extracted feature points. Then, the feature points of the currently acquired and recorded fundus image are extracted by the same method as described above, and further points that match the feature points extracted from the past fundus image are further extracted. Finally, an OCT scan position is set based on the position information of the feature points extracted from the current fundus image and the calculated relative position information.

  The OCT scan position is not limited to the automatic extraction as described above. As shown in FIG. 5, you may select manually from a window.

  In a display area 510 that is an example of the first display area, a current fundus image 511 that is captured by the PS-SLO 140 and generated by the image generation unit 193 is displayed. A fundus luminance image is displayed as the fundus image 511, but may be a fundus image based on a polarization signal. A guide 512 indicating the imaging position of the PS-OCT 100 is superimposed on the fundus image 511.

  In a display area 520 that is an example of the second display area, a past fundus image 521 that is captured by the PS-SLO 140 and generated by the image generation unit 193 is displayed. A fundus luminance image is displayed as the fundus image 521, but may be a fundus image based on a polarization signal. On the fundus image 521, a guide 522 indicating the imaging position of the PS-OCT 100 that has taken an image in the past is superimposed and displayed.

  The OCT scan position corresponds to the positional relationship between the past fundus image 521 displayed in the display area 520 and the guide 522 displayed on the fundus image 521, and the fundus image 511 displayed in the display area 510. The guide 512 superimposed on is set by a mouse click operation or a drag operation.

<Tomography> to <Generation of tomographic luminance image>
In steps S105 to S106, the measurement light is emitted from the light source 101, the return light from the retina Er is received by the line cameras 129 and 133, and the tomographic luminance image is generated by the image generation unit 193 as described above. To do.

  By repeating steps S105 to S106 N times for the set tomographic luminance image position, N pieces of tomographic luminance images are acquired. Note that the operator may arbitrarily determine the acquisition procedure. That is, after step S105 is repeated N times to acquire N pieces of tomographic luminance image data, step S106 may be performed collectively, or steps S105 to S106 are performed when one piece of tomographic luminance image is acquired. , It may be repeated N times.

  In addition, steps S102 to S103 are executed in parallel at an arbitrary timing during photographing and generation of the tomographic luminance image in steps S105 to S106, and the minute movement amount of the SLO image is detected by the signal processing unit 190. The drive control unit 180 may have a tracking function by performing feedback. For example, the continuously acquired SLO image data is passed to the signal processing unit 190, and the minute movement amount in the translation direction and the rotation direction is calculated for the relative position of each SLO image. Next, there is a method of providing a tracking function by generating a scanner drive waveform for correcting the calculated minute movement amount by the drive control unit 180 and driving the X scanner 107 and the Y scanner 110.

<OCT tomographic image overlay>
After N images are captured and processed, in step S107, the image superimposing unit 195, which is an example of an alignment unit, first aligns a plurality of tomographic luminance images. Hereinafter, the alignment method will be described with reference to FIG. Here, for alignment of the plurality of tomographic luminance images, for example, eye movement is detected by performing pattern matching of the second luminance image 602 with respect to the first luminance image 601 serving as a reference. Pattern matching is a technique for searching for a region having the highest degree of similarity to a reference image. A characteristic part is extracted from the first luminance image serving as a reference, pattern matching is performed on the second luminance image to search for a portion having the highest degree of coincidence or similarity, and an eyeball between image acquisitions from the coordinates. Motion may be detected. For example, pattern matching can be performed using the macular portion 603 in the luminance image 601.

  Pattern matching is performed in the image superimposing unit 195, and the similarity between each of the other plurality of luminance images is calculated with respect to the reference first luminance image. For example, a correlation function can be used for calculating the similarity.

  In the present embodiment, for example, when N tomographic luminance images are overlapped at the same location of the subject, each of the N−1 luminance images has the highest similarity to the first luminance image. Pattern matching may be performed so that the degree is appropriate. In addition, if similarity is displayed as a parameter when pattern matching is performed, it can be used as an index for determining whether or not tomographic images are to be superimposed when tomographic luminance images are superimposed. That is, by displaying the similarity, the user can determine that a tomographic luminance image having a low similarity is not used for superposition.

  After performing pattern matching, the image superimposing unit 195 stores a displacement amount by which the luminance image is moved in order to obtain the highest similarity. For example, in FIG. 7, the displacement amount of the luminance image when the similarity of the luminance image at time t (m + 1) is the highest with respect to the luminance image at time tm is (x (m + 1), y (m + 1)). The displacement amount (x (m + 1), y (m + 1)) is stored. Here, the amount of displacement to be stored is not limited to parallel movement. For example, it is possible to store the amount of displacement of rotation or expansion / contraction as required. Further, the displacement amount stored in the image superimposing unit 195 can be applied to all the images acquired at the same timing and generated in the image generating unit 193.

  The image superimposing unit 195 deforms each image as described above with respect to the tomographic luminance image generated by the image generating unit 193, and averages the pixels at the same position of the deformed images, so that the superimposed image is obtained. Is generated. At this time, it is preferable to correct misalignment of the plurality of tomographic luminance images based on the detected eye movement. Moreover, it is preferable to remove the tomographic luminance image from which a constant luminance value cannot be obtained by blinking from the superimposed image. When the superimposition process is completed, the display control unit 191 generates output information and outputs it to the display unit 192 for display. Further, the comparison unit 196 records the generated superimposed image data.

<Comparison>
In step S108, the retardation of corresponding pixels is subtracted in both images of the past tomographic luminance image 831 acquired in the past and generated by superposition and the current tomographic luminance image 841 currently acquired and generated by superposition. To make a comparison. Therefore, first, the past tomographic luminance image 831 and the current tomographic luminance image 841 are aligned for comparison. In the alignment, the current tomographic luminance image 841 is deformed by performing processing such as affine transformation so that the correlation function is highest as compared with the past tomographic luminance image 831. At this time, with respect to the past tomographic luminance image 831 to be compared, the common region is extracted and deformed so as to display the same region as the current tomographic luminance image 841 to be deformed. Note that both the modified past tomographic luminance image 831 and current tomographic luminance image 841 are reconstructed by interpolating the luminance value and polarization parameter of each pixel. As the interpolation method, for example, nearest neighbor interpolation, bilinear interpolation, bicubic interpolation, or the like is performed. In the present invention, the past tomographic image and the current tomographic image may be a plurality of tomographic images obtained by imaging the subject at different times.

  Next, the comparison unit 196, which is an example of the difference information generation unit, performs comparison by subtracting the retardation of pixels corresponding to each other in the past tomographic luminance image 831 and the current tomographic luminance image 841. That is, the difference information generation unit generates information indicating a difference between the past polarization tomographic image corresponding to the past tomographic luminance image 831 and the current polarization tomographic image corresponding to the current tomographic luminance image 841. Here, the information indicating the difference is, for example, a difference image, a graph indicating the difference, or a difference value. Prior to generating the information indicating the difference, the past polarization tomographic image and the current polarization tomographic image are aligned based on the past tomographic luminance image and the current tomographic luminance image. Thereby, in the polarization tomographic image, it is possible to perform alignment in a region other than the region where the polarization, which is an example of the predetermined region, is eliminated. For this reason, alignment can be performed with high accuracy even when the region where the polarization is eliminated has changed over time due to illness or the like. At this time, it is preferable to correct the positional deviation of the plurality of polarization tomographic images corresponding to the plurality of tomographic luminance images based on the detected eye movement. As shown in FIG. 8, the subtraction result is displayed as a difference image 821 in the display area 820. By reading the result of the obtained subtraction process, it is possible to follow a change with time regarding the density of the nerve fiber layer. For example, a region where the subtraction value is a positive value is a region where birefringence is weakened, while a region where the negative value is negative is a region where birefringence is increased. Here, in the present embodiment, an example of subtracting a retardation that is an example of a current polarized tomographic image corresponding to the current tomographic luminance image 841 from a retardation that is an example of a past polarized tomographic image corresponding to the past tomographic luminance image 831. Indicated. However, in the present embodiment, the retardation corresponding to the past tomographic luminance image 831 may be subtracted from the retardation corresponding to the current tomographic luminance image 841. In this case, it is suggested that the region where the subtraction value is negative is a region where the birefringence is weakened, and the region where the positive value is positive is a region where the birefringence is increased.

  In step S108, the current RNFL film thickness information and RNFL retardation information are measured and recorded. The film thickness information and retardation information of the RNFL can be arbitrarily selected by the operator. The film thickness information of RFNL is calculated by calculating the difference between two Z components having the same X coordinate from the coordinate values of two boundary lines indicating RNFL extracted by segmentation. You can ask. Of the film thickness data acquired in this way, the film thickness data of an arbitrary X coordinate or the average value of the film thickness data of an arbitrary X coordinate section is used as the RFNL film thickness information.

  Moreover, the retardation information of RNFL is acquired as the retardation in the RNFL on the A scan line corresponding to the X coordinate from which the film thickness information is acquired, or the average value of the retardation.

<Output>
Next, each generated image and the analysis result output processing step S109 will be described. In the output process in the present embodiment, the image acquired and generated in steps S102 to S108 and the comparison result are displayed.

  When the image generation unit 193, the image analysis unit 194, and the image superposition unit 195 in the signal processing unit 190 complete the generation, analysis, and superposition of each image, the display control unit 191 outputs output information based on the results. Generate and output to the display unit 192 for display.

  FIG. 8 is a display example on the display unit 192 in the present embodiment. In the figure, reference numeral 800 denotes a window displayed on the display unit 192, and includes display areas 810, 820, 830, and 840.

  In a display area 810 that is an example of a first display area, a fundus image 511 that is captured by the PS-SLO 140 and generated by the image generation unit 193 is displayed. A fundus luminance image is displayed as the fundus image 511, but may be a fundus image based on a polarization signal. On the fundus image 511, a guide 522 indicating the imaging position of the PS-OCT 100 that has taken the image is superimposed and displayed.

  In the display area 820 that is the second display area, the difference between the retardations of substantially the same location acquired in the past and the present is displayed as a tomographic image 821. At this time, in addition to the difference image, segmentation may be displayed in a superimposed manner so that each layer is made explicit.

  Instead of the retardation difference image 820, a graph indicating comparison information of the selected area may be displayed. In FIG. 9, regarding the RNFL film thickness and retardation acquired in step S108, a graph 921 showing a comparison with the previously acquired value, and the retard per film thickness obtained by dividing the retardation by the film thickness. The example which the graph 922 which shows the comparison with the past acquisition value regarding a foundation value is displayed is shown. The horizontal axis of the graph is the date, and the acquired data is arranged in time series on the horizontal axis. In addition, as a result of follow-up over a long period of time, if there are a large number of acquired data, arbitrary past acquired data can be selected from the comparison unit 196 and displayed on the graph.

  A past tomographic image 831 is displayed in a display area 830 which is an example of a third display area. The tomographic image 831 is deformed so as to display the same region as the tomographic image 841. In addition to the retardation image, segmentation may be superimposed and each layer may be clearly indicated.

  The currently acquired tomographic image 841 is displayed in the display area 840 that is an example of the fourth display area. The tomographic image 841 is deformed by enlarging, rotating, and extracting the image so that the correlation (correlation function value) is larger than the threshold value compared to the tomographic image 831 (an example of alignment). In addition to the retardation image, segmentation may be superimposed and each layer may be clearly indicated.

  The display control unit 191 may display a retardation map in any of the display areas of the display unit 192 instead of the above-described retardation tomographic image. Further, the display control unit 191 may display the retardation map so as to overlap the fundus luminance image 511.

(Second Embodiment)
A second embodiment will be described with reference to FIGS. 10 and 11. In the present embodiment, a 3D image (three-dimensional image) is generated from the OCT tomographic image, and a tomographic image having a high similarity is extracted from the currently acquired 3D image data with respect to the OCT tomographic image used in the past in the diagnosis. A method for comparison will be described.

  As shown in FIG. 10, each B-scan image constituting the 3D image is formed by superposition. For example, the tomographic brightness image 1001 is generated by superimposing N tomographic brightness image groups 1011 acquired at the same scan position. Similarly, tomographic luminance images 1002 to 1006 are also generated by superimposing corresponding N pieces of tomographic luminance images 1012 to 1016, respectively. In this way, a 3D image in which each B-scan image is composed of superimposed images is created.

[Processing operation]
Next, a characteristic processing operation of the present embodiment will be described using the flowchart of FIG. Note that description of processing operations similar to those of the first embodiment is omitted here.

  In the shooting step of step S202, the drive control unit 180 controls the drive angles of the X scanner 107 and the Y scanner 110, respectively, and takes N B-scan images while acquiring 3D image data. For example, the Y scanner 110 is fixed and the X scanner 107 is scanned N times to acquire N pieces of tomographic luminance images in the same area, and then the Y scanner 110 sends the scan position by one step. Controlled by. By scanning the set range by the Y scanner 110, it is possible to acquire 3D image data having N B scan images.

  Next, in step S204, the superimposing unit 195 superimposes the corresponding N-1 B scan images at the same location on each B scan image, thereby forming a 3D image composed of the superimposed images. An image is generated, and the 3D image data generated by the comparison unit 196 is recorded.

  In step S205, a comparison position between the past tomographic luminance image and the current tomographic luminance image is designated based on the 3D image data configured in step S204. That is, in step S205, the current tomographic luminance image subjected to the overlay process is compared with the past tomographic luminance image, and the current tomographic luminance image having the highest similarity is extracted from the 3D image. The similarity is calculated from, for example, a correlation function. Since the image data to be compared for similarity is already subjected to the overlay process, it is possible to extract a comparison position with higher accuracy.

  As described above, by extracting the same target tissue of the subject from the luminance image and evaluating the change with time from the retardation difference as in the present embodiment, it is possible to provide information useful for a doctor performing pathological diagnosis. For example, when the affected eye has glaucoma, when the image is periodically acquired as a follow-up for medical care, there is a case where the birefringence changes while the luminance image hardly changes. By using this property, by performing alignment with a luminance image that is difficult to change over time, while avoiding the risk of misalignment during follow-up observation, by evaluating the difference in retardation of the same target tissue, It is possible to visualize the extent of lesion progression of the same target tissue that hardly changes in the luminance image.

  Furthermore, information effective for diagnosis can be provided by periodically acquiring the RNFL film thickness and retardation and performing follow-up observation. For example, when the density of the retinal nerve fiber of the subject is decreased, the birefringence is decreased, so that even if the RNFL film thickness is equal, data with decreasing retardation can be obtained, which contributes to early detection of glaucoma. I can do it.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (19)

A tomographic luminance image and a polarized tomographic image of a subject obtained by processing a common OCT signal by the return light and the reference light from the subject irradiated with the measurement light, obtained by photographing the subject at different times A plurality of tomographic image acquisition means for acquiring a plurality of tomographic luminance images and a plurality of polarized tomographic images corresponding to the plurality of tomographic luminance images;
Alignment means for aligning the plurality of polarization tomographic images acquired using the positional deviation information of the plurality of acquired tomographic luminance images;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, further comprising a generation unit configured to generate information indicating a difference between the plurality of polarization tomographic images subjected to the alignment.   The image processing apparatus according to claim 2, wherein the generation unit generates a difference image of the plurality of polarization tomographic images subjected to the alignment as information indicating the difference.   The image processing apparatus according to claim 2, further comprising display control means for causing the display means to display information indicating the generated difference. The tomographic image acquisition means acquires a past tomographic luminance image and a current tomographic luminance image as the plurality of tomographic luminance images, and the past polarized tomographic image corresponding to the past tomographic luminance image as the plurality of polarized tomographic images and the Obtain the current polarization tomographic image corresponding to the current tomographic luminance image,
The alignment means performs alignment of the acquired past polarization tomographic image and current polarization tomographic image using the positional deviation information of the acquired past tomographic luminance image and current tomographic luminance image,
5. The image processing apparatus according to claim 2, wherein the generation unit generates information indicating a difference between the past polarization tomographic image and the current polarization tomographic image in which the alignment is performed. . The tomographic image acquisition means acquires a plurality of past tomographic luminance images and a plurality of current tomographic luminance images as the plurality of tomographic luminance images, and corresponds to the plurality of past tomographic luminance images as the plurality of polarized tomographic images. Obtaining a plurality of current polarization tomographic images corresponding to a plurality of past polarization tomographic images and the plurality of current tomographic luminance images;
The alignment means performs alignment of the acquired plurality of past polarization tomographic images using positional deviation information of the acquired plurality of past tomographic luminance images, and the plurality of acquired current tomographic luminance images. Alignment of the plurality of current polarization tomographic images acquired using the positional deviation information,
The generation means superimposes a new past polarization tomographic image obtained by superimposing the plurality of past polarization tomographic images on which the alignment has been performed and a plurality of current polarization tomographic images on which the alignment has been performed. 5. The image processing apparatus according to claim 2, wherein information indicating a difference from the new current polarization tomographic image is generated.   Each time the generation means images the subject, it records at least one of the film thickness information and retardation information of the subject, and in the follow-up observation, the information in the current photographing and the past photographing The image processing apparatus according to claim 2, wherein information indicating a difference from the information is generated.   The image processing apparatus according to claim 1, further comprising a generation unit configured to generate a new polarization tomographic image using the plurality of polarization tomographic images subjected to the alignment. The tomographic image acquisition means acquires a previous polarized tomographic image and a current polarized tomographic image as the plurality of polarized tomographic images,
The image processing apparatus according to claim 8, wherein the generation unit generates a difference image between the past polarization tomographic image and the current polarization tomographic image on which the alignment has been performed, as the new polarization tomographic image.   The image processing apparatus according to claim 8, wherein the generation unit generates a superimposed image of the plurality of polarization tomographic images subjected to the alignment as the new polarization tomographic image. The generation means generates a past polarization tomographic image and a current polarization tomographic image as the superimposed image,
The alignment unit is configured to generate the past polarization tomographic image generated based on the past tomographic luminance image corresponding to the generated past polarization tomographic image and the current tomographic luminance image corresponding to the generated current polarization tomographic image. Aligning the generated current polarization tomographic image,
The image processing apparatus according to claim 10, wherein the generation unit generates information indicating a difference between the past polarization tomographic image and the current polarization tomographic image on which the alignment is performed. The positional deviation information is a correlation between the acquired plurality of tomographic luminance images,
12. The alignment unit according to claim 1, wherein the alignment unit aligns the plurality of acquired polarization tomographic images so that a correlation between the acquired plurality of tomographic luminance images is increased. The image processing apparatus according to item 1.   The alignment means deforms at least one of the acquired plurality of polarization tomographic images so that a correlation between the acquired plurality of tomographic luminance images exceeds a threshold value, thereby obtaining the plurality of acquired polarization tomographic images. The image processing apparatus according to claim 12, wherein alignment of images is performed.   The tomographic image acquisition means is based on light of different polarizations obtained by dividing light obtained by combining return light from the subject irradiated with measurement light and reference light corresponding to the measurement light. The image processing apparatus according to claim 1, wherein a plurality of tomographic luminance images and the plurality of polarization tomographic images are acquired. It is connected so as to be communicable with an imaging device having a detection means for detecting light of different polarizations,
The image processing apparatus according to claim 14, wherein the tomographic image acquisition unit acquires the plurality of tomographic luminance images and the plurality of polarized tomographic images based on the detected lights of different polarizations. . Plane image acquisition means for acquiring a plurality of plane images at different times indicating the polarization states of the object based on lights of different polarizations obtained by dividing return light from the object irradiated with light;
Detecting means for detecting the amount of movement of the subject using positional deviation information of the plurality of planar images;
Control means for controlling the imaging apparatus so as to correct the acquisition positions of the plurality of tomographic luminance images and the plurality of polarized tomographic images using information on the detected movement amount;
The image processing apparatus according to claim 15, further comprising: The image processing apparatus according to any one of claims 1 to 16 subject to being a subject's eye. A tomographic luminance image and a polarized tomographic image of a subject obtained by processing a common OCT signal by the return light and the reference light from the subject irradiated with the measurement light, obtained by photographing the subject at different times Obtaining a plurality of tomographic luminance images and a plurality of polarization tomographic images corresponding to the plurality of tomographic luminance images;
Using the positional deviation information of the plurality of acquired tomographic luminance images to perform alignment of the plurality of acquired polarization tomographic images;
An image processing method comprising: A program causing a computer to execute each step of the image processing method according to claim 18 .