JP2013085758A - Tomographic apparatus and correction processing method of tomographic image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tomographic apparatus capable of executing low-cost and highly accurate position correction processing in a short period of time.SOLUTION: The tomographic apparatus includes: a reference image preparation means for preparing a reference image having a prescribed region including a peak value (P point) of the data of A-scan at a 1/4 position from the end of a B-scan image; an evaluation function calculation means for calculating the total sum (evaluation function) of differences between the pixel values of the reference image in the respective pixels and the pixel values of the adjacent B-scan images while moving the reference in parallel within the adjacent B-scan images; a relative positional deviation amount calculation means for detecting a position at which the evaluation function is minimum and calculating a relative positional deviation amount between the adjacent B-scan images; an absolute positional deviation amount calculation means using the relative positional deviation amount to calculate the absolute positional deviation amount of the respective B-scan images with a No.1 B-scan image as a reference; and a position correction means for correcting the positions of the respective B-scan images by using the absolute positional deviation amount.

Description

  The present invention relates to a tomographic imaging apparatus and a tomographic image correction processing method.

In recent years, optical coherence tomography (Optical) has been used as an inspection device used for ophthalmic examinations.
There has been provided an optical coherence tomography apparatus that captures a tomographic image of a subject's eye (eyeball) by Coherence Tomography (OCT).

  The optical coherence tomography apparatus uses a time domain method called a time domain method, which uses a time domain OCT that acquires a tomographic image while moving a mirror and mechanically changes the optical path length of reference light, and a spectroscope called a Fourier domain method. There is a spectral domain OCT that detects spectral information and acquires a tomographic image, or an optical frequency sweep OCT that detects a spectral interference signal using a wavelength scanning light source and acquires a tomographic image.

  In general, in OCT, a one-dimensional signal in the depth direction of the eye to be examined is acquired (A-scan), and a two-dimensional tomographic image is acquired by scanning the measurement light with respect to the eye to be examined one-dimensionally (B-). Scanning), and further obtaining a three-dimensional image by repeatedly obtaining a two-dimensional tomographic image while shifting the position with respect to the eye to be examined (C-scan).

  However, in an optical coherence tomography apparatus for ophthalmologic examination, even if the eye to be examined is held in a fixation state, it continuously performs minute movement (fixation fine movement) unconsciously. In particular, since the imaging time for obtaining a three-dimensional image is relatively long, the photographed three-dimensional tomographic image is blurred due to the influence of the fixation eye movement of the eye under examination, and a high-quality image is obtained. There was nothing.

  In the time domain OCT, since the tomographic image is acquired while moving the mirror and mechanically changing the optical path length of the reference light as described above, the B-scan time is relatively long, whereas the Fourier domain OCT is performed. Since it is not necessary to move the mirror and mechanically change the optical path length of the reference light, the B-scan time can be acquired in a very short time (several milliseconds). The influence of fixation eye movement of the eye to be examined is small, and the blur of the captured three-dimensional tomographic image is considered to be mainly caused by the positional deviation of the B-scan image during C-scan.

  Patent Document 1 discloses a method for detecting a positional deviation of such a B-scan image and correcting the position with a correction value of each obtained B-scan image. In other words, a region of interest (ROI) in a B-scan image is determined, and an SSD (sum of squares difference) is minimized while the ROI is translated with respect to an adjacent B-scan image using a pattern matching method. The positional deviation amount at a certain position is used as a positional deviation correction value of the adjacent B-scan image, and the correction is performed sequentially from the reference tomographic image (B-scan image) selected by the tomographic image selection means. Use to correct the position.

  Further, Patent Document 2 includes an OCT for acquiring a tomographic image of the fundus and an optical scanning optometry apparatus (an ophthalmic SLO (Scanning Laser Ophthalmoscope)) for acquiring a tomographic image of the fundus. Discloses a method of correcting a positional shift of a tomographic image (OCT image) by detecting a positional shift of an eye to be examined based on the SLO image.

JP 2011-019576 A JP 2008-029467 A

  However, although the method of Patent Document 2 may enable highly accurate displacement correction, the apparatus becomes complicated because the SLO optical system is added to the OCT optical system originally intended to obtain a tomographic image of the eye to be examined. As a result, it becomes expensive.

  On the other hand, although the method of Patent Document 1 is a correction method that can be performed by the OCT alone, it is considered that there are the following problems.

  As a specific example, the tomographic image selecting means for selecting the reference tomographic image at the time of correction uses, as a specific example, a B-scan image having the maximum integrated value of contrast change in the image from all the acquired B-scan images. Have selected as. This method using the tomographic image selection means seems to have an advantage that, for example, the same B-scan image or a B-scan image close thereto is always selected when measuring the same location of the retina a plurality of times. When determining the correction value, the correction value is calculated from the amount of positional deviation between the adjacent B-scan images. Therefore, only the first B-scan image for starting the correction is determined, and a three-dimensional image is converted. Since it is necessary to analyze the entire B-scan image in order to select the reference tomographic image every time measurement is performed, it is considered that the effect is small although it takes a great deal of time for analysis.

  Moreover, although patent document 1 does not have the detailed description about ROI, it is presumed from other patent documents of the same applicant that it is an area | region including a macula, an optic disc, etc. Therefore, in order to determine the ROI, the macula and optic nerve head are extracted, so analysis is necessary for each B-scan image, and the ROI itself is considered to be different for each B-scan image. However, it is not considered effective for complicated analysis.

  Furthermore, since the correction method of Patent Document 1 that sequentially corrects from the reference tomographic image has a high possibility that the amount of positional deviation increases as the distance from the reference tomographic image increases, the range in which the ROI moves is determined when obtaining the minimum value of the SSD. It needs to be widened in advance, which may increase the processing time.

  The present invention is a correction method that can be performed by a single OCT, and the positional deviation of each B-scan image without using the tomographic image selection means for selecting a region of interest (ROI) or a reference tomographic image described in Patent Document 1. The correction value can be obtained, and further, the correction can be performed without widening the moving range of the reference image (corresponding to the ROI in Patent Document 1) when obtaining the displacement correction value of each B-scan image. Another object of the present invention is to provide a tomographic apparatus capable of performing a position correction process with high accuracy at a low cost in a short time.

  In order to achieve the above object, a tomographic apparatus of the present invention is a tomographic imaging apparatus that creates a three-dimensional tomographic image by superimposing a plurality of B-scan images (tomographic images). A reference image creating means for creating a reference image having a predetermined area including a position (P point) obtained under a predetermined condition from A-scan data at a predetermined position of one B-scan image in the image; While the reference image is translated in the B-scan image adjacent to the one B-scan image, the difference between the pixel value of the reference image and the pixel value of the adjacent B-scan image in each pixel is calculated. An evaluation function calculating unit that calculates a sum (evaluation function); a relative position shift amount calculating unit that detects a position where the evaluation function is minimum and calculates a relative position shift amount between adjacent B-scan images; This relative Using the relative displacement amount obtained for each of the plurality of B-scan images by the displacement amount calculation means, any one B-scan image of the plurality of B-scan images is used as a reference. As the absolute positional deviation amount calculating means for calculating the absolute positional deviation amount of each B-scan image and the absolute positional deviation amount obtained by this absolute positional deviation amount calculating means, And a position correcting means for correcting the position of the first (invention of claim 1).

  According to the above configuration, the reference image (corresponding to the ROI in Patent Document 1) creating means includes a predetermined value including a peak value (P point) of A-scan data at a position ¼ from the end of the B-scan image, for example. In order to obtain an image of an area (for example, 192 × 192 pixels), as disclosed in Patent Document 1, it is not necessary to perform an analysis for extracting an area including the macula and the optic disc at the time of reference image creation means, and is used for position correction. Since the reference tomographic image (reference B-scan image) selects an arbitrary position (for example, No. 1 image), all the B-scan images are analyzed when the reference tomographic image is selected as in Patent Document 1. The method of the present invention for correcting the position based on the absolute positional deviation amount based on the selected one B-scan image is not necessary when the minimum evaluation function is obtained. B-scan image position Because it requires about differences can be narrowed from the reference tomographic image as in the prior document 1, more correct the positions in turn, the movement range of the reference image to obtain the minimum evaluation function.

  As described above, according to the tomographic imaging apparatus and the tomographic image correction processing method of the present invention, the positional deviation correction of each B-scan image can be performed by the OCT alone, so other optical systems such as an SLO and a fundus camera are used. Since it is not required and the movement range of the reference image can be set narrow by adopting the absolute displacement amount, an excellent effect is achieved in that a highly accurate position correction process can be performed in a short time at a low cost.

It is the figure which showed the detail of the tomogram acquisition part. It is the figure which showed the structure of the tomography apparatus. It is the figure which showed the flowchart which shows the flow of tomography and correction | amendment. It is a figure which shows the tomographic image acquisition position in the fundus, and the acquired 3D tomographic image. It is a figure explaining the method of the reference image preparation means. It is the figure which took out the reference image from the B-scan image (tomographic image). It is the figure which showed the movement on the adjacent B-scan image of the produced reference image. (A) A value indicating the amount of relative displacement in each B-scan image. (B) No. using the relative displacement amount of each B-scan image. The absolute positional deviation amount in each B-scan image calculated on the basis of 1 B-scan image. It is the figure which showed the flowchart which shows calculation of the amount of relative displacement in a 2nd Example. It is a figure explaining the method of the reference image preparation means in 2nd Example.

Hereinafter, a tomographic imaging apparatus according to the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 1 shows a detailed configuration of the tomographic image acquisition unit 100.

  As shown in FIG. 1, the tomographic image acquisition unit 100 shoots a three-dimensional tomographic image of the fundus oculi Er by irradiating measurement light onto the fundus oculi (fundus retina) Er of the eye E. In this embodiment, a Fourier domain (optical frequency sweep) method using a wavelength scanning light source 101 that scans while changing the wavelength with time is employed.

  That is, the light output from the wavelength scanning light source 101 is input to the polarization controller 102 and the isolator 103 through the optical fiber, and then input to the first fiber coupler 104 through the optical fiber. In the first fiber coupler 104, for example, The reference light and the measurement light are demultiplexed and output at a ratio of 10:90. Of these, the reference light passes through the optical fiber and enters the collimator lens 112 and enters the delay line unit 113. The delay line unit 113 is a unit for adjusting the optical path length that aligns the reference optical path on the retina of the fundus and adjusts the measurement optical path length and the reference optical path length before measuring the OCT tomographic image.

  The reference light radiated from the delay line unit 113 is input from the collimator lens 114 through the optical fiber to the polarization controller 115 and then input to the first input unit of the second fiber coupler 116 through the optical fiber.

  On the other hand, the measurement light output from the first fiber coupler 104 is input to the collimator lens 105 through the optical fiber and input to the galvanometer mirror unit 106. The galvano mirror unit 106 is for scanning the measurement light, and the galvano driver 107 scans the measurement light in the horizontal direction and the vertical direction on the fundus of the eye to be inspected. .

  The measurement light output from the galvanometer mirror unit 106 passes through the lens 108, exits from an inspection window (not shown) through the objective lens 109, and enters the eye E to be examined. The measurement light incident on the eye E is reflected by each tissue part (retina, choroid, etc.) of the fundus Er, and the reflected light is incident from the examination window. 108, the light is input to the collimator lens 105 through the galvanometer mirror unit 106. Then, the reflected light passes through the first fiber coupler 104 through the optical fiber, and then is input to the second input unit of the second fiber coupler 116 through the optical fiber.

  In the second fiber coupler 116, the reflected light from the fundus Er and the reference light input through the optical fiber are combined at a ratio of, for example, 50:50, and the signal is transmitted through the optical fiber. Are input to the differential amplification detector 117. In the detector 117, interference for each wavelength is measured, and the measured interference signal is input to the AD board 201 provided in the control device 200. Further, the arithmetic unit 202 provided in the control device 200 performs processing such as Fourier transform on the interference signal, and thus obtains a tomographic image of the fundus retina Er along the scanning line. (Figure 2)

  At this time, as will be described in detail later, the scan pattern of the measurement light by the galvano mirror unit 106, in other words, the direction of the scanning line (B-scan) is set in the control device 200. The galvano driver 107 controls the galvanometer mirror unit 106 based on a command signal from the control device 200 (arithmetic unit 202). The obtained tomographic image data of the fundus oculi Er is stored in the storage unit 203. (Figure 2)

  Next, the B-scan image capturing and position correction processing method will be described with reference to FIGS. FIG. 3 shows a series of processing flows of the tomographic imaging apparatus of the present invention, from B-scan image capturing to correction processing and further to construction of a three-dimensional image.

  Before starting imaging with OCT, the reference mirror in the delay line unit 113 is moved to match the measurement optical path length with the reference optical path length (step 301). Thereafter, the tomographic image acquisition unit 100 acquires a tomographic image (B-scan image) (step 302).

  FIG. 4 shows a state in which a tomographic image (B-scan image) is acquired by the tomographic image acquisition unit 100. 4A shows an example of the fundus retina of the eye E, and FIG. 4B shows a plurality of two-dimensional tomograms (B-scan images) of the fundus retina 401 obtained from the tomogram acquisition unit 100. An example is shown. 4A and 4B, the x-axis indicates the B-scan scan direction, and the y-axis indicates the C-scan direction. Further, the z-axis in FIG. 4B indicates the depth direction of the A-scan signal.

  Reference numeral 404 in FIG. 4B denotes an acquired two-dimensional tomogram, which is created by the calculation unit 202 reconstructing the A-scan signal 403 while scanning the galvanometer mirror unit 106 in the x direction. This two-dimensional tomographic image is a B-scan image, and is defined by a two-dimensional cross section in the x direction perpendicular to the depth direction (z direction) with respect to the fundus retina 401, that is, the x axis and z axis in FIG. It is a two-dimensional tomographic image in a plane. Reference numeral 402 in FIG. 4A indicates the photographing position of the two-dimensional tomographic image 404.

  Further, the B-scan image at the shooting position 402 is acquired by continuously shifting the shooting position 402 of the B-scan image in the y-axis direction. FIG. 4B shows a three-dimensional tomographic image (C-scan image) composed of a plurality of B-scan images at each photographing position.

  Three-dimensional tomographic images (a plurality of B-scan images) generated by the tomographic image acquisition unit 100 are stored in the storage unit 203.

  In step 303, the tomographic image acquisition unit 100 calculates the relative positional deviation amount of each of the plurality of B-scan images acquired at each imaging position of the fundus retina 401. The calculation method is performed according to the flow of FIG.

  FIG. 3B shows details of step 303. First, a reference image in any one of a plurality of acquired B-scan images is created (step 310). A B-scan image 501 in FIG. 5A is an arbitrary one of a plurality of acquired B-scan images, W is the width (scan width) of the B-scan image, and H is the depth in the depth direction ( A-scan width). FIG. 5B shows an A-scan signal at a position 1/4 (W / 4) from the end of the B-scan image.

  A point P in the B-scan image is obtained from the peak value of the A-scan signal, and a reference image 602 in a predetermined region (for example, 192 × 192 pixels) centered on the point P is created as shown in FIG. The created reference image 602 becomes a reference image in this B-scan image.

  Next, as shown in FIG. 7, the reference image 602 created in step 310 is translated on the B-scan image adjacent to this B-scan image (step 311). At this time, the difference between the pixel value of the reference image 602 and the pixel value of the adjacent B-scan image that is opposite is obtained for all the pixels of the reference image 602, and the sum of the absolute values is calculated. This sum value is called an evaluation function (step 312). As shown in FIG. 7, the reference image 602 is moved around the point P, for example, ± 4 pixels vertically and horizontally, one pixel at a time, and an evaluation function at each position is obtained. A coordinate difference S = (Δx, Δz) between the position where the evaluation function is minimum and the point P is detected (step 313), and this S value is used as the relative positional deviation amount of the adjacent B-scan (step 314).

  Steps 310 to 314 are performed on all the B-scan images, and the amount of relative displacement in each B-scan image is calculated (step 303).

  FIG. 1 to No. The graph showing the relative displacement amount in each of the B-scan images up to 256, and shows the result of the implementation of the apparatus of this example. The horizontal axis is the B-scan image No. And the vertical axis represents the amount of relative displacement.

  FIG. 8B shows the data of No. 8 from the data of FIG. It is a graph which shows the result converted into the amount of absolute position shifts on the basis of 1 B-scan image. The horizontal axis is the B-scan image No. The vertical axis represents the absolute positional deviation amount. In step 304, the relative position shift amount of each B-scan image is used to determine the No. An absolute positional shift amount based on one B-scan image is calculated for each B-scan image.

  In an example implemented by the apparatus of the present embodiment, as can be seen from the result of FIG. 8A, the amount of positional deviation (relative positional deviation) between adjacent B-scan images is 3 pixels at the maximum. From (b), no. It can be seen that the absolute displacement amount calculated with reference to one B-scan image is 15 pixels at the maximum.

  That is, in the present invention using the absolute positional deviation amount calculation means, the reference image may be moved about ± 4 pixels in this example, but in Patent Document 1 that does not have the absolute positional deviation amount calculation means, the ROI (present The “reference image” of the invention needs to be moved by about ± 16 pixels. In this example, it is necessary to move the range about 16 times that of the present invention, and the superiority of the present invention is understood. obtain.

  Using this absolute displacement amount, the position of each B-scan image is corrected, and the corrected B-scan image is stored in the storage unit 203 (306).

  The corrected B-scan image is subjected to addition averaging processing with one or more adjacent B-scan images (step 307), and then reconstructed into a three-dimensional tomographic image and stored in the storage unit 203.

  The three-dimensional tomographic image stored in the storage unit 203 is displayed on a monitor or the like.

  In this embodiment, the position of the A-scan signal at the time of creating the reference image is set to 1/4 position from the end of the B-scan image. However, the position is not limited to 1/4 and may be any position. Absent. Further, when the reference image is created, the point P is set as the peak value of the A-scan signal, but the present invention is not limited to this, and it may be the first position of the A-scan. If so, the average position may be used.

  In the first embodiment, one reference image is used for obtaining the relative displacement amount of each B-scan image, but the peak value of A-scan data is set to P as in the above-described embodiment. If it is a point, the P point is likely to be a retinal pigment epithelium. There is no problem as long as the retinal pigment epithelium of the eye E is aligned with the fundus surface, but the retinal pigment epithelium is often a curve with a certain radius. When calculating the relative positional deviation amount of each B-scan image, the curves of the retinal pigment epithelium of two adjacent B-scan images that are the object are considered to be slightly different. In this case, there is a possibility that an error may occur in the difference or correction of the radius of the curve of the retinal pigment epithelium between two adjacent B-scan images. In the following second embodiment, a method using three reference images at three locations will be described as a countermeasure.

[Second Embodiment]
Since the tomographic image acquisition unit is the same as that in the first embodiment described above, a description thereof will be omitted.

  FIG. 9 is a flowchart for calculating the relative displacement amount in the second embodiment. First, a first reference image of a plurality of acquired B-scan images is created (step 901). A B-scan image 1001 in FIG. 10A is any one of a plurality of acquired B-scan images, W is the width (scan width) of the B-scan image, and H is the depth in the depth direction ( A-scan width). FIG. 10B shows an A-scan signal at a position 1/4 (W / 4) from the end of the B-scan image.

  A P1 point in the B-scan image is obtained from the peak value of the A-scan signal, and a reference image of a predetermined region (for example, 192 × 192 pixels) around the P1 point is created. The created reference image is the first reference image in this B-scan image.

  Next, the created first reference image is translated on the B-scan image adjacent to the B-scan image (step 902). At this time, the difference between the pixel value of the reference image and the pixel value of the adjacent B-scan image is calculated for all the reference image pixels, and the sum of the absolute values is calculated. This sum value is called an evaluation function (step 903). The movement is performed around the point P1, and the first reference image is, for example, ± 4 pixels vertically and horizontally, every pixel, and the evaluation function at each position is obtained. A coordinate difference S1 = (Δx1, Δz1) between the position where the evaluation function is minimized and the point P1 is obtained (step 904).

  Next, a second reference image is created (step 901). FIG. 10C shows an A-scan signal at a position 1/2 (W / 2) from the end of the B-scan image. From the peak value of the A-scan signal, the point P2 in the B-scan image is obtained, and a reference image of a predetermined region (for example, 192 × 192 pixels) around the point P2 is created. The created reference image is the second reference image in this B-scan image.

  As in the case of the first reference image, an evaluation function is obtained between adjacent B-scan images (steps 902 to 903), and the coordinate difference S2 = (Δx2, Δz2) between the position where the evaluation function is minimum and the point P2 ) Is obtained (step 904).

  Next, a third reference image is created (step 901). FIG. 10D shows an A-scan signal at a position 3/4 (W × 3/4) from the end of the B-scan image. From the peak value of the A-scan signal, the point P3 in the B-scan image is obtained, and a reference image of a predetermined region (for example, 192 × 192 pixels) centered on the point P3 is created. The created reference image is the third reference image in this B-scan image.

  As in the case of the first reference image, an evaluation function is obtained between adjacent B-scan images (steps 902 to 903), and the coordinate difference S3 = (Δx3, Δz3) between the position where the evaluation function is minimum and the point P3. ) Is obtained (step 904).

The average value Sa of these S1, S2, and S3 values is set as the relative displacement amount of the adjacent B-scan (step 905).
Sa = ((Δx1 + Δx2 + Δx3) / 3, (Δz1 + Δz2 + Δz3) / 3)

  Since the following processing is the same as that of the first embodiment, a description thereof will be omitted. Although the reference image is created at 1/4, 1/2, and 3/4 from the end of the B-scan image, the present invention is not limited to this. Other positions may be used as long as the distance between the positions is a predetermined distance or more. In the present embodiment, the number of places is three, but it may be two or four or more.

  Further, when obtaining the absolute positional deviation amount (step 304), in the above example, No. The absolute displacement amount was calculated based on one B-scan image, but each B-scan image was calculated based on the B-scan image closest to the averaged position of all the acquired B-scan images. The absolute positional deviation amount may be calculated.

  Further, an average absolute displacement amount of each B-scan image may be obtained, and the absolute displacement amount of each B-scan image may be calculated again by setting the value to 0. In this case, since the correction amount can be reduced as a whole, there is an advantage that the processing time can be shortened because the movement amount of the image data during correction is reduced.

  The embodiments of the present invention have been described in detail above. However, these are merely examples, and the present invention is not construed as being limited by specific descriptions in the embodiments. The present invention can be carried out in a mode in which various changes, modifications, improvements, etc. are added based on the knowledge, and such a mode is within the scope of the present invention as long as it does not depart from the gist of the present invention. It should be understood that it is included in.

  As described above, according to the present embodiment, highly accurate misalignment correction can be easily performed in a short processing time.

100 .. Tomographic image acquisition unit 101. Wavelength scanning light source 104. First fiber coupler 106. Galvano mirror unit 113. Delay line unit 116. Second fiber coupler 201. AD board 202. Calculation Part 203 .. storage part

Claims (6)

In a tomographic imaging apparatus that creates a three-dimensional tomographic image by superimposing a plurality of B-scan images (tomographic images),
A reference image having a predetermined region including a position (P point) obtained under a predetermined condition from A-scan data at a predetermined position of one B-scan image among the plurality of B-scan images is created. A reference image creating means for
While the reference image is translated in the B-scan image adjacent to the one B-scan image, the sum of the difference between the pixel value of the reference image and the pixel value of the adjacent B-scan image in each pixel An evaluation function calculating means for calculating (evaluation function);
A relative positional deviation amount calculating means for detecting a position where the evaluation function is minimum and calculating a relative positional deviation amount between adjacent B-scan images;
Using the relative displacement amount obtained for each of the plurality of B-scan images by the relative displacement amount calculation means, any one B-scan of the plurality of B-scan images is used. Absolute positional deviation amount calculating means for calculating an absolute positional deviation amount of each B-scan image with reference to the image;
Position correcting means for correcting the position of each B-scan image using the absolute position deviation amount obtained by the absolute position deviation amount calculating means;
A tomography apparatus comprising:   The predetermined position of the one B-scan image in the reference image creating means is one of 1/4, 1/2, 3/4 from the end of the B-scan image. The tomography apparatus according to claim 1. The reference image creating means has two predetermined areas including respective positions (Pn points) obtained under certain conditions of A-scan data at two or more predetermined positions of the one B-scan image. Create the above reference image,
The evaluation function calculation means obtains an evaluation function at two or more positions of the adjacent B-scan image using the two or more reference images.
The relative positional deviation amount calculating means detects a position where each of the evaluation functions is minimum, and calculates an average value of the calculated relative positional deviation amounts at two or more places as the relative position of the adjacent B-scan image. The amount of deviation is
The tomography apparatus according to claim 1, wherein the tomography apparatus is characterized.   The two or more predetermined positions of the one B-scan image in the reference image creating means according to claim 3 are any one or more of 1/4, 1/2, 3/4 from an end of the B-scan image. The tomography apparatus according to claim 3, wherein the tomographic apparatus is a position including   The absolute misregistration amount calculating means calculates again the absolute misregistration amount of each B-scan image by setting the average absolute misregistration amount in each B-scan image calculated by the means to 0. The tomography apparatus according to claim 1, wherein the tomography apparatus is characterized.   After the plurality of B-scan images are corrected by the position correcting unit, an averaging process is performed on each B-scan image of the plurality of B-scan images using one or more adjacent B-scan images. The tomography apparatus according to claim 1, wherein a three-dimensional tomographic image is reconstructed.

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