JP2012176291A - Tomographic imaging apparatus, image processing apparatus, image processing system, and method and program for controlling image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To create a tomographic image of low noise and high resolution with the influence of flicks of eyeballs or movement of the head suppressed as much as possible.SOLUTION: A tomographic imaging apparatus includes: a detector for detecting an amount of movement of an eye ball to be inspected; and a determiner for determining the number of scan lines, and the number of images to be taken such that the larger the amount of movement of the eye ball is, the fewer the number of scan lines for taking two-dimensional images of the eye ball and the more the number of two-dimensional images of the eye ball.

Description

  The present invention relates to a tomographic imaging apparatus, an image processing apparatus that processes a tomographic image captured by the tomographic imaging apparatus, and an image processing method.

  In an ophthalmic tomography apparatus such as an optical coherence tomography (OCT), interference light is acquired by causing interference between reflected light of near-infrared light irradiated on the retina and reference light. A tomographic image is generated based on the interference light. In general, the image quality of a tomographic image generated based on interference light in this way depends on the intensity of near-infrared light incident on the retina. For this reason, in order to improve the image quality of tomographic images, it is necessary to increase the intensity of near-infrared light that irradiates the retina. There is a certain limit.

For this reason, it is desired to generate a high-quality tomographic image while irradiating near-infrared light within a safe intensity range for safety. In response to such demands, efforts have been made mainly by the following two methods.
(I) Method of using oversampling (ii) Method of using superposition Hereafter, the approach by the two methods will be briefly described.

First, the oversampling method will be described with reference to FIG. FIG. 9A is a diagram illustrating an example of a tomographic image of the retina photographed by the tomographic image photographing apparatus. In FIG. 9A, T _i represents a two-dimensional tomographic image (B-scan image), and A _ij represents a scanning line (A-scan). As shown in FIG. 9A, the two-dimensional tomographic image T _i is composed of a plurality of scanning lines A _ij located on the same plane.

FIG. 9 (c), in the shooting of the two-dimensional tomographic images T _i shown in FIG. 9 (a), irradiation in the case of near infrared light irradiated on the retina, looking toward the fundus oculi surface to the depth direction of the retina It is a figure which shows an example of distribution. In FIG. 9C, the ellipses indicated by A _{i1 to} A _im represent the beam diameter of near infrared light.

On the other hand, FIG. 9B is an example of a tomographic image of the retina taken by the tomographic imaging apparatus, and a two-dimensional tomogram when the same imaging range as that of FIG. 9A is taken with twice the number of scanning lines. It is a figure which shows image _Ti '. FIG. 9D shows the near-infrared light irradiated on the retina viewed from the fundus surface toward the depth of the retina in the photographing of the two-dimensional tomographic image T _i ′ shown in FIG. 9B. It is a figure which shows an example of the irradiation distribution in a case. In FIG. _9D , the ellipses shown in A _{i1 to} A _i2m represent the beam diameter of near infrared light.

  As can be seen from FIGS. 9A and 9B, when the imaging range is the same, the resolution of the two-dimensional tomographic image increases as the number of scanning lines increases. Further, as can be seen from FIGS. 9C and 9D, when increasing the number of scanning lines in order to increase the resolution, the near-infrared light irradiated on the retina is overlapped between adjacent beams. It is necessary to irradiate.

  A method of generating a high-resolution two-dimensional tomographic image by irradiating the adjacent beams so as to overlap each other is generally called an oversampling method.

  On the other hand, the superposition method generates a cross-sectional image with less noise by superimposing and synthesizing multiple tomographic images captured by scanning the same imaging range multiple times with the same number of scanning lines. (For example, refer to Patent Document 1 below).

JP 2008-237238 A

C. Tomasi and T. Kanade, “Detection and tracking of point features”, Technical report, CMUCS-91-132, 1991

  However, the above two methods for generating a high-quality tomographic image have the following problems. For example, in the case of the superposition method disclosed in Patent Document 1, a plurality of tomographic images synthesized by superposition are tomographic images taken at different times. Since the respective tomographic images are used to average the pixel values of the corresponding pixels, it is effective in reducing noise included in each tomographic image. However, since the tomographic images themselves have the same resolution, it is difficult to generate a high-resolution tomographic image by combining them.

  On the other hand, in the case of the oversampling method, it is possible to generate a tomographic image with higher resolution by increasing the number of scanning lines and widening the overlap width. However, as the number of scanning lines increases, the time taken to capture a single tomographic image increases, and it is likely to be affected by eye movements of the eyeball, movements of the head, and the like. As a result, distortion occurs in the captured tomographic image.

  Therefore, in order to generate a high-quality tomographic image, it is possible to generate a high-resolution tomographic image with as little noise as possible under imaging conditions that are not easily influenced by eye movements of the eyeball or movement of the head. It is desirable to perform shooting. On the other hand, there are individual differences in the size of eye movements and head movements, and the shooting conditions that are not easily affected by eye movements or head movements are not always constant. .

  The present invention has been made in view of the above problems, and an object of the present invention is to generate a low-noise and high-resolution tomographic image in which the influences of eye movements of the eyeball and movement of the head are suppressed as much as possible. .

In order to achieve the above object, an image processing apparatus according to the present invention comprises the following arrangement. That is,
Detection means for detecting the amount of movement of the eye to be examined;
As the amount of movement increases, the number of scanning lines and the number of scanning lines when acquiring a two-dimensional tomographic image of the eye to be examined are decreased and the number of scanning lines for acquiring the two-dimensional tomographic image of the eye to be examined is increased. And determining means for determining the number of sheets.

  According to the present invention, it is possible to generate a low-noise and high-resolution tomographic image in which the influences of eyeball fine movement and head movement are suppressed as much as possible.

It is a figure which shows the structure of an image processing system. It is a flowchart which shows the flow of the tomographic image process in an image processing apparatus. It is the schematic which shows an example of a tomographic image and a fundus image. It is the schematic which shows an example of the relationship between the number of scanning lines and the number of imaging | photography. It is a figure for demonstrating a tomographic image generation process. It is a figure which shows the structure of an image processing system. It is a flowchart which shows the flow of the tomographic image process in an image processing apparatus. It is a flowchart which shows the flow of the tomographic image process in an image processing apparatus. It is a figure for demonstrating the oversampling method.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Note that the image processing apparatus according to the present embodiment detects the amount of movement of the subject's eye when performing imaging by the oversampling method or the superposition method, and performs imaging based on the imaging condition corresponding to the detected amount of movement. It is characterized by that.

  According to the present embodiment, since the photographing is performed by the oversampling method or the superposition method under the photographing condition corresponding to the amount of eye movement for each individual, the influence of eye movements of the eyeball or the movement of the head is minimized. It is possible to generate a tomographic image with low noise and high resolution.

  Hereinafter, details of the image processing system including the image processing apparatus according to the present embodiment will be described.

<Configuration of image processing system>
FIG. 1 is a diagram illustrating a configuration of an image processing system 100 including an image processing apparatus 110 according to the present embodiment. As shown in FIG. 1, the image processing system 100 is configured by connecting an image processing apparatus 110 to a tomographic image capturing apparatus 120 and a fundus image capturing apparatus 130 via an interface.

  The tomographic imaging apparatus 120 is an apparatus that captures a tomographic image of the eye, and examples of the apparatus include time domain OCT and Fourier domain OCT. Since the tomographic imaging apparatus 120 is a known apparatus, detailed description thereof is omitted, and here, the operation content is changed according to the number of scanning lines, the number of captured images, and the like set by an instruction from the image processing apparatus 110. Only the functions to be described will be described.

  In FIG. 1, a galvanometer mirror 121 controls the irradiation position of near infrared light. Further, the galvanometer mirror driving unit 122 defines the number of scanning lines in the plane direction (scanning speed in the plane direction).

  The parameter setting unit 123 sets various parameters used for controlling the operation of the galvano mirror 121 by the galvano mirror driving unit 122 in the galvano mirror driving unit 122. Based on the parameters set by the parameter setting unit 123, imaging conditions for tomographic image capturing by the tomographic image capturing apparatus 120 are determined. Specifically, the scanning speed in the main scanning direction in the planar direction and the sub-scanning direction in the planar direction is determined by the number of scanning lines and the number of captured images set in accordance with an instruction from the image processing apparatus 110.

  The fundus image capturing apparatus 130 is an apparatus that captures a fundus image of an eye part. Examples of the apparatus include a fundus camera and an SLO.

  The image processing apparatus 110 processes the tomographic image captured by the tomographic image capturing apparatus 120 and generates a tomographic image displayed on the display unit 117. The image processing apparatus 110 includes an image acquisition unit 111, a storage unit 112, a first motion detection unit 113, a second motion detection unit 114, a determination unit 115, an image creation unit 116, and a display unit 117. Is provided.

  The image acquisition unit 111 acquires a tomographic image and a fundus image captured by the tomographic image capturing device 120 and the fundus image capturing device 130 and stores them in the storage unit 112. The first motion detection unit 113 detects the amount of motion in the depth direction of the eye to be examined based on the reflected light intensity (signal intensity) measured at the time of imaging in the tomographic imaging apparatus 120. The second motion detection unit 114 detects the amount of motion in the planar direction of the subject's eye based on the fundus image captured by the fundus image capturing device 130.

  The determination unit 115 is a parameter (scanning) for performing imaging by the oversampling method or the superposition method based on the amount of movement of the eye to be examined detected by the first motion detection unit 113 and the second motion detection unit 114. (Number of lines, number of shots, etc.).

  The image creation unit 116 processes the tomographic image captured by the oversampling method or the superposition method under the parameters determined by the determination unit 115 and generates a tomographic image displayed on the display unit 117. The display unit 117 displays the tomographic image generated by the image creation unit 116.

<Flow of tomographic image processing in image processing apparatus>
Next, the flow of tomographic image processing in the image processing apparatus 110 of this embodiment will be described with reference to FIGS. 2 and 3.

  In step S <b> 201, based on an instruction from the image processing device 110, the tomographic image capturing device 120 and the fundus image capturing device 130 capture the eye to be examined in order to detect the amount of movement of the eye to be examined. The image acquisition unit 111 acquires a tomographic image captured by the tomographic image capturing device 120 and a fundus image captured by the fundus image capturing device 130 (these are collectively referred to as a motion detection image).

  FIG. 3 is a diagram illustrating an example of a motion detection image acquired by the image acquisition unit 111. 3A illustrates an example of a tomographic image captured by the tomographic image capturing apparatus 120, and FIG. 3B illustrates an example of a fundus image captured by the fundus image capturing apparatus 130. In FIG. 3B, the reference symbol F indicates the fundus.

  In step S202, the first motion detector 113 and the second motion detector 114 detect the amount of motion of the eye to be examined. In the first motion detection unit 113, the depth direction of the eye is based on the reflected light intensity (the intensity of the reflected signal) of near-infrared light irradiated to the eye when the tomographic image capturing apparatus 120 captures a tomographic image. The amount of motion in the z-axis direction (FIG. 3A) is detected.

  Further, the second motion detection unit 114 tracks feature points such as a blood vessel bifurcation in the fundus image acquired from the fundus image capturing apparatus 130, so that the planar direction of the eye (xy in FIG. 3B) is obtained. Axis direction) is detected. Note that feature point detection and tracking is performed using, for example, the KLT method (see Non-Patent Document 1) or the like (however, feature point detection and tracking is not limited to the KLT method). Absent).

  In step S <b> 203, the determination unit 115 sets the imaging conditions when the tomographic imaging apparatus 120 performs imaging according to the amount of eye movement detected by the first motion detection unit 113 and the second motion detection unit 114. Determine the parameters to configure. Further, the determined parameter is set in the parameter setting unit 123 of the tomographic imaging apparatus 120. Details of the parameter determination process in the determination unit 115 will be described later.

  In step S <b> 204, the image acquisition unit 111 acquires a tomographic image obtained by the tomographic imaging apparatus 120 performing imaging using the parameters determined by the determination unit 115 based on an instruction from the image processing apparatus 110. To do.

  In step S205, the image creating unit 116 processes the tomographic image acquired in step S204 (for example, calculates a pixel value of each pixel by performing an averaging process of a plurality of pixels) and displays it on the display unit 117. A tomographic image is generated. Details of the tomographic image generation processing in the image creation unit 116 will be described later. In step S <b> 206, the display unit 117 displays the tomographic image generated by the image creation unit 116.

<Details of processing in each part>
Next, details of processing of each unit constituting the image processing apparatus 110 will be described.

<Details of Parameter Determination Process in Determination Unit 115>
First, details of the parameter determination process in the determination unit 115 will be described. In the image processing apparatus 110 according to the present embodiment, the number of pixels n (n> 1) is used as the number of pixels used for the averaging process per pixel in order to generate a high-quality tomographic image.

  The determination unit 115 determines each parameter (the number of captured images and the number of scanning lines) so as to realize the addition averaging process with the number of pixels n and prevent distortion in one tomographic image. . Details will be described below.

When the lateral resolution during the tomographic image generation rx, the number of scanning lines of shots of the tomographic image at the same section in k, 1 tomographic image and A _m, and lateral resolution rx, the number of scanning lines and number of shots k relationship between a _m is as (1).

  On the other hand, when the frequency of the light source used in the tomographic image capturing apparatus 120 is f [Hz], the time t [s] required to capture one tomographic image can be obtained from the equation (2).

  Here, the lateral resolution ORx and the depth resolution ORz of the tomographic image can be obtained based on the wavelength of the light source used in the tomographic imaging apparatus 120.

  Then, in order to prevent distortion from occurring in one tomographic image, the determination unit 115 calculates the average value or the center of the amount of movement of the eye to be detected detected during the time for photographing one tomographic image. The parameter is determined so that the value does not exceed the resolution.

That is, if the time required for the eye to move the horizontal resolution ORx is t _ORx [s] and the time required for the depth resolution ORz to move is t _ORz [s], t _ORx and t _ORz are t. Determine the parameters not to exceed. Specifically, the number of scanning lines _Am is obtained from equation (3) using equation (2).

  Further, the number of shots k is obtained from equation (4) using equations (1) and (3).

Next, with reference to FIG. 4, the number of scanning lines A _m in one tomographic image, the relationship between the number of shots k in the same cross-section will be described. The vertical scale in FIG. 4 is a numerical value when the horizontal resolution rx at the time of tomographic image shooting is 512 and the number of pixels n used for the averaging process is 4.

4, the solid line of the vertical axis and the graph on the left represents the number of scanning lines A _m, is a broken line of the vertical axis and the graph of the right represents the number of shots k. The horizontal axis represents the amount of eye movement. As shown in FIG. 4, if the parameter so as not to distort is determined in one tomographic image, as the motion amount of the eye increases, the number of the number A _m scanning lines decreases, shooting The number of sheets will increase.

In FIG. 4, since the number of scanning lines _{A m} three stages of 512, 1024, 2048, graph has become step functions like, the number of scanning lines _{A m} is not limited thereto . For example, it may be configured to be a linear function or a non-linear function with a downward slope corresponding to an arbitrary number of scanning lines.

<Details of Tomographic Image Generation Processing in Image Creation Unit 116>
Next, details of the tomographic image generation processing in the image creation unit 116 will be described. FIG. 5A is a diagram for explaining tomographic image generation processing (addition averaging processing of scanning lines located on the same tomographic image) for processing a tomographic image captured by the oversampling method to generate a tomographic image. is there.

  FIG. 5B is a tomographic image generation process for processing a plurality of tomographic images photographed by the superposition method to generate a tomographic image (addition average of scanning lines photographed at different times and located on different tomographic images. It is a figure for demonstrating a process.

  FIG. 5C shows a tomographic image generation process for generating a tomographic image by processing a tomographic image captured by a combination of the oversampling method and the superposition method (scan lines located on the same tomographic image and different tomographic images). It is a figure for demonstrating an addition average process. FIG. 5D shows a tomographic image generated by the tomographic image generation process. Details of each process will be described below.

(1) Tomographic image generation process based on a tomographic image captured by the oversampling method First, a tomographic image generation process based on a tomographic image captured by the oversampling method will be described with reference to FIG. Here, an example will be described in which shooting is performed at a resolution twice the horizontal resolution rx.

In FIG. 5A, A _i2j ′ and A _{i2j + 1} ′ represent each scanning line. A _{i2j + 1} ′ indicates a scanning line captured 1 / f [s] after capturing A _i2j ′. FIG. 5D is a tomographic image generated by performing an averaging process using n pixels for each pixel.

That is, in FIG. 5D, A _ij is a new scanning line calculated by performing the averaging process on the corresponding scanning line. In the case of FIG. 5A, A _ij is calculated by performing an averaging process on the scanning lines of A _i2j ′ and A _{i2j + 1} ′. Note that the method of tomographic image generation processing for a tomographic image photographed by the oversampling method is not limited to addition averaging processing, and median calculation processing, weighted addition averaging processing, or the like may be used.

(2) Tomographic image generation processing for a tomographic image photographed by the superposition method Next, a tomographic image generation processing based on a tomographic image photographed by the superposition method will be described with reference to FIG. Here, a case where the number of shots k in the same cross section is 2 will be described.

When performing superimposition processing based on a plurality of tomographic images, it is necessary to align the tomographic images (T _i ″ and T _{i + 1} ″) in advance in an alignment unit (not shown). . As the alignment processing between tomographic images, for example, an evaluation function representing the similarity between two tomographic images is defined in advance, and the tomographic image is deformed so that the value of this evaluation function becomes the best. As the evaluation function, for example, a method of evaluating with a pixel value is cited (for example, a method of performing evaluation using mutual information amount is cited). In addition, as the tomographic image deformation process, for example, a process of performing translation or rotation using affine transformation or changing an enlargement ratio can be cited. In the following description, it is assumed that the alignment process between tomographic images has already been completed in the overlay process with a plurality of tomographic images.

In FIG. 5B, T _i ″ and T _{i + 1} ″ are tomographic images taken at the same time at the same cross section. A _ij ″ and A _{(i + 1) j} ″ represent respective scanning lines in the tomographic images T _i ″ and T _{i + 1} ″. A _{(i + 1) j} ″ represents a scanning line photographed after A _m / f + β [s] in which A _ij ″ is photographed. Here, β is a time for returning the position of the scanning line from the last position (A _{im in} FIG. 5B) to the first position (A _{i1 in} FIG. 5B) of the tomographic image.

When the tomographic image of FIG. 5 (d) is generated from the tomographic image of FIG. 5 (b), A _ij in FIG. 5 (d) is an average of the scanning lines of A _ij ″ and A _{(i + 1) j} ″. Calculated by performing processing.

(3) Tomographic image generation processing for a tomographic image photographed by a combination of the oversampling method and the superposition method Next, using FIG. 5C, the image was photographed by a combination of the oversampling method and the superposition method. A tomographic image generation process based on a tomographic image will be described. Here, a case will be described in which the number n of superpositions per pixel is 4, the lateral resolution is twice the resolution of rx, and the number of shots k in the same cross section is 2.

In FIG. 5C, A _i2j ″ ″ and A _{i2j + 1} ″ ″ represent respective scanning lines in the tomographic image T _i ″ ″, and A _{(i + 1) 2j} ′ ″, A _{(i + 1) 2j + 1} ″. 'Represents each scanning line in the tomographic image T _{i + 1} '''.

When the tomographic image of FIG. 5 (d) is generated from the tomographic image of FIG. 5 (c), A _ij in FIG. 5 (d) is A _i2j ′ ″, A _{i2j + 1} ′ ″, A _{(i + 1) 2j} ′. ″, A _{(i + 1) 2j + 1} ′ ″ is calculated by performing an averaging process on the scanning line.

  As is clear from the above description, in the present embodiment, shooting conditions are set after detecting the amount of eye movement for each individual, and shooting is performed using the oversampling method or the superposition method under the shooting conditions. The tomographic image obtained in the above is processed.

  As a result, it has become possible to generate a low-noise and high-resolution tomographic image in which the influences of eye movement and head movement are suppressed as much as possible.

  In the present embodiment, the method for generating one high-quality two-dimensional tomographic image has been described. However, the present invention is not limited to this. For example, a similar method may be used to generate a three-dimensional tomographic image. Furthermore, a high-quality tomographic image can be generated by a similar method even in a tomographic image scanned in a radial or circular shape.

[Second Embodiment]
In the first embodiment, the configuration is such that imaging for detecting the amount of motion is performed, imaging conditions are set, and a tomographic image is captured again. However, the present invention is not limited to this. For example, it may be configured to perform processing according to the amount of movement of the eye to be examined when imaging is performed under a predetermined imaging condition and the acquired tomographic image is processed. Details of this embodiment will be described below.

<Configuration of image processing system>
FIG. 6 is a diagram illustrating a configuration of an image processing system 600 including the image processing apparatus 610 according to the present embodiment. As shown in FIG. 6, the functional configuration of an image processing apparatus 610 is different from the image processing system 100 described in the first embodiment. Therefore, in the following, the difference will be mainly described.

  As shown in FIG. 6, the image processing apparatus 610 includes an image acquisition unit 111, a storage unit 112, a first motion detection unit 613, a second motion detection unit 614, an image creation unit 616, and a display unit. 117 and a determination unit 615. Among these, the image acquisition unit 111, the storage unit 112, and the display unit 117 have the same functions as those in the first embodiment, and thus description thereof is omitted here.

  The first motion detection unit 613 detects the amount of motion in the depth direction of the eye to be examined based on the reflected light intensity (signal intensity) measured at the time of imaging in the tomographic imaging apparatus 120. Further, when a motion amount exceeding the depth direction resolution ORz obtained from the wavelength of the light source used in the tomographic image capturing apparatus 120 is detected while capturing one tomographic image, the time at the time of detection is stored in the storage unit 112. Record.

  The second motion detection unit 614 detects the amount of motion in the planar direction of the eye to be inspected based on the fundus image captured by the fundus image capturing device 130. Further, while the tomographic image capturing apparatus 120 captures a single tomographic image, a motion amount exceeding the lateral resolution ORx obtained from the wavelength of the light source used in the tomographic image capturing apparatus 120 is detected based on the fundus image. In such a case, the time at the time of detection is recorded in the storage unit 112.

  The determining unit 615 selects a cross-sectional image with a small amount of motion as a reference cross-sectional image, and determines the presence or absence of a pixel whose amount of motion exceeds a predetermined threshold based on the recording result of the storage unit 112. Further, when there is a pixel whose motion amount exceeds a predetermined threshold, a scanning line used for the averaging process is selected for the pixel.

  Of the cross-sectional images recorded in the storage unit 112, the image creating unit 616 selects a cross-sectional image selected as the reference cross-sectional image by the determining unit 615 for pixels whose movement amount exceeds a predetermined threshold. Addition averaging processing is performed using the scanned lines.

<Flow of tomographic image processing in image processing apparatus>
Next, the flow of tomographic image processing in the image processing apparatus 610 of this embodiment will be described with reference to FIG.

In step S701, based on an instruction from the image processing device 610, the tomographic image photographing device 120 and the fundus image photographing device 130 each photograph the eye to be examined. In tomographic imaging apparatus 120 performs imaging of the subject's eye by using the parameters set in advance in the parameter setting section 123 (e.g., taking a number of scanning lines A _m 2048, as 4 of shots k in the same cross-sectional I do).

  In step S702, the first motion detector 613 and the second motion detector 614 detect the amount of motion of the eye to be examined. Since the motion amount detection method has already been described in the first embodiment, description thereof is omitted here. In the first motion detection unit 613 and the second motion detection unit 614, a motion amount exceeding the lateral resolution ORx and the depth direction resolution ORz obtained from the wavelength of the light source is obtained while capturing one tomographic image. If there is, this is detected, and the detected time is recorded in the storage unit 112.

  In step S703, based on the amount of motion detected in step S702 and the tomographic image captured in step S701, the determination unit 615 performs a composite image selection process that selects pixels for which the averaging process is performed. Here, the details of the composite pixel selection process (step S703) will be described with reference to the flowchart of FIG.

Incidentally, when the description of the composite pixel selecting process (step S703), 4 is the number of pixels n used in the averaging process in the selected pixels, lateral resolution rx 512, the scanning line number _{A m} is 2048, in the same cross-sectional It is assumed that the number of shots k is 4.

  In step S710, the determination unit 615 selects a reference tomographic image from a plurality of tomographic images. In step S702, the reference tomographic image is selected by selecting a tomographic image having no eye movement amount exceeding the lateral resolution ORx and the depth resolution ORz within the time to capture one tomographic image. If there is no tomographic image that satisfies the conditions, a tomographic image with the smallest maximum motion amount or a tomographic image with the smallest average motion amount is selected within the time to capture one tomographic image. Alternatively, each tomographic image is set as a reference tomographic image, and alignment is performed between the other tomographic images and the respective tomographic images, and the tomographic image having a high average value of the alignment evaluation values with the other tomographic images. Finally select.

  In step S720, it is determined whether the reference tomographic image satisfies a predetermined condition. Specifically, it is determined whether or not the amount of movement of the eye to be examined in the reference tomographic image selected in step S710 exceeds the horizontal resolution and depth resolution. If it is determined in step S720 that the horizontal resolution and the depth resolution are not exceeded, the composite pixel selection process is terminated.

  On the other hand, if it is determined that the amount of movement of the eye in the reference tomographic image exceeds the lateral resolution or depth resolution, the scanning line of the tomographic image taken by the combination of the oversampling method and the overlay method is added. In order to perform the averaging process, the process proceeds to step S730.

  In step S730, the determination unit 615 associates the time at which each scanning line is captured with the time at which a motion amount exceeding the horizontal resolution ORx or the depth direction resolution ORz is detected in each scanning line of the reference tomographic image. A scan line of the reference tomographic image taken at the time when the amount of motion exceeding the lateral resolution or the depth direction resolution is detected, and a reference tomographic image other than the reference tomographic image on the same cross section that performs an averaging process between the scan line A scan line of a tomographic image is selected.

  Returning to the description of FIG. In step S <b> 704, the image creation unit 616 processes the tomographic image captured by the tomographic image capturing apparatus 120. Here, the averaging process is performed on the reference tomographic image selected in step S710 using the scanning line selected in step S730, and a tomographic image displayed on the display unit 117 is generated. Note that the averaging process is performed for each scanning line based on the method shown in step S205.

  As is clear from the above description, in the present embodiment, the amount of movement of the eye to be examined is detected while photographing the eye to be examined, and processing corresponding to the detected amount of movement is performed on the acquired tomographic image. The configuration is to be performed.

  As a result, it has become possible to generate a low-noise and high-resolution tomographic image in which the influences of eye movement and head movement are suppressed as much as possible.

[Third Embodiment]
In the first embodiment, a parameter is determined based on a tomographic image and a fundus image acquired in imaging for detecting the amount of movement of the eye to be examined, and acquired by imaging using the determined parameter. The tomographic image is processed. However, the present invention is not limited to this. For example, the amount of movement is detected during shooting using the determined parameter, and when a movement amount equal to or greater than a predetermined threshold is detected, the parameter is determined again and the shooting is automatically performed again. You may comprise as follows.

  With such a configuration, even if a large change such as blinking or microsaccade occurs during shooting, the parameters are reset from the amount of motion detected during shooting, so a high-quality tomographic image Can be maintained.

  Hereinafter, details of the present embodiment will be described with reference to FIG. Note that the functional configuration of the image processing apparatus of the present embodiment is the same as the functional configuration of the image processing apparatus of the first embodiment. Of the tomographic image processing (FIG. 8) in the image processing apparatus of the present embodiment, the processing from step S801 to step S804 is the step of tomographic image processing (FIG. 2) in the image processing apparatus of the first embodiment. This is the same as the processing from S201 to step S204. Furthermore, the processes of step S805, step S807, and step S808 are the same as the processes of step S202, step S205, and step S206. For this reason, only the process of step S806 will be described below.

  In step S806, the determination unit 115 determines whether to perform imaging again when the amount of movement of the eye to be examined exceeds a certain threshold value. Specifically, when a situation occurs in which the position of the eye is greatly shifted due to the subject's blinking or microsaccade while taking one tomographic image, the determination unit 115 performs steps Returning to S803, a determination is made to reset the parameters. When a position shift of the eye to be examined occurs, the position is also shifted from the tomographic image of the same cross section taken so far. For this reason, the parameters are set again and photographing is performed (step S804).

  As is clear from the above description, in the present embodiment, the amount of motion is detected even during tomographic image capturing, and when the detected amount of motion exceeds a predetermined threshold, capturing is performed again. As a result, even if a major change such as blinking or microsaccade occurs during imaging, re-imaging is performed automatically, so it is possible to maintain the generation of high-quality tomographic images. It becomes.

[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, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (23)

Detection means for detecting the amount of movement of the eye to be examined;
As the amount of movement increases, the number of scanning lines and the number of scanning lines when acquiring a two-dimensional tomographic image of the eye to be examined are decreased and the number of scanning lines for acquiring the two-dimensional tomographic image of the eye to be examined is increased. An image processing apparatus comprising: determining means for determining the number of sheets.   The image processing apparatus according to claim 1, further comprising an alignment unit configured to align a plurality of two-dimensional tomographic images of the eye to be examined based on a similarity between the two-dimensional tomographic images.   The image forming means for creating one two-dimensional tomographic image by adding and averaging pixel values of corresponding pixels of each of the plurality of two-dimensional tomographic images of the eye to be examined is further provided. Or the image processing apparatus of 2.   The said detection means detects the amount of movements of the depth direction of the said to-be-tested eye using the signal obtained when acquiring a two-dimensional tomographic image, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. Image processing apparatus.   The detection means detects a movement amount in a plane direction of the eye to be inspected based on a signal obtained when acquiring a two-dimensional tomographic image and a fundus image of the eye to be inspected. 5. The image processing apparatus according to any one of 4 above.   The determining means determines the number of scanning lines so that a movement amount of at least one of a depth direction and a planar direction of the eye to be examined does not exceed a resolution when acquiring the two-dimensional tomographic image. The image processing apparatus according to claim 1, wherein:   The image processing apparatus according to claim 3, wherein the detection unit further detects a movement amount of the eye to be examined while acquiring a plurality of two-dimensional tomographic images of the eye to be examined. Selecting means for selecting, as a reference tomographic image, a two-dimensional tomographic image with the smallest amount of motion detected by the detecting means from a plurality of two-dimensional tomographic images of the eye to be examined;
The image creating means includes
Among the pixels included in the reference tomographic image, for the pixel acquired when a motion amount exceeding a predetermined threshold is detected, the pixel value of the pixel is included in another corresponding two-dimensional tomographic image. 8. The image according to claim 7, wherein one two-dimensional tomographic image is created by performing an averaging process using the pixel value of the pixel or the pixel value of the pixel corresponding to the plurality of scanning lines overlapping with the pixel. Processing equipment.   8. The determination unit according to claim 7, wherein the determination unit re-determines the number of scanning lines and the number of sheets again when a motion amount equal to or greater than a predetermined threshold is detected by the detection unit. Image processing device.   10. The image according to claim 1, wherein the determination unit determines a scanning speed in a planar direction of the eye to be examined according to the determined number and number of scanning lines. Processing equipment.   The scanning speed in the planar direction of the eye to be examined includes a scanning speed in the main scanning direction in the planar direction of the eye to be examined and a scanning speed in the sub-scanning direction in the planar direction of the eye to be examined. The image processing apparatus according to 10.   The detection means detects the amount of movement in the depth direction of the subject eye based on the intensity of the reflected light from the subject eye irradiated with light through the scanning means, and the feature region of the fundus image of the subject eye The image processing apparatus according to any one of claims 1 to 11, wherein a movement amount in a planar direction of the eye to be examined is detected based on the information.   The image according to any one of claims 1 to 12, wherein the detection unit detects a movement amount exceeding a resolution in a depth direction corresponding to a wavelength of a light source as the movement amount of the eye to be examined. Processing equipment.   When the detection means detects a movement amount exceeding the resolution in the depth direction corresponding to the wavelength of the light source as the movement amount of the eye to be examined, the detection means further comprises recording means for recording the detected time. The image processing apparatus according to claim 13.   The relationship between the amount of movement of the eye to be examined and the number of scanning lines when acquiring the two-dimensional tomographic image of the eye to be examined, and the relationship between the amount of movement of the eye to be examined and the number of images to acquire the two-dimensional tomographic image of the eye to be examined The image processing device according to claim 1, wherein each of the image processing devices is represented by any one of a linear function, a nonlinear function, and a step function. The image creating means includes
The pixel values of the corresponding pixels of each of the plurality of two-dimensional tomographic images of the eye to be examined are subjected to an averaging process, a median calculation process, or a weighted averaging process. The image processing apparatus according to claim 3, wherein a two-dimensional tomographic image is created.   The image processing apparatus according to claim 9, wherein the movement amount equal to or greater than the predetermined threshold is a movement amount corresponding to a micro saccade of the eye to be examined. Detecting the amount of movement of the eye to be examined;
As the amount of movement increases, the number of scanning lines and the number of scanning lines when acquiring a two-dimensional tomographic image of the eye to be examined are decreased and the number of scanning lines for acquiring the two-dimensional tomographic image of the eye to be examined is increased. A step of determining the number of sheets;
A control method for an image processing apparatus, comprising: Detection means for detecting the amount of movement of the eye to be examined;
As the amount of movement increases, the number of scanning lines and the number of scanning lines when acquiring a two-dimensional tomographic image of the eye to be examined are decreased and the number of scanning lines for acquiring the two-dimensional tomographic image of the eye to be examined is increased. Determining means for determining the number of sheets;
A tomographic imaging apparatus comprising: Scanning means for scanning the light applied to the eye to be examined;
Control means for controlling the scanning means based on the determined number and number of scanning lines;
The tomographic imaging apparatus according to claim 19, comprising: The determining means determines a scanning speed in a plane direction of the eye to be examined according to the determined number of scanning lines;
21. The tomographic imaging apparatus according to claim 20, wherein the control unit controls the scanning unit at the scanning speed. Detection means for detecting the amount of movement of the eye to be examined, and the larger the amount of movement, the smaller the number of scanning lines when obtaining the two-dimensional tomographic image of the eye to be examined, and obtaining the two-dimensional tomographic image of the eye to be examined An image processing system comprising: the number of scanning lines and a determining unit that determines the number of scanning lines so as to increase the number of sheets.   A program for causing a computer to execute each function of the image processing apparatus according to any one of claims 1 to 17.

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