JP2020014566A - Image processing apparatus, image processing method, and program - Google Patents

Abstract

To provide a versatile image processing apparatus capable of correcting a part in which signal strength of a reflection signal is deteriorated by simple processing.SOLUTION: An image processing apparatus subjects image data to frequency conversion processing in a depth direction, and converts it to frequency data (S2), smooths frequency data of a low frequency including at least a zero order of the frequency data in a detector arrangement direction, generates smoothed frequency data (S3), subjects the frequency data including the smoothed frequency data to frequency inverse conversion processing, and outputs image data after correction (S6).SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to an image processing device, an image processing method, and a program.

  2. Description of the Related Art Conventionally, in the field of imaging a measurement target based on a reflected signal, there has been a problem of deterioration of imaging accuracy due to a decrease in signal intensity of the reflected signal. For example, if a high absorber or the like is present in the ultrasonic echo, its back becomes a low signal region in which the signal intensity of the reflected signal is reduced, making it difficult to detect a disease state. Further, in the case of an optical coherence tomography (hereinafter, referred to as OCT), if a blood vessel is present, the signal intensity of a reflected signal deeper than the blood vessel is reduced, making it difficult to diagnose a disease.

  FIG. 12 is a diagram showing an ultrasonic echo image. In FIG. 12, a high-absorber (gallstone) that absorbs ultrasonic waves exists at a site indicated by an arrow A. For this reason, the ultrasonic signal hardly reaches the region (shaded region indicated by arrow B) on the back (deep side), and the intensity of the reflected signal decreases. In addition, even when there is a portion where the acoustic impedance greatly changes, since the strong reflection occurs at the portion, the ultrasonic signal hardly reaches the deep side, and the signal of the reflected signal is similar to the case where the high absorber exists. Strength decreases. Such a region where the signal strength of the reflected signal is reduced is also called an acoustic shadow.

  FIG. 13 is a diagram showing an OCT image. In FIG. 13, a blood vessel that absorbs an optical signal exists at a site indicated by arrows C1 and C2. For this reason, the optical signal hardly reaches the region (vertical shaded region indicated by arrows D1 and D2) on the back (deep side) of the blood vessel, and the signal intensity of the reflected signal decreases. In particular, in the region behind the blood vessels, there is an optic disc opening important for diagnosis of diabetes and the like, and the visibility of this region greatly affects the diagnosis performance of the disease.

  On the other hand, for example, in Patent Literature 1, the presence or absence of an acoustic shadow is determined from a high-luminance portion in a tomographic image obtained from a reflected signal of an ultrasonic wave and the luminance of a back portion thereof. A method of performing correction so as to increase the luminance value of the back region by using the acoustic shadow effect coefficient is disclosed (see paragraphs [0066] to [0073]).

  Further, in Patent Literature 2, an obstacle that reflects an ultrasonic signal between an element and a subject exists, and when an ultrasonic signal cannot be correctly received by some elements, the ultrasonic signal can be correctly received. A method of performing an ultrasonic analysis based on only a reception signal of a normal element is disclosed. Thereby, even if there is an element (error element) that cannot receive an ultrasonic signal correctly due to an acoustic shadow or the like, the influence can be suppressed.

JP 2005-103129 A Japanese Patent Application Laid-Open No. 2015-53961

  However, in the method of Patent Literature 1, since it is necessary to search for a high-luminance portion for all pixel columns of a tomographic image, the amount of processing is large and the calculation load is high. Further, the acoustic shadow effect coefficient that determines the correction amount of the luminance value includes a plurality of experimentally determined coefficients, and these coefficients must be appropriately adjusted in order to obtain the effect of improving the shadow area. Further, in Patent Literature 2, since only the reception signal of the normal element is used, there is a possibility that the resolution of imaging is reduced or noise such as aliasing is generated. Also, this method is specialized for beamforming, and cannot be applied to all imaging techniques based on reflected signals.

  The present invention has been made in view of the above-described problems, and has high versatility, and can correct, by a simple process, a portion where the signal intensity of a reflected signal is reduced, and an image processing apparatus and an image processing method. , And to provide programs.

  A first invention for achieving the above-mentioned object is an image processing apparatus for correcting image data visualized in a measurement target, which is obtained by receiving a reflected signal reflected from the inside of a measurement target by a plurality of detectors. And performing frequency conversion processing on the image data in a first axial direction that is an axial direction corresponding to a depth direction among two axial directions that define a coordinate system of the image data. A frequency conversion unit that converts the data into data, and among the frequency data, smoothes low-frequency data including at least the 0th order in a second axis direction orthogonal to the first axis direction to generate smoothed frequency data And an inverse frequency conversion unit that performs an inverse frequency conversion process on the frequency data including the smoothed frequency data and outputs corrected image data. It is a management apparatus.

  According to the first aspect, the image data obtained by visualizing the inside of the measurement target based on the reflection signal is subjected to frequency conversion processing in the first axial direction (depth direction) to be converted into frequency data. Low-frequency components including at least the zero-order component of the frequency data are smoothed in the second axis direction (the direction in which the detectors are arranged). Then, the frequency data on which the low-frequency component has been smoothed is subjected to frequency inverse transform processing to obtain corrected image data. In particular, in the smoothing process, the zero-order component (DC component) corresponding to the average value of the signals obtained by the respective detectors is smoothed in the direction in which the detectors are arranged. The average value is made uniform. This makes it possible to mathematically correct the portion where the intensity of the reflected signal is reduced. For example, in the ultrasonic echo, the visibility of the back of the high-absorber is improved, and the pathological condition can be easily grasped. Further, in the OCT image, it is easy to confirm the optic disc opening, which has been difficult due to the blood vessel image, and the diagnostic ability of a disease such as diabetes can be improved. The processing of the present invention does not require any processing for detecting a reduced intensity portion (shaded portion) of the reflected signal, and can be applied to all imaging techniques based on the reflected signal, so that it is highly versatile and simple. Through the processing, it is possible to correct a portion where the signal strength of the reflected signal is reduced.

  In the first aspect, the smoothing unit may further smooth primary frequency data. Further, the smoothing unit may further smooth secondary frequency data. The first-order and second-order components are gradual trend components of the signal strength in the signal propagation direction, and by smoothing the components in the same manner, the correction accuracy of the portion where the intensity of the reflected signal is reduced is further improved. Be improved.

  Further, in the first invention, a recovery area specifying unit that specifies, as a low frequency recovery area, a second axial direction area in which a low frequency component has been recovered by smoothing, and the frequency data including the smoothed frequency data. In the low-frequency recovery region, a filter processing unit that emphasizes a component of a predetermined intermediate frequency band set in advance may be further provided. This makes it possible to recover not only the low frequency components but also the signal components in the intermediate frequency band where the signal components have decreased.

  At this time, the filter processing unit may amplify components in a predetermined intermediate frequency band and reduce components in a predetermined high frequency band set in advance. Thereby, the influence of noise included in the high frequency band can be suppressed.

  A second invention is an image processing method for correcting image data obtained by visualizing the inside of a measurement target, which is obtained by a computer receiving a reflection signal reflected from the inside of the measurement target by a plurality of detectors. Frequency conversion processing is performed on the data in a first axis direction, which is an axis direction corresponding to the depth direction, of the two axis directions defining the coordinate system of the image data, and the frequency is converted into frequency data. A converting step; and a smoothing step of smoothing low-frequency data including at least 0th order in the second axial direction orthogonal to the first axial direction, among the frequency data, and generating smoothed frequency data. And performing a frequency inverse transform process on the frequency data including the smoothed frequency data to output corrected image data. An image processing method.

  According to the second aspect, the image data obtained by visualizing the inside of the measurement target based on the reflection signal is subjected to frequency conversion processing in the first axial direction (depth direction) to be converted into frequency data. Low-frequency components including at least the zero-order component of the frequency data are smoothed in the second axis direction (the direction in which the detectors are arranged). Then, the frequency data on which the low-frequency component has been smoothed is subjected to frequency inverse transform processing to obtain corrected image data. In particular, in the smoothing process, the zero-order component (DC component) corresponding to the average value of the signals obtained by the respective detectors is smoothed in the direction in which the detectors are arranged. The average value is made uniform. This makes it possible to mathematically correct the portion where the intensity of the reflected signal has decreased. For example, in the ultrasonic echo, the visibility of the back of the high-absorber is improved, and the pathological condition can be easily grasped. Further, in the OCT image, it is easy to confirm the optic disc opening, which has been difficult due to the blood vessel image, and it is possible to improve the ability to diagnose diseases such as diabetes. The processing of the present invention does not require any processing for detecting a reduced intensity portion (shaded area) of the reflected signal, and can be applied to all imaging techniques based on the reflected signal, so that it is highly versatile and simple. By the processing, it is possible to correct a portion where the signal strength of the reflected signal is reduced.

  A third invention is a program for causing a computer to function as an image processing device that corrects image data obtained by receiving a reflection signal reflected from the inside of a measurement target by a plurality of detectors and visualizing the inside of the measurement target. And performing a frequency conversion process on the image data in a first axial direction that is an axial direction corresponding to a depth direction among two axial directions defining a coordinate system of the image data, A frequency conversion unit configured to convert the frequency data into low-frequency data including at least 0th order in the second axis direction orthogonal to the first axis direction to generate smoothed frequency data; Function as a smoothing unit that performs frequency inversion processing on frequency data including the smoothed frequency data, and outputs corrected image data. It is a program characterized by.

  By installing the program according to the third invention on a general-purpose computer, the image processing apparatus according to the first invention can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the versatility is high and the part where the signal intensity of the reflected signal fell can be corrected by simple processing.

FIG. 2 is a diagram illustrating a hardware configuration of the image processing apparatus 1. Flow chart showing the operation of the image processing apparatus 1 Diagram showing image data f Diagram showing frequency data F The figure which shows a mode that the low frequency component of the frequency data F is smoothed. Comparison plot of 0-order component (DC component) before and after smoothing The figure showing the frequency data F 'in which the low frequency component was smoothed. Diagram illustrating an example of specifying a low-frequency recovery region Bandpass filter to emphasize intermediate frequency band The figure which shows the low frequency recovery area | region in the frequency data F ' Diagram showing OCT images before and after correction processing Diagram showing an ultrasonic echo image in the presence of a high absorber Diagram showing OCT image when blood vessels are present

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating a hardware configuration of the image processing apparatus 1 according to the present embodiment. As shown in FIG. 2, the image processing apparatus 1 includes a control unit 11, a storage unit 12, a media input / output unit 13, a communication control unit 14, an input unit 15, a display unit 16, a peripheral device I / F unit 17, and the like. It is realized by a general-purpose computer connected via the bus 18. However, without being limited to this, various configurations can be adopted according to the application and purpose.

The control unit 11 includes a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a ROM (Read Only
Memory), a RAM (Random Access Memory), a frame memory (Frame Memory), and the like. The CPU and the GPU call and execute a program stored in the storage unit 12, the ROM, the recording medium, and the like into the work memory area on the RAM and the frame memory, and drive and control each device connected via the bus 18, The processing described below (see FIG. 2) performed by the image processing apparatus 1 is realized.

  The GPU and the frame memory are mounted on a video card of the image processing device 1, for example. The ROM is a non-volatile memory, and permanently stores a computer boot program, a program such as a BIOS, data, and the like. The RAM and the frame memory are volatile memories, and temporarily store programs, data, and the like loaded from the storage unit 12, the ROM, the recording medium, and the like, and a work area used by the control unit 11 to perform various processes. Is provided.

  The storage unit 12 is a HDD (Hard Disk Drive) or the like, and stores a program executed by the control unit 11, data necessary for executing the program, an OS (Operating System), and the like. As for the program, a control program corresponding to the OS and an application program for causing a computer to execute processing described later are stored. Each of these program codes is read as needed by the control unit 11, transferred to the RAM and the frame memory, read by the CPU and the GPU, and executed as various means.

  The media input / output unit 13 (drive device) performs data input / output, and for example, media such as a CD drive (-ROM, -R, -RW, etc.) and a DVD drive (-ROM, -R, -RW, etc.) It has an input / output device. The communication control unit 14 has a communication control device, a communication port, and the like, is a communication interface that mediates communication between a computer and a network, and controls communication with another computer via the network. The network may be wired or wireless.

  The input unit 15 inputs data, and includes, for example, a keyboard, a pointing device such as a mouse, and an input device such as a numeric keypad. Through the input unit 15, an operation instruction, an operation instruction, data input, and the like can be performed on the computer. The display unit 16 includes a display device such as a liquid crystal panel, and a logic circuit (video adapter or the like) for realizing a video function of a computer in cooperation with the display device. The input unit 15 and the display unit 16 may be integrated like a touch panel display.

  The peripheral device I / F (Interface) unit 17 is a port for connecting a peripheral device to the computer, and the computer transmits and receives data to and from the peripheral device via the peripheral device I / F unit 17. The peripheral device I / F unit 17 is configured by a USB (Universal Serial Bus), IEEE1394, RS-232C, or the like, and usually has a plurality of peripheral device I / Fs. The connection form with the peripheral device may be wired or wireless. The bus 18 is a path that mediates transmission and reception of control signals, data signals, and the like between the devices.

Next, the operation of the image processing apparatus 1 will be described with reference to FIGS.
FIG. 2 is a flowchart illustrating the overall operation of the image processing apparatus 1.

  First, the control unit 11 of the image processing apparatus 1 inputs image data f to be processed (Step S1 in FIG. 2). The image data f transmits a signal (an ultrasonic signal in the case of an ultrasonic echo, an optical signal in the case of an OCT) into a living body, and arranges a plurality of reflected signals (echoes) reflected in the living body (for example, in a line shape). This is an image visualizing the state inside the living body, which is obtained by receiving with the arrayed detectors, and is typically an ultrasonic echo image or an OCT image.

  FIG. 3 is a diagram illustrating the image data f. The image data f is represented as a function f (x, y) using the coordinates x and the coordinates y as variables. At each pixel (x, y) of f (x, y), the signal intensity of the reflected signal at each position is held as a luminance value. Here, of the two axial directions (x direction and y direction) defining the coordinate system of the image data f, the axial direction corresponding to the depth direction (signal transmission direction) is defined as the y direction (first axial direction). And the axial direction corresponding to the arrangement direction of the detectors is defined as the x direction (second axial direction).

  Subsequently, the control unit 11 performs one-dimensional frequency conversion on the image data f in the depth direction (y direction), and converts the image data f into frequency data F (step S2 in FIG. 2). As the frequency transform, for example, a Fourier transform or a wavelet transform can be used, but it is not limited to these.

  FIG. 4 shows frequency data F, and particularly frequency data F obtained by performing one-dimensional frequency conversion on the image data f of FIG. 3 in the depth direction (y direction). Since the depth direction (y direction) is transformed into the frequency domain, the direction becomes the frequency axis direction (v direction).

  As illustrated in FIG. 4, the control unit 11 determines that the center of the frequency data F in the v direction is the 0th-order component F (x, 0), and the adjacent components are the primary components F (x, 1), F (x, −1). ), And the frequency components are rearranged such that the adjacent components are the secondary components F (x, 2), F (x, -2). That is, the frequency components are rearranged so that the frequency increases as the distance from the center in the v direction increases.

  Note that, after performing frequency conversion on the image data f in the depth direction (y direction), the control unit 11 may further perform frequency conversion on the detector arrangement direction (x direction). That is, the image data f may be subjected to two-dimensional frequency conversion in the depth direction (y direction) and the direction in which detectors are arranged (x direction).

  Subsequently, the control unit 11 smoothes the low-frequency data of the frequency data F in the direction in which the detectors are arranged (x-direction), and generates frequency data in which the low-frequency component is smoothed (FIG. 2). Step S3). This processing will be described with reference to FIGS.

  First, as shown in FIG. 5A, the control unit 11 extracts 0th-order (DC) to 2nd-order low-frequency components F (x, v) (v = −2 to 2) from the frequency data F. Then, the low-frequency components are smoothed in the detector arrangement direction (x-direction), and as shown in FIG. 5B, the smoothed low-frequency components F ′ (x, v) (v = -2-2) (smoothing frequency data) is obtained.

  The method of smoothing is not particularly limited. For example, the control unit 11 performs frequency conversion on each low-frequency component F (x, v) (v = −2 to 2) in the x-direction, Each low-frequency component is smoothed by applying an ideal low-pass filter (cutoff frequency = third-order) that passes only the second to second-order components. Alternatively, smoothing may be performed by applying a Butterworth filter (cutoff frequency = third order).

  FIG. 6 is a diagram in which the 0th order component (DC component) before and after smoothing is compared and plotted. By the smoothing, the zero-order component (DC component) corresponding to the average value of the signal of each detector is smoothed in the direction in which the detectors are arranged (x direction), so that the average value of the signal obtained by each detector is obtained. Is made uniform. As a result, as shown by the arrow in the figure, the low frequency component in the depth direction that has been reduced due to the presence of blood vessels and the like is recovered.

  Then, as shown in FIG. 7, the control unit 11 converts the smoothed low-frequency component F ′ (x, v) (v = −2 to 2) (smoothed frequency data) into the original frequency data F. The frequency data F ′ embedded at the same position is generated.

Returning to the description of the flowchart of FIG.
Subsequently, the control unit 11 specifies a region (hereinafter, referred to as a “low-frequency recovery region”) in the arrangement direction (x direction) of the detectors whose low-frequency components have been recovered by the smoothing (Step S4 in FIG. 2). .

For example, the control unit 11 detects that the difference between the value of the zero-order component F (x, 0) before smoothing and the value of the zero-order component F ′ (x, 0) after smoothing continuously exceeds a predetermined threshold value. The region in the arrangement direction (x direction) of the vessels is specified as a low-frequency recovery region. Thus, as shown in FIG. 8, the low-frequency recovery area R1 _(the area of the x 1 ~x _2), R2 _(region of x 3 ~x ₄₎ are identified.

  In the above example, the low-frequency recovery region is specified by comparing the zero-order components before and after the smoothing. However, the components obtained by combining the zero-order components and the first-order components before and after the smoothing, Alternatively, the low-frequency recovery region may be specified by comparing components obtained by combining the zeroth-order component and the second-order component before and after the smoothing.

  Here, in the low-frequency recovery regions R1 and R2, since the low-frequency component has been recovered, the shadow of the blood vessel appearing in the form of vertical stripes is reduced, and a decrease in density in a portion below the blood vessel position is suppressed. However, due to the presence of blood vessels and the like, the signal components in the intermediate frequency band at a deeper portion are also reduced.

  Therefore, the control unit 11 also restores the lowered intermediate frequency band signal component by emphasizing the intermediate frequency band component in the specified low frequency recovery regions R1 and R2 (step S5 in FIG. 2).

For example, as illustrated in FIG. 9, the control unit 11 may set a predetermined intermediate frequency band v _{m1 to} v _m2 (for example, when the number of pixels in the depth direction y of the image data f is 512 (Nyquist frequency = 256 (next), v _m1 = 3 (next), v _m2 = 170 (next), etc.), and a band-pass filter with a gain of 1.0 or more is generated. This band pass filter is applied to the low frequency recovery regions R1 and R2 (see FIG. 10). At this time, if the gain is too large, strange vertical stripes appear in the arrangement direction (x direction) of the detectors. Therefore, the gain in the intermediate frequency band is desirably about 1.1 to 1.2 times.

In order to reduce the noise component in the depth direction (y direction), it is desirable to lower the gain in the high frequency band (less than 1.0) as shown in FIG. The high frequency band refers to at least a frequency band higher than the upper limit frequency v _m2 of the intermediate frequency band (a frequency band satisfying “ _{vm 2} <v ≦ Nyquist frequency”). The high frequency band in which the gain is reduced is appropriately set according to the frequency of the noise component to be suppressed.

  Then, the control unit 11 performs inverse frequency conversion on the frequency data F ′ obtained by applying the band-pass filter to the low-frequency recovery regions R1 and R2, and outputs corrected image data f ′ (FIG. Step S6). The frequency inverse transform is, for example, an inverse Fourier transform when the frequency transform in step S2 is a Fourier transform, and an inverse wavelet transform when the frequency transform is a wavelet transform.

The image data f ′ output by the above processing is an image in which the intensity reduction portion of the reflection signal of the input image data f has been corrected.
FIG. 11 is a diagram illustrating the effect of the correction. 11 is a diagram showing image data f (OCT image inside the retina) before the correction process (the same image as in FIG. 13), and FIG. 11 right is a diagram showing image data f ′ after the correction process. is there. On the left in FIG. 11 (before the correction processing), the intensity of the reflected signal on the back is reduced due to the influence of blood vessels, and the visualization accuracy is deteriorated. On the other hand, in the right of FIG. It can be confirmed that the signal strength of the reflected signal is recovered by the smoothing of the component, and the visibility behind the blood vessel is improved.

  The present embodiment has been described with reference to the drawings. According to the embodiment of the present disclosure, image data f such as an ultrasonic echo image or an OCT image is subjected to frequency conversion processing in the depth direction y to be converted into frequency data F (step S2 in FIG. 2). . The zero-order component (DC component) obtained at this time is the average value of the signals obtained by the detectors. Therefore, the zero-order component (DC component) is smoothed in the direction x in which the detectors are arranged (step S3 in FIG. 2), and then the frequency is inversely transformed (step S6 in FIG. 2). The average value of the obtained signal intensities is made uniform, and it is possible to obtain the image data f ′ in which the portion where the intensity of the reflected signal is reduced is corrected. Thereby, for example, in the ultrasonic echo image, the visibility of the back of the high-absorbent body is improved, and the pathological condition can be easily grasped. Further, in the OCT image, it is easy to confirm the optic disc opening, which has been difficult due to the blood vessel image, and the diagnostic ability of a disease such as diabetes can be improved. The processing according to the present embodiment does not require any processing for detecting a reduced intensity portion (shaded portion) of the reflected signal, and can be applied to all imaging techniques based on the reflected signal. With a simple process, it is possible to correct a portion where the signal strength of the reflected signal is reduced.

  The primary and secondary components are trend components in which the signal intensity is gradual in the signal propagation direction, and this component is similarly subjected to smoothing (step S3 in FIG. 2) to obtain the reflected signal. Can be further improved in the correction accuracy of the reduced intensity portion.

  By amplifying the intermediate frequency band component in the region where the low frequency component has been recovered, the signal component in the intermediate frequency band where the signal component has been reduced can also be recovered (steps S4 and S5 in FIG. 2). At the same time, the effect of noise included in the high frequency band can be suppressed by reducing the components in the high frequency band.

  As described above, in step S2 of FIG. 2, the control unit 11 may perform two-dimensional frequency conversion on the image data f '. In this case, the control unit 11 executes the smoothing process in the arrangement direction of the detectors (Step S3 in FIG. 2) not in the real domain but in the frequency domain. In step S6 in FIG. 2, the control unit 11 performs two-dimensional inverse frequency transformation on the frequency data F ', and outputs corrected image data f'. The two-dimensional inverse frequency transform is, for example, a two-dimensional inverse Fourier transform when the frequency transform in step S2 is a two-dimensional Fourier transform, and a two-dimensional inverse wavelet transform when the frequency transform is a two-dimensional wavelet transform. is there.

  In addition, examples in which the method of the present disclosure is applied to image quality improvement in the medical field such as an ultrasonic echo image and an OCT image have been mainly described, but the application target of the present invention is not limited thereto. The present invention is applicable to a field having the same problems as those described at the beginning. For example, the present invention can be applied to image quality improvement in non-destructive inspection (e.g., ultrasonic inspection test, SAT test) using an echo technique.

  As described above, the preferred embodiments of the image processing apparatus and the like according to the present invention have been described with reference to the accompanying drawings, but the present disclosure is not limited to such examples. In addition, it is clear that those skilled in the art can conceive various changes or modifications within the scope of the technical idea disclosed in the present application, and these naturally belong to the technical scope of the present disclosure. It is understood.

1: Image processing device f: Image data before correction f ': Image data after correction F: Frequency data F': Frequency data R1 in which low-frequency components have been smoothed: Low-frequency recovery region R2: Low-frequency recovery region

Claims (7)

An image processing device for correcting image data visualized in the measurement target, which is obtained by receiving a reflection signal reflected from the measurement target by a plurality of detectors,
The image data is subjected to a frequency conversion process in a first axis direction which is an axis direction corresponding to a depth direction among two axis directions defining a coordinate system of the image data, and is converted into frequency data. A frequency conversion unit,
A smoothing unit that smoothes low-frequency data including at least 0th order in the second axis direction orthogonal to the first axis direction, among the frequency data, and generates smoothed frequency data;
A frequency inverse transform unit that performs frequency inverse transform processing on the frequency data including the smoothed frequency data, and outputs corrected image data.
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the smoothing unit further smoothes primary frequency data.   The image processing device according to claim 2, wherein the smoothing unit further smoothes secondary frequency data. A recovery region specifying unit that specifies a region in the second axial direction in which the low frequency component has been recovered by the smoothing as a low frequency recovery region;
The filter processing unit according to claim 1, further comprising: a filter processing unit configured to emphasize a component of a predetermined intermediate frequency band set in the low-frequency recovery region of the frequency data including the smoothed frequency data. 3. The image processing device according to any one of 3. The image processing apparatus according to claim 4, wherein the filter processing unit amplifies a component in a predetermined intermediate frequency band and reduces a component in a predetermined high frequency band set in advance. A computer is an image processing method for correcting image data obtained by visualizing the inside of a measurement target, which is obtained by receiving a reflection signal reflected from within the measurement target by a plurality of detectors,
The image data is subjected to a frequency conversion process in a first axis direction which is an axis direction corresponding to a depth direction among two axis directions defining a coordinate system of the image data, and is converted into frequency data. Frequency conversion step,
A smoothing step of, among the frequency data, smoothing low-frequency data including at least 0th order in a second axis direction orthogonal to the first axis direction, and generating smoothed frequency data;
For frequency data including the smoothed frequency data, performing a frequency inverse transform process, frequency inverse transform step of outputting corrected image data,
An image processing method comprising: A program for causing a computer to function as an image processing device that corrects image data obtained by visualizing the inside of the measurement target, which is obtained by receiving a reflection signal reflected from the inside of the measurement target by a plurality of detectors,
The image data is subjected to a frequency conversion process in a first axis direction which is an axis direction corresponding to a depth direction among two axis directions defining a coordinate system of the image data, and is converted into frequency data. Frequency converter,
A smoothing unit that smoothes low-frequency data including at least 0th order in a second axis direction orthogonal to the first axis direction, among the frequency data, and generates smoothed frequency data;
A frequency inverse transform unit that performs frequency inverse transform processing on the frequency data including the smoothed frequency data, and outputs corrected image data.
A program characterized by functioning as a program.