CN114965693A - Ultrasound C-scan automatic alignment system based on virtual-real registration - Google Patents

Abstract

The invention relates to the technical field of image processing, in particular to an ultrasonic C-scan automatic alignment system based on virtual-real registration, comprising a three-axis moving device, an optical camera, a calibration plate and an ultrasonic probe, wherein the optical camera is installed on the three-axis moving device On the Z-axis fixed frame of the three-axis moving device, the X and Y axes of the three-axis moving device drive the optical corresponding horizontal plane to move, the ultrasonic probe is installed on the Z-axis of the three-axis moving device, and the calibration plate is placed on the water test piece table. By realizing system processing, the present invention can complete the automatic alignment and scanning process of any position area, reduce manual alignment and scanning time for non-concerned areas, and improve scanning efficiency.

Description

Ultrasound C-scan automatic alignment system based on virtual-real registration

technical field

The invention relates to the technical field of image processing, in particular to an ultrasonic C-scan automatic alignment system based on virtual-real registration.

Background technique

In the ultrasonic C-scanning process, the start and end points of the C-scanning path need to be set before scanning. Due to the refraction of light in the water and other reasons, the relative position of the specimen is inconvenient to observe, and sometimes the workpiece only needs to scan some specific areas, so manually select the start and end points to operate. Time-consuming and labor-intensive, and the accuracy is not high.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the purpose of the present invention is to provide an ultrasonic C-scan automatic alignment system based on virtual-real registration, so as to solve the problems of inconvenient operation, time-consuming and inaccurate alignment operation in the prior art, Through the technical solution, the automatic setting of the scanning area can be realized, thereby achieving the effect of streamlined automatic scanning.

In order to achieve the above object, the present invention provides the following technical solutions: an ultrasonic C-scan automatic alignment system based on virtual-real registration, comprising a three-axis moving device, an optical camera, a calibration plate and an ultrasonic probe, and the optical camera is installed on the three-axis. On the Z-axis fixed frame of the mobile device, the X and Y axes of the three-axis mobile device drive the optical corresponding horizontal plane to move, the ultrasonic probe is installed on the Z-axis of the three-axis mobile device, and the calibration plate is placed on the water sample table. Use as:

(1) Set the scanning starting point as the origin of the X and Y axes of the three-axis mobile device, and set the scanning end point as the preset value position of the X and Y axes of the three-axis mobile device to ensure that the calibration plate is located in the entire scanning area;

(2) Ultrasonic C-scan imaging is performed on the calibration plate area through an ultrasonic probe;

(3) after acquiring the scanned image, extract the pixel coordinate values of four fixed points of imaging, and based on the known overall scanning area, calculate the projection matrix _Hw2c of the workpiece reference plane to the ultrasonic C-scanning image according to two groups of points;

(4) process the ultrasonic C-scanning acoustic image and the camera optical image, and calculate the transformation matrix H _c2o from the ultrasonic C-scanning image to the optical image;

(5) Complete the system calibration operation based on the above steps, then take out the calibration plate from the test piece table in the water, and place the workpiece to be detected on the test piece table;

(6) place the Z axis and the camera at the initial position of the origin, take an optical photo of the workpiece in the water, use the HSV color gamut threshold segmentation to identify the contour of the workpiece, and then solve the minimum circumscribed rectangle as the scanning area;

(7) Obtain the scanning starting point A and the end point B in a group of optical images, and inversely solve the two-dimensional space under the workpiece reference plane coordinate system according to the transformation matrix obtained by the calibration;

(8) Set the coordinates of the starting point and the end point as the scanning parameters to perform automatic scanning.

Preferably, the calibration plate is a plate with holes evenly distributed. According to step (4), the acoustic image processing is as follows: when the ultrasonic probe performs ultrasound on the surface of the calibration plate, the surface of the calibration plate in the acoustic image is strongly reflected, while the holes are The positional reflection is zero, so the imaging contrast is high. Therefore, the threshold segmentation algorithm is used to extract the outline of the hole, and then the Hough circle fitting algorithm is used to extract the center of the hole.

Preferably, the calibration plate is made of a single material and has a fixed color. According to step (4), the optical image processing is to convert the image to the HSV color gamut, binarize the image based on the Hue hue value, and then use the Hough circle to approximate the image. The combined algorithm extracts the center of the hole.

Preferably, the homography transformation matrix is fitted and solved based on the two sets of points obtained by the acoustic image processing and the optical image processing, and the transformation matrix H _c2o from the ultrasonic C-scan image to the optical image is obtained by calculation.

Preferably, according to steps (7) and (8), the two-dimensional space under the workpiece reference plane coordinate system is:

Starting point: A'=A· _{Hw2cT ·} ^{Hc2oT ;}

End point: B'=B· _{Hw2cT ·} ^{Hc2oT .}

Compared with the prior art, the present invention has the beneficial effects that the system only needs one calibration operation to complete the automatic alignment and scanning process of any position area, reduce manual alignment and scanning time for non-concerned areas, and improve scanning efficiency. .

1) The present invention is an automatic alignment process, which can save the operator's time for manual operation, achieve the effect of saving time and effort, and improve the accuracy of starting point and end point positioning, saving scanning time.

2) Improve the automation rate of the scanning process, making the ultrasonic C-scanning system more widely used in industrial scenarios

3) Virtual-real registration can realize augmented reality fusion display, which has broad prospects in application.

Description of drawings

1 is a plan view of a calibration plate of the present invention;

2 is a schematic diagram of the system device assembly of the present invention;

FIG. 3 is a flow chart of the system method of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Virtual-real registration is the key technology of augmented reality. Due to the characteristics of small computational complexity and strong real-time performance, the use of planar templates for virtual-real registration is widely used.

The homography transformation is used to describe the position mapping relationship between the world coordinate system and the pixel coordinate system. The homography of a plane is defined as the projection mapping from one plane to another plane, and the corresponding transformation matrix is called a homography matrix.

Ultrasonic C-scanning technology is a technology that integrates ultrasonic testing with microcomputer control and microcomputer for data acquisition, storage, processing, and image display. ) echo information to form a two-dimensional image technology, its principle is simple, can obtain information of different sections, widely used in semiconductor, life science, material science, nanotechnology and other fields.

1 to 3, the present invention provides a technical solution: an ultrasonic C-scan automatic alignment system based on virtual-real registration, including a three-axis moving device, an optical camera, a calibration plate and an ultrasonic probe, the optical camera is installed in the On the Z-axis fixed frame of the three-axis moving device, the X and Y axes of the three-axis moving device drive the optical corresponding horizontal plane to move, the ultrasonic probe is installed on the Z-axis of the three-axis moving device, and the calibration plate is placed on the water sample table. The system is used in the following ways:

(1) Set the scanning starting point as the origin of the X and Y axes of the three-axis mobile device, and set the scanning end point as the preset value position of the X and Y axes of the three-axis mobile device to ensure that the calibration plate is located in the entire scanning area;

(2) Ultrasonic C-scan imaging is performed on the calibration plate area through an ultrasonic probe;

(3) after acquiring the scanned image, extract the pixel coordinate values of four fixed points of imaging, and based on the known overall scanning area, calculate the projection matrix _Hw2c of the workpiece reference plane to the ultrasonic C-scanning image according to two groups of points;

(4) the ultrasonic C-scanning acoustic image and the camera optical image are processed, and the transformation matrix H _c2o from the ultrasonic C-scanning image to the optical image is obtained by calculation;

(5) Complete the system calibration operation based on the above steps, then take out the calibration plate from the test piece table in the water, and place the workpiece to be detected on the test piece table;

(6) place the Z axis and the camera at the initial position of the origin, take an optical photo of the workpiece in the water, use the HSV color gamut threshold segmentation to identify the contour of the workpiece, and then solve the minimum circumscribed rectangle as the scanning area;

(7) Obtain the scanning starting point A and the end point B in a group of optical images, and inversely solve the two-dimensional space under the workpiece reference plane coordinate system according to the transformation matrix obtained by the calibration;

(8) Set the coordinates of the starting point and the end point as the scanning parameters to perform automatic scanning.

The calibration plate is a plate with holes evenly distributed. According to step (4), the acoustic image processing is as follows: when the ultrasonic probe performs ultrasound on the surface of the calibration plate, the surface of the calibration plate in the acoustic image is strongly reflected, and the reflection at the position of the hole is: Therefore, the threshold segmentation algorithm is used to extract the outline of the hole, and then the Hough circle fitting algorithm is used to extract the center of the hole.

The calibration plate is made of a single material and has a fixed color. According to step (4), the optical image processing is to transform the image into the HSV color gamut, binarize the image based on the Hue hue value, and then use the Hough circle fitting algorithm to extract the image. Hole center.

Based on the two sets of points obtained by acoustic image processing and optical image processing, the homography transformation matrix is fitted and solved, and the transformation matrix H _c2o from the ultrasonic C-scan image to the optical image is calculated.

According to steps (7) and (8), the two-dimensional space under the workpiece reference plane coordinate system is:

Starting point: A′=A· _{Hw2cT ·} ^{Hc2oT ;}

End point: B'=B· _{Hw2cT ·} ^{Hc2oT .}

Through this technical solution, in the actual setting, a 150mm*150mm calibration plate is used, and the scanning end point of the three-axis mobile device is set to 200mm; Realize the fixation of the camera's spatial reference position;

Then, the scanned area is scanned and imaged by an optical camera and an ultrasonic probe. After the C-scan image is obtained, the pixel coordinate values of the four vertices of the imaging are first extracted, and the two-dimensional space coordinate points (0,0), ( 0,200), (200,0), (200,200), the coordinate unit is millimeter, and the projection matrix _Hw2c from the workpiece reference plane to the C-scan image can be calculated according to the two sets of points;

The C-scan acoustic image and the camera optical image are then processed. In the acoustic image, the surface of the calibration plate has strong reflection, but the reflection at the hole position is zero, so the imaging contrast is high, so the threshold segmentation algorithm is used to extract the hole contour, and then the Hough circle fitting algorithm is used to extract the hole center; in the optical image, considering the water The bottom plate of the test piece is made of a single material and the color is fixed. Therefore, the image is converted to the HSV color gamut, and the image is binarized based on the Hue hue value, and then the Hough circle fitting algorithm is used to extract the center of the hole. Here, the optical imaging process undergoes a refraction in water, but it still conforms to the law of plane projection transformation. Therefore, the obtained two sets of points are sorted and sorted, and the homography transformation matrix is fitted and solved, and the transformation matrix H _c2o from the C scan image to the optical image can be obtained by calculation.

In this way, the system calibration operation is completed, the calibration plate can be taken out from the pool, and the workpiece to be tested is placed on the test piece table. At this time, the Z axis and the camera are at the initial position of the origin, and an optical photo of the workpiece in the water is taken. The automatic algorithm can use HSV color gamut threshold segmentation to identify the contour of the workpiece, and then solve the minimum circumscribed rectangle as the scanning area; or use it directly in the host computer program. Select the ROI area with the mouse as the area to be scanned.

From this, the scanning start point A and the end point B in a set of optical images can be obtained. According to the transformation matrix obtained by the calibration, the two-dimensional space in the workpiece reference plane coordinate system can be reversely solved.

The starting point A'=A·H _w2c ^T ·H _c2o ^T and the end point B'=B·H _w2c ^T ·H _c2o ^T , the unit is millimeter.

Automatic scanning can be performed by setting the coordinates of the starting point and the end point as the scanning parameters.

Realize virtual and real registration of C-scan equipment through the camera and calibration plate installed on the Z axis;

C-scan automatic alignment is realized by image processing of optical and acoustic images;

Compared with the prior art, the present invention has the following advantages:

1) The present invention is an automatic alignment process, which can save the operator's time for manual operation, achieve the effect of saving time and effort, and improve the accuracy of starting point and end point positioning, saving scanning time.

2) Improve the automation rate of the scanning process, making the ultrasonic C-scanning system more widely used in industrial scenarios

3) Virtual-real registration can realize augmented reality fusion display, which has broad prospects in application.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (5)

1. An ultrasonic C scanning automatic alignment system based on virtual-real registration is characterized in that: including triaxial mobile device, optical camera, calibration board and ultrasonic transducer, optical camera installs on triaxial mobile device's Z axle mount, and the X, Y axle through triaxial mobile device drives the corresponding horizontal plane of optics and removes, and ultrasonic transducer installs on triaxial mobile device's Z axle, and the calibration board is arranged in aquatic test piece bench, and its system's user mode is:

(1) setting a scanning starting point as an X, Y axle original point of the three-axle moving device, and setting a scanning end point as a preset value position of a X, Y axle of the three-axle moving device, so as to ensure that the calibration plate is positioned in the whole scanning area;

(2) carrying out ultrasonic C scanning imaging on the region of the calibration plate through an ultrasonic probe;

(3) after the scanned image is obtained, pixel coordinate values of four fixed points are extracted, and based on the known whole scanning area, a projection matrix H from the workpiece reference plane to the ultrasonic C scanning image is calculated according to the two groups of points _w2c ；

(4) Processing the ultrasonic C scanning acoustic image and the optical image of the camera, and calculating to obtain a transformation matrix H from the ultrasonic C scanning image to the optical image _c2o ；

(5) Completing system calibration operation based on the steps, then taking out the calibration plate from the underwater test piece table, and placing the workpiece to be detected on the test piece table;

(6) setting the Z axis and the camera at an initial position of an original point, shooting an optical photo of the workpiece in water, adopting HSV color gamut threshold segmentation to identify the outline of the workpiece, and then solving a minimum circumscribed rectangle as a scanning area;

(7) obtaining a scanning starting point A and a scanning end point B in a group of optical images, and reversely solving a two-dimensional space under a workpiece reference plane coordinate system according to a transformation matrix obtained by calibration;

(8) and the automatic scanning can be carried out by setting the coordinates of the starting point and the end point as scanning parameters.

2. The virtual-real registration based ultrasonic C-scan automatic alignment system of claim 1, wherein: and (4) processing the acoustic image by using a plate with holes uniformly distributed, wherein when the ultrasonic probe performs ultrasonic treatment on the surface of the calibration plate, the surface of the calibration plate in the acoustic image is strongly reflected, and the hole position reflection is zero, so that the imaging contrast is higher, the hole contour is extracted by using a threshold segmentation algorithm, and then the hole center is extracted by using a Hough circle fitting algorithm.

3. The virtual-real registration based ultrasonic C-scan automatic alignment system of claim 2, wherein: and (4) the calibration plate is made of a single material and is fixed in color, according to the step (4), the optical image processing is that the image is transformed into an HSV color gamut, binarization is carried out on the image based on Hue value of Hue value, and then a Hough circle fitting algorithm is used for extracting the circle center of the hole.

4. The virtual-real registration based ultrasound C-scan automatic alignment system according to claim 3, wherein: sorting and ordering two groups of points obtained based on acoustic image processing and optical image processing to perform homography transformation matrix fitting solving, and calculating to obtain a transformation matrix H from an ultrasonic C scanning image to an optical image _c2o 。

5. The virtual-real registration based ultrasonic C-scan automatic alignment system of claim 1, wherein: according to the steps (7) and (8), the two-dimensional space of the workpiece reference plane coordinate system is as follows:

starting point: a' ═ A · H _w2c ^T ·H _c2o ^T ；

End point: b' ═ B · H _w2c ^T ·H _c2o ^T 。

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