A method for improving the measurement accuracy of the ultrasonic power by the acousto-optic method

Abstract

The present invention belongs to the technical field related to ultrasonic power measurement, and discloses a method for improving the measurement accuracy of ultrasonic power by the acousto-optic method. The method includes the following steps: S1 Using an ultrasonic measurement system based on the acousto-optic effect to collect images of diffraction spots of different spot levels formed by the combined action of laser and ultrasonic waves; S2 Performing super-resolution reconstruction processing on the images obtained in step S1, and splicing the reconstructed diffraction spot images of different spot levels, thereby splicing the images of different spot levels into one image to obtain an image of multi-level diffraction spots; S3 Processing and calculating the image of multi-level diffraction spots obtained in step S2, thereby obtaining the ultrasonic power of the ultrasonic measurement system. Through the present invention, the problem of low measurement accuracy of ultrasonic power in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to ultrasonic power measurement, and more specifically, relates to a method for improving the measurement accuracy of ultrasonic power by the acousto-optic method. Background Art

[0002] Since the 1930s, ultrasonic waves have been widely used in the medical field, in detection diagnosis and physical therapy. When the ultrasonic aggregation area is small, the ultrasonic power is too large, and the time is long, a thermal effect will be generated. Excessive ultrasonic energy can cause thermal damage to tissues. High-intensity ultrasonic waves can generate enough heat to damage tissues, including cell rupture, protein denaturation, and necrosis. This may lead to tissue dysfunction or damage. The thermal effect of ultrasonic waves may also cause blood vessel dilation and increase local blood flow. Although this is beneficial in some treatments, excessive blood vessel dilation may trigger a drop in blood pressure or other circulatory system problems. The tissue damage caused by the thermal effect of ultrasonic waves will also trigger an inflammatory response. The inflammatory response may cause local edema, redness, swelling, pain and other discomforts. In some cases, the thermal effect of ultrasonic waves will also have an adverse effect on the surrounding nerves. Excessive energy absorption may cause damage to nerve tissue, resulting in paresthesia, pain or motor dysfunction. In particular, during fetal ultrasound examination, too high ultrasonic power will also have an adverse effect on the fetus. Ultrasonic waves in medical applications usually reduce the risk of thermal effects by controlling parameters, time and intensity. This requires precise control of the ultrasonic power used. Therefore, accurately and conveniently measuring the power of ultrasonic waves is the key to avoiding damage to the human body caused by ultrasonic waves.

[0003] Commonly used ultrasonic power measurement methods include the radiation force balance method and the acousto-optic method based on the acousto-optic effect. The radiation force balance method is a method for directly measuring the ultrasonic radiation force. By placing a balance in the ultrasonic propagation path, the ultrasonic radiation force on the balance is measured. This method is based on Newton's second law and uses the relationship between the radiation force and the mass of an object to calculate the ultrasonic power. The advantage of this method is that it can provide accurate power measurement results and is applicable to ultrasonic waves with different frequencies and beam shapes. However, the equipment of the radiation force balance method is complex and requires precise force sensors and calibration processes. Therefore, it is more cumbersome to use and is not conducive to use in medical diagnosis and treatment. The acousto-optic method is an indirect method for measuring ultrasonic power. By measuring the change in the light intensity of an optical medium caused by ultrasonic waves, the power is estimated. This method is based on the optical absorption and acousto-optic conversion effects caused by ultrasonic waves in the medium, and infers the ultrasonic power by measuring the change in the optical signal. The acousto-optic method has simple equipment and convenient operation compared with the radiation force balance method, and is suitable for real-time measurement and monitoring. However, the measurement error of the acousto-optic method is relatively large. Therefore, a method for improving the measurement accuracy of ultrasonic power by the acousto-optic method is needed. Summary of the Invention

[0004] In view of the above deficiencies or improvement requirements of the prior art, the present invention provides a method for improving the accuracy of ultrasonic power measurement by the acousto-optic method, which solves the problem of low accuracy of ultrasonic power measurement in the prior art.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a method for improving the accuracy of ultrasonic power measurement by the acousto-optic method, the method comprising the following steps:

[0006] S1 Use an ultrasonic measurement system based on the acousto-optic effect to collect images of diffraction spots of different spot levels formed by the combined action of laser and ultrasonic waves;

[0007] S2 Perform super-resolution reconstruction processing on the images obtained in step S1, and splice the reconstructed diffraction spot images of different spot levels, so as to splice the images of different spot levels in one image to obtain an image of multi-level diffraction spots;

[0008] S3 Process and calculate the image of multi-level diffraction spots obtained in step S2, so as to obtain the ultrasonic power of the ultrasonic measurement system.

[0009] Further preferably, in step S1, for the 0-level spot, a short exposure time is adopted; for the 1-level and 2-level spots, a long exposure time is adopted for collection.

[0010] Further preferably, in step S1, when collecting the 1-level and 2-level spots, the position where the 0-level spot is located is blocked in front of the camera to avoid the camera being exposed to the 0-level spot for a long time.

[0011] Further preferably, in step S2, the maximum a posteriori probability algorithm is adopted for the super-resolution reconstruction.

[0012] Further preferably, the posterior probability function is as follows:

[0013]

[0014] where L k is the low-resolution image sequence before reconstruction, H MAP is the high-resolution image, \(\hat{H}\) is the predicted high-resolution image, and k is the number of low-resolution images.

[0015] Further preferably, the length and width resolution of the reconstructed image is between 1.5 times and 2.5 times that of the image before reconstruction.

[0016] Further preferably, in step S2, after splicing the diffraction spots of different levels, the gray value of the image is corrected.

[0017] Further preferably, in step S3, the processing and calculation of the image of the multi-level diffraction spots include image grayscale conversion, image binarization, positioning of the diffraction spots, and calculation of the Raman-Nath parameter ν value, so as to obtain the power of the ultrasonic wave.

[0018] According to another aspect of the present invention, there is provided an ultrasonic power calculation system, including a processor, and the processor is used to execute the method for improving the measurement accuracy of the acousto-optic generated ultrasonic power described above.

[0019] According to still another aspect of the present invention, there is provided a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the method for improving the measurement accuracy of the acousto-optic generated ultrasonic power described above is implemented.

[0020] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following beneficial effects are achieved:

[0021] 1. In the present invention, by collecting diffraction spots of different levels and splicing them in one image, and then processing and calculating the image, the power of the ultrasonic wave is obtained. This method solves the risk of camera burnout caused by too high brightness of the 0-level spot when the camera collects it, and collects multiple levels of spots, making the measurement of the ultrasonic power more accurate;

[0022] 2. The present invention reconstructs the collected image through SR technology, improves the image resolution, makes the positioning of the spot center more accurate, and improves the accuracy of measuring the ultrasonic power by the acousto-optic method;

[0023] 3. In the present invention, through the light blocking strip, the 1st and 2nd level spots are collected using a longer exposure time, and at the same time, the CCD camera is protected from damage by the high-brightness 0-level spot;

[0024] 4. In the present invention, through image splicing and correction of the gray value of the spot, 0, 1, and 2 level spots are included in the same image, so as to measure the ultrasonic power. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flowchart of the method for improving the measurement accuracy of the acousto-optic ultrasonic power constructed according to the preferred embodiment of the present invention;

[0026] Figure 2 is a schematic structural diagram of the acousto-optic ultrasonic power measurement system constructed according to the preferred embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of the image splicing method constructed according to the preferred embodiment of the present invention;

[0028] Figure 4It is a schematic diagram of gray value correction constructed according to a preferred embodiment of the present invention.

[0029] In all the drawings, the same reference numerals are used to represent the same elements or structures, where:

[0030] 1 - Laser, 2 - Beam expander, 3 - Filter, 4 - Ultrasonic signal generator, 5 - Ultrasonic transducer, 6 - Water tank, 7 - Convex lens, 8 - Light blocking strip, 9 - CCD camera, 10 - Computer analysis system. Detailed implementation manners

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] A method for improving the measurement accuracy of the ultrasonic power by the acousto - optic method, the method comprising the following steps:

[0033] S1 Use an ultrasonic measurement system based on the acousto - optic effect to collect the diffraction images. In order to obtain as many diffraction images as possible, the exposure time needs to be extended.

[0034] Since the light intensity of the 0th - order spot is too large, an excessive exposure time will damage the CCD camera. Therefore, first use a metal light blocking strip to block the position corresponding to the 0th - order spot, then set a long exposure time so that the 1st - and 2nd - order spots are clearly visible, and continuously collect a set of images. Then remove the light blocking strip, set a short exposure time so that the 0th - order spot is clearly visible, and continuously collect a set of images. When collecting a set of image sequences, the time interval is generally 0.5 s, and a set is generally 7 pictures to achieve a balance between improving accuracy and processing time; specifically, first set the CCD camera to a short exposure time to ensure that the 0th - order spot will not damage the camera, and then adjust the position of the metal light blocking strip so that the 0th - order spot is completely blocked. Then switch to a long exposure time and check whether the 1st - and 2nd - order spots are visible. If the 0th - order spot is not visible under the short exposure time, and the 1st - and 2nd - order spots are visible under the long exposure time, the position of the light blocking strip is appropriate at this time, and subsequent picture - taking operations can be carried out.

[0035] First, use a short exposure time to collect the 0th - order diffraction spot pattern, then use a metal light blocking strip, and adjust the position and angle of the light blocking strip and the CCD camera so that the light blocking strip just blocks the position of the 0th - order spot. Then use a long exposure time, generally twice the short exposure time, to collect the 1st - and 2nd - order diffraction spot images.

[0036] AsFigure 2 The ultrasonic measurement system based on the acousto-optic effect shown in the figure includes a laser 1, a beam expander 2, a filter 3, an ultrasonic signal generator 4, an ultrasonic transducer 5, a water tank 6, a convex lens 7, a light blocking strip 8, a CCD camera 9, and a computer analysis system 10. After the laser 1 emits laser light, it passes through the beam expander 2 and the filter 3 and reaches the water tank 6. At the same time, the ultrasonic signal generator 4 emits ultrasonic waves, which reach the water tank under the action of the ultrasonic transducer 5. The laser and the ultrasonic waves act together on the water in the water tank. The light reflected by the water enters the convex lens 7, is converged, and then enters the CCD camera for imaging. The ultrasonic power is obtained by analyzing the image through the computer analysis system 10.

[0037] S2 performs super-resolution processing on the collected 0th-order and 1st- and 2nd-order diffraction pictures respectively, and obtains a high-resolution image for each. Then the two obtained high-resolution images are spliced together to form a high-resolution image containing multi-order diffraction spots. Since the exposure times used when collecting the 0th-order spots are different, the empirical function of the exposure time and the image gray value is used to correct the gray value of the 0th-order speckle, and the final multi-order diffraction spot image is obtained;

[0038] The exposure times for the 0th-order spots and the 1st- and 2nd-order spots should be adjusted according to different camera models and lens parameters to ensure that the spot brightness in the collected pictures is appropriate. Generally, the long exposure time is twice the short exposure time.

[0039] Since the exposure times used when collecting the 0th-order spots are different, the empirical function of the exposure time and the image gray value is used to correct the gray value of the 0th-order spots.

[0040] A high-resolution image means that the length and width resolution of the reconstructed image is between 1.5 times and 2.5 times that of the image before reconstruction.

[0041] The splicing of the images refers to splicing the 0th-order spots collected during short exposure into the corresponding areas blocked by the light blocking strip in the 1st- and 2nd-order spot images collected during long exposure.

[0042] The super-resolution processing and reconstruction adopt the maximum a posteriori probability algorithm, and the posterior probability function is as follows:

[0043]

[0044] Among them, L k is the low-resolution image sequence before reconstruction, H MAP is the high-resolution image, H is the predicted high-resolution image, and k is the number of low-resolution images

[0045] S3 processes and calculates the multi-order images obtained in S2 to obtain the ultrasonic power measurement result.

[0046] The processing procedure for processing and calculating a multi-level image to obtain the ultrasonic power measurement result includes image grayscale conversion, image binarization, positioning of the diffraction spot, and calculation of the Raman-Nath parameter ν value, so as to obtain the power of the ultrasonic wave.

[0047] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for improving the measurement accuracy of the ultrasonic power generated by acousto-optic effect, characterized in that, The method includes the following steps: S1 Use an ultrasonic measurement system based on the acousto-optic effect to collect images of diffraction spots at different spot levels formed by the combined action of laser and ultrasonic waves; for the 0-level spot, use a short exposure time; for the 1-level and 2-level spots, use a long exposure time for collection; when collecting the 1-level and 2-level spots, block the position where the 0-level spot is located in front of the camera to avoid the camera being exposed to the 0-level spot for a long time; S2 Perform super-resolution reconstruction processing on the images obtained in step S1, splice the diffraction spot images at different spot levels after the reconstruction processing, and use the empirical function of the exposure time and the image gray value to correct the gray value of the 0-level speckle, so as to splice the images at different spot levels into one image to obtain an image of multi-level diffraction spots; S3 Process and calculate the image of the multi-level diffraction spots obtained in step S2 to obtain the ultrasonic power of the ultrasonic measurement system.

2. The method for improving the measurement accuracy of the ultrasonic power generated by acousto-optic effect according to claim 1, characterized in that, In step S2, the maximum a posteriori probability algorithm is used for the super-resolution reconstruction.

3. The method for improving the measurement accuracy of the ultrasonic power generated by acousto-optic effect according to claim 2, characterized in that, The posterior probability function is in accordance with the following relational expression: Among them, L k is the low-resolution image sequence before reconstruction, H MAP is the high-resolution image after reconstruction, H is the predicted high-resolution image, and k is the number of low-resolution images.

4. The method for improving the measurement accuracy of the ultrasonic power generated by acousto-optic effect according to claim 3, characterized in that, The length and width resolution of the reconstructed image is between 1.5 times and 2.5 times the length and width resolution of the image before reconstruction.

5. The method for improving the measurement accuracy of the ultrasonic power generated by acousto-optic effect according to claim 1 or 2, characterized in that, In step S2, after splicing the diffraction spots at different levels, correct the gray value of the image.

6. The method for improving the measurement accuracy of the ultrasonic power generated by acousto-optic effect according to claim 1, characterized in that, In step S3, process and calculate the image of the multi-level diffraction spots, including image grayscale conversion, image binarization, positioning of the diffraction spots, and calculation of the Raman-Nath parameter ν value, so as to obtain the ultrasonic power.

7. An ultrasonic power calculation system, characterized in that, It includes a processor, and the processor is used to execute the method for improving the measurement accuracy of acousto-optic generated ultrasonic power according to any one of claims 1-6.

8. A computer-readable storage medium, on which a computer program is stored, characterized in that, When the computer program is executed by the processor, it realizes the method for improving the measurement accuracy of acousto-optic generated ultrasonic power according to any one of claims 1-6.

Images