An automatic calibration device for two-dimensional hard X-ray imaging system based on pan-tilt

Abstract

The present invention discloses an automatic calibration device for a two-dimensional hard X-ray imaging system based on a pan-tilt platform. A dual-axis pan-tilt platform is used as a carrier of a hard X-ray emitting device to realize X-ray position scanning with two degrees of freedom. The X-ray emitting device adopts a mini X-ray tube to realize linear scanning of X-ray emission energy and intensity. The detector of the X-ray receiving device adopts a cadmium zinc telluride two-dimensional array detector, and the acquisition system is composed of a multi-channel digital pulse amplitude analyzer. The upper computer software integrates the X-ray emitting device control, pan-tilt platform rotation control, cadmium zinc telluride detector imaging and energy spectrum measurement functions. The present invention is aimed at the performance test of the two-dimensional imaging detector, and can greatly improve the test efficiency, repeatability and reliability.

Description

Technical Field

[0001] The present invention proposes an automatic calibration device for a two-dimensional hard X-ray imaging system based on a pan-tilt system, which relates to the field of automatic detection and calibration of detectors, and is particularly directed to a two-dimensional array imaging detector with multiple pixels and its imaging electronics system. The present invention can be used in the batch production factory test link of detectors to speed up the detection efficiency and comprehensiveness. In the field of scientific research, it can also be used to calibrate and study the performance changes of detectors after use in different environments or working conditions. Background Art

[0002] Two-dimensional X-ray imaging can be used in many fields such as security, inspection and quarantine, nuclear devices, medical treatment, industrial flaw detection and exploration, and has broad application prospects. However, the existing technology mainly uses CCD detectors for imaging, and the energy resolution is not high enough, so the accuracy of nuclide identification is not high. As a new generation of hard X-ray detectors, cadmium zinc telluride two-dimensional array detectors can detect hard X-rays in the energy range of 20keV-700keV, and the optimal energy resolution can reach 4%-5%. After forming an X-ray imaging system, it can improve the accuracy of nuclide identification.

[0003] During the production and processing of CdZnTe two-dimensional array detectors, it is necessary to measure the performance of each pixel, such as energy response and intensity response, to determine whether there are any processing defects in the pixels. However, the traditional method of large-area direct irradiation cannot measure whether there are problems such as crosstalk between adjacent pixels. At the same time, the linearity of energy response and intensity response cannot be automatically measured. The test process is time-consuming, and the repeatability of the test is difficult to guarantee. During the use of CdZnTe two-dimensional array detectors, it is also necessary to study the performance changes after use in different environments or working conditions. A repeatable automatic calibration platform is also required to achieve the measurement of each pixel of the detector.

[0004] Therefore, the present invention develops an automatic calibration device for a two-dimensional hard X-ray imaging system based on a dual-axis pan / tilt platform to solve the above problems encountered in practical applications. Summary of the invention

[0005] The present invention proposes an automatic calibration device for a two-dimensional hard X-ray imaging system based on a pan-tilt system, the purpose of which is to solve the problems of automatically calibrating the energy response and intensity response of each pixel point and the crosstalk between pixels during the production, processing and use of a cadmium zinc telluride array detector. At the same time, the device can also be applied to the response calibration test of other semiconductor two-dimensional imaging detectors with multiple pixels. By controlling the horizontal and vertical rotation directions of the pan-tilt system, the present invention can automatically inspect and calibrate each pixel point in a scanning manner, and by automatically adjusting the energy and intensity of the X-ray generating device, it can also automatically measure the energy response linearity and intensity response linearity of each pixel point.

[0006] The present invention is achieved through the following technical solutions:

[0007] An automatic calibration device for a two-dimensional hard X-ray imaging system based on a pan-tilt platform, the automatic calibration device comprising a hard X-ray emitting device, a pan-tilt platform, an X-ray receiving device, a preamplifier, and an imaging and energy spectrum acquisition system;

[0008] The gimbal is a dual-axis gimbal, and the hard X-ray emitting device uses the dual-axis gimbal as a carrier to perform X-ray position scanning with two degrees of freedom; the hard X-ray emitting device uses a mini hard X-ray tube to achieve linear scanning with adjustable X-ray emission energy and intensity; the detector of the X-ray receiving device uses a cadmium zinc telluride two-dimensional array detector; the imaging and energy spectrum acquisition system is composed of a multi-channel digital pulse amplitude analyzer;

[0009] The dual-axis pan-tilt head and the CdZnTe two-dimensional array detector are fixed on an optical platform and their relative positions are kept fixed;

[0010] After receiving the X-ray signal, the detector converts it into a current pulse signal, and amplifies the signal through the preamplifier. The amplified effective signal is transmitted to the imaging and energy spectrum acquisition system for signal acquisition.

[0011] Furthermore, a collimator with a diameter of 0.4 mm is arranged at the X-ray output window of the hard X-ray emitting device. The collimator is 18 mm long and is made of pure copper metal material. The distance between the front end of the collimator and the detector is kept no more than 35 mm.

[0012] Furthermore, the dual-axis gimbal is used to fix the mini rigid X-ray tube. The dual-axis gimbal can rotate 360 ​​degrees in the horizontal direction and can pitch ±60 degrees in the vertical direction, and its steering accuracy can reach 0.1 degrees.

[0013] Furthermore, the hard X-ray emission device can adjust the energy and intensity of the emitted X-rays respectively by adjusting the acceleration voltage and the excitation current;

[0014] Furthermore, the automatic calibration device is configured to control and adjust the X-ray energy and intensity generated by the hard X-ray emitting device and the rotation of the gimbal, and integrates two-dimensional hard X-ray imaging function as well as energy spectrum analysis function and calibration function, thereby realizing automatic calibration of the two-dimensional hard X-ray imaging system.

[0015] Furthermore, the automatic calibration device is configured to realize that the X-ray spot is scanned from the first pixel point to the last pixel point in a "Z"-shaped route, and the center position of the pixel point is determined by the maximum value of the pixel point collected. When the spot is moved to the center position of the pixel point, the energy or intensity of the X-ray is adjusted to perform linear scanning, thereby calibrating the linearity of the energy measurement and intensity measurement of the pixel point. The steps and results of the automated measurement can be saved in the test configuration file and the test report file respectively.

[0016] The advantages of the present invention are as follows: the present invention combines a pan / tilt, an X-ray emission device and a two-dimensional array imaging measurement system of a cadmium zinc telluride detector. The energy response and intensity response of each pixel are calibrated and measured by linear scanning. At the same time, the signal crosstalk between two adjacent pixels can also be calibrated by the present invention. After setting the configuration file parameters of the calibration test, all test work can be completed automatically, and the test results can be saved in a database or output as a test report file. For the same detector, after solidifying the test parameters, the test efficiency, repeatability and reliability can be greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the automatic calibration device system structure;

[0018] Figure 2 This is the optical path design diagram of the automatic calibration device system;

[0019] Figure 3 This is the interface diagram of the host computer software of the automatic calibration device system. DETAILED DESCRIPTION

[0020] The following describes the present invention in combination with specific implementation methods.

[0021] The present invention is a two-dimensional hard X-ray imaging system automatic calibration device based on a pan-tilt system, which can be applied to the factory performance test of the detector production and processing, and can also be used for the calibration or performance research of the detector in the use process of scientific research and industry. The structure of the system design is as follows Figure 1As shown. The hardware of the system mainly includes: hard X-ray emission device, pan-tilt, detector, preamplifier, imaging and spectrum acquisition system based on PXIE chassis, etc. The host computer software of the automatic calibration device runs in the main controller of the PXIE chassis; the pan-tilt is a dual-axis pan-tilt, the hard X-ray emission device is an X-ray tube, and the hard X-ray emission device uses the dual-axis pan-tilt as a carrier to perform two-degree-of-freedom X-ray position scanning; the detector uses a cadmium zinc telluride two-dimensional array detector, and the acquisition system consists of a multi-channel digital pulse amplitude analyzer. The control of the entire automatic calibration device is completed by the self-developed integrated host computer software.

[0022] The dual-axis gimbal fixes the mini hard X-ray emitting device to the top of the dual-axis gimbal through an aluminum alloy fixed adapter plate. The gimbal can rotate 360 ​​degrees horizontally and can pitch ±60 degrees vertically. The minimum rotation control accuracy is 0.1 degrees. The slowest rotation speed of the gimbal can reach 0.01 degrees per second, and the rotation process can maintain a uniform speed.

[0023] The dual-axis pan-tilt head and cadmium zinc telluride two-dimensional array detector need to be fixed on an optical platform and keep their relative positions fixed. In order to ensure that the X-ray spot emitted by the hard X-ray emitting device falls within a pixel of the detector (1.5mm×1.5mm), it is necessary to add a 0.4mm diameter collimator to the X-ray output window of the hard X-ray emitting device. The collimator is 18mm long and made of pure copper metal material. And keep the front end of the collimator no more than 35mm away from the detector. According to the optical path calculation, it takes 0.9 degrees to rotate from the center of one pixel point to the center of another pixel point, so the pan-tilt head accuracy of 0.1 degrees can meet the experimental requirements. The optical path design is shown in the attached Figure 2 shown.

[0024] The hard X-ray emission device can adjust the energy and intensity of the emitted X-rays by adjusting the acceleration voltage and the excitation current. The adjustment function is integrated into the host computer software of the automatic calibration platform through programming, realizing an integrated automatic measurement system.

[0025] The host computer software of the automatic calibration platform is developed based on the open source software QT. The pan-tilt rotation control function, the two-dimensional hard X-ray imaging function and the energy spectrum analysis function are also integrated into one, and a calibration algorithm is added to realize the automatic calibration of the two-dimensional hard X-ray imaging system. The X-ray spot can be scanned from the first pixel point to the last pixel point in a Z-shaped route. The center position of the pixel point can also be determined by the maximum value of the pixel point collected. When the spot is moved to the center position of the pixel point, the energy or intensity of the X-ray can also be adjusted for linear scanning, so as to calibrate the linearity of the energy measurement and intensity measurement of the pixel point. The steps and results of the automated measurement can be saved in the test configuration file and the test report file respectively. The host computer software interface is shown in the attached figure. Figure 3 shown.

[0026] Through laboratory experiments, the system can automatically scan and test all pixels of the two-dimensional array detector by adjusting the rotation and pitch angle of the pan / tilt, and can control the X-ray tube to automatically adjust the beam energy and intensity, so as to measure and calibrate the linearity of the intensity response of each pixel of the detector, the consistency of the response of different pixels, the crosstalk between adjacent pixels and other parameters. After adding a collimator to the X-ray tube, the spot size of the X-ray irradiating the detector is slightly smaller than the size of a pixel, and the optical path design basically meets the experimental requirements.

[0027] The host computer software controls the X-ray tube to emit X-rays, and its intensity and energy are adjustable. By adjusting the rotation direction of the pan / tilt, the X-rays can be irradiated onto one of the pixels of the detector. When the detector receives the X-ray signal, it will be converted into a current pulse signal, and after the signal is amplified by the preamplifier, the amplified effective signal will be transmitted to the acquisition card for signal acquisition. After the acquisition card performs analog-to-digital conversion of the signal, it is processed by the FPGA algorithm in the acquisition card to obtain the energy and intensity information of the signal pulse. The host computer software processes the measurement results through the calibration algorithm, and can draw the energy and intensity response of the pixel into a test curve. After measuring a pixel, the X-ray spot can be automatically moved to the next pixel, and finally the measurement of the entire detector is completed.

Claims

1. An automatic calibration device for a two-dimensional hard X-ray imaging system based on a pan / tilt system, characterized in that: The automatic calibration device includes a hard X-ray emitting device, a pan / tilt table, an X-ray receiving device, a preamplifier, and an imaging and energy spectrum acquisition system; The gimbal is a dual-axis gimbal, and the hard X-ray emitting device uses the dual-axis gimbal as a carrier to perform X-ray position scanning with two degrees of freedom; the hard X-ray emitting device uses a mini hard X-ray tube to achieve linear scanning with adjustable X-ray emission energy and intensity; the detector of the X-ray receiving device is a cadmium zinc telluride two-dimensional array detector; the imaging and energy spectrum acquisition system is composed of a multi-channel digital pulse amplitude analyzer; The dual-axis pan-tilt head and the CdZnTe two-dimensional array detector are fixed on an optical platform and their relative positions are kept fixed; After receiving the X-ray signal, the detector converts it into a current pulse signal, and amplifies the signal through the preamplifier. The amplified effective signal is transmitted to the imaging and energy spectrum acquisition system for signal acquisition; The dual-axis gimbal is used to fix the mini hard X-ray tube. The dual-axis gimbal can rotate 360 ​​degrees in the horizontal direction and can pitch ±60 degrees in the vertical direction. The steering accuracy can reach 0.1 degrees. The automatic calibration device is configured to realize that the X-ray spot scans from the first pixel point to the last pixel point in a "Z"-shaped route, and determines the center position of the pixel point by collecting the maximum value of the pixel point. When the spot is moved to the center position of the pixel point, a linear scan is performed by adjusting the energy or intensity of the X-ray, thereby calibrating the linearity of the energy measurement and intensity measurement of the pixel point.

2. The automatic calibration device for a two-dimensional hard X-ray imaging system based on a pan / tilt platform according to claim 1, characterized in that: A collimator with a diameter of 0.4 mm is arranged at the X-ray output window of the hard X-ray emitting device. The collimator has a length of 18 mm and is made of pure copper metal material. The distance between the front end of the collimator and the detector is kept no more than 35 mm.

3. The automatic calibration device for a two-dimensional hard X-ray imaging system based on a pan / tilt platform according to claim 1, characterized in that: The hard X-ray emission device can adjust the energy and intensity of the emitted X-rays respectively by adjusting the acceleration voltage and the excitation current.

4. The automatic calibration device for a two-dimensional hard X-ray imaging system based on a pan / tilt platform according to claim 1, characterized in that: The automatic calibration device is configured to control and adjust the X-ray energy and intensity generated by the hard X-ray emitting device and the rotation of the pan / tilt table, and integrates two-dimensional hard X-ray imaging function, energy spectrum analysis function and calibration function, thereby realizing automatic calibration of the two-dimensional hard X-ray imaging system.

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