CN112684250A - Calibration method for high-power millimeter wave intensity measurement system - Google Patents
Calibration method for high-power millimeter wave intensity measurement system Download PDFInfo
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Abstract
The invention discloses a calibration method of a high-power millimeter wave intensity measurement system, and belongs to the technical field of millimeter waves. The method comprises the following steps: establishing a three-dimensional rectangular coordinate system by respectively taking the high-power millimeter wave output port and the geometric center of the target plate as references; at least 3 markers are respectively arranged on the plane where the high-power millimeter wave output port and the target plate are located; imaging each marker; based on the marker imaging coordinate and the corresponding three-dimensional coordinate, the imaging parameters transformed from the high-power millimeter wave output port and the target plate to the camera are obtained through coordinate transformation calculation, and then the rotation translation relation of the high-power millimeter wave output port transformed to the target plate is obtained; and adjusting the measuring system according to the rotating and translating relation converted from the high-power millimeter wave output port to the target plate to finish system calibration. The method has the advantages of low development difficulty, high reliability and strong universality, and can realize parameter calibration of a high-power millimeter wave intensity measurement system and improve the measurement accuracy.
Description
Technical Field
The invention belongs to the technical field of millimeter waves, and particularly relates to a calibration method of a high-power millimeter wave intensity measurement system.
Background
In the field of magnetic confinement controlled nuclear fusion research, the heating mode of plasma is various, wherein, the high-power millimeter wave is a heating mode widely used by fusion devices due to the advantages of good heating effect, good heating locality and the like. Generally, in the high-power millimeter wave in the heating system, besides the main mode signal, there are some proportion of mixed mode signals, and these mixed mode signals are usually deposited in the system in a thermal manner, and may affect the normal operation of the system in a serious case, even damage the system, so it is very important to analyze the mode purity information of the high-power millimeter wave and further reduce the proportion of the mixed mode signals.
In the mode purity analysis of the high-power millimeter wave output by the high-power millimeter wave source gyrotron, the most common mode is a mode analysis method based on phase reconstruction, the method needs to measure the intensity distribution information of the high-power millimeter wave output by the gyrotron and then analyze the intensity distribution information, and whether the intensity distribution information of the high-power millimeter wave output by the gyrotron can be accurately measured directly determines the accuracy of the mode analysis, so that the performance judgment of the gyrotron is influenced, and the unreasonable use is caused. In addition, in order to further reduce the mixed mode signal in the system and improve the mode purity of the main mode, an optical matching unit is usually added in the high-power millimeter wave transmission system; generally, the optical matching unit is designed based on the intensity distribution of high-power millimeter waves in a gyrotron or a transmission line, and the reliability of the performance of the optical matching unit is determined by accurate measurement of the intensity distribution of the high-power millimeter waves; the unreasonable designed optical matching unit can not only reduce the proportion of the mixed modes and improve the mode purity of the main mode, but also can cause ignition and damage the gyrotron in serious cases. Therefore, the important significance of accurate measurement of the intensity distribution of the high-power millimeter waves is achieved.
At present, a commonly used high-power millimeter wave intensity measurement system generally comprises a high-power millimeter wave output port, a target plate and an infrared camera, and whether the intensity distribution information of the high-power millimeter wave can be accurately measured is closely related to the positioning among the high-power millimeter wave output port, the target plate and the infrared camera. Generally, in the aspect of parameter adjustment of a high-power millimeter wave intensity measurement system, a laser level meter, a graduated scale or a means of visual observation is usually only used for carrying out spatial positioning on a high-power millimeter wave output port, a target plate and an infrared camera, and the accuracy of positioning parameters cannot be ensured, so that the high-power millimeter wave intensity measurement is inaccurate, the subsequent data processing result is unreliable, and a series of irreversible serious results are caused.
Disclosure of Invention
Aiming at the defects or the improvement requirements in the prior art, the invention provides a calibration method of a high-power millimeter wave intensity measurement system, and aims to solve the technical problem that the intensity distribution of high-power millimeter waves is inaccurate due to the fact that the relation among a high-power millimeter wave output port, a target plate and an infrared camera cannot be accurately positioned.
In order to achieve the above object, the present invention provides a calibration method for a high-power millimeter wave intensity measurement system, comprising:
s1, establishing a three-dimensional rectangular coordinate system by respectively taking a high-power millimeter wave output port and the geometric center of a target plate as references; the high-power millimeter wave output port and the plane where the target plate is located are respectively located in one two-dimensional plane in the corresponding three-dimensional rectangular coordinate system;
s2, at least 3 markers are respectively arranged in the plane where the high-power millimeter wave output port and the target plate are located, and three-dimensional coordinates corresponding to the markers are obtained;
s3, imaging the markers in the high-power millimeter wave output port and the target plate respectively to obtain imaging coordinate values of the markers in a camera imaging coordinate system;
s4, obtaining imaging parameters converted from the high-power millimeter wave output port and the target plate to the camera by adopting coordinate conversion calculation; the imaging parameters comprise a position (a) which is converted from a three-dimensional rectangular coordinate system of a high-power millimeter wave output port to an imaging coordinate system in a camera, needs a rotation angle alpha around an x axis, a rotation angle beta around a y axis and a rotation angle gamma around a z axis and translates according to each coordinate axis0,b0,c0) (ii) a And a position (p) which is converted from the three-dimensional rectangular coordinate system of the target plate to the imaging coordinate system in the camera, needs a rotation angle rho around the x-axis, a rotation angle sigma around the y-axis, a rotation angle omega around the z-axis, and is translated according to each coordinate axis0,q0,v0)；
S5, obtaining a rotation and translation relation of the high-power millimeter wave output port transformed to the target plate according to imaging parameters transformed to the camera from the high-power millimeter wave output port and the target plate;
and S6, adjusting the measurement system according to the rotation and translation relation converted to the target plate by the high-power millimeter wave output port to finish system calibration.
Further, the camera adopts an infrared camera.
Further, the infrared camera meets the requirements of temperature resolution, lens visual angle range and pixel size required in a high-power millimeter wave intensity measurement experiment.
Further, the label has a different radiance than the target plate.
Further, the difference in radiance of the target plate and the label is greater than 0.8.
Further, the marker is arranged in a cross shape.
Further, the size of the marker is matched to the parameters of the measurement system.
In general, the above technical solutions contemplated by the present invention can achieve the following advantageous effects compared to the prior art.
(1) The calibration method of the high-power millimeter wave intensity measurement system directly adds the marker made of the low-emissivity material on the basis of the original high-power intensity measurement system, the specific coordinates before and after the marker is imaged can be accurately measured, and the relative position relation between the high-power millimeter wave output port and the target plate can be accurately calculated by utilizing coordinate transformation.
(2) The calibration method of the invention is directly carried out by using the camera and the measured object provided with the marker, and the parameters of the measurement system are reversely calculated by adopting a coordinate system transformation method according to the camera imaging result of the marker under the real system parameters, and then the system state is adjusted, so that the calibration method can be flexibly applied to similar measurement systems using common cameras and infrared cameras, and has strong universality.
Drawings
FIG. 1 is a schematic diagram of a calibration method of a high-power millimeter wave intensity measurement system provided by the present invention;
fig. 2(a) is a schematic diagram of a tag arranged on a plane where a high-power millimeter wave output port provided by the invention is located;
FIG. 2(b) is a schematic view of a tag disposed on a plane of a target plate provided by the present invention;
FIG. 3 is a schematic diagram of the system for measuring the intensity of the high-power millimeter wave after the system state is adjusted according to the calculation parameters;
wherein, 1 is high power millimeter wave delivery outlet, 2 is the target plate, 3 is the marker, and 4 is infrared camera.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a calibration method of a high-power millimeter wave intensity measurement system, as shown in figure 1, the high-power millimeter wave intensity measurement system to be calibrated comprises the following steps: the high-power millimeter wave output port 1, the target plate 2 and the infrared camera 4; the frequency of the high-power millimeter wave is 30GHz-200GHz, and the power of the high-power millimeter wave is 200kW-1 MW; the infrared camera meets the temperature resolution, the lens visual angle range and the pixel size required in the high-power millimeter wave intensity measurement experiment;
two three-dimensional rectangular coordinate systems x are respectively established by taking the geometric centers of the high-power millimeter wave output port 1 and the target plate 2 as references1-y1-z1And x2-y2-z2Wherein, the plane of the high-power millimeter wave output port 1 and the plane of the target plate 2 respectively correspond to one two-dimensional plane rectangular coordinate system x in the two three-dimensional rectangular coordinate systems1-y1And x2-y2(ii) a As shown in fig. 2(a) and 2(b), markers 3 are provided in both of the two-dimensional rectangular plane coordinate systems, and these markers are provided3 has a fixed coordinate position; the positioning of the marker in a two-dimensional rectangular coordinate system is accurately realized, and the marker is designed into a cross shape;
further, assuming that the three-dimensional rectangular coordinate system of the high-power millimeter wave output port 1 is converted into the imaging coordinate system of the infrared camera 4, the rotation angle α around the x-axis, the rotation angle β around the y-axis, and the rotation angle γ around the z-axis are required, and then the translation is performed according to each coordinate axis (a)0,b0,c0) The three-dimensional rectangular coordinate system of the target plate 2 is converted into an imaging coordinate system in the infrared camera 4, the rotation angle rho around the x axis, the rotation angle sigma around the y axis and the rotation angle omega around the z axis are required, and then the translation is carried out according to each coordinate axis (p)0,q0,v0). 6 unknown parameters are involved in the imaging process of the high-power millimeter wave output port 1 or the target plate 2, and a two-dimensional coordinate plane is considered after the infrared camera 4 is imaged, so that only two equation equations can be established for each marker in the three-dimensional coordinate system before and after imaging, and if 6 unknown parameters are obtained, at least 3 markers are needed for each imaging.
Further, in order to obtain the above parameters of the high-power millimeter wave intensity measurement system and check the reliability of the obtained parameters, as shown in fig. 1, four markers are respectively set in a two-dimensional plane rectangular coordinate system where the high-power millimeter wave output port 1 and the target plate 2 are located; the three-dimensional coordinates corresponding to each marker in the high-power millimeter wave output port 1 are respectively A (a)1,b1,c1)、B(a2,b2,c2)、C(a3,b3,c3)、D(a4,b4,c4) The three-dimensional coordinates corresponding to each marker in the target plate 2 are respectively E (p)1,q1,v1)、F(p2,q2,v2)、G(p3,q3,v3)、H(p4,q4,v4). Respectively imaging the markers in the high-power millimeter wave output port 1 and the target plate 2 by using an infrared camera 4 to obtain imaging coordinate values of the markers, wherein the imaging coordinate value of the marker of the high-power millimeter wave output port 1 is set as A' (a)1′,b1′)、B′(a2′,b2′)、C′(a3′,b3′)、D′(a4′,b4') and the imaging coordinates of the marker of the target plate 2 are E' (p)1′,q1′)、F′(p2′,q2′)、G′(p3′,q3′)、H′(p4′,q4'). Further, let the coordinates before the transformation of the marker into the infrared camera 4 be (X, Y, Z), the focal length of the infrared camera be f.
Then, an equation for solving the system parameters can be established by the marker 3 set in the two-dimensional plane rectangular coordinate system where the high-power millimeter wave output port 1 and the target plate 2 are located, and the imaging result of the marker 3 in the infrared camera 4. Taking the marker a of the high-power millimeter wave output port 1 as an example, a coordinate transformation relation is established:
further, two equations are established for the 6 system parameter unknowns:
furthermore, taking any 3 markers in the markers set in the high-power millimeter wave output port 1 and the target plate 2, and establishing an equation system by adopting the above example, all imaging parameters, namely, alpha, beta, gamma, a, converted from the high-power millimeter wave output port 1 and the target plate 2 to the infrared camera 4 can be calculated and obtained0、b0、c0、ρ、σ、ω、p0、q0、v0All become known quantities. In particular, the remaining marker combinations may also be used to verify the reliability of the calculation.
Further, in order to obtain the relationship between the high-power millimeter wave output port 1 and the target plate 2, the infrared camera 4 is used as a reference, and according to the obtained rotation relationship of the coordinate system when transforming to the infrared camera 4, it can be known that the rotation relationship of the high-power millimeter wave output port 1 to the target plate 2 is: the rotation angle eta around the x axis is alpha-rho, the rotation angle xi around the y axis is beta-sigma, and the rotation angle phi around the z axis is gamma-omega; further, let a coordinate before the infrared camera 4 images:
then, based on the imaging coordinate transformation relation similar to the marker a, the coordinate values of the coordinates in the coordinate systems of the high-power millimeter wave output port 1 and the target plate 2, that is, the coordinate values of the same point in the two coordinate systems can be calculated, assuming that (x) is respectively assumed to be1,y1,z1) And (x)2,y2,z2) (ii) a At this time, according to the coordinate transformation relation from the high-power millimeter wave output port 1 to the target plate 2:
the translation (x) of each coordinate axis between the two can be directly calculated0,y0,z0)。
Further, the measurement system can be adjusted according to the above calculation result of the relationship between the high-power millimeter wave output port 1 and the target plate 2 (the horizontal distance, the vertical distance and the inclination angle of the target plate and the infrared camera can be adjusted), and finally, the coordinate axes of the two three-dimensional rectangular coordinate systems of the high-power millimeter wave output port 1 and the target plate 2 are parallel to each other, and the geometric centers are on the same horizontal axis, as shown in fig. 3, at this time, the system parameters include: distance L between high-power millimeter wave output port 1 and target plate 21Distance L between infrared camera 4 and target plate 22The infrared camera is off axis by an angle θ. Therefore, the accuracy and reliability of the high-power millimeter wave intensity measurement result can be realized after the system is calibrated by adopting the method.
The target plate is a high-emissivity material with certain hardness, uniform structure, clean and flat surface and no light surface, such as a polyvinyl chloride (PVC) plate. The marker is a low-emissivity material with certain elastic force, uniform material and clean and flat surface, such as tin foil paper, and the size of the marker is matched with the parameters of a measuring system and measuring equipment. When the infrared camera is adopted, the radiance of the adopted marker is different from that of the target plate, and further preferably, the radiance difference between the target plate and the marker is larger than 0.8, so that the coordinates of the high-power millimeter wave output port and the marker on the target plate after imaging through the infrared camera can be clearly and accurately positioned. Besides the infrared camera, the calibration method of the invention can also adopt a common camera, and when the common camera is adopted, a color resolution marker can be adopted.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. A calibration method for a high-power millimeter wave intensity measurement system is characterized by comprising the following steps:
s1, establishing a three-dimensional rectangular coordinate system by respectively taking a high-power millimeter wave output port and the geometric center of a target plate as references; the high-power millimeter wave output port and the plane where the target plate is located are respectively located in one two-dimensional plane in the corresponding three-dimensional rectangular coordinate system;
s2, at least 3 markers are respectively arranged in the plane where the high-power millimeter wave output port and the target plate are located, and three-dimensional coordinates corresponding to the markers are obtained;
s3, imaging the markers in the high-power millimeter wave output port and the target plate respectively to obtain imaging coordinate values of the markers in a camera imaging coordinate system;
s4, obtaining imaging parameters converted from the high-power millimeter wave output port and the target plate to the camera by adopting coordinate conversion calculation; the imaging parameters comprise a position (a) which is converted from a three-dimensional rectangular coordinate system of a high-power millimeter wave output port to an imaging coordinate system in a camera, needs a rotation angle alpha around an x axis, a rotation angle beta around a y axis and a rotation angle gamma around a z axis and translates according to each coordinate axis0,b0,c0) (ii) a And a position (p) which is converted from the three-dimensional rectangular coordinate system of the target plate to the imaging coordinate system in the camera, needs a rotation angle rho around the x-axis, a rotation angle sigma around the y-axis, a rotation angle omega around the z-axis, and is translated according to each coordinate axis0,q0,v0)；
S5, obtaining a rotation and translation relation of the high-power millimeter wave output port transformed to the target plate according to imaging parameters transformed to the camera from the high-power millimeter wave output port and the target plate;
and S6, adjusting the measurement system according to the rotation and translation relation converted to the target plate by the high-power millimeter wave output port to finish system calibration.
2. The method for calibrating a high-power millimeter wave intensity measurement system according to claim 1, wherein the camera is an infrared camera.
3. The method for calibrating a high-power millimeter wave intensity measurement system according to claim 2, wherein the infrared camera satisfies temperature resolution, lens view angle range and pixel size required in a high-power millimeter wave intensity measurement experiment.
4. The method for calibrating a high-power millimeter wave intensity measurement system according to claim 3, wherein the radiance of the marker is different from that of the target plate.
5. The method for calibrating a high-power millimeter wave intensity measurement system according to claim 4, wherein the radiance difference between the target board and the marker is greater than 0.8.
6. The method for calibrating the high-power millimeter wave intensity measurement system according to any one of claims 1 to 5, wherein the marker is set in a cross shape.
7. The method for calibrating a high-power millimeter wave intensity measurement system according to claim 6, wherein the size of the marker is matched with the parameters of the measurement system.
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