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CN-121977435-A - Beam spot cross-section size measuring method and system based on polychrome interferometer

CN121977435ACN 121977435 ACN121977435 ACN 121977435ACN-121977435-A

Abstract

The invention discloses a beam spot section size measurement method based on a polychrome interferometer, which comprises the following steps of S1, collecting interference images under a plurality of wavelengths by using a Bayer filter array of a color camera, S2, extracting the interference images to obtain interference images of R, G, B channels, S3, respectively carrying out fitting calculation on the interference images of each channel to obtain experimental measurement visibility corresponding to each channel, S4, carrying out weighted average on the visibility of all wavelengths of each channel through a spectrum weighted integral model to obtain the value of theoretical visibility of each channel, S5, regarding the visibility data of the three channels as the combined constraint on the same beam cluster, and finding out the transverse section size of the beam spot which can simultaneously lead the sum of the theoretical visibility of the three channels and the experimental measurement visibility difference to be minimum by constructing an objective function The value is the transverse cross-sectional dimension of the beam spot which is finally required to be obtained. The invention realizes simultaneous measurement of multiple spectrums, thereby improving the measurement speed.

Inventors

  • LENG YONGBIN
  • CHEN LIYING
  • GAO XINRU

Assignees

  • 中国科学技术大学

Dates

Publication Date
20260505
Application Date
20260210

Claims (10)

  1. 1. A beam spot cross-sectional dimension measuring method based on a polychrome interferometer, which is characterized by comprising the following steps: s1, synchronously acquiring interference images at a plurality of wavelengths in a single exposure by using a Bayer filter array of a color camera; S2, extracting the acquired interference image, and carrying out channel separation and recombination on the original image according to an RGGB mode of a camera to obtain interference images of R, G, B channels; S3, fitting calculation is carried out on the interference images of all the channels respectively to obtain experimental measurement visibility corresponding to all the channels; S4, assuming that under different beam spot transverse section sizes, carrying out weighted average on the visibility of all wavelengths of each channel through a spectrum weighted integration model to obtain the theoretical visibility value of each channel; S5, regarding the visibility data of the three channels as the joint constraint on the same beam cluster, and finding out the beam spot transverse cross section size which can simultaneously enable the sum of the theoretical visibility and the experimental measurement visibility difference of the three channels to be minimum by constructing an objective function The value is the transverse cross-sectional dimension of the beam spot which is finally required to be obtained.
  2. 2. The method of claim 1, wherein the even-numbered row and even-numbered column pixels are extracted in step S2 to form a red R-channel sub-image Extracting even lines, odd columns and even columns of pixels, averaging to form green G channel sub-image Extracting odd-numbered row and odd-numbered column pixels to form a blue B channel sub-image 。
  3. 3. The method for measuring the cross-sectional size of a beam spot based on a polychrome interferometer as recited in claim 2, wherein in step S3: For each channel Light intensity distribution of interference fringes thereof Can be expressed as cosine oscillations under the gaussian envelope: ; Wherein, the Is a channel In coordinates of A light intensity value at; Measuring visibility for the channel experiment to be solved; peak intensity amplitude of the Gaussian light spot of the interference fringe; Is the background light intensity; The position coordinates of the center of the light spot; the width parameter of the Gaussian light spot; Spatial frequency of interference fringes; for initial phase, the experimental measurement visibility of the three channels is extracted by fitting the above formula 。
  4. 4. A method of beam spot cross-sectional dimension measurement based on polychrome interferometry according to claim 3, wherein in step S4: For any channel Assume that the beam spot size is Theoretical visibility of it Defined as the weighted average of all monochromatic visibility over the spectral response range of the channel: ; Wherein, the Is a channel Is a function of the total spectral response of (2); at a wavelength of The beam spot size is And obtaining the theoretical visibility value of each channel by using the monochromatic light theoretical visibility.
  5. 5. A method for beam spot cross-sectional dimension measurement based on polychrome interferometer as recited in claim 4, characterized in that in step S5: Regarding the visibility data of R, G, B three channels as the joint constraint on the same cluster, constructing an objective function : ; To be used for Minimum corresponding beam spot size The transverse cross-sectional size of the beam spot is finally required to be obtained.
  6. 6. A beam spot cross-sectional dimension measuring system based on a polychromatic interferometer, characterized in that the beam spot cross-sectional dimension measuring method based on a polychromatic interferometer according to any one of claims 1-5 is applied, the system comprising: A color camera (8) provided with a Bayer filter array for synchronously collecting interference images of different wavelengths; a synchrotron radiation light source (1) for generating a light beam, the cross section of which is a beam spot having a transverse width and a longitudinal width; a beam splitter (2) for directing light beams having similar intensity and phase characteristics along an optical path; A diaphragm (3) for adjusting the size and shape of the light beam so that only the light of the central portion passes, eliminating stray light and noise; a polarizing plate (4) for screening the polarization state of the light beam, and allowing only polarized light in a specific direction to pass therethrough; A double slit (5) for generating interference fringes; A lens group for focusing the interference image to a color camera detection surface; The data processing unit is used for processing the acquired interference image by applying the beam spot cross section size measuring method based on the polychrome interferometer and calculating the transverse cross section size of the beam spot; The beam splitter (2), the diaphragm (3), the polaroid (4), the double slits (5), the lens group and the color camera are sequentially arranged along the propagation direction of the emergent beam of the synchronous radiation light source, so that the synchronous radiation light beam forms an interference pattern through the double slits (5) and then is imaged to the detection surface of the color camera (8), and the color camera (8) is electrically connected with the data processing unit to output an interference image for the data processing unit to calculate the transverse cross section size of the beam spot.
  7. 7. A beam spot cross-sectional dimension measuring system based on polychrome interferometer as claimed in claim 6, wherein the synchrotron radiation light source (1) is an extended light source with a certain width and is an incoherent light source.
  8. 8. A beam spot cross-sectional dimension measuring system based on polychrome interferometer according to claim 6, wherein the polarizer (4) is a linear polarizer.
  9. 9. The system of claim 6, wherein the double slit (5) comprises a pair of rectangular slit holes formed in an opaque light-shielding substrate.
  10. 10. The system of claim 6, wherein the lens group comprises a first convex lens (1) and a second convex lens (7), the first convex lens (1) is closely attached to the double slit, and the second convex lens (7) is located between the first convex lens (1) and the color camera (8) so that the interference pattern is focused on an imaging surface of the color camera (8).

Description

Beam spot cross-section size measuring method and system based on polychrome interferometer Technical Field The invention relates to the technical field of optical measurement methods based on polychrome interferometers, in particular to a beam spot cross-section size measurement method and system based on polychrome interferometers. Background The transverse beam size is one of the basic beam parameters of particle accelerators and transport lines, and the measurement speed and accuracy of the beam parameters affect the beam quality and the accelerator operation performance. Currently common methods for measuring the transverse dimension of the beam are methods based on optical methods, scanning wires and beam position detectors. The optical method can be divided into an interception type and a non-interception type, and the non-interception type measuring method does not influence the operation of the machine, so that the method is widely applied to various large light sources. Such a measurement method based on the synchronization light specifically includes a synchronization light imaging method, a synchronization light projection method, and a synchronization light interferometry method. Among them, the synchronous optical interferometry is widely used because of its high resolution and relatively simple system construction. The most representative synchronous optical interferometer is currently a dual-slit interferometer. The structure of the double slit interferometer comprises a front end device for leading out light beams from a light source, a band-pass filter, a linear polaroid, double slits, a focusing lens group and a charge coupled device. The measurement principle is that after the synchronous radiation light passes through the double slits, the synchronous radiation light is focused on the CCD through a lens to form an interference image, and the visibility of the analyzed stripes is obtained by VAN CITTERT-Zernike theorem to obtain the value of the beam spot size. At present, the research of the transverse section size of the beam cluster has a plurality of technical bottlenecks in measurement precision and speed, and the high-speed and high-precision diagnosis requirement is difficult to meet. The existing method acquires corresponding interference images by replacing filters with different wavelengths, and cannot acquire interference images with multiple wavelengths at the same time in a single exposure, which limits the improvement of measurement speed. The input stage part needs to perform wavelength filtering or spatial filtering, which can cause low utilization efficiency of original synchronous light, reduce signal-to-noise ratio of input signals, and further limit improvement of measurement accuracy. If the method of using the beam-splitting prism is used, beam splitting refocusing is needed, and the light path design and collimation are complex. Disclosure of Invention The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, the invention aims to provide a beam spot section size measuring method and system based on a polychrome interferometer, which can realize simultaneous measurement of multiple spectrums and further improve the measuring speed, remove optical filters in a light path, improve the utilization efficiency of synchronous light and further improve the measuring precision. In a first aspect, the invention provides a beam spot cross-section dimension measurement method based on a polychrome interferometer, which comprises the following steps: s1, synchronously acquiring interference images at a plurality of wavelengths in a single exposure by using a Bayer filter array of a color camera; S2, extracting the acquired interference image, and carrying out channel separation and recombination on the original image according to an RGGB mode of a camera to obtain interference images of R, G, B channels; S3, fitting calculation is carried out on the interference images of all the channels respectively to obtain experimental measurement visibility corresponding to all the channels; S4, assuming that under different beam spot transverse section sizes, carrying out weighted average on the visibility of all wavelengths of each channel through a spectrum weighted integration model to obtain the theoretical visibility value of each channel; S5, regarding the visibility data of the three channels as the joint constraint on the same beam cluster, and finding out the beam spot transverse cross section size which can simultaneously enable the sum of the theoretical visibility and the experimental measurement visibility difference of the three channels to be minimum by constructing an objective function The value is the transverse cross-sectional dimension of the beam spot which is finally required to be obtained. Preferably, in step S2, even rows and even columns of pixels are extracted to form a red R channel sub-imageExtra