A denoising method based on CNN for the measurement of far-field focal spot of high power laser using Schlieren method

Gang Li; Zhengzhou Wang; Li Wang; Meng Tan; Wei Wang; Dongchi Yi; Jitong Wei

doi:10.1117/12.2579390

5 November 2020 A denoising method based on CNN for the measurement of far-field focal spot of high power laser using Schlieren method

Gang Li, Zhengzhou Wang, Li Wang, Meng Tan, Wei Wang, Dongchi Yi, Jitong Wei

Author Affiliations +

Proceedings Volume 11567, AOPC 2020: Optical Sensing and Imaging Technology; 115671I (2020) https://doi.org/10.1117/12.2579390
Event: Applied Optics and Photonics China (AOPC 2020), 2020, Beijing, China

Abstract

Schlieren method is an effective method to measure the high dynamic range far-field focal spot of high power laser at present, it has been used in the comprehensive diagnosis system of the host facility of the national large scientific device. However, the background subtraction algorithm is used for denosing process of the main lobe and side lobe images in the experiment, which could not effectively remove the noise under the condition of strong radiation. In order to improve the reconstruction accuracy and reliability of far-field focal spot measurement based on schlieren method, there are two aspects have been proposed and optimized in this paper as follows, the mathematical model for the measurement of high dynamic range far-field focal spot is constructed, the noise of images captured by detected CCD is removed effectively. Firstly, the mathematical model of laser focal spot measurement is constructed, which provided a theoretical basis for the measurement of far-field focal spot based on schlieren method. Secondly, the denoising algorithm based on Convolutional Neural Network (DnCNN) is introduced into the denoising of main lobe and side lobe CCD image, which can effectively remove the noise of different levels (0-75db) of main lobe and side lobe CCD image.The experimental results show that the noise signal of main lobe and side lobe images are removed by using DnCNN algorithm, and the best reconstructed image of far-field focal spot of high power laser is obtained when the influencers of amplified noise of main lobe image is reduced greatly. After the above optimization and improvement, it will meet the requirements for accuracy and efficiency of the measurement of high dynamic range far-field focal spot.

Citation Download Citation

Gang Li, Zhengzhou Wang, Li Wang, Meng Tan, Wei Wang, Dongchi Yi, and Jitong Wei "A denoising method based on CNN for the measurement of far-field focal spot of high power laser using Schlieren method", Proc. SPIE 11567, AOPC 2020: Optical Sensing and Imaging Technology, 115671I (5 November 2020); https://doi.org/10.1117/12.2579390

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KEYWORDS

Denoising

Charge-coupled devices

Beam splitters

Interference (communication)

Signal attenuation

Convolution

Image processing

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