Research On On-line Detection System For Laser-induced Damage Of Optical Elements

Laser damage of optical components is one of the key factors limiting the laser energy output of high-power lasers.For the construction of high-power lasers,the on-line detection of laser-induced damage to optical elements is extremely important.At present,the surface damage of components is mainly measured by visual methods,which has low accuracy,strong subjectivity,and cannot quantitatively evaluate the damage.This paper focuses on the design of an optical element surface damage online detection system under pulsed laser irradiation and an online detection method based on dark field imaging.The main research contents are as follows.A micro-imaging system based on dark-field micro-scattering imaging was developed for real-time damage detection.A continuous laser is used as the detection beam to illuminate the pulsed laser-irradiated area.The microscopic imaging system collects images and combines them with image processing algorithms to obtain damage distribution images and statistical information.Through the supporting software,the automatic online detection of the laser damage of the component under test is fully realized,and a specific damage analysis report is finally output.Aiming at the characteristics of the damage images collected by the microscopic imaging system,the automatic identification and detection technology of the damage area was studied.According to the characteristics of obvious peaks in the differential image histogram before and after the damage,a damage discrimination algorithm based on the gray distribution characteristics is proposed.This algorithm only relies on the gray distribution statistics of the differential images of the images before and after pulsed laser irradiation,which reduces image processing.Difficulty can quickly and effectively detect whether damage has occurred.By freely adjusting the interval of gray-scale sampling,while ensuring the accuracy of discrimination,the image processing time is greatly reduced,thereby improving the efficiency of the algorithm.In order to realize the extraction of damaged areas,an image-based damage extraction algorithm is proposed.The algorithm uses median filtering to remove background noise,and uses Otsu threshold segmentation to perform binary processing.The connected domain of the latter image is first analyzed to create a labeled map,and then the connected domain of the latter image is traversed to calculate the two images.The similarity of the connected areas of the image,the similarity threshold is set to generate the damage result image.This algorithm can accurately and efficiently mark the damage area and calculate the damage information,and it can solve the interference problem of background noise in the image.A damage test platform was set up to verify the system detection resolution and algorithm performance.The damage threshold of the fused silica surface under the R-ON-1 detection process was tested.