An online laser-induced flaw inspection device for optical elements

The laser-induced damage experiments are very important to verify the reliability and lifespan of the optical elements. The optical elements are irradiated by the high energy laser frequently and the corresponding damage information is recorded by the researchers. A device was designed and constructed to inspect the surface flaws of the optical elements on line efficiently and automatically. The device was composed of six parts, which were automatic zoom microscopic camera, spectral confocal sensor, two dimensional scan movement axes, focus movement axis, fast reset platform and system controller. The laser irradiated area of the optical elements was scanned by the two dimensional scan movement axes according to the planned path. The work distance of the microscope was detected by the spectral confocal sensor and adjusted by the movement of the focus axis. The sub images were acquired by the microscopic camera and saved to the computer. Firstly, the main error factors that affect the image matching precision were analyzed and compensated by the image correction and so on. Then the image with large area and high resolution was obtained by stitching the corrected sub images. Lastly, the damage information was obtained after image processing. The experimental results show that the time is no more than 5 minutes to detect an area of 15 mm×15 mm. The resolution of the microscope imaging system is better than 228 lp/mm and the stitching error is better than 2 pixel. © 2018, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.