Based On BOS Technique For The Flow Field Measurements Of Laser Damage Material

In the pulsed laser-induced damage, the internal flow field of the material has many characteristics, such as fast airflow rate, high temperature and strong radiation of the visible and background lights. The changes in the flow field density(that is, refractivity or reflectivity) have great influence on overall optical system. The wavefront of the light while passing through the flow field will be distorted because of the presence of "air flow field". Then the disturbance, steering and defocus of the light beams are affected and the optical energy is weakened in the transmission. It’s hard to image the "air flow field" scalarly, so improving the system properties have great difficult. The “air flow field” contains the information of density, temperature and pressure the laser-induced damage material,therefore the study on the "air flow field" has great significance in determining the laser parameters by testing the air flow field in the laser-induced damage materials.There’re many methods to detect the traditional "air flow field", but they aren’t suitable for testing the air flow field of the laser-induced damage materials. In this paper, through the study of the air flow field of the laser-induced damage materials, by the combination of schlieren technique and particle tracking method, the dual-path background oriented schlieren technique is designed. The temperature distribution of the air flow of the damage materials is deduced by the refractive index changes of the background light in the air flow field. The detection system with high precision which is easy to set up to detect the changes of air flow field in small area requiring no high precision and expensive optical components meets the requirements of testing the air flow field of the laser-induced damage material.