Surface-scanning scattering system for defects detection of laser gyro reflector substrate

Based on microscopic imaging, optical systems can effectively detect defects on the surface of laser gyro reflector without causing damage. However, the minimum detection size is limited by the resolution of the microscopic imaging system. To detect submicron-level defects on laser gyro reflector substrate, a surface scanning dual-source scattering measurement scheme based on scattering measurement technology is proposed. Utilizing the Finite Difference Time Domain (FDTD) method and the detection scheme, an electromagnetic scattering model of the laser gyro reflector substrate is established to simulate the characteristics of defects and the distribution of electromagnetic fields. An experimental platform for surface scanning dual-source scattering measurement is established, and polystyrene latex (PSL) spheres with a diameter of 200nm are deposited on the surface of the laser gyro reflector substrate to verify the effectiveness of the proposed method. Scattering imaging experiments in both bright and dark fields are conducted on the USAF 1951 standard resolution plate to obtain the directional characteristics of dark field scattering. Additionally, standard-sized rectangular line patterns, dots, and checkerboard patterns of 1-10μm are fabricated using reactive ion beam etching to create defect samples of photomask patterns, and scattering imaging experiments are conducted on these samples to obtain the detection distribution of bright field patterns. The results indicate that the system can achieve a detection resolution better than 175nm. This method provides a reference for the detection of substrate in inertial guidance systems.