Automatic evaluation system for bulk defects in optics

Abstract In the high frequency laser system, the internal defects of optics will affect their damage threshold and downstream modulation, and even lead to subsequent surface damage. In order to efficiently and reliably evaluate the internal defects in optics, an automatic evaluation method of scattering defects in optics is proposed, and the corresponding three-dimensional (3D) precision measurement system is established. The detection principle, image acquisition, image processing and bulk defects (BDs) information extraction methods of the system are studied. Based on a 3D dark-field microscopic imaging (DFMI) technology, samples are scanned with multi-dimensional motion devices. Meanwhile, the scattered beam from the BD was collected by a detector, and finally combined with the digital image processing technology, the acquired images are processed in real time. Through real-time focusing and improved 3D reconstruction algorithm, the images with full aperture BD features are obtained, and the position and size information of defects are extracted. The system has detected the BD inside the fused silica samples. The results show that our system can distinguish the 612.7 lp/mm. Furthermore, the 3D distributions of the BD were also reconstructed.