Optical element surface defect measurement with lensless digital holographic microscopy

In order to measure optical element surface defects accurately, we proposed a fast and nondestructive microscopic observation method based on lensless digital holography technology. The basic principle of lensless digital holographic microscopy imaging technology based on spherical wave is introduced. CCD was adapted as photoelectric converter and almost-perfect spherical reference wave can be acquired by using optical fiber of high numerical aperture. The wave aberration induced by the defects is effectively recorded and then the accurate reconstruction result of the defect structure is obtained. This method will have potential application in the quantitative measurement for the defects on optical surface and is helpful for the further research and understanding the influence of surface defects on high-power laser system.