Digital holographic camera with extended stochastic illumination for non-destructive inspection of silicon optics

Abstract

In the present work, we propose a compact digital holographic camera (DHC) with extended stochastic illumination for full-field non-destructive inspection of silicon optics fabricated in a computerized numerical control machine. The developed technique overcomes the limitation of digital holography imparted by the finite size of the active area of the recording sensor that can image a specular surface. The original aspect of this research work is to develop a system that enables reconstruction and testing of a specular surface. For this a dual diffuser configuration is incorporated in a compact DHC developed for non-destructive testing (NDT) applications. The generation of a stochastic illumination beam using the diffusers is explained by simulating the propagation of a light beam through a random phase function of the scattering medium. The stochastic optical field produced by the combination of diffusers in the DHC makes the camera suitable for NDT of the specular surface of silicon optics. The effects of the number of diffusers and their relative positions on the imaging area of the specular object are studied for development of an optimized configuration of DHC. Applicability of the proposed scheme is demonstrated through detection of defects in silicon optics using digital holographic interferometry.