Two-step phase-shifting Fresnel incoherent correlation holography based on discrete wavelet transform*

Abstract

Fresnel incoherent correlation holography (FINCH) has the ability to generate three-dimensional images with a super-resolution by using incoherent sources. However, there are unwanted direct current term and twin image in interferograms, so it is of great significance to find a method to eliminate them. Phase-shifting technology is a most widely used technique for this task, but its three-step phase-shifting is not suitable for the instantaneous measurement of dynamic objects, and the quality of reconstructed image with the traditional two-step phase-shifting is lower. In this paper, we present a method of enhancing the resolution through using a two-step phase-shifting technology based on the discrete wavelet transform. After two-step phase-shifting, the resulting hologram is a superposition of multiple forms. The frequency of the resulting hologram is decomposed into different levels through using discrete wavelet transform, then the image is reconstructed after retrieving the low frequency band. Various experiments have verified the effectiveness of this method.