Deformation measurement based on digital holography

Digital holography is widely used as a fast, simple and robust method for the field of non-destruction and non-contact testing, especially in deformation measurement. In this paper, an in-line digital holographic interferometry setup is described, which is based on phase-shifting digital holography. Taking advantage of digital holography, the setup is able to measure the deformation of an object. In addition, two theoretical methods are briefly described: two-exposure technique and phase-shifting digital holography, which can both realize deformation measurement. This paper utilizes the whole information of the object in two different states in the hologram plane which can respectively be reconstructed onto the image plane with two different methods: two-exposure digital holographic interferometry and phase shifting digital holography interferometry, which are derived from the computer reconstruction of single hologram and reconstruction technique combined with phase shifting technique. Then the interference fringe pattern and the phase difference map between the two reconstructed images can both be obtained, which indicate the deformation of the tested object by analyzing some kind of quantitative mapping relationship. In this paper, practical measurement results are presented to verify the metrology. High precision is obtained simultaneously. Several error factors are analyzed and some corresponding suppression methods are described.