Deformation Measurements Of Object With Digital Holography

The deformation measurement of object is always to be the problem of the field of the engineering. The traditional way of deformation measurement of object is not exact enough, and it is complex. While the method of digital holographic interferometry has many good qualities such as high precision, simple facilities, no damage to the measured object and so on. It has been abroad used in projects, especially in deformation measurement with more advantages.With the development of electronic imaging devices and computer technology, holographic interferometry has also entered a new historical period. The following four aspects are mainly the innovation of this paper: Firstly, charge-coupled device(CCD) takes the place of the traditional recording media, to recode the hologram and the holographic interference fringes; Secondly, electrical addressed liquid crystal (EALCD) is connected with the computer interface, which shoule be accurately reseted in the position where CCD records holograms. Then holograms or holographic interferograms which are obtained at first step are inputed the EALCD. Thirdly, digital image processing technology is applied in the digital holographic interferometry in order to improve the contrast of the hologram or the holographic interference fringes; Fourth, owing to the four interferograms law principles, three-dimensional deformations of objects have been successfully obtained.In the experiment, as the test object of a dime coin, was carried out its Fresnel hologram and image plane hologram recording and reconstructed. Through digital image processing technology on the picture, reconstructions and interference fringes have been obtained. Simultaneously, based on four interferogram method of phase shifting, the three-dimensional deformation pattern has been acquired on the macro. Experimental results indicate that digital holographic interferometry, in which the CCD is combined with EALCD and digital imaging processing technology is used, can make deformation measurement come true. The method is simple, rapid, and feasible.