Optical EngineeringElectronic speckle pattern interferometry with a holographically generated reference wave
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A new method of electronic speckle pattern interferometry (ESPI) is introduced. It is a two-stage process. In the first stage a holographic optical element (HOE) is recorded in a usual holographic arrangement. This HOE illuminated later reconstructs an object wave that serves as an ESPI reference wave. Well suited HOEs are produced on photothermoplastic or silver halide media. In the case of silver halide media, both recording and momental monobath photoprocessing of the HOE are performed in presence of an intense polychromatic illumination to meet industrial requirements. Due to the introduction of HOE the second stage, ESPI implementation can be performed with an extremely simple optical setup. The number of optical elements, apart from the video camera, can be drastically reduced to only two elements: a plane mirror and the HOE. High accuracy alignment of the optical elements is not necessary. Our method also enables HOE recording in the ESPI setup practically without modifications. Both experimental results and the ready device are presented. Our optical setup is compact and needs no sophisticated vibration insulation and no dark room, thus it is ideally suited for industrial applications.