Two simple Electronic Speckle Pattern Interferometer (ESPI) configurations have been devised based on diffused reference beam which provides out-of-plane displacement data over the whole field. Both configurations use a tiny diffuser to generate the reference beam. This makes the system insensitive to reference beam misalignment, simplifies the construction of ESPI setup and allows larger area of observation unlike the conventional ESPI system. Thermal deflection studies on a cantilever plate have been carried out. Experimental results and features over the conventional ESPI system are discussed.
This paper describes a noncontact and computer compatible test setup to calibrate the angular motion of a life test model of a scanning mirror mechanism using a lateral-effect position sensitive photodetector (LPSD). Laser based measurements of its movements using the LPSD adds up the suitability of this mechanism to very high resolution radiometer effectively. The description of the scan mirror mechanism and the existing calibration test methods are briefed. The characteristic properties of the LPSD are discussed. Experimental details and the results obtained are presented.
Lateral-effect position sensitive photodetectors (PSDs) have received a great deal of attention as an alternative to scanning and array techniques for deriving spatially dependent information from incident radiation, since they have the advantages of instantaneous and fast measurements, greater position resolution, simplicity in circuitry and inexpensive. Basic physics, operation and demanding applications are reviewed. In this paper different experimental techniques which are established to evaluate transfer characteristics, repeatability, sensitivity of a single axis detector UDT SL-76 are presented. The percentage of nonlinearity and the Root Mean Square error have been calculated. An analog processing circuitry for position measurement is designed and presented. The cause of bias variation to the detector, laser beam intensity fluctuation and laser drift during warm-up in position measurements and the minimum intensity required to produce stable position information have also been presented.