Optical EngineeringOptimum analog-to-digital converters for a laser speckle correlation-based displacement and strain sensor with optical preprocessing
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We present a novel noncontact measurement procedure to determine displacements of and engineering strains within specimens at very high measurement rates. Appropriate hybrid optical and digital signal processing can be employed to realize two dimensional (2D) correlation processing. Due to appropriate optical signal processing, the data acquisition can be performed in one dimension through CCD line-scan cameras. As a result, only 1D digital signal processing algorithms have to be executed and hence the processing power requirements decrease greatly. in this way, the measuring rates are substantially increased. it is shown that optimal Lloyd-Max quantizers implemented in the analog-to- digital converter (ADC) used in combination with a particular digital correlation algorithm are able to yield a further increase of the measurement rates compared with standard digital correlation techniques.