Design of a USB camera system with onboard image processing capabilities
Strain measurement by laser-optical evaluation of laser speckle patterns on the test objects surface is a main research objective of the Institute for Measurement Technology of the Johannes Kepler University, Linz. Assuming that any movement of the speckle pattern occurs along its sensitive axis, recent projects used one or two line scan cameras to measure mechanical or thermal strain and the superposed rigid-body-motion in an uniaxial setup (see Figure 1). This assumption may be proven invalid if the setup or the sample shows asymmetries. A new approach is to use 2D image sensors to measure or at least detect the movement of the speckles in the second dimension. This diploma thesis is focused on the development of the camera shown in Figure 2. It features a versatile interface to accommodate the system on the needs of the measurement task. Furthermore the camera is able to execute simple image processing algorithms besides basic data acquisition tasks. The final goal is to use two cameras of this kind to capture a `stereoscopic' view of the speckle field, to be able to render the system insensitive to out-of-plane deformation. After a short introduction on laser speckles, the camera systems hard- and software and the application programming interfaces (APIs) of both the cameras firmware and the Windows application are depicted. Some sample images are shown and finally a small user guide demonstrates the use of this system as a stand-alone application (see Fig. 3) and in conjunction with Mathworks' Matlab.
August 11, 2009