Characterisation of a standard CCD video camera devoted to the design of an efficient particle image velocimetry instrument

Abstract

A particle image velocimetry (PIV) instrument using a video frame grabbing system and two unsynchronised CCD video arrays was constructed. In the optical device, the two CCD are positioned at two perpendicular axes, with an image splitter located at their intersection and a single imaging lens in front of it. An optical characterisation of each CCD array and the imaging lens is needed to ensure that the field of view is similar for each vision system. Firstly, the experimental method of Cornu was used to deduce the basic optical parameters of the imaging lens. A simple video model was then performed to extract the unknown optical parameters of the device such as the angular field of view, the efficient dimensions of each CCD array and the transfer function from the CCD to the TV screen. An identification method based on global magnification measurements allowed the resolution of the micrometric stages needed for the spatial calibration step of the final instrument, to be deduced. Experimental tests have shown that the aberration in image formation was minimum with this configuration.