Optical EngineeringDetermination of view vectors from image warping mapping functions
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The measurands of several reported laser-based measurement techniques are sensitive to both the propagation direction of the laser and the viewing direction from the region of interest to the detector. For such imaging techniques, the view vector must be determined uniquely for each pixel in the detector array. The bulk view vector is often physically measured and a simple model used to determine the view vector for each pixel. This, however, has limitations where access is limited, the distances involved are small, or the optical system employed introduces errors. We describe a procedure to determine the unique view vector from a planar region to the detector (CCD camera) for each element in a 2-D array based on a reference target aligned with the planar region of interest. Determination of the view vector is based on the spatial distribution of the mapping function used to dewarp the view. No physical measurement of the view vector is required. Good agreement is achieved when the procedure is compared to a simple pin-hole camera model of the view using a computed test target.