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Moire techniques can be a powerful tool to determine surface shape or deviation of a shape in progress from a final or desired shape. The presence of the high contrast viewing grating and the distorted grating of the final image plane makes the moire pattern hard to see. Moving grating techniques have been developed to improve the visibility of the moire pattern, but at the expense of complex moving parts. We have developed several variable resolution projection moire techniques that either move the grating or eliminate its presence electronically, and have neither mechanical moving parts nor any physical gratings. One system uses an acousto-optics cell to generate, project, and move the gratings, while the moire is viewed through a second synchronized A-O cell. The second system uses an interferometer to generate and project variable spacing gratings which are made to move across the target and across a reference surface by an A-O beam deflector. Video processing of the reference image generates the transmissive filter which produces the moire pattern. A third system removes the grating presence electronically but retains high contrast moire contours. Noise reduction is shown in moire images of targets ranging in size from 1 to 700 cm.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
