Optimization of a shape measurement system based on spatial light modulators

Jonathan Mark Huntley; C. R. Coggrave

doi:10.1117/12.360978

9 September 1999 Optimization of a shape measurement system based on spatial light modulators

Jonathan Mark Huntley, C. R. Coggrave

Proceedings Volume 3823, Laser Metrology and Inspection; (1999) https://doi.org/10.1117/12.360978
Event: Industrial Lasers and Inspection (EUROPTO Series), 1999, Munich, Germany

Abstract

A high speed shape measurement system has been developed based on the method of projected fringes. An optimized sequence of fringe pitches is used in which the spatial frequency is reduced exponentially from the maximum value. Temporal unwrapping of the phase values at each fringe pitch provides an independent co-ordinate from each camera pixel. A commercial data projector produces the fringe patterns at a rate of 30 s^-1; the images are analyzed in real time by means of a pipeline image processor. A total acquisition and analysis time of 0.87 s is required for 250,000 coordinates. The main results of an experimental study to optimize the measurement precision of the system (from the original value of one part in 2,000) are also described. Issues that have been investigated include (1) the relative performance of different phase-shifting algorithms (4-frame, 7-frame and 15-frame); (2) the relative performance of different temporal phase unwrapping algorithms; and (3) the effect of projector defocus. At the optimum focal position, a measurement precision of better than one part in 20,000 of the field of view was achieved.

Citation Download Citation

Jonathan Mark Huntley and C. R. Coggrave "Optimization of a shape measurement system based on spatial light modulators", Proc. SPIE 3823, Laser Metrology and Inspection, (9 September 1999); https://doi.org/10.1117/12.360978

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