Optical EngineeringHigh-speed two-dimensional fringe analysis using frequency demodulation
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A new high-speed 2-D fringe analysis technique in the time domain using an electric circuit based on frequency demodulation is described. A 1-D fringe analysis system based on this new technique has already been built, and its performance and characteristics were reported. With that system, a 1-D fringe pattern could be processed every 10 ms. The accuracy was better than 1/20 fringe. The principle of 1-D fringe analysis is expanded to two dimensions. New electric circuits that can process the horizontal (X) and vertical (Z) directions simultaneously are built. The principles are proposed for the design of such circuits, which combine two outputs, one for the X direction and the other for the Z direction. A new 2-D fringe analysis system is then built using both analog and digital processing circuits. Using this new fringe analysis method, high-speed 2-D image processing can be achieved. The system can process 14 images/s. The characteristics of a laboratory prototype of this fringe analysis system are tested. The error sources of the system are checked with a computer simulation.