Real-time fringe-pattern analysis

This is the authors' abstract. We don't add key points for this paper.

The task is to learn the phases of real positive intensity fringes from an optical testing interferometer. The introduction of substantial tilt into the interferometer establishes a field of finely spaced fringes that serve as a spatial heterodyne carrier. Sequential pixel values from a TV video signal of the picture are distributed among three separate signal channels, every third pixel going to the same channel. The distribution rate is set at ~3 pixels/fringe so that each channel senses one phase of a three-phase stroboscope or moiré. Complex weighting of the channel signals eliminates the common mode to provide in-phase and quadrature analog fringe signals. A direct analog-to-digital arctangent converter, with that analog signal pair as input, provides 4-bit (1/16-cycle resolution) fringe phase at a 5-MHz sampling rate. The converter is coupled to a turns counter that automatically registers unwrapped phase. The similarity of the signals to ntsc color TV encoding is noted along with certain other applications.