A Mach-Zehnder interferometer fringe projector for variable resolution video moire

A Mach-Zehnder based variable resolution fringe projection system has been built for 3-D video moire machine vision. This system uses the three main advantages of the Mach-Zehnder - 1) Them is no optical feedback to the laser source, 2) The interferometer can accept two different laser wavelengths simultaneonsly, and 3) The interferometer produces two orthogonal output beams. The lack of optical feedback makes the Mach-Zehnder especially attractive for use with high power laser diode sources which are sensitive to optical feedback. When the two input ports are used with two different wavelength lasers, the target can be illuminated by simultaneous projection of two different sets of colored fringes with two different spatial frequencies. This can allow more reliable reconstruction of the 3-D surface over discontinuous jumps. Finally, the lack of feedback to the source coupled with the dual outputs means that the Mach-Zehnder fringe projector is very efficient in that 100% of the laser light (minus losses in tbe beam splitters and mirrors) is projected onto the prime and reference targets. Setup and alignment of this interferometer will be discussed for both parallel and diverging light Plots of fringe visibility will be given for both outputs and both inputs. Application to a video moire based real time 3-D error map machine vision system will be discussed. Limitations and improvements in the current system will be discussed.