Mach-Zehnder interferometer fringe projector for variable resolution video moire
Kalmanson, Phillip C.
Hart, Chris L.
Blatt, Joel H.
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A Mach-Zehnder based variable resolution fringe projection system has been built for 3-D video moini machine vision. This system uses the three main advantages of the Mach-Zehnder - 1) There is no optical feedback to the laser source, 2) The interfemmeter can accept two different laser wavelengths simultaneously, and 3) The interferometer produces two orthngonal 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 axe 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-Zebnder fringe projector is vely efficient in that 100% of the laser light (minus losses in the beam splitters and mirrors) is projected onto the prime and reference targets. Setup and alignment of this interfemmeter 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 moini based seal time 3-D error map machine vision system will be discussed. Limitations and improvements in the current system will be discussed.