Multi-wavelength digital holographic metrology

摘要

A digital holographic metrology technique is described for measuring the three-dimensional shape of manufactured parts. The technique uses optical fibers to set up a near equal path interferometer, steps through multiple frequencies with a tunable laser, steps through multiple phases using a fiber based phase shifter, uses an off-axis parabolic mirror to collimate the light, and generates a digital hologram that leads to surface flatness measurements accuracies better than 1 micron over large surfaces. An example result for an automobile engine part is given using a Coherix Inc., ShapixTM 2000 instrument.