Profilometry using a diffractive element

Holographic, speckle, moirč interferometric techniques and ESPI have been proposed for surface profilometry

We introduced a new 3-D sensor based on a diffractive optical element (DOE). Structured light is obtained by the interference of two beams diffracted by a saw-tooth phase grating. Good quality projection fringes are obtained, as the two beams have approximately the same intensity.

A quantitative evaluation of the contour is performed by a Fourier transform method and a phase unwrapping based on least squares formulation

Figure 1

Figure 2
Figure 2 shows the three-dimensional plot of a terra-cotta lamp. The device has the potential of the traditional fringe projection technique with the distinct advantage of offering the freedom to choose and control the fringe period on the object in an easy way.

"Diffractive optical element-based  profilometer for surface inspection"
Optical Engineering 40, 44-52 (2001)