Application of a ferroelectric liquid-crystal-on-silicon display in fringe projection setups

When conducting three-dimensional measurements with fringe projection, the quality of the grating applied for the generation of the fringes is very important. It has a direct influence on the achievable height resolution when phase-shifting algorithms are used. Hence, the created fringes should have an ideal sinusoidal intensity profile. In the past, Ronchi gratings, placed in a defocused position, or gratings written in nematic liquid crystal displays (LCDs) or generated with digital micromirror devices (DMDs) have been used. The latest developments in the field of ferroelectric liquid-crystal-on-silicon (F-LCOS) displays make these devices interesting as the fringe generating element. They offer both high speed operation and high flexibility. Unlike other devices, F-LCOS displays can also be operated under oblique incidence, still generating sufficient fringe contrast. We report on the characterization of a F-LCOS display and its application in two different setups. A comparison to Ronchi gratings and gratings written in transmissive twisted nematic LCDs is given. The achievable measurement resolutions as well as the measurement times are discussed. Results of measurements conducted on technical and medical surfaces are presented.