Electronically addressed spatial light modulators (SLMs) are key elements for the reconstruction of digital holograms. Reflective liquid-crystal-on-silicon displays (LCOS) have great potential to fulfill this task due to their high fill factors of over 90% and their small pixel sizes of less than 15 μm. In order to obtain maximum diffraction efficiency of the holographic reconstruction, analog phase holograms have to be implemented making a maximum phase shift of 2π in each LCOS pixel necessary. Therefore, each LCOS display has to be thoroughly characterized prior to its use as a holographic element. In this publication, we report on a specially designed LCOS test bench. Here, displays can be characterized with respect to their phase and amplitude modulation (i.e. the complex transmittance) under a varying angle of the incident linearly polarized light. Additionally, the Jones matrix of the displays can be measured, which allows computation of the response of the displays to light of arbitrary polarization. The measurement of panel flatness is also possible which is necessary to compensate wave front aberrations. Results of measurements of two LCOS dis-plays are presented and a comparison to other measurement methods is given.
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.