Phase diffraction utilizing a liquid crystal diffraction device

In supertwisted nematic (STN) display technology, a chiral compound is added to a nematic liquid crystal in order to induce a twisting helix. This helix is then bound into some angular configuration by surface anchoring energies on the plate of the LCD. Due to this confinement of the helix, deformations occur in its structure when a voltage is applied. One of the most interesting deformations which can occur is the striped domain instability. By constructing a cell such that the cholesteric-nematic threshold voltage (Vth) is higher than the domain formation voltage (Vc) we can induce 3 dimensional periodic deformations in the molecular orientation of the liquid crystalline material before the helical geometry of the cell is destroyed. We have constructed several types of Liquid Crystal Diffraction Devices (LCDD) based on this principle. Here we describe the theory of operation, device construction, and performance of such switchable LCDDs.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.