Polarization Independent Microdisplays
National Science Foundation through a STTR Phase 1 grant (OII 0539552)
In collaboration with Imagineoptix, we have been successful in developing highly efficient Liquid Crystal On Silicon (LCOS) Microdisplays for projection applications. These revolutionary devices eliminate the need for polarizers through the innovative use of the unique diffractive properties of Liquid Crystal Polarization Gratings (LCPG) [ref:lcpg]. We recently demonstrated [ref:sid08] a prototype projection system using 256 x 256 LCOS microdisplay that proves this principle of operation. Already electrical contrasts approaching 1000:1 have been achieved over the entire visible range. Moreover these microdisplays have a fast dynamic response with sub ms switching times that allows for field sequential operation as demonstrated in the figure.
Impact and Future goals
By eliminating the need for polarizers, LCPG modulators can almost double the power efficiency of any application based on conventional LC devices. In the case of portable applications such as compact projectors, this can mean almost twice as much battery time and also reduction in size by using a smaller power source (Imagine 2 power cells instead of 4!). Another manifestation of this efficiency advantage in the case of display applications is an increased brightness for the same amount of power. LC Modulation itself does not limit the efficiency of LCPG SLMs, but larger angular separation of the diffracted orders is necessary to fully utilize the efficiency advantage. We continue to strive toward small grating periods (< 2um --> diffraction > 20 degrees) by optimizing different material parameters that determine the grating properties [ref:pre].