With the development of high power LED (light emitting diode) technology and color filter LCOS (liquid crystal on
silicon) technology, the research on LED based micro optical engine for mobile projection has been a hot topic recently.
In this paper one compact LED powered LCOS optical engine design is presented, which is intended to be embedded in
cell phone, digital camera, and so on. Compared to DLP (digital light processor) and traditional color sequential LCOS
technology, the color filter based LCOS panel is chosen for the compact optical engine, this is because only white LED
is needed. To further decrease the size of the optical engine, only one specifically designed plastic free form lens is
applied in the illumination part of the optical engine. This free form lens is designed so that it plays the roles of both
condenser and integrator, by which the output light of LED is condensed and redistributed, and light illumination of high
efficiency, high uniformity and small incident angle on LCOS is acquired. Besides PBS (polarization beam splitter),
LCOS, and projection lens, the compact optical engine contains only this piece of free form plastic lens, which can be
produced by plastic injection molding. Finally a white LED powered LCOS optical engine with a compact size of less
than 6.6 cc can be acquired. With the ray tracing simulation result, the light efficiency analysis shows that the output flux
is over 8.5 ANSI lumens and the ANSI uniformity of over 80%.