A CMOS/LCOS image transceiver chip for smart goggle applications

The design of a novel, CMOS-liquid-crystal-based image transceiver device (ITD) is described. The device combines both functions of imaging and display by means of a dual-function array formed in a single-processed chip. The image transceiver system design allows the integration of the see-through, aiming, imaging, and display of a superposed image into a single, compact, head-mounted goggle. The timing, sequencing, and control of the ITD array are designed in a pipeline array-processing scheme. The CMOS-based pixel elements are designed to provide efficient imaging in the visible range as well as driver capabilities for the overlying liquid crystal modulator. The image sensor part of the pixel consists of an n-well photodiode and a three-transistor readout circuit and is based on a back-illuminated sensor configuration. In order to provide a high imager fill-factor, two pixel configurations were conceived and analyzed: 1) a p++/p^-/p-well silicon structure using twin-well CMOS process and 2) an n-well processed silicon structure with a micro-lens array. The display portion of the ITD, based on LCOS micro-display technology, consists of a silicon-based reflective, active matrix driver, using a nematic liquid crystal. Details of the device design and its control system are presented.