One of the leading imaging technologies for implementing pico projectors is Liquid Crystal on Silicon (LCoS).
With LCoS, liquid crystals are sandwiched between a glass and the surface of a silicon chip. The silicon surface is coated with an aluminized layer and polished for optimum reflectivity.
Finally, the polished surface is protected with a passivation layer. A differential voltage is applied between the glass and the silicon surface causing the liquid crystal to align to a pre-define crystal direction. The twisting affect enable lights to be reflected by the reflective layer.
By modulating the liquid crystal, light level can be controlled to generate the full range of light intensity.