Constant power snapshot microemitter array with integral digital interface, isolated substrate current return, and linearized signal response

Abstract

A dual sample-and-hold architecture in each unit cell of a read-in-integrated-circuit (RIIC) provides maximum frame rate without frame overlap. Analog pixel signals are updated sequentially in one sample-and-hold capacitor, while an emitter element displays a pixel of a display frame in response to a stored analog signal voltage on an isolated second sample-and-hold capacitor. After all unit cells are updated, the signals on the two capacitors are combined, updating all emitter elements for the next frame. A voltage mode amplifier as an emitter driver provides a more nearly linear dependence of infrared power output on signal voltage than do previous transconductance amplifiers. A digital to analog converter (DAC) on the RIIC substrate results in a simplified interface to the RIIC and in an increased immunity to noise. A constant current source in the unit cell provides constant power dissipation and temperature, independent from variations in emitter element current, improving stability and scene dependent crosstalk. Emitter element current returns to an external ground plane through semiconductor substrate contacts for all unit cells. This configuration eliminates metal interconnects, which produce scene-dependent voltage drops in the return circuit, adversely affecting linearity and crosstalk.