Triple-mode read-in IC for improved image quality of infrared scene projectors

Abstract

In this thesis, research into read-in integrated circuits (RIICs) for infrared scene projectors (IRSPs) is described. In particular, unlike conventional RIICs, mode-selective RIICs are proposed to simultaneously satisfy the need for wide thermal range and fine thermal resolution. First, a novel RIIC containing switches, a feedback resistor and a diode-connected transistor is proposed. With switch control, a pixel can operate in three modes. The feedback resistor and diode-connected transistor in each pixel help to generate a dual-sloped input to output curve for fine resolution around 300K. The prototype was fabricated using the TSMC 0.35 $\mu$m CMOS process, and it was verified that the IR emitter driven by the proposed circuit could generate upto 745 K with < 30mK resolution around 300 K. Second, to guarantee data-sampling accuracy with high spatial resolution and high-speed operation, a column DAC design is proposed and a piece-wise linear DAC structure was adopted. The prototype was fabricated using the On-semiconductor 0.18 $\mu$m CMOS process, and from the measured data analysis, it was verified that the chip design could operate at the target speed. Its monotonicity was also confirmed by varying the 12-bit digital input. Third, to improve pixel-to-pixel uniformity, a new current-driven RIIC pixel is proposed. In particular, the proposed pixel can operate in snapshot mode, which enables it to emit radiation in array simultaneously for high-speed IR scene operation, without the need for a unity-gain buffer. The prototype was designed with the SK-Hynix 0.18 $\mu$m CMOS process. The nonuniformity immunity was tested taking account of the mismatch properties, and it was verified that the emitter current variation could be reduced from 20 $\mu$A to 0.1 $\mu$A. It was also confirmed that the uniformity, being the standard deviation of the radiance divided by the average radiance, could be reduced from 21% to 0.1%.