A 2 kfps Sub-µW/Pix Uncooled-PbSe Digital Imager With 10 Bit DR Adjustment and FPN Correction for High-Speed and Low-Cost MWIR Applications

Abstract

Mid-wavelength infrared (MWIR) thermography is an emerging technology with promising applications such as industrial monitoring, medicine and automotive, but its use in highspeed cameras is not yet widespread due to the lack of inexpensive sensor integration solutions and their common reliance on bulky cooling mechanisms. This work fills the gap by presenting a monolithic uncooled high-speed imager based on vapor-phase deposition lead selenide (VPD PbSe) photoconductors and a fully digital and configurable CMOS read-out integrated circuit (ROIC) to operate the MWIR imager. This ROIC features cancellation of PbSe dark current, compensation of its output capacitance and correction of the fixed pattern noise (FPN) caused by process non-uniformities in CMOS fabrication and detector deposition. The low-cost 80 × 80 imager has been integrated using 0.35 µm 2P4M standard CMOS technology and PbSe detector post-processing with 135 µm pixel pitch and 68% fill factor values. Experimental optoelectrical performance exhibits 10 bit real-time FPN compensation and DR calibration over the entire focal plane operating at 2 kfps, sub-0.5 LSB inter-pixel crosstalk, sub-µW pixel power consumption, and an overall figure of merit of 55 mK × ms.Index Terms-CMOS, digital pixel sensor (DPS), fixed pattern noise (FPN), high speed, imager, infrared, low cost, low power, MWIR, PbSe, uncooled.

Modified vapor phase deposition technology for high-performance uncooled MIR PbSe detectors

“…(NIT). [20][21][22][23][24][25][26][27][28] Technological evolution of VPD PbSe technology is shown in Fig. 2.…”

Compensation for Process and Temperature Dependency in a CMOS Image Sensor

“…However, CDS cancels the offset rather than the gain mismatches. Earlier efforts to further suppress FPN’s gain mismatch have been reported in [ 2 ], which adjusts both the gain and the offset in each digital pixel containing a 10 bit analog-to-digital converter (ADC). However, its 50 µm pixel pitch excludes its general usage in CIS and it does not consider any thermal effect on dark current or CG.…”

A CMOS-Imager-Pixel-Based Temperature Sensor for Dark Current Compensation

“…In other words, the temperature variations across the image sensor chip will affect the dark current and will increase DSNU, adding to the process variation components as the spatial dark Fixed Pattern Noise (FPN). Therefore, digital compensation of dark current and dark FPN [1] should be considered along with thermal compensation, especially for applications requiring a wide temperature range. The compensation can be performed using a reference dark frame taken with a physical shutter, which, however, is infeasible for low cost or very high speed video applications.…”