Very wide dynamic range SWIR sensors for very low background applications

Abstract

This paper describes a high performance 320 by 256 readout integrated circuit (ROIC) designed for P-on-N short wave infrared (SWIR) detectors including InGaAs and HgCdTe, which also has the ability to operate at low input current levels with N-on-P detectors. The ROIC/FPA will support a wide range of system requirements from very low background applications (nightglow) to daytime high illumination conditions. To accommodate the wide scene dynamic range requirements, two selectable integration capacitors are used to control the input circuit transimpedance gain. A 1 OfF integration capacitor is used for low noise and low flux levels down to iO ft Lambert, corresponding to approximately 2x10'° phlcm2-sec for O.9m to 1.7tm spectral band using f/l.5 optics, assuming a 2856 Kelvin blackbody distribution. For higher flux levels, a O.2lpF integration capacitor can be selected, thus providing over a factor of 20 dynamic range. A capacitive feedback transimpedance amplifier (CTIA) provides a low noise detector interface circuit capable of operating at low input currents without frame-to-frame image lag. A sample and hold capacitor is also part of the input unit cell architecture, which allows the FPA to be operated in full frame snapshot mode and provides the maximum integration time available. The integration time is electronically controlled (gated) by an external clock pulse, and is adjustable from O.5.tsec to approximately the frame time of 33.3msec for 30Hz operation. This produces an additional factor of 66,000 to the total system dynamic range. The combination of integration time control and selectable integration capacitors accommodates over nine orders ofmagnitude in scene dynamic range.

Extended short-wavelength spectral response from InGaAs focal plane arrays

“…Because FPA capability and performance is closely tied to the performance and capability of the ROIC, it is useful to review the specifications (Figure 1) of the ISC9809 ROIC. 3 This device was originally designed for use with InGaAs detectors and as such is also ideally suited for use with VisGaAs detectors. The ISC9809 is also one of several ROICs that interface to the Indigo Systems Phoenix camera allowing the FPA to be integrated into a complete camera system.…”

Research progress on digital ROIC of infrared focal plane array detector

“…These objectives are successfully accomplished by infrared detector components by combining multiple technologies, such as "HOT" operation, "Small" pixels, and "Digital" integration. The digital ROIC designers have proposed greater criteria because as the pixel pitch gets smaller and smaller ( ≤ 5μm), the detector operating temperature gets increasingly higher ( ≥ 150K) [51]. We can only fulfill these objectives by continually lowering the IC design line width and putting out advanced ADC architectures.…”

A high-performance readout circuit (ROIC) for VLWIR FPAs with novel current mode background suppression

“…It becomes almost impossible for the signals being read out to corrupt the signals being integrated [12). This insulation is especially effective for wiring on the integration capacitor to save area in the layout.…”