Current-Mode Self-Amplified CMOS Sensor Intended for 2D Temperature Microgradients Measurement and Imaging

Abstract

This paper presents the design of a current-mode CMOS self-amplified imager operating in dark conditions, for thermal imaging, which provides an innovative solution for precision thermal contact mapping. Possible applications of this imager range from 3D CMOS integrated circuits to the study of in-vivo biological samples. It can provide a thermal map, static or dynamic, for the measurement of temperature microgradients. Some adaptations are required for the optimization of this self-amplified image sensor since it responds exclusively to the dark currents of the photodiodes throughout the array. The sensor is designed in a standard CMOS process and requires no post-processing steps. The optimized image sensor operates with integration times as low as one μs and can achieve both SNR and dynamic range compatible to those of sensors available on the market, estimated as 87dB and 75dB, respectively; noise equivalent temperature difference can be as low as 10mK; and detection errors as low as ±1%. Furthermore, under optimal conditions the self-amplification process enables a simple form of CDS, enhancing the overall sensor noise performance.

A Review of Optical Sensors in CMOS

“…Consequently, any disruptions along the column line significantly affect the charge signal, resulting in reduced sensitivity and increased noise [78,80]. Figure 11b illustrates the second type of pixel, i.e., the active pixel sensor (APS) [65,[81][82][83][84][85][86][87], which consists of a matrix of pixels in the same way as the PPS, but with the difference of containing three MOSFETs, where M1 is the reset transistor, M2 is the amplifying transistor, and M3 is the pixel address transistor. The APS has three modes of The first type of pixel used on CMOS image sensors and presented in this paper is the passive pixel sensor (PPS) [65,77], whose structure is shown in Figure 11a.…”

“…Figure 11b illustrates the second type of pixel, i.e., the active pixel sensor (APS) [65,[81][82][83][84][85][86][87], which consists of a matrix of pixels in the same way as the PPS, but with the difference of containing three MOSFETs, where M 1 is the reset transistor, M 2 is the amplifying transistor, and M 3 is the pixel address transistor. The APS has three modes of operation: the reset mode, the integration mode, and the readout mode [12,22,35,[88][89][90].…”