15 February 2012 A 176×144 148dB adaptive tone-mapping imager
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Abstract
This paper presents a 176x144 (QCIF) HDR image sensor where visual information is simultaneously captured and adaptively compressed by means of an in-pixel tone mapping scheme. The tone mapping curve (TMC) is calculated from the histogram of a Time Stamp image captured in the previous frame, which serves as a probability indicator of the distribution of illuminations within the present frame. The chip produces 7-bit/pixel images that can map illuminations from 311μlux to 55.3 klux in a single frame in a way that each pixel decides when to stop observing photocurrent integration -with extreme values captured at 8s and 2.34μs respectively. Pixels size is 33x33μm2, which includes a 3x3μm2 Nwell- Psubstrate photodiode and an autozeroing technique for establishing the reset voltage, which cancels most of the offset contributions created by the analog processing circuitry. Dark signal (10.8 mV/s ) effects in the final image are attenuated by an automatic programming of the DAC top voltage. Measured characteristics are Sensitivity 5.79 V/lux·s , FWC 12.2ke-, Conversion Factor 129(e-/DN), and Read Noise 25e-. The chip has been designed in the 0.35μm OPTO technology from Austriamicrosystems (AMS). Due to the focal plane operation, this architecture is especially well suited to be implemented in a 3D (vertical stacking) technology using per-pixel TSVs.
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S. Vargas-Sierra, S. Vargas-Sierra, G. Liñán-Cembrano, G. Liñán-Cembrano, A. Rodríguez-Vázquez, A. Rodríguez-Vázquez, } "A 176×144 148dB adaptive tone-mapping imager", Proc. SPIE 8298, Sensors, Cameras, and Systems for Industrial and Scientific Applications XIII, 82980A (15 February 2012); doi: 10.1117/12.905240; https://doi.org/10.1117/12.905240
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