Wiring considerations in analog VLSI systems, with application to field-programmable networks
Wiring considerations in analog VLSI systems, with application to field-programmable networks
VLSI analogs of neuronal visual processing: a synthesis of form and function
VLSI analogs of neuronal visual processing: a synthesis of form and function
Translinear circuits in subthreshold MOS
Analog Integrated Circuits and Signal Processing - Special issue: translinear circuits
Motion Vision Sensor Architecture with Asynchronous Self-Signaling Pixels
CAMP '97 Proceedings of the 1997 Computer Architectures for Machine Perception (CAMP '97)
A Reconfigurable Neuromorphic VLSI Multi-Chip System Applied to Visual Motion Computation
MICRONEURO '99 Proceedings of the 7th International Conference on Microelectronics for Neural, Fuzzy and Bio-Inspired Systems
Retinomorphic Chips that see Quadrupple Images
MICRONEURO '99 Proceedings of the 7th International Conference on Microelectronics for Neural, Fuzzy and Bio-Inspired Systems
Arbitrated time-to-first spike CMOS image sensor with on-chip histogram equalization
IEEE Transactions on Very Large Scale Integration (VLSI) Systems
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Address Event Representation (AER) is an emergent technology for assembling modular multiblock bio-inspired sensory and processing systems. Visual sensors (retinae) are among the first AER modules to be reported since the introduction of the technology. Spatial-contrast AER retinae are of special interest since they provide highly compressed data flow without reducing the relevant information required for performing recognition. The reported AER contrast retinae perform a contrast computation based on the ratio between a pixel's local light intensity and a spatially weighted average of its neighborhood. This resulted in compact circuits but with the penalty of all pixels generating output signals even if they sensed no contrast. In this paper, we present a spatial-contrast retina with a signed output: Contrast is computed as the relative difference (not the ratio) between a pixel's local light and its surrounding spatial average and normalized with respect to ambient light. As a result, contrast is ambient light independent, includes a sign, and the output will be zero if there is no contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute contrast above the adjustable threshold. The pixel contrast-computation circuit is based on Boahen's biharmonic operator contrast circuit, which has been improved to include mismatch calibration and adaptive-current-based biasing. As a result, the contrast-computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. The retina includes an optional global reset mechanism for operation in ambient-light-independent Time-to-First-Spike contrast-computation mode. A 32 × 32 pixel test prototype has been fabricated in 0.35-µm CMOS. Experimental results are provided.