Physical computing circuit with no clock to establish Gaussian pyramid of SIFT algorithm

Physical computing scheme of active resistor network is proposed in this paper to set up a multi-scale Gaussian filter, which is also called Gaussian Pyramid in image signal processing. The analog output signal of each image photodiode could be directly processed by the circuit topology of an active resistor network, which has been pre-designed to meet the requirement of the complicated Gaussian Pyramid in SIFT algorithm. Since it is operated with no clock, the physical computing scheme, with only setup time of the whole processing circuits, is much faster than various current digital realizations. The circuit-level simulation with 65nm CMOS technology has been carried out, which shows the energy consumption of the Gaussian Pyramid processing circuit is around 74.79pJ to filter a frame of 256 × 256 pixel image, and the circuit setting time of the processing is about 138.03ps, considering the parasitic capacitances of each nodes of the circuits. Furthermore, the presented circuit is integrated into a smart CMOS image sensor architecture. With the same processing procedure, the new method of active resistor network could achieve 1.58X speedup when compared with its counterpart of FPGA implementation, in which the column-parallel readout technology of analog-to-digital convertor is used.