Design and Implementation of a Neuromorphic Vision System

• Main Authors: Lin, Shang-Yi, 林尚毅
• Other Authors: Tzi-Dar Chiueh
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/43089697605880069355

博士 === 國立臺灣大學 === 電機工程學系 === 85 === In this thesis, a neuromorphic vision system which simulates the neural circuitry (or functions) of the retina and primary visual cortexof vertebrates was proposed.The proposed silicon retina has the capability of original image extraction, smoothing, segmentation, edge detection, and edge enhancement. Pixel circuit of the silicon retina consists of a parasitic phototransistor, a Wilson current mirror, two coupling resistors (implemented by PMOS transistors), two resistive fuses, and some switches for mode selection.The resistive fuse, exhibiting independent tunability between its resistance and cutoff voltage, is responsible for image smoothing andsegmentation. By suitably biasing some transistors in pixels, totally six modes of the silicon retina are obtainable,each of these is dedicated to a specific image processing task. Functionality of the silicon retina had been experimentally verified.Moreover, a high-precision median filters, for both voltage and current mode, was developed to eliminate impulsive-like noise causedby mismatch between pixel circuits. To achieve real-time median filtering, a new current sample-and-hold circuit and animage scanning strategy is proposed. Measurements show that the median filter and the current sample-and-hold circuit function properly.Simple feature extraction performed in the primary visual cortex is realized by a Gaussian/Square similarity computation circuit. The circuit exhibits independent control between the width and the peak value of the Gaussian/square function.Specific edge features can be extracted by performing template matching throughout the image.Finally, several chips intended for specific image processing tasks are integrated on the same substrate for realization of a more complete neuromorphic vision system.