Devolopment of a parallel analog vision chip for early vision

视觉芯片是一种受视网膜结构和功能启发，采用模拟CMOS超大规模集成电路(VLSI)技术设计的新型图像处理系统。由于利用VLSI电路的动态特性对投影到芯片上的图像进行并行处理，该芯片有望突破传统数字图像处理系统在实时图像处理方面的致命缺陷。本项目的目的是设计一种视觉芯片，模拟视网膜双极细胞网络的功能和结构。1.建立了视网膜双极细胞的阻性网络模型，并对该网络的功能进行了定量研究。该电路能够再现视网膜双极细胞的响应特性，如对图像进行平滑和对比度增强操作。2.利用该模型，根据早期视觉的标准正则化理论，建立了视网膜双极细胞网络的函数。3.设计了该模型的模拟VLSI电路，并利用仿真软件PSPICE对电路的性能进行了分析。4.通过MOSIS制作了一个受该模型启发的视觉芯片。5.通过在模型中加入动力学元素，进一步研究了双极细胞网络的时间特性。该模型被发现解释了视网膜双极细胞反应的时间特性。

The vision chip is a novel image processing system, which is designed using analog CMOS Very Large Scale Integrated (VLSI) circuit technology, inspired by structures and functions of the retina. Since images projected on the chip are processed in parallel by dynamical properties of the VLSI circuit, the chip is expected to give a breakthrough to fatal disadvantages of conventional digital image processing systems in the real-time image processing. The purpose of this project is to design a vision chip which mimics functions and structures of the retinal bipolar cell network. The followings are the summary of results we obtained in 1994-1995.1.A resistive network model of the retinal bipolar cell was developed and the functions of the network were studied quantitatively. The circuit was found to reproduce the response properties of the retinal bipolar cell, e.g., smooting and contrast enhancement operations on images.2.Using the model, the function of retinal bipolar cell network was formulated in terms of the standard regularization theory of early vision.3.An analog VLSI circuit of the model was designed and performances of the circuit were analyzed with the simulation software PSPICE.4.A vision chip inspired by the model was fabricated through the MOSIS.5.We further studied temporal properties of bipolar cell network by incorporating dynamical elements in above model. The model was found to explaine the temporal properties of retinal bipolar cell response.