A super parallel vision system implemented with mixed analog and digital circuits

本研究的目的是开发一种新型的视觉系统，可以进行实时图像处理与混合模拟/数字架构。据此，我们设计并制作了由硅视网膜、模拟超大规模集成电路和现场可编程门阵列组成的系统。（FPGA）。硅视网膜模拟脊椎动物视网膜中发现的持续和瞬时反应。模拟持续反应的输出具有类Palladian-Gaussian感受野，因此对输入图像进行平滑和对比度增强。通过减去由电阻网络平滑的连续图像来获得仿真瞬态响应的输出。这两个通道的输出可以在室内照明中在不超过几十ms的时间延迟内以真实的时间交替地从硅视网膜获得。芯片的输出是偏移抑制模拟电压，因为晶体管特性的不可控失配借助于嵌入在每个像素电路中的采样/保持电路得到补偿。来自硅视网膜的模拟输出表示具有这些通道的预处理图像，通过A/D转换器传输到FPGA。FPGA执行数字图像计算，例如边缘检测、目标跟踪和深度感知。在本研究中开发的并行视觉系统是很容易在各种工程应用，如机器人视觉和多媒体领域。

The purpose of the present research is to develop a novel vision system that can carry out the real-time image processing with mixed analog/digital architecture. Accordingly, we have designed and fabricated the system consisting of a silicon retina, an analog Very Large Scale Integrated (VLSI) circuit and Field Programmable Gate Array. (FPGA). The silicon retina emulates the sustained and the transient responses found in the vertebrate retina. The output emulating sustained response possesses a Palladian-Gaussian-like receptive field and therefore carries out a smoothing and contrast-enhancement on input images. The output emulating the transient response was obtained by subtracting consecutive images that were smoothed out by the resistive network. The outputs of these two channels can be obtained alternately from the silicon retina in real time, within time delays not exceeding a few tens of ms, in indoor illumination. The outputs of the chip are offset-suppressed analog voltages since uncontrollable mismatches of transistor characteristics are compensated for with the aid of sample/hold circuits embedded in each pixel circuit. The analog outputs from the silicon retina representing the preprocessed image with these channels are transferred to the FPGA through a A/D converter. The FPGA carries out digital image computations such as edge detection, target tracking and depth perception. The parallel vision system developed in the present study is readily used in a variety of engineering applications such as the fields of robot vision and multi-media.