The revolutionary ideas implemented on silicon chips, which will be described in the following sections, are blooming and opening the doors for another information processing tool, smart-visual-sensing. This report is a survey of the vision chips that have been designed in the past decade. It tries to give a concise and simple description of each design and draw the reader's attention to the specific idea that a particular vision chip has brought about. For each chip a brief description about the function of the chip is given. Important architectural and circuit level design aspects are also presented. Basic principles of vision algorithms and circuit design will not be described, at least in detail. The reader is expected to have a good knowledge of image processing, and general knowledge on analog and digital VLSI design. Wherever available, some information about the fabricated chips, like cell size, chip size, and process are also provided. In future revisions more information about the performance of each chip will be presented. Of course, as the computer vision community is still faced with the lack of proper benchmarks and criteria for image processing performance at different levels, most of the performance measures will be those related to VLSI, such as speed, power, and contrast sensitivity, rather than computer vision related measures.
There are some links (in the html format of the report) to the relevant home pages of the authors of each work to make the vision-chip community as close together and as informed as possible from each other's work. Some of the documents are also linked to the online postscript format of the articles relevant to that chip, which can be downloaded and printed on a postscript printer.
In this third revision of the vision chips document, I have added many new vision chips, and the report now comprises more than fifty vision chips. The document encompasses seven chapters.
In chapter 2 Spatial Image Processing Vision Chips are presented. This includes chips for edge detection, smoothing, stereo processing, and contrast enhancement (silicon retinas), in addition to chips for finding global features of the image.
Chapter 3 covers Spatio-Temporal Image Processing Vision Chips, dominated by motion detection chips. Although motion detection chips intrinsically include spatial processing, the cooperative time-space processing makes them different from other vision chips. There are also a few purely temporal processing implementations.
Chapter 4 presents a few analog VLSI chips for vision processing. These chips do not have on-chip photodetectors, and the image is produced by external imagers. These implementations cannot be regarded as vision chips in any sense. It is rather the processing, and vision related implementations that makes them interesting for this report. They also represent the type of processing that can be performed - still in analog domain - on the output of any vision chip.
In chapter 5 Optical Neuro Chips are described. These chips architecturally belong to the analog VLSI neuro-chips family, with the exception that the medium for signal transmission is chosen to be optical. However, as the optical neuro chips designed so far aim at image processing, they are included in this report. The role of neural networks in many new image processing algorithms can also justify this inclusion.
Chapter 6 describes some of the active pixel sensor (APS) chips. Their relevance to this report is from the fact that in these imagers the attention is focused on the quality of the imaging, while in vision chips the implementation of an algorithm is the main concern. Many of the methods developed for enhancing the performance of APSs can be adopted for vision chips.
And finally, chapter 7, Designing Vision Chips: Principles and Building Blocks, presents general principles, design limitations, design variables, guidelines to be considered in the design of vision chips, and testing procedure. Also various components of vision chips, i.e. photodetector, photocircuits, spatial and temporal processing circuits are presented in more detail.
Appendices describe some information about this report, such as tools used to generate the document, and give reference to other major resources, on-line or off-line, about vision chips.