A Digital Vision Sensor

This paper presents a monolithic 128 x128 pixel optical sensor with analogue-to-digital converters, control and interface circuits designed specifically for direct connection to a host processor. The structure of the sensor leads to a reduction in the global complexity of the image-acquisition hardware and to the replacement of the noise-prone analogue line between sensor and host computer. Simplicity of use is maximized thanks to the encapsulation of all the critical analogue components within the chip. Key to the high integration level of the sensor is its implementation in standard CMOS technology which offers the possibility of integrating signal conditioning and interface functions on the standard voltages required by the conventional CCD sensors. Several features convenient in many machine-vision applications are included: square pixels, non-interlaced operation, adjustable sensitivity to light, acquisition of a frame of data on demand and extraction of a region-of-interest by addressing of a sub-block of the complete array. A complement of registers is included to control the operational parameters: integration time, analogue-to-digital converter resolution, and co-ordinates of the region of interest. Single 5-Volt operation is provided. The sensor was fabricated in a 2-um CMOS process and its functionality at up to 25 frames/s was demonstrate