A new foveated CMOS image sensor has been designed and fabricated. The photocell elements transform the light into current, and then, in a continuous way, into voltage without charge integration. This kind of sensing cell has been already employed in image sensors for normal cameras, but never in foveated sensors. The presented sensor tries to emulate the human eye pixel resulting in a sensor with a space variant distribution of pixels. Consequences of this distribution are the different size of the sensing elements in the pixel matrix, the non orthogonal shapes of the different elements that integrate the pixel, and, as a result, the different response of every cell in the sensor. A scaling mechanism is needed due to the different pixel size from circumference to circumference. A mechanism for current scaling is presented. This mechanism has been studied along with other effects, as the narrow channel effect on submicron MOS transistors, and the influence of the logarithmic response o...

Introduction One major drawback of active pixel sensors and, to a lesser extent, of CMOS passive pixels or photo diode arrays too, is that a significant part of the pixel's surface is used for readout circuitry, which is not part of the light receptor or photo diode. Light falling on these regions is collected by the junctions of this circuitry. This essentially is the reason for the low fill factor problem of active pixel sensors. 2. Proposed pixel structure A method to raise the fill factor should manage to get all (or a large part) of the photo generated charge into the collection junction, instead of into the unrelated junctions. We have realised this by placing a small but effective electrostatic barrier between the photo sensitive volume and the unrelated junctions, which is absent between the photo sensitive volume and the useful junction (fig. 1). n++ n++ n p+ p++ (substrate) p- potential minimum unrelated circuitry photo diode ee - e

The primate retina performs nonlinear "image" data reduction while providing a compromise between high resolution where needed, a wide field-of-view, and small output image size. For autonomous robotics, this compromise is useful for developing vision systems with adequate response times. This paper reviews the two classes of models of retino-cortical data reduction used in hardware implementations. The first class reproduces the retina to cortex mapping based on conformal mapping functions. The pixel intensities are averaged in groups called receptive fields (RF's) which are non-overlapping, and the averaging performed is uniform. As is the case in the retina, the size of the RF's increases with distance from the centre of the sensor. Implementations using this class of models are reported to run at video rates (30 frames per second). The second class of models reproduce, in addition to the variable-resolution retino-cortical mapping, the overlap feature of receptive fields of retinal...

A TV camera chip suitable for intelligent transportation system #ITS# applications such as adaptive cruise control and tra#c monitoring is presented. Brightness adaptability for rapidly varying and wide#intensity range highway scenes is achieved with a stepped reset gate voltage technique that is applied to a CMOS active pixel sensor array to increase dynamic range by 26 dB. The image acquisition #sensing array# and processing #A#D conversion# blocks are integrated on a single chip. A frame rate of 390 frames#sec is achieved using column#parallel output circuits. Switched#capacitor correlated double#sampling circuits reduce #xed-pattern noise to 4.0 mV #dark#. Cyclic analog#to#digital converters achieve approximately 9b accuracy. At 30 frames#sec, random noise is 0:56 mV #dark#, optical dynamic range is 96 dB, and power dissipation is 52 mW. I. Introduction T HE CMOS image sensor described in this paper is intended for intelligent transportation system #ITS# applications such as ada...

Most of today's video and digital cameras use CCD image sensors, where the electric charge collected by the photodetector array during exposure time is serially shifted out of the sensor chip resulting in slow readout speed and high power consumption. Recently developed CMOS image sensors, by comparison, are read out non-destructively and in a manner similar to a digital memory and can thus be operated at very high frame rates. A CMOS image sensor can also be integrated with other camera functions on the same chip ultimately leading to a single-chip digital camera with very compact size, low power consumption and additional functionality. CMOS image sensors, however, generally su#er from lower dynamic range than CCDs due to their high read noise and non-uniformity. Moreover, as sensor design follows CMOS technology scaling, well capacity will continue to decrease, eventually resulting in unacceptably low SNR.

Abstract—CMOS active pixel sensors (APS) have performance competitive with charge-coupled device (CCD) technology, and offer advantages in on-chip functionality, system power reduction, cost, and miniaturization. This paper discusses the requirements for CMOS image sensors and their historical development. CMOS devices and circuits for pixels, analog signal chain, and on-chip analog-to-digital conversion are reviewed and discussed. I.