A CMOS Image Sensor With Programmable Pixel-Level Analog Processing

Abstract

A prototype of a 34 x 34 pixel image sensor, implementing real-time analog image processing, is presented. Edge detection, motion detection, image amplification, and dynamic-range boosting are executed at pixel level by means of a highly interconnected pixel architecture based on the absolute value of the difference among neighbor pixels. The analog operations are performed over a kernel of 3 x 3 pixels. The square pixel, consisting of 30 transistors, has a pitch of 35 microm with a fill-factor of 20%. The chip was fabricated in a 0.35 microm CMOS technology, and its power consumption is 6 mW with 3.3 V power supply. The device was fully characterized and achieves a dynamic range of 50 dB with a light power density of 150 nW/mm2 and a frame rate of 30 frame/s. The measured fixed pattern noise corresponds to 1.1% of the saturation level. The sensor's dynamic range can be extended up to 96 dB using the double-sampling technique.

Analogue CMOS ASICs in Image Processing Systems

“…Intensive research on specialized high-speed analog vision chips with reduced supply power is observed. Confirmation of this fact can be found in the literature, where the analog vision chips [6][7][8][9][10][11][12][13][14][15][16] are faster and consume less power than the digital realizations [17][18]. The remainder of this paper is devoted to a general discussion, in Sec.…”

“…In this kind of matrix only simple vision processors occupying a small area can be used, otherwise the size of the entire array, and consequently the cost of its production will become excessively large. Examples of implementations of such systems in 0.35 µm CMOS technology are presented in [6,9,15], and [27][28][29][30][31].…”

A vision system for 2D real-time vector motion estimation of a random-sized moving pattern

“…between 5 and 10), it is possible to obtain images with high contrast, which can be efficiently binarized. Even though technical details on the vision sensor and its operating modes are reported in [1], it is worth to shortly describe how the sensor extracts the spatial edge, which is used for the presented application. Sensor embedded edge extraction is executed accumulating the absolute value of the pixel difference, as described in eq.…”

“…Several solutions have been proposed both at system and chip level using different approaches: correlation [2], block matching [3], gray-level tracking [4]. Different approaches have been proposed in the last decades to determine the motion vector [1,7]. Some [10,11] use a linear array, executing template matching between the reference and the current frames.…”

Characteristics of an Image Sensor with Early-Vision Processing Fabricated in Standard 0.35 μm Cmos Technology

“…The vision sensors are constructed using p-n diodes or transistors exposed to light, which convert light to an electrical signal. A relatively small photo-current in the pA range, generated by the photo-sensors, can be converted to voltage with an amplitude of about 1 V in order to allow processing in the voltage-mode analogue processors [10][11][12][13][14][15][16][17]. Another approach is to directly amplify the photo-current to the µA level, in order to be processed in the current-mode analogue processors [5][6][18][19].…”