Active Pixel Sensors Essay

INTRODUCTION

An Active Pixel Sensor (APS) is an imaging sensor which consists of an integrated circuit comprising of a collection of pixel sensors.

Each pixel comprises of an active amplifier and a photodetector.

Active Pixel Sensors are of many types. The most common one CMOS Active Pixel Sensor, is used in mobile phone cameras, web cameras and most DSLR cameras. This kind of an image sensor is manufactured by a CMOS or NMOS process.

The conversion of light signals into electric signals is done by the Active Pixel sensor. The electric signals then can be digitized and thus changed for variation in pixel parameters. The market for image sensors has drastically changed and in the last few years, increase in the sales and developments of image sensors based devices like cameras have been recorded.

Imaging sensors can be categorized into mainly two types:

i. Complementary Metal Oxide

An image with too much noise will have poor contrast and other unpleasant features.

ADVANTAGE OF ACTIVE PIXEL SENSOR OVER CHARGED COUPLED DEVICES

Active Pixel Sensors have in recent times emerged as a replacement to Charged Coupled Devices as they preserve all the desirable features of Charged Coupled Devices, yet circumvent the major weaknesses of the Charged Coupled Device technology.

Out of several advantages including lower cost, lower power consumption, higher speed and smaller size, the one thing that Active Pixel Sensors have also solved is the variation in the brightness of pixels that used to occur due to Signal and Noise.

The addition of an amplifier to each pixel solved the problems of high noise, lack of scalability, variation in brightness, etc. that occurred in Charged Coupled Devices and thus resulted in the creation of the Active Pixel Sensor.

Thus, we can say Active Pixel Sensors combine the image sensor function and image processing functions within the same integrated circuit.