- on Education & Information
- Published in issue 6/2002 on page 0
Alternative Image Sensors
redefining the pixel
Although the vast majority of image sensors in use are of the Charge Coupled Device (CCD) variety (particularly in consumer products), and those that are not are of the Complementary Metal Oxide Semiconductor (CMOS) type; other types are being used in a variety of applications or being developed. A number of these have interesting properties that would suit them to a wider market. And there are also variations on the CCD to adapt it to particular roles.However, it is worth noting that they all share the same underlying principle of operation. The sensitive area is divided into pixels; where impinging photons can produce electron-hole pairs in the silicon. Either the holes or, more usually, the electrons are then gathered into a potential well while the others are drained into the substrate. The charge in the well is then moved out, amplified, processed and, with the charges from all the other pixels, forms the picture.