Inexpensive Image Sensors Challenge CCD Supremacy
Terry Zarnowski, Tom Vogelsong and Jeff Zarnowski, Photon Vision Systems LLC, Cortland, N.Y.
Determining an application's parameters and requirements is important when shopping for an image sensor. The goal is to match the capabilities and limitations of the sensor to the application's price and performance needs.
Image sensor parameters include resolution, pixel size, speed, dynamic range, power consumption, read noise, full-well capacity, pixel response nonuniformity, fixed-pattern noise and sensitivity. These trade off with varying effects on imager performance.
Manufacturing processes may also allow the integration of many capabilities on a chip, as with complemetary metal oxide semiconductor (CMOS) imagers. On-chip features may include analog-to-digital converters, nondestructive readout, rolling shutter, full-frame electronic shutter and random-access decoders that enable functions such as random pixel access and subframe readout. The application determines the need for these features, which may produce additional trade-offs in the form of increased noise.
The CCD has long reigned over the field of imaging by providing excellent video quality when properly applied. CCD manufacturers use specialized fabrication processes that have their roots in the early days of metal oxide semiconductor integrated circuit manufacturing and are incompatible with the modern CMOS processes that make today's more complex mixed-signal integrated circuits.