Editing Charge-coupled device (section)

===Frame transfer CCD===
[[File:IECCD55-20.jpg|thumb|top|A frame transfer CCD sensor]]

The frame transfer CCD imager was the first imaging structure proposed for CCD Imaging by Michael Tompsett at Bell Laboratories. A '''frame transfer CCD''' is a specialized CCD, often used in [[astronomy]] and some [[professional video camera]]s, designed for high exposure efficiency and correctness.

The normal functioning of a CCD, astronomical or otherwise, can be divided into two phases: exposure and readout. During the first phase, the CCD passively collects incoming [[photon]]s, storing [[electron]]s in its cells. After the exposure time is passed, the cells are read out one line at a time. During the readout phase, cells are shifted down the entire area of the CCD. While they are shifted, they continue to collect light. Thus, if the shifting is not fast enough, errors can result from light that falls on a cell holding charge during the transfer. These errors are referred to as [[rolling shutter effect]], making fast moving objects appear distorted. In addition, the CCD cannot be used to collect light while it is being read out. A faster shifting requires a faster readout, and a faster readout can introduce errors in the cell charge measurement, leading to a higher noise level.

[[File:Propellor with rolling-shutter artifact.jpg|thumb|A [[de Havilland Canada Dash 8]] Q-400 six-blade propeller, with severe rolling shutter distortion from a [[Pixel 3]] camera]]

A frame transfer CCD solves both problems: it has a shielded, not light sensitive, area containing as many cells as the area exposed to light. Typically, this area is covered by a reflective material such as aluminium. When the exposure time is up, the cells are transferred very rapidly to the hidden area. Here, safe from any incoming light, cells can be read out at any speed one deems necessary to correctly measure the cells' charge. At the same time, the exposed part of the CCD is collecting light again, so no delay occurs between successive exposures.

The disadvantage of such a CCD is the higher cost: the cell area is basically doubled, and more complex control electronics are needed.