Time Delay and Integration

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A Time Delay and Integration (TDI) charge-coupled device (CCD) is widely used for observation of high speed moving objects undetectable by classic CCD. Useful in a wide range of imaging applications that require both high speed and high sensitivity: earth observation satellites, inline monitoring and inspection, guidance, sorting etc.

A TDI clock is used to synchronize the movement of charged packets in a CCD with that of another movement. For example, in some digital x-ray mammography systems, the x-ray tube and CCD detector move across the breast at a speed V+. At the same time, the CCD detector reads out the information in the opposite direction at speed V-. This compensatory motion essentially freezes the motion of the detected x-ray information. The TDI clock ensures that speed V+ equals V-.