Frame transfer
A Frame Transfer system consists in two matrices (X columns x Y lines) almost identical, one dedicated to image pixels and the other one to storage.
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The storage cells are structurally identical to sensitive cells but they are covered by an optical metallic shield to avoid any exposure to light. After the integration cycle, the charge is rapidly transferred from sensitive cells to storage cells. The transfer rate to the shielded part depends on the size of the matrix but is typically inferior to 500 µs. The smear is limited by the time taken to transfer the image to the storage area. All this process requires much less time than in a Full Frame Transfer (FFT) system.
As the CCD size is double, it is more complex than a simple Full Frame system. The matrix must have some false charge wells between the sensitive part and the storage part. These wells collect any anticipated leak of light. Some matrices can operate in full frame X x 2Y) mode or in frame transfer (X x Y) mode. In this case, the user must build the shield for the frame transfer mode.