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Features & Functionality
3.4.2 - Capture Sequence in Non-Frame Transfer Mode with an FT CCD
It is also possible to operate an FT CCD in a Non-Frame Transfer (NFT) mode. In this mode of operation, an FT CCD
acts much like a standard CCD. The capture sequence for this mode is illustrated here:
Step 1 Both Image and Storage areas of the CCD are fully cleared out.
Step 2 On receipt of a start acquisition command the CCD stops the Keep Clean Cycle and an acquisition begins. The image builds up in
the Image area of the CCD until the exposure time has elapsed, at which point the read-out process starts.
Step 3 The rst phase of this process is to quickly shift the charge built up in the Image area into the Storage area. The time required to move
the charge into the Storage area is the same as in Frame Transfer mode.
Step 4 With the image now in the Storage area the captured image is read out. The time taken to read out the image is again the same as in
the Frame Transfer mode.
Step 5 On completion of the read-out, the CCD is completely cleared, ready to acquire the next image. The CCD will remain in the Keep
Clean Cycle until the end of the accumulation or kinetic cycle time, depending on the acquisition mode, i.e. back to Step 1. As at least
one Keep Clean Cycle is performed between each exposure, the minimum exposure time is no longer set by the time to read out the
image.
Figure 23: Capture
sequence (NFT mode)
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