There are some special adaptations of frame-transfer devices, shown in Frame Transfer Variations.
Frame Transfer Variations
Standard frame transfer
Image 
Storage
High-Speed Framing The frame transfer concept can be extended to multiple frames by masking most of the parallel register and using only a small region as the image array. A scene is focused on the image array and a high-speed shutter or strobe light is used to time the exposure. After each exposure, charge from the image array is quickly shifted under the mask and a new image can be acquired. Once the parallel register is filled with images, it is read out.
Because fewer rows are clocked to shift the image array into storage, this mode works much faster than standard frame transfer.
The high-speed framing rate need not be constant, but may be varied in response to the needs of the observation being made. High-speed spectra of a decaying phosphor, for example, may be obtained with decreasing time resolution in response to the exponential decay time of the emitted light.
Spectral Framing In a mode particularly suited for spectroscopy, the CCD is masked so that only a single row of the parallel register is exposed. In this mode, one-dimensional line images can be acquired at a very high speed until the parallel register is filled up.
Spectral-framing CCDs are used in time-resolved spectroscopy. An observation could consist of hundreds of individual spectra, distributed over time. The CCD clocks are controlled by computer, so non-linear time bases are possible.
Interline Transfer The interline-transfer CCD has a parallel register that has been subdivided so that the masked storage area fits between columns of exposed pixels. The electronic image accumulates in the exposed area of the parallel register, just as it does in the frame-transfer CCD. At readout, the entire image is shifted under the interline mask. The masked pixels are read out in a fashion similar to the full-frame CCD.
To enhance the interline transfer CCD's sensitivity, micro lenses are applied directly to the CCD's surface. The micro lenses cover the entire pixel and part of the mask on either side of the pixel. In this way, the micro lenses help to focus light to the CCD's parallel register by funneling photons to active pixels rather than allowing them to bounce off of the masks.
36Advanced Camera Operation Manual
