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The Conversion Subsystem (CAD) consists of a small number (4 for
NICMOS3 and Hawaii) of analog to digital converters and some glue logic.
There are a small part of approach we are considering for the CAD,
and we can choose the best fit for each application.
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- 16 bits conversion
- This is the standard approach. It is well suited for
medium velocity applications (around .5Mhz per channel).
- 14 bits conversion
- This new approach proves successfully in fast (speckle)
instruments. It uses fast 14 bit converters to digitize each
pixel many times (4-16) and then apply a fast digital filter.
This approach appeares best suited for slower data rates at
low noise (less than 250Khz), and faster rates at a reduced
resolution.
- 1 Bit conversion
- This approach is suited for very fast (more than 16Mhz)
photon counting mode of L3CCD Marconi detectors.
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