Does it make sense to cool a scanner chip?

i was reading a lot of that cooling a scanner chip makes sense to

reach less noise in the scans. so the imacon 848 seems to be the same

machine than the 646, just with the difference that the chip is

aktively cooled. so isnt it possible to cool a ccd chip even if the

construction was manufactored without cooling? it should not be so

difficult to do this- with some cooling element which fits the chip

or a fan which is mounted over the chip.....could this be a way of

scanner tuning? does anyone have experience or advices about?

Seems like a good idea on the face of it. My fear is screwing up the the

camera or introducing vibration.

 

Then one would have to assume that the supporting electronics would

actually be up to processing the improved signal.

 

Scitex years ago were the first to get high performance out of a CCD. They

claimed it was the sophistication of the signal processing and the "trimming"

of the CCD.

 

I don't know how much of this was PR or if there are clues to the approach

one should take.

 

Good Luck.

Rainer,

 

Astrophotograpers use cooled CCD chips all the time, and kits and finished products are readily available for amatuers in that field. Those products cool CCDs as low as -20 F, but they are using exposure times of several minutes up to a few hours. In that situation, CCD cooling works extremely well.

 

But for shorter exposure times, CCD noise is not as pronounced compared to other CCD problems, particularly CCD signal bleed. So it is unclear how much that CCD cooling, by itself, has improved the 848. It would in theory tend to improve shadow details, but there seem to be no comments about any effect of cooling on the signal bleed problem.

 

Once when I tested some ASIC prototypes at -20 F, they quickly iced over because of condensation of atmospheric moisture. So if someone is going to cool a scanner sensor, the sensor has to be in a dry compartment where air born moisture can't get to it. Or, there has to be some other clever way to keep the sensor from fogging and icing over.

 

Some desk top scanners move the optics and sensor, and leave the film stationary during the scan process. For others, the film moves while the sensor and optics remain stationary. Perhaps scanners of the latter type would be easier to convert for cooling. CCD cooling might be done directly by a Peltier device, but due to space limitations within the scanner, an external design using circulating coolant might be more practical.

 

Someone who can easily afford to lose a scanner could possibly experiment with CCD cooling by just using a can of compressed refrigerant, a small length of flexible hose, and some duct tape. I suggets finding a scanner for around $200 or less to try this with. Then cool the CCD sensor as gradually as you can, and scan before fog and ice accumulate. This should be easier in a dry place like Arizona.

 

Rainer, would you please let us know if you develope or discover any practical scanner improvement techniques?

 

Cheers,

 

Charlie

One could solve the moisture problem with a couple packets of silica gel tossed on the bottom of the innards