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Good day Gentlemen,
Just a bit of personal experience with CCD sensors. Late in 1985, Ampex (where i was working back then) sold the entire Betacam range of products.
Sony was afraid of Matsushita, a much bigger company, and sought allies to make Betacam the ENG (Electronic News Gathering) standard. They therefore signed alliances with Ampex (USA), Thomson (France) and Bosch-Fernseh (Germany).
Several times i got frantic calls from customers commenting that their CCD camera had suddenly developed a rash of black or white permanent pixels and were therefore unfit for Broadcast use.
This is how we learned that Sony had in the UK a production line machine which would read the CCDs pixel by pixel, then reprogram a ROM mask which contained all the addresses of the "no good" pixels. This was a duplicate of a machine in the Japan OEM factory, and Sony was pretty "hush-hush" about its existence.
Apparently under certain conditions, heat being one of the them, the ROM would loose its memory and the defective pixels would appear. We would send them the optical prism block containing the 3 x CCDs factory-cemented to it (positioned to half a micron precision in the X/Y/Z directions) and would get it back a couple of weeks later producing again a perfect picture.
It would be interesting to know if the same scheme is still used today or if CCD production techniques have reached such a high level of quality that it is no longer necessary. Personally i think it's still used; getting 1920 x 1080 perfect pixels with a near 100% yield is a tall order to achieve, even today.
and oh by the way, a spare prism with 3 CCD sensors was US $16,000 back then...
Best Regards
jhalphen
Paris/France
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