> The cost of a commercial digital back for a 4x5 camera
> is about $25k +/-.  I did some poking around Kodak's site for CCD's,
> but cost for quantity 1 is also outrageous.

But how big is the piece of silicon and how many defect free CCD's
do they get out of a wafer ? I don't know about the ones you were
looking at, but from memory, the larger Kodak CCD's are back
exposed. That means that they are gound very thin and all the
metalization for the circuitry is on the opposite side from the
sensing face, making them more sensitive and decreasing the pixel
to pixel gap.

> So I was just wondering
> if anyone could suggest a good starting point.

Most CCD's are setup so that you can continually clock them and
what comes out is close enough to a video signal that very little
conditioning is required to get a complete video signal. Obviously,
this is the most common use and where the biggest market is. To
turn that into a still camera requires no more than a frame grabber.
Further down the track, you are still going to want something along
the lines of a frame grabber as you'll want to get the data out of the
CCD fast, even though the exposure is long.

Back in the olden days the drive circuitry was a bit more discrete
than the CCD cameras available now. If you could get to the clock
signals before they got level shifted to suit the CCD, you could gate
them with a little bit of logic and get the long integration times
required for astrophotography.

> CCD to USB of some sort would be
> fun to do.

I'd probably skip the USB part for two reasons. Firstly they are
invariably color CCD's which use filters over the sensor which is
fine for webcams but pretty useless for astronomy.
Secondly, the camera end is very integrated and the circuitry is a
CCD, a ccd to video chip and a few passives. Very hard to hack
into.

 Looking for a CCD project that doesn't involve a huge
> chipset to implement that could be used as a learning stepping stone
> to a higher end color project for the camera. Also wanted to make it
> modular enough to use for astrophotography as well, but that's more
> opto-mechanical than EE.

Have you looked at Richard Berry's cookbook approach ?
There also used to be a group called Southwest Cryostatics (or
similar) that published a good set of design notes for an
astronomical CCD camera based on a Kodak CCD. That was back
in the mid-90's and CCD's have come a long way (down in price
hopefully) since then.

Steve.

======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: steveb@tla.co.nz      fax +64 9 820-1929
======================================================

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