Backlit sensors
in [Digital Cameras]
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From: Martin Brown on 9 Mar 2010 04:46 Alfred Molon wrote: > In article <hn013e$1f7$1(a)news.eternal-september.org>, david- > taylor(a)blueyonder.co.uk.invalid says... > >> Yes. more light, but other problems caused by back-illumination, so >> there's a trade-off point where the problems caused by back-lighting are >> less than than the gains, and when that's reached, backlit sensors become >> a better choice. > > What other problems are you referring to? The main one for single shot colour is that for a front illuminated Bayer mask CCD the electronics structures help to prevent cross talk between adjacent pixels. When the CCD is back illuminated there is nothing in the way of stray photons at oblique angles. This gets trickier at short focal lengths with fast lenses. It doesn't matter so much for monochromatic scientific imaging systems as they are almost always oversampled anyway. But it does matter a lot when the adjacent channel is through a different colour filter. The astonishing thing remains that they can do this at all at a price and quality where consumer grade equipment can be made with them. Regards, Martin Brown
From: Alfred Molon on 9 Mar 2010 14:05 In article <KNoln.36306$_v6.14355(a)newsfe08.iad>, |||newspam|||@nezumi.demon.co.uk says... > The main one for single shot colour is that for a front illuminated > Bayer mask CCD the electronics structures help to prevent cross talk > between adjacent pixels. When the CCD is back illuminated there is > nothing in the way of stray photons at oblique angles. This gets > trickier at short focal lengths with fast lenses. I would have assumed that this is a non-issue, since the colour filters are directly on the imager, not far away from it. In any case, do you have any references for this for further reading? -- Alfred Molon ------------------------------ Olympus E-series DSLRs and micro 4/3 forum at http://tech.groups.yahoo.com/group/MyOlympus/ http://myolympus.org/ photo sharing site
From: Martin Brown on 10 Mar 2010 02:48 Alfred Molon wrote: > In article <KNoln.36306$_v6.14355(a)newsfe08.iad>, > |||newspam|||@nezumi.demon.co.uk says... > >> The main one for single shot colour is that for a front illuminated >> Bayer mask CCD the electronics structures help to prevent cross talk >> between adjacent pixels. When the CCD is back illuminated there is >> nothing in the way of stray photons at oblique angles. This gets >> trickier at short focal lengths with fast lenses. > > I would have assumed that this is a non-issue, since the colour filters > are directly on the imager, not far away from it. In any case, do you > have any references for this for further reading? You will have to look in the patent literature for details. I don't think there are any articles at all about the backlit Sony design apart from the ones already discussed. There is a nice article about colour imaging which doesn't get that far but otherwise has a lot of other good stuff. http://www.technologysupplies.co.uk/rapmankit.htm http://white.stanford.edu/~brian/psy221/reader/Wandell.Color%20Reproduction.pdf (and references therein) Regards, Martin Brown
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