Unlimited Dynamic Range

[iso rivolta]

I've got the same idea some time ago. More specific, clocking the overflow drains at individual pixel level. Of course, the circuitry must be more complex, but these type of gates already exist on many sensors, implemented mainly on CCDs for avoiding blooming artifacts. So, not like the CID sensors or the Samsung patent, where, even with nondestructive readings, dead times still exist. And for other types of sensors, the more readings method would introduce more noise. On the other hand, that would be nice - imagine live "light painting".

One possible mode of functioning for this proposed type of reading would be by storing the digital time values of reaching the full well at pixel level in a memory layer under the sensor. When all the pixels have reached that, the time value array is read. Of course, that would be for maximum quality, for tripod work and still scenes. But the sensor could also function in the normal way or in a more complex hybrid mode - after imposing a shutter speed, some photosites reach saturation, some not. Things are much more complicated, the threshold charge in the drain area is not just 1 electron and there will still be some "read" noise in the time values.
Some simplified tutorials on CCD blooming protection can be seen here:
http://www.olympusmicro.com/primer/digitalimaging/concepts/blooming.html
http://www.olympusmicro.com/primer/java/digitalimaging/ccd/blooming/index.html

 

[iso rivolta]

Seems to me that focusing on the sensor and on board processing to
control over exposure, wouldn't it be simpler to place the burden on
the lens? How about a coating that responds to overexposed areas and
reduces the transmission of that part of the picture.

The easiest optical way of increasing the captured dynamic range is by using low contrast lenses (like no or poorly coated old lenses, prone to flare) or by using flare inducing filters. With that in mind is designed the Tiffen Ultra Contrast filter, which is introducing a "fill light" flare for lifting dark areas, decreasing the highlights - shadows ratio. You can read here a discussion about this filter (with some samples): http://forums.dpreview.com/forums/readflat.asp?forum=1036&message=18085175&changemode=1