Posted by Ernie Atkins on August 14, 2008 at 10:42 PM
This may be a useful technique for very small pixel sensors because it eliminates the loss of response (fill factor reduction) which is especially problematic for small pixels. However, sensors in pro cameras have pixels as much as 20x larger than those used on the Sony camcorder chip and thus don't suffer anywhere near the response loss due to fill factor concerns of conventional (front illuminated) CMOS sensors. I wouldn't expect to see this in anything but p&s still cameras which also use very small sensors.
The Foveon chip with it's novel technique for color capture would be a real benefit for pro cameras and I would expect to see Nikon/Canon transition towards that approach for pre & prosumer cameras. But .... there may be issues that would prohibit that transition ... time will tell.
Ernie
Posted by David Bostedo on August 15, 2008 at 12:26 AM
Ernie - Can you explain "the response loss due to fill factor concerns of conventional (front illuminated) CMOS sensors"? I design chips for a living, but I don't have much experience with sensors. Is there a lot more circuitry in the camcorder type sensors that would create a smaller pixel area-to-circuit area ratio?
Seems to me this could be a good approach for any sensor depending on the fab process used to create the photo sites and how large they can be. It would certainly allow you to optimize the light gathering area. I wonder what kind of process they use on the backside too, and if they have to thin it or treat it somehow to create the necessary clarity and attach the films and micro lenses.
The Foveon approach, from what I can tell, has its own difficulties, mainly with the stacked color filters, and getting a clean separation of wavelengths through all three layers. I think that's why it hasn't caught on more.
Discussion
2 replieshttp://www.studiodaily.com/hdstudio/production/9805.html
The Foveon chip with it's novel technique for color capture would be a real benefit for pro cameras and I would expect to see Nikon/Canon transition towards that approach for pre & prosumer cameras. But .... there may be issues that would prohibit that transition ... time will tell.
Ernie
Seems to me this could be a good approach for any sensor depending on the fab process used to create the photo sites and how large they can be. It would certainly allow you to optimize the light gathering area. I wonder what kind of process they use on the backside too, and if they have to thin it or treat it somehow to create the necessary clarity and attach the films and micro lenses.
The Foveon approach, from what I can tell, has its own difficulties, mainly with the stacked color filters, and getting a clean separation of wavelengths through all three layers. I think that's why it hasn't caught on more.