The Quattro Sensor and Luma

Started Jul 18, 2014 | Discussions thread
OP xpatUSA Forum Pro • Posts: 24,778
Re: Response Spreadsheet and Curves Posted

Eric Fossum wrote:

xpatUSA wrote:

Eric, as a CMOS luminary, is there some good reason as to why Foveon did not 'quad' the middle layer instead of the blue?

Yes.

First, just making contact to four middle layer photodetectors while keeping the top layer large is a difficult layout issue eventually leading to low fill factor.

Understood.

Second, accomplishing complete charge transfer for the middle layers is much more difficult than for the top layer. Complete charge transfer is needed for low noise and low lag. Of course the middle and bottom layers of the quattro don't have complete charge transfer now, anyway, nor do any layers of previous X3 incarnations.

Had to Google "complete charge transfer" (blush icon) and first up was a Merrill patent which you might find interesting:

https://www.google.com/patents/US7132724

The way they did the quattro is an interesting response to pixel-shrink pressure from competitors and is a compromise between X3 and single layer systems. But, now interpolation of sorts is required to determine RGB at all pixel locations.

Yes, I am a purist myself, preferring fat to thin although I have recently ventured (again) into the SD14 zone - 7.8um pitch. Curiously, the Quattro top layer has the same pitch as my 12MP m4/3.

With quattro they also got to use a pinned photodiode on top for lower noise and better performance. Of course, that means they now infringe Caltech (my) patents and if they actually made any real money, they would need to pay up just like everyone else has.

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Cheers,
Ted

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