Now for a third company with unique technology out of the sensor business - Foveon. For those of you unfamiliar with Foveon, they started out to build three-chip, prism-based color cameras with custom CMOS sensors. When this market was discovered to be way too small, they acquired Dick Merrill and his inventions from National Semiconductor and developed sensors with stacked RGB photodiodes in which the silicon itself provided color separation. These were intended for DSLRs, then point-and-shoot cameras and then mobile phones. Didn't happen so, eventually, their only photographic customer, Sigma Photo, bought the assets for about 10 cents on the dollar and moved the work to Japan. Full disclosure - I sold Foveon sensors in the non-photo markets for about 10 years. Aside from Sigma, the only enduring legacy is the F13 on the ESA ExoMARS rover (now scheduled for an October 2028 launch).
Hi Dave, thanks for sharing the Foveon documentation.
ReplyDeleteThis is really a very interesting technology (despite of a few shortcomings) where the characteristics of silicon are being used to detect colour. It looks pretty straight forward, but the pixels are nice examples of clever design and lay-out. Unfortunately Foveon never mentioned that the basics of this technology were developed by someone else, namely Reinoud Wolffenbuttel. He developed the colour detection in silicon by 3 stacked photodiodes long before Foveon started with their X3 technology. Wolffenbuttel wrote a PhD thesis about his work (1988, Delft University of Technology, Delft, the Netherlands). The work of Wolffenbuttel was based on a single pixel, Foveon of course made complete arrays out of it.
Hi, Albert. if you can send me a link to the Wolffenbuttel thesis, I'll put it in the technology folder. There was also a two-layer CCD made by Kodak but I can't find the paper now. After Foveon, several companies tried making stacked-photodiode devices but none that I know of ever went on the market. Sigma has tried for new structures at least twice over the last few years then described their failures in detail.
ReplyDeleteHere is the link of his thesis:
ReplyDeletehttps://repository.tudelft.nl/islandora/object/uuid:03bb6f7e-0a52-439b-ab32-c95e90e9884b
I made a prior art folder under Foveon/Technology and put it there along with patents from Kodak and Xerox on multilayer CCDs. If I remember correctly, Kodak made a two-layer CCD work but no one ever succeeded in three layers.
DeleteHi, Dave
DeleteIs this patent a two-layer CCD work you remember?
https://patents.google.com/patent/US7423681B2
Here are patents related to Feveon. They were, however, filed later to Kodak 895 patent.
https://patents.google.com/patent/US4214264A
https://patents.google.com/patent/US4438455A
https://patents.google.com/patent/US4514755A
The story I heard (which was from a Kodak engineer) was that they had figured out what to do to make a three-layer device and patented it (probably the 895 patent) but they were never able to fabricate more than two working layers. This apparently had to do with running out of voltage while preserving enough well capacity.
Delete