At 12:22 PM +0000 10/28/02, olympus-digest wrote:
>Date: Sun, 27 Oct 2002 15:56:30 -0800
>From: Winsor Crosby <wincros@xxxxxxxxxxxxx>
>Subject: Re: [OM] Kodak's 14MP SLR
>
> >
> >Winsor,
> > It should be very approximately 3 time better for Foveon,
> >because the normal Beyer pattern reduces the area per colored pixel
> >by approximately 3, while the Foveon chip does not. (stacked
> >vertically rather than horitontally) This means if the depth of the
> >pixel diffusion layers in the case of Foveon, are the same as the
> >filter layer of a conventional chip the shading effect is greatly
> >reduced. The lateral angle of acceptance would be much greater
> >allowing wider angle lenses. It could be even better than this,
> >since the sensor pixel area is reduced still further by metalization
> >and interconnect between pixels on th chip surface. This added
> >overhead is probably greater for smaller pixels putting them even
> >deeper realtive to Foveon. One might guess the diffusions in
> >Foveon's chip are also thinner than an on-chip filter, improving
> >things further. In fact for the first layer there should be little
> >to no lat! eral effect. This means the sensitivity drop off with
> >lateral light rays is probably different for the three colors
> >leading to yet another variation in color sensitivity with extreme
> >wide angle lenses! This may be a negative for Foveon but given the
> >chip should work with much wider angle lenses to start with it is
> >probably still much better.
> >
> >Regards,
> >Tim Hughes
> >TimHughes@xxxxxxxx
>
>That is interesting and I am sure you are right, but I am not
>entirely convinced. If you put a recessed sensor in a chip and then
>create one 3 times as wide and 3 times as deep I am not sure that you
>have gained anything. Since the bigger sensor elements are probably
>thicker it is probably more than 3 times as deep.
>
>I looked at the Foveon site again and I really do not understand it.
>It seems to me that one would have to still filter the elements, but
>if you did the bottom two elements would get no light. They say they
>are using the silicon substrate essentially as a filter since
>different colors penetrate to different depths. Perhaps it is
>digital math. The top layer measures all the light. The second
>layer measures the red and the green, and the bottom layer measures
>just the red. Some subtraction and you get the values. So I guess the
>question is whether three transparent Foveon sensors and two silicon
>layers of the required filtering thickness is thicker than a single
>mosaic sensor and filter.
>- --
>Winsor Crosby
>Long Beach, California
>
Foveon's technology is patented. Search at the US Patent and Trademark
office's patent-search site <www.uspto.gov> for assignee="foveon" or
inventor="mead; carver" (the use of a semicolon is intentional).
Joe Gwinn
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