Advantages of Foveon sensor Locked

Started Jun 23, 2013 | Discussions thread
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bobn2
Forum ProPosts: 29,031
Re: There is at least one absolute, and you refuse it.
In reply to xpatUSA, Jun 23, 2013

xpatUSA wrote:

Bobn2 wrote:

xpatUSA wrote:

We seem to be forgetting Quantum Efficiency (QE) in this thread. QE is the measure of how many photons get converted to electrons and are thereby detected in the sensitive parts (diffusion zones) of the sensor. Most of the photons are not detected and many pass all the way through the silicon and exit unimpeded from the back of the slab.

That would make the silicon transparent, which it is not.

Such a statement can not be made without reference to wavelength or a spectral distribution thereof.

Certainly, I was assuming visible light, between about 0.45 and 0.75 μm, where as you see from your graph the transmission is zero.

The conversion rate for photons to free electrons is in fact pretty good in most silicon sensors. The problem is how much of that electron charge makes its way to the gates of the pixel source follower transistors. That depends on the right electric field patterns to transport those electrons to the gates. The ones that don't find their way to the gates in the end find their way to a 'hole', releasing the original photon energy as heat.

What is "pretty good"? Any references that define it?

Yes, but not to hand - in the 90%'s.

What is an "electric field pattern"?

The shape of an electric field. It's defined in a MOS sensor mostly by the doping profile (in a CCD by electrode potentials).

One of the reason for the Foveon's low QE is the difficulty in engineering the electric fields to ensure the collection of all the electrons.

The impression I get from this member's response is that he has read about optics but perhaps has yet to understand fully, based on his use of rather unusual descriptive phraseology.

Which member? If the member is me, I have said nothing about optics in the above, so if the 'phraseology' is unusual for optics it is not surprising.

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Bob

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