Re: ISO 200000 ?

In article <h%Izf.3828$wl.2955@xxxxxxxxxxxxxxxxxxxxxxxxxx>, David J Taylor <david-taylor@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> writes
Roger N. Clark (change username to rnclark) wrote:
Kennedy McEwen wrote: 
In article <43CE5538.80704@xxxxxxxxx>, "Roger N. Clark (change
username to rnclark)" <username@xxxxxxxxx> writes


Guys,

You are both right in your respective fields.  I was involved in
night-vision work some years ago, and the devices Kennedy is describing do
not have to be used with additional IR illuminators - natural lighting
only can be just as effective.

I would like to get a clearer understanding, though, of why the devices
work as they do, and how the "photon-limited performance" is apparently
bettered.

It isn't bettered, David, it is just that the useful photon limit is well below the level that Roger is suggesting. Useful images can be produced when less than one photon per pixel per frame is collected.

Are you, Kennedy, saying that there is effectively a noiseless
amplification of the light before it is turned into electrons?


Not in these devices.

The other point I wonder about is, when using these devices, how much is
the integration of the eye affecting the results.  Kennedy mentioned
taking a single frame of 1/50s exposure under overcast starlight
conditions.  (It would be interesting to see such an image - can you post
anything?).

Unfortunately, due to the use we put these to, I cannot make anything publicly available. However, if you go to the E2V web site and register with them you will be able to access all of the data sheets for available devices and technical application notes, some of which contain sample images. You can also view a range of video sequences from them some of which we made. Not all are under low light conditions, because the videos demonstrate different features of the technology as compared to competitive alternatives. For example, conventional intensifiers bloom badly in the presence of light sources - so some sequences demonstrate that the E2V does not suffer such problems.

 When used for night vision, is the eye integrating several
frames to be able to make out the content?

Yes, and this is why sub-photon per pixel per frame operation is not only possible, but highly useful, and why Roger's limit is wrong.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
.

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