Re: [ATM] webcam and foucault test?

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

Jeff Rowe wrote:


> .... To me it seems like the really weak
> link in this approach is the imaging lens. Could the cheesy lenses that
> come with webcams or the non flat field mini scopes that are added to
> testers be the source of  less than desirable results?

The light that is of interest passes *very* close to the KE, and if the lens
is not too far from it, and only a very small central portion is used -
unlike the expensive well corrected lenses that need as large light opening
as possible. And with this in mind, I don't believe a flat field will make
much difference, and I imagine a simple achromat will do well. Assume you
have a f/4 mirror, it will subtend an angle of 1/8, and if your chip has say
1/4 in. side, you could use a 50 mm f.l. lens to fill the chip with light!
Remember, you could use a fixed camera/KE and a moving light, as well as the
more common opposite.

Nils Olof


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