Re: [ATM] ATM chinese puzzler

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

I likewise thought that the testing device in the
'chinese fan' was a ronchi grating with a simple LED.
It shows, however, how poor the quality controls
actually are, and why those mirrors are sometimes good
and sometimes not. Amazing that the tester would not
write down or even orally transmit any specific
criticism of the offending mirrors, and that the
glass-pushers themselves had no way of independently
testing the optics they were working on. Or so my
source tells me.

Guy

--- Bob May <bobmay@nethere.com> wrote:
> I've done the Ronchi test with my portable Ronchi
> tester and yes, it can be
> done!
> The thing here is that as you move along the ROC of
> the mirror, the lines do
> show up and, quite supprisingly, you can see a lot
> of detail in the moving
> lines that you don't see in a stationary set of
> lines with ease.
> It does take a steady hand and a quick eye  but I'd
> not be supprised that
> somebody used to the system wouldn't have any real
> trouble seeing 1/4 wave
> accuracy on a production line of mirrors.  He's
> going to be seeing the same
> set of lines each time and having a reference mirror
> available will allow
> him to quickly reinforce the proper shape of the
> lines.
> Bob May
> http://nav.to/bobmay
> bobmay@nethere.com
> NEW! http://bobmay.astronomy.net
> 
> 
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> ATM mailing list http://www.atmlist.net/


=====
Guy  BrandenburgWashington, DChttp://home.earthlink.net/~gfbranden/GFB_Home_Page.html

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