Re: ATM Foucault test accuracy

["James W. Burrows" <burrjaw@halcyon.com>]

At 19:12 2001-06-09 -0700, Michael Spooner wrote:

>Perhaps we should pay a bit
>more attention to our testing circumstances and the effects of a varied
>background illumination (and one sided knife edge glare) on separated
>contrast comparisons. Food for thought anyway.

The mask should cover the whole mirror and be illuminated with standard 
interior brightness (10 millilambert).  Darker than this reduces the eye's 
contrast sensitivity.  Also the source should be sufficiently bright that 
the return from a fully illuminated mask hole is as bright as that or brighter.

Ref.:  W. J. Smith, "Modern Optical Engineering", p. 109.

         -- Jim Burrows  phone 206.244.2933, fax .0294
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