Re: [ATM] Star test with laser light sources

["Ray@J-Engineering.com" <Ray@J-Engineering.com>]

Mark,

Sorry, I used the wrong term.  Let me ask the question again.

I would guess, help me out here, that since we need to compare the 
brightness between the first and second *diffraction* rings, wider rings 
might make it easier to judge small differences in brightness?

Yes, we have been writing about what in-focus diffraction rings should 
look like when doing a start test with a laser source. Since we know 
that the monochromatic diffraction rings are narrow when compared to 
white light, I'm wondering if using monochromatic (includes LEDs and 
lasers) is less informative than the wider, more washed out appearance 
of white light rings.

Mark Suchting wrote:

> At 09:14 AM 7/28/2004 -0500, Ray@J-Engineering.com wrote:
>
>
>>  I would guess, help me out here, that since we need to compare the 
>> brightness between the first and second fresnel rings, wider rings 
>> might make it easier to judge small differences in brightness?
>
>
>  I was referring to studying in- focus diffraction rings ( first and 
> second ) . For a reasonable mirror, fresnel rings can tell you about 
> surface smoothness and seeing but not a lot else easily ( without some 
> sort of computer analysis )  . I know someone out there is using 
> software to deconvolve pictures of fresnel rings to measure wavefront.
> Snip...


Ray J

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