[RASMB] Dark interference fringe pattern

[Tom Laue]

Hi Arne-
My guess is that the bottom optical track is out of alignment and that 
you are looking at the first order diffraction image. Have your service 
man (or do it yourself) align the bottom track mirror (on the left hand 
end) to get the central envelop on your camera. You will then need to 
re-do the radial calibration. The total time to do this should be ~30 
minutes.
Best wishes,
Tom

Rufer, Arne wrote:
> Dear colleagues,
>  
> we recently encounter problems with the interference optical system on 
> our XLI (upgraded to Proteome Lab version) in that the fringe pattern 
> looks very dark (please see attached screenshots). Beckman field 
> service recommended to us to clean the lenses in the laser housing of 
> the monochomator arm (which we did paying attention to reinstall the 
> lens in the correct orientation) and to clean/exchange the filter 
> above the condensor lens. While intermittantly the brightness/contrast 
> of the fringe pattern improved, we are back to "very dark" after 
> trying to further clean things up. What remains also is a concentric 
> interference pattern superimposed to the expected fringes, which you 
> can see on the left side of the fringe patttern in the second screen 
> shot. This ghost pattern is also visible when we look at the scallop 
> position or an empty cell hole.
> Any suggestion as to how we can get our machine back to normal would 
> be greatly apprecieated.
>  
> Best regards,
>  
> Arne
>  
>  
>  
>  
>  
>  
>  
> Dr. Arne Rufer
> F. Hoffmann-La Roche AG
> PROBMO Optical Spectroscopy
> 065/207
> CH-4070 Basel
> Tel: 0041-(0)61-6882126
> arne.rufer at roche.com <mailto:arne.rufer at roche.com>
>  
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-- 
Department of Biochemistry and Molecular Biology
University of New Hampshire
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Phone: 603-862-2459
FAX:   603-862-0031
E-mail: Tom.Laue at unh.edu
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