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 Post subject: Minimonochromator for advanced users
PostPosted: Wed Nov 02, 2011 11:00 am 
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http://www.ebay.com/itm/ws/eBayISAPI.dl ... 64327&rd=1

This is actually a very nice buy. You would need to get some tech info on the stepper motor which moves the grating. The manufacturer would probably provide this or they could sell you a plug and play driver.

Stepper drivers are available now practically free with tons of designs and circuits available on the internet.

Optometrics also has software but it might be more economical to just kludge something together from other sources. ( I can help)

This would be a project for someone like Brian or for Mikko who has the computer horsepower to make it work. Perhaps some others.

This mono has a single concave mirror and a pretty good sized grating. with a sensitive detector (which I certainly could help any buyers with) it would blow a fiber optic spectrometer right out of the water in terms of resolution and especially sensitivity since the optical channel is relatively massive compared to a fiber optic unit.

One thing it can't do compared to a fiber optic unit is take a synoptic spectrum as with a flash lamp or Laser Induced Breakdown Spectroscopy. It needs time to scan. You could install a ccd multi channel detector on its output if you wanted.

An excellent and very compact little goodie.


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 Post subject: Re: Minimonochromator for advanced users
PostPosted: Wed Nov 02, 2011 12:10 pm 
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Okay, I don't know what this is or what it does, but something did catch my eye: In the description it says "removed from a working optics lab". I wonder if that lab is wondering where it went?! 8)

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 Post subject: Re: Minimonochromator for advanced users
PostPosted: Wed Nov 02, 2011 12:43 pm 
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It is very interesting little box. I tried to find it's wavelength scale with no success.
It would be really interesting project to build excitation photoluminescence spectrometer for making distinction between flux/hydrothermal and natural rubies.

http://www.gem-a.com/publications/journal-of-gemmology/issues-2008-to-date/bidney-et-al-2010.aspx

edited: small typo

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 Post subject: Re: Minimonochromator for advanced users
PostPosted: Wed Nov 02, 2011 1:40 pm 
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It is an interesting little box. Of course, you have to supply your own photodetector, and you have to set up the stepper-motor and signal collection. Then there'd be all the calibration work.

As mikko notes, there is no information about the grating, so it is difficult to tell what wavelength range for which it is set up.

Checking the optometrics website, the resolution is only about 0.5 nm in visible range for 50 micron slit width. But you can get a lot of light through that wide a slit.

Alas, right now I'm thinking about a monochromator that has 0.005 nm resolution. That means the path length will have to be about 100x longer. That means more money.

But still, it would be an interesting project to get it working.


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 Post subject: Re: Minimonochromator for advanced users
PostPosted: Wed Nov 02, 2011 1:53 pm 
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I doubt there is any concern about it being missing. That is standard language I see on all kinds of gear auctions. I looked through the guys' feedback and saw a large number of people I know from ebay. People I have bought from and sold too. He has cool stuff. I saw no red flags. JMO YMMV

There is no wavelength scale. You have to calibrate it with your detector in position using some accurate line sources same as a fiber optic. Instead of pixel position you have stepper motor step numbers.

Probably this dealer could tell you some particulars either on the grating or what its original use might have been. I thought it said removed from equipment but maybe I was thinking of a different auction.


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 Post subject: Re: Minimonochromator for advanced users
PostPosted: Wed Nov 02, 2011 2:14 pm 
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Quote:
There is no wavelength scale. You have to calibrate it with your detector in position using some accurate line sources same as a fiber optic.


My limited english again... :oops:
I meant wavelength range (min & max wavelength & blaze). The ruby excitation application I was referring to needs a monochromator capable for 250-350nm scan. 0.5nm resolution is more than enough.

This G&G issue contains more information about the application in case someone else finds it interesting: http://lgdl.gia.edu/pdfs/grc_2006.pdf
Search pdf file with keyword Alexei

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 Post subject: Re: Minimonochromator for advanced users
PostPosted: Thu Nov 03, 2011 3:45 am 
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http://www.optometrics.com/monochromator.html

More than you ever wanted to know about these units including links to plug and play controllers and software($1600 too much) slits detectors etc.


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