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prathmesh

DIY Fourier Transform Spectrometer in Visible range

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I want to make an Fourier Transform Spectrometer in the visible range. I am having problems with finding a proper linear stage.

The wavelength range is 400-1100nm, which makes out the smallest resolution and accuracy should be better than 150nm.

The wavelength resolution at 1100nm should be 1nm, which works out the track length to be greather than 2mm.

The system f# makes that the mirror should be of 50mm size, which makes its weight to be 50g.

I don't want to get into the argument that a dispersive system is better. I know that.

Please help me find a component which will help me displace 50g weight at a resolution of <150nm for a total track length of >2mm.

Thank you for your time.

 

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What's your budget? Thor labs have stepper stages they claim the min distance is 100nm.

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Ok, that's a reasonable sum. You should be able to get a decent stepper motor stage for that. My experience is with THz TDS rather than Fourier spectrometet, how repeatable do you need the position to be, is a min increment of 0.1um ok or do you need the reversible position accuracy to be similar?

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The resolution as well as bi directional repeatability and accuracy should be <0.15um. Just getting the resolution has no value if the true value is way off.

I am looking at some Piezo electric inertia actuators in Thorlabs (Thanks for that). Also Newport has some of those.

They are fulfilling my requirements.

 

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Newport would have been my second look. And given your reply I would have indeed pointed you towards piezo devices.

 

Good luck and let us know how it goes. I love spectrometers. Just a shame I don't get to play with them anymore.

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There are sound reasons why there are few, if any, FT uv/vis machines on the market.

Essentially, you don't gain anything from it, and the mechanics are more difficult.

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Have you guys ever made one?

@John Cuthber: do you know the major issues which will be faced while making one? Or any mistakes which I could make...

One more question, which kind of beam splitter can I use?

I want it to be :

polarisation insensitive

clear aperture: >38mm

Reflection/Transmisison=50%/50%

wavelength range=(less than 400nm) to (greater than 1100nm)

 

I zeroed in on https://www.thorlabs.com/thorproduct.cfm?partnumber=BSW27

 

are there any better options I might have missed, or a type of beam splitter I should rather look into.

There are also these cube beam splitters which could also do the job, but I don't know how they compare with plate beam splitters.

Thanks for your time guys.

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I get that the fellgate advantage will be missed. Most of our work is in the 400-700nm range.

Also we already have a grating based spectrometer so...

Mostly, I just want to explore FTS technology while still making some use out of it.

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