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OtterVIS LGL spectrophotometer

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A super cheap decently resolving open source VIS-spectrophotometer. The cheapest in the OtterVIS line.

Discussions

Jarral Ryter wrote 01/30/2018 at 23:15 point

I took apart a simple spectrometer from vernier.com that we use in our labs to see how it was put together. they just used simple plastic lenses. they look like miniature Fresnel lenses. And they just slip into slots along with the grating. Seems to give pretty good resolution. I think this will be a fun project to for our computer and our chemistry students! fun project.

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esben rossel wrote 01/31/2018 at 05:25 point

interesting. we have those at work too, I always suspected they were as cheap on the inside as they look on the outside, but I never tried to disassemble one. that said, they do a fair job between A=0.2 and A=1.1

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B. A. Bryce wrote 06/13/2016 at 09:20 point

I guess I mean is there a reason it needed to be a double Gauss lens? Why not some achromatic doublet? etc. 

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esben rossel wrote 06/13/2016 at 09:51 point

You can do that for the collimating lens. I'm not sure an achromat is the better option for the imaging lens. I'm by no means an expert on optics, but if I remember correctly they're not particularly well corrected for spherical abberations.

On top of that achromats are expensive (at least the ones I could find are 10x the price of a standard 50mm double gauss camera lens), and the whole point in this project is to keep the price down.

On a side note, I use an achromat for collimating the light from an optical fiber in the Raman spectrometer I'm also constructing. The achromat fits inside an SM1 lens tube from Thorlabs and this makes for an easy-to-focus setup. 

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B. A. Bryce wrote 06/13/2016 at 08:02 point

What were the considerations in picking the lens to use?

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esben rossel wrote 06/13/2016 at 08:29 point

The focal length is given by the grating and the sensor size, but size, accessibilty and price vs quality were the big factors. 


I considered 50mm's from all the big brands ie. Nikon, Canon, Olympus, Pentax, Minolta, Konica - and some of the bigger 3rd party manufactureres. I didn't want anything that would be too difficult to find, and ebay is littered with cheap 50mm 1.7, 1.8, 2 lenses.


I leaned mostly toward Olympus because of the Zuiko lenses small size, but in the end I chose the pentax SMC-A 50/2 because I found a seller who had a small lot where the aperture ring was glued stuck - so I got them for 6£ each.

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