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Thread: New toy: Spectroradiometer

  1. #1
    Join Date
    Aug 2006
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    Default New toy: Spectroradiometer

    Got another toy a couple months ago but due to getting the software I had not been able to play with it. Finally the Tech at Gamma Scientific was able to get me the right software for the machine.

    Its a Gamma Scientific Radoma Spectroradiometer. Its a little different than normal spectrometers where it can be calibrated to measure intensity of light as well as the spectrum for analyzing things like cockpit displays to meet federal display guidelines. It also has a whole bunch of math routines and can figure things like color temperature and the like.

    My plan is to use it to figure my tooling factor when I finally get around to making dielectric coatings in my vacuum system. The way that works is you pick a wavelength you want a filter for and make it. Measure the actual bandpass wavelength and use this info to correct the layer thicknesses for the filter.

    This is the unit, A Gamma Scientific GS-1271 interface and GS-1251 Head with a RS-22 175w Xenon light source


    Gamma Scientific Radoma Spectroradiometer by macona, on Flickr

    This is a spectrum plot of a mercury-argon UV lamp. You can see the mercury lines on the left and the argon lines on the right. At turn-on the peaks are about the same but as the lamp warms out the mercury lines are quickly overshadowed.


    Hg-Ar lamp, warm by macona, on Flickr

  2. #2
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    Making your own dichroic filters is going to be a real exercise in film thickness control. Good luck. I will be very interested to see how it works out.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  3. #3
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    I have a nice Sycon film thickness deposition controller. Uses the standard 6MHz quartz discs to detect deposition down to the angstrom. Still have some work to do, like building the sputter guns. I know a professor at Portland State and he gave me the drawings of the ones they are building so I am going to build a set for myself. Still waiting for details on a couple things. But for now I can do thermal deposition with what I have set up.

  4. #4
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    The main problem isn't controlling average thickness. It's controlling point thickness to be within a very narrow range over the entire area. That is an area where Xerox owns a huge portfolio of patents, many expired by now. They were the first to lay down very large area tightly controlled semiconductor films. Some of them were about 8 to 10 square feet of selenium on a flexible nickel substrate with a bend radius of a couple of inches. They now use semiconducter polymer films.

    With the films Xerox made the absolute thickness wasn't so important as the very well controlled uniformity of thickness over the entire area. For a filter both matter of course. Uniformity is the very hard part.
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  5. #5
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    I see what you are saying. I am just doing small optics up to maybe 2" so there is not a whole lot to worry about, especially if I am doing one at a time. For multiples they make planetaries that move around the chamber to get an even coating.

    Though, making some nice Hydrogen alpha filters for solar viewing could be neat, those would be bigger than the 2" filters I am thinking of.

  6. #6
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    Does one have to calibrate it, I suppose so, in which case i would bet that standards would cost a bit!, looks like an interesting bit of kit to play with, lol
    regards
    mark

  7. #7
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    Making hydrogen alpha filters will require uniformity and absolute thickness control to about 0.1 nanometre at least. If you can do that you have at least one customer.
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  8. #8
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    Quote Originally Posted by Evan
    Making hydrogen alpha filters will require uniformity and absolute thickness control to about 0.1 nanometre at least. If you can do that you have at least one customer.
    Make that 2 customers!

    Your onto a very exciting field of Physics.

    Tom M.

  9. #9
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    Cool stuff. You doing these coating for work or play?

  10. #10
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    I'm an optometrist. Our optics prof was a gold mine of interesting stuff. He said in the old days, they did the antireflective coatings just by eye. "Hey Bob, turn it off. It looks about right..."

    doug

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