I am trying to find a way to prepare optical filters without having to purchase them since they are considerably expensive. So, I've been wondering two options: either cast a transparent film of a polymer embedded with absorbing compounds, or attempt to enclose a saturated solution in between two transparent glasses, no air inside.
Would anyone with some experience in optics be able to tell me if these are completely insane ideas, or if they could actually work?
For example, imagine I wanted to filter out orange and red signals (roughly 590nm limit wavelenght). Would a frame of saturated methylene blue solution in the optical path work?
Many thanks in advance!
Rafael,
You certainly could produce a filter using the techniques you proposed. For example, large tanks of water were utilized to filter IR light from incandescent lights when illuminating a delicate sample.
However, you haven't stated your application. Intense light will degrade methylene blue, changing the filter's properties during use. Polymer filters (sometimes called 'gels') are used in theatrical and photographic applications routinely (e.g., Roscolux). Kodak Wratten filters provide more scientific grade versions.
Depending on your application, you may be able to use Wratten filters (or similar poly-films) or photographic filters. These are substantially less expensive than those designed for scientific use, although the specifications tend to be less precise.
Keep in mind that you'll spend time and money reinventing the perfect filter, so purchasing it may be a more efficient overall strategy.
r/
David
Dear David,
Thanks a lot for your answer!
My application would be fluorescence photography using a one-channel CCD. For color distinguishing (in the digital processing), I was hoping to have different photos using a set of different filters.
I already have a Kodak Wratten that cuts off everything below 500nm. We have ordered a red one too (not sure of the limit wavelenght).
Because of low-budget for this particular experiment, I was hoping I could improvise one that because of cutting yellow light out OR letting it pass, would allow me to subtract signal in a manner that would allow me to identify the spectral colors of one image in a relatively accurate way (of course, in ranges of wavelenght and never in single values).
Another option is using a DSLR with the 500nm long pass, but the sensitivity of the CCD I have is much greater and for this application I would benefit a lot from using it instead.
That being said, I will appreciate any further insight. Also, I will keep in mind your wise advice: reinventing something is equally time and money consuming.
Best regards
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