I am assembling a project wherein I will be using a full spectrum camera that captures from around 250nm on up into infrared. My goal is to primarily work within the lower wavelength (ultraviolet) / higher energy portion of the spectrum from 400nm down to 250nm, which is the lower bound on this camera.
I have been trying to find a filter (specifically a 37mm filter) that would limit this so that I could primarily work down in the lower wavelength, but I have really been at a loss thus far.
How would one go about either constructing or finding some kind of a UV pass filter such as this that has a higher range rather than highly specific wavelength parameters?
UV-pass filters are commercially available. Just a quick look in Amazon found 52mm UV Black #403 Glass Filter for Type "A" Ultra Violet Transmission and B&H Photo has Rosco Permacolor Glass UV Pass Woods-type Filter - 2" Round. Edmund Optics has pages of glass filters.
It will take some work to find one with acceptable transmission in the bands you want, and you might need to use sapphire for short-wave UV, rather than glass. If you do not find a 37 mm filter, you can use adapter rings or a filter holder (the Amazon filter is 52 mm).
I found that I was having a problem finding this initially due to my lack of full understanding of what the filter would accomplish and some missing terminology. Ultimately I did end up finding a pre-built lens that accomplishes my goals quite well.
There are two filters actually that would do the trick. One is a UV pass filter and the other is a UV + IR pass filter. The latter ends up actually serving my needs a little better and has the following wavelength filtering characteristics:
I found the second XNiteUVR a little more to my liking due to passing through both the UV and the IR around the visible portion of the spectrum.
Additionally this is available as a 37mm lens and was thrilled to see that they have reasonable prices on their order page.