Choose only invisible UV radiation from the diode?

Question

Do it yourself

Good afternoon. Are there any ways to select only the invisible part of the ~400nm LED radiation?
I understand correctly that the LED still emits some region of the spectrum, and not one wave?
Interested in what reflectors or absorbers. And if you propose to decompose into a spectrum and choose only what you need, then tell me where to find a small and transparent prism for UV rays) the thickness is of the order of a gel ampoule and the length is a couple cm.

Answer 1

Yes, an ordinary LED emits in the +- range from that stated in the passport.
You can try using a normal UV filter, but it won't do you much good - you need a specialized filter if you only need a certain range.
Why not use a UV laser? The range of generated radiation from lasers is usually narrower and the peak falls at a certain wavelength.

Answer 2

The lower (along the wavelength) boundary of the visible spectrum is, firstly, individual, and secondly, it depends on the intensity of the flux.
Absolute insensitivity - if you shine, say, a couple of milliwatts directly into the eye - it can start somewhere below 300 nm. Here already without mercury lamps in any way.
Whichever of the diodes you use, you need to think about the optical design so that direct radiation or possible glare does not fall into the field of view. So you can achieve acceptable secrecy.
Look on Chinese sites for indicators of the authenticity of currencies, similar to those used in exchangers.

Answer 3

I still do not understand what wavelength range you need? And in general, what parameters are needed in addition to the spectrum? It is best if you describe the problem you want to solve. Filters can be viewed here , here and here . In addition to a prism, a diffraction grating can be used for decomposition into a spectrum.

Answer 4

In a supposedly ultraviolet LED with a spectrum peak of 400 nm, all radiation is perfectly visible. Even the radiation of a nitrogen laser is visible with a direct hit. It looks like white light.