UV light diffusion?

[kit1980]

Is it possible to (easily) diffuse light for reflected UV-induced fluorescence?
Is it even needed or helpful if there is no visible light leak from the UV source?

[enricosavazzi]

Is it possible to (easily) diffuse light for reflected UV-induced fluorescence?
Is it even needed or helpful if there is no visible light leak from the UV source?

Depending on the wavelength range in which you are interested, it is both possible and easy. The easiest way is probably to get a UV-grade transparent acrylic sheet (the type certified for suntanning beds) and sand one or both surfaces. If you need a very good diffusion, use two sanded sheets spaced apart by a few cm. UV-grade acrylic transmits UVA and at least part of UVB.

If you need shorter wavelengths, you can sand a fused silica sheet. This material is more expensive, and sanding requires really hard abrasives like silicon carbide. This transmits very well down to 180-200 nm. It is overkill if you only need UVA.

Another way is to use a reflecting diffuser instead of a transmitting diffuser. Instead of directly illuminating the subject through a transmitting fiffuser, boounce the UV off a sanded or embossed aluminium sheet. This material is one of the best UV reflectors (as long as it is not coated, painted or anodized), effective down to 200 nm.

Edit - As far as whether it is necessary, this depends on the type of subject. Basically, if the subject would require diffusion (as opposed to direct illumination from a point-source of radiation) in the VIS, it will likely require diffusion also in the UV.