Some of the new uv LEDs exhibit very little visible light and would be less likely to cause unwanted visible response (due to excitation wavelengths) on a camera. Of course, certain plastics used over a CRT face could also block this same uv.
I'm working with some 365 nm LEDs right now that could give one a "sun" tan! Of course, these newer-model ones are surface mount. I wonder if ceramic bars could be improvised for use as a heat-sinking mount?
mescalero