I was walking around a hotel gift shop when I noticed a plain rectangular UV fixture. Actually I first noticed that a lot of items in the area were fluorescing and I had to really hunt to find the source of the UV light. It turned out to be this rectangular box with a flat Woods Glass filter in front of it and no discernible visible light emanating from it! The only thing that was glowing on the lamp itself was a few specks of lint on the glass. Wow. I have never seen a UV filter that good before. The cutoff curve must look like a brick wall.
The nameplate on the back of the lamp said Spectrachrome Model 93LIGHTB, Lamp 4-36w-PL. It was apparently built for demonstrating a brand of of t-shirts and jewelry featuring photochromic inks that change color in sunlight.
I held my cell camera up to the lamp and 'lo and behold, I could then see the bulbs. They appear to be a set of 4 BL-style "bug zapper" style bulbs. I was also surprised to find that my cell camera had some sensitivity beyond 370nm.
Finally got around to uploading some pictures of this lightbox. I wish these were available to the public but they appear to be a custom build. Because the cellphone camera has sensitivity into the UV range, the bulbs are clearly visible, but to the naked eye this lightbox emits no visible light whatsoever.
Last edited by PhotonWrangler; 05-30-2011 at 02:57 PM.