Re: Is there a spectacles lens that can read invisible utraviolet ink?

Unfortunately, I think that you're probably out of luck!

I know of no commercially available product that can provide a permanent 
marking on an arbitrary surface.

The sort of thing that you're looking for would have to be transparent in 
the visible part of the spectrum, but absorb in the ultraviolet and 
fluoresce (i.e., emit wavelength-shifted light) in the near infrared or 
visible part of the spectrum.  While there are lots of organic dyes that 
have this property, most are not particularly amenable to use in durable 
inks -- they could easily be scraped or washed off with an appropriate 
solvent.  

A better solution would be to incorporate a long-lasting fluorescent 
material into your product.  The best way to do that would be to use a 
fluorescent solid material contained in a glassy matrix -- but 
unfortunately such procedures work well only in the case where the 
material is a ceramic or metal that's capable of withstanding the high 
temperatures needed to melt and fuse the glass matrix onto the product.  
Not knowing what your product is, it's hard to guess that it might work 
well.  In any case, the type of solid that might work well is likely to be 
one which contains either a rare earth oxide or possibly uranium...  in 
general, though, it would take a lot of tailoring by a skilled ceramicist 
and physical chemist to get the right combination of material properties 
to make the whole thing work.

In any case, using a fluorescent material would require that you have an 
unique illumination source (i.e., black light or UV light) and an 
appropriate viewer -- probably a filter and your eye or an extended UV 
intensifier -- to see it.  No simple lens would allow you to do what you 
want to do...

My best suggestion would be, if your material is a solid rather than a 
fabric, would be to incorporate a very small laser mark in an inobtrusive 
location on the part.  The size of laser marks can be very small -- less 
than a millimeter -- and you can include lots of data on the origin and 
type of article that exists.  In most cases, a casual observer would never 
observe the mark.  If you're dealing with a fabric, you might consider an 
inobtrusive watermark -- they may not be entirely permanent, but they're 
easy to apply and you can easily tell whether the article has been 
tampered with or altered.

Hope this helps!


Steve