Violet laser used in a different application...

[ArdvarkOfDoom]

Ok... Completely random question.  I'm in the security field and I thought that it would be kinda cool to get a UV LED and make my own better looking and much cheaper counterfeit detector (can see the special logos on credit cards and driver's licenses as well as picking up special fibers in currency)... there's nothing special, it's just a led light... but with UV... Now here's the question...

Say you use one of the lower power diodes *ps3?* and have it run with no optics... would it act the same way as a lower powered laser where the light disperses?
(I.E.  This

 to this

)

Also... would it be powerful enough to show the "invisible markings" from close by?  I know the UV LEDs supposedly run 375 nm - 395 nm or so (some common ones I found from quick searching the other night) and the laser is ~405 nm... but that shouldn't be too far off to change the fluorescing characteristics.  Yes, it's probably completely overkill or just a waste.. but thought it would be a neat idea just for the hell of it.

 

[Helioplasma]

Re: Violet laser used in a different application..

It does work well on passports but not really much on ID cards.

 

[Switch]

Re: Violet laser used in a different application..

Yea it would work, and also I think only high end LEDs are ~375nm and cheap ones are higher and closer to 405nm.Of course diodes are not the same with each other either.I'd say it would fluoresce stuff at least as well as a LED, but some stuff on ID cards I haven't managed to make visible with LEDs or laser diodes.Only tubes seem to work on those,I guess they really need the lower wavelength. :-/

 

[ArdvarkOfDoom]

Re: Violet laser used in a different application..

Hmm... Yeah, I might need something closer to 375... but I've seen several "375 nm leds" on many mainstream sites used in "anti-counterfeit" pens... Oh well, thanks for the input guys

 

[Jimmymcjimthejim]

Re: Violet laser used in a different application..

The intense light of a 405nm laser will make it hard to notice the fluorescent markings, even if unfocused. Go with an ultraviolet LED.

 

[mikeeey]

Re: Violet laser used in a different application..

will a blu ray show the markings on a dollar bill that you can see under a black light?

 

[suiraM]

Re: Violet laser used in a different application..

Hmm... Yeah, I might need something closer to 375... but I've seen several "375 nm leds" on many mainstream sites used in "anti-counterfeit" pens... Oh well, thanks for the input guys

Blu-ray diodes have a wide sideband at lower wavelengths, especially at lower powers or lower temperatures.

At least, that's what my datasheets indicate. I haven't gotten around to checking the spectral response yet, due to unforeseen circumstances.

 

[suiraM]

Re: Violet laser used in a different application..

The intense light of a 405nm laser will make it hard to notice the fluorescent markings, even if unfocused. Go with an ultraviolet LED.  

The 405nm from a LED makes it hard to see fluorescence, too, at least for many folks. I don't have a problem with it, unless the fluorescence is in the bottom end of the blue-violet part of the spectrum, but I know my S.O. doesn't manage to see anything but the most pronounced responses. Pick up a pair of the 405nm goggles, and you shouldn't have a problem with it, I think.

 

[Switch]

Re: Violet laser used in a different application..

Yes I have a problem with this too, 405nm seems so bright to me, I need to really unfocus it to see watermarks on money.Maybe I got one of the "bluer" ones, but it seems a LOT brighter than my 16x that burns black tape better so I'll guess is actually more powerful.

 

[suiraM]

Re: Violet laser used in a different application..

I don't know about other people, but to me, the brightness and intensity seem seperate in my mind. If I point a 5mW green and a 5mW red at the same spot, the green will seem brighter, but no more intense. Similarly, with LEDs, the brightness depends on wavelength, but the intensity does not. A blackbody source through a diffraction grating appears to have almost constant intensity through the spectrum, but variable brightness. The Senkat seems far brighter than a 20mW green. In this sense, I have an odd feel for the power that seems distinct from the perceived brightness.

 

[Switch]

Re: Violet laser used in a different application..

What do you mean by intensity? Only visible caracteristics of light I can think of are brightness and color. :-?