Laser light outside of the visible spectrum

[Jem]

So how come we have blacklights allowed? Or am I missing something?

Blacklights tend to be in the UVA region (least harmful), as the wavelengths get shorter the damage threshold is less. Anything in the UVB or C catagory is the most harmful, you were specifically talking about 266nm which is within the UVC catagory and is therefore the most harmful.

Cataracts usually form over a period of many many years of exposure to low dose UV radiation from the sun. This could obviosly be accelerated by exposure to 'artificial' UV. UV isn't the only thing proven to cause cataracts, try googling cataracts and smoking

The following is from some technical info I had kicking around, i'm sorry, but I don't know the author, this explains it fairly well...

Ultra Violet (UV) light represents a section of the overall electromagnetic spectrum of light, extending from the blue end of the visible (400nm) to the x-ray region (100nm).

It is subdivided into three distinct wavelength regions described as either UV-A, UV-B or UV-C in increasing order of photon energy.

UV-A 400nm-315nm: Often referred to as 'blacklight', this is the longest wavelength region and lowest energy, it represents the largest portion of natural UV light.

UV-B 315nm-280nm: Partially blocked by the ozone layer this is the most aggressive component of natural UV light and largely responsible for sunburn (erythema).

UV-C 280nm-100nm: Only generally encountered from artificial light sources since it is totally absorbed by the earth's atmosphere.

Cheers

Jem

[bridge]

Bridge, UV is NOT eyesafe. UV is known as a cause of cataracts (cloudy lenses) in the eyes. It's certain wavelengths of UVB in the suns rays that cause cataracts in many older people, that's why it's recommended that you should always wear sunglasses with a UV block to 400nm just to be on the safe side. There is also evidence to suggest that use of sunbeds without adequate eye protection can also damage the crystaline lens, as well as damaging your skin with the possible consequence of premature skin cancers.

Look here...

http://www.sdearthtimes.com/et0998/et0998s13.html

and here...

http://www.bbc.co.uk/health/conditions/cataracts1.shtml

With regards to UV sensitive paint. You should perhaps contact 'Tocket' on this forum. I believe he was selling some UV sensitive stuff a while ago. He's a VERY knowledgeable guy when it comes to chemistry, at least he may be able to point you in the right direction.

Cheers

Jem

Thanks Jem
for correct informations,.
Best regards!
Bridge

[mixedgas]

I work with UV argons, they are a pain in the a$$. it takes a triple ionization of the argon ion (arIII+) to get you so you run at high current and short lifetime on the tube, But UV hecads and UV argons abound from sterolithography systems being upgraded to soild state.
You'd want a coherent model 328 in working order. ITs not much bigger then a I90 but produces 350 mW of UV.

UV has been used for some large commercial shows, usually with spectra 171s. One thing I tried was "DAYLIGHT' LASER SHOWS, I have a compound that turns from white to blue with a long persistance time in UV. Its works, but the decay time is too long for moving graphics, but it makes a nice billboard.

Steve Roberts

[tocket]

Still, the final power of the laser need not be high; it is the projection that is important, not the beams. Also I don't think fluorescent paint needs a high UV input to activate (somebody correct me if I'm wrong on this please) so maybe a final output of less than 30mw would suffice.

You don't need a lot of power to "activate" fluorescent paint; a single photon will probably do, but the emitted power of the fluorophore is proportional to the absorbed radiation according to:

P[emitted] = P[absorbed]*Φ*λ[absorbed]/λ[emitted]

Where Φ is the quantum yield of the fluorophore and λ the wavelength of the light. Extremely efficient fluorophores like fluorescein or rhodamin 101 can have quantum yields over 0.95 (95% of the absorbed photons cause an emission). Another thing to take note of is that the lower the wavelength of the UV laser, the more powerful it needs to be.

Let's look at an example. Say we have a 350nm source and a fluorophore that emits at 635nm with a quantum yield of 0.9. The efficiency is then 0.9*350/635=50%. Your 30mW in becomes a mere 15mW or 2.6 lm out. On a 1m² screen this corresponds to a luminous exitance of 2.6 lm/m² which is not very strong.

[trwalters001]

You know, this is what I was saying just the other day......

Say we have a 350nm source and a fluorophore that emits at 635nm with a quantum yield of 0.9. The efficiency is then 0.9*350/635=50%. Your 30mW in becomes a mere 15mW or 2.6 lm out. On a 1m² screen this corresponds to a luminous exitance of 2.6 lm/m² which is not very strong.

[greenalien]

A couple of years ago, I saw a travelling fun-fair that had all the cars in its dodgems ride painted in fluorescent paint, which looked very effective. I thought the blacklight tubes they were using to illuminate the ride looked a bit odd - too bright, and light blue rather than violet - so I asked the ride operator where he had got them from - he replied - 'out of a batch of scrap sunbeds'....

[RDZombie]

the Blu-ray 405 diodes out now are dirt cheap, flouresce many dyes quite nicely and are reasonably eye safe. just a thought

[mixedgas]

the Blu-ray 405 diodes out now are dirt cheap, flouresce many dyes quite nicely and are reasonably eye safe. just a thought

MI lasers is selling a Coherent 405 diode. Bit pricy though.
Steve

[RDZombie]

MI lasers is selling a Coherent 405 diode. Bit pricy though.
Steve

the 405 diode in the 16x blu ray burners can output about 100mw cw safely and can be had for around 300$

[heroic]

the 405 diode in the 16x blu ray burners can output about 100mw cw safely and can be had for around 300$

I tried this and it worked quite nicely; the glow-in-the-dark paints are also excited by this light and will glow very strongly, leaving nifty trails. Works really well! Now if only my 473nm blue was more than 80 mW... it still works with the 80 mW laser but it's really not bright enough.