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how big a magnifying glass would it take

qumefox

qumefox

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Gas lasers aren't pumped by anything, at least not optically. The gas in the optical cavity is simply stimulated (the S in laser) to emit photons either by direct current, or RF. The gas type, mirror coatings, and cavity length determine the wavelength. Gas lasers are more akin to neon lamps than florescent's.
 
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Benm

Benm

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Gryphon said:
Ive got a large lens about 1 foot square, on a nice sunny day it will set wood on fire in just a couple seconds, there is a load of power in sunlight.
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Yup, i have a couple of A4 sized fresnell lenses here. The maximum power foncussed by that is about 100 watts in optimal conditions, but even in far from optimal conditions you can light a bbq with those if you want to.

I've also seem them creditcard sized for survival, it seems you could start a campfire with those as long as the sun is out and you have some tinder.
 
DrSid

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A4 ? Where from ? I've seen those huge for van back doors, but those are concave lens.
 
qumefox

qumefox

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DrSid said:
A4 ? Where from ? I've seen those huge for van back doors, but those are concave lens.
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Pay for shipping and i'll send you a fresnel out of a bigscreen tv. :p The 62" mitsu I have on the bench now measures 55" x 32" to give an example of the size, though I have them from everything from 40" up to around 73" TV's

However your looking at a decent chunk of change to ship something that large.
 
DrSid

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That is cool. Why are they used on TVs ? If you tell me where you get them from, I could probably find them down here in Europe.
 
qumefox

qumefox

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DrSid said:
That is cool. Why are they used on TVs ? If you tell me where you get them from, I could probably find them down here in Europe.
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Um. I get them out of TV's we scrap, lol. TV/electronics repair is my day job.

And their function is the same as any other lens. They're used to straighten out the light before it makes it to the next layer of the screen, which is the lenticular. Think of them as big ass collimators.

Any tv repair shop that handles big screens is bound to have some old ones they'd probably sell you fairly cheap.
 
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