# Collimate a laser diode into a beam?



## blunt (Aug 20, 2007)

Hi Guys,

Please exscuse my Questions, as my knowledge about lasers is somewhat limited, but i'm trying to learn (Spent four hours reading SAMS laser faq.. maybe had a lil too much to smoke as my memory is shady)

I've extracted a Liteon DVD burner laser diode (16x).

When applying power to the diode in it's un-molested state, i see a brilliant red light with clear speckling in the 'atmosphere'(?) around it.

I was under the impression that since i left it contained, it would produce a visible red beam coming out of the top most DVD lense (closet to dvd disc)

Such was not the case. I then proceeded to extract the mirrors from the setup (some squares / lenses etc)

My main questin is, without a Aixiz laser module, how can i go about getting the laser light to focus itself into a tight visible red beam that projects itself across a room?

Where would i place the collimating lense? Do i only need that kind of lense? Should another lense be placed in front or behind?

As close as possiblt to the diode? i.e. mashed up against it? 5 cm's from it?

It's hard to test with my setup as i have some mickey mouse makeshift mad scientist lab, without the proper materials to anchor my peices in place etc...

any and all help suggestion are greatly appreciated..

thanks guys,

Blunt(ed)


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## Corona (Aug 20, 2007)

Get a cheap laser pointer and take it apart for it's collimating lens(es), this will illustrate to you how they are arranged. You really need to take the diode out of the burner carriage as there is other stuff (as you have found) in the beam path (diffraction grating, polarizer, what not) and the lens in the burner is not a collimator; it is intended to focus the laser to a very fine spot at a precise distance.

Oh, and leave the blunt out of the equation or you might have another kind of "red eye" to deal with; the burner laser is high enough in power to damage your eyesight permanently.

If you do get it working though, you might just be able to spark one up on laser power - a DVD burner laser can light a cigarette and the fine pointed end of a hand-rolled smoke is pretty easy to ignite (just leave a bit of "material" hanging out the end or else you will need to color the paper black to get it to absorb enough laser energy to ignite it).

Have fun, but be wary (not paranoid, _wary_)


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## blunt (Aug 20, 2007)

Corona said:


> Get a cheap laser pointer and take it apart for it's collimating lens(es), this will illustrate to you how they are arranged. You really need to take the diode out of the burner carriage as there is other stuff (as you have found) in the beam path (diffraction grating, polarizer, what not) and the lens in the burner is not a collimator; it is intended to focus the laser to a very fine spot at a precise distance.
> 
> Oh, and leave the blunt out of the equation or you might have another kind of "red eye" to deal with; the burner laser is high enough in power to damage your eyesight permanently.
> 
> Have fun, but be wary (not paranoid, _wary_)


 
Hey Bro,

Thanks for the info. Much much appreciated. It's like i've gotten laser fever or something lately. Trying to convince myself NOT to shell out 300+ dollars for a kik azz laser.

Ok, so that lense i was using was not even a collimating lens. Explains alot.

I did have an older cheap laser pointer.. But the damn thing was pretty much sodered together... i manage to dissect it, with a pair of needle nose pliers, a pair of scissors (don't ask) and about 4 smokes.

Anyways once i finished with it there was not much left.

I think one of my problems is getting the light contained without having any tubing type structure.

Should my lens be a BIT above the point where light is emmited from the diode? Perhaps sandwiched on it? (I guess if referring to laser pointer, then it should be a little above the actual light emitting window on the diode)

Am i correct to assume all i need is a collimating len to throw this into a beam?

thanks everyone. Nice community you have here.


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## comozo (Aug 21, 2007)

look around the web there is enough info on laser beam expanders other than Sams laser faq


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## AJ_Dual (Aug 21, 2007)

The Axiz module will help, but it won't technically collimate the beam. It will just focus it.

However, focusing it as far a distance as is practical will produce an effect indistinguishable to collimation to your eye. Unless you've got a specific technical or scientific need for collimation, that will most likely be sufficient.

(Hint), because of some DVD burner diode group-buy's going on right now, the cheap 5mW Axiz module most people are using as a host for higher power red diodes is on a pretty bad back-order. You might want to get one of their inexpensive IR modules, or look for Axiz on eBay and buy a bare module housing.


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## Hemlock Mike (Aug 21, 2007)

The focusing lens is very short focal length and is positioned almost on top of the LD window in order to gather as much light as possible. While the beam looks like a round dot, it is actually a tiny rectangle -- No matter. Be careful of your eyes. We can't say that enough here to new experimenters.

MIke


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