Old 07-27-2012, 02:32 AM #1
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Default Different lenses for green modules ?

I have a few greens. A couple of store bought and a few builds. All 200mw.
Just got another one today. (From laserland on ebay) been happy with their stuff. Decent price. Fast shipping. This one super bright and hits 214 on the meter.
Any way, this one in particular looks good but has a much "larger" beam/spot than others I have..(about 4-5 time the size of a 250mw red 650 and almost double of some other greens)
I notice on pretty much all of them the front lens is glued in place.
I assume they are prefocused at the factory and glued in place.
I have a focusable one from O-like and even at the sharpest focus it has a good size spot.
The question, is there any way to make a tighter beam, smaller spot with the green lasers?
Can a Different type of lens be used or is this just what you get.
I see different types for the blues like the G1 but can;t find anything for greens.
Again there are lots of "focusable" but these just make the spot larger like a flash light.


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Old 07-27-2012, 02:05 PM #2
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Default Re: Different lenses for green modules ?

Focusable lasers should also be able to focos at close distance. Dot size always has some limits, but you should be able to get dots under 0.1mm at 10cm or so with any laser and any focusable optics.
Also most green modules are focusable, just the focusing element is fixed with glue. If you remove the glue, you will be able to focus the module using screwdriver. I did that to all my greenies.
Hence there is no need for different optics. Just some kind of focusing head .. which would have to be custom made to fit the pointer.
There are different optics for blues, but there we use mostly standard modules .. so the optics can be easily changed. It's not the case with greens.
Also if you don't want to remove the glue, and you want to focus for close for burning, simply used additional convex lens (magnifying glass). Just be careful, any glass element will also reflect the laser, so have your protective goggles on.
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Old 07-27-2012, 07:18 PM #3
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Default Re: Different lenses for green modules ?

I need to question those numbers because I can't get anywhere near those with anything I have. (I'm an inch person)
0.1 mm is .00394 , call it .004 thousanthds inch at 10 cm, 4 inches.
I am lucky to get about 1/8" spot (3 mm).
Should this be doable with standard lens?
Have not tried it with magnifying glass.
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Old 07-27-2012, 08:09 PM #4
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Default Re: Different lenses for green modules ?

Normal pointers are usually focused to 'infinity'. It means they beam will stay more or less same size over few yards. It will start to increase eventually with distance, as all lasers do, but at near distance, the beam is fixed width, we call it collimated - as a column.
For burning we focus for closer distance - it's same as with camera. By moving the lens a bit away from collimated position the beam will converge into some distance, where it will achieve minimum spot size, and after that it will diverge again. For burning you usually use few inches. Focusable lasers should be able to do this, otherwise I see no point in focusing.
If the laser is focused for close distance, the dot size may vary, but it's usually very small dot with hard to guess size.
But as I said .. most green lasers have focusable optics (inside) fixed in collimated position with drop of glue. That drop is usually easy to remove, and the laser can be focused again.
Btw. you can use smoke to see the shape of your beam, or just pick something dark and non reflective and move it along the beam and watch how diameter evolves.
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Old 07-29-2012, 12:00 AM #5
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Default Different lenses for green modules ?

There are some green laser modules


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Old 07-29-2012, 02:57 AM #6
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Default Re: Different lenses for green modules ?

Could someone help me, I got a 100mw greenie, and the collimation lens has been replaced (coz the dot was dirty and had lots of spattering around it), the collimation lens I'm referring to is the lower lens in the first pic in the post above me, and it is a classic host, and now I notice the problem lies within the other lens, that is the bit that moves closer and further from the laser assembly. Is that lens that focuses the laser the top one in the first pic of the post above me?
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Old 07-29-2012, 11:53 AM #7
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Default Re: Different lenses for green modules ?

Both lens shape the beam.

The beam from the crystal is divergent, in angle of few degrees. To make it collimated, you use convex lens. That is 'clear' lens on the top picture. The 'last' lens in the pointer, near the aperture. But to get beam with low divergence, it also has to be thick at aperture, otherwise it will disperse too much because of diffraction. So optimum way how to do it is to use as much surface of the convex lens as possible. So you would place it in such distance from the crystal, that the beam covers all the convex lens.

This is how it is done with diode lasers. Beam from diodes has large divergence, 30 degrees or so, so the lens van be very close to the diode to be fully covered.

But green crystals have very thin beam, with low divergence, few degrees. You would have to place the convex lens several inches away from the crystal. To shorten the distance, the other lens is used. It is concave, and it makes the beam more divergent, so it fills the 'main' convex lens in shorter distance, making the assembly smaller.

Generally you don't need the concave lens. I have one laser (400mW o-like), where it can be easily removed, and the laser can be used and focused without it. But the beam does use smaller area of the output lens, is thinner at aperture, and has higher divergence.

In common green modules, the concave lens is glued to the crystal, and is not removable. In some older system this lens also acted as output coupler. It's first surface was flat, and covered with special wavelength filter. It was essential to beam generation, and the laser simply did not generate much of green light without it (it generated tons of IR though). Today output coupler is usually put on last surface of KTP crystal, and the lens is just that. But you can never be too sure. In other words, removing the convex lens, if it is glued to the crystal, is not a good idea. There also should be no reason to do it.
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200mw (35mw compared) FocalPrice cheap green AA - Review
500mw (estimated) 445nm Minimalistic Orange Emos Direct Drive. Thread
1500mw (estimated) 445nm Jayrob's Solarforce L2P. Review

Last edited by DrSid; 07-29-2012 at 11:53 AM.
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