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Green lasersight hack - pics - need ideas!

DCS

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Ebay green lasersight - the kind with dual-ring external adjustment mechanism.



This laser has a large "module carrier" nested in two eccentric-circle adjustment rings. You turn the rings until the lasersight is zeroed, then you lock down the rings with the set screws.

My project - take the green laser module out of carrier, replace with a similar-sized 1mw IR module to use with NV gear. My assumption was that it would be a simple module swap. I think I was wrong!

This is the module carrier in exploded form:

It has a double lens assy on the front, a filter or some other magic piece that was glued to the face of the laser with a spacer shim to provide the proper gap, and a laser bedded in a brass head that holds another lens. That's three lenses: 2 in front of, and one behind the magic piece. The aluminum bushing in the rear is the rearward eccentric adjustment ring.

Here's a view that shows all the lenses:


Here's two closer views of the laser:




I'm a noob. I need direction.

How does this laser work? Is it an IR-->Green with an IR filter? Is that magic piece an IR filter?

The laser diode is nested in the brass head. If my project is to succeed, I believe I need to separate the laser from the brass head, because the brass head must hold the IR laser module, correct? How do I get those things apart? I can't press it backwards because there is a lens on the front of it.

Alternately, I guess it's possible I've gone far enough because I can buy an IR module with that brass head already on it. Could it be that simple?

Lenses! What's the deal with all the lenses? Is this a standard config to enable precise dot size? Will the double-lens assy work with an IR laser replacing the green unit?

I understand that I may have already reached IR status just by removing the magic piece. If so, it will likely be in the 30mw range, way too hot for decent weapons sighting. I've tried 5mw IR lasers for sights, and the bloom is ferocious. It obscures the target. My goal is a ~1mw IR unit that makes a perceptible dot on targets to 200 yards. I don't need to be flagging enemy positions for airstrikes.

Thanks for your help!
 

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Search on Wikipedia for how a green laser works. It's a complex process of wavelength conversion.
:)
 

Kenom

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I recently rebuilt and remade a 5mw red laser gun sight into a 100mw gun sight. Total project took me two weeks to build and considering how easy it all was once I got it going it would be a peice of cake for me to explain how to get you a IR laser sight. Although if you want it to have any kind of range I'd recommend going with a higher output than 1mw. You could very easily remove the KTP and turn this into a IR laser. Give me time to look over your pictures and I'll get back to showing you how to do this!
 

DCS

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Thanks Kenom!

I'm not an expert on lasers, but I have used an 850nm 5mw-rated IR laser sight with Gen3 NV equipment. At 20, 50, 100, and 200 yards, the bloom from the laser obscures most of whatever target you are lasing. It's very star-wars looking and cool, but it defeats the purpose. You can't aim with it, unless you're okay with minute-of-beachball accuracy.

What I'm after is a laser that will make a visbile but not intensely bright dot on targets aout to 150 or maybe 200 yards.

I have a cheap red pointer rated for 5mw, it makes a small an clean dot at 50 and 100 yards at night, but a huge bloom when the NV is turned on.

So i want to start with a 1mw IR. If it's too dim, I'll ramp up from there.

Thanks!

Primary goal now is to get the current laser out of the brass head and find a 1mw IR unit that can be put in its place.
 

Kenom

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thats probably not going to work too well.  Your big problem is NV equipment amplifies the amount of light available.  so yeah your 1mw IR is going to be ideal.  One would think.  so is there a pot on the driver board? Yes there is.  Remove the ktp crystals and screw it back together.  Hook it up to 3v and turn it on.  do you see a nice tight dot or is it large? I've circled the ktp
 

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DCS

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I put it all back together except the ktp crystal piece and its related shim washer.

No dot.

But the Sony handycam sees a dot, which turns nice & bright & 10mm diameter on the wall 10' away when the nightshot mode is switched on.

I'll test it more tonight with NV, to see how bright it is compared to a known <5mw pointer. Also to see if i can focus it down a little.

What does ktp stand for?

It seems clear that this ebay green laser was emitting IR, unless one of those lenses up front was a filter. But they just look like simple lenses to me. What does an IR filter look like?

This is cool! I'm ready to start shopping lower output IR modules. Keep the info coming!
 

Kenom

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You won't need a lower powered IR. the laser has a ir diode in it already with a potentiometer on board. You should be able to turn the current down going into the laser diode and get very little output compared to what it normally puts out. it's NEAR ir. so the dot should be visible from night vision or NV googles.
 

DCS

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WOW! I'm thoroughly disgusted with this project!

I was getting ready to start soldering and cutting and grinding bits to fit and suddenly it's over. ;D ;D

Well, at least I learned what a pot looks like. Gotta love the internet.

Thanks Kenom! I'll post some pics of the results.
 

Kenom

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sorry to burst your bubble.  Try making a 100mw lasersight of red.  That was fun.  The biggest thing your going to run into as a problem with this project is setting the focus of the laser so that it is a beam over long distances.  it's easy to focus up close.  not so easy farther away.  especially when you've removed the crystals in the beam path.

Ir filter: http://www.novalasers.com/NOVAstore/pc/viewPrd.asp?idcategory=6&idproduct=68
 

DCS

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You were correct! Focus problems.

With NV, the beam makes a big dot, several rings, and lots of garbage light.

I cleaned the 2 front lens pieces so they look perfect under magnifying glass.

I used a qtip with alcohol on the diode lens. Bad idea. I got condensation under the lens and it's still there 36 hours later. Hair-drier and sunlit window = no help.

Also, the focusing lens on the front end won't budge. I steadily worked up to heat, pliers and major force on the screwdriver. The brass finally just shaved off.

Did I miss something? I thought a threaded front lens is always meant to be adjustable. The other brass cylinder threads had small quantities of threadlocker on them (thin stuff like clear fingernail polish) but they came apart easily. The lens screw was frozen as though it was glued with superglue. I got it damn hot, but it still wouldn't budge. It appears to be a glass lens. Help me out here: was that just bad luck, or did I miss something?

Bottom-line - I have to salvage and use the brass module carrier because it's the buss and because it fits in the alignment mechanism. My ability to focus the existing lens array is gone, and my diode is fogged.

I'm leaning back towards the original plan: integrate a focusable IR module into this carrier. That means drilling out the lenses in the front of the carrier so that it becomes simply a tube.

But I have always assumed that there is such a thing as a one-lens module that can be focused to a usable dot.

I need a better understanding of focus issues.

Is the following correct? :

A one-lens focusable module can make a dot of a certain size at a certain distance, and the dot diameter will grow with distance due to the divergence of the beam.
A 3-lens system can virtually eliminate divergence such that the beam diameter becomes fixed, and the dot will be almost the same size at 5 meters as it will be at 100 meters.

Any suggestions?
 

Kenom

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yeah you kinda got the focusing understood. It truly depends on the wavelength of the light your trying to focus. Now there is a big diffference between the focusability of green shorter wavelength and IR longer wavelength. You wouldn't be able to get affective focusing capabilities for very far because of this reason. I'm sure you can look online to get a graphical representation of the focus of IR. but basically when your green is focused the IR is going to blooom a lot! Ir is incredibly hard to "colimate" or turn into a beam that goes long distances, so I really don't know how effective your laser is going to be. Normally all of us are using high wattage IR diodes for raw burning power and nothing more cause it's just so hard to colimate. shine it at 2 feet and it's a burning beast but go out to 40 meters and it's a humungous dot many feet in diameter. I honestly don't know how possible your project is going to be.
 

Kenom

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I've not a clue what the focal properties of 1064nm would be but I'm sure it's going to be worse than 808nm being as it's even longer of a wavelength. I honestly don't know. someone with more knowledge will have to answer this one.
 

Kenom

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we can make a 1mw pointer that would be hopefully visible to NV but not to the naked eye.
 




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