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445nm LASER WITH DIY BEAM EXPANDER. 2" BEAM!

Ehgemus

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Just wanted to show off my new toy. This is a 445nm m140 diode. The lens is 3" diameter and it come out of an old projection tv. The beam coming out is 2" x 1" Dia, kind of egg shaped.
Wish I could get better pictures. The beam looks way better in person.

Lens














This picture shows where I put electrical tape in front of the lens and this takes away the wings

This picture shows the wings

This picture is after I put the tape on the lens.






 
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Alaskan

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Re: 2" Beam laser 445nm

Cool, what kind of batteries are you running, 18650? With that skinny handle (relative to the lens) it puts it in the mace of doom category! With the beam expanded that far the divergence is so low I bet you can put a spot on the under side of some high clouds with that thing. I've been wanting to make a host with a three inch diameter lens for awhile now, just difficult to find something to mount the lens in. I really didn't think putting tape across the front would work so well to get rid of the wings.

Oh man, I had to come back and edit a question in, what diameter is the aluminum part of the head the lens assembly is mounted to? I see you didn't use the out of focus G2 lens method I use with mine, because of that you won't be able to adjust the beam any wider and remain at the focal point, but on the plus side you have absolutely no loss from having an extra lens in there, nice! On second thought, if your lens has a focal point which is so close to the diode that is as wide as the beam gets, using a out of focus G2 lens as an expander won't help, but if you mount a concave lens in front of the diode it could fill out further, if you wanted to use more of the aperture. But why make it more complex when it already has an awesomely wide beam and low divergence!

I've been wanting to build one that way too with only one lens, just hard to find the right lens holder which won't cut part of the beam off as it exits the diode, you made a nice find with that holder assembly. If you ever get a hankering to measure the divergence, I'd love to know!
 
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Ehgemus

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Yeah I didn't think the tape would work as well either but it does. I will probably find something more permanent later.
The head of the laser is 2 inch diameter. The front lens holder is black PVC and is a 2x3" reducer.
 

Alaskan

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I searched a lot without a solution looking to find something like that to put a big lens in, only this week could I find something, now you have a method too, thanks for sharing and the nice beam shots! What is the focal length of your lens? It's a PCX lens, right?

Edit: Ah, I see you just added photo's of the lens, wow, that lens is impressive, I like it, nearly a PCX. I have some smaller ones like that which aren't completely flat on the one side and they work great too.
 
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Ehgemus

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I know nothing about lenses so I posted pictures. The lens come from an old projection tv.
 

Alaskan

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Well,

Nice toy you have there, I just like big hosts with huge lenses!

Tonight I went outside and took a 3 inch diameter doublet, or bi-convex lens outside which has identical curves on both sides of the lens to see what the beam would do. I could focus it into a nice long laser beam just like using a PCX lens which are normally used for beam expanders that have a flat side on one side, curved on the other... So, from my observations tonight you can use a equally curved (both sides) bi-convex lens for a laser too, just that the beam doesn't stay fat the whole way, you must focus it on some distant object and it will become a very tiny spot in the distance, instead of remaining a fat beam the whole way. In a way, kind of anti-divergent due to the beam converging. Only thing is, I am not sure how far away I can focus a doublet or bi-convex lens, anyone know? I realize every lens has its natural FL, but tonight it seems I could greatly vary the distance my laser beam could focus upon something by moving the lens closer or further away from the laser source, it seemed what the beam could focus upon could be varied many thousands of feet, if not miles and miles, making the beam appear to be at infinity focus, but I don't think a doublet lens can really do that, so what am I seeing?

I don't want to hi-jack this thread, if someone can help me understand what is happening, please PM me... I'm just asking in this thread because when I saw Ehgemus lens I started thinking about this.
 
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Pman

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You will have to forgive me but the first thing I thought of was a toilet plunger. You need to add some spikes to make it medieval:)
Seriously though that beam probably looks pretty nice in person. You do great work Ehg and it's nice to see something of your own here. I'll try and REP but I probably can't yet:(
 

Ehgemus

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Thats funny, my wife thought the same thing. I had to show her that it was hard plastic instead of rubber.
You will have to forgive me but the first thing I thought of was a toilet plunger. You need to add some spikes to make it medieval:)
Seriously though that beam probably looks pretty nice in person. You do great work Ehg and it's nice to see something of your own here. I'll try and REP but I probably can't yet:(
 




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