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1W IR weird focus.

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Edi

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I just built a 1W 808nm IR laser. It works really well and burns nicely but only at about 5cm. No matter what distance I put the lens at it's focused only to one point. :confused:
I tried 3 different lenses that I had but they all do the same thing. I've built a green, red and violet laser before this one and didn't have a problem with them.
Any Ideas? Am I missing some info on IRs?

Thanks
 





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Edi

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Yea I have safety goggles for most of the wavelengths.
Any ideas concerning the topic?
 
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joeyss

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I belive most 1 watt IR lasers are multimode with very crappy divergence and beam specs. You'll Need good optics if you want to make it a distance burner. Also bear in mind IR is not the best WL for burning so once it losses even a little power it can make it hard to burn.
 
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Edi

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Also, I'm using a driver that specs for 100-500mw diode. It will just keep the diode from going full power right? Would it have any other affect on the diode?
 
Wolfman29

Wolfman29

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That driver is just giving a minimal amount of current, is all.

Regarding your focusing issue... that's interesting. Have you isolated the diode itself and tried putting a lens closer and further from it, to see what's going on?
 
Fenzir

Fenzir

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IRs often become focused into a line, or a dash. not a dot.
 
snoutke

snoutke

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My overspec 500mW 808nm IR laser (peaks at 630mW) burns a match only up to 30cm well focused.

I posted a question here asking whether I will be able to burn a match much further than 30cm if I buy a more powerful 2W Focusable NIR Infra Red Laser?
 
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Edi

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Yes, I've put the lens closer and farther away from the diode and it only focuses a few cm away from the lens regarding the distance the lens is from the diode.

I have a 300mw IR but I replaced it with the 1W cuz the 300mw was to weak. I'll try powering up my 300mw IR when I get the chance and see if i can focus it past a few cm.
 
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Edi

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So I tried the 300mw IR and it focuses fine. That means the diode is just really weird I guess. :undecided:
 
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honeyx

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The 1000mW IR diode is a multimode diode and therefore focusing as a line like Fenzir said. The 300mW diode is a singlemode diode and therefore focusing as a dot, so you 1000mW diode isn´t weird. It´s the nature of a multimode diode. To get it focused to a dot you need correction optics.
 
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Edi

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Ok, so any help with the kind of lens or whatever optics I need to focus it?
 
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honeyx

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You will need either two prisms to correct it, or a special lens that is a hybride between a lens and a prism. You can get such correction optics for blue Laserdiodes, but don´t know how good they will perform with IR laserdiodes.

There are also cylindrical lenses that can do the trick.
 
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