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Finely focusing a handheld laser (NUBM08)

Luxor144

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Aug 23, 2020
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I suppose this has been answered before, but all threads I've found dealt with more of a workshop setting, as far as I understand, and I'm looking specifically for a handheld pointer solution.
Long story short, I'm building a handheld laser pointer. I'm using
Survival Laser Stainless Steel Host Assembly,
445nm AR Coated Standard Glass Lens Assembly,
NUBM08 laser diode,
the rest is probably irrelevant
Everything works, but the thing is - I can't focus the beam at longer distances, it always appears as a rectangle. The diode seems to have some pretty good focusing by itself, as without a lens it has little dispersion (beam width at 3m is about 5cm). With lens, though, it's unsurprisingly a huge blob. Tried to use two identical lenses, but best I could do was to focus it back into the same line (or rectangle at longer distances) again.
Anyway, question - is there a practical, handheld applicable way to focus the beam into a dot, or at least prevent it from dispersing so much? I know that prisms can be used to shorten the line and make it more square, as well as cylindrical lenses, but these solutions seem more applicable to a lab or workshop setting, and are rather impractical for a handheld device. What could I do to focus it very finely?
 



gazer101

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Feb 23, 2020
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Probably most practical for you to swap out your current (G-2) lens for a 3-element glass lens and then buy a beam expander to allow for better focusing at a distance. The only way to get a "dot" out of a laser is for that laser to be outputting a dot in the first place... the BDR-209DBK is the only affordable (single-mode) diode I know of that can produce a "dot" at 1W+
 

Alaskan

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Yep, as single mode diodes go, I haven't seen anything else which can do what that diode does and can be focused into a burning spot at a further distance than any of the other visible diodes using only a 6 mm diameter lens. Part of the reason, aside from having a tiny emitter in the first place and being single mode, is the wavelength is so short, with a shorter wavelength you get a smaller spot due to that too, and the increased power density in that smaller area.

However, I have been able to focus a NUBM44 multimode diode which has a terrible amount of divergence and also has a wide striped beamshape 30 feet away to a burning point by using a 9 inch diameter PCX collimation lens, the larger the lens, the further you can focus it into a spot. In the case of the NUBM44, it still won't really be a spot, but a tiny rectangle the same shape, just so small it appears to be a spot.
 
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Zerosage

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Aug 2, 2020
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I just bought a NUBM08 9mm. Mostly seen these bought these(picture), then the diode died. I don't have lpm so temp time by comparison is unlikely accurate. I could sizzzle wood as it burned violet. So naturally i ordered a replacement diode before i owned a caliper. I'm asking necessary how and what pill would line up ?, pill?, 3 part collimination lens?, press ?. My first build so anything would be most appreciated. Thanks.
 




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