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Weird "Dust?" around the DOT
- Thread starter Fremo
- Start date
D
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What wavelength of laser?
What power?
and can you post some pictures.
What power?
and can you post some pictures.
Asherz
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You've probably burned something closed to the lens and some soot or dirt has got on the lens.
If you can get to the lens blow some air onto it with an pressurised air canister, or use your lungs.
If that doesn't work get a cotton Q-tip and give it a careful wipe.
That should clean it up.
If you can get to the lens blow some air onto it with an pressurised air canister, or use your lungs.
If that doesn't work get a cotton Q-tip and give it a careful wipe.
That should clean it up.
- Joined
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Both of my red lasers have the same thing. And it's not a lens artifact that can be cleaned, because I have repeatedly cleaned all my lens, and further, you can tell the lens artifacts (squiggly lines on the unfocused dot) from these.
I have a feeling it has something do with with it being open can....
It may also have something to do with not using an AR coated lens? Anyone know?
I have a feeling it has something do with with it being open can....
It may also have something to do with not using an AR coated lens? Anyone know?
ARG
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I just tested both my reds, one open can, one not, and the open can diode laser had a similar "dust effect" to the OP's. (May have been because the lens was dirty, I don't use my open can red that often.)
Last edited:
RayBurne
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If cleaning the diode does not work, it may not be a dust problem.
" In the focus of a diffraction-limited beam (i.e., at the location where the beam radius reaches its minimum), the optical wavefronts are flat. Any scrambling of the wavefronts, e.g. due to optical components with poor quality, spherical aberrations of lenses, thermal effects in a gain medium, diffraction at apertures, or by parasitic reflections, can spoil the beam quality. For monochromatic beams, the beam quality could in principle be restored e.g. with a phase mask which exactly compensates the wavefront distortions, but this is usually difficult in practice, even in cases where the distortions are stationary. A more flexible approach is to use adaptive optics in combination with a wavefront sensor."
Ref: Encyclopedia of Laser Physics and Technology - beam quality, laser beam, M2 factor, ISO Standard 11146, divergence, nonlinear frequency conversion
- Ray
" In the focus of a diffraction-limited beam (i.e., at the location where the beam radius reaches its minimum), the optical wavefronts are flat. Any scrambling of the wavefronts, e.g. due to optical components with poor quality, spherical aberrations of lenses, thermal effects in a gain medium, diffraction at apertures, or by parasitic reflections, can spoil the beam quality. For monochromatic beams, the beam quality could in principle be restored e.g. with a phase mask which exactly compensates the wavefront distortions, but this is usually difficult in practice, even in cases where the distortions are stationary. A more flexible approach is to use adaptive optics in combination with a wavefront sensor."
Ref: Encyclopedia of Laser Physics and Technology - beam quality, laser beam, M2 factor, ISO Standard 11146, divergence, nonlinear frequency conversion
- Ray
qumefox
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Looks like a dirty or scratched lens to me personally. About the only way i've ever been able to get lenses clean is to remove them and completely submerge them in rubbing alcohol and swish them around. ***DON'T DO THIS WITH MULTI ELEMENT LENSES*** heh. It won't hurt them but they'll take forever to dry out unless you dismantle them.
RayBurne
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Fremo: Do NOT polish the lens. Clean gently with non-lint Qtip or optical cloth using alcohol or a specialty fluid. Repeat at least twice. Personally, my 200mw O-like red laser has similar artifacts.
Lens in reasonable quality lasers are usually coated, any 'abrasive' will break down the coating since it is super-thin. Additionally, the lens may not be made of optical glass, but optical plastic (acrylic) which too is coated but is a softer material.
Wikipedia has a really nice writeup on 'Optical Coating' if you wish to read about it.
There probably should be a name for laser enthusiasts who seek artifacts in the beam... maybe 'laser anthropology'???
- Ray
Lens in reasonable quality lasers are usually coated, any 'abrasive' will break down the coating since it is super-thin. Additionally, the lens may not be made of optical glass, but optical plastic (acrylic) which too is coated but is a softer material.
Wikipedia has a really nice writeup on 'Optical Coating' if you wish to read about it.
There probably should be a name for laser enthusiasts who seek artifacts in the beam... maybe 'laser anthropology'???
- Ray
qumefox
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Just use 90%+ rubbing alcohol..
qumefox
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Um, you can get rubbing alcohol in pretty much any drugstore. turpentine is going to eat your coatings and/or lens if it's acrylic.. the AR coatings are delicate... so are the lenses. Never use paint thinner on anything you want to keep.
RayBurne
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Do not clean it with water,
Do not clean it with wine,
And certainly never clean a lens,
With spirits of turpentine.
-Ray
Do not clean it with wine,
And certainly never clean a lens,
With spirits of turpentine.
-Ray
