Collimating the collimated

[laserdelic]

I have 2 fixed focus 405´s with a quite big round dot. One of them can reach 1cm diameter at 4-5meters. Is there some way to "recollimate" the beam to get a paralell thin beam? :thinking:

 

[Bionic-Badger]

You'd need to make the opposite of a beam expander. The problem with reducing the beam diameter is that the divergence increases (inverse relationship). So you'd actually end up with a bigger spot at long distances.

If you still want to try, get a convex and concave lens like in the link above and use the concave lens to cause the beam to converge to the size you want. then use the concave lens to cause the beam to diverge again. It'll take precise alignment, lenses of the right focal length, etc. though.

 

[RA_pierce]

You can probably just take the laser apart and adjust the lens.
More info on the pointer, please.

 

[Things]

1cm at 4-5 metres doesn't sound bad to me - keep in mind that your eyes tend to see this annoying blur that will make the dot look bigger than it actually is, 1 pitfall of the 405nm wavelength.

 

[ryansoh3]

Any idea why we get the hazy blur?

I thought it was just me. :na:

 

[Kartracer00]

its just how it is with our eyes. same effect you get if you purposely un-focus your eyesight on any light emitting source.
i think its pretty cool but can give you a serious headache the 405 can.

 

[Cyparagon]

Any idea why we get the hazy blur?

Long wave UV and violet causes fluorescence in the eye, so not only does the laser spot glow, parts of your eye glow a bit, too.

 

[ryansoh3]

Interesting! Did not know, thanks! :beer:

Long wave UV and violet causes fluorescence in the eye, so not only does the laser spot glow, parts of your eye glow a bit, too.

 

[Kartracer00]

Long wave UV and violet causes fluorescence in the eye, so not only does the laser spot glow, parts of your eye glow a bit, too.

that is cool. i just knew it was with lower wave light.
:thanks: cyparagon.

 

[steve001]

Any idea why we get the hazy blur?

I thought it was just me. :na:

It's actually do to refraction. Blue - violet light is refracted much more than other wavelengths as it passes through the eyes lenses.

 

[Cyparagon]

^Wrong. Your eye can focus. That's what the lens is for. If it were chromatic aberration as you say, it would be simply larger or smaller than you'd expect. It would not be hazy. Besides, wearing (or not wearing) eyeglasses would cause different colors to look hazy if that were true.

I present as proof:

Put a black light near a mirror and see for yourself.

 

[Bionic-Badger]

It really is neat seeing the ambient glow of the fluorescence in your field of vision when observing black lights. It's like being in purple fog.

 

[laserdelic]

Long wave UV and violet causes fluorescence in the eye, so not only does the laser spot glow, parts of your eye glow a bit, too.

Great

 

[steve001]

^Wrong. Your eye can focus. That's what the lens is for. If it were chromatic aberration as you say, it would be simply larger or smaller than you'd expect. It would not be hazy. Besides, wearing (or not wearing) eyeglasses would cause different colors to look hazy if that were true.

I present as proof:

Put a black light near a mirror and see for yourself.

You state this with such absolute authority. Provide a citation that the above statement is the reason instead of refraction. I have not found that to be the explanation.

If what you state is true then one should see a fuzzy blob of violet light, that's not what I see. Right now looking at a laser spot on the wall. I see a somewhat distinct larger that then actual size spot of light created by the laser. I do not see wash of violet hazy light across my entire field of vision as would be created by florescence. I'd like to point out that the only part of the eye that seems to be fluorescing is the sclera. I say seems because the colors I see don't appear shifted to longer wavelengths. Perhaps florescence at that wavelength is minimal. I also note that the skin also appears to be fluorescing, but as you know skin does not fluoresce at that wavelength. Note too the pupil is no brighter then the surrounding skin. This gives me even more reasons to suspect the photo shows no florescence. I'll have to pull out my blacklight and see for myself.