Idea for ir filter mabee?

lasersbee said:

[quote author=wannaburn link=1232169680/0#14 date=1233000866]"
it you try to put an aperture in front of your lens, the IR will still spread like a flashlight, as it still isnt collimated "

Where do you guys get this idea?  Without an IR filter, depending on the laser, at 20ft away you can have a 4in IR dot with a 5mm green dot. IR does NOT spread like that of a flashlight, although it seems to be a common myth around these parts.

Yes it does diverge differently than that of the green, but it wont make a 10ft dot at 20ft away like one would expect from a flashlight.

Common misconceptions should not be posted as fact. Before an answer is given, perhaps trying it first and seeing for yourself will stop such myths from travelling around as fact.


Just a thought

Click to expand...

Isn't this the Science Fiction section.... :-?
I must have made a wrong turn somewhere... :-/

Jerry[/quote]


No, but that would be a good start  You forgot to make a left at Albuquerque ;D

sorry, i know that, but i exaggerated the whole thing for simplicitiys sake.

also it is hard to draw a diagram where the cones of light only differ a few %


EDIT: changed the text in the original post to be more specific

Yeah, I'm not buying those illustrations either.. In my experience, an aperture will help contain the IR almost completely. Also, the IR may diverge slightly more than the green, but not significantly enough to act like a flashlight. Maybe a tiny fraction of a mrad more than the green.

IR is not of any real concern in green lasers with an output less than 50mW anyway, since the IR output is not significant.

The major concern about IR at higher powers deals with the possibility of accidentally catching a reflection in the eye, since as long as you keep your eyes out of the beam path (which you should be anyway) you won't have to worry about it at all. Rear-surface mirrors, glass, and other reflective surfaces can act as prisms or beamsplitters, thus separating the green from the IR and causing a hazard since you can no longer be sure where the IR beam is in relation to the green.

Quote from BeavRat:

How would you attatch either the optotronics one or the bg38 filter to the laser? Also, where can I buy a sandstone green laser?

Click to expand...

That's entirely up to you. I really only build lab-style lasers, so I've never tried to mount one to a pointer. I can tell you that these filters like to be mounted at a slight angle to minimize reflections and keep the beam profile clean (you could even calculate the brewster angle if you're feeling adventurous).

EDIT: As for the standstone modules, they can be found at: www.o-like.com

ElektroFreak said:

Yeah, I'm not buying those illustrations either.. In my experience, an aperture will help contain the IR almost completely. Also, the IR may diverge slightly more than the green, but not significantly enough to act like a flashlight. Maybe a tiny fraction of a mrad more than the green.

Click to expand...

well, if you put the aperture further away from the optics, it will work better. as you say you build lab style lasers, this is possible. but with a pointer and an aperture directly after the lens, this wouldn't work at all

wummi said:

[quote author=ElektroFreak link=1232169680/0#18 date=1233006191]Yeah, I'm not buying those illustrations either.. In my experience, an aperture will help contain the IR almost completely. Also, the IR may diverge slightly more than the green, but not significantly enough to act like a flashlight. Maybe a tiny fraction of a mrad more than the green.

Click to expand...

well, if you put the aperture further away from the optics, it will work better. as you say you build lab style lasers, this is possible. but with a pointer and an aperture directly after the lens, this wouldn't work at all[/quote]

An excellent point. I would agree with that statement, since the distance between the output lens and the aperture is quite important.

wait, i think all of you people are right. the IR is both collimated and flashlight-style, simply, because a greenie emits two IR wavelengths!
the 808nm should be mostly spill which didnt hit the crystal and reflecting stuff, but could be quite much, as the pumpdiode may be in the watts range.
the 1064nm IR is fairly collimated. its oriented perfectly for a "IR beam", the collimating distance is just a bit off (since its tuned for 532nm). but then there are lasers with worse green beams than what may come out of your laser in 1064nm!

that answers why lasers may have silly high readings if you stick them right in front of a meter (808), lose power quickly with distance, but can still be very dangerous in far distance (1064).

yes, an old webcam may be the easiest and quickest source for a filter. better than nothing anyway. but then, with such low prices and availability: everyone get a real IR filter please!

manuel