What will a 808nm 3w laser burn

Ive heard many people say that many IR has difficulty burning many objects because of the wavelength.

I know from experience a 650nm 300 mw is barely able to burn white paper while a 150mw 405nm can burn thru easily.

Question is will a 3.2 W have problems burning anything

regards
sbdwag

A lot has to do with pinpoint focus....

Jerry

I understand It has a lot to do with focus but some comments were made that IR lasers are difficult to focus. Meaning because you cannot see the beam or are there other characteristics of IR that make it difficult to focus?

regards
sbdwag

The 1 Watt IR laser that I have has a square beam that diverges at
about 5-10 degrees on all sides... that is because the beam is made
up of multiple emitters...
My 2 Watt IR laser has a rectangular shaped beam... where the long
sides diverge more than the short sides..
To focus the 2 Watt would require 2 to 3 lenses...

For my applications I don't need a lens so can't tell you what type of
lens is needed..
There are other members here that are more knowledgeable than I...


Jerry

Multimode diodes will not focus to as small of a point as single-mode but they can be focused down for burning purposes using the optics that are built in to your module, sbdwag.

With 808nm, you can use the dim spot of red on a diffuse surface to judge whether it's in focus. Another option is to obtain an IR detector card. I think ebay seller snoctony sells them. These contain a film that fluoresces when the beam from an IR laser hits it. You can use this to see the spot size and find a focal point, although I don't know how much power they can handle.

Yet another option is to use an external lens to focus the beam, but before you use your IR laser, find the focal length using a red laser. The difference between 660nm and 808nm isn't significant enough that their respective focal points will be much different, maybe a couple mm at worst.

Finally, you can find the focal point by finding a black non-glossy material and viewing the burning ability (with goggles on) along the beam path. Adjust the lens of the laser until you think you've got the focal point pretty near and then test the burning. Wherever the burining is strongest is the focal point.

Perhaps looking at the IR beam through a video camera would
be easier to see the beam...

Jerry

Can I see the beam on a regular camera say a Nikon L18

Also how can I tell what kind of beam the O-like 3.2 w has. I cannot seem to find any spec other than <3mrads divergence

regards
sbdwag

Yes, you can use a camera to see the spot, but usually the detail on most cameras at those wavelenghs isn't so good. There will be significant glare and artifacts with most cameras, so it's unlikely that you'll be able to see if the beam is truly focused or not.

At those powers the o-like module is multimode. All diode lasers that are that powerful will be multimode.

3W should be enough to burn just about anything with proper focus.
I have burned through white paper with the same wavelength at around 2.5 watts. As long as there is a speck of dust for the beam to catch (with small beam diameter) it will burn white paper and cardboard easily. The amount of power you're pouring into the tiny spot is enough to overcome poor absorption at that wavelength in most objects.

I actually used the 2.5W laser to heat up a metal thermometer. It reached 165 degrees Fahrenheit within 8 seconds and I stopped. The thermometer was too hot to touch.
With that laser you should have no problem setting cardboard and other materials on fire.

The O-like lasers look like they are focusable, so I'm sure you can get a decent burning range for that laser. I would expect you'd be able to burn easily up to ten feet or so. The only thing is, as others have explained, you will not be able to get a very precise spot since the diode is multimode.

You can use any cheap b/w camera (video type) that is always sensitive to IR, or any cheap (non-filtered) webcam too (only in pro models they add IR filters in the lens assembly, in the cheap models i never found them)

Also, i suggest you to use an assembly bw cam/monitor or webcam/pc, cause if any reflection hard enough hit directly the camera, the correspondent area of the CCD can die permanently ..... and, well, you can be unhappy, if you burn a $10 webcam, but i personally think you can be MUCH MORE unhappy if you burn some hunderd $ of digital camera .....

EDIT: also, get some ND attenuation filter, cause the ccd usually get saturated very quickly, from laser focus points (after all, you're concentrating 3 W in a point of 1/10 or less of mm, the halo can be extremely large, especially on a camera) ..... maybe some 100:1 (or more, depend from the camera sensitivity) attenuation can permit you to see the focus point much better on the monitor, also with the camera close to the focus point ..... or also, substituting the diaphragm inside the lens assembly with a homemade one with a hole of 1/10 of mm or similar (a very thin needle can do that) can help if there's no attenuators enough dark ..... this require to disassemble and reassemble the lens assembly of the webcam, but works very good, and also increase a lot the field deepth of the camera, making the focus of the camera assembly much easy to do

HIMNL9 said:

You can use any cheap b/w camera (video type) that is always sensitive to IR, or any cheap (non-filtered) webcam too (only in pro models they add IR filters in the lens assembly, in the cheap models i never found them)

Also, i suggest you to use an assembly bw cam/monitor or webcam/pc, cause if any reflection hard enough hit directly the camera, the correspondent area of the CCD can die permanently ..... and, well, you can be unhappy, if you burn a $10 webcam, but i personally think you can be MUCH MORE unhappy if you burn some hunderd $ of digital camera .....

EDIT: also, get some ND attenuation filter, cause the ccd usually get saturated very quickly, from laser focus points (after all, you're concentrating 3 W in a point of 1/10 or less of mm, the halo can be extremely large, especially on a camera) ..... maybe some 100:1 (or more, depend from the camera sensitivity) attenuation can permit you to see the focus point much better on the monitor, also with the camera close to the focus point ..... or also, substituting the diaphragm inside the lens assembly with a homemade one with a hole of 1/10 of mm or similar (a very thin needle can do that) can help if there's no attenuators enough dark ..... this require to disassemble and reassemble the lens assembly of the webcam, but works very good, and also increase a lot the field deepth of the camera, making the focus of the camera assembly much easy to do

Click to expand...

^^ the camer thing works really well i used it for my 808nm and the beam shows up like a normal one and it easy to tell the focus point

^What kind of camera? Getting good results with a camera IS NOT guaranteed. There is a huge amount of variation in IR sensitivity. Most cameras will see IR no problem. Whether it sees it in great detail or not is up to chance mostly. You could get lucky, or not.

sbdwag said:

Ive heard many people say that many IR has difficulty burning many objects because of the wavelength.

I know from experience a 650nm 300 mw is barely able to burn white paper while a 150mw 405nm can burn thru easily.

Question is will a 3.2 W have problems burning anything

regards
sbdwag

Click to expand...

I have a 1W 808nm laser. It burns many things. Paper, wood, plastic, boils electric tape, make funny sounds when focused on black stones in water. Yes it burns. However, different substrates do absorb different wavelengths differently. Coal absorbs almost anything. Black things absorbs almost anything. Wood does have a molecule structure, and color that is mostly reflecting 808nm, but not all. As soon as the laser has made a tiny darker spot, the spot converts into coal instantly and starts to glow bright white, and with all that smoke!!

With the same laser I'm unable to burn skin in even close focus. I don't even feel anything, but I can feel the heat on my lips - even unfocused.

808nm, even if it is visible, the wavelength force the eyes to focus much closer to see the dot sharp and clear. I am far-sighted and are not able to see the dot sharp if I take off my glasses. I must have my glasses on, and pretend that the dot is closer than the object I'm playing with. Then the object gets blurry, but the dot is sharp. Therefor it is hard to know when the dot is fully focused. You'll get a sort of confirmation if things starts to glow very bright white. Then you have hit the right focus -at least close.

A 405nm light will be absorbed by many substrates because the wavelength is very short. That said, transparent glass and plexiglass is absorbing 10600nm very well - which is about 12 - 13 times the wavelength of a 808nm laser. CO2 lasers are well known in date marking applicaions for bottles made up of glass and transparent plastic.

So different materials absorbs different wavelengths.

Br.

Vidar

Everyone

Thank you for all the productive informative information about IR lasers.

This thread already has a tremendous plethora of experience that I could have googled for hours and not found as much.

I think I got the big guns out of hiding on this one.


Regards
sbdwag

We only responded 'cause you asked nice.........:crackup::crackup:

Jerry

ElektroFreak said:

^What kind of camera? Getting good results with a camera IS NOT guaranteed. There is a huge amount of variation in IR sensitivity. Most cameras will see IR no problem. Whether it sees it in great detail or not is up to chance mostly. You could get lucky, or not.

Click to expand...

I used lots of cheap BW/IR cameras, for those experiments, without problems.

Like as example these ones, that i still have around, and occasionally use for night survey installations



being ccd (except the second one, that is old type cmos), they have decent resolution and sensitivity to IR, and overall, if you fry one of them with a direct shot, you don't have to regret same as if you fry your new pro photocam