Focus and Filter a green laser.

[ElektroFreak]

I watched one with a 45W CO2 where the beam was burning a cinder block at at what looks to be close to 3m. I'll see if I can find the link.. here it is: http://uk.youtube.com/watch?v=0Ia4Z1WuuTw&feature=related

I think maybe what's happening here is a misunderstanding of just what collimation is. Collimation in lasers is the light's ability to be formed into a nearly parallel beam. Coherence length is more what you are describing. A collimated beam may not have burning power at an extreme distance, but it could theoretically still harm your vision.

As I said previously, the thing that defines a laser is the light's ability to be collimated. If the beam can't be collimated by running it through a collimating lens then it's not a laser.

One thing you should consider when posting a response is to include some evidence of why you feel the way you do. You've got to support your argument, and it helps my ability to understand where you are coming from...

 

[Cyparagon]

The thing that defines a laser is the light's ability to be collimated.

I think someone needs a dictionary.

It CAN be collimated but is not. Either way, it is a laser.

If it "pisses light in all directions like a torch" after it's been through a collimating lens then it's not a laser.

There is no set distance, focal length, lens material, and lens coating that works for all beam profiles and all wavelengths. A DPSS profile AND wavelength are much different from that of a direct injection laser and will thus not be collimated identically.

Don't believe anyone on here that can't at least explain the science behind why IR is dangerous.

Surely you mean focused laser light in the IR range, because my eyes themselves emit IR.

 

[ElektroFreak]

[quote author=ElektroFreak link=1234914014/0#12 date=1235413536]The thing that defines a laser is the light's ability to be collimated.

I think someone needs a dictionary.

It CAN be collimated but is not. Either way, it is a laser.

No dictionary necessary. That's why I said the light's ABILITY (ability means it has the necessary qualities to be collimated) to be collimated. You are correct here. The light doesn't have to be collimated to be laser light. Ordinary light simply cannot be fully collimated at all.. If you cannot under any circumstances get the light to become collimated, then the light in question is not laser light. That is my point. Previously in this thread it was stated that IR laser light cannot be collimated. This is untrue.

If it "pisses light in all directions like a torch" after it's been through a collimating lens then it's not a laser.

There is no set distance, focal length, lens material, and lens coating that works for all beam profiles and all wavelengths. A DPSS profile AND wavelength are much different from that of a direct injection laser and will thus not be collimated identically.

You are again correct. At no point did I state that all wavelengths and beam profiles can be collimated identically..

Don't believe anyone on here that can't at least explain the science behind why IR is dangerous.

Surely you mean focused laser light in the IR range, because my eyes themselves emit IR.

That is what I mean. I should have been more specific.

[/quote]



Throughout your responses, you haven't really stated that what I wrote isn't factual. You do have an interesting way of more or less agreeing with someone, tho..

 

[GAFFNEYYY]

Nah you said the ability defines the laser.

It's established that unless the laser creates enough ir, that IS focused, to damage the eye, then yes, it should have an IR filter. Unless the laser burns without it, it's not so necessary. Widely distributed IR is not harmful to the eye at the length of expusure you will normally get with a handheld laser. Co2 lasers are another topic alltogether.

 

[ElektroFreak]

Nah you said the ability defines the laser.

[highlight]It's established that unless the laser creates enough ir, that IS focused, to damage the eye, then yes, it should have an IR filter. Unless the laser burns without it, it's not so necessary. Widely distributed IR is not harmful to the eye at the length of expusure you will normally get with a handheld laser. Co2 lasers are another topic alltogether.[/highlight]

I'll say this once again, and try to be a little more clear. If you can't understand this then you need to work on your understanding of the English language:

The highlighted portion above is correct, and I'm fairly sure if you would take the time to read all the posts in this thread you would see that at no time have I said anything that counters what you just said here. All I've been trying to say is that coherent IR is emitted by unfiltered green DPSS lasers along with the green output, so unless you are so comfortable in your understanding of light and physics that you can absolutely guarantee yourself (and your eyes) that there will never be any problem, then obtaining an IR filter for peace of mind seems like a simple and inexpensive way to guarantee this. This is just common sense.

I did say that the light's ability to be collimated is the thing that defines a laser. What I mean by this is that this quality, the ability to be collimated, is what separates laser light from regular light. Regular incoherent light CANNOT be truly collimated. You can focus incoherent light, and even get a fairly tight beam, but it will never be even remotely close to what coherent laser light is capable of. I will stand by this until someone can PROVE otherwise. Not come on here and just say otherwise.. PROVE it. The proof that supports my argument is easily found. Just google the terms "light collimation" "Laser" and go read a bit of Sam's FAQ. Check here as well: http://www.rp-photonics.com/encyclopedia.html.

 

[murrat]

I watched one with a 45W CO2 where the beam was burning a cinder block at at what looks to be close to 3m. I'll see if I can find the link.. here it is: http://uk.youtube.com/watch?v=0Ia4Z1WuuTw&feature=related

I think maybe what's happening here is a misunderstanding of just what collimation is. Collimation in lasers is the light's ability to be formed into a nearly parallel beam. Coherence length is more what you are describing. A collimated beam may not have burning power at an extreme distance, but it could theoretically still harm your vision.

As I said previously, the thing that defines a laser is the light's ability to be collimated. If the beam can't be collimated by running it  through a collimating lens then it's not a laser.

One thing you should consider when posting a response is to include some evidence of why you feel the way you do. You've got to support your argument, and it helps my ability to understand where you are coming from...

You are right and also I do
It has a bad divergence as you can see it in the video. The dots gets 3 times bigger at 3m than it is at 1m
Guess what will be the power at 3meters with a 150mW pointer
I've just tell a bit wrong.
I mean to collimate CO2 10600nm light you need special made (IIRC it is ZnSe ) lens.
Therefore lens that collimates green light does not collimate IR light in the same way.
Green laser having 1,2mRad divergence can have 2,5mRad or much more divergence figura for IR light!
Because of this reason, IR coming out of a medium powered 75-100mW laser pointer (pensized ones, as more expensive ones need to have IR filters ) does not harm your eyes unless you are so near to the aperture of the laser.

I don't say we don't need IR filters but we have to be careful even we have them
So IR filter is not something that makes a quality laser

By the way thanks for the 45Watt CO2 link. It is the first I've seen burning that far Huge power 45Watt,360 times the power of my most powerful laser ;D

 

[Cyparagon]

Here's my 60W lighting paper at 20 feet. 0.6MB

 

[ElektroFreak]

You are right and also I do
It has a bad divergence as you can see it in the video. The dots gets 3 times bigger at 3m than it is at 1m
Guess what will be the power at 3meters with a 150mW pointer  
I've just tell a bit wrong.
I mean to collimate CO2 10600nm light you need special made (IIRC it is ZnSe ) lens.
Therefore lens that collimates green light does not collimate IR light in the same way.
Green laser having 1,2mRad divergence can have 2,5mRad or much more divergence figura for IR light!
Because of this reason, IR coming out of a medium powered 75-100mW laser pointer (pensized ones, as more expensive ones need to have IR filters ) does not harm your eyes  unless you are so near to the aperture of the laser.

I don't say we don't need IR filters but we have to be careful even we have them
So IR filter is not something that makes a quality laser

By the way thanks for the 45Watt CO2 link. It is the first I've seen burning that far Huge power 45Watt,360 times the power of my most powerful laser  ;D

Everything you say here is true.. so it's up to you if you even feel that there is a risk. I haven't been trying to say that there is danger when in fact there is none, I just want everyone to understand that there is a potential for IR leakage. If you feel there's a risk involved, then buy an IR filter. If you're comfortable with using your laser without one, then that's fine too. It's up to the user. I'm on the side of caution myself so I recommend filtering, especially when using higher-powered cheap Chinese lasers.

If you're using a green laser professionally or scientifically, it is often desirable to have IR filters installed to ensure that the laser emits only a single wavelength rather than several wavelengths. In this regard, IR filtering does constitute a higher quality laser.

Personally, if I buy a 532nm laser, then I want it to emit 532nm light only. If I want 1064nm or 808nm output, then I'd buy a laser specifically for those wavelengths, although I've seen some pretty neat systems from Coherent that output filtered 532nm from one aperture and 1064nm from another aperture in the same laser. This requires a ring cavity and some fancy optics, however.