My first laser pointer....IR question

[Brian321]

Hello, I just received my first laser pointer. It is the 50mw one from the LED Shoppe. I also read the "damaged eyes" sticky at the top.

My question: Is it bad to shine the laser on the wall and look at the beam from about 4-5feet away? Will it damage my eyes in anyway?

I really like this laser but i really worry about damageing my eyes from looking at it on the wall or from it emitting to much IR.

Thanks,
Brian

 

[Steve K]

the risk is having the laser beam enter the eye and put the concentrated energy onto the rods and cones in the eye. Looking at the light reflected off the wall is safe.

"IR" usually stands for Infra-Red, meaning light that is lower frequency than red, and invisible to the human eye. This seems unlikely for a laser pointer. I assume you meant something else?

regards,
Steve K.

 

[yellow]

and invisible to the human eye. This seems unlikely for a laser pointer.

cheap pointer --> no IR filter --> "weak" beam but still able to pop Ballons / cut black tape --> no IR filter for sure.

bad in 2 ways: no as "bright" beam than similar power IR filtered (more expensive) lasers + totally no reaction from the eye when exposed (but a direct hit from a 50 mW laser ... there will be pretty no difference if filtered or not)


differently to that, there is a difference from spill / reflection.
The IR filtered laser's reflection / spill light will appear "too bright" at that distance, the human will quickly learn, that 4-5 feet is something like a minimum safety distance (when doing bursts)
the non-IR-filtered will not seem so bright, prolonged use might be possible --> damage to the eyes possible
Dont use a 5+ mW inside rooms


PS: at that price (led shoppe) there is a very high chance of a cheapo non-IR-filtered.

 

[Brian321]

cheap pointer --> no IR filter --> "weak" beam but still able to pop Ballons / cut black tape --> no IR filter for sure.

bad in 2 ways: no as "bright" beam than similar power IR filtered (more expensive) lasers + totally no reaction from the eye when exposed (but a direct hit from a 50 mW laser ... there will be pretty no difference if filtered or not)


differently to that, there is a difference from spill / reflection.
The IR filtered laser's reflection / spill light will appear "too bright" at that distance, the human will quickly learn, that 4-5 feet is something like a minimum safety distance (when doing bursts)
the non-IR-filtered will not seem so bright, prolonged use might be possible --> damage to the eyes possible
Dont use a 5+ mW inside rooms


PS: at that price (led shoppe) there is a very high chance of a cheapo non-IR-filtered.

Thanks for the info. From what you said im guessing that mine has an IR filter.

It seems extremly bright up close and i tried to put a hole in a black trash bag by holding the laser pointer up against it for about 20-30 seconds and it did nothing.

Brian

 

[bshanahan14rulz]

If you look at it through your safety glasses, you can see a halo of IR around the green dot.

You can also take it to radioshack and point it at one of their IR testing cards, though the green might wash it out.

You can also try using a digital camera to see if you can see the IR.

The IR doesn't collimate with the green, though it is pretty close. for my "30mW" green pointer, I see a halo about 4 or 5 mm across when the green dot is about 1.5mm across.

 

[Steve K]

I know that green LEDs will produce more than one wavelength, but I'm surprised to hear that a green laser can produce emissions that have a wide enough spectrum to include IR! Or is this just the IR that results from the warm semiconductor, and not an output of that Stimulated Emission that is making the green light?

Steve K.

 

[LED_astray]

I know that green LEDs will produce more than one wavelength, but I'm surprised to hear that a green laser can produce emissions that have a wide enough spectrum to include IR! Or is this just the IR that results from the warm semiconductor, and not an output of that Stimulated Emission that is making the green light?

Steve K.

There are no green laser diodes. (At least outside of development labs, maybe some there, but none in consumer products.)

Green laser light is produced starting with an 808nm IR laser diode and sending it through a set of crystals. The first converts (shifts?) the laser to 1064nm (deeper IR) and the second converts that to 532nm (Green). The problem is that less than perfect conversion efficiency and alignment can allow IR to escape the laser. The better lasers have IR filters (& probably leak less anyway.) The cheapies omit the filter and may or may not have a significant leak. Since you can't see IR, do you feel lucky?

 

[Steve K]

thanks for the explanation! I knew that this sort of thing had been done, but assumed that the technology had progressed to the point where someone had figured out how to get green light to lase. Since we can make green LEDs, is it just the mechanical aspects that have to solved? Maybe I need to go poke around the web and get updated (it's been a while since my last solid state physics course).

thanks,
Steve K.