How to estimate the power of a laser pointer

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Discussion Overview

The discussion revolves around the safety and power estimation of a laser pointer, specifically a model identified as "JD-303". Participants explore concerns about potential eye damage from accidental exposure to the laser's reflection and seek methods to estimate the laser's power output, given its stated specifications and observed performance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant expresses concern about potential eye damage from a laser pointer reflecting off a mirror, questioning the safety of exposure to the beam.
  • Another participant suggests using a volt/amp meter to measure the current and voltage to estimate the laser's power output, indicating that this may require some improvisation.
  • Some participants challenge the belief that the laser is indeed 500mW, citing its inability to burn materials like matches or paper as evidence of lower power.
  • There is a discussion about the distinction between power and intensity, with one participant noting that high intensity is necessary for burning, regardless of power levels.
  • Concerns are raised about the safety of shining lasers into hotel rooms, with warnings about potential legal repercussions.
  • Participants express uncertainty about the authenticity of the laser, given its purchase from a street vendor, and discuss the implications of using a laser of unknown power.
  • Some participants emphasize the importance of avoiding eye exposure to lasers, suggesting that even low-intensity hits can cause damage.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the actual power of the laser pointer, with multiple competing views regarding its effectiveness and safety. Concerns about eye safety are generally acknowledged, but there is no agreement on the extent of potential damage or the reliability of the laser's specifications.

Contextual Notes

Participants note limitations in their ability to measure the laser's power and express uncertainty about the authenticity of the product. There are unresolved questions regarding the relationship between the laser's stated power and its actual performance.

CookieSalesman
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Not sure if this is the right place, but I'm hoping to ask two questions:
1. I shine a laser pointer at a mirror at night, and the reflecting beam glaces off of my eye. Obviously it's quite bright, and I want to know if this has caused any serious damage. Of course I shut my eye, but apparently only 5mW is safe for eyes.

2. Does anyone know how to estimate the power of this pointer?
All that's said on the laser is that its max power output is less than 1000 milliwatts. That's obvious.
The model is apparently a "JD-303". I looked that up, and it's a 500mW laser, which doesn't seem right.

From this video , it seems that 500 mW should be able to burn anything, from my eyeball to my bedsheets- which mine can't do.
It's quite bright- At night, if I shine it out of my window, it (the whole beam, not the dot) clearly goes for quite a few kilometers. (allowing me to point it into hotel rooms and such.)

The battery in the laser:
"BRC 18650 4800mAh
3.7Volts lithium ion battery"
Perhaps that helps.

is it just that my laser has a bad focus/lens, since it's apparently not very powerful?

Perhaps the battery stats can help explain the power output of this laser. Will I need to see a doc...?oh. and I bought this laser off the street... In China. I honestly don't know if it's a fake, but from what I can tell, so far it is actually quite authentic. I don't think that just because I purchased this off the street that it should be considered fake, although it's a possibility. I'm not sure if street peddlers can really sell fake lasers though.
 
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You wrote,

"
All that's said on the laser is that its max power output is less than 1000 milliwatts. That's obvious.
The model is apparently a "JD-303". I looked that up, and it's a 500mW laser, which doesn't seem right."

Why don't you believe that number, I would?

To estimate power use a volt/amp meter to determine current passing out of the battery and the battery voltage while the laser is working, this will likely require some jury rigging. Current times voltage gives power. Google the efficiency of solid state lasers?

https://www.google.com/search?sourc...id state lasers&aqs=chrome..69i57j0.11126j0j8

Notice anything wrong with your vision?

Be careful with dangerous tools.
 
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I don't believe it because it's far from burning matches, or paper.

I unfortunately don't have the items or ability to measure this sort of stuff.

I don't think anything is wrong with my vision... I suppose I wouldn't be asking here if there was something wrong.
 
CookieSalesman said:
I don't believe it because it's far from burning matches, or paper.
To burn things, you need high intensity, not high power. How much Watt higher do you think the lamp in your room has, and you are still alive?
 
Ok...
Well the beam seems pretty darn well like a laser beam...

I can't possibly focus it more than it already is. And I feel absolutely no heat even if I stick the laser on my hand. ??
 
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Yes, taking even a low-intensity laser hit in your eye can start to create damage. Please do your best to avoid that. It would be a good idea for you to have an eye exam, and talk to the doctor about laser safety.

And why are you shining your laser into hotel rooms? That can earn you an assault or battery charge if you are caught...
 
CookieSalesman said:
1. I shine a laser pointer at a mirror at night, and the reflecting beam glaces off of my eye. Obviously it's quite bright, and I want to know if this has caused any serious damage.
This is impossible to tell based on that description.
CookieSalesman said:
(allowing me to point it into hotel rooms and such.)
To ruin other's vision? ...

The power drawn from the batteries is probably a good start - it gives a very hard upper limit on laser power and allows to make a reasonable estimate.
An even better idea is to not use lasers of unknown power.
 
berkeman said:
Yes, taking even a low-intensity laser hit in your eye can start to create damage. Please do your best to avoid that. It would be a good idea for you to have an eye exam, and talk to the doctor about laser safety.

And why are you shining your laser into hotel rooms? That can earn you an assault or battery charge if you are caught...
Yep. I'll try to avoid that... I assure you I didn't stick my eye in front of the laser...

I assure you, if it was your first time getting a neat laser like that you wouldn't be able to resist doing that.
But I'm also not in the US, people don't get beat up for small things like this :-]
 
Thread is done.
 

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