6 ms·

I believe that I can't see that wavelength, but the energy has to go somewhere (similarly, I can't see microwave radiation, but don't want to put my head in a r

I believe that I can't see that wavelength, but the energy has to go somewhere (similarly, I can't see microwave radiation, but don't want to put my head in a running microwave, a la Infinite Jest). I think the better question is: Will it blind you/me/animals?

goodcanadian 9y ago
Indeed, I find it mildly painful to look at IR emitters, for example, on a "night vision" security camera. I don't believe it is dangerous or will blind anyone, or anything, but it is plausible to me that there could be an unanticipated effect. EDIT: It appears that this is given a passing mention in the article: . . . it can receive at a wavelength of 1550 nanometers, deep in the infrared part of the spectrum. That makes this wavelength much safer for human eyes than today’s standard wavelength, 905 nm.
splawn 9y ago
It depends on the power density. I have an IR laser that is invisible and it would burn your eyes out of your head.
- hwillis 9y ago
  ~40 mW peak, ~10 nS pulses
hueving 9y ago
>similarly, I can't see microwave radiation, but don't want to put my head in a running microwave, a la Infinite Jest Yet wireless access points spew microwave radiation at you all day.
- p1esk 9y ago
  Not at 1,000W.
  - hwillis 9y ago
    However, you do receive a couple hundred watts of near infrared radiation (ie the 1550 nm in the laser) just by being in direct sunlight: https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spe...
    - p1esk 9y ago
      But even though I can't see it, I can definitely feel it.
      - hwillis 9y ago
        The premise of the parent comment is that even invisible lasers could be harmful. You pointed out that microwaves may not be as harmful at lower levels of power. I pointed out that the output of a lidar beam is far below the level that you get from sunlight, which doesn't even cause cancer and certainly doesn't blind people. Just because I like running numbers, here's the comparison: the laser in this lidar has a power of ~40 mW, ~1000x less than sunlight. Lidar pulses are on the order of 10 nanoseconds, 100,000,000x less than a second. The energy on your eyes is less than 100 billion times less than a second in bright sunlight. There is certainly no mechanism for thermal damage to occur.
        deleted 9y ago
        [deleted]
        p1esk 9y ago
        40mW would be dangerous for a constant laser (class 3b), but I'm not sure about a short pulsed one. I think you should look at the amount of energy per pulse.
        hwillis 9y ago
        It would be class 3r, for which direct retina exposure is "low risk". In general for pulsed lasers you can use the duty cycle. I did more analysis in another comment: Using a maximum permissible exposure chart gives a better sense of danger. Lidar pulses are on the order of 10 nanoseconds, or 1/100th the smallest division on this chart[2]. Even so, you can see that the maximum safe power for 1550 nm is somewhere between 8 and 10,000 watts, at least 800x more than the lidar emits. 1550 nm doesn't chemically damage biological receptors. The damage would have to be thermal, but the laser is pulsed for an incredibly short time and even if it wasn't it's well under what you can be exposed to indefinitely. [2] https://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png https://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png
hwillis 9y ago
The laser in the article is on the order of tens of milliwatts. Even directly into your eye would not damage it. It would be painful, especially if it was in a visible wavelength, but the laser spot from a lidar is in one location for less than a microsecond. In terms of direct heating, tens of milliwatts isn't even enough to really make a human-detectable rise.
- kwhitefoot 9y ago
  > is in one location for less than a microsecond When it is working properly.
  - jhall1468 9y ago
    And self-diagnostics will know when it isn't.
  - hwillis 9y ago
    Same with elevators, microwaves, airbags, and in fact literally anything that plugs into the wall. 120 volts can kill you if you contact it. The laser is eye-safe, meaning you can look directly at it continuously and be fine. Though, if you did, you would deserve injury. Kind of like sticking your hand in a blender. The device will not manage to malfunction and miraculously shoot you in the eye from meters away.
- jhall1468 9y ago
  Would it even be painful at that wavelength?
  - hwillis 9y ago
    No, although lasers can sometimes be dangerous without being painful. Even if they aren't, by the time it hurts it is too late.

goodcanadian 9y ago

Indeed, I find it mildly painful to look at IR emitters, for example, on a "night vision" security camera. I don't believe it is dangerous or will blind anyone, or anything, but it is plausible to me that there could be an unanticipated effect. EDIT: It appears that this is given a passing mention in the article: . . . it can receive at a wavelength of 1550 nanometers, deep in the infrared part of the spectrum. That makes this wavelength much safer for human eyes than today’s standard wavelength, 905 nm.

splawn 9y ago

It depends on the power density. I have an IR laser that is invisible and it would burn your eyes out of your head.

hwillis 9y ago
~40 mW peak, ~10 nS pulses

hueving 9y ago

>similarly, I can't see microwave radiation, but don't want to put my head in a running microwave, a la Infinite Jest Yet wireless access points spew microwave radiation at you all day.

p1esk 9y ago
Not at 1,000W.
- hwillis 9y ago
  However, you do receive a couple hundred watts of near infrared radiation (ie the 1550 nm in the laser) just by being in direct sunlight: https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spe...
  - p1esk 9y ago
    But even though I can't see it, I can definitely feel it.
    - hwillis 9y ago
      The premise of the parent comment is that even invisible lasers could be harmful. You pointed out that microwaves may not be as harmful at lower levels of power. I pointed out that the output of a lidar beam is far below the level that you get from sunlight, which doesn't even cause cancer and certainly doesn't blind people. Just because I like running numbers, here's the comparison: the laser in this lidar has a power of ~40 mW, ~1000x less than sunlight. Lidar pulses are on the order of 10 nanoseconds, 100,000,000x less than a second. The energy on your eyes is less than 100 billion times less than a second in bright sunlight. There is certainly no mechanism for thermal damage to occur.
      - deleted 9y ago
        [deleted]
      - p1esk 9y ago
        40mW would be dangerous for a constant laser (class 3b), but I'm not sure about a short pulsed one. I think you should look at the amount of energy per pulse.
        hwillis 9y ago
        It would be class 3r, for which direct retina exposure is "low risk". In general for pulsed lasers you can use the duty cycle. I did more analysis in another comment: Using a maximum permissible exposure chart gives a better sense of danger. Lidar pulses are on the order of 10 nanoseconds, or 1/100th the smallest division on this chart[2]. Even so, you can see that the maximum safe power for 1550 nm is somewhere between 8 and 10,000 watts, at least 800x more than the lidar emits. 1550 nm doesn't chemically damage biological receptors. The damage would have to be thermal, but the laser is pulsed for an incredibly short time and even if it wasn't it's well under what you can be exposed to indefinitely. [2] https://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png https://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png

hwillis 9y ago

The laser in the article is on the order of tens of milliwatts. Even directly into your eye would not damage it. It would be painful, especially if it was in a visible wavelength, but the laser spot from a lidar is in one location for less than a microsecond. In terms of direct heating, tens of milliwatts isn't even enough to really make a human-detectable rise.

kwhitefoot 9y ago
> is in one location for less than a microsecond When it is working properly.
- jhall1468 9y ago
  And self-diagnostics will know when it isn't.
- hwillis 9y ago
  Same with elevators, microwaves, airbags, and in fact literally anything that plugs into the wall. 120 volts can kill you if you contact it. The laser is eye-safe, meaning you can look directly at it continuously and be fine. Though, if you did, you would deserve injury. Kind of like sticking your hand in a blender. The device will not manage to malfunction and miraculously shoot you in the eye from meters away.
jhall1468 9y ago
Would it even be painful at that wavelength?
- hwillis 9y ago
  No, although lasers can sometimes be dangerous without being painful. Even if they aren't, by the time it hurts it is too late.