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Just because I can't see infrared doesn't mean it won't damage my retinas through my fully dilated pupils at night when you pump up the power by 40x. Edit: Emp

by Sephr 9y ago

Just because I can't see infrared doesn't mean it won't damage my retinas through my fully dilated pupils at night when you pump up the power by 40x. Edit: Emphasis on fully dilated. The amount of infrared energy that reaches my retinas in daylight is reduced due to pupil contraction. Additionally, this has moving parts so what if it suddenly fails to spin and you are exposed to a continuous IR beam with fully dilated pupils at night? I'm sure that it's possible for it to heat and damage your retina in this failure scenario.

IanCal 9y ago
No, it doesn't just mean that. But it's rather a quick judgement to suggest that's their line of thinking. It may well be fine to do this if increasing the wavelength to over 900nm makes a beam far less damaging. A more useful comment would be to ask what the wavelength-damage relationship is for different power levels.
- deleted 9y ago
  [deleted]
hwillis 9y ago
Nah, you'll be fine. You receive a couple hundred watts of near infrared radiation (ie the 1550 nm in the laser) just by being in direct sunlight. That's spread over your entire body, of course. The laser in this lidar has a power of ~40 mW, which technically puts it out of being a class 1[1] laser, ie you can shine it directly into your pupil through a magnifying glass without fear. However the class is just a guideline. 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. [1] https://en.wikipedia.org/wiki/Laser_safety#/media/File:Laser_class_EN_60825-1.en.png https://en.wikipedia.org/wiki/Laser_safety#/media/File:Laser... [2] https://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png https://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png
- Sephr 9y ago
  > You receive a couple hundred watts of near infrared radiation (ie the 1550 nm in the laser) just by being in direct sunlight. The visible light in sunlight makes pupils dilate, decreasing the amount of infrared energy that reaches and heats the retina.
  - valuearb 9y ago
    You don't think the safety charts don't already understand that effect?
  - hwillis 9y ago
    That's irrelevant, this assumes the spot is smaller than the pupil. The pupil would have to grow to 800x the area for it to even matter in the first place.
- deepnotderp 9y ago
  You seem to know a lot about LIDAR, I'd love to chat sometime if you'd be interested. I couldn't find your email anywhere. Care to give me a ping at sixsamuraisoldier[at]gmail[dot]com?

by Sephr 9y ago

IanCal 9y ago

No, it doesn't just mean that. But it's rather a quick judgement to suggest that's their line of thinking. It may well be fine to do this if increasing the wavelength to over 900nm makes a beam far less damaging. A more useful comment would be to ask what the wavelength-damage relationship is for different power levels.

deleted 9y ago
[deleted]

hwillis 9y ago

Nah, you'll be fine. You receive a couple hundred watts of near infrared radiation (ie the 1550 nm in the laser) just by being in direct sunlight. That's spread over your entire body, of course. The laser in this lidar has a power of ~40 mW, which technically puts it out of being a class 1[1] laser, ie you can shine it directly into your pupil through a magnifying glass without fear. However the class is just a guideline. 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. [1] https://en.wikipedia.org/wiki/Laser_safety#/media/File:Laser_class_EN_60825-1.en.png https://en.wikipedia.org/wiki/Laser_safety#/media/File:Laser... [2] https://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png https://en.wikipedia.org/wiki/File:IEC60825_MPE_W_s.png

Sephr 9y ago
> You receive a couple hundred watts of near infrared radiation (ie the 1550 nm in the laser) just by being in direct sunlight. The visible light in sunlight makes pupils dilate, decreasing the amount of infrared energy that reaches and heats the retina.
- valuearb 9y ago
  You don't think the safety charts don't already understand that effect?
- hwillis 9y ago
  That's irrelevant, this assumes the spot is smaller than the pupil. The pupil would have to grow to 800x the area for it to even matter in the first place.
deepnotderp 9y ago
You seem to know a lot about LIDAR, I'd love to chat sometime if you'd be interested. I couldn't find your email anywhere. Care to give me a ping at sixsamuraisoldier[at]gmail[dot]com?