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Comment by EgoIncarnate | Hacker News Reader

Seems... dangerous? Project states it uses "3mw 780nm Infrared IR Diode Laser". 3mw is enough to damage your eye if you don't blink or turn away. Since it's infrared, you won't blink, or possible even notice anything (there are no pain receptors in the retina) until it's too late.

Wikipedia list "780–1400 nm (near-IR) - Pathological effect: cataract, retinal burn"

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Laser is rotating fast enough so it is less dangerous. Also laser current is modulated, so laser's average power decreased twice.

Which safeguards are implemented to detect that rotation and modulation are taking place as intended?

I was just going to mention the THERAC 25: https://en.wikipedia.org/wiki/Therac-25

Now that is a question only a true engineer would ask.

(If you didn't ask the same question then demote yourself down to "Computer Nerd")

In the US 5mW is the legal limit for laser pointers. I think that can be used as a guideline, 3mW IR is much less energetic than a 5mW green/blue laser, perhaps it's not powerful enough to cause huge concern? But I agree no amount of laser is safe for the eye. Police LIDAR guns are 905nm at 50mW, that can technically damage you too.

https://en.wikipedia.org/wiki/LIDAR_traffic_enforcement#How_...

Wouldn't it matter how narrow the laser beam is? 50mW spread out over a larger surface area sounds like it should be safer.

Of course, then the question is whether that also comes with an equal reduction in sensitivity, or whether a larger sensor can compensate for that.

The limit for visible light is as high as it is because of the blink reflex. An IR laser, having a beam you don't perceive as being bright, won't make you blink.

Well, actually it's near infrared so at this "high" power (3mw) you will definitely see it. You can actually see past 800nm if the source is bright, but I don't recommend it.

The wavelength range where optical radiation is visible does not have sharp borders. Here, the wavelength band of 380 nm to 780 nm is used.

https://www.icnirp.org/en/frequencies/visible/index.html

Agreed - I don't enough to say about this particular project, but the lasers in LiDAR sensors do have the potential to be powerful enough to harm eyesight, so I would advise caution. This is not a concern for most commercial sensors, as they are constrained by regulations to a certain power for this same reason. I'm guessing there's no rules for DIY, but it's something to keep in mind if a product came out of this.

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