I'm trying to create a simple homemade 3D laser rangefinder using a generic line laser and an IR camera, similar to the setup described [here][1]. The line laser and camera would detect depth in two dimensions. I'd then mount these on a servo to sweep it across an angle to track the third dimension. My goal is to use it on a cheap indoor mobile robot for experiments with room mapping without spending $5000 on a "real" 3d laser rangefinder.

Being mindful of eye safety, I'm trying to find an appropriate line laser rated as class 2, but this has become quite difficult. The few line lasers I can find, [like this one][2], give a description (25mW, 810nm, 5V) but don't provide a safety classification.

Based on [this description][3] of the safety classifications, the 25mW power rating would seem to imply it's a class IIIb, and therefore potentially quite dangerous:

> CLASS IIIb LASERS are systems with power levels of 5 mW to 500 mW 
> (CW) and some pulsed lasers. These lasers will produce an eye hazard
> if viewed directly. This includes specular reflections. 
> Administrative, Engineering, and PPE control measures are required.
> (Especially laser safety glasses!)

Does this classification and danger seem correct?

Since my application involves shining it around a home, I want to make sure it doesn't blind anyone. How can I ensure this is safe for home use?

Ideally, I'd like to find a 2.5-5mW infrared line laser, but no one seems to sell anything like this. Most seem to be 25mW or stronger. Could I control a stronger 5V laser's duty cycle by connecting it's +5V lead to an Arduino pin and generate a PWM output of 10% to give a 25mW laser an effective 2.5mW output?

Also, what minimum power would I need to make an effect laser rangefinder? Even if I did find a 5mW line laser, would that be bright enough to detect a couple meters away?

  [1]: https://sites.google.com/site/todddanko/home/webcam_laser_ranger
  [2]: http://www.amazon.com/gp/product/B00STMRX38
  [3]: https://www.phys.ksu.edu/personal/macf/safety-training/jrml-web-training.htm