How to make a safe homemade 3D laser rangefinder

How to make a safe homemade 3D laser rangefinder

Postby suisui » 2017-Dec-Thu-03-Dec

hi to all, I'm trying to create a simple homemade 3D laser rangefinder using a generic line laser and an infrared camera, similar to the one described Webcam Based DIY Laser Rangefinder. Line lasers and cameras will detect two-dimensional depth. I then installed the servers in an Angle to track the third dimension. My goal is to use it for indoor mapping experiments on cheap indoor mobile robots, without paying $5,000 for 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, give a description (25mW, 810nm, 5V) but don't provide a safety classification.

Based on this description 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?
Thanks all advice!
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How to make a safe homemade 3D laser rangefinder

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Re: How to make a safe homemade 3D laser rangefinder

Postby RetireeJay » 2017-Dec-Thu-07-Dec

Your questions are good ones, but they are so far off topic for discussion in a forum about 3D printers that you probably won't get a good response here.
Personally, I'd be very leery of the idea of pulsing a high powered laser to make it "safe"; I doubt that it works that way - but I'm not an expert. Is there a reason you want to use IR instead of visible light? Little red lasers are sold for a few dollars as toys for cats in pet stores, and they can project a dot 20 feet away easily.

But speaking of pulsing, it may be advantageous to use pulsed light because then your receiver can look for the difference between the "on" and "off" condition, which helps to overcome the problem of random ambient light and colors in a typical uncontrolled environment.
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