Device that emits a safe beam of light - doesn't have to be visible (Like laser, but safer)

Question

I am looking for a light emitting device, which can produce a narrow and accurate beam, with a small "dot" size, for a significant distance (around the 100-150 meters) similar to that of a laser, but that it would be safer when comes in contact with eyes / other body parts.

**Edit: My goal is that I want to be able to point 1 device at another, and that the other device will detect it was pointed at (But it should be placed on the body so that's why I want it to be safe), so the beam doesn't actually needs to be visible

Does such device exist?

Answer 1

There are eye-safe lasers, both in the visible and IR. For your detection system, make sure you understand the power required for your target (receiver) to register a hit. Pretty much any commercial diode laser will have a small enough divergence (assuming you include a collimating lens) that point-spread over 150 m is minimal.

However, you also need to consider dwell time on target. If the person is moving, the beam may hit the detector too briefly to produce an alarm. Check the pulse-width or, equivalently, minimum energy (not power) required by the detector you pick out.