A comprehensive resource for safe and responsible laser use
Worldwide: Review of laser "stars" projector; question about aircraft interference
The reviewer, Bill Kuch, says the green-only version contains a Class IIIa laser that uses diffractive holographic optics to create the beams. According to the instruction pamphlet, “Each individual laser beam is less than 5 mW, which is about the same as an average laser pointer.”
He then talks about testing the unit indoors and outdoors. Kuch said that after aiming at the tree canopy around his cabin in the woods, his neighbors came out, commented positively, and asked where they could purchase one.
In the final paragraph, he says when he pointed the projector up into the trees, “that begs the question: could it interfere with aircraft flying overhead?”
Review of the Viatek Night Stars Landscape Lighting from the Gadgeteer.
Instead, it is highly likely that the laser output is higher than Class IIIa, but each individual beamlet is below 5 mW, as stated in the Viatek instruction manual. This would be a more viable product, with brighter “stars”.
While individual laser “stars” could not be seen on clouds, clear sky or the Moon (!), this photo illustration from Viatek does give an idea of the number and density of the stars at a moderate distance such as 15 feet from the projector.
CAN THE BEAMS INTERFERE WITH AIRCRAFT?
Regarding whether the beams could interfere with aircraft, it depends on the nature of the “interference”. Flying a helicopter at low altitude through the hundreds of green beams would probably be visually distracting to a pilot. Whether they could cause visual interference such as glare or temporary flashblindness depends on the power of the beamlets and the distance to the helicopter.
- If the projector uses a Class IIIa laser (less than 5 mW) and then diffracts it into a hundred or more beamlets, each beamlet would very weak. As a rough approximation, a single beamlet 1/100 of 5 mW (e.g., 0.05 mW) with a moderate divergence such as 1 milliradian, would be a glare hazard up to about 110 feet from the projector. It would cause temporary flashblindness up to about 25 feet from the projector. The distraction distance would be about 1100 feet.
- However, if the projector uses a laser more powerful than Class IIIa, so that the maximum power of a beamlet is just below 5 mW in power, The beamlet would be a glare hazard up to about 1,100 feet from the projector, and it could cause temporary flashblindness up to about 250 feet away. The distraction distance is about 2.1 miles.
The short answer is that for safety, the beams should be terminated onto a solid surface such as a building wall or dense foliage.
IS AIMING A LASER STAR PROJECTOR INTO THE SKY ILLEGAL?
Whether aiming a laser projector like this into the sky is illegal under U.S. federal law is another question.
Under the February 14 2012 law signed by President Obama, it is illegal to “knowingly aim the beam of a laser pointer at an aircraft ... or at the flight path of such an aircraft.” The definition of laser pointer is a laser “that emits a beam designed to be used by the operator as a pointer or highlighter to indicate, mark, or identify a specific position, place, item, or object.”
A defendant could argue that they did not “knowingly” aim at an aircraft or its flight path. They could also argue that they were not using a laser pointer, but instead a laser star projector not intended “to indicate, mark or identify a specific position, place, item, or object.”
Whether a person is prosecuted or convicted may depend on how egregious the usage is. For example, is the laser projector simply pointed straight up in a high-traffic area so a helicopter is likely to intercept dozens of the beams? Or is it used in a way such that only a relatively few beams escape through or past foliage into the sky of a low-air-traffic rural area?
Also, the above only discusses U.S. federal law. There may be state or local laws with a different definition of aiming at aircraft, and of laser devices, that would be easier to apply to a laser star projector.
Again, the suggested best course of action is to terminate the beams so that they do not go into the night sky.