A comprehensive resource for safe and responsible laser use
Michael Reeves’ tongue-in-cheek narration states “…it’s really doing its job of lasering me in the eye which is the real innovation here. To my pleasant surprise I found that this machine also solved another of society's problems; the fact that you're not seeing little tiny dots in your vision all day long. I know where to go when I wanted to see little dots, now I can't focus on anything.”
The laser in the video looks substantially more powerful than the U.S. FDA limit of 5 milliwatts. (However, it can be difficult to estimate laser power from a video. For example, the camera may be more red-sensitive than human eyes which might explain why the beam seems so large and bright.)
Anyone doing this should be aware of the problem of laser pointers often being more powerful than the label states, and more powerful than the U.S. limit of 5 mW.
Fortunately for Reeves’ vision, the laser is mechanically aimed by two devices that move it left-right and up-down. This makes the aiming relatively slow and lagging the facial recognition, so the beam can be dodged much of the time. He moves to avoid the beam, and is hit in or very near to an eye about once every couple of seconds.
The screenshot below shows the camera (blue arrow) and a laser module mounted on two servos (yellow arrow).
As befits a student budget, the housing is an old pizza box. Reeves wrote the facial recognition and aiming program in C#, using Emgu CV, a .Net wrapper for the OpenCV computer vision library.
In about a day, the video received 80,000 views as well as being featured at tech blog The Verge.
From The Verge. Original YouTube video here.
UPDATED April 19 2017: Michael Reeves told C/Net “My eyes are fine. A lot of people seem concerned about that, which I admit is warranted. I used a 5 mW laser diode, and never had it in my vision for more than a fraction of a second."
The system is intended for use in cockpits, and is self-contained — it does not need to interface with any aircraft instruments. For location, altitude and orientation data, it has a GPS and a 3-axis magnetic compass.
A laser is detected by a camera sensor, currently with 1024 x 1024 pixel resolution. The camera detects the bright “bloom” from a direct or near-direct laser illumination (left image, below). To distinguish laser light from a bright non-laser light such as the sun, it looks at surrounding pixels to see whether they saturate the green channel of the sensor. (The system currently looks only for green laser beams since those represent over 90% of FAA-reported laser incidents. But future versions could look for other color laser beams as well.)
As the laser aims away from the camera, the bright center of the laser is still visible (right image, above). The system then looks at the center of the bright area to find the pixel location. Knowing the camera’s orientation, location and altitude, a Raspberry Pi computer running a Python program written by Hough calculates the approximate location. This is automatically sent via text message to pre-programmed recipients which could include law enforcement.
In ground testing on a slope, at a relatively short distance, the error was 15 meters. As the photo diagram shows, the system was successful in determining an approximate distance and location.
Hough notes that the system is a low-cost proof-of-concept. Suggested improvements include “more precise location sensors [that] would improve target location accuracy. Tapping into the high quality compass and GPS sensors on a commercial aircraft, for example, would drastically improve the ability of the system.” He also stated that smartphones include all the equipment needed: camera, compass, GPS, processor and display. So it should be possible to make a smartphone application to accomplish the same task.
From “Detection and Location System for Laser Interference with Aircraft”, December 2016. Thanks to Nate Hough for bringing this to our attention and allowing us to host the PDF. Note: A similar system, which does not calculate the laser source location, is the Laser Event Recorder.