Multi-scan Laser For Outdoor Area Safety

Outdoor area protection.  Back in the 2000-2010 era when lasers scanners were not as cheap as they were today and didn’t work very well outdoors for safety applications, I created a solution to obstacle detection for railroad crossings.

An Australian customer posed the problem and needed a cost effective solution.  Prior to this problem, I had created a laser distance measuring device which had a fanned output beam for road traffic applications.  It was being used as a camera trigger and so need to cover the width of a traffic lane when mounted above on a gantry.  Its performance as a distance measuring device was massively impaired, but since the road surface didn’t move, the laser was very good at detecting change, ie the presence of an object.  The spread of the beam would affect the size of the object that could be detected.  However a spread beam would mean that rain drops were invisible too.

The biggest component cost to manufacture of any laser rangefinder device is in the receiver electronics and processing.  So by having a small array of laser diodes, mounted at different angles with a single receiver/processor circuit, the device can effectively scan by sequentially firing the lasers and using a single receiver unit.  Having slight fanned output of the lasers, creates an area of coverage.

Mounting one device (as shown) in each of the barrier mounts on the crossing, it is possible to detect if there is an object trapped on the crossing before the barriers are lowered, or at least to alert a central hub of a potential problem.