3D Radar Light Curtain - Research combines tested technology for this “smart” system.

by Matt Davies

Infrared (IR)-based light curtains have been the accepted way of protecting passengers from closing elevator doors since the 1990s. However, over the last five years, there have been numerous tradeshow exhibits with new and exciting technology purporting to render light-curtain technology obsolete. More recently, the update to ASME 17.1-2019 requires detection not just for the area between the closing doors, but also of approaching passengers on the landing. However, despite these bold announcements in the market, little appears to have changed. This article looks to separate the facts from the hyperbole and so set realistic expectations on what to expect over the coming years.

Current IR light-curtain technology is, conceptually, relatively simple. IR light waves are pulsed through a series of diodes running the height of the door. At the other side of the door opening, IR detectors running the height of the door look to detect these IR light waves. A break in the signal means there is something blocking the passage of these waves. This system generates its own signal, and, in doing so, is in full control of the frequencies and timing used. This fact, combined with object detection by signal blockage, rather than reflection, makes IR light curtains inherently reliable.