Laser light shows are impressive to watch when projected away from the audience. In some countries, where laser eye safety regulations permit, the laser light show may include scanning the audience. The effect is stunning. However, the high power lasers have the potential to cause eye damage. They are eye safe ONLY when they are rapidly scanned so eye exposure is extremely brief. The concern is, if the scanning system fails so the beam is static, it can inflict permanent vision damage.
Polygon scanners in a laser slight show are a mechanism to provide a fail safe method of scanning the audience. A polygon scanner runs at thousands of RPM, and, like a gyroscope, it cannot stop instantaneously. Polygon scanners give an AT SPEED signal to the system when it is at the commanded RPM. If, for any reason, the polygon deviates from the commanded RPM, the AT SPEED signal is dropped. At that point, it may take a minute for the polygon to coast down to a stop. That loss of AT SPEED signal gives the light show controller immediate notification to turn the laser off while providing a large margin of safety before the polygon slows down enough to present an eye safety hazard.
In addition to the laser eye safety benefit, polygon scanners can offer new visual effects from its high speed scanning. Precision Laser Scanning offers two Off-The-Shelf polygon scanners suitable for laser light shows. The Gecko-5-OTS has an 8.5mm aperture and scans up to 5,000 RPM. The Gecko-33-OTS has a 4.5mm aperture and scans up to 33,000 RPM! Both scanners ship from stock and cost less than $1000 each. They are compact and easy to install.