Road Runner 70,000 RPM polygon scanner solves the noise problem

Polygon scanners are used for high speed laser scanning.  A multi-faceted polygon can be rotated at tens of thousands of RPM to produce scan rates far higher than galvanometer scanners.  Galvanometer aka Galvo scanners are limited primarily by the inertia of the reciprocating mechanism.  The practical top speed of a rotating polygon mirror is typically limited by the motor, the motor bearing and/or the aerodynamic drag.  A secondary limitation is the wind noise caused by the facets cutting through the air at high speed.  The wind noise is a function of the size, speed and aerodynamics of the mirror.  The speed of the mirror facet tips = the circumference of the polygon x the rotation rate.  A common 55,000 RPM polygon scanner with 72 facets has a diameter of 2.5 inches = 7.85 inch circumference.  55,000 RPM / 60 = 917 Revolutions Per Second.  7.85 x 917 = 7200 inches per second = 600 ft/sec = 409 MPH = 660 KPH.  An open air polygonal mirror 2.5 inches in diameter spinning at 55K RPM is loud.  It sounds like a siren.  The noise is not a problem where the scanner is used for inspecting steel or patterning ITO in a factory.  However, the noise is a serious issue should the high speed scanner be integrated into a home video display or a retinal imaging instrument in a doctor’s office.

There are biomedical and inspection applications that would benefit from faster scanning.  But, noise is a problem and it takes more than a bigger motor to go faster.  Ball bearings have a short life when run at over 25,000 RPM.  An air bearing is needed at greater speed but high speed air bearings require significant R&D plus ultra-precise manufacturing methods to produce.  Road Runner polygon scanner, introduced by Precision Laser Scanning in 2016 as the world’s fastest polygon scanner, breaks the 55,000 RPM speed limit with a top speed of 70,000 RPM.  This gives a facet tip speed of 520 MPH = 840 KPH but Road Runner is very quiet.  If the 70,000 RPM polygon mirror was operated in the open air, it would sound like a painfully loud siren.  This would not be acceptable in most environments.  Road Runner dramatically reduces the noise with a totally enclosed mirror housing. 

The laser beam enters and exits through a glass window.  The window is AR coated and tilted away from the scan plane to reduce back reflections.  The totally enclosed mirror housing has a dramatic quieting effect.  The polygon itself is whisper quiet.  The motor hums at an audio frequency of about 14KHz.

Sealing the mirror housing does trap heat that is normally removed by the free flow of air over an open polygon.  For heat transfer, the mirror housing has cooling fins and a small fan must be used to move air through the fins. 

At 70,000 RPM, Road Runner is 27% faster and far quieter than the common but loud 55,000 RPM polygonal scanners.  Road Runner has solved the noise problem which allows it to be used in noise sensitive environments and faster than ever before possible!

ROAD RUNNER POLYGON SCANNER