Advances in Galvanometer Scanning Technology Allow Lasers to Perform a Variety of "dances"

Once built around the latest polychromatic laser systems primarily around bulky and expensive krypton ion lasers, the laser light show experience can be enhanced with improved scanning systems and advanced software programmability. Optical scanners for guiding, positioning or "scanning" a laser beam within a desired area are widely used throughout the industrial, medical and recreational laser industries. Recent advances in galvo-based optical scanners can greatly improve the effectiveness of laser systems, thereby enhancing the customer experience of laser light shows.

Since light beams are only affected by refraction, diffraction, or reflection, optical scanners have been developed to take advantage of each of these methods. Therefore, in a broad sense, optical scanners can be divided into three types: acousto-optic scanners that deflect light beams by diffraction; electro-optic scanners that deflect light beams by refraction; and mechanical scanners that deflect light beams by reflection. While all of these scanner types have been in use for decades, the galvo scanning system in the third type of scanner works best.

With their scanning speeds in excess of 100kHz, acousto-optic and electro-optic scanners can rapidly scan beams in arbitrary directions. However, their scan angles are usually limited to a few degrees or less, and often these scanners cannot use multiple wavelengths simultaneously. Moreover, the optical transmittance of acousto-optic scanners on a single axis is limited to about 80% or less, which makes them unsuitable for laser light shows.

1. Resonance and polygon galvo mirror scanners

On the other hand, mechanical scanners that work by rotating physical mirrors can be coated to reflect any wavelength or combination of wavelengths with very high reflectivity—and therefore have very high optical transmittance. Using this physical mirror, both resonant and polygon scanners can scan beams over very wide angles, but they are limited in that they can only scan the same pattern over and over again. For some applications, such as printing, this is highly desirable, but for applications where the beam needs to be scanned in a non-repeating pattern or positioning within a random area, galvo mirror scanners are the only option.

2. Galvo mirror scanners

Galvo-based mechanical scanners, simply called scanning galvos, contain physical mirrors that are driven by some kind of motor. Most of the time the mirror is attached to the shaft of the motor, but in some designs the mirror and motor may be a single integrated unit. The galvo motor has been expertly designed to rotate within a limited angular range, rather than simply rotating. The galvo motor also incorporates a high-precision position detector that provides feedback to a separate controller for pointing repeatability.

Galvo mirror scanners and almost all mechanical scanners reflect the beam off a rotating mirror, so that the optically achievable scan angle is twice the actual rotation angle of the motor. For scanning galvos, this means they can project beams at maximum scan angles as wide as 80° and beyond, and can be configured for dual-axis scanning with relative ease.