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Keywords
Lasers, Optical scanning
Abstract
The closed loop galvanometer-based optical scanners continues to be an advanced technology for the integration and enabling of a broader range of laser system applications and uses. Advances in the technology have provided major improvements in galvo positioning speed, accuracy, size and cost. This paper will introduce the benefits, operating ranges and recent advances in galvanometer technology for scanning applications along with some of the other components and issues related to system design for high performance scanning applications. Several different actuator and position detector technologies and designs will be presented including moving coil actuators, moving magnet actuators and patented capacitive and optical position detector designs that offer positioning speeds as fast as 100 mus and positioning respectability to single microradians. The performance and system design trade-offs that one should consider during the selection of the appropriate galvanometer technology and the optical systems design will be discussed along with a performance comparison of the galvanometer to other optical scanning technologies.
Introduction
Galvanometer-based optical scanners are finding a place as positioning solutions for an increasingly broad range of laser applications. While a number of scanning approaches are available, galvanometer-based scanners commonly called "galvos" - offer flexibility, speed and accuracy at an attractive cost. With continued advances in galvo technology, the devices today offer closed-loop bandwidths of hundreds of hertz even for larger beams, step-response times in the 100 As range, single microradian-level positioning resolution, lower costs per axis and flexible positioning control to describe a variety of motions across wide angles.
This has enabled new levels of performance in laser marking and other materials processing applications, via drilling, high-resolution print and imaging applications, DNA analysis and drug discovery systems, and low-cost biomedical systems that bring screening and detection capabilities from the research lab to the doctor's office. The design requirements of each application, however, place varying emphasis on speed, accuracy, size and cost.
Fortunately, many galvo configurations and capabilities enable system designers to select the optimal product for the requirements of the target application (Plate 1).
Galvanometer basics and technology options
There are three main elements to a closed loop galvanometer system - the positioning actuator, the position detector and the closed loop servo control electronics for high...