Unique advanced homodyne laser interferometer system provides a cost-effective and simple position feedback solution for precision motion control applications

摘要

Semiconductor manufacturing and associated industries contain many applications that require precise positioning. Indeed, as feature sizes decrease, applications that could once utilise standard scale encoders for position feedback must migrate to high-accuracy laser interferometers. Traditionally, these interferometer systems have been perceived as being expensive, complex and intrusive. This paper covers a range of recent homodyne interferometer developments, including a novel fringe detection scheme that utilises an integrated photodetector, and also a fibre optic laser beam delivery system that enables light to be routed straight to the measurement axis without additional external steering optics. The resultant system provides the user with low noise, low latency, position feedback signals that can be interpolated to provide sub nano-meter resolution. These and other developments directly address the negatives associated with traditional interferometer architectures and firmly establish homodyne interferometry as comparable in performance to the more complex heterodyne schemes.