Optical Heterodyne Laser Encoder for In-plane Nanopositioning

摘要

Laser encoders as an optical displacement measurement technique have many applications such as modernmanufacturing, scanning probe microscopy (SPM) and nanomanipulation. For the measurement scale down to thenanometer range, the stability, sensitivity and tolerance to dynamic runout are the key issues for laser encoders. Thispaper presents a novel laser encoder for sub-nanometer displacement measurement. It is based on optical heterodyneinterferometry and conjugate optics with a symmetric and quasi-common-path optical configuration. It offers highstability, high resolution, low uncertainty displacement measurements and can break through the dynamic runoutproblem in laser encoders. Experimental results reveal that the laser encoder can detect a displacement variation of 26pm, and can thus be applied to sub-nanometer or even picometer positioning.