A Submicron Automated Precision Line Scale Calibration System Developed at the Standards and Calibration Laboratory (SCL)

A submicron automated precision line scale calibration system was developed at the Standards and Calibration Laboratory (SCL) in Hong Kong. The system provided a measuring capability for line scale of range 0.01 to 750 mm with measurement uncertainty of[0.152 + (0.0005*l)2]1/2 μm (l in mm). The fully automated system used the displacement method and employed an air bearing stage driven by a piezoelectric motor. A pixel-counting system was integrated with a microscope to enhance accuracy. The system used only one laser interferometer to compensate the Abbe error in two lateral directions. Without further calculation, any angular movement leading to an Abbe error would be automatically compensated. The uncertainty contributed from Abbe effects was evaluated to be within 30nm, an error reduction of over 95 % of the Abbe effect when such an arrangement was not in place.