Laser Beam as a Straight Datum and Its Application to Straightness Measurement at Nanometer Level

Abstract A feasibility study is made for the utility and the application of laser beam as a straight datum. By using the quadrant photodiode position sensor and the piezo-compensator with nanometer resolution, the carriage on a slide table is so designed and built as to travels straight along the laser beam as a “perfect” straight datum. Using this set up, the geometrical accuracy of an optical flat and a precision straightedge is measured by a displacement sensor fixed on the carriage in “perfect” straight motion with sufficient resolution and repeatability of 3 nm over the measuring distance of about 100 mm.