An optical straightness measurement sensor for the KRISS watt balance. (February 2015)

• Record Type: Journal Article
• Authors: Kang, Chu-Shik; Kim, Jong-Ahn; Jin, Jonghan; Eom, Tae Bong; Kim, Jae Wan
• Is Part Of: Measurement. Volume 61(2015:Feb.)
• Page Start: 257
• Page End: 262
• Publication Date: 2015-02
• Subjects: Optical sensor -- Straightness error -- Watt balance -- Right angle reflector; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2014.10.055
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: We developed an optical sensor to measure straightness error of a stage. The sensor is vacuum compatible, non-magnetic, thus suitable for watt balance. Resolution is 10 nm, nonlinearity is less than 0.5%, sensitivity is 0.003624 μm −1 . Sensitivity is obtained as a function of the position of cube-corner prism. Measurement results agree with that of laser interferometer within ±60 nm over 40 mm. Abstract: We present an optical straightness measurement sensor applicable to the watt balance experiment. Key parts of the sensor are a cube-corner prism and a right angle reflector having a sharp edge. Beam reflected from the cube-corner prism is split into two opposite directions by the right angle reflector, and collected by photo detectors connected to a lock-in amplifier. Straightness error is measured by monitoring the normalized intensity difference of the two lock-in signals. We describe in detail about the implemented sensor and evaluated performance on its resolution, sensitivity, and nonlinearity comparing with a laser interferometer. Straightness measurement result of a translation stage agreed with that obtained by a laser interferometer within ±60 nm over the measurement range of 40 mm.