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TitleDevelopment of an automatic line scale measuring instrument
Publication TypeConference Paper
Year of Publication2001
AuthorsHowick, E.F., and Sutton C.M.
Conference NameProceedings of SPIE - The International Society for Optical Engineering
Date Published2001
KeywordsAutomatic line scale measuring instrument, Engineering rules, Error compensation, Imaging systems, Interferometers, Laser applications, Laser interferometer, Laser measurement system, Line scales, Line sensing system, Optical design, Optical sensors, Photodiodes, Position measurement, Projection systems, Reflection, Semiconductor lasers, Steel tapes, Tapes, Trolley cars
AbstractLine scales such as engineering rules and steel tapes are still used for many routine measurements despite the existence of more sophisticated devices. MSLNZ's Automatic Line Scale Measuring Instrument is based on a heterodyne laser interferometer used in a configuration that compensates for Abbe errors. The position of each scale graduation is detected by monitoring the change in the diffuse reflection of a focused line of diode laser light, as a motorised trolley travels along above the scale. The signal from the diffuse reflection is used to trigger the laser measurement system at the edge of each graduation. The instrument is capable of measuring the position of every graduation on a rigid scale up to four metres in length with an uncertainty of √(10μm)2 + (7.5×10-6 L)2 (95% confidence level). Measurement time (after set up) for a one-metre scale is less than 2 minutes.

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