title: Multiple-wavelength digital holographic interferometry using tunable laser diodes.
abstract: Here we present multiple-wavelength digital holographic interferometry with a wide measurement range using laser diodes. Small wavelength differences can be easily realized by the wavelength tuning of laser diodes with injection current controls. A contour map of an object with a wide measurement range and a high sensitivity is demonstrated by combining a few contour maps with several measurement sensitivities. Synthetic wavelengths are calibrated using a known height difference. This alleviates the need to have high precise knowledge of the recording wavelengths. The synthetic wavelengths ranged from ~3 mm for high measurement sensitivity to ~4 cm for wide measurement range. An rms error of ~35 mum for a ~1 cm height measurement is shown. The measured profile of holographic interferometry agrees with a standard stylus instrument.
authors.affiliation: Department of Applied Physics, Tokyo University of Science, Tokyo, Japan. wada@rs.kagu.tus.ac.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Wada
authors.forename: Makoto
authors.initials: M
authors.lastname: Kato
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Ishii