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 for high measurement sensitivity to for wide measurement range. An rms error of for a height measurement is shown. The measured profile of holographic interferometry agrees with a standard stylus instrument.
© 2008 Optical Society of America
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