Dual-wavelength off-axis digital holography using a single light-emitting diode.

We propose a new low-coherence interferometry system for dual-wavelength off-axis digital holography. By utilizing diffraction gratings, two beams with narrower bandwidths and different center wavelengths could be filtered in a single light-emitting diode. The characteristics of the system are analytically determined to extend the coherence length and field-of-view enough for off-axis configuration. The proposed system enables the fast and accurate measurement of the surface profile with more than a micrometer step height and less noise. The performance of the system is verified by the experimental results of a standard height sample.