  We present an external interferometric setup that is able to simultaneously
acquire three wavelengths of the same sample instance without scanning or
multiple exposures. This setup projects onto the monochrome digital camera
three off-axis holograms with rotated fringe orientations, each from a
different wavelength channel, without overlap in the spatial-frequency domain,
and thus allows the full reconstruction of the three complex wavefronts from
the three wavelength channels. We use this new setup for three-wavelength phase
unwrapping, allowing phase imaging of thicker objects than possible with a
single wavelength, but without the increased level of noise. We demonstrate the
proposed technique for micro-channel profiling and label-free cell imaging.
