We present quantitative phase images of cells and other microscopic samples, using three-wavelength optical phase unwrapping. Laser diodes and a ring dye laser are used in a standard 4-frame phase shifting interferometer to obtain phase profiles with larger beat wavelengths, thus removing 2pi  ambiguities without increasing phase noise. The effectiveness of three-wavelength optical phase unwrapping with both laser diodes and a ring dye laser as light sources is demonstrated.       

LED-based multi-wavelength phase imaging interference microscopy combines phase-shifting interferometry with multi-wavelength optical phase unwrapping. This technique consists of a Michelson-type interferometer illuminated with a LED. The reference mirror is dithered for obtaining interference images at four phase quadratures, which are then combined to calculate the phase of the object surface. The 2π ambiguities are removed by repeating the experiment using two or more LEDs at different wavelengths, which yields phase images of effective wavelength much longer than the original. The resulting image is a profile of the object surface with a height resolution of several nanometers and range of several microns. The interferographic images using broadband sources are significantly less affected by coherent noise.