Phase-shifting digital holography using two low-coherence light sources with different wavelength

To observe an object shape in a light scattering medium, the low-coherence interferometry exercises its power to omit undesired light derived from multiple-light scattering. The phase-shifting digital holography is used to obtain the complex amplitude of the object from a few interference patterns. When the object has a height difference more than the wavelength of a light source, the obtained phase distribution has 2 pi ambiguity. Therefore, a phase-unwrapping technique is required to contour the object surface. When an object is in light-scattering media, the interference signal has much noise originating from multiple-light scattering, and therefore the phase unwrapping becomes harder. Two-wavelength interferometry set free from the unwrapping procedure. We propose a new method based on a combination of the phase-shifting digital holography, the two-wavelength interferometry, and the low-coherence interferometry. We demonstrate a topographic imaging of an object in light scattering media.