Phase imaging using multi-wavelength digital holography

A holographic phase-imaging method comprising the steps of:

• recording a first hologram image at a first wavelength;
• recording an first object image at a first wavelength;
• recording a first reference image at a first wavelength;
• generating a first phase map at a first wavelength from the recorded first hologram image, first object image and first reference image;
• recording a second hologram image at a second wavelength, the second wavelength longer than the first wavelength;
• recording a second object image at a second wavelength;
• recording a second reference image at a second wavelength;
• generating a second phase map at a second wavelength from the recorded second hologram image, second object image and second reference image;
• subtracting the second phase map from the first phase map;
• resolving the fringe number for each pixel phase value;
• referencing the digital holographic phase map at the first wavelength;
• and calculating a topographical map of the object.

A digital holographic phase-imaging system comprising:

• a digital holographic imager to provide a first hologram image, a first object image and a first reference image at a first wavelength and a second hologram image, a second object image and a second reference image at a second wavelength;
• a phase map generator to receive the first hologram image, the first object image, the first reference image, the second hologram image, the second object image and the second reference image and to generate a first phase map comprising a plurality of pixels at a first wavelength and a second phase map comprising a plurality of pixels at a second wavelength;
• a contour generator to determine the fringe number of the plurality of pixels of the plurality of phase maps;
• and
• a resolution generator to produce sub-wavelength resolution of the object image.