The SLIM module is connected to the imaging port of a Phase Contrast microscope, with a camera connected at its output. The microscope separates the illumination into a sample and a reference beam that pass through the sample and are collected at the imaging port with a phase shift between them. The beams pass through the SLIM module where an electro-optical system introduces four accurately controlled phase delays between them. The SLIM camera acquires an intensity image for each phase delay. The intensity images are combined by interference and a recombination algorithm outputs the quantitative OPL map of the entire field of view of the microscope objective. The OPL map is converted to specimen height/volume, dry mass, and refractive index.