A method and system for determining a characteristic of a biological sample including directing light at the biological sample and receiving that light; directing the light at a reference reflecting device and receiving that light; adjusting an effective light path length to facilitate an interference of the light reflected from the biological sample corresponding to a first depth and the light reflected from the reference reflecting device; and detecting the broadband light resulting from the interference, to provide an interference signal. The method also includes: determining a first phase associated with the interference signal corresponding to the first depth; varying the effective light path length to define a second depth; determining a second phase associated with the interference signal corresponding to the second depth; and determining the characteristic of the biological sample from the phases.