Low coherence interferometry for detecting and characterizing plaques

A system for determining a characteristic of tissue in a biological sample, the system comprising:

• a broadband light source for providing a broadband light;
• a sensing light path receptive to said broadband light from said broadband light source, said sensing light path configured to direct said broadband light at the biological sample and to receive said broadband light reflected from the biological sample;
• a reflecting device;
• a reference light path receptive to said broadband light from said broadband light source, said reference light path configured to direct said broadband light at said reflecting device and to receive said broadband light reflected from said reflecting device;
• a modulator associated with at least one of said reference light path and said sensing light path, said modulator for modulating at about a distance of a center wavelength of said broadband light an effective light path length of said at least one of said reference light path and said sensing light path;
• a detector receptive to said broadband light resulting from said broadband light reflected from the biological sample and said broadband light reflected from said reflecting device, said detector generating signals indicative of an interference of said broadband light reflected from the biological sample and said broadband light reflected from said reflecting device, which said signals are product of cosine functions;
• means for changing an effective light path length of at least one of said reference light path and said sensing light path;
• and
• a processor configured to;
• (1) determine a first phase component that is an argument of the corresponding cosine function of said signal indicative of said interference of said broadband light reflected from a first depth in the biological sample and said broadband light reflected from said reflecting device based, said first depth defined by said effective light path length of said sensing light path and said effective light path length of said reference light path, (2) determine a second phase component that is an argument of the corresponding cosine function of said signal indicative of said interference of said broadband light reflected from a second depth in the biological sample and said broadband light reflected from said reflecting device based, said second depth defined by said effective light path length of at least one of said sensing light path and said reference light path having been changed, and (3) determine a characteristic of the biological sample from said first phase component and said second phase component.