US 6,982,790 B1
Coherent imaging in turbid media
Meir Gershenson, Panama City, Fla. (US)
Assigned to The United States of America as represented by the Secretary of the Navy, Washington, D.C. (US)
Filed on Jan. 27, 1998, as Appl. No. 9/14,011.
Int. Cl. G01B 9/02 (2006.01)
U.S. Cl. 356—349 6 Claims
OG exemplary drawing
 
1. A system for forming an image of an object in a turbid medium, comprising:
a laser light source for producing a coherent light beam of a selected frequency;
a lens arranged to receive the coherent light beam output from the laser;
a beamsplitter arranged to receive the coherent light beam that has passed through the lens and produce a reference beam directed along a reference optical path and a signal beam that is directed along a signal optical path to impinge upon the object in the turbid medium and reflect back toward the beamsplitter;
means for modulating the reference beam;
a mirror arranged to reflect the reference beam back toward the beamsplitter for combination with the signal beam to produce an output optical signal, the output optical signal having a beat frequency when the signal beam and the modulated reference beam have equal optical path lengths;
a photodetector arranged to received the output optical signal from the beamsplitter; and
a heterodyne detector connected to the photodetector and arranged to produce a beat signal when the first and second optical paths have matching lengths.