Interferometry systems and methods

Abstract

An interferometry system includes a plurality of coherent light sources that each generate a beam of coherent light. Separate waveguide pathways are optically associated with each coherent light source. Each separate waveguide pathway has an endpoint configured to emit at least a portion of the beam of coherent light from the associated light source. A plurality of photodetectors is optically associated with waveguide pathways. In some cases, a retroreflector receives the light emitted from the endpoints, modulates the received light, and directs the modulated light back to the endpoints. The modulated light and a portion of the coherent light reflected from the endpoint of the waveguide pathway receiving the modulated light is directed a photodetector.

What is claimed is: 
     
         1 . An interferometry system, comprising:
 a plurality of light sources, each light source of the plurality of light sources being operable to generate a beam of coherent light;   separate waveguide pathways optically associated with each light source of the plurality of light sources, each separate waveguide pathway having an endpoint configured to emit at least a portion of the beam of light from the associated light source;   a plurality of photodetectors, at least one photodetector of the plurality of photodetectors optically associated with each waveguide pathway; and   a retroreflector configured to receive the light emitted from each of the endpoints, the light emitted from each of the endpoints being modulated either prior to emission from the endpoints or by the retroreflector, the retroreflector being configured to and direct the modulated light back to the endpoints, wherein each of the waveguide pathways directs an optical interference signal to the associated photodetector, the optical interference signal being formed of the modulated light received by the endpoint of the waveguide pathway and a portion of the coherent light from the waveguide pathway receiving the modulated light, wherein each waveguide pathway is configured to direct a separate optical interference signal toward a respective photodetector.   
     
     
         2 . The system of  claim 1 , wherein each of the plurality of light sources is configured to emit a beam of coherent light at a unique wavelength. 
     
     
         3 . The system of  claim 1 , wherein at least one of the light sources is operable to emit a beam of light having a wavelength of from 400 nm to 5000 nm. 
     
     
         4 . The system of  claim 1 , wherein each of the separate waveguide pathways comprises a fiber coupler. 
     
     
         5 . The system of  claim 4 , wherein each fiber coupler comprises a first side and a second side, the first side having two waveguide pathways connected thereto, and the second side having one waveguide pathway connected thereto. 
     
     
         6 . The system of  claim 5 , wherein each light source is optically coupled to a first waveguide pathway of the two waveguide pathways and each photodetector is optically coupled to a second waveguide pathway of the two waveguide pathways and wherein the one waveguide pathways connected to the second sides of the fiber couplers comprise the endpoints. 
     
     
         7 . The system of  claim 1 , wherein each of the light sources is configured to produce light with different phases, amplitudes, or frequencies from one another or to phase, amplitude, or frequency modulate the light produced thereby. 
     
     
         8 . The system of  claim 1 , wherein the retroreflector is configured to phase modulate the light emitted from each of the endpoints. 
     
     
         9 . The system of  claim 1 , wherein the retroreflector comprises a plurality of retroreflectors mounted on a rigid object. 
     
     
         10 . The system of  claim 9 , wherein each of the plurality of retroreflectors is configured to receive the light emitted from each of the endpoints, modulate the received light, and direct the modulated light back to the endpoints, wherein each of the waveguide pathways directs an optical interference signal to the associated photodetector, the optical interference signal being formed of the modulated light from each of the plurality of retroreflectors and received by the endpoint of the waveguide pathway. 
     
     
         11 . A method of determining a position of an object, comprising:
 directing first, second, and third beams of light along respective first, second, and third waveguide pathways;   emitting a portion of the first, second, and third beams of light from respective first, second, and third endpoints associated with the respective first, second, and third waveguide pathways;   receiving the emitted portions of the first, second, and third beams of light at a retroreflector;   modulating the first, second, and third beams of light either prior to emission from the first, second, and third endpoints or modulating the emitted portions of the first, second, and third beams of light at the retroreflector to form first, second, and third modulated beams;   directing the first modulated beam and a portion of the first beam of light to a first photodetector to generate a first photocurrent;   directing the second modulated beam and a portion of the second beam of light to a second photodetector to generate a second photocurrent;   directing the third modulated beam and a portion of the third beam of light to a third photodetector to generate a third photocurrent; and   relating a difference between the first, second, and third photocurrents at the first, second, and third photodetectors to a distance between each of the first, second, and third endpoints and the retroreflector.   
     
     
         12 . The method of  claim 11 , wherein directing the first modulated beam and a portion of the first beam of light to a first photodetector comprises directing the first modulated beam and the portion of the first beam of light along the first waveguide pathway. 
     
     
         13 . The method of  claim 11 , wherein modulating the emitted portions of the first, second, and third beams of light comprises modulating at least one of a phase, frequency, or amplitude of the first, second, and third beams of light. 
     
     
         14 . The method of  claim 11 , wherein receiving the emitted portions of the first, second, and third beams of light at a retroreflector comprises receiving each of the emitted portions of the first, second, and third beams of light at a plurality of retroreflectors. 
     
     
         15 . The method of  claim 11 , wherein modulating the emitted portions of the first, second, and third beams of light to form first, second, and third modulated beams further comprises modulating the emitted portions of the first, second, and third beams of light with three retroreflectors to further form fourth, fifth, sixth, seventh, eighth, and ninth modulated beams. 
     
     
         16 . The method of  claim 15 , further comprising producing fourth, fifth, sixth, seventh, eighth, and ninth photocurrents with the fourth, fifth, sixth, seventh, eighth, and ninth modulated beams and the first, second, and third beams of light. 
     
     
         17 . The method of  claim 16 , further comprising relating signals associated with the first, second, third, fourth, fifth, sixth, seventh, eighth, and ninth photocurrents at the first, second, and third photodetectors to a distance between each of the first, second, and third endpoints and each of the three retroreflectors. 
     
     
         18 . A two-stage interferometry system, comprising:
 a first stage, comprising:
 a plurality of light sources, each being operable to generate a beam of light; 
 separate waveguide pathways optically associated with each light source of the plurality of light sources, each separate waveguide pathway having an endpoint configured to emit at least a portion of the beam of light from the associated light source; 
 at least one photodetector optically associated with each waveguide pathway; 
 a gimbal plate selectively movable about one or more axes; and 
 a plurality of retroreflectors mounted on the gimbal plate and configured to receive the light emitted from each of the endpoints, modulate the received light, and reflect the modulated light back to the endpoints, wherein each of the waveguide pathways is configured to direct an optical interference signal to the associated photodetector, the optical interference signal being formed of the modulated light received by the endpoint of the waveguide pathway and a portion of the light from the waveguide pathway receiving the modulated light; and 
   a second stage, comprising:
 a light source operable to generate a beam of light; 
 a waveguide pathway optically associated with the light source of the second stage, the waveguide pathway having an endpoint configured to emit at least a portion of the beam of light from the light source of the second stage, the endpoint of the waveguide pathway of the second stage being connected to the gimbal plate such that movement of the gimbal plate moves the endpoint connected thereto; 
 a photodetector optically associated with the waveguide pathway of the second stage; 
 a retroreflector configured to receive the light emitted from the endpoint of the second stage, modulate the received light, and reflect the modulated light back to the endpoint of the second stage, wherein the waveguide pathway is configured to direct an optical interference signal to the photodetector to determine a distance between the endpoint and the retroreflector of the second stage, the optical interference signal being formed of the modulated light received by the endpoint of the second stage and a portion of the light from the waveguide pathway of the second stage; and 
 a beam splitter positioned between the endpoint and the retroreflector of the second stage, the beam splitter being configured to direct a portion of the modulated light to a position sensitive photodetector to detect when the portion of the light beam emitted from the endpoint of the second stage is centered on the retroreflector. 
   
     
     
         19 . The two-stage interferometry system of  claim 18 , wherein the position sensitive photodetector comprises a four-quadrant detector. 
     
     
         20 . The two-stage interferometry system of  claim 18 , further comprising one or more motors associated with the gimbal plate, the one or more motors being configured to reorient the gimbal plate to center the portion of the light beam emitted from the endpoint of the second stage on the retroflector. 
     
     
         21 . The two-stage interferometry system of  claim 18 , wherein the first stage is configured to determine or monitor the position and/or orientation of the gimbal plate. 
     
     
         22 . The two-stage interferometry system of  claim 18 , wherein the second stage comprises a plurality of retroreflectors associated with a target.