Frequency modulated laser radar

Claim 3

Apparatus as claimed in claim 1, wherein said processing means includes: first detector means, coupled to said ranging interferometer means, for detecting the fringes in said first wave interference pattern; first counting means, operatively connected to said first detector means, for counting the number N r of said fringes detected by said first detector means for a sweep in the frequency of said radiation from a first frequency to a second frequency; second detector means, coupled to said reference interferometer means, for detecting the fringes in said second wave interference pattern; second counting means, operatively coupled to said second detector means, for counting the number N ref of fringes detected by said detector means for said sweep in the frequency of said radiation; and range calculating means, responsive to said counts of said first and second counting means, for calculating the distance R to said target, said distance given by

Claim 4

Apparatus as claimed in claim 1 or claim 2, wherein said frequency modulating means includes: ramp generator means for producing a modulating signal the level of which varies and is continuous between a first predetermined level and a second predetermined level; and phase shift means, optically coupled to said radiation source means and responsive to said modulating signal, for modulating the phase of said ' - radiation.

Claim 5

Apparatus as claimed in any one of claims 1 to 3, wherein said ranging interferometer means includes means for focusing said first portion of said ranging beam onto said target.

Claim 6

Apparatus as claimed in any one of claims 1 to 4, wherein said ranging interferometer means includes: ranging beam splitting means, optically coupled to said first beam splitting means, for splitting said ranging beam into said first and second portions, for directing said second portion of said ranging beam along said first path and for directing said first portion of said ranging beam along a ranging path, said ranging path comprising the round-trip path to said target and said first path; and ranging phase difference determining means, optically coupled to said ranging beam splitting means, for producing a first signal, said first signal indicative of the phase difference between the first portion of said ranging beam after travelling over said ranging path and the second portion of said ranging beam after travelling over said first path.

Claim 7

Apparatus as claimed in any one of claims 1 to 7, wherein said ranging interferometer means comprises collimating means, optically coupled to said ranging beam splitting means, for focusing said first portion of said ranging beam onto said target.

Claim 8

Apparatus as claimed in any one of claims 1 to 6; wherein said reference interferometer means includes: reference beam splitting means, optically coupled to said first beam splitting means, for directing said second portion of said reference beam along said second path and for directing said first portion of said reference beam along said reference path, said reference path comprising a fourth path of predetermined known distance and said second path; and reference phase difference determining means, optically coupled to said reference beam splitting means, for producing said second signal, said second signal indicative of the phase difference between the first portion of said reference beam after travelling over said reference path and the second portion of said reference beam after travelling over said second path.

Claim 9

Apparatus as claimed in any one of claims 1 to 7, including surface roughness processing means, responsive to the amplitude of said first wave interference pattern produced by said ranging interferometer means, for characterizing the roughness of the scattering surface of said target.

Claim 10

Apparatus as claimed in claim 8, wherein said surface roughness processing means includes: means for varying the angle of incidence of said beam on said surface; means, coupled to said ranging interferometer means, for detecting the amplitude of said first wave interference pattern, said detected amplitude proportional to the intensity of the radiation scattered by said surface; and data processing means for processing the detected amplitude of said first wave interference pattern for a plurality of angles of incidence to produce indicia of said surface roughness.

Claim 11

Apparatus as claimed in claim 9, wherein said amplitude-detecting means includes means for characterizing modulations in the scattered radiation, said modulations produced by interference between radiation scattered by different points of said surface; and said data processing means further includes means for deriving, from said characterization of the modulations, indicia of the roughness of said surface.

Claim 12

Apparatus as claimed in claim 8, wherein said surface roughness processing means includes: detecting means, coupled to said ranging interferometer means, for detecting the amplitude of said first wave interference pattern, said detected amplitude proportional to the intensity of the radiation scattered by the surface; characterizing means, responsive to said detected amplitudes, for characterizing modulations in the scattered radiation, said modulations produced by interference between portions of said first portion of said ranging beam scattered by different points on said surface; and means for deriving, from said characterization of the modulations, indicia of the roughness of said surface.

Claim 13

Apparatus for measuring the distance R to an arbitrary target, said apparatus comprising: radiation source means for producing a beam of'coherent radiation, said radiation source means including means for sweeping the frequency of said produced radiation from a first to a second frequency, said sweep defined by a continuously increasing function of time; first star coupling means, including an input port and first and second output ports, said radiation source means coupled to said input port, said first star coupling means for splitting said beam produced by said radiation source means into a ranging beam and a reference beam, said ranging bean exiting said first star coupling means at said first output port, said reference beam exiting said first star coupling means at said second output port; ranging beam splitting star coupling means, including an input port and first and second output ports, for splitting said ranging beam into first and second beams, said first beam produced at said first output port, said second beam produced at said second output port, said ranging beam splitting star coupling means including means for coupling said input port of said ranging beam splitting star coupling means to said first output port of said first star coupling means; first collimating means, coupled to said first output of said ranging beam splitting star coupling means, for focusing said first beam on said target; ranging beam combining star coupling means for combining said first and second beams to produce a first wave interference pattern, said ranging beam combining star coupling means including first and second input ports and at least one output port; first optical fiber means for coupling said second output port of said ranging beam splitting star coupling means to said second input port of said ranging beam combining star coupling means, said first optical fiber means defining a fixed path length; second collimating means, positioned in proximity with said first collimating means and aimed at said target, for coupling a portion of said first beam scattered by said target to said first input port of said ranging beam combining star coupling means; ranging detector means, coupled to said output port of said ranging beam combining star coupling means, for detecting the fringes in said first wave interference pattern: ranging counting means, responsive to said detected fringes of said reference detector means, for counting the number of fringes N r in said first wave interference pattern produced during said sweep in frequency; reference beam splitting star coupling means, including an input port and first and second output ports, for splitting said ranging beam into third and fourth beams, said third beam produced at said first output port, said fourth beam produced at said second output port, said reference beam splitting star coupling means including means for coupling said input port of said reference beam splitting star coupling means to said second output port of said first star coupling means; reference beam combining star coupling means for combining said third and fourth beams to produce a second wave interference pattern, said reference beam combining star coupling means including first and second input ports and at least one output port; second optical fiber means for coupling said second output port of said reference beam splitting star coupling means to said second input port of said reference beam combining star coupling means, said second optical fiber means defining a fixed path length; reference optical fiber means for coupling said first output port of said reference beam splitting star coupling means to said first input port of said reference beam combining star coupling means, said reference optical fiber means defining a path of predetermined known fixed length X ref , X ref being approximately equal to the distance R to be measured; reference detector means, coupled to said output port of said reference beam combining star coupling means, for detecting the fringes in said second wave interference pattern; reference counting means, responsive to said detected fringes of said reference detector means, for counting the number of fringes N ref in said second wave interference pattern produced during said sweep in frequency; and processing means, responsive to said counts N r and N ref , for calculating the distance R to said target, said distance R given by

Claim 14

Apparatus for measuring the distance R to an arbitrary target, said apparatus comprising: radiation source means for producing a beam of'coherent radiation, said radiation source means including means for sweeping the frequency of said produced radiation from a first to a second frequency, said sweep defined by a continuously increasing function of time; first star coupling means, including an input port and first and second output ports, said radiation source means coupled to said input port, said first star coupling means for splitting said beam produced by said radiation source means into a ranging beam and a reference beam, said ranging bean exiting said first star coupling means at said first output port, said reference beam exiting said first star coupling means at said second output port; ranging beam splitting star coupling means, including an input port and first and second output ports, for splitting said ranging beam into first and second beams, said first beam produced at said first output port, said second beam produced at said second output port, said ranging beam splitting star coupling means including means for coupling said input port of said ranging beam splitting star coupling means to said first output port of said first star coupling means; first collimating means, coupled to said first output of said ranging beam splitting star coupling means, for focusing said first beam on said target; ranging beam combining star coupling means for combining said first and second beams to produce a first wave interference pattern, said ranging beam combining star coupling means including first and second input ports and at least one output port; first optical fiber means for coupling said second output port of said ranging beam splitting star coupling means to said second input port of said ranging beam combining star coupling means, said first optical fiber means defining a fixed path length; second collimating means, positioned in proximity with said first collimating means and aimed at said target, for coupling a portion of said first beam scattered by said target to said first input port of said ranging beam combining star coupling means; ranging detector means, coupled to said output port of said ranging beam combining star coupling means, for detecting the fringes in said first wave interference pattern: ranging counting means, responsive to said detected fringes of said reference detector means, for counting the number of fringes N r in said first wave interference pattern produced during said sweep in frequency; reference beam splitting star coupling means, including an input port and first and second output ports, for splitting said ranging beam into third and fourth beams, said third beam produced at said first output port, said fourth beam produced at said second output port, said reference beam splitting star coupling means including means for coupling said input port of said reference beam splitting star coupling means to said second output port of said first star coupling means; reference beam combining star coupling means for combining said third and fourth beams to produce a second wave interference pattern, said reference beam combining star coupling means including first and second input ports and at least one output port; second optical fiber means for coupling said second output port of said reference beam splitting star coupling means to said second input port of said reference beam combining star coupling means, said second optical fiber means defining a fixed path length; reference optical fiber means for coupling said first output port of said reference beam splitting star coupling means to said first input port of said reference beam combining star coupling means, said reference optical fiber means defining a path of predetermined known fixed length X ref , X ref being approximately equal to the distance R to be measured; reference detector means, coupled to said output port of said reference beam combining star coupling means, for detecting the fringes in said second wave interference pattern; reference counting means, responsive to said detected fringes of said reference detector means, for counting the number of fringes N ref in said second wave interference pattern produced during said sweep in frequency; and processing means, responsive to said counts N r and N ref , for calculating the distance R to said target, said distance R given by

Claim 15

Apparatus as claimed in claim 12, wherein said frequency sweeping means includes: ramp generator means for producing a modulating signal the level of which varies and is continuous between a first predetermined level and a second predetermined level; and phase shift means, optically coupled to said radiation source means and responsive to said modulating signal, for modulating the phase of said radiation.

Claim 16

Apparatus as claimed in claim 12 or claim 13, including surface roughness processing means, responsive to the amplitude of the fringes detected by said ranging detector means, for characterizing the roughness of the scattering surface of said target scattering said first beam.

Claim 19

A method as claimed in claim 15, wherein said processing step (8) includes the steps of: detecting the fringes in said first wave interference pattern; counting the number N r of said detected fringes in said first wave interference pattern for a sweep in the frequency of said radiation from a first frequency to a second frequency; detecting the fringes in said second wave interference pattern; counting the number N ref of said detected fringes in said second wave interference pattern for said sweep in the frequency of said radiation; and calculating the distance R to said target, said distance given by

Claim 20

17 . A method as claimed in claim 15 or claim 16, wherein said modulating step (2) includes the steps of: producing a modulating signal the level of which varies and is continuous between a first predetermined level and a second predetermined level; and modulating the phase of said produced radiation with said modulating signal.

Claim 23

A method as claimed in claim 19, wherein said surface roughness characterizing step includes the steps of: varying the angle of incidence of said beam on said surface; measuring the amplitude of said first wave interference pattern produced by said producing step (5), said detected amplitude proportional to the intensity of the radiation scattered by said surface; and processing the detected amplitude for a plurality of angles of incidence to produce indicia of said surface roughness.

Claim 24

A method as claimed in claim 20, wherein said angle varying step includes the step of successively directing said first portion of said ranging beam onto a plurality of points on said surface, said steps (5)-(8) being performed for each of said plurality of points; and said detected amplitude processing step includes the step of estimating an angle of incidence of said beam onto each of said plurality of points from the plurality of determined distances produced by said processing step (8).