Atmospheric measurement system

• US 8,797,550 B2
• Filed: 10/19/2011
• Issued: 08/05/2014
• Est. Priority Date: 04/21/2009
• Status: Active Grant

• Current Assignee: Michigan Aerospace Corporation
• Original Assignee: Michigan Aerospace Corporation
• Inventors: Hays, Paul Byron, Johnson, David Keith, Zuk, David Michael, Lindemann, Scott Kevin
• Primary Examiner(s): HANSEN, JONATHAN M
• Application Number:
  US13/276,853
• Publication Number:
  US 20120050750A1
• Time in Patent Office: 1,021 Days
• Field of Search: 356/519, 356/454
• US Class Current: 356/519
• CPC Class Codes: G01J 9/04 by beating two waves of a same source but of different frequency and measuring the phase shift of the lower frequency obtained
• CPC Class Codes: G01P 5/26 by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
• CPC Class Codes: G01S 17/003 Bistatic lidar systems; Multistatic lidar systems
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 17/95 for meteorological use
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

A fringe pattern from an interferometer is imaged onto a digital micromirror device containing an array of micromirrors in an associated pattern of pixel mirror rotational states that provide for sampling the circular fringe pattern in cooperation with one or more associated photodetectors, so as to provide for generate a corresponding set of associated complementary signals. A plurality of different sets of associated complementary signals generated for a corresponding plurality of mutually independent associated patterns of pixel mirror rotational states are used to determine at least one metric associated with the circular fringe pattern.

Claims

1. A method of processing a fringe pattern from a Fabry-Perot interferometer, comprising:

a. generating at least one portion of a circular fringe pattern with a Fabry-Perot interferometer responsive to at least one light signal incident thereupon, wherein said at least one portion of said circular fringe pattern is formed of light from said at least one light signal;

b. imaging said at least one portion of said circular fringe pattern from said Fabry-Perot interferometer onto a digital micromirror device (DMD), wherein said digital micromirror device (DMD) comprises a plurality of micromirrors arranged in an array, wherein each micromirror of said plurality of micromirrors constitutes a pixel that can be rotationally positioned to a plurality of different pixel-mirror rotational states, and each pixel-mirror rotational state of said plurality of different pixel-mirror rotational states corresponds to a particular associated rotational position of said micromirror;

c. processing said at least one portion of said circular fringe pattern, comprising;

i. setting said pixel-mirror rotational state of each of said plurality of micromirrors of said array so as to form at least one pattern of associated pixel-mirror rotational states at a corresponding at least one point in time, wherein each said at least one pattern of associated pixel-mirror rotational states comprises a plurality of subsets of said plurality of micromirrors, wherein for each subset of said plurality of subsets, each said micromirror of said subset is set to a common said pixel-mirror rotational state, and said micromirrors of different said subsets are set to different said pixel-mirror rotational states;

ii. for each said subset of said plurality of micromirrors, reflecting from said plurality of micromirrors of said subset of said plurality of micromirrors a corresponding portion of said light of said at least one portion of said circular fringe pattern, wherein different corresponding portions of said light corresponding to different said subsets of said plurality of micromirrors are reflected in different directions in accordance with said pixel-mirror rotational state associated with said subset of said plurality of micromirrors;

iii. for each of a plurality of said subsets of said plurality of micromirrors, detecting said corresponding portion of said light reflected from each said subset of said plurality of micromirrors at said at least one point in time, wherein the operation of detecting said corresponding portion of said light comprises either

a) separately detecting different said corresponding portions of said light for a common said pattern of associated pixel-mirror rotational states, wherein said different said corresponding portions of said light are relatively disjoint with respect to one another and collectively constitute a set of disjoint portions of said light, and the operation of separately detecting said different said corresponding portions of said light provides for generating a corresponding set of complementary detected signals;

OR

b) sequentially detecting different said corresponding portions of said light for different said patterns of associated pixel-mirror rotational states at different points in time, wherein said different said corresponding portions of said light are relatively disjoint with respect to one another and collectively constitute a set of disjoint portions of said light, and the operation of detecting different said corresponding portions of said light provides for generating a corresponding set of complementary detected signals;

iv. processing said corresponding set of complementary detected signals so as to provide for characterizing said at least one light signal incident upon said Fabry-Perot interferometer.

2. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein the operations of setting said pixel-mirror rotational states, reflecting from said plurality of micromirrors and detecting said corresponding portion of said light for each of said subset of said plurality of subsets of said plurality of micromirrors are repeated for a plurality of sets of said disjoint portions of said light so as to generate a corresponding plurality of sets of said complementary detected signals, wherein said plurality of sets of said disjoint portions of said light are algebraically spatially independent with respect to one another;

and the operation of processing said corresponding set of complementary detected signals is performed for said corresponding plurality of sets of said complementary detected signals so as to provide for characterizing said at least one light signal incident upon said Fabry-Perot interferometer.

3. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein said at least one light signal comprises a plurality of light signals that are incident upon different portions of a Fabry-Perot etalon of said Fabry-Perot interferometer, the operation of generating said at least one portion of said circular fringe pattern comprises generating a plurality of different portions of said circular fringe pattern, wherein each different portion of said plurality of different portions of said circular fringe pattern is generated for a corresponding different said light signal of said plurality of light signals, and the operation of processing said at least one portion of said circular fringe pattern is performed separately for different said different portions of said circular fringe pattern.

4. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 3, wherein during the operation of separately processing one of said different portions of said circular fringe pattern, a remaining subset of said plurality of micromirrors associated with a remaining portion of said circular fringe pattern are set to a pixel-mirror rotational state that provides for reflecting light associated with said remaining portion of said circular fringe pattern so as to prevent said light associated with said remaining portion of said circular fringe pattern from being detected during the operation of detecting said corresponding portion of said light reflected from each said subset of said micromirrors at said at least one point in time for said one of said different portions of said circular fringe pattern.

5. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 4, wherein the operation of preventing said light associated with said remaining portion of said circular fringe pattern from being detected comprises reflecting said light associated with said remaining portion of said circular fringe pattern to a light block.

6. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 3, wherein the operation of processing said at least one portion of said circular fringe pattern is performed sequentially for different said different portions of said circular fringe pattern.

7. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein for each said set of disjoint portions of said light, said at least one pattern of associated pixel-mirror rotational states comprises a corresponding single pattern of associated pixel-mirror rotational states corresponding to said set of disjoint portions of said light, wherein said corresponding single pattern of associated pixel-mirror rotational states comprises:

a. a first subset of said plurality of micromirrors in a first pixel-mirror rotational state, wherein said first subset of said plurality of micromirrors provides for reflecting a first portion of said light in a first direction; and

b. a second subset of said plurality of micromirrors in a second pixel-mirror rotational state, wherein said second subset of said plurality of micromirrors provides for reflecting a second portion of said light in a second direction different from said first direction; and

c. the operation of separately detecting said different said corresponding portions of said light comprises separately detecting said first and second portions of said light.

8. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 7, wherein the operation of separately detecting said different said corresponding portions of said light comprises substantially simultaneously detecting said first and second portions of said light separately.

9. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein the operation of sequentially detecting different said corresponding portions of said light for different said patterns of associated pixel-mirror rotational states at said different points in time comprises:

a. setting said pixel-mirror rotational state of each of said plurality of micromirrors of said array so as to form a first said pattern of associated pixel-mirror rotational states at a corresponding first point in time, wherein said first said pattern of associated pixel-mirror rotational states comprises a first subset of said plurality of micromirrors, wherein each said micromirror of said first subset of said plurality of micromirrors is set to a common first pixel-mirror rotational state;

b. reflecting from said plurality of micromirrors of said first subset a corresponding first portion of said light of a first portion of said circular fringe pattern in a first direction in accordance with said common first pixel-mirror rotational state associated with said first subset of said plurality of micromirrors;

c. detecting said corresponding first portion of said light reflected from said first subset of said plurality of micromirrors with said plurality of micromirrors of said array set in accordance with said first said pattern of associated pixel-mirror rotational states so as to generate a corresponding first detected signal of said corresponding set of complementary detected signals;

d. setting said pixel-mirror rotational state of each of said plurality of micromirrors of said array so as to form a second said pattern of associated pixel-mirror rotational states at a corresponding second point in time, wherein said second said pattern of associated pixel-mirror rotational states comprises a second subset of said plurality of micromirrors, wherein each said micromirror of said second subset of said plurality of micromirrors is set to said common first pixel-mirror rotational state;

e. reflecting from said plurality of micromirrors of said second subset a corresponding second portion of said light of said first portion of said circular fringe pattern in said first direction in accordance with said common first pixel-mirror rotational state associated with said second subset of said plurality of micromirrors; and

f. detecting said corresponding second portion of said light reflected from said second subset of said plurality of micromirrors with said plurality of micromirrors of said array set in accordance with said second said pattern of associated pixel-mirror rotational states so as to generate a corresponding second detected signal of said corresponding set of complementary detected signals, wherein said corresponding first and second portions of said light collectively constitute said set of disjoint portions of said light.

10. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein said at least one light signal comprises either a reference light signal or at least one backscatter light signal, or both, associated with an atmospheric measurement system, wherein said reference light signal is derived from a light source, and said at least one backscatter light signal is received from light of said light source that had been projected into an atmosphere and backscattered therefrom.

11. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 2, wherein said at least one light signal comprises a reference light signal and at least one backscatter light signal associated with an atmospheric measurement system, wherein said reference light signal is derived from a light source, said at least one backscatter light signal is received from light of said light source that had been projected into an atmosphere and backscattered therefrom, the operation of processing said corresponding plurality of sets of said complementary detected signals is performed separately for said reference light signal and said at least one backscatter light signal, and information from said reference light signal is used to process said at least one backscatter light signal.

12. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein said set of said disjoint portions of said light constitutes first and second portions of a corresponding light signal of said at least one light signal reflected from respective first and second subsets of said plurality of micromirrors in accordance with an effective pattern of said plurality of micromirrors of said digital micromirror device (DMD), said effective pattern is responsive to at least one function related to an optical response underlying said at least one portion of said circular fringe pattern, and said at least one function is responsive to at least one parameter.

13. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein said set of said disjoint portions of said light constitutes first and second portions of a corresponding light signal of said at least one light signal reflected from respective first and second subsets of said plurality of micromirrors in accordance with an effective pattern of said plurality of micromirrors of said digital micromirror device (DMD), and said effective pattern is defined responsive to a method comprising:

a. defining a first function providing a model of an optical response underlying said at least one portion of said circular fringe pattern, wherein said first function incorporates at least one parameter that provide for characterizing said at least one light signal;

b. defining a second function responsive to a partial derivative of said first function with respect to one said at least one parameter, wherein said first and second functions are each dependent upon a variable associated with a radial dimension of said at least one portion of said circular fringe pattern relative to said digital micromirror device (DMD); and

c. defining said effective pattern by associating said first subset of said plurality of micromirrors with a first set of locations on said digital micromirror device (DMD) for which said second function exceeds a first threshold value, and associating said second subset of said plurality of micromirrors with a second set of locations on said digital micromirror device (DMD) for which said second function is less than a second threshold value;

d. wherein the operation of processing said corresponding set of complementary detected signals provides for determining a value of said at least one parameter responsive to said corresponding set of complementary detected signals.

14. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein said at least one light signal comprises either a reference light signal or at least one backscatter light signal, or both, associated with an atmospheric measurement system, wherein said reference light signal is derived from a light source, and said at least one backscatter light signal is received from light of said light source that had been projected into an atmosphere and backscattered therefrom, and said one said at least one parameter is responsive to a measure selected from a number of photons scattered by aerosol particles in said atmosphere, a number of photons scattered by molecules in said atmosphere, a number of background photons from said atmosphere, a temperature of said atmosphere, and a velocity of aerosol particles and molecules of said atmosphere.

15. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 14, wherein said first function is of the form I(phi)=A*H(phi,mA)+M*H(phi,mM)+B*T^2/(1−

R^2), wherein I is an intensity of said at least one portion of said circular fringe pattern responsive to phi, phi is a function responsive to one said at least one parameter corresponding to a velocity of said molecules and aerosol particles in said atmosphere and responsive to said radial dimension of said at least one portion of said circular fringe pattern, A is one said at least one parameter representative of a number of photons scattered by aerosol particles in said atmosphere, mA is a molecular mass of said aerosol particles, M is one said at least one parameter representative of a number of photons scattered by molecules in said atmosphere, mM is a molecular mass of said molecules, B is one said at least one parameter representative of a number of background photons from said atmosphere, T is a transmissivity of a Fabry-Perot etalon of said Fabry-Perot interferometer, R is a reflectivity of said Fabry-Perot etalon, and H is a function responsive to at least one measure of defects of said Fabry-Perot etalon and responsive to one said at least one parameter responsive to a temperature of said atmosphere.

16. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein said first and second threshold values are equal to one another.

17. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein at least one of said first or second threshold values is equal to zero.

18. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein said first and second threshold values are dependent upon said at least one parameter.

19. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein the operation of detecting said corresponding portion of said light reflected from each said subset of said plurality of micromirrors at said at least one point in time comprises detecting said light for a period of time commencing with one said at least one point in time so as to generate a corresponding detected signal of said corresponding set of complementary detected signals, for each detected signal of said corresponding set of complementary detected signals, and a duration of said period of time is dependent upon said one said at least one parameter associated with said corresponding set of complementary detected signals.

20. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein said effective pattern is responsive to said value of said at least one parameter.

21. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein said at least one light signal comprises a reference light signal and at least one backscatter light signal associated with an atmospheric measurement system, said reference light signal is derived from a light source, said at least one backscatter light signal is received from light of said light source that had been projected into an atmosphere and backscattered therefrom, and the operation of processing said corresponding set of complementary detected signals is performed separately for both said reference light signal and said at least one backscatter light signal and comprises determining a corresponding at least one value of each said at least one parameter for said reference light signal and said at least one backscatter light signal, wherein information from said reference light signal is used to process said at least one backscatter light signal.

22. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 15, wherein said at least one light signal comprises a reference light signal and at least one backscatter light signal, wherein the operation of processing said corresponding plurality of sets of said complementary detected signals is performed separately for both said reference light signal and said at least one backscatter light signal, and information from said reference light signal is used to characterize said at least one measure of defects of said Fabry-Perot etalon.

23. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 22, wherein said at least one measure of defects of said Fabry-Perot etalon is determined responsive to both a Fourier transform of said reference light signal and a Fourier transform of a corresponding ideal response of said Fabry-Perot etalon.

24. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein said Fabry-Perot interferometer comprises a Fabry-Perot etalon and said corresponding set of complementary detected signals is processed using a calibration of said Fabry-Perot etalon responsive a measure of temperature of said Fabry-Perot etalon.

25. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein said Fabry-Perot interferometer comprises a Fabry-Perot etalon and said corresponding set of complementary detected signals is processed using an apriori calibration of said Fabry-Perot etalon responsive to a reference light signal.

26. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein the operation of determining a corresponding at least one value of each said at least one parameter comprises minimizing a cost functional representative of a difference between said complementary detected signals and corresponding estimates of said complementary detected signals responsive to a parameterized model, wherein said parameterized model is parameterized with respect to said at least one parameter.

27. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 13, wherein the operation of minimizing said cost functional comprises a Levenberg-Marquardt nonlinear least squares method.

28. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein said set of said disjoint portions of said light constitutes first and second portions of a corresponding light signal of said at least one light signal reflected from respective first and second subsets of said plurality of micromirrors in accordance with an effective pattern of said plurality of micromirrors of said digital micromirror device (DMD), and said effective pattern is defined by associating said first subset of said plurality of micromirrors with a first plurality of locations on said digital micromirror device (DMD) for which a radius relative to a center of said circular fringe pattern exceeds a first threshold value, and associating said second subset of said plurality of micromirrors with a second plurality of locations on said digital micromirror device (DMD) for which said radius is less than a second threshold value, wherein said first and second threshold values are either equal to, or different from one another.

29. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 28, wherein the operation of detecting said corresponding portion of said light reflected from each said subset of said plurality of micromirrors at said at least one point in time comprises detecting said corresponding portion of said light for a period of time commencing with a point in time of said at least one point in time so as to generate a corresponding detected signal of said corresponding set of complementary detected signals, for each detected signal of said corresponding set of complementary detected signals, said effective pattern is responsive to at least one function related to an optical response underlying said at least one portion of said circular fringe pattern, said at least one function is responsive to at least one parameter, said corresponding set of complementary detected signals is associated with a corresponding said at least one parameter, and a duration of said period of time is dependent upon a value of said corresponding said at least one parameter associated with said corresponding set of complementary detected signals.

30. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 28, wherein said effective pattern is responsive to at least one function related to an optical response underlying said at least one portion of said circular fringe pattern, said at least one function is responsive to at least one parameter, and said effective pattern is responsive to a value of said at least one parameter.

31. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 2, wherein said at least one pattern of associated pixel-mirror rotational states comprises a plurality of patterns of associated pixel-mirror rotational states and said plurality of sets of said disjoint portions of said light are generated from a corresponding plurality of said patterns of associated pixel-mirror rotational states that are generated by dyadic divisions in radii relative to a center of said circular fringe pattern.

32. A method of processing a fringe pattern from a Fabry-Perot interferometer as recited in claim 1, wherein said set of said disjoint portions of said light is generated from a corresponding said pattern of associated pixel-mirror rotational states that is responsive to a probability distribution for which a fraction of associated said micromirrors in one of two said pixel-mirror rotational states at a location in proximity to a given radius relative to a center of said circular fringe pattern is dependent upon said probability distribution.

33. A system for processing at least one light signal, comprising:

a. a Fabry-Perot interferometer comprising;

i. a Fabry-Perot etalon; and

ii. an imaging lens, wherein said Fabry-Perot interferometer is arranged so that the at least one light signal is projected through at least a portion of said Fabry-Perot etalon, and then onto and through said imaging lens;

b. at least one digital micromirror device (DMD), wherein each said at least one digital micromirror device (DMD) comprises a plurality of micromirrors arranged in an array, each micromirror of said plurality of micromirrors comprises an associated reflective surface, each said micromirror and said associated reflective surface of said plurality of micromirrors is rotationally positionable to any of a plurality of rotational states responsive to a micromirror control signal, and each rotational state of said plurality of rotational states corresponds to a different rotational position of said micromirror and said associated reflective surface;

when in a non-rotated state, said plurality of micromirrors are arranged along and substantially coincident with a reference surface, and said digital micromirror device (DMD) is located relative to said Fabry-Perot interferometer so that said reference surface is nominally aligned with a focal surface of said imaging lens upon which the at least one light signal is imaged by said imaging lens as at least a first portion of a corresponding circular fringe pattern;

c. at least one detector positioned so as to be able to receive light of the at least one light signal reflected by said plurality of micromirrors of said digital micromirror device when said plurality of micromirrors are positioned in one of said plurality of rotational states;

d. a data processor, wherein said data processor provides for generating said micromirror control signal for each of said plurality of micromirrors, and said micromirror control signal provides for controlling a first subset of said plurality of micromirrors to a first said rotational state, and said micromirror control signal provides for controlling a second subset of said plurality of micromirrors to a second said rotational state, wherein said first subset of said plurality of micromirrors is different from said second subset of said plurality of micromirrors, and either

i. said at least one detector comprises first and second detectors and said first and second subsets of said plurality of micromirrors provide for simultaneously reflecting first and second disjoint portions of at least a second portion of said first portion of said corresponding circular fringe pattern to corresponding said first and second detectors, respectively, OR

ii. said first subset of said plurality of micromirrors in a first said rotational state provide for reflecting a first disjoint portion of at least a second portion of said first portion of said corresponding circular fringe pattern to said at least one detector at a first point in time, and said second subset of said plurality of micromirrors in said first said rotational state provide for reflecting a second disjoint portion of said at least said second portion of said first portion of said corresponding circular fringe pattern to said at least one detector at a second point in time, wherein said first and second disjoint portions are relatively disjoint with respect to one another.

34. A system for processing at least one light signal as recited in claim 33, further comprising:

a. a light source that provides for generating a first beam of light;

b. at least one beam splitter that provides for splitting said first beam of light into a reference beam of light and at least one second beam of light, wherein said at least one beam splitter alone or in combination with at least one beam forming optic provide for projecting said at least one second beam of light into an atmosphere;

c. at least one receive optic that provides for generating at least one corresponding backscattered light signal from light of said at least one second beam of light backscattered from at least one interaction region in said atmosphere, wherein said at least one interaction region is defined by an intersection of said at least one second beam of light with at least one field of view of a corresponding said at least one receive optic, wherein the at least one light signal comprises at least one element of the group selected from a reference light signal from said reference beam of light and said at least one corresponding backscattered light signal.

35. A system for processing at least one light signal as recited in claim 33, further comprising at least one bandpass optical filter located either within or ahead of said Fabry-Perot interferometer.

36. A system for processing at least one light signal as recited in claim 33, further comprising a temperature sensor in thermal communication with said Fabry-Perot etalon and operatively coupled to said data processor, wherein said temperature sensor provides for transmitting a temperature signal to said data processor and said temperature signal provides a measure of temperature of said Fabry-Perot etalon.

37. A system for processing at least one light signal as recited in claim 33, further comprising a temperature control system in thermal communication with said Fabry-Perot etalon wherein said temperature control system provides for maintaining a temperature of said Fabry-Perot etalon.

38. A system for processing at least one light signal as recited in claim 33, wherein said data processor provides for generating at least one measure representative of the at least one light signal responsive to a plurality of signals from said at least one detector, wherein said plurality of signals are generated by said at least one detector responsive to at least one detection of said first and second disjoint portions of said at least said second portion of said first portion of said corresponding circular fringe pattern.

39. A system for processing at least one light signal as recited in claim 33, further comprising a light block located so as to receive at least a portion of light of said corresponding circular fringe pattern not otherwise reflected by said plurality of micromirrors toward said at least one detector.