Lidar atmospheric wind detector

• US 5,796,471 A
• Filed: 09/18/1996
• Issued: 08/18/1998
• Est. Priority Date: 09/18/1995
• Status: Expired due to Term

• Current Assignee: Utah State University
• Original Assignee: Utah State University
• Inventors: Wilkerson, Thomas D., McKay, Jack A.
• Primary Examiner(s): Oen, William L.
• Application Number:
  US08/718,150
• Time in Patent Office: 699 Days
• Field of Search: 359/17, 359/18, 356/4.01, 356/4.02, 356/4.03, 356/4.04, 356/4.05, 356/5.01, 356/5.03, 356/5.05, 356/27, 356/28, 356/28.5, 356/337, 356/338, 356/342, 356/345, 356/347, 356/372 , 356/376, 364/550, 364/560, 364/561, 73/170.16, 73/170.01, 73/170.06, 73/170.07, 73/170.08, 73/170.11
• US Class Current: 356/28.5
• 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 17/95 for meteorological use
• 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

The present invention is a lidar for detecting characteristics of the atmosphere, and in particular for detecting the speed and direction of objects such as air-borne particles and molecules in the atmosphere in order to determine the speed and direction of wind which is carrying them. The lidar comprises at least one lasing transmitter which transmits at least one lasing beam of radiation in the frequency range of ultraviolet light and which is swept along a path in the atmosphere so as to strike objects in the atmosphere causing backscatter radiation which is received by a receiver for determination of the Doppler shift of the objects being struck. The lidar is moved in a vehicle such as a satellite, so that wind speeds and directions at a number of altitudes and over a large area can be measured.

Claims

1. A method for detecting and measuring wind speed, said method comprising the steps of:

(a) projecting a first laser beam from a moving airborne vehicle onto a first predetermined area when the airborne vehicle resides at a first airborne position;

(b) projecting a second laser beam from a moving airborne vehicle onto the first predetermined area when the airborne vehicle has moved to a second airborne position;

(c) receiving first and second backscattered laser light originating from the first and second laser beams, respectively, which light has been backscattered from at least one object moving within the first predetermined area;

(d) calculating Doppler shifts in the first and second backscattered light and producing Doppler shift data therefrom representing components of Doppler shifting caused only by movement effects of the at least one object, and thus without movement effects of the airborne vehicle; and

(e) calculating from the Doppler shift data a movement speed of the at least one object, and thus wind speed of wind carrying the at least one object.

2. A method for detecting and measuring wind speed as defined in claim 1 and also for determining and measuring wind velocity, wherein step (e) further comprises determining a movement direction of the at least one object from the Doppler shift data and from known angles of orientation of the first and second laser beams.

3. The method as defined in claim 1, wherein steps (a) and (b) further collectively comprise projecting a plurality of laser beams onto a two-dimensional, substantially cycloid pattern with respect to earth.

4. The method as defined in claim 3, wherein steps (a) and (b) further collectively comprise conically sweeping a plurality of laser beams about a three-dimensional, substantially conical path with respect to the airborne vehicle.

5. The method as defined in claim 1, wherein steps (a), (b) and (d) further collectively comprise altering frequency of the laser beams responsive to movement of the airborne vehicle.

6. The method as defined in claim 5, wherein steps (a), (b) and (d) further collectively comprise altering electrical current within an injection diode to thereby alter the frequency of the laser beams.

7. The method as defined in claim 1, wherein step (a) further comprises projecting the first laser beam from the first airborne position onto the at least one object when said object is traveling along a movement path such that said first laser beam is disposed in a substantially nonorthogonal orientation relative to said movement path of said object.

8. The method as defined in claim 7, wherein step (b) further comprises projecting the second laser beam from the second airborne position onto the traveling object such that said second laser beam is disposed in a substantially nonorthogonal orientation relative to the movement path of the object.

9. The method as defined in claim 1, wherein step (a) further comprises projecting a plurality of first laser beams from a laser source while conically sweeping said laser source about a conical path with respect to the airborne vehicle, and wherein steps (d) and (e) further collectively comprise producing the Doppler shift data to represent components of Doppler shifting caused only by movement effects of the at least one object, and thus without movement effects of the conical sweeping of the laser source, and calculating from the Doppler shift data a movement speed of the at least one object.

10. The method as defined in claim 1, wherein step (a) further comprises projecting a plurality of first laser beams from a laser source while conically sweeping said laser beams about a conical path with respect to the airborne vehicle, and wherein steps (d) and (e) further collectively comprise producing the Doppler shift data to represent components of Doppler shifting caused only by movement effects of the at least one object, and thus without movement effects of the conical sweeping of the laser beams, and calculating from the Doppler shift data a movement speed of the at least one object.

11. The method as defined in claim 10, wherein steps (a) and (d) further collectively comprise altering frequency of the laser beams sufficiently to adjust for movement effects of both the airborne vehicle and the conical sweeping of the laser beams to thereby cause Doppler shifting in the backscattered light to be equivalent to Doppler shifting which would have occurred in the absence of movement of the airborne vehicle and conical sweeping of the laser beams.

12. The method as defined in claim 11, wherein step (d) further comprises altering electrical current within an injection diode to thereby alter the frequency of the laser beams.

13. A method for detecting and measuring wind direction, said method comprising the steps of:

(a) projecting a first laser beam from a moving airborne vehicle onto a first predetermined area when the airborne vehicle resides at a first airborne position;

(b) projecting a second laser beam from a moving airborne vehicle onto the first predetermined area when the airborne vehicle has moved to a second airborne position;

(c) receiving first and second backscattered laser light originating from the first and second laser beams, respectively, which light has been backscattered from at least one object moving within the first predetermined area;

(d) calculating Doppler shifts in the first and second backscattered light and producing Doppler shift data therefrom representing components of Doppler shifting caused only by movement effects of the at least one object, and thus without movement effects of the airborne vehicle; and

(e) determining a movement direction of the at least one object from the Doppler shift data and from known angles of orientation of the first and second laser beams, and thereby determining wind direction of wind carrying the at least one object.

14. A method for detecting and measuring wind velocity, said method comprising the steps of:

(a) projecting a first laser beam from a moving airborne vehicle onto a first predetermined area when the airborne vehicle resides at a first airborne position;

(b) projecting a second laser beam from a moving airborne vehicle onto the first predetermined area when the airborne vehicle has moved to a second airborne position, wherein steps (a) and (b) further collectively comprise conically sweeping a plurality of laser beams about a three-dimensional, substantially conical path with respect to the airborne vehicle;

(c) receiving first and second backscattered laser light originating from the first and second laser beams, respectively, which light has been backscattered from at least one object moving within the first predetermined area;

(d) calculating Doppler shifts in the first and second backscattered light and producing Doppler shift data therefrom representing components of Doppler shifting caused only by movement effects of the at least one object, and thus without movement effects of the airborne vehicle or of the conical sweeping of the laser beams; and

(e) calculating from the Doppler shift data and from known angles of orientation of the first and second laser beams, a velocity of the at least one object in the form of a movement speed and a movement direction of said object, and thus wind velocity of wind carrying the at least one object;

wherein steps (a) and (b) further collectively comprise projecting a plurality of laser beams onto a two-dimensional, substantially cycloid pattern with respect to earth;

wherein steps (a), (b) and (d) further collectively comprise altering frequency of the laser beams sufficiently to adjust for movement effects of both the airborne vehicle and the conical sweeping of the laser beams to thereby cause Doppler shifting in the backscattered light to be equivalent to Doppler shifting which would have occurred in the absence of movement of the airborne vehicle and conical sweeping of the laser beams;

wherein steps (a), (b) and (d) further collectively comprise altering electrical current within an injection diode to thereby alter the frequency of the laser beams;

wherein step (a) further comprises projecting the first laser beam from the first airborne position onto the at least one object when said object is traveling along a movement path such that said first laser beam is disposed in a substantially nonorthogonal orientation relative to said movement path of said object;

wherein step (b) further comprises projecting the second laser beam from the second airborne position onto the traveling object such that said second laser beam is disposed in a substantially nonorthogonal orientation relative to the movement path of the object.

15. An apparatus for detecting and measuring wind speed from a moving airborne vehicle, said apparatus comprising:

laser means for (i) projecting a first laser beam from the airborne vehicle onto a first predetermined area when the airborne vehicle resides at a first airborne position, and (ii) projecting a second laser beam from the airborne vehicle onto the first predetermined area when the airborne vehicle has moved to a second airborne position;

receiving means attachable to the airborne vehicle for receiving first and second backscattered laser light originating from the first and second laser beams, respectively, which light has been backscattered toward said airborne vehicle from at least one object moving within the first predetermined area;

data-producing means for calculating Doppler shifts in the first and second backscattered light and producing Doppler shift data therefrom representing components of Doppler shifting caused only by movement effects of the at least one object, and thus without movement effects of the airborne vehicle; and

speed calculating means for calculating from the Doppler shift data a movement speed of the at least one object, and thus wind speed of wind carrying the at least one object.

16. An apparatus for detecting and measuring wind speed as defined in claim 15 and also for determining and measuring wind velocity, wherein the data-producing means and the speed calculating means collectively further comprise a means for determining a movement direction of the at least one object from the Doppler shift data and from known angles of orientation of the first and second laser beams.

17. The apparatus as defined in claim 15, wherein the laser means comprises guiding means for guiding a plurality of laser beam pulses onto a two-dimensional, substantially cycloid pattern with respect to earth.

18. The apparatus as defined in claim 17, wherein the laser means comprises a laser beam projector and wherein the guiding means comprises rotation means for conically sweeping the laser beam projector about a three-dimensional, substantially conical movement path with respect to the airborne vehicle.

19. The apparatus as defined in claim 17, wherein the laser means comprises means for conically sweeping a plurality of laser beams about a three-dimensional, substantially conical path with respect to the airborne vehicle.

20. The apparatus as defined in claim 15, wherein the data-producing means further comprises:

means for producing control signals corresponding to movement of the airborne vehicle; and

tuning means for altering frequency of the laser beams projected by the laser means responsive to the control signals.

21. The apparatus as defined in claim 20, wherein the tuning means comprises:

an injection diode driven by electrical current; and

means for altering the electrical current.

22. The apparatus as defined in claim 15, wherein the laser means further comprises a plurality of alexandrite rods.

23. The apparatus as defined in claim 15, wherein the laser means further comprises a rotational holographic optical element having optical properties which produce a deflection angle in a laser beam passing therethrough.

24. A lidar comprising:

at least one transmitter means for generating at least one laser beam of electromagnetic radiation and then selectively emitting said at least one laser beam;

tuning means for selectively varying at least one frequency of the at least one laser beam before emitting said at least one laser beam;

scanning means for sweeping the at least one laser beam along a selectively variable path such that the at least one laser beam strikes objects in the atmosphere and creates backscatter; and

receiving means for detecting said backscatter from the objects in the atmosphere so as to determine a Doppler shift of the at least one laser beam.

25. A method of using lidar, comprising the steps of:

(a) transmitting at least one laser beam of electromagnetic radiation;

(b) bending said at least one beam by passing said beam through a holographic optical element;

(c) rotating said holographic optical element to selectively vary the direction of said at least one beam such that said beam strikes objects in the atmosphere and creates backscatter;

(d) detecting said backscatter from the objects in the atmosphere with a receiver so as to determine a Doppler shift of the at least one beam.