Optical detection of oscillating targets using modulation of scattered laser light

• US 7,511,624 B2
• Filed: 01/25/2006
• Issued: 03/31/2009
• Est. Priority Date: 01/25/2005
• Status: Active Grant

• Current Assignee: Montana State University
• Original Assignee: Montana State University
• Inventors: Repasky, Kevin S., Hoffman, David S., Shaw, Joseph A., Carlsten, John L., Spangler, Lee H.
• Primary Examiner(s): Bugg; George A
• Assistant Examiner(s): LAU, HOI CHING
• Application Number:
  US11/338,806
• Publication Number:
  US 20060254522A1
• Time in Patent Office: 1,161 Days
• Field of Search: 340/573.1, 702/19, 702/5, 738/66, 250/221, 342/54
• US Class Current: 340/573.1
• CPC Class Codes: A01K 29/005 Monitoring or measuring activity, e.g. detecting heat or mating
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

The present invention provides systems and methods using a temporal-frequency sensitive receiver to detect laser light that is scattered by an oscillating object, thereby allowing remote monitoring of the object'"'"'s position and movement.

Claims

1. A method for detecting an oscillating target, the method comprising:

illuminating a measurement region using a pulsed laser beam;

collecting, for each of a plurality of ranges to one or more potential oscillating targets for which a return signal is present, a time series of return signals for that range;

computing a frequency-domain transform of each collected time series; and

analyzing the frequency-domain transform of each collected time series to determine whether modulation is present within a predetermined range of frequencies spanning an oscillation frequency associated with the oscillating target.

2. The method of claim 1, wherein a pulse repetition frequency of the pulsed laser beam substantially exceeds a Nyquist sampling frequency associated with the oscillation frequency.

3. The method of claim 1, wherein the oscillating target is one of a flying insect, a flying bird, a flying mammal, and a propeller-driven object.

4. The method of claim 3, wherein the flying insect is one of a fly, a bee, and a wasp, the oscillation frequency being produced by the beating of wings.

5. The method of claim 4, wherein the bee is a honeybee.

6. The method of claim 3, wherein the flying insect is trained or conditioned to locate a specific chemical.

7. The method of claim 6, wherein the specific chemical is associated with explosives.

8. The method of claim 7, wherein the explosives are associated with landmines.

9. The method of claim 1, wherein the frequency-domain transform is a Fourier transform.

10. The method of claim 1, wherein the oscillation frequency is greater than that of any wind-blown vegetation in the measurement region.

11. The method of claim 1, wherein the plurality of ranges are derived from measured times of flight of the pulsed laser beam.

12. A system for detecting an oscillating target, the system comprising:

a pulsed laser to illuminate a measurement region;

an optical detector;

an optical receiving apparatus to collect return signals and feed the return signals to the optical detector, the optical detector producing an output signal; and

a computing device to receive the output signal from the optical detector, the computing device being configured to;

collect, for each of a plurality of ranges to one or more potential oscillating targets for which a return signal is present, a time series of return signals for that range;

compute a frequency-domain transform of each collected time series; and

analyze the frequency-domain transform of each collected time series to determine whether modulation is present within a predetermined range of frequencies spanning an oscillation frequency associated with the oscillating target.

13. The system of claim 12, wherein the oscillating target is one of a flying insect, a flying bird, a flying mammal, and a propeller-driven object.

14. The system of claim 13, wherein the flying insect is one of a fly, a bee, and a wasp, the oscillation frequency being produced by the beating of wings.

15. The system of claim 14, wherein the bee is a honeybee.

16. The system of claim 13, wherein the flying insect is trained or conditioned to locate a specific chemical.

17. The system of claim 16, wherein the specific chemical is associated with explosives.

18. The system of claim 17, wherein the explosives are associated with landmines.

19. The system of claim 12, wherein the optical detector includes a photomultiplier tube.