Method and apparatus for remote measurement of vibration and properties of objects

• US 7,073,384 B1
• Filed: 08/23/2000
• Issued: 07/11/2006
• Est. Priority Date: 08/23/1999
• Status: Expired due to Fees

• Current Assignee: The Trustees of The Stevens Institute of Technology (Stevens Institute Of Technology)
• Original Assignee: Stevens Institute Of Technology
• Inventors: Whittaker, Edward A., Sedunov, Nikolay, Donskoy, Dimitri
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): SAINT SURIN, JACQUES M
• Application Number:
  US10/069,696
• Time in Patent Office: 2,148 Days
• Field of Search: 736/57, 736/55, 735/79, 736/46, 736/27, 736/02, 735/99, 735/96, 73/18.2, 356/358, 356/345, 356/357, 356/432, 356/5.1, 356/5.11, 702/39, 702/40, 702/128, 702/901, 367/87
• US Class Current: 73/657
• CPC Class Codes: G01N 2291/015 Attenuation, scattering
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 29/2412 using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects

Abstract

A method and apparatus (10) is provided which employs phase or amplitude modulated electromagnetic probing waves (20) (in optical or microwave frequency ranges or both) emitted toward a vibrating object (8). The optical and/or microwave probing signals (20) remotely irradiate an object (8) of interest. The object (8) reflects and/or scatters the probing wave (20) toward a receiver (22). The reflected/scattered modulated signal (24) is received with a remote sensor (receiver) (22). Vibration causes additional phase modulation to the probing wave (20). At the receiving end, the signal is demodulated to extract and analyze the vibration waveform (26,28). The present invention can be utilized for nondestructive testing, monitoring of technological processes, structural integrity, noise and vibration control, mine detection, etc.

Claims

1. An electromagnetic wave vibrometer apparatus comprising:

a signal generator for generating an electromagnetic signal;

an amplitude modulator for amplitude modulating the electromagnetic signal to produce an amplitude modulated signal;

a first transmitter for transmitting the amplitude modulated signal at a vibrating object;

a first receiver for receiving a reflected amplitude modulated signal from the vibrating object;

a second vibration receiver mounted with the first receiver for compensation of unwanted background or coupled vibration;

a demodulator for demodulating the reflected amplitude modulated signal to produce a demodulated signal; and

a signal processor for extracting and analyzing a vibration waveform from the demodulated signal.

2. The apparatus of claim 1 wherein the electromagnetic signal is an optical signal.

3. The apparatus of claim 2 wherein the optical signal is amplitude modulated with a microwave frequency signal.

4. The apparatus of claim 1 wherein the electromagnetic signal is a microwave signal.

5. The apparatus of claim 1 wherein the electromagnetic signal is a combination of optical and microwave signals.

6. The apparatus of claim 5 wherein the optical and microwave signals are modulated at the same frequency.

7. The apparatus of claim 1 further comprising a laser signal source.

8. The apparatus of claim 1 further comprising an LED signal source.

9. The apparatus of claim 1 further comprising a second vibration transmitter mounted with the first receiver for calibration of the apparatus and to determine an angle of reflection.

39. The method of claim 1, wherein the amplitude modulated signal is modulated in the GHz range.

10. An apparatus for remotely measuring properties of an object comprising:

a signal generator for generating an electromagnetic signal;

an amplitude modulator for amplitude modulating the electromagnetic signal with a modulating signal to produce an amplitude modulated signal;

a transmitter for transmitting the amplitude modulated signal at an object;

means for vibrating the object to modulate the amplitude modulated signal transmitted at the object;

a first receiver for receiving a reflected amplitude modulated signal from the object;

a second vibration receiver mounted with the first receiver for compensation for unwanted background or coupled vibration;

a demodulator for demodulating the reflected amplitude modulated signal using the modulating signal to produce a demodulated signal; and

a signal processor for extracting and analyzing a vibration waveform from the demodulated signal.

11. The apparatus of claim 10 wherein the electromagnetic signal is an optical signal.

12. The apparatus of claim 11 wherein the optical signal is amplitude modulated with a microwave frequency signal.

13. The apparatus of claim 10 wherein the electromagnetic signal is a microwave signal.

14. The apparatus of claim 10 wherein the electromagnetic signal is a combination of optical and microwave signals.

15. The apparatus of claim 14 wherein the optical and microwave signals are modulated at the same frequency.

16. The apparatus of claim 10 further comprising a laser signal source.

17. The apparatus of claim 10 further comprising an LED signal source.

18. The apparatus of claim 10 further comprising a second vibration transmitter mounted with the first receiver for calibration of the apparatus and to determine an angle of reflection.

19. The method of claim 10, wherein the amplitude modulated signal is modulated in the GHz range.

20. A method of remotely measuring vibration comprising:

generating an electromagnetic signal;

amplitude modulating the electromagnetic signal with an amplitude modulating signal to produce an amplitude modulated signal;

transmitting the amplitude modulated signal at a vibrating object using a first transmitter;

receiving a reflected amplitude modulated signal from the vibrating object using a first receiver;

demodulating the reflected amplitude modulated signal using the amplitude modulating signal to produce a demodulated signal;

compensating for vibration errors by determining displacements of the transmitter and receiver; and

analyzing the demodulated signal.

21. The method of claim 20 wherein the electromagnetic signal is an optical signal.

22. The method of claim 20 wherein the electromagnetic signal comprises a microwave signal.

23. The method of claim 20 wherein the electromagnetic signal comprises a combination of microwave and optical signals.

24. The method of claim 23 wherein the optical and microwave signals are modulated at the same frequency.

25. The method of claim 20 wherein the electromagnetic signal is generated by a laser or a laser diode.

26. The method of claim 20 wherein the electromagnetic signal is generated by an LED.

27. The method of claim 20 further comprising providing a second vibration receiver mounted with the first receiver for compensating for unwanted background or coupled vibration.

28. The method of claim 27 further comprising providing a second vibration transmitter mounted with the first receiver for calibrating the vibrometer and to determine an angle of reflection.

29. The method of claim 20, wherein the amplitude modulated signal is modulated in the GHz range.

30. A method for remotely determining properties of an object comprising:

amplitude modulating an electromagnetic signal with an amplitude modulating signal to produce an amplitude modulated signal;

transmitting the amplitude modulated signal at an object;

vibrating the object;

receiving reflected amplitude modulated signals from the vibrating object using a first receiver;

compensating for unwanted vibration using a second receiver mounted with the first receiver; and

processing the reflected amplitude modulated signals to extract information about the properties of the object.

31. The method of claim 30 wherein the electromagnetic signal is an optical signal.

32. The method of claim 30 wherein the electromagnetic signal comprises a microwave signal.

33. The method of claim 30 wherein the electromagnetic signal comprises a combination of microwave and optical signals.

34. The apparatus of claim 30 wherein the optical and microwave signals are modulated at the same frequency.

35. The method of claim 30 wherein the electromagnetic signal is generated by a laser or a laser diode.

36. The method of claim 30 wherein the electromagnetic signal is generated by an LED.

37. The method of claim 30 wherein the electromagnetic signal is split into first and second signals and the second signal is transmitted to a demodulator for comparing the second signal with the reflected amplitude modulated signals.

38. The method of claim 30 further comprising providing a second vibration transmitter mounted with the first receiver for calibrating the vibrometer and to determine an angle of reflection.

40. The method of claim 30, wherein the amplitude modulated signal is modulated in the GHz range.

41. A method of remotely measuring vibration, comprising:

providing a non-coherent beam of light;

amplitude modulating the non-coherent beam of light with an amplitude modulating signal to produce an amplitude modulated beam of light;

transmitting the amplitude modulated beam of light at a vibrating object;

object using a transmitter;

receiving a reflected amplitude modulated beam of light from the vibrating object using a receiver;

compensating for vibration errors by determining displacements of the transmitter and the receiver; and

demodulating the reflected amplitude modulated beam of light using the amplitude modulating signal to extract vibration information from the amplitude modulated signal.

42. The method of claim 41, wherein the non-coherent beam of light is produced by an LED.

43. The method of claim 41, wherein the non-coherent beam of light is an optical signal.

44. The method of claim 41, further comprising compensating for unwanted background or coupled vibration using a second receiver.

45. The method of claim 44, further comprising determining an angle of reflection using a second vibration transmitter mounted with the receiver.

46. A microwave vibrometer, comprising:

a signal generator for generating a first microwave frequency signal;

a power splitter for splitting the first microwave signal into a reference signal and a signal to be transmitted;

a circulator for transmitting the signal to be transmitted at a vibrating object, for receiving a phase modulated reflected signal from the vibrating object, and for decoupling the transmitted signal from the reflected signal;

a first mixer for mixing the phase modulated reflected signal with an intermediate frequency signal to produce a first mixed signal;

a second mixer for mixing the reference signal with the intermediate frequency signal to produce a second mixed signal;

an I &

Q demodulator for mixing the first mixed signal and the second mixed signal to produce a demodulated signal; and

means for extracting and analyzing a vibration waveform from the demodulated signal.