1. A method for measuring strain, comprising the steps of:
providing a substrate surface coated with at least one coating layer, said coating layer including at least one luminophore for providing luminescence and at least one photoelastic material for providing photoelasticity;
illuminating said coating layer with polarized excitation light having a first polarization state, wherein longer wavelength light is emitted having a second polarization state which is modified from said first polarization state by said photoelastic material by passage through said coating dependent upon stress or strain in said coating layer;
measuring said second polarization state, and
determining strain on said substrate surface from said second polarization state relative to said first polarization state.
2. The method of claim 1, wherein said photoelastic material comprises at least 40% by weight of said coating.
3. The method of claim 1, wherein said luminophore is a polarization preserving material.
4. The method of claim 1, wherein said coating layer is optically transparent in at least a portion of the visible light range.
5. The method of claim 1, wherein said photoelastic material provides a strain optic sensitivity at least equal to a strain optic sensitivity provided by BGM.
6. The method of claim 1, wherein said polarized light comprises elliptically polarized light.
7. The method of claim 1, wherein said characteristic comprises at least one selected from the group consisting of the maximum principal strain, the minimum principal strain and the maximum shear strain on said substrate surface.
8. The method of claim 1, wherein said characteristic comprises directions of maximum principal strain and the minimum principal strain on said substrate surface.
9. The method of claim 1, wherein said coating layer consists of only a single layer.
10. method of claim 1, wherein said at least one coating layer comprises at least two layers, said at least two layers comprising a luminescent layer disposed on said substrate surface and a photoelastic layer disposed on said luminescent layer.
11. The method of claim 10, wherein said luminescent layer includes a first luminophore and said photoelastic coating includes a second luminophore, wherein said first and second luminophore provide different emission wavelengths.
12. The method of claim 11, wherein an emission wavelength of said first luminophore corresponds to an absorption spectrum of said second luminophore.
13. The method of claim 1, further comprising the step of optical filtering to selectively pass said higher wavelength light and reject said excitation light.
14. The method of claim 1, wherein said illuminating step comprises a process comprising oblique incidence, said determining step providing individual values for maximum principal strain and minimum principal strain on said substrate exclusively using said method.
15. The method of claim 1, further comprising the step of scanning said excitation light across said substrate surface, wherein regions of high strain are identified.
16. An apparatus for measuring strain, comprising:
an excitation light source for illuminating a surface of a substrate with polarized excitation light having a first polarization state, said substrate including a coating which provides at least one luminophore for providing luminescence and at least one photoelastic material for providing photoelasticity;
a detector for measuring light emitted by said substrate surface responsive to said excitation light, said emitted light being at a longer wavelength and having a second polarization state which is modified from said first polarization state by said photoelastic material by passage through said coating as compared to said, and
a computer for determining strain on said substrate surface from said second polarization state relative to said first polarization state.
17. The apparatus of claim 16, wherein said polarized light is elliptically polarized light.
18. The apparatus of claim 16, wherein said computer provides at least one selected from the group consisting of the maximum principal strain, the minimum principal strain and the maximum shear strain on said substrate surface.
19. The apparatus of claim 16, wherein said wherein said computer provides directions of maximum principal strain and the minimum principal strain on said substrate surface.
20. The apparatus of claim 16, further comprising a linear polarizer or a combination of a quarter wave plate and linear polarizer disposed between said object and said detector.
21. A coating for indicating strain of an underlying surface, comprising:
at least one coating layer, said coating layer being optically transparent in at least a portion of the visible light range and including at least one luminophore for providing luminescence and at least one photoelastic material for providing photoelasticity, wherein said coating layer emits longer wavelength light having an altered polarization responsive to illumination with polarized excitation light.
22. The coating of claim 21, wherein said luminophore is a polarization preserving luminophore.
23. The coating of claim 21, wherein said coating layer consists of a single layer.
24. The coating claim 21, wherein said at least one coating layer comprises at least two layers, said at least two layers comprising a luminescent layer disposed on said substrate surface and a photoelastic layer disposed on said luminescent layer.
25. The coating of claim 24, wherein said luminescent layer includes a first luminophore and said photoelastic coating includes a second luminophore, wherein said first and second luminophore provide different emission wavelengths.
26. The coating of claim 25, wherein an emission wavelength of said first luminophore corresponds to an absorption spectrum of said second luminophore.
27. The coating of claim 21, wherein said coating layer comprises a bisphenol A diglycidyl ether or a bisphenol A glycerolate diacrylate based polymer.
28. A coated structural member, comprising:
a substrate having a substrate surface, and
a coating layer disposed on said substrate surface, said coating layer being optically transparent in at least a portion of the visible light range and including at least one luminophore for providing luminescence and at least one photoelastic material for providing photoelasticity, wherein said coating layer emits longer wavelength light having an altered polarization responsive to illumination with polarized excitation light.
29. The coated member of claim 28, wherein said luminophore is a polarization preserving luminophore.
30. The coated member of claim 28, wherein said coating layer consists of only a single layer.
31. The coated member claim 28, wherein said coating layer comprises at least two layers, said at least two layers comprising a luminescent layer disposed on said substrate surface and a photoelastic layer disposed on said luminescent layer.
32. The coated member of claim 31, wherein said luminescent layer includes a first luminophore and said photoelastic coating includes a second luminophore, wherein said first and second luminophore provide different emission wavelengths.
33. The coated member of claim 32, wherein an emission wavelength of said first luminophore corresponds to an absorption spectrum of said second luminophore.
34. The coated member claim 28, wherein said coating layer comprises a bisphenol A diglycidyl ether or a bisphenol A glycerolate diacrylate based polymer.
35. A method for real-time monitoring of strain on surfaces of mechanical components, comprising the steps of:
providing a mechanical element having at least one surface, said surface including at least one coating layer for indicating strain on said surface, said coating layer being optically transparent in at least a portion of the visible light range and including at least one luminophore for providing luminescence and at least one photoelastic material for providing photoelasticity, wherein said coating layer emits longer wavelength light having an altered polarization dependent upon stress or strain on said coating responsive to illumination with polarized excitation light;
utilizing said mechanical element in a stress inducing application;
monitoring strains developed on said mechanical element during said utilizing step, said monitoring step comprising illuminating said surface with said polarized excitation light having a first polarization state, and
measuring a second polarization state of said emitted light, and
determining strain on said surface from said second polarization state relative to said first polarization state.
36. The method of claim 35, wherein said photoelastic material comprises at least 40% by weight of said coating layer.
37. The method of claim 36, wherein said coating layer comprises at least two layers, said at least two layers comprising a luminescent layer disposed on said substrate surface and a photoelastic layer disposed on said luminescent layer, said luminescent layer including a first luminophore and said photoelastic coating includes a second luminophore, wherein said first and second luminophore provide different emission wavelengths.
38. The method of claim 37, wherein an emission wavelength of said first luminophore corresponds to an absorption spectrum of said second luminophore.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus to determine an interference between a primary network and a secondary network, the apparatus comprising:
a signal receiver to receive a first signal of the primary network and a second signal of the secondary network;
a correlator to compute a correlation value of a first cyclic prefix included in the first signal and a correlation value of a second cyclic prefix included in the second signal; and
an interference determination unit to determine an interference level or whether the interference occurs between the primary network and the secondary network based on the correlation value of the first cyclic prefix and the correlation value of the second cyclic prefix.
2. The apparatus as claimed in claim 1, wherein:
the first signal includes a first processing cyclic prefix and the second signal includes a second processing cyclic prefix, the first processing cyclic prefix is generated by processing the first cyclic prefix using a first processing code;
the second processing cyclic prefix is generated by processing the second cyclic prefix using a second processing code;
the correlator computes a correlation value of the first processing cyclic prefix and a correlation value of the second processing cyclic prefix; and
the interference determination unit determines the interference level or whether the interference occurs between the primary network and the secondary network based on the correlation value of the first processing cyclic prefix and the correlation value of the second processing cyclic prefix.
3. The apparatus as claimed in claim 2, wherein the first processing code is a first pseudo-noise code corresponding to the primary network and the second processing code is a second pseudo-noise code corresponding to the secondary network.
4. The apparatus as claimed in claim 1, wherein the interference determination unit determines the interference level or whether the interference occurs between the primary network and the secondary network based on a pattern according to a time of the correlation value of the first cyclic prefix and the correlation value of the second cyclic prefix.
5. The apparatus as claimed in claim 1, wherein, when the interference occurs between the primary network and the secondary network, or when the interference level is greater than a predetermined threshold, the interference determination unit generates an alarm signal.
6. The apparatus as claimed in claim 5, wherein the alarm signal is transmitted to a terminal of the secondary network and the terminal of the secondary network either uses an updated wireless resource or suspends a communication operation.
7. The apparatus as claimed in claim 1, wherein the interference determination unit compares the correlation value of the first cyclic prefix with the correlation value of the second cyclic prefix, and determines the interference level or whether the interference occurs between the primary network and the secondary network based on the result of the comparison.
8. The apparatus as claimed in claim 1, wherein the correlator computes the correlation value of the first cyclic prefix and the correlation value of the second cyclic prefix using a length of the first cyclic prefix, a length of the second cyclic prefix, a window length of a fast Fourier transform (FFT) of the first signal, andor a window length of an FFT of the second signal.
9. The apparatus as claimed in claim 1, wherein the first signal and the second signal are encoded using an orthogonal frequency division multiplexing (OFDM) scheme.
10. The apparatus as claimed in claim 1, wherein:
the first signal includes either a downlink signal or an uplink signal of the primary network; and
the second signal includes either a downlink signal or an uplink signal of the secondary network.
11. The apparatus as claimed in claim 1, wherein the primary network has priority over the secondary network regarding use of a wireless resource.
12. A method of determining an interference between a primary network and a secondary network, the method comprising:
receiving a first signal of the primary network and a second signal of the secondary network;
computing a correlation value of a first cyclic prefix included in the first signal and a correlation value of a second cyclic prefix included in the second signal; and
determining an interference level or whether the interference occurs between the primary network and the secondary network based on the correlation value of the first cyclic prefix and the correlation value of the second cyclic prefix.
13. The method as claimed in claim 12, wherein:
the first signal includes a first processing cyclic prefix and the second signal includes a second processing cyclic prefix;
the first processing cyclic prefix is generated by processing the first cyclic prefix using a first processing code;
the second processing cyclic prefix is generated by processing the second cyclic prefix using a second processing code;
the computing of the correlation value comprises computing a correlation value of the first processing cyclic prefix and a correlation value of the second processing cyclic prefix; and
the determining of the interference comprises determining the interference level or whether the interference occurs between the primary network and the secondary network based on the correlation value of the first processing cyclic prefix and the correlation value of the second processing cyclic prefix.
14. The method as claimed in claim 12, wherein the determining of the interference comprises determining the interference level or whether the interference occurs between the primary network and the secondary network based on a pattern according to a time of the correlation value of the first cyclic prefix and the correlation value of the second cyclic prefix.
15. The method as claimed in claim 12, wherein, when the interference occurs between the primary network and the secondary network, or when the interference level is greater than a predetermined threshold, the determining of the interference comprises generating an alarm signal.
16. The method as claimed in claim 12, wherein the determining of the interference level comprises:
comparing the correlation value of the first cyclic prefix with the correlation value of the second cyclic prefix; and
determining the interference level or whether the interference occurs between the primary network and the secondary network based on the result of the comparison.
17. A computer-readable recording medium storing a program to implement a method of determining an interference between a primary network and a secondary network, the method comprising:
receiving a first signal of the primary network and a second signal of the secondary network;
computing a correlation value of a first cyclic prefix included in the first signal and a correlation value of a second cyclic prefix included in the second signal; and
determining an interference level or whether the interference occurs between the primary network and the secondary network based on the correlation value of the first cyclic prefix and the correlation value of the second cyclic prefix.