Method for measuring temperature of substances from measurement of absorption coefficients
Determining the temperature of the water by measuring the absorption coefficient of water ( 32 ). The method for determining temperature of a first substance comprising: acquiring a measurement of the absorption coefficient of the first substance at least one wavelength ( 30 ); and determining the temperature using the measurement of the absorption coefficient and known values of the absorption coefficient as a function of temperature at the at least one wavelength.
1. A method for determining temperature of a first substance that is a component of a second substance, the method comprising:
acquiring a measurement of the absorption coefficient of the second substance at at least one wavelength for which the absorption coefficient of the second substance is substantially equal to the absorption coefficient of the first substance; and
determining the temperature of the first substance using the measurement of the absorption coefficient and known values of the absorption coefficient of the first substance as a function of temperature at the at least one wavelength.
2. A method according to claim 1 wherein the at least one wavelength is a single wavelength.
3. A method according to claim 2 wherein the first substance is water.
4. A method according to claim 1 wherein the at least one wavelength is a plurality of wavelengths.
5. A method according to claim 4 wherein determining temperature comprises determining to which particular curve of a plurality of curves the coefficient measurements best fit, wherein each of the plurality of curves describes dependence of the absorption coefficient of the first substance on wavelength for a different constant temperature and determining the temperature of the substance to be the constant temperature of the particular curve.
6. A method according to claim 5 wherein the first substance is water.
7. A method according to claim 5 wherein determining a particular best fit curve comprises determining from the coefficient measurements a wavelength for which the absorption spectrum has a peak and determining which of the plurality of curves has a peak at substantially the same wavelength.
8. A method according to claim 7 wherein the first substance is water.
9. A method according to claim 8 wherein a measurement of the absorption coefficient is acquired at a wavelength or near to a wavelength for which the absorption coefficient of water has a peak.
10. A method according to claim 9 wherein a measurement of the absorption coefficient is acquired at at least two wavelengths that straddle a wavelength at which the absorption coefficient peaks.
11. A method according to claim 1 wherein the first substance is water.
12. A method according to claim 1 and comprising using the measurement of the temperature of the first substance as the temperature of the second substance.
13. A method according any of claims 12 wherein the second substance is a biological tissue.
14. A method according to claim 13 wherein the second substance is blood.
15. A method according to claim 1 wherein acquiring a measurement of an absorption coefficient comprises acquiring the measurement using a photoacoustic effect.
16. A method according to claim 15 wherein acquiring a measurement of an absorption coefficient comprises acquiring the measurement as a function of position.
17. A method according to claim 16 wherein determining temperature comprises determining temperature as a function of position.
18. A method for determining temperature of a first substance that is a component of a second substance the method comprising:
acquiring first measurements of the absorption coefficient of the second substance at a plurality of wavelengths for which the absorption coefficients of the first substance and other components of the material are substantially independent of, or only weakly dependent on, temperature;
determining concentrations of the first substance and the other components of the material from the acquired first measurements;
acquiring a second measurement of the absorption coefficient of the second substance at at least one wavelength for which the absorption coefficient of the first substance is temperature dependent;
determining the absorption coefficient for the first substance from the second measurement and the determined concentrations; and
determining the temperature using the determined absorption coefficient for the first substance and known values of the absorption coefficient of the first substance as a function of temperature at the at least one wavelength.
19. A method according to claim 18 and comprising using the measurement of the temperature of the first substance as the temperature of the second substance.
20. A method according to claim 19 wherein the second substance is a biological tissue.
21. A method according to claim 20 wherein the second substance is blood.
22. A method for determining temperature of a first substance comprised in a second substance comprising:
acquiring a measurement of the absorption coefficient of the second substance at a plurality of wavelengths in a wavelength region of the absorption spectrum of the second substance for which the shape of the wavelength and temperature dependence of the absorption spectrum of the second substance is substantially the same as that of the absorption spectrum of the first substance; and
determining the temperature using the measurement of the absorption coefficient and known values of the absorption coefficient of the first substance as a function of temperature at the plurality of wavelengths.
23. A method according to claim 22 wherein determining temperature comprises determining to which particular curve of a plurality of curves the coefficient measurements best fit, wherein each of the plurality of curves describes dependence of the absorption coefficient of the first substance on wavelength for a different constant temperature and determining the temperature of the first substance to be the constant temperature of the particular curve.
24. A method according to claim 23 wherein determining a particular best fit curve comprises determining from the coefficient measurements a wavelength for which the absorption spectrum has a peak and determining which of the plurality of curves has a peak at substantially the same wavelength.
25. A method according to claim 22 wherein the first substance is water.
26. A method according to claim 25 wherein a measurement of the absorption coefficient is acquired at a wavelength or near to a wavelength for which the absorption coefficient of water has a peak.
27. A method according to claim 26 wherein a measurement of the absorption coefficient is acquired at at least two wavelengths that straddle a wavelength at which the absorption coefficient peaks.
28. A method according to claim 25 and comprising using the measurement of the temperature of the water as the temperature of the second substance.
29. A method according to claim 28 wherein the second substance is a biological tissue.
30. A method according to claim 29 wherein the second substance is blood.
31. A method according to claim 22 and comprising using the measurement of the temperature of the first substance as the temperature of the second substance.
32. A method according any of claim 31 wherein the second substance is a biological tissue.
33. A method according to claim 32 wherein the second substance is blood.
34. A method according to claim 22 wherein acquiring a measurement of an absorption coefficient comprises acquiring the measurement using a photoacoustic effect.
35. A method according to claim 34 wherein acquiring a measurement of an absorption coefficient comprises acquiring the measurement as a function of position.
36. A method according to claim 35 wherein determining temperature comprises determining temperature as a function of position.