CA2188478C - Ruby decay-time fluorescence thermometer - Google Patents
Ruby decay-time fluorescence thermometer Download PDFInfo
- Publication number
- CA2188478C CA2188478C CA 2188478 CA2188478A CA2188478C CA 2188478 C CA2188478 C CA 2188478C CA 2188478 CA2188478 CA 2188478 CA 2188478 A CA2188478 A CA 2188478A CA 2188478 C CA2188478 C CA 2188478C
- Authority
- CA
- Canada
- Prior art keywords
- cndot
- high degree
- fluorescent
- light
- probe material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000010979 ruby Substances 0.000 title claims abstract description 23
- 229910001750 ruby Inorganic materials 0.000 title claims abstract description 23
- 239000013078 crystal Substances 0.000 claims abstract description 8
- 239000000463 material Substances 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 17
- 239000000523 sample Substances 0.000 claims description 14
- 239000013307 optical fiber Substances 0.000 claims description 10
- 239000007850 fluorescent dye Substances 0.000 claims description 6
- 229910001369 Brass Inorganic materials 0.000 claims 2
- 239000010951 brass Substances 0.000 claims 2
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 claims 2
- 239000002019 doping agent Substances 0.000 claims 1
- 238000012994 industrial processing Methods 0.000 claims 1
- 230000003287 optical effect Effects 0.000 abstract description 19
- 238000009529 body temperature measurement Methods 0.000 abstract description 10
- 238000004020 luminiscence type Methods 0.000 abstract description 2
- 238000005259 measurement Methods 0.000 description 9
- 230000010363 phase shift Effects 0.000 description 9
- 230000008859 change Effects 0.000 description 7
- 238000010586 diagram Methods 0.000 description 5
- 239000000835 fiber Substances 0.000 description 5
- 238000012544 monitoring process Methods 0.000 description 5
- 230000001419 dependent effect Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000003595 spectral effect Effects 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 229910052761 rare earth metal Inorganic materials 0.000 description 3
- 150000002910 rare earth metals Chemical class 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 239000003814 drug Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 231100001261 hazardous Toxicity 0.000 description 2
- 230000002631 hypothermal effect Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000012552 review Methods 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- -1 Cr3+ ions Chemical class 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 206010028980 Neoplasm Diseases 0.000 description 1
- 108010076504 Protein Sorting Signals Proteins 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000002479 acid--base titration Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- 201000011510 cancer Diseases 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000003211 malignant effect Effects 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 230000000926 neurological effect Effects 0.000 description 1
- 238000011275 oncology therapy Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000004861 thermometry Methods 0.000 description 1
- 238000004448 titration Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
- G01K11/3213—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering using changes in luminescence, e.g. at the distal end of the fibres
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/20—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using thermoluminescent materials
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
- Radiation Pyrometers (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
An optical temperature measurement sensor utilizes the decay fluorescent characteristic of ruby crystal that is excited to luminescence by a light emitting diode source (excited light source). The sensor measures over a temperature rang of 20 - 170 °C with accuracy between ~ 0.03 and ~ 0.15 °C.
Description
RUBY DECAY-TIME FLUORESCENCE THERMOMETER
Background of the Invention This invention relates generally to the art of optical temperature measurements, and more particularly to those made with the use of fluorescence materials that emit radiation having a measurable characteristic that varies as a function of temperature.
Temperature sensing and the control of the temperature are important in many situations arising in medicine, industrial operation, and scientific research. In many cases, temperature measurement must be conducted remotely because the process or machinery must be monitored it is inaccessible or involves hazardous components, such as, high -radiation levels, high intensity magnetic or electrical field, high pressures and temperatures.
In medicine the need for temperature monitoring arises in several contexts, such as is used of controlled heat for purposes of cancer treatment. In operations involving artificial hypothermia, such as heart and neurological cases, temperature monitoring is critical.
Accurate temperature monitoring is also critical where local hypothermia is induced as means of cancer therapy. The differences between normal cells and malignant cells in their sensitivities to thermal killing are often no more than a few tenths of a degree.
In industrial process control the need for temperature monitoring during electronics fabrication. These fabrication processes are utilized in the manufacture of integrated circuits, microwave circuits, magnetic recording media, and optical components Temperature measurement can be made with well-known devices such as thermocouples, thermistors, resistance thermometers and the like. These devices contain electrically conducting components that generate temperature-dependent electrical signals.
The signals are amplified and converted into temperature readings or used in control functions. Such devices often give erroneous readings due to electrical interference problems. The devices are subject to field perturbation effects when used in the presence of electromagnetic field such as those produced by electric motors, generators, power cables and the like.
Many of these problems can be overcome by using remote in situ optical sensors coupled to a detector by optical fibers. Optical sensors contain essentially no metallic or electrically conducting components. Optical fibers are durable, corrosion-resistant, heat-resistant, and impervious to electrical or magnetic interference. The fibers allow remote monitoring of sensors in inaccessible andlor hazardous locations. In addition, signals can be transmitted over optical fibers with low attenuation and without prior conversion or conditioning.
Many types of optical temperature sensors are available. Several devices use temperature-dependent changes in the absorption spectra of materials such as neodymium-doped glass by kleinerman, U.S Pat. No. 4,708,494 and Snitzer, U.S. Pat. No. 4,302,970 employs rare earth absorption. The fluorescence intensities of glasses or ceramics doped with neodymium (Angel, et al., U.S. Pat.No. 4,729,668) are used for temperature measurement. Sensors based on temperature-dependent fluorescent or phosphorescent properties of materials include a device for measuring the intensity ratio of two distinct and optically isolatable fluorescent emission lines of selected rare earth -doped compounds (Wickersheim, U.S. Pat. Nos. 4,448,547, 4,560,286, 4,215,275, 4,075,493).
pH sensor based on fluorescent absorption of acid-based Titrations ( Publication B,Grattan et al.). Sensor based on temperature-dependent fluorescent of ruby (Publication C, Grattan et al.). All of these techniques are fiber optics temperature sensor relying upon intensity -based measurements and subject to inaccuracy caused by poor resolution, drift, and variable optical losses in the transmitting fibers. The measurements may be affected by thermal expansion/ contraction of the probe materials, so each probe must be individually calibrated before use.
Intensity independent phase modulation method (Publication A, Grattan et al.) is overcome the problem that describes in above sensors. Limitations of this sensor include restricted accuracy of the measurement. Limitation of the change of the phase shift employed, as well as the inability of this sensor to take measurement in low temperature.
An excited light source employed 125-Hz modulation frequency causes a small change in the phase shift with the temperature about 0.2 ms. Narrow changes in the phase shift make this sensor capable only for measuring high temperature spatially 120-160 °C.
another temperature sensor (Publication D, Grattan et al.) operates at biomedical range.
Limitations of this sensor include restricted accuracy of the measurement, as well as the inability of this sensor to take measurements in high temperature.
There is a need for an inexpensive optical temperature sensor method and apparatus that provides intensity independent measurement, accurate reproducible data for use in both bio-medical and industrial region and with out need for extensive calibration procedures.
Summary of the Invention The present invention includes a method and apparatus for optically measuring temperature. The invention is based on the fluorescent decay of ruby. The fluorescent material is excited with sinusoidally modulated light, which result in a sinusoidal fluorescent emission, which lags in phase the original excitation. The two sine waves are not in phase and their phase difference cp is related to the frequency f and i by:
tancp=2~fi Where cp is the phase difference between the input and the fluorescence optical signals at frequency f ; and i is the time constant of the fluorescence decay. The phase angle cp is thus, a function of the frequency of the sine wave and the decay-time constant. By operating at fixed frequency f and measuring the phase difference cp between the input and output sinusoidal signals. The temperature relating to the phase difference can be obtained.
Background of the Invention This invention relates generally to the art of optical temperature measurements, and more particularly to those made with the use of fluorescence materials that emit radiation having a measurable characteristic that varies as a function of temperature.
Temperature sensing and the control of the temperature are important in many situations arising in medicine, industrial operation, and scientific research. In many cases, temperature measurement must be conducted remotely because the process or machinery must be monitored it is inaccessible or involves hazardous components, such as, high -radiation levels, high intensity magnetic or electrical field, high pressures and temperatures.
In medicine the need for temperature monitoring arises in several contexts, such as is used of controlled heat for purposes of cancer treatment. In operations involving artificial hypothermia, such as heart and neurological cases, temperature monitoring is critical.
Accurate temperature monitoring is also critical where local hypothermia is induced as means of cancer therapy. The differences between normal cells and malignant cells in their sensitivities to thermal killing are often no more than a few tenths of a degree.
In industrial process control the need for temperature monitoring during electronics fabrication. These fabrication processes are utilized in the manufacture of integrated circuits, microwave circuits, magnetic recording media, and optical components Temperature measurement can be made with well-known devices such as thermocouples, thermistors, resistance thermometers and the like. These devices contain electrically conducting components that generate temperature-dependent electrical signals.
The signals are amplified and converted into temperature readings or used in control functions. Such devices often give erroneous readings due to electrical interference problems. The devices are subject to field perturbation effects when used in the presence of electromagnetic field such as those produced by electric motors, generators, power cables and the like.
Many of these problems can be overcome by using remote in situ optical sensors coupled to a detector by optical fibers. Optical sensors contain essentially no metallic or electrically conducting components. Optical fibers are durable, corrosion-resistant, heat-resistant, and impervious to electrical or magnetic interference. The fibers allow remote monitoring of sensors in inaccessible andlor hazardous locations. In addition, signals can be transmitted over optical fibers with low attenuation and without prior conversion or conditioning.
Many types of optical temperature sensors are available. Several devices use temperature-dependent changes in the absorption spectra of materials such as neodymium-doped glass by kleinerman, U.S Pat. No. 4,708,494 and Snitzer, U.S. Pat. No. 4,302,970 employs rare earth absorption. The fluorescence intensities of glasses or ceramics doped with neodymium (Angel, et al., U.S. Pat.No. 4,729,668) are used for temperature measurement. Sensors based on temperature-dependent fluorescent or phosphorescent properties of materials include a device for measuring the intensity ratio of two distinct and optically isolatable fluorescent emission lines of selected rare earth -doped compounds (Wickersheim, U.S. Pat. Nos. 4,448,547, 4,560,286, 4,215,275, 4,075,493).
pH sensor based on fluorescent absorption of acid-based Titrations ( Publication B,Grattan et al.). Sensor based on temperature-dependent fluorescent of ruby (Publication C, Grattan et al.). All of these techniques are fiber optics temperature sensor relying upon intensity -based measurements and subject to inaccuracy caused by poor resolution, drift, and variable optical losses in the transmitting fibers. The measurements may be affected by thermal expansion/ contraction of the probe materials, so each probe must be individually calibrated before use.
Intensity independent phase modulation method (Publication A, Grattan et al.) is overcome the problem that describes in above sensors. Limitations of this sensor include restricted accuracy of the measurement. Limitation of the change of the phase shift employed, as well as the inability of this sensor to take measurement in low temperature.
An excited light source employed 125-Hz modulation frequency causes a small change in the phase shift with the temperature about 0.2 ms. Narrow changes in the phase shift make this sensor capable only for measuring high temperature spatially 120-160 °C.
another temperature sensor (Publication D, Grattan et al.) operates at biomedical range.
Limitations of this sensor include restricted accuracy of the measurement, as well as the inability of this sensor to take measurements in high temperature.
There is a need for an inexpensive optical temperature sensor method and apparatus that provides intensity independent measurement, accurate reproducible data for use in both bio-medical and industrial region and with out need for extensive calibration procedures.
Summary of the Invention The present invention includes a method and apparatus for optically measuring temperature. The invention is based on the fluorescent decay of ruby. The fluorescent material is excited with sinusoidally modulated light, which result in a sinusoidal fluorescent emission, which lags in phase the original excitation. The two sine waves are not in phase and their phase difference cp is related to the frequency f and i by:
tancp=2~fi Where cp is the phase difference between the input and the fluorescence optical signals at frequency f ; and i is the time constant of the fluorescence decay. The phase angle cp is thus, a function of the frequency of the sine wave and the decay-time constant. By operating at fixed frequency f and measuring the phase difference cp between the input and output sinusoidal signals. The temperature relating to the phase difference can be obtained.
It is a primary object of the present invention is to further improve the phase modulation method that has been used in earlier sensors.
Another object of the invention is to provide an optical temperature sensor, which is capable of measuring temperature in medical and industrial applications.
Briefly, the present invention accomplishes the above- mentioned objects by relying on several features that have been used to improve the previous sensors.
Feature #1:
A special class of ruby as a suitable fluorescent material is selected. Ruby crystal is an insulator, doped with optically active doping ions. Ruby consists of the pure oxide material (A1203) Sapphire in which about 0.1% of A13+ ions are replaced by Cr3+ ions.
Ruby has been studied at many different concentrations from less than 0.01 %-0.5 % by Tolstois et al, Publication E. The chromium concentration influences not only the absolute value of i of individual lines but also the behavior of temperature dependence of i. According to this study. The specific ruby used in this invention has the advantage over commercial ruby laser rod, which shows in the high accuracy achieved.
Feature #2:
Fluorescent signal collection efficiency is further enhanced, in accordance with the present invention, by providing the fluorescent probe material in a shape, which consist of a ruby prism with two angles of 45° and one of 90° as shown in figure 3.
This shape providing a total reflection in the prism and allows a greater fraction of fluorescence being emitted from the probe to be collected and transmitted by the fiber optic.
Feature #3:
A bright LED excited light with 400mcad employed a low frequency modulation, is used in this invention. Because the phase shift is a function of the frequency over a temperature range of 20-170°C. A significant change in the phase shift at a low frequency is clearly shown in figure#9, which is the change in the phase shift about l.4ms. This is a large change comparing with the prior art.
Feature #4:
The powerful LED of 400mcad is used. Powerful LED is used to achieve a strong fluorescence signal.
Feature #5:
A photodiode with large surface area of 7mm2 is used to give excellent sensitivity in the visible spectral region.
Another object of the invention is to produce such an optical temperature sensor, which is stable and produces a temperature reading (20-170°C) to a high degree of accuracy between ~ 0.03 and ~ 0.15°C.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
Drawing descriptions Figure #1 is a schematic diagram of a temperature probe according to the present invention Figure #2 shows a spectral profile of the short pass 16 and long pass filter 14.
Figure #3 shows the prism angles and a total internal reflection in the prism probe of figure 1.
Figure #4 is a schematic diagram of a second temperature probe Figure #5 is a block diagram of a temperature sensor according to the invention.
Figure #6 is a prior art diagram showing the sine wave generator and LED
drives circuit.
Figure #7 shows a photograph of the following electrical signal sequence:
a) two sine waves of the light source emission and the fluorescence emission b) two sine waves were converting to the square wave c) the phase shift between the two signals Figure #8 is a prior art diagram showing the microprocessor system.
Figure #9 shows a graph of the significant phase change at the 30 Hz modulated light versus the temperature.
Detailed Description Referring to the figure 5, the apparatus comprises essentially. Green LED 11 with a peak emission at 565 nm wavelength and luminous intensity 400 mcad is employed and driven by an oscillator 15 at frequency of 30Hz as shown in figure 6. The LED 11 emission has a long tail expanding into the red region of the spectrum. This emission mixes with fluorescence signal and caused amplitude and phase variations in the final detected signal. The light was filtered by the short-pass interference filter 16 to eliminate the effect of this red emission from the LED.
The light passed down 1000 ~n PCS optical fiber 12 to the probe 10. A second 1000pm PCS optical fiber 13 coupling the light from the probe lO.The received fluorescent radiation 22 was filtered by a long pass filter 14 to eliminate the green signal from the fluorescence radiation. And allow only the red fluorescence to be detected. A
photodiode with an integral amplifier I7 was used to detect the red fluorescent emission 22. The large surface area (7mm2) of this device 17 gave excellent sensitivity in the visible spectral region. This signal 22 received by the photodiode consists of a sine wave super imposed on a do level and high-frequency noise. This signal 22 is farther amplified and filtered through a 4-stage active band pass filter 18 whole components are chosen to give a high transmission at the value of the light frequency used and to eliminate the higher and lower unwanted noise frequencies in the detected signal 22. The signal 22 then passed through a zero crossing detector 19 to provide a square wave of the same frequency, and for reference, the drive signal of the LED 11 is similarly processed by passing through a zero crossing detector 20. These two, out-of phase, square wave signals represent the fluorescence 22 and the green LED emission 11 and are fed to an exclusive-or gate 21 to produce pulses whose lengths correspond to the phase difference between the reference 11 and the detected signal 22. Figure 7 shown the sequence of the electrical signals. The value from 21 is stored in a microprocessor 23 programmed to average 256 samples and display the reading on 24.
Figure 9 shows the calibration graph of the sensor over a temperature range of 20 °C to 170 °C. and also a non-linear curve of the phase shift measurement versus temperature with significant change in the phase delay. Since the calibration curve is nonlinear, the resolution of the sensor varies along this curve. Therefore, at higher temperature regions between 155-160 °C the accuracy was ~ 0.03 °C, and 50-135°C, it reduces to ~ 0.1 °C, and at lower temperature region 31-48 °C, it reduces to ~ 0.15 °C
There are two kind probe designs, the first design 25 as shown in figure 4.
Apiece of ruby oblong shape 25 cut to a length of 3mm and a cross-sectional area of 2mm2 as shown in figure 4. The crystal 25 was polished on both ends and placed in adapter housing 10 used for coupling the light to and from the ruby. The second design 25a consists of a small piece of ruby prism with two angles of 45° and one of 90° as shown in figure 1. The crystal 25a with polished sides placed in adapter housing 10 used for coupling the light to and from the ruby. Two green LEDs were used as a source to achieve a strong fluorescence signal and passes through optical fibers 12 and 12a.
In conclusion, it is seen that there is provided a simple effective and easily maintained thermometry system consisting of a temperature probe which used fluorescent decay time phenomenon. The advantage of using the phase shift to measure the temperature is that the temperatures in this method are insensitive to changes in intensity of the excited light source, a very important consideration in fiber-optic sensors.
References U.S Patent No. Issued Inventors) Tltle 4,708,494 11 11987 kleinerman, Methods and devices for the optical measurement of temperature with luminescent materials.
4,302,970 12 /1981 Snitzer, Optical temperature probe employing rare earth absorption.
4,729,668 311988 Angel, et al., Method and apparatus for optical temperature measurements.
4,448,547; 5 /1984 Wickersheim, Optical temperature measurement technique utilizing phosphors.
4,560,286; 12 /1985 Wickersheim, Optical temperature measurement technique utilizing phosphors.
4,215,275; 7 /1980 Wickersheim, Optical temperature measurement technique utilizing phosphors.
4,075,493). 211978 Wickersheim, Optical temperature measurement technique utilizing phosphors.
K.T.V. Grattan et al., "ruby Decay-Time Fluorescence Thermometer in a Fiber-Optic Configuration", Review of Scientific instruments, Vo1.59, No. 8, August 1988, pp. 1328-(Hereinafter referred to as publication A) K.T.V. Grattan et al., "Development of Simple Optical pH sensors for Use in Acid-Base Titrations", Journal of Outical Sensors, vol. 2, No. 5, October-December 1987, pp.371-381.
(Hereinafter referred to as publication B) K.T.V. Grattan et al., "Ruby Fluorescence Wavelength Division Fiber-Optic Temperature Sensor", Review of Scientific instruments, vol. 58, no. 7, July 1987, pp. 1231-1234.
(Hereinafter referred to as publication C) K.T.V. Grattan et al., "Biomedical Thermometry-A Simple Fiber Optic Approach", IEEE
Transactions on Biomedical En ink Bering, Vol. 35, No. 8, August 1988, pp. 618-622.
(Hereinafter referred to as publication D) N.A. Tolstoi, et al., "Investigation of the Spectral Distribution of the Luminescence, Decay Time of Ruby the Pulse Taumeter Method", O_ptics atttd Spectroscopy, Vol.6, No:S; lVt~y f959, pp.427-429.
(~erei~er referred to as pub~fc~tion E).
s
Another object of the invention is to provide an optical temperature sensor, which is capable of measuring temperature in medical and industrial applications.
Briefly, the present invention accomplishes the above- mentioned objects by relying on several features that have been used to improve the previous sensors.
Feature #1:
A special class of ruby as a suitable fluorescent material is selected. Ruby crystal is an insulator, doped with optically active doping ions. Ruby consists of the pure oxide material (A1203) Sapphire in which about 0.1% of A13+ ions are replaced by Cr3+ ions.
Ruby has been studied at many different concentrations from less than 0.01 %-0.5 % by Tolstois et al, Publication E. The chromium concentration influences not only the absolute value of i of individual lines but also the behavior of temperature dependence of i. According to this study. The specific ruby used in this invention has the advantage over commercial ruby laser rod, which shows in the high accuracy achieved.
Feature #2:
Fluorescent signal collection efficiency is further enhanced, in accordance with the present invention, by providing the fluorescent probe material in a shape, which consist of a ruby prism with two angles of 45° and one of 90° as shown in figure 3.
This shape providing a total reflection in the prism and allows a greater fraction of fluorescence being emitted from the probe to be collected and transmitted by the fiber optic.
Feature #3:
A bright LED excited light with 400mcad employed a low frequency modulation, is used in this invention. Because the phase shift is a function of the frequency over a temperature range of 20-170°C. A significant change in the phase shift at a low frequency is clearly shown in figure#9, which is the change in the phase shift about l.4ms. This is a large change comparing with the prior art.
Feature #4:
The powerful LED of 400mcad is used. Powerful LED is used to achieve a strong fluorescence signal.
Feature #5:
A photodiode with large surface area of 7mm2 is used to give excellent sensitivity in the visible spectral region.
Another object of the invention is to produce such an optical temperature sensor, which is stable and produces a temperature reading (20-170°C) to a high degree of accuracy between ~ 0.03 and ~ 0.15°C.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
Drawing descriptions Figure #1 is a schematic diagram of a temperature probe according to the present invention Figure #2 shows a spectral profile of the short pass 16 and long pass filter 14.
Figure #3 shows the prism angles and a total internal reflection in the prism probe of figure 1.
Figure #4 is a schematic diagram of a second temperature probe Figure #5 is a block diagram of a temperature sensor according to the invention.
Figure #6 is a prior art diagram showing the sine wave generator and LED
drives circuit.
Figure #7 shows a photograph of the following electrical signal sequence:
a) two sine waves of the light source emission and the fluorescence emission b) two sine waves were converting to the square wave c) the phase shift between the two signals Figure #8 is a prior art diagram showing the microprocessor system.
Figure #9 shows a graph of the significant phase change at the 30 Hz modulated light versus the temperature.
Detailed Description Referring to the figure 5, the apparatus comprises essentially. Green LED 11 with a peak emission at 565 nm wavelength and luminous intensity 400 mcad is employed and driven by an oscillator 15 at frequency of 30Hz as shown in figure 6. The LED 11 emission has a long tail expanding into the red region of the spectrum. This emission mixes with fluorescence signal and caused amplitude and phase variations in the final detected signal. The light was filtered by the short-pass interference filter 16 to eliminate the effect of this red emission from the LED.
The light passed down 1000 ~n PCS optical fiber 12 to the probe 10. A second 1000pm PCS optical fiber 13 coupling the light from the probe lO.The received fluorescent radiation 22 was filtered by a long pass filter 14 to eliminate the green signal from the fluorescence radiation. And allow only the red fluorescence to be detected. A
photodiode with an integral amplifier I7 was used to detect the red fluorescent emission 22. The large surface area (7mm2) of this device 17 gave excellent sensitivity in the visible spectral region. This signal 22 received by the photodiode consists of a sine wave super imposed on a do level and high-frequency noise. This signal 22 is farther amplified and filtered through a 4-stage active band pass filter 18 whole components are chosen to give a high transmission at the value of the light frequency used and to eliminate the higher and lower unwanted noise frequencies in the detected signal 22. The signal 22 then passed through a zero crossing detector 19 to provide a square wave of the same frequency, and for reference, the drive signal of the LED 11 is similarly processed by passing through a zero crossing detector 20. These two, out-of phase, square wave signals represent the fluorescence 22 and the green LED emission 11 and are fed to an exclusive-or gate 21 to produce pulses whose lengths correspond to the phase difference between the reference 11 and the detected signal 22. Figure 7 shown the sequence of the electrical signals. The value from 21 is stored in a microprocessor 23 programmed to average 256 samples and display the reading on 24.
Figure 9 shows the calibration graph of the sensor over a temperature range of 20 °C to 170 °C. and also a non-linear curve of the phase shift measurement versus temperature with significant change in the phase delay. Since the calibration curve is nonlinear, the resolution of the sensor varies along this curve. Therefore, at higher temperature regions between 155-160 °C the accuracy was ~ 0.03 °C, and 50-135°C, it reduces to ~ 0.1 °C, and at lower temperature region 31-48 °C, it reduces to ~ 0.15 °C
There are two kind probe designs, the first design 25 as shown in figure 4.
Apiece of ruby oblong shape 25 cut to a length of 3mm and a cross-sectional area of 2mm2 as shown in figure 4. The crystal 25 was polished on both ends and placed in adapter housing 10 used for coupling the light to and from the ruby. The second design 25a consists of a small piece of ruby prism with two angles of 45° and one of 90° as shown in figure 1. The crystal 25a with polished sides placed in adapter housing 10 used for coupling the light to and from the ruby. Two green LEDs were used as a source to achieve a strong fluorescence signal and passes through optical fibers 12 and 12a.
In conclusion, it is seen that there is provided a simple effective and easily maintained thermometry system consisting of a temperature probe which used fluorescent decay time phenomenon. The advantage of using the phase shift to measure the temperature is that the temperatures in this method are insensitive to changes in intensity of the excited light source, a very important consideration in fiber-optic sensors.
References U.S Patent No. Issued Inventors) Tltle 4,708,494 11 11987 kleinerman, Methods and devices for the optical measurement of temperature with luminescent materials.
4,302,970 12 /1981 Snitzer, Optical temperature probe employing rare earth absorption.
4,729,668 311988 Angel, et al., Method and apparatus for optical temperature measurements.
4,448,547; 5 /1984 Wickersheim, Optical temperature measurement technique utilizing phosphors.
4,560,286; 12 /1985 Wickersheim, Optical temperature measurement technique utilizing phosphors.
4,215,275; 7 /1980 Wickersheim, Optical temperature measurement technique utilizing phosphors.
4,075,493). 211978 Wickersheim, Optical temperature measurement technique utilizing phosphors.
K.T.V. Grattan et al., "ruby Decay-Time Fluorescence Thermometer in a Fiber-Optic Configuration", Review of Scientific instruments, Vo1.59, No. 8, August 1988, pp. 1328-(Hereinafter referred to as publication A) K.T.V. Grattan et al., "Development of Simple Optical pH sensors for Use in Acid-Base Titrations", Journal of Outical Sensors, vol. 2, No. 5, October-December 1987, pp.371-381.
(Hereinafter referred to as publication B) K.T.V. Grattan et al., "Ruby Fluorescence Wavelength Division Fiber-Optic Temperature Sensor", Review of Scientific instruments, vol. 58, no. 7, July 1987, pp. 1231-1234.
(Hereinafter referred to as publication C) K.T.V. Grattan et al., "Biomedical Thermometry-A Simple Fiber Optic Approach", IEEE
Transactions on Biomedical En ink Bering, Vol. 35, No. 8, August 1988, pp. 618-622.
(Hereinafter referred to as publication D) N.A. Tolstoi, et al., "Investigation of the Spectral Distribution of the Luminescence, Decay Time of Ruby the Pulse Taumeter Method", O_ptics atttd Spectroscopy, Vol.6, No:S; lVt~y f959, pp.427-429.
(~erei~er referred to as pub~fc~tion E).
s
Claims (10)
1. A high degree of accuracy sensor for measuring temperature of an electrical equipment and industrial processing, used for measuring a temperature over a range of 20 - 170 °C, comprises:
.cndot. a single LED luminous intensity of 400 mcad is used to illuminate a fluorescent probe material to cause fluorescent emission light;
.cndot. two single optical fibers, one to carry the modulated excited light to the probe material and the second to collect the fluorescent emission light from the probe material;
.cndot. the fluorescent probe material placed in a housing adapter to couple the light to and from the probe material;
.cndot. a photodiode with large surface area of 7mm2 which is connected to the second optical fiber in order to detect the fluorescent emission light;
.cndot. two comparators and exclusive-OR gate to compare the excited light and the fluorescent emission light.
.cndot. a single LED luminous intensity of 400 mcad is used to illuminate a fluorescent probe material to cause fluorescent emission light;
.cndot. two single optical fibers, one to carry the modulated excited light to the probe material and the second to collect the fluorescent emission light from the probe material;
.cndot. the fluorescent probe material placed in a housing adapter to couple the light to and from the probe material;
.cndot. a photodiode with large surface area of 7mm2 which is connected to the second optical fiber in order to detect the fluorescent emission light;
.cndot. two comparators and exclusive-OR gate to compare the excited light and the fluorescent emission light.
2. The high degree of accuracy sensor of claim1 in which the LED is emitted with peak at 565nm.
3. The high degree of accuracy sensor of claim2 in which the LED is sine wave modulated light at frequency of 30 Hz.
4. The high degree of accuracy sensor of claim1 in which the fluorescent probe material placed in a housing adapter made of brass.
5. The high degree of accuracy sensor of claim1 in which a ruby crystal, with dopant concentration Cr2O3 of 0.05 %, used as a fluorescent probe material.
6. The high degree of accuracy sensor of claims in which the ruby crystal is cut to a length of 3 mm and a cross sectional area of 2 mm2.
7. The high degree of accuracy sensor of claim6 in which the ruby crystal is polished on both ends.
8. The high degree of accuracy sensor of claim5 in which the ruby crystal is shaped as a prism.
9. The high degree of accuracy sensor of claim8 in which the prism is comprised of two angles of 45° and one of 90°, with polished sides.
10. A method of measuring temperature over a range of 20 - 170 °C with accuracy of ~ 0.03°C, comprising the following steps:
.cndot. illuminating a fluorescent probe material with sinusoidal modulated excited light at frequency of 30 Hz with intensity of 400 mcad to cause sinusoidal fluorescent emission light, by a first optical fiber;
.cndot. collecting said sinusoidal fluorescent emission light by a second optical fiber through a housing adapter made of brass ;
.cndot. detecting said emission light by a photodiode with large surface area of 7mm2;
measuring the phase difference between the excited and fluorescent emission light;
.cndot. relating the phase difference measured to the temperature of an electrical equipment.
.cndot. illuminating a fluorescent probe material with sinusoidal modulated excited light at frequency of 30 Hz with intensity of 400 mcad to cause sinusoidal fluorescent emission light, by a first optical fiber;
.cndot. collecting said sinusoidal fluorescent emission light by a second optical fiber through a housing adapter made of brass ;
.cndot. detecting said emission light by a photodiode with large surface area of 7mm2;
measuring the phase difference between the excited and fluorescent emission light;
.cndot. relating the phase difference measured to the temperature of an electrical equipment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2188478 CA2188478C (en) | 1996-10-22 | 1996-10-22 | Ruby decay-time fluorescence thermometer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2188478 CA2188478C (en) | 1996-10-22 | 1996-10-22 | Ruby decay-time fluorescence thermometer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2188478A1 CA2188478A1 (en) | 1998-04-22 |
| CA2188478C true CA2188478C (en) | 2005-05-17 |
Family
ID=4159128
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2188478 Expired - Fee Related CA2188478C (en) | 1996-10-22 | 1996-10-22 | Ruby decay-time fluorescence thermometer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2188478C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102020202077A1 (en) | 2020-02-19 | 2021-08-19 | Technische Hochschule Nürnberg Georg Simon Ohm | Method and device for contactless detection of the temperature of a rotating part of an electrical machine |
| DE102020202074A1 (en) | 2020-02-19 | 2021-08-19 | Technische Hochschule Nürnberg Georg Simon Ohm | Method and device for contactless detection of the temperature of a rotating part of an electrical machine |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| PL233598B1 (en) * | 2017-07-19 | 2019-11-29 | Inst Niskich Temperatur I Badan Strukturalnych Im Wlodzimierza Trzebiatowskiego Polskiej Akademii Na | Method for no-contact optical measuring of the objects' temperature |
| CN109945986B (en) * | 2019-04-01 | 2020-07-10 | 中国计量大学 | An integrated optical quantum thermometer with nanoscale resolution |
-
1996
- 1996-10-22 CA CA 2188478 patent/CA2188478C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102020202077A1 (en) | 2020-02-19 | 2021-08-19 | Technische Hochschule Nürnberg Georg Simon Ohm | Method and device for contactless detection of the temperature of a rotating part of an electrical machine |
| DE102020202074A1 (en) | 2020-02-19 | 2021-08-19 | Technische Hochschule Nürnberg Georg Simon Ohm | Method and device for contactless detection of the temperature of a rotating part of an electrical machine |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2188478A1 (en) | 1998-04-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Grattan et al. | Fiber optic fluorescence thermometry | |
| US5499313A (en) | Distributed and spatially averaged fiber optic temperature sensors and method using same | |
| US5351268A (en) | Modular luminescence-based measuring system using fast digital signal processing | |
| US5096277A (en) | Remote measurement of physical variables with fiber optic systems | |
| US5991479A (en) | Distributed fiber optic sensors and systems | |
| US4729668A (en) | Method and apparatus for optical temperature measurements | |
| US5928222A (en) | Fiber optic sensing techniques in laser medicine | |
| US5696863A (en) | Distributed fiber optic temperature sensors and systems | |
| US4542987A (en) | Temperature-sensitive optrode | |
| US5348396A (en) | Method and apparatus for optical temperature measurement | |
| Rai | Temperature sensors and optical sensors | |
| US4374328A (en) | Photoluminescent indicator | |
| US5222810A (en) | Fiber optic systems for sensing temperature and other physical variables | |
| EP0377549A2 (en) | Remote measurement of physical variables with fiber optic systems | |
| Alaruri et al. | High-temperature remote thermometry using laser-induced fluorescence decay lifetime measurements of Y/sub 2/O/sub 3: Eu and YAG: Tb thermographic phosphors | |
| WO1992018838A1 (en) | Temperature measurement with combined photoluminescent and black body sensing techniques | |
| Seat et al. | Single-crystal ruby fiber temperature sensor | |
| Zhang et al. | Fiber optic temperature sensor based on the cross referencing between blackbody radiation and fluorescence lifetime | |
| CN111982189A (en) | High-precision sensing method for simultaneously realizing temperature and strain based on photon detection technology | |
| Vaguine et al. | Multiple sensor optical thermometry system for application in clinical hyperthermia | |
| CA2188478C (en) | Ruby decay-time fluorescence thermometer | |
| US4338516A (en) | Optical crystal temperature gauge with fiber optic connections | |
| Fernicola et al. | Investigations on exponential lifetime measurements for fluorescence thermometry | |
| EP0378817B1 (en) | Sensor and device for the measurement of radiant energy, in particular the energy associated with radio-frequency, microwave and light radiation signals | |
| Sun et al. | Frequency-domain fluorescence based fiber optic fire alarm system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |