CN114608719A - Laser temperature measuring device for high-temperature object - Google Patents
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Abstract
The invention discloses a laser temperature measuring device of a high-temperature object, which belongs to the technical field of temperature measurement and comprises a photoelectric phase-locked loop, a temperature detection unit, a photoelectric detector and a signal processing unit, wherein the temperature detection unit comprises an optical fiber circulator, a transmission optical fiber, an aspherical mirror and an F-P etalon arranged on the object to be measured, linear frequency modulation light output by the photoelectric phase-locked loop passes through the optical fiber circulator, the transmission optical fiber light and the aspherical mirror to the F-P etalon, is transmitted back to the optical fiber circulator after being reflected, then passes through the photoelectric detector to the signal processing unit for processing, and the temperature of the object to be measured is calculated by collecting the time of two adjacent strongest light intensities of reflected light and combining the relationship of the frequency of the linear frequency modulation light along with the time change. The invention also provides a photoelectric phase-locked loop for realizing the nonlinear correction. The invention realizes the temperature measurement of a high-temperature object, and performs frequency sweep measurement on the longitudinal mode interval, thereby improving the test precision.
Description
Technical Field
The invention belongs to the technical field of temperature measurement, and particularly relates to a laser temperature measuring device for a high-temperature object.
Background
In industrial production, scientific control of temperature is always a very important work content, and particularly when a product works in a high-temperature environment, the temperature determines the quality of the produced product, and meanwhile, the temperature is closely related to the production efficiency, and further, the overall flow and condition of production can be influenced. Therefore, the method is of great significance for measuring the temperature in industrial production.
The temperature is a physical quantity for representing the cold and hot degree of an object, and the temperature test can be divided into a contact type and a non-contact type according to the measurement mode. The contact temperature measuring instrument measures the temperature by fully contacting the sensitive element with the measured object to carry out heat exchange, and the method is simple, visual and reliable and has high measurement precision.
The contact type temperature measuring instrument can be divided into four types according to different temperature measuring principles: expansion thermometers, thermistor thermometers, thermocouple thermometers, and PN junction integrated temperature sensors. The thermal resistance thermometer converts the measurement of temperature into the measurement of resistance, and the temperature measurement principle is that the resistance value of a conductor or a semiconductor changes along with the change of temperature. The thermocouple temperature sensor converts the measured temperature into a thermoelectromotive force signal for output, and a temperature measuring system is formed by connecting a lead with a display instrument to realize temperature measurement. The thermal resistor has the characteristics of high measurement precision, wide measurement range and the like. Generally, a thermocouple is used for measuring a higher temperature of more than 500 ℃, and a thermal resistor is used for measuring an ambient temperature of less than 500 ℃, because in a medium-low temperature region of less than 500 ℃, the output thermoelectric force of the thermocouple is very small, the requirement on anti-interference measures of a secondary instrument is very high, and the thermocouple is usually difficult to realize accurate measurement. In a lower temperature area, the relative error caused by the temperature change of the cold end is also very prominent, and the general use of a thermal resistance temperature measuring instrument is more suitable.
Non-contact thermometry is more commonly infrared thermometry, which measures by thermal radiation. It has the advantages that: the measurement does not interfere with the measured temperature field and does not influence the distribution of the temperature field, thereby having higher measurement accuracy; the temperature measurement range is wide, theoretically, no upper measurement limit exists, and quite high temperature can be measured; the response time of the detector is short, the reaction speed is high, and the rapid and dynamic measurement is easy; the contact with the measured object is not needed, and the operation is convenient; the temperature of the micro-object can be determined.
However, the existing temperature measurement technology still has many defects, the size of the temperature sensing part of the thermal resistor is large, and the temperature measurement reaction is slow; the thermocouple temperature measurement needs to compensate the lead, and the soldering tin and high-frequency magnetic field environment can also influence the temperature measurement, so that a large error exists; more importantly, thermal resistors and thermocouples limit the upper range of temperature measurement due to their physical characteristics. The infrared temperature measurement is greatly influenced by external environment factors, the spectral radiance of a black body has an extreme value, and the change of the extreme value is slow along with the temperature change, so that the measurement error is large.
Disclosure of Invention
The present invention is directed to solve the above problems in the prior art, and an object of the present invention is to provide a laser temperature measuring device for high temperature objects.
The technical scheme adopted by the invention is as follows:
the laser temperature measuring device for the high-temperature object is characterized by comprising a photoelectric phase-locked loop, a temperature detection unit, a photoelectric detector and a signal processing unit; the temperature detection unit comprises an optical fiber circulator, a transmission optical fiber, an aspherical mirror and an F-P (Fabry-Perot) etalon, wherein the F-P etalon is arranged on an object to be detected;
the photoelectric phase-locked loop is used for outputting linear frequency modulation light, and the output port of the photoelectric phase-locked loop is optically connected to the laser input port of the optical fiber circulator; the duplex port of the optical fiber circulator is connected to the optical input port of the aspherical mirror through transmission optical fiber light, and the optical output port of the aspherical mirror is optically connected with the F-P etalon; the signal light output port of the optical fiber circulator is optically connected with the input end of the photoelectric detector, and the output end of the photoelectric detector is electrically connected with the signal processing unit.
Furthermore, the photoelectric phase-locked loop comprises a broadband tunable laser, a micro-optical lens, a first coupler, an MZ (Mach-Zehnder) interferometer, a second coupler, a balanced photoelectric detector, a phase discriminator, a loop filter, a rising/falling switch control circuit and an integrator which are sequentially connected end to end;
the broadband tunable laser outputs frequency-modulated light, the frequency-modulated light is coupled to the first coupler through a micro-optical lens, two light beams are output, one light beam serves as the output of the photoelectric phase-locked loop, and the other light beam is input to the input port of the MZ interferometer; an output port of the MZ interferometer is optically connected to an input port of the balanced photoelectric detector through the second coupler, and an output port of the balanced photoelectric detector is electrically connected to an input port of the phase discriminator; the phase discriminator mixes the input signal with a sinusoidal reference frequency signal to obtain a frequency error signal, the frequency error signal is transmitted to a loop filter through an output port of the phase discriminator to obtain a frequency control signal, and then the frequency control signal sequentially passes through an up/down switch control circuit and an integrator to output a triangular wave signal which is fed back to the broadband tunable laser, so that the nonlinear correction of the broadband tunable laser is realized, and the photoelectric phase-locked loop outputs linear frequency-modulated light.
Further, the crystal material of the F-P etalon is aluminum oxide or YAG (yttrium aluminum garnet).
Furthermore, the linear frequency modulation light output by the photoelectric phase-locked loop is converged into parallel light through the aspheric mirror and transmitted to the F-P etalon, the F-P etalon emits reflected light which is sequentially transmitted back to the duplex port of the optical fiber circulator, the reflected light is output from the signal light output port to the photoelectric detector and converted into an electric signal, and the electric signal is processed by the signal processing unit to obtain the temperature T of the object to be measured.
Further, the ratio of the intensity of the reflected light emitted by the F-P etalon to the intensity of the received incident light is:
wherein, IrIs the intensity of reflected light; i isiIs the intensity of the incident light; r1And R2Respectively the reflectivity of the front and back reflecting surfaces of the F-P etalon; δ is the loop phase delay, which is related to the incident light frequency v by:
wherein n is the refractive index of the F-P etalon crystal material; l is the distance between the front and back reflecting surfaces of the F-P etalon; c is the speed of light propagation in vacuum (3X 10)8m/s)；
The longitudinal mode interval (i.e. the frequency difference between two adjacent strongest light intensities) Δ v of the reflected light is obtained as:
since n and L in equation (3) are related to temperature T, the temperature derivatives across equation (3) can be obtained:
and further obtaining the relationship between the longitudinal mode interval delta nu and the temperature T of the object to be measured as follows:
wherein, T0Is at room temperature; beta is the thermo-optic coefficient of the F-P etalon crystal material; alpha is the linear thermal expansion coefficient of the F-P etalon crystal material; both α and β are constants; Δ v0The initial longitudinal mode interval of the reflected light of the F-P etalon before temperature measurement;
the signal processing unit acquires the frequency sweeping frequency values corresponding to the two adjacent strongest light intensities of the reflected light according to the relation that the frequency of the linear frequency-modulated light changes along with time by collecting the time of the two adjacent strongest light intensities of the reflected light, and the frequency difference between the two strongest light intensities is the longitudinal mode interval delta ν, so that the temperature T of the measured object is calculated.
Further, setting the initial longitudinal mode interval delta v of the reflected light of the F-P etalon before temperature measurement0Not less than 5 GHz.
Further, when the crystal material of the F-P etalon is aluminum oxide, the refractive index n is 1.53; when the F-P etalon crystal material is YAG, the refractive index n is 1.82.
Furthermore, the frequency modulation bandwidth of the broadband tunable laser is larger than the initial longitudinal mode interval delta v0Twice, the longitudinal mode interval delta v of a plurality of reflected lights is obtained in one frequency modulation bandwidth, and the temperature T of the object to be measured is obtained by calculating the average value, so that the test precision of the laser temperature measuring device is improved.
Further, the temperature tested by the laser temperature measuring device is higher than 1200 ℃.
Furthermore, the laser temperature measuring device comprises a plurality of temperature detection units, a first optical switch array and a second optical switch array, and is used for measuring the temperature of a plurality of objects to be measured; the output port of the photoelectric phase-locked loop is respectively optically connected to the laser input port of the optical fiber circulator in each temperature detection unit through the first optical switch array, the signal light output port of the optical fiber circulator in each temperature detection unit is optically connected to the photoelectric detector through the second optical switch array, and the F-P etalon of each temperature detection unit is arranged on the corresponding object to be detected.
The beneficial effects of the invention are as follows:
1. the invention provides a laser temperature measuring device for a high-temperature object, which utilizes the temperature sensitivity characteristic of an F-P etalon and measures the light intensity change period of reflected light through incident linear frequency modulation light, thereby obtaining a sweep frequency value corresponding to the period time, namely the size of a longitudinal mode interval, and further obtaining the temperature of the object;
2. the frequency-modulation bandwidth of the broadband tunable laser is set, so that the sweep frequency measurement of the longitudinal mode interval is realized, and the test precision is improved;
3. preferably, the invention provides a photoelectric phase-locked loop, which realizes the nonlinear correction of a broadband tunable laser through closed-loop control to output linear frequency modulation light so as to ensure the measurement accuracy;
4. preferably, the transmission optical fiber is adopted to transmit the reflected light, and the optical switch technology (multi-path optical switching) is combined to realize multi-object measurement.
Drawings
Fig. 1 is a schematic structural diagram of a laser temperature measuring device for a high-temperature object according to embodiment 1 of the present invention;
fig. 2 is a schematic structural view of an F-P etalon in embodiment 1 of the present invention;
FIG. 3 is a schematic diagram of a port structure of the optical fiber circulator in embodiment 1 of the present invention;
FIG. 4 is a graph showing the relationship between the frequency of the chirp light output from the optical PLL in accordance with embodiment 1 of the present invention;
FIG. 5 is a graph showing a spectrum of a reflected light from an F-P etalon in example 1;
FIG. 6 is a graph showing the relationship between the longitudinal mode interval Δ v and the temperature T in example 1 of the present invention;
fig. 7 is a schematic structural diagram of a laser temperature measuring device for a high-temperature object according to embodiment 2 of the present invention;
the reference symbols in the drawings are as follows:
1. a broadband tunable laser; 2. a fiber optic circulator; 3. a transmission optical fiber; 4. an aspherical mirror; an F-P etalon; 6. a photodetector; 7. a signal processing unit; 8. a micro-optical lens; 9-1. a first coupler; 9-2. a second coupler; a MZ interferometer; 11. a balanced photodetector; 12. a phase discriminator; 13. a loop filter; 14. a rise/fall switch control circuit; 15. an integrator; 16. a first optical switch array; 17. a second optical switch array.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
The present embodiment provides a laser temperature measuring device for high temperature objects, which has a structure as shown in fig. 1, and includes a photoelectric phase-locked loop, a temperature detecting unit, a photoelectric detector 6, and a signal processing unit 7; the temperature detection unit sequentially comprises an optical fiber circulator 2, a transmission optical fiber 3, an aspherical mirror 4 and an F-P etalon 5, wherein the F-P etalon 5 is arranged on an object to be detected; the photoelectric phase-locked loop comprises a broadband tunable laser 1, a micro-optical lens 8, a first coupler 9-1, an MZ interferometer 10, a second coupler 9-2, a balanced photoelectric detector 11, a phase discriminator 12, a loop filter 13, a rising/falling switch control circuit 14 and an integrator 15 which are sequentially connected end to end.
The broadband tunable laser 1 outputs frequency-modulated light, the frequency-modulated light is coupled to a first coupler 9-1 through a micro-optical lens 8, two light beams are output, one light beam serves as the output of a photoelectric phase-locked loop, and the other light beam is input to an input port of an MZ interferometer 10; an output port of the MZ interferometer 10 is optically connected to an input port of the balanced photodetector 11 through the second coupler 9-2, and an output port of the balanced photodetector 11 is electrically connected to an input port of the phase detector 12; the phase discriminator 12 mixes the input signal with a sinusoidal reference frequency signal with the same frequency to obtain a frequency error signal, the frequency error signal is transmitted to the loop filter 13 through an output port of the phase discriminator 12 to obtain a frequency control signal, and then the triangular wave signal is output through the rising/falling switch control circuit 14 and the integrator 15 in sequence and fed back to the broadband tunable laser 1, so that the nonlinear correction of the broadband tunable laser 1 is realized, and the photoelectric phase-locked loop outputs linear frequency-modulated light. Fig. 4 shows the relationship of the time-dependent change in the output chirp optical frequency in this embodiment, and the bandwidth of the chirp optical frequency is 60 GHz.
The linear frequency modulation light output by the photoelectric phase-locked loop is transmitted to a laser input port of the optical fiber circulator 2 through an output port of the linear frequency modulation light; the duplex port of the optical fiber circulator 2 is optically connected to the optical input port of the aspherical mirror 4 through the transmission optical fiber 3, and the optical output port of the aspherical mirror 4 is optically connected with the F-P etalon 5; the signal light output port of the optical fiber circulator 2 is optically connected with the input end of the photoelectric detector 6, and the output end of the photoelectric detector 6 is electrically connected with the signal processing unit 7.
Specifically, chirped light output by the photoelectric phase-locked loop is converged into parallel light through the aspheric mirror 4 and transmitted to the F-P etalon 5, reflected light (parallel light) emitted by the F-P etalon 5 is converged and coupled to the optical fiber end face of the transmission optical fiber 3 through the aspheric mirror 4, then transmitted back to the duplex port of the optical fiber circulator 2, output from the signal light output port to the photoelectric detector 6 and converted into an electrical signal, and the electrical signal is processed by the signal processing unit 7 to obtain the temperature change of the object to be measured.
The broadband tunable laser 1 employs a DBR (distributed bragg reflector) semiconductor laser chip having an independent frequency modulation port, and performs a linear frequency modulation by injecting a triangular wave.
The frequency variation of the photoelectric signal output from the output port of the balanced photoelectric detector 11 reflects the frequency modulation linearity.
The phase discriminator 12 is a laser frequency error measuring circuit designed based on a mixing principle, and an output frequency error signal is a measure of a phase error between an input signal and a sinusoidal reference frequency signal, so that the circuit bandwidth can be improved, and the circuit delay can be reduced; frequency measurement errors caused by laser amplitude modulation are reduced through digitization, and signal quality is improved.
The loop filter 13 filters and shapes the frequency error signal and not only filters out the high frequency waveform, but also more importantly functions to establish the dynamics of the feedback loop and provide a suitable frequency control signal.
The up/down switch control circuit 14 periodically performs integral reset on the integrator 15 under the control of the frequency control signal, and continuously drives the broadband tunable laser 1 by a triangular wave signal output after the integral reset until the frequency and the phase of the output signal of the phase-locked loop are stable.
The port structure of the optical fiber circulator 2 is shown in fig. 3, and includes a laser input port, a duplex port and a signal light output port, which has good isolation, so that crosstalk between an input optical signal and reflected signal light does not occur, and the reflected light is received and output.
The transmission optical fiber 3 is used for transmitting light, and the distance between an object to be measured and the measuring device can be flexibly changed.
The F-P etalon 5 is a blocky crystal, has a structure shown in figure 2, is made of YAG materials, and is made of linear frequency modulation light which is emitted from the front reflecting surface and is emitted after being reflected by the front reflecting surface and the rear reflecting surface; the ratio of the intensity of the reflected light emitted from the F-P etalon 5 to the intensity of the incident light received is:
wherein, IrIs the intensity of reflected light; i isiIs the intensity of the incident light; r1And R2The reflectivities of the front reflection surface and the rear reflection surface of the F-P etalon 5, respectively; δ is the loop phase delay, and the relationship with the incident light frequency v is as follows:
wherein n is 1.82, which is the refractive index of YAG of the F-P etalon 5; l is the distance between the front and rear reflective surfaces of the F-P etalon 5; c is the speed of light propagation in vacuum (3X 10)8m/s)；
The longitudinal mode interval (i.e. the frequency difference between two adjacent strongest light intensities) Δ v of the reflected light is obtained as:
the initial longitudinal mode interval delta v of the reflected light of the F-P etalon 5 before temperature measurement can be adjusted by setting the distance L and the refractive index n between the front reflecting surface and the rear reflecting surface of the F-P etalon 50In this embodiment, the initial longitudinal mode interval Δ v of the reflected light from the F-P etalon 5 before temperature measurement is set0At 10GHz, the free spectrum of the reflected light is shown in fig. 5.
Since n and L in equation (3) are related to the temperature T, the derivation of both sides of equation (3) can be found:
the relationship between the longitudinal mode spacing Δ v and the temperature T is therefore obtained as:
wherein, T0At room temperature, taking T0＝27℃；β＝7.3×10-6℃-1A thermo-optical coefficient of YAG of the F-P etalon 5; α ═ 7.8 × 10-6℃-1A linear thermal expansion coefficient of YAG of the F-P etalon 5; both α and β are constants; the relationship between the longitudinal mode spacing Δ ν and the temperature T in this embodiment is substantially linear as shown in fig. 6. Under the high temperature condition, the relationship between the longitudinal mode interval delta ν and the temperature T needs to be further calibrated according to the working environment.
The reflected light emitted by the F-P etalon 5 is transmitted to the photoelectric detector 6 through the aspherical mirror 4, the transmission optical fiber 3 and the optical fiber circulator 2 in sequence to be converted into an electric signal, and then the electric signal is transmitted to the signal processing unit 7; the signal processing unit 7 acquires the time of two adjacent strongest light intensities of the reflected light through the oscilloscope, and obtains sweep frequency values corresponding to the two adjacent strongest light intensities of the reflected light according to the relation that the frequency of the linear frequency modulation light changes along with the time as shown in fig. 4, wherein the frequency difference between the two sweep frequency values is the longitudinal mode interval delta ν; 6 longitudinal mode intervals delta v of reflected light of the F-P etalon 5 in a 60GHz frequency modulation bandwidth are obtained through measurement, temperature values corresponding to the longitudinal mode intervals delta v are obtained through calculation, and the temperature of the object to be measured is obtained through calculation of an average value.
Example 2
The present embodiment provides a laser temperature measuring device for a high-temperature object, which has a structure shown in fig. 7, and includes a photoelectric phase-locked loop, three temperature detecting units, a photoelectric detector 6, a signal processing unit 7, a first optical switch array 16, and a second optical switch array 17.
The temperature detection unit sequentially comprises an optical fiber circulator 2, a transmission optical fiber 3, an aspherical mirror 4 and an F-P etalon 5, wherein the F-P etalon 5 is arranged on a corresponding object to be detected, and the working principle of the temperature detection unit is the same as that of the embodiment 1.
The photoelectric phase-locked loop comprises a broadband tunable laser 1, a micro-optical lens 8, a first coupler 9-1, an MZ interferometer 10, a second coupler 9-2, a balanced photoelectric detector 11, a phase discriminator 12, a loop filter 13, a rising/falling switch control circuit 14 and an integrator 15 which are sequentially connected end to end, and the working principle of the photoelectric phase-locked loop is the same as that of the embodiment 1.
The output port of the photoelectric phase-locked loop is optically connected to the laser input port of the optical fiber circulator 2 in each temperature detection unit through the first optical switch array 16, and the signal optical output port of the optical fiber circulator 2 in each temperature detection unit is optically connected to the photoelectric detector 6 through the second optical switch array 17, and further connected to the signal processing unit 7. The temperature of the corresponding objects to be measured is selected by controlling the first optical switch array 16 and the second optical switch array 17, so that the temperature of the objects to be measured is measured.
The above-mentioned embodiment is only an example of the high temperature object measurement proposed by the present invention, the internal optical path and circuit structure thereof are not used to limit the present invention, and only to help understand the principle of the present invention, the protection scope of the present invention is not limited to the above-mentioned configuration and embodiment, and those skilled in the art can make other specific modifications and combinations according to the disclosure without departing from the spirit of the present invention, and still fall within the protection scope of the present invention.
Claims (8)
1. The laser temperature measuring device for the high-temperature object is characterized by comprising a photoelectric phase-locked loop, a temperature detection unit, a photoelectric detector and a signal processing unit; the temperature detection unit comprises an optical fiber circulator, a transmission optical fiber, an aspherical mirror and an F-P etalon arranged on an object to be detected;
the photoelectric phase-locked loop is used for outputting linear frequency modulation light, and the output port of the photoelectric phase-locked loop is optically connected to the laser input port of the optical fiber circulator; the duplex port of the optical fiber circulator is connected to the optical input port of the aspherical mirror through transmission optical fiber light, and the optical output port of the aspherical mirror is optically connected with the F-P etalon; the signal light output port of the optical fiber circulator is optically connected with the input end of the photoelectric detector, and the output end of the photoelectric detector is electrically connected with the signal processing unit.
2. The laser temperature measurement device of the high-temperature object according to claim 1, wherein the optoelectronic phase-locked loop comprises a broadband tunable laser, a micro-optical lens, a first coupler, an MZ interferometer, a second coupler, a balanced photodetector, a phase discriminator, a loop filter, a rising/falling switch control circuit and an integrator which are sequentially connected end to end;
the broadband tunable laser outputs frequency-modulated light, the frequency-modulated light is coupled to the first coupler through a micro-optical lens, two light beams are output, one light beam serves as the output of the photoelectric phase-locked loop, and the other light beam is input to the input port of the MZ interferometer; an output port of the MZ interferometer is optically connected to an input port of the balanced photoelectric detector through the second coupler, and an output port of the balanced photoelectric detector is electrically connected to an input port of the phase discriminator; the phase discriminator mixes the input signal with a sinusoidal reference frequency signal to obtain a frequency error signal, the frequency error signal is transmitted to a loop filter through an output port of the phase discriminator to obtain a frequency control signal, and then the frequency control signal sequentially passes through a rising/falling switch control circuit and an integrator to output a triangular wave signal which is fed back to the broadband tunable laser.
3. The laser temperature measuring device of claim 1, wherein the crystal material of the F-P etalon is aluminum oxide or YAG.
4. The laser temperature measuring device of claim 1, wherein the reflected light intensity I of the F-P etalon isrWith the intensity of incident light IiThe ratio of (A) to (B) is:
wherein R is1And R2Respectively the reflectivity of the front and back reflecting surfaces of the F-P etalon; δ is the loop phase delay, and the relationship with the incident light frequency v is as follows:
wherein n is the refractive index of the F-P etalon crystal material; l is the distance between the front and back reflecting surfaces of the F-P etalon; c is the speed of light propagation in vacuum;
the longitudinal mode spacing Δ ν of the obtained reflected light is:
the temperature on both sides of equation (3) is derived as:
and further obtaining the relation between the longitudinal mode interval delta nu and the temperature T as follows:
wherein, T0Is at room temperature; beta is the thermo-optic coefficient of the F-P etalon crystal material; alpha is the linear thermal expansion coefficient of the F-P etalon crystal material; both α and β are constants; Δ ν0Is the initial longitudinal mode spacing of the reflected light;
the signal processing unit acquires the frequency sweeping frequency values corresponding to the two adjacent strongest light intensities of the reflected light according to the relationship between the frequency and the time of the linear frequency modulation light by collecting the time of the two adjacent strongest light intensities of the reflected light, and the frequency difference between the two strongest light intensities is the longitudinal mode interval delta ν, so that the temperature T of the measured object is calculated.
5. The laser temperature measurement device of claim 4, wherein the initial longitudinal mode spacing Δ ν is set0Not less than 5 GHz.
6. The laser thermometry apparatus of claim 4 wherein the bandwidth of the tunable broadband laser is greater than the initial longitudinal mode spacing Δ ν0And at the moment, the longitudinal mode interval delta v of a plurality of reflected lights is obtained in one frequency modulation bandwidth, and the temperature T of the object to be measured is obtained by calculating the average value.
7. The laser thermometry device of claim 1, wherein the laser thermometry device measures a temperature greater than 1200 ℃.
8. The laser temperature measuring device for the high-temperature object according to claim 1, comprising a plurality of temperature detecting units, a first optical switch array and a second optical switch array, for measuring the temperature of a plurality of objects to be measured; the output port of the photoelectric phase-locked loop is respectively optically connected to the laser input port of the optical fiber circulator in each temperature detection unit through the first optical switch array, the signal light output port of each optical fiber circulator is optically connected to the photoelectric detector through the second optical switch array, and each F-P etalon is arranged on the corresponding object to be detected.
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