CN102680114A - Whole optical fiber colorimetric temperature measuring method based on optical fiber bragg grating - Google Patents

Abstract

The invention discloses a whole optical fiber colorimetric temperature measuring method based on optical fiber bragg grating. Optical fiber bragg gratings FBG1 and FBG2 are used as filters; a spectrum received by a sensing head reaches to the first to second ports of a three-terminal circulator (10) to be coupled to an incidence end of the FBG1; the reflection optical wave of the FBG1 is transmitted to a first photoelectric detector (12) through second to third ports of the three-terminal circulator (10) for photoelectric conversion; similarly, a transmitted spectrum of the FBG1 is transmitted to the incidence terminal of the FBG2 through the first to second ports of the three-terminal circulator (10); the reflection optical wave generated by the FBG2 reaches to a second photoelectric detector (13) through the second to third ports of the three-terminal circulator (11) so as to accomplish the photoelectric conversion to obtain two electric signals of different wavelengths; and the two electric signals of different wave lengths are processed to obtain the tested temperature subsequently. The filter of the system adopts the optical fiber bragg grating to replace an existing light filtering sheet; and the method has the advantages of optical fiber coupling easiness and installation convenience.

Description

Full fiber ratio color temp measuring method based on Fiber Bragg Grating FBG

Technical field

The present invention relates to the radiation temperature measuring technology in temperature field, be specifically related to contactless color comparison temperature measurement technology and filtering technique thereof.The present invention adopts Fiber Bragg Grating FBG to replace traditional optical filter, realizes the narrow-band filtering of two kinds of different wave lengths, by optical fiber three end circulators with light wave transmissions to photodetector, have full Optical Fiber Transmission, Installation and Debugging make things convenient for and be convenient to integrated advantage; This method optical system is simple, can merge with optical fiber, adapts to and under rugged surroundings, measures.

Background technology

The temperature test method can be divided into contact type measurement and contactless measurement.Under rugged environment relatively, contact type measurement makes sensor damage easily, and has destroyed tested temperature field, therefore, can realize that the radiation temperature measurement method of different principle of non-contact measurement is developed.

For the radiant type temp measuring method, remolding sensitivity is higher, and response speed is fast, and it is high to measure upper temperature limit.But it is bigger that measuring accuracy is influenced by measurand emissivity and intermediate medium.And emissivity receives environment, the influence of the various factorss such as surface smoothness of temperature and material, and its uncertainty is the measurement difficult problem of present spectroscopic temperature measurement.

The eighties in 20th century; The color comparison temperature measurement technology begins to rise; The method of two kinds of wavelength signals comparisons of this techniques make use has been eliminated the influence of emissivity and environment well, has improved temperature measurement accuracy effectively, has a wide range of applications at aspects such as commercial production, scientific researches.When especially the application of radiation thermometry carries out the test of blast temperature field; Measured target is gas, the solid, liquid multiphase mixture of swiftly flowing fuel, air and detonation product; Its constituent and emissivity change rapidly in time; Adopt monochromatic radiation thermometry and total radiation ther to bring very big error, use the color comparison temperature measurement technology and can reduce of the influence of target emissivity preferably, thereby obtain the temperature of measured target temperature measurement accuracy to temperature measurement accuracy.

But color comparison temperature measurement system in the past still exists some to be unfavorable for the factor of using.As adopted optical lens to collect the radiation of high temp objects in the past, and these optical lens are made up of different optical mirror slips, and assembling and debugging are complicated, and volume is bigger; In order to obtain the optical filter of desired two kinds of different centre wavelengths, the high-performance optical filter that adopt special film system to process increases cost.

How color comparison temperature measurement method in the past improves from the photoelectricity demodulation part, and less from the improvement of light path.The interference filter that remains the different centre wavelengths of employing like Chinese patent 200810115098.X " based on the two band color comparison temperature measurement method of single colourful CCD video camera " is filtered into two narrow band light in the wave band with all band light.

Summary of the invention

The present invention proposes a kind of full fiber ratio color temp measuring method based on Fiber Bragg Grating FBG (FBG, Fiber Bragg Grating), and this method belongs to noncontact radiometric temperature measurement method.

The present invention adopts following technical scheme:

A kind of full fiber ratio color temp measuring method based on Fiber Bragg Grating FBG, with optical fiber bragg grating FBG 1, FBG2 as wave filter; 1 → 2 port that the spectrum that is received by sensing head arrives three end circulators (10) is coupled to the incident end of FBG1, and the reflecting light of FBG1 to first photodetector (12), carries out opto-electronic conversion by 2 → 3 port transmission of three end circulators (10); Equally; The transmitted spectrum of FBG1 is by 1 → 2 port transmission of three end circulators (11) the incident end to FBG2; The reflecting light that is produced by FBG2 arrives second photodetector (13) through 2 → 3 ports of three end circulators (11); Accomplish the electric signal that opto-electronic conversion obtains two kinds of different wave lengths, the electric signal of two different wave lengths obtains the temperature value of being surveyed after handling through signal processing circuit.

Described method, the photodetection of described system and transmission path are all optical fibre structure.

Described method, the structure of sensing head is: the spheric collector of making large-numerical aperture in the end plating of optical fiber near the rete of black matrix emissivity 1 or at an end of optical fiber.

Described method, described Fiber Bragg Grating FBG are the single-mode fiber Bragg grating.

The advantage of this method is:

1, the Fiber Bragg Grating FBG of two different bragg wavelengths of narrow-band filtering employing has and is convenient to the advantage integrated with optical fiber as wave filter, can realize full Optical Fiber Transmission.Optical system is simple, and is flexible for installation, is convenient to use in rugged surroundings.

2, the Fiber Bragg Grating FBG that is adopted has the narrow advantage of filtering bandwidth, more approaches monochromatic radiation.

The bragg wavelength of two different gratings that 3, adopted can be selected as requested, and both bragg wavelengths can be selected nearer, and two wave spectrum emissivity more near equating, have improved the precision of color comparison temperature measurement.

4, the used circulator of system is optical fiber three end circulators, merges conveniently with optical fiber and Fiber Bragg Grating FBG, can realize the full Optical Fiber Transmission of sensor-based system.

5, traditional optical filter method need adopt the beam split light path, has weakened the light signal on each road; Light path of the present invention adopts same Optical Fiber Transmission, does not need beam split, can not weaken luminous power, helps surveying.

6, the blackbody chamber Fibre Optical Sensor that is easy to light harvesting is adopted in the design of sensing head, than traditional collector lens structure easy mounting and adjusting.

Description of drawings

Fig. 1 is the system works schematic diagram based on Fiber Bragg Grating FBG;

Fig. 2 is the radiation spectrum distribution of certain temperature spot radiation source and the reflectance spectrum of two Bragg gratings;

Fig. 3 is one of sensing head structure;

Fig. 4 is two of a sensing head structure;

Fig. 5 is Fiber Bragg Grating FBG structure and spectral response synoptic diagram;

Fig. 6 is the optical fiber circulator contour structures;

Embodiment

Below in conjunction with specific embodiment, the present invention is elaborated.

The color comparison temperature measurement principle that this method is used is narrated as follows:

Thermodynamic temperature is the non-black-body material of T, its radiation and be distributed with the Planck radiation law and describe:

$M(\mathrm{\λ},T)=\frac{\mathrm{\ϵ}(\mathrm{\λ},T)\·c_1}{{\mathrm{\λ}}^5(e^{c_2/\mathrm{\λT}}-1)}---\left(1\right)$

In the formula: (λ is T) for the monochromatic radiation emittance of spectrum wavelength X when temperature is T for M; (λ T) is the spectral emittance of object in wavelength X to ε; C wherein ₁=2 π hc ²=3.74 * 10 ^-16(Wm ²) be first radiation constant; c ₂=hc/k=1.44 * 10 ^-2(mK) be second radiation constant.As λ T c ₂The time, Planck can replace by Wien formula is approximate, can be reduced to:

$M(\mathrm{\λ},T)=\frac{\mathrm{\ϵ}(\mathrm{\λ},T)\·c_1}{{\mathrm{\λ}}^5\·e^{c_2/\mathrm{\λT}}}---\left(2\right)$

Can make like this and discuss and calculate greatly and simplify.

Color comparison temperature measurement is confirmed object temperature according to the ratio that gives off colourity of object under two adjacent wavelength.If temperature is that the same point of the high temp objects of T is λ at wavelength ₁, λ ₂Under the monochromatic radiation emittance be respectively M (λ ₁, T), M (λ ₂, T), wavelength X then ₁, λ ₂The ratio R (T) of place's radiation power:

$R\left(T\right)=\frac{M({\mathrm{\λ}}_1,T)}{M({\mathrm{\λ}}_2,T)}=\frac{\mathrm{\ϵ}({\mathrm{\λ}}_1,T)}{\mathrm{\ϵ}({\mathrm{\λ}}_2,T)}{\left(\frac{{\mathrm{\λ}}_2}{{\mathrm{\λ}}_1}\right)}^5\exp \left[\frac{C_2}{T}(\frac{1}{{\mathrm{\λ}}_2}-\frac{1}{{\mathrm{\λ}}_1})\right]---\left(3\right)$

Spectral emittance ε (λ when hypothesis two wavelength ₁, T) ≈ ε (λ ₂, in the time of T),

$R\left(T\right)={\left(\frac{{\mathrm{\λ}}_2}{{\mathrm{\λ}}_1}\right)}^5{e}^{\frac{C_2}{T}(\frac{1}{{\mathrm{\λ}}_2}-\frac{1}{{\mathrm{\λ}}_1})}---\left(4\right)$

The temperature that record this moment just is called colour temperature T _cThe true temperature T of object and colour temperature T _cError be:

$\frac{1}{T}-\frac{1}{T_c}=\frac{{\mathrm{\λ}}_1{\mathrm{\λ}}_2}{C_2({\mathrm{\λ}}_2-{\mathrm{\λ}}_1)}\ln \left(\frac{\mathrm{\ϵ}({\mathrm{\λ}}_1,T)}{\mathrm{\ϵ}({\mathrm{\λ}}_2,T)}\right)---\left(5\right)$

Under the situation of known two wavelength, know that R (T) just can obtain colour temperature T _c, just can know the actual temperature of object again through the emissivity correction.This temp measuring method precision is high, and antijamming capability is strong, so color comparison temperature measurement is the effective ways that improve temperature measurement accuracy in the radiation temperature measurement.

Like Fig. 1 is the system works schematic diagram based on Fiber Bragg Grating FBG.The spectral range and the distribution Planck radiation law of the tested radiation source emission under certain temperature provide, and be as shown in Figure 2.According to system requirements, select certain bragg wavelengths ₁And λ ₂Two fiber grating FBG1 and FBG2 as the wave filter of radiation spectrum.The radiation spectrum of this testee is absorbed by sensing head or collects entering optical fiber and transmits to far-end.1 → 2 port that the spectrum that is received by sensing head arrives three end circulators 10 is coupled to FBG1 (λ ₁) the incident end, FBG1 (λ ₁) reflecting light by 2 → 3 port transmission of three end circulators 10 to first photodetector 12, carry out opto-electronic conversion; Equally, FBG1 (λ ₁) transmitted spectrum by 1 → 2 port transmission of three end circulators 11 to FBG2 (λ ₂) the incident end, by FBG2 (λ ₂) reflecting light that produces arrives second photodetector 13 through 2 → 3 ports of three end circulators 11, accomplishes the electric signal that opto-electronic conversion obtains two kinds of different wave lengths, the electric signal of two different wave lengths obtains the temperature value of being surveyed after handling through signal processing circuit.

The structure of sensing head has two kinds of Fig. 3 and Fig. 4, and wherein Fig. 3 is at the end plating of the optical fiber rete near black matrix emissivity 1, more absorbed radiation spectrum; Fig. 4 is a spheric collector of making large-numerical aperture at an end of optical fiber, can well collect the radiation spectrum of object equally.

Should be understood that, concerning those of ordinary skills, can improve or conversion, and all these improvement and conversion all should belong to the protection domain of accompanying claims of the present invention according to above-mentioned explanation.

Claims (4)

1. the full fiber ratio color temp measuring method based on Fiber Bragg Grating FBG is characterized in that, with optical fiber bragg grating FBG 1, FBG2 as wave filter; 1 → 2 port that the spectrum that is received by sensing head arrives three end circulators (10) is coupled to the incident end of FBG1, and the reflecting light of FBG1 to first photodetector (12), carries out opto-electronic conversion by 2 → 3 port transmission of three end circulators (10); Equally; The transmitted spectrum of FBG1 is by 1 → 2 port transmission of three end circulators (11) the incident end to FBG2; The reflecting light that is produced by FBG2 arrives second photodetector (13) through 2 → 3 ports of three end circulators (11); Accomplish the electric signal that opto-electronic conversion obtains two kinds of different wave lengths, the electric signal of two different wave lengths obtains the temperature value of being surveyed after handling through signal processing circuit.

2. method according to claim 1 is characterized in that, the photodetection of described system and transmission path are all optical fibre structure.

3. method according to claim 1 is characterized in that, the structure of sensing head is: the spheric collector of making large-numerical aperture in the end plating of optical fiber near the rete of black matrix emissivity 1 or at an end of optical fiber.

4. method according to claim 1 is characterized in that, described Fiber Bragg Grating FBG is the single-mode fiber Bragg grating.

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