CN218566431U - High-temperature-resistant reflection type optical fiber displacement measurement sensor - Google Patents
High-temperature-resistant reflection type optical fiber displacement measurement sensor Download PDFInfo
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- CN218566431U CN218566431U CN202120581890.5U CN202120581890U CN218566431U CN 218566431 U CN218566431 U CN 218566431U CN 202120581890 U CN202120581890 U CN 202120581890U CN 218566431 U CN218566431 U CN 218566431U
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Abstract
The utility model discloses a high temperature resistant reflection type optical fiber displacement measuring sensor, which comprises a metal shell, wherein one end of the metal shell is provided with a mounting groove, sapphire glass is mounted in the mounting groove, and a cooling cavity is formed between the sapphire glass and the mounting groove; an optical fiber bundle is arranged in the cooling cavity, and one ends of the transmitting optical fiber, the first receiving optical fiber and the second receiving optical fiber are respectively converged to the optical fiber bundle arranged in the cooling cavity through optical fiber conversion connectors; the interior of the cooling chamber is cooled by inert gas. The utility model discloses a high temperature resistant sapphire glass can keep apart outside high temperature, high-pressure gas, prevents that it from getting into the inside damage sensing element of sensor to at the inside cooling chamber that sets up of metal casing of sensor, can work in high temperature environment at the sensor, take away the heat through the air conditioning circulation, guarantee the normal work of sensor, have better practicality.
Description
Technical Field
The utility model belongs to the technical field of reflection formula optic fibre displacement sensor, concretely relates to high temperature resistant reflection formula optic fibre displacement measurement sensor.
Background
In a nano-micron positioning system, sensors are required to detect information about minute forces and displacements. At present, the micro-displacement sensor has more principles for micro-displacement detection, such as various types of optical displacement sensors, photoelectric displacement sensors, inductive displacement sensors, capacitive displacement sensors, piezoelectric displacement sensors, ultrasonic displacement sensors and the like. However, most of these displacement sensors cannot be directly and permanently applied to severe environments such as high temperature and high pressure.
Displacement sensors, also known as linear sensors, are one of the most widely used sensors. The capacitance displacement sensor has small measuring range which is less than 1mm, high precision and is generally used for thickness measurement, but the conductivity of a measured body needs to be calibrated in advance and then measured, the response frequency is different from thousands of hertz to dozens of kilohertz, the measuring range is generally mm level, and the precision is generally mum level. The ultrasonic sensor belongs to a non-contact measurement sensor, has high precision, but can only realize quasi-real-time displacement detection but not real-time displacement measurement because certain intervals exist among sound wave pulses. The inductance type displacement sensor is composed of a fixed coil and a movable iron core according to the structure and principle, and when the iron core moves in the coil along the axial direction, the purpose of detecting the displacement is achieved through the change of the inductance of the coil. The traditional displacement sensors have the problems of narrow measurement range, complex structure, easy electromagnetic interference, limited application occasions and the like.
With the rapid development of optical fiber manufacturing technology and the intensive research on optical fiber materials, the optical fiber sensing technology has also been rapidly developed. Compared with various traditional sensors, the optical fiber sensor has a series of unique advantages of high sensitivity, strong anti-electromagnetic interference capability, corrosion resistance, high temperature resistance, simple structure, small volume, light weight and the like. Therefore, the method has good application prospect in the fields of high temperature and high pressure, radiation environment, working condition monitoring, micro electro mechanical system and the like. The most advantages of using light as sensing and conducting medium are large transmission capacity, strong anti-electromagnetic interference capability, and chemical inertness and flexibility of optical fiber (optical waveguide) as light wave carrier, and optical fiber is not only used as transmission carrier of optical signal in sensing field, but also begins to become sensing unit of sensing. The optical signal is modulated by a series of means such as intensity modulation and phase modulation, and the optical signal is directly used as a measuring means for sensing quantities such as displacement, temperature, pressure, and strain. The optical fiber sensor is a measurement means with competitiveness in the aspects of monitoring of intelligent materials, intelligent structures and large-scale structures, high voltage, strong magnetic fields, nuclear radiation, biomedicine and the like. Over the years, fiber optic sensors have gained importance in research and industrial applications, primarily due to the fundamental differences between optical fibers and metal conductors, which are due to their unique advantages:
(1) Strong anti-electromagnetic interference capability, electric insulation, corrosion resistance and intrinsic safety. Because the optical fiber sensor utilizes light waves to transmit information, and the optical fiber is an electrically insulating and corrosion-resistant transmission medium, the optical fiber sensor can be conveniently and effectively applied to various severe environments such as large electromechanics, petrochemical industry, mines and the like with strong electromagnetic interference, flammability, explosiveness and the like.
(2) The sensitivity is high. The optical fiber sensor may process the optical signal by a series of means such as intensity modulation, frequency modulation, and phase modulation. With the progress of the technology, the luminous efficiency of the light source, the stability of the output power and the like are obviously improved, and the sensitivity of measurement by adopting the phase dry method is very high due to the very high frequency of the optical signal, which is far higher than that of a common sensor. Are currently used in many fields: optical fiber sensors for measuring physical quantities such as underwater sound, acceleration, radiation, magnetic field, etc.; fiber optic chemical sensors that measure various gas concentrations; fiber optic biosensors that measure various biomasses, and the like.
(3) Small volume, light weight and flexibility. The optical fiber has the advantages of small volume and light weight, and also has the advantage of flexibility, so that various sensors with small size, light weight and convenient bending and coiling can be manufactured by using the optical fiber, and the optical fiber is beneficial to aerospace and application in narrow space.
(4) The measurement object is wide. At present, optical fiber sensors with different performances for measuring various physical quantities and chemical quantities are used in the field.
(5) Has little influence on the measured medium, and is beneficial to the application in the fields with complex environments such as medicine, health and the like.
(6) Convenient multiplexing and networking. The optical fiber sensor is beneficial to forming a telemetry network and an optical fiber sensing network with the existing optical communication technology.
(7) The cost is low. There are many types of fiber optic sensors that will cost significantly less than existing sensors of the same type.
However, the major problems of the fiber sensor used for practical measurement are long-time drift effect, the drift effect of the fiber sensor comes from attenuation of the fiber transmission line, imperfect characteristics of the coupler and the beam splitter, unstable output of the light source, influence of the detector and the like. If longitudinal displacement, transverse displacement or focal power deviation occurs on the two optical fiber end faces, the coupling efficiency is reduced. Mode coupling, particularly coupling of a guided mode and a radiation mode, occurs in the optical fiber under severe bending conditions, so that the transmission loss of the optical fiber is increased.
When the reflective optical fiber displacement sensor works, light has a certain emission angle when being emitted from the end face of the optical fiber bundle, the light which is equivalent to a cone-shaped light beam is emitted and irradiates on the surface of a measured object when being viewed from the end face of the optical fiber bundle, and the light beam is reflected back by a larger light cone after being reflected by the surface of the measured object and is received by a receiving end in the optical fiber bundle. The reflective displacement sensor has the advantages that the detection distance is short, the detection precision is high, and the reflective displacement sensor is not in contact with a detected object, so that the reflective displacement sensor can be applied to the special fields of distance detection of generator blades, engine speed detection, detection of micro displacement in a strong radiation environment and the like. The optical fiber reflection type displacement detection requires that the reflection surface of the measured object is flat and smooth, so that the reflection efficiency of light can be increased, the optical power coupling into the receiving optical fiber is higher, and the further processing of the received optical signal by the photoelectric conversion device is facilitated. When the method is used for detecting the blade distance in the generator, the tiny distance between the blade rotor and the stator can be analyzed and obtained by analyzing the intensity of the received optical signal; meanwhile, the rotating speed information of the generator can be obtained through calculation according to the periodic variation rule of the received light intensity.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a high temperature resistant reflection-type optic fibre displacement measurement sensor aims at solving present displacement sensor and measures inaccurately under high temperature, forceful electric magnetic environment, the problem of becoming invalid easily. The utility model discloses a high temperature resistant sapphire glass can keep apart outside high temperature, high-pressure gas, prevents that it from getting into the inside damage sensing element of sensor to at the inside cooling chamber that sets up of metal casing of sensor, can take away the heat through the air conditioning circulation when sensor work in high temperature environment, guarantee the normal work of sensor, have better practicality.
The utility model discloses mainly realize through following technical scheme:
a high temperature resistant reflection type optical fiber displacement measurement sensor comprises a metal shell, sapphire glass, an optical fiber bundle, an optical fiber conversion connector, a transmitting optical fiber, a first receiving optical fiber and a second receiving optical fiber; one end of the metal shell is provided with an installation groove, sapphire glass is installed in the installation groove, and a cooling cavity is formed between the sapphire glass and the installation groove; an optical fiber bundle is arranged in the cooling cavity, and one ends of the transmitting optical fiber, the first receiving optical fiber and the second receiving optical fiber are respectively converged to the optical fiber bundle arranged in the cooling cavity through optical fiber conversion connectors; the interior of the cooling chamber is cooled by inert gas.
The transmitting (receiving) end composed of one transmitting optical fiber and two receiving optical fibers forms an optical fiber bundle inside the optical fiber conversion connector according to a certain arrangement mode, an optical signal is transmitted out through one end of the optical fiber bundle and is irradiated on the surface of a measured object after being refracted by high-temperature-resistant sapphire glass, meanwhile, the receiving optical fibers in the optical fiber bundle are used for receiving a reflected light intensity signal, and the light intensity signal is analyzed to obtain the distance between the end face of the optical fiber bundle and the surface of the measured object at the moment.
In order to better realize the utility model, the utility model further comprises a cooling circulation system, and both sides of the metal shell are respectively provided with a cooling gas input channel and a cooling gas output channel which are connected with a gas outlet and a gas inlet of the cooling circulation system; and the cooling gas input channel and the cooling gas output channel are respectively communicated with the cooling cavity. The cooling circulation system is prior art and will not be described in detail.
In order to realize better the utility model discloses, furtherly, still include fixed clamping ring, the inside bearing seat that is provided with of mounting groove, sapphire glass installs on bearing the seat, fixed clamping ring stretches into the mounting groove and compresses tightly sapphire glass.
In order to better realize the utility model discloses, furtherly, fixed clamping ring and mounting groove threaded connection.
In order to better realize the utility model, the device further comprises a PD1 photoelectric detector, a PD2 photoelectric detector, a driving circuit, a light source and an optical isolator which are connected in sequence from front to back; the light source is connected with the other end of the transmitting optical fiber through an optical isolator; and the other ends of the first receiving optical fiber and the second receiving optical fiber are respectively connected with the PD1 photoelectric detector and the PD2 photoelectric detector.
In order to better realize the utility model discloses, furtherly, emission optic fibre, first receiving fiber, second receiving fiber are single mode fiber respectively.
In order to better realize the utility model discloses, furtherly, emitting optic fibre, first receiving optic fibre, second receive optic fibre the arrangement of optic fibre in the optic fibre bundle for any one in semicircle type, random type, coaxial type, two bunch types, two circular, the coaxial random type.
The utility model discloses in the use, the light signal that the light source sent gets into the optic fibre bundle through input optic fibre, goes out and shines the surface of testee at the terminal surface light signal transmission of optic fibre bundle. After the optical signal is reflected by the surface of the object to be measured, part of the optical signal is coupled into the first receiving optical fiber and the second receiving optical fiber, the tail ends of the first receiving optical fiber and the second receiving optical fiber are connected with the photoelectric detector, and the received optical signal is converted into an electric signal by the photoelectric detector and then is input into the demodulation system. Under the condition of keeping other parameters of the system to be constant values, the light intensity coupled into the receiving optical fiber only changes along with the distance between the reflecting surface of the measured object and the end face of the optical fiber bundle. The distance between the end face of the optical fiber bundle and the surface of the measured object can be obtained by comparing the intensities of the two paths of optical signals, namely, the tiny displacement change is measured in a non-contact way. The displacement measurement part of the technical scheme adopts an all-optical device, so that the anti-electromagnetic interference capability is strong, and the measurement precision is higher.
Non-contact measurement: the utility model discloses a survey the size of two way receiving optical fiber received luminous intensity, calculate the distance that obtains transmission fiber end face distance testee surface. The light output by the light source irradiates the reflecting surface through the emitting optical fiber, the light is reflected by the reflecting surface to form a reflecting cone, part of the reflected light is coupled into the receiving optical fiber and then is transmitted to the photoelectric detector to be converted into an electric signal, under the condition that other parameters are kept to be constant values, the light intensity coupled into the receiving optical fiber can only change along with the distance d between the reflecting surface and the end surface of the optical fiber, and the light power received by the photoelectric detector at the moment only depends on the distance d, as shown in fig. 3. According to the definition of the light intensity modulation function, the ratio of the light power or luminous flux received by the Receiving Fiber (RF) and the light power or luminous flux output by the Transmitting Fiber (TF) in the reflective intensity modulation type fiber displacement sensor is the light intensity modulation function M which is a direct reflection of the reflective light intensity modulation characteristic.
As shown in fig. 4, it can be known from the scattering theory that the light emitted from the emission fiber (TF) is irradiated on the reflective surface to generate specular reflection and diffuse reflection, wherein the specular reflection conforms to the geometric optics theory, and the diffuse reflection is related to the processing method, surface roughness, curvature radius, material, and other factors of the reflective surface. When the reflection angle of diffuse reflection exceeds the numerical aperture angle of the optical fiber, the reflected light can not be coupled into a receiving optical fiber (RF), and the part is the light intensity of diffuse reflection loss; under the condition of diffuse reflection, the diffuse reflection angle of part of the optical fiber is smaller than the numerical aperture angle of the optical fiber, and the part of the optical fiber can be coupled into the receiving optical fiber, the part is an effective part of diffuse reflection, and a reflection type light intensity modulation characteristic curve in practical application is shown in fig. 4.
Definition d in FIG. 4 0 The initial distance of the characteristic curve of the optical fiber sensor is determined when the distance d between the measured reflecting surface and the end surface of the optical fiber is less than d 0 At this time, the reflected optical signal cannot be coupled into the receiving fiber, so [0,d 0 ]This interval is called a dead zone range. Measured distance d corresponding to the time when the characteristic curve reaches the peak value p Called peak distance, corresponding to a characteristic function of the intensity modulation type, M p Referred to as the peak modulation factor. [ d ] 0 ，d p ]The section is a forward slope of a characteristic curve, has higher sensitivity and better linearity but smaller linear range, and is suitable for displacement measurement with smaller range but higher resolution requirement; d p The subsequent curve is a back slope of the characteristic curve, the sensitivity of the back slope is low, but the linear measurement range is large, and the method is suitable for displacement measurement with low resolution and large measuring range.
The utility model has the advantages that:
(1) The utility model discloses a high temperature resistant sapphire glass can keep apart outside high temperature, high-pressure gas, prevents that it from getting into the inside damage sensing element of sensor to at the inside cooling chamber that sets up of metal casing of sensor, can take away the heat through the air conditioning circulation when sensor work in high temperature environment, guarantee the normal work of sensor, have better practicality.
(2) The high-temperature-resistant sapphire glass can play a role in isolating external high-temperature and high-pressure gas to a certain extent and protect internal sensitive elements. The cold air circulating structure of the sensor can be filled with cold air through the external cooling circulating system to cool the sensor probe, so that the sensor is further protected to be safely used in high-temperature and high-pressure severe environments. The utility model has the advantages of anti-electromagnetic interference, high temperature resistant, sensitivity is high, non-contact measurement, be convenient for the installation and can real time monitoring, can be used for small displacement measurement, generator rotational speed measurement and acceleration measurement etc.
(3) Anti-electromagnetic interference: because the optical signal is anti-electromagnetic interference essentially, the electromagnetic environment has no influence on the parameters of the phase, amplitude and the like of the optical signal, and the metal shell only plays a role in protecting and reinforcing the sensor, the sensor with the structure can avoid the interference of the surrounding environment and has higher anti-electromagnetic interference capability.
(4) The measurement accuracy is higher: when other parameters are fixed, the reflected light intensity signal is only related to the distance between the surface of the measured object and the end face of the emitted optical fiber bundle, so that the distance of the measured object can be obtained through non-contact measurement. When the light spot of the sensor is circular and the designed detection range is 3.2mm, the linear range is 1mm, and the resolution of the sensor is 3.6 mu m under the 200KHz working frequency; the resolution of the sensor is 1.7 mu m under the working frequency of 20 KHz; the resolution of the sensor reaches 0.3 μm at an operating frequency of 100 Hz.
(5) High temperature resistance: the upper part of the sensor is provided with a piece of high-temperature resistant sapphire glass with an airtight effect, the sapphire glass is directly contacted with severe environments such as high-temperature and high-pressure gas, and the sapphire glass can isolate the external high-temperature and high-pressure gas and prevent the external high-temperature and high-pressure gas from entering the sensor to damage a sensitive element; meanwhile, because the sapphire glass has good light transmission, the optical signal emitted by the sensor can be transmitted to the surface of the measured object almost without loss. The structure can ensure that the optical fiber bundle of the sensitive element can work normally under severe environments such as high temperature, high pressure and the like, and can not influence the transmission of the measuring optical signal.
(6) Edge portion has air conditioning circulation structure about the metal casing of sensor, when the sensor work under adverse circumstances such as high temperature, high pressure, cooling circulation system passes through the cooling gas input channel with pure nitrogen gas and inputs between sensor upper portion sapphire glass and the fiber bundle, the heat of sensor inside and sapphire glass interior accumulation can be taken away to the cooling gas of external input to derive the heat through cooling gas output channel, further guarantee that the sensor can be at high temperature, stable work under the high pressure environment.
(7) The utility model provides an inductance and capacitanc displacement sensor because its self principle, appear inefficacy and measure inaccurate phenomenon easily under extreme temperature and electromagnetic interference condition. The sensitive part of the sensor has no electronic components and has good performance in high-temperature environment and complex electromagnetic environment.
Drawings
FIG. 1 is a schematic structural diagram of a reflective optical fiber displacement sensor;
FIG. 2 is a block diagram of the measurement principle of the reflective optical fiber displacement measurement sensor;
FIG. 3 is a schematic diagram of displacement measurement of the reflective optical fiber displacement sensor;
fig. 4 is a graph of the light intensity modulation characteristic of the reflective optical fiber displacement measuring sensor.
Wherein: 1. transmitting optical fiber, 2, first receiving optical fiber, 3, second receiving optical fiber, 4, optical fiber conversion connector, 5, optical fiber bundle, 6, cooling gas input channel, 7, cooling gas output channel, 8, sapphire glass, 9, metal shell, the system comprises a fixed compression ring 10, a driving circuit 11, a light source 12, an optical isolator 13, a PD1 photoelectric detector 14, a PD2 photoelectric detector 15, an A/D converter 16, a divider 17, a demodulation system 18, a cooling circulation system 19.
Detailed Description
Example 1:
a high temperature resistant reflection type optical fiber displacement measurement sensor is shown in figure 1 and comprises a metal shell 9, sapphire glass 8, an optical fiber bundle 5, an optical fiber conversion connector 4, a transmitting optical fiber 1, a first receiving optical fiber 2 and a second receiving optical fiber 3; one end of the metal shell 9 is provided with an installation groove, sapphire glass 8 is installed in the installation groove, and a cooling cavity is formed between the sapphire glass 8 and the installation groove; an optical fiber bundle 5 is arranged in the cooling cavity, and one ends of the transmitting optical fiber 1, the first receiving optical fiber 2 and the second receiving optical fiber 3 are respectively converged to the optical fiber bundle 5 arranged in the cooling cavity through optical fiber conversion connectors 4; the interior of the cooling chamber is cooled by inert gas.
The utility model discloses in the use, the transmission/receiving end of constituteing by launching optic fibre 1 and two way receiving optic fibre all the way constitutes optic fibre bundle 5 according to certain arrangement inside optic fibre conversion connector 4, light signal launches away through the one end of optic fibre bundle 5, shine on the testee surface after 8 refractions of high temperature resistant sapphire glass, utilize the light intensity signal that the receiving optic fibre in optic fibre bundle 5 received the reflection simultaneously, carry out the analysis to light intensity signal and obtain this moment the distance between 5 terminal surfaces of optic fibre bundle and the testee surface.
The sapphire glass 8 is directly contacted with severe environments such as high-temperature and high-pressure gas. The sapphire glass 8 can isolate external high-temperature and high-pressure gas, so that the gas is prevented from entering the interior of the sensor to damage a sensitive element; meanwhile, the sapphire glass 8 has good light transmission, so that the optical signal emitted by the sensor can be transmitted to the surface of the measured object almost without loss. The design of the structure can not only ensure the normal work of the sensitive element optical fiber bundle 5 under severe environments of high temperature, high pressure and the like, but also can not influence the transmission of the measuring optical signal.
The utility model discloses a high temperature resistant sapphire glass 8 can keep apart outside high temperature, high-pressure gas, prevents that it from getting into the inside damage sensing element of sensor to 9 inside cooling chamber that set up at the metal casing of sensor can be when the sensor work in high temperature environment, takes away the heat through the air conditioning circulation, guarantees the normal work of sensor, has better practicality.
Example 2:
the present embodiment is optimized on the basis of embodiment 1, and as shown in fig. 2, the present embodiment further includes a cooling circulation system 19, and a cooling gas input channel 6 and a cooling gas output channel 7 connected to a gas outlet and a gas inlet of the cooling circulation system 19 are respectively disposed on two sides of the metal shell 9; and the cooling gas input channel 6 and the cooling gas output channel 7 are respectively communicated with the cooling cavity. The cooling circulation system 19 delivers the cold air into the optical signal emitting portion of the sensor probe through the cooling gas input passage 6, and then the cold air is discharged from the cooling gas output passage 7 to thereby function as a cooling for the sensor probe.
Further, still include fixed clamping ring 10, the inside bearing seat that is provided with of mounting groove, sapphire glass 8 installs on bearing the seat, fixed clamping ring 10 stretches into the mounting groove and compresses tightly sapphire glass 8.
Further, the fixed compression ring 10 is in threaded connection with the installation groove.
The utility model discloses in the use, when the sensor work under adverse circumstances such as high temperature, high pressure, cooling circulation system 19 passes through cooling gas input channel 6 with pure nitrogen gas and inputs between sensor upper portion sapphire glass 8 and the fiber bundle 5, and the heat of accumulation in sensor inside and sapphire glass 8 can be taken away to the cooling gas of external input to derive the heat through cooling gas output channel 7, thereby further guarantee that the sensor can be in high temperature, stable work under the high-pressure environment.
Other parts of this embodiment are the same as embodiment 1, and thus are not described again.
Example 3:
the present embodiment is optimized on the basis of embodiment 1 or 2, and as shown in fig. 2, the present embodiment further includes a PD1 photodetector 14, a PD2 photodetector 15, and a driving circuit 11, a light source 12, and an optical isolator 13 connected in sequence from front to back; the light source 12 is connected with the other end of the emission optical fiber 1 through an optical isolator 13; the other ends of the first receiving optical fiber 2 and the second receiving optical fiber 3 are respectively connected with a PD1 photoelectric detector 14 and a PD2 photoelectric detector 15. The driving circuit 11 drives the light source 12 to generate an optical signal with a sufficiently high optical power and a stable output optical power.
Further, the transmitting optical fiber 1, the first receiving optical fiber 2, and the second receiving optical fiber 3 are single mode optical fibers, respectively. Two receiving optical fibers, namely a first receiving optical fiber 2 and a second receiving optical fiber 3, are arranged at the receiving end of the optical fiber micro-displacement sensor, and a linear region with light intensity change can be obtained by processing the ratio of two receiving optical signals, so that the linear region is used as the effective range of the micro-displacement sensor, and the measurement error caused by unstable output power of the light source 12 can be reduced.
Further, the arrangement of the transmitting optical fiber 1, the first receiving optical fiber 2, and the second receiving optical fiber 3 in the optical fiber bundle 5 is any one of a semicircular type, a random type, a coaxial type, a dual-beam type, a double-circular type, and a coaxial random type.
The utility model discloses in the use, the light signal that light source 12 sent gets into fiber bundle 5 through input optical fiber, goes out and shines the surface of testee at the terminal surface light signal transmission of fiber bundle 5. After the optical signal is reflected by the surface of the object to be measured, part of the optical signal is coupled into the first receiving optical fiber 2 and the second receiving optical fiber 3, the tail ends of the first receiving optical fiber 2 and the second receiving optical fiber 3 are connected with the photoelectric detector, and the received optical signal is converted into an electric signal by the photoelectric detector and then input into the demodulation system 18. Under the condition of keeping other parameters of the system to be constant values, the light intensity coupled into the receiving optical fiber only changes along with the distance between the reflecting surface of the measured object and the end surface of the optical fiber bundle 5. The distance between the end face of the optical fiber bundle 5 and the surface of the measured object can be obtained by comparing the intensities of the two paths of optical signals, namely, the tiny displacement change is measured in a non-contact way. The displacement measurement part of the technical scheme adopts an all-optical device, so that the anti-electromagnetic interference capability is strong, and the measurement precision is higher.
The rest of this embodiment is the same as embodiment 1 or 2, and therefore, the description thereof is omitted.
Example 4:
a high temperature resistant reflective optical fiber displacement measurement sensor, as shown in fig. 1 and 2, comprises a light source 12 part, a cold air circulation part, a displacement measurement part and a signal demodulation part.
The light source 12 part comprises a driving circuit 11, a light source 12 and an optical isolator 13, wherein the driving circuit 11 loads a driving electric signal on the light-emitting light source 12 to serve as an output optical signal of the sensor, and the output optical signal is input into the sensor transmitting optical fiber 1 through the optical isolator 13.
The cold gas circulation section includes a cooling circulation system 19, a cooling gas input passage 6, and a cooling gas output passage 7. The cooling circulation system 19 compresses clean air by an air compressor, so that low-temperature air enters the sensor through the cooling gas input channel 6 when the sensor works in a high-temperature environment, and redundant heat is taken out of the sensor from the cooling gas output channel 7 through air circulation. The temperature between the sensor optical fiber bundle 5 and the sapphire glass 8 structure can be controlled by controlling the flow rate of the air output by the air compressor, and the sensor is protected in a high-temperature environment.
The displacement measuring part comprises an optical signal transmitting optical fiber 1, a first receiving optical fiber 2, a second receiving optical fiber 3, an optical fiber conversion connector 4 and sapphire glass 8, wherein the optical signal transmitting optical fiber 1, the first receiving optical fiber 2, the second receiving optical fiber 3, the optical fiber conversion connector and the sapphire glass are protected inside by a metal shell 9. An optical fiber conversion connector 4 is installed inside a metal shell 9 of the sensor, an optical signal transmitting optical fiber 1, a first receiving optical fiber 2 and a second receiving optical fiber 3 are integrated at the lower part of the optical fiber conversion connector 4, and three optical fibers form an optical fiber bundle 5 inside the optical fiber conversion connector 4 according to a certain arrangement mode. The optical signal is emitted from the end face of the optical fiber bundle 5, is refracted through the air medium at a certain emission angle, enters the sapphire glass 8, is irradiated to the surface of a measured object through the sapphire glass 8, and is reflected to form a reflecting cone. After reflection, the optical signals are partially coupled into the first receiving fiber 2 and the second receiving fiber 3, the optical signals in the first receiving fiber 2 are transmitted into the PD1 photodetector 14, and the optical signals in the second receiving fiber 3 are transmitted into the PD2 photodetector 15. The two paths of electric signals after photoelectric conversion are preprocessed and input into the demodulation system 18, and because the intensity of the optical signals coupled into the two beams of receiving optical fibers only changes along with the distance between the reflecting surface of the measured object and the sensor probe under the condition that other parameters of the system are constant values, the distance between the sensor probe and the surface of the measured object can be demodulated by using the optical signals received by the photoelectric detector PD1 and the photoelectric detector PD2, and the micro displacement of the measured object can be detected through continuous monitoring.
The signal demodulation part comprises photoelectric detectors PD1 and PD2 connected with two receiving optical fibers, an A/D converter 16, a divider 17 and a demodulation system 18. The optical signals received by the two receiving optical fibers are transmitted to the photoelectric detector through the optical fibers, are converted into corresponding electric signals by the photoelectric detector, are converted into digital signals through analog-to-digital conversion, the light intensity information is converted into digital information capable of signal processing, the digital information is processed, and the corresponding relation between displacement and light intensity can be obtained, so that the corresponding displacement information is obtained by detecting the change of the light intensity.
Assuming that the transmitting optical fiber 1 (TF) and the receiving optical fiber (RF) both use single-mode optical fibers, wherein the numerical aperture of the transmitting optical fiber 1 (TF) is NA, and the fiber coreRadius r T The core radius of the Receiving Fiber (RF) is r R S is the axial distance between two optical fibers, h represents the offset distance between the two optical fiber ends, P 0 For the optical power of the light source 12 coupled into the transmitting fiber 1 (TF), δ is the reflectivity of the reflecting surface and d is the distance from the transmitting fiber 1 to the reflecting surface. Let the emergent light field of emission optical fiber 1 (TF) terminal surface accord with the quasi-Gaussian distribution, namely:
where ρ represents the radial distance from the center of the emitting fiber 1, and w (d) is the mode field radius at the end face d from the emitting fiber 1 (TF), expressed as
As known from snell's theorem, the light intensity distribution emitted from the transmitting fiber 1 (TF) and reflected by the reflecting surface and transmitted to the end surface of the Receiving Fiber (RF) is equivalent to the light intensity distribution of the light emitted from the transmitting fiber 1 (TF) and transmitted to the end surface of the Receiving Fiber (RF). Therefore, the radius of the cone mode field of the reflected light at this time
Wherein:
d′＝2d+h
represents the propagation distance of the optical wave when the transmitting optical fiber 1 (TF) is projected to the end face of the receiving optical fiber (RF). The intensity distribution at the end face of the Receiving Fiber (RF) can be obtained by multiplying the above equation by the reflectivity delta, i.e.
The optical power coupled into the Receiving Fiber (RF) is then:
wherein S R Is the overlapping area of the core diameter of the Receiving Fiber (RF) and the reflected light spot. Defining the characteristic function of the reflective intensity-type structure as
M＝f(r T ，r R ，s，NA，h，d)
The optical power received by the Receiving Fiber (RF) is
P(d)＝δP 0 f(r T ，r R ，s，NA，h，d)
When the value of d is small, the reflected light cone mode field area and the fiber core of the receiving optical fiber (RF) do not intersect, the received optical power is zero, and a dead zone is generated; with the increase of the distance d, the received optical power increases sharply with the increase of the overlapping area of the Receiving Fiber (RF) and the reflected light cone mode field, and when the reflected light cone mode field area completely covers the core of the Receiving Fiber (RF), the maximum optical power can be received, and then the optical intensity modulation function M reaches the maximum value. As the distance d continues to increase, the intensity of the reflected light cone decreases, while the overlapping area of the two is constant, resulting in a decrease of the optical power coupled to the Receiving Fiber (RF), so that the intensity modulation function M is only related to the distance d between the end face of the Receiving Fiber (RF) and the surface of the object to be measured, with other parameters being constant.
The whole system adopts an optical signal intensity detection method to realize displacement detection, as shown in fig. 2, the specific working principle is as follows: light emitted by a light source 12 enters a sensor transmitting optical fiber 1 through an optical isolator 13, the transmitting optical fiber 1, a first receiving optical fiber 2 and a second receiving optical fiber 3 form an optical fiber bundle 5 in an optical fiber conversion connector 4 in a certain arrangement mode, optical signals are transmitted out from the end face of the optical fiber bundle 5 and irradiate on the surface of a measured object through sapphire glass 8, the optical signals are reflected on the surface of the measured object to form a reflecting cone, a part of the optical signals are received by the first receiving optical fiber 2 and the second receiving optical fiber 3 and are coupled into the optical fibers, under the condition that other parameters of the whole system are determined, the intensity of the optical signals coupled into the first receiving optical fiber 2 and the second receiving optical fiber 3 is only related to the distance between the end face of the optical fiber bundle 5 and the surface of the measured object, and non-contact displacement measurement can be realized by measuring the intensity change of the optical signals.
The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention in any form, and all the technical matters of the present invention are all within the protection scope of the present invention for any simple modification and equivalent change of the above embodiments.
Claims (7)
1. A high-temperature-resistant reflection-type optical fiber displacement measurement sensor is characterized by comprising a metal shell (9), sapphire glass (8), an optical fiber bundle (5), an optical fiber conversion connector (4), a transmitting optical fiber (1), a first receiving optical fiber (2) and a second receiving optical fiber (3); an installation groove is formed in one end of the metal shell (9), sapphire glass (8) is installed in the installation groove, and a cooling cavity is formed between the sapphire glass (8) and the installation groove; an optical fiber bundle (5) is arranged in the cooling cavity, and one ends of the transmitting optical fiber (1), the first receiving optical fiber (2) and the second receiving optical fiber (3) are respectively converged to the optical fiber bundle (5) arranged in the cooling cavity through optical fiber conversion connectors (4); the interior of the cooling chamber is cooled by inert gas.
2. The high temperature resistant reflective optical fiber displacement measurement sensor according to claim 1, further comprising a cooling circulation system (19), wherein a cooling gas input channel (6) and a cooling gas output channel (7) connected with a gas outlet and a gas inlet of the cooling circulation system (19) are respectively arranged on two sides of the metal shell (9); and the cooling gas input channel (6) and the cooling gas output channel (7) are respectively communicated with the cooling cavity.
3. The high temperature resistant reflective optical fiber displacement measurement sensor according to claim 1, further comprising a fixing press ring (10), wherein a bearing seat is arranged inside the installation groove, the sapphire glass (8) is installed on the bearing seat, and the fixing press ring (10) extends into the installation groove and presses the sapphire glass (8).
4. The high temperature resistant reflective optical fiber displacement measuring sensor according to claim 3, wherein the fixed compression ring (10) is in threaded connection with the mounting groove.
5. The high temperature resistant reflective optical fiber displacement measurement sensor according to claim 1, further comprising a PD1 photodetector (14), a PD2 photodetector (15), and a driving circuit (11), a light source (12), and an optical isolator (13) connected in sequence from front to back; the light source (12) is connected with the other end of the emission optical fiber (1) through an optical isolator (13); the other ends of the first receiving optical fiber (2) and the second receiving optical fiber (3) are respectively connected with a PD1 photoelectric detector (14) and a PD2 photoelectric detector (15).
6. The high temperature resistant reflective optical fiber displacement measuring sensor according to claim 5, wherein the transmitting optical fiber (1), the first receiving optical fiber (2), and the second receiving optical fiber (3) are single mode optical fibers.
7. The sensor according to claim 1, wherein the arrangement of the transmitting optical fiber (1), the first receiving optical fiber (2), and the second receiving optical fiber (3) in the optical fiber bundle (5) is any one of a semi-circular type, a random type, a coaxial type, a dual-beam type, a double-circle type, and a coaxial random type.
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