Scanning method of scanning type optical fiber displacement sensor

Abstract

The invention discloses a scanning method of a scanning type optical fiber displacement sensor, and belongs to the technical field of optical fiber displacement sensors. S1, establishing a scanning platform; s2, a scanning surface and the area of the scanning surface are determined, a scanning light path outputs laser through a lens in a voice coil motor to irradiate an object to be scanned, diffuse reflection occurs on the object to be scanned, and after a scanning platform receives information light reflected by the object to be measured, the voice coil motor is used for moving the laser to a next position, and the scanning surface of the object to be measured is scanned; s3, in the scanning process, displacement information d of the to-be-measured object is calculated and obtained by means of the optical power reflected by the scanning surface and the optical power emitted by the scanning platform. According to the method, an existing point type optical fiber displacement sensor is improved into the scanning type optical fiber displacement sensor, surface type scanning is more accurate than single-point surface scanning, and the change of an object in the direction can be measured.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber displacement sensors, and in particular to a scanning method of a scanning optical fiber displacement sensor. Background Art

[0002] Among modern sensors, fiber optic sensors stand out from many sensors due to their light size, low price, good stability, excellent resistance to electromagnetic corrosion, and the unique advantage of integrating information sensing and transmission. They use light as a signal carrier and optical fiber as a sensing device, thus integrating the technologies of "transmission" and "sensing" in two different fields, overcoming the drawbacks of conventional detection technology. Therefore, sensor technology occupies a certain position in the field of modern detection and measurement. At present, the commonly used method is to measure displacement through mechanical contact, and fiber optic sensors have become a hot direction in the field of sensors because of their advantages such as non-contact real-time measurement, long-distance measurement, and resistance to electromagnetic interference. As a very important characteristic parameter in the production industry, the development of fiber optic sensing provides support for industrial development. In order to meet actual needs, the requirements for micro-displacement measurement have become higher and higher in recent years. In current fiber optic sensors, there are a series of problems such as the increase in measurement range causing the reduction of accuracy and the need to calibrate objects. Summary of the invention

[0003] The purpose of the present invention is to provide a scanning method for a scanning optical fiber displacement sensor. By adding a voice coil motor to the optical fiber displacement sensor, conventional point measurement is converted into surface measurement, so that the displacement information of an object can be measured more accurately and a more accurate calculation result can be obtained.

[0004] To achieve the above object, the present invention provides a scanning method of a scanning optical fiber displacement sensor, comprising the following steps:

[0005] S1: Establishing a scanning platform, the scanning platform includes a scanning circuit and an object to be scanned, a voice coil motor is arranged in a scanning optical path in the scanning circuit, and a lens is arranged in the voice coil motor;

[0006] S2: Determine the scanning surface and the area of ​​the scanning surface. The scanning light path outputs the laser through the lens in the voice coil motor to illuminate the object to be scanned. Diffuse reflection occurs on the object to be scanned. After the scanning platform receives the information light reflected by the object to be measured, the voice coil motor is used to move the laser to the next position to scan the scanning surface of the object to be measured.

[0007] S3: During the scanning process, the displacement information d of the object to be measured is calculated and obtained by using the light power reflected from the scanning surface and the light power emitted by the scanning platform.

[0008] Preferably, in step S1, the scanning circuit comprises a modulation power supply, a laser diode, a scanning optical path, a photoelectric conversion, a phase-locked amplifier, an AD conversion, an FPGA and a host computer connected in sequence;

[0009] The scanning optical path includes a transmitting optical fiber, a voice coil motor, and a receiving optical fiber connected in sequence along the optical path. The transmitting optical fiber and the receiving optical fiber are arranged in the same plane. The spacing between the transmitting optical fiber and the receiving optical fiber is set to p. The material of the transmitting optical fiber and the receiving optical fiber is quartz. The radius of the transmitting optical fiber and the receiving optical fiber is r.

[0010] Preferably, in step S2, the scanning process is specifically as follows:

[0011] The scanning optical path generates laser light, which is pointed vertically to the object to be measured through the transmitting optical fiber, the receiving optical fiber receives the reflected light, and the voice coil motor controls the lens to point to the next position for detection until the detection is completed.

[0012] Preferably, in step S3, the process of calculating the displacement information is as follows:

[0013] According to the scanning area, calculate the average emitted light power P T and the average received optical power P R ;

[0014] The radius of the light spot emitted by the optical fiber at the object to be measured is:

[0015] R(d)=r1+dtanθ N ;

[0016] The change in the received light intensity and the distance between the object being measured is expressed as:

[0017]

[0018] In the above formula, R d is the radius of the spot under Gaussian distribution of light intensity, and ρ is the radial coordinate of the spot;

[0019] The numerical aperture angle formula of the receiving fiber and the transmitting fiber is:

[0020] θ N =arcsinNA;

[0021] In the above formula, NA is the numerical aperture of the transmitting fiber and the receiving fiber. When the outgoing light hits the surface of the object to be measured and then reflects, the model with the information of the object to be measured is as follows:

[0022]

[0023] In the above formula, h is the roughness of the reflecting surface, γ is the comprehensive reflectivity of the object being measured, and the light intensity received by the optical fiber after reflection is:

[0024]

[0025] The optical power received by the optical fiber after reflection is:

[0026]

[0027] In the above formula, the area where the reflected light beam intersects with the receiving optical fiber is S R ;

[0028] In the polar coordinate system, the formula for the crossover area of ​​the transmitting and receiving optical fibers is as follows:

[0029] dS R =2βρdρ;

[0030] The β is a calculation parameter, and the formula is as follows:

[0031]

[0032] Then the formula of intensity modulation function M is:

[0033]

[0034] In the above formula, the displacement information d is calculated based on the relationship between M and the displacement information d.

[0035] Therefore, the present invention adopts the above-mentioned scanning method of a scanning optical fiber displacement sensor, which has the following advantages:

[0036] In the present invention, a voice coil motor is arranged in the scanning optical path to convert the single-point measurement of the conventional optical fiber displacement sensor into a multi-point combined surface scanning, so as to obtain more information of the measured object through the surface scanning, and improve the accuracy of the second scanning result through the continuous scanning method.

[0037] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of a scanning platform in a scanning method of a scanning optical fiber displacement sensor of the present invention;

[0039] Figure 2 It is a structural schematic diagram of a scanning surface in a scanning method of a scanning optical fiber displacement sensor of the present invention;

[0040] Figure 3 It is a front view of a sending optical fiber and a receiving optical fiber in a scanning method of a scanning optical fiber displacement sensor of the present invention;

[0041] Figure 4This is an experimental data diagram of a scanning optical fiber displacement sensor of the present invention;

[0042] Figure 5 It is the characteristic relationship curve between displacement and voltage. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations. The specific model specifications need to be selected and determined according to the actual specifications of the device, and the specific selection calculation method adopts the existing technology in the field, so it will not be described in detail.

[0044] Example

[0045] like Figure 1-Figure 3 As shown, the present invention provides a scanning method of a scanning optical fiber displacement sensor, comprising the following steps:

[0046] S1: Establishing a scanning platform, the scanning platform includes a scanning circuit and an object to be scanned, a voice coil motor is arranged in a scanning optical path in the scanning circuit, and a lens is arranged in the voice coil motor;

[0047] The scanning circuit comprises a modulation power supply, a laser diode, a scanning optical path, a photoelectric conversion, a phase-locked amplifier, an AD conversion, an FPGA and a host computer which are connected in sequence;

[0048] The scanning optical path includes a transmitting optical fiber, a voice coil motor, and a receiving optical fiber connected in sequence along the optical path. The transmitting optical fiber and the receiving optical fiber are arranged in the same plane. The spacing between the transmitting optical fiber and the receiving optical fiber is set to p. The material of the transmitting optical fiber and the receiving optical fiber is quartz. The radius of the transmitting optical fiber and the receiving optical fiber is r.

[0049] S2: Determine the scanning surface and the area of ​​the scanning surface. The scanning light path outputs the laser through the lens in the voice coil motor to illuminate the object to be scanned. Diffuse reflection occurs on the object to be scanned. After the scanning platform receives the information light reflected by the object to be measured, the voice coil motor is used to move the laser to the next position to scan the scanning surface of the object to be measured. The specific process is as follows:

[0050] The scanning optical path generates laser, which is pointed vertically to the object to be measured through the transmitting optical fiber. The receiving optical fiber receives the reflected light, and the voice coil motor controls the lens to point to the next position for detection. Each position is detected for 1 second until the detection is completed.

[0051] S3: During the scanning process, the displacement information d of the object to be measured is calculated by using the light power reflected from the scanning surface and the light power emitted by the scanning platform. The process of calculating the displacement information is as follows:

[0052] According to the scanning area, calculate the average emitted light power P T and the average received optical power P R ;

[0053] The radius of the light spot emitted by the optical fiber at the object to be measured is:

[0054] R(d)=r1+dtanθ N ;

[0055] The change in the received light intensity and the distance between the object being measured is expressed as:

[0056]

[0057] In the above formula, R d is the radius of the spot under Gaussian distribution of light intensity, and ρ is the radial coordinate of the spot;

[0058] The numerical aperture angle formula of the receiving fiber and the transmitting fiber is:

[0059] θ N =arcsinNA;

[0060] In the above formula, NA is the numerical aperture of the transmitting fiber and the receiving fiber. When the outgoing light hits the surface of the object to be measured and then reflects, the model with the information of the object to be measured is as follows:

[0061]

[0062] In the above formula, h is the roughness of the reflecting surface, and γ is the comprehensive reflectivity of the object being measured, which is related to the material of the object being measured and its processing method. From the knowledge of optics, we know that after the light is reflected to the receiving optical fiber, the light intensity is the light intensity at the output end 2d away multiplied by γ. After the light is reflected back, the light intensity received by the optical fiber is:

[0063]

[0064] The optical power received by the optical fiber after reflection is:

[0065]

[0066] In the above formula, the area where the reflected light beam intersects with the receiving optical fiber is S R ;

[0067] In the polar coordinate system, the cross area of ​​the transmitting and receiving optical fibers can be expressed as:

[0068] dSR =2βρdρ

[0069] The β is a calculation parameter, and the formula is as follows:

[0070]

[0071] Then the formula of intensity modulation function M is:

[0072]

[0073] By introducing actual values ​​into the above formula, the displacement information d of the object to be measured can be calculated based on the relationship between M and the displacement information d.

[0074] The specific use process is as follows: the voice coil motor is used to drive the lens to move, which can quickly change the position of the emitting optical fiber imaging in real time, thereby improving the measurement range. Each time the lens moves, there will be a corresponding change in the image position. Since the motor moves very fast and the object being measured is relatively slow compared to the motor, the object being measured can be considered to be stationary.

[0075] When the lens inside the VCM motor is given different displacements, the sensor system is tested to see if it can normally output the corresponding voltage value. In the sensitivity experiment, the optical fiber probe is fixed and the lens is given different displacements, and the movement of the lens can be controlled by the software program.

[0076] like Figure 4 As shown in the figure, V3 is the voltage value measured when the lens is 3.52mm away from the optical fiber probe for the first time, V2 is the voltage value measured when the lens is moved to 3.53mm for the second time, and V1 is the voltage value measured when the lens is moved to 3.54mm for the third time. Then, the distance of the measured object is changed in sequence by moving the platform. Figure 4 The characteristic relationship curve between displacement and voltage is drawn from the data in the figure. Figure 5 shown.

[0077] In the embodiment of the present invention, when the object under test is in diffuse reflection and the output curve of the sensor is on the front slope, k1 is used to represent the sensitivity of the sensor, and the expression is:

[0078]

[0079] The linear range of the front slope of the scanning optical fiber displacement sensor under diffuse reflection is d (0.3-0.8 mm), V (0.244-1.382 V). The calculation results show that k1 = 2.276 V / mm, which is the front slope curve sensitivity of the scanning optical fiber displacement sensor under diffuse reflection.

[0080] When the output curve is on the back slope, k2 is used to represent its sensitivity, and the expression is:

[0081]

[0082] from Figure 5 It can be seen that the linear range of the back slope of the scanning optical fiber displacement sensor under diffuse reflection is d (0.8-3mm), V (1.424-0.321V). It can be calculated that k2 = 0.502V / mm, which is the back slope curve sensitivity of the scanning optical fiber displacement sensor under diffuse reflection.

[0083] Therefore, it can be seen that the front slope sensitivity of this embodiment under the rough surface condition is k1=2.276V / mm, the linear range is 0.5mm, and the back slope sensitivity is k2=0.502V / mm, the linear range is 2.2mm. The experimental effect is good and basically meets the design requirements, thus verifying the feasibility of the scanning optical fiber displacement sensor.

[0084] Therefore, the present invention adopts a scanning method of a scanning optical fiber displacement sensor, and converts conventional point measurement into surface measurement by adding a voice coil motor to the optical fiber displacement sensor, which can more accurately measure the displacement information of the object and obtain more accurate calculation results.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A scanning method for a scanning optical fiber displacement sensor, characterized in that: The following steps are involved: S1: Establishing a scanning platform, the scanning platform includes a scanning circuit and an object to be scanned, a voice coil motor is arranged in a scanning optical path in the scanning circuit, and a lens is arranged in the voice coil motor; S2: Determine the scanning surface and the area of ​​the scanning surface. The scanning light path outputs the laser through the lens in the voice coil motor to illuminate the object to be scanned. Diffuse reflection occurs on the object to be scanned. After the scanning platform receives the information light reflected by the object to be measured, the voice coil motor is used to move the laser to the next position to scan the scanning surface of the object to be measured. S3: During the scanning process, the displacement information d of the object to be measured is calculated and obtained by using the light power reflected from the scanning surface and the light power emitted by the scanning platform.

2. The scanning method of a scanning optical fiber displacement sensor according to claim 1, characterized in that: In step S1, the scanning circuit comprises a modulation power supply, a laser diode, a scanning optical path, a photoelectric conversion, a phase-locked amplifier, an AD conversion, an FPGA and a host computer connected in sequence; The scanning optical path includes a transmitting optical fiber, a voice coil motor, and a receiving optical fiber connected in sequence along the optical path. The transmitting optical fiber and the receiving optical fiber are arranged in the same plane. The spacing between the transmitting optical fiber and the receiving optical fiber is set to p. The material of the transmitting optical fiber and the receiving optical fiber is quartz. The radius of the transmitting optical fiber and the receiving optical fiber is r.

3. The scanning method of a scanning optical fiber displacement sensor according to claim 2, characterized in that: In step S2, the scanning process is as follows: The scanning optical path generates laser light, which is pointed vertically to the object to be measured through the transmitting optical fiber, the receiving optical fiber receives the reflected light, and the voice coil motor controls the lens to point to the next position for detection until the detection is completed.

4. The scanning method of a scanning optical fiber displacement sensor according to claim 3, characterized in that: In step S3, the process of calculating the displacement information is as follows: According to the scanning area, calculate the average emitted light power P T and the average received optical power P R ; The radius of the light spot emitted by the optical fiber at the object to be measured is: R(d)=r1+dtanθ N ; The change in the received light intensity and the distance between the object being measured is expressed as: In the above formula, R d is the radius of the spot under Gaussian distribution of light intensity, and ρ is the radial coordinate of the spot; The numerical aperture angle formula of the receiving fiber and the transmitting fiber is: θ N =arcsinNA; In the above formula, NA is the numerical aperture of the transmitting fiber and the receiving fiber. When the outgoing light hits the surface of the object to be measured and then reflects, the model with the information of the object to be measured is as follows: In the above formula, h is the roughness of the reflecting surface, γ is the comprehensive reflectivity of the object being measured, which is related to the material of the object being measured and its processing method. The light intensity received by the optical fiber after reflection is: The optical power received by the optical fiber after reflection is: In the above formula, the area where the reflected light beam intersects with the receiving optical fiber is S R ; In the polar coordinate system, the formula for the crossover area of ​​the transmitting and receiving optical fibers is as follows: dS R =2bdp; The β is a calculation parameter, and the formula is as follows: Then the formula of intensity modulation function M is: In the above formula, the actual value is substituted and the displacement information d is calculated based on the relationship between M and the displacement information d.

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