A scanning method of a scanning optical fiber displacement sensor

Abstract

The application discloses a scanning method of a scanning optical fiber displacement sensor and belongs to the technical field of optical fiber displacement sensors; S1: a scanning platform is established; S2: a scanning surface and the area of the scanning surface are determined; scanning light passes through a lens in a voice coil motor to output laser to irradiate on a to-be-scanned object; diffuse reflection occurs on the to-be-scanned object; after the scanning platform receives the reflected information light of the to-be-measured object, the voice coil motor is used to move the laser to a next position, and the scanning surface of the to-be-measured object is scanned; S3: in the scanning process, the displacement information d of the to-be-measured object is calculated and acquired by means of the reflected light power of the scanning surface and the light power emitted by the scanning platform. The present application improves the existing point type optical fiber displacement sensor into a scanning optical fiber displacement sensor, and the surface scanning is more accurate than single-point scanning, and the change of the object in the direction can be measured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber displacement sensors, and particularly to a scanning method of a scanning optical fiber displacement sensor. BACKGROUND

[0002] In modern sensors, optical fiber sensors stand out from numerous sensors due to their advantages of light weight, low price, good stability, excellent anti-electromagnetic corrosion, and unique advantages of integrating information sensing and transmission. The optical fiber sensor uses light as a signal carrier and a sensing device, thereby combining the technologies in the fields of "transmission" and "sensing" and overcoming the drawbacks in conventional detection technologies. Therefore, the sensor technology occupies a certain position in the modern detection and measurement field. The commonly used method is to measure displacement through mechanical contact, and the optical fiber sensor has the advantages of non-contact real-time measurement, long-distance measurement, and anti-electromagnetic interference, and thus it has become a popular direction in the field of sensors. As a very important characteristic parameter in the production industry, the development of optical fiber sensing provides support for industrial development. In order to meet the actual needs, the requirement for micro-displacement measurement is higher and higher in recent years. In the current optical fiber sensor, there are a series of problems such as the increase of the measurement range causing the reduction of the precision and the need for calibration of the object. SUMMARY

[0003] The purpose of the present application is to provide a scanning method of a scanning optical fiber displacement sensor, which converts the conventional point measurement into area measurement by adding a voice coil motor in the optical fiber displacement sensor, can more accurately measure the displacement information of the object, and obtain more accurate calculation results.

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

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

[0006] S2: determining a scanning surface and an area of the scanning surface, the scanning light path outputs laser irradiation on the object to be scanned through the lens in the voice coil motor, and the laser irradiation occurs diffuse reflection on the object to be scanned; after the scanning platform receives the reflected information light of the object to be measured, the voice coil motor moves the laser to the next position to scan the scanning surface of the object to be measured;

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

[0008] Preferably, in the step S1, the components of the scanning circuit include a modulated power supply, a laser diode, a scanning optical path, a photoelectric conversion, a phase-locked amplifier, an AD converter, an FPGA and an upper computer connected in sequence.

[0009] The scanning optical path includes an emitting optical fiber, a voice coil motor and a receiving optical fiber connected in sequence along the optical path, the emitting optical fiber and the receiving optical fiber are arranged on the same plane, the distance between the emitting optical fiber and the receiving optical fiber is p, the materials of the emitting optical fiber and the receiving optical fiber are quartz, and the radius of the emitting optical fiber and the receiving optical fiber is r.

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

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

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

[0013] According to the scanning area, the average emitted light power P is calculated T and the average received light 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 of the distance between the received light intensity and the measured object is expressed as:

[0017]

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

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

[0020] θ N = arcsin NA.

[0021] In the above formula, NA is the numerical aperture of the emitting optical fiber and the receiving optical fiber, and when the emitted light irradiates the surface of the measured object and then is reflected, the model with the information of the measured object is as follows:

[0022]

[0023] In the above formula, h is the roughness of the reflecting surface, γ is the comprehensive reflectivity of the measured object, 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 of the light reflected back and intersecting the receiving optical fiber is S R ;

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

[0029] dS R = 2βρdρ;

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

[0031]

[0032] The intensity modulation function M is as follows:

[0033]

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

[0035] Therefore, the scanning method of the scanning optical fiber displacement sensor has the following advantages:

[0036] In the present application, the voice coil motor is arranged in the scanning light path, and the single-point measurement of the conventional optical fiber displacement sensor is converted into a multi-point combined surface scanning, more information of the measured object is obtained through the surface scanning, and the accuracy of the scanning result is further improved through the continuous scanning method.

[0037] The technical solutions of the present application will be further described in detail below through the drawings and examples. DESCRIPTION OF DRAWINGS

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

[0039] Figure 2 FIG. 3 is a structural schematic diagram of a scanning surface in the scanning method of the scanning optical fiber displacement sensor of the present application;

[0040] Figure 3 FIG. 5 is a front view of the transmitting optical fiber and the receiving optical fiber in the scanning method of the scanning optical fiber displacement sensor of the present application;

[0041] Figure 4An experimental data graph of the scanning optical fiber displacement sensor of the present application;

[0042] Figure 5 A characteristic curve between displacement and voltage. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings 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. The specific selection calculation method adopts the existing technology in the art, and therefore will not be described in detail.

[0044] EMBODIMENT

[0045] As shown in the figure, the present application provides a scanning method of a scanning optical fiber displacement sensor, comprising the following steps: Figures 1-3

[0046] S1: Establish a scanning platform, which comprises a scanning circuit and an object to be scanned. A voice coil motor is arranged in the scanning light path in the scanning circuit, and a lens is arranged in the voice coil motor.

[0047] The composition of the scanning circuit comprises a modulated power supply, a laser diode, a scanning light path, a photoelectric conversion, a phase-locked amplification, an AD conversion, an FPGA and an upper computer connected in sequence.

[0048] The scanning light path comprises a transmitting optical fiber, a voice coil motor and a receiving optical fiber connected in sequence along the light path. The transmitting optical fiber and the receiving optical fiber are arranged on the same plane, the distance between the transmitting optical fiber and the receiving optical fiber is p, the materials of the transmitting optical fiber and the receiving optical fiber are quartz, and 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 laser light through the lens in the voice coil motor to irradiate on the object to be scanned, and the laser light occurs diffuse reflection on the object to be scanned. After the scanning platform receives the reflected information light of the object to be measured, the voice coil motor moves the laser light to the next position to scan the scanning surface of the object to be measured. The specific process is as follows:

[0050] The scanning light path generates laser light, which is vertically directed to the object to be measured through the transmitting optical fiber. The receiving optical fiber receives the reflected light. 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: In the scanning process, the displacement information d of the object to be measured is calculated by means of the light power reflected by 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, the average emitted light power P is calculated T and the average received light 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 of the distance between the received light intensity and the measured object is represented as:

[0056]

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

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

[0059] θ N = arcsin NA;

[0060] In the above formula, NA is the numerical aperture of the transmitting optical fiber and the receiving optical fiber. When the outgoing light irradiates the surface of the measured object and then reflects, the model with the information of the measured object 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 measured object, which is related to the material of the measured object and the processing method thereof. According to optical knowledge, the light intensity after the light is reflected to the receiving optical fiber is the product of the light intensity of the outgoing end 2d distance and γ. The light intensity received by the optical fiber after reflection is:

[0063]

[0064] The light 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 intersection area of the transmitting and receiving optical fibers can also be represented as:

[0068] dSR = 2βρdρ

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

[0070]

[0071] The intensity modulation function M formula is:

[0072]

[0073] Through the above formula, the actual value is introduced, according to the relationship between M and displacement information d, the displacement information d of the measured object can be calculated.

[0074] The specific use process is as follows: the lens is driven to move by using a voice coil motor, the position of the imaging fiber emitting light can be changed in real time and quickly, so that the range measurement is improved, and each movement of the lens corresponds to a change in image position. Since the motor moves very fast, and the measured object is relatively slow compared with the motor movement, the measured object can be considered as stationary.

[0075] In the case of giving different moving displacement amounts of the internal lens of the VCM motor, it is tested whether the sensor system can normally output corresponding voltage values. In the sensitivity experiment, the fiber probe is fixed, different moving amounts are given to the lens, and the moving amount of the lens can be controlled by a software program.

[0076] As shown in Figure 4 , V3 is the voltage value measured when the lens is moved to 3.52mm from the 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 turn by moving the platform, and the characteristic relationship curve between displacement and voltage is drawn according to the data in Figure 4 , as shown in Figure 5 .

[0077] In the embodiment of the application, in the case of diffuse reflection of the measured object, the output curve of the sensor is in the front slope, and 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 fiber displacement sensor in the case of diffuse reflection is d(0.3-0.8mm), V(0.244-1.382V). It is calculated that k1=2.276V / mm, which is the sensitivity of the front slope curve of the scanning fiber displacement sensor in the case of diffuse reflection.

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

[0081]

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

[0083] Therefore, it can be seen that the forward slope sensitivity of this embodiment on a rough surface is k1 = 2.276 V / mm, with a linear range of 0.5 mm, and the backward slope sensitivity is k2 = 0.502 V / mm, with a linear range of 2.2 mm. The experimental results are good and basically meet the design requirements, thus verifying the feasibility of the scanning fiber optic displacement sensor.

[0084] Therefore, the present invention adopts a scanning method of 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, 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 solutions of the present invention rather than to limit the same. 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 solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions 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, which includes a scanning circuit and an object to be scanned. A voice coil motor is provided in a scanning optical path of the scanning circuit, and a lens is provided in the voice coil motor. 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, and the distance between the transmitting optical fiber and the receiving optical fiber is set to The material of the transmitting fiber and the receiving fiber is quartz, and the radius of the transmitting fiber and the receiving fiber is ; S2: Determine the scanning surface and its area. The scanning light path outputs laser light through the lens in the voice coil motor and irradiates 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 of the object to be measured is calculated using the light power reflected from the scanning surface and the light power emitted by the scanning platform. ; In step S3, the process of calculating the displacement information is as follows: Calculate the average emitted light power based on the scan area and the average received optical power ; The radius of the light spot emitted by the optical fiber at the object to be measured is: ； The change in the received light intensity and the distance between the object being measured is expressed as: ； In the above formula, Indicates that the displacement information is In the case of , the radius of the spot under Gaussian distribution of light intensity is, is the radial coordinate of the light spot; The numerical aperture angle formula of the receiving fiber and the transmitting fiber is: ； In the above formula, is the numerical aperture of the transmitting and receiving optical fibers. When the outgoing light hits the surface of the object and is then reflected, the model containing the information of the object is as follows: ； In the above formula, is the roughness of the reflecting surface, 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 ; In the polar coordinate system, the formula for the cross-area of ​​the transmitting and receiving optical fibers is as follows: ； Among them To calculate the parameters, the formula is as follows: ； Then the intensity modulation function M The formula is: ； In the above formula, put in the actual value, according to and displacement information The relationship between the two is used to calculate the displacement information. .

2. The scanning method of a scanning optical fiber displacement sensor according to claim 1, characterized in that: In step S2, the scanning process is as follows: The scanning optical path generates laser light, which is pointed vertically at 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.

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