RU2489679C1 - Fibre-optic displacement sensor - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device has an optical radiation source, first and second output fibre-optic guides, first and second fibre-optic guides for optical communication, an input light-guide, first and second photodetectors, a reflecting element, an optical splitter and an electronic signal processing unit. The output o the optical radiation source is connected to the input of the input fibre-optic guide. Outputs of the first and second output fibre-optic guides are connected to inputs of the corresponding first and second photodetectors. The reflecting element is attached to the displaced object on which inputs of the first and second fibre-optic guides for optical communication are directed. Outputs of the first and second fibre-optic guides for communication are connected through the optical splitter to the output of the input fibre-optic guide and to outputs of the corresponding first and second output fibre-optic guides. Outputs of the first and second photodetectors are connected to corresponding inputs of the electronic signal processing unit, which is capable of calculating displacement. The output of the signal processing unit is the output of the entire fibre-optic displacement sensor.

EFFECT: high accuracy of measuring displacement of an object.

3 cl, 3 dwg

Description

The invention relates to measuring equipment, namely to fiber-optic displacement transducers, and can be used to measure acceleration, vibration and pressure.

A known displacement sensor [1], containing a light source, a light guide made in the form of packets of input and output flexible light guides, a photoelectronic multiplier and a recording device.

A disadvantage of the known device is the low accuracy of the conversion of the movement of the object to the modulation of the optical signal due to the dependence of the conversion coefficient on the optical power emitted by the light source and the reflection coefficient of the surface of the object.

The closest technical solution to the proposed one is an optical displacement sensor [2] (prototype), containing a light source, a light guide made in the form of packets of input and output flexible light guides, a photomultiplier and a recording device, equipped with a light control unit made in the form of optically coupled light guides , a photodetector and a light source connected to the latter, and the second end of the light guide is combined in one package with the first two light guides. The output of the packet of optical fibers looks at the reflective element, which is the moving object itself.

In this device, the accuracy of measuring the movement of an object is improved by reducing the dependence of the result of measuring the movement of an object on the power of the radiation source by adjusting the power of the radiation source by an electric signal proportional to the optical power reflected from the moving object.

The disadvantage of the proposed optical displacement sensor is the insufficient accuracy of measuring the displacement of the object, due to the fact that the power of the light source is regulated by an external electrical signal, which is not unique due to thermal fluctuations.

The technical result is to increase the accuracy of measuring the movement of an object.

The technical result is achieved in that the fiber-optic displacement sensor containing an optical radiation source, the output of which is connected to the input of the input fiber-optic optical fiber, the first and second output fiber-optic optical fibers, the outputs of which are connected to the inputs of the first and second photodetectors respectively, contains a reflective an element attached to a moving object, to which the inputs of the first and second fiber optical fibers are directed, an optical splitter, an electric nny signal processing unit configured to calculate displacement using the formula Δs:

, $$\Delta s=k\frac{U_{\mathrm{one}}-U_2}{U_{\mathrm{one}}+U_2}$$

,

where k is the conversion coefficient; U ₁ , U ₂ - signals from the first and second photodetectors, respectively, and the outputs of the first and second fiber communication optical fibers are connected through an optical splitter to the output of the fiber supply optical fiber and to the inputs of the corresponding first and second output fiber optical fibers, the outputs of the first and second photodetectors are connected to the corresponding the inputs of the electronic signal processing unit, the output of which is the output of the entire fiber-optic displacement sensor.

The technical result is also achieved in that the reflective element is made in the form of a rectangle of light-reflecting material located on a non-reflective surface so that the projections of the light spots from the inputs of the first and second optical communication optical fibers in the absence of object movements are divided in half.

The technical result is also achieved by the fact that the reflective element is made in the form of two rectangular strips adjacent to each other, each of which is divided into reflective and non-reflective regions, the reflective region of the first strip adjacent to the non-reflective region of the second strip, and the non-reflective region of the first strip adjacent to the reflective areas of the second strip so that the boundaries of the reflecting regions of both bands are divided in half the projections of the light spots from the inputs of the first and second optical communication optical fibers and object movements.

Figure 1 shows a diagram of a device.

Figure 2 shows a reflective element in the form of a rectangle of material reflecting light placed on a non-reflective surface, indicating the projections of the inputs of the first and second communication fibers onto the reflective element.

Figure 3 shows the reflective element in the form of two adjacent to each other rectangular regions indicating the projections of the inputs of the first and second communication fibers on the reflective element.

Accepted designations:

1 - reflective element;

2 _1,2 - the first and second fiber optical fibers of optical communication;

3 - optical splitter;

4 _1,2 - the first and second output fiber optic fibers,

5 - lead fiber

6 - source of optical radiation,

7 _1,2 - the first and second photodetectors,

8 - electronic signal processing unit.

The device consists of a reflecting element 1, the first and second optical fiber optical links 2 _{1, 2} , the optical splitter 3, the first and second output fiber optical fibers 4 _1,2 , the input optical fiber 5, the optical radiation source 6, the first and second photodetectors 7 _{1, 2} , the electronic signal processing unit 8.

The reflecting element 1 is attached to a moving object. It is optically coupled to the first and second fiber optic communication optical fibers 2 _1,2 so that the projections of the light spots from the inputs of the optical fibers 2 _1,2 in the absence of movement of the object are divided in half, as shown in Figure 2 or Figure 3. The outputs of the optical fibers 2 _1,2 through the optical splitter 3 are connected to the output of the input fiber 5 and the inputs of the output fibers 4 _1,2 . The input of the input fiber 5 is connected to the optical radiation source 6. The outputs of the optical fibers 4 _{1,2 are} connected to the inputs of the electronic signal processing unit 8 through the respective photodetectors 7 _1,2 . The output of the electronic signal processing unit 8 is the output of the entire fiber-optic displacement sensor.

Fiber optic displacement sensor operates as follows.

After turning on the sensor, the optical radiation source 6 emits a constant-power light beam P ₀ , which is transmitted through an input fiber 5 to an optical splitter 3, in which it is divided into two half-beam beams P ₁ , P ₂ into the first and second optical fibers 2 _1,2, respectively:

P ₁ = k _a P _0/2 , P ₂ = k _a P _0/2 ,

where k _a - power loss in the input fiber 5 and in the optical splitter 3.

, $$P_2^{\text{'}}$$

и вводятся обратно в световоды 2_1,2, в соответствии с формулами:These two beams P ₁ , P ₂ through optical fibers 2 _1,2 are transmitted to the reflecting element 1, from which are reflected in the form $$P_{\mathrm{one}}^{\text{'}\text{'}}$$

, $$P_2^{\text{'}\text{'}}$$

and introduced back into the optical fibers 2 _1,2 , in accordance with the formulas:

,

,

,

,

where k _R is the reflection coefficient of the reflecting element 1;

R, S is the radius and projection area of the end face of each of the optical fibers 2 _1,2 on the plane of the reflecting element 1;

Δs is the desired displacement.

, $$P_2^{\text{'}}$$

поступают в отводящие световоды 4_1,2, по которым передаются на оптические входы фотоприемников 7_1,2, где оптические мощности световых пучков преобразуются в электрические аналоги U₁, U₂ On optical fibers 2 _1.2 through an optical splitter 3 light signals $$P_{\mathrm{one}}^{\text{'}\text{'}}$$

, $$P_2^{\text{'}\text{'}}$$

enter the output fibers 4 _1,2 , through which they are transmitted to the optical inputs of the photodetectors 7 _1,2 , where the optical power of the light beams are converted into electrical analogues U ₁ , U ₂

,

,

,

,

where S _ph is the conversion factor of the photodetectors 7 _1.2 optical power into an electrical signal.

These analogues go to the electronic signal processing unit 8, where the output of the sensor Δs is calculated by the formula:

$$\Delta s=k\frac{U_{\mathrm{one}}-U_2}{U_{\mathrm{one}}+U_2},\left(\mathrm{one}\right)$$

where k is the conversion coefficient of the electronic signal processing unit

. $$k=\frac{S}{2R}$$

.

The reflecting element 1 can be made by applying an aluminum or silver coating to the surface of the moving object.

As the optical fibers 2 _1,2 , 4 _1,2 , 5 and the optical splitter 3 can be used fiber-optic components used in fiber-optic communication lines.

As the source of optical radiation 6, you can use the LED L10762 company HAMAMATSU PHOTONICS.

As the photodetectors 712, you can use photodiodes with a preamplifier S8745-01 company HAMAMATSU PHOTONICS.

As the electronic signal processing unit 8, you can use the ADuC841 micro-converter from Analog Devices, which includes analog-to-digital converters of the input signals from photodetectors 7 _1,2 , a microprocessor to perform calculations according to formula (1), and a digital-to-analog converter of the output signal.

Thus, at the output of the sensor, a signal is obtained proportional to the movement of the moving object, which does not depend on fluctuations in the power of the radiation source 6, as in the prototype.

Information sources

1. USSR copyright certificate No. 225464, cl. G01B 11/02, 1968

2. USSR author's certificate No. 938029, cl. G01H 1/00, 1982

Claims (3)

1. Fiber-optic displacement sensor containing an optical radiation source, the output of which is connected to the input of the input fiber optic fiber, the first and second output fiber optic fibers, the outputs of which are connected to the inputs of the first and second photodetectors, characterized in that it contains reflective an element attached to a moving object, to which the inputs of the first and second fiber optic optical fibers are directed, an optical splitter, an electronic processing unit signals, configured to calculate the displacement Δs by the formula:
$$\Delta s=k\frac{U_{\mathrm{one}}-U_2}{U_{\mathrm{one}}+U_2}$$

,
where k is the conversion coefficient; U ₁ , U ₂ - signals from the first and second photodetectors, respectively, and the outputs of the first and second fiber communication optical fibers are connected through an optical splitter to the output of the fiber supply optical fiber and to the inputs of the corresponding first and second output fiber optical fibers, the outputs of the first and second photodetectors are connected to the corresponding the inputs of the electronic signal processing unit, the output of which is the output of the entire fiber-optic displacement sensor. 2. The fiber-optic displacement sensor according to claim 1, characterized in that the reflective element is made in the form of a rectangle of light-reflecting material located on a non-reflective surface so that the projections of light spots from the inputs of the first and second optical communication optical fibers in the absence of object movements divided in half. 3. The fiber-optic displacement sensor according to claim 1, characterized in that the reflective element is made in the form of two rectangular bands adjacent to each other, each of which is divided into a reflective and non-reflective region, the reflective region of the first strip adjacent to the non-reflective region of the second strip and the non-reflecting region of the first strip adjoins the reflecting region of the second strip so that the boundaries of the reflecting regions of both bands divide in half the projections of the light spots from the inputs of the first and second optical fibers communication in the absence of object movements.

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