RU125728U1 - DEVICE FOR MEASURING LINEAR MOVEMENTS OF OBJECTS WITH A FLAT MIRROR-REFLECTING SURFACE - Google Patents

Abstract

A device for measuring linear displacements of objects with a flat mirror-reflecting surface, containing a central fiber, peripheral output fiber fibers with the same aperture angle Θ, photodetectors optically coupled to the central and peripheral optical fibers, respectively, a signal ratio generating unit, a collimation device located between the radiation source and a central fiber waveguide, characterized in that the central fiber is made in the form of a fiber optic cable, with holding input optical fibers coupled to a radiation source and output optical fibers coupled to a photodetector, and signals from output optical fibers of a central optical fiber cable and peripheral optical fibers assembled into a single bundle are connected to the signal ratio generating unit, the ratio of the input and output optical fibers in the optical fiber cable is 3: 4, and the mirror-reflecting surface is located relative to the end of the optical fiber matic cable at a distance x> τ, where τ- distance beamforming.

Description

The proposed technical solution relates to measuring technology and can be used in fiber-optic measuring systems for non-contact measurements of various physical quantities, for example, pressure, temperature, linear displacements, etc.

The closest technical solution is a device for measuring the linear displacements of objects with a flat mirror-reflecting surface, containing a central fiber, peripheral output fiber fibers with the same aperture angle Θ, photodetectors optically coupled to the central and peripheral fibers, a collimation device located between the radiation source and the central fiber light guide (see RF patent No. 78946, class G01N 21/55).

The disadvantage of the analogue is the low accuracy of measurements associated with errors due to energy losses in the blocks and nodes of the device and their instability.

The main contribution to the energy loss of the system is made by:

- node input optical radiation from a radiation source into the optical fiber;

- attenuation of radiation in driving optical fibers;

- informative and non-informative loss of optical power in the measuring transducer;

- attenuation of radiation in the output optical fibers;

- node input optical radiation from the output optical fibers into the photodetector.

The purpose of this technical solution is to compensate for the optical loss introduced and to increase the measurement accuracy and sensitivity of the device.

The solution to this problem is ensured by the fact that the central fiber is made in the form of a fiber optic cable (FOC), containing the supply optical fibers (POV), coupled to the radiation source, and the output optical fibers (BOB), coupled to the radiation receiver, and to the formation unit signal ratios, signals are connected from the OOK VOK of the central fiber and the peripheral optical fibers assembled into a single bundle, while the numerical ratio of the OVO and OOV in the VOK is 3: 4, and the mirror-reflecting surface (RF) is located ene respect to the end FOC at a distance x _0> τkr where τ _cr - distance beamforming.

Figure 1 shows the device, a top view, that is, the relative position of the optical fibers located in the same plane of the end face of the wok, figure 2 presents a functional diagram of the device.

The device (figure 1) contains a Central fiber, made in the form of a fiber optic cable 1 containing POV and OOB. Around the wok there are additional (peripheral) OOBs assembled in one bundle 2.

The lead-in optical fibers 3, 4, 5, assembled into a bundle, and the lead-out optical fibers 6, 7, 8, 9 are placed in the wok as shown in FIG.

Additional (peripheral) OOV 10 are placed around the wok 1, which minimizes the loss of optical radiation when it is reflected from the RF. The ends of all optical fibers 3-10 lie in the same plane and face the RF.

The number and location of SOMs and SFAs in woks are not accidental. Of all the possible options for the placement of SOMs and SOMs in the end face of the wok (1: 6, 4: 3, 3: 4, etc.), the proposed arrangement of fibers (3: 4) has maximum efficiency.

With this arrangement of the POV and OOB, the maximum sensitivity of the device is achieved and the maximum output power of the optical signal is provided at the output, that is, only in this case each of the emitting fibers (POV) will make the maximum contribution to the response of the radiation receiver. In addition, the proposed ratio of POV and OOB (3: 4) minimizes losses when pairing the radiation source (AI) and POV and facilitates adjustment by the level of the output signal with angular mismatch of the radiation pattern of the AI with the input end of the POV.

Figure 2 shows the wok 1 containing POV 3, 4, 5 and OOB 6, 7, 8, 9. Around the wok 1 there are additional (peripheral) OOB 10 assembled into a bundle 11. AI 12 through the collimation device 13 is paired with 3, 4, 5. In turn, OOBs 6, 7, 8, 9 are docked with photodetector 14, peripheral OOBs assembled in bundle 2 are docked with photodetector 15. Photodetectors 14 and 15 are connected to signal ratio generating unit 16.

The reflecting mirror surface 17 positioned relative to end FOC 1 at a certain distance x _0> τkr where τ _kr - distance on X axis from the end of FO to CP 17, wherein reflected from the CP 17, the luminous flux is a ring forming a uniform illuminance Z plane perpendicular to X, τ _cr is called the distance of formation of the light beam.

The device operates as follows (figure 2).

Formed by the collimation device 13, the light beam from the radiation source 12 through the POV 3, 4, 5 enters the mirror-reflecting surface of the RF 17, is reflected from it, returns to the output end of the wok 1 and then through the OOV 6, 7, 8, 9 and an additional bundle OOB 2 hits the photodetector 14 and the photodetector 15, respectively.

The signal processing unit 16 generates the ratio of the signals taken from the photodetectors 14 and 15. If the end face of the wok 1 is in contact with the RF 17, that is, x = 0, then the light flux reflected from the RF 17 does not fall on the ends of the OOV 6, 7, 8 , 9, neither at the ends of the peripheral OOB 2. As x increases, the area of the “spot” reflected from the RF 17 increases and, consequently, the power of the light flux transmitted to the end face of the wok 1 increases.

At x = τ _{cr, the} reflected spot on the end face of the wok 1 is a ring whose outer radius is R _int (x) = 2 · x · tgΘ _NA , and the inner R _intm (x) = R _int (x) -2 · r _c ,

where r _c is the radius of the fiber. The area of the ring is

and will depend on the distance x between the end face of the wok 1 and ZP 17.

Inside the ring, the illumination of the end face of the wok 1 is uniform.

As x increases further, the light “ring” reflected from the RF 17, moving along the end face of the VOK 1, reaches the peripheral OOV 2, illuminates their ends, the photodetector 15 captures the power of the light flux transmitted through the bundle 2. Block 16 fixes the ratio of signals taken from photodetectors 14 and 15.

The device conversion function is a complex multi-stage dependence of the photodetector current I (x) on external influences (movements). For the output optical fibers OOB 3, it has the form

,

,

where Ф ₀ is the radiation intensity of the light source;

Ф _ип1 (х) - conversion function for the path "POV-ZP-OOV";

To ₁ is the coefficient of optical radiation power loss in the area from the radiation source 12 to the photodetector 14;

Q ₁ is the integrated sensitivity of the photodetector 14.

The value of the coefficient K ₁ is determined from the ratio:

,

,

where k ₁ is the coefficient of radiation power loss when pairing the radiation source 12 with POV;

k ₂ - attenuation coefficient of the radiation power in the POV;

k ₃ - informative and non-informative loss of radiation power from RF 17 to the end of the wok 1;

k ₄ - attenuation coefficient of radiation power in OOB;

k ₅ - coefficient of radiation power loss when pairing OOV with the photodetector 14.

The transformation function Φ _IP1 (x) is written as

,

,

where ρ is the reflection coefficient of the RFP 17,

ΣS _IP1 (x) - the total illuminated area of the ends of the OOB, fully or partially located in the illuminated area,

ΣS _K (x) is the total area of the end face of the wok 1, illuminated by the light flux reflected from the RF 17 projecting into the ring.

We finally get

.

.

From the expression (1) it follows that the instability of the output signal I ₁ (x) at a constant value of the input parameters of the device is determined by the instability of the parameters k _1,2,3,4,5 .

Unless special measures are taken to stabilize them, the instability of the output signal I ₁ (x) can be significant, which reduces the accuracy of measurements and their reliability.

In order to stabilize the output signal, an additional OOB 2 harness is introduced into the circuit.

Similarly to expression (1), for the photocurrent taken from the photodetector 15, the expression

,

,

where Ф _ИП2 (х) is the conversion function for the path “POV-ZP-OOV” for peripheral OOV assembled into a bundle 2;

To ₂ is the coefficient of optical radiation power loss in the area from the radiation source 12 to the photodetector 15;

Q ₂ is the integrated sensitivity of the photodetector 15.

The value of the coefficient K _{2 is} described by the expression

,

,

where k ₆ is the coefficient of radiation power loss in the additional tow 2,

k ₇ - coefficient of radiation power loss when pairing the photodetector 15 with the output end of the additional tow 2.

The transformation function Φ _IP2 (x) is written as

,

,

where ΣS _IP2 (x) is the total illuminated area of the ends of the OOB in additional tow 2, which are fully or partially located in the illuminated zone.

Finally get

.

.

, фиксируемое в блоке 16, равно Р (согласно формулам (1) и (2))Photocurrent Ratio

fixed in block 16 is equal to P (according to formulas (1) and (2))

.

.

From expression (3) it follows that the parameter P does not depend on the main destabilizing factors: the instability of the radiation intensity of the light source Φ ₀ , the instability of the reflection coefficient ρ ZP 17 and, therefore, on S _K.

It also follows from expression (3) that if the linear displacement water supply contains identical photodetectors for which the integral sensitivity is Q ₁ ≈ Q ₂ and the optical fibers are made of the same material, i.e., k ₄ ≈k ₆ , and the loss at pairing with photodetectors 14 and 15 of the bundles 6, 7, 8, 9 and 2, respectively, are the same, that is, the approximate equality k ₅ ≈k ₇ is achieved, then expression (3) is reduced to

.

.

Figure 3 shows typical graphs of the functions I ₁ (x), I ₂ (x), P (x).

The graph of the function P (x) in the ascending section at x> x ₀ sharply increases to a certain maximum value, after which the modulation depth drops sharply.

From the expression (4) it follows that the steepness of the characteristic P (x) and the range of measurements of the input influences depend on the numerical ratio of the OOB in the wok 1 and the peripheral OW in the additional wiring harness 2, illuminated by a given number of SOW in the wok 1.

Thus, the proposed technical solution differs from the analogue in its expanded functional capabilities, that is, it allows to satisfy a priori specified requirements for water supply due to the numerical ratio of POV and OOB and their corresponding placement, with high measurement accuracy and sensitivity of the device.

Claims (1)

A device for measuring linear displacements of objects with a flat mirror-reflecting surface, containing a central fiber, peripheral output fiber fibers with the same aperture angle Θ _NA , photodetectors optically coupled to the central and peripheral optical fibers, respectively, a signal ratio generating unit, a collimation device located between the radiation source and a Central fiber waveguide, characterized in that the Central fiber is made in the form of a fiber optic cable, containing optical fibers coupled to the radiation source and optical fibers coupled to the photodetector, and signals from the optical fibers of the central optical fiber and peripheral optical fibers assembled into a single bundle are connected to the signal ratio generating unit, the ratio of the input and output optical fibers in the fiber optic cable is 3: 4, and the mirror-reflecting surface is located relative to the end of the fiber pticheskogo cable at a distance x _0> τ _cr, where T _cr - distance beamforming.

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