CN106840366A - A kind of homodyne orthogonal fibre interferes vibration detecting device - Google Patents

Abstract

A homodyne orthogonal optical fiber interference vibrometer device, said device comprising: a laser light source (1), a first polarization controller (2), a polarization-maintaining 2×2 coupler (3), a second polarization controller (4 ), piezoelectric ceramics (5), vibration sensing probe (8), first reflector (6), second reflector (7), polarizing beam splitter (9), photodetector 1 (11), photoelectric Detector 2 (10), vibration demodulation module (12). The linearly polarized light emitted by the laser light source is transformed into circularly polarized light by the first polarization controller, and is divided into two beams by the polarization-maintaining 2×2 coupler. The first beam passes through the second polarization controller, piezoelectric ceramics, and the first reflector Reflection; the second beam passes through the vibration sensing probe, reflected by the second mirror, and the two reflected lights are transmitted to the polarization beam splitter through the polarization-maintaining 2×2 coupler and are divided into two orthogonal interference signals, which are respectively received by the photodetector 1 and Received by the photodetector 2, the two orthogonal interference signals are demodulated by the vibration demodulation module to obtain high-precision measured vibration information.

Description

A Homodyne Orthogonal Optical Fiber Interferometric Vibration Measurement Device

technical field

The invention belongs to the field of detection instruments, and mainly introduces a homodyne orthogonal optical fiber interference vibration measurement device.

Background technique

In recent years, with the rapid development of modern industry and new technologies, the precision of vibration measurement devices has become higher and higher. Optical methods for high-precision measurement of vibration signals have received extensive attention, especially in some specific research fields, such as Micro-nano measurement in precision machining, calibration of high-precision and high-sensitivity detectors, etc., have increasingly urgent application requirements. Therefore, high-precision vibration measurement has important practical significance. Therefore, how to find a more accurate method and device for measuring micro-vibration is a very important task.

Based on the existing technology, related instruments and measurement methods have appeared one after another, such as: dual-frequency laser interferometric vibrometer (Cheng Zhaogu; Gao Haijun, dual-frequency laser interferometer, CN200410052915.3), homodyne laser interferometric vibrometer (Wang Ming etc. Orthogonal homodyne laser interferometer and its measurement method, CN201510287943.1), but these instruments have the disadvantages of bulky, discrete optical components, complex optical path adjustment, etc., so how to improve the accuracy and simplify the device at the same time to realize automation Adjusting the measurements and obtaining higher-precision measurements is an urgent problem to be solved.

Contents of the invention

The purpose of the present invention is to provide a homodyne orthogonal optical fiber interference vibration measurement device. The present invention is aimed at the application of high-precision vibration measurement and provides a high-precision, high-stability optical fiber type vibration measurement device based on homodyne orthogonal interference technology. .

A homodyne orthogonal optical fiber interference vibrometer device of the present invention, said device comprising: a laser light source (1), a first polarization controller (2), a polarization maintaining 2×2 coupler (3), a second polarization controller device (4), piezoelectric ceramics (5), vibration sensing probe (8), first reflector (6), second reflector (7), polarizing beam splitter (9), photodetector 1 (11 ), photodetector 2 (10), vibration demodulation module (12). The linearly polarized light emitted by the laser light source becomes circularly polarized light through the first polarization controller, and is divided into two beams through the polarization maintaining 2×2 coupler. The first beam passes through the second polarization controller, piezoelectric ceramics, and the first mirror Reflection; the second beam passes through the vibration sensing probe, reflected by the second mirror, and the two reflected lights are transmitted to the polarization beam splitter through the polarization-maintaining 2×2 coupler and are divided into two orthogonal interference signals, which are respectively received by the photodetector 1 and Received by the photodetector 2, the two orthogonal interference signals are demodulated by the vibration demodulation module to obtain high-precision measured vibration information.

As shown in Figure 3, the orthogonal signals I ₁ (t) and I ₂ (t) received by photodetector 1 and photodetector 2 are respectively:

Here, I ₀ is the light intensity of the light emitted by the laser light source, k _v is the visibility of interference fringes, The relationship between the phase change signal of the measured interferometer and the elongation ΔL of the vibration sensing probe fiber caused by the measured vibration is as follows:

Here n is the refractive index of the fiber core, and _λ0 is the wavelength propagating in vacuum.

The demodulation module analyzes the combination of signals received by photodetector 1 and photodetector 2, and uses the electrical signal of photodetector 1 to perform interference signal changes to record the corresponding optical fiber elongation of the vibration sensing probe, and the optical fiber elongation When the amount increases by half the wavelength length λ ₀ /2 (point A changes from bottom to top in Figure 3), the signal of photodetector 1 changes by π, while the electrical signal of photodetector 2 changes from small to large and passes through the DC bias I ₀ , while the elongation of the optical fiber is shortened by half the wavelength length λ ₀ /2 (point A in Figure 3, changing from top to bottom), the signal of photodetector 1 changes by π, and the electrical signal of photodetector 2 changes from large to Small passing through the DC bias I ₀ , so the photodetector 2 is the vibration direction judgment signal, and the photodetector 1 is the interference signal accumulation signal, and the two are used together to obtain high-precision vibration change information.

Advantages of the present invention:

(1) The optical path directly obtains two orthogonal optical signals, reducing the difficulty of demodulation module design;

(2) The all-fiber optical path is easy to adjust, the structure is simple, the real-time performance is good, it is convenient for measurement, the measurement speed is fast, and the measurement efficiency is improved;

(3) The probe is easy to make and has high sensitivity;

(4) The piezoelectric ceramic in the optical path is a high-precision control device, which is used to compensate the initial phase difference, thereby improving the accuracy of the entire device.

Description of drawings

FIG. 1 is a structural schematic diagram of a homodyne orthogonal optical fiber interference vibration measuring device of the present invention.

Fig. 2 is the vibration sensing probe of the present invention. The vibration sensing probe includes three parts: a cylindrical elastic element (81), an input polarization-maintaining optical fiber (82), and an output polarization-maintaining optical fiber (83).

FIG. 3 is the detection signals of photodetector 1 and photodetector 2 .

detailed description

The specific embodiment of the present invention is described below in conjunction with accompanying drawing:

As shown in Figure 1, a homodyne orthogonal optical fiber interference vibrometer device of the present invention includes a laser light source (1), a first polarization controller (2), a polarization-maintaining 2×2 coupler (3), a second polarization Controller (4), piezoelectric ceramics (5), vibration sensor probe (8), first mirror (6), second mirror (7), polarization beam splitter (9), photodetector 1 ( 11), photodetector 2 (10), vibration demodulation module (12). The linearly polarized light emitted by the laser light source is transformed into circularly polarized light by the first polarization controller, and is divided into two beams by the polarization-maintaining 2×2 coupler. The first beam passes through the second polarization controller, piezoelectric ceramics, and the first reflector Reflection; The second beam passes through the vibration sensor probe, reflected by the second mirror, and the two reflected lights are transmitted to the polarization beam splitter through the polarization-maintaining 2×2 coupler and are divided into two orthogonal interference signals, which are respectively received by the photodetector 1 and Received by the photodetector 2, the two orthogonal interference signals are demodulated by the vibration demodulation module to obtain high-precision measured vibration information.

As shown in Figure 2, when measuring vibration, the vibration sensing probe is placed directly below the direction in which the measured vibration is applied to directly feel the measured vibration. The present invention provides a probe structure for an orthogonal interference vibration measuring device. The structure is as follows:

The material with high elasticity is processed into a cylindrical elastic element (81), and the specific diameter size is determined by the measured environmental requirements and the minimum curvature radius of the optical fiber. When vibration is applied to the optical fiber, the vibration causes the length of the optical fiber to change, and the light is input from the input polarization-maintaining optical fiber (82), passes through the cylindrical surface and uniformly winds the polarization-maintaining optical fiber, and then is output by the output polarization-maintaining optical fiber (83) carrying vibration information.

Figure 3 shows the signal changes measured by photodetector 1 and photodetector 2. The demodulation module analyzes the combination of signals received by photodetector 1 and photodetector 2, and uses the electrical signal of photodetector 1 to perform The change record of the interference signal corresponds to the elongation of the optical fiber of the vibration sensing probe, and the elongation of the optical fiber increases by half the wavelength length λ ₀ /2 ((point A in Figure 3, changing from bottom to top)), the photodetector 1 signal changes by π, while the electrical signal of photodetector 2 passes through the DC bias value I ₀ from small to large, and the fiber elongation shortens half the wavelength length λ ₀ /2 (point A in Figure 3, from top to down)), the signal of photodetector 1 changes by π, and the electrical signal of photodetector 2 passes through the DC bias value I ₀ from large to small, so photodetector 2 is a signal for judging the vibration direction, while photodetector 1 The signal is accumulated for the interference signal, and the two are used together to obtain high-precision vibration change information.

Claims (7)

1. A homodyne orthogonal optical fiber interference vibrometer device comprising: a laser light source, a first polarization controller, a polarization maintaining 2×2 coupler, a second polarization controller, piezoelectric ceramics, a vibration sensing probe, and a first reflection mirror, a second mirror, a polarizing beam splitter, a photodetector 1, a photodetector 2, and a vibration demodulation module. The linearly polarized light emitted by the laser light source is transformed into circularly polarized light by the first polarization controller, and is divided into two beams by the polarization-maintaining 2×2 coupler. The first beam passes through the second polarization controller, piezoelectric ceramics, and the first reflector Reflection; the second beam passes through the vibration sensing probe, reflected by the second mirror, and the two reflected lights are transmitted to the polarization beam splitter through the polarization-maintaining 2×2 coupler and are divided into two orthogonal interference signals, which are respectively received by the photodetector 1 and Received by the photodetector 2, the two orthogonal interference signals are demodulated by the vibration demodulation module to obtain high-precision measured vibration information. 2 . A homodyne orthogonal optical fiber interference vibrometer according to claim 1 , wherein the laser light source is a laser light source that outputs polarization-maintaining laser light. 3. A homodyne orthogonal optical fiber interference vibrometer according to claim 2, characterized in that the first polarization controller changes the polarization state of light into circularly polarized light. 4. A homodyne orthogonal optical fiber interference vibrometer according to claim 2, characterized in that: the polarization maintaining 2×2 coupler has a splitting ratio of 50:50. 5. A homodyne orthogonal optical fiber interference vibration measurement device according to claim 2, characterized in that the piezoelectric ceramic is a high-precision control device, which is used to compensate the initial phase difference, thereby improving the accuracy of the entire device. 6. A homodyne orthogonal optical fiber interference vibrometer device according to claim 2, characterized in that: the polarization beam splitter divides the interference signal into two beams of orthogonal interference signals. 7. A homodyne orthogonal optical fiber interference vibrometer according to claim 2, characterized in that: the vibration demodulation module records the change of the interference signal according to the electrical signal of the photodetector 1 and records the corresponding vibration sensing probe The elongation of the optical fiber, when the elongation of the optical fiber changes by half the wavelength length (micron order), the signal of the photodetector 1 changes by π, and the electric signal of the photodetector 2 is used to judge the vibration direction, so as to obtain high-precision vibration change information.