CN108662988A - A kind of inclination angular misalignment optical intensity modulation type fiber-optic sensor probe - Google Patents

Abstract

The invention relates to a tilt angle dislocation reflective intensity modulation optical fiber sensor probe, which includes a sending optical fiber, a receiving optical fiber, and a sleeve for encapsulating the sending optical fiber and the receiving optical fiber; one end of the sending optical fiber is connected to a laser emitting light, and the receiving optical fiber and The optical paths are respectively connected to the photodetectors; the characteristic is that the optical fiber sensor probe takes the center of the sending fiber as the axis, the sending fiber is arranged in the center of the probe, the receiving fiber and the sending fiber form a β angle, and are evenly distributed around the sending fiber, and the receiving fiber is evenly distributed around the sending fiber. The end of the optical fiber and the sending optical fiber are all closely arranged, that is, the optical fiber sensor probe is a coaxial structure; the probe of the present invention can complete the effective measurement of the point with a large curvature on the surface, not only can reduce the dead zone, improve the sensitivity but also The range of the linear measurement interval can be expanded, and the performance of the reflective intensity modulation optical fiber sensor is greatly improved.

Description

An inclination angle dislocation reflective intensity modulation optical fiber sensor probe

technical field

The invention belongs to the technical field of optical fiber sensing, and in particular relates to an inclination angle dislocation reflective intensity modulation optical fiber sensor probe.

Background technique

Optical fiber sensor is a new type of sensor developed rapidly in the 1970s. In recent decades, with the continuous development of fiber optic technology, fiber optic sensor technology has matured in a variety of non-contact measurement systems. Reflective intensity modulation (RIM) fiber optic sensors are widely used in Surface topography measurement.

When measuring the surface topography of an object, it is inevitable to encounter a point with a large curvature. At this time, the angle of the reflected light will be large. If there are more points with a large curvature change on the measured surface, the light entering the receiving fiber will be correspondingly reduced. . Moreover, the RIM-type optical fiber sensor measures the surface topography through the change of light intensity, so the compensation of light intensity is particularly important. Therefore, in order to improve the measurement area and measurement range of the measurement system, it is necessary to improve the structure of the fiber optic probe.

At present, the end faces of common reflective fiber optic sensor probes are mainly planes, that is, the fiber ends of the outgoing fiber and the incident fiber are on the same plane, and the internal fiber bundles are mainly arranged in random, parallel, coaxial and semicircular shapes. Arrangement, various arrangements affect the size of the measurement range and the level of sensitivity. Most of the optical fiber probes for measuring the surface topography or roughness of two objects are single-turn coaxial or double-turn coaxial structures. The end faces of these two structures are flat, and the sending fiber and receiving fiber are in the same plane. . Because the sending fiber and receiving fiber are closely arranged, the structure in the same plane will lose a lot of data when measuring the plane of the point with larger curvature.

When compensating the light intensity, the commonly used compensation structure is divided into two types, one is to use a three-fiber compensation structure, and the other is to introduce a reference optical path from the laser as compensation. The three-ray compensation structure can use the correlation and difference of two sets of information to process data to achieve the purpose of compensation, but there is no way to eliminate the problems of light source fluctuation and zero drift.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings and deficiencies of the structure of the optical fiber sensor probe, and propose a tilt angle dislocation reflective intensity modulation optical fiber sensor probe that can reduce the dead zone, increase the linear measurement range, and improve the measurement sensitivity.

For realizing the above object, technical scheme of the present invention is:

An inclination angle dislocation reflective intensity modulation optical fiber sensor probe, comprising a sending fiber 1, a receiving fiber 2, and a metal sleeve encapsulating the sending fiber 1 and receiving fiber 2; one end of the sending fiber is connected to a laser emitting light , the receiving optical fiber and the reference optical path are respectively connected to the photodetector; it is characterized in that: the optical fiber sensor probe is based on the center of the transmitting optical fiber, the transmitting optical fiber is arranged in the center of the probe, and the receiving optical fiber and the transmitting optical fiber form an angle of β 4. They are evenly distributed around the sending optical fiber, and the ends of the receiving optical fiber and the sending optical fiber are closely arranged, that is, the optical fiber sensor probe is a coaxial structure.

There are six receiving optical fibers, and there is an inwardly shrinking misalignment 3 between the end faces of the sending optical fibers and the receiving optical fibers.

The receiving optical fiber, the reference light path and the photodetector are all coupled and connected by FC connectors.

The transmitting optical fiber is a multimode optical fiber with a core diameter of 9 μm, and the receiving optical fiber is a multimode optical fiber with a core diameter of 65 μm.

The receiving optical fiber and the sending optical fiber form an inclination angle β=2°.

The misalignment between the end face of the sending fiber and the end face of the receiving fiber is 200um.

Compared with the prior art, the present invention has substantive features and remarkable effects:

The probe structure of the present invention is improved based on the single-circle coaxial probe structure to adopt a misplaced optical fiber probe structure including an inclination angle, which can complete the effective measurement of points on the surface including large curvature, not only can reduce the dead zone, but also improve the sensitivity. The range of the linear measurement interval can be expanded, and the performance of the reflective intensity modulation optical fiber sensor is greatly improved.

Description of drawings

Fig. 1 is a structural schematic diagram of an inclination angle dislocation reflective intensity modulation optical fiber sensor probe of the present invention.

Fig. 2 is an axonometric three-dimensional schematic diagram of the present invention.

Fig. 3 is a structural diagram including a reference optical path of the measurement system of the present invention.

Fig. 4 is a comparison diagram of the modulation characteristic curves of the misaligned fiber optic probe and the coaxial fiber optic probe including the inclination angle of the present invention.

Detailed ways

As shown in FIG. 1 and FIG. 2 , it is a structural schematic diagram and an axonometric view of an inclination angle dislocation reflective intensity modulation optical fiber sensor probe of the present invention. This specific implementation takes the structure with two layers of receiving optical fibers as an example, and the metal sleeve encapsulating the transmitting optical fiber 1 and receiving optical fiber 2; the protection scope of the present invention is not limited to the example.

An inclination angle dislocation reflective intensity modulation optical fiber sensor probe is composed of one sending optical fiber and six inclined receiving optical fibers. The sending fiber is located in the center of the fiber optic probe, and the tail ends of the six inclined receiving fibers forming an angle of β with the sending fiber are closely arranged due to the sending light. The misalignment h is the indentation h (μm) parallel to the direction of the receiving fiber to the inside of the probe. In the figure, r1 and r2 are the radii of the sending fiber and receiving fiber respectively, θ is the maximum exit angle of the sending fiber, θ=arcsin(NA), and NA is the numerical aperture of the sending fiber. d is the distance between the fiber optic probe and the reflecting surface.

The gap between the transmitting optical fiber and the receiving optical fiber can be packaged as the probe of the optical fiber sensor by the metal sleeve after the relative position is fixed.

As shown in Fig. 3, the measuring system of a kind of inclination angle dislocation reflective intensity modulation optical fiber sensor of the present invention, this system comprises host computer, light source (laser), photodetector, optical fiber sensor probe of the present invention, and measured object ;

One end of the sending fiber of the optical fiber sensor probe of the present invention is coupled and connected with the tail fiber of the laser, and the other end is divided into two paths, one is used as the sending fiber in the fiber optic probe, and the other is used as the reference optical path, and a fusion fiber with minimal loss is used here. The six receiving optical fibers and the reference light path are respectively coupled and connected to the two ports of the photodetector using FC connectors. The receiving optical fiber carries a wavelength of 1550nm and a light intensity of I(r)

Gaussian light reflected by the surface of the measured object; where: P ₀ is the power of the laser, w(2d) is the beam radius of the outgoing light at a distance of 2d from the end face of the sending fiber, and d is the distance between the fiber probe and the reflecting surface . r is the radial integration variable.

The reference optical path only carries the information of the light source, and the ratio of the two signals obtained by the photodetector can eliminate the error caused by the fluctuation and drift of the light source to the measurement system. The data information after the ratio is the relationship between displacement and light intensity, that is, the modulation characteristic curve. This corresponding relationship can be used to scan the surface of the measured object to restore the measured surface topography.

The experimental measurement system adopts LR-SFJ-1550/10Mw laser and JW101 desktop photodetector. The sending fiber adopts a single-mode fiber with a diameter of 9 μm and a cladding diameter of 125 μm and a numerical aperture of NA=0.12, and the receiving fiber adopts a multimode fiber with a diameter of 65 μm and a cladding diameter of 125 μm. The reason why the ends of single-mode fiber and multimode fiber are closely arranged is that the gap will cause the increase of dead zone and the decrease of sensitivity. The maximum exit angle of single-mode fiber θ = arcsin (NA). The numerical aperture NA=0.17 is adopted in the experiment, so the maximum exit angle of the sending fiber is 6°. The misalignment amount is selected as h=200μm, and the inclination angle β=2° is used for the simulation experiment.

The modulation characteristic curve can be obtained through the simulation experiment, as shown in Fig. 4 . By comparing with the modulation characteristic curve of the coaxial fiber optic probe whose end face is flat, it can be seen that the dead zone of the modulation characteristic curve of the misplaced fiber optic probe structure including the inclination angle β=2 is reduced from the original 92.4 μm to 15.5 μm, The reduced dead zone facilitates the measurement of less rough surfaces. The peak value increased from 2.38×10 ^-2 to 3.37×10 ^-2 . The anterior slope linear measurement interval and the posterior slope linear measurement interval increased by 60 μm and 37 μm, respectively. The sensitivity can be fitted by the least square method, and it is increased to 1.94×10 ^-4 compared with the coaxial fiber optic probe, which is nearly 2 times higher.

Therefore, the misplaced optical fiber probe structure including the tilt angle really improves the performance of the reflective intensity-modulated optical fiber sensor.

Claims (6)

1. a kind of inclination angular misalignment optical intensity modulation type fiber-optic sensor probe, including send optical fiber (1), reception optical fiber (2), and encapsulation send optical fiber and reception optical fiber sleeve；One end of the transmission optical fiber and the laser of transmitting light connect It connects, reception optical fiber and reference path are connect with photodetector respectively；It is characterized in that：The fiber-optic sensor probe be with Transmission fiber optic hub is axis, and the transmissions fiber arrangement is at the center of probe, reception optical fiber and transmission optical fiber degree (4) at an angle β, And inclined be evenly distributed on sends around optical fiber, the end of reception optical fiber and send optical fiber be all it is compact arranged, i.e., it is described Fiber-optic sensor probe be coaxial configuration.

2. a kind of inclination angular misalignment optical intensity modulation type fiber-optic sensor probe according to claim 1, feature It is：The reception optical fiber has the six roots of sensation, the oriented magnitude of misalignment inside contracted between transmission fiber end face and the reception optical fiber end face (3)。

3. a kind of inclination angular misalignment optical intensity modulation type fiber-optic sensor probe according to claim 1, feature It is：It is all of coupled connections using FC connectors between the reception optical fiber and reference path and photodetector.

4. a kind of inclination angular misalignment optical intensity modulation type fiber-optic sensor probe according to claim 1, feature It is：The launching fiber is the multimode fibre of 9 μm of core diameter, and reception optical fiber is the multimode fibre of 65 μm of core diameter.

5. a kind of inclination angular misalignment optical intensity modulation type fiber-optic sensor probe according to claim 1, feature It is：The reception optical fiber is with transmission optical fiber at angle of inclination beta=2 °.

6. a kind of inclination angular misalignment optical intensity modulation type fibre optical sensor according to claim 1, it is characterised in that： The magnitude of misalignment sent between fiber end face and reception optical fiber end face is 200um.