The light waveguide measuring apparatus of micro angular displacement and method
Technical field
What the present invention relates to is a kind of light waveguide measuring method and device of measurement mechanism and method, particularly a kind of micro angular displacement of micro angular displacement.Belong to the exact instrument technical field.
Background technology
The measurement of micro angular displacement is important influence in geophysics, engineering practice and scientific experiment.In recent decades, along with the development of capacitive sensing techniques, the micro angular displacement sensor has obtained using widely.Micro angular displacement sensor based on capacitance sensing has been widely used in the fields such as detection that the earth's crust tilts at present.Find by literature search, Wu Shuchao etc. are at " Chinese Physics Letters " Vol.20, " the Measurement of the floor tilt in experimental determination of thegravitational constant " that delivers on No.8 (2003) pp1210-1213 (measures the measurement of terrain slope in the universal gravitational constant experiment, " Chinese physics wall bulletin ") literary composition, introduced micro angular displacement sensor in this article based on capacitance sensing, this capacitive angular sensor mainly by: mechanical vibrator and capacitance sensing circuit are formed.Oscillator is a variable capacitance, with the extraneous tilt variation of its response.When oscillator base during with earth's crust run-off the straight, oscillator will be that the center twists with framework relatively with its hitch point, and the pendulum and the electric capacity that constituted of the ceramic external polar plate of plated film of oscillator will change this moment.Because it is very strong to hang the torsion bar rigidity of oscillator, therefore extraneous inclination causes that reversing of detector pendulum is very little, by differential capacitance electric bridge sensing circuit, signal is amplified.For example: it is 1.0 * 10 that the mechanical vibrator base tilts
-7During rad, the displacement of oscillator pendulum correspondence has only 1.3 * 10
-10M.This sensor for temperature and magnetic field are all insensitive, can detect 10 of capacitance
-7Change relatively.But this capacitance sensing detection method has inevitable defective: 1. have electrostatic attraction between pole plate and pendulum, pendulum is not freely to understand fully to influence measurement result; 2. the change of whole polar plate spacing is depended in capacitance measurement, causes the inhomogeneous of capacitor plate spacing and reverse around the pendulum of torsion bar, brings nonlinear effect to measurement; 3. the influence of stray capacitance is big, has influenced sensitivity, has brought interference; 4. the high resistant output state is restricted load capacity.Above factor has determined based on the degree of accuracy of capacitance sensing method angular displacement sensor limited, and the non-constant of long-time stability.
Summary of the invention
The objective of the invention is to overcome the deficiency in existing measuring method and the device, a kind of light waveguide measuring apparatus and method of micro angular displacement are provided, promptly coat the micro angular displacement measuring method and the device of waveguide based on the double-sided metal of mechanical vibrator, utilize reflected light that the ducting layer spacing is changed the variation that responsive characteristic detects the relative optical glass distance between plates of pendulum, accurately determine the angular displacement of pendulum, it is reached to detect 10 around torsion bar
-10The angular displacement of rad.
The present invention is achieved by the following technical solutions, and apparatus of the present invention are accepted part three parts by optics rotation platform, mechanical vibrator structure and photoelectricity and formed.The mechanical vibrator structure is fixed on the optics rotation platform, the optics rotation platform supports whole mechanical vibrator structure, photoelectricity receiving portion branch comprises: laser instrument, polarizer, the optics aperture, photodetector, laser instrument, polarizer, the optics aperture is fixed on outside the rotation platform, they keep contour coaxial, optical axis points to the center of mechanical vibrator structure, photodetector, laser instrument is about the central shaft symmetry of mechanical vibrator structure, the photodetector of the part of photoelectricity acceptance simultaneously is fixed on the optics rotation platform, the optics rotation platform is under the situation that laser positions is fixed, at the uniform velocity change incident light relatively and the incident angle of mechanical vibrator structure, photodetector is with the reverse rotation of twice angular velocity simultaneously, reflected light is dropped on the photodetector, thereby realize the scanning of resonance angle.
The optics rotation platform is made of base for supporting, driving interface and two-layer up and down rotating disk, base for supporting is supporting two-layer rotating disk up and down, driving interface is by the side of screw retention at base for supporting, the rotation center of two-layer rotating disk is coaxial up and down, when motor drives the top rotary table uniform rotation by driving interface, lower rotary table relatively and top rotary table rotate in the opposite direction with twice angular velocity.
The mechanical vibrator structure is fixed on the center of the top rotary table of optics rotation platform.The mechanical vibrator structure comprises: outside framework, pendulum, torsion bar, optical flat, be deposited on metal film, air-gap on the optical flat, be deposited on the metal film on the pendulum, its annexation is: pendulum links to each other with outside framework by torsion bar, metal film deposition is on optical flat, optical flat is fixed on the side of outside framework by screw, metal film face on the optical flat is towards pendulum, and the certain air-gap of middle maintenance.The metal film, air-gap, the pendulum that wherein are deposited on the optical flat constitute a double-sided metal coating waveguiding structure.
Photoelectricity receiving portion branch comprises: laser instrument, polarizer, optics aperture, photodetector.Photodetector is fixed on the outer ring of lower rotary table of optics rotation platform, and laser instrument, polarizer, optics aperture are installed on the outer fixed position of optics rotation platform, and they keep contour coaxial, the center of optical axis sensing mechanical vibrator structure.The laser instrument emitted laser is by polarizer outgoing single polarization, behind the optics aperture, incide the central shaft of mechanical vibrator structure, photodetector, laser instrument are about the central shaft symmetry of mechanical vibrator structure, when guaranteeing to carry out angle scanning with any angular velocity, photodetector can both receive the laser from the optical flat bottom reflection.
When rotation platform is static, open laser instrument, shoot laser passes through polarizer, select single polarization, through obtaining the center of the light incident mechanical vibrator structure of certain spot size behind the optics aperture, reflected light through optical flat and metal film boundary reflection enters photodetector, photodetector links to each other with the digital to analog converter (A/D) of computing machine, computing machine begins data acquisition, drive the optics rotation platform by programmed control, the relative mechanical vibrator of laser instrument mechanism incident angle just changes, observe the result of image data, select to stop to drive the optics rotation platform after the suitable incident angle Continuous Observation record under this incident angle, by the change of light intensity, the angular displacement of inverting oscillator.
In apparatus of the present invention, the mechanical vibrator structure is with being freely between optics glass, there is not the influence of the electrostatic force in the capacitance detecting scheme, light intensity changes very responsive to the spacing between pendulum and the optical glass simultaneously, when pendulum when fork rotates, just can measure micro angular displacement accurately by the variation that detects spacing.
Based on above measurement mechanism, the measuring method of micro angular displacement of the present invention is: the laser instrument emitted laser incides optical flat, after satisfying coupling condition, light enters in the mechanical vibrator structure by optical flat, metal film, air-gap, the double-sided metal that pendulum constitutes coats in the waveguide, utilize reflected light to change very responsive characteristic with the change of air layer thickness, change and change from the light intensity of optical flat bottom reflection spacing along with pendulum optical flat and the mechanical vibrator structure, variable quantity by the detection of reflected light intensity, measure the change of the relative optical glass Board position of pendulum, thereby obtain the angular displacement size of pendulum.
Below the inventive method is done further restriction, method step is as follows:
The first step: select suitable material and relevant parameters for use, the double-level-metal that forms the metal film-air-gap be deposited on the optical flat-be deposited on metal film on the pendulum coats waveguiding structure.The mechanical vibrator structure can be selected the higher materials of hardness such as alloy aluminum usually for use, be processed into the structure that pendulum is connected with outside framework by torsion bar, keep one to connect torsion bar by the line cutting mode between framework and the pendulum, the thickness of pendulum is slightly less than the thickness (about 0.1~1mm) of outside framework, then the pendulum surface is polished with the optics abrasive method, with thickness is that the optical glass of 5mm~10mm is processed into the identical circle of framework radius, and with the optics abrasive method its surface is polished.Sputter coating on pendulum after the polishing and optical flat, metal film can be selected gold or silver for use, the strict control of the thickness requirement of plated film, the thickness of optical glass surface metal film is 30~50nm, the thickness of pendulum metal film on surface is greater than 300nm.Glass plate behind the plated film is assembled with the pendulum structure, and the thickness that constitutes ducting layer in the middle of and be air is about the two-sided clad metal waveguide of the mechanical vibrator structure of 0.1mm~1mm.
Second step: the top rotary table that the mechanical vibrator structure is fixed on the optics rotation platform, and make the bottom surface of optical flat pass through the center of rotation platform, photodetector is fixed on the lower rotary table of optics rotation platform, make that laser instrument and photodetector and optical waveguide are contour, and they are about optical waveguide intermediate shaft symmetry.
The 3rd step: select suitable optical maser wavelength, incident angle and polarizing method; the operation wavelength of LASER Light Source is selected in 560nm~890nm scope; the laser beam of laser instrument output incides on the optical flat with certain incident angle; the selection of incident angle requires in the scope of energy excitation resonance absorption peak; and be in the negative edge of absorption peak; polarization mode rotatory polarization sheet is according to actual needs selected TE mould or the incident of TM mould, regulates slit simultaneously and makes that the hot spot of incident beam is less.
The 4th step: when physical construction response is extraneous when tilting, measure light intensity, calculate pendulum position and angular displacement in real time according to the variation of reflective light intensity from optical flat and metal film boundary reflection laser.
Among the present invention, utilize attenuated total reflection guided mode absorption peak with the highstrung characteristics of pendulum change in location, the laser instrument incident angle is selected in the range of linearity of guided mode absorption peak, utilizes the continuous coverage of photo-detector, just can obtain the micro-displacement of pendulum in real time light intensity.
Compared with prior art, the present invention can be widely used in the measurement of the micro angular displacement of dam, the earth's crust, buildings.The present invention can realize high sensitivity, measure in real time fast, guarantee simultaneously instrument have manufacturing process simple, be easy to realization, miniaturization, contour technical feature is easy to carry.
Description of drawings
Fig. 1 apparatus of the present invention structural representation
Fig. 2 apparatus of the present invention structure vertical view
Fig. 3 apparatus of the present invention mechanical vibrator structural representation (one)
Fig. 4 apparatus of the present invention mechanical vibrator structural representation (two)
Fig. 5 apparatus of the present invention optical flat and metal film structures synoptic diagram ()
Fig. 6 apparatus of the present invention optical flat and metal film synoptic diagram (two)
Embodiment
Arrive shown in Figure 6 as Fig. 1, apparatus of the present invention are by optics rotation platform 1, mechanical vibrator structure 2, accepting part 3 three parts with photoelectricity forms, mechanical vibrator structure 2 is fixed on the optics rotation platform 1, optics rotation platform 1 supports whole mechanical vibrator structure 2, photoelectricity is accepted part 3 and is comprised: laser instrument 4, polarizer 5, optics aperture 6, photodetector 7, laser instrument 4, polarizer 5, optics aperture 6 is fixed on outside the optics rotation platform 1, they keep contour coaxial, optical axis points to the center of mechanical vibrator structure 2, photodetector 7, laser instrument 4 is about the central shaft symmetry of mechanical vibrator structure 2, photodetector 7 is fixed on the optics rotation platform 1 simultaneously, optics rotation platform 1 is under the situation of laser instrument 4 stationkeeping, at the uniform velocity change incident light relatively and the incident angle of mechanical vibrator structure 2, photodetector 7 drops on the photodetector 7 reflected light with the reverse rotation of twice angular velocity simultaneously.
Optics rotation platform 1 is by two-layer rotating disk 8,9 up and down, base for supporting 10 and driving interface 11 constitute, base for supporting 10 is supporting two-layer rotating disk 8,9 up and down, driving interface 11 is by the side of screw retention at base for supporting 10, the rotation center of two-layer up and down rotating disk 8,9 is coaxial, when motor drives top rotary tables 8 uniform rotation by driving interface 11, lower rotary table 9 relatively and top rotary table 8 rotate in the opposite direction with twice angular velocity, photodetector 7 is fixed on the outer ring of lower rotary table 9.
Mechanical vibrator structure 2 is fixed on the center of the top rotary table 8 of optics rotation platform 1, mechanical vibrator structure 2 comprises: outside framework 12, pendulum 13, torsion bar 14, optical flat 15, be deposited on the metal film 16 on the optical flat, air-gap 17, be deposited on the metal film 18 on the pendulum, its annexation is: pendulum 13 is fixing with outside framework 12 by torsion bar 14, metal film 16 is deposited on the optical flat 15, optical flat 15 is fixed on the side of outside framework 12 by screw, 16 metal films 18 on pendulum 13 of metal film on the optical flat 15, and the centre maintains air-gap 17.
Metal-plated membrane respectively on pendulum 13 and the optical flat 15 wherein is deposited on metal film 16, air-gap 17 on the polished surface of optical flat 15, is deposited on metal film 18 on the polished surface of pendulum 13 and constitutes a double-sided metal and coat waveguide.
Content below in conjunction with the inventive method provides embodiment:
Embodiment 1:
The first step: the double-sided metal of making the mechanical vibrator structure coats waveguide.The pendulum external diameter is R=60.0mm, thickness h=9.8mm, and the long b=1.0mm of pendulum torsion bar, the wide w=1.0mm of torsion bar, framework external diameter are D=72.0mm, the spacing of metallic film surface is d=0.1mm on middle pendulum and the outer glass plate.At thickness is 5mm, and refractive index is to plate the golden film that thickness is 36nm on 1.73 the glass plate, and middle pendulum coating film thickness is greater than the golden film of 300nm.
Second step: the double-sided metal coating waveguide of mechanical vibrator structure is installed on the top rotary table of optics rotation platform, photomultiplier is fixed on the lower rotary table of optics rotation platform, make that laser instrument and photomultiplier are contour with optical waveguide, and they are about optical waveguide intermediate shaft symmetry.
The 3rd the step: the wavelength of incident laser is 560.0nm, the refractive index that records golden film be ε=-8.2+i1.79.Computer drives optics rotation platform makes the incident angle of laser beam beam incident optical glass plate be about 2.755 °.At this moment, excitation resonance absorption peak on request, and be in the negative edge of guided mode linear zone.Incident light is a transverse electric wave.
The 4th step: when the extraneous inclination of mechanical vibrator structural response, receive and measure the light intensity of reflector laser, data processing obtains the angular displacement of pendulum.
Show that according to calculating the measurement to spacing can reach 3.5 * 10
-11M, corresponding angles displacement detection accuracy is 5.8 * 10
-10Rad (the intensity of reflected light variation approximates 0.2%).When pendulum and glass plate spacing changed, the variation of reflective light intensity was listed as follows:
Pendulum and glass plate spacing (rice) | Counter-bevel changes (radian) | Reflective light intensity (number percent) |
1.0×10
-4+3.5×10
-11 1.0×10
-4+7.0×10
-11 1.0×10
-4+1.05×10
-11 1.0×10
-4+1.4×10
-10 1.0×10
-4+1.75×10
-10 | 5.8×10
-10 1.16×10
-9 1.74×10
-9 2.32×10
-9 2.9×10
-9 | 43.9% 44.1% 44.3% 44.5% 44.7% |
Embodiment 2:
The first step: the double-sided metal of making the mechanical vibrator structure coats waveguide.The pendulum external diameter is R=60.0mm, thickness h=9.0mm, and the long b=1.0mm of pendulum torsion bar, the wide w=1.0mm of torsion bar, framework external diameter are D=72.0mm, the spacing of metallic film surface is d=0.5mm on middle pendulum and the glass plate.Be about 5mm at thickness, refractive index is to plate the golden film that thickness is 39nm on 1.73 the glass plate, plates the golden film of thickness greater than 300nm on middle pendulum.
Second step: the double-sided metal coating waveguide of mechanical vibrator structure is installed on the top rotary table of optics rotation platform, photomultiplier is fixed on the lower rotary table of optics rotation platform, make that laser instrument and photomultiplier are contour with optical waveguide, and they are about optical waveguide intermediate shaft symmetry.
The 3rd the step: optical maser wavelength is 690.0nm, the refractive index that records golden film be ε=-14.4+i1.22.Computer drives optics rotation platform makes the incident angle of laser beam beam incident optical glass plate be about 0.81 °.At this moment, can require the excitation resonance absorption peak, and be in the negative edge of guided mode linear zone.Incident light is a transverse electric wave.
The 4th step: when the extraneous inclination of mechanical vibrator structural response, receive and measure the light intensity of reflector laser, data processing obtains the angular displacement of pendulum.
Show that according to calculating the measurement to spacing can reach 1.5 * 10
-11M, corresponding angles displacement detection accuracy is 2.5 * 10
-10Rad (the intensity of reflected light variation approximates 0.2%).When pendulum and glass plate spacing changed, the variation of reflective light intensity was listed as follows:
Pendulum and glass plate spacing (rice) | Counter-bevel changes (radian) | Reflective light intensity (number percent) |
1.0×10
-4+1.5×10
-11 1.0×10
-4+3.0×10
-11 1.0×10
-4+4.5×10
-11 1.0×10
-4+6.0×10
-11 1.0×10
-4+7.5×10
-10 | 2.5×10
-10 5.0×10
-10 7.5×10
-10 1.0×10
-9 1.25×10
-9 | 41.0% 41.2% 41.4% 41.6% 41.8% |
Embodiment 3:
The first step: the double-sided metal of making the mechanical vibrator structure coats waveguide.The pendulum external diameter is R=60.0mm, thickness h=8mm, and the long b=1.0mm of torsion bar, the wide w=1.0mm of torsion bar, framework external diameter are D=72.0mm, middle oscillator is d=1.0mm with the spacing on outer layer metal film surface.At thickness is 5mm, and refractive index is to plate the golden film that thickness is 30nm on 1.73 the glass plate, plates the golden film of thickness greater than 300nm on middle pendulum.
Second step: the double-sided metal coating waveguide of mechanical vibrator structure is installed on the top rotary table of optics rotation platform, photomultiplier is fixed on the lower rotary table of optics rotation platform, make that laser instrument and photomultiplier are contour with optical waveguide, and they are about optical waveguide intermediate shaft symmetry.
The 3rd the step: optical maser wavelength is 890.0nm, the refractive index that records golden film be ε=-34.5+i2.47.The rotary optical platform makes the incident angle of the outer glass plate of laser beam incident be about 1.125 °.Excitation resonance absorption peak on request, and be in the negative edge of guided mode linear zone.Incident light is a transverse electric wave.
The 4th step: when the extraneous inclination of mechanical vibrator structural response, receive and measure the light intensity of reflector laser, data processing obtains the angular displacement of pendulum.
Show that according to calculating the measurement to spacing can reach 1.3 * 10
-11M, corresponding angles displacement detection accuracy is 2.2 * 10
-10Rad (the intensity of reflected light variation approximates 0.2%).When pendulum and glass plate spacing changed, reflective light intensity changed and is listed as follows:
Pendulum and glass plate spacing (rice) | Counter-bevel changes (radian) | Reflective light intensity (number percent) |
1.0×10
-4+1.3×10
-11 1.0×10
-4+2.6×10
-11 1.0×10
-4+3.9×10
-11 1.0×10
-4+5.2×10
-11 1.0×10
-4+6.5×10
-10 | 2.2×10
-10 4.4×10
-10 6.6×10
-10 8.8×10
-10 1.1×10
-9 | 36.8% 37.0% 37.2% 37.4% 37.6% |