CN205785077U - Accurate displacement measurement system based on the double difference interference of laser - Google Patents

Abstract

The disclosed accurate displacement measurement system based on the double difference interference of laser of this utility model, including laser instrument, it is respectively fed to reference interferometer and stellar interferometer after the laser light splitting that laser instrument is launched, reference interferometer and stellar interferometer are connected with frequency mixer, controller in turn after being connected respectively the second Frequency Measurement System and the first Frequency Measurement System, the first Frequency Measurement System and the second Frequency Measurement System parallel connection.Accurate displacement measurement system based on the double difference interference of laser of the present utility model utilizes two groups of heterodyne signals to constitute two groups of interferometers, the laser of two groups of optical interference circuits has been carried out acousto-optic frequency translation respectively, the light beam in each interference group is made to carry out difference interference, detector carries out the average of time domain and frequency-domain demodulation after receiving echo beat signal, so process traditional space-domain signal to become and be changed to time domain process by transform of spatial domain, improve the robustness of measurement system so that the precision measuring system is greatly improved.

Description

Accurate displacement measurement system based on the double difference interference of laser

Technical field

This utility model belongs to technical field of measuring equipment, is specifically related to a kind of displacement essence based on the double difference interference of laser Close measurement system.

Background technology

The development of engineering and manufacturing progress, profound influence the research of Novel measuring detecting instrument.By right Understanding in depth of measurement technology mechanism routine testing work, finds that displacement accurate measurement has general demand and the highest wanting Asking, the geometry state to universal testing machine extensometer displacement, the displacement of machine tool rotary axle, igneous rock cracks as on-the-spot in detection is joined The measurement etc. of the reel machine displacement of number displacement, papermaking and the marsupialisation upper and lower cylinder of processing equipment band.But, current displacement The reading process generally existed during detection is loaded down with trivial details, certainty of measurement is low, measurement error is big, measure time length, cannot be on-the-spot fast The problems such as speed judgement, bring many puzzlements to detection work.

It is currently based on the method that interference technique carries out accurate measurement to displacement more, by regulating the light path of interference system Difference can realize interference fringe movement in receiving plane, and the process to striped is also limited to spatial domain.Due to commercial production ring Border produces the impact on measuring of high-frequency vibration that the displacement of equipment produces the biggest, be easily caused interference fringe spatially Phase distortion.

Utility model content

The purpose of this utility model is to provide a kind of accurate displacement measurement system based on the double difference interference of laser, solves The interference fringe phase distortion in space of displacement measuring device is caused, so that measure owing to producing equipment high-frequency vibration The problem that precision is poor.

This utility model be the technical scheme is that accurate displacement measurement system based on the double difference interference of laser, bag Include laser instrument, after the laser light splitting that laser instrument is launched, be respectively fed to reference interferometer and stellar interferometer, reference interferometer and survey Amount interferometer has been connected respectively the second Frequency Measurement System and the first Frequency Measurement System, the first Frequency Measurement System and the second Frequency Measurement System altogether It is connected with frequency mixer, controller in turn after using same crystal oscillator, the first Frequency Measurement System and the second Frequency Measurement System parallel connection.

Feature of the present utility model also resides in,

Reference interferometer is identical with stellar interferometer structure, all include along light path arrange an Amici prism, two Prism of corner cube and photodetector, laser reflects the same light of tailing edge respectively through two prism of corner cubes after Amici prism light splitting Road enters photodetector.

Photodetector is APD avalanche diode.

The laser that laser instrument is launched is scored eventually through light splitting by diaphragm after collimating lens carries out beam shaping again Reference interferometer and stellar interferometer it is respectively fed to after light.

Frequency mixer be model be the analog multiplier of MC1496.

Laser instrument has been also respectively connected with temperature controller.

Also include current source and PZT modulation voltage source, the first Frequency Measurement System and the second frequency measurement being powered for laser instrument System shares the synchronizing signal that PZT modulation voltage source occurs and makees the control signal of frequency measurement time.

Phase-locked loop circuit it is additionally provided with between frequency mixer and controller.

The integrated chip of phaselocked loop that phase-locked loop circuit uses model to be 74HC4046.

The beneficial effects of the utility model are: accurate displacement measurement system based on the double difference interference of laser of the present utility model System solves the interference fringe phase distortion in space causing displacement measuring device owing to producing equipment high-frequency vibration, so that Obtain the problem that certainty of measurement is poor.Accurate displacement measurement system based on the double difference interference of laser of the present utility model utilizes two groups Heterodyne signal constitutes two groups of interferometers, the laser of two groups of optical interference circuits has been carried out acousto-optic frequency translation respectively, has made each Light beam in interference group carries out difference interference, and detector carries out the average of time domain and Frequency Domain Solution after receiving echo beat signal Adjust, so traditional space-domain signal process is become and be changed to time domain process by transform of spatial domain, improve the Shandong of measurement system Rod so that the precision measuring system can reach 0.01mm.

Accompanying drawing explanation

Fig. 1 is the structural representation of accurate displacement measurement system based on the double difference interference of laser of the present utility model.

In figure, 1. laser instrument, 2. reference interferometer, 3. stellar interferometer, 4. the second Frequency Measurement System, 5. the first frequency measurement system System, 6. crystal oscillator, 7. frequency mixer, 8. controller, 9. collimating lens, 10. diaphragm, 11. temperature controllers, 12. current sources, 13.PZT modulation voltage source.

Detailed description of the invention

With detailed description of the invention, this utility model is described in detail below in conjunction with the accompanying drawings.

The structure of the accurate displacement measurement system based on the double difference interference of laser that this utility model provides as it is shown in figure 1, Its interference system is made up of the class Michelson's interferometer that two structures are identical, is divided into reference interferometer 2 and stellar interferometer 3. Two interferometer utilizations are that the same source laser after same frequency modulation(PFM) beam splitting is interfered.Wherein reference interferometer 2 by Amici prism BS, prism of corner cube CCP, photoelectric detector PD 2 form, and its operating distance dr is constant reference distance；Measure dry Interferometer 3 is made up of Amici prism BS, prism of corner cube CCP and photoelectric detector PD 1 equally, its operating distance dm namely tested Distance.When two photoelectric detector PD 1 are entered recording signal two corresponding Frequency Measurement Systems of feeding respectively with photoelectric detector PD 2 After row mixing, the beat frequency amount of available signal.The circuit structure of the first Frequency Measurement System and 5 second Frequency Measurement Systems 4 is identical, and shares The quartz crystal oscillator signal of one crystal oscillator 6 makees markers, and the synchronizing signal sharing PZT modulation voltage source 13 makees the control of frequency measurement time Signal processed, so their work schedule is identical.Within the measurement time, they measure reference interferometer 2 He the most respectively The photo-beat signal frequency of stellar interferometer 3 output, and measurement data is stored in controller 8 reads measurement data, then count According to process, and then output result of calculation.

The metering system of accurate displacement measurement system based on the double difference interference of laser of the present utility model, has level and erects Straight two kinds.A kind of horizontal displacement being mainly used between guide rail is measured, and first laser interferometry system is fixed in measured object In the metastable plane in body side, it is ensured that unobstructed during laser beam irradiation measured surface, prism of corner cube is fixed on tested table Face, in order to the laser of reflection interferometer outgoing.The fixing seat of prism of corner cube also needs to be fixed on tested surface, and is designed with fine setting Device, the pitching of scalable prism of corner cube and deflection angle so that light beam can return along emergent light axis to participate in interfering and calculate；Separately A kind of displacement measurement being mainly used in the vertical direction such as puller system, including reflecting mirror and the prism of corner cube being fixed on measured surface, The same azimuth regulating prism of corner cube so that light beam is through the correct return of reflecting mirror reflection.

The light source of accurate displacement measurement system based on the double difference interference of laser of the present utility model selects the HONGGUANG of 632nm Semiconductor laser does light source, modulates reference frequency 10MHz, and the wavelength being considered as detector when therefore selecting detector comprises 650nm, response time is in nanosecond.So selecting AD5009-9 type avalanche diode, its parameter is as follows:

Spectral response range: 400～1100nm；Responsiveness: 0.5A/W；

Response time: 0.55ns；Repercussion bias voltage 180～240V.

When utilizing beat measurement, need a stable local oscillation signal carry out with it difference frequency obtain in one, low frequency signal. Local oscillation signal has a stable and the least frequency difference with the main signal that shakes.In order to obtain the frequency signal of high stable low drifting, this The accurate displacement measurement system based on the double difference interference of laser of utility model has selected phase-locked loop circuit.Due to phase-locked loop circuit In be a signal source, by frequency dividing, frequency multiplication produce, therefore can ignore the error that frequency drift is brought.

King oiscillator is produced sinusoidal modulation signal by the active crystal oscillator of 10MHz, becomes the side of 10MHz through zero-crossing comparator Ripple signal, becomes the 5kHz reference signal as phaselocked loop through 2000 frequency dividings, and phaselocked loop is by the reference signal of the 5kHz of input 1999 frequencys multiplication have just obtained the local oscillation signal of we required 9.995MHz, of the present utility model based on the double difference interference of laser Accurate displacement measurement system use the integrated chip of 74HC4046 phaselocked loop.

Additionally, frequency mixer 7 main in accurate displacement measurement system based on the double difference interference of laser of the present utility model Effect is to carry out the local oscillation signal that modulation distance measuring signal and phaselocked loop produce being mixed the intermediate-freuqncy signal obtained as surveying circuitry phase Reference signal, echo ranging signal and local oscillation signal that photodetector receives carry out difference frequency and obtain an intermediate-freuqncy signal conduct Survey the distance measuring signal of circuitry phase.

Accurate displacement measurement system based on the double difference interference of laser of the present utility model uses analog multiplier to be mixed Device, it is few that its mixting circuit constituted has parasitic disturbances, and conversion gain is big, the advantages such as output signal spectrum is pure, to local oscillator electricity The size requirements of pressure amplitude value is low, and between port, isolation is higher.Compare by analysis, use the MC1496 mould of Motorala company Quasi-multiplication device is as frequency mixer.

Exocoel is partly led the frequency of not laser emitting light and is changed by triangular wave rule in time, injects the unequal ginseng of brachium Examine in interferometer and stellar interferometer.Ramping with in descending branch at triangular wave, the frequency of laser of frequency modulation can represent respectively For f_up(t)=f₀+ at and f_down(t)=f₀-at, wherein f₀For laser center frequency, a is laser frequency modulation rate.Then, dry In interferometer, the phase contrast of two coherent light waveses is:

$\mathrm{\φ}\left(t\right)=\frac{4\mathrm{\π}d}{c}(f_0\±at)$

In formula, d is interferometer two-arm length difference, and c is the light velocity in vacuum.

Due to incident laser frequency linearity consecutive variations, interferometer output when reference mirror and measurement mirror are the most static One alternation optical signal, normally referred to as photo-beat.The intensity of photo-beat is:

$I\left(t\right)=I_1\left(t\right)+I_2\left(t\right)+2\sqrt{I_1\left(t\right)I_2\left(t\right)}\·cos(2\mathrm{\π}\frac{2ad}{c}\±\frac{4\mathrm{\π}d}{c}{f}_0)$

Wherein I₁(t) and I₂T () is the light intensity change that laser frequency modulation causes.From above formula, the frequency of photo-beat is

$f_b=\frac{2ad}{c}$

I.e. light beat frequency is directly proportional to interferometer two-arm length difference.

Laser of frequency modulation is injected simultaneously in stellar interferometer and reference interferometer, one in order to measure distance, one in order to Reference is provided.The two-arm length difference d of stellar interferometer_mFor tested distance；The two-arm length difference d of reference interferometer_rImmobilize, For reference distance.Two beat signals can be obtained by above analysis:

f_bm=2ad_m/ c and f_br=2ad_r/c

Thus can obtain find range formula:

$d_m=\frac{f_{bm}}{f_{br}}{d}_r$

Due to reference distance d_rFor it is known that so by respectively measure two interferometers output light beat signal frequency, Tested distance can be directly obtained, it is achieved without guide rail range measurement.

This ranging scheme i.e. utilizes the beat frequency amount of two frequencies and the operating distance of reference interference system to calculate, therefore Certainty of measurement depends on the modulation degree of beat frequency amount, accurate displacement measurement system based on the double difference interference of laser of the present utility model Middle beat frequency is regulated to 100khz, this with the 1Ghz frequency of laser for accounting the least, therefore can realize higher measurement smart Degree.

During use, reference interferometer of the present utility model and stellar interferometer light path are adjusted so that it is form one Complete transmitting and return light path, go out the laser set and respectively enter the light of reference interferometer and stellar interferometer after light path reflects Electric explorer is converted into the signal of telecommunication, be then respectively fed to after the first Frequency Measurement System and the second Frequency Measurement System again through frequency mixer, Final measurement distance value d is obtained by controller after being calculated by above computing formula after phase-locked loop circuit_m。

Claims (9)

1. accurate displacement measurement system based on the double difference interference of laser, it is characterised in that include laser instrument (1), described laser Be respectively fed to reference interferometer (2) and stellar interferometer (3) after the laser light splitting that device (1) is launched, described reference interferometer (2) and Stellar interferometer (3) has been connected respectively the second Frequency Measurement System (4) and the first Frequency Measurement System (5), described first Frequency Measurement System (5) and the second Frequency Measurement System (4) shares same crystal oscillator (6), described first Frequency Measurement System (5) and the second Frequency Measurement System (4) frequency mixer (7), controller (8) it are connected with after parallel connection in turn.

2. accurate displacement measurement system based on the double difference interference of laser as claimed in claim 1, it is characterised in that described ginseng Examine interferometer (2) identical with stellar interferometer (3) structure, all include an Amici prism along light path setting, two pyramids Prism and photodetector, described laser reflects the same light of tailing edge respectively through two prism of corner cubes after Amici prism light splitting Road enters photodetector.

3. accurate displacement measurement system based on the double difference interference of laser as claimed in claim 2, it is characterised in that described light Electric explorer is APD avalanche diode.

4. accurate displacement measurement system based on the double difference interference of laser as claimed in claim 1, it is characterised in that described sharp The laser that light device (1) is launched is scored eventually through light splitting by diaphragm (10) after collimating lens (9) carries out beam shaping again Reference interferometer (2) and stellar interferometer (3) it is respectively fed to after light.

5. accurate displacement measurement system based on the double difference interference of laser as claimed in claim 1, it is characterised in that described mixed Frequently device (7) be model be the analog multiplier of MC1496.

6. accurate displacement measurement system based on the double difference interference of laser as claimed in claim 1, it is characterised in that described sharp Light device (1) is also associated with temperature controller (11).

7. accurate displacement measurement system based on the double difference interference of laser as claimed in claim 1, it is characterised in that also include The current source (12) being powered for described laser instrument (1) and PZT modulation voltage source (13), described first Frequency Measurement System (5) and The synchronizing signal that the shared PZT modulation voltage source of second Frequency Measurement System (4) occurs makees the control signal of frequency measurement time.

8. accurate displacement measurement system based on the double difference interference of laser as claimed in claim 1, it is characterised in that described mixed Frequently it is additionally provided with phase-locked loop circuit between device (7) and controller (8).

9. accurate displacement measurement system based on the double difference interference of laser as claimed in claim 8, it is characterised in that described lock The integrated chip of phaselocked loop that phase loop circuit uses model to be 74HC4046.