CN102243136A - Laser gyro optical resonant cavity loss measurement system based on resonance method - Google Patents

Abstract

The invention discloses a laser gyro optical resonant cavity loss measurement system which mainly solves the problem that the traditional measurement system needs additional systems to complete nonlinear correction of piezoelectric ceramics. The whole measurement system comprises a laser (1), a spherical reflector (2), a two-dimensional parallel flat plate (3), a polaroid (4), a 1/2 wave plate (5), a resonant cavity fixing device (6), a resonance optical signal measurement control device (7), a main control computer (11) and a piezoelectric ceramic driver (12), wherein the laser emits a laser beam, and the laser beam enters a laser gyro resonant cavity to be measured through the spherical reflector, the two-dimensional parallel flat plate, the polaroid and the 1/2 wave plate and generates a resonance light, nonlinearity on the piezoelectric ceramics is accurately corrected by applying different bias voltages to the piezoelectric ceramics, and then the resonant cavity loss is figured out through measuring full width at half maximum of a resonant light power spectral line. The invention has the advantages of high efficiency, low cost and accuracy in measurement, and is suitable for high-precision measurement on laser gyro resonant cavity loss.

Description

Laser gyro optical resonator loss measurement system based on resonance method

Technical field

The invention belongs to field of measuring technique, relate to a kind of measuring system of optical resonator, be mainly used in measurement laser gyro optical resonance cavity loss.

Background technology

At present, about the loss measurement of laser gyro optical resonator, mainly contain two kinds of methods: one is based on the optical cavity ring-down method that the resonator cavity damping time constant is measured, two resonance methods based on the measurement of resonator cavity Free Spectral Range.The optical cavity ring-down method is not subjected to the influence of resonator cavity incoming laser beam light stability, but only can measure lower loss, and to higher loss, measuring accuracy reduces; And resonance method, then one is used for the accurate measurement to middle and high loss.In addition, also have the direct method of measurement based on the saturating anti-instrument of DF, this method is measured simple, but only is applicable to high loss measurement and to the less demanding situation of measuring accuracy.

Domestic measurement Research to the loss of resonator is more, document " the laser gyro loss of resonator and phase difference measurement " (field seapeak etc., 2006, Chinese inertial technology journal) the laser gyro optical resonator loss measurement method based on resonance method has all been done detailed argumentation on principle and device.This method can reach higher precision in theory under the situation of middle and high loss, but owing to the non-linear measuring accuracy influence to this method of piezoelectric ceramics in the frequency sweep laser instrument is bigger.Therefore in actual measurement, at first to carry out gamma correction, so that the laser beam of frequency sweep laser instrument output frequency linear change guarantees the precision of measuring to piezoelectric ceramics; Carry out the accurate measurement of the loss of resonator afterwards again.One measuring method is at present: outside loss of resonator measuring system, correction is measured and finished to an additional in addition cover special measurement device to piezoelectric ceramics non-linear, this measuring system not only increases the complexity of measuring process and measures cost, and has reduced efficiency of measurement.

Summary of the invention

The objective of the invention is to overcome the deficiency of above-mentioned prior art, proposed a kind of laser gyro optical resonator loss measurement system,, reduce cost, improve efficiency of measurement with the simplified measurement process based on resonance method.

For achieving the above object, measuring system of the present invention comprises: laser instrument, spherical reflector, two-dimentional parallel flat, polaroid, 1/2 wave plate, resonator cavity stationary installation, harmonic light signal measurement control device, main control computer and driver circuit for piezoelectric ceramics, wherein, laser instrument adopts single mode frequency sweep laser instrument, this laser instrument is under the control of driver circuit for piezoelectric ceramics, and output frequency is periodically and the laser beam of continuous linear change; The laser beam of this laser instrument output is passed through spherical reflector, two-dimentional parallel flat, polaroid and 1/2 wave plate successively, incide in the testing laser gyro resonator cavity of placing on the resonator cavity stationary installation, in testing laser gyro resonator cavity, excite a plurality of eigenmodes, produce harmonic light, this harmonic light carries out opto-electronic conversion and digital-to-analog conversion through harmonic light signal measurement control device, is transferred on the main control computer; Be provided with USB driver module, gamma correction module, loss measurement module and display interface module in the main control computer, the USB driver module is used to drive instruction transmission and the data acquisition between main control computer and the harmonic light signal measurement control device, and the data that collect are shown in real time and preserves by the display interface module; The gamma correction module applies different bias voltages by the control driver circuit for piezoelectric ceramics to the piezoelectric ceramics on the laser instrument, obtain the different power spectral line of one group of pulsewidth of testing laser gyro resonator cavity output, with this group spectral line is foundation, proofread and correct the non-linear of piezoelectric ceramics, and measure the loss of testing laser gyro resonator cavity by the loss measurement module.

Described driver circuit for piezoelectric ceramics, comprise two DDS signal generators and two high pressure amplifying, each DDS signal generator connects a high pressure amplifying respectively, each DDS signal generator produces the waveform adjustable voltage of 0～5V, by high pressure amplifying with this voltage amplification to 0～240V, and the two ends that are applied to piezoelectric ceramics on the laser instrument are as driving voltage and bias voltage, with the variation of control laser beam frequency.

Described spherical reflector and two-dimentional parallel flat are placed between laser instrument and the resonator cavity stationary installation, are used to regulate angle and the translational movement that laser output laser beam incides testing laser gyro resonator cavity, improve coupling efficiency.

Described polaroid and 1/2 wave plate are placed between laser instrument and the resonator cavity stationary installation, are used for regulating laser beam polarization state, polarization direction and the light intensity that incides testing laser gyro resonator cavity according to measuring needs.

Described harmonic light signal measurement control device, comprise photodetector, A/D analog to digital converter and USB interface, this A/D analog to digital converter will carry out opto-electronic conversion through photodetector and become digital signal with the harmonic light conversion of signals that signal amplifies, and output to the enterprising line data of main control computer by USB interface and handle, main control computer transmits control signal to piezoelectric ceramic actuator by USB interface, makes it produce Piezoelectric Ceramic voltage.

The present invention has the following advantages:

1) the present invention is owing to adopt single mode frequency sweep laser instrument, this laser instrument is under the control of driver circuit for piezoelectric ceramics, output frequency is periodically and the laser beam of continuous linear change, in a frequency sweep cycle of laser instrument, excite a plurality of eigenmodes, measure when having realized a plurality of eigenmodes loss.

2) the present invention utilizes laser gyro loss of resonator measuring system, having proposed a kind of is the piezoelectric ceramics non-linear correction method of foundation with harmonic light power spectral line halfwidth, guarantee correction accuracy, avoiding in addition, employing equipment carries out the piezoelectric ceramics gamma correction, reduced cost, improve efficient, simplified measuring process.

3) driver circuit for piezoelectric ceramics among the present invention, comprise two DDS signal generators and two high pressure amplifying, realize the flexible output voltage waveforms, and can export simultaneously two voltage signals to the two ends of piezoelectric ceramics as driving voltage and bias voltage.

4) the present invention adopts the combination of spherical reflector and two-dimentional parallel flat, the laser beam incident angle and the translational movement of testing laser gyro resonator cavity incided in meticulous adjusting simultaneously, incoming laser beam and testing laser gyro resonator cavity are carried out pattern match, effectively cross-couplings between the minimizing pattern improves coupling efficiency.

5) the present invention realizes being converted into the laser beam polarization state, polarization direction and the light intensity that are mapped to testing laser gyro resonator cavity according to measuring needs owing to adopt polaroid and 1/2 wave plate, and the noise that the filtering parasitic light causes improves measuring accuracy.

Description of drawings

Fig. 1 is the laser gyro loss of resonator measuring system structured flowchart that the present invention is based on resonance method;

Fig. 2 is that the present invention uses resonance method to measure the principle schematic of the laser gyro loss of resonator;

Fig. 3 is that the present invention uses resonance method to measure the process flow diagram of the laser gyro loss of resonator;

Fig. 4 is in test process of the present invention, when carrying out loss of resonator measurement, and the harmonic light power spectral line of testing laser gyro resonator cavity output;

Fig. 5 is in test process of the present invention, when carrying out the piezoelectric ceramics gamma correction, the piezoelectric ceramics on the laser instrument is applied different bias voltages, by the harmonic light power spectral line of testing laser gyro resonator cavity output.

Fig. 6 changes the bias voltage be applied to piezoelectric ceramics on the laser instrument, and non-linear by piezoelectric ceramics obtains at one group of harmonic light power spectrum line chart.

Embodiment

Describe system architecture of the present invention in detail below with reference to accompanying drawing.

With reference to Fig. 1, measuring system of the present invention comprises optical system, harmonic light signal measurement control device 7, main control computer 11 and driver circuit for piezoelectric ceramics 12, optical system produces light signal, and be transferred to main control computer 11 by harmonic light signal measurement control device 7, this main control computer 11 is simultaneously by harmonic light signal measurement control device 7, control driver circuit for piezoelectric ceramics 12 applies driving voltage and bias voltage and gives optical system.Wherein:

Optical system comprises laser instrument 1, spherical reflector 2, two-dimentional parallel flat 3, polaroid 4,1/2 wave plate 5 resonant cavity stationary installations 6, this laser instrument 1, adopt single mode frequency sweep laser instrument, has piezoelectric ceramics on it, by the control piezoelectric ceramics, the frequency of tunable laser 1 outgoing laser beam after this laser instrument 1, is placed with spherical reflector 2, two-dimentional parallel flat 3, polaroid 4,1/2 wave plate 5 resonant cavity stationary installations (6) successively.Spherical reflector 2 and two-dimentional parallel flat 3 can accurately be regulated the angle and the position of incoming laser beam, reduce light path and regulate difficulty, improve the coupling efficiency of incoming laser beam and testing laser gyro resonator cavity; The laser beam polarization state, polarization direction and the light intensity that are mapped to testing laser gyro resonator cavity be regulated and be converted into to polaroid 4 and 1/2 wave plate 5 can according to measuring needs; Resonator cavity stationary installation (6) is used to place testing laser gyro resonator cavity; The outgoing laser beam of this laser instrument 1 incides in the testing laser gyro resonator cavity that is positioned on the resonator cavity stationary installation (6) via spherical reflector 2, two-dimentional parallel flat 3, polaroid 4 and 1/2 wave plate 5; If incoming laser beam identical with the natural frequency of testing laser gyro resonator cavity, will produce in the testing laser gyro resonator cavity and export resonance light in frequency continually varying process.

Harmonic light signal measurement control device 7, comprise photodetector 8, A/D analog to digital converter 9 and usb 10, photodetector 8 is positioned at harmonic light signal measurement control device 7 front ends and imports as it, be provided with A/D analog to digital converter 9 after photodetector 8, A/D analog to digital converter 9 links to each other with usb 10 again.Photodetector 8 is converted to analog electrical signal with incident optical signal, and this analog electrical signal is converted to digital signal through A/D analog to digital converter 9, and exports to main control computer by USB interface.

Be provided with the measurement control module in the main control computer 11, comprise USB driver module, gamma correction module, loss measurement module and display interface module.Gamma correction module, loss measurement module and display interface module are independent separately, and all link to each other with the USB driver module; The USB driver module is used for carrying out data acquisition and order transmission by USB interface and external unit; The gamma correction module realizes the piezoelectric ceramics gamma correction; The loss measurement module is finished the measurement to the laser gyro loss of resonator to be measured; The display interface module is carried out graphic presentation with the data that collect.

Piezoelectric ceramic actuator 12, comprise two DDS signal generators and two high pressure amplifying, each DDS signal generator connects a high pressure amplifying respectively, each DDS signal generator produces the waveform adjustable voltage of 0～5V, by high pressure amplifying this voltage amplification to 0～240V is also exported.

The principle of utilizing said system to carry out loss measurement is described as follows with reference to Fig. 2:

Laser instrument 14 is under the control of driver circuit for piezoelectric ceramics 13, output frequency is the laser beam of periodicity and continuous linear change in time and incides in the testing laser gyro resonator cavity 15, when this laser beam frequency during near certain natural frequency of testing laser gyro resonator cavity, the harmonic light light intensity of testing laser gyro resonator cavity output increases, during away from this natural frequency, the harmonic light light intensity of testing laser gyro resonator cavity output reduces.The harmonic light of testing laser gyro resonator cavity output carries out opto-electronic conversion through photodetector 16, and is handled and demonstration by data handling system 17, can draw the time dependent spectrum of harmonic light power, as shown in Figure 5.The loss of this spectral line halfwidth and laser gyro resonator cavity has following relation:

$\mathrm{\δ}=\mathrm{\π}\frac{L_{\mathrm{res}}}{L_{\mathrm{las}}}\frac{\mathrm{\Δt}}{T}$

Wherein, δ is the loss of resonator, and Δ t is a harmonic light power spectral line halfwidth, L _ResFor testing laser gyro resonator cavity chamber long, L _LasLong for the resonator cavity chamber of laser instrument, T is the frequency sweep cycle of laser instrument.

By following formula as can be known, obtain laser gyro resonator cavity export resonance luminous power spectral line, and measure the half width of spectral line, just can obtain the loss of resonator cavity.

With reference to Fig. 3, measuring process of the present invention is as follows:

Step 1 is proofreaied and correct the piezoelectric ceramics of system is non-linear.

With reference to Fig. 4, the concrete enforcement of this step is as follows:

1.1) main control computer 11 is by usb 10 control driver circuit for piezoelectric ceramics 12, the driving voltage of output offset voltage and zig-zag, this voltage is applied to the piezoelectric ceramics two ends on the laser instrument 1, utilize the non-linear of piezoelectric ceramics, make the frequency of laser instrument 1 outgoing laser beam be nonlinearities change;

1.2) the frequency nonlinearities change laser beam incident of laser instrument 1 output is in the testing laser gyro resonator cavity that is positioned over resonator cavity stationary installation 6, and in testing laser gyro resonator cavity, produce harmonic light, this harmonic light is converted to digital signal and is transferred to main control computer 11 through harmonic light signal measurement control device 7, demonstrates the time dependent spectrum of this harmonic light power by main control computer 11;

1.3) changing the bias voltage be applied to piezoelectric ceramics on the laser instrument 1, non-linear by piezoelectric ceramics obtains one group of harmonic light power spectrum line chart, and as shown in Figure 6, this group spectral line halfwidth difference is respectively Δ t1, Δ t2, Δ t3, Δ t4, Δ t5...;

1.4) gamma correction module on the computing machine 11 is with 1.3) and in the halfwidth of the one group of spectral line that obtained be foundation, regulate the driving voltage waveform of piezoelectric ceramic actuator output, make laser instrument 1 output frequency be the laser beam of linear change, finish the gamma correction of piezoelectric ceramics.

Step 2, main control computer 11 be by usb 10 control driver circuit for piezoelectric ceramics 12, and the piezoelectric ceramics of the driving voltage after output waveform is proofreaied and correct to the laser instrument 1 makes laser instrument 1 output frequency be the laser beam of linear change periodically continuously.

Step 3, the frequency linearity of laser instrument 1 output change laser beam incident and excite harmonic light in testing laser gyro resonator cavitys, and this harmonic light signal is transferred to main control computer 11 by measuring and controlling 7, obtains harmonic light power spectral line.

Step 4, main control computer 11 are measured harmonic light power spectral line halfwidth, and according to following formula, calculate loss of resonator value:

$\mathrm{\δ}=\mathrm{\π}\frac{L_{\mathrm{res}}}{L_{\mathrm{las}}}\frac{\mathrm{\Δt}}{T}$

Wherein: Δ t is the harmonic light power spectral line halfwidth of measuring, L _ResFor testing laser gyro resonator cavity chamber long, L _LasLong for the resonator cavity chamber of laser instrument, T is the frequency sweep cycle of laser instrument.

Claims (6)

1. laser gyro loss of resonator measuring system, comprise laser instrument (1), spherical reflector (2), two-dimentional parallel flat (3), polaroid (4), 1/2 wave plate (5), resonator cavity stationary installation (6), harmonic light signal measurement control device (7), main control computer (11) and driver circuit for piezoelectric ceramics (12), it is characterized in that:

Laser instrument (1) adopts single mode frequency sweep laser instrument, and this laser instrument is under the control of driver circuit for piezoelectric ceramics (12), and output frequency is periodically and the laser beam of continuous linear change; The laser beam of this laser instrument (1) output is passed through spherical reflector (2), two-dimentional parallel flat (3), polaroid (4) and 1/2 wave plate (5) successively, inciding resonator cavity stationary installation (6) goes up in the testing laser gyro resonator cavity of placing, in testing laser gyro resonator cavity, excite a plurality of eigenmodes, produce harmonic light, this harmonic light carries out opto-electronic conversion and digital-to-analog conversion through harmonic light signal measurement control device (7), is transferred on the main control computer (11);

Be provided with USB driver module, gamma correction module, loss measurement module and display interface module in the main control computer (11), the USB driver module is used to drive instruction transmission and the data acquisition between main control computer and the harmonic light signal measurement control device (7), and the data that collect are shown in real time and preserves by the display interface module; The gamma correction module applies different bias voltages by control driver circuit for piezoelectric ceramics (12) to the piezoelectric ceramics on the laser instrument, obtain the different power spectral line of one group of pulsewidth of testing laser gyro resonator cavity output, with this group spectral line is foundation, proofread and correct the non-linear of piezoelectric ceramics, and measure the loss of testing laser gyro resonator cavity by the loss measurement module.

2. laser gyro loss of resonator measuring system according to claim 1, it is characterized in that driver circuit for piezoelectric ceramics (12), comprise two DDS signal generators and two high pressure amplifying, each DDS signal generator connects a high pressure amplifying respectively, each DDS signal generator produces the waveform adjustable voltage of 0～5V, by high pressure amplifying with this voltage amplification to 0～240V, and the two ends that are applied to the last piezoelectric ceramics of laser instrument (1) are as driving voltage and bias voltage, with the variation of control laser beam frequency.

3. laser gyro loss of resonator measuring system according to claim 1, it is characterized in that, spherical reflector (2) and two-dimentional parallel flat (3) are placed between laser instrument (1) and the resonator cavity stationary installation (6), be used to regulate angle and the translational movement that laser instrument (1) outgoing laser beam incides testing laser gyro resonator cavity, improve coupling efficiency.

4. laser gyro loss of resonator measuring system according to claim 1, it is characterized in that, polaroid (4) and 1/2 wave plate (5) are placed between laser instrument (1) and the resonator cavity stationary installation (6), are used for regulating laser beam polarization state, polarization direction and the light intensity that incides testing laser gyro resonator cavity according to measuring needs.

5. laser gyro loss of resonator measuring system according to claim 1, it is characterized in that, harmonic light signal measurement control device (7), comprise photodetector (8), A/D analog to digital converter (9) and USB interface (10), this A/D analog to digital converter will carry out opto-electronic conversion through photodetector (8) and become digital signal with the harmonic light conversion of signals that signal amplifies, and output to the enterprising line data of main control computer (11) by USB interface (10) and handle, main control computer (11) transmits control signal to piezoelectric ceramic actuator (12) by USB interface (10), makes it produce Piezoelectric Ceramic voltage.

6. a method of utilizing the described system of claim 2 that the laser gyro loss of resonator is measured comprises the steps:

(1) proofread and correct the piezoelectric ceramics of system is non-linear:

1.1) main control computer controls driver circuit for piezoelectric ceramics by USB interface, the driving voltage of output offset voltage and zig-zag, this voltage is applied to the piezoelectric ceramics two ends on the laser instrument, utilizes the non-linear of piezoelectric ceramics, makes the laser instrument output frequency be the laser beam of nonlinearities change;

1.2) frequency of laser instrument output is the nonlinearities change laser beam, incide in the testing laser gyro resonator cavity and produce harmonic light, this harmonic light is converted to digital signal through harmonic light signal measurement control device, and is transferred to main control computer and demonstrates its time dependent spectrum;

1.3) changing the bias voltage be applied to piezoelectric ceramics on the laser instrument, non-linear by piezoelectric ceramics obtains one group of harmonic light power spectrum line chart that halfwidth is different;

1.4) with 1.3) and in the halfwidth of the one group of spectral line that obtained be foundation, the driving voltage waveform that the adjusting piezoelectric ceramic actuator is exported makes the laser instrument output frequency be linear change, finishes the gamma correction of piezoelectric ceramics;

(2) main control computer is controlled driver circuit for piezoelectric ceramics by USB interface, and the piezoelectric ceramics of the driving voltage after output waveform is proofreaied and correct to the laser instrument makes the laser instrument output frequency be the laser beam of linear change;

(3) laser beam incident of laser instrument output produces harmonic light in testing laser gyro resonator cavity, this harmonic light is converted to digital signal through harmonic light signal measurement control device, and is transferred to main control computer and demonstrates the time dependent spectrum of this harmonic light power;

(4) main control computer calculates loss of resonator value by measuring harmonic light power spectral line halfwidth:

$\mathrm{\δ}=\mathrm{\π}\frac{L_{\mathrm{res}}}{L_{\mathrm{las}}}\frac{\mathrm{\Δt}}{T}$

Wherein, δ is the loss of resonator, and Δ t is a harmonic light power spectral line halfwidth, L _ResFor testing laser gyro resonator cavity chamber long, L _LasLong for the resonator cavity chamber of laser instrument, T is the frequency sweep cycle of laser instrument.

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