CN103063128A - Dynamic electronic signal phase measurement system for double-frequency laser interferometer - Google Patents
Dynamic electronic signal phase measurement system for double-frequency laser interferometer Download PDFInfo
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Abstract
A dynamic electronic signal phase measurement system for a double-frequency laser interferometer comprises a radio sonde (RS) receiver, a field programmable gate array device, a pulse interval measurement chip and a measurement calculation module, wherein the field programmable gate array device comprises a difference entire cycle counting unit, a pulse extraction unit, a phase measurement control unit and an input / output (I/O) control unit. The difference entire cycle counting unit is used for calculating the number of pulses of a reference signal in real time and a measurement signal which passes through a logical unit in unit time, the pulse extraction unit is used for converting the input periodic reference signal and the measurement signal to two sets of pulse signals, and the phase measurement control unit is used for receiving measurement results measured by an interval measurement unit. The pulse interval measurement chip is used for receiving the two sets of the pulse signals which are output by the pulse extraction unit and converting the time interval among the pulses to digital quantity, and the measure calculation module calculates the phase differences between the reference signal and the measurement signal and obtains displacement distance of a target to be measured. The dynamic electronic signal phase measurement system for the double-frequency laser interferometer can accurately measure the phase of a dynamic signal and broaden application places of the double frequency laser interferometer.
Description
Technical field
The invention belongs to laser interferometer signal phase place and displacement measuring technology field, particularly a kind of dynamic electron signal phase measuring system for two-frequency laser interferometer.
Background technology
Therefore two-frequency laser interferometer has a wide range of applications in the high precision displacement fields of measurement because adaptive capacity to environment is strong, and measurement result can be traced to the source to optical maser wavelength.Usually, the opticator that two-frequency laser interferometer is used for measuring is Michelson interferometer, double frequency cross polarization laser that two-frequency laser sends one the tunnel incides fixedly and forms reference arm on the pyramid after through the polarization splitting prism light splitting, and another road is incided on the target to be measured and formed gage beam.The Doppler shift that the movement of target to be measured can make catoptrical frequency introduce owing to motion in the stack of original frequency basis, and then the difference on the frequency of generation gage beam signal and reference arm signal.The integration of difference on the frequency signal on time domain can obtain the phase differential of signal.Utilize photodetector reception laser interference signal and be translated into electric signal, by the phase differential of electronic system measuring reference signals and measuring-signal.The periodicity of laser interference signal in addition, 360 ° of the every variations of the phase differential of reference signal and measuring-signal, corresponding displacement to be measured is 1/2nd of laser light wavelength.Therefore two-frequency laser interferometer can obtain the displacement of target to be measured by the phase differential of accurate measurement laser interference signal.
Principle of work by two-frequency laser interferometer in order to realize high-precision displacement measurement, need to have reliable signal phase measurement means as can be known.The signal processing system that can carry out at present the electronic signal phase measurement can be divided into three classes.The first kind is to fill the result obtain within 360 ° by high-frequency impulse, again by phase jump point (360 ° to 0 °) counted to get result's complete cycle.The deficiency of this method is that complete cycle, count results can be introduced counting error because of the shake of light signal, so the phase measurement of the method and unreliable.Equations of The Second Kind is by input signal is carried out phase locking frequency multiplying, measures the phase differential within 360 ° of the signals after the frequency multiplication, multiply by Clock Multiplier Factor again and obtains measuring phase differential with reference signal.The deficiency of this method is to guarantee good phase-frequency characteristic when realizing high frequency, and is subjected to the mimic channel temperature to float drift to limit, and phase measurement accuracy is low.The 3rd class signal processing system is the Bidirectional differential digital phase detection, carries out XOR with reference to signal and measuring-signal first, then measures high level and low level duration, and then obtains phase value.The deficiency of this method is to require measuring-signal identical with reference signal frequency, and namely target to be measured is static, therefore can not realize dynamic signal processing and the phase measurement that target travel process to be measured is central.
Summary of the invention
In order to overcome the shortcoming of above-mentioned prior art, the object of the present invention is to provide a kind of dynamic electron signal phase measuring system for two-frequency laser interferometer, phase place that can the Measurement accuracy Dynamic Signal, thereby the application scenario that can widen two-frequency laser interferometer.
To achieve these goals, the technical solution used in the present invention is:
Be used for the dynamic electron signal phase measuring system of two-frequency laser interferometer, comprise:
Be used for receiving the RS485 receiver 1 of reference signal and measuring-signal;
Be used for two group pulse signals of received pulse extraction unit 4 outputs and be converted into the pulse interval measurement unit 6 of digital quantity the time interval between the pulse;
Connect the on-site programmable gate array FPGA device of RS485 receiver 1 and pulse interval measurement unit 6, described on-site programmable gate array FPGA device comprises for difference counting unit complete cycle 2 of calculating in real time described reference signal and the measuring-signal pulse number by this logical block in the unit interval, be used for periodic reference signal that will input and the DISCHARGE PULSES EXTRACTION unit 4 that measuring-signal is converted to two group pulse signals, the phase measurement control module 3 of received pulse interval measurement unit 6 measurement results and the I/O control module 5 that is used for difference counting unit complete cycle 2 and phase measurement control module 3 measurement results are sent to measuring and calculating module 7;
For the phase differential of computing reference signal under Windows operating system and measuring-signal, then calculate and demonstrate the measuring and calculating module 7 of the displacement of target to be measured.
Described RS485 receiver 1, pulse interval measurement unit 6 and on-site programmable gate array FPGA device are integrated into two-frequency laser interferometer kinetic measurement phase place card.
Described reference signal and measuring-signal are the square-wave signals with the difference form input, are converted into the single-ended signal of standard Transistor-Transistor Logic level in RS485 receiver 1.
Described phase measurement control module 3 provides clock signal and steering order to pulse interval measurement unit 6, the feedback signal of received pulse interval measurement unit 6, according to feedback signal starting impulse extraction unit 4, the measurement result of final received pulse interval measurement unit 6.
Described DISCHARGE PULSES EXTRACTION unit 4 is to arrive the moment as sampling instant with the measuring-signal rising edge, and periodic reference signal and the measuring-signal of inputting is converted to two group pulse signals: the first group pulse signal carries the time interval information of sampling instant reference signal and the adjacent rising edge of measuring-signal; The second group pulse signal carries the information of cycle reference signal value.
Described measuring and calculating module 7 receives the measurement result of difference counting unit complete cycle 2 and phase measurement control module 3 according to universal serial bus protocol.
Described measuring and calculating module 7 comprises the data entry element for logging data
Described measuring and calculating module 7 comprises the Data Management Unit for data management.
Compared with prior art, the invention has the advantages that:
1. adopt the DISCHARGE PULSES EXTRACTION logic, periodic signal is converted to the pulse signal that comprises the sampling instant phase information, cooperate with high precision pulse interval measurement unit, realize the signal phase difference Measurement accuracy in the dynamic process.
2. adopt special-purpose pulse interval measurement module to replace the high frequency clock of FPGA inside, remove the inner high frequency clock frequency of FPGA to the restriction of digital phase measuring system measuring accuracy, realize more high-precision phase measurement.
3. adopt the digital phase measuring system, simple in structure than analog phase measuring system, antijamming capability is strong, and cost of development is low.
Description of drawings
Fig. 1 is phase measuring system block diagram of the present invention.
Fig. 2 is pulse interval survey sheet of the present invention.
Fig. 3 is the phase measuring system of the present invention as a result figure of stability test that works long hours.
Fig. 4 is phase measuring system phase measurement accuracy test result figure of the present invention.
Embodiment
Describe embodiments of the present invention in detail below in conjunction with drawings and Examples.
As shown in Figure 1, measuring system of the present invention comprises: RS485 receiver 1, difference counting unit complete cycle 2, phase measurement control module 3, DISCHARGE PULSES EXTRACTION unit 4, I/O control module 5, pulse interval measurement unit 6 and measuring and calculating module 7.Wherein difference counting unit complete cycle 2, phase measurement control module 3, DISCHARGE PULSES EXTRACTION unit 4, I/O control module 5 are integrated in field programmable gate array (FPGA) device.
The reference square wave of difference form and measurement square wave are as the input signal of RS485 receiver 1, and when the reference signal amplitude was higher than measuring-signal amplitude 200mV, receiver was output as high level; Otherwise when the measuring-signal amplitude was higher than reference signal amplitude 200mV, receiver was output as low level.In this way, RS485 receiver 1 is converted to single-ended signal with differential input signal and sends into FPGA.After single-ended signal entered FPGA, a part entered difference counting unit complete cycle 2, and another part enters DISCHARGE PULSES EXTRACTION unit 4.
Difference counting unit complete cycle 2 comes real-time computing reference signal and measuring-signal unit interval by the difference of the pulse number of this logical block by one 28 counter, is designated as N, and corresponding phase differential is 360 ° * N.When target to be measured was static, reference signal was identical with the measuring-signal frequency, and the Output rusults of difference counting unit complete cycle 2 is 0; When target travel to be measured, because Doppler shift, measuring-signal is different with reference signal frequency, and the Output rusults that difference counting unit complete cycle 2 is differentiated logic according to internal symbol carries out addition or subtraction.
Phase measurement control module 3, DISCHARGE PULSES EXTRACTION unit 4 consist of the phase subdivision measuring unit with pulse interval measurement unit 6.Pulse interval measurement unit digital conversion chip 6 service time TDC-GP21.This chip utilizes the gate delay of self inside, measures the time interval of input pulse, uses measurement range 2 mode of operations, resolution 45ps, measurement range 500ns ~ 4ms.Under the control of phase measurement control module 3, electrification reset is finished in pulse interval measurement unit 6, and the initialize routines such as self calibration are waited for input pulse.Phase measurement control module 3 after receiving the feedback signal that 6 initialization of pulse interval measurement unit finish, starting impulse extraction unit 4.In DISCHARGE PULSES EXTRACTION unit 4, measuring-signal and reference signal are passed through first the d type flip flop frequency division, and divide ratio is designated as K.For the signal behind the frequency division, get the arrival of measuring-signal rising edge and constantly be sampling instant, the signal behind the frequency division is converted to two group pulse signals, as shown in Figure 2.This mode can avoid the 500ns blind area of TDC-GP21 on the impact of phase measurement scope.Pulse interval measurement unit 6 measuring intervals of TIME Δ t and T, corresponding phase differential
Wherein K is divide ratio, phase differential
positive and negatively differentiate logic by the symbol in the DISCHARGE PULSES EXTRACTION unit 4 and finish.The phase subdivision result contains part complete cycle time value, realizes the redundant measurement of complete cycle time value, improves accuracy of measurement results complete cycle.
The measurement result that latchs in difference counting unit complete cycle 2 and the phase measurement control module 3 in the Survey Software 7 extraction two-frequency laser interferometer kinetic measurement phase place cards under the Windows operating system.This module is synthesized the phase differential ψ of measuring-signal and reference signal according to complete cycle counting and phase subdivision result, and then calculates corresponding displacement of targets to be measured
Except real-time demonstration displacement of targets to be measured, application software also provides the Data Logging and Management function.
In order to test the stability that works long hours for the dynamic electron signal phase measuring system of two-frequency laser interferometer, the signal that the 33522A signal generator of use Agilent produces is as reference signal and measuring-signal, signal frequency is set as 1MHz, once sampled in per 1 second, experimental result as shown in Figure 3.From experimental result, can find out, kinetic measurement guarantees within ± 0.4 ° scope with the stability of display of phase place card, the maximum forward shake is 0.394845 °, and maximum negative sense shake is-0.34204 °, and does not occur the situation of obvious measurement result transition in the middle of the measuring process.
In order to test the phase measurement accuracy for the dynamic electron signal phase measuring system of two-frequency laser interferometer, use the 33522A signal generator of Agilent as signal source, phase adjustment range to be measured is 0 ~ 3600 °, every 90 ° of comparisons of once sampling, signal frequency is 1MHz, and experimental result as shown in Figure 4.Experimental result is converted into displacement and represents, analyzes experimental result as can be known, and the phase measuring system regression equation is y=x-0.0004, maximum measured deviation 0.001062 μ m.
In sum, cooperation by complete cycle counting unit and the phase subdivision measuring unit that extracts based on dynamic pulse, the dynamic electron signal phase measuring system that is used for two-frequency laser interferometer can be measured the transient state phase differential of measuring-signal and reference signal, and then realizes the real-time measurement to displacement of targets to be measured in the middle of the motion process.
Claims (8)
1. be used for the dynamic electron signal phase measuring system of two-frequency laser interferometer, it is characterized in that, comprising:
Be used for receiving the RS485 receiver (1) of reference signal and measuring-signal;
Be used for two group pulse signals of received pulse extraction unit (4) output and be converted into the pulse interval measurement unit (6) of digital quantity the time interval between the pulse;
Connect field programmable gate array (FPGA) device of RS485 receiver (1) and pulse interval measurement unit (6), described field programmable gate array (FPGA) device comprises for difference counting unit complete cycle (2) of calculating in real time described reference signal and the measuring-signal pulse number by this logical block in the unit interval, be used for periodic reference signal that will input and the DISCHARGE PULSES EXTRACTION unit (4) that measuring-signal is converted to two group pulse signals, the phase measurement control module (3) of received pulse interval measurement unit (6) measurement result and the I/O control module (5) that is used for difference counting unit complete cycle (2) and phase measurement control module (3) measurement result are sent to measuring and calculating module (7);
For the phase differential of computing reference signal under Windows operating system and measuring-signal, then calculate and demonstrate the measuring and calculating module (7) of the displacement of target to be measured.
2. the dynamic electron signal phase measuring system for two-frequency laser interferometer according to claim 1, it is characterized in that, described RS485 receiver (1), pulse interval measurement unit (6) and field programmable gate array (FPGA) device are integrated into two-frequency laser interferometer kinetic measurement phase place card.
3. the dynamic electron signal phase measuring system for two-frequency laser interferometer according to claim 1, it is characterized in that, described reference signal and measuring-signal are the square-wave signals with the difference form input, are converted into the single-ended signal of standard Transistor-Transistor Logic level in RS485 receiver (1).
4. the dynamic electron signal phase measuring system for two-frequency laser interferometer according to claim 1, it is characterized in that, described phase measurement control module (3) provides clock signal and steering order to pulse interval measurement unit (6), the feedback signal of received pulse interval measurement unit (6), according to feedback signal starting impulse extraction unit (4), the measurement result of final received pulse interval measurement unit (6).
5. the dynamic electron signal phase measuring system for two-frequency laser interferometer according to claim 1, it is characterized in that, described DISCHARGE PULSES EXTRACTION unit (4) is to arrive the moment as sampling instant with the measuring-signal rising edge, and periodic reference signal and the measuring-signal of inputting is converted to two group pulse signals: the first group pulse signal carries the time interval information of sampling instant reference signal and the adjacent rising edge of measuring-signal; The second group pulse signal carries the information of cycle reference signal value.
6. the dynamic electron signal phase measuring system for two-frequency laser interferometer according to claim 1, it is characterized in that, described measuring and calculating module (7) receives the measurement result of difference counting unit complete cycle (2) and phase measurement control module (3) according to universal serial bus protocol.
7. the dynamic electron signal phase measuring system for two-frequency laser interferometer according to claim 1 is characterized in that, described measuring and calculating module (7) comprises the data entry element for logging data.
8. according to claim 1 or 7 described dynamic electron signal phase measuring systems for two-frequency laser interferometer, it is characterized in that, described measuring and calculating module (7) comprises the Data Management Unit for data management.
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| WO2020200257A1 (en) * | 2019-04-04 | 2020-10-08 | 清华大学 | High-resolution phase detection method and system based on plane grating laser interferometer |
| CN112212783A (en) * | 2020-09-21 | 2021-01-12 | 清华大学 | Phase discrimination system and method based on dynamic response time measurement method |
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| CN112212783B (en) * | 2020-09-21 | 2021-11-05 | 清华大学 | Phase discrimination system and method based on dynamic response time measurement method |
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