CN103063128B - 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
Two-frequency laser interferometer due to adaptive capacity to environment strong, measurement result can be traced to the source to optical maser wavelength, therefore has a wide range of applications in high precision displacement fields of measurement.Usually, two-frequency laser interferometer is Michelson interferometer for the opticator measured, double frequency cross polarization laser road after polarization splitting prism light splitting that two-frequency laser sends is incided on fixing pyramid and is formed reference arm, and another road is incided in target to be measured and formed gage beam.The movement of target to be measured can make the frequency of reflected light superpose on original frequency base due to the Doppler shift introduced that moves, and then produces the difference on the frequency of gage beam signal and reference arm signal.The integration of frequency difference signal in time domain can obtain the phase differential of signal.Utilize photoelectric detector 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, the phase differential of reference signal and measuring-signal often changes 360 °, and 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 accurately measuring laser interference signal.
Known by the principle of work of two-frequency laser interferometer, in order to realize high-precision displacement measurement, need reliable signal phase measurement means.The signal processing system can carrying out electronic signal phase measurement at present can be divided into three classes.The first kind fills by high-frequency impulse the result obtained within 360 °, then by counting to get result complete cycle to phase jump point (360 ° to 0 °).The deficiency of this method is that complete cycle count results can because counting error be introduced in the shake of light signal, therefore the phase measurement of the method unreliable.Equations of The Second Kind is by carrying out phase locking frequency multiplying to input signal, the phase differential after measurement frequency multiplication within signal 360 °, then the phase differential being multiplied by that Clock Multiplier Factor obtains measurement and reference signal.The deficiency of this method is to ensure good phase-frequency characteristic while realizing high frequency, and limits by mimic channel temperature drift drift, and phase measurement accuracy is low.3rd class signal processing system is Bidirectional differential digital phase detection, and first Reference Signal and measuring-signal carry out XOR, then measures high level and low level duration, and then obtains phase value.The deficiency of this method is to require that measuring-signal is identical with reference signal frequency, and namely target to be measured is static, therefore can not realize the dynamic signal processing in the middle of target travel process to be measured and phase measurement.
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, can the phase place of Measurement accuracy Dynamic Signal, thus the application scenario of two-frequency laser interferometer can be widened.
To achieve these goals, the technical solution used in the present invention is:
For the dynamic electron signal phase measuring system of two-frequency laser interferometer, comprising:
For receiving the RS485 receiver 1 of reference signal and measuring-signal;
The time interval between pulse is also converted into the pulse interval measurement unit 6 of digital quantity by the two group pulse signals exported for received pulse extraction unit 4;
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 comprise for calculate described reference signal in real time and in the measuring-signal unit interval by difference counting unit complete cycle 2 of the pulse number of this logical block, for the periodic reference signal of input and measuring-signal being converted to the DISCHARGE PULSES EXTRACTION unit 4 of 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 for difference counting unit complete cycle 2 and phase measurement control module 3 measurement result being sent to measuring and calculating module 7,
For the phase differential of computing reference signal and measuring-signal under Windows operating system, 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 with the square-wave signal of 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 arrives the moment as sampling instant using measuring-signal rising edge, the periodic reference signal of input and measuring-signal is converted to two group pulse signals: the first group pulse signal carries the time interval information of sampling instant reference signal and measuring-signal adjacent rising edges; Second group pulse signal carries the information of cycle reference signal value.
Described measuring and calculating module 7, according to universal serial bus protocol, receives the measurement result of difference counting unit complete cycle 2 and phase measurement control module 3.
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 DISCHARGE PULSES EXTRACTION logic, periodic signal is converted to the pulse signal comprising sampling instant phase information, coordinates with high-precision pulse interval measurement unit, realize the signal phase difference Measurement accuracy in dynamic process.
2. adopt special pulse interval measurement module to replace the high frequency clock of FPGA inside, remove FPGA internal high frequency clock frequency to the restriction of digital phase measuring system measuring accuracy, realize more high-precision phase measurement.
3. adopt digital phase measuring system, compared to analog phase measuring system, structure is simple, and antijamming capability is strong, and cost of development is low.
Accompanying drawing explanation
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 that phase measuring system of the present invention works long hours stability test result figure.
Fig. 4 is phase measuring system phase measurement accuracy test result figure of the present invention.
Embodiment
Embodiments of the present invention are described 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.
Reference square wave and the input signal of measurement square wave as RS485 receiver 1 of difference form, when reference signal amplitude is higher than measuring-signal amplitude 200mV, receiver exports as high level; Otherwise when measuring-signal amplitude is higher than reference signal amplitude 200mV, receiver exports as low level.In this way, differential input signal is converted to single-ended signal and sends into FPGA by RS485 receiver 1.After single-ended signal enters FPGA, a part enters 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 the counter of 28, and be designated as N, corresponding phase differential is 360 ° × N.When target to be measured is static, reference signal is identical with measuring-signal frequency, and the Output rusults of difference counting unit complete cycle 2 is 0; When target travel to be measured, due to Doppler shift, measuring-signal is different with reference signal frequency, according to internal symbol, difference counting unit complete cycle 2 differentiates that the Output rusults of logic carries out addition or subtraction.
Phase measurement control module 3, DISCHARGE PULSES EXTRACTION unit 4 form phase subdivision measuring unit with pulse interval measurement unit 6.Pulse interval measurement unit 6 digital conversion service time chip TDC-GP21.This chip utilizes the gate delay of therein, measures the time interval of input pulse, uses measurement range 2 mode of operation, resolution 45ps, measurement range 500ns ~ 4ms.Under the control of phase measurement control module 3, pulse interval measurement unit 6 completes electrification reset, the initialize routines such as self calibration, waits for input pulse.Phase measurement control module 3 after receiving the feedback signal that pulse interval measurement unit 6 initialization completes, starting impulse extraction unit 4.In DISCHARGE PULSES EXTRACTION unit 4, measuring-signal and reference signal are first through d type flip flop frequency division, and divide ratio is designated as K.For the signal after frequency division, getting the measuring-signal rising edge arrival moment is sampling instant, the signal after 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
the positive and negative symbol by DISCHARGE PULSES EXTRACTION unit 4 differentiate that logic completes.Phase subdivision result contains part complete cycle time value, realizes the redundant measurement of complete cycle time value, improves the accuracy of measurement result complete cycle.
Survey Software 7 under Windows operating system extracts the measurement result latched in difference counting unit complete cycle 2 and phase measurement control module 3 in two-frequency laser interferometer kinetic measurement phase place card.This module according to complete cycle counting and phase subdivision result synthesize the phase differential ψ of measuring-signal and reference signal, and then calculate corresponding displacement of targets to be measured
except showing displacement of targets to be measured in real time, application software also provides Data Logging and Management function.
In order to test the stability that works long hours of the dynamic electron signal phase measuring system for two-frequency laser interferometer, use the signal of the 33522A signal generator generation of Agilent as reference signal and measuring-signal, signal frequency is set as 1MHz, within every 1 second, once sample, experimental result as shown in Figure 3.As can be seen from experimental result, the stability of display of kinetic measurement phase place card ensures within the scope of ± 0.4 °, 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 measuring process.
In order to test the phase measurement accuracy of the dynamic electron signal phase measuring system for 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, analysis design mothod result is known, and phase measuring system regression equation is y=x-0.0004, maximum measured deviation 0.001062 μm.
In sum, by counting unit and the cooperation of phase subdivision measuring unit of extracting based on dynamic pulse complete cycle, dynamic electron signal phase measuring system for two-frequency laser interferometer can be measured the transient phase difference of measuring-signal and reference signal, and then realizes the real-time measurement to displacement of targets to be measured in the middle of motion process.
Claims (7)
1., for the dynamic electron signal phase measuring system of two-frequency laser interferometer, it is characterized in that, comprising:
For receiving the RS485 receiver (1) of reference signal and measuring-signal;
The time interval between pulse is also converted into the pulse interval measurement unit (6) of digital quantity by the two group pulse signals exported for received pulse extraction unit (4);
Connect field programmable gate array (FPGA) device of RS485 receiver (1) and pulse interval measurement unit (6), described field programmable gate array (FPGA) device comprise for calculate described reference signal in real time and in the measuring-signal unit interval by difference counting unit complete cycle (2) of the pulse number of this logical block, for the periodic reference signal of input and measuring-signal being converted to the DISCHARGE PULSES EXTRACTION unit (4) of 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) for difference counting unit complete cycle (2) and phase measurement control module (3) measurement result being sent to measuring and calculating module (7), described DISCHARGE PULSES EXTRACTION unit (4) arrives the moment as sampling instant using measuring-signal rising edge, the periodic reference signal of input and measuring-signal is converted to two group pulse signals: the first group pulse signal carries the time interval information of sampling instant reference signal and measuring-signal adjacent rising edges, second group pulse signal carries the information of cycle reference signal value,
For the phase differential of computing reference signal and measuring-signal under Windows operating system, 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 with the square-wave signal of 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 measuring and calculating module (7), according to universal serial bus protocol, receives the measurement result of difference counting unit complete cycle (2) and phase measurement control module (3).
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) comprises the data entry element for logging data.
7. the dynamic electron signal phase measuring system for two-frequency laser interferometer according to claim 1 or 6, it is characterized in that, described measuring and calculating module (7) comprises the Data Management Unit for data management.
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| CN109990713B (en) * | 2019-04-04 | 2020-08-18 | 清华大学 | High-resolution phase detection method based on planar grating laser interferometer |
| CN110988467B (en) * | 2019-12-18 | 2022-01-11 | 北京自动化控制设备研究所 | Frequency measurement system and frequency measurement method thereof |
| 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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| CN101059542A (en) * | 2006-04-17 | 2007-10-24 | 中国科学院半导体研究所 | Method and circuit for measuring same-frequency signal phase difference using fixed phase shift |
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| CN102130682A (en) * | 2011-01-20 | 2011-07-20 | 中国计量学院 | Phase discriminator |
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| CN101059542A (en) * | 2006-04-17 | 2007-10-24 | 中国科学院半导体研究所 | Method and circuit for measuring same-frequency signal phase difference using fixed phase shift |
| CN101907656A (en) * | 2009-06-03 | 2010-12-08 | 中国科学院半导体研究所 | Method for measuring phase difference of common-frequency signal with fixed phase drift |
| CN102445600A (en) * | 2010-09-30 | 2012-05-09 | 上海华建电力设备股份有限公司 | Optimization method based on traditional phase difference measurement and circuit |
| CN102130682A (en) * | 2011-01-20 | 2011-07-20 | 中国计量学院 | Phase discriminator |
| CN102540865A (en) * | 2012-01-04 | 2012-07-04 | 西安近代化学研究所 | High-precision time interval measurement method based on phase modulation |
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