CN113671521A - Phase laser ranging device and method for difference frequency modulation and demodulation of rough and fine measuring scales - Google Patents
Phase laser ranging device and method for difference frequency modulation and demodulation of rough and fine measuring scales Download PDFInfo
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Abstract
The invention relates to a phase laser ranging device and a ranging method for difference frequency modulation and demodulation of a rough and fine measuring scale. The distance measuring device comprises a multi-frequency generation module, a laser modulation module, a measuring light path and an optical signal receiving and processing module; the distance measurement method starts a laser and a multi-frequency generation module; laser modulation produces accurate measuring rule c/v1Secondary rough measuring rule c/v2And a rough scale c/f, wherein the passing frequency is v3And v3The + f signal is subjected to difference frequency modulation to generate a rough measuring scale c/f; dividing the laser into reference light and measuring distance; the frequency of the accurate measuring ruler is v1‑f1And detecting the difference frequency signal f1Obtaining the accurate measurement result, and detecting the c/v of the secondary rough measurement ruler2And c/f, and acquiring a phase, and synthesizing phase difference data to obtain the measured distance. The invention breaks through the limitations of laser interference coherence length, detector bandwidth and modulation bandwidth, and can realize the accuracy of sub-millimeter or even micron level in the measurement range requirement of hundreds of thousands of meters in the futureAnd (6) measuring.
Description
Technical Field
The invention relates to the technical field of absolute distance laser measurement, in particular to a phase laser ranging device and a ranging method for difference frequency modulation and demodulation of a rough and fine measuring scale.
Background
The laser ranging technology has the advantages of high measurement accuracy, strong anti-interference capability, high space-time and vertical resolution and the like, is widely applied to the fields of large-scale equipment manufacturing, spacecraft deep space navigation, rendezvous and docking, distributed formation satellites and the like, and becomes an indispensable key technology in aerospace, major scientific devices and national economic development research. With the development of scientific technology, especially the rapid advance of aerospace technology, higher performance requirements are put forward on the measurement range, measurement precision and stability of the measurement technology. In recent years, aiming at a space physical exploration research task, collaborative exploration of complex physical processes in space by using formation minisatellites becomes a research hotspot, such as GRACE-FO satellites of NASA in the United states, NMP ST-5 plan, Proba-3 satellites of European Bureau, Gemini satellites of Germany and the like, the distance between the minisatellites is from hundreds of meters to dozens of kilometers, and the measurement precision requirement of the distance reaches millimeter, submillimeter or even dozens of micrometers. In the research of space gravitational wave detection, the maximum arm length difference caused by the dissociation of the inter-satellite orbit respectively reaches 30 ten thousand kilometers, and in order to correctly capture gravitational wave signals, the absolute distance measurement precision of the arm length needs to reach 30 cm. The processing and integral assembly of large components also put forward higher requirements for distance measurement technology, and large and ultra-large single radio telescopes are taken as examples, in order to ensure the detection sensitivity and imaging precision of celestial bodies and interplanetary molecules, the caliber of the reflecting surface of hundreds of meters to thousands of meters is measured in real time and integrally controlled, and the measurement precision requirement of each reflecting surface is superior to several millimeters or even hundreds of micrometers. Therefore, with the enlargement of the space exploration range and the improvement of the detection precision requirement of people, the distance measurement technology is urgently required to simultaneously consider the ultra-long acting distance, the precision measurement accuracy and the high real-time performance, and the sub-millimeter or even micron-scale precision measurement of the fast moving target in the range of hundreds of meters to hundreds of thousands of meters is realized.
However, the ultra-precise measurement methods such as laser interference ranging and the ultra-long distance measurement methods such as differential GPS ranging, pseudo-random code modulation ranging, pulse laser ranging, visible light vision measurement technology, electro-optical modulation optical frequency comb absolute ranging, etc. adopted at present limit further improvement of the performance thereof in principle or technology. For example, patent [ remote laser ranging system based on high-speed pseudo-random code modulation and photon counting, publication No.: the pseudo-random code modulation ranging method proposed by CN102928832A is similar to the pulse laser ranging method, is a measuring method based on pulse time, is limited by the influence of principle errors and device noise, and has centimeter-level measuring accuracy approaching the technical limit. Patent [ femtosecond optical frequency comb-based sine phase modulation interference absolute distance measuring device and method, publication No.: CN108120378A ] proposed optical frequency comb absolute distance measurement method is high in measurement accuracy, but it is limited by coherence length and difficult to be used for measurement distances of hundreds of kilometers to hundreds of thousands of kilometers.
Patent [ multifrequency synchronous modulation wide-range high-precision fast laser ranging method and device, publication No.: CN1825138A ] the proposed method and apparatus for measuring distance by using multi-wavelength modulated phase laser measure the absolute distance between the modulated light wave emitted from the measuring end and the modulated light wave reflected back from the measured target. The method adopts a modulation method to generate a plurality of measuring rule wavelengths from coarse to fine for step-by-step measurement and step-by-step optimization, wherein a longer measuring rule is used for meeting the measurement range, a shorter measuring rule is used for realizing the measurement precision, and the other measuring rules are used as transition measuring rules for connecting the coarse measuring rule and the fine measuring rule. Aiming at the distance measurement requirement of realizing micron-scale precision in a measurement range of more than hundreds of kilometers, the wavelength of a rough measurement ruler is more than 200km, the frequency of the corresponding rough measurement ruler is lower than 1.5KHz, and under the condition that the phase discrimination precision is 0.08 degrees, the required wavelength of a synthetic precise measurement ruler is 9mm, the frequency of the corresponding measurement ruler is 33.3GHz, so that the modulation bandwidth of laser at least covers 1.5KHz to 33.3 GHz. The current modulation method in this patent cannot achieve linear modulation bandwidths up to tens of GHz. The measurement range and measurement accuracy cannot meet the background application requirements.
Patent [ a laser phase method range unit, publication No.: CN202351429U adopts an electro-optical modulator to generate a measuring tape signal with the frequency of more than 1GHz, but the high-bandwidth electro-optical modulator (more than 10G) is influenced by radio frequency line impedance, radio frequency joule effect and the like, so that the physical properties of an electrode and a waveguide are changed, the low-frequency modulation effect is poor, and the high-bandwidth electro-optical modulator cannot be simultaneously used for modulating low-frequency signals below 1MHz under the condition of ensuring the precision. Therefore, the modulation method used at present cannot meet the ultra-wide modulation range from tens of Hz to tens of GHz, which causes the limitation of the multi-frequency/wavelength modulation phase laser ranging method in micron-level high-precision measurement in the ultra-long distance range, and further research on the high-bandwidth laser modulation method, i.e. the measuring tape generation method, is needed, especially overcoming the non-ideal characteristic of low-frequency signal modulation, and expanding the measurement range.
Secondly, the phase laser ranging technology needs a photoelectric detector to convert a rough measuring rule and a fine measuring rule into electric signals to perform subsequent signal processing and phase discrimination, but the existing photoelectric detector has poor detection effect or even can not directly detect measuring rule signals up to dozens of GHz or even hundreds of GHz. Patent [ superheterodyne and heterodyne combined anti-optical aliasing laser ranging device and method, publication No.: CN104049248A adopts a photoelectric detection method combining heterodyne and superheterodyne, and obtains a precision phase measurement result by detecting superheterodyne signals, thereby avoiding direct detection of precision measurement ruler signals up to dozens to hundreds of GHz. However, since the optical paths of the measurement light and the reference light are different, when the optical path difference is larger than the coherence length, the interference signal-to-noise ratio is lowered, and it is difficult to perform phase extraction. Therefore, the method is limited by the coherence length, and the measurement range is limited to several kilometers and is difficult to further improve while ensuring high-precision measurement.
In summary, the limitations of laser modulation bandwidth, detection bandwidth and interference coherence length are broken through, the measurement range of the multi-wavelength modulation phase laser ranging technology is expanded while the measurement accuracy is improved, and a laser ranging method needs to be further improved, so that accurate measurement of submillimeter or even micrometer level can be achieved in the future measurement range requirements of hundreds of thousands of meters.
Disclosure of Invention
The invention breaks through the limitations of interference coherence length, detection bandwidth and modulation bandwidth in laser ranging, further improves the measurement range and precision of the multi-wavelength modulation interference measurement method, realizes the accurate measurement reaching sub-millimeter or even micron level in the measurement range requirement of hundreds of thousands of meters in the future, and can meet the requirements of the fields of large equipment manufacturing, spacecraft deep space navigation, rendezvous and docking, distributed formation satellites and the like in the future, and provides a phase laser ranging device and a ranging method for coarse and fine measurement scale difference frequency modulation and demodulation, and the invention provides the following technical scheme:
a coarse-fine scale difference frequency modulated and demodulated phase laser ranging device, the device comprising: the device comprises a multi-frequency generation module, a laser modulation module, a measuring optical path and an optical signal receiving and processing module, wherein the multi-frequency generation module generates three paths of output, two paths of output are input into the laser modulation module to modulate laser, and the other path of output is input into the optical signal processing and receiving module; the output light of the laser modulation module is input to a measuring light path, and the two output lights of the measuring light path are respectively measuring light and reference light which are input to the optical signal receiving and processing module for phase measurement.
Preferably, the multi-frequency generation module comprises a first crystal oscillator, a second crystal oscillator, a third crystal oscillator, a first phase-locked frequency doubling circuit, a second phase-locked frequency doubling circuit, a third phase-locked frequency doubling circuit, a fourth phase-locked frequency doubling circuit, a first to fifth amplification circuits, a first power synthesizer and a second power synthesizer;
the output end of the first crystal oscillator is connected to the input end of the first phase-locked frequency doubling circuit and passes through the first amplifying circuit; the output signal of the first crystal oscillator is connected to the input end of the second phase-locked frequency doubling circuit and passes through the second amplifying circuit, the output end of the second crystal oscillator is connected to the input end of the third amplifying circuit, and the output signal of the third crystal oscillator is connected to the input end of the third phase-locked frequency doubling circuit and passes through the fourth amplifying circuit; the output signal of the third crystal oscillator is connected to the input end of the fourth phase-locked frequency multiplier circuit and passes through the fifth amplifying circuit; the output end of the first amplifying circuit and the output end of the fifth amplifying circuit are respectively input to two input ends of a first power synthesizer, the output end of the first power synthesizer is connected to the input end of the first electro-optical modulator to be used as a driving signal, the output end of the second power synthesizer is connected to the input end of the second electro-optical modulator to be used as a driving signal, and the output end of the second amplifying circuit (14) is connected to the input ends of the third electro-optical modulator and the fourth electro-optical modulator to be used as a driving signal.
Preferably, the laser modulation module comprises a laser, a first electro-optic modulator, a second electro-optic modulator, a first double-path light splitting optical fiber and a second double-path light splitting optical fiber; the output of the laser is connected to the first double-path branching optical fiber and divided into two paths, one path of output end of the first double-path branching optical fiber is connected to the input end of the first electro-optical modulator, the other path of output end of the first double-path branching optical fiber is connected to the input end of the second electro-optical modulator, the output ends of the first electro-optical modulator and the second electro-optical modulator are respectively connected to the two input ends of the second double-path branching optical fiber, and the output end of the second double-path branching optical fiber is connected to the input end of the measuring optical path.
Preferably, the measurement light path comprises a first collimator, a second collimator, a third collimator, a spectroscope, a beam expander set and a measurement pyramid; the output of No. two way branching optic fibre is connected to the input of a collimater, the output of a collimater is connected to the spectroscope, the output of spectroscope is connected to the input of No. two collimaters as reference light all the way, the output of No. two collimaters is connected to an input of light signal receiving and processing module, another way output of spectroscope is connected to the input of beam expanding mirror group, the output of beam expanding mirror group is connected to the input of measuring pyramid, the output of measuring pyramid is connected to the input of spectroscope through beam expanding mirror group, the output of spectroscope is connected to the input of No. three collimaters as the measuring light, No. three collimaters' output is to another input of light signal receiving and processing module.
Preferably, the optical signal receiving and processing module comprises a third double-path light splitting optical fiber, a fourth double-path light splitting optical fiber, a third electro-optical modulator, a fourth electro-optical modulator, a first to fourth photoelectric detectors, a sixth to ninth amplifying circuit, a first to fourth filter circuit and a high-precision phase measurement board card; one output end of the measuring light path is used as reference light and is connected with the input end of a third double-path light splitting optical fiber and then is divided into two paths, one output end of the third double-path light splitting optical fiber is connected to the input end of a third electro-optical modulator, the input end of the third electro-optical modulator is connected to the input end of a first photoelectric detector, the output end of the first photoelectric detector, a sixth amplifying circuit and a first filtering circuit are sequentially connected, the output end of the first filtering circuit is connected to the high-precision phase measurement board card, and the other output end of the third double-path light splitting optical fiber is connected to the input end of a second photoelectric detector, and then is sequentially connected to the high-precision phase measurement board card through a seventh amplifying circuit and a second filtering circuit;
the other output end of the measuring light path is used as measuring light and is connected with the input end of a fourth double-path branching optical fiber and is divided into two paths, one output end of the fourth double-path branching optical fiber is connected to the input end of a fourth electro-optical modulator, the output end of the fourth electro-optical modulator, a third photoelectric detector, an eighth amplifying circuit and a third filtering circuit are sequentially connected, and the output end of the third filtering circuit is connected to the high-precision phase measurement board card; and the other output end of the fourth double-path branching optical fiber is connected to the input end of the fourth photoelectric detector and is connected to the high-precision phase measurement board card sequentially through a ninth amplifying circuit and a fourth filter circuit.
A phase laser ranging method for difference frequency modulation and demodulation of a rough and fine measuring scale comprises the following steps:
step 1: turning on the multi-frequency generation module and the laser with an output frequency v1、v1-f1、v2、v3And v3The output laser is divided into two laser beams by a first two-path light-splitting optical fiber, wherein one laser beam is input to a first electro-optical modulator at a frequency v1And v3Driven by sine wave of the laser, the other laser is input into a second electro-optical modulator at a frequency v2And v3The intensity is modulated under the drive of the sine wave of + f, and the two paths of modulated output laser beams are combined into a laser beam through a second path of light splitting optical fiber;
step 2: one beam of laser generated in the step 1 is incident to the spectroscope through the first collimator and is divided into two beams of laser, one beam of laser is input to the optical signal receiving and processing module as reference light through the second collimator, and the other beam of laser is emitted to the measuring pyramid prism as measuring light through the beam expander group;
and step 3: moving the measurement pyramid prism to a target end, reflecting the measurement light by the pyramid prism, then passing the reflected measurement light through the beam expander set to enter the spectroscope, and inputting the measurement light carrying distance information, which is output by the spectroscope, into the optical signal receiving and processing module through the third collimator;
and 4, step 4: the reference light input into the optical signal receiving and processing module according to the step 2 is divided into two beams of laser through a third two-way light splitting optical fiber, wherein one beam enters a third electro-optical modulator at the frequency v1-f1Is driven by sine wave to carry out intensity modulation, and the light intensity change frequency in the reference light is v1The precision measuring ruler generates a difference frequency signal f after being modulated1The phase information of the precision measuring ruler is amplified and filtered by a photoelectric detector, a six-amplification circuit and a filter circuit in sequence, and only the output frequency is f1The other beam of the third double-path light splitting optical fiber passes through a second photoelectric detector, a seventh amplifying circuit and a second filtering circuit, then signals with extra frequency are filtered, and only signals with the frequency v are respectively output2And f;
and 5: the measuring light input into the optical signal receiving and processing module according to the step 3 is divided into two beams through a four-way light splitting optical fiber, wherein one beam enters a four-way electro-optical modulator at the frequency v1-f1Is driven by sine wave to carry out intensity modulation, and the light intensity change frequency in the measuring light is v1The precision measuring ruler generates a difference frequency signal f after being modulated1The distance measurement phase information with the precision measuring ruler is amplified and filtered by a third photoelectric detector, an eighth amplifying circuit and a third filter circuit in sequence, and only the output frequency is f1After the other beam of output of the four-path light-splitting optical fiber passes through a four-photoelectric detector, a nine-amplifying circuit and a four-filtering circuit, signals with extra frequency are filtered, and only signals with the frequency v are output respectively2And f;
step 6, high-precision phase measurement board card respectively measures the frequency f1、v2Reference to and fMeasuring the phase difference between the signal and the measured signal, the phase difference being
And
data synthesis of high-precision phase measurement board card
The distance measurement of the measuring tape is represented by the following formula:
wherein the floor () function is a rounding function with a frequency v1The signal of (A) is a precision measuring ruler with a wavelength of lambda1；
The measured distance is represented by:
preferably, the reference light and the measured return light are subjected to secondary intensity modulation to realize difference frequency demodulation, and the frequency v is used1-f1Sine signal pair of measuring precision measuring ruler signal in return light
Performing a second intensity modulation, wherein
When located at the linear modulation operating point, the modulated output optical signal is represented by:
the difference frequency signal is generated by:
the phase includes fine phase information, and the detector is used to detect the difference frequency signal f with lower frequency1And carrying out phase discrimination to obtain a precision measurement result.
Preferably, the coarse rule is generated by difference frequency modulation of double high-frequency signals, and the laser is subjected to high-frequency v in the laser modulation module through the electro-optical modulator3And v3+ f light intensity modulation, detecting the difference frequency signal of f frequency in the measuring light and the reference light as the rough measuring scale in the light signal receiving and processing module, and expressing the frequency v at the photoelectric detector by the following formula3And v3Measurement optical signal of + f:
the light intensity signal detected by the photodetector at frequency f is then represented by:
as the rough scale signal, the phase is the rough ranging result.
Preferably, the frequency generated by the multi-frequency generation module is v1And v1-f1The signals of the signal source are from the same signal source crystal oscillator I.
The invention has the following beneficial effects:
in the high-precision distance measurement system, the precision which can be achieved by the distance measurement system is determined by the distance measurement result of the precision measurement ruler, the higher the frequency of the precision measurement ruler is, the higher the distance measurement precision is, but in the process of receiving and measuring optical signals, the detection of the precision measurement ruler signals of dozens of GHz is difficult or the detection effect is poor due to the limitation of the bandwidth of the existing detection device. The detection frequency value can be reduced by a common heterodyne or superheterodyne photoelectric detection method, however, when the optical path difference is greater than the coherence length, the interference signal-to-noise ratio is reduced, the phase extraction is difficult to perform, and the improvement of the precision of the ranging system is further limited.
The present invention utilizes an electric light intensity modulator to measure the precise measuring rule signal (frequency is v) in reference light and measuring light1) Performing secondary modulation at a frequency v1-f1As a modulation signal, when the electro-optical modulator is operated in a linear operation region, a frequency f is generated1The phase of the difference frequency signal contains the phase information measured by the precision measuring ruler, so that the difference frequency demodulation of the precision measuring ruler signal is realized. Demodulated by detecting the measuring signal and the reference signal to have a frequency f1And measuring the phase of the difference frequency signal, wherein the measured value is the measuring result of the precision measuring ruler. In a high-precision distance measuring system, the device and the method are used for carrying out difference frequency demodulation on a precision measuring scale, and a difference frequency signal with lower frequency (the frequency is f)1) The method and the device have the advantages that the distance measurement information of the precision measurement ruler is obtained, the optical signal of the precision measurement ruler is prevented from being directly detected, the problem that the high-frequency optical signal is difficult to detect or the detection effect is poor is solved, the limitation of the bandwidth of a detection device and the laser coherence length on the distance measurement precision is broken, and the precision of a sub-millimeter or even dozens of micrometers distance measurement system can be realized. This is one of the innovative points of the present invention to distinguish existing devices.
In the invention, in a high-precision large-range distance measurement system, the measurement range of the distance measurement system is determined by the distance measurement result of the coarse measurement ruler, the lower the frequency of the coarse measurement ruler is, the larger the distance measurement range is, but due to radio frequency line impedance, radio frequency joule effect and the like, a high-bandwidth electro-optic modulator cannot be used for low-frequency signal modulation (lower than 1MHz), so that the modulation of the coarse measurement ruler and the fine measurement ruler cannot be synchronously generated in the same modulation device while the distance measurement precision is ensured, and the expansion of the distance measurement range is influenced by the modulation bandwidth.
The invention adopts the electro-optical modulator to respectively carry out double high frequencies (v) in the laser modulation module3And v3+ f) difference frequency modulation; using frequency v3And v3And (5) ranging the + f signal, wherein the difference frequency signal f in the measurement light and the reference light is detected to be used as a rough measuring scale signal, and the phase is the rough measuring scale ranging result. In a high-precision large-range ranging system, the device and the method are utilized to generate the rough measuring scale through difference frequency modulation, a high-bandwidth modulator is prevented from being used for low-frequency modulation, the ranging information of the rough measuring scale can be obtained by detecting the difference frequency signal of two high-frequency signals, the limit of the modulation bandwidth on the range expansion is broken, and the ranging range can reach hundreds of meters to hundreds of thousands of meters. This is the second innovation of the present invention to distinguish the existing devices.
Drawings
FIG. 1 is a schematic diagram of the general structure of the laser distance measuring device of the present invention;
FIG. 2 is a schematic diagram of a multi-frequency generation module;
FIG. 3 is a schematic structural diagram of a laser modulation module;
FIG. 4 is a schematic structural diagram of a measurement optical path;
fig. 5 is a schematic structural diagram of an optical signal receiving and processing module.
1 is a multi-frequency generation module, 2 is a laser modulation module, 3 is a measurement light path, 4 is an optical signal receiving and processing module, 5 is a first crystal oscillator, 6 is a second crystal oscillator, 7 is a third crystal oscillator, 8 is a first phase-locked frequency doubling circuit, 9 is a second phase-locked frequency doubling circuit, 10 is a third phase-locked frequency doubling circuit, 11 is a fourth phase-locked frequency doubling circuit, 12 is a first amplifying circuit, 13 is a second amplifying circuit, 14 is a third amplifying circuit, 15 is a fourth amplifying circuit, 16 is a fifth amplifying circuit, 17 is a first power synthesizer, 18 is a second power synthesizer, 19 is a laser, 20 is a first double-path light splitting optical fiber, 21 is a first electro-optical modulator, 22 is a second electro-optical modulator, 23 is a second double-path optical fiber, 24 is a first light splitter, 25 is a second light splitter, 26 is a third light splitter, 27 is a beam expander set, 28 is a beam expander set, 29 is a measurement pyramid, 30 is No. three double-path light splitting optical fiber, 31 is No. four double-path light splitting optical fiber, 32 is No. three electro-optical modulator, 33 is No. four electro-optical modulator, 34 is No. one photoelectric detector, 35 is No. two photoelectric detectors, 36 is No. three photoelectric detectors, 37 is No. four photoelectric detectors, 38 is No. six amplifying circuit, 39 is No. seven amplifying circuit, 40 is No. eight amplifying circuit, 41 is No. nine amplifying circuit, 42 is No. one filter circuit, 43 is No. two filter circuit, 44 is No. three filter circuit, 45 is No. four filter circuit, 46 is high-precision phase measurement board card.
Detailed Description
The present invention will be described in detail with reference to specific examples.
The first embodiment is as follows:
according to fig. 1 to 5, referring to fig. 1 to 5, a phase laser distance measuring device for rough and fine measurement scale difference frequency modulation and demodulation includes a multi-frequency generation module 1, a laser modulation module 2, a measurement optical path 3 and an optical signal receiving and processing module 4, where the multi-frequency generation module 1 generates three outputs, two of which are input to the laser modulation module 2 to modulate laser, the other is input to the optical signal processing and receiving module 4, output light of the laser modulation module is input to the measurement optical path 3, and two output lights of the measurement optical path 3 are respectively input to the optical signal receiving and processing module 4 for phase measurement for measurement light and reference light;
the multi-frequency generation module 1 comprises a first crystal oscillator 5, a second crystal oscillator 6, a third crystal oscillator 7, a first phase-locked frequency doubling circuit 8, a second phase-locked frequency doubling circuit 9, a third phase-locked frequency doubling circuit 10, a fourth phase-locked frequency doubling circuit 11, first to fifth amplifying circuits 12 to 16, a first power synthesizer 17 and a second power synthesizer 18, wherein the output end of the first crystal oscillator 5 is connected to the input end of the first phase-locked frequency doubling circuit 8 and passes through the first amplifying circuit 12, the output signal of the first crystal oscillator 5 is connected to the input end of the second phase-locked frequency doubling circuit 9 and passes through the second amplifying circuit 13, the output end of the second crystal oscillator 6 is connected to the input end of the third amplifying circuit 14, the output signal of the third crystal oscillator 7 is connected to the input end of the third phase-locked frequency doubling circuit 10 and passes through the fourth amplifying circuit 15, the output signal of the third crystal oscillator 7 is connected to the input end of the fourth phase-locked frequency doubling circuit 11, and passes through a fifth amplifying circuit 16; the output end of the first amplifying circuit 12 and the output end of the fifth amplifying circuit 16 are respectively input to two input ends of a first power synthesizer 17, the output end of the first power synthesizer 17 is connected to the input end of a first electro-optical modulator 21 to be used as a driving signal, the output end of a second power synthesizer 18 is connected to the input end of a second electro-optical modulator 22 to be used as a driving signal, and the output end of a second amplifying circuit 14 is connected to the input ends of a third electro-optical modulator 32 and a fourth electro-optical modulator 33 to be used as a driving signal;
the laser modulation module 2 comprises a laser 19, a first electro-optical modulator 21, a second electro-optical modulator 22, a first double-path light splitting optical fiber 20 and a second double-path light splitting optical fiber 23. The output of the laser 19 is connected to the first double-path branching optical fiber 20 and is divided into two paths, one output end of the first double-path branching optical fiber 20 is connected to the input end of the first electro-optical modulator 21, the other output end of the first double-path branching optical fiber is connected to the input end of the second electro-optical modulator 22, the output ends of the first electro-optical modulator 21 and the second electro-optical modulator 22 are respectively connected to the two input ends of the second double-path branching optical fiber 23, and the output end of the second double-path branching optical fiber 23 is connected to the input end of the measuring optical path 3;
the measurement light path 3 includes a first collimator 24, a second collimator 25, a third collimator 26, a beam splitter 27, a beam expander set 28, and a measurement pyramid 29. The output end of the second two-way branching optical fiber 23 is connected to the input end of the first collimator 24, the output end of the first collimator 24 is connected to the spectroscope 27, one output of the spectroscope 27 is connected to the input end 25 of the second collimator as reference light, the output end of the second collimator 25 is connected to one input end of the optical signal receiving and processing module 4, the other output of the spectroscope 27 is connected to the input end of the beam expander set 28, the output end of the beam expander set 28 is connected to the input end of the measurement pyramid 29, the output end of the measurement pyramid 29 is connected to the input end of the spectroscope 27 through the beam expander set 28, the output end of the spectroscope 27 is connected to the input end of the third collimator 26 as measurement light, and the output end of the third collimator 26 reaches the other input end of the optical signal receiving and processing module 4;
the optical signal receiving and processing module 4 comprises a third double-path light splitting optical fiber 30, a fourth double-path light splitting optical fiber 31, a third electro-optical modulator 32, a fourth electro-optical modulator 33, first to fourth photoelectric detectors 34 to 37, sixth to ninth amplifying circuits 38 to 41, first to fourth filter circuits 42 to 45 and a high-precision phase measurement board card 46. An output end of the measuring optical path 3 is used as reference light and is connected with an input end of a third double-path light splitting optical fiber 30 and then divided into two paths, an output end of the third double-path light splitting optical fiber 30 is connected with an input end of a third electro-optical modulator 32, an input end of the third electro-optical modulator 32 is connected with an input end of a first photoelectric detector 34, an output end of the first photoelectric detector 34, a sixth amplifying circuit 38 and a first filtering circuit 42 are sequentially connected, an output end of the first filtering circuit 42 is connected with the high-precision phase measurement board card, and the other output end of the third double-path light splitting optical fiber 30 is connected with an input end of a second photoelectric detector 35 and then is connected with the high-precision phase measurement board card after sequentially passing through a seventh amplifying circuit 39 and a second filtering circuit 43; the other output end of the measuring optical path 3 is used as measuring light and connected with the input end of the fourth double-path branching optical fiber 31 and is divided into two paths, one output end of the fourth double-path branching optical fiber 31 is connected with the input end of the fourth electro-optical modulator 33, the output end of the fourth electro-optical modulator 33, the third photoelectric detector 36, the eighth amplifying circuit 40 and the third filter circuit 44 are sequentially connected, and the output end of the third filter circuit 44 is connected with the high-precision phase measurement board card 46; the other output end of the fourth double-path branching optical fiber 31 is connected to the input end of the fourth photoelectric detector 37, and is connected to the high-precision phase measurement card 46 through the ninth amplifying circuit 41 and the fourth filter circuit 45 in sequence.
A phase laser ranging method for difference frequency modulation and demodulation of a rough and fine measuring scale is applied to the phase laser ranging device for difference frequency modulation and demodulation of the rough and fine measuring scale, and is characterized by comprising the following steps:
step 4, the reference light input into the optical signal receiving and processing module 4 from step 2 is divided into two laser beams by a third two-way light-splitting optical fiber 30, wherein one laser beam enters a third electro-optical modulator 32 at the frequency v1-f1Is driven by sine wave to carry out intensity modulation, and the light intensity change frequency in the reference light is v1The precision measuring ruler generates a difference frequency signal f after being modulated1And phase information of the precision measuring ruler is provided, and the phase information is amplified and filtered by a first photoelectric detector 34, a sixth amplifying circuit 38 and a first filter circuit 42 in sequence, so that only high-frequency signals with the output frequency f are output1The other beam of the third two-way beam splitting optical fiber 30 passes through the second photoelectric detector 33, the seventh amplifying circuit 39 and the second filter circuit 43, and then signals with other frequencies are filtered out, and only signals with the frequency v are respectively output2And f;
step 6, the high-precision phase measurement board card 4 respectively measures the frequency f1、v2The phase difference between the reference signal and the measurement signal of the sum is measured, the phase difference being
And
the data synthesis unit of the high-precision phase measurement board card synthesizes the three phase difference values to generate a distance value, the frequency of the rough measurement ruler is f, the wavelength is lambda, and the distance measurement value of the rough measurement ruler is
Frequency v2The signal of (a) is a secondary rough measuring scale with a wavelength of lambda2The distance measured value of the secondary rough measuring rule is
Frequency v1The signal of (A) is a precision measuring ruler with a wavelength of lambda1The measured distance is
To solve the problem of the frequency v of the precision measuring ruler1And if the light intensity is too high, the detection is difficult or the detection effect is poor, and the reference light and the measured return light are subjected to secondary intensity modulation to realize difference frequency demodulation. Using frequency v1-f1Sine signal pair of measuring precision measuring ruler signal in return light
Performing a second intensity modulation, wherein
When the linear modulation working point is located, the modulated output optical signal is
Generates a difference frequency signal
The phase of which contains phase information of the fine measurement, and a detector is used to detect a difference frequency signal f with a lower frequency1And carrying out phase discrimination to obtain a precision measurement result.
In order to solve the problem that the low-frequency modulation effect of the electro-optical modulator is poor, a coarse measuring scale is generated through double high-frequency signal difference frequency modulation. High-frequency v is carried out on the laser by the electro-optical modulator in the laser modulation module3And v3+ f light intensity modulation, detecting the difference frequency signal of f frequency between the measured light and the reference light as the rough measuring scale in the light signal receiving and processing module, and setting the frequency v at the photoelectric detector3And v3The measured optical signal of + f is:
wherein
The light intensity signal with frequency f that can be detected by the photodetector is:
the signal is used as a rough measuring scale signal, and the phase position of the signal is a rough measuring distance measuring result.
The frequency generated by the multi-frequency generation module 1 is v1And v1-f1The signals of the same signal source are from a first crystal oscillator5, the fine measurement difference frequency signal f thus detected1Common mode noise is eliminated, and the frequency stability is better.
The above description is only a preferred embodiment of the coarse and fine measuring scale differential frequency modulation and demodulation phase laser ranging device and the ranging method, and the protection range of the coarse and fine measuring scale differential frequency modulation and demodulation phase laser ranging device and the ranging method is not limited to the above embodiments, and all technical schemes belonging to the idea belong to the protection range of the invention. It should be noted that modifications and variations which do not depart from the gist of the invention will be those skilled in the art to which the invention pertains and which are intended to be within the scope of the invention.
Claims (9)
1. A phase laser distance measuring device for difference frequency modulation and demodulation of a rough and fine measuring ruler is characterized in that: the device comprises: the device comprises a multi-frequency generation module, a laser modulation module, a measuring optical path and an optical signal receiving and processing module, wherein the multi-frequency generation module generates three paths of output, two paths of output are input into the laser modulation module to modulate laser, and the other path of output is input into the optical signal processing and receiving module; the output light of the laser modulation module is input to a measuring light path, and the two output lights of the measuring light path are respectively measuring light and reference light which are input to the optical signal receiving and processing module for phase measurement.
2. The rough/fine scale difference frequency modulation and demodulation phase laser ranging device according to claim 1, wherein: the multi-frequency generation module comprises a first crystal oscillator, a second crystal oscillator, a third crystal oscillator, a first phase-locked frequency doubling circuit, a second phase-locked frequency doubling circuit, a third phase-locked frequency doubling circuit, a fourth phase-locked frequency doubling circuit, a first to fifth amplifying circuits, a first power synthesizer and a second power synthesizer;
the output end of the first crystal oscillator is connected to the input end of the first phase-locked frequency doubling circuit and passes through the first amplifying circuit; the output signal of the first crystal oscillator is connected to the input end of the second phase-locked frequency doubling circuit and passes through the second amplifying circuit, the output end of the second crystal oscillator is connected to the input end of the third amplifying circuit, and the output signal of the third crystal oscillator is connected to the input end of the third phase-locked frequency doubling circuit and passes through the fourth amplifying circuit; the output signal of the third crystal oscillator is connected to the input end of the fourth phase-locked frequency multiplier circuit and passes through the fifth amplifying circuit; the output end of the first amplifying circuit and the output end of the fifth amplifying circuit are respectively input to two input ends of a first power synthesizer, the output end of the first power synthesizer is connected to the input end of the first electro-optical modulator to be used as a driving signal, the output end of the second power synthesizer is connected to the input end of the second electro-optical modulator to be used as a driving signal, and the output end of the second amplifying circuit (14) is connected to the input ends of the third electro-optical modulator and the fourth electro-optical modulator to be used as a driving signal.
3. The rough/fine scale difference frequency modulation and demodulation phase laser ranging device according to claim 2, wherein: the laser modulation module comprises a laser, a first electro-optic modulator, a second electro-optic modulator, a first double-path light splitting optical fiber and a second double-path light splitting optical fiber; the output of the laser is connected to the first double-path branching optical fiber and divided into two paths, one path of output end of the first double-path branching optical fiber is connected to the input end of the first electro-optical modulator, the other path of output end of the first double-path branching optical fiber is connected to the input end of the second electro-optical modulator, the output ends of the first electro-optical modulator and the second electro-optical modulator are respectively connected to the two input ends of the second double-path branching optical fiber, and the output end of the second double-path branching optical fiber is connected to the input end of the measuring optical path.
4. The rough/fine scale difference frequency modulation and demodulation phase laser ranging device according to claim 3, wherein: the measuring light path comprises a first collimator, a second collimator, a third collimator, a spectroscope, a beam expander set and a measuring pyramid; the output of No. two way branching optic fibre is connected to the input of a collimater, the output of a collimater is connected to the spectroscope, the output of spectroscope is connected to the input of No. two collimaters as reference light all the way, the output of No. two collimaters is connected to an input of light signal receiving and processing module, another way output of spectroscope is connected to the input of beam expanding mirror group, the output of beam expanding mirror group is connected to the input of measuring pyramid, the output of measuring pyramid is connected to the input of spectroscope through beam expanding mirror group, the output of spectroscope is connected to the input of No. three collimaters as the measuring light, No. three collimaters' output is to another input of light signal receiving and processing module.
5. The rough/fine scale difference frequency modulation and demodulation phase laser ranging device according to claim 4, wherein: the optical signal receiving and processing module comprises a third double-path light splitting optical fiber, a fourth double-path light splitting optical fiber, a third electro-optic modulator, a fourth electro-optic modulator, a first to fourth photoelectric detectors, a sixth to ninth amplifying circuit, a first to fourth filter circuit and a high-precision phase measurement board card; one output end of the measuring light path is used as reference light and is connected with the input end of a third double-path light splitting optical fiber and then is divided into two paths, one output end of the third double-path light splitting optical fiber is connected to the input end of a third electro-optical modulator, the input end of the third electro-optical modulator is connected to the input end of a first photoelectric detector, the output end of the first photoelectric detector, a sixth amplifying circuit and a first filtering circuit are sequentially connected, the output end of the first filtering circuit is connected to the high-precision phase measurement board card, and the other output end of the third double-path light splitting optical fiber is connected to the input end of a second photoelectric detector, and then is sequentially connected to the high-precision phase measurement board card through a seventh amplifying circuit and a second filtering circuit;
the other output end of the measuring light path is used as measuring light and is connected with the input end of a fourth double-path branching optical fiber and is divided into two paths, one output end of the fourth double-path branching optical fiber is connected to the input end of a fourth electro-optical modulator, the output end of the fourth electro-optical modulator, a third photoelectric detector, an eighth amplifying circuit and a third filtering circuit are sequentially connected, and the output end of the third filtering circuit is connected to the high-precision phase measurement board card; and the other output end of the fourth double-path branching optical fiber is connected to the input end of the fourth photoelectric detector and is connected to the high-precision phase measurement board card sequentially through a ninth amplifying circuit and a fourth filter circuit.
6. A coarse-fine scale frequency difference modulation and demodulation phase laser ranging method, which is based on the coarse-fine scale frequency difference modulation and demodulation phase laser ranging device of claim 5, and is characterized in that: the method comprises the following steps:
step 1: turning on the multi-frequency generation module and the laser with an output frequency v1、v1-f1、v2、v3And v3The output laser is divided into two laser beams by a first two-path light-splitting optical fiber, wherein one laser beam is input to a first electro-optical modulator at a frequency v1And v3Driven by sine wave of the laser, the other laser is input into a second electro-optical modulator at a frequency v2And v3The intensity is modulated under the drive of the sine wave of + f, and the two paths of modulated output laser beams are combined into a laser beam through a second path of light splitting optical fiber;
step 2: one beam of laser generated in the step 1 is incident to the spectroscope through the first collimator and is divided into two beams of laser, one beam of laser is input to the optical signal receiving and processing module as reference light through the second collimator, and the other beam of laser is emitted to the measuring pyramid prism as measuring light through the beam expander group;
and step 3: moving the measurement pyramid prism to a target end, reflecting the measurement light by the pyramid prism, then passing the reflected measurement light through the beam expander set to enter the spectroscope, and inputting the measurement light carrying distance information, which is output by the spectroscope, into the optical signal receiving and processing module through the third collimator;
and 4, step 4: the reference light input into the optical signal receiving and processing module according to the step 2 is divided into two beams of laser through a third two-way light splitting optical fiber, wherein one beam enters a third electro-optical modulator at the frequency v1-f1Is driven by sine wave to carry out intensity modulation, and the light intensity change frequency in the reference light is v1The precision measuring ruler generates a difference frequency signal f after being modulated1The phase information of the precision measuring ruler is amplified and filtered by a photoelectric detector, a six-amplification circuit and a filter circuit in sequence, and only the output frequency is f1The other beam of the third double-path optical splitting fiber passes through the secondAfter photoelectric detector, seventh amplifying circuit and second filtering circuit are electrified, extra frequency signals are filtered out, and only signals with v frequency are output respectively2And f;
and 5: the measuring light input into the optical signal receiving and processing module according to the step 3 is divided into two beams through a four-way light splitting optical fiber, wherein one beam enters a four-way electro-optical modulator at the frequency v1-f1Is driven by sine wave to carry out intensity modulation, and the light intensity change frequency in the measuring light is v1The precision measuring ruler generates a difference frequency signal f after being modulated1The distance measurement phase information with the precision measuring ruler is amplified and filtered by a third photoelectric detector, an eighth amplifying circuit and a third filter circuit in sequence, and only the output frequency is f1After the other beam of output of the four-path light-splitting optical fiber passes through a four-photoelectric detector, a nine-amplifying circuit and a four-filtering circuit, signals with extra frequency are filtered, and only signals with the frequency v are output respectively2And f;
step 6, high-precision phase measurement board card respectively measures the frequency f1、v2And f, measuring the phase difference between the reference signal and the measurement signal, the phase difference being
And
high-precision data of photo board card
The distance measurement of the secondary rough rule is represented by:
wherein the floor () function is a rounding function with a frequency v1The signal of (A) is a precision measuring ruler with a wavelength of lambda1；
The measured distance is represented by:
7. the method of claim 6, wherein the method comprises: performing secondary intensity modulation on the reference light and the measured return light to realize difference frequency demodulation, wherein the frequency is v1-f1Sine signal pair of measuring precision measuring ruler signal in return light
Performing a second intensity modulation, wherein
When located at the linear modulation operating point, the modulated output optical signal is represented by:
the difference frequency signal is generated by:
the phase includes fine phase information, and the detector is used to detect the difference frequency signal f with lower frequency1And carrying out phase discrimination to obtain a precision measurement result.
8. The method of claim 6, wherein the method comprises:
generating a rough measuring scale by difference frequency modulation of double high-frequency signals, and respectively carrying out high-frequency v on laser in a laser modulation module through an electro-optical modulator3And v3+ f light intensity modulation, detecting the difference frequency signal of f frequency in the measuring light and the reference light as the rough measuring scale in the light signal receiving and processing module, and expressing the frequency v at the photoelectric detector by the following formula3And v3Measurement optical signal of + f:
the light intensity signal detected by the photodetector at frequency f is then represented by:
as the rough scale signal, the phase is the rough ranging result.
9. The method of claim 6, wherein the method comprises:
the frequency generated by the multi-frequency generation module is v1And v1-f1The signals of the signal source are from the same signal source crystal oscillator I.
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