CN110006418B - Angular velocity measuring method, device and application system - Google Patents
Angular velocity measuring method, device and application system Download PDFInfo
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- CN110006418B CN110006418B CN201910299406.7A CN201910299406A CN110006418B CN 110006418 B CN110006418 B CN 110006418B CN 201910299406 A CN201910299406 A CN 201910299406A CN 110006418 B CN110006418 B CN 110006418B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/58—Turn-sensitive devices without moving masses
- G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
- G01C19/72—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
Abstract
The invention relates to an angular velocity measuring method, an angular velocity measuring device and an application system, wherein the angular velocity measuring method comprises the following steps: the measuring device comprises a first emitter, a second emitter, a first optical splitter, a first measuring optical path, a second measuring optical path and a fourth optical splitter, wherein the fourth optical splitter emits interference signals, and the application system applies the measuring device. According to the invention, the angular velocity is measured in high precision through the first measuring optical path, the angular velocity is measured in a large range through the second measuring optical path, the two calculated angular velocities are combined to calculate the final angular velocity, the measuring range of the angular velocity is improved on the basis of the high-precision angular velocity measurement in a rough and precise combination mode, and the method has higher practicability.
Description
Technical Field
The invention relates to the technical field of measurement, in particular to an angular velocity measurement method, an angular velocity measurement device and an application system.
Background
The Sagnac interferometer is a high-precision interferometer applying the Sagnac effect, the laser Sagnac interferometer can be used for measuring relative angular velocity, the laser measurement technology is revolutionarily developed along with the invention of the femtosecond optical frequency comb, great technical breakthrough is made in the fields of absolute distance measurement, spectral analysis, long-distance time transmission and the like, and the laser Sagnac interferometer is rapidly applied to various fields of the precision measurement industry.
With the development of the optical fiber gyroscope, the Sagnac interferometer develops towards the direction of all optical fibers, but the measurement range is small, and large-range measurement cannot be performed, although the angular velocity can be measured by the traditional optical frequency comb, if the measurement precision needs to be improved, the length of the Sagnac optical fiber interferometer needs to be increased, or the area of the Sagnac optical fiber interferometer needs to be increased, but the mode has the defects of serious dispersion, large occupied volume and the like, and the requirement of high-precision measurement of the angular velocity cannot be met.
Disclosure of Invention
The invention aims to provide an angular velocity measuring method, an angular velocity measuring device and an application system, so as to realize large-range and high-precision measurement of angular velocity.
The technical scheme adopted by the invention for solving the technical problems is as follows:
an angular velocity measuring method comprising the steps of:
emitting measurement light and dividing the measurement light into first measurement light and second measurement light;
the first measuring light enters the first measuring light path and obtains a first angular velocity value, and the second measuring light enters the second measuring light path and obtains a second angular velocity value;
and combining the first angular velocity value and the second angular velocity value to calculate a final angular velocity value.
In a preferred embodiment, the first angular velocity value is measured as follows:
the first measuring light enters the first measuring light path and is divided into two paths at the initial end of the first measuring light path, the two paths of light are transmitted in the first measuring light path in opposite directions and are converged at the initial end of the first measuring light path, amplitude change of phase difference of the two paths of light is obtained, and a first angular velocity value is calculated according to the amplitude change.
In a preferred embodiment, the second angular velocity value is measured as follows:
and emitting local oscillator light, wherein the local oscillator light and the second measuring light have a repeated frequency difference and an overlapped spectrum range, the second measuring light enters the second measuring light path and is divided into two paths at the starting end of the second measuring light path, the two paths of light are transmitted in the second measuring light path in opposite directions and return to the starting end of the second measuring light path to be combined and output a combined light signal, the combined light signal and the local oscillator light signal are subjected to optical heterodyne interference to output an interference signal, the interference signal is obtained, and a second angular velocity value is calculated according to the interference signal.
In a preferred embodiment, two light beams split from the second measurement light are pulse-separated by separate optical paths having different optical lengths.
The present invention also provides an angular velocity measuring apparatus, including:
a first emitter for emitting measurement light;
the second transmitter is used for transmitting local oscillation light;
the first optical splitter is used for receiving the measuring light and splitting the measuring light into first measuring light and second measuring light;
the first measuring optical path comprises a second optical splitter, the second optical splitter receives the first measuring light, and a first annular optical path extends out based on the second optical splitter;
the second measuring light path comprises a third optical splitter, the third optical splitter receives the second measuring light and extends out of a second annular light path based on the third optical splitter, and a first separation light path and a second separation light path which have different optical distances are arranged in the second annular light path;
and the fourth optical splitter is used for receiving the local oscillator light and outputting an interference signal.
In a preferred embodiment, the second measures the light path and includes fifth optical splitter and sixth optical splitter, be connected with between fifth optical splitter and the sixth optical splitter first separation light path, second annular light path is located one section between fifth optical splitter and the sixth optical splitter forms second separation light path, be equipped with first optical isolator on the first separation light path, be equipped with second optical isolator on the second separation light path, the light transmission direction of first optical isolator and second optical isolator is opposite.
In a preferred embodiment, the optical module further includes a light combining optical path, an input port of the light combining optical path is communicated with the third optical splitter, and an output port of the light combining optical path is communicated with the fourth optical splitter.
In a preferred embodiment, the optical module further comprises a detection optical path, an input end of the detection optical path is communicated with the second emitter, and both the detection optical path and the light combining optical path are communicated with the fourth optical splitter.
In a preferred embodiment, the optical measurement system further includes a detection element and an output element, the detection element is configured to detect output signals in the first measurement optical path and the second measurement optical path, and the output element includes a signal acquisition module and a data processing module.
The invention also discloses an application system applying the angular velocity measuring device.
The invention has at least the following beneficial effects:
the first measuring optical path and the second measuring optical path share a measuring light source, the angular velocity is measured in high precision through the first measuring optical path, the angular velocity is measured in a large range through the second measuring optical path, the two angular velocities obtained through calculation are combined and calculated to obtain the final angular velocity, the measuring range of the angular velocity is widened on the basis of high-precision measurement of the angular velocity in a rough and precise combination mode, and the practicability is high.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a flow chart of one embodiment of a method of measuring angular velocity;
FIG. 2 is a system diagram of one embodiment of an angular velocity measurement device;
fig. 3 is a schematic diagram of an optical path of an embodiment of the angular velocity measuring apparatus.
Detailed Description
The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings to fully understand the objects, the features, and the effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention. In addition, all the connection/connection relations referred to in the patent do not mean that the components are directly connected, but mean that a better connection structure can be formed by adding or reducing connection auxiliary components according to specific implementation conditions. The technical characteristics of the invention can be combined interactively on the premise of not conflicting with each other.
Referring to fig. 1, the angular velocity measurement method in the present embodiment includes the steps of:
emitting measurement light and dividing the measurement light into first measurement light and second measurement light;
the first measuring light enters the first measuring light path and obtains a first angular velocity value, and the second measuring light enters the second measuring light path and obtains a second angular velocity value;
and combining the first angular velocity value and the second angular velocity value for calculation to obtain the required angular velocity value.
The first angular velocity value is measured as follows: the first measuring light enters the first measuring light path and is divided into two paths at the initial end of the first measuring light path, the first measuring light path is an annular light path, the two paths of light are transmitted in the first measuring light path in opposite directions and converge after returning to the initial end of the first measuring light path, the amplitude change of the phase difference of the two paths of light is obtained, and the first angular velocity value can be calculated according to the amplitude change.
According to the Sagnac effect, two paths of light in the first measuring light path are transmitted in reverse directions, when an object to be measured rotates, the optical paths of the two paths of light in the first measuring light path are changed and have different phase delays, so that the interference pulse intensity of the first measuring light is changed, the output signal intensity in the first measuring light path is obtained, the signal intensity change corresponds to the rotating angular speed, and the first angular speed value can be obtained.
The first angular velocity is measured by adopting a laser pulse interference method, two related lights interfered in a first measuring light path are collected after being coupled, the intensity of an interference peak value after the coherent light coupling is obtained, and the first angular velocity is obtained by calculating through amplitude subdivision.
When two paths of light pulses in the first measuring light path are overlapped, the amplitudes of the two paths of light are the highest, the first angular velocity value can be obtained by obtaining the amplitudes and subdividing the amplitudes, but the measuring time is short and is only one fourth of the whole period, so that the measuring precision of the first angular velocity value is high, and the measuring range is small.
According to the interference principle of the Sagnac effect, different annular light paths cannot be accurately matched due to different measurement parameters, so that other measurement loops need to be arranged to expand the measurement range of the angular velocity. In the embodiment, on the basis of the measurement of the first angular velocity, a second angular velocity measurement method is further provided to increase the measurement range of the angular velocity.
The second angular velocity is measured as follows: and emitting local oscillator light, wherein the local oscillator light and the second measuring light have a repeated frequency difference and an overlapped spectrum range, the second measuring light enters the second measuring light path and is divided into two paths at the starting end of the second measuring light path, the two paths of light are transmitted in the second measuring light path in opposite directions and return to the starting end of the first measuring light path to be combined and output a combined light signal, the combined light signal and the local oscillator light signal are subjected to optical heterodyne interference to output an interference signal, the interference signal is obtained, and a second angular velocity value is calculated according to the interference signal.
Two light paths with different optical paths are arranged in the second measuring light path, the light transmission directions of the two light paths are different, two paths of light split by the second measuring light respectively pass through the two light paths and return to the initial end of the second measuring light path to converge, and pulses of the two paths of light after passing through the light paths are forcibly separated, so that the measuring dead zone of the angular velocity can be eliminated, and the measuring range of the angular velocity is enlarged.
The method for calculating the second angular velocity value includes the following steps:
intercepting two interference signals in one interference period, and calculating the time difference delta tau corresponding to the centers of the two interference signals;
calculating a second angular velocity value omega of the signal in a single interference period;
the above
In the above formula, n is the number of winding turns of the optical fiber in the measuring optical path, c is the speed of light, A is the area enclosed by the measuring optical path, and Δ frIs the repetition frequency difference between the second measurement light and the local oscillator light, fsΔ τ is the difference between the centers of the two interference signals in one interference period, which is obtained by fourier transform and least square fitting, for the repetition frequency of the second measurement light.
And the repetition frequency of the second measuring light is fLOBy the formula Δ fr＝fS-fLOThen, Δ f can be obtainedr。
Further, the method for calculating the time difference Δ τ includes the steps of:
acquiring the time difference t corresponding to two interference signals in two time intervals in one intercepted interference period0；
Carrying out fast Fourier change on the two truncated interference signals, respectively calculating phase frequency spectrums, then carrying out subtraction, and fitting a slope k by using a least square method;
time difference delta tau corresponding to two interference signal centers is k + t0。
Based on the calculation method, the second angular velocity value omega in a single interference period can be obtained.
In signal processing, a single interference period is used as a processing period, angular velocity measurement and calculation are performed once in each period, and the second measurement light and the local oscillator light are output in a measurement optical path in two paths of light, so that two obvious interference signals can be observed in one interference period. And since the difference in slope of the phase spectrum is equal to the time shift of the signal, by the slope k and the given time shift t being known0The corresponding difference delta tau between the centers of the two interference signals in one interference period can be obtained.
On the premise of eliminating the measurement dead zone, multi-heterodyne interference is carried out on the local oscillator light and the light combining optical comb signal to form an interference signal, the interference signal is collected, analyzed and calculated to obtain the absolute angular velocity of the object, and the measurement range of the angular velocity is enlarged.
After the calculation of the first angular velocity value and the second angular velocity value is completed, the accurate value of the first angular velocity value and the range value of the second angular velocity are respectively obtained, and combined calculation is carried out to obtain the final angular velocity value.
The angular velocity measurement method in the embodiment improves the measurement range of the angular velocity on the premise of ensuring the measurement accuracy, and can be used for measuring the absolute angular velocity of a moving object, such as an aircraft, a spacecraft, a cruise ship, an automobile and the like, in the flight process of the flying object.
Referring to fig. 2 and 3, the present invention also provides an angular velocity measuring apparatus, including:
a first emitter 10, the first emitter 10 for emitting measurement light 101;
a second transmitter 20, the second transmitter 20 being configured to transmit local oscillator light 102;
a first beam splitter 71, wherein the first beam splitter 71 can receive the measuring light 101 and split the measuring light into a first measuring light 103 and a second measuring light 104;
a first measurement optical path 30, wherein the first measurement optical path 30 includes a second beam splitter 31, the second beam splitter 31 receives the first measurement light 103, and extends out of a first annular optical path 32 based on the second beam splitter 31;
a second measuring optical path 40, wherein the second measuring optical path 40 includes a third beam splitter 41, the third beam splitter 41 receives the second measuring light 104, and extends out of a second annular optical path 42 based on the third beam splitter 41, and a first separated optical path 43 and a second separated optical path 44 with different optical lengths are arranged in the second annular optical path 42;
the fourth optical splitter 61 and the fourth optical splitter 61 are configured to receive the local oscillator light 102 and output an interference signal 106.
The second beam splitter 31 receives the first measuring light 103, and splits the first measuring light 103 into a first detecting light 1031 and a second detecting light 1032 which are transmitted in opposite directions, and the first detecting light 1031 and the second detecting light 1032 are transmitted once in the first annular light path 32 and return to the second beam splitter 31 for coupling. The first measuring optical path 30 is further provided with a first detecting element 33, the first detecting element 33 is configured to detect an optical signal obtained by coupling the first detecting light 1031 and the second detecting light 1032 at the second optical splitter 31, process the coupled optical signal by using a pulse interference method, and calculate a first angular velocity value by using the intensity of an interference peak.
Preferably, the first angular velocity is measured by an amplitude subdivision method, the second beam splitter 31 is a 50:50 coupler, the first measurement light 103 passes through the second beam splitter 31 and is divided into a first detection light 1031 and a second detection light 1032, the first detection light 1031 and the second detection light 1032 are transmitted in the first annular light path 32 in opposite directions, the first detection light 1031 and the second detection light 1032 pass through the same optical path, the first detection light 1031 and the second detection light 1032 are coupled at the second beam splitter 31, a phase difference is generated after the first detection light 1031 and the second detection light 1032 interfere with each other, when the object to be measured rotates, the phase difference is generated and changes the phase amplitude, and an accurate angular velocity signal can be obtained by corresponding the amplitude to the angular velocity.
Preferably, the number of turns around the first annular light path 32 can be selected according to practical requirements, the higher the number of turns, the more significant the Sagnac effect, the larger the phase shift between the first detection light 1031 and the second detection light 1032, and the smaller the size of the first annular light path 32.
The second measurement optical path 40 includes a fifth optical splitter 45 and a sixth optical splitter 46, a first split optical path 43 is connected between the fifth optical splitter 45 and the sixth optical splitter 46, a section of the second annular optical path 42 located between the fifth optical splitter 45 and the sixth optical splitter 46 is a second split optical path 44, a first optical isolator 431 is arranged on the first split optical path 43, a second optical isolator 441 is arranged on the second split optical path 44, and the transmission directions of light allowed to pass through by the first optical isolator 431 and the second optical isolator 441 are opposite.
The third beam splitter 41 receives the second measuring light 104 and splits the second measuring light 104 into a third detecting light 1041 and a fourth detecting light 1042, and the third detecting light 1041 and the fourth detecting light 1042 enter the second annular light path 42. Since the transmission directions of the third detection light 1041 and the fourth detection light 1042 are opposite, the directions of the light allowed to pass through the first optical isolator 431 and the second optical isolator 441 are opposite, the transmission directions of the light allowed to pass through the first optical isolator 43 and the first optical isolator 431 are the same, and the transmission directions of the light allowed to pass through the second optical isolator 44 and the second optical isolator 441 are the same, (it is assumed herein that the light transmission direction of the first optical isolator 43 is the same as the transmission direction of the third detection light 1041, and the light transmission direction of the second optical isolator 44 is the same as the transmission direction of the fourth detection light 1042), the third detection light 1041 returns to the third optical splitter 41 through the first optical isolator 43, and the fourth detection light 1042 can only return to the third optical splitter 41 through the second optical isolator 44 and combine with the third detection light 1041 to form a combined light signal 105, and the above-mentioned arrangement can avoid the repeated transmission of the light beams in the optical paths, the frequency spectrum overlapping is caused, and the measurement precision is influenced; the fourth optical splitter 61 receives the local oscillator light 102 and the combined optical signal 105, and the local oscillator light 102 and the combined optical signal 105 perform multi-heterodyne interference at the fourth optical splitter 61 and output an interference signal 106. Since the optical paths of the first split optical path 43 and the second split optical path 44 are different, the optical pulses of the third detection light 1041 passing through the first split optical path 43 and the fourth detection light 1042 passing through the second split optical path 44 are forcibly separated, which overcomes the defect that when the object rotation speed is small, the measurement dead zone cannot be detected, and enlarges the measurement range of the angular velocity.
Preferably, a first end (left side in the drawing) of the first split optical path 43 communicates with a first end of the second split optical path 44 at the fifth beam splitter 45, and a second end (right side in the drawing) of the first split optical path 43 communicates with a second end of the second split optical path 44 at the sixth beam splitter 46. The fifth optical splitter 45 receives the third detection light 1041 transmitted from the third optical splitter 41 and splits the third detection light 1041, but due to the isolation of the light by the first optical isolator 431 and the second optical isolator 441, the third detection light 1041 can only pass through the first split optical path 43 and be transmitted to the sixth optical splitter 46, and the third detection light 1041 is transmitted from the sixth optical splitter 46 and is returned to the third optical splitter 41; the sixth beam splitter 46 receives the fourth detection light 1042 transmitted from the third beam splitter 41, the fourth detection light 1042 can only pass through the second split optical path 44 and be transmitted to the fifth beam splitter 45, the fourth detection light 1042 transmits from the fifth beam splitter 45 and returns to the third beam splitter 41, and the fourth detection light 1042 and the third detection light 1041 are combined to form a combined optical signal 105.
Preferably, the optical system further comprises a light combining optical path 50, an input port of the light combining optical path 50 is communicated with the third optical splitter 41, an output port of the light combining optical path 50 is communicated with the fourth optical splitter 61, and a third optical isolator 51 is further disposed on the light combining optical path 50. The light transmission direction of the third optical isolator 51 is the same as the transmission direction of the combined light signal 105, so that light beams in other directions are prevented from entering the combined light path 50 to influence the measurement precision; the combined optical signal 105 is transmitted from the third optical splitter 41, and then enters the combined optical path 50, and enters the fourth optical splitter 61 through the combined optical path 50 to perform optical heterodyne interference with the local oscillation light 102, so as to form an interference signal 106.
Preferably, the optical detection device further includes a detection optical path 60, the fourth optical splitter 61 is located on the detection optical path 60 and receives the local oscillator light 102, the local oscillator light 102 performs multi-heterodyne interference with the combined optical signal 105 entering the fourth optical splitter 61 and outputs an interference signal 106, the detection optical path 60 further includes a second detection element 62, and the second detection element 62 is configured to detect the interference signal 106.
Preferably, the optical path system further comprises an output optical path 70, an input end of the output optical path 70 is communicated with the first emitter 10, the first beam splitter 71 is positioned on the output optical path 70, the first emitter 10 emits the measuring light 101 and is received by the first beam splitter 71, the first beam splitter 71 splits the measuring light 101 into a first measuring light 103 and a second measuring light 104, one output end of the output optical path 70 is communicated with the second beam splitter 31, and the other output end of the output optical path 70 is communicated with the third beam splitter 41. The first measurement light 103 enters the first measurement light path 30 to perform high-precision angular velocity measurement, the second measurement light 104 enters the third optical splitter 41 and is divided into the first detection light 1031 and the second detection light 1032 by the third optical splitter 41, and the first detection light 1031 and the second detection light 1032 reversely transmit in the second measurement light path 40, so that the wide-range angular velocity measurement is realized. A fourth optical isolator 72 is arranged between the first optical splitter 71 and the second optical splitter 31, and the light transmission direction of the fourth optical isolator 72 is the same as the transmission direction of the first measuring light 103 in the reverse direction; a fifth optical isolator 73 is arranged between the first optical splitter 71 and the third optical splitter 41, and the light transmission direction of the fifth optical isolator 73 is the same as the transmission direction of the second measuring light 104; the light beam returning from the first measurement light path 30 or the second measurement light path 40 is prevented from returning to the output light path 70 again, and the signal transmission and the measurement accuracy are prevented from being affected.
And a second detecting element 62 and an output element (not shown), wherein the second detecting element 62 is connected with the output element and is positioned on the detecting optical path 60, and the second detecting element 62 is used for detecting the interference signal 106 and carrying out signal transmission. The output element comprises a signal acquisition module and a data processing module, wherein the signal acquisition module receives the interference signal 106 and transmits the interference signal to the data processing module for calculation. Preferably, the signal acquisition module comprises a high-speed signal acquisition part and an interference signal intercepting part, the data processing module comprises a fast Fourier transform operation part, a least square method fitting slope calculation part and a formula substituting and angular velocity solving part, and the high-speed signal acquisition part, the interference signal intercepting part, the fast Fourier transform operation part, the least square method fitting slope part and the formula substituting and angular velocity solving part are sequentially connected.
Preferably, the first transmitter 10 and the second transmitter 20 are optical frequency comb lasers with stable frequencies, the measurement light 101 and the local oscillator light 102 both use an optical frequency comb as a signal source, and the measurement light 101 and the local oscillator light 102 have a slight repetition frequency difference and have overlapping spectral ranges. By adopting the all-fiber structure, the signal-to-noise ratio of the whole measurement light path system can be improved, and the measurement precision is improved. The repetition frequencies f of the second measuring light 104LOAnd the repetition frequency of the local oscillator light 102 is fSDifference in repetition frequency Δ fr＝fS-fLO. Because the measurement system uses all-fiber measurement, the signal-to-noise ratio is high, and the intensities of the second measurement light 104 and the local oscillation light 102 are respectively adjusted, so that the signal-to-noise ratio of the whole measurement system is optimized to be maximum when the optical power of the local oscillation light 102 is one half of the optical power of the second measurement light 104.
The first detecting element 33 and the second detecting element 62 can be single-point detectors, and two paths of measuring signals can be detected simultaneously and independently by one single-point detector, so that the measuring precision is high. A narrow-band filter is arranged between the fourth optical splitter 61 and the second detection element 62, the interference signal 106 is received by the high-bandwidth detector after passing through the narrow-band filter, and the multi-heterodyne interference of the double-optical-frequency comb can be ensured not to generate spectrum overlapping by using the filter.
Preferably, the optical filter with adjustable central wavelength and broadband is used, the central wavelength and the broadband are optimized according to the time domain waveform and the spectrum position of the detector signal, when the number of points of the time domain interference part is enough and the spectrum center is located at the quarter position of the optical frequency comb repetition frequency, the signal aliasing reaches the minimum, and the accuracy of the angular velocity measurement system reaches the maximum.
A filter is arranged between the second detection element 62 and the output element, the signal sent by the second detection element 62 passes through a low-pass filter with a broadband about the common repetition frequency, and then the output element is used for signal collection, the arrangement can remove the incoherent part in the signal, can directly obtain the continuous interference signal 106, and the sampling period of the output element can be reasonably set according to the actual situation.
The optical frequency comb is represented as a femtosecond carrier envelope pulse in a time domain, the optical frequency comb is used as a light source of a measurement optical path, when an object to be measured generates an angular velocity, a Sagnac effect is generated at the third optical splitter 41 by the third detection light 1041 and the fourth detection light 1042, optical paths of the third detection light 1041 and the fourth detection light 1042 in the second annular optical path 42 are changed, and have different phase delays, a single pulse of an original light combination signal 105 is split into two pulses with constant time shift, that is, two beams of light generate two interference signals 106 with different positions. The amplitude of these interference signals 106 is approximately the same, the time shift between the two pulses is small, and the measurement is difficult in a general detection method, so that it is necessary to perform multi-heterodyne interference with two groups of measurement light pulses by using one local oscillator light 102 having a small repetition frequency difference with the second measurement light. If the pulse signal of the local oscillator light 102 is used as an external clock for starting sampling, the collected point is the cross-correlation function of the local oscillator light 102 and the two groups of measurement light pulses, a fixed multiple relation exists between the time delay between the two groups of cross-correlation functions and the original time delay, and the time delay between the two groups of cross-correlation functions can be obtained by respectively fitting the slope of the Fourier transform phase spectrum. That is, the two measurement optical comb signals and the local oscillator light 102 are subjected to multi-heterodyne interference to form an interference signal 106, and the interference signal 106 is acquired and analyzed to obtain the angular velocity value of the rotation of the second measurement optical path 40.
The single interference period is taken as a processing period, angular velocity measurement is performed once for each processing period, the second detection element 62 intercepts the interference signal 106 in each interference period, since light is output in two paths in the second measurement optical path 40, two obvious interference signals 106 can be intercepted in one interference period, the time difference Δ τ corresponding to the centers of the two interference signals 106 is obtained by fourier transform and least square fitting, and the angular velocity Ω of the object to be measured in a single period can be obtained by the following formula.
In the above formula, n is the winding number of the second annular light path 42, c is the speed of light, A is the area enclosed by the second annular light path 42, Δ frIs the repetitive frequency difference, Δ f, between the second measurement light 104 and the local oscillator light 102rΔ τ is a time difference corresponding to the center of the interference signal 106 on both sides obtained by fourier transform and least square fitting, which is the repetition frequency of the second measurement light 104.
Recording the time difference t corresponding to two time intervals in an interference period0(ii) a Performing fast Fourier transform on the two truncated segments of interference signals 106, respectively calculating phase frequency spectrums, then subtracting, and fitting a slope k by using a least square method; since the difference in slope of the phase spectrum is equal to the time shift of the signal, by the slope k and the given time shift t being known0The angular velocity value within a single interference period, i.e., Δ τ ═ k + t, can be calculated0。
The above calculation formula of angular velocity can be deformed as follows:
in the above measurement process, when the object generates an angular velocity, the formation of the double pulses with constant time shift in the second measurement optical path 40 by the third detection light 1041 and the fourth detection light 1042 is based on the situation that the angular velocity of the object is large, when the angular velocity of the object is small, the difference between the two double pulses is small and almost coincident, the two double pulses are basically not detected by the common detection device, and there is a measurement dead zone of the angular velocity.
The first and second light splitting paths 43 and 44 are disposed in the second measuring light path 40, the optical lengths of the first and second light splitting paths 43 and 44 are different, and the transmission directions of the light allowed to pass through are opposite, so that the third and fourth detecting lights 1041 and 1042 can only pass through different light splitting paths, and the pulses of the third and fourth detecting lights 1041 and 1042 are forcibly separated due to the different optical lengths of the first and second light splitting paths 43 and 44, so as to avoid a dead measurement region. On the premise of eliminating dead zones, the angular velocity measuring system can rapidly measure absolute angular velocity, can obtain a measuring result every 1ms, and has high real-time performance.
After the calculation of the first angular velocity value and the second angular velocity value is completed, the accurate value of the first angular velocity value and the range value of the second angular velocity are respectively obtained, and combined calculation is carried out to obtain the final angular velocity value.
This embodiment adopts the measurement mode that thick smart combines, and first measurement light path 30 and second measurement light path 40 sharing frequency comb light source have realized measuring on a large scale of angular velocity on the basis of carrying out high accuracy angular velocity measurement, and whole device structure is succinct, and occupation space is little, and convenient to use has higher practicality.
The invention also provides an application system which applies the angular velocity measuring device and can be any movable object, such as an aircraft, a ship, a vehicle and the like.
The angular velocity measuring method, the measuring device and the application system not only can eliminate the measuring dead zone of the angular velocity, but also have higher measuring precision and measuring range; the whole system is simple in structure and high in measuring speed, the measuring system is placed in an object to be measured during detection, the detection element can receive interference signals, the angular speed of the object is obtained through signal acquisition and data processing, and the use is rapid and convenient.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. An angular velocity measuring method, characterized by comprising the steps of:
emitting measurement light and dividing the measurement light into first measurement light and second measurement light;
the first measuring light enters a first measuring light path and obtains a first angular velocity value, and the second measuring light enters a second measuring light path and obtains a second angular velocity value;
the first angular velocity value and the second angular velocity value are combined and calculated to obtain a final angular velocity value;
the measuring method of the second angular velocity value is as follows: and emitting local oscillator light, wherein the local oscillator light and the second measuring light have a repeated frequency difference and an overlapped spectrum range, the second measuring light enters the second measuring light path and is divided into two paths at the starting end of the second measuring light path, the two paths of light are transmitted in the second measuring light path in opposite directions and return to the starting end of the second measuring light path to be combined and output a combined light signal, the combined light signal and the local oscillator light signal are subjected to optical heterodyne interference to output an interference signal, the interference signal is obtained, and a second angular velocity value is calculated according to the interference signal.
2. The angular velocity measurement method according to claim 1, wherein the first angular velocity value is measured as follows:
the first measuring light enters the first measuring light path and is divided into two paths at the initial end of the first measuring light path, the two paths of light are transmitted in the first measuring light path in opposite directions and are converged at the initial end of the first measuring light path, amplitude change of phase difference of the two paths of light is obtained, and a first angular velocity value is calculated according to the amplitude change.
3. The method according to claim 1, wherein two light beams split from the second measurement light are pulse-separated via separate optical paths having different optical paths.
4. An angular velocity measuring apparatus, comprising:
a first emitter for emitting measurement light;
the second transmitter is used for transmitting local oscillation light;
the first optical splitter is used for receiving the measuring light and splitting the measuring light into first measuring light and second measuring light;
the first measuring light path comprises a second optical splitter, the second optical splitter receives the first measuring light, and the first measuring light extends out of a first annular light path based on the second optical splitter, the first measuring light can pass through the second optical splitter and is divided into first detecting light and second detecting light, and the first detecting light and the second detecting light are transmitted in the first annular light path in opposite directions and are coupled at the second optical splitter;
a second measuring optical path, including a third optical splitter, where the third optical splitter receives the second measuring light, and extends out of a second annular optical path based on the third optical splitter, a first separation optical path and a second separation optical path having different optical paths are arranged in the second annular optical path, the second measuring light can pass through the third optical splitter and be split into a third detecting light and a fourth detecting light, and the third detecting light and the fourth detecting light respectively pass through the first separation optical path and the second separation optical path and return to the third optical splitter to form a combined optical signal;
and the fourth optical splitter is used for receiving the local oscillator light and the combined light signal and outputting an interference signal.
5. The angular velocity measurement device according to claim 4, wherein the second measurement optical path includes a fifth optical splitter and a sixth optical splitter, the first split optical path is connected between the fifth optical splitter and the sixth optical splitter, a section of the second annular optical path located between the fifth optical splitter and the sixth optical splitter forms a second split optical path, a first optical isolator is disposed on the first split optical path, a second optical isolator is disposed on the second split optical path, and light transmission directions of the first optical isolator and the second optical isolator are opposite.
6. The device according to claim 4, further comprising a light combining path, an input port of the light combining path communicating with the third optical splitter, and an output port of the light combining path communicating with the fourth optical splitter.
7. The device according to any one of claims 4 to 6, further comprising a detection optical path, an input end of the detection optical path being communicated with the second emitter, and the detection optical path and the light combining optical path being communicated with the fourth optical splitter.
8. The device according to any one of claims 4 to 6, further comprising a detection element and an output element, wherein the detection element is configured to detect output signals in the first and second measurement optical paths, and the output element includes a signal acquisition module and a data processing module.
9. An application system characterized by applying the angular velocity measuring apparatus according to any one of claims 4 to 8.
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