CN218120898U - Phase type distance measuring device based on double-electro-optical heterodyne modulation - Google Patents
Phase type distance measuring device based on double-electro-optical heterodyne modulation Download PDFInfo
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Abstract
The utility model discloses a phase type distance measuring device based on two electric light heterodyne modulations, including light path unit, signal generation module, signal conditioning and collection module and digital processing system, the light path unit includes laser instrument, first electric light intensity modulator, circulator, fiber probe and second electric light intensity modulator; the laser, the first electro-optic intensity modulator and the circulator are sequentially connected through optical fibers; the circulator is respectively connected with the optical fiber probe and the second electro-optic intensity modulator through optical fibers, and the emergent direction of the optical fiber probe is opposite to the target to be measured; the signal generating module is respectively connected with the first electro-optical intensity modulator, the second electro-optical intensity modulator and the A/D analog-digital signal converter; the signal conditioning and collecting module comprises a photoelectric conversion device, an amplifying circuit, a filter circuit and an A/D analog-digital signal converter which are connected in sequence.
Description
Technical Field
The utility model belongs to non-contact distance measurement field. Specifically speaking, the utility model relates to a laser phase formula distance on-line measuring device, especially one kind utilizes electro-optical modulator to realize the distance on-line measuring device of light signal amplitude secondary heterodyne modulation.
Background
The precision distance measurement technology has wide application requirements in advanced technologies and advanced science fields of national defense, military industry, aerospace and the like, and especially plays an important role in the processes of manufacturing large precision machinery and assembling major rotating equipment. The online measurement of the internal clearance of the major equipment is an important link of equipment health management and is a key for ensuring the working efficiency and the operation safety. Typical equipment clearances comprise axial clearances and blade tip clearances, and the characteristics of axial clearances with slow change, continuity and large measuring range and the characteristics of blade tip clearances with pulse, discontinuity and small measuring range put different requirements on the measuring method. However, the internal space of the equipment is narrow, the introduction path of the signal transmission cable is long, the probe of the gap measurement methods such as the traditional capacitance method, the eddy current method and the microwave method is large in size, the signal attenuation is serious during long-distance transmission, and the requirement for online measurement of the gap of the equipment is difficult to meet. The optical method adopts a laser measurement means based on optical fibers, the diameter sizes of the probe and the transmission optical fibers are small, the probe and the transmission optical fibers have the characteristics of small size and flexibility, and the probe and the transmission optical fibers can effectively extend into major equipment and are more suitable for measuring equipment gaps.
The optical distance measuring method mainly includes a pulse method, a frequency method, and a phase method depending on the form of a transmission signal. In the traditional distance measurement method, a pulse method is limited by receiving and transmitting switching time, a distance measurement blind zone exists, and the measurement precision cannot meet the requirement of precise distance measurement; the measurement precision of the frequency method is limited by frequency modulation frequency difference, the distance measurement precision is not high in sub-millimeter distance, the measurement response speed is low due to limitation of frequency sweeping speed, and the frequency method is difficult to apply to blade tip clearance measurement; the phase method modulates the intensity of the laser signal, and realizes distance measurement by comparing the phases of the measuring optical signal and the reference optical signal; the device and the method for dynamically measuring the rotor-stator axial gap based on the phase type laser ranging (202110464019.1) proposed in the earlier stage adopt the principle of electrical down-conversion, utilize a photoelectric conversion device to directly receive back optical signals, and the light intensity modulation frequency is in a microwave frequency band.
SUMMERY OF THE UTILITY MODEL
The utility model aims at overcoming the not enough among the prior art, provide a phase type distance measuring device based on two electric-optical heterodyne modulations. The optical down-conversion principle is adopted, the optical modulator is used for carrying out secondary heterodyne modulation on the amplitude of an optical signal, and a feasible scheme is provided for measuring the equipment gap by an optical method.
The utility model aims at realizing through the following technical scheme:
a phase type distance measuring device based on double-electro-optical heterodyne modulation comprises a light path unit, a signal generation module, a signal conditioning and acquisition module and a digital processing system, wherein the light path unit comprises a laser, a first electro-optical intensity modulator, a circulator, an optical fiber probe and a second electro-optical intensity modulator; the laser, the first electro-optic intensity modulator and the circulator are sequentially connected through optical fibers; the circulator is respectively connected with the optical fiber probe and the second electro-optic intensity modulator through optical fibers, and the emergent direction of the optical fiber probe is opposite to the target to be measured;
the signal generation module is respectively connected with the first electro-optic intensity modulator, the second electro-optic intensity modulator and the A/D analog-digital signal converter; the signal generation module outputs the first electro-optical intensity modulator with the frequency f M1 To the second electro-optical intensity modulator with an output frequency f M2 For the A/D analog-to-digital signal converter, the output frequency is f IM Sine wave intermediate frequency signal of, and f IM ＝|f M1 -f M2 |；
In the optical path unit, the laser generates an optical signal, which is transmitted to the second optical fiberAn electro-optical intensity modulator in which the optical signal is applied at a frequency f M1 The modulated sine wave signal is transmitted to the circulator and the optical fiber probe in turn through the optical fiber after being modulated, the optical fiber probe projects an optical signal to a target to be measured and receives a return optical signal reflected from the target to be measured, the return optical signal is transmitted to the circulator and the second electro-optical intensity modulator in turn through the optical fiber, and the return optical signal is transmitted to the circulator and the second electro-optical intensity modulator in turn through the second electro-optical intensity modulator with the frequency of f M2 Carrying out heterodyne modulation on the sine wave modulation signal;
the signal conditioning and collecting module comprises a photoelectric conversion device, an amplifying circuit, a filter circuit and an A/D analog-digital signal converter which are connected in sequence; the photoelectric conversion device converts the heterodyne modulated return light signal into an electric signal, and the electric signal is amplified by the amplifying circuit and filtered by the filtering circuit in sequence and has the frequency f IM The sine wave intermediate frequency signals are collected by an A/D analog digital signal converter, and the generated digital signals are transmitted to a digital processing system for phase identification and comparison to generate a phase difference which forms a one-to-one mapping relation with the distance to be measured;
the digital processing system utilizes the obtained phase difference data to solve the measured distance based on the phase ranging principle.
Further, the optical path unit adopts a single-wavelength or dual-wavelength structure.
Furthermore, when the optical path unit is of a single-wavelength structure, only one first laser is arranged for generating the light with the wavelength of lambda 0 As measuring light.
Furthermore, when the optical path unit is in a dual-wavelength structure, a second laser and a coupler are further arranged, wherein the first laser generates a wavelength lambda 0 As measuring light, a second laser generating a laser beam with a wavelength lambda 1 The laser as the reference light, the measuring light and the reference light are combined into a path of dual-wavelength light beam through a coupler, the first electro-optical intensity modulator simultaneously modulates the dual-wavelength optical signal, the second electro-optical intensity modulator simultaneously heterodynes the dual-wavelength optical signal, the end face of the optical fiber probe (8) is coated with a film, and the film has the wavelength of lambda 0 Is totally transmitted to the laser with the wavelength of lambda 1 The measuring light is projected to be measuredThe target is reflected, and the reference light is directly reflected at the end face of the fiber-optic probe.
Further, when the optical path unit is in a dual-wavelength structure, the optical fiber probe adopts a dual-probe structure or a common-path structure; when the optical fiber probe adopts a double-measuring-head structure, a double-wavelength optical signal is divided into two paths of light beams by a second wavelength division multiplexer, the first measuring head transmits measuring light and receives a return light signal of a target to be measured, and the second measuring head totally reflects reference light and receives the reflected return light signal; when the optical fiber probe adopts a common optical path structure, a dual-wavelength optical signal is divided into two paths of light beams of measuring light and reference light after reaching the end face of the probe, the measuring light is projected to a target to be measured and reflected, the reference light is directly reflected on the end face of the probe, and the optical fiber probe receives a reflected return light signal.
Further, when the optical path unit is of a dual-wavelength structure, the signal conditioning and collecting module includes a first photoelectric conversion device, a first amplifying circuit, a first filter circuit, a second photoelectric conversion device, a second amplifying circuit, a second filter circuit, an a/D analog-to-digital signal converter, and a first wavelength division multiplexer; dividing the dual-wavelength optical signal into two paths of light beams of a measuring optical signal and a reference optical signal by a first wavelength division multiplexer; the measurement optical signal is transmitted to the A/D analog-digital signal converter through the first photoelectric conversion device, the first amplifying circuit and the first filter circuit in sequence; the reference light signal is transmitted to the A/D analog-digital signal converter through the second photoelectric conversion device, the second amplifying circuit and the second filter circuit in sequence.
Furthermore, the signal generation mode of the signal generation module selects an analog frequency synthesis technology, a direct digital frequency synthesis technology or a phase-locked loop frequency synthesis technology.
Furthermore, the frequency of the sine wave modulation signal is 8-10 GHz, and the frequency of the sine wave intermediate frequency signal is 3-7 MHz.
Compared with the prior art, the utility model discloses a beneficial effect that technical scheme brought is:
1. overcome traditional distance measuring device and be difficult to realize under the narrow space equipment clearance on-line measuring's shortcoming, signal attenuation serious scheduling problem when avoiding methods such as electric capacity method, eddy current method, microwave method's probe size great, long distance transmission, the utility model provides an equipment clearance measuring device based on optic fibre utilizes the characteristics that optic fibre size is small and exquisite, the structure is flexible, can effectively stretch into inside the major equipment, realizes equipment clearance on-line measuring under the narrow working space.
2. Overcome pulse method, frequency method among traditional optical distance measurement method and can not satisfy the shortcoming that accurate range finding required, solve earlier stage based on electricity down the frequency conversion phase formula laser range finding method to device performance requirement high, the relatively poor problem of signal to noise ratio, the utility model provides a phase formula distance measuring device based on two electric-optical heterodyne modulations utilizes two modulation of electric light modulator to carry out twice modulation of light signal range, and optics down frequency conversion back is taked care of and is gathered, improves the received signal SNR.
3. Frequency f of the modulated signal M1 And f M2 The range can be selected according to the range of the distance to be measured, and the higher the frequency of the modulation signal is, the higher the distance measurement precision is under the condition of ensuring that the half wavelength of the modulation signal is greater than the range; frequency f of intermediate frequency signal IM The selection is carried out according to the dynamic response performance requirement of the measuring device, and the dynamic response speed of the measuring device is higher when the frequency of the intermediate frequency signal is higher under the condition that the intermediate frequency signal can be sampled by the A/D analog-digital signal converter without distortion, so that flexible and accurate modulation and measurement are realized.
4. The digital processing system adopts a digital phase discrimination algorithm, simultaneously extracts the phases of the measurement electric signal and the reference electric signal, and obtains the phase difference of the two signals; when the structure and the measuring environment of the measuring device are unchanged, the phase difference between the measuring electrical signal and the reference electrical signal only changes in real time along with the change of the distance to be measured; the utility model provides a light path unit of dual wavelength structure can further make the phase difference of measuring the signal of telecommunication and the reference signal of telecommunication overcome the influence of ambient temperature change, vibration, guarantees the measurement accuracy of distance measuring device under high temperature, vibration environment.
Drawings
Fig. 1 is a schematic structural diagram of an optical path unit in a phase distance measuring device according to the present invention, which adopts a single-wavelength structure.
Fig. 2 is a schematic structural diagram of the optical path unit in the phase distance measuring device of the present invention adopting a dual-wavelength structure.
Fig. 3 is a schematic structural diagram of the optical fiber probe of the present invention when a dual probe is used.
Reference numerals: the device comprises a light path unit, a 2-signal generating module, a 3-signal conditioning and collecting module, a 4-digital processing system, a 5-laser, a 6-electro-optical intensity modulator, a 7-circulator, an 8-optical fiber probe, a 9-electro-optical intensity modulator, a 10-photoelectric conversion device, an 11-amplifying circuit, a 12-filter circuit, a 13-A/D analog-to-digital signal converter, a 14-laser, a 15-coupler, a 16-wavelength division multiplexer, a 17-photoelectric conversion device, an 18-amplifying circuit, a 19-filter circuit, a 20-wavelength division multiplexer, a 21-measuring head and a 22-measuring head.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and specific embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention.
Example 1
In the phase distance measuring device based on dual-electrical-heterodyne modulation provided in this embodiment, the optical path unit 1 adopts a single-wavelength structure, and only the measurement light and no reference light exist, as shown in fig. 1, the measuring device mainly includes: the device comprises a light path unit 1, a signal generating module 2, a signal conditioning and collecting module 3 and a digital processing system 4; the optical path unit 1 mainly comprises a laser 5, an electro-optic intensity modulator 6, a circulator 7, an optical fiber probe 8 and an electro-optic intensity modulator 9; the signal conditioning and collecting module 3 mainly comprises a photoelectric conversion device 10, an amplifying circuit 11, a filter circuit 12 and an A/D analog-digital signal converter 13 which are connected in sequence; the laser 5, the electro-optic intensity modulator 6 and the circulator 7 are sequentially connected through optical fibers; the circulator 7 is respectively connected with the optical fiber probe 8 and the electro-optic intensity modulator 9 through optical fibers, and the emergent direction of the optical fiber probe 8 is opposite to the target to be measured; the signal generating module 2 is respectively connected with the electro-optical intensity modulator 6, the electro-optical intensity modulator 9 and the A/D analog-digital signal converter 13.
The signal generation module 2 outputs a path of frequency f M1 The other path of the sine wave modulation signal has the frequency f M2 And a sine wave modulation signal of frequency f IM Sine wave intermediate frequency signal of, and f IM ＝|f M1 -f M2 |。
In the light path unit 1, a laser 5 generates an optical signal which is transmitted via an optical fiber to an electro-optical intensity modulator 6, where the optical signal is at a frequency f M1 The signal modulation is carried out, after the signal is transmitted to the circulator 7 by the optical fiber, the optical fiber probe 8 transmits and receives the optical signal, the return optical signal is transmitted to the circulator 7 by the optical fiber and then transmitted to the electro-optical intensity modulator 9, and the frequency of the return optical signal is f at the electro-optical intensity modulator 9 M2 Is heterodyne modulated.
In the signal conditioning and collecting module 3, the photoelectric conversion device 10 converts the intensity of the heterodyne-modulated measurement return optical signal into a measurement electrical signal, and the measurement electrical signal is amplified by the amplifying circuit 11 and filtered by the filtering circuit 12, so that the signal-to-noise ratio is improved; will have a frequency of f IM The measured electrical signal and the reference electrical signal are collected by the a/D analog-to-digital signal converter 13, and a digital signal is generated and transmitted to the digital processing system 4 for phase discrimination and comparison, thereby generating a phase difference in a one-to-one mapping relationship with the distance to be measured.
The digital processing system 4 obtains the distance measurement value on line in real time by using the phase difference data and the calibration curve, and meanwhile, the software of the system has the functions of on-line display, off-line analysis and the like.
Example 2
In the phase distance measuring device based on dual-electrical-optical heterodyne modulation provided in this embodiment, the optical path unit 1 adopts a dual-wavelength structure, and has both measuring light and reference light, as shown in fig. 2, the measuring device mainly includes:
the system comprises a light path unit 1, a signal generating module 2, a signal conditioning and collecting module 3 and a digital processing system 4; the optical path unit 1 mainly comprises a laser 5, a laser 14, a coupler 15, an electro-optical intensity modulator 6, a circulator 7, an optical fiber probe 8 and an electro-optical intensity modulator 9; the signal conditioning and collecting module 3 comprises a wavelength division multiplexer 16, a photoelectric conversion device 10, a photoelectric conversion device 17, an amplifying circuit 11, an amplifying circuit 18, a filter circuit 12, a filter circuit 19 and an A/D analog-digital signal converter 13; the laser 5 and the laser 14 are connected with the coupler 15 through optical fibers, and the coupler 15 is sequentially connected with the electro-optical intensity modulator 6 and the circulator 7 through the optical fibers; the circulator 7 is respectively connected with the optical fiber probe 8 and the electro-optic intensity modulator 9 through optical fibers, and the emergent direction of the optical fiber probe 8 is opposite to the target to be measured; the signal generating module 2 is respectively connected with the electro-optical intensity modulator 6, the electro-optical intensity modulator 9 and the A/D analog-digital signal converter 13. The electro-optical intensity modulator 9 is connected with a wavelength division multiplexer 16, the output end of the wavelength division multiplexer 16 is divided into two paths, and one path is connected with a photoelectric conversion device 10, an amplifying circuit 11, a filter circuit 12 and an A/D analog-digital signal converter 13 which are sequentially connected; and the other path is a photoelectric conversion device 17, an amplifying circuit 18, a filter circuit 19 and an A/D analog-digital signal converter 13 which are connected in sequence.
When the optical path unit 1 adopts a dual-wavelength structure, the optical fiber probe 8 can adopt a dual-measuring-head structure or a common-path structure; for the dual probe structure (see fig. 3), the wavelength division multiplexer 20 divides the dual wavelength optical signal into two beams, the probe 21 emits the measurement light and receives the return optical signal of the end face of the rotor, and the probe 22 reflects the reference light on the end face thereof; for the common path structure (see fig. 2), the end face of the optical fiber probe is coated with a coating having a wavelength λ 0 Is transmitted so that the wavelength is lambda 1 The laser total reflection; the coating film can be selected from lambda 0 Wave band antireflection film and lambda 1 A reflective film of a wavelength band.
The signal generation module 2 outputs a path of frequency f M1 Another path of the sine wave modulation signal has a frequency of f M2 And a sine wave modulation signal of frequency f IM Sine wave intermediate frequency signal of, and f IM ＝|f M1 -f M2 |。
For the measuring apparatus using the dual wavelength structure for the optical path unit 1, the laser 5 generates the wavelength λ 0 As measuring light, the laser 14 generates a laser beam with a wavelength λ 1 The measuring light and the reference light are combined into a path of light beam with double wavelengths in a coupler 15, and the electro-optical intensity modulator 6 simultaneously modulates the optical signals with the double wavelengthsThe electro-optical intensity modulator 9 performs heterodyne modulation on the dual-wavelength optical signal, the measurement light is projected to the end surface to be measured, namely the end surface of the rotor and is reflected, and the reference light is directly reflected on the end surface of the optical fiber probe. Since the reference light and the measuring light exist simultaneously, the wavelength division multiplexer 16 divides the dual-wavelength optical signal into two beams, i.e., a measuring optical signal and a reference optical signal.
For the processing of the measurement optical signal, the photoelectric conversion device 10 converts the intensity of the measurement optical signal into a measurement electrical signal, and the measurement electrical signal is amplified by the amplifying circuit 11 and filtered by the filtering circuit 12 in sequence, so that the signal-to-noise ratio is improved;
for the processing of the reference optical signal, the photoelectric conversion device 17 converts the intensity of the reference optical signal into a reference electrical signal, and the reference electrical signal is amplified by the amplifying circuit 18 and filtered by the filtering circuit 19 in sequence, so that the signal-to-noise ratio is improved; the measurement electrical signal, the reference electrical signal and the intermediate frequency signal are collected by the a/D analog-to-digital signal converter 13, and then digital signals are generated and transmitted to the digital processing system 4 for phase discrimination and comparison.
The digital processing system 4 obtains the distance measurement value on line in real time by using the phase difference data and the calibration curve, and meanwhile, the software of the system has the functions of on-line display, off-line analysis and the like.
Further, in the two embodiments:
the signal generation mode of the signal generation module 2 can select an analog frequency synthesis technology, a direct digital frequency synthesis technology or a phase-locked loop frequency synthesis technology; in this embodiment, the signal generating module 2 may be a phase-locked loop, and is composed of a controller, a clock reference, a phase discriminator, a loop filter, a voltage-controlled oscillator, a frequency divider, and the like; the controller can be an STM32 series single chip microcomputer; the clock reference provides stable frequency reference for the system, and a temperature compensation crystal oscillator with higher frequency stability can be selected; the loop filter plays a role in suppressing phase noise and spurious noise, and can be a passive filter or an active filter; the signal generating module 2 generates two paths of modulation signals and one path of intermediate frequency signal, the higher the frequency of the modulation signal is, the higher the ranging precision is, but the half wavelength of the modulation signal is larger than the range, so as to avoid the problem of phase ranging ambiguity; for example, the range of 15mm, the modulation signal frequency of 8-10 GHz can be selected; the frequency selection of the intermediate frequency signal needs to consider the influence of the intermediate frequency signal on the dynamic response performance of the phase distance measurement system, namely, the phase measurement generally needs 3 to 5 signal periods, taking the measurement of the blade tip clearance as an example, the lower limit of the frequency selection of the intermediate frequency signal needs to ensure that the effective measurement can be obtained when the end face of the blade passes through the sensor; the upper limit of the frequency of the intermediate frequency signal is selected to take into account the sampling speed of the a/D adc 13 and avoid undersampling, for example, the frequency of the intermediate frequency signal is selected to be 5 MHz.
The laser 5 and the laser 14 can be semiconductor butterfly packaged lasers; the coupler 15 can be a 3dB optical fiber coupler; the circulator 7 can be a three-port optical fiber circulator; quartz polarization maintaining optical fibers can be selected for the optical fibers of all the optical paths; the electro-optical intensity modulator 6 and the electro-optical intensity modulator 9 can be selected from a lithium niobate Mach-Zehnder type intensity modulator; a fiber amplifier may be arranged in the light path from the circulator 7 to the electro-optical intensity modulator 9 to increase the signal-to-noise ratio.
The wavelength division multiplexer 16 and the wavelength division multiplexer 20 may be a coarse wavelength division multiplexer or a dense wavelength division multiplexer; the photoelectric conversion devices 10 and 17 may be avalanche photodiodes or PIN photodiodes; the amplifier circuit 11 and the amplifier circuit 18 may be transimpedance amplifiers.
The digital processing system 4 can comprise a lower computer and an upper computer, wherein the lower computer can be a Field Programmable Gate Array (FPGA), and the upper computer can be a computer or an industrial personal computer; the lower computer uploads the data from the lower computer to the upper computer by using a high-speed data transmission method based on a PCI/PCIE/USB3.0 communication bus; the software of the upper computer has the functions of online display, data storage, data back display, offline analysis and the like.
Specifically, the online distance measuring method for realizing optical signal amplitude quadratic heterodyne modulation by using the electro-optical modulator by using the rotor end face as the target to be measured by combining the measuring devices provided by the two embodiments includes the following specific contents:
firstly, a signal generating module generates a modulating signal and an intermediate frequency signal in the form of sine waves; two modulation signals are respectively represented by an equation (1) and an equation (2):
wherein A is M1 And A M2 Representing the amplitude of the modulated signal, f M1 And f M2 Which is indicative of the frequency of the modulated signal,
and
representing an initial phase of the modulated signal;
a path of intermediate frequency signals, represented by formula (3):
wherein A is IM Representing the amplitude of the intermediate frequency signal, f IM Which is indicative of the frequency of the intermediate frequency signal,
representing an initial phase of the intermediate frequency signal;
f M1 and f M2 Selecting according to the range of the distance to be measured, and under the condition of ensuring that the half wavelength of the modulation signal is greater than the range, the higher the frequency of the modulation signal is, the higher the distance measurement precision is; f. of IM The selection is carried out according to the dynamic response performance requirement of the measuring system, and the dynamic response speed of the system is higher when the frequency of the intermediate frequency signal is higher under the condition that the intermediate frequency signal can be sampled by the A/D analog-digital signal converter 13 without distortion;
further, the optical path unit 1 uses the optical signal as a carrier wave and utilizes the principle of electro-optical modulation to be controlled by the frequency f M1 And f M2 Twice modulating the signal of (3); light path unit1 when adopting a single-wavelength structure, the laser 5 generates a wavelength of lambda 0 The laser light of (2) is used as measuring light without reference light; when the optical path unit 1 adopts a dual-wavelength structure, the laser 14 generates a wavelength λ 1 The laser as reference light, the measuring light and reference light are combined into one light beam in the coupler 15, the electro-optical intensity modulator 6 modulates the dual-wavelength optical signal, the electro-optical intensity modulator 9 modulates the heterodyne of the dual-wavelength optical signal, the end face of the optical fiber probe 8 is coated with a film with the wavelength of lambda 0 Is totally transmitted to the laser with the wavelength of lambda 1 The measuring light is projected to the end face of the rotor and reflected, and the reference light is directly reflected on the end face of the optical fiber probe.
The light intensities of the measurement light and the reference light after modulation by the electro-optical intensity modulator 6 are represented by equation (4) and equation (5), respectively:
wherein A is λ0 And A λ1 Respectively representing the magnitude of the change in the measured and reference light intensities,
and
indicating the initial phases of the measurement light and the reference light, respectively.
After the measurement light and the reference light which are modulated for the first time undergo different propagation processes, different phase changes are introduced, the measurement light and the reference light return to the circulator along the original optical path and then reach the electro-optical intensity modulator 9, and the light intensities of the measurement light and the reference light are respectively expressed by an equation (6) and an equation (7):
wherein the content of the first and second substances,
and
the induced phase variations are propagated in the optical fiber, the optics,
measuring phase changes introduced for light propagation in a gap space between the fiber probe and the target to be measured; after the measurement light and the reference light are modulated for the second time in the electro-optical intensity modulator 9, the light intensities are respectively expressed by the following equations (8) and (9):
wherein the content of the first and second substances,
and
after passing through the electro-optical intensity modulator 9, the measurement light and the reference light respectively propagate the introduced phase change in the optical fiber and the optical device before reaching the photoelectric conversion device.
Furthermore, the optical fiber probe 8 is responsible for projecting optical signals to the rotor direction and receiving optical signals reflected by the end face of the rotor; when the optical path unit 1 adopts a dual-wavelength structure, the optical fiber probe 8 can adopt a dual-probe structure or a common-path structure; for the dual probe structure (see fig. 3), the wavelength division multiplexer 20 divides the dual wavelength optical signal into two beams, the probe 21 emits the measurement light and receives the return optical signal of the end face of the rotor, and the probe 22 reflects the reference light on the end face thereof; for the common optical path structure (see fig. 2), after reaching the end face of the probe, the dual-wavelength optical signal is divided into two paths of beams of measuring light and reference light, the measuring light is projected to a target to be measured and reflected, the reference light is directly reflected on the end face of the probe, and the optical fiber probe 8 receives the reflected return light signal.
Further, the signal conditioning and collecting module 3 is used for realizing functions of photoelectric conversion, signal amplification and filtering, analog signal collection and the like; the signal received by the photoelectric conversion device is an intermediate frequency intensity modulated optical signal, and the signal conditioning and collecting module 3 only needs to adjust the frequency f IM Processing the intermediate frequency signal;
when the optical path unit 1 adopts a single-wavelength structure, see fig. 1, without the reference optical signal, the photoelectric conversion device 10 will measure the intensity I ″) of the optical signal " λ0 (t) conversion into a measurement Electrical Signal IF m (t) represented by formula (10):
signal IF m (t) the signal-to-noise ratio is improved through the processing of the amplifying circuit 11 and the filtering circuit 12 in sequence; at this time, IF m (t) as a measurement electrical signal, and the intermediate frequency signal IF (t) generated by the signal generation module 2 as a reference electrical signal; the measurement electric signal and the reference electric signal are collected by the A/D analog-digital signal converter 13 and then transmitted to the digital processing system 4;
when the optical path unit 1 adopts a dual-wavelength structure, as shown in fig. 2, reference light and measuring light exist at the same time, and the wavelength division multiplexer 16 divides a dual-wavelength optical signal into two light beams, namely a measuring optical signal and a reference optical signal; for the processing of the reference light signal, the photoelectric conversion device 17 converts the intensity I of the reference light signal " λ1 (t) conversion into a reference electric signal IF r (t) represented by formula (11):
signal IF r (t) the signal-to-noise ratio is improved by processing the signal by the amplifying circuit 18 and the filtering circuit 19 in sequence; at this time, IF m (t) as measuring electrical signals, IF r (t) as a reference electrical signal; the measurement electrical signal, the reference electrical signal, and the intermediate frequency signal IF (t) are collected by the a/D analog-to-digital signal converter 13 and transmitted to the digital processing system 4.
Further, the digital processing system 4 is used for realizing digital phase discrimination and phase comparison of two paths of signals of the measured electric signal and the reference electric signal, performing distance calculation based on phase difference data, and realizing functions of online display, data storage, data redisplay, offline analysis and the like of the measured distance; the digital processing system 4 can control the a/D analog-to-digital signal converter 13 to synchronously sample the measurement electrical signal and the reference electrical signal by using a frequency multiplication signal of the intermediate frequency signal IF (t).
The digital processing system 4 adopts a digital phase discrimination algorithm, simultaneously extracts the phases of the measurement electric signal and the reference electric signal, and obtains the phase difference of the two signals; for the single-wavelength structure, the phase difference is represented by formula (12); for the two-wavelength structure, the phase difference is represented by equation (13):
right side of equations (12) and (13), only
The phase quantity is changed in real time along with the distance to be measured, and other phase quantities are not changed when the system structure and the measurement environment are not changed; compared with a single-wavelength structure, the double-wavelength structure utilizes the characteristic that the measuring light and the reference light are transmitted in the same optical path and is influenced by the change of environmental temperature and vibration
And
the changes of the two parts are almost consistent, and the two parts can be mutually offset, so that the environmental adaptability is improved.
The digital processing system utilizes the phase difference data and solves the measured distance based on the phase distance measuring principle, and the measured distance is expressed as an equation (14):
obtaining phase difference data corresponding to each distance value in a measuring range by adopting a calibration technology of traversing the distance to be measured at equal intervals, and establishing a mapping relation between the phase difference and the distance to be measured by utilizing a curve fitting method to obtain a distance calibration curve; the utility model discloses utilize phase difference measuring result and calibration curve, can realize equipping clearance on-line measuring.
The present invention is not limited to the above-described embodiments. The above description of the embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above embodiments are merely illustrative and not restrictive. Without departing from the spirit of the invention and the scope of the appended claims, the person skilled in the art can make many changes in form and detail within the teaching of the invention.
Claims (8)
1. A phase type distance measuring device based on double electro-optic heterodyne modulation is characterized by comprising a light path unit (1), a signal generating module (2), a signal conditioning and collecting module (3) and a digital processing system (4), wherein the light path unit (1) comprises a laser, a first electro-optic intensity modulator (6), a circulator (7), an optical fiber probe (8) and a second electro-optic intensity modulator (9); the laser, the first electro-optic intensity modulator (6) and the circulator (7) are sequentially connected through optical fibers; the circulator (7) is respectively connected with the optical fiber probe (8) and the second electro-optic intensity modulator (9) through optical fibers, and the emergent direction of the optical fiber probe (8) is opposite to the target to be measured;
the signal generation module (2) is respectively connected with the first electro-optic intensity modulator (6), the second electro-optic intensity modulator (9) and the A/D analog-digital signal converter (13); the signal generation module (2) outputs a frequency f to the first electro-optical intensity modulator (6) M1 Is output to the second electro-optical intensity modulator (9) at a frequency f M2 The sine wave modulation signal of (2) outputs a frequency f to an A/D analog-to-digital signal converter (13) IM Sine wave intermediate frequency signal of, and f IM ＝|f M1 -f M2 |；
In the light path unit (1), the laser generates an optical signal, which is transmitted to the first electro-optical intensity modulator (6) via the optical fiber, and the optical signal is modulated by the first electro-optical intensity modulator (6) at a frequency f M1 The sine wave modulation signal is modulated and then sequentially transmitted to a circulator (7) and an optical fiber probe (8) through an optical fiber, the optical fiber probe (8) projects a light signal to a target to be measured and receives a return light signal reflected from the target to be measured, the return light signal is sequentially transmitted to the circulator (7) and a second electro-optical intensity modulator (9) through the optical fiber and is subjected to frequency f in the second electro-optical intensity modulator (9) M2 Carrying out heterodyne modulation on the sine wave modulation signal;
the signal conditioning and collecting module (3) comprises a photoelectric conversion device, an amplifying circuit, a filter circuit and an A/D analog-digital signal converter (13) which are connected in sequence; the photoelectric conversion device converts the heterodyne modulated return light signal into an electric signal, and the electric signal is amplified by the amplifying circuit and filtered by the filtering circuit in sequence and has the frequency f IM The sine wave intermediate frequency signals are collected by an A/D analog digital signal converter (13), and the generated digital signals are transmitted to a digital processing system (4) for phase identification and comparison to generate a phase difference which forms a one-to-one mapping relation with the distance to be measured;
the digital processing system (4) utilizes the obtained phase difference data to solve the measured distance based on the phase distance measuring principle.
2. The phase distance measuring device based on double-electric-optical heterodyne modulation as recited in claim 1, wherein the optical path unit (1) adopts a single-wavelength or double-wavelength structure.
3. Phase distance measuring device based on double electrical heterodyne modulation as claimed in claim 2, characterized in that, when the optical path unit (1) is of single-wavelength construction, only one first laser (5) is provided for generating the wavelength λ 0 As measuring light.
4. The phase distance measuring device based on double-electric-optical heterodyne modulation as recited in claim 2, wherein when the optical path unit (1) is a dual-wavelength structure, a second laser (14) and a coupler (15) are further provided, and the first laser (5) generates the light with a wavelength λ 0 As measuring light, a second laser (14) generates light with a wavelength λ 1 The laser as the reference light, the measuring light and the reference light are combined into a path of dual-wavelength light beam through a coupler (15), a first electro-optical intensity modulator (6) simultaneously modulates dual-wavelength optical signals, a second electro-optical intensity modulator (9) simultaneously performs heterodyne modulation on the dual-wavelength optical signals, the end face of the optical fiber probe (8) is provided with a coating film, and the coating film is used for coating the wavelength of lambda 0 Is totally transmitted to the laser with the wavelength of lambda 1 The measuring light is projected to a target to be measured and reflected, and the reference light is directly reflected on the end face of the optical fiber probe (8).
5. The phase type distance measuring device based on double-electric-optical heterodyne modulation is characterized in that when the optical path unit (1) is in a double-wavelength structure, the optical fiber probe (8) adopts a double-measuring-head structure or a common-optical-path structure; when the optical fiber probe (8) adopts a double-measuring-head structure, a double-wavelength optical signal is divided into two paths of light beams by a second wavelength division multiplexer (20), a first measuring head (21) emits measuring light and receives a return light signal of a target to be measured, and a second measuring head (22) totally reflects reference light and receives the reflected return light signal; when the optical fiber probe (8) adopts a common optical path structure, a dual-wavelength optical signal is divided into two paths of light beams, namely measuring light and reference light after reaching the end face of the probe, the measuring light is projected to a target to be measured and reflected, the reference light is directly reflected on the end face of the probe, and the optical fiber probe (8) receives a reflected return light signal.
6. The phase distance measuring device based on double-electric-optical heterodyne modulation is characterized in that when the optical path unit (1) is of a dual-wavelength structure, the signal conditioning and collecting module (3) comprises a first photoelectric conversion device (10), a first amplifying circuit (11), a first filter circuit (12), a second photoelectric conversion device (17), a second amplifying circuit (18), a second filter circuit (19), an A/D analog-to-digital signal converter (13) and a first wavelength division multiplexer (16); the dual-wavelength optical signal is divided into two paths of light beams of a measuring optical signal and a reference optical signal by a first wavelength division multiplexer (16); the measurement optical signal is transmitted to an A/D analog-digital signal converter (13) through a first photoelectric conversion device (10), a first amplifying circuit (11) and a first filter circuit (12) in sequence; the reference optical signal is transmitted to the A/D analog-digital signal converter (13) through the second photoelectric conversion device (17), the second amplifying circuit (18) and the second filter circuit (19) in sequence.
7. The phase distance measuring device based on double-electrical-optical heterodyne modulation as recited in claim 1, wherein the signal generating module (2) is selected from an analog frequency synthesis technique, a direct digital frequency synthesis technique or a phase-locked loop frequency synthesis technique.
8. The phase type distance measuring device based on double-electric-optical heterodyne modulation as recited in claim 1, wherein the frequency of the sine wave modulation signal is 8-10 GHz, and the frequency of the sine wave intermediate frequency signal is 3-7 MHz.
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