CN218120898U - A Phase Distance Measuring Device Based on Dual Electro-optical Heterodyne Modulation - Google Patents

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

A Phase Distance Measuring Device Based on Dual Electro-optical Heterodyne Modulation

technical field

The utility model belongs to the field of non-contact distance measurement. Specifically, the utility model relates to a laser phase distance on-line measuring device, in particular to an on-line distance measuring device which uses an electro-optic modulator to realize secondary heterodyne modulation of the optical signal amplitude.

Background technique

Precision ranging technology has a wide range of application requirements in the fields of advanced technology and cutting-edge science such as national defense, aerospace and aerospace, especially in the manufacture of large-scale precision machinery and the assembly of major rotating equipment. On-line measurement of the internal clearance of major equipment is an important part of equipment health management and the key to ensuring work efficiency and operation safety. Typical equipment clearances include axial clearance and blade tip clearance. Slowly varying, continuous, and longer-range axial clearance signal characteristics and pulse, intermittent, and smaller-range blade tip clearance signal characteristics put forward different requirements for measurement methods. However, the internal space of the equipment is narrow, the lead-in path of the signal transmission cable is long, the probe size of the traditional capacitance method, eddy current method, microwave method and other gap measurement methods is large, and the signal attenuation is serious during long-distance transmission, which is difficult to meet the equipment gap on-line Measurement needs. The optical method adopts the laser measurement method based on optical fiber. The diameter of the probe and transmission optical fiber is small, which is compact and flexible. It can effectively penetrate into the interior of major equipment and is more suitable for equipment gap measurement.

According to the different forms of transmitted signals, the optical distance measurement methods mainly include pulse method, frequency method and phase method. In the traditional distance measurement method, the pulse method is limited by the switching time of transmitting and receiving, and there is a ranging blind zone, and the measurement accuracy cannot meet the requirements of precise ranging; the measurement accuracy of the frequency method is limited by the frequency difference of frequency modulation, and the ranging accuracy is not good at submillimeter distances. High, and limited by the sweep rate, the measurement response speed is low, and it is difficult to apply to the tip clearance measurement; the phase method modulates the intensity of the laser signal, and realizes the distance measurement by comparing the phase of the measurement optical signal and the reference optical signal; the previous proposal The "Dynamic Measuring Device and Method for Axial Gap of Rotor-Stator Based on Phase Laser Rangefinder" (202110464019.1) adopts the principle of electrical down-conversion, uses photoelectric conversion devices to directly receive the return light signal, and its light intensity modulation frequency is in the microwave frequency band. The bandwidth performance requirements of photoelectric conversion devices are extremely high, and due to the constraints of the gain-bandwidth product of the preamplifier, the signal-to-noise ratio of the output electrical signal is poor.

Utility model content

The purpose of the utility model is to provide a phase distance measuring device based on double electro-optic heterodyne modulation in order to overcome the deficiencies in the prior art. Using the principle of optical down-conversion, the electro-optic modulator is used to perform second-order heterodyne modulation of the optical signal amplitude, which provides a feasible solution for the optical method to measure the gap of equipment.

The purpose of this utility model is achieved by the following technical solutions:

A phase-type distance measuring device based on double electro-optical heterodyne modulation, including an optical path unit, a signal generation module, a signal conditioning and acquisition module, and a digital processing system. The optical path unit includes a laser, a first electro-optic intensity modulator, a circulator, The fiber optic probe and the second electro-optic intensity modulator; the laser, the first electro-optic intensity modulator, and the circulator are connected in sequence through optical fibers; the circulator is connected with the fiber optic probe and the second electro-optical intensity modulator through optical fibers, the target under test;

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-to-digital signal converter; the signal generation module outputs a sine wave modulation of f _M1 to the first electro-optic intensity modulator output frequency Signal, the second electro-optical intensity modulator output frequency is the sine wave modulation signal of f _M2 , and the sine wave intermediate frequency signal of f _IM to the A/D analog-to-digital signal converter output frequency, and f _IM =|f _M1 -f _M2 |;

In the optical circuit unit, the laser generates an optical signal, which is transmitted to the first electro-optical intensity modulator through an optical fiber, and the optical signal is modulated by a sine wave modulation signal with a frequency of f _M1 in the first electro-optical intensity modulator, and then transmitted to the circulator and Optical fiber probe, the optical fiber probe projects the optical signal to the target to be measured and receives the return light signal reflected from the target to be measured, the return light signal is transmitted to the circulator and the second electro-optical intensity modulator in sequence through the optical fiber, and is transmitted to the second electro-optical intensity modulator Heterodyne modulation is performed by a sinusoidal modulation signal with frequency f _M2 ;

The signal conditioning and acquisition module includes a photoelectric conversion device, an amplifier circuit, a filter circuit, and an A/D analog-to-digital signal converter connected in sequence; the photoelectric conversion device converts the heterodyne modulated return light signal into an electrical signal, which is amplified by the amplifier circuit successively , filter circuit filtering, and the sine wave intermediate frequency signal with frequency f _IM is collected by the A/D analog-to-digital signal converter, and the generated digital signal is transmitted to the digital processing system for phase identification and comparison, and the generated signal is equal to the distance to be measured A phase difference of the mapping relationship;

The digital processing system uses the obtained phase difference data to solve the measured distance based on the principle of phase distance measurement.

Further, the optical path unit adopts a single-wavelength or dual-wavelength structure.

Further, when the optical path unit has a single-wavelength structure, only one first laser is provided to generate laser light with a wavelength of _λ0 as the measurement light.

Further, when the optical path unit is a dual-wavelength structure, it is also provided with a second laser and a coupler, the first laser produces a laser with a wavelength of _λ0 as the measurement light, and the second laser produces _a laser with a wavelength of λ1 as a reference light, and the measurement The light and the reference light are combined into a dual-wavelength beam through a coupler. The first electro-optic intensity modulator simultaneously modulates the dual-wavelength optical signal, and the second electro-optic intensity modulator simultaneously performs heterodyne modulation on the dual-wavelength optical signal. The fiber optic probe (8 ) is coated on the end face, the film completely transmits the laser with a wavelength _{of λ0} , and totally reflects the laser with a wavelength of λ1. The measurement light is projected onto the target to be measured and reflected, and the reference light is directly reflected on the end face of the fiber optic probe.

Further, when the optical path unit has a dual-wavelength structure, the optical fiber probe adopts a dual-probe structure or a common optical-path structure; when the optical fiber probe adopts a dual-probe structure, the dual-wavelength optical signal is divided into two beams by the second wavelength division multiplexer , the first measuring head emits measuring light and receives the light return signal of the target to be measured, the second measuring head reflects all the reference light and receives the reflected light return signal; when the optical fiber probe adopts a common optical path structure, the dual-wavelength optical signal reaches the end face of the probe Finally, it is divided into two beams of measurement light and reference light. The measurement light is projected onto the target to be measured and reflected. The reference light is directly reflected on the end face of the probe, and the fiber optic probe receives the reflected return light signal.

Further, when the optical path unit has a dual-wavelength structure, the signal conditioning and acquisition module includes a first photoelectric conversion device, a first amplification circuit, a first filter circuit, a second photoelectric conversion device, a second amplification circuit, a second filter circuit, A/D analog-to-digital signal converter and first wavelength division multiplexer; through the first wavelength division multiplexer, the dual-wavelength optical signal is divided into two beams of measurement optical signal and reference optical signal; the measurement optical signal is sequentially passed through the first photoelectric The conversion device, the first amplification circuit, and the first filter circuit are transmitted to the A/D analog-digital signal converter; the reference optical signal is transmitted to the A/D analog-digital signal through the second photoelectric conversion device, the second amplification circuit, and the second filter circuit in turn. signal converter.

Further, the signal generating mode of the signal generating module adopts analog frequency synthesis technology, direct digital frequency synthesis technology or phase-locked loop frequency synthesis technology.

Further, 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 beneficial effects brought by the technical solution of the utility model are:

1. To overcome the shortcomings of traditional distance measurement devices that are difficult to realize online measurement of equipment gaps in narrow spaces, and to avoid problems such as large probe sizes and serious signal attenuation during long-distance transmission in capacitance methods, eddy current methods, and microwave methods, this practical The newly provided equipment gap measurement device based on optical fiber can effectively penetrate into the interior of major equipment by taking advantage of the characteristics of small size and flexible structure of optical fiber, and realize online measurement of equipment gap in narrow working space.

2. Overcome the shortcomings of the pulse method and frequency method in the traditional optical distance measurement method that cannot meet the requirements of precise distance measurement, and solve the problem that the phase laser distance measurement method based on electrical down-conversion in the early stage has extremely high requirements on device performance and poor signal-to-noise ratio Problem, the phase distance measuring device based on dual electro-optical heterodyne modulation provided by the utility model uses dual electro-optic modulators to perform two modulations of the optical signal amplitude, and adjusts and collects after optical down-conversion to improve the signal-to-noise ratio of the received signal.

3. The frequencies f _M1 and f _M2 of the modulation signal can be selected according to the range of the distance to be measured. Under the condition that the half-wavelength of the modulation signal is greater than the range, the higher the frequency of the modulation signal, the higher the accuracy of the distance measurement; the frequency f _IM of the intermediate frequency signal is based on The dynamic response performance of the measurement device requires selection. Under the condition that the intermediate frequency signal can be sampled by the A/D analog-to-digital signal converter without distortion, the higher the frequency of the intermediate frequency signal, the faster the dynamic response of the measurement device, realizing flexible and accurate modulation and measure.

4. The digital processing system uses a digital phase detection algorithm to simultaneously extract the phases of the measurement electrical signal and the reference electrical signal, and obtain the phase difference between the two; when the structure of the measuring device and the measurement environment remain unchanged, the measurement electrical signal and the reference electrical signal The phase difference only changes in real time with the change of the distance to be measured; the optical path unit of the dual-wavelength structure provided by the utility model can further make the phase difference between the measurement electrical signal and the reference electrical signal overcome the influence of environmental temperature changes and vibrations, and ensure the distance The measurement accuracy of the measuring device under high temperature and vibration environment.

Description of drawings

Fig. 1 is a structural schematic diagram of the phase-type distance measuring device of the present invention when the optical path unit adopts a single-wavelength structure.

Fig. 2 is a structural schematic diagram of the phase-type distance measuring device of the present invention when the optical path unit adopts a dual-wavelength structure.

Fig. 3 is a structural schematic view of the optical fiber probe of the present invention when dual probes are used.

Reference signs: 1-optical path unit, 2-signal generation module, 3-signal conditioning and acquisition module, 4-digital processing system, 5-laser, 6-electro-optic intensity modulator, 7-circulator, 8-fiber probe, 9-electro-optic intensity modulator, 10-photoelectric conversion device, 11-amplifying circuit, 12-filtering circuit, 13-A/D analog-to-digital signal converter, 14-laser, 15-coupler, 16-wavelength division multiplexer , 17-photoelectric conversion device, 18-amplifying circuit, 19-filtering circuit, 20-wavelength division multiplexer, 21-probe, 22-probe.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the utility model is described in further detail. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

Example 1

In the phase-type distance measuring device based on double electro-optic heterodyne modulation provided in this embodiment, the optical path unit 1 adopts a single-wavelength structure, with only measuring light and no reference light. As shown in Figure 1, the measuring device mainly includes: an optical path unit 1. Signal generation module 2, signal conditioning and acquisition module 3 and digital processing system 4; wherein, the optical path unit 1 mainly includes 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 The conditioning and acquisition module 3 mainly includes a photoelectric conversion device 10, an amplifying circuit 11, a filter circuit 12, and an A/D analog-to-digital signal converter 13 connected in sequence; a laser 5, an electro-optic intensity modulator 6, and a circulator 7 are sequentially connected through optical fibers; The circulator 7 is connected to the fiber optic probe 8 and the electro-optic intensity modulator 9 through optical fibers, and the outgoing direction of the fiber optic probe 8 is facing the target to be measured; the signal generation module 2 is respectively connected to the electro-optic intensity modulator 6, the electro-optic intensity modulator 9 and the A/D The analog-to-digital signal converter 13 is connected.

The signal generating module 2 outputs a sinusoidal modulation signal with frequency f _M1 , another sinusoidal modulation signal with frequency f _M2 and a sinusoidal intermediate frequency signal with frequency f _IM , and f _IM =|f _M1 −f _M2 |.

In the optical circuit unit 1, the laser 5 generates an optical signal, which is transmitted to the electro-optic intensity modulator 6 through an optical fiber, where it is modulated by a signal with a frequency of f _M1 at the electro-optical intensity modulator 6, and is transmitted to the circulator 7 through an optical fiber, and then transmitted by the optical fiber probe 8 transmits and receives optical signals, and the return optical signal is transmitted to the circulator 7 through the optical fiber, and then transmitted to the electro-optic intensity modulator 9, where it is heterodyned by a signal with a frequency of f _M2 .

In the signal conditioning and acquisition module 3, the photoelectric conversion device 10 converts the intensity of the measured return light signal after heterodyne modulation into a measurement electrical signal, and the measurement electrical signal is successively amplified by the amplification circuit 11 and filtered by the filter circuit 12 to improve the signal-to-noise ratio The frequency is the sine wave intermediate frequency signal of f _IM as the reference electrical signal, and the measurement electrical signal and the reference electrical signal are collected by the A/D analog-to-digital signal converter 13 together, and the digital signal is generated and transmitted to the digital processing system 4 for phase identification Compared with and, a phase difference that has a one-to-one mapping relationship with the distance to be measured is generated.

The digital processing system 4 uses the phase difference data and the calibration curve to obtain the distance measurement value online in real time, and the system software has functions such as online display and offline analysis.

Example 2

In the phase-type distance measuring device based on dual electro-optical heterodyne modulation provided in this embodiment, the optical path unit 1 adopts a dual-wavelength structure, which has both measuring light and reference light. As shown in Figure 2, the measuring device mainly includes:

Optical path unit 1, signal generation module 2, signal conditioning and acquisition module 3 and digital processing system 4; wherein, optical path unit 1 mainly includes laser 5, laser 14, coupler 15, electro-optical intensity modulator 6, circulator 7, fiber optic probe 8. Electro-optical intensity modulator 9; signal conditioning and acquisition module 3 includes wavelength division multiplexer 16, photoelectric conversion device 10, photoelectric conversion device 17, amplifying circuit 11, amplifying circuit 18, filter circuit 12, filter circuit 19, A/ D analog-to-digital signal converter 13; laser 5, laser 14 are connected with coupler 15 by optical fiber, coupler 15 is connected with electro-optic intensity modulator 6, circulator 7 successively by optical fiber; circulator 7 is respectively connected with optical fiber probe 8, circulator 7 by optical fiber The electro-optical intensity modulator 9 is connected, and the output direction of the fiber optic probe 8 is directly to the target to be measured; the signal generation module 2 is connected with the electro-optical intensity modulator 6, the electro-optical intensity modulator 9 and the A/D analog-to-digital signal converter 13 respectively. The electro-optical intensity modulator 9 is connected to the wavelength division multiplexer 16, and the output end of the wavelength division multiplexer 16 is divided into two circuits, one of which is a photoelectric conversion device 10, an amplifier circuit 11, a filter circuit 12, and an A/D analog-digital circuit connected in sequence. The signal converter 13 is connected; the other is a photoelectric conversion device 17 , an amplifying circuit 18 , a filter circuit 19 , and an A/D analog-to-digital signal converter 13 connected in sequence.

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 optical path structure; for a dual-probe structure (see Figure 3), the wavelength division multiplexer 20 divides the dual-wavelength optical signal into two beams, Measuring head 21 emits measuring light and receives the return light signal of the rotor end face, and measuring head 22 reflects reference light on its end face; for the common optical path structure (see Figure 2), the end face of the optical fiber probe is coated, and the coating makes the wavelength λ ₀ The laser is fully transmitted, so that the laser with a wavelength of λ ₁ is totally reflected; the coating can be an anti-reflective coating in the λ ₀ band and a reflective coating in the λ ₁ band.

The signal generating module 2 outputs a sinusoidal modulation signal with frequency f _M1 , another sinusoidal modulation signal with frequency f _M2 and a sinusoidal intermediate frequency signal with frequency f _IM , and f _IM =|f _M1 −f _M2 |.

For optical path unit 1 adopts the measuring device of dual-wavelength structure, laser 5 produces the laser light of wavelength λ ₀ as measuring light, and laser 14 produces the laser light of wavelength λ ₁ as reference light, and measuring light and reference light are combined into one way at coupler 15 For the dual-wavelength light beam, the electro-optical intensity modulator 6 simultaneously modulates the dual-wavelength optical signal, and the electro-optical intensity modulator 9 simultaneously performs heterodyne modulation on the dual-wavelength optical signal. Reflected directly at the end face of the fiber optic probe. Since the reference light and the measurement light exist at the same time, the wavelength division multiplexer 16 divides the dual-wavelength optical signal into two beams of the measurement optical signal and the 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 successively amplified by the amplification circuit 11 and filtered by the filter circuit 12 to improve the signal-to-noise ratio;

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 successively amplified by the amplification circuit 18 and filtered by the filter circuit 19 to improve the signal-to-noise ratio; the measurement electrical signal, the reference electrical signal After the signal and the intermediate frequency signal are collected by the A/D analog-to-digital signal converter 13, a digital signal is generated and transmitted to the digital processing system 4 for phase identification and comparison.

The digital processing system 4 uses the phase difference data and the calibration curve to obtain the distance measurement value online in real time, and the system software has functions such as online display and offline analysis.

Further, in the above two embodiments:

The signal generating mode of signal generation module 2 can be selected analog frequency synthesis technology or direct digital frequency synthesis technology or phase-locked loop frequency synthesis technology; In the present embodiment, signal generation module 2 can be phase-locked loop, by controller, clock reference , phase detector, loop filter, voltage-controlled oscillator, frequency divider, etc.; the controller can choose STM32 series single-chip microcomputer; the clock reference provides a stable frequency reference for the system, and a temperature-compensated crystal with high frequency stability can be selected Oscillator; loop filter plays the role of suppressing phase noise and spurious noise, can choose passive filter or active filter; Higher, the higher the ranging accuracy, but the half-wavelength of the modulated signal should be larger than the range to avoid the ambiguity of phase ranging; for example, the range of 15mm, you can choose the frequency of the modulated signal from 8 to 10GHz; the frequency selection of the intermediate frequency signal needs to consider its The influence of the dynamic response performance of the phase distance measurement system, that is, the phase measurement generally requires 3 to 5 signal cycles. Taking the blade tip clearance measurement as an example, the lower limit of the frequency selection of the intermediate frequency signal must ensure that the blade end face can be effectively measured when it passes the sensor. The upper limit of the frequency selection of the intermediate frequency signal should take into account the sampling speed of the A/D analog-to-digital signal converter 13 to avoid under-sampling, for example, select an intermediate frequency signal frequency of 5MHz.

Laser 5 and laser 14 can be semiconductor butterfly packaged lasers; coupler 15 can be a 3dB fiber coupler; circulator 7 can be a three-port fiber circulator; all optical fibers can be quartz polarization-maintaining fiber; electro-optic intensity modulator 6 And the electro-optical intensity modulator 9 can be a lithium niobate Mach-Zehnder type intensity modulator; an optical fiber amplifier can be set on the optical path from the circulator 7 to the electro-optical intensity modulator 9 to improve the signal-to-noise ratio.

The wavelength division multiplexer 16 and the wavelength division multiplexer 20 can be selected as a coarse wavelength division multiplexer or a dense wavelength division multiplexer; the photoelectric conversion device 10 and the photoelectric conversion device 17 can be selected from an avalanche photodiode or a PIN type photodiode; The circuit 11 and the amplifying circuit 18 may be transimpedance amplifiers.

The digital processing system 4 can include a lower computer and an upper computer, the lower computer can select a field programmable gate array (FPGA), and the upper computer can use a computer or an industrial computer; the lower computer utilizes high-speed data based on the PCI/PCIE/USB3.0 communication bus The transmission method is to upload data from the lower computer to the upper computer; the software of the upper computer has functions such as online display, data storage, data echo, and offline analysis.

Specifically, in combination with the measurement devices provided in the above two embodiments, and with the rotor end face as the target to be measured, the specific content of the online distance measurement method using the electro-optic modulator to realize the second-order heterodyne modulation of the optical signal amplitude is as follows:

First, the signal generation module generates a modulating signal and an intermediate frequency signal in the form of a sine wave; the two modulating signals are expressed by formula (1) and formula (2) respectively:

和

表示调制信号的初相位；Among them, A _M1 and A _M2 represent the amplitude of the modulation signal, f _M1 and f _M2 represent the frequency of the modulation signal,

and

Indicates the initial phase of the modulating signal;

One channel of intermediate frequency signal is represented by equation (3):

表示中频信号的初相位；Wherein, A _IM represents the amplitude of the intermediate frequency signal, f _IM represents the frequency of the intermediate frequency signal,

Indicates the initial phase of the intermediate frequency signal;

f _M1 and f _M2 are selected according to the range of the distance to be measured. Under the condition that the half-wavelength of the modulated signal is greater than the range, the higher the frequency of the modulated signal, the higher the ranging accuracy; f _IM is selected according to the dynamic response performance requirements of the measurement system. Under the condition that the intermediate frequency signal can be sampled by the A/D analog-to-digital signal converter 13 without distortion, the higher the frequency of the intermediate frequency signal, the faster the dynamic response speed of the system;

Further, the optical path unit 1 takes the optical signal as the carrier, utilizes the principle of electro-optic modulation, and is modulated twice by signals with frequencies _fM1 and _{fM2 ;} Measuring light without reference light; when optical path unit ₁ adopts a dual-wavelength structure, laser 14 produces laser light with a wavelength of λ1 as reference light, and measuring light and reference light are combined into a beam of light at coupler 15, and electro-optic intensity modulator 6 simultaneously Two-wavelength optical signal modulation, the electro-optical intensity modulator ₉ simultaneously heterodyne-modulates the dual-wavelength optical signal, and the end face _of the optical fiber probe 8 is coated with a film. Reflection, the measurement light is projected onto the end face of the rotor and is reflected, and the reference light is directly reflected on the end face of the fiber optic probe.

The light intensities of the measuring light and the reference light modulated by the electro-optical intensity modulator 6 are represented by formula (4) and formula (5) respectively:

和

分别表示测量光和参考光的初始相位。Among them, A _λ0 and A _λ1 represent the intensity variation range of the measuring light and the reference light respectively,

and

denote the initial phases of the measurement light and the reference light, respectively.

After the first modulated measurement light and reference light undergo different propagation processes, different phase changes are introduced, return to the circulator along the original optical path, and then reach the electro-optical intensity modulator 9, at this time the light intensity of the measurement light and reference light Respectively represented by formula (6) and formula (7):

和

分别为测量光和参考光在到达电光强度调制器9之前，在光纤、光学器件中传播引入的相位变化，

为测量光在光纤探头与待测目标之间的间隙空间中传播引入的相位变化；测量光和参考光在电光强度调制器9内经过第二次调制后，光强分别由式(8)和式(9)表示：in,

and

Respectively, before the measurement light and the reference light reach the electro-optic intensity modulator 9, the phase changes introduced by the propagation in the optical fiber and the optical device,

In order to measure the phase change introduced by the propagation of light in the gap space between the optical 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-optic intensity modulator 9, the light intensity is respectively expressed by formula (8) and Formula (9) expresses:

和

分别为测量光和参考光在经过电光强度调制器9之后，到达光电转换器件之前，在光纤、光学器件中传播引入的相位变化。in,

and

Respectively, after the measuring light and the reference light pass through the electro-optical intensity modulator 9 and before reaching the photoelectric conversion device, the phase changes introduced by propagating in the optical fiber and the optical device are introduced.

Further, the fiber optic probe 8 is responsible for both projecting optical signals to the direction of the rotor 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 measuring head structure or a common optical path structure; for Double measuring head structure (see Figure 3), the wavelength division multiplexer 20 divides the dual-wavelength optical signal into two beams, the measuring head 21 emits the measuring light and receives the return light signal from the end face of the rotor, and the measuring head 22 reflects the reference light on its end face ; For the common optical path structure (see Figure 2), after the dual-wavelength optical signal reaches the end face of the probe, it is divided into two beams of measurement light and reference light. The probe 8 receives the reflected return light signal.

Further, the signal conditioning and acquisition module 3 is used to realize functions such as photoelectric conversion, signal amplification and filtering, and analog signal acquisition; the signal received by the photoelectric conversion device is an optical signal modulated by an intermediate frequency intensity, and the signal conditioning and acquisition module 3 only needs to perform an optical signal with a frequency of The intermediate frequency signal of f _IM is processed;

When the optical path unit 1 adopts a single-wavelength structure, as shown in Fig. 1, there is no reference optical signal, and the photoelectric conversion device 10 converts the intensity I" _λ0 (t) of the measurement optical signal into the measurement electrical signal IF _m (t), by formula (10 )express:

The signal IF _m (t) is successively processed by the amplification circuit 11 and the filter circuit 12 to improve the signal-to-noise ratio; at this time, the IF _m (t) is used as a measurement electrical signal, and the intermediate frequency signal IF (t) generated by the signal generation module 2 is used as a reference Electrical signal; after the measurement electrical signal and the reference electrical signal are collected by the A/D analog-to-digital signal converter 13, they are transmitted to the digital processing system 4;

When the optical path unit 1 adopts a dual-wavelength structure, as shown in FIG. 2, the reference light and the measurement light exist at the same time, and the wavelength division multiplexer 16 divides the dual-wavelength optical signal into two beams of the measurement optical signal and the reference optical signal; for the reference optical signal Processing, the photoelectric conversion device 17 converts the intensity I" _λ1 (t) of the reference optical signal into a reference electrical signal IF _r (t), represented by formula (11):

The signal IF _r (t) is successively processed by the amplifier circuit 18 and the filter circuit 19 to improve the signal-to-noise ratio; at this time, IF _m (t) is used as the measurement electrical signal, and IF _r (t) is used as the 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 then transmitted to the digital processing system 4 .

Further, the digital processing system 4 is used to realize the digital phase detection and phase comparison of the two signals of the measurement electrical signal and the reference electrical signal, and calculate the distance based on the phase difference data, which can realize the online display, data storage, and data return of the measurement distance. functions such as display and offline analysis; the digital processing system 4 can use the frequency multiplied signal of the intermediate frequency signal IF(t) to control the A/D analog-to-digital signal converter 13 to sample the measurement electrical signal and the reference electrical signal synchronously.

The digital processing system 4 adopts a digital phase detection algorithm to simultaneously extract the phases of the measurement electrical signal and the reference electrical signal, and obtain the phase difference between the two; for the single-wavelength structure, the phase difference is represented by formula (12); for the dual-wavelength structure, the phase The difference is represented by formula (13):

随待测距离实时发生变化，当系统结构、测量环境不变时，其他相位量不发生改变；与单波长结构相比，双波长结构利用测量光与参考光在同一光路中传输的特点，受环境温度变化、振动影响导致

和

的变化几乎一致，可以相互抵消，提升环境适应性。The right side of equation (12) and equation (13), only

It changes in real time with the distance to be measured. When the system structure and measurement environment remain unchanged, other phase quantities do not change; Changes in ambient temperature and vibration

and

The changes are almost the same, which can offset each other and improve environmental adaptability.

The digital processing system uses the phase difference data to solve the measured distance based on the principle of phase ranging, which is expressed as formula (14):

The calibration technology of traversing the distance to be measured at equal intervals is used to obtain the phase difference data corresponding to each distance value in the range, and the curve fitting method is used to establish the mapping relationship between the phase difference and the distance to be measured to obtain the distance calibration curve; the utility model uses phase Differential measurement results and calibration curves can realize online measurement of equipment clearance.

The present invention is not limited to the embodiments described above. The above description of specific embodiments is intended to describe and illustrate the technical solution of the present utility model, and the above specific embodiments are only illustrative and not restrictive. Without departing from the purpose of the utility model and the scope protected by the claims, those skilled in the art can also make many forms of specific transformations under the inspiration of the utility model, and these all belong to the protection scope of the utility model Inside.

Claims (8)

1. A phase-type distance measuring device based on double electro-optic heterodyne modulation, characterized in that it includes an optical path unit (1), a signal generation module (2), a signal conditioning and acquisition module (3) and a digital processing system (4) , the optical path unit (1) includes a laser, a first electro-optical intensity modulator (6), a circulator (7), an optical fiber probe (8) and a second electro-optical intensity modulator (9); the laser, the first electro-optic intensity modulator (9); The intensity modulator (6) and the circulator (7) are sequentially connected through an optical fiber; the circulator (7) is respectively connected with the optical fiber probe (8) and the second electro-optical intensity modulator (9) through an optical fiber, and the output of the optical fiber probe (8) The direction is facing the target to be measured; The signal generating module (2) is respectively connected with the first electro-optic intensity modulator (6), the second electro-optical intensity modulator (9) and the A/D analog-to-digital signal converter (13); the signal generating module (2) is connected to the The first electro-optical intensity modulator (6) output frequency is the sine wave modulation signal of f _M1 , the second electro-optic intensity modulator (9) output frequency is the sine wave modulation signal of f _M2 , to the A/D analog-to-digital signal converter (13) The output frequency is a sine wave intermediate frequency signal of f _IM , and f _IM =|f _M1 -f _M2 |; In the optical path unit (1), the laser generates an optical signal, which is transmitted to the first electro-optical intensity modulator (6) through an optical fiber, and the optical signal is modulated by a sine wave modulation signal with a frequency of f _M1 in the first electro-optic intensity modulator (6) After that, it is transmitted to the circulator (7) and the fiber optic probe (8) sequentially through the optical fiber. The fiber optic probe (8) projects the optical signal to the target to be measured and receives the return light signal reflected from the target to be measured, and the return light signal is sequentially transmitted to the A circulator (7) and a second electro-optic intensity modulator (9), and in the second electro-optic intensity modulator (9), the sine wave modulation signal of frequency f _M2 carries out heterodyne modulation; The signal conditioning and acquisition module (3) includes a photoelectric conversion device, an amplifier circuit, a filter circuit, and an A/D analog-to-digital signal converter (13) connected in sequence; the photoelectric conversion device converts the heterodyne-modulated return light signal into an electrical signal , successively through the amplifying circuit amplifying, filtering circuit filtering, together with the sinusoidal intermediate frequency signal of f _IM being collected by the A/D analog-to-digital signal converter (13), the digital signal generated is transmitted to the digital processing system (4) for processing Phase identification and comparison, to generate a phase difference that has a one-to-one mapping relationship with the distance to be measured; The digital processing system (4) uses the obtained phase difference data to calculate the measured distance based on the principle of phase distance measurement. 2 . A phase distance measurement device based on dual electro-optic heterodyne modulation according to claim 1 , wherein the optical path unit ( 1 ) adopts a single-wavelength or dual-wavelength structure. 3 . 3. A kind of phase distance measuring device based on double electro-optical heterodyne modulation according to claim 2, characterized in that, when the optical path unit (1) is a single-wavelength structure, only a first laser (5) is set for generating Laser light with a wavelength of _λ0 is used as the measurement light. 4. A kind of phase distance measuring device based on double electro-optic heterodyne modulation according to claim 2, characterized in that, when the optical path unit (1) is a dual-wavelength structure, a second laser (14) and a coupler are also provided (15), the first laser device (5) produces the laser light that wavelength is λ ₀ as measuring light, and the second laser device (14) produces the laser light that wavelength λ ₁ is as reference light, and measuring light and reference light combine by coupler (15) It is a dual-wavelength light beam, the first electro-optic intensity modulator (6) simultaneously modulates the dual-wavelength optical signal, the second electro-optical intensity modulator (9) simultaneously performs heterodyne modulation on the dual-wavelength optical signal, and the optical fiber probe (8) The end face is provided with a coating, the coating is fully transmissive to the laser with a wavelength _{of λ0} , and is totally reflected to the laser with a wavelength of λ1. The measurement light is projected onto the target to be measured and reflected, and the reference light is directly reflected on the end face of the fiber optic probe (8). 5. A phase distance measuring device based on dual electro-optic heterodyne modulation according to claim 2 or 4, characterized in that, when the optical path unit (1) is a dual-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, the dual-wavelength optical signal is divided into two beams by the second wavelength division multiplexer (20), and the first measuring head (21) emits the measuring light and Receiving the light return signal of the target to be measured, the second probe (22) reflects all the reference light and receives the reflected light return signal; when the optical fiber probe (8) adopts a common optical path structure, after the dual-wavelength optical signal reaches the end face of the probe, it is divided into There are two beams of measuring light and reference light, the measuring light is projected onto the 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. 6. According to claim 2 or 4, a phase-type distance measuring device based on dual electro-optic heterodyne modulation is characterized in that, when the optical path unit (1) is a dual-wavelength structure, the signal conditioning and acquisition module (3) includes The first photoelectric conversion device (10), the first amplifier circuit (11), the first filter circuit (12), the second photoelectric conversion device (17), the second amplifier circuit (18), the second filter circuit (19), A/D analog-to-digital signal converter (13) and first wavelength division multiplexer (16); through the first wavelength division multiplexer (16), the dual-wavelength optical signal is divided into two beams of measurement optical signal and reference optical signal The measurement optical signal is transmitted to the A/D analog-to-digital signal converter (13) successively through the first photoelectric conversion device (10), the first amplifying circuit (11), and the first filter circuit (12); the reference optical signal is successively passed through the first The second photoelectric conversion device (17), the second amplifying circuit (18), and the second filter circuit (19) are transmitted to the A/D analog-to-digital signal converter (13). 7. A kind of phase-type distance measuring device based on double electro-optic heterodyne modulation according to claim 1, characterized in that, the signal generation mode of the signal generating module (2) selects analog frequency synthesis technology or direct digital frequency synthesis technology Or phase-locked loop frequency synthesis technology. 8. A phase distance measuring device based on dual electro-optic heterodyne modulation according to 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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