CN105699980A - High-precision laser range unit and measurement method - Google Patents

Abstract

The invention discloses a high-precision laser range unit and measurement method. The high-precision laser range unit includes a laser, an optical fiber isolator, an optical fiber light splitter, an optical fiber polarized light splitter, a polarization modulator, a square wave sweep frequency signal source, an optical fiber coupler and a reflector. According to the invention, a problem that the range precision is difficult to improve due to low phase discrimination precision in a traditional phase telemetry method is solved and problems of complex optical paths, comparatively small modulation band width and limited range field in spatial light polarization modulation range are also solved. According to the invention, the measurement device is simplified and the measurement precision and the stability of a measurement system are improved.

Description

A high-precision laser distance measuring device and measuring method

technical field

The invention relates to the technical field of optical detection, in particular to a high-frequency polarization modulation ranging device and measurement method based on optical fiber optical path waveguide modulation.

Background technique

Absolute precision ranging in large-scale space is an important key technology in my country's large-scale equipment manufacturing. Traditional absolute distance measurement methods include pulse time-of-flight method, phase ranging method, multi-wavelength interferometry, frequency modulation continuous wave measurement method and so on. However, the measurement accuracy of the pulse time-of-flight method and the phase ranging method cannot meet the accuracy requirements of precision ranging; the multi-wavelength interferometry and frequency modulation continuous wave ranging method have high requirements for the stability of the measurement light, and the poor anti-interference performance cannot meet Industrial site measurement needs.

The distance measurement method based on Fizeau gear measuring the speed of light proposed by the Swiss Leica company converts the phase difference information of the outgoing wave and the echo into light intensity information, and finds the modulation frequency of the zero phase difference point, and finally calculates the distance information. The distance measurement method It has high measurement accuracy. However, this method has extremely high requirements on the collimation of light in the spatial optical path, and the spatial light modulator used is limited by the driving voltage and modulation bandwidth, and its stability is low, which limits the measurement range.

Contents of the invention

In view of this, the object of the present invention is to propose a high-precision laser ranging device and measurement method to solve the problem of low phase detection accuracy in the traditional phase ranging method, thereby improving the measurement accuracy and the stability of the measurement system.

Based on the above purpose, the present invention provides a distance measuring device, including a laser, an optical fiber isolator, an optical fiber beam splitter, an optical fiber polarization beam splitter, a polarization modulator, and a square wave sweep signal arranged in sequence from left to right source, fiber couplers and mirrors.

In some embodiments of the present invention, the laser is used to emit P-type linearly polarized light, and the fiber isolator is used to isolate the backward P-type linearly polarized light so that the forward P-type linearly polarized light is transmitted to the fiber optic beam splitter, so The fiber optic beam splitter is used as an energy beam splitter for transmitting the P-type linearly polarized light to the fiber polarized beam splitter, and the fiber optic polarized beam splitter is used for transmitting the P-type linearly polarized light to the polarization modulator, while using to transmit the returned P-type linearly polarized light to the optical fiber beam splitter.

In some embodiments of the present invention, the polarization modulator is used to change the polarization state of the light to form P-type and S-type periodically alternately polarized light, and at the same time transmit the light to the fiber coupler, and the fiber coupler is used to light is transmitted to a mirror for reflecting light to the fiber coupler for transmitting light to a polarization modulator;

The square-wave frequency-sweeping signal source is used to apply an alternating-level signal to the polarization modulator.

In some embodiments of the present invention, the polarization modulator is a waveguide modulator, and the driving voltage generated by the square-wave sweep signal source reaches the half-wave voltage of the polarization modulator.

Optionally, the reflector may be a metal-coated corner cube, and the metal may be metals such as platinum, chromium, rhodium or iridium, so as to maintain polarization of polarized light before and after reflection.

In some embodiments of the present invention, the distance measuring device further includes a fiber 1/4 wave plate, and the fiber 1/4 wave plate is located between the fiber polarization beam splitter and the polarization modulator, and is used to convert the outgoing line Polarized light is converted to circularly polarized light. After being modulated by the modulator, alternating left-handed and right-handed circularly polarized light propagates in the atmosphere, and the backward circularly polarized light modulated by the modulator is restored to linearly polarized light. Circularly polarized light is less affected by the atmosphere than linearly polarized light, so it is more conducive to improving the ranging accuracy.

In some embodiments of the present invention, the ranging device further includes a first photodetector and a second photodetector, the first photodetector is used to receive the photovoltage signal from the optical fiber polarizing beam splitter, The second photodetector is used to receive the photovoltage signal from the optical fiber beam splitter.

In some embodiments of the present invention, the distance measuring device further includes a measurement control unit, which is used to process the voltage signals output by the first photodetector and the second photodetector; at the same time, perform frequency sweep control on the square wave sweep signal source , and collect the frequency value to calculate the distance to be measured.

In some embodiments of the present invention, the distance to be measured

where C is the speed of light;

f ₁ is the modulation frequency when the first photodetector outputs a low level and the second photodetector outputs a high level;

f2 is based _on the low level output of the first photodetector and the high level output of the second photodetector. After continuing to unidirectionally sweep the modulation frequency, the pulse width of the pulse signal output by the second photodetector gradually decreases. Until the pulse signal disappears and the voltage remains zero, the first photodetector outputs a pulse signal with a gradually larger pulse width until the voltage value is the maximum. At this time, the second photodetector outputs a low level, and the first photodetector outputs a high level. modulation frequency.

The present invention also provides a measurement method using the distance measuring device, comprising the following steps:

Let the P-type linear polarized light emitted by the laser enter the free space, reach the mirror and return to the optical path of 2D, where D is the distance to be measured;

Sweep the modulation frequency of the polarization modulator in one direction. If the optical path 2D is an integer multiple of the modulation wavelength at the modulation frequency f ₁ , the re-modulated light is all P-type polarized light, and the output of the first photodetector is low. level, the second photodetector outputs a high level, then

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}$

Among them, C is the speed of light, N ₁ is a positive integer;

Continue to perform one-way frequency sweep on the modulation frequency. During the frequency sweep, the pulse width of the pulse signal output by the second photodetector gradually decreases until the pulse signal disappears, the voltage remains zero, and the output pulse width of the first photodetector gradually increases. The pulse signal until the voltage value is the largest, at this time the _second photodetector outputs low level, and the modulation frequency when the first photodetector outputs high level, at this time, under the modulation frequency f2, the optical path 2D is the modulation wavelength times, then,

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}$

in,

Combining the above two formulas, we get

It can be seen from the above formula that the measurement accuracy of the measured distance D is determined by the order of magnitude and measurement accuracy of the modulation frequencies f1 and f2. At present, the frequency measurement accuracy is much higher than the phase detection accuracy, therefore, the measurement method provided by the present invention can improve the measurement accuracy of the measured distance D.

From the above, it can be seen that the distance measuring device and measurement method based on optical fiber optical path waveguide modulation provided by the present invention can find the phase zero point by detecting the minimum value of light intensity, which solves the problem of low phase detection accuracy in the traditional phase ranging method. At the same time, by using the broadband characteristics of the waveguide modulator, it also solves the problem of complex optical path and small modulation bandwidth in spatial light polarization modulation ranging, which limits the ranging range. The invention simplifies the measuring device, improves the measuring precision and the stability of the measuring system.

Description of drawings

FIG. 1 is a schematic structural diagram of a ranging device according to an embodiment of the present invention;

Fig. 2 is the phase comparison result of the first modulated wave and the second modulated wave according to the embodiment of the present invention.

Among them: 1-laser, 2-fiber isolator, 3-fiber beam splitter, 4-fiber polarization beam splitter, 5-fiber 1/4 wave plate, 6-polarization modulator, 7-square wave sweep Signal source, 8-fiber coupler, 9-mirror, 10-first photodetector, 11-second photodetector, 12-measurement control unit.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

It should be noted that all expressions using "first" and "second" in the embodiments of the invention are used to distinguish two entities with the same name but different parameters or parameters that are not the same. It can be seen that "first" and "second" are only For the convenience of expression, it should not be understood as a limitation on the embodiments of the invention, and the following embodiments will not describe them one by one.

Referring to FIG. 1 , it is a schematic structural diagram of a distance measuring device according to an embodiment of the present invention. As an embodiment of the present invention, the high-frequency circular polarization modulation ranging device includes a laser 1, a fiber isolator 2, a fiber optic beam splitter 3, a fiber polarization beam splitter 4, a polarization modulator 6, a square wave scanning Frequency signal source 7, fiber coupler 8 and reflector 9, as shown in Figure 1, described laser device 1, fiber isolator 2, fiber optic beam splitter 3, fiber optic polarization beam splitter 4, polarization modulator 6, The square wave sweep signal source 7, the fiber coupler 8 and the reflector 9 are arranged in sequence from left to right.

The laser 1 is used to emit P-type linearly polarized light, and the fiber isolator 2 is used to isolate the backward P-type linearly polarized light to avoid damage to the laser 1, and at the same time transmit the forward P-type linearly polarized light to the fiber optic beam splitter 3. The optical fiber beam splitter 3 is used as an energy beam splitter for transmitting the P-type linearly polarized light to the optical fiber polarized beam splitter 4 and introducing the return light into the second photodetector 11 at the same time. The fiber optic polarized beam splitter 4 is used to transmit the P-type linearly polarized light to the polarization modulator 6, and is simultaneously used to transmit the returned P-type linearly polarized light to the fiber optic beam splitter 3, and introduce the S-type linearly polarized light into the first A photodetector 10 .

The polarization modulator 6 is used to change the polarization state of the light to form P-type and S-type periodically alternately polarized light, and at the same time transmit the light to the fiber coupler 8, and the fiber coupler 8 is used to transmit the light to the reflection mirror 9, the mirror 9 is used to reflect the light to the fiber coupler 8, and the fiber coupler 8 is used to transmit the light to the polarization modulator 6. Optionally, the reflector 9 may be a metal-coated corner cube, and the metal may be metals such as platinum, chromium, rhodium or iridium, so as to maintain polarization of polarized light before and after reflection.

The square wave sweep signal source 7 is used to apply an alternating level signal to the polarization modulator 6, that is, the polarization modulator 6 is driven by the alternating level signal generated by the square wave sweep signal source 7, and the square wave sweep signal The driving voltage generated by the source 7 must reach the half-wave voltage of the polarization modulator 6 .

Preferably, the polarization modulator 6 is a waveguide modulator with a small half-wave voltage and does not generate too much power. In a preferred embodiment of the present invention, the distance measuring device further includes an optical fiber 1/4 wave plate 5, and the optical fiber 1/4 wave plate 5 is located between the optical fiber polarization beam splitter 4 and the polarization modulator 6 , which is used to convert linearly polarized light into circularly polarized light (that is, convert P-type linearly polarized light into circularly polarized light). Circularly polarized light is less affected by the atmosphere than linearly polarized light, so it is more conducive to improving the distance measurement accuracy.

Preferably, the distance measuring device may further include a first photodetector 10 and a second photodetector 11, and the optical fiber beam splitter 3 introduces the return light into the second photodetector 11 at the same time, and the second The photodetector 11 is then used to receive the photovoltage from the optical fiber beam splitter 3, and the optical fiber polarized beam splitter 4 simultaneously introduces the S-shaped linearly polarized light into the first photodetector 10, and the first photodetector 10 is used for receiving the optical voltage signal transmitted from the optical fiber polarizing beam splitter 4. Preferably, the performance of the first photodetector 10 and the second photodetector 11 are exactly the same, and both may be high-speed photodetectors.

In a preferred embodiment of the present invention, the distance measuring device further includes a measurement control unit 12, the measurement control unit 12 is used to process the voltage signals output by the first photodetector 10 and the second photodetector 11, To carry out the phase comparison of the round-trip wave; at the same time, carry out frequency sweep control on the signal source 7, and collect frequency values to calculate the distance to be measured.

It can be seen that after the P-type linear polarized light is emitted from the laser, the P-type linear polarized light passes through the optical fiber isolator 2, the optical fiber beam splitter 3, the optical fiber polarized beam splitter 4 and the optical fiber 1/4 wave plate 5 in turn, and from the reflector 9 In the reflected light, only P-type linearly polarized light exists in the optical path from fiber optic polarized beam splitter 4-fiber optic beam splitter 3-fiber isolator 2 (S-type polarized light is separated by fiber optic polarized beam splitter 4 ), and is detected by the second photodetector 11.

It should be noted that the polarization modulator 6 utilizes the electric birefringence effect of its birefringent crystal, and only when the power level is high, the polarization modulator 6 will work to change its polarization state, so applying a square wave sweep signal is In order to generate alternately polarized modulated waves, the wavelength of the modulated waves can be changed by changing the modulation frequency at the same time.

The square wave sweep signal source 7 and the polarization modulator 6 are combined to form a photoelectric switch, and a square wave signal with continuously adjustable frequency is applied to the polarization modulator 6, and when the applied level is high, it enters the polarization modulator 6 (the first modulation) P-type linearly polarized light is deflected by 90 degrees to form S-type linearly polarized light, otherwise it is not deflected. After the modulated light enters the spatial optical path, it goes back and forth and passes through the polarization modulator 6 again (second modulation). If the modulation level is still high at this time, the polarization state is deflected again, and the S-type linearly polarized light becomes a P-type line. All the polarized light passes through the beam splitter 4 and enters the fiber beam splitter 3 for splitting. After splitting, it is received by the second detector 11. The second detector 11 outputs a high level, and the first photodetector 10 outputs a low level. flat. At this time, the distance D to be measured is an integer multiple of the modulation half wavelength. By continuously adjusting the modulation frequency in one direction, two continuous half-wavelength modulations can be obtained when the photovoltage is zero, and then the distance to be measured can be calculated.

The purpose of secondary modulation of the round-trip wave with the polarization modulator is to compare the first modulated wave with the second modulated wave. The phase comparison result is shown in Figure 2, which is divided into three states:

1) The two modulated waves are in the same phase, which is equivalent to the S-shaped linearly polarized light modulated by the polarization modulator 6 for the first time is completely demodulated by the polarization modulator 6 when it is returned, and the return wave is completely output from the optical fiber polarized beam splitter 4 For P-type linearly polarized light, the first photodetector 10 outputs a low level, and the second photodetector 11 outputs a high level;

2) When the phases of the two modulated waves are completely reversed, it is equivalent to that the unmodulated P-type linearly polarized light is also modulated when it passes through the polarization modulator 6 for the first time, and the return wave is polarized from the optical fiber The optical beam splitter 4 completely outputs S-type linearly polarized light, the second photodetector 11 outputs a low level, and the first photodetector 10 outputs a high level;

3) When neither the same phase nor the opposite phase, both the first photodetector 10 and the second photodetector 11 will appear periodic pulse waves. At this time, frequency modulation needs to be continued to make the above two situations appear.

Calculated by the first state and the second state, the distance to be measured D,

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; ,</span>$

where C is the speed of light;

f ₁ is the modulation frequency when the first photodetector outputs a low level and the second photodetector outputs a high level;

f2 is based _on the low level output of the first photodetector and the high level output of the second photodetector. After continuing to unidirectionally sweep the modulation frequency, the pulse width of the pulse signal output by the second photodetector gradually decreases. Until the pulse signal disappears and the voltage remains zero, the first photodetector outputs a pulse signal with a gradually larger pulse width until the voltage value is the maximum. At this time, the second photodetector outputs a low level, and the first photodetector outputs a high level. modulation frequency.

The present invention also provides a measurement method based on the distance measuring device, including:

Let the P-type linear polarized light emitted by the laser 1 enter the free space to reach the reflector 9 and then return to an optical path of 2D, where D is the distance to be measured;

Sweep the modulation frequency of the polarization modulator 6 in _one direction. If the optical path 2D is an integer multiple of the modulation wavelength at the modulation frequency f1, all the re-modulated light is P-type polarized light, and the voltage value output by the detector is In the first state, that is, the first photodetector 10 outputs a low level, and the second photodetector 11 outputs a high level, then

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, C is the speed of light, N ₁ is a positive integer;

Continue to perform one-way frequency sweep on the modulation frequency. During the frequency sweep, the pulse width of the pulse signal output by the second photodetector gradually decreases until the pulse signal disappears, the voltage remains zero, and the output pulse width of the first photodetector gradually increases. The pulse signal until the voltage value is maximum, the voltage output by the detector is in the second state, that is, the second photodetector 11 outputs a low level, and the first photodetector ₁₀ outputs a high level, at this time at the modulation frequency f2 , the optical path 2D is the modulation wavelength times, that is, the phase difference between the outgoing light and the returning light is exactly π, at this time,

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

in,

Simultaneously (1) (2) two formulas, can get

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Calculate the distance D to be measured.

Specific embodiment: the structure shown in Figure 1, the light source is a linearly polarized laser with a wavelength of 1550nm, and the polarization ratio is 500:1. The optical fiber splitter 3 is an energy type optical fiber splitter with a splitting ratio of 1:20, and the optical fiber splitter 4 is a polarization type splitter to separate S light and P light respectively. The polarization modulator 6 is a polarization switch with a bandwidth of DC-12GHz and a half-wave voltage of 7V. The first photodetector 10 and the second photodetector 11 are InGaAs PIN photosensitive diodes with a detection frequency of 40 GHz and a rise time of 7 ps.

Turn on the laser 1 and the polarization modulator 6, and make the square-wave frequency-sweeping signal source 7 generate a continuous frequency-sweeping square-wave signal with a signal amplitude of 7V. Read the output signals of the first photodetector 10 and the second photodetector 11 respectively, find out that during the frequency sweep process, the two detectors successively obtain the frequency values f ₁ and f ₂ under the minimum value of light intensity, and pass (3 ) to calculate the distance D to be measured.

Preferably, if the background noise can be reasonably eliminated, and the frequency sweep step size and frequency measurement accuracy reach the Hz level, the distance measurement accuracy can reach the sub-μm level.

It can be seen that, compared with the prior art, the present invention has the following beneficial effects:

1. Simplify the ranging system by using the optical fiber optical path, avoid the additional polarization generated by the beam divergence angle on the polarization modulator when using the spatial light polarization modulation, and also avoid the refractive index change caused by high driving power, thereby improving the measurement accuracy and system stability sex;

2. Using the ultra-wide modulation bandwidth of the waveguide modulator, the ranging range from meters to kilometers can be obtained;

3. Use the fiber 1/4 wave plate to generate circularly polarized light less affected by the atmosphere, which can improve the ranging accuracy of long-distance ranging;

4. High-frequency modulation reduces the fuzzy range of ranging and improves ranging accuracy;

5. Simultaneous detection by dual detectors reduces the scanning range and improves the measurement speed;

6. The device has the advantages of simple design, simple structure, high measurement accuracy and low cost, and is suitable for large-scale and high-precision measurement in industrial occasions.

Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is exemplary only, and is not intended to imply that the scope of the present disclosure (including claims) is limited to these examples; under the idea of the present invention, the above embodiments or Combinations between technical features in different embodiments are also possible, steps may be carried out in any order, and there are many other variations of the different aspects of the invention as described above, which are not presented in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. A high-precision laser ranging device is characterized by comprising a laser, an optical fiber isolator, an optical fiber beam splitter, an optical fiber polarization beam splitter, a polarization modulator, a square wave frequency sweeping signal source, an optical fiber coupler and a reflector which are sequentially arranged from left to right.

2. The high precision laser ranging device according to claim 1, wherein the laser is configured to emit P-type line polarized light, the fiber isolator is configured to isolate backward P-type line polarized light, and transmit forward P-type line polarized light to the fiber splitter, the fiber splitter is configured to serve as an energy splitter and transmit P-type line polarized light to the fiber splitter, and the fiber splitter is configured to transmit P-type line polarized light to the polarization modulator and transmit returning P-type line polarized light to the fiber splitter.

3. The high precision laser ranging device as claimed in claim 1, wherein the polarization modulator is configured to change the polarization state of light to form P-type and S-type periodically alternating polarized light and transmit the light to a fiber coupler, the fiber coupler is configured to transmit the light to a mirror, the mirror is configured to reflect the light to the fiber coupler, and the fiber coupler is configured to transmit the light to the polarization modulator;

the square wave swept-frequency signal source is used for applying an alternating level signal to the polarization modulator.

4. The high precision laser ranging device as claimed in claim 3, wherein the polarization modulator is a waveguide type modulator, and the driving voltage generated by the square wave swept signal source reaches a half-wave voltage of the polarization modulator.

5. The high-precision laser ranging device as claimed in claim 1, further comprising an optical fiber 1/4 wave plate, wherein the optical fiber 1/4 wave plate is located between the optical fiber polarization beam splitter and the polarization modulator and is used for converting linearly polarized light into circularly polarized light.

6. The high precision laser ranging device as claimed in claim 1, further comprising a first photo detector for receiving the photo voltage signal from the fiber polarization beam splitter and a second photo detector for receiving the photo voltage signal from the fiber polarization beam splitter.

7. The high-precision laser ranging device as claimed in claim 1, further comprising a measurement control unit for processing the voltage signals output by the first and second photodetectors; and meanwhile, carrying out frequency sweep control on the square wave frequency sweep signal source, and acquiring a frequency value to solve the distance to be measured.

8. The apparatus as claimed in claim 7, wherein the distance to be measured is a distance between the two electrodes

Wherein C is the speed of light;

f₁outputting a low level for the first photodetector, and outputting a modulation frequency at a high level for the second photodetector;

f₂the pulse width of a pulse signal output by the second photoelectric detector is gradually reduced until the pulse signal disappears and the voltage is constant to zero after unidirectional frequency sweeping is continuously carried out on the modulation frequency, the pulse signal with the gradually increased pulse width is output by the first photoelectric detector until the voltage value is maximum, the low level is output by the second photoelectric detector at the moment, and the modulation frequency is output by the first photoelectric detector at the high level.

9. A measuring method according to any one of claims 1 to 8, characterized by comprising the steps of:

enabling P-type line polarized light emitted by a laser to enter a free space and return to a reflector, wherein the optical path of the P-type line polarized light is 2D, and D is the distance to be measured;

performing unidirectional frequency sweep on the modulation frequency of the polarization modulator at the modulation frequency f₁If the lower optical path 2D is an integral multiple of the modulation wavelength, all the light after re-modulation is P-type polarized light, the first photodetector outputs low level, and the second photodetector outputs high level, then

$D=\frac{1}{2}\&times;\frac{C}{f_1}\&times;N_1$

Wherein C is the speed of light, N₁Is a positive integer;

continuing to perform unidirectional frequency sweep on the modulation frequency, wherein in the frequency sweep, the pulse width of the pulse signal output by the second photoelectric detector is gradually reduced until the pulse signal disappears, the voltage is constant to zero, the first photoelectric detector outputs the pulse signal with the gradually increased pulse width until the voltage value is maximum, the second photoelectric detector outputs a low level, the first photoelectric detector outputs a high level, and at the moment, the modulation frequency f is at the modulation frequency₂With a lower optical path 2D of the modulated wavelengthAnd (4) multiplying the sum of the obtained product,

$D=\frac{1}{2}\&times;\frac{C}{f_2}\&times;N_2$

wherein,

the two formulas are combined to obtain