阅读说明：本技术 一种基于激光外差探测的相位测距装置及方法 (Phase distance measuring device and method based on laser heterodyne detection ) 是由 刘玉周 冯静 于 2019-09-20 设计创作，主要内容包括：本发明公开了一种基于激光外差探测的相位测距装置,包括红外光纤激光器、第一光纤耦合器、第一电光强度调制器、第二电光强度调制器、望远镜、光纤准直器、第二光纤耦合器、A/D采集电路和计算机,还包括用于产生中频正弦信号和超高频正弦信号的信号发生电路、第一自动增益控制电路、第二自动增益控制电路、光电探测器以及光电检测转化电路。利用该装置能够有效解决在超高频调制相位法测距中,由于光强变化和探测器相位不均匀性引起的相位波动问题,具有测量精度高的特点。本发明还公开了一种基于激光外差探测的相位测距的方法。(The invention discloses a phase distance measuring device based on laser heterodyne detection, which comprises an infrared fiber laser, a first optical fiber coupler, a first electro-optic intensity modulator, a second electro-optic intensity modulator, a telescope, an optical fiber collimator, a second optical fiber coupler, an A/D acquisition circuit, a computer, a signal generation circuit for generating intermediate-frequency sinusoidal signals and ultrahigh-frequency sinusoidal signals, a first automatic gain control circuit, a second automatic gain control circuit, a photoelectric detector and a photoelectric detection conversion circuit. The device can effectively solve the problem of phase fluctuation caused by light intensity change and detector phase nonuniformity in the ultrahigh frequency modulation phase method distance measurement, and has the characteristic of high measurement precision. The invention also discloses a phase distance measurement method based on laser heterodyne detection.)

1. A phase distance measuring device based on laser heterodyne detection is characterized by comprising an infrared fiber laser (1), a first optical fiber coupler (2), a first electro-optical intensity modulator (3), a second electro-optical intensity modulator (4), a telescope (8), an optical fiber collimator (10), a second optical fiber coupler (11), an A/D acquisition circuit (14) and a computer (15), wherein the optical path output end of the infrared fiber laser (1) is connected with the optical path input end of the first optical fiber coupler (2), the two optical path output ends of the first optical fiber coupler (2) are respectively connected with the optical path input end of the first electro-optical intensity modulator (3) and the optical path input end of the second electro-optical intensity modulator (4), the optical path output end of the first electro-optical intensity modulator (3) is connected with the optical path inlet of the telescope (8), the optical fiber collimator (10) is connected with a return optical path outlet of the telescope (8), the optical path output end of the second electro-optic intensity modulator (4) and the optical path output end of the optical fiber collimator (10) are connected with the optical path input end of the second optical fiber coupler (11), the photoelectric detection device further comprises a signal generating circuit (5) for generating intermediate-frequency sinusoidal signals and ultrahigh-frequency sinusoidal signals, a first automatic gain control circuit (6), a second automatic gain control circuit (7), a photoelectric detector (12) and a photoelectric detection conversion circuit (13), the first ultrahigh-frequency sinusoidal signal output end of the signal generating circuit (5) is connected with the first intensity modulator (3) through a first automatic gain control circuit (6), the second ultrahigh-frequency sinusoidal signal output end of the signal generating circuit (5) is connected with the second electro-optic intensity modulator (4) through a second automatic gain control circuit (7), the intermediate frequency sinusoidal signal output end of the signal generating circuit (5) is connected with an A/D acquisition circuit (14), the photoelectric detector (12) and the photoelectric detection conversion circuit (13) are sequentially arranged between the second optical fiber coupler (11) and the A/D acquisition circuit (14), and the A/D acquisition circuit (14) is connected with a computer (15).

2. The phase distance measuring device based on laser heterodyne detection as recited in claim 1, wherein the signal generating circuit (5) comprises a constant temperature crystal oscillator (16), a first fractional-n phase-locked loop (18), a second fractional-n phase-locked loop (21), a direct digital frequency synthesizer (24), a first low-pass filter (20), a second low-pass filter (23), a first band-pass filter (26), a controller (17) and a plurality of low noise amplifiers (19), wherein the controller (17) is respectively connected with the first fractional-n phase-locked loop (18), the second fractional-n phase-locked loop (21) and the direct digital frequency synthesizer (24), and a signal output end of the constant temperature crystal oscillator (16) is respectively connected with a signal input end of the first fractional-n phase-locked loop (18), a signal input end of the second fractional-n phase-locked loop (21), a signal output end of the constant temperature crystal oscillator (16), a direct digital frequency synthesizer (24, The signal input end of a direct digital frequency synthesizer (24) is connected, the signal output end of a first fractional-N phase-locked loop (18) is connected with the signal input end of a first low-pass filter (20) through a low-noise amplifier (19), the signal output end of the first low-pass filter (20) is connected with the signal input end of a first automatic gain control circuit (6), the signal output end of a second fractional-N phase-locked loop (21) is connected with the signal input end of a second low-pass filter (23) through a low-noise amplifier (19), the signal output end of the second low-pass filter (23) is connected with the signal input end of a second automatic gain control circuit (7), the signal output end of the direct digital frequency synthesizer (24) is connected with the signal input end of a first band-pass filter (26) through the low-noise amplifier (19), the signal output end of the first band-pass filter (26) is connected with the signal input end of the A/D acquisition circuit (14).

3. The phase distance measuring device based on laser heterodyne detection as recited in claim 1, wherein the photoelectric detection conversion circuit (13) comprises a boost power supply module (27), an APD detector (28), a current-voltage conversion module (29), an adjustable gain amplification module (30) and a second band-pass filter (31) which are sequentially arranged.

4. The phase distance measuring device based on laser heterodyne detection as recited in claim 1, wherein the a/D acquisition circuit (14) is a dual-channel a/D acquisition circuit (14).

5. A phase-finding device based on laser heterodyne detection according to claim 1, characterized in that the telescope (8) is located on the same optical path as the target object to be detected.

6. The method of claim 1, wherein the method comprises the steps of splitting an infrared laser into a measuring beam and a reference beam, modulating the measuring beam and emitting the modulated measuring beam to a target to be measured, combining the beam returned by the target to be measured and the modulated reference beam to obtain a combined beam, converting the combined beam into a voltage signal to obtain a heterodyne detection signal, synchronously acquiring, converting, processing and calculating the heterodyne detection signal and the reference signal to obtain the distance to be measured.

7. The method for phase distance measurement based on laser heterodyne detection as recited in claim 6, comprising the steps of:

(1) infrared laser is divided into a measuring beam and a reference beam through a first optical fiber coupler (2), and a signal generating circuit (5) is utilized to simultaneously generate two ultrahigh frequency sinusoidal signals and an intermediate frequency sinusoidal signal to obtain a main vibration signal, a local vibration signal and an intermediate frequency reference signal;

(2) amplifying the main vibration signal, loading the amplified main vibration signal to a first electro-optical intensity modulator (3), modulating the intensity of the measuring beam, emitting the modulated main vibration signal to a measured target and returning the modulated main vibration signal to the measured target to obtain a measuring return beam, amplifying the local vibration signal, loading the amplified local vibration signal to a second electro-optical intensity modulator (4), and modulating the intensity of the reference beam to obtain a modulated reference beam;

(3) after the measurement return beam and the modulation reference beam are combined by the second optical fiber coupler (11), the measurement return beam and the modulation reference beam are converted into voltage signals by the photoelectric detector (12) and the photoelectric detection conversion circuit (13) to obtain heterodyne detection signals;

(4) and (3) synchronously inputting the heterodyne detection signal and the intermediate frequency reference signal obtained in the step (1) into an A/D acquisition circuit (14) and then calculating the distance to be measured.

8. The method for phase distance measurement based on laser heterodyne detection as recited in claim 7, wherein in the step (1), the frequencies of the main oscillation signal and the local oscillation signal are both 14.6 to 15GHz, and the difference between the frequencies of the main oscillation signal and the local oscillation signal is 2 MHz.

9. The method for phase distance measurement based on laser heterodyne detection as recited in claim 7, wherein in the step (1), the frequency of the intermediate frequency reference signal is 2 MHz.

Technical Field

The invention relates to a laser ranging technology, in particular to a phase ranging device based on laser heterodyne detection; the invention also relates to a phase distance measurement method based on laser heterodyne detection.

Background

The laser phase method distance measurement is suitable for absolute measurement of medium-short distance and has wide application in many fields, but the millimeter-scale precision of the traditional phase method distance measurement cannot meet the requirements of applications such as giant manufacturing, three-dimensional accurate target identification and the like. Increasing the frequency of the laser modulation signal is the most effective means for increasing the distance measurement accuracy, but when the modulation frequency is increased to above gigahertz level, the ratio of the phase fluctuation caused by the light intensity variation irradiated on the ultrahigh frequency detection detector and the phase error caused by the phase nonuniformity of the photoelectric detector in the whole distance measurement error is greatly increased, which becomes the main factor for restricting the distance measurement accuracy. With the difference of the position, material or surface roughness of the target to be detected, the light intensity returned to the detector is different, so that the APD multiplication factor is changed, and finally, the phase of the electric signal after the ultrahigh frequency detection generates larger fluctuation, namely, the phase fluctuation caused by the light intensity change is shown. When the center of the receiving light spot moves on the photosensitive surface of the detector, the phase change of the electric signal generated after the ultrahigh frequency electro-optical intensity modulation signal is detected, namely the phase nonuniformity of the photoelectric detector is caused. It is difficult to effectively eliminate the phase fluctuation caused by the two factors by adopting the method of measurement compensation.

Disclosure of Invention

The invention aims to provide a phase distance measuring device based on laser heterodyne detection, which can effectively solve the problem of phase fluctuation caused by light intensity change and detector phase nonuniformity in the ultra-high frequency modulation phase method distance measurement and has the characteristic of high measurement precision.

The invention also aims to provide a phase ranging method based on laser heterodyne detection.

The former technical scheme adopted by the invention is as follows:

a phase distance measuring device based on laser heterodyne detection comprises an infrared fiber laser, a first optical fiber coupler, a first electro-optic intensity modulator, a second electro-optic intensity modulator, a telescope, an optical fiber collimator, a second optical fiber coupler, an A/D acquisition circuit and a computer, wherein the optical path output end of the infrared fiber laser is connected with the optical path input end of the first optical fiber coupler, the two optical path output ends of the first optical fiber coupler are respectively connected with the optical path input end of the first electro-optic intensity modulator and the optical path input end of the second electro-optic intensity modulator, the optical path output end of the first electro-optic intensity modulator is connected with the optical path inlet of the telescope, the optical fiber collimator is connected with the return optical path outlet of the telescope, the optical path output end of the second electro-optic intensity modulator and the optical path output end of the optical fiber collimator are both connected with the optical path input end of the second optical fiber coupler, the photoelectric detection device comprises a signal generation circuit, a first automatic gain control circuit, a second automatic gain control circuit, a photoelectric detector and a photoelectric detection conversion circuit, wherein the signal generation circuit is used for generating an intermediate-frequency sinusoidal signal and an ultrahigh-frequency sinusoidal signal, a first ultrahigh-frequency sinusoidal signal output end of the signal generation circuit is connected with a first electro-optic intensity modulator through the first automatic gain control circuit, a second ultrahigh-frequency sinusoidal signal output end of the signal generation circuit is connected with a second electro-optic intensity modulator through the second automatic gain control circuit, an intermediate-frequency sinusoidal signal output end of the signal generation circuit is connected with an A/D acquisition circuit, the photoelectric detector and the photoelectric detection conversion circuit are sequentially arranged between a second optical fiber coupler and the A/D acquisition circuit, and the A/D acquisition circuit is connected with a computer.

The latter technical scheme adopted by the invention is as follows:

a phase distance measuring method based on laser heterodyne detection is characterized in that infrared laser is divided into a measuring beam and a reference beam, the measuring beam is modulated and then emitted to a measured target, the beam returned by the measured target and the modulated reference beam are combined to obtain a combined beam, the combined beam is converted into a voltage signal to obtain a heterodyne detection signal, and the heterodyne detection signal and the reference signal are synchronously acquired and converted and are processed and calculated to obtain a distance to be measured.

Further, the method comprises the following steps:

(1) the method comprises the following steps of dividing infrared laser into a measuring beam and a reference beam through a first optical fiber coupler, and simultaneously generating two ultrahigh frequency sinusoidal signals and an intermediate frequency sinusoidal signal by using a signal generating circuit to obtain a main oscillation signal, a local oscillation signal and an intermediate frequency reference signal;

(2) amplifying the main vibration signal, loading the amplified main vibration signal to a first electro-optical intensity modulator to perform strong modulation on the measurement light beam, emitting the modulated main vibration signal to a measured target and returning the modulated main vibration signal to the measured target to obtain a measurement return light beam, amplifying the local vibration signal, and loading the amplified local vibration signal to a second electro-optical intensity modulator to perform intensity modulation on the reference light beam to obtain a modulated reference light beam;

(3) after the measurement return light beam and the modulation reference light beam are combined by the second optical fiber coupler, the measurement return light beam and the modulation reference light beam are converted into voltage signals through the photoelectric detector and the photoelectric detection conversion circuit to obtain heterodyne detection signals;

(4) and (3) synchronously inputting the heterodyne detection signal and the intermediate frequency reference signal obtained in the step (1) into the A/D acquisition circuit 1, and then calculating the distance to be measured.

Compared with the prior art, the invention has the beneficial effects that:

1. the same constant temperature crystal oscillator respectively passes through the decimal frequency division phase-locked loop to simultaneously generate a main oscillation signal and a local oscillation signal in the signal generating circuit, and simultaneously the constant temperature crystal oscillator also drives a direct digital frequency device to generate an intermediate frequency reference signal, so that the frequency accuracy of a modulation signal and an intermediate frequency sinusoidal signal can be ensured, a mixing circuit is not needed, high-frequency signal crosstalk generated by circuit mixing can not occur, and the distance period error caused by the high-frequency signal crosstalk is weakened.

2. The phase nonuniformity of the detector is obvious only in high-frequency detection, and the nonuniformity error is greatly reduced in medium-low frequency detection. The invention adopts the photoelectric detector with lower response frequency to carry out optical fiber heterodyne detection, replaces the traditional high-frequency detection and then circuit frequency mixing processing by the intermediate frequency detection after the optical fiber heterodyne detection, and avoids the problem that the high-frequency detector generates large phase error due to phase nonuniformity.

3. The measuring beam has small light intensity after returning through the distance to be measured, and the light intensity of heterodyne detection mainly depends on the light intensity of the modulated reference beam, so that the relative change rate of the light intensity is small, and the phase fluctuation caused by the fluctuation of the detected light intensity is greatly reduced.

4. And the heterodyne detection signal and the intermediate frequency reference signal are synchronously sampled by two-channel data, and the phase difference between the heterodyne detection signal and the intermediate frequency reference signal is calculated, so that the phase difference calculation precision is improved.

Drawings

FIG. 1 is a block diagram of the present invention;

fig. 2 is a block diagram of the signal generating circuit of the present invention.

Fig. 3 is a block diagram of the structure of the photodetection conversion circuit of the present invention.

Detailed Description

The technical solution of the present invention will be described in further detail with reference to the following embodiments, but the present invention is not limited thereto.

Referring to fig. 1 to 3, the phase distance measuring device based on laser heterodyne detection of the present invention includes an infrared fiber laser 1, a first fiber coupler 2, a first electro-optical intensity modulator 3, a second electro-optical intensity modulator 4, a telescope 8, a fiber collimator 10, a second fiber coupler 11, an a/D acquisition circuit 14, and a computer 15, where an optical path output end of the infrared fiber laser 1 is connected to an optical path input end of the first fiber coupler 2, two optical path output ends of the first fiber coupler 2 are respectively connected to an optical path input end of the first electro-optical intensity modulator 3 and an optical path input end of the second electro-optical intensity modulator 4, an optical path output end of the first electro-optical intensity modulator 3 is connected to an optical path inlet of the telescope 8, and the fiber collimator 10 is connected to a return optical path outlet of the telescope 8, and the light path output end of the second electro-optical intensity modulator 4 and the light path output end of the optical fiber collimator 10 are both connected with the light path input end of the second optical fiber coupler 11. Also comprises a signal generating circuit 5 for generating an intermediate frequency sinusoidal signal and an ultrahigh frequency sinusoidal signal, a first automatic gain control circuit 6, a second automatic gain control circuit 7, a photoelectric detector 12 and a photoelectric detection converting circuit 13, a first ultrahigh frequency sinusoidal signal output end of the signal generating circuit 5 is connected with the first electro-optical intensity modulator 3 through a first automatic gain control circuit 6, the second ultrahigh frequency sinusoidal signal output end of the signal generating circuit 5 is connected with the second electro-optical intensity modulator 4 through a second automatic gain control circuit 7, the intermediate frequency sinusoidal signal output end of the signal generating circuit 5 is connected with an A/D acquisition circuit 14, the photoelectric detector 12 and the photoelectric detection conversion circuit 13 are sequentially arranged between the second optical fiber coupler 11 and the A/D acquisition circuit 14, and the A/D acquisition circuit 14 is connected with the computer 15.

The infrared fiber laser 1 emits laser with the wavelength of 1550nm, the laser is guided into the first optical fiber coupler 2 through optical fibers, and the first optical fiber coupler 2 divides light beams into two paths: one path is a measuring beam and is guided into the first electro-optic intensity modulator 3 through the optical fiber for modulation, and the other path is a reference beam and is guided into the second electro-optic intensity modulator 4 through the optical fiber for modulation. The first electro-optical intensity modulator 3 and the second electro-optical intensity modulator 4 are each a mach-zehnder modulator having a modulation bandwidth better than 20 GHz. The modulated measuring beam is guided into a telescope 8 through an optical fiber to be collimated and then is emitted to a measured target 9, the measured beam is reflected by the measured target 9 and then enters the telescope 8, the measured beam is contracted by the telescope 8 and then is guided into an optical fiber collimator 10, the measured beam is guided into a second optical fiber coupler 11 through the optical fiber, and the modulated reference beam also enters the second optical fiber coupler 11 through the optical fiber. After entering the second fiber coupler 11 and being combined, the two light beams are guided into the photoelectric detector 12 through the optical fiber, the heterodyne signal is converted into a current signal, the phase of the current signal contains a phase delay which is in direct proportion to the distance to be measured, and redundant additional phases can be eliminated after calibration.

In the traditional laser phase method distance measurement, the direct photoelectric detection is adopted on the measuring beam which returns from the distance to be measured after modulation. Accurate measurement of the phase difference is the guarantee of high-precision distance measurement by a laser phase method, and the improvement of the laser modulation frequency is the most effective means for improving the distance measurement precision by the laser phase method. Due to the inevitable existence of photoelectric white noise in the detection signal, the phase difference measurement accuracy cannot exceed the Cramer-Rao limit. Therefore, in order to further improve the ranging accuracy, the modulation frequency has to be increased. However, when the modulation frequency is higher than gigahertz, the light intensity returned to the photodetector changes greatly due to the change of the measured distance, the change of the measured target material or the change of roughness, and the like, and the change of the detected light intensity can cause the change of the multiplication factor of the APD detector, so that the fluctuation of several degrees or even tens of degrees of the phase of the electrical signal after detection can be caused, that is, the great phase fluctuation is caused by the change of the light intensity. In addition, when the direct photoelectric detection is performed on the measuring beam, even if the distances are the same, the large phase change is generated on the electric signal after the ultrahigh frequency electro-optical intensity modulation signal is detected, namely the obvious phase nonuniformity of the photoelectric detector, when the center of the received light spot moves on the photosensitive surface of the detector due to the difference of the detected targets or the change of the postures of the detected targets. Phase fluctuation caused by light intensity change and phase nonuniformity of the photoelectric detector are two main factors for restricting the ranging precision of the ultrahigh frequency laser phase method.

The phase distance measuring device based on laser heterodyne detection guides a measurement return beam returned after passing through a target to be measured and a modulated reference beam into a second optical fiber coupler 11, then heterodyne detection is adopted, a photoelectric detector 12 with very low response frequency can be used, and the position of the center of a light spot on the photosensitive surface of the photoelectric detector 12 with a tail fiber is basically fixed, so that the distance measuring error caused by the non-uniformity of the phase of the photoelectric detector 12 is greatly reduced. Although the intensity of the measurement return beam returned after passing through the target to be measured changes, the light intensity of the measurement return beam is far less than that of the reference beam, so that the light intensity of heterodyne detection is basically kept unchanged, and phase fluctuation caused by intensity change is greatly reduced. The signal output by the photoelectric detector 12 is converted, amplified and filtered by the photoelectric detection conversion circuit 13, and then synchronously converted into a digital signal by the dual-channel A/D acquisition circuit 14 together with the intermediate frequency sinusoidal signal generated by the signal generation circuit 5, and finally the two columns of digital signals are processed in the computer 15, and the phase difference is calculated by a phase-shift correlation algorithm, so that the distance to be measured is calculated after the phase change caused by the additional phase and the correction temperature is eliminated.

The signal generating circuit 5 comprises a constant temperature crystal oscillator 16, a first fractional-N phase-locked loop 18, a second fractional-N phase-locked loop 21, a direct digital frequency synthesizer 24, a first low-pass filter 20, a second low-pass filter 23, a first band-pass filter 26, a controller 17 and a plurality of low-noise amplifiers 19, wherein the controller 17 is respectively connected with the first fractional-N phase-locked loop 18, the second fractional-N phase-locked loop 21 and the direct digital frequency synthesizer 24, a signal output end of the constant temperature crystal oscillator 16 is respectively connected with a signal input end of the first fractional-N phase-locked loop 18, a signal input end of the second fractional-N phase-locked loop 21 and a signal input end of the direct digital frequency synthesizer 24, a signal output end of the first fractional-N phase-locked loop frequency-divided loop 18 is connected with a signal input end of the first low-pass filter 20 through the low-noise amplifier 19, a signal output end of the first low-pass filter 20 is connected with a signal input, the signal output end of the second fractional-N PLL 21 passes throughThe low noise amplifier 19 is connected with a signal input end of a second low pass filter 23, a signal output end of the second low pass filter 23 is connected with a signal input end of a second automatic gain control circuit 7, a signal output end of the direct digital frequency synthesizer 24 is connected with a signal input end of a first band-pass filter 26 through the low noise amplifier 19, and a signal output end of the first band-pass filter 26 is connected with a signal input end of the A/D acquisition circuit 14. The main vibration signal f generated by the ultrahigh frequency sinusoidal signal generating circuit 5₁Amplified by the first automatic gain control circuit 6 and loaded on the first electro-optical intensity modulator 3 to generate a local oscillation signal f₂And the amplified light is loaded on a second electro-optical intensity modulator 4 through a second automatic gain control circuit 7, and the intensity modulation is respectively realized on the measuring light beam and the reference light beam. Principal vibration signal f₁And local oscillator signal f₂The frequencies of the two signals are all 14.6-15 GHz, and the main vibration signal f₁And local oscillator signal f₂With a frequency difference of 2 MHz. Principal vibration signal f₁And local oscillator signal f₂The high-precision constant-temperature crystal oscillator 16 provides clock signals for the first fractional frequency division phase-locked loop 18 and the second fractional frequency division phase-locked loop 21, and the controller 17 synchronously rewrites frequency control words of the first fractional frequency division phase-locked loop 18 and the second fractional frequency division phase-locked loop 21, so that the first fractional frequency division phase-locked loop 18 and the second fractional frequency division phase-locked loop 21 output 5 pairs of ultra-high frequency sinusoidal signals with the frequency of 14.6-15 GHz in a time-sharing manner, but the difference frequency of the two ultra-high frequency sinusoidal signals is always 2 MHz. Principal vibration signal f₁And local oscillator signal f₂After being amplified by a low noise amplifier 19, the intermediate frequency reference signal f with the frequency of 2MHz is filtered by a first low pass filter 20 and a second low pass filter 23 respectively₃Generated by a direct digital frequency synthesizer 24, and using the same clock source as the first fractional-N phase-locked loop 18 and the second fractional-N phase-locked loop 21 to ensure the frequency f of the heterodyne detection signal and the intermediate frequency reference signal₃Are completely consistent. Intermediate frequency reference signal f₃Amplified by a low noise amplifier 19 and filtered by a first band pass filter 26 before being output to the two-channel A/D acquisition circuit 14.

The photoelectric detection conversion circuit 13 includes a boost power supply module 27, an APD detector 28, a current-voltage conversion module 29, an adjustable gain amplification module 30, and a second band-pass filter 31, which are sequentially arranged. The boosting power supply module 27 provides a high-stability power supply for the APD detector 28, a current signal output by the APD detector 28 is converted into a voltage signal through the current-voltage conversion module 29, the voltage signal is amplified by the adjustable gain amplification module 30, and the voltage signal is filtered by the second band-pass filter 31 and then output to the a/D acquisition circuit 14.

The A/D acquisition circuit 14 is a dual-channel A/D acquisition circuit 14. The telescope 8 and the detected target object are positioned on the same optical path.

The invention relates to a phase distance measurement method based on laser heterodyne detection, which comprises the steps of dividing an infrared laser into a measuring beam and a reference beam, modulating the measuring beam and then emitting the modulated measuring beam to a measured target, combining the beam returned by the measured target and the modulated reference beam to obtain a combined beam, converting the combined beam into a voltage signal to obtain a heterodyne detection signal, synchronously acquiring and converting the heterodyne detection signal and the reference signal, processing and calculating to obtain a distance to be measured.

The method specifically comprises the following steps:

(1) the infrared laser is divided into a measuring beam and a reference beam through the first optical fiber coupler 2, and a signal generating circuit 5 is utilized to simultaneously generate two ultrahigh frequency sinusoidal signals and a medium frequency sinusoidal signal to obtain a master vibration signal f₁And local oscillator signal f₂And an intermediate frequency reference signal f₃. The frequency of the main vibration signal and the local vibration signal is 14.6-15 GHz, and the frequency of the main vibration signal f is₁And local oscillator signal f₂With a frequency difference of 2 MHz. The intermediate frequency reference signal f₃Has a frequency of 2 MHz.

(2) The main vibration signal f₁After amplification, the amplified signal is loaded to a first electro-optical intensity modulator 3 to modulate the intensity of the measuring beam, then the measuring beam is emitted to a measured target and returns to obtain a measuring return beam, and a local oscillator signal f is transmitted to a local oscillator₂After being amplified, the amplified reference beam is loaded to a second electro-optical intensity modulator 4 to modulate the intensity of the reference beam to obtain a modulated reference beam;

(3) the measurement return beam and the modulation reference beam are combined by the second optical fiber coupler 11 and then converted into voltage signals by the photoelectric detector 12 and the photoelectric detection conversion circuit 13 to obtain heterodyne detection signals;

(4) heterodyne detection signal and intermediate frequency reference signal f obtained in step (1)₃The distance to be measured is calculated after the synchronous input of the A/D acquisition circuit 14.

The method for phase distance measurement based on laser heterodyne detection guides a measurement return beam returned by a target to be detected and a modulated reference beam into a second optical fiber coupler 11, heterodyne detection is adopted, a photoelectric detector 12 with low response frequency is used, and the position of the spot center of the combined beam on the photosensitive surface of the photoelectric detector 12 is basically fixed, so that the phase error generated by the phase nonuniformity of the photoelectric detector 12 is greatly reduced. The signal output by the photoelectric detector 12 is subjected to current-voltage conversion, amplification and filtering by the photoelectric detection conversion circuit 13, and is synchronously converted into a digital signal by the dual-channel A/D acquisition circuit 14 together with the intermediate-frequency sinusoidal signal generated by the signal generation circuit 5, and the phase difference is calculated by a phase-shifting correlation algorithm, so that after the phase change caused by additional phase and correction temperature is eliminated, the accuracy of calculating the distance to be measured is higher.

The above description is only exemplary of the invention, and any modification, equivalent replacement, and improvement made within the spirit and scope of the present invention should be considered within the scope of the present invention.