CN100394211C - Multi-frequency synchronous modified large range high precision fast laser ranging method and apparatus - Google Patents

Abstract

The invention belongs to the technical field of laser ranging, in particular to a large-range, high-precision and fast laser ranging method and device based on multi-frequency synchronous modulation. In the laser emission unit, the multi-frequency modulation signal is subjected to characteristic pre-compensation, weighted summation, and then the power of the laser is modulated to perform distance measurement. At the same time, a synchronous band-pass filter frequency selection phase measurement corresponding to the modulation method is adopted in the reception. Signal processing is carried out in a manner that changes the existing multi-frequency serial asynchronous modulation ranging mode into a parallel synchronous modulation ranging mode. By adopting the method and device of the present invention, the ranging results of each measuring ruler frequency in the multi-frequency modulation ranging can be obtained at the same time, and then the final ranging value can be obtained, thereby ensuring the ranging speed and real-time performance. On the one hand, it realizes the rapid measurement of the target distance on the basis of ensuring the measurement accuracy and large range. On the other hand, it avoids the ranging error caused by the change of the target position when using multi-frequency time-division measurement when measuring the distance of the moving target.

Description

Multi-frequency synchronous modulation laser ranging method and device

technical field

The invention belongs to the technical field of laser ranging, in particular to a large-range, high-precision and fast laser ranging method and device based on multi-frequency synchronous modulation.

Background technique

Laser ranging is a comprehensive technology that integrates various technologies such as optics, laser, optoelectronics and integrated electronics. Semiconductor laser ranging devices are widely used in military, aerospace, robot vision, industrial automatic production lines and other fields due to their advantages of non-contact, high precision, small size, low cost, and long service life. For absolute distance measurement, the commonly used laser ranging methods are pulse method and phase method. The pulse method has the advantages of wide measurement range, fast speed, suitable for non-cooperative targets, etc., but its measurement accuracy is low. The distance measuring device using a pulsed semiconductor laser can measure up to several kilometers, and the accuracy is generally 0.1 to 1m. The phase method usually has a slow measurement speed, but it can obtain ranging accuracy of millimeters or even higher, so it is more used in ranging occasions that require higher accuracy.

The phase method laser ranging is to irradiate the laser beam whose intensity is modulated according to a certain frequency to the target, and measure the distance by measuring the phase difference between the emitted laser beam and the target reflected laser beam due to the target distance. The measured distance can be given by formula (1)

为发射光信号与接收光信号相位差。由于实际测量过程中相差测量只能介于0～2π之间，所以该测距方法的理论最大测程D_max由调制频率决定，D_max＝c/2πf，要增大测程就必须降低调制频率。而对该式微分得：Among them: D is the measured distance, c is the speed of light, f is the modulation frequency,

is the phase difference between the transmitted optical signal and the received optical signal. Since the phase difference measurement can only be between 0 and 2π in the actual measurement process, the theoretical maximum range D _max of this distance measurement method is determined by the modulation frequency, D _max = c/2πf, and the modulation must be reduced to increase the range frequency. And the differential of this formula is:

相同的条件下调制频率f越低测距精度越低，测量精度和量程产生矛盾。但在很多应用场合，不但要求测距装置测程远，还要求测量精度高且测量速度快。针对相位法激光测距及其量程和精度矛盾问题，国内外已经有很多专利和研究方法。From formula (2), it can be known that the phase measurement accuracy

Under the same conditions, the lower the modulation frequency f is, the lower the ranging accuracy is, and there is a contradiction between the measurement accuracy and the range. However, in many applications, not only the distance measuring device is required to measure a long distance, but also high measurement accuracy and fast measurement speed are required. There have been many patents and research methods at home and abroad for the phase-based laser ranging and its range and accuracy contradictions.

Based on its patents (US5815251, EP0738899, EP0932835), the Swiss Leica Company launched the DISTO series of handheld laser rangefinders, which use the multi-frequency phase method for distance measurement, with a maximum range of 200m and a maximum accuracy of ±3.0mm. The shortest measurement time is 0.16s (Leica DISTO series laser range finder product manual, 2004).

The document "A dual-frequency modulation laser rangefinder" (Stephane Poujouly and Bernard Journet, Atwofold modulation frequency laser range finder, J.Opt A: Pur Appt.Opt.4(2002) s356-S363) describes a method using Dual-frequency modulation phase method laser distance measuring device, the modulation frequency is respectively selected as 10MHz and 240MHz, the measurement range is 15m, and the accuracy is 0.35mm.

The DCH2-E semiconductor infrared rangefinder developed by Tsinghua University and Beijing Surveying and Mapping Instrument Factory adopts the dual-frequency modulation phase laser ranging method, and the frequency of the measuring ruler adopts the indirect frequency selection method. The frequency is 149.856KHz, the maximum measurement range is 2000m, the accuracy is ±10mm, and the single measurement time is 5.0s.

The above-mentioned existing ranging devices and researches all adopt the same method in solving the contradiction between the range and precision of the phase method laser ranging, that is, the multi-frequency modulation method, which is also a method commonly used in existing research. The principle of multi-frequency modulation phase laser ranging is shown in Figure 1. It is mainly composed of 9 parts, namely multi-frequency signal generation unit 4, multi-channel electronic switches 3 and 8, laser power modulation drive unit 2, laser 1, laser Receiving lens 5 , measurement light photoelectric detector 6 , measurement light photoelectric conversion circuit 7 , phase difference measurement and distance synthesis unit 9 . The method uses multiple modulation frequencies to measure the distance of the target, in which the low-frequency modulation signal (coarse scale frequency) is used to increase the measurement range, and the high-frequency modulation signal (fine scale frequency) is used to ensure measurement accuracy. During the measurement, the control unit controls the electronic switch to time-division each modulation signal to measure the distance of the target, and then performs data fusion processing on the distance measurement values obtained by each measuring ruler, and then obtains the final distance measurement result. The shortcomings of this method are mainly manifested in the following two points: First, the measurement speed is slow. During the measurement, it is necessary to measure the target at multiple frequencies, and then obtain the final measurement result through data fusion. The total ranging time varies with the number of measuring ruler frequencies Second, when measuring the distance of a moving target, the position of the target may change during the multi-frequency sub-measurement process, resulting in measurement errors.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of the prior art, and provide a large-range high-precision fast laser ranging method and device based on multi-frequency synchronous modulation. The present invention has mainly carried out following improvement on the basis of existing multi-frequency modulation technology: (1) replace original multi-channel electronic switch unit at transmitting unit and be multi-frequency signal characteristic pre-compensation weighted sum processing unit; (2) at transmitting unit The receiving unit replaces the original multi-channel electronic switch unit with a multi-channel synchronous band-pass filter frequency selection and phase measurement unit. Therefore, the existing multi-frequency serial asynchronous modulation ranging mode is changed to a parallel synchronous modulation ranging mode, so that the multi-frequency modulation ranging can be carried out synchronously, that is, the ranging values of each measuring ruler frequency are obtained at the same time, and the total ranging time does not change with time. The increase in the frequency of the measuring ruler increases. On the one hand, it realizes the rapid measurement of the target distance on the basis of ensuring the measurement accuracy and large range. The ranging error caused by the change.

The present invention also provides a large-scale high-precision fast laser distance measuring device based on multi-frequency synchronous modulation on the basis of the above measuring method.

The technical solution of the present invention is: a multi-frequency synchronously modulated laser ranging method, the method comprising the following steps:

(1) Using multiple measuring ruler frequencies f ₀ , f ₁ , f ₂ ...f _n to measure the distance of the target, the measuring ruler frequency adopts the method of direct measuring ruler frequency selection, take f ₀ =mf ₁ =mf ₂ = ...=mf _n , then the ranging accuracy ΔD ₀ =mΔD ₁ =mΔD ₂ =...=mΔD _n , the measuring range D ₀ =1/mD ₁ =1/mD ₂ =...=1/mD _n , m value is 100 to 1000;

其中：E_t为最终合成的调制信号，A为正弦信号幅度，为正弦信号的初始相位，然后采用该信号对激光器功率进行调制并对目标实施测距；(2) _Select the sinusoidal signal according to the frequency f ₀ , f ₁ , f ₂ .

Where: E _t is the final synthesized modulation signal, A is the amplitude of the sinusoidal signal, is the initial phase of the sinusoidal signal, which is then used to modulate the laser power and perform ranging on the target;

最后通过数据融合处理可求得最终测距结果D。(3) The electrical signal obtained after the return light signal reflected by the target passes through the photoelectric conversion circuit is: Among them: k _i is the conversion gain of the receiving circuit to the frequency , φ _i is the phase delay generated by the optical signal with the modulation frequency f _i reflected by the target, and the processing circuit adopts multi-channel parallel band-pass filter frequency selection processing for the signal E _r Obtain each signal component, and measure the phase delay φ _i between each signal and the transmitted signal at the same time, and then obtain the ranging results of each measuring ruler frequency at the same time

Finally, the final ranging result D can be obtained through data fusion processing.

相应的接收信号为

α_i为针对光电接收系统对频率为f_i的调制光信号的频率衰减特性设定的抗衰减特性预补偿因子，α_i的取值应使得α_i·k_i＝C，C为常数，即接收系统对回光信号中各测尺频率的光信号产生相同的增益。The characteristic pre-compensation is also used in the weighted sum synthesis process, and the modulated signal after compensation is

The corresponding received signal is

α _i is the anti-attenuation characteristic precompensation factor set for the frequency attenuation characteristic of the modulated optical signal with frequency f _i in the photoelectric receiving system, the value of α _i should be such that α _i k _i =C, C is a constant, that is The receiving system produces the same gain for the light signals of each measuring ruler frequency in the return light signal.

The multi-frequency synchronously modulated large-scale high-precision fast laser ranging device used in the above method includes a multi-frequency signal generating unit, a laser, a laser power modulation drive unit, a laser emitting lens, a laser receiving lens, a measuring light photodetector, a measuring light Photoelectric conversion circuit, reference light photodetector, reference light photoelectric conversion circuit, data fusion distance calculation unit, also includes multi-frequency signal synthesis unit, spectroscope, multi-channel band-pass frequency-selective filter unit, multi-channel synchronous phase measurement unit;

The multi-frequency signal generation unit generates multi-channel sinusoidal signals of corresponding frequencies according to the selected frequency of the measuring scale. After the multi-channel signal is synthesized by the multi-frequency signal synthesis unit, it acts on the synchronous modulation unit to modulate the power of the laser. The modulated laser The beam is sent to the beam splitter through the laser emitting lens. After passing through the beam splitter, the reflected light forms a measuring beam and shoots to the measured target. The measuring beam is reflected by the target and is received by the laser receiving lens. After passing through the measuring light photoelectric detector, it is converted by the measuring light The circuit is converted into a measurement electrical signal, the transmitted light forms a reference light, and the reference light photoelectric detector passes through the reference light photoelectric conversion circuit to form a reference electrical signal. The measurement electrical signal and the reference electrical signal are synchronized by multiple channels after passing through a band-pass frequency-selective filter unit. The phase measurement unit provides the phase difference generated by the frequency of the measuring ruler after the target reflection, and the distance synthesis calculation unit synthesizes the measured phase difference to obtain the final distance measurement result.

The present invention has following characteristics and good effect:

The existing multi-frequency modulation laser ranging technology adopts the method of time-division gating modulation signal to modulate the laser power and then implement the ranging method. The ranging time of this method increases with the frequency of the measuring ruler. It is difficult to obtain real-time ranging results, which will cause ranging errors. The invention proposes a multi-frequency synchronous modulation laser ranging method, that is, the laser power is modulated after the multi-frequency modulation signal is synthesized by the laser emitting unit, and at the same time, a multi-channel synchronous band-pass filter corresponding to the modulation method is used when receiving Signal processing is carried out by means of frequency selective phase measurement. Using this method, the ranging results of each measuring ruler frequency in the multi-frequency modulation ranging can be obtained at the same time, and then the final ranging value can be obtained, which ensures the ranging speed and real-time performance. This is one of the innovations different from the existing technology ;

The present invention also proposes a processing method for performing characteristic pre-compensation, weighted summation and synthesis of multi-frequency modulation signals for the proposed multi-frequency synchronous modulation laser ranging method. In the laser ranging method, the optical power signal modulated by the frequency of the measuring ruler with a large frequency difference produces the same gain, which avoids the saturation of the low-frequency modulated optical signal and the high-frequency modulated optical signal due to the frequency attenuation characteristics of the photoelectric receiving unit. When receiving, the signal-to-noise ratio is reduced due to too much attenuation, which is the second innovative point different from the prior art.

The multi-frequency synchronous modulation large-range high-precision fast laser ranging method and device proposed by the present invention will be described in detail below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is the principle block diagram of the multi-frequency modulation phase method laser ranging method adopted in the prior art

Fig. 2 is the schematic diagram of multi-frequency synchronous modulation phase method laser distance measuring device of the present invention

Fig. 3 is a schematic diagram of the multi-frequency synchronous modulation characteristic pre-compensation method of the present invention

Fig. 4 is a schematic diagram of the characteristic precompensation factor setting method of the present invention

Fig. 5 is the multi-channel synchronous band-pass filtering frequency selective phase measurement schematic diagram of the present invention

Figure 6 is a schematic diagram of a dual-frequency synchronously modulated phase laser ranging device provided by the present invention

Fig. 7 is a schematic diagram of the coaxial laser transmitting and receiving structure in the present invention

Fig. 8a is a schematic diagram of beam splitting of reference light and measuring light by using beam splitting prism 36 in the present invention

Fig. 8b is a schematic diagram of beam splitting of reference light and measuring light by using hole-setting mirror 37 in the present invention

Fig. 8c is a schematic diagram of the hole reflector 37 of the present invention

Detailed ways

Multi-frequency synchronous modulation large-scale high-precision fast laser ranging method

FIG. 3 shows a schematic diagram of synchronously modulating laser power after multi-frequency modulation signals are precompensated and weighted to be synthesized by the present invention.

First of all, the multi-frequency modulation method is adopted to solve the contradiction between the measurement accuracy and the range of the laser ranging by the phase method, that is, a variety of modulation frequencies (measurement frequency) f ₀ , f ₁ , f ₂ ... f _n are used to measure the distance of the target . The measuring ruler frequency adopts the method of direct measuring ruler frequency selection, that is, f ₀ =mf ₁ =mf ₂ =...=mf _n . The value of m can be from 100 to 1000 according to the phase measurement accuracy, and the typical value is 100. Then the multi-frequency signal generating unit 4 generates sinusoidal signals of corresponding frequencies according to the measuring scale frequencies f ₀ , f ₁ , f ₂ ... f _n

为信号初始相位，i＝0...n。where A is the signal amplitude,

is the initial phase of the signal, i=0...n.

After the sinusoidal signal passes through the pre-compensation factor setting unit 18, the amplitude correspondingly changes according to the difference of the compensation factor, that is,

Where α _i is a pre-compensation factor, i=0...n.

The function of the multi-frequency signal synthesis unit 10 is to synthesize the frequency signals of each measuring scale, so that the frequency signals of each measuring scale can act on the laser at the same time, that is, realize multi-frequency synchronous modulation. The synthesized signal is

The signal implements multi-frequency synchronous modulation on the laser 1 through the laser power modulation drive unit 2 . Figure 4 shows the setting method of the characteristic pre-compensation factor.

In the multi-frequency modulation phase laser ranging, in order to improve the ranging accuracy, the frequency of the fine measuring ruler needs to be increased, and in order to increase the range, the frequency of the coarse measuring ruler needs to be reduced, so as to realize the modulation signal during large-range and high-precision ranging The bandwidth is very wide, generally from a few kilohertz to tens of megahertz, and the photoelectric detection circuit has a certain bandwidth, which usually produces different degrees of attenuation for high-frequency signals. The higher the frequency, the greater the attenuation. Its characteristics are shown in the curve in Figure 4 21. In the present invention, the power of the laser device has adopted multi-frequency synchronous modulation. If the modulation signal amplitude of the corresponding measuring ruler frequency is the same, when the photoelectric conversion circuit gain G is set to ensure that the low frequency (coarse measuring ruler frequency) component signal does not produce saturation distortion, the high The signal-to-noise ratio will be reduced due to attenuation, and the measurement accuracy will be reduced; when the gain G of the photoelectric conversion circuit is set to ensure that the high-frequency (precision measuring ruler frequency) component signal meets a certain amplitude requirement, Low-frequency signals will produce saturation distortion and cause phase measurement errors.

For this reason, the present invention proposes to adopt characteristic pre-compensation method to solve the above-mentioned problem, and the basic idea of characteristic pre-compensation is to carry out certain adjustment to the amplitude of each frequency component of multi-frequency modulation signal in laser power modulation unit according to the frequency characteristic of photoelectric receiving circuit , so that the photoelectric receiving circuit produces the same gain for the laser modulation signal of each frequency component. Curve 21 in Fig. 4 is the frequency characteristic of the photoelectric receiving circuit, and its gain to measuring scale frequencies f ₀ , f ₁ , f ₂ ... f _n is k ₀ , k ₁ , k ₂ ... k _n . In order to make the photoelectric receiving circuit produce the same gain C as shown in the straight line 20 for the optical signal of each measuring scale frequency, draw a curve 19 in the figure, the curve and curve 21 are symmetrical about the straight line 20, then the prediction of the corresponding measuring scale frequency can be obtained Compensation factors α ₀ , α ₁ , α _{2 .} . . α _n such that α _i · _ki = C, i=0, 1...n.

Figure 5 shows the implementation method of multi-channel synchronous band-pass filter frequency selection and phase measurement.

其中：k_i为接收电路对频率为f_i的调制光信号的转换增益，φ_i为调制频率为f_i的光信号经目标反射后产生的相位延迟，α_i的取值应使得α_i·k_i＝C，C为常数。而经参考光光电探测器13及参考光光电转换电路14得到的参考信号为

其中：β_i为内光路产生的相位延迟。The distance measurement signal obtained after the emitted laser beam is reflected by the target after the return light signal passes through the measurement light photoelectric detector 6 and the measurement light photoelectric conversion circuit 7 is

Among them: k _i is the conversion gain of the receiving circuit for the modulated optical signal with frequency f _i , φ _i is the phase delay generated by the optical signal with modulated frequency f _i reflected by the target, and the value of α _i should be such that α _i · k _i =C, where C is a constant. And the reference signal obtained by the reference light photodetector 13 and the reference light photoelectric conversion circuit 14 is

Among them: β _i is the phase delay generated by the inner optical path.

In order to simultaneously measure the phase difference of each frequency component in the ranging signal _Er and the reference signal _E'r , the present invention adopts multi-channel synchronous band-pass filter frequency selective phase measurement, that is, the distance measuring signal _Er and the reference signal E' The frequency of each measuring scale in _r sets the multi-channel band-pass frequency-selective filter unit 15, and then the multi-channel synchronous phase measuring unit 16 simultaneously provides the phase difference φ _i -β _i corresponding to each measuring scale frequency, i=0, 1. ..n. Finally, the final ranging result of the distance calculation unit 17 is fused with the data, and displayed by the distance display unit 22 .

Using the above method, the ranging results of each measuring ruler frequency in the multi-frequency modulation ranging can be obtained at the same time, and then the final ranging value can be obtained. Without losing the multi-frequency modulation phase method, laser ranging can meet the characteristics of range and accuracy requirements at the same time. On the basis of improving the ranging speed to ensure the real-time ranging.

Multi-frequency synchronous modulation phase laser distance measuring device

The multi-frequency synchronously modulated phase-type laser ranging device is mainly composed of a multi-frequency signal generating unit 4, a multi-frequency signal combining unit 10, a laser power modulation drive unit 2, a laser 1, a laser emitting lens 11, a laser receiving lens 5, a beam splitter 12, Measurement light photodetector 6, measurement light photoelectric conversion circuit 7, reference light photoelectric detector 13, reference light photoelectric conversion circuit 14, multi-channel band-pass frequency-selective filter unit 15, multi-channel synchronous phase measurement unit 16, data fusion distance calculation Unit 17 is composed.

The multi-frequency signal generation unit 4 generates sinusoidal signals of corresponding frequencies according to the selected measuring scale frequencies f ₀ , f ₁ , f ₂ ... f _n , and the signals are applied to the laser power modulation drive unit after passing through the multi-frequency signal synthesis unit 10 2. Modulate the power of the laser 1. The modulated laser beam is emitted to the beam splitter 12 through the laser emitting lens 11. After passing through the beam splitter, the reflected light forms a measurement beam and shoots to the measured target. The measurement beam is received by the laser after being reflected by the target. After the lens 5 receives the measurement light, it is converted into a measurement electrical signal by the measurement light photoelectric conversion circuit 7 after passing through the measurement light photoelectric detector 6, and the transmitted light forms a reference light, which is sent to the reference light photodetector 13 and passes through the reference light photoelectric conversion circuit 14 to form a reference electrical signal After the measurement electrical signal and the reference electrical signal are passed through the multi-channel band-pass frequency-selective filter unit 15, the multi-channel synchronous phase measurement unit 16 provides a phase difference generated after the measuring ruler frequency is reflected by the target, and the data fusion distance calculation unit 17 will The measured phase difference is synthesized to obtain the final ranging result.

Example 1

Dual frequency synchronous modulation phase laser distance measuring device

As shown in Figure 6, the device is mainly composed of a semiconductor laser 23, a laser emitting lens 11, a beam splitter 12, a converging lens 29, a reference light photodetector (PIN) 13, a laser receiving lens 5, and a measuring light photodetector (APD) 6. Measurement light photoelectric conversion circuit 7, reference light photoelectric conversion circuit 14, laser power modulation drive unit 2, dual-frequency signal characteristic pre-compensation weighted sum processing unit 24, signal generation units 25 and 26, high-frequency band-pass filter unit 31 and 34, low-frequency band-pass filtering units 33 and 36, high-frequency mixing units 37 and 39, fine local oscillator and coarse local oscillator generating units 32 and 35, low-frequency mixing units 38 and 40, low-pass filtering units 41 and 42, Low-pass filter units 43 and 44, phase difference measurement units 45 and 46, microprocessor unit 47, and distance display unit 22 constitute.

The signal generating units 25 and 26 are realized by direct digital synthesis technology, and respectively generate fine measuring ruler frequency f0 and rough measuring ruler frequency f ₁ signals, fine measuring frequency f ₀ is 7.500MHz, corresponding maximum measuring range is 20m, rough measuring frequency f ₁ takes 75KHz, and the corresponding maximum measurement range is 2Km. The two-way signals act on the laser power modulation drive unit 2 to modulate the power of the semiconductor laser 23 after the dual-frequency signal characteristic pre-compensation weighted sum processing unit 24 . The dual-frequency signal characteristic pre-compensation weighted sum processing unit is realized by a gain-programmable operational amplifier and an operational amplifier; the laser power modulation drive unit adopts a constant current-driven injection current power modulation method. The laser beam emitted by the semiconductor laser 23 passes through the laser emitting lens 11 to produce a beam 47, which is incident on the beam splitter 12 along the optical axis 27, and is divided into beams 48 and 51, and the beam 48 is irradiated along the optical axis 28 to the target The measurement cooperation target (retroreflector), after being reflected by the target, returns along the original optical path and is converged by the converging laser receiving lens 5 to the photosensitive surface of the measurement light photoelectric detector (avalanche photodiode APD) 6, through the measurement light photoelectric conversion circuit 7 After conversion, the measured electrical signal E _r (f ₀ , f ₁ ) is obtained. The light beam 51 is used as an internal reference light beam and converges to the photosensitive surface of the reference light photodetector (silicon photodiode PIN) 4 after passing through the converging lens 29. After being converted by the reference light photoelectric conversion circuit 14, the reference electrical signal E' _r (f ₀ , f ₁ ). The measurement signal E _r (f ₀ , f ₁ ) and the reference signal E′ _r (f ₀ , f ₁ ) pass through the band pass with the center frequency f ₀ to obtain the precise measurement signals E _r (f ₀ ) and E′ _r (f ₀ ), and at the same time pass through the band-pass filter with the center frequency f ₁ to obtain rough measurement signals E _r (f ₁ ) and E′ _r (f ₁ ). When carrying out dual-channel synchronous band-pass filter frequency selection phase measurement, the center frequency of band-pass filter 31 and 33 is 7.500MHz, and the -3dB bandwidth is 40KHz; the center frequency of band-pass filter 33 and 36 is 75KHz, and the -3dB bandwidth is 5KHz;

In order to obtain high-precision phase difference measurement, this device adopts a heterodyne processing method, that is, the precise measurement signals E _r (f ₀ ) and E′ _r (f ₀ ) are compared with the signal E (f _L0 ) generated by the fine local oscillator generation unit. Frequency mixing and low-pass filtering: the rough measurement signals E _r (f ₁ ) and E′ _r (f ₁ ) are mixed and low-pass filtering with the signal E(f _L1 ) generated by the rough local oscillator generation unit. Among them, the frequency mixing is realized by analog multiplier, the low-pass filter adopts the second-order voltage-controlled oscillation source low-pass filter, the local oscillator signal is generated by direct digital synthesis technology, the fine local oscillator signal f _L0 is 7.502MHz, and the coarse local oscillator signal f _L1 takes 77KHz. The frequency of the intermediate frequency signal after the measurement signal and the reference signal are mixed is 2KHz.

The signals passing through the low-pass filters 41 and 42 enter the phase difference measuring unit 45 to obtain the phase difference φ ₀ , and the signals passing through the low-pass filters 43 and 44 enter the phase difference measuring unit 46 to obtain the phase difference φ ₁ . The microprocessor unit 47 performs distance calculation and data fusion processing on the two phase difference signals to finally obtain a distance measurement result, which is displayed on the display unit 22 . The phase difference measurement adopts synchronous digital phase measurement, the phase measurement accuracy is 360°/20000, and the theoretical distance measurement accuracy is 1mm. Since the microprocessor unit 47 can obtain the phase measurement results of the phase measurement units 45 and 46 at the same time, data fusion can be performed quickly and a final distance measurement result can be given.

In this example, the laser beam emitting and receiving unit adopts the coaxial optical structure shown in FIG. 7 . In this structure, the laser beam that semiconductor laser 23 sends forms light beam 47 after passing through laser emitting lens 11 and irradiates to beam splitter 12 along optical axis 27, and beam splitter 12 is positioned at the intersection of optical axis 27 and 28, and with optical axis 27 and 28 They all form an included angle of 45°, and the optical axes 27 and 28 are perpendicular to each other. After the light beam 47 passes through the beam splitter 12 , the reflected light beam 48 irradiates to the measured object along the optical axis 28 , and the transmitted light beam 51 irradiates to the converging lens 29 along the optical axis 27 and is converged onto the photosensitive surface of the reference light photodetector 13 . The laser beam 48 returns along the optical axis 28 after being reflected by the cooperative target (retroreflector), and is converged by the laser receiving lens 5 onto the photosensitive surface of the measuring light photodetector 6 . This structure is adopted for the emission and reception of the laser beam to ensure that the return light signal is always converged on the optical axis where the photodetector 6 of the measurement light is located, eliminating the problem that the off-axis optical structure causes the beam to deviate from the optical axis where the photodetector is located when the target distance is relatively close. blind spot. At the same time, the coaxial optical structure also has the advantage of compact structure.

Wherein, the beam splitter 12 can be realized by a beam splitter prism 50, and the optical path is shown in FIG. 8a. Among them, the reflectivity may be 80%-90%, and the transmittance may be 20%-10%.

The beam splitter 12 can also be a mirror with a hole as shown in FIG. 7c, and the optical path is as shown in FIG. 8b. Wherein reflector center is provided with light hole 53, and the area of light hole is only 20%～10% with reflective part area ratio; Here the shape of reflector and light hole can be circular, also can be square, also It may be a centrosymmetric polygon or the like.

Example 2

Three-frequency synchronous modulation phase laser distance measuring device

As shown in Figure 6, on the basis of the dual-frequency synchronously modulated phase-type laser ranging device, this example adds a modulation signal to the transmitting unit, that is, the frequency f ₂ of the coarse measuring scale, and f ₂ is 750 Hz, and the signal is also used directly Digital synthesis technology is realized; correspondingly, a band-pass filter frequency selection phase measurement circuit is added to the receiving unit, in which the center frequency of the band-pass filter is 750Hz, and the -3dB bandwidth is 100Hz; the phase difference measurement unit is adjusted to three-frequency synchronous digital phase measurement. Other units and working principles of this example are the same as Example 1. The theoretical range of the distance measuring device is 200Km.

The specific embodiment of the present invention has been described above in conjunction with the accompanying drawings, but these descriptions can not be interpreted as limiting the scope of the present invention, the protection scope of the present invention is defined by the appended claims, any claims on the basis of the present invention The changes made are within the protection scope of the present invention.

Claims (10)

1. multiple frequency synchronous modulated laser distance-finding method is characterized in that this method may further comprise the steps:

(1) adopts multiple modulation frequency f ₀, f ₁, f ₂... f _nTarget is found range, and the method that modulation frequency adopts direct modulation frequency to select is got f ₀=mf ₁=mf ₂=...=mf _n, distance accuracy Δ D then ₀=m Δ D ₁=m Δ D ₂=...=m Δ D _n, ranging D ₀=1/mD ₁=1/mD ₂=...=1/mD _n, the m value is 100 to 1000;

(2) according to above-mentioned modulation frequency f ₀, f ₁, f ₂... f _nChoose sinusoidal signal and carry out the synthetic processing of weighted sum, obtain

Wherein: E _tBe final synthetic modulation signal, A is the sinusoidal signal amplitude, Be the initial phase of sinusoidal signal, adopt this signal that laser power is modulated then and target is implemented range finding;

(3) obtaining electric signal through the heliogram of target reflection behind photoelectric switching circuit is:

Wherein: k _iBe the conversion gain that receiving circuit to frequency is, φ _iFor modulating frequency is f _iThe phase delay that behind target reflection, produces of light signal, treatment circuit is to signal E _rAdopt the frequency-selecting of multidiameter delay bandpass filtering to handle and obtain each component of signal, record each signal and the phase delay φ that transmits simultaneously _i, and then try to achieve the range finding result of each modulation frequency simultaneously

I=0,1,2...n tries to achieve final range finding D as a result by Data Fusion at last.

2. method according to claim 1 is characterized in that also having adopted the characteristic precompensation in the synthetic processing of weighted sum, and the modulation signal after the compensation is

Corresponding received signal is

α _iFor being f to frequency at photoelectric receiving system _iThe antidamping characteristic precompensation factor set of the frequency attenuation characteristic of modulated light signal, α _iValue should make α _iK _i=C, C are constant, i.e. the receiving system gain identical to the light signal generating of each modulation frequency in the heliogram.

3. method according to claim 1 and 2 is characterized in that the m value is 100.

4. the multiple frequency synchronous modulated laser distance measuring equipment that uses of the described method of a claim 1, comprise multiple-frequency signal generating unit, laser instrument, laser power modulation driver element, Laser emission camera lens, laser pick-off camera lens, measuring light photodetector, measuring light photoelectric switching circuit, reference light photodetector, reference light photoelectric switching circuit, data fusion metrics calculation unit, it is characterized in that also comprising that multiple-frequency signal synthesis unit, spectroscope, the logical frequency selecting and filter unit of multichannel band, multichannel are with the pacing facies unit;

The multiple-frequency signal generating unit produces the multichannel sinusoidal signal of corresponding frequencies according to selected modulation frequency, affacting the synchronous modulation unit after synthetic processing of this multiple signals process multiple-frequency signal synthesis unit modulates the power of laser instrument, laser beam after the modulation is launched to spectroscope by the Laser emission camera lens, through behind the spectroscope, reflected light forms measuring beam directive measured target, measuring beam is through being received after convert the measurement electric signal to by the measuring light photoelectric switching circuit behind the measuring light photodetector by the laser pick-off camera lens behind the target reflection, transmitted light forms reference light directive reference light photodetector and form reference electrical signal behind the reference light photoelectric switching circuit, measure electric signal and reference electrical signal and give the phase differential of the generation after there emerged a modulation frequency process target reflection with the pacing facies unit by multichannel after with logical frequency selecting and filter unit, the synthetic computing unit of distance synthesizes the phase differential that records handles the result that finally found range.

5. device according to claim 4 is characterized in that said multiple-frequency signal generating unit is two-frequency signal generating unit or three signal generating unit frequently.

6. device according to claim 4 is characterized in that said laser power modulation driver element is that the signal that adopts the multiple-frequency signal synthesis unit to provide is modulated the driving of laser power, and its modulation system is internal modulation mode or external modulation mode.

7. device according to claim 4 is characterized in that said multichannel band leads to frequency selecting and filter unit and is made up of side by side the multichannel bandpass filter.

8. device according to claim 4, its feature have adopted emission to receive coaxial optical texture being made of the laser transmitting-receiving antenna said Laser emission camera lens, laser instrument, laser pick-off camera lens and spectroscope.

9. device according to claim 4 is characterized in that said spectroscope has adopted Amici prism beam split mode, and the transmitance of Amici prism is 10%～20%, and reflectivity is 90%～80%.

10. device according to claim 4, it is characterized in that said spectroscope has adopted the beam split mode of putting the hole catoptron, the catoptron center is provided with light hole, the ratio of the area of light hole and catoptron reflector segment area is 10%～20%, and the shape of catoptron and light hole is circular, square or centrosymmetric polygon here.

Images