CN102692622A - Laser detection method based on dense pulses - Google Patents

Abstract

The invention relates to the field of laser detection, and discloses a laser detection method based on dense pulses, comprising the steps of: a laser emits grouped detection laser pulses to the target to be measured, the number of groups of detection laser pulses is greater than or equal to 1, and each group of detection laser pulses Contains dense multiple pulses; the first photoelectric converter receives the echo laser pulse and the ambient light noise after the detection laser pulse is reflected by the measured target, and converts the echo laser pulse and optical noise into corresponding electrical signals, and the echo The laser pulse contains the information of the measured target; the signal processor processes the electrical signal converted by the detection unit, highlights the electrical signal corresponding to the echo laser pulse according to the time interval between dense pulses, and suppresses the electrical signal and circuit corresponding to optical noise The electrical noise generated by itself, and the information of the measured target is obtained according to the electrical signal corresponding to the echo laser pulse. The method of the invention can suppress the noise, highlight the signal, improve the signal-to-noise ratio and reduce the minimum detectable optical power.

Description

Laser detection method based on dense pulse

technical field

The invention relates to the technical field of laser detection, in particular to a dense pulse-based laser detection method.

Background technique

The development of weak light detection devices and their corresponding weak signal processing circuits has made the light power that people can detect smaller and smaller. Certain specifications of photomultiplier tubes and avalanche photodiodes (APD) can respond to a single photon, so the application For single photon detection (WolfgangBecker.Advanced time-correlated single photon counting techniques[M].2005, Berlin, Heidelberg: Springer Verlag Berlin Heidelberg), for 500nm visible light, the corresponding single photon energy is 4×10 ^-19 J, visible Its detectable light energy is very small, so it can be used for extremely weak light detection. In practical applications, when performing light detection, in many cases, in addition to the signal light entering the photodetector, stray light from the surrounding environment will also enter. To accurately measure the signal light, there must be a certain signal between the signal light and the stray light. The noise ratio generally requires that the intensity ratio be greater than 5, which makes the minimum optical power of the signal light that the detector can detect largely depends on the optical power of the stray light. In order to reduce the minimum detectable signal optical power and improve the signal The simplest and most direct way to improve the noise ratio is to increase the transmit power of signal light or reduce the power of stray light. Increasing the transmitting power of the signal light will increase the volume and energy consumption of the laser, so it cannot be increased indefinitely; reducing the noise optical power can be achieved by reducing the receiving field of view through the design of the detector and its corresponding optical antenna or by designing The narrow-band filter corresponding to the emission wavelength of the laser filters the light entering the detector. The receiving field angle of the detector cannot be small, otherwise the detection and alignment requirements will be very high, and the field angle that is too small will To limit the signal light entering the detector, the bandwidth of the filter should not be too narrow. The narrower the bandwidth, the lower the transmittance. When the stray light attenuates, the signal light will also attenuate. Moreover, the narrower the bandwidth, the more difficult it is to manufacture. The higher the cost, it is very uneconomical. Therefore, the stray light power cannot be reduced infinitely.

The multi-pulse superposition time-correlation detection technology or optical heterodyne detection method can effectively improve the signal-to-noise ratio and reduce the minimum detectable signal optical power, but these two methods have limitations in practical applications.

The method of multi-pulse superposition is to send a pulse, and then send the next pulse after receiving the echo signal of the detection pulse, which takes a long time and is not suitable for the detection of faster moving targets, because when the target moves, the participating The correlation degree of each related signal pulse will decrease, and the correlation effect will decrease, and the faster the target moves, the worse the correlation effect will be. When the time difference between the two signal pulses caused by the target motion is greater than the time width of the pulse itself, Time correlation will not be possible (Hu Guangshu. Digital Signal Processing - Theory, Algorithm and Implementation (Second Edition) [M], 2003, Beijing: Tsinghua University Press: 33-38). This is because the time correlation of laser echoes mainly depends on the interval between adjacent pulses, and the time correlation of adjacent pulse signals is determined from the time difference Δt ₀ between two adjacent laser pulse echo signals relative to the transmitted signal (main wave) ,satisfy:

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; V</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, V is the line-of-sight distance change speed of the target relative to the measurement point, T _P is the time interval between two adjacent laser pulses, c is the speed of light, and the value of Δt ₀ is mainly limited by the width of the detection laser (generally 15 ns), It can be known from formula (1) that when Δt ₀ is determined, the line-of-sight distance change speed V of the target relative to the measurement point is inversely proportional to the time interval T _P between two adjacent laser pulses. The larger T _P is, the more pulse superposition can be used The smaller the velocity V of the measured target, the shorter the time interval T _P between the measurement pulses, and the use of pulse train technology can increase V, but because the distance L between the measurement point and the target satisfies:

L=cT _P (2)

It can be seen that reducing the time interval T _P between measurement pulses will correspondingly reduce the range of laser detection, which is mainly because the "door guard" laser ranging system in the US missile defense system uses (Wang Rongrui. US missile defense lidar technology [J]. Laser and Infrared, 1999, 29(5): 263-266) uses 3 laser pulses to form a pulse train, and the time interval between pulses is 8ms, which can Realize ranging from 100 to 1,000 kilometers; the pulse train laser ranging technology proposed by the North China Institute of Optoelectronic Technology also uses 3 pulses to form a pulse train. It is 112km (Zhong Shengyuan, Li Songshan. Research on Pulse Train Laser Ranging Technology [J]. Laser and Infrared, 2006, 36 (Supplement): 797-799).

The optical heterodyne detection method requires high coherence of light. When the laser is transmitted in the atmosphere, the atmospheric turbulence effect will seriously affect the coherence of the laser. Therefore, the application of the optical heterodyne detection method in the atmosphere is limited ( Guo Peiyuan, Fu Yang. Photoelectric Detection Technology and Application (Second Edition) [M], 2011, Beijing: Beijing University of Aeronautics and Astronautics Press).

In addition, in the artificial satellite laser ranging technology, high repetition frequency laser pulses (several KHz) can be used, and the time interval between laser pulses is equal and less than the time required for the laser to go back and forth between the observation system and the measured artificial satellite. , in this method, the detection laser continuously emits high-repetition laser pulses to the measured target, records the emission time of each detection laser pulse, the detector detects the echo pulse returned by the target, and records the reception time of the echo pulse , pre-calculate the time it takes for the light to go back and forth between the detection device and the target according to the orbit of the artificial satellite, determine the detection laser pulse corresponding to each echo pulse according to this calculation time, and then according to the corresponding receiving time and emission The distance information of the measured artificial satellite is obtained at all times. Compared with the traditional laser ranging below 10Hz, the high-repetition laser ranging greatly increases the amount of echo data, thereby greatly improving the measurement accuracy, but this detection method requires the calculation of the satellite relative to the observation system in advance. distance, so as to judge which echo pulse corresponds to which launch pulse (DEGNAN J J.Satelite laser ranging in the 1990's: report of the 1994 belmont workshop[R].Maryland: NASA, Conference Publication, 1994: 3283), artificial satellite In laser ranging, the measured target is a cooperative target, and the target running speed measurement is aimed at the angular velocity of the artificial satellite, which has little effect on the time interval of the echo laser pulse.

To sum up, when the low-light detector is used for direct light detection, the signal-to-noise ratio is low due to the influence of environmental stray light; although the time-correlated detection technology of multi-pulse superposition or optical heterodyne detection method can improve the signal-to-noise ratio, Reduce the minimum detectable signal optical power, but the time-correlated detection technology of multi-pulse superposition is not conducive to long-distance detection of fast-moving targets because the time interval between adjacent detection laser pulses is too large, while the method of optical heterodyne detection is affected by the atmosphere. The impact of turbulence is greater. The high repetition frequency laser ranging technology used in artificial satellite laser ranging needs to know the calculated distance between the measured target and the measuring point in advance. If the distance of the measured target is not known in advance or the deviation between the calculated distance and the time distance If it is too large, the distance information of the target cannot be obtained by this method, and the high repetition frequency laser detection pulse is continuously emitted, the time interval between adjacent detection pulses is equal, and the measured target is a cooperative target.

Contents of the invention

(1) Technical problems to be solved

The technical problem to be solved by the present invention is: how to improve the signal-to-noise ratio during laser detection of fast-moving targets with unknown distances, reduce the minimum detectable optical power, and the detection method is not affected by atmospheric turbulence and has strong adaptability.

(2) Technical solutions

In order to solve the above-mentioned technical problems, the present invention provides a laser detection method based on dense pulses. The detection laser pulses emitted by the laser to the measured target are not continuously emitted, but grouped, which can detect fast-moving non-cooperative targets with unknown distances. detection, and is not affected by atmospheric turbulence, the method includes the following steps:

S1. The detection signal generator controls the laser to emit grouped detection laser pulses to the measured target, wherein the number of groups of the detection laser pulses is greater than or equal to 1;

S2. The first photoelectric converter receives the echo laser pulse and the optical noise formed by the ambient light after the detection laser pulse is reflected by the target, and converts the echo laser pulse and the optical noise into corresponding electrical signals;

S3. Process the converted electrical signal, detect the echo electrical pulse corresponding to the echo laser pulse, and determine the detection laser pulse corresponding to each echo electrical pulse, according to the echo The electric pulse obtains the signal of the measured target;

Each group of detection laser pulses contains a plurality of laser pulses whose time interval is less than the time required for light to reflect from the laser through the target to reach the first photoelectric converter. The time interval between adjacent laser pulses is not fixed, and the specific value Determined according to actual needs, the multiple laser pulses form a group of dense pulses.

Preferably, in step S1, the laser emits a group of dense pulses to the target at a time, and in step S3, after the first photoelectric converter receives the echo laser pulses, the laser then Sending the next group of dense pulses to the measured target.

Preferably, in step S1, the detection signal generator, while controlling the laser to emit detection laser pulses, also sends a reference to the signal processor performing step S3, which includes information on the time interval between pulses in the dense pulses signal; or

In step S1, the laser emits laser pulses, which are separated by a beam splitter, and a part of them is directed to the measured target to form the detection laser pulse, and a part is used as a reference laser pulse, and the reference laser pulse is formed by the second photoelectric converter. The reference signal is handed over to the signal processor for processing.

Preferably, step S3 is specifically: for the converted electrical signal, the difference between the time interval between adjacent electrical pulses and the time interval between corresponding adjacent detection laser pulses provided by the reference signal is less than or equal to The electrical pulses with a time interval deviation tolerance of adjacent pulses are echo electrical pulses; the detection laser corresponding to each echo electrical pulse is determined according to the time sequence of transmission and reception or the time interval information between the echo electrical pulses pulse.

Preferably, the deviation tolerance of the adjacent pulse time interval depends on the relative movement speed of the measured target relative to the laser and the first photoelectric receiver, the greater the relative movement speed, the more adjacent The pulse interval deviation tolerance is also larger.

Preferably, the echo laser pulses contain characteristic information of the measured target.

Preferably, the characteristic information of the measured target includes the size of the measured target, the distance from the laser and the first photoelectric receiver, the moving speed, acceleration, reflectivity, reflectivity distribution and relative reflectivity distribution.

Preferably, in step S2, the first photoelectric converter is used to convert the echo laser pulse and the optical noise into corresponding electrical signals, and the echo laser pulse is processed by an optical antenna and a narrow-band filter, and then The reference laser pulse enters the second photoelectric converter and is converted into a corresponding reference signal.

Preferably, according to the characteristic parameters of the first photoelectric converter, the narrowband filter and the optical antenna, the peak power of a single pulse in the echo laser pulse and the peak power reaching the first photoelectric converter are calculated. Time, according to the characteristic parameters of the second photoelectric converter and the spectroscopic mirror, calculate the time required for the detection laser pulse to reflect from the laser through the measured target to reach the first photoelectric converter and the received The ratio of the peak power of a single pulse in each of the echo laser pulses to the peak power of a single pulse in the corresponding detection laser pulse is processed to obtain characteristic information of the measured target.

(3) Beneficial effects

The above-mentioned technical scheme has the following advantages: compared with the traditional time-correlated light detection technology, the laser detection method based on dense pulses of the present invention has a detection distance only limited by the interval between pulse groups and not limited by the time interval of dense pulses. Therefore, In the same time, the correlation calculation of multiple dense pulses can be realized, which greatly saves the detection time; in addition, because the time correlation of dense pulses in a group is not a simple superposition of pulses one by one, but each group Carry out correlation as a whole, which improves the flexibility of operation, can make the detected echo signal cross-correlate with the reference pulse signal, and can also perform phase-locking, heterodyne amplification and other processing on the echo signal to maximize Improve the signal-to-noise ratio and reduce the minimum detectable optical power.

Description of drawings

Fig. 1 is method flowchart of the present invention;

2 is a schematic diagram of a detection device based on an implementation of the laser detection method of the present invention;

3 is a schematic diagram of pulse distribution based on an implementation of the laser detection method of the present invention;

Fig. 4 is a device schematic diagram of the relative reflectivity surface distribution of the measured target based on the laser detection method of the present invention;

Fig. 5 is a schematic diagram of the pulse distribution of the relative reflectivity surface distribution of the measured target based on the laser detection method of the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Referring to Fig. 1, Fig. 2 and Fig. 3, the laser detection method based on dense pulses of the present invention is described below. The detection laser pulses emitted by the laser to the target are not emitted continuously, but in groups, and the time interval between the detection laser pulses can be equal or not Not equal, the measured target can be a cooperative target or a non-cooperative target, the distance of the measured target relative to the laser and the first photoelectric receiver can be unknown, suitable for the detection of fast moving targets, and is not affected by the atmosphere The effect of turbulence.

Fig. 1 is the flow chart of the laser detection method based on the dense pulse of the present invention, the laser detection method based on the dense pulse of the present invention comprises three steps:

S1. The detection signal generator controls the laser to emit grouped detection laser pulses to the measured target, wherein the number of groups of detection laser pulses is greater than or equal to 1.

S2. The first photoelectric converter receives the echo laser pulse after the detection laser pulse is reflected by the target and the optical noise formed by the surrounding light, and converts the echo laser pulse and optical noise into a corresponding electrical signal, and the echo laser pulse contains the information of the measured target;

S3. The signal processor processes the electrical signal converted by the first photoelectric converter: detects the echo electrical pulse corresponding to the echo laser pulse according to the time interval between the pulses in the dense pulse, and determines the electrical signal corresponding to each echo electrical signal. The pulse corresponds to the detection laser pulse, and the information of the measured target is obtained according to the echo electric pulse;

Wherein, each group of detection laser pulses includes a plurality of laser pulses whose time interval is shorter than the time required for the light to reflect from the laser through the measured object and reach the first photoelectric converter, and the plurality of laser pulses form a group of dense pulses.

The time intervals between two adjacent groups of dense pulses are all the same, or the time intervals between part of the adjacent two groups of dense pulses are the same, or the time intervals between all adjacent groups of dense pulses are different.

In each group of dense pulses, the time intervals between adjacent laser pulses are the same, or the time intervals between some adjacent laser pulses are the same, or the time intervals between all adjacent laser pulses are different.

The number of laser pulses included in each group of dense pulses is the same, or the number of laser pulses included in some groups of dense pulses is the same, or the number of laser pulses included in each group of dense pulses is different.

The energy of each laser single pulse in each group of dense pulses is the same, or the energy of part of the laser single pulses is the same, or the energy of each laser single pulse is not the same.

A schematic diagram of a detection device based on an implementation of the dense pulse-based laser detection method of the present invention is shown in FIG. 2 , and a corresponding pulse distribution schematic diagram is shown in FIG. 3 .

According to the steps given in Fig. 1, the detection signal generator 1 in Fig. 2 controls the laser 2 to emit grouped detection laser pulses 3 according to the detection pulse signal form shown in Fig. The reference signal of the time interval information, the laser 2 may include a transmitting optical antenna, which is used to reduce the divergence angle of the detection laser, and each group of detection pulses G _i in the detection pulse signal 12 in Fig. 3 contains a plurality of time intervals less than the light from the laser 2. The pulse _Cj reflected by the measured target 4 and reaching the first photoelectric converter 8 forms a group of dense pulses 11. During one detection, the detection laser pulse 3 can be a group of dense pulses or multiple groups of dense pulses. Pulse, when the detection pulse 3 is multiple groups of dense pulses, the number of laser pulses contained in each group of dense pulses can be the same, or the number of laser pulses contained in some groups of dense pulses can be the same, or each The number of laser pulses contained in a group of dense pulses is not the same; the time interval ΔG _i of two adjacent groups of dense pulses can be the same, or the time interval ΔG _i of partly adjacent two groups of dense pulses can be the same, or all adjacent The time interval ΔG _i of two groups of dense pulses is different; in each group of dense pulse G _i , the time interval ΔC _j between two adjacent laser pulses can be the same, or partly between two adjacent laser pulses The time interval ΔC _j of all laser pulses can be the same, or the time interval ΔC _j between all adjacent two laser pulses can be different; in addition, in each group of dense pulses, the energy of each single laser pulse can be the same, or part of the laser pulse The single pulse energy is the same, or the energy of each laser single pulse is not the same; for the detection pulse 3 is the case of multiple groups of dense pulses, the laser 2 emits a group of dense pulses to the measured target 4, and the first photoelectric converter 8 receives After the corresponding echo laser pulses, the laser 2 emits the next group of intensive pulses to the measured target 4 . After the detection laser pulse 3 is reflected by the measured target 4 in Fig. 2, the echo laser pulse 5 passes through the optical antenna 6 and the narrow-band filter 7, and then converges to the photoelectric converter 8. At the same time, the optical noise 51 generated in the external environment will also converge. To the photoelectric converter 8, if the optical power density of the echo laser pulse 5 is large enough, the optical antenna 6 does not need to converge the echo laser pulse 5, and the photoelectric converter 8 can also normally detect the echo laser pulse 5, then the optical antenna 6 can be removed; if within the response spectrum range of the photoelectric converter 8, the optical power of the echo laser pulse 5 is much greater than the optical power of the ambient light noise 51, or outside the spectral range of the echo laser pulse 5, the ambient light noise 51 If the optical power of the optical antenna 6 and the narrowband filter 7 are very low, the narrowband filter 7 can be removed; it can be seen that whether the optical antenna 6 and the narrowband filter 7 are used or not should be determined according to the actual situation. The photoelectric converter 8 converts the optical signal (echo laser pulse and optical noise) into an electrical signal and then passes it to the signal processor 9 for processing. The signal processor 9 is based on the time interval between the detection laser pulses given by the detection signal generator 1 , and estimate the relative motion speed of the measured target 4 with respect to the laser and the first photoelectric receiver, and determine the deviation tolerance of the time interval between adjacent pulses according to the size of the relative motion speed, and then judge the conversion of the photoelectric converter 8 The echo electrical pulse in the final electrical signal, and determine the detection laser pulse corresponding to each echo electrical pulse, the specific steps are: for the converted electrical signal, satisfy the time interval between adjacent electrical pulses and the reference The electric pulse provided by the signal corresponding to the time interval difference between adjacent detection laser pulses is less than or equal to the deviation tolerance of the adjacent pulse time interval is the echo electric pulse; if the emitted detection laser pulses are dense, the time of each laser pulse If the intervals are equal, the detection laser pulse corresponding to the echo electrical pulse can be determined according to the time sequence of transmission and reception. Of course, the detection laser pulse corresponding to each echo electrical pulse can also be determined according to the time interval information between the echo electrical pulses. For laser pulses, for example, the detection laser pulses corresponding to the first and last two echo electrical pulses can be determined first, and then the detection laser pulses corresponding to other echo electrical pulses can be determined according to the time interval between the other echo electrical pulses and the two echo electrical pulses. Laser pulses; for dense pulses, the time interval between each pulse is not equal, of course, the detection laser pulse corresponding to the echo electrical pulse can also be determined according to the time sequence of emission and reception, or the echo electrical pulse can be determined according to the time sequence of the echo electrical pulse. The time interval information between pulses determines the detection laser pulse corresponding to each echo electric pulse. At this time, since the time interval between adjacent echo electric pulses is different, it can be directly based on the time interval of adjacent echo electric pulses. Determine the corresponding probe laser pulse.

Obviously, the electric pulse that cannot be judged as the echo electric pulse is either the electric pulse signal caused by the optical noise 51 generated by the external environment, or the electric noise generated by the circuit itself, which can be ignored. Since the echo laser pulse 5 contains the information of the measured target 4 , the electrical pulse corresponding to the echo laser pulse 5 is processed to obtain the information of the measured target 4 in FIG. 2 , which is displayed on the display 10 .

Taking the measurement of the relative reflectivity distribution of the surface of the measured target as an example, the dense pulse-based laser detection method of the present invention will be described below. This embodiment is not intended to limit the present invention. Any modification, equivalent replacement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

The schematic diagram of the relative reflectivity distribution of the measured target using the laser detection method based on dense pulses according to the present invention refers to Fig. Distribution schematic diagram Referring to FIG. 5 , the measured target 4 is stationary relative to the detection point. The detection signal generator 1 in FIG. 4 controls the laser 2 in FIG. 4 to emit a group of dense laser pulses in the form of a pulse signal shown at 14 in FIG. 5 . In this embodiment, a group of dense laser pulses are used for each detection of each point, which includes six adjacent time intervals that are much smaller than the time required for light to reflect from the laser 2 through the measured target 4 and reach the first photoelectric converter 8. The laser pulses are respectively C ₁ , C ₂ , C ₃ , C ₄ , C ₅ and C ₆ , the time intervals between adjacent pulses are equal, both are ΔC, and the single pulse energy of each laser pulse is equal, as shown in Figure 4 The laser 2 emits a laser pulse sequence in the shape of 14 in Figure 5, and is divided into a detection laser pulse 3 and a reference laser pulse 12 after the beam splitter 11'. After the detection laser pulse 3 is reflected by the measured object 4 in Figure 4, the echo The laser pulse 5 enters the photoelectric converter 8 through the optical antenna 6 and the narrow-band filter 7, and the pulse distribution of the echo laser pulse 5 is shown as 15 in Fig. 5, corresponding to the detection laser pulse distribution 14, each group of echo The laser pulse G' includes 6 laser pulses, namely C' ₁ , C' ₂ , C' ₃ , C' ₄ , C' ₅ and C' ₆ , and the interval between two adjacent laser pulses is also ΔC, While the echo laser pulse 5 enters the photoelectric converter 8, the optical noise 51 generated in the surrounding environment also enters the photoelectric converter 8 through the optical antenna 6 and the narrow-band filter 7, and the photoelectric converter 8 converts the optical signal into an electrical signal and then transmits Processed by the signal processor 9; the reference laser pulse 12 enters the reference photoelectric converter 13', and enters the signal processor 9 for processing after being converted into an electrical signal. Since the splitting ratio of the beam splitter 11' is known in advance, the reference laser pulse 12 The intensity of the detection laser pulse 3 can be inferred: in the signal processor 9, the intensity of the six electrical pulses converted by the reference laser pulse 12 in the reference photoelectric converter 13' is judged, according to the reference photoelectric converter 13' The characteristic parameters of each reference laser pulse are obtained from the peak power of each reference laser pulse (Jeff Hecht. Translated by Jia Dongfang et al. Fiber Optics [M], Beijing: People's Posts and Telecommunications Press, 2004, 333-338), the reference laser pulse 12 in 6 Calculate the average value of the peak power of the reference laser pulses to obtain the average peak power of a single optical pulse, and then obtain the average peak power of a single pulse in the detection laser pulse 3 according to the splitting ratio of the beam splitter 11'.

For the electrical signal output by the photoelectric converter 8, the signal processor 9 combines the reference signal (also can be replaced by the reference laser pulse 12) that the detection signal generator 1 provides to the time between the electrical pulse signals that the photoelectric converter 8 passes in. Calculate and compare the intervals, when the time interval of the electrical pulse signal introduced by the photoelectric converter 8 is equal to the time interval between the reference signal pulses, that is, when it is equal to the pulse time interval of the detection laser pulse 3, the corresponding electrical pulse signal is The electrical pulse signal converted by the echo laser pulse 5, correspondingly, the pulse time interval is not equal to the reference signal is the electrical pulse corresponding to the optical noise 51 generated by the surrounding environment or the electrical noise of the circuit itself. It should be noted that in this embodiment, Since the relative distance between the detection device (including all devices on the left side of the measured target 4 in Figure 4) and the measured target does not change during the detection process, the pulse time interval of the echo laser pulse 5 and the reference signal The pulse intervals are equal, if the target is moving, there will be a slight difference. After the electrical pulse signal corresponding to the echo laser pulse 5 is determined, the signal processor 9 calculates the intensity of the electrical signal input by the photoelectric converter 8 and the photoelectric conversion characteristic parameters of the photoelectric converter 8 to obtain the incident incident photoelectric converter 8 The peak power of the optical pulse (Jeff Hecht. Translated by Jia Dongfang et al. Fiber Optics [M], Beijing: People's Posts and Telecommunications Press, 2004, 333-338), then according to the peak power of the optical pulse incident to the photoelectric converter 8, The transmittance of the narrowband filter 7 and the magnitude of the background light noise introduced due to the certain transmission spectrum range of the narrowband filter 7 are calculated to obtain the peak power of the echo laser pulse 5 incident on the narrowband filter 7 . The optical antenna 6 has a converging effect on light and is used to enhance the optical signal entering the photoelectric converter 8. Its receiving aperture, transmittance and receiving angle range all have an impact on the converging effect. According to these parameters, it can be obtained by entering the narrow-band filter The laser pulse peak power of 7 is back-calculated to obtain the laser pulse peak power of the incident optical antenna 6 (Mao Densen, Zhang Jilong. Application of weak laser radiation detection technology in laser warning equipment [J]. Journal of Testing Technology, 2004, 18(4): 373-376), and then average the peak power of all six pulses to obtain the average peak power of a single pulse of the echo laser pulse, and compare it with the average peak power of a single pulse of the detection laser pulse to obtain the measured target The relative reflectivity of the corresponding detection points of 4, because the purpose of this embodiment is to measure the relative reflectivity distribution of the target, therefore, as long as the position of the incident light is adjusted, the measured target 4 can be scanned in a plane perpendicular to the paper surface. The surface relative reflectance distribution characteristics of the measured target 4 are obtained and displayed by the display 10 .

Compared with the traditional time-correlated light detection technology, the laser detection method based on dense pulses described in the present invention is only limited by the pulse group interval, not by the time interval of dense pulses. Therefore, within the same time , which can realize the correlation operation of multiple dense pulses, which greatly saves the detection time; in addition, because the time correlation of dense pulses in a group is not a simple way of superimposing pulses one by one, but correlates each group as a whole , which improves the flexibility of operation, can make the detected echo signal cross-correlate with the reference pulse signal, and can also perform phase-locking and heterodyne amplification on the echo signal to maximize the signal-to-noise ratio. To reduce the minimum detectable optical power, 3 pulses are used as a pulse train in the pulse train laser ranging technology, and 4 or more laser pulses can be used as a group of dense pulses in the method proposed by the present invention.

Compared with the traditional optical heterodyne detection technology, the laser detection method based on dense pulses in the present invention has the advantages of strong operability and can be applied in the atmosphere. The traditional optical heterodyne detection technology has the advantages of The frequency, phase, and polarization state are strongly dependent, the system adjustment accuracy is high, and the operability is poor. Considering that when the laser is transmitted in the atmosphere, the atmospheric turbulence effect will seriously affect the coherence of the laser. Therefore, the optical heterodyne detection method is used in the atmosphere. Applications are restricted. The dense pulse-based laser detection method of the present invention first performs photoelectric conversion, and then performs heterodyne processing on the electrical signal, which also has the effect of heterodyne amplification, but no longer requires the coherence of light. Therefore, it can be used detection of targets in the atmosphere.

Compared with the high-repetition-frequency laser ranging in the artificial satellite laser ranging technology, the dense pulse-based laser detection method of the present invention does not need to predict the measured target and the measuring point (which can be considered as the laser and the first The calculated distance between photoelectric receivers), that is, it is not necessary to estimate the distance of the measured target, and the method proposed by the present invention can be directly used to measure the distance of the target, which widens the scope of application of distance measurement, especially for unknown distances The high repetition frequency laser ranging method in artificial satellite laser ranging cannot be used, but the laser ranging method based on dense pulses proposed by the present invention can be used normally.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and replacements can also be made, these improvements and replacements It should also be regarded as the protection scope of the present invention.

Claims (9)

1. A laser detection method based on dense pulse, is characterized in that, comprises the following steps: S1. The detection signal generator controls the laser to emit grouped detection laser pulses to the measured target, wherein the number of groups of the detection laser pulses is greater than or equal to 1; S2. The first photoelectric converter receives the echo laser pulse and the optical noise formed by the ambient light after the detection laser pulse is reflected by the target, and converts the echo laser pulse and the optical noise into corresponding electrical signals; S3. Process the converted electrical signal, detect the echo electrical pulse corresponding to the echo laser pulse, and determine the detection laser pulse corresponding to each echo electrical pulse, according to the echo Obtain the information of the measured target by electric pulse; Wherein, each group of detection laser pulses includes a plurality of laser pulses whose time interval is less than the time required for the light to reflect from the laser to the first photoelectric converter through the measured target, and the time interval between adjacent laser pulses is not fixed, The plurality of laser pulses form a dense set of pulses. 2. The method according to claim 1, wherein in step S1, the laser emits a group of dense pulses once to the measured target, and in step S3, the first photoelectric converter receives After the echo laser pulse, the laser emits the next group of dense pulses to the measured target. 3. The method according to claim 1, characterized in that, in step S1, the detection signal generator, while controlling the laser to emit detection laser pulses, also sends a signal containing the a reference signal for the time interval information between pulses in the dense pulses; or In step S1, the laser emits laser pulses, which are separated by a beam splitter, and a part of them is directed to the measured target to form the detection laser pulse, and a part is used as a reference laser pulse, and the reference laser pulse is formed by the second photoelectric converter. The reference signal is handed over to the signal processor for processing. 4. The method according to claim 3, characterized in that step S3 is specifically: for the converted electrical signal, satisfying the time interval between adjacent electrical pulses and the corresponding adjacent detection laser light provided by the reference signal The electrical pulse whose time interval difference between pulses is less than or equal to the deviation tolerance of adjacent pulse time intervals is an echo electrical pulse; each The echo electrical pulse corresponds to the probe laser pulse. 5. The method according to claim 4, wherein the deviation tolerance of the time interval between adjacent pulses depends on the relative motion speed of the measured target relative to the laser and the first photoelectric receiver, The greater the relative motion speed, the greater the pulse time interval deviation tolerance. 6 . The method according to claim 1 , wherein the echo laser pulse contains characteristic information of the measured target. 6 . 7. The method according to claim 6, wherein the characteristic information of the measured target includes the size of the measured target, distance from the laser and the first photoelectric receiver, speed of motion, acceleration, Reflectance, reflectance distribution and relative reflectance distribution. 8. The method according to claim 1, wherein in step S2, the echo laser pulse and the optical noise are converted into corresponding electrical signals by using the first photoelectric converter, and the echo After being processed by an optical antenna and a narrow-band filter, the first-wave laser pulse is converged to the first photoelectric converter for conversion; the reference laser pulse enters the second photoelectric converter to be converted into a corresponding reference signal. 9. method as claimed in claim 8, is characterized in that, according to the characteristic parameter of described first photoelectric converter, described narrow-band filter and described optical antenna, calculate the single pulse in the described echo laser pulse The peak power and the time to reach the first photoelectric converter are calculated according to the characteristic parameters of the second photoelectric converter and the spectroscopic mirror. The time required for a photoelectric converter and the ratio of the peak power of a single pulse in each of the received echo laser pulses to the peak power of a single pulse in the corresponding detection laser pulse are processed to obtain the measured target characteristic information.

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