CN115877394A - Laser radar ranging method and system based on pulse position modulation technology - Google Patents
Laser radar ranging method and system based on pulse position modulation technology Download PDFInfo
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Abstract
The invention provides a laser radar ranging method and a laser radar ranging system based on a pulse position modulation technology, and relates to the technical field of laser radar ranging. The method comprises the steps of modulating two groups of sequences with different periods into a transmitting sequence based on a pulse position modulation technology, generating laser pulses based on the transmitting sequence and transmitting the laser pulses to a target to be measured, generating a synchronous signal every time a period T passes, measuring the time interval between the arrival of the reflected echo laser pulses at a signal acquisition device and the synchronous signal, and arranging the echo pulses into a received signal sequence according to the arrival sequence and the time interval; and finally, decoding the received signal sequence according to the transmitting sequence to obtain the distance of the target to be measured. Compared with the prior art, the method can improve the detection distance in multiples under the condition of keeping high laser emission frequency, and has the characteristics of high measurement range, high real-time performance and the like.
Description
Technical Field
The invention relates to the technical field of laser radar ranging, in particular to a laser radar ranging method and a laser radar ranging system based on a pulse position modulation technology.
Background
The laser radar has the advantages of high ranging precision, high resolution, strong anti-interference performance and the like, and is widely applied to the fields of topographic mapping, precise guidance, automatic driving and the like in recent years. Lidar ranging typically uses a method of measuring pulse time of flight: and emitting laser pulses to the target according to a certain time period, measuring the arrival time of a target reflection signal, and calculating the target distance. However, when the time interval between the pulse transmissions is less than the time of flight of the light pulses to and from the target, a range ambiguity problem arises.
At present, two methods are generally adopted for improving the unambiguous distance, one method is to reduce the repetition frequency of transmitting laser pulses and improve the pulse transmission interval duration, but the single pulse energy can be improved, the improvement of the single pulse energy is easily limited by the damage threshold of a device, the measurement range limitation is large, and the low measurement range of the laser radar can be caused; the other is laser pulse ranging using two or more repetition frequencies, respectively, and the real distance of the target is calculated by using the distances measured at different repetition frequencies, but this ranging requires measuring the target distance multiple times, which reduces the real-time performance of the system.
Therefore, the existing laser radar ranging technology has the problems of low measuring range and poor real-time performance.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a laser radar ranging method and a ranging system thereof based on a pulse modulation technology, and solves the problems of low measuring range and poor real-time performance of the conventional laser radar ranging technology.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme:
in a first aspect, the present invention first provides a laser radar ranging method based on a pulse position modulation technique, where the method includes:
modulating two groups of sequences with different periods into transmitting sequences based on a pulse position modulation technology;
generating laser pulses based on the emission sequence while generating a synchronization signal every time a period T elapses;
sending the laser pulse to a target to be measured, and receiving a reflected echo laser pulse;
measuring the time interval between the time of the echo laser pulse reaching the signal acquisition device and the time of the synchronous signal reaching the signal acquisition device, and arranging the echo laser pulse into a received signal sequence according to the sequence of reaching the signal acquisition device and the time interval;
and decoding the received signal sequence according to the transmitting sequence to obtain the distance of the target to be measured.
Preferably, the modulating two sets of sequences with different periods into the transmission sequence based on the pulse position modulation technique includes:
mapping two groups of sequences with different periods into a transmitting sequence according to a multi-pulse position modulation mode; wherein, the mapping calculation formula is:
S(n)＝A(n)+B(n+Δt)
wherein, A (n) and B (n) are two sequences with different periods respectively; s (n) represents a transmit sequence; Δ t represents the amount of positional shift of the sequence B (n) with respect to a (n).
Preferably, the measuring the time of arrival of the echo laser pulse at the signal acquisition device includes:
and identifying effective signals in the echo laser pulses by adopting an over-threshold detection technology, converting the effective signals into electric signals, inputting the electric signals into a signal acquisition device, and recording the time of inputting the electric signals into the signal acquisition device by the signal acquisition device.
Preferably, the decoding the received signal sequence according to the transmission sequence to obtain the distance to the target to be measured includes:
wherein, C (n) represents a signal sequence obtained by performing cross-correlation operation on X (n) and S (n); x (n) represents a received signal sequence; s (n) represents a transmit sequence;
representing a cross-correlation operation; r represents the distance of the target to be measured; tp represents the maximum value position when C (tp) is made the maximum value among C (n); and c represents the speed of light.
In a second aspect, the present invention further provides a lidar ranging system based on pulse position modulation technology, where the system includes:
the system comprises a sequence generation module, an equipment synchronization module, a pulse laser, a transmitting optical module, a receiving optical module, a photoelectric detector, a signal acquisition and storage module and a data processing module; wherein the content of the first and second substances,
the sequence generating module is used for generating two groups of sequences with different periods and modulating the two groups of sequences with different periods into transmitting sequences based on a pulse position modulation technology;
the device synchronization module is used for generating an external trigger level to the pulse laser based on the emission sequence and controlling the pulse laser to output a corresponding laser pulse; meanwhile, a synchronous signal is generated every time a period T passes and is input into the signal acquisition and storage module;
the pulse laser is used for sending the laser pulse to the transmitting optical module;
the transmitting optical module is used for transmitting the laser pulse to a target to be measured after collimation and beam expansion;
the receiving optical module is used for receiving the echo laser pulse reflected from the target to be measured and inputting the echo laser pulse into the photoelectric detector;
the photoelectric detector is used for identifying effective signals in the echo laser pulses, converting the effective signals into electric signals and then inputting the electric signals into the signal acquisition and storage module;
the signal acquisition and storage module is used for measuring the time interval between the time of the echo laser pulse reaching the signal acquisition and storage module and the time of the synchronous signal reaching the signal acquisition and storage module, and arranging the echo laser pulse into a received signal sequence according to the arrival sequence and the time interval;
and the data processing module is used for decoding the received signal sequence according to the transmitting sequence to obtain a target distance.
Preferably, the modulating the two sets of sequences with different periods into the transmission sequence by the sequence generating module based on the pulse position modulation technique includes:
mapping two groups of sequences with different periods into a transmitting sequence according to a multi-pulse position modulation mode; wherein, the mapping calculation formula is:
S(n)＝A(n)+B(n+Δt)
wherein, A (n) and B (n) are two sequences with different periods respectively; s (n) represents a transmit sequence; Δ t represents the amount of positional shift of the sequence B (n) with respect to a (n).
Preferably, the measuring, by the signal acquisition and storage module, the time of the echo laser pulse reaching the signal acquisition and storage module includes:
and identifying effective signals in the echo laser pulses by adopting an over-threshold detection technology, converting the effective signals into electric signals, and inputting the electric signals into a signal acquisition device, wherein the signal acquisition device records the time of inputting the electric signals into the signal acquisition device.
Preferably, the decoding, by the data processing module, the received signal sequence according to the transmission sequence to obtain the target distance includes:
R＝tp×c/2
wherein, C (n) represents a signal sequence obtained by performing cross-correlation operation on X (n) and S (n); x (n) represents a received signal sequence; s (n) represents a transmit sequence;
representing cross-correlation operations(ii) a R represents the distance of the target to be measured; tp represents the maximum value position when C (tp) is made the maximum value among C (n); and c represents the speed of light.
Preferably, the emission optical module comprises a pulse laser and an emission lens group; the emission lens group is used for expanding and collimating laser pulse light generated by the pulse laser and then sending the laser pulse light to a target to be detected in a detection area.
Preferably, the photodetector includes a signal discriminator and a receiving lens group; the signal discriminator is used for discriminating the effective signal in the echo laser pulse and converting the effective signal into an electric pulse signal.
(III) advantageous effects
The invention provides a laser radar ranging method and a laser radar ranging system based on a pulse position modulation technology. Compared with the prior art, the method has the following beneficial effects:
1. the method comprises the steps of modulating two groups of sequences with different periods into a transmitting sequence based on a pulse position modulation technology, generating laser pulses based on the transmitting sequence and transmitting the laser pulses to a target to be measured, generating a synchronous signal every time a period T passes, measuring the time interval between the arrival of the reflected echo laser pulses at a signal acquisition device and the synchronous signal, and arranging the echo pulses into a received signal sequence according to the arrival sequence and the time interval; and finally, decoding the received signal sequence according to the transmitting sequence to obtain the distance of the target to be measured. Compared with the prior art, the method can improve the detection distance in multiples under the condition of keeping high laser emission frequency, and has the characteristics of high measurement range and high real-time performance.
2. The invention does not need to switch the repetition frequency of the laser pulse to measure the same target for multiple times, thus improving the real-time property of the system; meanwhile, the pulse sequence is modulated in a multi-pulse position modulation mode, and compared with the sequence before modulation, the measurement distance of the system is doubled without reducing the pulse repetition frequency.
3. The invention only increases the processing process in the digital logic device without increasing the number of key hardware such as a pulse laser, an optical receiving system, a photoelectric detector and the like, and compared with the prior art, the system has simpler structure and lower hardware cost.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a flow chart of a laser radar ranging method based on pulse modulation technique according to the present invention;
FIG. 2 is a schematic diagram of a transmit sequence generated in an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating a principle of extracting a distance of a target to be measured according to an embodiment of the present invention;
fig. 4 is a structural diagram of a lidar ranging system based on a pulse position modulation technique in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the application provides a laser radar ranging method and a ranging system based on a pulse modulation technology, solves the problems of low measuring range and poor real-time performance of the existing laser radar ranging technology, and achieves the purpose of improving the detection distance in multiples under the condition of keeping high laser emission frequency.
In order to solve the technical problems, the general idea of the embodiment of the present application is as follows:
the technical scheme of this application is in order to solve the problem that current laser radar range finding technique has that measuring range is low and the real-time is poor, adopts pulse position modulation technique, modulates the laser emission sequence that the cycle is different into a set of longer sequence of cycle to solve the target distance information that contains in the received signal sequence according to certain rule, can improve the detection distance by multiples under the condition that keeps high laser emission frequency, have the characteristics of high measuring range, high real-time.
In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.
Example 1:
in a first aspect, the present invention first provides a laser radar ranging method based on a pulse modulation technique, and referring to fig. 1, the method includes:
s1, modulating two groups of sequences with different periods into a transmitting sequence based on a pulse position modulation technology;
s2, generating laser pulses based on the emission sequence, and simultaneously generating a synchronous signal every time a period T passes;
s3, sending the laser pulse to a target to be measured, and receiving a reflected echo laser pulse;
s4, measuring a time interval between the time when the echo laser pulse reaches the signal acquisition device and the time when the synchronous signal reaches the signal acquisition device, and arranging the echo laser pulse into a received signal sequence according to the sequence of reaching the signal acquisition device and the time interval;
and S5, decoding the received signal sequence according to the transmitting sequence to obtain the distance of the target to be measured.
It can be seen that, in this embodiment, two groups of sequences with different periods are modulated into a transmitting sequence based on a pulse position modulation technique, a laser pulse is generated based on the transmitting sequence and sent to a target to be measured, a synchronous signal is generated every time a period T passes, then the time interval between the reflected echo laser pulse reaching a signal acquisition device and the synchronous signal is measured, and the echo pulse is arranged into a received signal sequence according to the arrival sequence and the time interval; and finally, decoding the received signal sequence according to the transmitting sequence to obtain the distance of the target to be measured. Compared with the prior art, the embodiment can improve the detection distance in multiples under the condition of keeping high laser emission frequency, and has the characteristics of high measurement range and high real-time performance.
The following describes the implementation of an embodiment of the present invention in detail with reference to the accompanying drawings, and with reference to fig. 1 to 3, and the explanation of the specific steps of S1 to S5.
S1, modulating two groups of sequences with different periods into a transmitting sequence based on a pulse position modulation technology.
First, two periodic sequences having different periods are generated, and the generated two periodic sequences having different periods are modulated into a transmission sequence based on a pulse position modulation technique.
In this embodiment, a sequence generation module is used to generate a binary periodic sequence a (n) with Ta as a period and a binary periodic sequence B (n) with Tb as a period, respectively (the binary periodic sequence is characterized by being composed of numbers "0" and "1", and Ta is the smallest integer that can satisfy a (n) = a (n + Ta) for all n), and map the sequences into a transmission sequence S (n) in a multi-pulse position modulation manner. Wherein, the mapping calculation formula can be expressed as:
S(n)＝A(n)+B(n+Δt)
where Δ t represents the amount of positional shift of the sequence B (n) with respect to a (n) such that a (n) is not 1 at the same time as B (n + Δ t) for any n; this is such that S (n) is also a periodic sequence and the period T is: t = Ta Tb.
Referring to fig. 2, fig. 2 is a schematic diagram of generating a transmission sequence in this embodiment. For example, the period of sequence a (n) is 40 microseconds, and the period of sequence B (n) is 50 microseconds. Selecting delta t as 0.5 microsecond, and modulating the sequences A (n) and B (n) according to S (n) = A (n) + B (n + delta t) through a sequence generation module to obtain a pulse transmitting sequence S (n). The period of the sequence S (n) subjected to pulse position modulation reaches 200 microseconds, and compared with the sequence before modulation, the unambiguous distance measured by a system can be doubled.
And S2, generating laser pulses based on the emission sequence, and generating a synchronous signal every time a period T passes.
And generating an external trigger level to the pulse laser based on the emission sequence, controlling the pulse laser to output corresponding laser pulses, and generating a synchronous signal every time a period T passes. In this embodiment, the rule when generating the trigger level signal is: converting the number '1' in the sequence S (n) into high level; the digital "0" transitions to a low level.
And S3, sending the laser pulse to a target to be measured, and receiving the reflected echo laser pulse.
In this embodiment, the modulated laser pulse is collimated and beam-expanded to the target to be measured. The laser pulse reflects an echo laser pulse signal after contacting a ranging target in a ranging area to be measured.
And S4, measuring the time interval between the time of the echo laser pulse reaching the signal acquisition device and the time of the synchronous signal reaching the signal acquisition device, and arranging the echo laser pulse into a received signal sequence according to the sequence of reaching the signal acquisition device and the time interval.
Specifically, an over-threshold detection technology is adopted, effective signals in echo laser pulses are identified according to whether the voltage value exceeds a set signal identification level (noise and effective signals are identified through the identification level set by an identifier in a photoelectric detector, the effective signals are judged to be effective signals when the peak voltage is higher than the identification level, the effective signals are judged to be noise when the peak voltage is lower than the identification level), and the effective signals are converted into electric signals and then input into a signal acquisition device. Then the signal acquisition device measures the time interval between the time when the electric signal reaches the signal acquisition device and the time when the synchronous signal reaches the signal acquisition device, and the signal acquisition device and the synchronous signal are arranged into a received signal sequence according to the arrival sequence and the time interval.
And S5, decoding the received signal sequence according to the transmitting sequence to obtain the distance of the target to be measured.
The received signal sequence X (n) is decoded according to the sequence S (n) to obtain the target distance. In this embodiment, when calculating the target distance, first, X (n) and S (n) are cross-correlated to obtain a signal sequence C (n), that is, a signal sequence C (n) is obtained
Then searching a maximum position tp to enable C (tp) to be equal to the maximum value in C (n); finally by R =tp × c/2 calculates the target distance R. Referring to fig. 3, fig. 3 is a schematic diagram illustrating a principle of extracting a distance of a target to be measured in the embodiment. After the pulse laser emits light pulses to a target according to an emission sequence S (n), a signal acquisition and storage module receives signals and stores the signals into a received signal sequence X (n). And performing cross-correlation operation on the S (n) and the X (n) to obtain C (n). And searching the time tp corresponding to the maximum value in C (n), and calculating the target distance by adopting a formula R = tp multiplied by C/2, wherein C represents the light speed.
Thus, the whole process of the laser radar ranging method based on the pulse modulation technology of the embodiment is completed.
Example 2:
in a second aspect, the present invention firstly proposes a lidar ranging system based on pulse position modulation technology, and referring to fig. 4, the system includes:
the device comprises a sequence generation module, a device synchronization module, a pulse laser, a transmitting optical module, a receiving optical module, a photoelectric detector, a signal acquisition and storage module and a data processing module;
wherein the content of the first and second substances,
the sequence generation module is used for generating a binary periodic sequence and modulating the binary periodic sequence into a transmission sequence based on a pulse position modulation technology;
the device synchronization module is used for generating an external trigger level to the pulse laser based on the emission sequence and controlling the pulse laser to output a corresponding laser pulse; meanwhile, a synchronous signal is generated every time a period T passes and is input into the signal acquisition and storage module;
the pulse laser is used for sending the laser pulse to the transmitting optical module;
the transmitting optical module is used for transmitting the laser pulse to a target to be measured after collimation and beam expansion;
the receiving optical module is used for receiving the echo laser pulse reflected from the target to be measured and inputting the echo laser pulse into the photoelectric detector;
the photoelectric detector is used for identifying effective signals in the echo laser pulses, converting the effective signals in the echo laser pulses into electric signals and then inputting the electric signals into the signal acquisition and storage module;
the signal acquisition and storage module is used for measuring the time interval between the time when the electric signal reaches the signal acquisition and storage module and the time when the synchronous signal reaches the signal acquisition and storage module, and arranging the signals into a received signal sequence according to the arrival sequence and the time interval;
and the data processing module is used for decoding the received signal sequence according to the transmitting sequence to obtain a target distance.
The implementation of one embodiment of the present invention will be described in detail below with reference to fig. 2-4, and an explanation of specific structures and functions thereof.
In the lidar ranging system based on the pulse modulation technique according to this embodiment, as shown in fig. 4, the lidar ranging system includes: the device comprises a sequence generation module, a device synchronization module, a pulse laser, a transmitting optical module, a receiving optical module, a photoelectric detector, a signal acquisition and storage module and a data processing module. Specifically, the functions of the modules and components and the signal flow process between the modules and the components are as follows:
and the sequence generation module is used for generating a binary periodic sequence and modulating the binary periodic sequence into a transmission sequence based on a pulse position modulation technology.
And respectively generating a binary periodic sequence A (n) with a period of Ta and a binary periodic sequence B (n) with a period of Tb by using a sequence generating module, mapping the sequences into a transmitting sequence S (n) according to a multi-pulse position modulation mode, and inputting the sequences into the equipment synchronization module. The mapping calculation formula can be expressed as:
S(n)＝A(n)+B(n+Δt)
where Δ t represents the amount of positional shift of the sequence B (n) with respect to a (n) such that a (n) is not 1 at the same time as B (n + Δ t) for any n; thus S (n) is also a periodic sequence and the period T is: t = Ta Tb.
Referring to fig. 2, fig. 2 is a schematic diagram of the sequence generation module generating the transmission sequence in this embodiment. For example, the period of the sequence a (n) is 40 microseconds, and the period of the sequence B (n) is 50 microseconds. Selecting delta t as 0.5 microsecond, modulating the sequences A (n) and B (n) by a sequence generation module according to S (n) = A (n) + B (n + delta t), and pulsing the sequence S (n). The period of the sequence S (n) subjected to pulse position modulation reaches 200 microseconds, and compared with the sequence before modulation, the unambiguous distance measured by the system can be doubled.
The device synchronization module is used for generating an external trigger level to the pulse laser based on the emission sequence and controlling the pulse laser to output a corresponding laser pulse; and simultaneously, a synchronous signal is generated every time a period T passes and is input into the signal acquisition and storage module.
The device synchronization module generates an external trigger level signal according to the emission sequence S (n), inputs the signal into the pulse laser, controls the pulse laser to output corresponding laser pulse, and generates a synchronization signal every time period T is passed and inputs the synchronization signal into the signal acquisition and storage module to start time measurement. Wherein, the equipment synchronization module generates the trigger level signal as follows: the number "1" in the sequence S (n) is converted to high level; the digital "0" transitions to a low level.
And the pulse laser is used for sending the modulated laser pulse to the transmitting optical module.
And the transmitting optical module is used for transmitting the modulated laser pulse to the target to be measured after collimation and beam expansion. In the present embodiment, the emission optical module includes a pulse laser and an emission lens group. The emitting lens is used for expanding and collimating pulse light generated by the pulse laser and then sending the pulse light to a target to be detected in a detection area.
The pulse signal reflects the echo laser pulse signal after contacting a ranging target in a ranging region to be measured.
And the receiving optical module is used for receiving the echo laser pulse reflected from the target to be measured and inputting the echo laser pulse into the photoelectric detector.
And the photoelectric detector is used for identifying the effective signals in the echo laser pulses, converting the effective signals in the echo laser pulses into electric signals and inputting the electric signals into the signal acquisition and storage module.
An over-threshold detection technique is used to identify valid signals. After identifying the effective signal in the echo laser pulse, the photoelectric detector converts the effective signal into an electric signal, and inputs the electric signal into a signal acquisition and storage module to wait for subsequent processing. In the present embodiment, the photodetector includes a signal discriminator and a receiving lens group. The signal discriminator is used for discriminating the optical signal reflected by the target and converting the effective optical signal into an electric pulse signal.
And the signal acquisition and storage module is used for measuring the time interval between the time of the signal arriving at the signal acquisition and storage module and the time of the synchronous signal arriving at the signal acquisition and storage module, and arranging the signals into a received signal sequence according to the arrival sequence and the time interval.
And the data processing module is used for decoding the received signal sequence according to the transmitting sequence to obtain the target distance.
And the data processing module decodes the received signal sequence X (n) according to the sequence S (n) to obtain the target distance. In this embodiment, when the data processing module calculates the target distance, first, the cross-correlation operation is performed on X (n) and S (n) to obtain a signal sequence C (n), that is, the signal sequence C (n) is obtained
Then searching a maximum position tp to enable C (tp) to be equal to the maximum value in C (n); finally, the target distance R is calculated by R = tp × c/2. Referring to fig. 3, fig. 3 is a schematic diagram illustrating an extraction principle of the distance of the target to be measured in the embodiment. After the pulse laser emits light pulses to a target according to an emission sequence S (n), a signal acquisition and storage module receives signals and stores the signals into a received signal sequence X (n). And performing cross-correlation operation on S (n) and X (n) in the data processing module to obtain C (n). And searching the time tp corresponding to the maximum value in the C (n), and calculating the target distance by adopting a formula R = tp multiplied by C/2.
It can be understood that, the laser radar ranging system based on the pulse modulation technique provided in the embodiment of the present invention corresponds to the laser radar ranging method based on the pulse modulation technique, and the explanations, examples, and beneficial effects of the relevant contents thereof may refer to the corresponding contents in the laser radar ranging method based on the pulse modulation technique, and are not repeated herein.
In summary, compared with the prior art, the method has the following beneficial effects:
1. the method comprises the steps of modulating two groups of sequences with different periods into a transmitting sequence based on a pulse position modulation technology, generating laser pulses based on the transmitting sequence and transmitting the laser pulses to a target to be measured, generating a synchronous signal every time a period T passes, measuring the time interval between the arrival of the reflected echo laser pulses at a signal acquisition device and the synchronous signal, and arranging the echo pulses into a received signal sequence according to the arrival sequence and the time interval; and finally, decoding the received signal sequence according to the transmitting sequence to obtain the distance of the target to be measured. Compared with the prior art, the method can improve the detection distance in multiples under the condition of keeping high laser emission frequency, and has the characteristics of high measurement range and high real-time performance.
2. The invention does not need to switch the repetition frequency of the laser pulse to measure the same target for multiple times, thus improving the real-time property of the system; meanwhile, the pulse sequence is modulated in a multi-pulse position modulation mode, and compared with the sequence before modulation, the measurement distance of the system is doubled without reducing the pulse repetition frequency.
3. The invention only increases the processing process in the digital logic device without increasing the number of key hardware such as a pulse laser, an optical receiving system, a photoelectric detector and the like, and compared with the prior art, the system has simpler structure and lower hardware cost.
It should be noted that, in this document, relational terms such as first and second, and the like are only used for distinguishing one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.
The above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A laser radar ranging method based on a pulse position modulation technology is characterized by comprising the following steps:
modulating two groups of sequences with different periods into transmission sequences based on a pulse position modulation technology;
generating laser pulses based on the emission sequence while generating a synchronization signal every time a period T elapses;
sending the laser pulse to a target to be measured, and receiving a reflected echo laser pulse;
measuring the time interval between the time of the echo laser pulse reaching the signal acquisition device and the time of the synchronous signal reaching the signal acquisition device, and arranging the echo laser pulse into a received signal sequence according to the sequence of reaching the signal acquisition device and the time interval;
and decoding the received signal sequence according to the transmitting sequence to obtain the distance of the target to be measured.
2. The method of claim 1, wherein modulating two sets of periodically different sequences into transmission sequences based on a pulse position modulation technique comprises:
mapping two groups of sequences with different periods into a transmitting sequence according to a multi-pulse position modulation mode; wherein, the mapping calculation formula is:
S(n)＝A(n)+B(n+Δt)
wherein, A (n) and B (n) are two sequences with different periods respectively; s (n) represents a transmit sequence; Δ t represents the amount of positional shift of the sequence B (n) with respect to a (n).
3. The method of claim 1, wherein said measuring the time of arrival of the echo laser pulse at a signal acquisition device comprises:
and identifying effective signals in the echo laser pulses by adopting an over-threshold detection technology, converting the effective signals into electric signals, inputting the electric signals into a signal acquisition device, and recording the time of inputting the electric signals into the signal acquisition device by the signal acquisition device.
4. The method of claim 1, wherein said decoding said received signal sequence in accordance with said transmitted sequence to obtain a target distance to be measured comprises:
R＝tp×c/2
wherein, C (n) represents a signal sequence obtained by performing cross-correlation operation on X (n) and S (n); x (n) represents a received signal sequence; s (n) represents a transmit sequence;
representing a cross-correlation operation; r represents the distance of the target to be measured; tp represents the maximum value position when C (tp) is made the maximum value among C (n); and c represents the speed of light.
5. A lidar ranging system based on pulse position modulation techniques, the system comprising:
the system comprises a sequence generation module, an equipment synchronization module, a pulse laser, a transmitting optical module, a receiving optical module, a photoelectric detector, a signal acquisition and storage module and a data processing module; wherein, the first and the second end of the pipe are connected with each other,
the sequence generating module is used for generating two groups of sequences with different periods and modulating the two groups of sequences with different periods into transmitting sequences based on a pulse position modulation technology;
the device synchronization module is used for generating an external trigger level to the pulse laser based on the emission sequence and controlling the pulse laser to output a corresponding laser pulse; meanwhile, a synchronous signal is generated every time a period T passes and is input into the signal acquisition and storage module;
the pulse laser is used for sending the laser pulse to the emission optical module;
the transmitting optical module is used for transmitting the laser pulse to a target to be measured after collimation and beam expansion;
the receiving optical module is used for receiving the echo laser pulse reflected from the target to be measured and inputting the echo laser pulse into the photoelectric detector;
the photoelectric detector is used for identifying effective signals in the echo laser pulses, converting the effective signals into electric signals and inputting the electric signals into a signal acquisition and storage module;
the signal acquisition and storage module is used for measuring the time interval between the time of the echo laser pulse reaching the signal acquisition and storage module and the time of the synchronous signal reaching the signal acquisition and storage module, and arranging the echo laser pulse into a received signal sequence according to the arrival sequence and the time interval;
and the data processing module is used for decoding the received signal sequence according to the transmitting sequence to obtain a target distance.
6. The system of claim 5, wherein the sequence generation module modulates two sets of periodically different sequences into a transmit sequence based on a pulse position modulation technique comprises:
mapping two groups of sequences with different periods into a transmitting sequence according to a multi-pulse position modulation mode; wherein, the mapping calculation formula is as follows:
S(n)＝A(n)+B(n+Δt)
wherein, A (n) and B (n) are two sequences with different periods respectively; s (n) represents a transmit sequence; Δ t represents the amount of positional shift of the sequence B (n) with respect to a (n).
7. The system of claim 5, wherein the signal acquisition and storage module measuring the time of arrival of the echo laser pulse at the signal acquisition and storage module comprises:
and identifying effective signals in the echo laser pulses by adopting an over-threshold detection technology, converting the effective signals into electric signals, and inputting the electric signals into a signal acquisition device, wherein the signal acquisition device records the time of inputting the electric signals into the signal acquisition device.
8. The system of claim 5, wherein said data processing module decoding said received signal sequence according to said transmitted sequence to obtain a target range comprises:
R＝tp×c/2
wherein, C (n) represents a signal sequence obtained by performing cross-correlation operation on X (n) and S (n); x (n) represents a received signal sequence; s (n) represents a transmit sequence;
representing a cross-correlation operation; r represents the distance of the target to be measured; tp represents the maximum value position when C (tp) is made the maximum value among C (n); and c represents the speed of light.
9. The system of claim 5, wherein the emission optics module comprises a pulsed laser and an emission lens group; the emission lens group is used for expanding and collimating laser pulse light generated by the pulse laser and then sending the laser pulse light to a target to be detected in a detection area.
10. The system of claim 5, wherein the photodetector comprises a signal discriminator and a receive lens group ； The signal discriminator is used for discriminating the effective signal in the echo laser pulse and converting the effective signal into an electric pulse signal.
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