CN111538026A - Laser ranging method and system - Google Patents
Laser ranging method and system Download PDFInfo
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- CN111538026A CN111538026A CN202010421451.8A CN202010421451A CN111538026A CN 111538026 A CN111538026 A CN 111538026A CN 202010421451 A CN202010421451 A CN 202010421451A CN 111538026 A CN111538026 A CN 111538026A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/487—Extracting wanted echo signals, e.g. pulse detection
- G01S7/4876—Extracting wanted echo signals, e.g. pulse detection by removing unwanted signals
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Abstract
The invention relates to the technical field of distance measurement, in particular to a laser distance measurement method and a laser distance measurement system, wherein the method comprises the following steps: the method comprises the steps that a transmitting end transmits laser pulses to a target detection area, and the laser pulses are obtained by amplitude modulation according to preset modulation signals; a receiving end receives an echo pulse, demodulates the echo pulse and obtains a first amplitude sequence of the echo pulse, wherein the echo pulse comprises a reflected pulse obtained by reflecting a laser pulse by a detection object in the target detection area; the receiving end acquires a second amplitude sequence of the laser pulse; the receiving end carries out autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and determines a time interval from the emission of the laser pulse to the reception of the reflected pulse; and the receiving end determines the distance information of the detection object according to the time interval. The laser ranging method can improve the measurement precision and the anti-interference capability of the ranging system.
Description
Technical Field
The invention relates to the technical field of distance measurement, in particular to a laser distance measurement method and a laser distance measurement system.
Background
The laser detection and ranging technique is commonly referred to as lidar technology. The laser radar technology integrates the technology and knowledge of different subjects such as optics, mechanics, electronics, algorithms, very large scale integrated circuits, integrated optics and the like. In recent years, with the development of laser technology, embedded technology, and integrated optical technology, lidar is being developed toward low cost, miniaturization, high reliability, and high security.
The conventional laser radars can be roughly classified into four types according to the laser beam control method of the laser radar. The first type is a traditional mechanical rotation multiline laser radar, which mainly adopts a certain mechanical element to enable the laser radar or partial components to rotate at a high speed, thereby realizing specific scanning of a detection space. The second type is a phased array laser radar, which realizes beam scanning in a certain space range by changing the wave front of the emitted laser to move the beam direction, and is one of solid state laser radars, the system precision and the service life are greatly improved, but the disadvantages are that the scanning range is limited and the scanning speed is low. The third type is a laser radar which utilizes a micro-electro-mechanical system galvanometer to realize the spatial scanning of light beams, and is also one of solid-state laser radars, and has the advantages of simple system, low power consumption and the defects of larger influence of mechanical parts and poorer precision. The fourth type is a non-scanning Flash (Flash) laser radar, which uses a pulse phase modulation-based mode to detect the distance, and because the transmitting system has no mechanical motion, the whole field range can be recorded quickly, and various interferences caused by the movement of a target or the laser radar in the scanning process are avoided.
The conventional Flash laser radar is based on the Time-of-Flight ranging principle, but the Flash type laser radar based on Indirect Time-of-Flight (ITOF) measurement needs to integrate an echo signal, is easily interfered by ambient light or stray signal light, is related to ranging accuracy and detection distance, and has high requirements on the dynamic range of a receiving end pixel. While the flash type laser radar based on Direct Time-of-Flight (DTOF) mainly depends on the rising edge or the falling edge of the modulation pulse for demodulation, and the anti-interference capability is weak.
Disclosure of Invention
In view of the above problems in the prior art, an object of the present invention is to provide a laser ranging method and system, which can improve the measurement accuracy and the anti-interference capability of the ranging system.
In order to solve the above problem, the present invention provides a laser ranging method, including:
the method comprises the steps that a transmitting end transmits laser pulses to a target detection area, and the laser pulses are obtained by amplitude modulation according to preset modulation signals;
a receiving end receives an echo pulse, demodulates the echo pulse and obtains a first amplitude sequence of the echo pulse, wherein the echo pulse comprises a reflected pulse obtained by reflecting a laser pulse by a detection object in the target detection area;
the receiving end acquires a second amplitude sequence of the laser pulse;
the receiving end carries out autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and determines a time interval from the emission of the laser pulse to the reception of the reflected pulse;
and the receiving end determines the distance information of the detection object according to the time interval.
Further, the receiving end performs an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and determining a time interval from the emission of the laser pulse to the reception of the reflected pulse includes:
the receiving end determines a plurality of subsequences based on the first amplitude sequence and generates a subsequence set;
the receiving end carries out self-correlation operation on each subsequence in the subsequence set and the second amplitude sequence to determine a target subsequence;
and the receiving end determines the time interval from the emission of the laser pulse to the reception of the reflected pulse according to the phase relation between the target subsequence and the second amplitude sequence.
Specifically, the receiving end determines a plurality of subsequences based on the first amplitude sequence, and generating a subsequence set includes:
the receiving end obtains the sequence length of the second amplitude sequence and the pulse width corresponding to a single amplitude value in the second amplitude sequence;
and the receiving end intercepts a subsequence with the length equal to the sequence length from the first amplitude sequence by taking the pulse width as a stepping value, and generates a subsequence set.
Specifically, the receiving end performs an autocorrelation operation on each subsequence in the subsequence set and the second amplitude sequence, and determining a target subsequence includes:
the receiving end calculates the autocorrelation coefficient between each subsequence in the subsequence set and the second amplitude sequence;
and the receiving end acquires the subsequence with the minimum autocorrelation coefficient with the second amplitude sequence as a target subsequence.
Further, the receiving end performs an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and before determining a time interval from the emission of the laser pulse to the reception of the reflected pulse, the receiving end further includes:
and the receiving end performs Kalman filtering on the first amplitude sequence.
Further, the receiving end includes a detector array, the detector array includes a plurality of detection units, each detection unit includes a focusing microlens, a single-point detector, a transimpedance amplifier, an analog-to-digital converter and a random access memory, the focusing microlenses correspond to the single-point detectors one by one, the transimpedance amplifier is electrically connected to the single-point detector, the transimpedance amplifier is disposed below the single-point detector, and the analog-to-digital converter is electrically connected to the transimpedance amplifier and the random access memory respectively;
the receiving end receives the echo pulse, demodulates the echo pulse, and obtains a first amplitude sequence of the echo pulse, including:
the focusing micro lens converges the echo pulse to the single-point detector;
the single-point detector receives the echo pulse and converts the echo pulse into a current signal;
the trans-impedance amplifier converts the current signal into a voltage signal;
the analog-to-digital converter collects the voltage signal and converts the voltage signal into a digital pulse signal; and sending the digital pulse signal to the random access memory for storage to obtain the first amplitude sequence.
Furthermore, the receiving end further comprises a narrow-band filter, and the narrow-band filter is used for filtering the ambient light in the echo pulse.
Further, the acquiring, by the receiving end, the second amplitude sequence of the modulated signal laser pulses includes:
the receiving end acquires the modulation signal, and takes the amplitude sequence of the modulation signal as a second amplitude sequence of the laser pulse;
alternatively, the first and second electrodes may be,
the receiving end acquires amplitude information output by the monitoring photodiode, and the amplitude information is used as a second amplitude sequence of the laser pulse; wherein the monitor photodiode is configured to monitor the laser pulse.
Further, the transmitting end comprises a driving assembly, a laser transmitter and an emergent optical element, wherein the driving assembly is electrically connected with the laser transmitter;
the emitting end emits laser pulses to the target detection area, and the emitting end comprises:
the driving component generates a driving pulse signal according to the preset modulation signal and sends the driving pulse signal to the laser transmitter;
the laser transmitter transmits laser pulses to the target detection area in response to the driving pulse signal;
and the emergent optical element performs beam splitting processing on the laser pulse, so that the laser pulse subjected to beam splitting processing uniformly illuminates the whole target detection area.
The invention protects a laser ranging system on the other hand, comprising a transmitting end and a receiving end;
the transmitting end is used for transmitting laser pulses to a target detection area, and the laser pulses are obtained by amplitude modulation according to a preset modulation signal;
the receiving end is used for receiving an echo pulse by the receiving end, demodulating the echo pulse and obtaining a first amplitude sequence of the echo pulse, wherein the echo pulse comprises a reflected pulse obtained by reflecting a laser pulse by a detection object in the target detection area; acquiring a second amplitude sequence of the laser pulses; performing an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence to determine a time interval from the emission of the laser pulse to the receipt of the reflected pulse; and determining the distance information of the detection object according to the time interval.
Due to the technical scheme, the invention has the following beneficial effects:
according to the laser ranging method, the laser pulse is transmitted to the detection object in a flash mode, the self-correlation operation is carried out on the amplitude sequence of the received echo pulse and the amplitude sequence of the laser pulse, the distance information between the detection object and the transmitting end is determined, and the measuring accuracy of the ranging system can be improved. And secondly, because the pseudo-random code is used as a modulation signal, and after the echo pulse is obtained, the narrow-band filter is used for filtering the echo pulse, and the anti-interference capability of the ranging system is further improved. In addition, Kalman filtering is carried out on the amplitude sequence of the echo pulse before correlation operation is carried out, and the reliability of a distance measurement result is improved.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings used in the description of the embodiment or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 is a flow chart of a laser ranging method provided by one embodiment of the present invention;
fig. 2 is a schematic structural diagram of a transmitting end according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a receiving end according to an embodiment of the present invention;
FIG. 4 is a timing diagram illustrating a ranging principle of a laser ranging method according to an embodiment of the present invention;
FIG. 5 is a flow chart of a laser ranging method according to another embodiment of the present invention;
fig. 6 is a schematic structural diagram of a laser ranging system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The technical scheme provided by the embodiment of the invention is suitable for any distance measurement scene, particularly a long-distance high-precision distance measurement scene, such as a scene for performing long-distance high-precision distance measurement on an obstacle during automatic driving. In this scenario, because the distance between the ranging device and the object to be measured is long, the energy of the echo signal collected by the receiving end of the ranging device is limited by the transmission power, and the receiving end of the ranging device can also receive an ambient light signal and other signals to cause interference on the echo signal, which easily causes ranging failure or ranging accuracy reduction.
The technical scheme provided by the embodiment of the invention can be applied to various systems, and is particularly practical in scenes with a long distance measurement range. For example, an automatic driving system implemented on an expressway. The technical scheme provided by the embodiment of the invention relates to a detection object and a distance measuring device, wherein in different systems, the detection object can be different objects, and the distance measuring device can also be different devices (or systems). In the embodiment of the present invention, the detection object may be a person, an animal, a moving object, or a fixed object, the distance measuring device may be a laser radar device, and the laser radar device may also be referred to by other names, for example, a laser distance measuring radar detector, and the like.
Referring to the specification and fig. 1, a flow of a laser ranging method according to an embodiment of the invention is shown. The laser ranging method can be applied to a laser ranging system, the laser ranging system comprises a transmitting end and a receiving end, and the transmitting end and the receiving end can be arranged in the same ranging device or different ranging devices. As shown in fig. 1, the laser ranging method may include:
s110: and the transmitting end transmits laser pulses to the target detection area, and the laser pulses are obtained by performing amplitude modulation according to a preset modulation signal.
In the embodiment of the invention, the transmitting terminal can transmit laser pulses to the target detection area in a Flash mode. The preset modulation signal may be a pseudo-random code, and the code value may be used to determine the current output amplitude of the laser transmitter.
In one possible embodiment, referring to fig. 2 in combination with the description, the emitting end may include a driving assembly, a laser emitter, and an exit optical element, the driving assembly being electrically connected to the laser emitter; the emitting of the laser pulse to the target detection area by the emitting end may include:
the driving component generates a driving pulse signal according to the preset modulation signal and sends the driving pulse signal to the laser transmitter; the laser transmitter transmits laser pulses to the target detection area in response to the driving pulse signal; and the emergent optical element performs beam splitting processing on the laser pulse, so that the laser pulse subjected to beam splitting processing uniformly illuminates the whole target detection area.
In practical applications, the driving component may include a random number generator (randomizer), a Digital-to-Analog Converter (DAC), and a driving modulation circuit electrically connected to each other. When the driving component receives a control signal generated by a main controller such as a Field-Programmable Gate Array (FPGA), the random number generator may generate a pseudo-random code, the digital-to-analog converter may generate a corresponding analog electrical signal according to the pseudo-random code, and the analog electrical signal acts on the driving modulation circuit to generate a driving pulse signal and is sent to the laser transmitter. The driving modulation circuit can adopt a triode amplifying circuit working in a linear region, the laser transmitter can transmit corresponding laser pulses according to the on-off and amplitude response of the triode, and the emergent optical element can project amplitude modulated light output by the laser transmitter into a target detection region in a flash mode, so that the target detection region is covered completely at one time. In particular, the exit optical element may comprise a refractive optical element or a diffractive optical element or the like.
For example, the output pulse width of the laser transmitter may be set to be in a range of 50-100 ns, the output power of the laser transmitter may be 10-100 w, and the output frequency of the DAC may be 1 ghz.
S120: and a receiving end receives the echo pulse, demodulates the echo pulse and obtains a first amplitude sequence of the echo pulse, wherein the echo pulse comprises a reflection pulse obtained by reflecting the laser pulse by a detection object in the target detection area.
In the embodiment of the present invention, the receiving end may start receiving the echo pulse when the laser transmitter transmits the laser pulse, and stop receiving the echo pulse when the time reaches the preset time threshold. The preset time threshold may be determined by estimating a maximum measurement distance of the laser ranging system, for example, if the total detection distance is estimated to be 120 meters, the laser round-trip time length is 800 nanoseconds, and the time threshold may be set to 800 nanoseconds.
In one possible embodiment, referring to fig. 3 in conjunction with the description, the receiving end may include a detector array, the detector array may include a plurality of detection units, each of the detection units may include a focusing microlens, a single-point detector, a transimpedance Amplifier (ADC), an Analog-to-Digital Converter (ADC), and a Random Access Memory (RAM), the focusing microlenses correspond to the single-point detectors one by one, the transimpedance amplifier is electrically connected to the single-point detector, the transimpedance amplifier is disposed below the single-point detector, and the Analog-to-Digital Converter is electrically connected to the transimpedance amplifier and the RAM;
the receiving end receives the echo pulse, and demodulates the echo pulse to obtain the first amplitude sequence of the echo pulse may include:
the focusing micro lens converges the echo pulse to the single-point detector;
the single-point detector receives the echo pulse and converts the echo pulse into a current signal;
the trans-impedance amplifier converts the current signal into a voltage signal;
the analog-to-digital converter collects the voltage signal and converts the voltage signal into a digital pulse signal; and sending the digital pulse signal to the random access memory for storage to obtain the first amplitude sequence.
In practical applications, the detector array may be an M-row and N-column pixel array, where the values of M and N are related to the field angle and the resolution of the laser ranging system, and total to M × N detection units, and each detection unit constitutes one detection channel and is completely consistent. The focusing micro lens can focus the light reflected to the focusing lens in the fast axis direction and the slow axis direction for projecting to the corresponding pixel, so that the photoelectric detection probability of the single-point detector can be improved; the single-point detector can adopt a focal plane imaging mode, namely, a pixel point is arranged at the position of the focal length of the focusing micro lens, and the single-point detector can be a Photodiode (PD), an Avalanche Photodiode (APD), a Silicon Photomultiplier (Silicon Photomultiplier), or the like; the trans-impedance amplifier is arranged below the detector, and integrally forms a three-Dimensional Stack (3-Dimensional Stack, 3D-Stack) structure, so that the area of a photosensitive surface occupied by a circuit can be reduced, and the filling factor of a pixel unit is improved; the ADC may adopt a Voltage Controlled Oscillator (VCO) type Analog-to-time converter (ATC), and may implement a high-frequency low-cost Analog-to-digital converter scheme; the RAM can be used for storing a current sampling value of the ADC and realizing real-time caching of large-area array data, the depth of the RAM is related to pulse width and pulse carrier frequency, and the depth of the RAM or a First Input First Output (FIFO) queue is not lower than the ratio of the pulse width to the sampling period of the ADC; the sampling frequency of the ADC and the frequency of the DAC are related and may, for example, be set to be the same.
In one possible embodiment, the receiving end may further include a narrow-band filter for filtering the ambient light in the echo pulse. Specifically, the narrow-band filter can cover on whole detector array for the ambient light outside the transmission laser bandwidth scope of filtration can improve the SNR of echo pulse, so that discern and gather.
S130: the receiving end acquires a second amplitude sequence of the laser pulses.
In the embodiment of the present invention, the receiving end may directly obtain the modulation signal from the transmitting end, and determine the second amplitude sequence according to the modulation signal, or may monitor the laser pulse transmitted by the laser transmitter through a photoelectric sensor such as a photodiode, and collect a monitoring signal of the photodiode to determine the second amplitude sequence.
In one possible embodiment, the acquiring, by the receiving end, the second amplitude sequence of the modulated signal laser pulses includes:
the receiving end acquires the modulation signal, and takes the amplitude sequence of the modulation signal as a second amplitude sequence of the laser pulse;
or, the receiving end acquires amplitude information output by the monitoring photodiode, and the amplitude information is used as a second amplitude sequence of the laser pulse; wherein the monitor photodiode is configured to monitor the laser pulse.
Specifically, after the laser emitter emits the laser pulse, a part of light (for example, 1% or 5%) of the laser pulse may be emitted onto the monitoring photodiode, the monitoring photodiode outputs amplitude information of the laser pulse in real time, and the ADC may acquire the amplitude information output by the monitoring photodiode to obtain the second amplitude sequence of the laser pulse. Specifically, the ADC is electrically connected to the monitor photodiode, the monitor photodiode and the ADC may be disposed at the transmitting end, and the ADC may send the obtained second amplitude sequence to the receiving end. Wherein, the ADC can also be configured with a RAM for storing the sampling value of the ADC.
In a possible embodiment, the monitoring photodiode and the ADC may also be disposed at the receiving end, or the monitoring photodiode is disposed at the transmitting end and the ADC is disposed at the receiving end, and the second amplitude sequence of the laser pulses may be obtained by acquiring amplitude information output by the monitoring photodiode through the ADC.
S140: and the receiving end performs autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and determines a time interval from the emission of the laser pulse to the reception of the reflected pulse.
In the embodiment of the present invention, the time information of the received reflected pulse may be calculated by using the first amplitude sequence and the second amplitude sequence. Exemplarily, referring to fig. 4 in the attached description, which shows a schematic diagram of a ranging principle of a laser ranging method provided by an embodiment of the present invention, as shown in fig. 4, the upper sequence represents a second amplitude sequence (which may be denoted as y0), the sequence length is n, the lower sequence represents a first amplitude value (which may be denoted as y) of a received echo pulse after a preset time threshold T elapses with a laser pulse emission time as a start time, and the total sequence length is m. The time of arrival of a reflected pulse obtained by reflecting the laser pulse by the detection object is t, and if the value of t needs to be determined, autocorrelation calculation needs to be performed based on y0 and y.
In a possible embodiment, the receiving end performs an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and before determining a time interval from the emission of the laser pulse to the reception of the reflected pulse, may further include:
and the receiving end performs Kalman filtering on the first amplitude sequence.
Specifically, by filtering the detected first amplitude sequence, the accuracy of the first amplitude sequence can be improved, and the reliability of the ranging result is increased.
In one possible embodiment, referring to fig. 5 in combination with the description, the determining, by the receiving end, a time interval from the emission of the laser pulse to the reception of the reflected pulse by performing an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence may include:
s141: and the receiving end determines a plurality of subsequences based on the first amplitude sequence and generates a subsequence set.
In one possible embodiment, the receiving end determines a plurality of subsequences based on the first amplitude sequence, and generating the set of subsequences may include:
the receiving end obtains the sequence length of the second amplitude sequence and the pulse width corresponding to a single amplitude value in the second amplitude sequence;
and the receiving end intercepts a subsequence with the length equal to the sequence length from the first amplitude sequence by taking the pulse width as a stepping value, and generates a subsequence set.
Illustratively, with reference to fig. 4 of the drawings, in conjunction with this description, assuming that the pulse width corresponding to a single amplitude value in the second amplitude sequence y0 is 1 ns, i.e., the output frequency of the DAC is 1 ghz, the pulse width of the entire sequence is n ns. Since the width of a single pulse is 1 ns, the subsequences with length n in the first amplitude sequence y can be segmented and truncated from the start time to 1 ns, so as to obtain a subsequence set with m-n subsequences, which is denoted as { yi (i ═ 1,2, …, m-n) }.
S142: and the receiving end performs autocorrelation operation on each subsequence in the subsequence set and the second amplitude sequence to determine a target subsequence.
In one possible embodiment, the receiving end performs an autocorrelation operation on each subsequence in the set of subsequences and the second amplitude sequence, and determining a target subsequence may include:
the receiving end calculates the autocorrelation coefficient between each subsequence in the subsequence set and the second amplitude sequence;
and the receiving end acquires the subsequence with the minimum autocorrelation coefficient with the second amplitude sequence as a target subsequence.
Illustratively, referring to fig. 4 in conjunction with the description, an autocorrelation calculation may be performed on each subsequence yi and y0 in the truncated subsequence set { yi (i ═ 1,2, …, m-n) }, to obtain an autocorrelation coefficient between the subsequence yi and y0, where the calculation formula is as follows:
wherein pi represents the autocorrelation coefficient between the subsequences yi and y0, m-n autocorrelation coefficient values can be obtained through calculation, and the subsequence corresponding to the minimum autocorrelation coefficient value pi is found and used as the target subsequence.
S143: and the receiving end determines the time interval from the emission of the laser pulse to the reception of the reflected pulse according to the phase relation between the target subsequence and the second amplitude sequence.
In the embodiment of the present invention, the time for emitting the laser pulse may be counted as 0, after the target subsequence is determined, the sequence number corresponding to the target subsequence may be determined, and then the value of the time t for the reflected pulse to arrive may be determined according to the sequence number and the step value.
Exemplarily, referring to fig. 4 in the attached description, assuming that the sequence number of the target subsequence is k, since the step value is 1 ns, it can be determined that the time t of arrival of the reflected pulse is k ns.
S150: and the receiving end determines the distance information of the detection object according to the time interval.
In this embodiment of the present invention, the distance of the detection object may be a distance between the detection object and the transmitting end, and the distance of the detection object may be calculated as follows:
where d represents the distance, c represents the speed of light, and t represents the time interval.
It should be noted that, the steps S110 to S140 may also be repeated multiple times to obtain multiple values of t, and the time interval is determined according to the multiple values of t, so as to determine the distance of the detection object, thereby improving the accuracy of ranging, where the number of repetitions is related to the operating frequency and the frame rate required by system design.
In summary, the laser ranging method of the present invention transmits the laser pulse to the detection object by using the flash mode, performs the autocorrelation operation on the amplitude sequence of the received echo pulse and the amplitude sequence of the laser pulse, determines the distance information between the detection object and the transmitting end, and can improve the measurement accuracy of the ranging system. And secondly, because the pseudo-random code is used as a modulation signal, and after the echo pulse is obtained, the narrow-band filter is used for filtering the echo pulse, and the anti-interference capability of the ranging system is further improved. In addition, Kalman filtering is carried out on the amplitude sequence of the echo pulse before correlation operation is carried out, and the reliability of a distance measurement result is improved.
Referring to the specification fig. 6, which illustrates the structure of a laser ranging system according to an embodiment of the present invention, as shown in fig. 6, the system may include a transmitting end 610 and a receiving end 620;
the transmitting terminal 610 is configured to transmit a laser pulse to a target detection area, where the laser pulse is obtained by performing amplitude modulation according to a preset modulation signal;
the receiving end 620 is configured to receive an echo pulse, demodulate the echo pulse, and obtain a first amplitude sequence of the echo pulse, where the echo pulse includes a reflected pulse obtained by reflecting a laser pulse by a detection object in the target detection area; acquiring a second amplitude sequence of the laser pulses; performing an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence to determine a time interval from the emission of the laser pulse to the receipt of the reflected pulse; and determining the distance information of the detection object according to the time interval.
In this embodiment of the present invention, the transmitting end 610 and the receiving end 620 may be disposed in the same ranging apparatus, or may be disposed in different ranging apparatuses, which is not limited in this embodiment of the present invention. After the transmitting end 610 projects the modulated laser pulse signal to a target detection area, the receiving end 620 collects a reflected pulse signal reflected by a detection object in the target detection area, and determines a distance between the detection object and the transmitting end 610 by calculating a turn-back time of the reflected pulse signal.
In one possible embodiment, the emitting end 610 may include a driving assembly, a laser emitter, and an exit optical element, the driving assembly being electrically connected to the laser emitter, and the driving assembly may include a random number generator, a digital-to-analog converter, and a driving modulation circuit, which are electrically connected.
In one possible embodiment, the receiving end 620 may include a detector array, the detector array includes a plurality of detecting units, each detecting unit includes a focusing microlens, a single-point detector, a transimpedance amplifier, an analog-to-digital converter, and a random access memory, the focusing microlenses correspond to the single-point detectors one to one, the transimpedance amplifier is electrically connected to the single-point detector, the transimpedance amplifier is disposed below the single-point detector, and the analog-to-digital converter is electrically connected to the transimpedance amplifier and the random access memory, respectively.
In one possible embodiment, the receiving end 620 may further include a narrow-band filter segment, which is covered on the whole detector array.
The foregoing description has disclosed fully preferred embodiments of the present invention. It should be noted that those skilled in the art can make modifications to the embodiments of the present invention without departing from the scope of the appended claims. Accordingly, the scope of the appended claims is not to be limited to the specific embodiments described above.
Claims (10)
1. A laser ranging method, comprising:
the method comprises the steps that a transmitting end transmits laser pulses to a target detection area, and the laser pulses are obtained by amplitude modulation according to preset modulation signals;
a receiving end receives an echo pulse, demodulates the echo pulse and obtains a first amplitude sequence of the echo pulse, wherein the echo pulse comprises a reflected pulse obtained by reflecting a laser pulse by a detection object in the target detection area;
the receiving end acquires a second amplitude sequence of the laser pulse;
the receiving end carries out autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and determines a time interval from the emission of the laser pulse to the reception of the reflected pulse;
and the receiving end determines the distance information of the detection object according to the time interval.
2. The method of claim 1, wherein the receiving end performs an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and wherein determining a time interval from the emission of the laser pulse to the receipt of the reflected pulse comprises:
the receiving end determines a plurality of subsequences based on the first amplitude sequence and generates a subsequence set;
the receiving end carries out self-correlation operation on each subsequence in the subsequence set and the second amplitude sequence to determine a target subsequence;
and the receiving end determines the time interval from the emission of the laser pulse to the reception of the reflected pulse according to the phase relation between the target subsequence and the second amplitude sequence.
3. The method of claim 2, wherein the receiving end determines a plurality of subsequences based on the first amplitude sequence, and wherein generating a set of subsequences comprises:
the receiving end obtains the sequence length of the second amplitude sequence and the pulse width corresponding to a single amplitude value in the second amplitude sequence;
and the receiving end intercepts a subsequence with the length equal to the sequence length from the first amplitude sequence by taking the pulse width as a stepping value, and generates a subsequence set.
4. The method of claim 2, wherein the receiving end performs an autocorrelation operation on each subsequence in the set of subsequences and the second amplitude sequence, and wherein determining a target subsequence comprises:
the receiving end calculates the autocorrelation coefficient between each subsequence in the subsequence set and the second amplitude sequence;
and the receiving end acquires the subsequence with the minimum autocorrelation coefficient with the second amplitude sequence as a target subsequence.
5. The method according to claim 1 or 2, wherein the receiving end performs an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence, and before determining a time interval from the emission of the laser pulse to the reception of the reflected pulse, further comprises:
and the receiving end performs Kalman filtering on the first amplitude sequence.
6. The method according to claim 1 or 2, wherein the receiving end comprises a detector array, the detector array comprises a plurality of detection units, each detection unit comprises a focusing microlens, a single-point detector, a transimpedance amplifier, an analog-to-digital converter and a random access memory, the focusing microlenses correspond to the single-point detectors one by one, the transimpedance amplifier is electrically connected with the single-point detector, the transimpedance amplifier is arranged below the single-point detector, and the analog-to-digital converters are respectively electrically connected with the transimpedance amplifier and the random access memory;
the receiving end receives the echo pulse, demodulates the echo pulse, and obtains a first amplitude sequence of the echo pulse, including:
the focusing micro lens converges the echo pulse to the single-point detector;
the single-point detector receives the echo pulse and converts the echo pulse into a current signal;
the trans-impedance amplifier converts the current signal into a voltage signal;
the analog-to-digital converter collects the voltage signal and converts the voltage signal into a digital pulse signal; and sending the digital pulse signal to the random access memory for storage to obtain the first amplitude sequence.
7. The method of claim 6, wherein the receiving end further comprises a narrow-band filter for filtering the ambient light in the echo pulse.
8. The method of claim 1 or 2, wherein the receiving end acquiring the second amplitude sequence of the laser pulses comprises:
the receiving end acquires the modulation signal, and takes the amplitude sequence of the modulation signal as a second amplitude sequence of the laser pulse;
alternatively, the first and second electrodes may be,
the receiving end acquires amplitude information output by the monitoring photodiode, and the amplitude information is used as a second amplitude sequence of the laser pulse; wherein the monitor photodiode is configured to monitor the laser pulse.
9. The method of claim 1, wherein the emitting end comprises a drive assembly, a laser emitter, and an exit optical element, the drive assembly being electrically connected to the laser emitter;
the emitting end emits laser pulses to the target detection area, and the emitting end comprises:
the driving component generates a driving pulse signal according to the preset modulation signal and sends the driving pulse signal to the laser transmitter;
the laser transmitter transmits laser pulses to the target detection area in response to the driving pulse signal;
and the emergent optical element performs beam splitting processing on the laser pulse, so that the laser pulse subjected to beam splitting processing uniformly illuminates the whole target detection area.
10. The utility model provides a laser ranging system, includes transmitting terminal and receiving terminal, its characterized in that:
the transmitting end is used for transmitting laser pulses to a target detection area, and the laser pulses are obtained by amplitude modulation according to a preset modulation signal;
the receiving end is used for receiving an echo pulse by the receiving end, demodulating the echo pulse and obtaining a first amplitude sequence of the echo pulse, wherein the echo pulse comprises a reflected pulse obtained by reflecting a laser pulse by a detection object in the target detection area; acquiring a second amplitude sequence of the laser pulses; performing an autocorrelation operation based on the first amplitude sequence and the second amplitude sequence to determine a time interval from the emission of the laser pulse to the receipt of the reflected pulse; and determining the distance information of the detection object according to the time interval.
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