WO2020182217A1

WO2020182217A1 - Spread spectrum modulation-based laser ranging system and method

Info

Publication number: WO2020182217A1
Application number: PCT/CN2020/079333
Authority: WO
Inventors: 张高飞; 王俊亚; 尤政
Original assignee: 清华大学
Priority date: 2019-03-14
Filing date: 2020-03-13
Publication date: 2020-09-17
Also published as: CN109884654B; CN109884654A

Abstract

A spread spectrum modulation-based laser ranging system and method. The system comprises: an FPGA (100), for generating a high-frequency clock, using the high-frequency clock to generate a pseudo random sequence code by driving, performing frequency division processing on the high-frequency clock to obtain a high-frequency periodic code, and using the pseudo random sequence code and the high-frequency periodic code to modulate a low-frequency data code to obtain a modulation signal; a laser emitting module (200), for modulating a laser signal according to the modulation signal to obtain a modulated optical signal, and emitting the modulated optical signal to a target to be detected; a laser receiving module (300), for receiving an echo optical signal reflected by said target, and converting the echo optical signal into a digital sequence. The FPGA (100) is further used to determine a distance between the system and said target according to the digital sequence, the pseudo random sequence and the high-frequency periodic code. The system and method implement laser ranging satisfying high speed, high precision and long range.

Description

Laser ranging system and method based on spread spectrum modulation

Cross references to related applications

This application claims the priority of the Chinese Patent Application No. “201910192859.X” filed by Tsinghua University on March 14, 2019 with the title of “Laser Ranging System and Method Based on Spread Spectrum Modulation”.

Technical field

The present invention relates to the technical field of signal processing, in particular to a laser ranging system and method based on spread spectrum modulation.

Background technique

Laser ranging is one of the key technologies of lidar, especially micro-electromechanical systems (MEMS) solid-state lidar. In the application of MEMS solid-state imaging lidar, especially the solid-state lidar used for autonomous driving, laser power, radar resolution, frame rate, accuracy, and range are required to meet certain conditions, as well as vehicle regulations and costs. Requirements.

In related technologies, commonly used laser ranging methods include pulse method, phase method and coherent method. Among them, the ranging accuracy of the pulse method is limited by the clock frequency and stability of its counter. A stable counter of hundreds of megabytes is very expensive, and a dedicated time interval measurement chip requires a complex pulse-shaping analog circuit; the phase method requires Larger power lasers can meet the corresponding range and accuracy, and it requires multiple rulers for time-sharing measurement, so the frame rate is low; the coherent method has a short range when used on the ground, and must meet the signal light and The local oscillator has the same direction and polarization direction, so its receiving optical antenna is very complicated.

Therefore, for low-power MEMS solid-state imaging lidars, how to improve the range and measurement accuracy under the limitation of low-power lasers and ensure a certain frame frequency has become an urgent problem to be solved.

Summary of the invention

The present invention proposes a laser ranging system and method based on spread spectrum modulation to realize laser ranging that meets high speed, high precision, and long range at the same time.

The embodiment of the first aspect of the present invention proposes a laser ranging system based on spread spectrum modulation. The system includes: a field programmable gate array FPGA, a laser emitting module and a laser receiving module,

The FPGA is used to generate a high-frequency clock, use the high-frequency clock to drive to generate a pseudo-random sequence code, and perform frequency division processing on the high-frequency clock to obtain a high-frequency periodic code, and use the pseudo-random sequence code Modulate the low-frequency data code with the high-frequency periodic code to obtain a modulated signal;

The laser emission module is configured to modulate the laser signal according to the modulation signal to obtain a modulated light signal, and transmit the modulated light signal to the target to be measured;

The laser receiving module is configured to receive the echo optical signal reflected by the target to be measured, and convert the echo optical signal into a digital sequence;

The FPGA is also used to determine the distance value between the system and the target under test according to the digital sequence, the pseudo-random sequence, and the high-frequency periodic code.

In the laser ranging system based on spread spectrum modulation of the embodiment of the present invention, a high-frequency clock is generated through FPGA, a pseudo-random sequence code is generated by the high-frequency clock drive, and the high-frequency clock is frequency-divided to obtain a high-frequency periodic code. Pseudo-random sequence code and high-frequency periodic code modulate the low-frequency data code to obtain a modulated signal, and then modulate the laser signal according to the modulated signal through the laser transmitter module to obtain a modulated light signal, and emit modulated light to the target under test The laser receiving module receives the echo optical signal reflected by the target to be measured, and converts the echo optical signal into a digital sequence. Finally, the FPGA determines the system and the system to be tested based on the digital sequence, pseudo-random sequence, and high-frequency periodic code The distance value between targets. In the present invention, the hardware structure of the system is simple, does not require hardware mixing and complex optical antennas, has little dependence on laser power, can achieve high-speed, high-precision, and long-range laser ranging at the same time, and is suitable for low laser power requirements. However, in equipment that requires long range, high accuracy, and fast speed, such as MEMS solid-state imaging lidar.

An embodiment of the first aspect of the present invention proposes a laser ranging method based on spread spectrum modulation, including:

Obtaining a pseudo-random sequence code and a high-frequency periodic code; wherein the pseudo-random sequence code is generated by driving a high-frequency clock, and the high-frequency periodic code is obtained by frequency-dividing the high-frequency clock;

Modulate the low-frequency data code by using the pseudo-random sequence code and the high-frequency periodic code to obtain a modulated signal;

According to the modulation signal, modulate the laser signal to obtain a modulated optical signal, and transmit the modulated optical signal to the target to be measured;

Receiving the echo optical signal reflected by the target to be measured, and converting the echo optical signal into a digital sequence;

According to the digital sequence, the pseudo-random sequence, and the high-frequency periodic code, the distance value between the system and the target to be measured is determined.

According to the laser ranging method based on spread spectrum modulation in the embodiment of the present invention, the pseudo-random sequence code and the high-frequency periodic code are obtained, and the low-frequency data code is modulated by the pseudo-random sequence code and the high-frequency periodic code to obtain the modulated signal. Modulate the signal to modulate the laser signal to obtain the modulated optical signal, and transmit the modulated optical signal to the target under test, and receive the echo optical signal reflected by the target under test, and convert the echo optical signal into a digital sequence. Finally, According to the digital sequence, pseudo-random sequence, high-frequency periodic code, determine the distance between the system and the target under test. As a result, it is possible to realize laser ranging that meets high-speed, high-precision, and long-range measurement at the same time. It is suitable for distance measurement equipment that requires less laser power, but requires a long range, high accuracy, and fast speed. For example, it can be used Used in MEMS solid-state imaging lidar.

The additional aspects and advantages of the present invention will be partly given in the following description, and partly will become obvious from the following description, or be understood through the practice of the present invention.

Description of the drawings

The above and/or additional aspects and advantages of the present invention will become obvious and easy to understand from the following description of the embodiments in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic structural diagram of a laser ranging system based on spread spectrum modulation provided by Embodiment 1 of the present invention;

2 is a schematic diagram of the principle of a laser ranging method based on spread spectrum modulation provided by the second embodiment of the present invention;

3 is a schematic structural diagram of a laser ranging system based on spread spectrum modulation provided by Embodiment 3 of the present invention;

4 is a schematic structural diagram of a laser ranging system based on spread spectrum modulation provided by the fourth embodiment of the present invention;

5 is a schematic flowchart of a laser ranging method based on spread spectrum modulation according to Embodiment 5 of the present invention;

6 is a schematic flowchart of a laser ranging method based on spread spectrum modulation provided by Embodiment 6 of the present invention.

detailed description

The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention, but should not be construed as limiting the present invention.

The laser ranging system and method based on spread spectrum modulation according to embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic structural diagram of a laser ranging system based on spread spectrum modulation provided by Embodiment 1 of the present invention.

As shown in FIG. 1, the laser ranging system based on spread spectrum modulation may include: a Field-Programmable Gate Array (FPGA) 100, a laser emitting module 200, and a laser receiving module 300.

Among them, FPGA100 is used to generate a high-frequency clock, use the high-frequency clock to drive to generate a pseudo-random sequence code, and divide the high-frequency clock to obtain a high-frequency periodic code, and use the pseudo-random sequence code and the high-frequency periodic code to pair The low-frequency data code is modulated to obtain a modulated signal.

In the embodiment of the present invention, the FPGA 100 may include a phase-locked loop (Phase-Locked Loop, PLL for short) circuit. The PLL circuit inside the FPGA 100 generates a high-frequency clock as the clock of the pseudo-random sequence code, and uses the high-frequency clock to drive to generate a A high-frequency pseudo-random sequence code, for example, if the frequency of the high-frequency clock is 150 MHz, the frequency of the pseudo-random sequence code is 150 MHz. In the present invention, the advantage of providing a high-frequency clock by a PLL circuit is that it can avoid the phase jitter and drift caused by the signal processing through the multi-stage circuit, facilitate the subsequent laser receiving module 300 to perform code synchronization and frame synchronization, and facilitate circuit sampling synchronization , Which greatly improves the error caused by phase drift.

In the embodiment of the present invention, the high-frequency periodic code is a high-frequency periodic square wave code, and the high-frequency periodic code is obtained by frequency-dividing the high-frequency clock generated by the PLL circuit. For example, if the frequency of the high-frequency clock is 150MHz, the high-frequency clock is divided by 10 to obtain the periodic square wave code, and the obtained periodic square wave code is used as the high-frequency periodic code, then the frequency of the high-frequency periodic code is 15MHz.

In the embodiment of the present invention, the low-frequency data code is a low-rate data code. For example, the frequency of the low-frequency periodic code may be 150KHz, and the bandwidth may be 2Kb. The low-frequency data code can carry device information (such as device ID), pixel information (such as pixel ID for imaging radar), verification information, and so on in the system. For example, the low-frequency data code may be an all-zero sequence, an all-one sequence, or other sequences, which is not limited in the present invention. Among them, the pseudo-random sequence code, the high frequency periodic code and the low frequency data code are the same clock.

In the embodiment of the present invention, the low frequency data code can be spread spectrum modulated by the high frequency periodic code first to obtain the spread spectrum signal, and then the pseudo random sequence code is used to modulate (spread spectrum) the above spread spectrum signal to obtain the modulated signal. For example, referring to FIG. 2, the high-frequency periodic code F1 and the low-frequency data code D can be XORed to obtain a spread-spectrum signal, and then the spread-spectrum signal and the pseudo-random sequence code M can be XORed to obtain the modulated signal S.

The laser emission module 200 is used to modulate the laser signal according to the modulation signal to obtain a modulated light signal, and transmit the modulated light signal to the target to be measured.

In the embodiment of the present invention, the target to be tested may be a human, animal, plant, building, etc., which is not limited in the present invention.

In the embodiment of the present invention, after the modulation signal is obtained, the laser signal can be used as a carrier signal to modulate the laser signal according to the modulation signal to obtain a modulated optical signal, and transmit the modulated optical signal to the target to be measured.

As shown in FIG. 3, the laser emitting module 200 may include: a high-speed laser driving circuit (for example, a laser diode driving circuit), a pulsed laser (for example, a laser diode), and a transmitting optical antenna. Specifically, the high-speed laser drive circuit can modulate the laser signal generated by the pulse laser according to the modulation signal to generate a measurement beam, which is referred to as a modulated optical signal in the present invention. After that, the modulated light signal can be transmitted to the target under test through the transmitting optical antenna.

The laser receiving module 300 is used to receive the echo optical signal reflected by the target to be measured, and convert the echo optical signal into a digital sequence.

In the embodiment of the present invention, when the modulated light signal irradiates the surface of the target to be measured, the reflected laser signal is recorded as the echo light signal received by the laser receiving module 300 and converted into a digital sequence that the FPGA 100 can process.

As shown in Figure 3, the laser receiving module may include a receiving optical antenna, a photodetector, an amplifier, and a high-speed analog comparator. Among them, the receiving optical antenna is used to receive the echo optical signal reflected by the target to be measured; the photodetector is used to convert the echo optical signal into an electrical signal; the amplifier is used to amplify the electrical signal; a high-speed analog comparator, Used to convert the amplified electrical signal into a digital sequence. For example, a high-speed analog comparator can compare the electrical signal with a preset standard value. When the electrical signal is greater than or equal to the standard value, output high (or low) electrical When the electrical signal is less than the standard value, the output low (or high) level, so that the converted digital sequence can be obtained.

Among them, the photodetector can be a photodiode, an avalanche diode, a silicon photomultiplier tube, and so on.

FPGA100 is also used to determine the distance between the system and the target under test according to the digital sequence, pseudo-random sequence, and high-frequency periodic code.

In the embodiment of the present invention, after the laser receiving module 300 processes the digital sequence, the FPGA 100 can determine the distance between the system and the target to be measured according to the digital sequence, pseudo-random sequence, and high-frequency periodic code.

In the embodiment of the present invention, a rough first distance value can be obtained by calculation first according to the pseudo-random sequence and the digital sequence. Specifically, a pseudo-random sequence code can be used to demodulate the digital sequence to obtain the first sequence, and the first distance value can be calculated according to the first sequence and the low-frequency data code.

Among them, the rough measurement result, that is, the accuracy of the first distance value is determined according to the frequency of the high-frequency periodic code, the frequency of marking the high-frequency periodic code is f, then the measurement accuracy of the system is c/(2f), and c is the speed of light. For example, when the frequency of the high-frequency periodic code is 150MHz, the measurement accuracy is 3*10 ⁸ /(2*1.5*10 ⁸ )=1m. In addition, the measurement range of the system is determined according to the code length and measurement accuracy of the pseudo-random sequence code. For example, if the length of the pseudo-random sequence code is 1023 and the accuracy is 1m, the measurement range is 1023 meters, and the one-way measurement range is 1023/ 2=511.5 meters. The ranging speed or frame rate of the system is determined by the speed of the high-speed analog comparator.

Refer to Figure 2 to mark the digital sequence as R. You can first XOR the pseudo-random sequence code with the digital sequence R to obtain the first sequence. At this time, you can compare the first sequence with the low-frequency data code and count the first sequence. The number of elements at the corresponding position in the low-frequency data code is different, and the first distance value is determined according to the number of statistics.

For example, if the values of the elements at N positions in the first sequence and the low-frequency data code are different, the first distance value is: N*c/(2f), where N is the code not greater than the pseudo-random sequence code Long natural number. For example, when the frequency of the high-frequency data code is 150MHz, the measurement accuracy is 1m, and if N=5, the first distance value is 5m.

It should be noted that the accuracy of the rough measurement result obtained by the measurement of the above system is determined according to the frequency of the high-frequency periodic code. For example, when the frequency of the high-frequency periodic code is 150MHz, the measurement accuracy is 1m. The result is an integer, that is, the first distance value is an integer, and the accuracy or accuracy of the measurement result is not high.

Therefore, in the embodiment of the present invention, in order to improve the accuracy of the ranging result, the high-frequency periodic code and the first sequence can also be used to calculate a precise second distance value. Specifically, the first sequence can be demodulated according to the high-frequency periodic code to obtain the second sequence, and the first sequence can be demodulated according to the phase-shifted high-frequency periodic code to obtain the third sequence, and calculate The phase difference between the second sequence and the third sequence is calculated according to the phase difference to obtain the second distance value.

For example, referring to Figure 2, the first sequence can be XORed with the high-frequency periodic code to obtain the second sequence, the high-frequency periodic code is phase-shifted by 90 degrees, and the high-frequency periodic code after the 90-degree phase shift is processed. Perform exclusive OR processing with the first sequence to obtain the third sequence. After that, the phase difference between the second sequence and the third sequence can be calculated, and the second distance value can be calculated according to the formula of phase difference and distance in the related technology.

In the present invention, the calculated second distance value is determined based on the phase difference, and the precision measurement result is a decimal value. Therefore, the first distance value and the second distance value can be added to obtain the distance between the system and the target to be measured. The distance value, thereby, improves the accuracy of the ranging result.

In summary, the ranging accuracy of the laser ranging system based on spread spectrum modulation is determined based on the frequency and phase difference of the high-frequency periodic code, and the ranging accuracy is high; the ranging is based on the code length and measurement of the pseudo-random sequence code The accuracy is determined. When the code length of the pseudo-random sequence code is large, the measurement range is longer; the ranging speed or frame frequency is determined by the speed/frequency of the high-speed analog comparator. When the frequency of the high-speed analog comparator is higher or When the speed is faster, the ranging speed is faster. Therefore, the laser ranging system based on spread spectrum modulation according to the embodiment of the present invention can achieve high-speed, high-precision, and long-range laser ranging at the same time. It is suitable for low laser power requirements, but long range and accuracy Among high-speed, high-speed equipment, such as MEMS solid-state imaging lidar.

In the embodiment of the present invention, the system combines the simple hardware of pulse laser ranging, the high precision of the phase method and the long measurement range of the coherent heterodyne method. It greatly simplifies the design of the hardware circuit, avoids the phase shift problem that may be caused by multiple circuit links, avoids the complicated optical system of optical heterodyne detection, and directly converts the electrical signal into a high-speed digital sequence for processing by the FPGA after amplification. The final ranging result. In addition, the hardware transmitting and receiving circuits similar to the pulse method are used, the phase method is used to improve the ranging accuracy, and the coherent heterodyne method is used to improve the measurement range. There is no need for high-resolution counters, hardware mixers, and optical mixing. It reduces the cost of a single machine and increases the reliability of the system.

In the laser ranging system based on spread spectrum modulation in the embodiment of the present invention, a pseudo-random sequence code is generated by the FPGA high-frequency clock and driven by the high-frequency clock, and the high-frequency clock is frequency-divided to obtain the high-frequency periodic code. Random sequence code and high frequency periodic code modulate low frequency data code to obtain modulation signal, and then through laser emission module according to modulation signal, modulate laser signal to obtain modulated light signal, and transmit the modulated light signal to the target under test , And receive the echo optical signal reflected by the target under test through the laser receiving module, and convert the echo optical signal into a digital sequence. Finally, the FPGA determines the system and the target under test according to the digital sequence, pseudo-random sequence, and high-frequency periodic code The distance value between. In the present invention, the hardware structure of the system is simple, does not require hardware mixing and complex optical antennas, has little dependence on laser power, can achieve high-speed, high-precision, and long-range laser ranging at the same time, and is suitable for low laser power requirements. However, in equipment that requires long range, high accuracy, and fast speed, such as MEMS solid-state imaging lidar.

As a possible implementation, in order to avoid noise data and interference with the ranging result, see Figure 4. Based on the embodiment shown in Figure 3, a high-pass filter can also be set between the amplifier and the high-speed analog comparator. , The amplified electrical signal is filtered.

It should be noted that in actual applications, the echo optical signal received by the laser receiving module 300 may not be reflected by the modulated optical signal through the target to be measured. For example, when the system transmits a modulated light signal to the target under test, the user transmits to the target under test through other laser signals. At this time, the echo optical signal received by the laser receiving module 300 may also be interference from the user’s emission. signal. Therefore, in the present invention, referring to FIG. 2, after the second sequence is determined, the second sequence can be compared with the low-frequency data code. If the second sequence is inconsistent with the low-frequency data code, the echo light received by the laser receiving module 300 is determined The signal is an interference signal. At this time, the second sequence, the first sequence, and the digital sequence can be discarded.

If the second sequence is consistent with the low-frequency data code, the first sequence is demodulated according to the phase-shifted high-frequency periodic code to obtain the third sequence, and then according to the phase difference between the second sequence and the third sequence , To determine the second distance value between the system and the target under test.

In order to realize the above embodiments, the present invention also proposes a laser ranging method based on spread spectrum modulation.

FIG. 5 is a schematic flowchart of a laser ranging method based on spread spectrum modulation according to Embodiment 5 of the present invention.

As shown in FIG. 5, the laser ranging method based on spread spectrum modulation may include the following steps:

Step 101: Obtain a pseudo-random sequence code and a high-frequency periodic code; wherein the pseudo-random sequence code is generated by driving a high-frequency clock, and the high-frequency periodic code is obtained by dividing the high-frequency clock.

The laser ranging method based on spread spectrum modulation in the embodiment of the present invention can be applied to the laser ranging system based on spread spectrum modulation in the embodiments shown in FIG. 1 to FIG. 4.

In the embodiment of the present invention, a high-frequency clock can be generated by the PLL circuit inside the FPGA as the clock of the pseudo-random sequence code, and a high-frequency pseudo-random sequence code is generated by the high-frequency clock drive. For example, the frequency of the high-frequency clock is 150MHz, the frequency of the pseudo-random sequence code is 150MHz.

Step 102: Use the pseudo-random sequence code and the high-frequency periodic code to modulate the low-frequency data code to obtain a modulated signal.

In the embodiment of the present invention, the low frequency data code can be spread spectrum modulated by the high frequency periodic code first to obtain the spread spectrum signal, and then the pseudo random sequence code is used to modulate (spread spectrum) the above spread spectrum signal to obtain the modulated signal. For example, referring to Figure 2, the high-frequency periodic code F1 and the low-frequency data code D can be XORed to obtain a spread spectrum signal. After that, the spread spectrum signal and the pseudo-random sequence code M can be XORed to obtain a modulated signal S.

Step 103: According to the modulation signal, modulate the laser signal to obtain a modulated optical signal, and transmit the modulated optical signal to the target to be measured.

Step 104: Receive the echo optical signal reflected by the target to be measured, and convert the echo optical signal into a digital sequence.

In the embodiment of the present invention, when the modulated light signal irradiates the surface of the target to be measured, the reflected laser signal is referred to as the echo light signal in the present invention, and can be determined by the laser receiving module in the laser ranging system based on spread spectrum modulation. Receive and convert to digital signals that FPGA can process.

Specifically, the laser receiving module can convert the echo optical signal into an electrical signal, perform amplifying processing on the electrical signal, and convert the amplified electrical signal into a digital sequence.

Step 105: Determine the distance between the system and the target to be measured according to the digital sequence, the pseudo-random sequence, and the high-frequency periodic code.

Among them, the rough measurement result, that is, the accuracy of the first distance value is determined according to the frequency of the high-frequency periodic code, the frequency of marking the high-frequency periodic code is f, then the measurement accuracy of the system is c/(2f), and c is the speed of light. For example, when the frequency of the high-frequency periodic code is 150MHz, the measurement accuracy is 3*10 ⁸ /(2*1.5*10 ⁸ )=1m. In addition, the measurement range of the system is determined according to the code length and measurement accuracy of the pseudo-random sequence code. For example, if the length of the pseudo-random sequence code is 1023 and the accuracy is 1m, the measurement range is 1023 meters, and the one-way measurement range is 1023/ 2=511.5 meters. The ranging speed or frame rate of the system is determined by the speed/frequency of the high-speed analog comparator.

In the present invention, the calculated second distance value is determined based on the phase difference, and the precision measurement result is a decimal value. Therefore, the first distance value and the second distance value can be added to obtain the distance between the system and the target to be measured. Distance value.

It should be noted that in actual applications, the received echo optical signal may not be reflected by the modulated optical signal through the target to be measured. For example, when the system transmits a modulated light signal to the target under test, the user transmits to the target under test through other laser signals. At this time, the echo optical signal received by the laser receiving module may also be an interference signal transmitted by the user. . Therefore, in the present invention, after the second sequence is determined, the second sequence can be compared with the low-frequency data code. If the second sequence is inconsistent with the low-frequency data code, it is determined that the echo optical signal received by the laser receiving module is an interference signal. At this time, the second sequence, the first sequence, and the digital sequence can be discarded. The above process will be described in detail below with reference to FIG. 6.

As shown in FIG. 6, based on the embodiment shown in FIG. 5, step 105 may specifically include the following sub-steps:

Step 201: Perform demodulation processing on the digital sequence according to the pseudo-random sequence code to obtain the first sequence.

For example, referring to Figure 2, marking the digital sequence as R, the pseudo-random sequence code and the digital sequence R can be XORed first to obtain the first sequence.

Step 202: According to the first sequence and the low-frequency data code, a first distance value is calculated.

In the embodiment of the present invention, the first sequence can be compared with the low-frequency data code, the number of elements at corresponding positions in the first sequence and the low-frequency data code with different values is counted, and the first distance value is determined according to the counted number .

For example, if the number of elements with different values in the corresponding positions in the first sequence and the low-frequency data code is marked as N, the first distance value is: N*c/(2f).

Step 203: Perform demodulation processing on the first sequence according to the high frequency periodic code to obtain the second sequence.

For example, referring to FIG. 2, the first sequence and the high-frequency periodic code can be XORed to obtain the second sequence.

It should be noted that the present invention only uses step 203 to perform an example after step 202. In practical applications, in order to improve the real-time performance of ranging, step 203 can be performed in parallel with step 202, or step 203 can also be performed before step 202. There is no restriction on this.

Step 204: Determine whether the second sequence is consistent with the low-frequency data code, if yes, execute step 206, if not, execute step 205.

Step 205: Discard the second sequence, the first sequence, and the digital sequence.

In the embodiment of the present invention, when the second sequence is inconsistent with the low-frequency data code, it can be determined that the received echo optical signal is an interference signal. At this time, the second sequence, the first sequence, and the digital sequence can be discarded.

Step 206: Perform demodulation processing on the first sequence according to the high-frequency periodic code after the phase shift processing to obtain the third sequence.

For example, referring to FIG. 2, the high-frequency periodic code can be phase-shifted by 90 degrees, and the high-frequency periodic code after the 90-degree phase-shift processing can be XORed with the first sequence to obtain the third sequence.

Step 207: Calculate the phase difference between the second sequence and the third sequence, and calculate the second distance value according to the phase difference.

In the embodiment of the present invention, after the phase difference between the second sequence and the third sequence is calculated, the second distance value may be calculated based on the formula of the phase difference and the distance in the related technology.

Step 208: Determine the distance value between the system and the target to be measured according to the first distance value and the second distance value.

In the embodiment of the present invention, the first distance value and the second distance value may be added to obtain the distance value between the system and the target to be measured. Therefore, the accuracy of the ranging result can be improved.

In the description of this specification, descriptions with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean specific features described in conjunction with the embodiment or example , Structure, materials or features are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples and the characteristics of the different embodiments or examples described in this specification without contradicting each other.

The scope of the preferred embodiments of the present invention includes additional implementations, which may not be in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order according to the functions involved. The embodiments of the invention are understood by those skilled in the art to which the embodiments of the invention belong.

It should be understood that each part of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if it is implemented by hardware as in another embodiment, it can be implemented by any one or a combination of the following technologies known in the art: Discrete logic gate circuits for implementing logic functions on data signals Logic circuit, application specific integrated circuit with suitable combinational logic gate, programmable gate array (PGA), field programmable gate array (FPGA), etc.

The functional units in each embodiment of the present invention may be integrated into one processing module, or each unit may exist alone physically, or two or more units may be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or software functional modules. If the integrated module is implemented in the form of a software function module and sold or used as an independent product, it may also be stored in a computer readable storage medium.

The aforementioned storage medium may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can comment on the foregoing within the scope of the present invention. The embodiment undergoes changes, modifications, substitutions and modifications.

Claims

A laser ranging system based on spread spectrum modulation, characterized in that the system comprises: a field programmable gate array FPGA, a laser emitting module and a laser receiving module,

The FPGA is used to generate a high-frequency clock, use the high-frequency clock to drive to generate a pseudo-random sequence code, and perform frequency division processing on the high-frequency clock to obtain a high-frequency periodic code, and use the pseudo-random sequence code Modulate the low-frequency data code with the high-frequency periodic code to obtain a modulated signal;

The laser emission module is configured to modulate the laser signal according to the modulation signal to obtain a modulated light signal, and transmit the modulated light signal to the target to be measured;

The laser receiving module is configured to receive the echo optical signal reflected by the target to be measured, and convert the echo optical signal into a digital sequence;

The FPGA is also used to determine the distance value between the system and the target under test according to the digital sequence, the pseudo-random sequence, and the high-frequency periodic code.
The system of claim 1, wherein the laser receiving module comprises: a receiving optical antenna, a photodetector, an amplifier and a high-speed analog comparator,

The receiving optical antenna is used to receive the echo optical signal reflected by the target to be measured;

The photodetector is used to convert the echo optical signal into an electrical signal;

The amplifier is used to amplify the electrical signal;

The high-speed analog comparator is used to convert the amplified electrical signal into the digital sequence.
The system of claim 2, wherein the laser receiving module further comprises: a high-pass filter,

The high-pass filter is used for filtering the amplified electrical signal.
The system according to claim 1, wherein the FPGA includes a phase-locked loop circuit, and the high-frequency clock is generated by the phase-locked loop circuit.
The system according to claim 1, wherein the FPGA is specifically used for:

Performing demodulation processing on the digital sequence according to the pseudo-random sequence code to obtain a first sequence;

According to the first sequence and the low-frequency data code, a first distance value is calculated.
The system of claim 5, wherein the FPGA is also used for:

Performing demodulation processing on the first sequence according to the high-frequency periodic code to obtain a second sequence;

Judging whether the second sequence is consistent with the low-frequency data code;

If they are consistent, perform demodulation processing on the first sequence according to the high-frequency periodic code after phase shift processing to obtain a third sequence;

Calculate the phase difference between the second sequence and the third sequence, and calculate the second distance value according to the phase difference.
The system of claim 6, wherein the FPGA is also used for:

According to the first distance value and the second distance value, the distance value between the system and the target to be measured is determined.
A laser ranging method based on spread spectrum modulation, characterized in that the method includes the following steps:

Obtaining a pseudo-random sequence code and a high-frequency periodic code; wherein the pseudo-random sequence code is generated by driving a high-frequency clock, and the high-frequency periodic code is obtained by frequency-dividing the high-frequency clock;

Modulate the low-frequency data code by using the pseudo-random sequence code and the high-frequency periodic code to obtain a modulated signal;

According to the modulation signal, modulate the laser signal to obtain a modulated optical signal, and transmit the modulated optical signal to the target to be measured;

Receiving the echo optical signal reflected by the target to be measured, and converting the echo optical signal into a digital sequence;

According to the digital sequence, the pseudo-random sequence, and the high-frequency periodic code, the distance value between the system and the target to be measured is determined.
The method according to claim 8, wherein the determining the distance value between the system and the target under test according to the digital sequence, the pseudo-random sequence, and the high-frequency periodic code, include:

Performing demodulation processing on the digital sequence according to the pseudo-random sequence code to obtain a first sequence;

Calculating a first distance value according to the first sequence and the low-frequency data code;

Performing demodulation processing on the first sequence according to the high-frequency periodic code to obtain a second sequence;

Judging whether the second sequence is consistent with the low-frequency data code;

If the second sequence is consistent with the low-frequency data code, performing demodulation processing on the first sequence according to the high-frequency periodic code after phase shift processing to obtain a third sequence;

Calculating a phase difference between the second sequence and the third sequence, and calculating a second distance value according to the phase difference;

According to the first distance value and the second distance value, the distance value between the system and the target to be measured is determined.
The method of claim 9, wherein the method further comprises:

If the second sequence is inconsistent with the low-frequency data code, the second sequence, the first sequence, and the digital sequence are discarded.