CN212845916U - Light emitting module, optical signal detection module, optical system and laser radar system - Google Patents

Abstract

Disclosed herein are a light emitting module, a light signal detecting module, an optical system and a laser radar system. The light emitting module includes: the high-frequency modulation signal output unit is used for outputting preset high-frequency modulation signals with at least two different frequencies; the laser emission unit is connected with the high-frequency modulation signal output unit and is arranged to emit at least two laser beams with different frequencies which are respectively modulated by the at least two high-frequency modulation signals with different frequencies; the laser emission unit comprises a laser, the laser comprises a seed source and an optical fiber amplifier, and the optical fiber amplifier is used for amplifying an optical signal emitted by the seed source.

Description

Light emitting module, optical signal detection module, optical system and laser radar system

Technical Field

The embodiment of the application relates to the technical field of laser ranging, for example to a light emitting module, an optical signal detection module, an optical system and a laser radar system.

Background

The laser radar system is a radar system that detects characteristic quantities such as a position and a speed of a target by emitting a laser beam (a detection light signal). The lidar system may detect, track, and identify a target object by detecting information about the target object, such as parameters of the target object's orientation, distance, altitude, velocity, attitude, and even shape. The laser radar system is an indispensable core sensor in the fields of automobile automatic driving, robot positioning navigation, space environment mapping, security and protection and the like. In practical applications, laser radar systems can be divided into, according to different principles: the system comprises a triangular laser radar system, a pulse laser radar system based on time flight and a phase laser radar system. The phase method laser radar system loads a sine modulation signal with a certain frequency on a laser, and measures the distance of a measured target object by using distance information contained in a phase difference between a transmitting signal (a probe light signal) and a receiving signal (an echo signal).

However, the existing phase-method lidar scheme mainly uses dual-transmission to implement signal comparison, the stability of the transmitter is lower than that of the receiver, and the dual-transmission causes the stability of the whole system to be affected to a certain extent.

SUMMERY OF THE UTILITY MODEL

The application provides a light emission module, light signal detection module, optical system and laser radar system to the high stability realizes carrying out the high detection precision to target object, the range measurement of big detection range.

In a first aspect, a light emitting module includes:

the high-frequency modulation signal output unit is used for outputting preset high-frequency modulation signals with at least two different frequencies;

the laser emission unit is connected with the high-frequency modulation signal output unit and is arranged to emit at least two laser beams with different frequencies which are respectively modulated by the at least two high-frequency modulation signals with different frequencies;

the laser emission unit comprises a laser, the laser comprises a seed source and an optical fiber amplifier, and the optical fiber amplifier is used for amplifying an optical signal emitted by the seed source.

In a second aspect, an optical signal detection module includes:

an echo signal receiving unit configured to receive a first high-frequency echo signal and a second high-frequency echo signal, where the first high-frequency echo signal is a laser beam obtained by reflecting a first laser beam by a target object, and the second high-frequency echo signal is a laser beam obtained by reflecting a second laser beam by the target object;

a reference signal receiving unit configured to receive a first reference signal and a second reference signal, wherein the first reference signal is a reference signal modulated by a first high-frequency modulation signal, and the second reference signal is a reference signal modulated by a second high-frequency modulation signal;

the first laser beam is a laser beam modulated by the first high-frequency modulation signal, and the second laser beam is a laser beam modulated by the second high-frequency modulation signal; the frequency of the first high-frequency modulation signal is greater than the frequency of the second high-frequency modulation signal;

the signal processing unit is simultaneously electrically connected with the echo signal receiving unit and the reference signal receiving unit; the signal processing unit is configured to: acquiring a first reference distance value of the target object according to a first phase difference between the first reference signal and the first high-frequency echo signal; acquiring a second reference distance value of the target object according to the first phase difference and the second phase difference, and determining a measurement distance value of the target object according to the first reference distance value and the second reference distance value; wherein the second phase difference is a phase difference between the second reference signal and the second high frequency echo signal.

In a third aspect, an optical system includes: the optical signal detection module and the light emitting module connected with the optical signal detection module;

the light emitting module comprises a high-frequency modulation signal output unit and a laser emitting unit, wherein the high-frequency modulation signal output unit is set to output preset high-frequency modulation signals with at least two different frequencies; the laser emission unit is set to emit at least two laser beams with different frequencies which are respectively modulated by at least two high-frequency modulation signals with different frequencies;

a part of the laser beams with at least two different frequencies is emitted out to be reflected by a target object and received by the echo signal receiving unit; the other part of the two laser beams with different frequencies is directly received by the reference signal receiving unit as a reference signal;

the laser emission unit comprises a laser, the laser comprises a seed source and an optical fiber amplifier, and the optical fiber amplifier is used for amplifying an optical signal emitted by the seed source.

In a fourth aspect, a lidar system comprising an optical system as described above

The optical transmission module provided by the embodiment of the application adopts the laser comprising the seed source and the optical fiber amplifier, so that the transmission power is greatly improved; the optical signal detection module adopts a double-receiving scheme of the echo signal receiving unit and the reference signal receiving unit, and the stability of the receiver is higher than that of the transmitter, so that the stability of an optical system and a laser radar system applying the optical signal detection module is greatly improved. In addition, the emitted laser is modulated by at least two high-frequency modulation signals, so that the measurement precision and the measuring range can be considered.

Drawings

Fig. 1 is a schematic structural diagram of an optical transmit module according to an embodiment of the present disclosure;

fig. 2 is a schematic diagram illustrating an operation principle of a frequency synthesizer according to an embodiment of the present application;

fig. 3 is a schematic structural diagram of a laser emitting unit provided in an embodiment of the present application;

fig. 4 is a schematic structural diagram of an optical signal detection module according to an embodiment of the present disclosure;

fig. 5 is a schematic diagram of a differential frequency phase detection technique provided in an embodiment of the present application;

fig. 6 is a schematic flow chart of a digital phase discrimination technique provided in an embodiment of the present application;

fig. 7 is a schematic structural diagram of a laser transmitting unit and a signal receiving unit provided in an embodiment of the present application;

fig. 8 is a block diagram of an optical system according to an embodiment of the present disclosure;

fig. 9 is a schematic diagram of a hardware principle of a laser radar according to an embodiment of the present disclosure;

FIG. 10 is a schematic diagram illustrating a workflow of a lidar system according to an embodiment of the present disclosure;

fig. 11 is a schematic algorithm flow diagram of a laser radar system according to an embodiment of the present application.

Detailed Description

The present application will be described with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. It should be further noted that, for the convenience of description, only some of the structures related to the present application are shown in the drawings, not all of the structures.

The light emitting module and the optical signal detection module provided by the embodiment of the application can be applied to a laser radar system, and the light emitting module and the optical signal detection module are explained in combination with an application scene.

Fig. 1 is a schematic structural diagram of an optical transmit module according to an embodiment. Referring to fig. 1, the light emitting module includes: a high-frequency modulation signal output unit 10 and a laser emitting unit 20.

In an embodiment, the high frequency modulation signal output unit 10 is configured to output preset high frequency modulation signals with at least two different frequencies; and the laser emitting unit 20 is connected with the high-frequency modulation signal output unit 10 and is configured to emit at least two laser beams with different frequencies, which are respectively modulated by the high-frequency modulation signals with at least two different frequencies.

In one embodiment, each high-frequency modulation signal is a master oscillator high-frequency modulation signal; the high frequency modulation signal output unit 10 is further configured to output at least two local oscillator high frequency modulation signals with different frequencies, where the at least two local oscillator high frequency modulation signals correspond to the at least two main oscillator high frequency modulation signals one to one, and each local oscillator high frequency modulation signal differs from the corresponding main oscillator high frequency modulation signal by a preset frequency.

In an embodiment, the high frequency modulation signal output unit 10 includes at least two sets of phase-locked loops, each set of phase-locked loops includes at least two phase-locked loops, and the at least two sets of phase-locked loops are respectively configured to output a main oscillation high frequency modulation signal and a local oscillation high frequency modulation signal corresponding to the main oscillation high frequency modulation signal.

In one embodiment, the absolute value of the difference between the frequencies of the different master oscillator high frequency modulation signals is within a predetermined frequency range. For example, the predetermined frequency range is 0 to 100 MHz.

In an embodiment, the high frequency modulation signal output unit 10 includes two sets of phase-locked loops, each set of phase-locked loops includes four phase-locked loops, each phase-locked loop in one set of phase-locked loops may output a main-oscillation high frequency modulation signal, and each phase-locked loop in the other set of phase-locked loops may output a local-oscillation high frequency modulation signal. At least two sets of phase-locked loops can output at least four sets of high-frequency modulation signals with different frequencies. The Phase-Locked Loop is a feedback control circuit, referred to as a Phase-Locked Loop (PLL).

In this embodiment, the group of high-frequency modulation signals includes a main-oscillator high-frequency modulation signal and a local-oscillator high-frequency modulation signal corresponding to the main-oscillator high-frequency modulation signal.

It is understood that in other embodiments, a Direct Digital Synthesizer (DDS) may be used in the high-frequency modulation signal output unit 10 instead of the phase-locked loop.

Illustratively, fig. 2 is a schematic diagram of an operating principle of a DDS provided in an embodiment. Referring to fig. 2, the DDS includes a phase accumulator 111, a sine look-up table 112, a Digital-to-analog converter (DAC) 113, and a low pass filter (LTP) 114, and the clock signal fc is respectively input to the phase accumulator 111 and the sine look-up table 112, and the frequency control word K is input to the phase accumulator 111.

Where the phase accumulator 111 is the core of the DDS. The phase accumulator 111 is formed by an N-bit binary adder and an N-bit register sampled by the clock signal fc and functions to linearly accumulate the frequency control word K (decimal). The phase accumulator 111 is used to perform phase accumulation and store the accumulation result. When the phase accumulator 111 accumulates the full amount, an overflow is generated to complete a cycle, which is a frequency cycle of the synthesized signal of the DDS system, and the overflow frequency of the phase accumulator 111 is the frequency of the output signal.

The sine lookup table 112 is a programmable read-only memory, and stores a sampling code value of a periodic sine signal with a phase as an address, including digital amplitude information of the periodic sine wave, and each address corresponds to a phase point in the range of 0-2 pi in the sine wave (the phase of 0-2 pi is equally divided into M parts).

The digital-to-analog converter 113 functions to convert a digital signal into an analog signal. In one embodiment, the sinusoidal amplitude sequence is converted to a sine wave. The higher the resolution of the digital-to-analog converter 113 is, the better the continuity of the output sine wave is; when the resolution of the digital-to-analog converter 113 is low, the output sine wave is a trapezoidal waveform, and the trapezoidal waveform becomes an analog waveform fout with a quality (mainly referred to as waveform continuity) meeting the requirement after being filtered by the low-pass filter 114 (the low-pass filter may also be a band-pass filter). The frequency of the output analog waveform fout can be varied here by varying the clock signal fc, the number of bits N of the phase accumulator 111 or the number of bits M of the sine look-up table 112.

In one embodiment, the laser emitting unit 20 may include a laser, which is a laser diode that emits a laser beam having a wavelength of 1550nm band or 2000nm band.

Fig. 3 is a schematic structural diagram of a laser emitting unit according to an embodiment. Referring to fig. 3, the laser emission unit 20 includes a seed source 201, a pump source 202, and at least one stage of a fiber amplifier 203. The seed source 201 is used for emitting a laser beam with one or more wavelengths modulated by the high-frequency modulation signal, and the laser beam may be a continuous sine wave or cosine wave optical signal. The pump source 202 is used for supplying energy to the optical fiber amplifier 203, and the optical fiber amplifier 203 is used for amplifying the modulated laser beam output by the seed source and outputting the amplified modulated laser beam.

In one embodiment, the seed source 201 emits a laser beam having a wavelength in the 1550nm band or 2000nm band, and the fiber amplifier 203 is an erbium doped fiber amplifier or a thulium doped fiber amplifier. The damage threshold of human eyes at 1550nm waveband and 2000nm waveband is high, so the waveband is also called as 'eye-safe waveband', and the output power can be greatly improved by the amplification of the optical fiber amplifier 203.

In one embodiment, the fiber amplifier 203 may be a one-stage amplifier or a multi-stage amplifier connected in series, which may be configured according to actual requirements.

It should be noted that fig. 3 only shows the laser emitting unit 20 including the first-stage fiber amplifier 203 by way of example. In other embodiments, a multi-stage fiber optic pigtail may be used. In addition, a collimating lens may be disposed between any two optical elements in the propagation path of the light beam to reduce the divergence angle of the light beam, or a collimating element may be disposed directly inside the seed source 201, which is not strictly limited herein. In one embodiment, the collimating lens may be a spherical lens.

In one embodiment, the frequency values of the high frequency modulation signals of the four preset different frequencies output by the high frequency modulation signal output unit 10 are: the main oscillation high-frequency modulation signal fg1 is 1093.75MHz, and the local oscillation high-frequency modulation signal fg 1' is 1000 MHz; the main oscillation high-frequency modulation signal fg2 is 1091.75MHz, and the local oscillation high-frequency modulation signal fg 2' is 998 MHz; the main-oscillator high-frequency modulation signal fg3 is 1081.75MHz, the local-oscillator high-frequency modulation signal fg3 is 988MHz, the main-oscillator high-frequency modulation signal fg4 is 1073.75MHz, and the local-oscillator high-frequency modulation signal fg3 is 980MHz, and after the main-oscillator high-frequency modulation signal in each group of high-frequency modulation signals is loaded to the laser emitting unit 20, the laser emitting unit 20 can emit laser beams with corresponding frequencies.

It should be noted that the specific frequency values of the four sets of high-frequency modulation signals are only exemplary, and are not limited; meanwhile, the number of groups of the high-frequency modulation signals output by the high-frequency modulation signal output unit 10 is also merely an exemplary description, and is not limited thereto, and for example, two or four or more groups of high-frequency modulation signals may be output. In other embodiments, the frequency value of the high-frequency modulation signal may be selected according to the actual requirements of the lidar system on the light emitting module, which is not strictly limited herein.

The embodiment of the application provides a light emitting module, through the high frequency modulation signal output unit 10 output preset at least two different frequency's high frequency modulation signal to load on the laser emission unit so that the laser emission unit launches the laser beam of at least two different frequencies, adopt the laser beam of more than two different frequencies to go to survey same distance, can guarantee measuring accuracy while still guaranteed measuring range. Meanwhile, the seed source and the optical fiber amplifier are used as light sources, so that the output power can be greatly improved.

In a phase method laser radar system in the related art, the frequency of a transmitted signal is modulated by using an electrical element, the modulation speed of the transmitted signal is low, and the electromagnetic interference is serious, so that the detection speed of the existing phase method laser radar system is low.

Illustratively, the probe optical signal may include a high frequency transmit signal of 1093.75MHz and a high frequency transmit signal of 1091.75 MHz; by carrying out difference frequency on 1093.75MHz and 1091.75MHz, a low-frequency transmitting signal of 2MHz can be obtained. The high-frequency emission signal can be used as a fine ruler to measure more accurate distance, and the low-frequency emission signal can be used as a coarse ruler to measure farther distance.

It should be noted that the specific frequency values of the high-frequency transmission signal and the low-frequency transmission signal are only exemplary, and are not limited; meanwhile, the selection of the frequency value of the detection light signal is merely an exemplary illustration and is not a limitation. In other embodiments, the frequency values of the high-frequency transmitting signal and the low-frequency transmitting signal and the selection of the frequency value of the detection light signal may be set according to the actual requirement of the laser radar system on the light transmitting unit.

In the scheme provided by the embodiment of the disclosure, a high-frequency emission signal is obtained by using an optical mixing technology, and a low-frequency emission signal is obtained by using a difference frequency technology, so that the problem that a detection optical signal is easily interfered by an electromagnetic signal when an electric element is used for modulating a light beam is avoided. Therefore, the stability of the probe optical signal is high.

The embodiment of the application also provides an optical signal detection module for detecting the echo signal. Fig. 4 is a schematic structural diagram of an optical signal detection module according to an embodiment of the present application. Referring to fig. 4, the optical signal detection module includes: an echo signal receiving unit 42, a reference signal receiving unit 44 and a signal processing unit 50.

In an embodiment, the at least two high frequency modulated signals of different frequencies comprise a first high frequency modulated signal and a second high frequency modulated signal, and the reference signal receiving unit 44 is configured to receive a first reference signal and a second reference signal; the first reference signal is a reference signal which is modulated by a first high-frequency modulation signal and then directly reaches the reference signal receiving unit 44 through an inner light path, and the second reference signal is a reference signal which is sent by the laser transmitting unit and directly reaches the reference signal receiving unit 44 through the inner light path after being modulated by a second high-frequency modulation signal; the echo signal receiving unit 42 is configured to receive a first high-frequency echo signal and a second high-frequency echo signal, the first high-frequency echo signal being a laser beam of the first laser beam reflected by the target object, the second high-frequency echo signal being a laser beam of the second laser beam reflected by the target object; the first laser beam is modulated by a first high-frequency modulation signal, and the second laser beam is modulated by a second high-frequency modulation signal; the frequency of the first high-frequency modulation signal is greater than that of the second high-frequency modulation signal; the signal processing unit 50 is configured to: acquiring a first reference distance value of the target object according to a first phase difference between the first reference signal and the first high-frequency echo signal; acquiring a second reference distance value of the target object according to the first phase difference and the second phase difference, and determining a measurement distance value of the target object according to the first reference distance value and the second reference distance value; wherein the second phase difference is a phase difference between the second reference signal and the second high frequency echo signal.

For example, the first reference distance and the second reference distance may be subjected to a fusion process to obtain the measured distance of the target object, for example, a sum of an integer part of the first reference distance and a fraction point after the second reference distance is used as the measured distance of the target object.

In one embodiment, the at least two reference signals of different frequencies are at least two reference laser beams of different frequencies or at least two reference electrical signals of different frequencies.

In one embodiment, in the case that the at least two reference signals of different frequencies are reference laser beams of at least two different frequencies, the at least two reference signals may be transmitted through the laser transmitting unit and then reach the reference signal receiving unit through the inner optical path.

In one embodiment, the echo signal receiving unit 42, the reference signal receiving units 44 are all connected to the laser transmitting unit 20 in the light emitting module of the above embodiment, the first high-frequency modulation signal is a high-frequency modulation signal with the highest frequency among the high-frequency modulation signals with at least two different frequencies output by the high-frequency modulation signal output unit 10, the second high-frequency modulation signal is all high-frequency modulation signals except the high-frequency modulation signal with the highest frequency among the high-frequency modulation signals with at least two different frequencies output by the high-frequency modulation signal output unit 10, the number of the second high-frequency modulation signals may be one or more, the first reference signal is a signal which is transmitted by the laser transmitting unit 20 and reaches the reference signal receiving unit 44 through the inner optical path after being modulated by the first high-frequency modulation signal, and the second reference signal is a signal which is transmitted by the laser transmitting unit 20 and reaches the reference signal receiving unit 44 through the inner optical path after being modulated by the second high-frequency modulation signal.

In an embodiment, when the second high-frequency modulation signal is multiple, the number of the second laser beams and the number of the second reference signals are multiple, the multiple second laser beams can respectively obtain multiple second high-frequency echo signals, and further can respectively obtain a second phase difference between each second high-frequency echo signal in the multiple second high-frequency echo signals and a second reference signal corresponding to the second high-frequency echo signal, a second reference distance value is obtained according to the multiple second phase differences and one first phase difference, for example, the multiple second reference distance values are obtained according to a third phase difference between each second phase difference in the multiple second phase differences and the first phase difference, and the measured distance value of the target object is determined according to the first reference distance value and the multiple second reference distance values.

In an embodiment, the first reference signal and the second reference signal are a first reference laser beam and a second reference laser beam, respectively, or a first reference electrical signal or a second reference electrical signal, respectively.

In an embodiment, the echo signal receiving unit 42 and the reference signal receiving unit 44 are further configured to: receiving a first local oscillator high-frequency modulation signal; converting the first high-frequency echo signal into a corresponding electric signal, and mixing the electric signal corresponding to the first high-frequency echo signal with a first local oscillator high-frequency modulation signal to obtain a first difference frequency ranging signal; converting the first reference laser beam into a corresponding electric signal and mixing the electric signal corresponding to the first reference laser beam with a first local oscillator high-frequency modulation signal, or mixing the first reference electric signal with the first local oscillator high-frequency modulation signal to obtain a first difference frequency reference signal; receiving a second local oscillator high-frequency modulation signal, converting a second high-frequency echo signal into a corresponding electric signal, and mixing the electric signal corresponding to the second high-frequency echo signal with the second local oscillator high-frequency modulation signal to obtain a second difference frequency ranging signal; converting the second reference laser beam into a corresponding electric signal and mixing the electric signal corresponding to the second reference laser beam with a second local oscillator high-frequency modulation signal, or mixing the second reference electric signal with the second local oscillator high-frequency modulation signal to obtain a second difference frequency reference signal; the first high-frequency modulation signal is a first main-vibration high-frequency modulation signal, the second high-frequency modulation signal is a second main-vibration high-frequency modulation signal, the frequency difference between the first main-vibration high-frequency modulation signal and the first local-vibration high-frequency modulation signal is a preset frequency, and the frequency difference between the second main-vibration high-frequency modulation signal and the second local-vibration high-frequency modulation signal is a preset frequency; the signal processing unit 50 is arranged to obtain a first reference distance value of the target object from the first phase difference between the first reference signal and the first high frequency echo signal by: comparing the first difference frequency ranging signal with the first difference frequency reference signal to obtain a first phase difference, and acquiring a first reference distance value of the target object according to the first phase difference; the signal processing unit 50 is arranged to obtain a second reference distance value of the target object from the first phase difference and the second phase difference by: comparing the second difference frequency ranging signal with a second difference frequency reference signal to obtain a second phase difference; calculating a third phase difference between the second phase difference and the first phase difference; and acquiring a second reference distance value of the target object according to the third phase difference.

In this embodiment, the first local oscillator high frequency modulation signal is a local oscillator high frequency modulation signal output by the modulation signal output unit 10 and corresponding to the first main oscillator high frequency modulation signal, and the second local oscillator high frequency modulation signal is a local oscillator high frequency modulation signal output by the modulation signal output unit 10 and corresponding to the second main oscillator high frequency modulation signal.

In this embodiment, the echo signal receiving unit 42 is configured to receive a high-frequency echo signal reflected by a target object, convert the high-frequency echo signal into a high-frequency electrical signal, and convert the high-frequency electrical signal into a low-frequency electrical signal; the signal processing unit 50 is configured to convert the low-frequency analog electrical signal into a low-frequency digital signal and obtain phase information by using a correlation algorithm, thereby obtaining a distance value of the target object.

The echo signal receiving unit 42 and the reference signal receiving unit 44 actually use a difference frequency phase detection technique in the process of converting the high-frequency electrical signal into the low-frequency electrical signal. The difference frequency phase detection technology is a technology of converting a high-frequency signal into a low-frequency signal, keeping phase information unchanged, and then performing phase detection by using the low-frequency signal.

Fig. 5 is a schematic diagram of a principle of a difference frequency phase detection technique according to an embodiment. Referring to fig. 5, the high frequency modulation signal output unit in the optical transmission module corresponds to a high frequency signal source, and includes a main oscillator and a local oscillator, and each set of high frequency modulation signals output by the high frequency signal source includes a main oscillator high frequency modulation signal and a local oscillator high frequency modulation signal that is different from the main oscillator high frequency modulation signal by a fixed frequency (e.g., 93.75 MHZ). Taking the example of obtaining the first phase difference in the above embodiment, the first master oscillator high frequency modulation signal is loaded on the laser beam to modulate and emit the modulated laser beam (this embodiment mainly explains the principle process of whole optical path ranging, please refer to the above description for specific modulation and amplification of laser, which is not repeated here), the emitted laser beam is divided into two parts, one part reaches the target object, the target object reflects the laser beam to the echo signal receiving unit of the optical signal detection module, the receiver of the echo signal receiving unit receives the first high frequency echo signal obtained by reflecting the laser beam by the target object and converts the first high frequency echo signal into a high frequency electrical signal, the ranging signal mixer in the echo signal receiving unit mixes the high frequency electrical signal with the first local oscillator high frequency modulation signal, a first difference frequency ranging signal of low frequency is obtained.

The other part of the emitted laser beams directly reach a reference receiving signal receiving unit in the optical signal detection module through an inner optical path as a first reference signal, a receiver of the reference receiving unit receives the first reference signal and converts the first reference signal into a high-frequency electric signal, and a reference signal mixer in the reference receiving unit mixes the high-frequency electric signal with a first local oscillator high-frequency modulation signal to obtain a first difference frequency reference signal with a low frequency. The signal processing unit is arranged to obtain a first phase difference by comparing the first difference frequency ranging signal with a first difference frequency reference signal, and further obtain a first reference distance value of the target object through the first phase difference.

In this embodiment, the principle of acquiring the second phase difference is the same as that of acquiring the first phase difference, and details thereof are not repeated here. After the second phase difference is obtained, a third phase difference between the second phase difference and the first phase difference can be calculated, a second reference distance of the target object is further obtained, and the measurement distance of the target object is obtained according to the first reference distance and the second reference distance.

In an embodiment, before determining the measured distance of the target object according to the first reference distance and the second reference distance, the signal processing unit 40 may be further configured to obtain a third reference distance value of the target object according to the second phase difference, calculate a fourth reference distance value according to the third reference distance value and the first reference distance value, and replace the first reference distance value with the fourth reference distance value.

In an embodiment, an average value of the third reference distance value and the first reference distance value may be used as the fourth reference distance value, or the fourth reference distance value may be determined by using a table lookup or the like.

In this embodiment, the phase difference between the difference frequency ranging signal and the high-frequency echo signal is the phase of the local oscillator high-frequency modulation signal, and the phase difference between the main oscillator high-frequency modulation signal and the difference frequency reference signal is also the phase of the local oscillator high-frequency modulation signal, so that the phase difference between the difference frequency ranging signal and the difference frequency reference signal is equal to the phase difference between the high-frequency echo signal and the main oscillator high-frequency modulation signal, that is, since the phase information remains unchanged, the high-frequency signal can be converted into a low-frequency signal for processing, and phase detection is performed by using the low-frequency signal, which reduces the requirement on the analog-to-digital conversion chip, that is, the bandwidth of the post-processing circuit is reduced. On the other hand, due to the reciprocal relation between the frequency and the period, the frequency of the signal to be detected is reduced by the difference frequency phase discrimination technology, so that the period of the signal to be detected is widened, and meanwhile, as the low-frequency signal processing technology is more mature compared with the high-frequency signal processing technology, the high-frequency signal is converted into the low-frequency signal for processing, so that the phase discrimination resolution can be improved, and the phase discrimination precision is improved.

Illustratively, the complete process of sending out and detecting the optical signal shown in fig. 5 is as follows: main vibration high frequency modulation signal respectively generated by main vibration device and local vibration device in high frequency signal source

Modulating signal with local oscillator high frequency

Both are high frequency signals, but different phases, different frequencies, and difference frequenciesIs a low frequency signal. Master vibration high frequency modulation signal

Loaded on a laser beam, emitted to a target object and reflected by the target object to form a high-frequency echo signal

Is received by the signal receiving unit. The high frequency echo signal

And master oscillator high frequency modulation signal

The same frequency, the phase changes, and the amount of change in phase is related to the distance of the target object. The high frequency echo signal

Modulating signal with local oscillator high frequency

Mixing the frequency signals, passing through a Low Pass Filter (LPF), and generating a Low-frequency difference frequency ranging signal

The signal processing path for generating the difference frequency reference signal is as follows: master vibration high frequency modulation signal

Modulating signal with local oscillator high frequency

Mixing the frequency and generating a difference frequency reference signal with low frequency after passing through a low pass filter LPF

Then, the signal processing unit compares the low-frequency difference frequency ranging signal

Difference frequency reference signal with low frequency

Respectively detecting the phase information of the difference frequency ranging signal and the difference frequency reference signal and calculating the phase difference between the phase difference and the high-frequency modulation signal of the master oscillator

And high frequency echo signal

Are the same. Therefore, phase difference information carried by the high-frequency signal can be obtained by processing the low-frequency signal subsequently, and the measured distance value of the target object is finally obtained.

In one embodiment, the signal processing unit detects the phase information using digital phase detection. Digital phase discrimination is a method of digitizing a signal to be detected and then discriminating the phase information of the signal. Fig. 6 is a schematic flowchart of a digital phase detection method according to an embodiment of the present application. Referring to fig. 6, the flow of the digital phase detection method includes: analog quantity signals x (t) to be detected are converted into digital quantity signals x (n) (wherein n is a positive integer) through analog-to-digital conversion, and phase information is obtained through a correlation algorithm. In one embodiment, the core processing unit of the digital phase detection method may be a computer or a microprocessor. The digital phase discrimination method does not depend on a circuit, the whole phase discrimination process is fully digital, and the influence of electromagnetic interference existing in the circuit on a phase discrimination result is avoided, so that the digital phase discrimination method has good anti-interference capability and further has higher phase discrimination precision. Meanwhile, the operation speed is high, and the size is small. The digital phase discrimination method is applied to the laser radar system, so that the speed and the precision (also called resolution) of the distance measurement of the laser radar system can be improved.

It should be noted that, in the above embodiments, the "high frequency" refers to a frequency in the order of hundreds of MHz (for example, above 100 MHz), and the "low frequency" refers to a frequency in the order of MHz (for example, 1MHz to 10 MHz).

In an embodiment, the echo signal receiving unit 42 and the reference signal receiving unit 44 each include a photodetector.

By the arrangement, the three functions of receiving, converting and mixing the first reference signal, the second reference signal, the first high-frequency echo signal and the second high-frequency echo signal can be realized equivalently by using the two photoelectric detectors, so that the number of elements in the optical signal detection module is reduced, the structure of the optical signal detection module is simplified, and the volume of the optical signal detection module is reduced. The photoelectric detector is applied to the laser radar system, and the miniaturization design of the laser radar system is facilitated.

It should be noted that the above-mentioned photodetector is only one design way for the echo signal receiving unit 42 and the reference signal 44, and is not limited. In other embodiments, the functions of receiving, converting and mixing may also be implemented by two or three components. At the moment, the functions realized by the elements are relatively independent, when the signal detection is abnormal, the examination can be rapidly carried out, and the cost for replacing the elements is low.

Fig. 7 is an optical structure schematic diagram of a laser emitting unit and a signal receiving unit according to an embodiment. Referring to fig. 7, each of the echo signal receiving unit 42 and the reference signal receiving unit 44 may further include a receiving lens 213 and an optical filter 214, respectively, the receiving lens 213, the optical filter 214, and the photodetector 211 being sequentially arranged along the propagation direction of the light beam; taking the echo signal receiving unit 42 as an example, the receiving lens 213 is arranged to focus the first high frequency echo signal and the second high frequency echo signal on the photodetector 211; the filter 214 is configured to filter interference signals with other wavelengths through the first high-frequency echo signal and the second high-frequency echo signal, that is, the interference signals are not detected by the photodetector 211, so that the signal-to-noise ratio of the optical signal detection module is improved. The use of filter 214 in a lidar system increases the detection range of the system in high light.

Wherein, due to scattering on the surface of the target object, the echo signal generated by the reflection of the target object will generally diverge, and the intensity of the echo signal received by the photodetector can be enhanced by focusing the diverging echo signal on the photodetector 211 through the receiving lens 213.

In an embodiment, the side of the receiving lens 213 close to the laser emitting unit 20 further includes a short-distance optical path compensation mirror 2131 attached to the light exit surface side of the receiving lens 213, and the short-distance optical path compensation mirror 2131 is configured to focus an echo signal generated by reflection of a short-distance target object onto the photodetector 211, so as to reduce a dead zone caused by a non-coaxial system. Exemplarily, the blind area of the laser radar applied to the laser radar of the non-coaxial system can be reduced to be less than 20 cm.

In one embodiment, the signal processing unit 50 includes an operational amplifier, an analog-to-digital converter, and a field programmable gate array; the input end of the operational amplifier is electrically connected with the signal receiving unit, the output end of the operational amplifier is electrically connected with the input end of the analog-to-digital converter, and the output end of the analog-to-digital converter is electrically connected with the field programmable gate array; the operational amplifier is arranged to amplify the first difference frequency ranging signal, the first difference frequency reference signal, the second difference frequency ranging signal and the second difference frequency reference signal transmitted by the signal receiving unit respectively; the analog-to-digital converter is used for converting the first difference frequency ranging signal, the first difference frequency reference signal, the second difference frequency ranging signal and the second difference frequency reference signal amplified by the operational amplifier from analog quantity signals into digital quantity signals; the field programmable gate array is set to compare a digital quantity signal corresponding to the first difference frequency ranging signal with a digital quantity signal corresponding to the first difference frequency reference signal to obtain a first phase difference, and a first reference distance value of the target object is calculated according to the first phase difference; comparing the digital quantity signal corresponding to the second difference frequency ranging signal with the digital quantity signal corresponding to the second difference frequency reference signal to obtain a second phase difference; calculating a third phase difference between the second phase difference and the first phase difference, and calculating a second reference distance value of the target object according to the third phase difference; and determining a measured distance value of the target object according to the first reference distance value and the second reference distance value.

In one embodiment, the optical signal detection module further includes: the device comprises a power supply unit, a microprocessor unit and a high-voltage regulating unit; the power receiving end of the signal processing unit and the power receiving end of the microprocessor unit are respectively electrically connected with the power supply unit, the first control end of the microprocessor unit is electrically connected with the signal processing unit, and the second control end of the microprocessor unit is electrically connected with the signal receiving unit through the high-voltage adjusting unit; the power supply unit is used for supplying power to the signal processing unit and the microprocessor unit; the microprocessor unit is arranged to control the signal processing unit and is further arranged to adjust the voltage applied to the signal receiving unit by the high voltage adjusting unit so that the signal receiving unit receives echo signals with different intensities.

In one embodiment, the optical signal detection module further comprises a temperature detection unit, a high voltage detection unit and a standard voltage detection unit, wherein the output end of the temperature detection unit, the output end of the high voltage detection unit and the output end of the standard voltage detection unit are respectively electrically connected with the input end of the microprocessor unit; the temperature detection unit is set as the temperature value of the detection signal receiving unit, the high-voltage detection unit is set as the high-voltage value of the detection signal receiving unit, and the standard voltage detection unit is set as the standard voltage value of the detection signal receiving unit; the microprocessor unit is also configured to regulate the voltage output by the high voltage regulation unit according to the temperature value, the high voltage value or the standard voltage value.

Fig. 8 is a block diagram of an optical system according to an embodiment. Referring to fig. 8, the optical system provided in this embodiment may include the light emitting module 60 provided in any embodiment of the above embodiments and the optical signal detecting module 70 provided in any embodiment of the above embodiments, where the optical signal detecting module 70 is connected to the light emitting module 60.

The principle of the light emitting module 60 and the light signal detecting module 70 in this embodiment is the same as that in the above embodiment, and the description thereof is omitted.

In one embodiment, the optical path layout between the optical emitting module 60 and the optical signal detecting module 70 includes: coaxial systems, single transmit and dual receive systems.

The application also provides a laser radar, which comprises the light emitting module and the optical signal detection module provided in any of the above embodiments. Therefore, the laser radar provided by the embodiment of the application has the beneficial effects of the light emitting module and the light signal detection module. The beneficial effects not shown in detail herein can refer to the contents of the light emitting module and the optical signal detecting module in the above embodiments, and are not described herein again.

Fig. 9 is a schematic diagram of a hardware principle of a laser radar according to an embodiment. The principle of lidar light emission and detection is described below in connection with the hardware architecture of the lidar. Referring to fig. 9, the optical transmit module of the lidar includes two sets of phase-locked loops, each set of phase-locked loops includes four phase-locked loops, and the four phase-locked loops perform frequency switching through a switch. The two groups of phase-locked loops are controlled by the field programmable gate array, and the high-frequency modulation signals output by the two groups of phase-locked loops respectively comprise main-vibration high-frequency modulation signals and local-vibration high-frequency modulation signals. Thus, 4 differential rulers can be generated, and the range of the distance measurement can reach 150 meters. Four groups of signals are generated respectively, one group of high-frequency modulation signals are sequentially selected through two four-to-one selector switches respectively, and each group of high-frequency modulation signal source and the line are shielded and isolated independently to prevent mutual crosstalk.

In this embodiment, for example, the first main-oscillator high-frequency modulation signal and the first local-oscillator high-frequency modulation signal, and the second main-oscillator high-frequency modulation signal and the second local-oscillator high-frequency modulation signal are output through two sets of phase-locked loops respectively. Firstly, a phase-locked loop is selected through a selector switch to output a first main-oscillator high-frequency modulation signal and a first local-oscillator high-frequency modulation signal. The first master oscillator high-frequency modulation signal can be loaded on the laser diode after being amplified by the amplifying circuit 1. The first main vibration high-frequency modulation signal is loaded on the laser diode and then emits a first laser beam which is modulated by the frequency corresponding to the first main vibration high-frequency modulation signal, the first laser beam is divided into two parts, one part of the first laser beam is reflected back after reaching a target object through an external light path, and the emitted laser beam is a first high-frequency echo signal. Since the emitted laser beam is modulated by the high-frequency modulation signal, the echo signal is also a high-frequency signal. The first local oscillator high-frequency modulation signal is amplified by the amplifying circuit 2 and then can be loaded on the first photoelectric detector and the second photoelectric detector respectively.

After detecting the first high-frequency echo signal, the second photodetector will firstly convert the first high-frequency echo signal into a high-frequency electric signal, which is a demodulated electric signal of the first laser beam modulated by the first master oscillator high-frequency modulation signal after the first laser beam travels to and from the target object, and has a delayed phase difference with the first master oscillator high-frequency modulation signal. The first high-frequency electrical signal and the first local oscillator high-frequency modulation signal are mixed to obtain a low-frequency electrical signal (i.e., the first difference frequency ranging signal in the above embodiment). And the low-frequency electric signal is subjected to signal amplification and analog-to-digital converter conversion, and a low-frequency digital electric signal (represented by eD) is output to a Field-Programmable Gate Array (FPGA).

In order to perform phase comparison, after the first master oscillator high-frequency modulation signal is loaded to the laser diode, another part of the first laser beam modulated in frequency corresponding to the first master oscillator high-frequency modulation signal is emitted, and the other part of the first laser beam directly reaches the first photoelectric detector through the internal optical path to obtain a first reference laser beam, the first reference laser beam is subjected to photoelectric conversion by the first photoelectric detector, and then is subjected to frequency mixing processing with the amplified first local oscillator high-frequency modulation signal to obtain a first difference frequency reference signal with a low frequency, and the first difference frequency reference signal with the low frequency is also subjected to amplification and analog-to-digital conversion to obtain a low-frequency reference digital electrical signal (denoted by e 0) serving as the phase comparison. Since e0 does not traverse the outer optical path, e0 does not have the phase delay generated in the image eD. Therefore, the field programmable gate array compares the phases of eD and e0 to obtain a first phase difference for obtaining a first reference distance value of the target object, and further obtain the first reference distance value.

And selecting another phase-locked loop through the selector switch, and outputting a second main-oscillator high-frequency modulation signal and a second local-oscillator high-frequency modulation signal. Similarly, the field programmable gate array can obtain the second phase difference, further calculate a third phase difference between the second phase difference and the first phase difference, obtain a second reference distance value according to the third phase difference, and further obtain the measured distance value of the target object according to the first reference distance value and the second reference distance value.

In this embodiment, the selector switch configured to select the phase-locked loop is controlled by the fpga, the two sets of phase-locked loops can output at least four sets of different high-frequency modulation signals, and the frequency values of the four sets of high-frequency modulation signals are concentrated, i.e., the difference between each two sets of frequency values is small, so that a unified high-frequency processing circuit can be adopted, and the hardware circuit design is simple. The group with the highest frequency value (illustratively, the frequency of the main-oscillator high-frequency modulation signal is 1093.75MHZ, and the frequency of the local-oscillator high-frequency modulation signal is 1000MHZ) is used as a pair of fine scales, so that the measurement accuracy of the system can be ensured. And the other three groups (illustratively, the frequency of the main vibration high-frequency modulation signal is 1091.75MHZ, the frequency of the local vibration high-frequency modulation signal is 998MHZ, the frequency of the main vibration high-frequency modulation signal is 1081.75MHZ, the frequency of the local vibration high-frequency modulation signal is 988MHZ, the frequency of the main vibration high-frequency modulation signal is 1073.75MHZ, and the frequency of the local vibration high-frequency modulation signal is 880MHZ) are used as auxiliary scales, and the difference frequency between the fine scale and the three auxiliary scales (illustratively, the difference frequency can be respectively 20MHZ and 6MHZ and the like) can be used as two middle scales and one thick scale of the extended range to ensure the measuring range of the system. It can be understood that if only two phase-locked loops are provided, the group with high frequency value is used as a fine rule, the other group is used as an auxiliary rule, and the difference frequency between the fine rule and the auxiliary rule can be used as a coarse rule for expanding the measuring range.

On one hand, the configuration time of the low-frequency measuring scale is reduced while the high-precision and wide-range measurement is guaranteed, and therefore the detection speed of the laser radar is improved. On the other hand, the frequency of the modulated detection light signal is concentrated, so that the circuit can conveniently process signals with similar frequencies, and circuits do not need to be designed for high-frequency signals and low-frequency signals respectively, so that the circuit design difficulty is low, and the circuit structure is simple.

In one embodiment, the signal amplification circuit is an operational amplifier that amplifies weak signals, thereby improving the signal-to-noise ratio of the signals. Illustratively, the operational amplifier can adopt a multi-stage signal amplification circuit, the former stage is current mode signal and voltage mode signal processing, and the latter stages adopt low-noise, high-speed and high-precision signal amplification processing. In this embodiment, a switch is disposed after the first photodetector and the second photodetector, and signals received by the first photodetector and the second photodetector are selectively switched by the switch and transmitted to the 3-stage signal amplification circuit. Which one of the signal amplifying circuits is selected according to the requirement. For example: when the signal output by the first photodetector or the second photodetector is weak, a signal amplification circuit with 2-level amplification can be used, and if the 2-level amplification is too small, a signal amplification circuit with 3-level amplification can be selected. In addition, in the limiting case, if the signal is saturated by using the signal amplification circuit with 3-stage amplification factor, the signal amplification circuit with 2-stage amplification factor may be used, and if the signal is saturated by using the signal amplification circuit with 2-stage amplification factor, the signal amplification circuit with 1-stage amplification factor may be used. Generally, the sets of circuits can basically contain most of the measuring environment.

The input end of the operational amplifier is electrically connected with the output end of the photoelectric detector, the output end of the operational amplifier is electrically connected with the input end of the analog-to-digital converter, and the output end of the analog-to-digital converter is electrically connected with the field programmable gate array.

In one embodiment, the analog-to-digital converter is configured to acquire signals quickly, and the field programmable gate array is configured to perform high-speed phase frequency calculation on the signals acquired by the analog-to-digital converter (for example, a smoothing filter subunit and a 260-point fast fourier transform subunit may be integrated on the FPGA), so that the lidar has the advantages of high measurement speed, high interference resistance and high precision. Meanwhile, the field programmable gate array can abandon unstable data and only acquire stable data for processing, so that the data consistency is good and the data stability is high.

In addition, the laser radar can adopt a professional tape-out technology by setting the analog-to-digital converter for high-speed signal acquisition and the FPGA for high-speed phase calculation, so that the integration level of the product is higher, the area is smaller, the reliability and the stability are higher, the cost is lower, and the miniaturization is easy to realize. Meanwhile, the boundary scan Test technology of Joint Test Action Group (JTAP) is adopted, so that the Test cost can be reduced, and the Test time can be shortened, thereby shortening the time for the product to appear.

With continued reference to fig. 9, the lidar further includes a power supply Unit, a Microprocessor (MCU) and a high voltage regulating Unit; the power supply unit and the microprocessor, FPGA, first laser diode, second laser diode isoelectrical connection are in order to realize the power supply, microprocessor's first control end is connected in order to realize multiple data interaction and program control with FGPA electricity, microprocessor's second control end is connected in order to realize adjusting photodetector's voltage through high-pressure regulating element and photoelectric detector electricity to make photoelectric detector can amplify the echo signal of multiple different reflection back.

In one embodiment, the power supply unit may convert the external power supply into voltages required by the plurality of components of the module according to the module requirements and supply the plurality of components with power, respectively. And microprocessor can control power supply unit, realizes that a plurality of components in the laser radar independently supply power.

In one embodiment, the High voltage adjusting unit may adjust a magnitude of a High Voltage (HV) applied to the photodetector by means of Pulse Width Modulation (PWM).

Illustratively, the higher the duty cycle, the higher the voltage value during pulse width modulation high voltage.

With continued reference to fig. 9, the laser radar further includes a temperature detection unit (AD _ NTC), a high voltage detection unit (AD _ HV), and a standard voltage detection unit (AD _ VBAS), wherein an output end of the temperature detection unit, an output end of the high voltage detection unit, and an output end of the standard voltage detection unit are electrically connected to an input end of the microprocessor, respectively; the temperature detection unit is set to detect the temperature value of the photoelectric detector, the high-voltage detection unit is set to detect the high-voltage value of the photoelectric detector, and the standard voltage detection unit is set to detect the standard voltage value of the photoelectric detector; the microprocessor is also configured to regulate the output voltage based on the temperature value and various feedback signals.

In this embodiment, in order to make laser radar be applicable to different environments, the temperature detection unit, the high voltage detection unit, and the standard voltage detection unit are designed to monitor the service environment of the photodetector, and adjust the voltage value applied to the photodetector according to the environmental information (including the temperature value, the high voltage value, and the standard voltage value).

Illustratively, according to the influence of temperature on the photoelectric detector, the change of the echo signal received by the photoelectric detector caused by the temperature change is compensated by the voltage difference. Illustratively, according to the difference of the intensity of the echo signal generated by the surface emission of the target object, the voltage difference is used for compensating the change of the echo signal received by the photoelectric detector caused by the intensity change of the echo signal. Thus, the optical signal detection module can be suitable for various environments.

In this embodiment, a constant-current constant-voltage constant-power driving circuit (not shown in fig. 9) is further used to provide a stable power supply system for the laser emitting unit (including the first laser diode and the second laser diode), and meanwhile, the working point of the laser emitting unit is stabilized through the voltage feedback of the laser emitting unit itself.

In one embodiment, the switching is performed by a high-speed switch, so that the time for switching the frequency is greatly prolonged. The high-speed Switch (SW) is applied to the laser radar, so that the measurement precision can be effectively improved.

In one embodiment, the optical path system layout of the lidar includes: coaxial systems, single transmit and dual receive systems.

In one embodiment, the laser radar further comprises an angle detection unit, wherein the angle detection unit is electrically connected with a signal processing unit in the optical signal detection module; the angle detection unit is used for detecting the rotation angle value of the laser radar; the signal processing unit is further arranged to correlate the amount of change in the distance value with the amount of change in the angle value.

In one embodiment, the light emitting module can rotate within a range of 360 degrees, and the angle detection unit is arranged to detect the rotation angle of the light emitting module, so that the laser radar can realize horizontal 360-degree two-dimensional scanning detection within a range of at least 0.01 meter (m) -150m, and thus obtain two-dimensional position information of the surrounding environment. In one embodiment, the detection accuracy of the laser radar can reach millimeter level, so that the laser radar can be widely applied to the fields of laser scanning systems, monitoring systems, space mapping (space modeling), collision prevention, robots, environment detection, military reconnaissance and the like.

In one embodiment, the laser radar is driven to rotate by a transmission mode comprising: a brush motor, a brushless motor, or wireless power.

In an embodiment, the lidar further comprises a communication unit; the communication unit is electrically connected with the signal processing unit in the optical signal detection module; the communication unit is configured to transmit at least one of the distance value, the angle value, and the association between the variation of the distance value and the variation of the angle value, which are obtained by the signal processing unit, to a feedback signal receiving unit.

In an embodiment, the feedback signal receiving unit may be an optical transmitting module, and the optical transmitting module adjusts the intensity of the emitted detection light signal according to the received information, so as to be suitable for different detection environments.

In an embodiment, the feedback signal receiving unit may also be a microcontroller, which is configured to further process the detected data, so as to monitor the surrounding environment or to implement an automated control.

In one embodiment, the communication mode of the communication unit may include: optical communication, bluetooth communication or WIFI communication.

By the arrangement, data transmission is performed in a wireless transmission mode, so that the number of external interfaces of the laser radar can be reduced, and the structure of the laser radar is simplified; on the other hand, the application range of the laser radar can be wider, and the laser radar can be applicable to a damp or water environment for example.

Illustratively, fig. 10 is a schematic workflow diagram of a lidar provided in an embodiment of the present application. Referring to fig. 10, the operation flow of the laser radar includes the following steps.

And step S5110, electrifying the motor to rotate.

Wherein, the rotatory module group (mainly including optical transmission module and light signal detection module) of can driving of motor (motor) rotates to laser radar can realize 360 degrees within ranges scanning and survey.

Step S5120, emitting a detection light signal.

The detection light signal may be an infrared laser beam modulated by a high-frequency modulation signal. The detection light signal is emitted by the laser emitting unit.

And step S5130, receiving an echo signal.

The echo signal is a reflected light signal formed after a detection light signal sent by the light emitting module is reflected by a target object. The echo signal is received by a signal receiving unit in the optical signal detection module.

Step S5140 calculates a distance from the phase difference.

Wherein the phase difference between the probe light signal and the echo signal is related to the distance of the target object.

Illustratively, the formula for ranging using the phase method is:

where D is the distance to be detected, c is the speed of light,

is the detected phase difference and f is the modulation frequency of the detected optical signal. Therefore, the distance to be detected can be calculated by detecting the phase difference between the detection light signal and the echo signal. The optical signal detection module provided by the embodiment can realize high-speed data calculation, so that the optical signal can be quickly processed, and the distance to be detected can be quickly obtained.

And step S5150, uploading data.

Wherein, this step may include feeding back the data obtained in step S5140 to the light emitting module performing step S5120 and the optical signal detecting module performing step S5130. Therefore, a closed-loop self-feedback adjusting system is formed, the intensity of the detection optical signal and the intensity of the echo signal are adjusted, and the detection result is more accurate.

Meanwhile, this step may further include uploading the data obtained in step S5140 to a feedback signal receiving unit, i.e., performing step S5160.

And step S5160, outputting data.

The step can realize the display of the two-dimensional detection point cloud picture data, and can also realize automatic control by taking the output data as a control instruction.

For example, fig. 11 is a schematic flowchart of an algorithm of a lidar according to an embodiment of the present disclosure. Referring to fig. 11, the work flow of the lidar includes the following steps.

Step S5200 starts measurement.

The step can be realized by pressing a start button in the laser radar, clicking a start button on a screen of the laser radar or performing remote control in a wireless transmission mode.

Step S5210, frequency configuration.

The step is executed by the light emitting module, and the high-frequency modulation signal output by the high-frequency modulation signal output unit is loaded to the laser emitting unit to modulate the detection light signal with the frequency meeting the requirement.

Step S5220, temperature, high voltage, Bias (Bias) point detection.

The step is executed by the optical signal detection module, and the accuracy of the detection result in different use environments can be improved by detecting the application environment of the laser radar, for example, the application environment parameters of the signal receiving unit, and then adjusting the voltage applied to the signal receiving unit, that is, executing step S5230, so that the laser radar can be applied to more test environments.

After step S5200, before step S5220, the following three steps may be included to achieve the lidar rotation.

And step S5310, starting the radar motor.

The motor can drive the light emitting module and the signal receiving unit (or the whole optical signal detection module) in the laser radar system to rotate by rotation.

And S5320, controlling the rotating speed.

The rotating speed can be adjusted to a preset range according to the density of detection points in each 360-degree range or the actual requirement of the detection range.

For example, a higher rotational speed may be used when the demand for density of probe points per 360 degrees is lower; lower rotational speeds may be used when the demand for density of probe points per 360 degree range is high.

For example, the control of the rotational speed may be accomplished by adjusting a knob that controls the rotational speed or by inputting a desired rotational speed value.

And S5330, measuring a code disc signal.

Wherein this step is performed by the angle detection unit. The detection of the rotation angle and the monitoring of the rotation speed can be realized by executing the step.

After step S5220, step S5230 is executed.

Step S5230, high pressure regulation.

Wherein this step can be realized by pulse width modulation. After step S5230 is completed, the receiving unit is in an operating state suitable for the use environment, and starts to transmit and receive signals at this time, including the following steps.

Step S5410, frequency selection 1. The selection of the frequency can be realized by controlling the selector switch to select the phase-locked loop through the FPGA.

Step S5420, switching to the inner optical path. The switching between the inner optical path and the outer optical path may also be realized by a switch.

And step S5430, collecting the inner optical path signal.

Step S5440, signal processing, and calculating an inner optical path phase.

Step S5450, switch to the outer optical path.

And step S5460, collecting an outer light path signal.

Step S5470, signal processing, and calculation of the external optical path phase.

Step S5480 calculates the phase difference 1.

And step S5490, calculating the distance measured by the measuring tape 1.

Generally, since the distance measured by one measuring tape is not accurate enough due to the ranging by the phase method, a plurality of measuring tapes are needed to be matched, and therefore, the method further comprises the step of detecting the distance of the target object by at least one detecting optical signal with a frequency different from that of the step S5410, and the method comprises the following steps.

Step S5510, frequency selection 2. The frequency can be selected by controlling the selector switch to select the phase-locked loop through the FPGA.

And step S5520, switching to an inner light path.

And S5530, collecting an inner optical path signal.

Step S5540, signal processing, calculating an internal optical path phase.

And step S5550, switching to an external optical path.

And S5560, collecting an outer light path signal.

Step S5570, signal processing is performed to calculate the external optical path phase.

Step S5580, phase difference 2 is calculated.

Step S5590, the distance measured by the measuring tape 2 is calculated.

Step S5610 is executed based on the distance measured by the measuring tape 1 in step S5490 and the distance measured by the measuring tape 2 in step S5590.

And step S5610, joining the measuring ruler.

The measuring tape connection means that the distance measured by the measuring tape 1 is combined with the distance measured by the measuring tape 2 on one hand, and the measuring tape 1 and the measuring tape 2 are subjected to difference frequency on the other hand to calculate a new distance value.

Illustratively, the measuring tape 1 and the measuring tape 2 are used as a coarse rule by a software algorithm to make a difference frequency, the distance calculated by the coarse rule is 100m, the measuring tape 2 is a fine rule, the distance measured by the fine rule is 0.8m, and the distance obtained by joining is 100.8 m.

The specific values of the distances are merely exemplary and are not intended to be limiting.

Step S5620, calculate the final distance.

The distance obtained in step S5610 is usually a relative distance value, and there is a distance error value, and the relative distance value and the absolute distance value have a one-to-one correspondence relationship, so that the absolute distance value can be obtained by looking up the table, and the absolute distance value is used as the final distance.

Step S5630 ends the measurement.

Illustratively, corresponding to step S5200, the measurement may be ended by means of a button, a key, or a remote control; or the measurement can be automatically finished after the threshold range set by the laser radar detection is set. When the measurement is finished, the laser radar can be in a standby state or a power-off state.

It should be noted that both the working flow of the lidar system shown in fig. 10 and the algorithm flow of the lidar system shown in fig. 11 are executed based on the lidar provided in the embodiment of the present application, where details of a plurality of steps are not described in detail, and may be understood by referring to working principles of a plurality of components of the lidar in the above embodiment, and details are not described herein again.

In addition, fig. 11 only explains the algorithm flow based on the principle feasibility, and in actual operation, other flows may be adopted, for example, the modulated light beam is directly split into the inner light path and the outer light path through the optical element without switching the inner and outer light paths. For another example, the inner optical path of all the beams with different frequencies is directly measured and then switched to the outer optical path.

Claims (12)

1. An optical transmit module, comprising:

the high-frequency modulation signal output unit is used for outputting preset high-frequency modulation signals with at least two different frequencies;

the laser emission unit is connected with the high-frequency modulation signal output unit and is arranged to emit at least two laser beams with different frequencies which are respectively modulated by the at least two high-frequency modulation signals with different frequencies;

the laser emission unit comprises a laser, the laser comprises a seed source and an optical fiber amplifier, and the optical fiber amplifier is used for amplifying an optical signal emitted by the seed source.

2. The optical transmit module of claim 1, wherein the laser emits a laser beam having a wavelength in a 1550nm band or a 2000nm band.

3. The optical transmit module of claim 2 wherein the fiber amplifier is an erbium doped fiber amplifier or a thulium doped fiber amplifier.

4. The optical transmit module of claim 1, wherein each high frequency modulation signal is a master oscillator high frequency signal;

the high-frequency modulation signal output unit is further configured to output at least two local oscillator high-frequency signals with different frequencies to the signal receiving unit, wherein the at least two local oscillator high-frequency signals correspond to the at least two main oscillator high-frequency signals one to one, and each local oscillator high-frequency signal differs from the corresponding main oscillator high-frequency signal by a preset frequency.

5. The optical transmit module of claim 4, wherein the high frequency modulation signal output unit comprises at least two sets of phase-locked loops, each set of phase-locked loops being respectively configured to output a master oscillator high frequency signal and a local oscillator high frequency signal corresponding to the master oscillator high frequency signal.

6. An optical signal detection module, comprising:

an echo signal receiving unit configured to receive a first high-frequency echo signal and a second high-frequency echo signal, where the first high-frequency echo signal is a laser beam obtained by reflecting a first laser beam by a target object, and the second high-frequency echo signal is a laser beam obtained by reflecting a second laser beam by the target object;

a reference signal receiving unit configured to receive a first reference signal and a second reference signal, wherein the first reference signal is a reference signal modulated by a first high-frequency modulation signal, and the second reference signal is a reference signal modulated by a second high-frequency modulation signal;

the first laser beam is a laser beam modulated by the first high-frequency modulation signal, and the second laser beam is a laser beam modulated by the second high-frequency modulation signal; the frequency of the first high-frequency modulation signal is greater than the frequency of the second high-frequency modulation signal;

the signal processing unit is simultaneously electrically connected with the echo signal receiving unit and the reference signal receiving unit; the signal processing unit is configured to: acquiring a first reference distance value of the target object according to a first phase difference between the first reference signal and the first high-frequency echo signal; acquiring a second reference distance value of the target object according to the first phase difference and the second phase difference, and determining a measurement distance value of the target object according to the first reference distance value and the second reference distance value; wherein the second phase difference is a phase difference between the second reference signal and the second high frequency echo signal.

7. The optical signal detection module of claim 6, wherein the first and second reference signals are first and second reference laser beams, respectively, or first or second reference electrical signals, respectively.

8. The optical signal detection module of claim 6, wherein the first reference signal is a first reference laser beam; the second reference signal is a second reference laser beam; the echo signal receiving unit and the reference signal receiving unit are further configured to: receiving a first local oscillator high-frequency modulation signal; converting the first high-frequency echo signal into a corresponding electric signal, and mixing the electric signal corresponding to the first high-frequency echo signal with the first local oscillator high-frequency modulation signal to obtain a first difference frequency ranging signal; converting the first reference laser beam into a corresponding electric signal and mixing the electric signal corresponding to the first reference laser beam with the first local oscillator high-frequency modulation signal, or mixing the first reference electric signal with the first local oscillator high-frequency modulation signal to obtain a first difference frequency reference signal; receiving a second local oscillator high-frequency modulation signal; converting the second high-frequency echo signal into a corresponding electric signal, and mixing the electric signal corresponding to the second high-frequency echo signal with the second local oscillator high-frequency modulation signal to obtain a second difference frequency ranging signal; converting the second reference laser beam into a corresponding electrical signal and mixing the electrical signal corresponding to the second reference laser beam with the second local oscillator high-frequency modulation signal, or mixing the second reference electrical signal with the second local oscillator high-frequency modulation signal to obtain a second difference frequency reference signal; the first high-frequency modulation signal is a first main-vibration high-frequency modulation signal, the second high-frequency modulation signal is a second main-vibration high-frequency modulation signal, the frequency difference between the first main-vibration high-frequency modulation signal and the first local-vibration high-frequency modulation signal is a preset frequency, and the frequency difference between the second main-vibration high-frequency modulation signal and the second local-vibration high-frequency modulation signal is the preset frequency;

the signal processing unit is arranged to obtain a first reference distance value of the target object from a first phase difference between the first reference signal and the first high frequency echo signal by: comparing the first difference frequency ranging signal with the first difference frequency reference signal to obtain a first phase difference, and acquiring a first reference distance value of the target object according to the first phase difference;

the signal processing unit is arranged to obtain a second reference distance value of the target object from the first phase difference and the second phase difference by: comparing the second difference frequency ranging signal with the second difference frequency reference signal to obtain a second phase difference; calculating a third phase difference between the second phase difference and the first phase difference; and acquiring a second reference distance value of the target object according to the third phase difference.

9. The optical signal detection module of claim 6, wherein the echo signal receiving unit and/or the reference signal receiving unit each comprise a photodetector.

10. The optical signal detection module of claim 8, wherein the signal processing unit comprises an operational amplifier, an analog-to-digital converter, and a field programmable gate array;

the input end of the operational amplifier is electrically connected with the signal receiving unit, the output end of the operational amplifier is electrically connected with the input end of the analog-to-digital converter, and the output end of the analog-to-digital converter is electrically connected with the field programmable gate array;

the operational amplifier is configured to amplify the first difference frequency ranging signal, the first difference frequency reference signal, the second difference frequency ranging signal and the second difference frequency reference signal transmitted by the echo signal receiving unit and the reference signal receiving unit respectively;

the analog-to-digital converter is arranged to convert the first difference frequency ranging signal, the first difference frequency reference signal, the second difference frequency ranging signal and the second difference frequency reference signal amplified by the operational amplifier from analog quantity signals to digital quantity signals respectively;

the field programmable gate array is set to compare a digital quantity signal corresponding to the first difference frequency ranging signal with a digital quantity signal corresponding to the first difference frequency reference signal to obtain a first phase difference, and a first reference distance value of the target object is calculated according to the first phase difference; comparing the digital quantity signal corresponding to the second difference frequency ranging signal with the digital quantity signal corresponding to the second difference frequency reference signal to obtain a second phase difference; calculating a third phase difference between the second phase difference and the first phase difference, and calculating a second reference distance value of the target object according to the third phase difference; and determining the measured distance value of the target object according to the first reference distance value and the second reference distance value.

11. An optical system, comprising: the optical signal detection module of any one of claims 6-10, and an optical transmit module coupled to the optical signal detection module;

the light emitting module comprises a high-frequency modulation signal output unit and a laser emitting unit, wherein the high-frequency modulation signal output unit is set to output preset high-frequency modulation signals with at least two different frequencies; the laser emission unit is set to emit at least two laser beams with different frequencies which are respectively modulated by at least two high-frequency modulation signals with different frequencies;

a part of the laser beams with at least two different frequencies is emitted out to be reflected by a target object and received by the echo signal receiving unit; the other part of the two laser beams with different frequencies is directly received by the reference signal receiving unit as a reference signal;

the laser emission unit comprises a laser, the laser comprises a seed source and an optical fiber amplifier, and the optical fiber amplifier is used for amplifying an optical signal emitted by the seed source.

12. A lidar system comprising the optical system of claim 11.

Images