WO2021026709A1

WO2021026709A1 - Laser radar system

Info

Publication number: WO2021026709A1
Application number: PCT/CN2019/100132
Authority: WO
Inventors: 王超
Original assignee: 深圳市速腾聚创科技有限公司
Priority date: 2019-08-12
Filing date: 2019-08-12
Publication date: 2021-02-18
Also published as: CN112805595A; CN112805595B

Abstract

A laser radar system, comprising: an emission module (100), an optical transmission system (200), a detection module (300) and a signal processing module (400). The emission module (100) generates and transmits a plurality of emission laser signals with different modulation frequencies. The optical transmission system (200) transmits each emission laser signal to a detection region according to a scanning angle range corresponding thereto, so that the plurality of emission laser signals illuminate the entire detection region after being emitted. The detection module (300) receives a plurality of reflected laser signals and converts same into reflected electrical signals. The signal processing module (400) acquires a phase offset according to each received reflected electrical signal, calculates, according to each phase offset, a ranging value of an emission laser signal corresponding thereto, thereby detecting a near-field detection region by using an emission laser signal with a relatively high modulation frequency, and detects a far-field detection region by using an emission laser signal with a relatively low modulation frequency, achieving a high near-field ranging precision and a far ranging capability.

Description

Lidar system

Technical field

This application relates to the field of laser radar technology, in particular to a laser radar system.

Background technique

The statements here only provide background information related to this application, and do not necessarily constitute prior art.

Lidar is a system that detects characteristic information such as the position and speed of a target by emitting laser light of a specific wavelength and direction. According to the different light emitting methods of lidar, existing lidars can be roughly divided into two categories: scanning and non-scanning, among which non-scanning radar mainly refers to flash radar.

The main advantage of Flash radar is that the launch system does not have any mechanical movement and can quickly record the entire detection scene. While obtaining the detection target distance information, it can also obtain grayscale imaging information, avoiding the movement of the target or the lidar itself during the scanning process. Interference. However, the ranging capability of Flash lidar based on continuous wave phase measurement is affected by the parameters of the outgoing module, which makes the system unable to obtain better ranging results.

Summary of the invention

Based on this, it is necessary to provide a lidar system for the problem that the radar system cannot obtain a better ranging effect due to the influence of the parameters of the emission module.

This application provides a lidar system, including:

The emission module is used to generate and emit multiple emission laser signals with different modulation frequencies, and the multiple emission laser signals are all frequency-modulated continuous waves;

The transmitting optical system is used to project each of the outgoing laser signals to the detection area according to its corresponding scan angle range, so that the plurality of outgoing laser signals illuminate the entire detection area after emission, wherein the scan angle range Refers to the horizontal and vertical angular ranges covered by the emitted laser signal after being emitted;

The detection module is used to receive a plurality of reflected laser signals and convert the plurality of reflected laser signals into reflected electrical signals, wherein the reflected laser signal is returned after the outgoing laser signal is reflected by an object in the detection area Laser signal; and

The signal processing module is configured to receive the multiple reflected electrical signals, obtain the corresponding phase offset between the emitted laser signal and the reflected laser signal according to each of the reflected electrical signals, and according to each of the reflected electrical signals The phase offset calculates the ranging value.

In one of the embodiments, the emission module emits the multiple emission laser signals in a time division, or the emission module simultaneously emits the multiple emission laser signals.

In one of the embodiments, the emission module simultaneously emits the multiple emission laser signals, and the scanning angle ranges corresponding to the multiple emission laser signals are all different.

In one of the embodiments, the exit module includes:

Modulator, used to generate a first-level modulation signal;

The frequency divider is used to perform frequency division processing on the primary modulation signal to generate multiple secondary modulation signals with different modulation frequencies and send them separately; and

The emission array includes a plurality of light sources and is divided into a plurality of emission areas, each of the emission areas correspondingly receives one of the second-level modulation signals, and modulates them by the second-level modulation signals to emit A laser signal beam composed of the outgoing laser signals with the same frequency.

In one of the embodiments, the light source of each exit area emits the exit laser signal simultaneously.

In one of the embodiments, a plurality of the exit regions emit the laser signal beam in a time-sharing manner, or a plurality of the exit modules simultaneously emit the laser signal beam.

In one of the embodiments, the emission array includes an LED light source and/or a VCSEL light source.

In one of the embodiments, the light sources located in the same exit area are the same, and they are all LED light sources or VCSEL light sources.

In one of the embodiments, when the emitting array includes an LED light source, the lidar system further includes a first driving circuit, and the first driving circuit is electrically connected to the LED light source for driving the LED light source Glow

When the emitting array includes a VCSEL light source, the lidar system further includes a second driving circuit for driving the VCSEL light source to emit light.

In one of the embodiments, among the multiple modulation frequencies, the minimum modulation frequency is f, and the other modulation frequencies are all integer multiples of f.

In one of the embodiments, the emission optical system includes a plurality of emission optical sub-systems, and the emission optical sub-systems correspond to the emission area one to one.

In one of the embodiments, the transmitting optical sub-system directs the laser signal beams emitted from the corresponding exit area toward different scanning angle ranges; the scanning angles of the multiple laser signal beams The spliced range covers the entire detection area.

In one of the embodiments, the emission optical sub-system directs the laser signal beam emitted from the corresponding emission area toward the entire detection area.

In one of the embodiments, the lidar system further includes a receiving optical system for receiving the reflected laser signal, and performing convergence and shaping processing on the reflected laser signal to make the reflected laser signal The spot size of the laser signal is adapted to the size of the receiving surface of the detection module.

In one of the embodiments, the receiving optical system includes a focusing mirror and a reshaping mirror, the focusing mirror is used for condensing the reflected laser signal, and the reshaping mirror is used for shaping the converged reflected laser signal .

In one of the embodiments, the detection module includes a detection array, and the detection array includes a plurality of detectors for receiving the reflected laser signal and converting the reflected laser signal into the reflected electrical signal.

In one of the embodiments, the detectors are all CCD image sensors or CMOS image sensors.

In one of the embodiments, the detection module further includes a readout array, including a plurality of readout circuits, and the readout circuits correspond to the detectors one-to-one for amplifying the reflected electrical signal and The latter reflected electric signal is subjected to noise reduction processing to obtain the amplified and noise-reduced reflected electric signal, and sent to the signal processing module.

In one of the embodiments, the relationship between the phase offset corresponding to the same laser signal and the ranging value is

Wherein, the d is the distance measurement value corresponding to the outgoing laser signal, c is the speed of light, and f is the modulation frequency of the outgoing laser signal,

Is the phase offset.

In the above-mentioned lidar system, a plurality of outgoing laser signals with different modulation frequencies are generated and emitted by the emitting module, and then each outgoing laser signal is projected to the detection area according to its corresponding scanning angle range through the emitting optical system, so that the outgoing laser After the signal is emitted, the entire detection area is illuminated, so it is possible to detect the detection area in the near field by using the outgoing laser signal with a higher modulation frequency to obtain a higher range accuracy of the near field detection area, and at the same time use the modulation frequency The lower outgoing laser signal detects the detection area of the far field to obtain a larger ranging range of the lidar system, thereby solving the restriction relationship between the ranging accuracy and the ranging range in the lidar system. The system has both high near-field ranging accuracy and far ranging capability, eliminating the influence of a single modulation frequency on the ranging effect.

Description of the drawings

FIG. 1 is a schematic structural diagram of a lidar system provided by an embodiment of the application;

2 is a schematic structural diagram of another lidar system provided by an embodiment of the application;

FIG. 3 is a schematic diagram of a working mode of a lidar provided by an embodiment of the application.

detailed description

In order to make the above objectives, features and advantages of the present application more obvious and understandable, the specific implementation of the present application will be described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are explained in order to fully understand this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of this application. Therefore, this application is not limited by the specific implementation disclosed below.

1 and 2 together, an embodiment of the present application provides a laser radar system. The laser radar system includes an emission module 100, an emission optical system 200, a detection module 300, and a signal processing module 400.

The emission module 100 is used to generate and emit multiple emission laser signals with different modulation frequencies, and the multiple emission laser signals are all frequency-modulated continuous waves.

The transmitting optical system 200 is used to project each of the outgoing laser signals to the detection area according to its corresponding scanning angle range, so that after a plurality of the outgoing laser signals are emitted, the entire detection area is illuminated, wherein the scanning The angular range refers to the horizontal and vertical angular ranges covered by the emitted laser signal after being emitted.

The detection module 300 is configured to receive a plurality of reflected laser signals, and convert the plurality of reflected laser signals into reflected electrical signals respectively, wherein the reflected laser signal is after the outgoing laser signal is reflected by an object in the detection area The returned laser signal.

The signal processing module 400 is configured to receive a plurality of the reflected electrical signals, obtain the corresponding phase offset of the outgoing laser signal and the reflected laser signal according to each of the reflected electrical signals, and according to each The phase offset calculates the ranging value.

It can be understood that the falsh lidar based on continuous wave phase measurement has higher theoretical accuracy than the traditional pulse TOF ranging scheme. According to its ranging principle, ranging accuracy is directly related to SNR (Signal to Noise Ratio) and modulation frequency. In the case of a certain signal-to-noise ratio, the higher the modulation frequency, the smaller the ranging range; on the contrary, the smaller the phase difference that can be resolved, the higher the ranging accuracy. The public expression of ranging accuracy is:

Among them, σ is the ranging accuracy, Δd is the ranging range, SNR is the signal-to-noise ratio, c is the speed of light, λ is the wavelength of the outgoing laser signal, and f is the modulation frequency of the outgoing laser signal; the smaller the value of σ, the lidar The higher the ranging accuracy of the system. In the case of selecting the appropriate power of the light source, the design of the lidar system is aimed at the detection needs of the near field, and a higher modulation frequency is selected to obtain a higher ranging accuracy. Theoretically, it can reach the order of millimeters in an outdoor environment, which can fully meet Face recognition and even fine discrimination accuracy requirements; the design of the lidar system is aimed at the detection needs of the far field, and a lower modulation frequency is selected to obtain a larger ranging range, so that the theoretical ranging range can cover the ranging needs of the far field .

Therefore, in this embodiment, a plurality of outgoing laser signals with different modulation frequencies are generated and emitted by the emitting module 100, and each outgoing laser signal is projected to the detection area according to its corresponding scanning angle range through the emitting optical system 200, so that a plurality of After the laser signal is emitted, the entire detection area is illuminated; therefore, the detection area of the near-field detection area can be detected by the emitted laser signal with a higher modulation frequency to obtain a higher ranging accuracy of the near-field detection area. At the same time, the modulation frequency is relatively high. The low outgoing laser signal detects the detection area in the far field to obtain a larger ranging range of the lidar system, thereby solving the restriction relationship between the ranging accuracy and the ranging range in the lidar system. At the same time, it has high near-field ranging accuracy and long-distance ranging capability to eliminate the restriction and influence of a single modulation frequency on the ranging effect.

In one of the embodiments, the emission module 100 emits a plurality of the emission laser signals in a time division, or the emission module simultaneously emits a plurality of the emission laser signals. It can be understood that multiple outgoing laser signals can be emitted to the corresponding scanning angle range in a time division according to a preset order, or can be emitted to the corresponding scanning angle range at the same time.

In one of the embodiments, the emitting module 100 includes a transmitting array 110, a modulator 120 and a frequency divider 130, please refer to FIG. 3.

The modulator 120 is used to generate a first-level modulation signal.

The frequency divider 130 is used to perform frequency division processing on the primary modulation signal to generate multiple secondary modulation signals with different modulation frequencies, and send them separately.

The emission array 110 includes a plurality of light sources, which are divided into a plurality of emission areas 111, each of the emission areas 111 correspondingly receives one of the second-level modulation signals, and modulates the second-level modulation signals to emit those with the same modulation frequency. A plurality of the outgoing laser signals form a laser signal beam.

In this embodiment, the first-level modulation signal is generated by the modulator 120, and the first-level modulation signal is a modulation signal wave. After the primary modulation signal is divided by the frequency divider 130, multiple secondary modulation signals are generated. Each secondary modulation signal corresponds to a modulation frequency, and the modulation frequencies of the multiple secondary modulation signals are different. Each exit area corresponds to receiving a secondary modulation signal, that is, the light source of the exit region 111 is modulated by the same secondary modulation signal to generate and emit an exit laser signal; the light source of the exit region 111 is modulated by the secondary modulation signal and then emitted The outgoing laser signals with the same modulation frequency form a laser signal beam, that is, the outgoing laser signal contained in each laser signal beam has the same modulation frequency; therefore, each outgoing area 111 corresponds to a secondary modulation signal, and at the same time a corresponding emission Laser signal beam with modulation frequency. The emitting array is divided into a plurality of emitting areas 111, each emitting area 111 corresponds to a secondary modulation signal, that is, the modulation frequency of each emitting area 111 is different, and the emitting array 110 can emit multiple laser signal beams with different modulation frequencies. In addition, the exit module 100 may further include a plurality of modulators 120, the modulator 120 corresponds to the exit area 111 one-to-one, and directly sends a first-level modulation signal to the corresponding exit area for modulation to form a laser signal beam. It can be known from the principle of laser ranging that the ranging range is inversely proportional to the modulation frequency of the outgoing laser signal, so the outgoing laser modulated by the secondary modulation signal can reach a different range. For example, when the modulation frequencies of the multiple secondary modulation signals are respectively f ₀ , 1.3f ₀ , 1.5f ₀ , 1.8f ₀ , 2f ₀ , etc., the measurement ranges of the corresponding outgoing laser signals are S ₀ , S ₀ /1.3, S ₀ /1.5, S ₀ /1.8, S ₀ /2... etc. The subsequent lidar system can form images with depth by splicing image information acquired in different measurement ranges.

In one of the embodiments, the light source of each exit area emits the exit laser signal simultaneously. It can be understood that light sources located in the same exit area emit laser signals at the same time, so that laser signal beams with the same modulation frequency can be simultaneously emitted and directed to the corresponding field of view for detection; and, control and drive the laser signals located in the same exit area The light source is turned on or off at the same time, which helps simplify the design of the transmitting circuit.

In one of the embodiments, a plurality of the exit regions emit the laser signal beam in a time sharing manner, or a plurality of the exit regions simultaneously emit the laser signal beam. It can be understood that each secondary modulation signal corresponds to a modulation frequency. Therefore, the modulation frequencies of the laser signal beams respectively emitted from multiple exit areas are different, and the detection distances that they can reach are also different, so whether they are simultaneously transmitted or divided When launching at time, the lidar system can simultaneously have higher near-field ranging accuracy and longer ranging capability, so as to eliminate the restriction and influence of a single modulation frequency on the ranging effect.

In one of the embodiments, the emission energy density of the multiple exit regions increases as the modulation frequency of the corresponding secondary modulation signal decreases. During operation, the output power of the lidar system must be large enough to ensure that enough photons reach the target in the detection area of the far field and return to the detector to be detected. If the emission power of the light sources in the emission array is the same and arranged uniformly, the emission energy density of the entire emission array is the same. In order to meet the detection requirements of the far field, the emission array needs to emit a higher energy density, that is, the emission array needs to be larger The output power works; this leads to the fact that the energy in the near field is redundant, which increases the cost of the lidar system and reduces the service life. In this embodiment, when the modulation frequency of the corresponding secondary modulation signal is smaller, the detection distance of the laser signal emitted from the exit area is farther, and the exit area is controlled to have a larger emission energy density to ensure There are enough photons to reach the target in the detection area of the far field and return to the detector to be detected. When the modulation frequency of the corresponding secondary modulation signal is larger, the detection distance of the outgoing laser signal emitted by the outgoing area is closer, and the emission energy density of the outgoing area is also lower. By controlling the emission of the outgoing area Energy density to achieve near-field measurement while reducing the output power of the emitting array and improving the deterioration of the quantum effect of the light source by the heat accumulation effect in the emitting array.

In the specific structure, a variety of designs can be used to realize that the output area of the secondary modulation signal corresponding to a smaller modulation frequency has a higher emission energy density, and the output area of the secondary modulation signal corresponding to a larger modulation frequency has a higher emission energy density. Small emission energy density. E.g:

Solution 1, as shown in FIG. 3, the emission array 110 includes a plurality of the emission areas 111, so the emission power of each emission area 111 can be individually controlled, for example, all areas corresponding to the far-field detection area can be increased. The output power of the light source in the exit area 111 reduces the output power of the light source in the exit area 111 corresponding to the near-field detection area, thereby reducing the total power of the lidar system and improving the quantization efficiency of the light source due to the heat accumulation effect Deteriorating the problem, which in turn increases the life of the lidar system.

Solution 2: When the same light source is used to form the emission array, the greater the arrangement density of the light sources in the emission area, the greater the emission energy density of the emission area. Therefore, the arrangement density of the light sources in each emission area can be individually set. To change the emission energy density of the exit area. For example, increase the arrangement density of light sources in the exit area 111 corresponding to the far-field detection area, and reduce the arrangement density of light sources in the exit area 111 corresponding to the near-field detection area to ensure that sufficient photons arrive The target in the detection area of the far field can be detected after returning to the detector, while reducing the total power of the lidar system.

In the third solution, different types of light sources have different luminous characteristics. Therefore, one or more types of light sources can be individually selected for each exit area 111 to change the emission energy density of the exit area. For example, VCSEL (Vertical Cavity Surface Emitting Laser) light source and LED (Light Emitting Diode) light source have the advantages of good light characteristics, concentrated beam and high energy density, and the light-emitting characteristics of VCSEL light source It is better. Therefore, in the exit area corresponding to the secondary modulation signal with a smaller modulation frequency, the emission energy density in the exit area can be increased by using VCSEL and/or LED light source, specifically by changing the same exit area The ratio of the number of VCSEL light sources and LED light sources inside changes the emission energy density of the exit area. In addition, the VCSEL light source also has the advantage of fast response rate, so it is mostly suitable for detection areas that require high ranging accuracy and spatial resolution, or special detection field of view that requires high energy distribution. The LED light source also has the advantages of low driving circuit design difficulty, simple hardware system and low cost. It can take into account performance and cost to a certain extent. It is generally used in a longer-distance detection area or a detection area with a larger field of view, such as When designing a system with a longer detection distance, priority can be given to LED light sources that give consideration to cost performance. Of course, the above two light sources can also be used together, taking into account their respective advantages and actual system performance requirements.

In one of the embodiments, the light sources located in the same exit area 111 are the same, and they are all LED light sources or VCSEL light sources. It can be understood that because the response speed of the LED light source and the VCSEL light source are different, different driving circuits are required for driving, and when the light sources in the same exit area 111 are all LED light sources or all VCSEL light sources, only one driver is needed. The circuit drives the light source in the exit area 111, which is beneficial to simplify the hardware design.

In one of the embodiments, when the emitting array 110 includes an LED light source, the lidar system further includes a first driving circuit, and the first driving circuit is electrically connected to the LED light source for driving the LED. The light source emits light; when the emitting array 110 includes a VCSEL light source, the lidar system further includes a second driving circuit for driving the VCSEL light source to emit light. It can be understood that due to the different response speeds of the LED light source and the VCSEL light source and the different driving circuits, when the emitting array 110 includes both the LED light source and the VCSEL light source, the LED light source is driven by the first driving circuit, and the LED light source is driven by the second driving circuit. The circuit drives the VCSEL light source, and can separately control and modulate the VCSEL light source and the LED light source to emit laser signals by setting corresponding parameters, so that the control of the emission array is more accurate, and errors are avoided in the emission module.

In one of the embodiments, among the multiple modulation frequencies, the minimum modulation frequency is f, and the other modulation frequencies are all integer multiples of f. In this embodiment, the lidar system selects an appropriate modulation frequency, such as f1, according to the required farthest ranging capability, so that its range covers the farthest ranging index. According to the determined modulation frequency f1, set several other modulation frequencies of the system at the same time, such as f2, f3,..., f2 and f3. These modulation frequencies are correspondingly integer multiples of f1, so choosing the modulation frequency can reduce the system The complexity of hardware design, frequency loading and real-time input also helps to reduce crosstalk between reflected laser signals of different frequencies.

For example, the emission module 100 of the lidar system includes a 5×4 emission array. According to different ranging capability requirements, the modulation frequencies of the secondary modulation signals of the light sources of different rows are different. Assuming that the third row of light sources needs to detect the farthest distance S ₀ , the second-level modulation signal corresponding to the third row of light sources has the lowest modulation frequency, which is f ₀ , the second and fourth rows of light sources correspond to the second-level modulation signals The modulation frequency is 2f ₀ , and the modulation frequency of the secondary modulation signal corresponding to the first and fifth rows of light sources is 3f ₀ , and the detection distance is S ₀ /2 and S ₀ /3 respectively, so that the output laser signal obtained by modulation is The theoretical ranging range can cover the ranging requirements in the entire detection area of the system. When the lidar system is working, the light sources in the emitting array 110 can emit light at the same time to illuminate the entire detection field of view area, or they can be turned on line by line to scan the corresponding field of view area. Correspondingly, when the scanning angle ranges of the multiple laser signal beams are spliced to cover the entire detection area, the reflected laser signals of different frequencies are received and demodulated respectively, and finally a complete spatial point cloud of the detection area is obtained by splicing information.

In one of the embodiments, the exit module further includes a collimator lens 140, and the collimator lens 140 corresponds to the exit area 111 in a one-to-one manner, and is used to collimate the output from the corresponding exit area. Emit the laser signal. In this embodiment, the collimator used for collimating the outgoing laser signal is a transmissive collimator, and generally one collimating lens or a collimating lens group composed of multiple lenses is used. After the outgoing laser signal is collimated by the collimator lens, it is incident on the object in the detection area through the emitting optical system 200.

In one of the embodiments, the emitting optical system 200 includes a plurality of emitting optical sub-systems 210, and the emitting optical sub-systems 210 correspond to the emitting area one to one. Each emitting optical sub-system 210 emits the laser signal beam emitted from the corresponding emitting area to the detection area according to its corresponding preset scanning angle range. It can be understood that the laser signal beam emitted from each exit area is directed to the detection area with a preset scanning angle range through the corresponding emitting optical subsystem, so that the laser signal beams emitted by multiple exit areas of the emitting array can cover the entire detection area ; And the different emission energy density and modulation frequency of each emission area make its detection performance different. The emission optics subsystem sends the laser signal beam emitted from the emission area with low modulation frequency and high emission energy density to the scanning angle that requires far-field detection Range, the laser signal beam emitted from the exit area with high modulation frequency and low emission energy density is directed to the scanning angle range that requires near-field detection, so that the entire lidar system has higher near-field ranging accuracy and farther ranging Ability, while reducing the energy consumption of the entire lidar system.

In one of the embodiments, the transmitting optical sub-system 210 directs the laser signal beams emitted from the corresponding exit area 111 toward different scanning angle ranges; the plurality of laser signal beams After the scan angle range is spliced, the entire detection area is covered. For example, the emission module 100 of the lidar system includes a 5×4 emitting array, and the detection field angle of the lidar system is 40°×50°. By designing a reasonable optical system, each row has an emission area, and the light source of each emission area is responsible for a part of the field of view area such as 40°×10°, that is, the scanning angle range of each emission area is 40°×10°, so that The scanning angle ranges of the 5 laser signal beams emitted by this emitting array are spliced to cover a detection area with a detection field angle of 40°×50°.

In addition, the modulation frequencies of the light sources in different rows are different according to the requirements of the ranging capability of different regions. Assuming that the lidar system has the highest detection requirements for the central field of view area and the farthest distance to be detected, the modulation frequency of the light source corresponding to the central field of view area is the lowest f ₀ , and the light sources of the remaining rows are measured according to the corresponding field The range capability requirement is to determine the modulation signal whose modulation frequency is an integer multiple of f ₀ , so that the theoretical range measurement range of the emitted laser signal obtained by modulation can cover the range measurement requirement of the system in the field of view area.

In one of the embodiments, the emission optical sub-system directs the laser signal beam emitted from the corresponding emission area toward the entire detection area. For example, for the 5×4 emitting array in the foregoing embodiment, by designing a reasonable optical system, each row has an emitting area, and the scanning angle range of each emitting area is 40°×50°. When the scanning angle range of the laser signal beam generated by each exit area is the entire field of view, the emission optical subsystem will need the laser signal beam emitted by the corresponding exit area to face the entire detection Area to realize the detection of the entire detection area within different ranging ranges and improve the accuracy of the near-field detection area.

In one of the embodiments, the emission optical system is an integral emission optical system. In this embodiment, a plurality of the exit areas emit laser signal beams, which are emitted to the corresponding scanning angle range in the detection area through the integral emitting optical system.

In one of the embodiments, the integral transmitting optical system directs the laser signal beams emitted from the exit area toward different scanning angle ranges; after the scanning angle ranges of the multiple laser signal beams are spliced Cover the entire detection area.

In one of the embodiments, the lidar system further includes a receiving optical system 500 for receiving the reflected laser signal, and performing convergence and shaping processing on the reflected laser signal, so that the The spot size of the reflected laser signal is adapted to the size of the receiving surface of the detection module 300.

In one of the embodiments, the receiving optical system 500 includes a focusing mirror 510 and a reshaping mirror 520. The focusing mirror 510 is used for condensing the reflected laser signal, and the reshaping mirror 520 is used for converging the reflected laser signal. The laser signal is reshaped. In this embodiment, the focusing mirror 510 converges the reflected laser signal, and the converged reflected laser signal is shaped by the shaping mirror 520, so that the spot size of the reflected laser signal is adapted to the receiving surface of the detection module 300 The size of the detection module improves the energy utilization of the reflected laser signal; and the reflected laser signal is directly irradiated on the surface of the receiving module in the form of a plane wave to eliminate the difference in pixels caused by different detection areas and different illuminances, thereby improving imaging quality.

In one of the embodiments, the detection module 300 includes a detection array 310, and the detection array 310 includes a plurality of detectors for receiving the reflected laser signal and converting the reflected laser signal into the reflected laser signal. signal.

In one of the embodiments, the detector is a CCD image sensor or a CMOS image sensor. It can be understood that because CCD image sensors have small size, light weight, high resolution, high sensitivity, wide dynamic range, high geometric accuracy of photosensitive elements, wide spectral response range, low working voltage, low power consumption, long life, and shock resistance And a series of advantages such as good impact resistance, immunity from electromagnetic field interference and high reliability, so a CCD image sensor can be used to form the detection array 310. The CMOS image sensor also has the advantages of the above-mentioned image sensor CCD image sensor. In addition, the CMOS image sensor also has the advantages of low production cost and fast readout rate. Therefore, a CMOS image sensor can also be used to form the detection array 310. In addition, photosensitive elements such as photodiodes and photomultipliers can also be used as detectors to form the detection array 310.

In one of the embodiments, the detection module 300 further includes a readout array 320, the readout array 320 includes a plurality of readout circuits, and the readout circuits correspond to the detectors one-to-one for amplifying The reflected electrical signal is subjected to noise reduction processing on the amplified reflected electrical signal to obtain the amplified and noise-reduced reflected electrical signal, which is sent to the signal processing module 400. In this embodiment, the readout circuit is an ADC (Analog-to-Digital Converter) readout circuit. Because the ADC readout circuit has the advantages of low power consumption and simple circuit design, it is more suitable for columnarization. Integration. It can be understood that when a CCD image sensor or a CMOS image sensor is working, noise will be generated during the photoelectric conversion, signal charge storage and transfer process. The noise is superimposed on the signal charge, which will interfere with the signal and reduce the reflected electrical signal actually detected. Accuracy. In this embodiment, the ADC readout circuit can make the reflected electrical signal change linearly with the target brightness without losing image details, while reducing various noise signals as much as possible and improving the signal-to-noise ratio of the reflected electrical signal.

The basic working principle of the lidar system provided by any of the above embodiments is: the phase offset between the outgoing laser signal and the reflected laser signal, and the distance between the object in the detection area and the detection module 300 (ie The distance measurement value of the outgoing signal is proportional to, so the absolute distance of the object in the detection area can be calculated according to the phase offset.

Assuming that the outgoing laser signal of the frequency-modulated continuous wave is a sine wave and its modulation frequency is f, the relationship between calculating the distance measurement value of the outgoing laser signal according to the phase offset is

Wherein, d is the distance measurement value of the outgoing laser signal, c is the speed of light,

Is the phase offset.

To sum up, in the lidar system provided by the embodiment of the present application, a plurality of outgoing laser signals with different modulation frequencies are generated and emitted by the emitting module 100, and each outgoing laser signal is scanned according to its corresponding scan by the emitting optical system 200 The angular range is directed to the detection area, so that the multiple outgoing laser signals illuminate the entire detection area after they are emitted. Therefore, it is possible to detect the near-field detection area by using higher-frequency outgoing laser signals to increase the near-field detection area. The accuracy of ranging and the use of low-frequency outgoing laser signals to detect the far-field detection area to improve the ranging range of the radar system, thereby solving the restriction between ranging accuracy and ranging range in the flash lidar system Relationship, to achieve a higher near-field ranging accuracy and a longer ranging ability.

The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express a few implementation modes of the present application, and their description is relatively specific and detailed, but they should not be understood as a limitation on the scope of the patent application. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can be made, and these all fall within the protection scope of this application. Therefore, the scope of protection of the patent of this application shall be subject to the appended claims.

Claims

A lidar system is characterized in that it comprises:

The emission module is used to generate and transmit multiple emission laser signals with different modulation frequencies, and the multiple emission laser signals are all frequency-modulated continuous waves;

The transmitting optical system is used to project each of the outgoing laser signals to the detection area according to its corresponding scan angle range, so that after a plurality of the outgoing laser signals are emitted, the entire detection area is illuminated, wherein the scan angle range Refers to the horizontal and vertical angular ranges covered by the emitted laser signal after being emitted;

The detection module is used to receive a plurality of reflected laser signals and convert the plurality of reflected laser signals into reflected electrical signals respectively, wherein the reflected laser signal is returned after the outgoing laser signal is reflected by an object in the detection area Laser signal; and

The signal processing module is configured to receive a plurality of the reflected electrical signals, and obtain the phase offset of the outgoing laser signal and the reflected laser signal corresponding to each of the reflected electrical signals according to each of the reflected electrical signals. The phase offset calculates the ranging value.
The lidar system according to claim 1, wherein the emission module emits a plurality of the emission laser signals in a time division, or the emission module simultaneously emits a plurality of the emission laser signals.
The lidar system of claim 1, wherein the exit module comprises:

Modulator, used to generate a first-level modulation signal;

The frequency divider is used to perform frequency division processing on the primary modulation signal to generate multiple secondary modulation signals with different modulation frequencies and send them separately; and

The emission array includes a plurality of light sources and is divided into a plurality of emission areas, and each of the emission areas correspondingly receives one of the second-level modulation signals, and modulates the second-level modulation signals to emit the same modulation frequency A plurality of the outgoing laser signals form a laser signal beam.
The lidar system of claim 3, wherein the light source of each exit area emits the exit laser signal simultaneously.
The lidar system according to claim 3, wherein a plurality of the exit regions emit the laser signal beam in a time sharing manner, or a plurality of the exit regions simultaneously emit the laser signal beam.
The lidar system according to any one of claims 3 to 5, wherein the emission energy density of the multiple exit areas increases as the modulation frequency of the corresponding secondary modulation signal decreases.
The lidar system according to any one of claims 3 to 5, wherein the emitting array includes an LED light source and/or a VCSEL light source.
8. The lidar system according to claim 7, wherein the light sources located in the same exit area are the same, and they are all the LED light sources or are all the VCSEL light sources.
The lidar system of claim 7, wherein when the emitting array includes an LED light source, the lidar system further comprises a first driving circuit, and the first driving circuit is electrically connected to the LED light source , Used to drive the LED light source to emit light;

When the emitting array includes a VCSEL light source, the lidar system further includes a second driving circuit for driving the VCSEL light source to emit light.
The lidar system according to claim 1, wherein among the plurality of modulation frequencies, the minimum modulation frequency is f, and the other modulation frequencies are all integer multiples of f.
5. The lidar system of claim 3, wherein the emission optical system comprises a plurality of emission optical sub-systems, and the emission optical sub-systems correspond to the emission area one to one.
The lidar system according to claim 11, wherein the transmitting optical sub-system directs the laser signal beams emitted from the exit area corresponding to the laser signal beam toward different scanning angle ranges; The scanning angle range of the laser signal beam is spliced to cover the entire detection area.
11. The lidar system according to claim 11, wherein the transmitting optical subsystem directs the laser signal beam emitted from the corresponding exit area toward the entire detection area.
5. The lidar system of claim 1, further comprising a receiving optical system, the receiving optical system is used to receive the reflected laser signal, and perform convergence and shaping processing on the reflected laser signal.
The lidar system of claim 14, wherein the receiving optical system comprises a focusing mirror and a shaping mirror, the focusing mirror is used to converge the reflected laser signal, and the shaping mirror is used to The reflected laser signal undergoes shaping processing.
The lidar system of claim 1, wherein the detection module includes a detection array, and the detection array includes a plurality of detectors for receiving the reflected laser signal and converting the reflected laser signal Into the reflected electrical signal.
The lidar system of claim 16, wherein the detector is a CCD image sensor or a CMOS image sensor.
The lidar system according to claim 16, wherein the detection module further comprises a readout array, the readout array includes a plurality of readout circuits, and the readout circuits correspond to the detectors one to one. , For amplifying the reflected electrical signal, and performing noise reduction processing on the amplified reflected electrical signal to obtain the amplified and noise-reduced reflected electrical signal, and send it to the signal processing module.
The lidar system of claim 1, wherein the relationship between the phase offset corresponding to the same outgoing laser signal and the ranging value is

Wherein, the d is the distance measurement value corresponding to the outgoing laser signal, c is the speed of light, and f is the modulation frequency of the outgoing laser signal,
Is the phase offset.