WO2022083198A1

WO2022083198A1 - Multi-line scanning distance measurement system

Info

Publication number: WO2022083198A1
Application number: PCT/CN2021/107931
Authority: WO
Inventors: 刘超; 闫敏
Original assignee: 深圳奥锐达科技有限公司
Priority date: 2020-10-21
Filing date: 2021-07-22
Publication date: 2022-04-28
Also published as: CN112394362B; CN112394362A

Abstract

A multi-line scanning distance measurement system (10), comprising: an emitter (11), which comprises a column light source composed of a plurality of light sources (211, 212), and is used for emitting pulsed light beams to a target; a collector (12), which comprises a plurality of sampling areas (221), wherein each sampling area (221) comprises a pixel array composed of a plurality of pixels (311), and a plurality of control circuits (312), the control circuits (312) being connected to the pixels (311) in one-to-one correspondence, so as to independently control the working modes of the pixels, and the plurality of sampling areas (221) being associated with the column light source, and only a subset of pixels within the sampling areas (221) is activated for collecting the reflected pulsed light beams; a rotating component (13), which is used for controlling the emitter (11) and the collector (12) to synchronously rotate to complete 360-degree scanning of the target, so as to form a plurality of scanning lines in a target field of view; and a processing circuit (14), which is connected to the emitter (11) and the collector (12), and is used for synchronizing trigger signals of the emitter (11) and the collector (12), processing photon signals of pixel collection light beams, and calculating distance information of the target on the basis of a flight time from the emission of the pulsed light beams to the reception thereof by the collector (12).

Description

A Multi-Line Scanning Distance Measurement System

technical field

The invention relates to the technical field of distance measurement, in particular to a multi-line scanning distance measurement system.

Background technique

The time of flight principle (TOF, Time of Flight) can be used to measure the distance of the target to obtain a depth image containing the depth value of the target, and the distance measurement system based on the time of flight principle has been widely used in consumer electronics, unmanned aerial vehicles, AR/VR and other fields. The distance measurement system based on the time-of-flight principle usually includes an emitter and a collector. The emitter is used to emit a pulsed beam to illuminate the target field of view, and the collector is used to collect the reflected beam, and the time required for the beam to be reflected and received is calculated to calculate the distance of the object. .

At present, the lidar based on the time-of-flight method is mainly divided into mechanical and non-mechanical. The mechanical type realizes the distance measurement of a large 360-degree field of view by rotating the base. Its advantages are concentrated beam intensity, large measurement range and high precision. Mechanical lidar can be single-line lidar and multi-line lidar. Among them, single-line lidar has only one transmitter and collector, and the scanning range is limited. Therefore, multi-line lidar is proposed, but multi-line lidar is used in the system. Strict alignment is required during assembly and adjustment, which is the main reason why the current multi-line lidar design process is difficult, expensive, and difficult to mass-produce.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to propose a multi-line scanning distance measurement system, so as to solve the problem that the existing multi-line laser radar in the prior art needs to be strictly aligned when the system is installed and adjusted, which leads to the difficulty of the current multi-line laser radar design process and high cost. , technical problems difficult to mass production.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A multi-line scanning distance measurement system, comprising: a transmitter, including a column light source composed of a plurality of light sources, for emitting pulsed beams to a target object; a collector, including a plurality of sampling areas with the same number as the light sources, each Each of the sampling regions includes a pixel array composed of a plurality of pixels and a plurality of control circuits, and the control circuits are connected to the pixels in a one-to-one correspondence to individually control the operation modes of the pixels; the plurality of sampling regions associated with the column of light sources, and only a subset of the pixels within the sampling area are activated for collecting the reflected pulsed light beam; a rotating assembly, connected to the emitter and the collector, for controlling The transmitter and the collector rotate synchronously to complete the 360-degree scanning of the target object to form a plurality of scanning lines in the target field of view; a processing circuit, connected with the transmitter and the collector, uses In order to synchronize the trigger signals of the transmitter and the collector, and process the photon signal of the pixel collection beam, the target is calculated based on the time of flight of the pulsed beam from emission to reception by the collector. The distance information of the object.

Preferably, the column of light sources includes a plurality of the light sources arranged at intervals in the vertical direction.

Preferably, the transmitter further includes an emission optical component for receiving and shaping the pulsed light beam emitted by the light source, and projecting the shaped light beam to the target object.

Preferably, the collector includes a receiving optical assembly and the receiving optical assembly and the transmitting optical assembly are configured to include the same telecentric lens.

Preferably, the collector further includes a plurality of readout circuits connected to the plurality of sampling areas in a one-to-one correspondence, for recording the flight time of photons from emission to being collected and outputting a photon time signal, and using the photon time signal Build a histogram.

Preferably, the readout circuit includes a TDC circuit and a histogram memory, and all pixels in the sampling area share one TDC circuit; or, the readout circuit includes a TDC circuit array and a histogram memory, the The number of TDC circuits in the TDC circuit array is the same as the number of the pixels in the sampling area, and each of the pixels is connected to the TDC circuits in a one-to-one correspondence.

Preferably, the size of the sampling area is determined according to the offset caused by the system tolerance.

Preferably, the position of the pixel in the active state in the sampling area is determined by means of pre-calibration.

Preferably, the subset of pixels is configured to be a sensing area comprising at least two of said pixels.

Preferably, the transmitter and the collector are attached to the rotating assembly, and the rotating assembly controls the transmitter and the collector to rotate synchronously in a horizontal direction around the same rotation axis.

The beneficial effect of the present invention is that: by designing the sampling area, it is no longer necessary to strictly align the light source and the pixel one by one during the adjustment process, and it is only necessary to determine the imaging position of the reflected light beam during the calibration process, and perform distance measurement. When only a subset of the pixels in the sampling area are activated to collect the reflected light beam and generate photon signals, this can greatly reduce the difficulty of using the ranging system, improve the ranging accuracy, and avoid the degradation of ranging accuracy caused by difficult alignment. The problem. In addition, a subset of pixels in the active state in the sampling area is determined by pre-calibration as the sensing area. For example, you can select an indoor with small ambient light for calibration, and the control circuit controls all pixels in the sampling area to be activated, traversing all pixels. The pixels with the strongest signal strength are determined as a subset of the pixels to be activated for collecting reflected light beams in the ranging process, while the remaining pixels are in an off state, so that the ranging accuracy can be improved.

Description of drawings

1 is a system block diagram of a multi-line scanning distance measurement system according to an embodiment of the present invention;

2 is a system block diagram of a multi-line scanning distance measurement system according to another embodiment of the present invention;

FIG. 3 is a schematic block diagram of a collector according to an embodiment of the present invention.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the embodiments of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

It should be noted that the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first", "second" may expressly or implicitly include one or more of that feature. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

FIG. 1 is a system block diagram of a multi-line scanning distance measurement system according to an embodiment of the present invention. The distance measurement system 10 includes a transmitter 11 , a collector 12 , a rotating component 13 and a processing circuit 14 . The transmitter 11 is used for emitting a pulsed beam to the target area, the pulsed beam is emitted into the space of the target area to illuminate the target object in the space, and the pulsed beam reflected by the target is received by the collector 12 . The rotation component 13 is used to control the transmitter 11 and the collector 12 to rotate synchronously around the rotation axis y in the horizontal direction to complete a 360-degree scan of the target field of view, so as to form multiple scan lines in the target field of view. Wherein, the transmitter 11 and the collector 12 are attached to the rotating assembly 13, and can be arranged on the same substrate or on different substrates. The processing circuit 14 is connected with the transmitter 11 and the collector 12, and is used for synchronizing the trigger signals of the transmitter 11 and the collector 12 to calculate the flight time required by the pulse beam from being transmitted to being received by the collector 12, so as to calculate the distance information of the target .

Specifically, the distance D of the corresponding point on the target object can be calculated by the following formula (1):

D=c t/2 (1)

where c is the speed of light and t is the flight time.

Continuing to refer to FIG. 1 , the transmitter 11 includes a driver 111 , a light source 112 , an emission optical component 113 and the like. Wherein, the driver 111 is used to control the light source 112 to emit pulsed light beams at certain time intervals. The light source 112 may be a single light source, or may be a one-dimensional light source array composed of multiple light sources. The light source may be a light emitting diode (LED), a laser diode (LD), an edge emitting laser (EEL), a vertical cavity surface emitting laser (VCSEL), or the like. In one embodiment, the light source 112 is configured as a one-dimensional column of light sources that are arranged in a vertical direction (rotation axis y direction) by a plurality of light sources at a certain interval, and each light source emits n pulsed light beams under the control of the driver 111 As the rotating component 13 controls the transmitter 11 to rotate 360 degrees in the horizontal direction around the rotation axis y, a plurality of scanning lines are finally formed in the target field of view. The number of light sources in the column light source can determine the range measurement system Resolution in the vertical direction. It will be appreciated that a part of the processing circuit 14 or a sub-circuit existing independently of the processing circuit 14 may also be utilized to control the light source 112 to emit light beams.

The emission optical component 113 receives the light beam emitted from the light source 112 and shapes it to project it to the target area. In one embodiment, the transmitting optical component 113 receives the pulsed light beam from the light source 112, performs optical modulation on the pulsed light beam, such as modulation of diffraction, refraction, reflection, etc., and then emits the modulated light beam into space, such as a focused beam, Flood beams, structured light beams, etc. The emission optical component 113 may be one or more combinations of lenses, liquid crystal elements, diffractive optical elements, microlens arrays, metasurface optical elements, masks, mirrors, MEMS galvanometers, and the like.

Continuing to refer to FIG. 1 , the collector 12 includes a pixel array 122 and a receiving optical component 123, and the receiving optical component 123 is used to receive at least part of the light beam reflected back by the target and guide it to the pixel array 122 to form an imaging spot. The arrangement of the pixel array 122 is associated with the light source array 112, that is, each light source corresponds to each pixel one-to-one, and the light beam emitted by the light source irradiates a certain point of the target object and is reflected back to the corresponding pixel. When receiving the light signal in the reflected light beam, the size of a single light spot is usually set to correspond to a sensing area including a plurality of pixels, for example, corresponding to 2×2=4 pixels, then each light source is associated with each sensing area. Wherein, the pixel can be a single photon sensing device such as APD (Avalanche Photodiode), SPAD (Single Photon Avalanche Diode), SiPM (Silicon Photomultiplier), and each pixel can respond to an incident single photon and output it A photon signal indicating the corresponding arrival time of the received photons at each pixel is used such as time-correlated single photon counting (TCSPC) to achieve the acquisition of weak light signals and the calculation of time-of-flight.

In one embodiment, the receiving optical component 123 further includes an aperture set on the focal plane of the lens, which is used to limit the interference of ambient light and adjust the light intensity of the reflected pulse beam to evenly distribute on the pixels, for example, the pixels may be SiPM, SiPM integrates more single-photon response elements and has a larger size. Furthermore, an internal light-reflecting channel can be set between the small hole and the pixel, and the light beam passing through the small hole is reflected by the internal light-reflecting channel for multiple times and then exits the pixel to form a square light spot with approximately the same size as the pixel. All response elements.

Generally, a readout circuit 121 composed of one or more of a signal amplifier, a time-to-digital converter (TDC), a digital-to-analog converter (ADC) and other devices is also connected to the pixel array 122 . These circuits can either be integrated with the pixel or be part of the processing circuit 14 . In one embodiment, the readout circuit 121 includes a TDC circuit and a histogram memory, the TDC circuit is used to record the time of flight of photons from emission to acquisition and output a photon time signal, and use the photon time signal to access the histogram memory, multiple times The measurements are input into the histogram memory to construct the histogram.

The processing circuit 14 synchronizes the trigger signals of the transmitter 11 and the collector 12, processes the photon signal of the pixel collected beam, and calculates the distance information of the target object based on the flight time of the reflected beam. In one embodiment, the processing circuit 14 processes the histogram using algorithms such as peak matching and filter detection to identify the time-of-flight of the reflected beam from emission to reception. It can be understood that the processing circuit 14 may be an independent dedicated circuit, such as a dedicated SOC chip, an FPGA chip, an ASIC chip, etc., or may include a general-purpose processing circuit.

In the aforementioned ranging system, since the arrangement of the pixel array is associated with the column light source, that is, each light source corresponds to the pixel one-to-one, during system assembly, each light source needs to be strictly aligned with the corresponding sensing area, that is, the light spot. Incident at the center of the sensing area increases the difficulty of the assembly process, and the spot shift caused by temperature and oscillation during the system ranging process reduces the ranging accuracy, which affects the service life of the ranging system.

2 is a system block diagram of a multi-line scanning distance measurement system according to an embodiment of the present invention. The distance measurement system 20 includes a transmitter 21 , a collector 22 , a rotating component 13 and a processing circuit 14 . Wherein, the transmitter 21 includes a first column of light sources formed by a plurality of light sources arranged at intervals in the vertical direction, for emitting pulsed light beams toward the target object, preferably the light source is a VCSEL light source; the collector 22 includes a plurality of sampling areas, Each sampling area includes a pixel array composed of a plurality of pixels and a plurality of control circuits, each control circuit is associated with a pixel and independently controls the operation mode of the corresponding pixel (activation or shutdown of the pixel); the sampling area is related to the column light source Each sampling area is associated with a corresponding light source, and only a subset of the pixels within the sampling area are activated to collect reflected pulsed beams and generate photon signals; rotating assembly 13 is used to control emitter 21 and collector 22 Rotating in the horizontal direction, its function is the same as that of the ranging system in the previous embodiment; the processing circuit 14 is connected with the transmitter 21 and the collector 22 to calculate the distance information of the target, and the specific calculation process is the same as the ranging system in the previous embodiment. system, which will not be repeated here.

The number of light sources of the transmitter 21 determines the scanning resolution. In one embodiment, the transmitter 21 further includes a second column of light sources composed of a plurality of light sources, and the second column of light sources and the first column of light sources are staggered in the vertical direction. Further, it can also include a third column of light sources, a fourth column of light sources, etc. All the column light sources are staggered in the vertical direction to ensure that the scanning lines formed by the light beams emitted by all the light sources in the target field of view do not overlap, due to the sampling area. The setting of the column light source is associated with the column light source, and the sampling area is set correspondingly according to the setting of the column light source, including adding the same number of sampling areas and staggered arrangement of the sampling areas.

FIG. 3 is a schematic diagram of the collector of the distance measurement system shown in FIG. 2 . It should be noted that the collector 22 includes a plurality of sampling areas. FIG. 3 only schematically shows one sampling area 221 in the collector 22 and Its readout circuit 313, the sampling area 221 includes a pixel array composed of a plurality of pixels 311 and a plurality of control circuits 312 with the same number as the pixels 311, each control circuit 312 is associated with each pixel 311, and is used to independently control and The working mode of the corresponding pixel connected to it, that is, the control pixel is in the active or off state. The readout circuit 313 is associated with the sampling area 221 and is used for processing the photon signals output by the sampling area. The readout circuit 313 includes a TDC circuit 314 and a histogram memory 315 . The readout circuit 313 may include a TDC circuit and a histogram memory, and all the pixels in the sampling area 221 share one TDC circuit. In another embodiment, the readout circuit 313 may include a TDC circuit array and a histogram memory, wherein the number of TDC circuits is the same as the number of pixels in the sampling area 221, and each pixel is connected to the TDC circuit in a one-to-one correspondence, and each Each TDC circuit receives the photon signal from the pixel and outputs the photon time signal, and all the photon time signals are distributed in the same histogram memory.

In the embodiment shown in FIG. 2, it is assumed that the column light source includes two

light sources

211 and 212. Since the sampling area is associated with the column light source, preferably, the number of light sources and the sampling area are the same and correspond one-to-one, that is, the collector includes two

Sampling areas

221, 222. Based on the multi-line scanning distance measurement system involved in the prior art, it is assumed that 4 pixels are used as a sensing area for receiving the reflected light beam, and the process design of strict alignment needs to be considered, the light beam emitted by the light source 211 needs to be incident on the An imaging light spot 225 is formed in the sampling area 221 . In this embodiment, a plurality of pixels more than the sensing area are designed to form the sampling area 221 for receiving the light beams emitted by the light source 211 and reflected back by the target. The size of the sampling area is determined according to the offset caused by the system tolerance. In other words, add the side length of the sensing area to the offset as the size of the sampling area. For example, as shown in Figure 2, the sensing area is 2×2mm, including 4 pixels, and the offset caused by the system tolerance is about 4mm. Then the size of the sampling area can be designed to be 10×10mm, including 100 pixels. It can be understood that the above data are only illustrative, and do not specifically limit the present invention.

By designing the sampling area, the system no longer needs to strictly align the light source and the sensing area one by one during the installation and adjustment process. It only needs to determine the imaging position of the reflected beam during the calibration process, and only the sampling area is required for distance measurement. A subset of the pixels within are activated to collect the reflected light beam and generate a photonic signal. Among them, a subset of the pixels in the active state in the sampling area is determined by pre-calibration as the sensing area. For example, you can select an indoor with small ambient light for calibration, and the control circuit controls all pixels in the sampling area to be activated, and traverse all the pixels. The pixels with the strongest signal strength are determined as a subset of the pixels to be activated for collecting the reflected beam during ranging, while the remaining pixels are turned off. As shown in FIG. 2 , according to the pre-calibration result, the pixel position corresponding to the light spot 224 formed by the reflected light beam incident on the sampling area during the ranging process can be determined. Strict alignment can effectively reduce the design difficulty of the system.

Furthermore, considering that the temperature change of the device, mechanical oscillation and other influencing factors will cause the light spot emission to shift during the ranging process, in this embodiment, the incident position of the light spot can be tracked in real time during the ranging process. For example, during the ranging process, the position of the sensing area corresponding to the light spot is re-calibrated at regular intervals, which is beneficial to improve the accuracy of ranging. For example, after recalibrating after a period of time, it is determined that the reflected beam is incident on the sampling area to form a light spot 223, then the pixel area corresponding to the light spot 223 is used as the sensing area, and the control circuit controls the pixels in the sensing area to activate and collect the reflected beam.

The transmitter 21 further includes a transmitting optical component, and the collector 22 further includes a receiving optical component. Preferably, the transmitting optical component and the receiving optical component include the same telecentric lens. Then, the light beam emitted by the VCSEL column light source can be projected with a large field of view after passing through the telecentric lens, and the light beam projected by each light source can be collimated. The receiving optical component uses the same telecentric lens to realize the conjugate relationship between the center of the transmitter and the center of the receiver, which reduces the offset error of the light spot.

The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art to which the present invention belongs, under the premise of not departing from the concept of the present invention, several equivalent substitutions or obvious modifications can be made, and the performance or use is the same, which should be regarded as belonging to the protection scope of the present invention.

Claims

A multi-line scanning distance measurement system, comprising:

a transmitter, including a column light source composed of a plurality of light sources, for emitting a pulsed beam to the target object;

The collector includes a plurality of sampling areas with the same number as the light sources, each of the sampling areas includes a pixel array composed of a plurality of pixels and a plurality of control circuits, and the control circuits are connected to the pixels to individually control the mode of operation of the pixels; the plurality of sampling regions are associated with the column of light sources, and only a subset of the pixels within the sampling regions are activated for collecting the reflected pulsed light beam;

A rotating assembly, connected with the transmitter and the collector, for controlling the transmitter and the collector to rotate synchronously to complete a 360-degree scan of the target object to form multiple scans in the target field of view Wire;

A processing circuit, connected with the transmitter and the collector, is used for synchronizing the trigger signals of the transmitter and the collector, and processing the photon signal of the pixel collection beam, based on the pulse beam from the The distance information of the target object is calculated from the time of flight transmitted to the time of flight received by the collector.
The multi-line scanning distance measurement system according to claim 1, wherein the column of light sources includes a plurality of the light sources arranged at intervals in the vertical direction.
The multi-line scanning distance measurement system according to claim 1, wherein the transmitter further comprises an emission optical component for receiving the pulsed beam emitted by the light source and shaping it, and projecting the shaped beam to the the target object.
4. The multi-line scanning distance measurement system of claim 3, wherein the collector includes a receiving optical assembly, and the receiving optical assembly and the transmitting optical assembly are configured to include the same telecentric lens.
The multi-line scanning distance measurement system according to claim 1, wherein the collector further comprises a plurality of readout circuits connected with the plurality of sampling regions in a one-to-one correspondence, for recording photons from emission to being received. Acquire the time of flight and output the photon time signal, and use the photon time signal to construct a histogram.
The multi-line scanning distance measurement system according to claim 5, wherein the readout circuit comprises a TDC circuit and a histogram memory, and all pixels in the sampling area share a TDC circuit;

Alternatively, the readout circuit includes a TDC circuit array and a histogram memory, the number of TDC circuits in the TDC circuit array is the same as the number of the pixels in the sampling area, and each pixel is associated with the TDC circuit One-to-one connection.
The multi-line scanning distance measurement system according to claim 1, wherein the size of the sampling area is determined according to the offset caused by the system tolerance.
The multi-line scanning distance measurement system according to claim 1, wherein the position of the pixel in the active state in the sampling area is determined by means of pre-calibration.
2. The multi-line scanning distance measurement system of claim 1, wherein the subset of pixels is configured as a sensing area, the sensing area including at least two of the pixels.
The multi-line scanning distance measurement system of claim 1, wherein the transmitter and the collector are attached to the rotating assembly, the rotating assembly controlling the transmitter and the collector Synchronized horizontal rotation around the same rotation axis.