CN111103574A

CN111103574A - Multi-channel driving system, laser radar comprising same and laser driving method

Info

Publication number: CN111103574A
Application number: CN201911164381.6A
Authority: CN
Inventors: 尹辉; 向少卿
Original assignee: Hesai Photonics Technology Co Ltd
Current assignee: Hesai Photonics Technology Co Ltd
Priority date: 2019-11-25
Filing date: 2019-11-25
Publication date: 2020-05-05

Abstract

The invention relates to a multi-channel driving system for a laser radar transmitting end, which comprises: a digital control unit having a plurality of sets of outputs; a plurality of single channel laser drive circuits, each coupled to one of the set of outputs of the digital control unit, wherein the digital control unit is configured to selectively gate one of the plurality of single channel laser drive circuits to output a laser drive signal.

Description

Multi-channel driving system, laser radar comprising same and laser driving method

Technical Field

The present invention generally relates to the field of optoelectronic technologies, and in particular, to a multi-channel driving system for a lidar transmitting end, a lidar including the same, and a method for driving a plurality of lasers through the multi-channel driving system.

Background

With the rapid development of artificial intelligence technology, application scenarios such as automatic driving, face recognition, 3D photographing and the like are gradually mature. LiDAR is a general name of laser active detection sensor equipment, and the working principle of the LiDAR is roughly as follows: laser radar's transmitter launches a bundle of laser, and after laser beam met the object, through diffuse reflection, returned to laser receiver, radar module multiplies the velocity of light according to the time interval of sending and received signal, divides by 2 again, can calculate the distance of transmitter and object. Depending on the number of laser beams, there are generally, for example, a single line laser radar, a 4-line laser radar, an 8/16/32/64-line laser radar, and the like. One or more laser beams are emitted along different angles in the vertical direction and scanned in the horizontal direction to realize the detection of the three-dimensional profile of the target area. The multiple measurement channels (lines) correspond to the scan planes at multiple tilt angles, so that the more laser beams in the vertical field, the higher the angular resolution in the vertical direction, and the greater the density of the laser point cloud.

The lidar is taken as an important stereo imaging induction interface, and can be said to be a basic condition for the development of the application directions. In order to ensure the robustness and reliability of the system, reduce power consumption and improve efficiency, the integration level of the laser driving system needs to be continuously improved, and the change of system parameters needs to be monitored and adjusted in time.

The statements in the background section are merely prior art as they are known to the inventors and do not, of course, represent prior art in the field.

Disclosure of Invention

The invention provides a multi-channel driving system for a laser radar transmitting end, which comprises:

a digital control unit having a plurality of sets of outputs;

a plurality of single channel laser drive circuits, each single channel laser drive circuit coupled to one of the sets of outputs of the digital control unit,

wherein the digital control unit is configured to selectively gate one of the plurality of single channel laser drive circuits to output a laser drive signal.

According to one aspect of the invention, each of the plurality of sets of outputs includes a differential signal and an enable signal, and each of the single-channel laser driving circuits is gated according to the enable signal and generates and outputs the laser driving signal according to the differential signal.

According to one aspect of the invention, each of the single channel laser drive circuits includes a narrow pulse generator configured to receive the differential signal and the enable signal and generate a narrow pulse, and a multi-stage inverter configured to receive the narrow pulse and amplify it in stages to generate the laser drive signal.

According to one aspect of the invention, the digital control unit is an integrated circuit chip.

According to one aspect of the invention, each of the single-channel laser driving circuits comprises an abnormal state detection unit configured to detect an abnormal state in the single-channel laser driving circuit and report information of the abnormal state to the digital control unit.

According to one aspect of the invention, the abnormal condition comprises one or more of an overcurrent, an overtemperature and a short circuit, and the digital control unit is configured to stop gating the single-channel laser driving circuit when receiving abnormal condition information from one of the single-channel laser driving circuits.

According to an aspect of the invention, the multi-channel driving system further comprises a temperature detection unit coupled to the digital control unit and configured to detect a temperature of the multi-channel driving system, the digital control unit being configured to calibrate the multi-channel driving system according to the temperature.

According to one aspect of the invention, the multichannel drive system further comprises a voltage converter that can adjust the amplitude of the laser drive signal.

The present invention also provides a laser radar comprising:

a multi-channel drive system as described above; and

a plurality of lasers corresponding to a plurality of single channel laser drive circuits of the multi-channel drive system, the plurality of lasers being driven by the corresponding single channel laser drive circuits.

The present invention also provides a method of driving a plurality of lasers using a multi-channel drive system as described above, comprising:

determining one or more lasers to be driven;

and gating one or more single-channel laser driving circuits corresponding to the one or more lasers through the digital control unit, and outputting laser driving signals.

According to one aspect of the invention, the method further comprises:

and sequentially gating each of the plurality of single-channel laser driving circuits according to a preset mode so as to drive each laser.

In the embodiment of the invention, the digital control unit can realize multi-channel fully differential control, can realize fine adjustment of the width of the transmitted pulse, and avoids parasitic parameters of discrete devices such as inductance, resistance and capacitance during board-level routing. According to a preferred embodiment of the present invention, the crosstalk problem of external power lines, ground lines, etc. is avoided by fully-differential routing inside the chip.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 shows a schematic diagram of a multi-channel drive system according to one embodiment of the invention;

FIG. 2 shows a schematic diagram of a single channel laser driver circuit according to a preferred embodiment of the present invention;

FIG. 3 shows signal waveforms in accordance with a preferred embodiment of the present invention;

fig. 4 illustrates a method of driving multiple lasers according to one embodiment of the present invention.

Detailed Description

In the following, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the description of the present invention, it should be noted that unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection, either mechanically, electrically, or in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly above and obliquely above the second feature, or simply meaning that the first feature is at a lesser level than the second feature.

The following disclosure provides many different embodiments or examples for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize applications of other processes and/or uses of other materials.

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

FIG. 1 illustrates a multi-channel drive system 10, such as may be used at a lidar transmit end, according to one embodiment of the invention. Described in detail below with reference to fig. 1.

As shown in fig. 1, the multi-channel drive system 10 includes a digital control unit 11 and a plurality of single-channel laser drive circuits 12, shown in fig. 1 as channel 1 laser drive circuit 12-1, channel 2 laser drive circuit 12-2, through to channel n laser drive circuit 12-n. Wherein the digital control unit 11 has a plurality of sets of outputs, each set of outputs being connected to one of the single channel laser driver circuits 12. The laser driving circuit 12 receives one set of outputs of the digital control unit 11, and generates a driving output signal Out for driving a laser (not shown) coupled thereto according to the received signal. When applied to driving lasers in a lidar, the number of the single-channel laser driving circuits 12 may correspond to the number of lasers in the lidar, or may correspond to the number of lines of the lidar, such as 1, 2, 4, 8, 16, 32, 40, 64, 128, etc., for example, and these are within the scope of the present invention. According to an embodiment of the present invention, the digital control unit 11 does not gate all of the single-channel laser driving circuits 12 simultaneously, but is configured to selectively gate one or more of the plurality of single-channel laser driving circuits to sequentially output the driving signals Out-1, Out-2, …, Out-n of the respective lasers.

The digital control unit is used as a control center of the system and can realize information interaction with the laser radar controller. For example, according to an embodiment of the present invention, a certain gating logic, such as the gating logic of channels 1-n, may be built in the digital control unit 11, and one or more of the n single-channel laser driving circuits 12 are sequentially gated in a certain order. Or alternatively, the digital control unit 11 may include an address input pin for inputting an address of the single-channel laser driving circuit 12 to be gated. Taking 64 line lidar as an example, it has 64 lasers and thus 64 single channel laser driver circuits. In order to encode the addresses of the 64 single-channel laser drive circuits, the digital control unit 11 needs to have 6 address input pins. For example, when the digital sequence input by six address input pins is 000100, the digital control unit 11 gates the 4 th single-channel laser driving circuit; when the input digital sequence of the six address input pins is 001100, the digital control unit 11 gates the 12 th single-channel laser driving circuit 12-12.

Each of the plurality of sets of output signals includes an enable signal ENB. Each single channel laser driver circuit 12 will decide whether it is gated or not based on the enable signal ENB it receives. For example, when the enable signal ENB is high, the strobe is indicated. The ENB signal is a digital signal and is 0 or 1. The ENB signal is consistent with the previous sequence of codes that characterize the channel address, e.g., channel 4 is on, ENB4 is high, which is the case when channel 4 is on and the ENBs for the other channels are 0 and are off.

In addition, according to an embodiment of the present invention, each of the plurality of sets of output signals includes a differential signal INN (first differential signal) and an INP (second differential signal) in addition to the enable signal ENB, and each of the single-channel laser driving circuits generates and outputs the laser driving signal Out based on the differential signals INN and INP after gating. The digital control unit 11 can realize multi-channel fully differential control, can realize fine adjustment of the width of the transmitted pulse, and avoids parasitic parameters of discrete devices such as inductance, resistance and capacitance during board-level routing. According to a preferred embodiment of the present invention, the crosstalk problem of external power lines, ground lines, etc. is avoided by fully-differential routing inside the chip.

In addition, according to an embodiment of the present invention, in a system where a FAULT TX (abnormal state monitoring module) signal is fed back, the FAULT TX may also be considered as a digital sequence, for example, when normal, the FAULT TX is at a low level, and when the above problem occurs, the channel level where the problem occurs becomes 1. At this time, the digital control unit detects this information and simultaneously generates an interrupt signal int, which turns off the chip using a pull-up resistor and then restarts the operation or the like.

According to a preferred embodiment of the present invention, the digital control unit 11 is an integrated circuit chip. Such as registers, digital processors DSP, etc., may be integrated on one integrated circuit chip.

Fig. 2 shows a schematic diagram of a single channel laser driver circuit 12 according to a preferred embodiment of the present invention. Described in detail below with reference to fig. 2.

As shown in fig. 2, each of the single-channel laser driving circuits 12 may include an inverter 121, an and gate 122, an inverter 123, and an inverter 124 connected in sequence. The first differential signal INN is inverted by the inverter 121, and then input to the and gate 122 together with the second differential signal INP and the enable signal ENB, and after the and operation of the first differential signal INN, the second differential signal INP, the enable signal ENB, the and gate, the inverter 123 and the inverter 124 are used to amplify the signals step by step, and finally the laser driving signal OUT is generated and output. Wherein the inverter 121 and the and gate 122 constitute a narrow pulse generator configured to receive the differential signal and the enable signal and generate a narrow pulse. As shown in fig. 3, waveforms of the first differential signal INN, the second differential signal INP, and the finally output laser drive signal OUT are shown. The leading edge transition time of the pulse of the first differential signal INN lags behind the leading edge transition time of the pulse of the second differential signal INP by a time Tpulse, and the pulse of the laser drive signal OUT having the same width Tpulse is finally output through the operation processing of the inverter and the and gate. When a switch of the laser (e.g., a GaN switch) receives the pulse, the switch closes, causing current to flow through the laser, which is driven to emit light.

The inclusion of two

inverters

123 and 124 on the output side of the narrow pulse generator, which amplifies the output of the narrow pulse generator in stages, is schematically shown in fig. 2. The present invention is not limited thereto and may include a greater or lesser number of inverters. The main purpose of the

inverters

123 and 124 is to amplify and output the laser driving signal OUT step by step, so the number of inverters can be determined according to the power and level requirements of the laser driving signal OUT and the amplification capability of the inverters. These are all within the scope of the present invention. The single-channel laser driving circuit adopts the most direct phase inverter to realize the fast driving of narrow pulses by pushing step by step. The gradual pushing of the inverters reduces the drive delay time from input to output to the maximum extent.

According to a preferred embodiment of the present invention, as shown in fig. 2, each of the single-channel laser driving circuits 12 may include an abnormal state detection unit 125. The abnormal state detection unit 125 is configured to detect an abnormal state in the single-channel laser driving circuit 12 corresponding thereto, and report information of the abnormal state to the digital control unit 11. As shown in fig. 1, between each single-channel laser driver circuit 12 and the digital control unit 11, there is a transmission of a signal FAULT. The signal FAULT may be a simple signal with or without an abnormal state, for example, represented by 0 and 1. Or may be a description of a particular abnormal condition. The abnormal state of the single channel laser driver circuit 12 may include, for example, one or more of an over-current, an over-temperature, and a short circuit of the circuit. For example, in order to detect the over-temperature of the circuit, the abnormal state detecting unit 125 may include a corresponding temperature sensor to detect the temperature of the circuit, and when the temperature exceeds a preset threshold, the abnormal state detecting unit 125 sends a signal of the over-temperature abnormal state to the digital control unit 11. To detect the current, the abnormal state detection unit 125 may include a corresponding current sensor to detect a current condition of one or more branches in the circuit and, when the current is abnormal, signal an abnormal state such as a short circuit or an overcurrent to the digital control unit 11. When receiving the abnormal state information from one of the single-channel laser driving circuits, the digital control unit 11 stops gating the single-channel laser driving circuit, and can timely give an alarm to prompt an operator that the laser driving circuit of one of the channels is in fault or abnormal.

In the conventional scheme, the abnormal state signal FAULT is generally not used because the feedback is too small to be processed. In the traditional scheme, the conditions of over-temperature, under-voltage, over-current and the like cannot be accurately and quickly sensed. Eye safety currently has no on-chip integration scheme worldwide. These are difficult to detect by external means due to the requirements on accuracy and speed. In the embodiment of the invention, on-chip integration is adopted, and high-precision and quick detection can be realized through circuit design. In the multi-channel scheme of the present invention, the abnormal state monitoring module feeds back the signal that has the problems of over-temperature, under-voltage, eye safety, over-current, etc. in the system, FAULT TX may also be regarded as a digital sequence, for example, in a normal state, it is at a low level, when the above problems occur, the channel level that has the problems becomes 1, at this time, the digital control unit detects this information and simultaneously generates the interrupt signal int, as shown in fig. 1, the interrupt signal turns off the chip (for example, turns off the driving high output of the digital control unit) by using the pull-up resistor, and then restarts the operation or the like.

As shown in fig. 1, the multi-channel driving system 10 further includes a temperature detection unit 13. A temperature detection unit 13 is coupled to the digital control unit 11 and is configured to detect the temperature of each of the multi-channel drive systems 10. The multi-channel drive system 10 includes a plurality of electronic devices whose operating performance may vary with temperature. Errors in changes in operating parameters and performance can cause serious problems when temperature changes exceed certain limits. In the present invention, the digital control unit 11 is coupled to the temperature detection unit 13 and receives the temperature information, and calibrates the multi-channel driving system 10 or other electronic devices thereon according to the temperature information. For example, the digital control unit 11 may adjust parameters such as the intensity, the leading edge inversion time, and the pulse width of the differential signals INP and INN, so as to adjust the laser driving signal OUT output by the corresponding single-channel laser driving circuit 12. Therefore, the temperature detection unit 13 can detect the temperature of the chip in real time and feed back the detection data to the digital control unit 11, so as to realize real-time calibration, thereby avoiding the outside temperature and parameter temperature drift caused by the temperature rise of the chip.

As shown in fig. 2, the single channel laser drive circuits 12 each further include a voltage converter 126, according to a preferred embodiment of the present invention, the voltage converter 126 adjusting the amplitude of the laser drive signal. Through the voltage converter module, the adjustment of the driving voltage can be realized, so that the channel driving capacity is controlled within a reasonable range. The voltage converter can be used for light intensity adjustment, namely the light intensity of the laser light of each channel can be different and can be adjusted.

Compared with the single-channel driving of the prior art, the embodiment of the invention adds a digital control unit and an abnormal state detection unit (which can output a FAULT signal, as shown in fig. 1 and 2). First, the digital control unit determines which channel is controlled to be turned on. For example, when receiving a sequence of numbers 000100 characterizing the channel address, channel 4 is turned on. In addition, the embodiment of the invention adopts differential signals. In the conventional scheme, each channel is to independently provide a differential signal, the circuit occupies a large area of the system, a digital sequence is provided for the digital control unit, and then the channel to which the differential signal is provided is determined, and the differential signal is as shown in fig. 3, so that an output signal Tpulse can be obtained, and the GaN switch can be driven. Through the abnormal state detection module, the problems of overcurrent, overtemperature and short circuit abnormality possibly generated by the channel driving circuit are detected and uploaded so as to be processed in the digital control unit in time.

The invention also relates to a laser radar, which comprises the multi-channel driving system 10 and a plurality of lasers, wherein the lasers correspond to a plurality of single-channel laser driving circuits of the multi-channel driving system and are driven by the corresponding single-channel laser driving circuits to emit the lasers. The digital control unit is used as a control center of the driving system to realize information interaction with the laser radar controller.

The invention also relates to a method 100 of driving a plurality of lasers, as shown in fig. 4, which may be implemented, for example, using a multi-channel drive system 100 as described above. As described in detail below with reference to fig. 4.

In step S101, one or more of the lasers to be driven is determined. In the plurality of lasers, one of the lasers is selected to be driven to emit light at a time according to a certain logic.

In step S102, a single-channel laser driving circuit corresponding to the laser is gated by the digital control unit, and a laser driving signal is output.

According to an embodiment of the invention, the method 100 further comprises sequentially gating each of the plurality of single-channel laser driving circuits according to a preset pattern to cyclically drive each laser.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-channel drive system usable with a lidar transmitting end, comprising:

a digital control unit having a plurality of sets of outputs;

2. The multi-channel drive system of claim 1, each of the plurality of sets of outputs comprising a differential signal and an enable signal, each of the single-channel laser drive circuits being gated based on the enable signal and generating and outputting the laser drive signal based on the differential signal.

3. A multi-channel drive system as defined in claim 2, wherein each of the single-channel laser drive circuits includes a narrow pulse generator configured to receive the differential signal and the enable signal and generate a narrow pulse and a multi-stage inverter configured to receive the narrow pulse and to amplify it in stages to generate the laser drive signal.

4. A multi-channel drive system as claimed in any one of claims 1 to 3 wherein said digital control unit is an integrated circuit chip.

5. A multi-channel drive system as defined in any one of claims 1 to 3, wherein each of said single-channel laser drive circuits comprises an abnormal state detection unit configured to detect abnormal states within said single-channel laser drive circuit and to report information of the abnormal states to said digital control unit.

6. A multi-channel drive system as claimed in claim 5 wherein the abnormal conditions include one or more of over-current, over-temperature, short circuit, the digital control unit being configured to stop gating one of the single channel laser drive circuits when abnormal condition information is received from the single channel laser drive circuit.

7. A multi-channel drive system as claimed in any one of claims 1 to 3, further comprising a temperature detection unit coupled to the digital control unit and configured to detect a temperature of the multi-channel drive system, the digital control unit being configured to calibrate the multi-channel drive system in dependence on the temperature.

8. A multi-channel drive system as defined in claim 3, further comprising a voltage converter that can adjust the amplitude of the laser drive signal.

9. A lidar comprising:

a multi-channel drive system as claimed in any one of claims 1 to 8; and

10. A method of driving a plurality of lasers using a multi-channel drive system as claimed in any one of claims 1 to 8, comprising:

determining one or more lasers to be driven;

11. The method of claim 10, further comprising: