WO2024104258A1

WO2024104258A1 - Lidar

Info

Publication number: WO2024104258A1
Application number: PCT/CN2023/130912
Authority: WO
Inventors: Fan Fei; Zhiwei MA; Shaoqing Xiang
Original assignee: Hesai Technology Co., Ltd.
Priority date: 2022-11-14
Filing date: 2023-11-10
Publication date: 2024-05-23
Also published as: CN118033603A

Abstract

A LiDAR includes a light emitter (30) and a monitoring circuit (20). The light emitter (30) includes a plurality of lasers. The monitoring circuit (20) includes a detection unit (21). The detection unit (21) includes a plurality of detectors. The monitoring circuit (20) is configured to monitor an operating state of the plurality of lasers based on stray light inside the LiDAR.

Description

LIDAR

CROSS-REFERENCE TO RELATED APPLICATION (S)

This application claims priority to Chinese Patent Application No. 202211418422.1, filed on November 14, 2022, the content of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the technical field of circuit monitoring, specifically to circuit monitoring of a LiDAR.

BACKGROUND

A LiDAR can transmit laser detection signals to a target space. Part of the laser detection signals can be reflected by an obstacle and return to the LiDAR. The reflected laser detection signals can form echo signals. The LiDAR can compare the echo signals with the laser detection signals to determine information of the obstacle, such as a distance, a position, a motion state, or the like. Typically, a laser of the LiDAR can transmit a beam of detection light. A detector corresponding to the laser can receive echo light reflected by the obstacle. The LiDAR can determine information associated with an angle based on information of the beam of detection light and the echo light. A detection channel of the LiDAR can include a laser (e.g., the above-described laser) and a detector corresponding to an azimuthal angle of a field of view of the laser. The detection channel can determine data along a line, such as a distance to the obstacle, an azimuthal angle, or the like.

The performance and the number of lines of LiDARs are increasing. If circuits at a LiDAR transmitter fail, for example, if a laser driver based on gallium nitride (GaN) materials fails or if a power supply circuit of the laser is disconnected, the laser can fail. If a laser in any of the channels fails, the number of lines of the LiDAR is reduced, which can further reduce the ranging performance. Therefore, it is beneficial to monitor each of the lasers in real time. Once a laser of a certain channel fails to emit light normally, the failed channel can be detected in time, and maintenance (e.g., replacement) can be performed.

In some existing techniques for monitoring lasers, a photosensitive element can be installed at the transmitter of the LiDAR. The light transmitted by a laser can be reflected by internal elements (e.g., optical elements such as a lens, or mechanical elements, or any other elements) of the LiDAR to generate stray light. The stray light can be irradiated on the photosensitive element to generate an electric signal. The electric signal can be used to determine whether the laser emits light normally. However, as the number of lines of the LiDAR increases, the transmitter can include a large number (e.g., 128, 256, or even more) of lasers. The large number of lasers can be installed in dispersed positions. In some cases, the photosensitive element cannot receive stray light from all lasers for detecting whether the lasers emit light normally, which can cause detection failure.

SUMMARY

An embodiment of the present disclosure provides a LiDAR that can perform real-time diagnosis on each of lasers in a light emitting unit inside the LiDAR and improve the accuracy of the diagnostic result.

For this purpose, the embodiments of the present disclosure provide the following technical solutions.

An embodiment of the present disclosure provides a LiDAR comprising a light emitting unit or a light emitter and a monitoring circuit, wherein, the light emitting unit or the light emitter comprises a plurality of lasers; the monitoring circuit comprises a detection unit, the detection unit comprises a plurality of detectors connected in parallel, and the monitoring circuit monitors an operating state of each of the lasers according to stray light inside the LiDAR.

Optionally, the monitoring circuit further comprises an integrating unit or the integrator and a coupling unit, and the coupling unit or the coupler is coupled to the detection unit and the integrating unit or the integrator respectively; wherein, the detection unit is configured for collecting an optical signal emitted by the light emitting unit or the light emitter and converting the optical signal into an electrical signal for outputting; the coupling unit or the coupler is configured for coupling and transmitting the electrical signal to the integrating unit or the integrator; and the integrating unit or the integrator is configured for converting the electrical signal transmitted by the coupling unit or the coupler into a voltage signal, wherein, the voltage signal is used to determine the operating state of the light emitting unit or the light emitter.

Optionally, the coupling unit or the coupler is a capacitor.

Optionally, the integrating unit or the integrator is an RC integrating circuit.

Optionally, the monitoring circuit further comprises an output voltage clamping unit connected in parallel with the integrating unit or the integrator and configured for controlling the voltage signal output by the integrating unit or the integrator not to exceed a preset amplitude.

Optionally, the output voltage clamping unit comprises any of the following: a Schottky diode, a stabilivolt, a transient voltage suppressor ( “TVS” ) , or an operational amplifier.

Optionally, the output voltage clamping unit comprises a plurality of Schottky diodes connected in series.

Optionally, the monitoring circuit further comprises a state switching unit or a state switch coupled with the integrating unit or the integrator and adapted for switching between different operating states.

Optionally, the state switching unit or the state switch is configured for discharging the integrating unit or the integrator before monitoring the light emitting unit or the light emitter, and controlling the integrating unit or the integrator to integrate the received electrical signal when monitoring the light emitting unit or the light emitter.

Optionally, the state switching unit or the state switch is further configured for compensating for the voltage signal output by the integrating unit or the integrator when activating the detection unit.

Optionally, the state switching unit or the state switch is a three-state buffer; wherein, an output terminal of the three-state buffer is connected to an output terminal of the integrating unit or the integrator.

Optionally, before monitoring the light emitting unit or the light emitter, the three-state buffer outputs a low level to discharge the integrating unit or the integrator; when monitoring the light emitting unit or the light emitter, an output of the three-state buffer is in a high-impedance state, so that the integrating unit or the integrator integrates the received electrical signal; and when the detection unit is activated, the three-state buffer outputs a high level to compensate for the voltage signal output by the integrating unit or the integrator.

Optionally, the monitoring circuit further comprises a power switch, the power switch is configured for activating the detection unit when monitoring the light emitting unit or the light emitter; and deactivating the detection unit after the monitoring is completed.

Optionally, the power switch comprises a first switching unit or a first switch and a second switching unit or a second switch, the first switching unit or a first switch is connected between a working power supply and a ground, and the second switching unit or a first switch is connected between the working power supply and an Enable terminal of the detection unit;

wherein, the first switching unit or a first switch is configured for controlling, according to an external control signal, the second switching unit or a second switch to connect the working power supply with the Enable terminal of the detection unit when monitoring the light emitting unit or the light emitter, and controlling the second switch unit to disconnect the working power supply from the Enable terminal of the detection unit after the monitoring is completed.

Optionally, the first switching unit or a first switch is an NMOS transistor, and the second switching unit or the second switch is a PMOS transistor.

Optionally, the detection unit comprises a plurality of SiPMs connected in parallel, and the plurality of SiPMs are disposed on a same chip.

Optionally, the detection unit of the monitoring circuit and the light emitting unit or the light emitter are disposed on a same circuit board.

Optionally, the LiDAR further comprises a control unit or a controller; the control unit or the controller sends a light emitting instruction to the light emitting unit or the light emitter and sends a monitoring instruction to the monitoring circuit; the monitoring circuit determines the operating state of the light emitting unit or the light emitter after receiving the monitoring instruction.

Optionally, the control unit or the controller controls the monitoring circuit to monitor the light emitting unit or the light emitter when the LiDAR does not perform obstacle detection.

An embodiment of the present disclosure provides a LiDAR comprising a light emitting unit comprising a plurality of lasers and a monitoring circuit comprising a detection unit, wherein the detection unit comprises a plurality of detectors, and the monitoring circuit is configured to monitor an operating state of the plurality of lasers based on stray light inside the LiDAR.

Optionally, the monitoring circuit further comprises an integrating unit and a coupling unit, the coupling unit being coupled to the detection unit and the integrating unit, the detection unit is configured to collect an optical signal emitted by the light emitting unit and convert the optical signal into an electrical signal for outputting, the coupling unit is configured to transmit the electrical signal to the integrating unit, and the integrating unit is configured to convert the electrical signal transmitted by the coupling unit into a voltage signal for determining the operating state of the light emitting unit.

Optionally, the coupling unit is a capacitor.

Optionally, the integrating unit is an RC integrating circuit.

Optionally, the monitoring circuit further comprises an output voltage clamping unit connected in parallel with the integrating unit and configured to control the voltage signal output by the integrating unit not to exceed a predetermined amplitude.

Optionally, the output voltage clamping unit comprises any of a Schottky diode, a stabilivolt, a transient voltage suppressor, or an operational amplifier.

Optionally, the monitoring circuit further comprises a state switching unit coupled with the integrating unit and configured to switch between different operating states.

Optionally, the state switching unit is configured to discharge the integrating unit before the light emitting unit is being monitored, and control the integrating unit to integrate the electrical signal when the light emitting unit is being monitored.

Optionally, the state switching unit is further configured to compensate for the voltage signal output by the integrating unit when activating the detection unit.

Optionally, the state switching unit comprises a three-state buffer, and an output terminal of the three-state buffer is connected to an output terminal of the integrating unit.

Optionally, the three-state buffer is configured to output a low level to discharge the integrating unit before the light emitting unit is being monitored, when the light emitting unit is being monitored, an output of the three-state buffer is in a high-impedance state, the three-state buffer is configured to cause the integrating unit to integrate the received electrical signal, and when the detection unit is activated, the three-state buffer outputs a high level to compensate for the voltage signal output by the integrating unit.

Optionally, the monitoring circuit further comprises a power switch, the power switch is configured to activate the detection unit when the light emitting unit is being monitored and deactivate the detection unit after the light emitting unit is being monitored.

Optionally, the power switch comprises a first switching unit and a second switching unit, the first switching unit is connected between a working power supply and a ground, and the second switching unit is connected between the working power supply and an enable terminal of the detection unit, and wherein the first switching unit is configured to control, based on an external control signal, the second switching unit to connect the working power supply with the enable terminal of the detection unit when monitoring the light emitting unit, and to control the second switch unit to disconnect the working power supply from the enable terminal of the detection unit after the light emitting unit is being monitored.

Optionally, the first switching unit comprises an NMOS transistor, and the second switching unit comprises a PMOS transistor.

Optionally, the detection unit comprises a plurality of silicon photomultipliers connected in parallel and disposed on a same chip.

Optionally, the detection unit and the light emitting unit are disposed on a same circuit board.

Optionally, the LiDAR further comprises a control unit, configured to send a light emitting instruction to the light emitting unit and send a monitoring instruction to the monitoring circuit, wherein the monitoring circuit is further configured to determine the operating state of the light emitting unit after receiving the monitoring instruction.

Optionally, the control unit control the monitoring circuit to monitor the light emitting unit when the LiDAR is not performing obstacle detection.

Optionally, the plurality of detectors are connected in parallel.

Optionally, the monitoring circuit is configured to monitor an operating state of each of the plurality of lasers.

An embodiment of the present disclosure provides a terminal device comprises: LiDAR described in above embodiments and a connector, configured to connect the LiDAR and the terminal device.

Optionally, the terminal device includes a car, a drone or a robot.

The LiDAR provided by the embodiments of the present disclosure uses a plurality of detectors connected in parallel to collect stray light signals from the light emitting unit or the light emitter inside the LiDAR, and monitor whether each laser in the light emitting unit or the light emitter emits light normally. The parallel connection of the plurality of detectors increases photosensitive surface of the detector, enhance the response ability of the detector to photons, so that the monitoring circuit can receive and detect stray light signals from all lasers in the light emitting unit or the light emitter. At the same time, the plurality of detectors connected in parallel could generate a larger current, which could generate a more effective detection signal, thereby improving monitoring accuracy and monitoring efficiency. In addition, the monitoring circuit provided by an embodiment of the present disclosure can be applied to a variety of LiDARs, which has strong versatility.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings form part of the present disclosure and provide further understanding to the present disclosure. The schematic drawings and the description thereof describes example embodiments of the present disclosure but do not form an improper limitation to the present disclosure.

FIG. 1 shows a schematic diagram illustrating a structure of an example LiDAR, consistent with some embodiments of this disclosure.

FIG. 2 shows a schematic diagram illustrating a structure of an example monitoring circuit, consistent with some embodiments of this disclosure.

FIG. 3 shows a schematic diagram illustrating a first example application structure of the example monitoring circuit of FIG. 2, consistent with some embodiments of this disclosure.

FIG. 4 shows a schematic diagram illustrating a second example application structure of the monitoring circuit of FIG. 2, consistent with some embodiments of this disclosure.

FIG. 5 shows a schematic diagram illustrating a structure of an example monitoring circuit having a Schottky diode for output voltage clamping, consistent with some embodiments of this disclosure.

FIG. 6 shows a schematic diagram illustrating a structure of another example monitoring circuit having two Schottky diodes for output voltage clamping, consistent with some embodiments of this disclosure.

FIG. 7 shows a schematic diagram illustrating a third example application structure of the monitoring circuit of FIG. 2, consistent with some embodiments of this disclosure.

FIG. 8 shows a schematic diagram illustrating a waveform of an example negative pulse signal generated at the OUT terminal in the example monitoring circuit of FIG. 4 when a negative power supply NVBIAS is powered on, consistent with some embodiments of this disclosure.

FIG. 9 shows a schematic diagram illustrating a waveform of an example negative pulse signal generated at the OUT terminal in the example monitoring circuit of FIG. 7 when a negative power supply NVBIAS is powered on, consistent with some embodiments of this disclosure.

FIG. 10 shows a schematic diagram illustrating a fourth application structure of the example monitoring circuit of FIG. 2, consistent with some embodiments of this disclosure.

FIG. 11 shows a schematic diagram illustrating a fifth application structure of the example monitoring circuit of FIG. 2, consistent with some embodiments of this disclosure.

FIG. 12 shows a block diagram illustrating an example power switch in the example monitoring circuit of FIG. 11, consistent with some embodiments of this disclosure.

FIG. 13 shows a schematic diagram illustrating a structure of the example power switch of FIG. 12, consistent with some embodiments of this disclosure.

FIG. 14 shows a schematic diagram illustrating a structure of an example LiDAR, consistent with some embodiments of this disclosure.

DETAILED DESCRIPTION

To make the purposes, features, and beneficial effects of this disclosure more clear and understandable, example embodiments are described below in conjunction with the accompanying drawings.

In some embodiments, the number of light emitting units or light emitters in a multi-line LiDAR can be large, and they can be installed in dispersed positions. In such scenarios, generated stray light can also be dispersed. In some existing techniques, one detector is used to monitor multiple light emitting unit or light emitters. In such cases, the detector cannot receive the stray light of all of the light emitting units or the light emitters, and thus it can be challenging to generate an effective monitoring signal, which may lead to monitoring failure.

Embodiments of this disclosure provide a LiDAR that includes a light emitting unit or a light emitter and a monitoring circuit. The light emitting unit or the light emitter includes multiple lasers. The monitoring circuit includes a detection unit that further includes multiple detectors. In some embodiments, the plurality of detectors can be connected in parallel. The monitoring circuit can monitor an operating state of the lasers (e.g., each of the lasers) based on stray light generated inside the LiDAR. In some embodiments, optical signals of the light emitting units or the light emitters (e.g., optical signals emitted by the light emitters and reflected by other objects, such as stray light) can be collected by the detectors connected in parallel. In such cases, the photosensitive surface of the detectors can be increased, thus enhancing the capability of the detectors for responding to photons. The detectors can also generate a larger current, thus generating more effective monitoring signals to improve monitoring accuracy. In addition, the example monitoring circuit consistent with the embodiments of this disclosure has wide applications and can be applied to various LiDARs.

As shown in FIG. 1, the LiDAR includes a light emitting unit or a light emitter 30 and a monitoring circuit 20. The light emitter 30 can include multiple lasers.

When the laser operates, light emitted by the laser can illuminates an object 10. An array of optical detectors can receive light reflected by the object 10. The array of optical detectors can generate an optical signal based on the received light and generate (e.g., by converting) an electrical signal based on the optical signal. The array of optical detectors can further determine a distance or other information associated with the object 10 based on the electrical signal.

In FIG. 1, for example, the monitoring circuit 20 includes a transmitting circuit board 11. The monitoring circuit 20 includes a detection unit 21. The detection unit 21 can include multiple detectors. In some embodiments, the detectors can be connected in parallel. In some embodiments, the monitoring circuit 20 can monitor an operating state of each of the lasers based on stray light generated inside the LiDAR. As shown in FIG. 1, for example, LiDAR elements (e.g., lens) can reflect light emitted by the light emitter 30 and generate stray light. The detection unit 21 in the monitoring circuit 20 can receive the stray light. The detection unit 21 can generate an electrical signal based on the stray light. The monitoring circuit 20 can determine the operating state (e.g., a state representing whether the laser emits light normally) of the laser based on the electrical signal.

As shown in FIG. 2, for example, the monitoring circuit includes a detection unit 21, an integrating unit or the integrator 22, and a coupling unit or the coupler 23. The coupler 23 is coupled to the detection unit 21 and the integrator 22. The detection unit 21 can includes multiple detector. In some embodiments, the detectors can be connected in parallel.

The detection unit 21 can receive an optical signal emitted by the light emitter (not shown in FIG. 2) , and determine an electrical signal to output based on the optical signal. For example, the optical signal can be a signal of stray light generated by light emitted by the light emitter then reflected by internal elements of the LiDAR.

The coupler 23 can transmit the electrical signal to the integrator 22 in a coupling manner.

The integrator 22 can generate (e.g., by converting) a voltage signal based on the electrical signal transmitted by the coupler 23. The voltage signal can be used to determine the operating state of the light emitting unit or the light emitter.

In some embodiments, the light emitting unit or the light emitter can include an array of lasers. In some embodiments, the light emitter can include other types of number of light emitting devices, and the embodiments of this disclosure do not limit the type of the light emitting units or the light emitters.

In some embodiments, the detector of the detection unit 21 can include multiple single-photon avalanche diodes ( “SPAD” ) . For example, the SPADs can be connected in parallel. A SPAD can have a high photoelectric gain and can be suitable for detecting weak optical signals. By using SPADs, the accuracy of monitoring the operating state of the light emitting unit or the light emitter can be improved.

In some embodiments, a detector in the detection unit 21 can be implemented using a silicon photomultiplier ( “SiPM” ) or a SPAD array. SiPM and SPAD arrays can be utilized at the receiving end of a LiDAR, allowing for direct packaging without increase additional costs for the detector.

In FIG. 3, as an example, the coupler 23 is implemented as a capacitor C1. The integrator 22 is implemented as an RC integrating circuit, including a resistor R2 and a capacitor C2 connected in parallel.

In some embodiments, cathodes of the detectors connected in parallel in the detection unit 21 can be connected to a common high-voltage power supply VDD. Anodes of the detectors can be connected to a common negative power supply NVBIAS via a resistor R1. The voltage difference between the high-voltage power supply VDD and the negative power supply NVBIAS can cause the detectors to operate in a Geiger mode. In the Geiger mode, after receiving photons, a detector enters into an avalanche state and generates a large reverse current. after the reverse current is generated, the bias voltage can temporarily decrease below a breakdown voltage by a quenching circuit (not shown in FIG. 3) , and the avalanche can be quenched. Then, the high-voltage power supply VDD and the negative supply NVBIAS can restore the voltage between two ends of the detector to a voltage above the breakdown voltage, and the detector can recover from quenching, waiting to detect a next photon.

In some embodiments, the detectors connected in parallel in the detection unit 21 can receive an optical signal from the light emitting unit or the light emitter and generate a current. The current can output by the capacitor C1 in a coupling manner to charge the capacitor C2 in the integrator 22. An integration value can be output from the output (represented by “OUT” in FIG. 3) terminal of the monitoring circuit. The integration value can be used to detect whether stray light is received by the detection unit 21 when the light emitting unit or the light emitter emits light.

In some embodiments, lasers in the light emitting unit or the light emitter of the LiDAR can be adjusted at different time periods, and the monitoring circuit can synchronously adjust the object to be monitored. For example, during a time period t0～t1, a first laser can emit light while the other lasers do not emit light, and the monitoring circuit can output an integration value at the output terminal for monitoring the operating state of the first laser.

In some embodiments, a voltage threshold can be set for determining whether the integration value output at the OUT terminal of the monitoring circuit exceeds the voltage threshold to determine the operating state of the light emitting unit or the light emitter. For example, when the light emitting unit or the light emitter in a certain channel emits light, if the integration value output at the OUT terminal exceeds the set voltage threshold, it can be determined that the light emitting unit or the light emitter emits light normally.

In some embodiments, the monitoring circuit and the light emitting units or the light emitters can be arranged together within the LiDAR. A distance from the light emitting units or the light emitters to the monitoring circuit can be shorter than a distance from the light emitting unit or the light emitter to external obstacles. In such cases, the light emitting unit or the light emitter can emit light with a lower intensity during monitoring and with a higher intensity during ranging.

In some embodiments, the voltage threshold can be determined based on various factors, such as the intensity of light emitted by the light emitting unit or the light emitter, proportion of stray light in the light emitted by the light emitting unit or the light emitter, or angle of the stray light relative to the detection unit. For example, after assembling the LiDAR, the monitoring circuit can be used to detect the stray light from a laser that emits light normally, and the output end of the monitoring circuit can output the integration value. The voltage threshold can be set based on the integration value.

Consistent with the embodiments of this disclosure, the monitoring circuit can collect light signals of the light emitting unit or the light emitter and monitor whether the light emitting unit or the light emitter emits light normally through multiple detectors connected in parallel. The parallel connection of the detectors can increase their photosensitive area and enhance their capability of responding to photons. The parallel connection of the detectors can generate a large current for generating more effective monitoring signals. By doing so, accuracy and efficiency of the monitoring can be improved.

Still referring to FIG. 3, in some embodiments, at an initial state, the detector does not receive any optical signal, and the voltage at right end of capacitor C1 can be 0V. When the light emitting unit or the light emitter emits light to activate the detection unit, a current can flow through the capacitor C1 and charge the capacitor C2, causing the voltage at the right end of capacitor C1 to increase. When the light emitting unit or the light emitter stops emitting light, the detector can be deactivated, and the charge stored in capacitor C2 can discharge through resistors R1 and R2, causing the voltage at the right end of capacitor C1 to return to 0V.

In some cases, the resistors R1 and R2 can have high resistance. In such cases, the time for the voltage recovery can be long. If the light emitting unit or the light emitter emits light again before the voltage at the right end of capacitor C1 returning to 0V, the voltage at the right end of capacitor C1 can increases again on top of its previous value. With multiple repetitions, the voltage at the right end of capacitor C1 can reach a high value.

FIG. 4 shows a schematic diagram illustrating a second example application structure of the monitoring circuit of FIG. 2, consistent with some embodiments of this disclosure. As shown in FIG. 4, the monitoring circuit includes an output voltage clamping unit 24 connected in parallel with the integrating unit or the integrator (e.g., integrator 22, integrating circuit or the like) . The output voltage clamping unit 24 is configured to control the voltage signal output from the integrator 22 not to exceed a preset amplitude. The output voltage clamping unit 24 is provided at the right end of C1 to control the maximum output voltage at the OUT terminal. By doing so, the voltage output at the OUT terminal can be within the load capacity of circuit components connected at the backend and can less affect normal operation of the backend circuit components or cause damage to the backend circuit components.

In some embodiments, the output voltage clamping unit 24 can include any combination of any number of Schottky diodes, stabilivolts, transient voltage suppressors (TVS) , operational amplifiers, or the like.

In some embodiments, the output voltage clamping unit 24 can include a Schottky diode. The cost for Schottky diodes is low, and its forward conduction leakage current is weak. Using a Schottky diode as the output voltage clamping unit for the monitoring circuit can reduce the cost and power consumption of the monitoring circuit.

As shown in FIG. 5, the right end of capacitor C1 is grounded through Schottky diode D1. The voltage at the right end of capacitor C1 can increase gradually and can increase up to a forward conduction voltage of the Schottky diode D1. When the voltage reaches the forward conduction voltage, the Schottky diode D1 can become conducted and reduce the voltage at the right end of capacitor C1. In such cases, the maximum voltage output by the monitoring circuit can be the forward conduction voltage of Schottky diode D1.

In some embodiments, using a Schottky diode as shown in FIG. 5 can keep the maximum output voltage of the monitoring circuit to be below 0.7V.

In some embodiments, the output voltage clamping unit 24 can include a plurality of Schottky diodes connected in series.

In an example, a predetermined amplitude of the output voltage of the integrating unit or the integrator in the monitoring circuit can be determined based on the load capacity of the backend circuit components. The Schottky diode can set the amplitude of the output voltage of the integrating unit or the integrator in the monitoring circuit to be the forward conduction voltage of the Schottky diode. By using a plurality of Schottky diodes connected in series, the amplitude of the output voltage of the integrating unit or the integrator can be adjusted. By way of example, with reference to FIG. 5, if the output voltage clamping unit 24 includes N Schottky diodes connected in series, the amplitude of the output voltage of the integrating unit or the integrator 22 can be N times of the forward conduction voltage of a Schottky diode. In such cases, the predetermined amplitude of the output voltage of the integrating unit or the integrator 22 can be adjusted by adjusting the number of Schottky diodes connected in series. By doing so, dynamic range of the output voltage signal of the monitoring circuit can be increased without exceeding the load capacity of the backend circuit.

When two Schottky diodes D1 and D2 connected in series are used as the output voltage clamping unit as shown in FIG. 6, the maximum output voltage of the monitoring circuit is the sum of the forward conduction voltage of the Schottky diodes D1 and D2. In an example, the forward conduction voltage of a Schottky diode can be 0.7V, and the maximum output voltage of the monitoring circuit in FIG. 6 can be 1.4V.

Consistent with embodiments of this disclosure, the monitoring circuit can improve the monitoring accuracy and efficiency and effectively reduces adverse effects on the backend circuit components by providing an output voltage clamping unit to ensure that the output voltage of the integrating unit or the integrator does not exceed the predetermined amplitude.

Compared with the example embodiment shown and described in association with FIG. 4, the monitoring circuit in FIG. 7 further includes a state switching unit or the state switch 25. The state switching unit or the state switch 25 is coupled to the integrating unit or the integrator 22 and is for switching between different operating states.

In some embodiments, before the monitoring circuit monitoring the light emitting unit or the light emitter, the integrating unit or the integrator 22 can be discharged, and the output of the integrating unit or the integrator 22 is cleared to zero. When the monitoring circuit is monitoring the light emitting unit, the integrating unit or the integrator 22 can perform an integral operation on the received electrical signal.

In some embodiments, the state switching unit or the state switch 25 can compensate for the voltage signal output by the integrating unit or the integrator 22 when the detection unit is activated. By doing so, the amplitude of the negative pulse voltage generated at the OUT terminal cannot exceed a range for the maximum input voltage of the back-end circuit or chip, which can affect the backend circuit or chip.

In some embodiments where the state switching unit or the state switch 25 is not included in the monitoring circuit, when the negative power supply NVBIAS is powered on, the voltage at the left end of the capacitor C1 can decrease, causing a large negative pulse generated at the OUT terminal, as shown in FIG. 8. FIG. 8 shows a schematic diagram illustrating a waveform of an example negative pulse signal generated at the OUT terminal in the example monitoring circuit of FIG. 4 when a negative power supply NVBIAS is powered on, consistent with some embodiments of this disclosure. The voltage drop caused by the negative pulse can reach -440mV, which is beyond the range for the maximum input voltage of the backend circuit or chip.

With reference back to FIG. 7, the state switching unit or the state switch 25 is in the monitoring circuit. When the negative power supply NVBIAS is powered on, the voltage signal output by the integrating unit or the integrator 22 can be compensated using the state switching unit or the state switch 25. The waveform of the compensated negative pulse signal is shown in FIG. 9. FIG. 9 shows a schematic diagram illustrating a waveform of an example negative pulse signal generated at the OUT terminal in the example monitoring circuit of FIG. 7 when a negative power supply NVBIAS is powered on, consistent with some embodiments of this disclosure. In some embodiments, by compensating for the voltage at the OUT terminal, the voltage drop at the OUT terminal can be reduced to below -40mV. By doing so, operation of the circuit components or chips connected to the backend can be safe.

In some embodiments, the state switching unit or the state switch 25 can include a tri-state buffer.

In some embodiments, before the monitoring circuit monitoring the light emitting unit or the light emitter, the tri-state buffer can output a low level to discharge the integrating unit or the integrator 22. When the monitoring circuit is monitoring the light emitting unit or the light emitter, the output of the tri-state buffer can be in a high impedance state. The integrating unit or the integrator 22 can integrate the received electrical signal. When the detection unit is activated, the tri-state buffer can output a high level to compensate for the voltage signal output by the integrating unit or the integrator 22.

As shown in FIG. 10, the tri-state buffer includes two inputs, an enable input terminal represented by “EN” and a signal input terminal represented by “IN. ” The tri-state buffer has an output terminal connected to the output terminal of the integrating unit or the integrator represented by “OUT” in FIG. 10. When the enable terminal EN is active, the level at the output terminal of the tri-state buffer can be the level at the signal input terminal IN. When the enable terminal EN is inactive, the output terminal of the tri-state buffer can be in a high impedance state.

Using the tri-state buffer, before the monitoring circuit monitoring the light emitting unit or the light emitter, an enable signal can be input to the enable input terminal EN of the tri-state buffer, and a low level can be input to the signal input terminal IN. The tri-state buffer can output a low level, and the integrating unit or the integrator 22 can discharge. When the monitoring circuit is monitoring the light emitting unit or the light emitter, a disable signal can be input to the enable input terminal EN of the tri-state buffer, and the output of the tri-state buffer can be in a high impedance state. The integrating unit or the integrator 22 can integrate the received electrical signal. When the detection unit is activated, the enable signal can be input to the enable input terminal EN of the tri-state buffer, and a high level can be input to the signal input terminal IN. The tri-state buffer can output a high level to compensate for the voltage signal output by the integrating unit or the integrator 22.

Consistent with embodiments of this disclosure, the monitoring circuit may clear the output of the integrating unit or the integrator to zero by the state switching unit or the state switch before the monitoring circuit is monitoring the light emitting unit or the light emitter. By doing so, the monitoring accuracy can be improved. Moreover, through the compensation for the voltage signal output by the integrating unit or the integrator, adverse effects on the backend circuit or chip can be effectively reduced.

In some situations where a plurality of detectors (e.g., connected in parallel) operate simultaneously, when the light emitting unit or the light emitter does not emit light and the detectors do not receive stray light signals from the light emitting unit or the light emitter, continuous current can still be generated under the influence of ambient light. The ambient light caused current generated by the plurality of detectors can be around a hundred mA, which can cause significant power consumption.

FIG. 11 shows a schematic diagram illustrating a fifth application structure of the example monitoring circuit of FIG. 2, consistent with some embodiments of this disclosure. As shown in FIG. 11, the monitoring circuit can further include a power switch 26 for activating the detection unit when the monitoring circuit is monitoring the light emitting unit or the light emitter and deactivate the detection unit after the monitoring is completed. For example, the power switch 26 can control the loading of the high-voltage power supply VDD. When it is being monitored whether the light emitting unit or the light emitter emits light properly, the power switch can be turned on to load the high-voltage power supply VDD onto the detection unit. The bias voltage of the detection unit can exceed the breakdown voltage, and the detection unit can operate in a normal operating state. After the monitoring is completed, the high-voltage power supply VDD can be disconnected. The bias voltage of the detection unit can be lower than the breakdown voltage. By doing so, the static power consumption can be reduced when no monitoring is being performed.

In FIG. 12, the power switch includes a first switch unit 61 and a second switch unit 62. The first switch unit 61 is connected between a working power supply VDD0 and the ground, and the second switch unit 62 is connected between the working power supply VDD0 and the enable terminal of the detection unit.

The first switch unit 61 can control, in response to an external control signal, the second switch unit 62 to connect the working power supply VDD0 with the enable terminal of the detection unit when the monitoring circuit is monitoring the light emitting unit or the light emitter. The working power supply VDD0 can apply the voltage VDD on the detection unit and control the second switch unit 62 to disconnect the working power supply VDD0 from the enable terminal of the detection unit after the monitoring is completed.

As shown in FIG. 13, the first switch unit is an NMOS transistor N1, and the second switch unit is a PMOS transistor P1.

Referring to FIG. 13, a drain of the NMOS transistor N1 is connected to the working power supply VDD0 through a resistor R3, and a source of the NMOS transistor N1 is grounded through a resistor R4. A source of the PMOS transistor P1 is connected to the working power supply VDD0, and a drain of the PMOS transistor P1 is connected to the enable terminal of the detection unit (e.g., similar to the high voltage power supply VDD terminal in the embodiments described in association with any of FIGS. 1-11) . A gate of the NMOS transistor N1 can input an external control signal, and a gate of the PMOS transistor P1 is connected to the drain of the NMOS transistor N1 through a resistor R8. Other resistors (e.g., R5, R6, R7, or R8) and the capacitor C3 can limit current and filtering, and the details thereof are not described herein.

When the monitoring circuit is not monitoring the light emitting unit or the light emitter, an external control signal can control the NMOS transistor N1 and the PMOS transistor P1 to disconnect. VDD is not applied on the detection unit. When the monitoring circuit is monitoring the light emitting unit or the light emitter, the external control signal can cause the gate voltage of the NMOS transistor N1 to increase. The gate-source voltage difference of NMOS transistor N1 can exceed the conduction voltage, and the NMOS transistor N1 conducts. Such a process generates a voltage drop across the resistor R3. The source-gate voltage difference of the PMOS transistor P1 can exceed its conduction voltage, and the PMOS transistor P1 conducts. In such a case, the voltage of the working power supply VDD0 can be applied on the enable terminal of the detection unit. For example, the high voltage power supply VDD mentioned above can be loaded.

Consistent with embodiments of this disclosure, the monitoring circuit can control the activation and deactivation of the detection unit by the power switch based on whether monitoring is to be performed. By doing so, the energy consumption of the detection unit can be reduced. Furthermore, by using a power switch including NMOS and PMOS transistors, the VDD power supply of the detection unit can be quickly turned on or off with a response time less than 1μs.

FIG. 14 shows a schematic diagram illustrating a structure of an example LiDAR, consistent with some embodiments of this disclosure. As shown in FIG. 14, in addition to the light emitting unit or the light emitter 30 and the monitoring circuit 20 shown and described in association with FIG. 1, the LiDAR further includes a control unit or a controller 40.

When the monitoring circuit is monitoring the light emitting unit or the light emitter 30, the control unit or the controller 40 can send a monitoring light-emitting instruction to the light emitting unit or the light emitter 30 and send a monitoring instruction to the monitoring circuit 20. For example, upon receiving the monitoring instruction, the monitoring circuit 20 can determine the operating state (e.g., whether the light emitter 30 is in a normal operation state or in a fault state) of the light emitting unit or the light emitter 30.

In some embodiments, the control unit or the controller 40 can control lasers activated by the light emitting unit or the light emitter 30 of the LiDAR during different time periods and synchronously adjust the objects monitored by the monitoring circuit. For example, during the time period t0～t1, the control unit or the controller 40 can send a monitoring light-emitting instruction to the light emitting unit or the light emitter 30 to cause a first laser to emit light while the other lasers do not emit light. At the same time, the control unit or the controller 40 can send to the monitoring circuit 20 a monitoring instruction for the first laser, and the monitoring circuit can output an integration value for monitoring the operating state of the first laser.

In some embodiments, the monitoring circuit 20 can perform real-time monitoring on the light emitting unit or the light emitter 30 during the operation of the LiDAR. The monitoring circuit 20 can also perform monitoring on the light emitting unit or the light emitter 30 between two detection cycles of the LiDAR. By way of example, when the LiDAR is not performing obstacle detection, the control unit or the controller 40 can control the monitoring circuit 20 to monitor the light emitting unit or the light emitter 30.

In some embodiments, when the LiDAR is not performing obstacle detection, the control unit or the controller 40 can control the monitoring circuit 20 to monitor the light emitting unit or the light emitter 30. For example, during the detection cycle of obstacle detection of the LiDAR, the monitoring circuit 20 does not operate. After the LiDAR completes the detection of a frame of point cloud in one detection cycle, there is a certain time interval before the next detection cycle. During the interval between the two detection cycles, the monitoring circuit 20 can monitor the operating state of the light emission unit 30.

In some embodiments, the light emitting unit or the light emitter 30 can include a laser array. Within an interval between the detection cycles of the LiDAR, the control unit or the controller 40 can send a monitoring light-emitting instruction to the light emitting unit or the light emitter 30. Each laser in the light emitting unit or the light emitter 30 can emit laser beams for monitoring in sequence. The control unit 40 can also send a monitoring instruction to the monitoring circuit 20 to sequentially monitoring the operating state of each laser. Therefore, the monitoring circuit 20 can obtain the operating state of each laser in the light emitting unit or the light emitter 30, improving the monitoring accuracy. Furthermore, without changing the structure of the monitoring circuit, the universality and flexibility of the monitoring circuit for various LiDARs can be improved.

It should be understood that each unit in the embodiments described in this disclosure can include one or more physical components in whole or in part. For example, a unit can be implemented as an emitter, a detector, an optic, a processor, a circuit, or any form of hardware component. As another example, a unit can include one or more hardware components and one or more software components. For example, the light emitting unit or the light emitter can include a light emitting circuit, vertical-cavity surface-emitting lasers (VCSELs) , edge-emitting lasers (EELs) , distributed feedback lasers (DFBs) , fiber lasers or the like. For example, the coupling unit or coupler can include a coupling circuit, a capacitor or the like. For example, the control unit or the controller can include a control circuit, a processor, or the like. For example, the integrating unit or the integrator can include an integrating circuit, a RC integrating circuit or the like. For example, the switching unit or the switch can include a switching circuit, one or more switches, or the like.

It should be understood that the term "and/or" in this disclosure is merely a description of the relationship between associated objects, which indicates three relationships, for example, A and/or B indicates: only A, only B, and both A and B. In addition, the sign "/" in this disclosure indicates an "or" relationship between the preceding and following associated objects.

The term "a plurality of" in this embodiment refers to two or more.

The first, second, and other descriptions in this embodiment are only used for illustration and distinction of the described objects, which do not indicate sequence, or indicate any special restrictions on the number of devices in this embodiment. They do not constitute any limitations on this embodiment.

The term "connection" in this embodiment refers to various connection methods such as direct connection or indirect connection to implement communication between devices. This embodiment does not impose any limitations on this.

Although this disclosure has been disclosed as above, this disclosure is not limited thereto. Any person skilled in the art can make various modifications and changes within the spirit and scope of this disclosure, and therefore, the scope of protection of this disclosure should be defined by the claims.

Claims

A LiDAR, comprising:

a light emitting unit comprising a plurality of lasers; and

a monitoring circuit comprising a detection unit, wherein the detection unit comprises a plurality of detectors connected in parallel, and the monitoring circuit is configured to monitor an operating state of the plurality of lasers based on stray light inside the LiDAR.
The LiDAR of claim 1, wherein the monitoring circuit further comprises an integrating unit and a coupling unit, the coupling unit being coupled to the detection unit and the integrating unit,

the detection unit is configured to collect an optical signal emitted by the light emitting unit and convert the optical signal into an electrical signal for outputting;

the coupling unit is configured to transmit the electrical signal to the integrating unit; and

the integrating unit is configured to convert the electrical signal transmitted by the coupling unit into a voltage signal for determining the operating state of the light emitting unit.
The LiDAR of claim 2, wherein the coupling unit is a capacitor.
The LiDAR of claim 2, wherein the integrating unit is an RC integrating circuit.
The LiDAR of any of claims 2 to 4, wherein the monitoring circuit further comprises an output voltage clamping unit connected in parallel with the integrating unit and configured to control the voltage signal output by the integrating unit not to exceed a predetermined amplitude.
The LiDAR of claim 5, wherein the output voltage clamping unit comprises any of a Schottky diode, a stabilivolt, a transient voltage suppressor, or an operational amplifier.
The LiDAR of claim 5 or 6, wherein the output voltage clamping unit comprises a plurality of Schottky diodes connected in series.
The LiDAR of any of claims 2 to 6, wherein the monitoring circuit further comprises a state switching unit coupled with the integrating unit and configured to switch between different operating states.
The LiDAR of claim 8, wherein the state switching unit is configured to discharge the integrating unit before the light emitting unit is being monitored, and control the integrating unit to integrate the electrical signal when the light emitting unit is being monitored.
The LiDAR of claim 9, wherein the state switching unit is further configured to compensate for the voltage signal output by the integrating unit when activating the detection unit.
The LiDAR of claim 8 or 9, wherein the state switching unit comprises a three-state buffer, and an output terminal of the three-state buffer is connected to an output terminal of the integrating unit.
The LiDAR of claim 11, wherein the three-state buffer is configured to output a low level to discharge the integrating unit before the light emitting unit is being monitored;

when the light emitting unit is being monitored, an output of the three-state buffer is in a high-impedance state, the three-state buffer is configured to cause the integrating unit to integrate the received electrical signal; and

when the detection unit is activated, the three-state buffer outputs a high level to compensate for the voltage signal output by the integrating unit.
The LiDAR of any of claims 1 to 12, wherein the monitoring circuit further comprises a power switch, the power switch is configured to activate the detection unit when the light emitting unit is being monitored and deactivate the detection unit after the light emitting unit is being monitored.
The LiDAR of claim 13, wherein the power switch comprises a first switching unit and a second switching unit, the first switching unit is connected between a working power supply and a ground, and the second switching unit is connected between the working power supply and an enable terminal of the detection unit; and

wherein the first switching unit is configured to control, based on an external control signal, the second switching unit to connect the working power supply with the enable terminal of the detection unit when monitoring the light emitting unit, and to control the second switch unit to disconnect the working power supply from the enable terminal of the detection unit after the light emitting unit is being monitored.
The LiDAR of claim 14, wherein the first switching unit comprises an NMOS transistor, and the second switching unit comprises a PMOS transistor.
The LiDAR of any of claims 1 to 15, wherein the detection unit comprises a plurality of silicon photomultipliers connected in parallel and disposed on a same chip.
The LiDAR of any of claims 1 to 16, wherein the detection unit and the light emitting unit are disposed on a same circuit board.
The LiDAR of any of claims 1 to 17, further comprising:

a control unit;

the control unit configured to send a light emitting instruction to the light emitting unit and send a monitoring instruction to the monitoring circuit, wherein the monitoring circuit is further configured to determine the operating state of the light emitting unit after receiving the monitoring instruction.
The LiDAR of claim 18, wherein the control unit control the monitoring circuit to monitor the light emitting unit when the LiDAR is not performing obstacle detection.
The LiDAR of any one of claims 1 to 19, wherein the monitoring circuit is configured to monitor an operating state of each of the plurality of lasers.