Laser radar detection method, computer storage medium, and laser radar

Abstract

The application provides a detection method of a laser radar, comprising the following steps: S11, controlling a laser to emit a detection beam at a first time; S12, applying a first working voltage to a detector from the first time to a second time, wherein the absolute value of the first working voltage is less than or equal to the breakdown voltage of the detector; S13, applying a second working voltage to the detector after the second time, wherein the absolute value of the second working voltage is greater than the breakdown voltage of the detector; S14, acquiring an electrical crosstalk signal of the detector; and S15, acquiring a return signal of the detection beam reflected by an object according to a detection signal received by the detector after the second time and the electrical crosstalk signal. The application measures the electrical crosstalk signal without introducing external light signals, and then obtains a real return signal according to the acquired detection signal and the electrical crosstalk signal, thereby not reducing the signal-to-noise ratio and reducing the near distance blind area of the laser radar.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection, and more particularly to detection methods for lidar, computer storage media, and lidar. Background Technology

[0002] As a commonly used ranging sensor, lidar has advantages such as long detection range, high resolution, strong resistance to active interference, small size, and light weight, and is widely used in fields such as intelligent robots, drones, and autonomous driving.

[0003] The optical path of a lidar can be divided into coaxial optical path and off-axis optical path. In a lidar with a coaxial optical path, the transmitting and receiving optical paths overlap to some extent. This overlap causes some of the emitted laser light to not exit the lidar for object detection but to directly enter the lidar's receiving optical path and be received by the detector. This causes the detector to saturate for a period of time. During the saturation period, the detector cannot respond to the laser light reflected back from the object, resulting in a near-range blind zone for the lidar. It is generally desirable to minimize the near-range blind zone.

[0004] The content of the background section only discloses the technology known to the inventors and does not necessarily represent the prior art in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention relates to a detection method for a lidar, wherein the lidar includes at least one laser and at least one detector, and for one of the lasers and its corresponding detector, the detection method includes:

[0006] S11: Controls the laser to emit a probe beam at the first moment;

[0007] S12: From the first moment to the second moment, a first operating voltage is applied to the detector, wherein the absolute value of the first operating voltage is less than or equal to the breakdown voltage of the detector;

[0008] S13: After the second moment, a second operating voltage is applied to the detector, wherein the absolute value of the second operating voltage is greater than the breakdown voltage of the detector;

[0009] S14: Acquire the electrical crosstalk signal of the detector;

[0010] S15: Based on the detection signal received by the detector after the second moment and the electrical crosstalk signal, obtain the echo signal reflected by the object from the detection beam.

[0011] According to one aspect of the invention, the detection method further includes the step of measuring electrical crosstalk signals, which includes:

[0012] S01: Apply a third operating voltage to the detector, wherein the absolute value of the third operating voltage is less than or equal to the absolute value of the first operating voltage;

[0013] S02: Apply the first operating voltage to the detector and acquire the output signal of the detector during the voltage switching process;

[0014] S03: Store the output signal as the electrical crosstalk signal.

[0015] According to one aspect of the invention, the step of measuring the electrical crosstalk signal further includes:

[0016] Steps S01 to S03 are repeated at preset time intervals, and the electrical crosstalk signal measured in the previous measurement is iterated.

[0017] According to one aspect of the invention, the step of measuring the electrical crosstalk signal further includes:

[0018] Detect the current ambient temperature;

[0019] The breakdown voltage, first operating voltage, second operating voltage, and third operating voltage are determined and adjusted based on the current ambient temperature.

[0020] Repeat steps S01 to S03, and iterate over the electrical crosstalk signal measured in the previous step.

[0021] According to one aspect of the invention, the lidar has at least partially overlapping transmit and receive optical paths, wherein the step of measuring electrical crosstalk signals is performed when the detector does not need to receive the detection signal.

[0022] According to one aspect of the invention, the detection method further includes storing electrical crosstalk signals at different temperatures, comprising:

[0023] S001: Determine the breakdown voltage of the detector at a certain temperature, and further determine the first operating voltage and the third operating voltage, wherein the absolute value of the third operating voltage is less than or equal to the absolute value of the first operating voltage;

[0024] S002: At this temperature, apply a third operating voltage to the detector and switch to the first operating voltage, acquire and store the output signal of the detector during the voltage switching process;

[0025] S003: Store the output signal as the electrical crosstalk signal of the detector at this temperature;

[0026] S004: Repeat steps S001 to S003 by changing the temperature, and store the electrical crosstalk signals corresponding to multiple temperatures.

[0027] Step S14 further includes: obtaining an electrical crosstalk signal corresponding to the current ambient temperature from the stored electrical crosstalk signals based on the current ambient temperature.

[0028] According to one aspect of the invention, the absolute value of the difference between the third operating voltage and the first operating voltage is equal to the absolute value of the difference between the first operating voltage and the second operating voltage.

[0029] According to one aspect of the invention, the absolute value of the first operating voltage is equal to the breakdown voltage of the detector.

[0030] According to one aspect of the invention, step S15 includes: subtracting the electrical crosstalk signal from the detection signal received by the detector to obtain the echo signal.

[0031] According to one aspect of the invention, the detector is a detector operating in Geiger mode.

[0032] The present invention also relates to a computer storage medium including computer executable instructions stored thereon, wherein the executable instructions, when executed by a processor, implement the detection method described above.

[0033] The present invention also relates to a lidar, comprising:

[0034] At least one laser configured to emit a probe beam;

[0035] At least one detector configured to receive optical signals; and

[0036] A control device, connected to the at least one laser and the at least one detector, wherein for one of the lasers and its corresponding detector, the control device is configured as follows:

[0037] Control the laser to emit a probe beam at the first moment;

[0038] From the first moment to the second moment, a first operating voltage is applied to the detector, wherein the absolute value of the first operating voltage is less than or equal to the breakdown voltage of the detector;

[0039] After the second moment, a second operating voltage is applied to the detector, wherein the absolute value of the second operating voltage is greater than the breakdown voltage of the detector;

[0040] Acquire the electrical crosstalk signal of the detector; and

[0041] Based on the detection signal received by the corresponding detector after the second moment and the electrical crosstalk signal, the echo signal reflected by the object from the detection beam is obtained.

[0042] According to one aspect of the invention, the control device is further configured to perform the following operation: measuring electrical crosstalk signals.

[0043] S01: Apply a third operating voltage to the detector, wherein the absolute value of the third operating voltage is less than or equal to the absolute value of the first operating voltage;

[0044] S02: Apply the first operating voltage to the detector and acquire the output signal of the detector during the voltage switching process;

[0045] S03: Store the output signal as the electrical crosstalk signal.

[0046] According to one aspect of the invention, the control device is further configured to: repeatedly execute steps S01 to S03 at preset time intervals, and iterate over the previously measured electrical crosstalk signal.

[0047] According to one aspect of the invention, the control device is further configured to:

[0048] Detect the current ambient temperature;

[0049] The breakdown voltage, first operating voltage, second operating voltage, and third operating voltage are determined and adjusted based on the current ambient temperature.

[0050] Repeat steps S01 to S03, and iterate over the electrical crosstalk signal measured in the previous step.

[0051] According to one aspect of the invention, the lidar has at least partially overlapping transmit and receive optical paths, and the control device is configured to perform the operation of measuring electrical crosstalk signals when the detector does not need to receive the detection signal.

[0052] According to one aspect of the invention, the lidar further includes a storage device configured to store electrical crosstalk signals corresponding to multiple temperatures; the control device is further configured to: acquire an electrical crosstalk signal corresponding to the current ambient temperature from the stored electrical crosstalk signals based on the current ambient temperature.

[0053] According to one aspect of the invention, the absolute value of the difference between the third operating voltage and the first operating voltage is equal to the absolute value of the difference between the first operating voltage and the second operating voltage.

[0054] According to one aspect of the invention, the absolute value of the first operating voltage is equal to the breakdown voltage of the detector.

[0055] According to one aspect of the invention, the control device is further configured to: subtract the electrical crosstalk signal from the detection signal received from the detector to obtain the echo signal.

[0056] According to one aspect of the invention, the detector is a detector operating in Geiger mode.

[0057] This invention controls the detector's bias voltage to be lower than its operating voltage for a short period during laser emission, and then adjusts the bias voltage back to the operating voltage for object detection. This prevents the detector from responding to laser light that has not yet been emitted and directly enters the detector, avoiding detector saturation and prolonged inability to measure distance. This reduces the time the detector is unable to measure distance, thereby lowering the near-range blind zone of the lidar. Simultaneously, it measures the electrical crosstalk signal caused by bias voltage changes without responding to ambient light, and then obtains the echo signal based on the detection signal and the electrical crosstalk signal, ensuring the accuracy of the echo signal without reducing the signal-to-noise ratio. The detection method and lidar of this invention reduce the near-range blind zone and ensure the accuracy of the measured echo signal. Attached Figure Description

[0058] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure. In the drawings:

[0059] Figure 1 A schematic diagram of a lidar system employing a coaxial transceiver system is shown.

[0060] Figure 2 A flowchart of a lidar detection method according to an embodiment of the present invention is shown;

[0061] Figure 3 A block diagram of a lidar according to an embodiment of the present invention is shown;

[0062] Figure 4 A schematic diagram showing a comparison of transmitting and receiving data according to an embodiment of the present invention is provided.

[0063] Figure 5 A schematic diagram of the detection circuit in an optical receiving device according to an embodiment of the present invention is shown;

[0064] Figure 6a It shows Figure 5 A schematic diagram of the waveform of the electrical crosstalk signal;

[0065] Figure 6b It shows Figure 5 A schematic diagram of the waveform of the electrical crosstalk signal superimposed on the echo signal;

[0066] Figure 6c It shows Figure 5 A schematic diagram of the waveform after removing electrical crosstalk;

[0067] Figure 7 A flowchart illustrating the measurement of electrical crosstalk signals according to an embodiment of the present invention is shown;

[0068] Figure 8 A flowchart illustrating the measurement of electrical crosstalk signals at different ambient temperatures according to an embodiment of the present invention is shown.

[0069] Figure 9a A schematic diagram of a detection method according to an embodiment of the present invention is shown;

[0070] Figure 9b An application of one embodiment of the present invention is shown. Figure 9a A schematic diagram of the detection circuit for the detection method;

[0071] Figure 9c A schematic diagram of a detection circuit according to another embodiment of the present invention is shown. Detailed Implementation

[0072] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0073] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0074] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0075] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0076] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0077] Figure 1A schematic diagram of a lidar system employing a coaxial transceiver system is shown. The lidar includes a light emitting device and a light receiving device. The detection beam L emitted by the light emitting device passes through a collimating component and a beam splitting component, and is finally reflected to the outside of the lidar by a scanning component. The echo L' reflected by the object passes through the scanning component, the beam splitting component, and the converging component before being received by the light receiving device. By emitting a detection beam and receiving the echo beam reflected by the object, the lidar can detect the distance and reflectivity of objects in the environment. The beam splitting component, for example, is a semi-transparent mirror or a pinhole mirror, used to overlap part of the receiving optical path to reduce the size of the lidar. However, this overlap of the receiving and receiving optical paths leads to the following problems: a portion of the laser energy of the detection beam L is emitted outside the lidar for ranging; another portion directly enters the detector in the light receiving device (the detector is a single-photon avalanche photodiode, such as a SPAD or SiPM). The laser directly entering the detector will saturate the detector, and once saturated, the detector cannot respond to the reflected laser. The detector gradually recovers its response to the laser after a short period of time (i.e., the dead time of SPAD or SiPM). Taking 20 ns as an example, based on the time-of-flight method, the response time is calculated as 20 ns × 3 × 10. 8 Objects within a range of m / s ÷ 2 = 3m cannot be detected. This undetectable distance is the radar's near-range blind zone. Ideally, the near-range blind zone should be as small as possible, for example, controlled within 1m.

[0078] This invention provides a detection method for lidar, comprising: S11: controlling a laser to emit a detection beam at a first moment; S12: applying a first operating voltage to a detector from the first moment to a second moment, wherein the absolute value of the first operating voltage is less than or equal to the breakdown voltage of the detector; S13: applying a second operating voltage to the detector after the second moment, wherein the absolute value of the second operating voltage is greater than the breakdown voltage of the detector; S14: acquiring the electrical crosstalk signal of the detector; S15: acquiring the echo signal reflected by the detection beam from an object based on the detection signal received by the detector after the second moment and the electrical crosstalk signal. This invention measures the electrical crosstalk signal caused by voltage changes, and then obtains the true echo signal based on the acquired detection signal and the electrical crosstalk signal, thereby reducing the near-range blind zone of the lidar without reducing the signal-to-noise ratio.

[0079] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0080] Figure 2 A flowchart of a lidar detection method according to an embodiment of the present invention is shown. Figure 3A block diagram of a lidar according to an embodiment of the present invention is shown. The lidar 20 includes a light emitting device 21 and a light receiving device 22, wherein the light emitting device 21 includes at least one laser 211, and the light receiving device 22 includes at least one detector 221. For one of the lasers 211 and its corresponding detector 221, the detection method includes steps S11-S15, as follows:

[0081] In step S11: control the laser 211 to emit a probe beam at the first moment.

[0082] Figure 4 A schematic diagram comparing the transmit and receive signals according to an embodiment of the present invention is shown. Laser 211 emits a probe beam at a first moment T1. The probe beam may include a single pulse or multiple pulses, and the present invention is not limited thereto. Figure 4 The diagram only illustrates the single-pulse case.

[0083] In step S12: from the first moment to the second moment, a first operating voltage is applied to the detector 221, wherein the absolute value of the first operating voltage is less than or equal to the breakdown voltage of the detector 211.

[0084] Continue to refer to Figure 4 When a positive voltage is applied to detector 221 (the cathode of detector 221 is closer to the applied voltage terminal, and the anode of detector 221 is closer to the ground terminal), a first operating voltage V1 is applied to detector 221 from the first time T1 to the second time T2, where the first operating voltage V1 is less than or equal to the breakdown voltage VBR. When a negative voltage is applied to detector 221 (the anode of detector 221 is closer to the applied voltage terminal, and the cathode of detector 221 is closer to the ground terminal), the first operating voltage (-V1) is less than or equal to the breakdown voltage VBR, that is, the absolute value of the first operating voltage is less than or equal to the breakdown voltage VBR of detector 211. For avalanche photodiodes (such as SPAD, SiPM, etc.), according to their working principle, when the bias voltage across their terminals is less than or equal to their breakdown voltage VBR, the avalanche photodiode cannot respond to photons to generate an electrical signal, that is, it cannot work.

[0085] Taking the application of positive voltage to detector 221 as an example, when laser 211 just emits light, detector 221 operates at a first operating voltage V1 that is less than or equal to the breakdown voltage VBR. Therefore, from the first moment T1 to the second moment T2, detector 221 will not respond to laser energy. That is, even if a portion of the laser energy of the detection beam enters detector 221, it will not cause detector 221 to saturate.

[0086] In step S13: After the second time T2, a second operating voltage V2 is applied to the detector 221, wherein the absolute value of the second operating voltage V2 is greater than the breakdown voltage of the detector 221.

[0087] Continue to refer to Figure 4 When a positive voltage is applied to detector 221 (with the cathode of detector 221 closer to the applied voltage terminal and the anode of detector 221 closer to the ground terminal), after the second time T2, a second operating voltage V2 is applied to detector 221, where the second operating voltage V2 is greater than the breakdown voltage VBR. At this time, detector 221 enters normal operating state (i.e., ranging mode) and begins to respond to the laser reflected back from the object. When a negative voltage is applied to detector 221 (with the anode of detector 221 closer to the applied voltage terminal and the cathode of detector 221 closer to the ground terminal), the absolute value of the second operating voltage V2 is greater than the breakdown voltage VBR of detector 221.

[0088] In step S14: Obtain the electrical crosstalk signal of detector 221.

[0089] Taking the application of a positive voltage to detector 221 as an example, detector 221 operates at a second operating voltage V2 higher than the breakdown voltage VBR. Therefore, after the second time T2, detector 221 enters ranging mode, begins to respond to the laser reflected from the object, and outputs an electrical signal, which is the echo signal. Ideally, detector 221 only outputs the echo signal. In reality, due to the presence of parasitic capacitance in the circuit, when the voltage rises from V1 to V2, electrical crosstalk signals are generated. The detection signal received by the detector includes both the echo signal and the electrical crosstalk signal.

[0090] Figure 5 A schematic diagram of a detection circuit in an optical receiving device according to an embodiment of the present invention is shown. The detection circuit includes a detector 221 composed of SiPM. After a bias voltage is applied to the detector 221, the detector 221 responds to laser energy and outputs a detection signal, which is then amplified by an amplifier and output to subsequent circuits. Due to the presence of parasitic capacitance in the detection circuit, during the process of the bias voltage of the detector 221 increasing from the first operating voltage V1 to the second operating voltage V2, the detection signal output by the detector 221 includes electrical crosstalk signals, such as... Figure 6a As shown, electrical crosstalk is a signal with a high instantaneous peak value; the echo signal from a nearby object overlaps with the electrical crosstalk signal to form a superimposed signal, such as... Figure 6b As shown, the echo signal may be very small compared to the electrical crosstalk signal. The signal formed by the superposition of the two can easily cause problems such as misjudgment and inaccurate reflectivity calculation. Therefore, it is necessary to remove the influence of the electrical crosstalk signal. How to obtain the electrical crosstalk signal of detector 221 will be described in detail below.

[0091] In step S15: Based on the detection signal and electrical crosstalk signal received by detector 221 after the second time T2, the echo signal reflected by the object from the detection beam is obtained.

[0092] Taking applying positive pressure to detector 221 as an example, combined with Figure 4 and Figure 6b After the bias voltage of detector 221 is increased from the first operating voltage V1 to the second operating voltage V2, detector 221 enters the ranging mode, and the acquired detection signal is a superimposed signal formed by the echo signal and the electrical crosstalk signal; based on the electrical crosstalk signal obtained in step S14, the electrical crosstalk signal in the superimposed signal is removed, such as... Figure 6c As shown.

[0093] According to a preferred embodiment of the present invention, step S15 includes: subtracting the electrical crosstalk signal from the detection signal received by the detector 221 to obtain the echo signal.

[0094] Based on the above analysis, during ranging, the detection signal output by detector 221 includes echo signal and electrical crosstalk signal. From the first time T1 to the second time T2, detector 221 does not respond to a portion of the detection beam's energy, leading to saturation. By appropriately setting T1 and T2, the near-range blind zone can be greatly reduced. For example, setting T2-T1 = 5ns can reduce the blind zone range of the lidar to 0.75m (5ns * x3 x 10). 8 m / s ÷ 2 = 0.75m.

[0095] In summary, the detection method has been introduced through steps S11-S15. This invention obtains the real echo signal by acquiring the detection signal and electrical crosstalk signal, thereby reducing the near-range blind zone of the lidar.

[0096] The following describes in detail how to obtain the electrical crosstalk signal of detector 221 in step S14 through an embodiment.

[0097] According to a preferred embodiment of the present invention, the detection method further includes the step of measuring electrical crosstalk signal, referring to... Figure 7 It includes:

[0098] Step S01: Apply a third operating voltage to detector 221, wherein the absolute value of the third operating voltage is less than or equal to the absolute value of the first operating voltage.

[0099] Continue to refer to Figure 4When a positive voltage is applied to detector 221, a third operating voltage V3 is applied, which is less than the first operating voltage V1. When a negative voltage is applied to detector 221, the absolute value of the third operating voltage V3 is less than the absolute value of the first operating voltage V1. Since the absolute value of the first operating voltage V1 is less than or equal to the breakdown voltage VBR, the absolute value of the third operating voltage V3 is also less than the breakdown voltage VBR. Therefore, when detector 221 operates at the third operating voltage V3, it will not respond to external light signals. Consequently, the electrical crosstalk signal measured in subsequent steps will not introduce additional ambient light noise, thus ensuring that the signal-to-noise ratio of the obtained echo signal is not reduced. This is because of the presence of ambient light noise. Therefore, the detection signal received by the lidar during normal ranging will inevitably introduce ambient light noise. If the electrical crosstalk signal is measured at a bias voltage higher than the breakdown voltage VBR, ambient light noise will also be introduced. Since ambient light noise is irregular, the process of subtracting the electrical crosstalk signal from the detection signal may cause an increase in ambient light noise, which will reduce the signal-to-noise ratio of the obtained echo signal, thus affecting the range-finding performance of the lidar. However, in the method for measuring ambient light noise in this embodiment, since the first operating voltage V1 and the third operating voltage V3 are both less than or equal to the breakdown voltage VBR, the detector does not respond to ambient light. Therefore, ambient light noise is not introduced during the measurement of electrical crosstalk, and the echo signal obtained by subtracting the electrical crosstalk signal from the echo signal does not reduce the signal-to-noise ratio.

[0100] Step S02: Apply a first operating voltage to detector 221 and acquire the output signal of detector 221 during the voltage switching process.

[0101] The magnitude of the electrical crosstalk signal output by detector 221 is affected by two factors: the range of change in the detector bias voltage and the magnitude of the bias voltage. When measuring distance and electrical crosstalk signals, the electrical crosstalk signals output by detector 221 are not exactly the same, but very close. When the two electrical crosstalk signals are very close, the electrical crosstalk signal generated when the third operating voltage V3 changes to the first operating voltage V1 can be used to replace the electrical crosstalk signal generated when the first operating voltage V1 changes to the second operating voltage V2. (Continue to refer to...) Figure 4In ranging mode, the bias voltage of detector 221 is increased from the first operating voltage V1 to the second operating voltage V2, with a voltage variation range of ΔV1 = V2 - V1 and a median bias voltage of Vm1 = V1 + ΔV1 / 2. When measuring electrical crosstalk signals, the bias voltage of detector 221 is increased from the third operating voltage V3 to the first operating voltage V1, with a voltage variation range of ΔV2 = V1 - V3 and a median bias voltage of Vm2 = V1 - ΔV2 / 2. By reasonably setting the first operating voltage V1 and the third operating voltage V3, the bias voltage variation ranges ΔV1 and ΔV2 are made as close as possible, and the median bias voltages Vm1 and Vm2 are also made as close as possible, resulting in similar electrical crosstalk signals. Preferably, by reasonably setting the first operating voltage V1 and the third operating voltage V3, the difference in electrical crosstalk signals is kept within 20%. According to a preferred embodiment of the present invention, the absolute value of the difference between the third operating voltage and the first operating voltage is equal to the absolute value of the difference between the first operating voltage and the second operating voltage.

[0102] The electrical crosstalk signal output by detector 221 is affected by the range of bias voltage variation. (Continue to refer to...) Figure 4 When measuring electrical crosstalk signals, the bias voltage of detector 221 is increased from the third operating voltage V3 to the first operating voltage V1, with a voltage variation range of ΔV2 = V1 - V3. In ranging mode, the bias voltage of detector 221 is increased from the first operating voltage V1 to the second operating voltage V2, with a voltage variation range of ΔV1 = V2 - V1. When ΔV2 = ΔV1, the electrical crosstalk signal generated in ranging mode is very close to the electrical crosstalk signal obtained when measuring electrical crosstalk signals. Therefore, when removing the electrical crosstalk signal from the detection signal, the accuracy of the obtained echo signal is very high, thus ensuring the accuracy of ranging.

[0103] In step S03: Store the output signal as an electrical crosstalk signal.

[0104] The electrical crosstalk signal is stored and invoked in step S14 of the detection method.

[0105] The above steps S01-S03 explain how to measure the electrical crosstalk signal. Detector 221 measures the electrical crosstalk signal without responding to the bias voltage of external light signals, thus not reducing the signal-to-noise ratio (SNR) of the echo signal. This is because ambient light noise is inevitably introduced during ranging, and this ambient light noise is irregular. If ambient light noise is also introduced when measuring the electrical crosstalk signal, the subtraction of the detected signal and the electrical crosstalk signal will increase the ambient light noise, reducing the SNR of the echo signal and affecting the radar's rangefinding performance. However, in this invention, the electrical crosstalk signal is measured by increasing the voltage from the third operating voltage to the first operating voltage. The absolute values ​​of both the third and first operating voltages are less than or equal to the breakdown voltage. That is, throughout the entire process of measuring the electrical crosstalk signal, detector 221 does not respond to external ambient light, meaning no ambient light noise is introduced during the measurement process. Therefore, the SNR of the detected signal does not decrease after subtracting the electrical crosstalk signal.

[0106] According to a preferred embodiment of the present invention, the step of measuring electrical crosstalk signal further includes: repeating steps S01 to S03 at preset time intervals, and iterating over the electrical crosstalk signal measured previously.

[0107] The method can perform the step of measuring the electrical crosstalk signal once at a preset time interval, store and iterate the electrical crosstalk signal measured in the previous step, and then obtain the measured and stored electrical crosstalk signal in step S14. Alternatively, the signal can be measured and stored in advance, and then the stored electrical crosstalk signal can be called in step S14 when the detection method is executed multiple times to reuse the electrical crosstalk signal and save computing power.

[0108] According to a preferred embodiment of the present invention, the step of measuring the electrical crosstalk signal further includes: detecting the current ambient temperature; determining and adjusting the breakdown voltage VBR, the first operating voltage V1, the second operating voltage V2 and the third operating voltage V3 based on the current ambient temperature; repeating steps S01 to S03 and iterating over the previously measured electrical crosstalk signal.

[0109] The breakdown voltage VBR of detector 21 is related to the ambient temperature. When the ambient temperature changes, the breakdown voltage VBR of detector 21 will also change. In order to obtain a more accurate electrical crosstalk signal, when measuring the electrical crosstalk signal, the breakdown voltage VBR is first adjusted according to the current ambient temperature, and then the first working voltage, the second working voltage and the third working voltage are determined based on the breakdown voltage VBR.

[0110] When the ambient temperature remains constant, the electrical crosstalk signal can be measured and stored only once, and then reused when the detection method is executed subsequently. When the ambient temperature changes, it is necessary to periodically determine the first working voltage, the second working voltage, and the third working voltage based on the adjusted breakdown voltage VBR, measure the electrical crosstalk signal, and iterate the previously measured electrical crosstalk signal.

[0111] According to a preferred embodiment of the present invention, the detection method further includes storing electrical crosstalk signals at different temperatures, for reference. Figure 8 It includes:

[0112] In step S001: Determine the breakdown voltage VBR of detector 221 at a certain temperature, and further determine the first operating voltage and the third operating voltage, wherein the absolute value of the third operating voltage is less than or equal to the absolute value of the first operating voltage;

[0113] In step S002: At this temperature, a third operating voltage V3 is applied to the detector 221 and switched to the first operating voltage V1, and the output signal of the detector 221 during the voltage switching process is acquired and stored;

[0114] In step S003: Store the output signal as the electrical crosstalk signal of detector 221 at this temperature;

[0115] In step S004: Change the temperature and repeat steps S001 to S003 to store the electrical crosstalk signals corresponding to multiple temperatures;

[0116] Step S14 in the detection method further includes: obtaining an electrical crosstalk signal corresponding to the current ambient temperature from the stored electrical crosstalk signals based on the current ambient temperature.

[0117] The preferred embodiment described above differs from the previous embodiment in that it acquires and stores electrical crosstalk signals at different temperatures, and determines the breakdown voltage VBR of the detector 221 based on the current ambient temperature each time the detection method is executed, so as to precisely control the detector 221 to enter the ranging mode. Furthermore, it calls up the corresponding electrical crosstalk signal based on the current ambient temperature and removes the electrical crosstalk signal from the detection signal, thereby reducing the near-range blind zone of the lidar 20 without reducing the signal-to-noise ratio of the echo signal.

[0118] According to a preferred embodiment of the present invention, the lidar 20 has at least partially overlapping transmit and receive optical paths, wherein the step of measuring electrical crosstalk signals is performed when the detector 221 does not need to receive detection signals.

[0119] For a coaxial optical path lidar, the transmitting and receiving optical paths at least partially overlap. The laser 211 emits a detection beam, with most of the energy exiting the lidar for detection, and a small portion directly entering the detector 221. To avoid interference from this energy and external optical signals, the inventors devised a method to measure electrical crosstalk signals when the detector 221 does not need to receive detection signals. Furthermore, the measurement of the electrical crosstalk signal is performed at a voltage less than or equal to the breakdown voltage VBR, ensuring that the acquired electrical crosstalk signal does not introduce additional interference signals or noise. The time when the detector 221 does not need to receive detection signals refers to the time when the lidar is not performing ranging operations. During this period, the laser does not emit a laser beam, and the detector does not need to prepare to receive detection signals. For example, in lidars using rotating mirrors, ranging is generally not performed at the junctions of multiple mirror surfaces, making it suitable for measuring electrical crosstalk signals. Similarly, in lidars using galvanometers, ranging is not performed when the galvanometer changes its reciprocating motion direction, making it suitable for measuring electrical crosstalk signals.

[0120] According to a preferred embodiment of the present invention, the absolute value of the first operating voltage is equal to the absolute value of the breakdown voltage VBR of the detector 221.

[0121] Figure 9a A schematic diagram of a detection method according to an embodiment of the present invention is shown. Figure 9b An application of one embodiment of the present invention is shown. Figure 9a The detection circuit diagram of the detection method includes a detector 221 composed of SiPM. A positive voltage is applied to the detector 221 (the cathode of the detector 221 is close to the voltage application terminal, and the anode of the detector 221 is close to the ground terminal). The breakdown voltage VBR is determined according to the current ambient temperature. For example, the first working voltage V1 = VBR, the second working voltage V2 = VBR + VOV, and the third working voltage = VBR - VOV. When measuring the electrical crosstalk signal, a bias voltage VBR-VOV is first applied to detector 221. Then, the bias voltage of detector 221 is increased from VBR-VOV to VBR, and the output signal of detector 221 during the voltage switching process is obtained. This output signal is the electrical crosstalk signal. Since the bias voltage of detector 221 is lower than VBR throughout the measurement process, it does not respond to laser energy, and the electrical crosstalk signal output by detector 221 will not introduce external light signals. During ranging, laser 211 emits light normally. A bias voltage VBR is first applied to detector 221 and maintained for a short period of time. During this period, laser 211 completes the emission of the detection beam. Then, the bias voltage of detector 221 is increased from VBR to VBR+VOV, and detector 221 receives the detection signal. The detection signal at this time includes the electrical crosstalk signal and the echo signal reflected by the object from the detection beam. The accurate echo signal can be obtained by subtracting the electrical crosstalk signal from the detection signal.

[0122] Figure 9c A schematic diagram of a detection circuit according to another embodiment of the present invention is shown. The detection circuit includes a detector 221 composed of SiPM, and... Figure 9b The difference in the embodiments is that a negative voltage is applied to the detector 221 (the anode of the detector 221 is close to the voltage application terminal, and the cathode of the detector is close to the ground terminal). In specific implementation, the breakdown voltage VBR is determined according to the current ambient temperature. For example, the first working voltage V1 = -VBR, the second working voltage V2 = -VBR-VOV, and the third working voltage = -VBR+VOV, where VBR and VOV are both positive numbers. When measuring the electrical crosstalk signal, a voltage of -VBR+VOV is first applied to the detector 221, and then the voltage is adjusted from -VBR+VOV to -VBR. The output signal of the detector 221 during the voltage switching process is obtained. This output signal is the electrical crosstalk signal. Since the bias voltage (absolute value of V1 and absolute value of V2) of the detector 221 is less than or equal to the breakdown voltage VBR throughout the measurement process, it does not respond to laser energy. Therefore, the electrical crosstalk signal output by the detector 221 will not introduce external light signals. When measuring distance, the laser 211 emits light normally. A voltage of -VBR is first applied to the detector 221 and maintained for a short period of time. During this period, the laser 211 completes the emission of the detection beam. Then the voltage is adjusted from -VBR to -VBR-VOV. The detector 221 receives the detection signal. The detection signal at this time includes the electrical crosstalk signal and the echo signal reflected by the object from the detection beam. The accurate echo signal can be obtained by subtracting the electrical crosstalk signal from the detection signal.

[0123] According to a preferred embodiment of the present invention, detector 221 is a detector operating in Geiger mode.

[0124] The detector 221 is selected from detectors operating in Geiger mode, such as SPAD, SiPM, etc. When a third working voltage or a first working voltage lower than the breakdown voltage VBR is applied to the detector 221, the responsivity of the detector 221 to laser energy is reduced to zero or almost no response, thereby ensuring the accuracy of the measured electrical crosstalk signal. Furthermore, by reasonably setting the time when the detector cannot measure distance, the near-range blind zone is reduced.

[0125] In summary, this invention reduces the time during which the detector 221 cannot measure distance by controlling the bias voltage of the detector 221 to a first operating voltage with an absolute value less than or equal to the breakdown voltage, and then increasing it from the first operating voltage to a second operating voltage with an absolute value greater than the breakdown voltage. This reduces the near-range blind zone problem of the lidar in the coaxial transceiver system. Furthermore, by controlling the bias voltage of the detector 221 to increase from a third operating voltage with an absolute value lower than the breakdown voltage to the first operating voltage, the electrical crosstalk signal generated during the voltage conversion process is measured. At this time, the detector 221 does not respond to external light signals, and the electrical crosstalk signal is subtracted from the received detection signal during distance measurement, thereby ensuring the accuracy of distance measurement without reducing the signal-to-noise ratio of the echo signal.

[0126] This specification provides the operational steps of the methods described in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operational steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only possible execution order. In actual system or device products, the methods shown in the embodiments or flowcharts can be executed sequentially or in parallel.

[0127] The present invention also relates to a computer storage medium including computer executable instructions stored thereon, wherein the executable instructions, when executed by a processor, implement the detection method described above.

[0128] The present invention also relates to a lidar, as shown in the reference. Figure 3 The lidar 20 includes:

[0129] At least one laser 211, such as laser 211-1, ..., laser 211-n, is configured to emit a probe beam;

[0130] At least one detector 221, such as detector 221-1, ..., detector 221-m, is configured to receive optical signals; and

[0131] Control device 23, connected to at least one laser 221 and at least one detector 221, wherein for one of the lasers 211 and its corresponding detector 221, the control device 23 is configured as follows:

[0132] Control laser 211 to emit a probe beam at the first moment T1;

[0133] From the first time T1 to the second time T2, a first operating voltage V1 is applied to the detector 221, wherein the absolute value of the first operating voltage V1 is less than or equal to the breakdown voltage VBR of the detector 221.

[0134] After the second time T2, a second operating voltage V2 is applied to the detector 221, wherein the absolute value of the second operating voltage V2 is greater than the breakdown voltage VBR of the detector 221;

[0135] Acquire the electrical crosstalk signal of the detector 221; and

[0136] Based on the detection signal received by the corresponding detector 221 after the second time T2 and the electrical crosstalk signal, the echo signal reflected by the object of the detection beam is obtained.

[0137] According to a preferred embodiment of the present invention, the control device 23 is further configured to perform the following operation: measuring electrical crosstalk signals:

[0138] In step S01: A third operating voltage V3 is applied to the detector 221, wherein the absolute value of the third operating voltage V3 is less than or equal to the absolute value of the first operating voltage V1;

[0139] In step S02: Apply the first operating voltage V1 to the detector 221 and acquire the output signal of the detector 221 during the voltage switching process;

[0140] In step S03: Store the output signal as the electrical crosstalk signal.

[0141] According to a preferred embodiment of the present invention, the control device 23 is further configured to: repeatedly execute steps S01 to S03 at preset time intervals, and iterate over the previously measured electrical crosstalk signal.

[0142] According to a preferred embodiment of the present invention, the control device 23 is further configured to:

[0143] Detect the current ambient temperature;

[0144] The breakdown voltage VBR, the first operating voltage V1, the second operating voltage V2, and the third operating voltage V3 are determined and adjusted based on the current ambient temperature.

[0145] Repeat steps S01 to S03, and iterate over the electrical crosstalk signal measured in the previous step.

[0146] According to a preferred embodiment of the present invention, wherein the lidar 20 has at least partially overlapping transmit and receive optical paths, and the control device 23 is configured to perform the operation of measuring electrical crosstalk signals when the detector 221 does not need to receive the detection signal.

[0147] According to a preferred embodiment of the present invention, the lidar 20 further includes a storage device 24 configured to store electrical crosstalk signals corresponding to multiple temperatures; the control device 23 is further configured to: obtain an electrical crosstalk signal corresponding to the current ambient temperature from the stored electrical crosstalk signals according to the current ambient temperature.

[0148] According to a preferred embodiment of the present invention, the absolute value of the difference between the third operating voltage V3 and the first operating voltage V1 is equal to the absolute value of the difference between the first operating voltage V1 and the second operating voltage V2.

[0149] According to a preferred embodiment of the present invention, the absolute value of the first operating voltage V1 is equal to the breakdown voltage VBR of the detector.

[0150] According to a preferred embodiment of the present invention, the control device 23 is further configured to: subtract the electrical crosstalk signal from the detection signal received by the detector 221 to obtain the echo signal.

[0151] According to a preferred embodiment of the present invention, the detector 221 is a detector operating in Geiger mode.

[0152] This invention measures electrical crosstalk signals without responding to external light signals by controlling the bias voltage of detector 221. The echo signal is then obtained based on the detected signal and the electrical crosstalk signal. This ensures the accuracy of the echo signal, maintains the signal-to-noise ratio, and reduces the time the detector cannot measure distance, thereby minimizing the near-range blind zone. Preferably, the detector's breakdown voltage VBR is adjusted according to the current ambient temperature, and the corresponding electrical crosstalk signal is invoked, thus ensuring the accuracy of the measured echo signal.

[0153] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A detection method for a lidar, the lidar comprising at least one laser and at least one detector, wherein for one of the lasers and its corresponding detector, the detection method comprises: S11: Controls the laser to emit a probe beam at the first moment; S12: From the first moment to the second moment, a first operating voltage is applied to the detector, wherein the absolute value of the first operating voltage is less than or equal to the breakdown voltage of the detector; S13: After the second moment, a second operating voltage is applied to the detector, wherein the absolute value of the second operating voltage is greater than the breakdown voltage of the detector; S14: Acquire the electrical crosstalk signal of the detector; S15: Based on the detection signal received by the detector after the second moment and the electrical crosstalk signal, obtain the echo signal reflected by the object from the detection beam; The detection method further includes the step of measuring electrical crosstalk signals, which includes: S01: Apply a third operating voltage to the detector, wherein the absolute value of the third operating voltage is less than or equal to the absolute value of the first operating voltage; S02: Apply the first operating voltage to the detector and acquire the output signal of the detector during the voltage switching process; S03: Store the output signal as the electrical crosstalk signal.

2. The detection method according to claim 1, wherein the step of measuring the electrical crosstalk signal further includes: Steps S01 to S03 are repeated at preset time intervals, and the electrical crosstalk signal measured in the previous measurement is iterated.

3. The detection method according to claim 1, wherein the step of measuring the electrical crosstalk signal further includes: Detect the current ambient temperature; The breakdown voltage, first operating voltage, second operating voltage, and third operating voltage are determined and adjusted based on the current ambient temperature. Repeat steps S01 to S03, and iterate over the electrical crosstalk signal measured in the previous step.

4. The detection method according to claim 1, wherein the lidar has at least partially overlapping transmitting and receiving optical paths, wherein the step of measuring the electrical crosstalk signal is performed when the detector does not need to receive the detection signal.

5. The detection method according to claim 1, further comprising storing electrical crosstalk signals at different temperatures, comprising: S001: Determine the breakdown voltage of the detector at a certain temperature, determine the first operating voltage and the third operating voltage, wherein the absolute value of the third operating voltage is less than or equal to the absolute value of the first operating voltage; S002: At this temperature, apply a third operating voltage to the detector and switch to the first operating voltage, acquire and store the output signal of the detector during the voltage switching process; S003: Store the output signal as the electrical crosstalk signal of the detector at this temperature; S004: Repeat steps S001 to S003 by changing the temperature, and store the electrical crosstalk signals corresponding to multiple temperatures. Step S14 further includes: obtaining an electrical crosstalk signal corresponding to the current ambient temperature from the stored electrical crosstalk signals, based on the current ambient temperature.

6. The detection method according to any one of claims 1 to 5, wherein the absolute value of the difference between the third operating voltage and the first operating voltage is equal to the absolute value of the difference between the first operating voltage and the second operating voltage.

7. The detection method according to any one of claims 1 to 5, wherein the absolute value of the first operating voltage is equal to the breakdown voltage of the detector.

8. The detection method according to any one of claims 1 to 5, wherein step S15 comprises: The echo signal is obtained by subtracting the electrical crosstalk signal from the detection signal received by the detector.

9. The detection method according to any one of claims 1 to 5, wherein the detector is a detector operating in Geiger mode.

10. A computer storage medium comprising computer-executable instructions stored thereon, the executable instructions, when executed by a processor, implementing the detection method as described in any one of claims 1-9.

11. A lidar, comprising: At least one laser configured to emit a probe beam; At least one detector is configured to receive optical signals; and A control device, connected to the at least one laser and the at least one detector, wherein for one of the lasers and its corresponding detector, the control device is configured as follows: Control the laser to emit a probe beam at the first moment; From the first moment to the second moment, a first operating voltage is applied to the detector, wherein the absolute value of the first operating voltage is less than or equal to the breakdown voltage of the detector; After the second moment, a second operating voltage is applied to the detector, wherein the absolute value of the second operating voltage is greater than the breakdown voltage of the detector; Acquire the electrical crosstalk signal of the detector; Based on the detection signal received by the corresponding detector after the second moment and the electrical crosstalk signal, the echo signal reflected by the object from the detection beam is obtained. The control device is further configured to perform the following operation: measuring electrical crosstalk signals. S01: Apply a third operating voltage to the detector, wherein the absolute value of the third operating voltage is less than or equal to the absolute value of the first operating voltage; S02: Apply the first operating voltage to the detector and acquire the output signal of the detector during the voltage switching process; S03: Store the output signal as the electrical crosstalk signal.

12. The lidar according to claim 11, wherein the control device is further configured to: repeatedly execute steps S01 to S03 at preset time intervals, and iterate the electrical crosstalk signal of the previous measurement.

13. The lidar according to claim 11, wherein the control device is further configured to: Detect the current ambient temperature; The breakdown voltage, first operating voltage, second operating voltage, and third operating voltage are determined and adjusted based on the current ambient temperature. Repeat steps S01 to S03, and iterate over the electrical crosstalk signal measured in the previous step.

14. The lidar of claim 11, wherein the lidar has at least partially overlapping transmit and receive optical paths, and the control device is configured to perform the operation of measuring the electrical crosstalk signal when the detector does not need to receive the detection signal.

15. The lidar according to claim 14 further includes a storage device configured to store electrical crosstalk signals corresponding to multiple temperatures; the control device is further configured to: obtain an electrical crosstalk signal corresponding to the current ambient temperature from the stored electrical crosstalk signals according to the current ambient temperature.

16. The lidar according to any one of claims 11 to 15, wherein the absolute value of the difference between the third operating voltage and the first operating voltage is equal to the absolute value of the difference between the first operating voltage and the second operating voltage.

17. The lidar according to any one of claims 11 to 15, wherein the absolute value of the first operating voltage is equal to the breakdown voltage of the detector.

18. The lidar according to any one of claims 11 to 15, wherein the control device is further configured to: subtract the electrical crosstalk signal from the detection signal received from the detector to obtain the echo signal.

19. The lidar according to any one of claims 11 to 15, wherein the detector is a detector operating in Geiger mode.

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