Detector control circuit, laser radar and detection method thereof

Abstract

The invention discloses a detector control circuit, a laser radar and a detection method thereof. The detector control circuit comprises at least two stages of low-side drivers which are connected in sequence; the at least two stages of low-side drivers connected in sequence are connected with the power supply voltage of a plurality of gears and the detector, and are used for outputting the power supply voltage of one gear to the detector according to a control signal. By utilizing the scheme of the invention, the dynamic range of the receiving end can be expanded while a close-range blind area caused by stray light is optimized, and the measured reflectivity accuracy and the distance measurement accuracy are ensured.

Description

Technical Field

[0001] The present invention relates to the field of circuit technology, and in particular to a detector control circuit, a laser radar and a detection method thereof. Background Art

[0002] Photodetectors can be used for light detection, such as APD (Avalanche Photo Diode), SPAD (Single Photon Avalanche Diode), SiPM (Silicon photomultiplier), etc. Photodetectors are widely used in various fields, such as lidar. With the development of photodetector preparation technology, the PDE (Photon Detection Efficiency) parameter of photodetectors is getting higher and higher. PDE refers to the probability of a photon being detected by the detector. The higher the PDE, the better the detector responds to the light signal. On the one hand, it will greatly improve the detection of low-reflectivity objects in the distance, but on the other hand, for high-reflectivity objects nearby, the photodetector is more likely to be strongly saturated, which will affect the accuracy of reflectivity measurement and ranging. Summary of the invention

[0003] The invention discloses a detector control circuit, a laser radar and a detection method thereof, which can expand the dynamic range of a receiving end of the detector and ensure the accuracy of distance measurement and reflectivity measurement.

[0004] In one aspect, the present invention provides a detector control circuit, comprising: at least two stages of low-side drivers connected in sequence;

[0005] The at least two stages of sequentially connected low-side drivers are connected to the power supply voltages of multiple gears and the detector, and are used to output the power supply voltage of one gear to the detector according to the control signal.

[0006] Optionally, the output end of the low-side driver of the previous stage of the at least two stages of low-side drivers connected in sequence is connected to the power supply end of the low-side driver of the next stage; the output end of the low-side driver of the last stage is connected to the detector; and the low-side drivers of each stage correspond to their own control signals respectively.

[0007] Optionally, the power supply terminal of the low-side driver includes a first power supply terminal and a second power supply terminal, and a power supply voltage connected to the first power supply terminal is greater than a power supply voltage connected to the second power supply terminal;

[0008] The output end of the previous low-side driver of the at least two stages connected in sequence is connected to the first power supply end of the next low-side driver, and the supply voltage connected to the second power supply end of the at least two stages connected in sequence decreases in sequence.

[0009] Optionally, the low-side driver includes two output terminals; the two output terminals of the low-side driver of the previous stage among the at least two stages of low-side drivers connected in sequence are connected to the first power supply terminal of the low-side driver of the next stage, and the first power supply terminal is also connected to a capacitor.

[0010] Optionally, among the at least two stages of sequentially connected low-side drivers, resistors are respectively connected between two output terminals of the previous stage of the low-side driver and the first power supply terminal of the next stage of the low-side driver.

[0011] Optionally, the input terminal of the low-side driver is connected to the control signal via a first DC blocking capacitor, and a diode and an input resistor are connected between the positive input terminal and the negative input terminal of the low-side driver.

[0012] Optionally, the low-side driver includes a first power supply terminal and a second power supply terminal, and the power supply voltage connected to the first power supply terminal is greater than the power supply voltage connected to the second power supply terminal; the output end of the previous low-side driver of the at least two stages of low-side drivers connected in sequence is connected to the second power supply terminal of the next low-side driver, and the power supply voltage connected to the first power supply terminal of the at least two stages of low-side drivers connected in sequence increases sequentially.

[0013] Optionally, the low-side drivers connected in sequence are two-stage, including: a first-stage low-side driver and a second-stage low-side driver; the first power supply terminal of the first-stage low-side driver is connected to a first power supply voltage, and the second power supply terminal of the first-stage low-side driver is connected to a second power supply voltage; the first output terminal and the second output terminal of the first-stage low-side driver are connected, and are connected to the first power supply terminal of the second-stage low-side driver; the second power supply terminal of the second-stage low-side driver is connected to a third power supply voltage; the first output terminal and the second output terminal of the second-stage low-side driver are connected, and are connected to the detector; wherein, the first power supply voltage>the second power supply voltage>the third power supply voltage.

[0014] Optionally, the input end of the first-level low-side driver is connected to a first control signal, and the input end of the second-level low-side driver is connected to a second control signal; the first-level low-side driver and the second-level low-side driver are used to output a first supply voltage, a second supply voltage, or a third supply voltage to the detector according to the first control signal and the second control signal.

[0015] Optionally, the circuit further includes: a negative pressure generating module, configured to generate the supply voltage.

[0016] Optionally, the negative pressure generating module includes a BOOST chip.

[0017] On the other hand, the present invention further provides a laser radar, the laser radar comprising a transmitter, a detector, and the detector control circuit described above;

[0018] The transmitter is used to emit detection light;

[0019] The detector is used to receive the echo generated by the detection light;

[0020] The detector control circuit is used to output a power supply voltage to the detector according to a control signal.

[0021] On the other hand, the present invention also provides a detection method based on the above-mentioned laser radar, characterized in that the method comprises:

[0022] The transmitter emits a laser;

[0023] The detector control circuit adjusts the supply voltage output to the detector according to the detection mode;

[0024] The detector receives the reflected echo signal and outputs an electrical signal;

[0025] The distance information of the object is determined according to the electrical signal.

[0026] Optionally, the detector control circuit adjusts the supply voltage output to the detector according to the detection mode, including:

[0027] The detector control circuit obtains a control signal corresponding to the current detection mode;

[0028] A power supply voltage of a gear is output to the detector according to the control signal.

[0029] Optionally, the detection mode includes a first detection mode and a second detection mode;

[0030] In the first detection mode, a first supply voltage is first output to the detector, and then switched to a second supply voltage after a first preset time;

[0031] In the second detection mode, the first supply voltage is first output to the detector, and then switched to the third supply voltage after a second preset time;

[0032] Among them, the detection probability of the detector increases successively under the first power supply voltage, the second power supply voltage, and the third power supply voltage.

[0033] Optionally, the method further comprises:

[0034] Performing detection using the first detection mode;

[0035] After the first detection mode fails to detect the high-reflectivity object, the second detection mode is used for detection.

[0036] Optionally, the method further includes: in the first detection mode, if the signal output by the detector is less than a first set threshold, determining that no high-reflectivity object is detected.

[0037] Optionally, the method further comprises:

[0038] performing detection using a second detection mode;

[0039] After the high-reflectivity object is detected in the second detection mode, the first detection mode is used for detection.

[0040] Optionally, the method further comprises:

[0041] In the second detection mode, if the signal output by the detector is greater than a second set threshold, it is determined that a high-reflectivity object is detected.

[0042] Optionally, the luminous intensity of the emitter in the first detection mode is lower than the luminous intensity of the emitter in the second detection mode.

[0043] The detector control circuit, laser radar, and detection method disclosed in the present invention utilize at least two low-side drivers connected in sequence, and at least two low-side drivers connected in sequence can output different levels of power supply voltage to the detector (APD, SiPM, or SPAD, etc.) according to different control signals, so that the PDE can be adjusted by adjusting the bias voltage of the detector (the lower the bias voltage, the lower the PDE, so the probability of detector saturation is low), and then when measuring close objects, a low bias voltage is used to reduce the problem of detector saturation (especially when detecting high reflectivity objects) affecting the measurement accuracy, thereby improving the accuracy of the measured reflectivity and the accuracy of the distance measurement. When measuring medium-distance or long-distance objects, a high bias voltage is used to ensure the distance measurement performance of the laser radar (that is, the ability to detect long-distance objects), so the dynamic range of the detector reception can be expanded by setting multiple levels of power supply voltage.

[0044] Furthermore, the detector control circuit in the present invention can quickly switch the power supply voltage output to the detector, that is, the voltage switching can be quickly completed within a detection time window, thereby meeting the detection requirements of the laser radar and ensuring that the laser radar can detect normally. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a schematic diagram of the echo pulse when there is no crosstalk between channels;

[0046] Figure 2 It is a schematic diagram of echo pulses when there is crosstalk between channels;

[0047] Figure 3 is a structural schematic diagram of a detector control circuit provided by an embodiment of the present invention;

[0048] Figure 4 is another structural schematic diagram of a detector control circuit provided in an embodiment of the present invention;

[0049] Figure 5 yes Figure 3 A specific structural schematic diagram of the detector control circuit shown;

[0050] Figure 6 The detector and Figure 5 A connection diagram of the output terminal of the detector control circuit and the readout circuit;

[0051] Figure 7 It is a structural schematic diagram of a detector control circuit including a multi-stage low-side driver provided in an embodiment of the present invention;

[0052] Figure 8 is a schematic diagram of the structure of a laser radar provided by an embodiment of the present invention;

[0053] Fig. 9 is a flow chart of a detection method provided by an embodiment of the present invention;

[0054] Fig.10 Schematic diagram of electrical crosstalk generated when the anode voltage of the detector is switched in the close-up frame in an embodiment of the present invention;

[0055] Fig.11 Schematic diagram of electrical crosstalk generated when the anode voltage of the detector is switched in a normal TOF frame in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0057] LiDAR can measure the distance information and reflectivity information of objects within its field of view. The position of the object can be determined based on the distance information, and subsequent object identification can be performed based on the reflectivity information. Therefore, the accuracy of LiDAR's measurement of object distance information and reflectivity information is very important.

[0058] When the laser radar detects an object, the laser emits a detection signal, and the detector detects the echo signal formed after the detection signal is reflected by the object and generates an electrical signal. The energy of the echo signal can be inferred based on the waveform of the generated electrical signal, and then the reflectivity of the object can be calculated. If the reflectivity of the object is very high (for example, the reflectivity is 70%), the energy of the reflected echo will be very strong, so the electrical signal output by the detector will be saturated. If an object with a higher reflectivity (for example, a reflectivity of 90%) is encountered, although the reflected echo energy is stronger, the electrical signal output by the detector will still be saturated, that is, the waveforms of the electrical signals corresponding to the echo signals of the two high-reflectivity objects mentioned above are very different, and it is impossible to distinguish two high-reflectivity objects with different reflectivity based on the difference in waveforms. That is, the reflectivity calculated based on the waveform of the electrical signal output by the detector is inaccurate. In addition, since the energy of the detection signal will attenuate when it propagates in the air, the longer the propagation distance, the more it attenuates, and the closer the propagation distance, the less it attenuates. Therefore, when the object is closer to the laser radar, it is easier to cause the detector to saturate, so when measuring close objects, it is easy to have inaccurate reflectivity measurement problems.

[0059] For the accuracy of ranging, if the reflectivity of the object is high, the energy of the reflected echo signal is relatively strong, which will cause a lot of crosstalk, including optical crosstalk and electrical crosstalk. LiDAR usually includes multiple measurement channels, each of which corresponds to a detector. When the intensity of the echo signal of a channel reaches a certain level, it will generate interference pulses for other channels. The interference pulses will be superimposed on the echo pulses caused by the real obstacles, and the real echo pulses are the basis for the subsequent calculation of distance and reflectivity. In this way, interference will occur in the measurement of distance and reflectivity, making the measurement results inaccurate.

[0060] The following takes two channels, channel 1 and channel 2, as an example to illustrate the difference in echo pulses (ie, the electrical signals generated by the aforementioned detector detecting the echo signals) when there is no crosstalk between the channels and when there is crosstalk between the channels.

[0061] When there is no crosstalk (including optical crosstalk and electrical crosstalk) between channels, the echo pulses received by each channel are as follows: Figure 1 See Figure 1 , each channel only receives the echo pulse reflected by the object corresponding to its own channel. The ranging result of object a can be calculated based on the leading edge and pulse width of the echo pulse. Of course, the distance can also be calculated based on the peak value of the echo pulse or other methods. In this case, an accurate ranging result can be obtained.

[0062] When there is crosstalk between channels (including optical crosstalk and electrical crosstalk), the echo pulses received by each channel are Figure 2 shown.

[0063] Reference Figure 2 , because of the existence of crosstalk, channel 1 not only receives the echo pulse 31 reflected by object a, but also receives the echo pulse reflected by object b (whose amplitude is smaller than the echo pulse 31). In fact, for the direction of channel 1, there is actually no object b, and the echo pulse reflected by object b should only appear in the direction corresponding to channel 2. In this case, the echo pulse corresponding to object a may be superimposed with the crosstalk echo pulse (i.e., the echo pulse corresponding to object b). Obviously, the leading edge and pulse width of the superimposed pulse 32 (hereinafter referred to as the superimposed echo pulse for the convenience of description) will change relative to the leading edge and pulse width of the echo pulse of object a. At this time, since the ranging result of object a is calculated by the leading edge and pulse width of the superimposed echo pulse 32, the calculated ranging result will have a certain deviation from the ranging result without crosstalk, and the degree of deviation depends on the degree of deviation of the leading edge and pulse width of the echo pulse.

[0064] Usually, the amplitude of the crosstalk echo pulse is smaller than the amplitude of the real obstacle echo pulse. Of course, in some cases, the amplitude of the crosstalk echo pulse may be larger.

[0065] In view of the above two problems, the embodiments of the present invention provide a detector control circuit, a laser radar and a detection method thereof. The PDE is adjusted by adjusting the bias voltage of the detector. When measuring close objects, a low bias voltage can be used to ensure that the detector is not saturated when detecting high-reflectivity objects, that is, the reflectivity accuracy and ranging accuracy of the measurement are guaranteed; when measuring distant objects, a high bias voltage is used to ensure the radar's distance measurement performance. At the same time, the detector control circuit disclosed in the embodiments of the present invention can realize fast voltage switching, which can meet the demand for fast switching of the detector bias voltage during the operation of the laser radar.

[0066] The detector control circuit provided by the embodiment of the present invention comprises: at least two levels of low-side drivers connected in sequence, the at least two levels of low-side drivers connected in sequence are connected to the power supply voltage of multiple gears and the detector, and are used to output a power supply voltage of one gear to the detector according to a control signal. The output end of the low-side driver of the first level of the at least two levels of low-side drivers connected in sequence is connected to the power supply end of the low-side driver of the next level; the output end of the low-side driver of the last level is connected to the detector; and the low-side drivers of each level correspond to their own control signals respectively.

[0067] exist Figure 3In the structural schematic diagram shown, the structure of a detector control circuit including two - stage low - side drivers is shown.

[0068] The detector control circuit in this example includes two - stage low - side drivers connected in sequence, as Figure 3 shown, which are the first - stage low - side driver 401 and the second - stage low - side driver 402 respectively. The first - stage low - side driver 401 is controlled by the control signal IN_CONTROL1, and the second - stage low - side driver 402 is controlled by the control signal IN_CONTROL2.

[0069] In this detector control circuit, each low - side driver includes two power supply terminals. For the convenience of description, they are respectively called the first power supply terminal and the second power supply terminal. Among them, the supply voltage connected to the first power supply terminal is greater than the supply voltage connected to the second power supply terminal. For example, Figure 3 in the first - stage low - side driver 401, the supply voltage V11 connected to the first power supply terminal is greater than the supply voltage V12 connected to its second power supply terminal. Similarly, for the second - stage low - side driver 402, the supply voltage V21 connected to the first power supply terminal is greater than the supply voltage V22 connected to its second power supply terminal.

[0070] In a non - restrictive embodiment, the output terminal of the previous - stage low - side driver in at least two - stage low - side drivers connected in sequence is connected to the first power supply terminal of the next - stage low - side driver, and the supply voltages connected to the second power supply terminals of at least two - stage low - side drivers connected in sequence decrease in turn. For example, Figure 3 in [the figure], the output terminal of the first - stage low - side driver 401 is connected to the first power supply terminal of the second - stage low - side driver 402, and the supply voltage V22 connected to the second power supply terminal of the second - stage low - side driver 402 is less than the supply voltage V12 connected to the second power supply terminal of the first - stage low - side driver 401, that is, V22 < V12. Since the supply voltage V22 connected to the second power supply terminal of the second - stage low - side driver 402 is less than the supply voltage V12 connected to the second power supply terminal of the first - stage low - side driver 401, no matter whether the output voltage of the first - stage low - side driver 401 is V11 or V12, it can ensure the normal operation of the second - stage low - side driver 402.

[0071] In another non - restrictive embodiment, the output terminal of the previous - stage low - side driver in at least two - stage low - side drivers connected in sequence is connected to the second power supply terminal of the next - stage low - side driver, and the supply voltages connected to the first power supply terminals of at least two - stage low - side drivers connected in sequence increase in turn. For example, Figure 4In the example shown, the output end of the first-stage low-side driver 401 is connected to the second power supply end of the second-stage low-side driver 402, and the power supply voltage V21 connected to the first power supply end of the second-stage low-side driver 402 is greater than the power supply voltage V11 connected to the first power supply end of the first-stage low-side driver 401, that is, V21>V11. Since the power supply voltage V21 connected to the first power supply end of the second-stage low-side driver 402 is greater than the power supply voltage V11 connected to the first power supply end of the first-stage low-side driver 401, no matter whether the first-stage low-side driver 401 outputs the voltage V11 or V12, the normal operation of the second-stage low-side driver 402 can be guaranteed.

[0072] During the detection process, the first low-side driver 401 and the second low-side driver 402 output a power supply voltage of one gear to the detector 500 according to the control signals IN_CONTROL1 and IN_CONTROL2. In practical applications, the output power supply voltage can be selected according to different detection modes, which will be described in detail later.

[0073] Below Figure 3 Taking the connection mode shown as an example, the structure and working process of the detector control circuit of the embodiment of the present invention are further described in detail.

[0074] like Figure 5 As shown, Figure 3 A specific structural schematic diagram of the detector control circuit shown.

[0075] In this embodiment, the two-stage low-side drivers are respectively as follows: Figure 5 As shown in U1 and U2 in FIG. 1 , each low-side driver includes two output terminals, which are referred to as a first output terminal and a second output terminal for ease of description.

[0076] Reference Figure 5 , the first power supply terminal of the first-stage low-side driver U1 is connected to the first power supply voltage VH, and the second power supply terminal is connected to the second power supply voltage VM. The first output terminal and the second output terminal of the first-stage low-side driver are connected, and are connected to the first power supply terminal of the second-stage low-side driver. The second power supply terminal of the second-stage low-side driver U2 is connected to the third power supply voltage VL. The first output terminal and the second output terminal of the second-stage low-side driver are connected, and are connected to the detector. In this embodiment, VH, VM, and VL represent three different voltages, respectively, and meet the following conditions: VH>VM>VL; VH, VM, and VL can all be negative voltages, for example, respectively -20V, -25V, and -30V, and VH, VM, and VL can also all be positive voltages, for example, respectively 20V, 25V, and 30V. Under different voltages, the detector is caused to be in different bias voltages, and then the detector exhibits different response results, as described in detail later.

[0077] In a non-limiting embodiment, the first output terminal 1 and the second output terminal 2 of the first-stage low-side driver U1 are connected to each other and are connected to the first power supply terminal of the second-stage low-side driver U2 .

[0078] In another non-limiting embodiment, resistors are respectively connected between the two output terminals of the first-stage low-side driver U1 and the first power supply terminal of the second-stage low-side driver U2. Figure 5 As shown in , a resistor RH1 is connected between the first output terminal 1 of the first-stage low-side driver U1 and the first power supply terminal of the second-stage low-side driver U2, and a resistor RL1 is connected between the second output terminal 2 and the first power supply terminal of the second-stage low-side driver U2. In this case, the first output terminal 1 and the second output terminal 2 of the first-stage low-side driver U1 are connected to the first power supply terminal of the second-stage low-side driver U2 through the resistors RH1 and RL1, respectively.

[0079] Similarly, the two output terminals of the second-stage low-side driver U2 can also adopt the above connection method, that is, the first output terminal and the second output terminal of the second-stage low-side driver U2 are connected to each other and connected to the detector 500; or Figure 5 As shown, resistors RH2 and RL2 are respectively connected between the two output terminals of the second low-side driver U2 and the detector 500. In this case, the first output terminal and the second output terminal of the second low-side driver U2 are respectively connected to the detector through resistors RH2 and RL2.

[0080] In a specific application, the resistance values ​​of resistors RH2 and RL2, and RH1 and RL1 may be the same or different. The specific resistance values ​​may be determined according to the parameters of the selected low-side driver and the required supply voltage, which is not limited in this embodiment of the present invention.

[0081] It should be noted that, in a circuit structure with multiple low-side drivers, the connection method of the output terminals of each low-side driver is similar to the above, and will not be repeated here.

[0082] In addition, in the detector control circuit provided by the present invention, the output end of each level of low-side driver is further connected to a capacitor for stabilizing the voltage, such as Figure 5 In the illustrated embodiment, the first power supply terminal of the second-stage low-side driver U2 is also connected to a capacitor C1, the input terminal of the detector 500 is also connected to a capacitor C2, and the other ends of the capacitors C1 and C2 are connected to a third power supply voltage VL, that is, the lowest-level power supply voltage.

[0083] Of course, corresponding to Figure 4 In the connection mode shown, the other end of the capacitor connected to the output of each level of low-side driver needs to be connected to the supply voltage of the highest level.

[0084] The input terminal of the low-side driver in the embodiment of the present invention includes a positive input terminal and a negative input terminal. The control signal of each low-side driver can be connected to the positive input terminal or the negative input terminal. Figure 5 As shown in the figure, the first control signal IN_CONTROL1 is connected to the positive input terminal of the first-stage low-side driver U1 through the DC-isolating capacitor C3, and the second control signal IN_CONTROL2 is connected to the positive input terminal of the second-stage low-side driver U2 through the DC-isolating capacitor C4. Since one of the positive input terminal and the negative input terminal of the low-side driver is connected to the control signal, and the other end is connected to the DC voltage, by setting the DC-isolating capacitor, it is possible to prevent the DC voltage connected to one input terminal of the low-side driver from being reversely input to the control module (such as FPGA, chip, etc.) used to output the control signal through the connection line of the control signal, causing damage to the control module.

[0085] Furthermore, a diode and an input resistor are connected between the positive input terminal and the negative input terminal of each low-side driver. Figure 5 A diode D1 and an input resistor R1 are connected between the two input terminals of the first-stage low-side driver U1, and a diode D2 and an input resistor R2 are connected between the two input terminals of the second-stage low-side driver U2. The diode and the input resistor connected between the positive input terminal and the negative input terminal of the low-side driver and the aforementioned capacitor together realize the DC isolation function, which can prevent damage to the control module while ensuring the control of the low-side driver.

[0086] Figure 5 In the illustrated embodiment, the first low-side driver U1 and the second low-side driver U2 output the first power supply voltage VH, the second power supply voltage VM, or the third power supply voltage VL to the detector 500 according to the first control signal IN_CONTROL1 and the second control signal IN_CONTROL2.

[0087] The detector 500 may be a SiPM or a SPAD or an APD or other types of photoelectric detectors. One end of the detector 500 is input with the power supply voltage, and the other end is grounded.

[0088] The following is based on Figure 5 The circuit structure is shown and its working principle is explained in detail.

[0089] Reference Figure 5 , Figure 5 The two low-side drivers U1 and U2 in the circuit output different voltage levels according to the voltage difference between their two input terminals. Taking the first-stage low-side driver U1 as an example, when the voltage difference across the input resistor R1 is greater than the set voltage value Vth, the first-stage low-side driver U1 outputs a voltage VH at the first output terminal 1; when the voltage difference across the input resistor R1 is less than the set voltage value Vth, the first-stage low-side driver U1 outputs a voltage VM at the second output terminal 2.

[0090] Detector 500 with Figure 5 The output terminal of the control circuit and the connection method of the readout circuit are as follows Figure 6 shown. Figure 5 The diagram shows how the detector circuit is connected when the power supply adopts negative high voltage or positive high voltage. It should be noted that when the bias voltage at both ends of the detector is greater than a certain threshold (taking a single-photon avalanche detector as an example, such as SiPM or SPAD or others, the threshold is the breakdown voltage of the detector), the detector can respond to the optical signal and output an electrical signal, and the greater the bias voltage, the higher the PDE of the detector. The control circuit can output three different voltages to make the detector not respond to the optical signal, respond to the optical signal with low PDE, and respond to the optical signal with high PDE.

[0091] Reference Figure 6 Taking the negative high voltage circuit on the left as an example, when the control circuit outputs negative high voltage VH (such as -20V) to the detector 500, the detector 500 does not respond to the light signal. When the control circuit outputs negative high voltage VM (such as -25V) to the detector 500, the detector 500 responds to the light signal but the detection probability (PDE) is low. When the control circuit outputs negative high voltage VL (such as -30V) to the detector 500, the detector 500 responds to the light signal and the detection probability (PDE) is high. The readout circuit 600 reads the electrical signal generated by the detector in response to the light signal. The electrical signal is used to subsequently determine information such as the distance and reflectivity of the target object. The same is true for the positive high voltage circuit. Figure 6 As shown in the positive high-voltage circuit on the left, when the control circuit outputs a positive high-voltage VH (such as 30V) to the detector 500, the detector 500 responds to the light signal and the detection probability (PDE) is high. When the control circuit outputs a positive high-voltage VM (such as 25V) to the detector 500, the detector 500 responds to the light signal but the detection probability (PDE) is low. When the control circuit outputs a positive high-voltage VL (such as 20V) to the detector 500, the detector 500 does not respond to the light signal.

[0092] Continue to refer to Figure 5 , depending on the control signal, the output voltage of the control circuit has the following situations:

[0093] When the first control signal IN_CONTROL1 and the second control signal IN_CONTROL2 are both at high levels, the control circuit outputs the first power supply voltage VH to the anode of the SiPM;

[0094] When the first control signal IN_CONTROL1 is at a low level and the second control signal IN_CONTROL2 is at a high level, the control circuit outputs a second power supply voltage VM level to the anode of the SIPM;

[0095] When the second control signal IN_CONTROL2 is at a low level, the control circuit outputs the third power supply voltage VL to the anode of the SIPM regardless of whether the first control signal IN_CONTROL1 is at a high level or a low level.

[0096] The control logic of the first control signal IN_CONTROL1 and the second control signal IN_CONTROL2 may be implemented by a Field Programmable Gate Array (FPGA).

[0097] Therefore, the output voltage can be quickly switched by adjusting the first control signal IN_CONTROL1 and the second control signal IN_CONTROL2.

[0098] Figure 5 When the power supply voltages VH, VM and VL are negative voltages, they can be generated by a corresponding negative voltage generating module (not shown), and the negative voltage generating module can include a BOOST chip, that is, generating the required power supply voltages in a manner similar to a charge pump; of course, other negative voltage generating circuits can also be used to generate the power supply voltages, which is not limited to this embodiment of the present invention.

[0099] Above Figure 5 A specific structure of a detector control circuit consisting of two-stage low-side drivers is presented, and the working principle of the detector control circuit is explained in detail.

[0100] Accordingly, in practical applications, the number of low-side driver stages can be selected as needed, for example, Figure 7 In the embodiment shown, the detector control circuit includes n+1 low-side drivers, namely Figure 7 The low-side drivers U1~Un+1 in the circuit have corresponding control signals HV_CONTROL1~HV_CONTROLn+1, and the output of the previous low-side driver is connected to the first power supply terminal of the next low-side driver. The second power supply terminals of each level of low-side driver are connected to the power supply voltages VM1~VMn and VL, respectively. In addition, the positive input terminals of each level of low-side driver are connected to the corresponding control signals, and the negative input terminals are connected to the power supply voltage VM.

[0101] Figure 7 The working principle of the detector control circuit including the multi-stage low-side driver is similar to that described above. Figure 5 The embodiments shown are the same and will not be described again here.

[0102] The detector control circuit provided by the embodiment of the present invention adopts a multi-level structure, which can meet the measurement requirements of laser radar in different scenarios. For example, in high-speed scenarios, long-distance measurement is expected, so a high PDE is required; while in urban scenarios, the probability of nearby objects appearing is high, so a lower PDE is required. In different scenarios, the required value of the negative high voltage output to the detector may be different.

[0103] Accordingly, an embodiment of the present invention further provides a laser radar, such as Figure 8 The figure is a schematic diagram of the structure of a laser radar provided in an embodiment of the present invention.

[0104] The laser radar 800 includes: a transmitter 801, a detector 802, and the detector control circuit 803 described above. Among them:

[0105] The transmitter 801 is used to transmit detection light;

[0106] The detector 802 is used to receive the echo generated by the detection light;

[0107] The detector control circuit 803 is used to output a power supply voltage to the detector according to a control signal.

[0108] Among them, the detector control circuit 803 includes at least two stages of low-side drivers connected in sequence, and the at least two stages of low-side drivers connected in sequence are connected to multiple levels of power supply voltage, which are used to output a level of power supply voltage to the detector 802 according to the control signal.

[0109] In this embodiment, each level of low-side driver corresponds to its own control signal. The number of levels of the low-side driver, the number and size of the power supply voltage can be determined according to the measurement requirements of the laser radar in different scenarios.

[0110] Using this lidar, the power supply voltage output to the detector can be adjusted according to the application scenario, and the adjustment can be done quickly (within 100ns), thereby achieving measurements in different scenarios and ensuring the accuracy of the measured reflectivity and ranging.

[0111] Based on the above laser radar, the embodiment of the present invention also provides a detection method, such as Fig. 9 The figure is a flow chart of a detection method provided by an embodiment of the present invention.

[0112] The method comprises the following steps:

[0113] Step 901: The transmitter emits laser.

[0114] Step 902: The detector control circuit adjusts the supply voltage output to the detector according to the detection mode.

[0115] Different detection modes require different control signals. Therefore, the detector control circuit obtains a control signal corresponding to the current detection mode and outputs a power supply voltage of a gear to the detector according to the control signal.

[0116] Step 903: The detector receives the reflected echo signal and outputs an electrical signal.

[0117] Step 904: Determine the distance information of the object according to the electrical signal.

[0118] In the embodiment of the present invention, the detection mode may include but is not limited to a first detection mode and a second detection mode.

[0119] The detector control circuit adopts the above Figure 5 Taking the structure of the two-stage low-side driver shown as an example, three levels of power supply voltage can be output to the detector, namely the first power supply voltage, the second power supply voltage, and the third power supply voltage, and the first power supply voltage> the second power supply voltage> the third power supply voltage. As mentioned above, the power supply voltages of these three levels can all be negative voltages, such as -20V, -25V, and -30V respectively. Correspondingly, the detection probability (i.e., PDE) of the detector increases successively under the first power supply voltage, the second power supply voltage, and the third power supply voltage. It should be noted that, as mentioned above, the power supply voltages of the three levels can also all be positive voltages, corresponding to different detection probabilities of the detector, which will not be elaborated here.

[0120] In the above case, the two detection modes may specifically be:

[0121] The first detection mode: the first power supply voltage VH is first output to the detector, and then switched to the second power supply voltage VM after a first preset time (such as 3ns, 5ns, or 10ns, etc.).

[0122] The second detection mode: first output the first power supply voltage VH to the detector, and then switch to the third power supply voltage VL after a second preset time (such as 3ns, 5ns, or 10ns, etc.).

[0123] In order to solve the problem of inaccurate distance and reflectivity measurement of laser radar caused by high-reflectivity objects at close range, when the laser radar is measuring, the light emission of the transmitter can include two light emission sequences: light emission sequence 1 - close-up frame, with a short reserved time window, used to detect high-reflectivity objects at close range; light emission sequence 2 - normal TOF (Time of flight) frame, used for normal detection of full TOF. If the detector of a channel in light emission sequence 1 detects a high-reflectivity object, the laser of this channel will not emit light in light emission sequence 2 to avoid crosstalk.

[0124] Since the echo signal of a high-reflectivity object at a close distance is very strong, reducing the bias voltage of the detector (SiPM or SPAD or APD, etc.) can avoid the problem of inaccurate measurement caused by detector saturation, thereby optimizing the reflectivity accuracy and ranging accuracy of objects with high reflectivity at close range. Furthermore, the light intensity adjustment at the transmitting end can be used, that is, the light intensity of the laser is reduced in the close-up frame, and normal intensity light is emitted in the normal TOF frame, which can better improve the accuracy of the measurement results.

[0125] Accordingly, in the embodiment of the present invention, the first detection mode may correspond to the light-emitting timing 1, that is, as a proximity detection frame; the second detection module may correspond to the light-emitting timing 2, that is, as a normal TOF frame. Figure 5 Provide detailed explanation.

[0126] Also refer to Figure 5 For the above-mentioned first detection mode, before the transmitter is launched, the first control signal IN_CONTROL1 and the second control signal IN_CONTROL2 are controlled to be high level. At this time, the power supply voltage output to the detector is VH (for example, the aforementioned -20V), and the detector basically has no response; then the first control signal IN_CONTROL1 is pulled down, which will cause the power supply voltage output to the detector to slowly switch from VH to VM (for example, the aforementioned -25V). By properly setting the recovery time of the detector bias, the bias voltage of the detector is restored to a suitable value. Under this bias voltage, the detector can respond to the optical signal to output an electrical signal, and the detection probability of the detector is low, reducing the detector saturation problem caused by the excessive intensity of the optical signal, so that this process can be used for close-range high-reflective object detection. The recovery time is specifically the RC time of the RC circuit composed of RL1+RH2 and C2 and RL1 and C1.

[0127] Continue to refer to Figure 5 For the above-mentioned second detection mode, the first control signal IN_CONTROL1 and the second control signal IN_CONTROL2 are both controlled to be high before light emission. At this time, the power supply voltage output to the detector is VH (for example, the aforementioned -20V), and the detector basically has no response; then the second control signal IN_CONTROL2 is pulled down (at this time, the first control signal IN_CONTROL1 can be a high level or a low level), which will cause the power supply voltage output to the detector to slowly switch from VH to VL (for example, the aforementioned -30V). By appropriately setting the recovery time of the detector bias, the bias low voltage of the detector is restored to a larger value, so that this process can be used for normal detection of the full TOF. The recovery time is specifically the RC time of the RC circuit composed of RL2 and C2.

[0128] like Fig.10 and Fig.11As shown, at time t1, the anode voltage of the detector starts to switch from VH to VM or VL, and at time t2, the switching is completed, that is, the anode voltage of the detector is VM or VL respectively. Since the bias change will bring electrical crosstalk (that is, as shown by the dotted line in the figure), the faster the voltage changes, the greater the electrical crosstalk. Therefore, it is necessary to properly adjust the recovery time of the bias voltage Vd of the detector (that is, the time from t1 to t3 in the figure), specifically the RC time, to slowly switch the anode voltage Vn of the detector, thereby suppressing the influence of the crosstalk caused by the bias switching. Specifically, the corresponding RC time can be controlled by selecting capacitors (that is, C1, C2) and resistors (that is, RL1, RH1, RL2, RH2) of appropriate sizes.

[0129] Based on the above principles, in the scheme of the present invention, accurate measurement can be achieved by using and switching the above two detection modes. In addition, since the detector hardly responds to light signals under the voltage VH, the above measurement method can also reduce the close-range blind area in the laser radar (especially the laser radar with coaxial optical path). Specifically, for some laser radars (such as laser radars with coaxial optical paths), there is a partial overlap between the internal outgoing optical path and the receiving optical path, so after the laser is emitted, some stray light will directly enter the detector end, causing the detector to saturate (for single-photon detectors, such as SiPM or SPAD, it is impossible to respond to other light signals during saturation). It usually takes about 20ns to gradually restore the response to light, so objects within the range of 20ns×0.15m / ns=3m cannot be detected, and this distance that cannot be detected is the close-range blind area of ​​the radar. It is usually hoped that the short-range blind zone is as short as possible. The shorter the short-range blind zone is, the greater the impact of high-reflectivity objects at close range on long-range detection. By adopting the measurement method of the present application, the short-range blind zone can be reduced by reasonably setting the time for adjusting the voltage. For example, if the aforementioned preset time is adjusted to 5ns, the short-range blind zone can be shortened to 5ns×0.15m / ns=0.75m.

[0130] For example, in a non-limiting embodiment, the first detection mode may be used for detection (i.e., first measure whether there is a high reflectivity object nearby), and after the first detection mode fails to detect a high reflectivity object, the second detection mode may be used for detection. Of course, if the first detection mode detects a high reflectivity object, the detection in the second detection mode may be stopped, for example, by stopping the emitter from emitting laser light, or by pulling the first control signal IN_CONTROL1 and the second control signal IN_CONTROL2 to a high level so that the detector does not respond to the light signal.

[0131] In the first detection mode, whether a high-reflectivity object is detected can be determined in the following manner: if the signal output by the detector is less than a first set threshold, it is determined that a high-reflectivity object is not detected; otherwise, it is determined that a high-reflectivity object is detected.

[0132] For example, in another non-limiting embodiment, the second detection mode may be used to perform detection first (ie, normal measurement of the object), and after the high-reflectivity object is detected in the second detection mode, the first detection mode may be used to perform detection.

[0133] Since normal TOF detection is performed in the second detection mode, if a high-reflectivity object is detected, the high-reflectivity object will affect the accuracy of the normal TOF detection result. Therefore, in this case, the detection result in the second detection mode is inaccurate. Therefore, for this situation, the first detection mode is performed again to obtain accurate detection results of the high-reflectivity object, such as the reflectivity or distance of the high-reflectivity object.

[0134] Similarly, in the second detection mode, whether a high-reflectivity object is detected may be determined in the following manner: if the signal output by the detector is greater than a second set threshold, it is determined that a high-reflectivity object is detected.

[0135] The first set threshold and the second set threshold may be determined according to hardware parameters and scenarios of the laser, which are not limited in this embodiment of the present invention.

[0136] Furthermore, in specific applications, the luminous intensity of the emitter in the two detection modes can be controlled to remain the same. Of course, it is more preferred to make the luminous intensity of the emitter in the first detection mode lower than the luminous intensity of the emitter in the second detection mode, so as to better realize the detection of highly reflective objects at a close distance, avoid the influence of highly reflective objects at a close distance on normal measurement, and ensure the measurement reflectivity accuracy and ranging accuracy.

[0137] It should be noted that in order to obtain more information about objects in space, laser radars usually set up multiple light sources, each of which corresponds to a different position in space. When multiple light sources work in parallel and the corresponding detectors collect data in parallel, there will be a large crosstalk problem between channels. Therefore, a patrol light emission method is often used, that is, multiple light sources emit light in turn (one at a time or several at a time), and the corresponding detectors receive data. Since the speed of light is fixed, the time tof required to generate a point at the upper limit of the ranging in the point cloud is also fixed. For the near-range frame, since the ranging upper limit is relatively close, the total time window can be reduced, or one light source can be emitted at a time. Furthermore, since the purpose of the near-range frame is to measure high-reflectivity objects nearby, some channels can be selected for measurement, such as selecting the channel in front of the corresponding laser radar close to the ground for measurement; all channels are selected for measurement in the normal TOF frame. That is, in the above-mentioned first detection mode, some channels are selected for measurement, and in the second detection mode, all channels are selected for measurement.

[0138] Compared with the prior art solution of using a single negative high voltage to solve the problem of close-range blind spots, the detection method of the embodiment of the present invention, based on a laser radar with a detector control circuit having multiple negative pressure outputs, has the following advantages:

[0139] 1) The solution disclosed in the present invention can achieve rapid adjustment (within 100ns) of the bias voltage of the detector, that is, two levels of bias voltage can be selected for detection for proximity measurement at one angle and a normal TOF frame.

[0140] 2) Since the ability to adjust the laser light intensity is limited, only adjusting the laser light intensity will result in insufficient dynamic range of the laser radar for close-range detection of high reflectivity. The solution disclosed in the present invention separately configures the speed and voltage of the high-voltage ramp-up for the close-range frame, which can significantly improve the detection performance.

[0141] It should be understood that the term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article indicates that the associated objects before and after are in an "or" relationship.

[0142] The “plurality” mentioned in the embodiments of the present invention refers to two or more than two.

[0143] The first, second, etc. descriptions appearing in the embodiments of the present invention are only used for illustration and distinction of the description objects. There is no order, nor does it indicate any special limitation on the number of devices in the embodiments of the present invention, and cannot constitute any limitation on the embodiments of the present invention.

[0144] The “connection” in the embodiments of the present invention refers to various connection modes such as direct connection or indirect connection to achieve communication between devices, and the embodiments of the present invention do not impose any limitation on this.

[0145] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A detector control circuit, characterized in that: include: At least two low-side drivers connected in sequence; The at least two stages of sequentially connected low-side drivers are connected to the power supply voltages of multiple gears and the detector, and are used to output the power supply voltage of one gear to the detector according to the control signal.

2. The detector control circuit according to claim 1, characterized in that: The output end of the low-side driver of the previous stage of the at least two stages of low-side drivers connected in sequence is connected to the power supply end of the low-side driver of the next stage; the output end of the low-side driver of the last stage is connected to the detector; and the low-side drivers of each stage correspond to their own control signals respectively.

3. The detector control circuit according to claim 2, characterized in that: The power supply terminal of the low-side driver includes a first power supply terminal and a second power supply terminal, and the power supply voltage connected to the first power supply terminal is greater than the power supply voltage connected to the second power supply terminal; The output end of the previous low-side driver of the at least two stages connected in sequence is connected to the first power supply end of the next low-side driver, and the supply voltage connected to the second power supply end of the at least two stages connected in sequence decreases in sequence.

4. The detector control circuit according to claim 3, characterized in that: The low-side driver includes two output terminals; The two output ends of the low-side driver of the previous stage of the at least two stages of sequentially connected low-side drivers are connected to the first power supply end of the low-side driver of the next stage, and the first power supply end is also connected to a capacitor.

5. The detector control circuit according to claim 4, characterized in that: Resistors are respectively connected between the two output terminals of the low-side driver of the previous stage and the first power supply terminal of the low-side driver of the next stage in the at least two stages of low-side drivers connected in sequence.

6. The detector control circuit according to claim 3, characterized in that: The input end of the low-side driver is connected to the control signal through a first DC blocking capacitor, and a diode and an input resistor are connected between the positive input end and the negative input end of the low-side driver.

7. The detector control circuit according to claim 2, characterized in that: The low-side driver comprises a first power supply terminal and a second power supply terminal, and the power supply voltage connected to the first power supply terminal is greater than the power supply voltage connected to the second power supply terminal; The output end of the previous low-side driver of the at least two stages connected in sequence is connected to the second power supply end of the next low-side driver, and the supply voltage connected to the first power supply end of the at least two stages connected in sequence increases in sequence.

8. The detector control circuit according to any one of claims 1 to 7, characterized in that: The sequentially connected low-side drivers are two-stage, including: a first-stage low-side driver and a second-stage low-side driver; The first power supply terminal of the first-level low-side driver is connected to a first power supply voltage, and the second power supply terminal of the first-level low-side driver is connected to a second power supply voltage; the first output terminal and the second output terminal of the first-level low-side driver are connected, and connected to the first power supply terminal of the second-level low-side driver; the second power supply terminal of the second-level low-side driver is connected to a third power supply voltage; the first output terminal and the second output terminal of the second-level low-side driver are connected, and connected to the detector; Among them, the first power supply voltage>the second power supply voltage>the third power supply voltage.

9. The detector control circuit according to claim 8, characterized in that: The input end of the first-level low-side driver is connected to the first control signal, and the input end of the second-level low-side driver is connected to the second control signal; the first-level low-side driver and the second-level low-side driver are used to output the first supply voltage, the second supply voltage, or the third supply voltage to the detector according to the first control signal and the second control signal.

10. The detector control circuit according to claim 1, characterized in that: The circuit further comprises: The negative pressure generating module is used to generate the supply voltage.

11. The detector control circuit according to claim 10, characterized in that: The negative pressure generating module includes a BOOST chip.

12. A laser radar, characterized in that: The laser radar comprises a transmitter, a detector, and a detector control circuit as described in any one of claims 1 to 11; The transmitter is used to emit detection light; The detector is used to receive the echo generated by the detection light; The detector control circuit is used to output a power supply voltage to the detector according to a control signal.

13. A detection method based on the laser radar according to claim 12, characterized in that: The method comprises: The transmitter emits a laser; The detector control circuit adjusts the supply voltage output to the detector according to the detection mode; The detector receives the reflected echo signal and outputs an electrical signal; The distance information of the object is determined according to the electrical signal.

14. The method according to claim 13, characterized in that The detector control circuit adjusts the supply voltage output to the detector according to the detection mode, including: The detector control circuit obtains a control signal corresponding to the current detection mode; A power supply voltage of a gear is output to the detector according to the control signal.

15. The method according to claim 13, characterized in that The detection mode includes a first detection mode and a second detection mode; In the first detection mode, a first supply voltage is first output to the detector, and then switched to a second supply voltage after a first preset time; In the second detection mode, the first supply voltage is first output to the detector, and then switched to the third supply voltage after a second preset time; Among them, the detection probability of the detector increases successively under the first power supply voltage, the second power supply voltage, and the third power supply voltage.

16. The method according to claim 15, characterized in that The method further comprises: Performing detection using the first detection mode; After the first detection mode fails to detect the high-reflectivity object, the second detection mode is used for detection.

17. The method according to claim 16, characterized in that The method further comprises: In the first detection mode, if the signal output by the detector is less than a first set threshold, it is determined that no high-reflectivity object is detected.

18. The method according to claim 15, characterized in that The method further comprises: performing detection using a second detection mode; After the high-reflectivity object is detected in the second detection mode, the first detection mode is used for detection.

19. The method according to claim 18, characterized in that The method further comprises: In the second detection mode, if the signal output by the detector is greater than a second set threshold, it is determined that a high-reflectivity object is detected.

20. The method according to any one of claims 15 to 19, characterized in that The luminous intensity of the emitter in the first detection mode is lower than the luminous intensity of the emitter in the second detection mode.

Images