WO2021213013A1 - 输出脉宽可调节的探测电路、接收单元、激光雷达 - Google Patents
输出脉宽可调节的探测电路、接收单元、激光雷达 Download PDFInfo
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- 238000001514 detection method Methods 0.000 title claims abstract description 112
- 238000012545 processing Methods 0.000 claims abstract description 22
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/487—Extracting wanted echo signals, e.g. pulse detection
- G01S7/4873—Extracting wanted echo signals, e.g. pulse detection by deriving and controlling a threshold value
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4816—Constructional features, e.g. arrangements of optical elements of receivers alone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/484—Transmitters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/4861—Circuits for detection, sampling, integration or read-out
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
- H04N25/77—Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
- H04N25/772—Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components comprising A/D, V/T, V/F, I/T or I/F converters
- H04N25/773—Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components comprising A/D, V/T, V/F, I/T or I/F converters comprising photon counting circuits, e.g. single photon detection [SPD] or single photon avalanche diodes [SPAD]
Definitions
- the present invention generally relates to the field of optoelectronic technology, and in particular to a detection circuit with an adjustable output pulse width, a receiving unit including the detection circuit, a lidar, and a method for echo detection.
- SPAD Single Photon Avalanche Diode
- the passively quenched SPAD unit is shown in Figure 1A.
- the diode 1 biased in Geiger mode in Fig. 1A triggers an avalanche and generates avalanche current 101 in Fig. 1B.
- the avalanche current 101 generates a voltage on the quenching resistor R (waveform 102 in Fig. 1B).
- the avalanche is quenched, node 2 is discharged back to ground potential by quenching resistor R, and diode 1 returns to the Geiger bias region.
- the waveform of node 2 becomes a digital pulse with a certain driving capability after passing through the buffer, and is output to the post-processing circuit (the waveform 103 on the right in Figure 1).
- the buffer is usually composed of multi-stage inverters with a fixed flip threshold.
- the SPAD unit of active quenching is shown in Figure 2.
- the NMOS tube connecting the diode anode and GND is turned off (because the NMOS gate voltage 3 is 0V),
- the NMOS is in a high resistance state, and the avalanche current generates a voltage at the drain of the NMOS tube, and then the avalanche is quenched.
- the node 22 maintains the high level (waveform 202 in FIG. 2B) until the delay of TDELAY (typical value is a few ns to tens of ns), and the high level propagates to the node 23 (waveform 203 in FIG. 2B), so that the NMOS Turning on, node 22 is discharged to 0V, and the diode returns to the Geiger bias region.
- TDELAY typically value is a few ns to tens of ns
- the pulse width of the node 22 is approximately equal to the time of TDELAY, and the waveform of the node 22 becomes a digital pulse with a certain driving capability after being buffered, and is output to the post-processing circuit (waveform 204 in FIG. 2B).
- the dotted line in the waveform 204 represents the dead time of SPAD.
- the circuit is not in a state of normal operation and waiting for photons to arrive. It is regarded as dead time until the NMOS tube returns to the cut-off state, and the circuit returns to the working state again.
- the flip threshold of the buffer is fixed, so the width of the output pulse is fixed.
- device saturation is likely to occur under strong ambient light, resulting in abnormal ranging.
- the output pulse width cannot be adjusted and cannot be adapted to the light pulse width, it is impossible to obtain an optimized signal-to-noise ratio in some processing circuits, and the ranging performance is degraded.
- the pulse width will not be broadened with the photon sequence, so the effective information required for ranging and ambient light intensity judgment is lost. In addition, there is dead time, which causes signal distortion.
- the invention provides a detection circuit with an adjustable output pulse width, a receiving unit that can be used for a laser radar, a laser radar including the receiving unit, and a method for using the receiving unit to perform echo detection.
- the present invention provides a detection circuit with adjustable output pulse width, including:
- a single-photon avalanche diode configured to generate a photocurrent according to incident photons
- a comparator a first input terminal of the comparator inputs an adjustable threshold signal, a second input terminal of the comparator is coupled to the single photon avalanche diode to input an electrical signal characterizing the photocurrent;
- the comparator is configured to output a waveform according to a comparison result of the electrical signal and the adjustable threshold signal.
- the cathode of the single-photon avalanche diode is coupled to a high voltage
- the anode of the single-photon avalanche diode is grounded through a quenching resistor
- the anode is coupled to the second input of the comparator Terminal, wherein the electrical signal is an analog voltage output by the single-photon avalanche diode.
- the cathode of the single-photon avalanche diode is coupled to a high voltage through a quenching resistor, the anode of the single-photon avalanche diode is grounded, and the cathode is coupled to the first of the comparator through a capacitor.
- the detection circuit further includes a threshold control unit configured to output the adjustable threshold signal, and the threshold control unit is coupled to the first input terminal of the comparator. Connected to provide the adjustable threshold signal to the first input terminal.
- the adjustable threshold signal increases as the intensity of the incident light increases.
- the present invention also provides a receiving unit that can be used for lidar, including:
- a detection circuit includes:
- a single-photon avalanche diode configured to generate photocurrent according to incident photons
- a comparator a first input terminal of the comparator inputs an adjustable threshold signal, a second input terminal of the comparator is coupled to the single photon avalanche diode to input an electrical signal characterizing the photocurrent;
- the comparator is configured to output a waveform according to a comparison result of the electrical signal and the adjustable threshold signal;
- a processing unit which is coupled to the output terminal of the comparator of the detection circuit and is configured to calculate the incident light intensity according to the waveform output by the comparator.
- the cathode of the single-photon avalanche diode is coupled to a high voltage
- the anode of the single-photon avalanche diode is grounded through a quenching resistor
- the anode is coupled to the second input of the comparator Terminal, wherein the electrical signal is the voltage on the quenching resistor.
- the cathode of the single-photon avalanche diode is coupled to a high voltage through a quenching resistor, the anode of the single-photon avalanche diode is grounded, and the cathode is coupled to the first of the comparator through a capacitor.
- the receiving unit further includes a threshold control unit, which is coupled to the processing unit and configured to adjust the adjustable threshold signal according to the incident light intensity, so The threshold control unit is coupled to the first input terminal of the comparator to provide the adjustable threshold signal to the first input terminal.
- the threshold control unit is configured to increase the adjustable threshold signal as the incident light intensity increases.
- the receiving unit includes a plurality of sets of the detection circuit and a summer, the output terminals of the comparators of the plurality of detection circuits are coupled to the input terminal of the summer, and the summation The summator performs a summation operation on the outputs of the multiple groups of detection circuits.
- the adjustable threshold signal of the detection circuit is set such that the width of the output waveform of the comparator of the detection circuit for a single photon matches the width of the laser pulse of the lidar.
- the adjustable threshold signal of the detection circuit is set such that: the width of the output waveform of the comparator of the detection circuit for a single photon is equal to the full width at half maximum of the laser pulse of the lidar.
- the processing unit is configured to calculate the number of incident photons according to the pulse width of the waveform output by the comparator.
- the present invention also provides a laser radar, including:
- a transmitting unit includes a laser configured to emit laser pulses to the outside of the lidar to detect a target;
- the receiving unit as described above, the receiving unit is configured to receive the echo of the laser pulse reflected on the target;
- a calculation unit which is coupled to the receiving unit and configured to calculate the distance and/or reflectivity of the target object according to the waveform output by the comparator of the receiving unit.
- the present invention also provides a method for echo detection using the receiving unit described above.
- the present invention also provides a laser detection method, including:
- the electrical signal characterizing the photocurrent is compared with an adjustable threshold signal to generate a digital signal output;
- the adjustable threshold signal is adjusted according to the output waveform of the digital signal.
- the step of adjusting the adjustable threshold signal according to the waveform of the digital signal output includes: increasing the adjustable threshold signal as the intensity of the incident light increases.
- the embodiment of the present invention provides a single-photon avalanche diode unit circuit (pixel level circuit), this unit circuit has two characteristics: when multiple photons are received by the single-photon avalanche diode in a short time, the pulse width of the circuit output signal It will be widened, so that the number of photons can be known through the signal pulse width, which expands the dynamic range of the single-photon avalanche diode device.
- the pulse width of the single-photon signal can be set and adjusted.
- this feature can be used to configure the single-photon signal pulse width to be close to the pulse width of the ranging light, which is convenient for the processing circuit to set a reasonable "integration time window" ", to obtain a better signal-to-noise ratio.
- Figures 1A and 1B respectively show a passively quenched single-photon avalanche diode detection circuit and its waveform
- Figures 2A and 2B respectively show the active quenching single-photon avalanche diode detection circuit and its waveform
- Figure 3A shows a detection circuit according to an embodiment of the first aspect of the present invention
- FIG. 3B shows a schematic diagram of waveforms of various nodes in the detection circuit of FIG. 3A;
- FIG. 4 shows a schematic diagram of adjusting the pulse width by adjusting the threshold in the circuit of FIG. 3A;
- Figure 5 shows a schematic diagram of increasing the dynamic range of a single-photon avalanche diode device by increasing the threshold when the ambient light is strong;
- Fig. 6A shows a detection circuit according to another embodiment of the first aspect of the present invention.
- FIG. 6B shows a schematic diagram of waveforms of various nodes in the detection circuit of FIG. 6A;
- Fig. 7 shows a schematic diagram of a receiving unit that can be used for lidar according to the second aspect of the present invention
- Fig. 8 shows a schematic diagram of a receiving unit according to a preferred embodiment of the second aspect of the present invention.
- FIG. 9 shows a schematic diagram of waveforms of various nodes in the receiving unit of FIG. 8 to illustrate the selection and optimization of the threshold
- Figure 10 shows a schematic diagram of a lidar according to the third aspect of the present invention.
- Fig. 11 shows a schematic diagram of a laser detection method according to the fourth aspect of the present invention.
- first and second are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with “first” and “second” may explicitly or implicitly include one or more of the features. In the description of the present invention, “plurality” means two or more than two, unless otherwise specifically defined.
- the terms “installation”, “connected”, and “connected” should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection.
- Connected or integrally connected It can be mechanically connected, or electrically connected or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium, which can be the internal communication of two components or the interaction of two components relation.
- an intermediate medium which can be the internal communication of two components or the interaction of two components relation.
- the "on” or “under” of the first feature of the second feature may include the first and second features in direct contact, or may include the first and second features Not in direct contact but through other features between them.
- the "above”, “above”, and “above” of the first feature on the second feature include the first feature directly above and diagonally above the second feature, or it simply means that the first feature is higher in level than the second feature.
- the “below”, “below” and “below” of the first feature of the second feature include the first feature directly above and diagonally above the second feature, or it simply means that the level of the first feature is smaller than the second feature.
- FIG. 3A shows a detection circuit 10 according to an embodiment of the first aspect of the present invention, the output pulse width of which can be adjusted and expanded so as to reflect the width of the light-emitting pulse, which will be described in detail below with reference to FIG. 3A.
- the detection circuit 10 includes a single photon avalanche diode 11 and a comparator 12.
- Single-photon avalanche diode is a photodetection avalanche diode with single-photon detection capability. It works in Geiger mode and can generate photocurrent based on incident photons, which can be used for the detection of extremely weak optical signals.
- the first input terminal of the comparator 12 (the inverting input terminal of the comparator 12 in FIG. 3A) inputs an adjustable threshold signal Threshold, and the second input terminal of the comparator 12 (the inverting input terminal of the comparator 12 in FIG.
- the input terminal +) is coupled to the single-photon avalanche diode 11 to input an electrical signal representing the photocurrent.
- the comparator 12 outputs a waveform according to the comparison result of the electrical signal and the adjustable threshold signal Threshold. For example, when the electrical signal is higher than the adjustable threshold signal Threshold, it outputs a high level; when the electrical signal is higher than the adjustable threshold signal Threshold, it outputs a high level; When the threshold signal is Threshold, it outputs low level.
- Threshold When the threshold signal is Threshold, it outputs low level.
- the detection circuit 10 may further include a quenching resistor 13.
- the cathode of the single-photon avalanche diode 11 is coupled to the high voltage +HV, and the anode is grounded through the quenching resistor 13. In Geiger mode, it can respond to incident photon input excitation P.
- the anode of the single-photon avalanche diode 11 is coupled to the second input terminal (non-inverting input terminal +) of the comparator 12, so that the analog voltage output by the single-photon avalanche diode 11 is provided to the comparator as an electrical signal 12.
- the single-photon avalanche diodes of these two structures can be used in the expandable and adjustable detection circuit of the present invention.
- FIG. 3B shows the waveform A2 of the non-inverting input terminal of the comparator 12 and the waveform A3 of the output terminal of the comparator 12 when the single-photon avalanche diode 11 receives the photon input excitation P in the circuit structure of FIG. 3A.
- the photon input excitation P is a photon
- the trailing edge of exponential decay corresponds to the recharge process of the single-photon avalanche diode.
- the high-voltage power supply +HV charges the junction capacitance of the single-photon avalanche diode through the quenching resistor 13 (resistance RQ) ,
- the charging time constant is RQxCD, thus forming an exponentially decayed single-photon signal trailing edge.
- the typical value of the charging time constant is from several ns to several tens of ns.
- the waveform A2 includes a corresponding number of multiple single-photon signal waveforms, each of which is The photon signal waveforms all include a steeply rising leading edge and an exponentially decayed trailing edge, as described above.
- the threshold value Threshold is low, which is lower than the trough of multiple consecutive single-photon signal waveforms, waveform A3 accordingly has a broadened output signal waveform.
- Figure 4 shows a schematic diagram of adjusting the pulse width by adjusting the threshold Threshold.
- Threshold1 the width of the waveform A3 obtained at the output of the comparator 12 is significantly wider; when a higher threshold value is used At Threshold2, the width of the waveform A3' obtained at the output end is significantly reduced. Therefore, by adjusting the inverted threshold of the comparator 12, the length of time for the analog signal waveform output by the single-photon avalanche diode 11 to exceed the threshold can be adjusted, thereby adjusting the width of the digital pulse output by the detection circuit 10 including the single-photon avalanche diode.
- the above-mentioned pulse width adjustment function can achieve good application effects in many occasions.
- the ambient light is strong (as shown in Figure 5, the incident photon excitation P includes multiple closely adjacent arrows)
- Threshold by increasing the threshold Threshold, single-photon avalanche diode devices can be added
- the dynamic range makes it less prone to saturation.
- Threshold1 when a lower threshold value Threshold1 is used, in the case of strong ambient light, the single-photon avalanche diode device 11 is frequently triggered by incident ambient photons to trigger avalanches, resulting in single-photon avalanche quenching.
- the avalanche diode 11 is not fully charged yet, and the avalanche is triggered again.
- the waveform A3 embodied at the output terminal of the comparator 12 is a continuously high-level waveform. At this time, the detection circuit 10 can no longer perform normal ranging measurement, nor can it accurately measure the ambient light intensity level.
- the signal of the waveform A3' at the output terminal of the comparator 12 can be changed from a continuous high level to a random pulse output.
- the single-photon avalanche diode device is not fully saturated and still has a certain ranging ability (usually when the noise is large, multiple measurements are required to increase the signal-to-noise ratio to extract the effective signal), and
- the actual intensity of ambient light can be evaluated by the noise pulse width, frequency and other information.
- the comparator 12 adopts a voltage comparator, but the present invention is not limited to this.
- the voltage comparator is only an embodiment, and a current comparator or other types can also be used.
- the above-mentioned embodiment of the present invention adds a comparator that can set a threshold value on the basis of passively quenching the SPAD unit.
- the comparator also functions as a buffer, and its output has a certain driving capability and can drive the subsequent processing circuit .
- the output signal of the single-photon signal has two characteristics: the width of the single-photon signal can be changed by adjusting the threshold; when the continuous photon sequence is reached, the output signal expands with the photon sequence.
- the output signal broadening is advantageous to a certain extent, and can be used to determine the intensity of incident light or the intensity of ambient light. The specific degree of widening can be determined according to specific usage scenarios, and is not limited in the present invention.
- Fig. 6A shows a detection circuit 10 according to another embodiment of the present invention.
- the circuit structure of Fig. 6 is suitable for a single-photon avalanche diode with an N-on-P structure, because its anode usually needs to be grounded.
- the cathode of the single-photon avalanche diode 11 is coupled to a high voltage +HV through a quenching resistor 13, and the anode of the single-photon avalanche diode 11 is grounded and is in Geiger mode.
- the cathode is coupled to the second input terminal (inverting input terminal in the figure) of the comparator 12 through a capacitor 14, so that the change in the cathode voltage of the single-photon avalanche diode 11 is used as the electrical signal Provided to the inverting input terminal of the comparator 12.
- the capacitor 14 can play the role of blocking direct current and passing alternating current. Therefore, only the variation of the cathode voltage of the single-photon avalanche diode 11 can be provided to the inverting input terminal of the comparator 12.
- the non-inverting input terminal of the comparator 12 is connected to the adjustable threshold Threshold.
- FIG. 6B shows the waveform A2 of the inverted input terminal of the comparator 12 and the waveform A3 of the output terminal of the comparator 12 according to the incident photon excitation P during the working process of the detection circuit 10 of FIG. 6A. Similar to that described above with reference to Fig. 3A, the difference is, for example, that in the circuit structure of Fig. 6A, the amount of change in the cathode voltage of the single-photon avalanche diode 11 (that is, the waveform A2) is a downward sharp pulse.
- the specific working mode please refer to the description of FIG. 3A above, which will not be repeated here.
- the detection circuit 10 further includes a bias resistor R B , and the inverting input terminal of the comparator 12 is connected to the bias voltage V BIAS through the bias resistor R B , as shown in FIG. 6A.
- the detection circuit 10 further includes a threshold control unit configured to generate and output the adjustable threshold signal according to the intensity of the ambient light, and the threshold control unit It is coupled to the first input terminal of the comparator to provide the adjustable threshold signal Threshold to the first input terminal.
- the threshold control unit can, for example, dynamically adjust the adjustable threshold signal, thereby changing the width of the single photon signal in the output waveform A3 of the detection circuit, and can make the output signal expand with the photon sequence when the continuous photon sequence is reached.
- the detection circuit according to the first aspect of the present invention is described above. Among them, when the single-photon avalanche diode is triggered by a photon, it will go through the quenching and charging process, and then return to the normal working state.
- the detection circuit unit proposed in the embodiment of the present invention if another or several photons are incident on the photosensitive area of the single-photon avalanche diode and trigger an avalanche during the charging recovery process, the output signal of the detection circuit will be expanded.
- the law of broadening is briefly described below.
- the total pulse width output by the detection circuit 10 is the total duration of the incident photon sequence plus the pulse width of the single photon output pulse width.
- the photon sequence in the meaning of the present invention means that the maximum time interval between adjacent photons in a photon sequence needs to be less than a single-photon pulse width. If the time interval between two adjacent photons in the photon sequence exceeds the pulse width of a single photon, then the output is not a stretched pulse, but two output pulses, and this photon sequence will be regarded as a two photon sequence.
- the broadening characteristic can play a considerable role in the optoelectronic system.
- the typical recovery time is a few ns to tens of ns
- the photosensitive area of the single-photon avalanche diode will not cause any change in the output signal of the single-photon avalanche diode.
- the recovery time of the single-photon avalanche diode is equivalent to the "dead time" of the detection circuit.
- the broadening characteristic of the present invention can obtain additional information, which can distinguish whether an output pulse is caused by a single photon or multiple continuous photons from the output pulse width.
- the pulse intensity information can still be obtained in the case of a strong saturated signal. Using this information, more accurate ranging results and target reflectivity measurement results can be obtained.
- the second aspect of the present invention relates to a receiving unit 20 that can be used for lidar, which includes the detection circuit 10 and the processing unit 21 as described above, as shown in FIG. 7.
- the detection circuit 10 shown in FIG. 7 is the same as that shown in FIG. 3A, but the present invention is not limited to this, and the detection circuit 10 shown in FIG. 6A can also be used, and these are all within the protection scope of the present invention.
- the specific structure and working mode of the detection circuit 10 are as described in detail above with reference to FIGS. 3A-6B, and will not be repeated here.
- the detection circuit 10 excites P according to the incident photons, and generates a digital waveform A3 at the output terminal of the comparator 12.
- the processing unit 21 is coupled to the output terminal of the comparator 12 of the detection circuit 10, so that it can receive the digital waveform A3, and calculate the intensity of the incident photon excitation P according to the waveform.
- the processing unit 21 is configured to calculate the number of incident photons according to the pulse width of the waveform output by the comparator 12, and to obtain the reflectance of the target object according to the calculation result.
- the detection circuit 10 further includes a threshold control unit 15, which is coupled to the processing unit 21 and is configured to adjust the adjustable threshold signal according to the incident light intensity
- the threshold control unit 15 is coupled to the first input terminal of the comparator 12 to provide the adjustable threshold signal Threshold to the first input terminal.
- the threshold control unit 15 may increase the adjustable threshold signal as the incident light intensity increases.
- the incident light intensity can be divided into multiple intervals, and each interval corresponds to an adjustable threshold signal. The higher the incident light intensity, the higher the adjustable threshold signal.
- the threshold control unit 15 can select an appropriate adjustable threshold signal according to the interval of the current incident light intensity.
- FIG. 8 shows a preferred embodiment according to the present invention, wherein the receiving unit 20 of the lidar includes multiple sets of the detection circuit 10 and the summator 22 to form a detection channel.
- Each detection circuit constitutes a pixel
- FIG. 8 schematically shows four pixels, which are pixels 1-4, respectively.
- FIG. 8 is a schematic example.
- a ranging circuit based on a single-photon avalanche diode array multiple single-photon avalanche diodes are usually formed into a channel (or called a macrocell).
- a channel/macrocell includes four single-photon avalanche diodes, but the present invention is not limited to this.
- a channel can be composed of one or more single-photon avalanche diodes of any number.
- the output terminals of the comparators 12 of the multiple sets of detection circuits 10 are all coupled to the input ends of the summer 22, and the summer 22 performs processing on the outputs of the multiple sets of detection circuits.
- the output terminal of the summer 22 can be connected to the processing unit 21 (not shown in the figure), for example.
- the signal-to-noise ratio can be further optimized and improved by adjusting the output pulse width of the single-photon signal to be adapted to the light-emitting pulse width of the lidar.
- the output digital signals of multiple pixels are accumulated and added ( ⁇ ). When the accumulated result exceeds a certain numerical threshold, it is determined that there is a valid signal at this time, that is, a valid ranging response is received. Wave pulse. This method of determining the ranging pulse signal is based on the fact that the noise signal caused by ambient light or the dark count of the single-photon avalanche diode is randomly distributed on the time axis (horizontal direction in Figure 9), and these noise signals occur simultaneously in a very narrow area.
- the processing circuit and algorithm program can extract the ranging information and target reflectivity information that the lidar needs to collect through the pulse trigger time and pulse waveform after the sum of the output signals of multiple pixels.
- the threshold value in a single pixel can be adjusted to adjust the width of the digital pulse signal output by the pixel. When the width is adapted to the width of the laser pulse, a more optimized ranging can be obtained.
- the threshold is adjusted so that the time width of the output digital signal of each pixel (or detection circuit) in response to a single photon input is equal to the full width at half maximum of the laser pulse. At this time, most of the energy of the light pulse signal emitted by the laser is concentrated in the time window corresponding to the full width at half maximum.
- the processing circuit shown in FIG. 8 accumulates the single photon counts that occur within this time window. In other words, by setting the pulse width of the output signal and setting the length of an integration time window, the processing circuit will accumulate the single-photon events that occur within the time window.
- the integration time window is set to be narrower than the laser pulse, the emitted light energy will be wasted, and most of the emitted effective signals will not be collected, so the ranging signal-to-noise ratio will decrease and the detection probability will decrease.
- the integration time window is set to be wider than the laser pulse, the total amount of signal does not change significantly, but the total amount of noise entering this wider time window will increase, so the ranging signal-to-noise ratio decreases and the detection probability decreases. Therefore, there is an optimal integration time window width. By adjusting the pulse width of the output signal of the detection circuit of the single-photon avalanche diode, this optimal time window width can be selected, thereby obtaining an optimized ranging signal-to-noise ratio and an optimized detection probability .
- the adjustable threshold signal of the detection circuit such that the width of the single-photon output waveform of the comparator of the detection circuit matches the width of the laser pulse of the lidar, the signal-to-noise ratio of the circuit can be improved.
- the width of the output waveform of the single photon of the comparator of the detection circuit is equal to the full width at half maximum of the laser pulse of the lidar.
- the time width w of the output digital signal of each pixel (that is, the waveform A3 output by the detection circuit) is equal to the full width at half maximum of the laser pulse, as shown by the waveforms of pixels 1 to 4, within the time width w, four Pixel produces output (that is, the rising edges of the output of the four pixels fall within the time width).
- the height of the waveform output by the summer 22 is four times the height of the waveform of a single pixel. .
- the probability of the noise signal occurring simultaneously within a time width w is extremely low, the output of the noise signal usually does not add up.
- the height of the output waveform is only twice the height of a single pixel waveform.
- the signal-to-noise ratio of the detection unit can be characterized as 4. If the threshold is further increased so that the time width w of the output digital signal of each pixel (that is, the waveform A3 output by the detection circuit) is reduced, then within the time width w, the output generated by the four pixels cannot be all accumulated, and the totalizer 22.
- the height of the output waveform is less than four times the height of a single pixel waveform, for example, it may be twice or three times. In this case, the signal-to-noise ratio is significantly reduced.
- the time width w of the output digital signal (ie signal waveform A3) of each pixel increases, although the output generated by the four pixels within the time width w can all be accumulated, the summator 22 outputs
- the height of the waveform is equal to four times the height of the waveform of a single pixel, but within this time width w, the noise signal may also be accumulated through the summer, so the signal-to-noise ratio will also decrease.
- the broadening characteristic can play a considerable role in the optoelectronic system.
- the typical recovery time is a few ns to tens of ns
- the photosensitive area of the single-photon avalanche diode will not cause any change in the output signal of the single-photon avalanche diode.
- the recovery time of the single-photon avalanche diode is equivalent to the "dead time" of the detection circuit.
- the broadening characteristic of the present invention can obtain additional information, which can distinguish whether an output pulse is caused by a single photon or multiple continuous photons from the output pulse width.
- the pulse intensity information can still be obtained in the case of a strong saturated signal. Using this information, more accurate ranging results and target reflectivity measurement results can be obtained.
- the threshold of SPAD flip can also be adjusted to obtain more accurate signal light pulse information, as described above with reference to FIG. 4.
- each unit 20 can be used as a unit, and each unit corresponds to a channel. It is arranged in an array to form a single-photon avalanche diode detection array and constitute multiple receiving channels of the lidar for measurement. Incident light, these are all within the protection scope of the present invention.
- the invention also relates to a method for echo detection using the receiving unit as described above.
- the output pulse width and recovery time of the single-photon avalanche diode detection circuit are required to be as short as possible. Such optimization can make the dynamic range of the single-photon avalanche diode device larger and less likely to be exposed to ambient light. Saturation occurs under noise. Some designs are needed to make the output pulse width and recovery time of the single-photon avalanche diode detection circuit as short as possible.
- the recovery time or quenching time constant is determined by the quenching resistance value and the junction capacitance of the single-photon avalanche diode.
- Reducing the quenching resistance value or reducing the junction capacitance of the diode can shorten the quenching time constant. If the quenching resistance is too small, the quenching may not succeed, and the lower limit is usually tens of k ohms. Reducing the junction capacitance usually requires reducing the photosensitive area of a single single-photon avalanche diode, and reducing the photosensitive surface of a single single-photon avalanche diode, which means that a larger number of single-photon avalanche diodes can be placed under the same total photosensitive surface area. Photon avalanche diode unit, which also increases the dynamic range of a channel/macro unit (and less likely to be saturated due to ambient light). Therefore, according to the preferred embodiment of the present invention, in lidar applications, usually a single single-photon avalanche diode The photosensitive area does not exceed 500um 2 .
- Fig. 10 shows a lidar 30 according to the third aspect of the invention.
- the lidar 30 includes a transmitting unit 31 and a receiving unit 20 as described above.
- the emitting unit 31 includes a laser array, and the laser array is configured to emit multiple laser beams to detect the target object OB. After the laser beam encounters the target object OB, diffuse reflection occurs, and part of the reflected echo returns to the lidar and is received by the receiving unit 20.
- the receiving unit 20 includes a single-photon avalanche diode and a comparator, which can receive the echo of the laser beam reflected by the detection target OB and convert it into a digital signal for output.
- the emitting unit 31 may also include an emitting lens group, located downstream of the optical path of the laser array, for modulating (collimating) the laser beam emitted by the laser array into parallel light. It is emitted into the environmental space around the lidar 30.
- the receiving unit 20 may also include a receiving lens group, the single-photon avalanche diode is located on its focal plane, and is used to converge the echo of the outgoing laser beam reflected by the detection target OB onto the single-photon avalanche diode.
- the laser beam L1 emitted by the emitting unit 31 is projected on the target OB, and diffusely reflected, and a part of the laser beam is reflected back to form an echo L1'.
- the receiving unit 20 receives the reflected echo L1' and converts it into an electrical signal.
- the processing unit 21 of the receiving unit 20 is configured to calculate the distance and/or reflectivity of the target object according to the waveform output by the comparator of the receiving unit. For example, the processing unit 21 can calculate the distance of the target according to the time of flight TOF of the echo (the time period from the laser emission to the reception of the single-photon avalanche diode) and the speed of light. Additionally or alternatively, the processing unit 21 calculates the reflectance of the target object according to the pulse width of the signal.
- the fourth aspect of the present invention provides a laser detection method 40, as shown in FIG. 11, which is described in detail below with reference to FIG. 11.
- step S41 a detection laser beam is emitted for detecting the target object.
- step S42 the echo from the target is received by a single-photon avalanche diode, wherein the single-photon avalanche diode generates a photocurrent according to incident photons.
- step S43 the electrical signal characterizing the photocurrent is compared with an adjustable threshold signal through a comparator to generate a digital signal output.
- step S44 the adjustable threshold signal is adjusted according to the output waveform of the digital signal.
- the step of adjusting the adjustable threshold signal according to the waveform of the digital signal output includes: increasing the adjustable threshold signal as the intensity of the incident light increases.
- the intensity of the incident light can be obtained according to its waveform. For example, the intensity of the incident light can be evaluated by calculating the number of incident photons, and then the adjustable threshold signal can be simultaneously increased according to the increase in intensity.
- the preferred embodiments of the four aspects of the present invention have been described in detail above.
- the dynamic range of the single-photon avalanche photodiode device can be increased, making it less likely to be saturated.
- an optimized signal-to-noise ratio can be achieved.
- this broadening characteristic can obtain additional information, which can distinguish from the output pulse width whether an output pulse is caused by a single photon or multiple continuous photons.
- the dynamic range of the photon avalanche photodiode device can obtain pulse intensity information in the case of a strong saturation signal. Using this information, more accurate ranging results and target reflectivity measurement results can be obtained. In addition, by adjusting the output pulse width of the single-photon signal and adapting it to the light-emitting pulse width of the lidar, an optimized signal-to-noise ratio can be achieved.
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Abstract
一种输出脉宽可调节的探测电路(10),包括:单光子雪崩二极管(11),可根据入射的光子产生光电流;比较器(12),第一输入端输入可调阈值信号(Threshold),第二输入端与单光子雪崩二极管(11)耦接,以输入表征光电流的电信号;比较器(12)配置成根据电信号与可调阈值信号(Threshold)的比较结果而输出波形。一种单元探测电路(10),具备以下特点:当有多个光子在短时间内被单光子雪崩二极管(11)接收时,电路输出信号的脉宽会展宽,从而通过信号脉宽能够获知光子数多少的信息,拓展了单光子雪崩二极管器件(11)的动态范围;另外可以调节单光子信号的脉宽,在测距应用中,可以将单光子信号脉宽配置到与测距发光脉冲宽度接近的程度,便于处理电路设置合理的"积分时间窗",获得更优的信噪比。
Description
本发明大致涉及光电技术领域,尤其涉及一种输出脉宽可调节的探测电路、包括该探测电路的接收单元、激光雷达以及回波探测的方法。
目前,在激光雷达测距应用中的SPAD(单光子雪崩二极管)单元可分为两类,主动淬灭和被动淬灭。被动淬灭的SPAD单元如图1A所示。当光子到达时,图1A中被偏置在盖革模式下的二极管1触发雪崩,产生图1B中的雪崩电流101,雪崩电流101在淬灭电阻R上产生电压(图1B中波形102),而后雪崩被淬灭,节点2被淬灭电阻R放电回地电位,二极管1重新回到盖革偏置区域。节点2的波形经过缓冲器后变成有一定驱动能力的数字脉冲,输出给后级处理电路(图1中右侧的波形103)。缓冲器通常由多级反相器构成,翻转阈值固定。主动淬灭的SPAD单元如图2所示。当光子到达时(图2B中的波形201),被偏置在盖革模式下的二极管21触发雪崩,此时连接二极管阳极和GND的NMOS管截止(因为NMOS的栅极电压3为0V),NMOS处于高阻的状态,雪崩电流在NMOS管漏极产生电压,而后雪崩被淬灭。节点22维持高电平(图2B中的波形202),直到经过TDELAY的延迟(典型值为几ns到几十ns),高电平传播到节点23(图2B中的波形203),使得NMOS导通,节点22被放电到0V,二极管重新回到盖革偏置区域。节点22的脉冲宽度近似等于TDELAY的时常,而节点22的波形经过缓冲后变成有一定驱动能力的数字脉冲,输出给后级处理电路(图2B中的波形204)。波形204中的虚线部分表示SPAD的死时间,在虚线对应的时间段内,由于NMOS管持续导通将节点22拉到GND,电路不处于正常工作、等待光子到达的状态中,这段时间被视为死时间,直到NMOS管回到截止状态,电路重新回复到工作状态。
在被动淬灭的SPAD单元中,缓冲器的翻转阈值固定,因而输出脉冲的宽度固定。当用在激光雷达中时,容易在强环境光下发生器件饱和,造成无法正常测距。另外由于输出脉冲宽度无法调节、无法与发光脉冲宽度适配,导致在某些处理电路的情况下,无 法获得优化的信噪比,测距性能下降。在主动淬灭的SPAD单元中,脉冲宽度宽不会随光子序列发生展宽,因而丢失了对于测距和环境光强度判断所需的有效信息。另外存在死时间,造成信号失真。
背景技术部分的内容仅仅是公开人所知晓的技术,并不当然代表本领域的现有技术。
发明内容
本发明提供一种输出脉宽可调节的探测电路、一种可用于激光雷达的接收单元、包括该接收单元的激光雷达以及使用该接收单元进行回波探测的方法。
本发明提供一种输出脉宽可调节的探测电路,包括:
单光子雪崩二极管,所述单光子雪崩二极管配置成可根据入射的光子产生光电流;和
比较器,所述比较器的第一输入端输入可调阈值信号,所述比较器的第二输入端与所述单光子雪崩二极管耦接,以输入表征所述光电流的电信号;所述比较器配置成根据所述电信号与所述可调阈值信号的比较结果而输出波形。
根据本发明的一个方面,所述单光子雪崩二极管的阴极耦接到高电压,所述单光子雪崩二极管的阳极通过淬灭电阻接地,所述阳极并且耦接到所述比较器的第二输入端,其中所述电信号为所述单光子雪崩二极管输出的模拟电压。
根据本发明的一个方面,所述单光子雪崩二极管的阴极通过淬灭电阻耦接到高电压,所述单光子雪崩二极管的阳极接地,所述阴极并且通过电容耦接到所述比较器的第二输入端,其中所述电信号为所述单光子雪崩二极管的阴极的电压的变化量。
根据本发明的一个方面,所述的探测电路还包括阈值控制单元,所述阈值控制单元配置成可输出所述可调阈值信号,所述阈值控制单元与所述比较器的第一输入端耦接以向所述第一输入端提供所述可调阈值信号。
根据本发明的一个方面,所述可调阈值信号随着所述入射光强度的增大而增大。
本发明还提供一种可用于激光雷达的接收单元,包括:
探测电路,所述探测电路包括:
单光子雪崩二极管,所述单光子雪崩二极管配置成可根据入射的光子产生光电流; 和
比较器,所述比较器的第一输入端输入可调阈值信号,所述比较器的第二输入端与所述单光子雪崩二极管耦接,以输入表征所述光电流的电信号;所述比较器配置成根据所述电信号与所述可调阈值信号的比较结果而输出波形;和
处理单元,所述处理单元耦接到所述探测电路的比较器的输出端,并配置成可根据所述比较器输出的波形计算入射光强度。
根据本发明的一个方面,所述单光子雪崩二极管的阴极耦接到高电压,所述单光子雪崩二极管的阳极通过淬灭电阻接地,所述阳极并且耦接到所述比较器的第二输入端,其中所述电信号为所述淬灭电阻上的电压。
根据本发明的一个方面,所述单光子雪崩二极管的阴极通过淬灭电阻耦接到高电压,所述单光子雪崩二极管的阳极接地,所述阴极并且通过电容耦接到所述比较器的第二输入端,其中所述电信号为所述单光子雪崩二极管的电压。
根据本发明的一个方面,所述的接收单元还包括阈值控制单元,所述阈值控制单元与所述处理单元耦接,并配置成可根据所述入射光强度调节所述可调阈值信号,所述阈值控制单元与所述比较器的第一输入端耦接以向所述第一输入端提供所述可调阈值信号。
根据本发明的一个方面,所述阈值控制单元配置成随着所述入射光强度增大而提高所述可调阈值信号。
根据本发明的一个方面,所述接收单元包括多组所述探测电路和求和器,所述多组探测电路的比较器的输出端耦接到所述求和器的输入端,所述求和器对所述多组探测电路的输出进行求和操作。
根据本发明的一个方面,所述探测电路的可调阈值信号设置成使得:所述探测电路的比较器对于单光子的输出波形的宽度与所述激光雷达的激光脉冲的宽度相匹配。
根据本发明的一个方面,所述探测电路的可调阈值信号设置成使得:所述探测电路的比较器对于单光子的输出波形的宽度与所述激光雷达的激光脉冲的半高全宽相等。
根据本发明的一个方面,所述处理单元配置成可根据所述比较器输出的波形的脉宽计算入射的光子数。
本发明还提供一种激光雷达,包括:
发射单元,所述发射单元包括激光器,所述激光器配置成可向所述激光雷达外部发 射激光脉冲以探测目标物;
如上所述的接收单元,所述接收单元配置成可接收所述激光脉冲在目标物上反射后的回波;
计算单元,所述计算单元与所述接收单元耦接,并配置成根据所述接收单元的比较器输出的波形,计算所述目标物的距离和/或反射率。
本发明还提供一种使用如上所述的接收单元进行回波探测的方法。
本发明还提供一种激光探测方法,包括:
发射探测激光束,用于探测目标物;
通过单光子雪崩二极管接收来自所述目标物的回波,其中所述单光子雪崩二极管根据入射的光子产生光电流;
通过比较器,将表征所述光电流的电信号与一可调阈值信号比较,产生数字信号输出;
根据所述数字信号输出的波形,调节所述可调阈值信号。
根据本发明的一个方面,所述根据数字信号输出的波形调节所述可调阈值信号的步骤包括:随着所述入射光强度的增大,增大所述可调阈值信号。
本发明的实施例提供一种单光子雪崩二极管单元电路(pixel level circuit),此单元电路具备两个特点:当有多个光子在短时间内被单光子雪崩二极管接收时,电路输出信号的脉宽会展宽,从而通过信号脉宽能够获知光子数多少的信息,拓展了单光子雪崩二极管器件的动态范围。可以设置调节单光子信号的脉宽,在dTOF测距应用中,可利用这一特性将单光子信号脉宽配置到与测距发光脉冲宽度接近的程度,便于处理电路设置合理的“积分时间窗”,获得更优的信噪比。
构成本公开的一部分的附图用来提供对本公开的进一步理解,本公开的示意性实施例及其说明用于解释本公开,并不构成对本公开的不当限定。在附图中:
图1A和1B分别示出了被动淬灭的单光子雪崩二极管探测电路及其波形;
图2A和2B分别示出了主动淬灭的单光子雪崩二极管探测电路及其波形;
图3A示出了根据本发明第一方面的一个实施例的探测电路;
图3B示出了图3A的探测电路中各个节点的波形示意图;
图4示出了在图3A电路中通过调节阈值来调节脉宽的示意图;
图5示出了当环境光较强时通过调高阈值来增加单光子雪崩二极管器件的动态范围的示意图;
图6A示出了根据本发明第一方面另一个实施例的探测电路;
图6B示出了图6A的探测电路中各个节点的波形示意图;
图7示出了根据本发明第二方面的一种可用于激光雷达的接收单元的示意图;
图8示出了根据本发明第二方面一个优选实施例的接收单元的示意图;
图9示出了图8的接收单元中各个节点的波形示意图,用于说明阈值的选择和优化;
图10示出了根据本发明第三方面的一种激光雷达的示意图;和
图11示出了根据本发明第四方面的一种激光探测方法的示意图。
在下文中,仅简单地描述了某些示例性实施例。正如本领域技术人员可认识到的那样,在不脱离本发明的精神或范围的情况下,可通过各种不同方式修改所描述的实施例。因此,附图和描述被认为本质上是示例性的而非限制性的。
在本发明的描述中,需要理解的是,术语"中心"、"纵向"、"横向"、"长度"、"宽度"、"厚度"、"上"、"下"、"前"、"后"、"左"、"右"、"竖直"、"水平"、"顶"、"底"、"内"、"外"、"顺时针"、"逆时针"等指示的方位或位置关系为基于附图所示的方位或位置关系,仅是为了便于描述本发明和简化描述,而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作,因此不能理解为对本发明的限制。此外,术语"第一"、"第二"仅用于描述目的,而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此,限定有"第一"、"第二"的特征可以明示或者隐含地包括一个或者更多个所述特征。在本发明的描述中,"多个"的含义是两个或两个以上,除非另有明确具体的限定。
在本发明的描述中,需要说明的是,除非另有明确的规定和限定,术语"安装"、"相连"、"连接"应做广义理解,例如,可以是固定连接,也可以是可拆卸连接,或一体地连接:可以是机械连接,也可以是电连接或可以相互通讯;可以是直接相连,也可以通过中间媒介间接相连,可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言,可以根据具体情况理解上述术语在本发明中的具体含义。
在本发明中,除非另有明确的规定和限定,第一特征在第二特征之"上"或之"下"可以包括第一和第二特征直接接触,也可以包括第一和第二特征不是直接接触而是通过它们之间的另外的特征接触。而且,第一特征在第二特征"之上"、"上方"和"上面"包括第一特征在第二特征正上方和斜上方,或仅仅表示第一特征水平高度高于第二特征。第一特征在第二特征"之下"、"下方"和"下面"包括第一特征在第二特征正上方和斜上方,或仅仅表示第一特征水平高度小于第二特征。
下文的公开提供了许多不同的实施方式或例子用来实现本发明的不同结构。为了简化本发明的公开,下文中对特定例子的部件和设置进行描述。当然,它们仅仅为示例,并且目的不在于限制本发明。此外,本发明可以在不同例子中重复参考数字和/或参考字母,这种重复是为了简化和清楚的目的,其本身不指示所讨论各种实施方式和/或设置之间的关系。此外,本发明提供了的各种特定的工艺和材料的例子,但是本领域普通技术人员可以意识到其他工艺的应用和/或其他材料的使用。
以下结合附图对本发明的优选实施例进行说明,应当理解,此处所描述的优选实施例仅用于说明和解释本发明,并不用于限定本发明。
第一方面
图3A示出了根据本发明第一方面的一个实施例的探测电路10,其输出脉宽可调节和展宽,从而可以反映出发光脉冲的宽度,下面参考图3A详细描述。
如图3A所示,探测电路10包括单光子雪崩二极管11和比较器12。单光子雪崩二极管是一种具有单光子探测能力的光电探测雪崩二极管,工作在盖革模式下,可根据入射的光子产生光电流,可用于极弱光学信号的探测。所述比较器12的第一输入端(图3A中比较器12的反相输入端-)输入可调阈值信号Threshold,所述比较器12的第二输入端(图3中比较器12的同相输入端+)与所述单光子雪崩二极管11耦接,以输入表征所述光电流的电信号。比较器12根据所述电信号与所述可调阈值信号Threshold的比较结果而输出波形,例如当电信号高于该可调阈值信号Threshold时,输出高电平;当电信号高于该可调阈值信号Threshold时,输出低电平。反之亦可。
如图3A所示,根据本发明的一个优选实施例,探测电路10还可包括淬灭电阻13。单光子雪崩二极管11的阴极耦接到高电压+HV,阳极通过淬灭电阻13接地,处于盖革模式下,可以对入射的光子输入激励P产生响应。所述单光子雪崩二极管11的阳极并且耦接到所述比较器12的第二输入端(同相输入端+),从而将所述单光子雪崩二极管 11输出的模拟电压作为电信号提供给比较器12。图3A所示的电路结构可适用于P-on-N结构的单光子雪崩二极管器件,因为这种结构的单光子雪崩二极管的阳极是不需要接地的,因此可以根据图3A所示的电路结构来进行配置。而N-on-P结构的单光子雪崩二极管的阳极通常需要接地,其具体电路结构将在下文具体描述。这两种结构的单光子雪崩二极管都可用于本发明的可展宽可调节的探测电路。
图3B示出了图3A的电路结构中,当单光子雪崩二极管11接收到光子输入激励P时,比较器12的同相输入端的波形A2以及比较器12的输出端的波形A3。当光子输入激励P为一个光子时,如图3B中光子输入激励P中单个箭头所示的,比较器12的同相输入端的波形A2对应于单光子的信号波形,包括一个陡峭上升的前沿和一个指数衰减的后沿。陡峭上升的前沿是由于雪崩和淬灭的过程发生得很快,通常时间<1ns,即单光子信号的前沿的上升时间<1ns。指数衰减的后沿对应单光子雪崩二极管的充电(Recharge)过程,在雪崩被淬灭电阻淬灭之后,高压电源+HV通过淬灭电阻13(电阻为RQ)给单光子雪崩二极管的结电容充电,充电时间常数为RQxCD,因而形成了指数衰减的单光子信号后沿。充电时间常数的典型值为从几ns到几十ns。通过比较器12,在比较器12的输出端产生了数字波形A3,其中当波形A2的电压高于阈值Threshold时,对应于波形A3的高电平,反之对应于波形A3的低电平。
当光子输入激励P包括多个连续的光子时,如图3B中光子输入激励P中相邻的三个箭头所示的,波形A2中包括数量相对应的多个单光子信号波形,每个单光子信号波形都包括一个陡峭上升的前沿和一个指数衰减的后沿,如上所述的。并且由于多个连续的光子间隔较近,并且阈值Threshold的值较低,低于连续的多个单光子信号波形的波谷,因此波形A3相应地具有展宽的输出信号波形。
图4示出了通过调节阈值Threshold来调节脉宽的示意图。如图4所示,对于同样的包括一个光子的光子输入激励P,当采用较低的阈值Threshold1时,在比较器12的输出端处获得的波形A3宽度明显较宽;当采用较高的阈值Threshold2时,输出端处获得的波形A3’的宽度明显减小。因此通过调节比较器12翻转的阈值,可以调节单光子雪崩二极管11输出的模拟信号波形超过阈值的时间长度,从而调节包括单光子雪崩二极管的探测电路10输出的数字脉冲的宽度。
上述脉宽调节功能在很多场合都能取得良好的应用效果。例如用在激光雷达***上,当环境光较强时(如图5所示,入射光子激励P包括多个紧密相邻的箭头),通过 调高所述阈值Threshold,可增加单光子雪崩二极管器件的动态范围,使其更不容易饱和。具体而言,如图5所示,当采用较低的阈值Threshold1时,遇到环境光较强的情况,单光子雪崩二极管器件11被入射的环境光子频繁触发雪崩,导致雪崩淬灭之后单光子雪崩二极管11还没有被完全充电,就被再次触发雪崩。体现在比较器12的输出端的波形A3就是持续高电平的波形,此时探测电路10已无法进行正常的测距测量,也无法准确地测量环境光强度水平。当调节采用较高的阈值Threshold2之后,比较器12的输出端的波形A3’的信号能从持续高电平变为随机的脉冲输出。此时虽然环境光噪声较大,但单光子雪崩二极管器件没有完全饱和,依然具备一定的测距能力(通常在噪声较大时需要多次测量提高信噪比,来提取出有效信号),并且能够通过噪声脉冲宽度、频率等信息来评估环境光的实际强度。
本领域技术人员容易理解,上面的实施例中,比较器12采用了电压比较器,但本发明不限于此,电压比较器仅是一个实施例,还可以采用电流比较器、或是其他类型的翻转阈值(动作阈值)可配置的电路结构。
本发明的上述实施例在被动淬灭SPAD单元的基础上,增加可设置阈值的比较器,比较器同时也起到缓冲器的作用,其输出具备一定的驱动能力,能够驱动后级的处理电路。使得单光子信号的输出信号具备两个特性:可以通过调节阈值改变单光子信号的宽度;当连续光子序列达到时,输出信号随着光子序列展宽。本领域技术人员理解,输出信号展宽在一定程度内是有利的,可以用于判断入射光的强度或者环境光的强度。具体展宽的程度可根据具体的使用场景来决定,本发明中不做限定。
图6A示出了根据本发明另一个实施例的探测电路10。图6的电路结构适用于N-on-P结构的单光子雪崩二极管,因为其阳极通常需要接地。如图6A所示,所述单光子雪崩二极管11的阴极通过淬灭电阻13耦接到高电压+HV,所述单光子雪崩二极管11的阳极接地,处于盖革模式下。所述阴极并且通过电容14耦接到所述比较器12的第二输入端(图中为反相输入端),从而将所述单光子雪崩二极管11的阴极电压的变化量作为所述电信号提供给比较器12的反相输入端。电容14可以起到隔直流、通交流的作用,因此可以仅将单光子雪崩二极管11的阴极电压的变化量提供给比较器12的反相输入端。同样的,比较器12的同相输入端连接到可调节阈值Threshold。图6B示出了图6A的探测电路10工作过程中,根据入射的光子激励P,所述比较器12的反向输入端的波形A2以及比较器12的输出端的波形A3。与上面参考图3A描述的类似,区别之处例如 在于,在图6A的电路结构中,单光子雪崩二极管11的阴极电压的变化量(即波形A2)为向下的尖脉冲。具体工作方式可参见上文关于图3A的描述,此处不再赘述。
另外优选的,探测电路10还包括偏置电阻R
B,所述比较器12的反相输入端通过该偏置电阻R
B连接到偏置电压V
BIAS,如图6A所示。
另外根据本发明的一个优选实施例,所述的探测电路10还包括阈值控制单元,所述阈值控制单元配置成可以根据环境光的强度生成并输出所述可调阈值信号,所述阈值控制单元与所述比较器的第一输入端耦接以向所述第一输入端提供所述可调阈值信号Threshold。下文将参考图7描述。阈值控制单元例如可以动态地调节所述可调阈值信号,从而改变探测电路的输出波形A3中单光子信号的宽度,并且可以使得当连续光子序列达到时,输出信号随着光子序列展宽。
上面描述了根据本发明第一方面的探测电路。其中,当单光子雪崩二极管被一个光子触发雪崩时,然后会经过淬灭和充电过程,再恢复到正常工作状态。对于本发明实施例提出的探测电路单元,如果在充电恢复过程中,由另一个或者另外几个光子入射到单光子雪崩二极管的光敏区域并且触发雪崩,会使得探测电路的输出信号展宽。下面简要描述展宽的规律。探测电路10输出的总脉宽为入射光子序列的总持续时长、加上单光子输出脉宽的时长(pulse width)。例如,在单光子输出脉宽为5ns的情况下,在7ns的时间长度内连续来了3个光子,那么探测电路输出的总脉宽为7ns+5ns=12ns。本发明意义下的光子序列是指:一个光子序列中各个相邻光子之间的最大时间间隔需要小于一个单光子脉宽。如果光子序列中存在两个相邻光子的时间间隔超过一个单光子脉宽,那么输出的就不是一个展宽的脉冲,而是两个输出脉冲,这个光子序列就会被视为两个光子序列。
展宽特性在光电***上能够起到相当大的作用。在一些不具有展宽特性的单光子雪崩二极管的探测电路中,在雪崩后恢复的时间段(恢复时间的典型值为几ns至数十ns)内,如果还有其他光子入射到单光子雪崩二极管的光敏区域,不会造成单光子雪崩二极管的输出信号发生任何变化,相当于单光子雪崩二极管的恢复时间就是探测电路的“死时间”。因此对于没有展宽特性的单光子雪崩二极管的探测电路,当回波信号强到一定程度后,无法辨别信号的强度,丢失了信息,从而会产生测距误差和无法测量反射率。相比没有展宽特性的单光子雪崩二极管的探测电路,本发明这种展宽的特性可以获得额外的信息,能够从输出脉冲宽度区分一个输出脉冲是由单个光子还是多个连续光子造成 的,因此增加了单光子雪崩二极管探测电路的动态范围,可以在强饱和信号的情况下,仍然能够获得脉冲强度信息,利用这些信息,可以获得更准确的测距结果和目标物反射率的测量结果。
第二方面
本发明的第二方面涉及一种可用于激光雷达的接收单元20,包括如上所述的探测电路10以及处理单元21,如图7所示。图7中所示的探测电路10与图3A所示的相同,但本发明不限于此,也可以采用如图6A所示的探测电路10,这些都在本发明的保护范围内。
探测电路10的具体结构和工作方式如上文参考图3A-6B所详细描述的,此处不再赘述。探测电路10根据入射的光子激励P,在比较器12的输出端的产生数字波形A3。处理单元21耦接到探测电路10的比较器12的输出端,因此可以接收该数字波形A3,并根据该波形计算入射的光子激励P的强度。根据本发明的一个实施例,所述处理单元21配置成可根据所述比较器12输出的波形的脉宽计算入射的光子数,进而可根据计算结果获取目标物的反射率。
另外如图7所示,探测电路10还包括阈值控制单元15,所述阈值控制单元15与所述处理单元21耦接,并配置成可根据所述入射光强度调节所述可调阈值信号,所述阈值控制单元15与所述比较器12的第一输入端耦接以向所述第一输入端提供所述可调阈值信号Threshold。例如,所述阈值控制单元15可以随着所述入射光强度增大而提高所述可调阈值信号。优选的,可以将入射光强度分为多个区间,每个区间对应一个可调阈值信号,入射光强度越高,可调阈值信号越高。阈值控制单元15可以根据当前入射光强度所处的区间来选择适当的可调阈值信号。
图8示出了根据本发明的一个优选实施例,其中所述激光雷达的接收单元20包括多组所述探测电路10和求和器22,构成一个探测通道。其中每个探测电路构成一个像素,图8中示意性示出了四个像素,分别为像素1-4。本领域技术人员容易理解,图8为一个示意性的实例,在基于单光子雪崩二极管阵列的测距电路中,通常会将多个单光子雪崩二极管组成一个通道(或者称为一个宏单元),下图的例子中一个通道/宏单元包括四个单光子雪崩二极管,但本发明不限于此,一个通道可以由一个及以上的任何数目的单光子雪崩二极管构成。如图8所示,所述多组探测电路10的比较器12的输出端均耦接到所述求和器22的输入端,所述求和器22对所述多组探测电路的输出进行求和操 作,求和器22的输出端例如可连接到所述处理单元21(图中未示出)。通过利用求和器22进行求和操作,可以使得有效信号得到累加,从而信号输出更加强烈,信噪比更高。
另外优选的,通过调节单光子信号输出脉宽,与激光雷达发光脉冲宽度适配,可以进一步优化和提高信噪比。图8的电路结构中,将多个像素的输出数字信号进行累加求和操作(Σ),当累加结果超过某个数值阈值时,判定为此时具有有效信号,即接收到有效的测距回波脉冲。这样判定测距脉冲信号的方法的依据是,环境光或者单光子雪崩二极管暗计数导致的噪声信号在时间轴(图9中水平方向)上是随机分布的,这些噪声信号同时发生在一个很窄的时间窗口(几ns)内的概率极低,因此当一个很窄的时间窗口内同时有多个单光子雪崩二极管的探测电路10产生输出信号(进而累加出一个较大的数值)时,很大概率这是由有效回波信号光脉冲所造成的。再进一步,处理电路和算法程序可通过多个像素的输出信号求和后的脉冲触发时间和脉冲波形,提取出激光雷达所需要采集的测距信息、目标物反射率信息等。而本发明的实施例中,可以通过调节单个像素内的阈值,以调节该像素输出的数字脉冲信号的宽度,当使这个宽度与激光脉冲的宽度相适配时,可以获得更优化的测距信噪比和更高的探测概率。根据本发明的一个优选实施例,调节该阈值使得各个像素(或探测电路)响应于单光子输入的输出数字信号的时间宽度等于激光脉冲的半高全宽。此时,激光器发出的光脉冲的信号的大部分能量集中在半高全宽所对应的时间窗口内,图8中所示的处理电路将在这个时间窗口内发生的单光子计数累加起来。换句话说,通过设置输出信号的脉宽,设置了一个积分的时间窗口的长度,处理电路会将时间窗口内发生的单光子事件累加在一起。如果将积分时间窗口设置得比激光脉冲更窄,那么会浪费发出的光能量,没有收集到大部分发出的有效信号,因而测距信噪比降低、探测概率降低。如果将积分时间窗口设置得比激光脉冲更宽,那么信号总量没有发生明显变化,但进入这个更宽的时间窗口的噪声的总量会增加,因而测距信噪比降低、探测概率降低。因此存在一个最优的积分时间窗口宽度,通过调节单光子雪崩二极管的探测电路的输出信号脉宽,可以选择这个最优的时间窗口宽度,因而获得优化的测距信噪比和优化的探测概率。因此,通过将探测电路的可调阈值信号设置成使得所述探测电路的比较器对于单光子的输出波形的宽度与所述激光雷达的激光脉冲的宽度相匹配,能够提高电路的信噪比。优选的,探测电路的比较器对于单光子的输出波形的宽度与所述激光雷达的激光脉冲的半高全宽相等。
以图9所示的波形进行详细说明。图9中,各个像素的输出数字信号(即探测电路输出的波形A3)的时间宽度w等于激光脉冲的半高全宽,如像素1-像素4的波形所示,在该时间宽度w内,四个像素产生输出(即四个像素的输出的上升沿均落在该时间宽度内),通过求和器22进行累加求和后,求和器22输出的波形的高度为单个像素波形高度的四倍。而由于噪声信号同时发生在一个时间宽度w内的概率极低,因此噪声信号的输出通常不会累加起来,即使经过求和器,其输出的波形的高度仅仅是单个像素波形高度的一倍。在此情况下,探测单元的信噪比可表征为4。如果进一步调高阈值,使得各个像素的输出数字信号(即探测电路输出的波形A3)的时间宽度w减小,那么在该时间宽度w内,四个像素产生的输出无法全部累加,求和器22输出的波形的高度小于单个像素波形高度的四倍,例如可能为两倍或三倍。在此情况下,信噪比明显降低。反之,如果进一步降低阈值,使得各个像素的输出数字信号(即信号波形A3)的时间宽度w增大,虽然在该时间宽度w内四个像素产生的输出可以全部累加,求和器22输出的波形的高度等于单个像素波形高度的四倍,但是在该时间宽度w内,噪声信号也可能通过求和器累加,因此信噪比同样会降低。
展宽特性在光电***上能够起到相当大的作用。在一些不具有展宽特性的单光子雪崩二极管的探测电路中,在雪崩后恢复的时间段(恢复时间的典型值为几ns至数十ns)内,如果还有其他光子入射到单光子雪崩二极管的光敏区域,不会造成单光子雪崩二极管的输出信号发生任何变化,相当于单光子雪崩二极管的恢复时间就是探测电路的“死时间”。因此对于没有展宽特性的单光子雪崩二极管的探测电路,当回波信号强到一定程度后,无法辨别信号的强度,丢失了信息,从而会产生测距误差和无法测量反射率。相比没有展宽特性的单光子雪崩二极管的探测电路,本发明这种展宽的特性可以获得额外的信息,能够从输出脉冲宽度区分一个输出脉冲是由单个光子还是多个连续光子造成的,因此增加了单光子雪崩二极管探测电路的动态范围,可以在强饱和信号的情况下,仍然能够获得脉冲强度信息,利用这些信息,可以获得更准确的测距结果和目标物反射率的测量结果。
当接收单元检测到当前回波信号过强时,也可调高SPAD翻转的阈值,获得更准确的信号光脉冲的信息,如上文参考图4所描述的。
另外,本领域技术人员理解,上述接收单元20可以作为一个单元,每个单元对应一个通道,采用阵列布置的形式,构成单光子雪崩二极管探测阵列,构成激光雷达的多 个接收通道,用于测量入射光,这些都在本发明的保护范围内。
本发明还涉及一种使用如上所述的接收单元进行回波探测的方法。
另外,当用于激光雷达时,需要的单光子雪崩二极管探测电路的输出脉冲宽度和恢复时间尽可能短,这样的优化可以使单光子雪崩二极管器件的动态范围更大,更不容易在环境光噪声下发生饱和。需要通过一些设计使得单光子雪崩二极管探测电路的输出脉冲宽度和恢复时间尽可能短。在本专利的单光子雪崩二极管探测电路中,恢复时间或者叫淬灭时间常数,是由淬灭电阻值和单光子雪崩二极管的结电容决定的。减小淬灭电阻值或者减小二极管的结电容可以缩短淬灭时间常数。淬灭电阻值过小,可能会导致淬灭无法成功,下限通常在几十k欧姆。减小结电容,通常需要通过减小单个单光子雪崩二极管的光敏面积,并且减小单个单光子雪崩二极管的光敏面,意味着可以在相同的总光敏面面积下,放置更多个数的单光子雪崩二极管单元,这也增加了一个通道/宏单元的动态范围(更不容易因环境光造成饱和),因此,根据本发明的优选实施例,在激光雷达应用中,通常单个单光子雪崩二极管的光敏面积不超过500um
2。
第三方面
图10示出了根据本发明的第三方面的激光雷达30。如图所示,该激光雷达30包括发射单元31以及如上所述的接收单元20。其中发射单元31包括激光器阵列,激光器阵列配置成可发出多个激光束用以探测目标物OB。激光束遇到目标物OB后发生漫反射,部分反射回波返回到激光雷达并且被接收单元20接收。接收单元20如前文所示,包括单光子雪崩二极管以及比较器,可接收激光束经探测目标物OB反射回来的回波并转换为数字信号输出。虽然未示出,但本领域技术人员容易理解,所述发射单元31还可包括发射透镜组,位于激光器阵列的光路下游,用于将激光器阵列出射的激光束调制(准直)成平行光并出射到激光雷达30周围的环境空间中。同样的,所述接收单元20也可包括接收透镜组,所述单光子雪崩二极管位于其焦平面上,用于将出射激光束经探测目标物OB反射的回波会聚到单光子雪崩二极管上。如图所示,发射单元31发射的激光束L1投射在目标物OB上,发生漫反射,一部分激光束则被反射回来形成回波L1′。所述接收单元20接收反射回来的回波L1′,并将其转换为电信号。所述接收单元20的处理单元21配置成根据所述接收单元的比较器输出的波形,计算所述目标物的距离和/或反射率。例如,处理单元21根据所述回波的飞行时间TOF(从激光器发射到单光子雪崩二极管接收的时间段),根据光速,可计算得到目标物的距离。另外的或者可替 换的,处理单元21根据所述信号的脉宽来计算目标物的反射率。
第四方面
本发明的第四方面提供一种激光探测方法40,如图11所示,下面参考图11详细描述。
在步骤S41,发射探测激光束,用于探测目标物。
在步骤S42,通过单光子雪崩二极管接收来自所述目标物的回波,其中所述单光子雪崩二极管根据入射的光子产生光电流。
在步骤S43,通过比较器,将表征所述光电流的电信号与一可调阈值信号比较,产生数字信号输出。
在步骤S44,根据所述数字信号输出的波形,调节所述可调阈值信号。
根据本发明的一个优选实施例,所述根据数字信号输出的波形调节所述可调阈值信号的步骤包括:随着所述入射光强度的增大,增大所述可调阈值信号。获得比较器的数字信号输出之后,可以根据其波形获得入射光的强度,例如通过计算入射的光子数来评价入射光的强度,然后可根据强度的增大来同时增大可调阈值信号。
以上对本发明四个方面的优选实施例进行了详细描述。通过本发明的优选实施例的方案,当环境光较强时,通过调高探测电路的阈值,可增加单光子雪崩光电二极管器件的动态范围,使其更不容易饱和。通过调节单光子信号输出脉宽,与激光雷达发光脉冲宽度适配,来实现优化的信噪比。相比没有展宽特性的单光子雪崩光电二极管的探测单元,这种展宽的特性可以获得额外的信息,能够从输出脉冲宽度区分一个输出脉冲是由单个光子还是多个连续光子造成的,增加了单光子雪崩光电二极管器件的动态范围,可以在强饱和信号的情况下,获得脉冲强度信息,利用这些信息,可以获得更准确的测距结果和目标物反射率的测量结果。另外,通过调节单光子信号输出脉宽,与激光雷达发光脉冲宽度适配,可以实现优化的信噪比。
最后应说明的是:以上所述仅为本发明的优选实施例而已,并不用于限制本发明,尽管参照前述实施例对本发明进行了详细的说明,对于本领域的技术人员来说,其依然可以对前述各实施例所记载的技术方案进行修改,或者对其中部分技术特征进行等同替换。凡在本发明的精神和原则之内,所作的任何修改、等同替换、改进等,均应包含在本发明的保护范围之内。
Claims (18)
- 一种输出脉宽可调节的探测电路,包括:单光子雪崩二极管,所述单光子雪崩二极管配置成可根据入射的光子产生光电流;和比较器,所述比较器的第一输入端输入可调阈值信号,所述比较器的第二输入端与所述单光子雪崩二极管耦接,以输入表征所述光电流的电信号;所述比较器配置成根据所述电信号与所述可调阈值信号的比较结果而输出波形。
- 如权利要求1所述的探测电路,其中所述单光子雪崩二极管的阴极耦接到高电压,所述单光子雪崩二极管的阳极通过淬灭电阻接地,所述阳极并且耦接到所述比较器的第二输入端,其中所述电信号为所述单光子雪崩二极管输出的模拟电压。
- 如权利要求1所述的探测电路,其中所述单光子雪崩二极管的阴极通过淬灭电阻耦接到高电压,所述单光子雪崩二极管的阳极接地,所述阴极并且通过电容耦接到所述比较器的第二输入端,其中所述电信号为所述单光子雪崩二极管的阴极的电压的变化量。
- 如权利要求1-3中任一项所述的探测电路,还包括阈值控制单元,所述阈值控制单元配置成可输出所述可调阈值信号,所述阈值控制单元与所述比较器的第一输入端耦接以向所述第一输入端提供所述可调阈值信号。
- 如权利要求1-3中任一项所述的探测电路,其中所述可调阈值信号随着所述入射光强度的增大而增大。
- 一种可用于激光雷达的接收单元,包括:探测电路,所述探测电路包括:单光子雪崩二极管,所述单光子雪崩二极管配置成可根据入射的光子产生光电流;和比较器,所述比较器的第一输入端输入可调阈值信号,所述比较器的第二输入端与所述单光子雪崩二极管耦接,以输入表征所述光电流的电信号;所述比较器配置成根据所述电信号与所述可调阈值信号的比较结果而输出波形;和处理单元,所述处理单元耦接到所述探测电路的比较器的输出端,并配置成可根据所述比较器输出的波形计算目标物的距离和/或入射光强度。
- 如权利要求6所述的接收单元,其中所述单光子雪崩二极管的阴极耦接到高电压,所述单光子雪崩二极管的阳极通过淬灭电阻接地,所述阳极并且耦接到所述比较器的第二输入端,其中所述电信号为所述淬灭电阻上的电压。
- 如权利要求6所述的接收单元,其中所述单光子雪崩二极管的阴极通过淬灭电阻耦接到高电压,所述单光子雪崩二极管的阳极接地,所述阴极并且通过电容耦接到所述比较器的第二输入端,其中所述电信号为所述单光子雪崩二极管的电压。
- 如权利要求6-8中任一项所述的接收单元,还包括阈值控制单元,所述阈值控制单元与所述处理单元耦接,并配置成可根据所述入射光强度调节所述可调阈值信号,所述阈值控制单元与所述比较器的第一输入端耦接以向所述第一输入端提供所述可调阈值信号。
- 如权利要求9所述的接收单元,其中所述阈值控制单元配置成随着所述入射光强度增大而提高所述可调阈值信号。
- 如权利要求6-8中任一项所述的接收单元,其中所述接收单元包括多组所述探测电路和求和器,所述多组探测电路的比较器的输出端耦接到所述求和器的输入端,所述求和器对所述多组探测电路的输出进行求和操作。
- 如权利要求6-8中任一项所述的接收单元,其中所述探测电路的可调阈值信号设置成使得:所述探测电路的比较器对于单光子的输出波形的宽度与所述激光雷达的激光脉冲的宽度相匹配。
- 如权利要求12所述的接收单元,其中所述探测电路的可调阈值信号设置成使得:所述探测电路的比较器对于单光子的输出波形的宽度与所述激光雷达的激光脉冲的半高全宽相等。
- 如权利要求6-8中任一项所述的接收单元,其中所述处理单元配置成可根据所述比较器输出的波形的脉宽计算入射的光子数。
- 一种激光雷达,包括:发射单元,所述发射单元包括激光器,所述激光器配置成可向所述激光雷达外部发射激光脉冲以探测目标物;如权利要求6-14中任一项所述的接收单元,所述接收单元配置成可接收所述激光脉冲在目标物上反射后的回波。
- 一种使用如权利要求6-14中任一项所述的接收单元进行回波探测的方法。
- 一种激光探测方法,包括:发射探测激光束,用于探测目标物;通过单光子雪崩二极管接收来自所述目标物的回波,其中所述单光子雪崩二极管根据入射的光子产生光电流;通过比较器,将表征所述光电流的电信号与一可调阈值信号比较,产生数字信号输出;根据所述数字信号输出的波形,调节所述可调阈值信号。
- 如权利要求17所述的接收单元,其中所述根据数字信号输出的波形调节所述可调阈值信号的步骤包括:随着所述入射光强度的增大,增大所述可调阈值信号。
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EP4249950A1 (de) * | 2022-03-25 | 2023-09-27 | Sick Ag | Erfassung und abstandsbestimmung eines objekts |
EP4283331A1 (de) * | 2022-05-24 | 2023-11-29 | Sick Ag | Optische erfassung und abstandsmessung |
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CN114199390B (zh) * | 2021-12-14 | 2024-05-03 | 中国电子科技集团公司第四十四研究所 | 快速主动淬灭主动恢复的单光子探测装置 |
CN114594493B (zh) * | 2022-01-13 | 2023-03-21 | 杭州宏景智驾科技有限公司 | 激光雷达***及其环境光感知方法 |
CN114594494B (zh) * | 2022-01-13 | 2022-10-21 | 杭州宏景智驾科技有限公司 | 激光雷达***及其环境光去噪方法 |
CN115047482B (zh) * | 2022-08-15 | 2022-11-01 | 中国科学院近代物理研究所 | 一种基于单光子雪崩二极管阵列探测器的激光探测*** |
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