CN111983586B - Control method and control system of photoelectric detector and laser radar - Google Patents
Control method and control system of photoelectric detector and laser radar Download PDFInfo
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- 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
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
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- 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
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Abstract
The embodiment of the invention provides a control method and a control system of a photoelectric detector and a laser radar, wherein the control method of the photoelectric detector comprises the following steps: acquiring the total current flowing through the photoelectric detector; acquiring the temperature of the photoelectric detector, and acquiring the dark current of the photoelectric detector according to the temperature of the photoelectric detector and a temperature characteristic curve; determining the background light intensity received by the photoelectric detector according to the total current and the dark current; and adjusting a noise threshold and a signal threshold for sampling the output signal of the photoelectric detector according to the background light intensity. The embodiment of the invention provides a control method and a control system of a photoelectric detector and a laser radar, so as to ensure that the laser radar can work normally.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a control method and a control system of a photoelectric detector and a laser radar.
Background
In the laser radar, a photoelectric detector is used as a light receiver for collecting light signals reflected back in the environment. However, the light signals reflected back from the environment include interference light signals, i.e., noise signals, in the environment in addition to the reflected light signals formed by the laser beams emitted by the optical transmitter of the lidar being reflected by objects in the environment. The interference light signal in the environment can be sunlight and laser beams emitted by laser radars mounted on other carriers. Therefore, in the whole working process of the laser radar, the interference light signals in the environment are random, the sampling of the output signals of the photoelectric detectors can be interfered by the random noise signals, the ADC sampling can not be normally carried out seriously, the output signals of the effective photoelectric detectors cannot be acquired, and the whole laser radar can not normally and stably work.
Disclosure of Invention
The embodiment of the invention provides a control method and a control system of a photoelectric detector and a laser radar, so as to ensure that the laser radar can work normally.
In a first aspect, an embodiment of the present invention provides a method for controlling a photodetector, including:
acquiring the total current flowing through the photoelectric detector;
acquiring the temperature of the photoelectric detector, and acquiring the dark current of the photoelectric detector according to the temperature of the photoelectric detector and a temperature characteristic curve;
determining the background light intensity received by the photoelectric detector according to the total current and the dark current;
and adjusting a noise threshold and a signal threshold for sampling the output signal of the photoelectric detector according to the background light intensity.
Optionally, after adjusting the noise threshold and the signal threshold for sampling the output signal of the photodetector according to the background light intensity, the method further includes:
increasing a bias voltage preset step value of the photoelectric detector;
collecting output signals of the photoelectric detector in at least one sampling period;
judging whether the bias voltage of the photoelectric detector reaches breakdown voltage or not according to the output signal of the photoelectric detector, a signal threshold and the noise threshold;
if so, reducing the bias voltage of the photoelectric detector by a preset deviation value to obtain an ideal bias voltage of the photoelectric detector.
Optionally, determining whether the bias voltage of the photodetector reaches the breakdown voltage according to the output signal of the photodetector, a signal threshold, and the noise threshold, includes:
acquiring the number of pulses with the pulse amplitude between the noise threshold and the signal threshold in the output signal in at least one sampling period;
and judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage or not according to the pulse number.
Optionally, determining whether the bias voltage of the photodetector reaches the breakdown voltage according to the output signal of the photodetector, a signal threshold, and the noise threshold, includes:
obtaining an average value of all the output signals in one sampling period;
and judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage or not according to the average value of the output signals and the noise threshold.
Optionally, after determining whether the bias voltage of the photodetector reaches the breakdown voltage according to the output signal of the photodetector, a signal threshold, and the noise threshold, the method further includes:
and if the bias voltage does not reach the breakdown voltage, returning to the step of executing the preset step value of the bias voltage for increasing the photoelectric detector.
Optionally, the photodetector serves as a light receiving element of the lidar, and the control method of the photodetector is executed at a start stage or an end stage of a scanning frame of the lidar.
In a second aspect, an embodiment of the present invention provides a control system for a photodetector, including:
a temperature sensor for detecting a temperature of the photodetector;
the current detection circuit is connected with the photoelectric detector and is used for detecting the total current flowing through the photoelectric detector;
the sampling circuit is connected with the output end of the photoelectric detector and is used for sampling the output signal of the photoelectric detector; and
the controller, respectively with photoelectric detector, temperature sensor, current detection circuit and the sampling circuit electricity is connected, the controller passes through current detection circuit acquires photoelectric detector's total current, passes through temperature sensor acquires photoelectric detector's temperature, and according to photoelectric detector's temperature characteristic curve, acquires photoelectric detector's dark current, according to total current and dark current confirms photoelectric detector received background light intensity, and according to background light intensity adjusts sampling circuit is right photoelectric detector's output signal carries out the noise threshold and the signal threshold of sampling.
Optionally, the photoelectric detector further comprises a current limiting resistor, a first end of the current limiting resistor is electrically connected with the photoelectric detector, and a second end of the current limiting resistor is electrically connected with the current detection circuit.
In a third aspect, an embodiment of the present invention provides a laser radar, including:
the light emitter is used for emitting laser beams to a target scanning area;
a photodetector for receiving the optical signal reflected from the target scanning area; and
a control system, the control system comprising:
a temperature sensor for detecting a temperature of the photodetector;
the current detection circuit is connected with the photoelectric detector and is used for detecting the total current flowing through the photoelectric detector;
the sampling circuit is connected with the output end of the photoelectric detector and is used for sampling the output signal of the photoelectric detector; and
the controller, respectively with photoelectric detector, temperature sensor, current detection circuit and the sampling circuit electricity is connected, the controller passes through current detection circuit acquires photoelectric detector's total current, passes through temperature sensor acquires photoelectric detector's temperature, and according to photoelectric detector's temperature characteristic curve, acquires photoelectric detector's dark current, according to total current and dark current confirms photoelectric detector received background light intensity, and according to background light intensity adjusts sampling circuit is right photoelectric detector's output signal carries out the noise threshold and the signal threshold of sampling.
Optionally, the photoelectric detector further comprises a current limiting resistor, a first end of the current limiting resistor is electrically connected with the photoelectric detector, and a second end of the current limiting resistor is electrically connected with the current detection circuit.
Optionally, the laser radar further comprises a galvanometer, wherein the galvanometer is used as an optical scanning element of the laser radar;
the control system is used for controlling the photoelectric detector at the beginning stage or the ending stage of each frame scanning of the galvanometer.
In the method for controlling a photodetector provided in the embodiments of the present invention, the temperature of the photodetector is obtained, the dark current of the photodetector is obtained according to the temperature of the photodetector and the temperature characteristic curve, the background light intensity received by the photodetector is determined according to the total current and the dark current, and the noise threshold and the signal threshold for sampling the output signal of the photodetector are adjusted according to the background light intensity. The embodiment of the invention also considers the influence of the irradiation of the background light on the total current flowing through the photoelectric detector, so that the noise threshold and the signal threshold are more reasonable after the noise threshold and the signal threshold are adjusted according to the background light intensity, the normal sampling of the output signal of the photoelectric detector can be realized by the sampling circuit under different environmental noises, and the normal work of the laser radar can be ensured.
Drawings
Fig. 1 is a flowchart of a control method for a photodetector according to an embodiment of the present invention;
fig. 2 is a flowchart of another control method for a photodetector according to an embodiment of the present invention;
FIG. 3 is a flow chart of another control method for a photo-detector according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a sampling result obtained by sampling the output signal of the photodetector by the sampling circuit;
fig. 5 is a schematic diagram of a control system of a photodetector according to an embodiment of the present invention;
fig. 6 is a schematic diagram of a laser radar according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a scanning track of a laser beam corresponding to one scanning frame of the laser radar.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Fig. 1 is a flowchart of a control method of a photodetector according to an embodiment of the present invention. The method can be executed by a controller in the control system provided by the embodiment of the invention, and the controller can be implemented in a software and/or hardware manner. The photodetector serves as a light receiving element for converting a received optical signal into an electrical signal and outputting it as an output signal. The photodetector may be applied in devices such as lidar. As shown in fig. 1, the control method specifically includes the following steps:
and S101, acquiring the total current flowing through the photoelectric detector.
The photodetector may convert the optical signal into an electrical signal. The total current of the photodetector is the total current flowing through the photodetector. At the beginning or end of each scanning frame of the laser radar, the light emitter can be in a non-emitting state, and the total current of the photoelectric detector comprises the dark current of the photoelectric detector and the photocurrent generated by the photoelectric detector due to background light irradiation. When the light emitter emits light after the scanning frame of the laser radar is started, because the laser radar adopts a pulse signal, the influence on the total current flowing through the photoelectric detector in the whole sampling period is extremely small, so that the influence can be approximately ignored, and therefore, the total current flowing through the photoelectric detector can be considered to comprise the dark current of the photoelectric detector and the photocurrent generated by the photoelectric detector due to background light irradiation. The dark current of the photodetector is a current flowing in the photodetector in a state where no light is applied.
Alternatively, the photodetector may include, for example, a photodiode, which is a semiconductor device composed of one PN junction, has a unidirectional conductive characteristic, and converts an optical signal into an electrical signal. The photodiode works under the action of reverse voltage, and when no light is emitted, reverse current is extremely weak, namely dark current; in the presence of light, the reverse current rapidly increases to tens of microamperes, referred to as photocurrent. The greater the intensity of the light, the greater the reverse current. The change in light causes a change in photodiode current, which converts the optical signal into an electrical signal, which becomes a photo-sensor device. It should be noted that the photodetector may include one photodiode, or may include an array of a plurality of photodiodes.
Alternatively, the photodetector may comprise an avalanche photodiode, for example. After a reverse bias is applied to the P-N junction of a photodiode made of silicon or germanium, the incident light is absorbed by the P-N junction to form a photocurrent. Increasing the reverse bias voltage produces an "avalanche" (i.e., a multiple surge in photocurrent) phenomenon, and such diodes are referred to as "avalanche photodiodes". The avalanche photodiode utilizes the avalanche multiplication effect of carriers to amplify the photoelectric signal to improve the sensitivity of detection. It should be noted that the photodetector may include one avalanche photodiode, or may include an array of a plurality of avalanche photodiodes.
S102, acquiring the temperature of the photoelectric detector, and acquiring the dark current of the photoelectric detector according to the temperature of the photoelectric detector and the temperature characteristic curve.
In this step, the temperature characteristic curve is a curve of a corresponding relationship between the dark current of the photodetector and the temperature. After the temperature of the photodetector is obtained, for example, a dark current corresponding to the current temperature of the photodetector can be searched from the temperature characteristic curve by means of a table lookup.
In one embodiment, a plurality of temperature characteristic curves may be stored in advance, each temperature characteristic curve corresponding to a temperature characteristic of the photodetector, so that the temperature characteristic curve corresponding to the temperature characteristic of the photodetector that needs to be controlled currently may be determined. Specifically, the temperature characteristic and thus the corresponding temperature characteristic curve may be determined by the type or kind of the photodetector. In another embodiment, a temperature characteristic curve corresponding to the current photodetector may also be directly stored, and the curve may be directly queried according to the temperature to obtain a corresponding dark current.
And S103, determining the background light intensity received by the photoelectric detector according to the total current and the dark current.
The total current due to the photodetector may include a dark current of the photodetector and a photocurrent of the photodetector due to the background light irradiation. Therefore, in this step, the photocurrent generated by the photodetector due to the irradiation of the background light can be obtained according to the total current and the dark current, and the photocurrent generated by the photodetector due to the irradiation of the background light is related to the intensity of the background light. Specifically, the larger the background light intensity is, the larger the photocurrent generated by the photodetector due to the background light irradiation is, and the smaller the background light intensity is, the smaller the photocurrent generated by the photodetector due to the background light irradiation is.
Illustratively, the photocurrent generated by the photodetector due to the background light irradiation is a difference between a total current of the photodetector and a dark current of the photodetector, and the photocurrent generated by the photodetector due to the background light irradiation is obtained by subtracting the dark current of the photodetector from the total current of the photodetector, so as to determine the intensity of the background light received by the photodetector.
And S104, adjusting a noise threshold and a signal threshold for sampling the output signal of the photoelectric detector according to the background light intensity.
In this step, when the intensity of the background light changes, the photoelectric current generated by the photoelectric detector due to the irradiation of the background light changes, which results in a change in the total current of the photoelectric detector, and besides the change in the total current, the background noise of the output signal of the photoelectric detector changes accordingly, wherein the change in the background noise results in a change in the signal-to-noise ratio of the photoelectric detector and the false alarm rate of the laser radar using the photoelectric detector. In order to ensure that the false alarm rate is not changed, the noise threshold and the signal threshold for sampling the output signal of the photodetector may be correspondingly adjusted. In the output signal sampled by the photoelectric detector, the pulse with the pulse amplitude between the noise threshold and the signal threshold is noise, and the pulse with the pulse amplitude larger than or equal to the signal threshold is a signal. The application of the false alarm rate is that in the detection process of the laser radar, when a threshold mechanism is adopted, a detector can adjust the probability or sensitivity of the laser radar for detecting signals by adjusting a noise threshold and a signal threshold.
Illustratively, as the background light intensity increases, the bias voltage of the photodetector decreases, and as the bias voltage of the photodetector gradually decreases, the photodetector gradually moves away from an optimal gain state adjacent to the breakdown voltage. When the background light intensity is reduced, the bias voltage of the photoelectric detector is increased, and the photoelectric detector works under the breakdown voltage along with the gradual increase of the bias voltage of the photoelectric detector, so that a large amount of noise is generated. Therefore, when the background light intensity changes, the noise threshold and the signal threshold for sampling the output signal of the photodetector need to be correspondingly adjusted according to the background light intensity, so that the output signal of the photodetector has a sufficiently high signal-to-noise ratio, and then the photodetector can work in an optimal gain state by adjusting the bias voltage of the photodetector in subsequent adjustment.
In the method for controlling a photodetector provided by the embodiment of the present invention, the temperature of the photodetector is obtained, the dark current of the photodetector is obtained according to the temperature of the photodetector and the temperature characteristic curve, the background light intensity received by the photodetector is determined according to the total current and the dark current, and the noise threshold and the signal threshold for sampling the output signal of the photodetector are adjusted according to the background light intensity. The embodiment of the invention also considers the influence of the irradiation of the background light on the total current flowing through the photoelectric detector, so that the noise threshold and the signal threshold are more reasonable after the noise threshold and the signal threshold are adjusted according to the background light intensity, the normal sampling of the output signal of the photoelectric detector can be realized by the sampling circuit under different environmental noises, and the normal work of the laser radar can be ensured.
Fig. 2 is a flowchart of another control method for a photodetector according to an embodiment of the present invention, as shown in fig. 2, the control method specifically includes the following steps:
s201, acquiring the total current flowing through the photoelectric detector.
S202, acquiring the temperature of the photoelectric detector, and acquiring the dark current of the photoelectric detector according to the temperature of the photoelectric detector and the temperature characteristic curve.
And S203, determining the intensity of the background light received by the photoelectric detector according to the total current and the dark current.
And S204, adjusting a noise threshold and a signal threshold for sampling the output signal of the photoelectric detector according to the background light intensity.
And S205, increasing the bias voltage of the photoelectric detector by a preset step value.
In this step, when the intensity of the background light changes, the photocurrent generated by the photodetector due to the background light irradiation changes, which causes the total current of the photodetector to change, and the bias voltage of the photodetector to change, so that the bias voltage of the photodetector needs to be modulated. In the embodiment of the present invention, a manner of increasing the bias voltage of the photodetector is adopted, that is, a step value is preset for increasing the bias voltage of the photodetector each time, for example, a step value is preset for increasing the bias voltage of the photodetector each time, the step value may be set according to the type of the laser radar, and the step value may be set to a voltage within 0.3V to 3V (including an end point value).
And S206, collecting the output signal of the photoelectric detector in at least one sampling period.
In this step, the output signal of the photodetector in one sampling period can be collected, and when the output signal of the photodetector in one sampling period is collected, the required sampling period is the minimum, so that the sampling time can be shortened, and the difficulty of subsequent data processing can be reduced. In the step, the output signals of the photoelectric detectors in a plurality of sampling periods are collected, and when the output signals of the photoelectric detectors in the plurality of sampling periods are collected, the quantity of the collected output signals of the photoelectric detectors is large, so that the statistical accuracy and the representativeness of the output signals are improved.
And S207, judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage according to the output signal of the photoelectric detector, the signal threshold and the noise threshold.
In this step, the noise level in the output signal can be obtained according to the output signal of the photodetector, the signal threshold and the noise threshold, and whether the bias voltage of the photodetector reaches the breakdown voltage can be judged according to the noise level in the output signal.
Illustratively, when the bias voltage of the photodetector does not reach the breakdown voltage, the noise level in the output signal of the photodetector is low. When the bias voltage of the photodetector reaches the breakdown voltage, noise in the output signal of the photodetector is significantly increased, and the noise level in the output signal of the photodetector is higher. The determination of the noise level in the output signal of the photodetector will be further described later.
And S208, if so, reducing the bias voltage of the photoelectric detector by a preset deviation value to obtain an ideal bias voltage of the photoelectric detector.
In this step, when the bias voltage of the photodetector reaches the breakdown voltage, in order to avoid that the photodetector operates at the breakdown voltage, the preset bias value of the bias voltage of the photodetector needs to be reduced, so that the bias voltage of the photodetector is smaller than the breakdown voltage, noise in an output signal of the photodetector is reduced, and the bias voltage of the photodetector is an ideal bias voltage close to the breakdown voltage, and at this time, the photodetector has an optimal gain state.
Illustratively, when the bias voltage of the photodetector reaches the breakdown voltage, the bias voltage of the photodetector may be decreased by 3 step values to obtain the ideal bias voltage of the photodetector. In other embodiments, the reduction of the bias voltage by the predetermined offset value after the breakdown occurs is determined according to the performance of the photodetector, and is not limited to a specific value.
In the embodiment of the invention, after the noise threshold and the signal threshold for sampling the output signal of the photoelectric detector are adjusted according to the background light intensity, the bias voltage of the photoelectric detector is gradually adjusted by adopting a mode of increasing the bias voltage of the photoelectric detector until the bias voltage of the photoelectric detector reaches the breakdown voltage, and then the bias voltage preset deviation value of the photoelectric detector is reduced to obtain the ideal bias voltage of the photoelectric detector, so that the noise in the output signal of the photoelectric detector is reduced, and the photoelectric detector has the optimal gain state.
Fig. 3 is a flowchart of another control method for a photodetector according to an embodiment of the present invention, and fig. 4 is a schematic diagram of a sampling result obtained by sampling an output signal of the photodetector by a sampling circuit, as shown in fig. 3 and 4, the control method specifically includes the following steps:
and S301, acquiring the total current flowing through the photoelectric detector.
S302, acquiring the temperature of the photoelectric detector, and acquiring the dark current of the photoelectric detector according to the temperature of the photoelectric detector and the temperature characteristic curve.
And S303, determining the background light intensity received by the photoelectric detector according to the total current and the dark current.
S304, adjusting a noise threshold and a signal threshold for sampling the output signal of the photoelectric detector according to the background light intensity.
And S305, increasing the bias voltage of the photoelectric detector to preset a step value.
S306, collecting the output signal of the photoelectric detector in at least one sampling period.
S307, acquiring the number of pulses of which the pulse amplitude is between the noise threshold and the signal threshold in the output signal in at least one sampling period.
In this step, the pulse with the pulse amplitude between the noise threshold and the signal threshold in the output signal is a noise pulse (i.e., noise), and the number of the noise pulses in the output signal in at least one sampling period is obtained.
For example, pulses in the output signal having a pulse amplitude between the noise threshold and the signal threshold may be counted cumulatively, and counted as 1 when the pulse amplitude in the output signal is first between the noise threshold and the signal threshold. The second time the pulse amplitude in the output signal is between the noise threshold and the signal threshold, it is counted as 2. And the like until at least one sampling period is completed.
And S308, judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage or not according to the pulse number.
In this step, when the bias voltage of the photodetector reaches the breakdown voltage, the photodetector operates at the breakdown voltage, the photodetector generates a large number of discrete noise pulses, and the counted number of pulses between the noise threshold and the signal threshold increases exponentially. Therefore, whether the photoelectric detector works under the breakdown voltage can be judged according to the accumulated pulse number between the noise threshold and the signal threshold.
And S309, if so, reducing the bias voltage of the photoelectric detector by a preset deviation value to obtain an ideal bias voltage of the photoelectric detector.
In the embodiment of the invention, whether the bias voltage of the photoelectric detector reaches the breakdown voltage is judged according to the pulse number of the pulse amplitude between the noise threshold and the signal threshold. If the pulse amplitude is between the noise threshold and the signal threshold, the pulse number is small, and the bias voltage of the photoelectric detector does not reach the breakdown voltage; if the pulse amplitude is between the noise threshold and the signal threshold, the number of pulses is large, and the bias voltage of the photoelectric detector reaches the breakdown voltage. When the bias voltage of the photoelectric detector reaches the breakdown voltage, the number of the noise pulses is exponentially increased, so that the accuracy of the judging mode of the embodiment of the invention is higher. In other embodiments, whether the bias voltage of the photodetector reaches the breakdown voltage may also be determined in other ways.
For example, in a possible embodiment, an average value of all output signals in a sampling period may be obtained, and then whether the bias voltage of the photodetector reaches the breakdown voltage may be determined according to the average value of the output signals and a noise threshold. In the embodiment of the invention, whether the bias voltage of the photoelectric detector reaches the breakdown voltage is judged according to the average value of all output signals in a sampling period and the noise threshold. If the difference between the average value of all output signals in a sampling period and the noise threshold is small, the bias voltage of the photoelectric detector does not reach the breakdown voltage; if the difference between the average value of all output signals in a sampling period and the noise threshold is large, the bias voltage of the photoelectric detector reaches the breakdown voltage.
Optionally, the control method of the photodetector may further include: and if the bias voltage does not reach the breakdown voltage, returning to the step of increasing the bias voltage preset step value of the photoelectric detector. That is to say, if the bias voltage does not reach the breakdown voltage, the method returns to step S305, continues to raise the bias voltage of the photodetector by the preset step value, then collects the output signal of the photodetector in at least one sampling period after raising the bias voltage of the photodetector, obtains the number of pulses in the output signal in at least one sampling period, determines whether the bias voltage of the photodetector reaches the breakdown voltage again according to the number of pulses until the bias voltage of the photodetector reaches the breakdown voltage, and executes step S309.
Optionally, a photodetector is used as a light receiving element of the laser radar, and the control method of the photodetector is executed in a start phase or an end phase of a scanning frame of the laser radar. Because the scanning speed of the slow axis is close to zero when the scanning frame of the laser radar is in the beginning stage and the end stage, a plurality of scanning lines of the fast axis are extruded together and are close to overlapping. The control method of the photoelectric detector is executed at the beginning stage or the ending stage of a scanning frame of the laser radar, and the control process of the photoelectric detector cannot obviously influence the point cloud output of the laser radar. In addition, when the control method of the photoelectric detector is executed at the beginning stage of the scanning frame of the laser radar, the point cloud data of the scanning frame is generated under the optimal gain state of the photoelectric detector, so that the intensity of the signal light is improved. When the control method of the photoelectric detector is executed at the end stage of the scanning frame of the laser radar, the point cloud data of the next scanning frame is generated under the optimal gain state of the photoelectric detector, so that the intensity of signal light is improved.
In an embodiment, the control method of the photodetector may be performed at the beginning or the end of each frame of scanning, so as to ensure that each frame of scanning result is an output result of the photodetector under an ideal bias voltage, thereby improving the accuracy of the output result. In another embodiment, the control of the photodetectors may also be performed once every fixed number of frames.
Fig. 5 is a schematic diagram of a control system of a photo detector according to an embodiment of the present invention, and referring to fig. 5, the control system of the photo detector includes a temperature sensor 11, a current detection circuit 12, a sampling circuit 17, and a controller 14. The temperature sensor 11 is used to detect the temperature of the photodetector 10. A current detection circuit 12 is connected to the photodetector 10, and the current detection circuit 12 is used to detect the total current flowing through the photodetector 10. The sampling circuit 17 is connected to an output end of the photodetector 10, and the sampling circuit 17 is configured to sample an output signal of the photodetector 10. The controller 14 is electrically connected to the photodetector 10, the temperature sensor 11, the current detection circuit 12, and the sampling circuit 17, respectively, the controller 14 obtains a total current of the photodetector 10 through the current detection circuit 12, obtains a temperature of the photodetector 10 through the temperature sensor 11, obtains a dark current of the photodetector 10 according to a temperature characteristic curve of the photodetector 10, determines a background light intensity received by the photodetector 10 according to the total current and the dark current, and adjusts a noise threshold and a signal threshold for sampling an output signal of the photodetector 10 by the sampling circuit 17 according to the background light intensity.
Embodiments of the present invention provide a control system of a photodetector, where a controller may execute the control method of the photodetector in the foregoing embodiments, and the control system of the photodetector is used to control the photodetector (for example, the control system of the photodetector is used to control a bias voltage of the photodetector). The embodiment of the invention also considers the influence of the irradiation of the background light on the total current flowing through the photoelectric detector, so that the noise threshold and the signal threshold are more reasonable after the noise threshold and the signal threshold are adjusted according to the background light intensity, the normal sampling of the output signal of the photoelectric detector can be realized by the sampling circuit under different environmental noises, and the normal work of the laser radar can be ensured.
Optionally, the control system of the photo detector further includes a current limiting resistor 15, a first end of the current limiting resistor 15 is electrically connected to the photo detector 10, and a second end of the current limiting resistor 15 is electrically connected to the current detection circuit 12. On one hand, the current limiting resistor 15 can prevent the control system from being damaged by the impact current, and plays a role in protecting the control system. On the other hand, a current limiting resistor 15 is provided between the current detection circuit 12 and the photodetector 10, and circuit noise generated by the current detection circuit 12 is attenuated by the current limiting resistor 15 before reaching the photodetector 10, thereby reducing the influence of the circuit noise generated by the current detection circuit 12 on the photodetector 10.
Illustratively, referring to fig. 5, the control system of the photodetector further includes a voltage dividing circuit 16, an amplifying circuit 13, a temperature detecting circuit 18, a current detecting circuit 19, a bias detecting circuit 20, and a high voltage generator 21. The voltage divider circuit 16 is electrically connected to the controller 14 and the current detection circuit 12, respectively, and the voltage divider circuit 16 is used to detect the bias voltage of the photodetector 10. The high voltage generator 21 is electrically connected to the controller 14 and the current detection circuit 12, respectively, and the high voltage generator 21 is used for adjusting the bias voltage of the photodetector 10. Illustratively, the controller 14 may control an output value (e.g., a voltage output value) of the high voltage generator 21 by means of a pulse width modulation signal, and the output value of the high voltage generator 21 is transmitted to the photo detector 10 through the current detection circuit 12 and the current limiting resistor 15, so as to adjust the bias voltage of the photo detector 10. The sampling circuit 17 is electrically connected to the controller 14 through an amplifying circuit 13, and the amplifying circuit 13 is used for amplifying the output signal of the photodetector 10. The temperature sensor 11 is electrically connected to the controller 14 through a temperature detection circuit 18, the current detection circuit 12 is electrically connected to the controller 14 through a current detection circuit 19, and the voltage division circuit 16 is electrically connected to the controller 14 through a bias detection circuit 20. The sampling circuit 17, the temperature detection circuit 18, the current detection circuit 19, and the bias detection circuit 20 all include analog-to-digital conversion circuits, that is, all have a circuit function of converting an acquired analog signal into a digital signal and transmitting the digital signal to the controller 14.
Fig. 6 is a schematic diagram of a laser radar according to an embodiment of the present invention, and fig. 7 is a schematic diagram of a scanning track of a laser beam corresponding to one scanning frame of the laser radar, and referring to fig. 6 and 7, the laser radar includes a light emitter 210, a photo detector 10, and a control system 240. The light emitter 210 is used to emit a laser beam to the target scanning area 230. The optical transmitter 210 may comprise, for example, a laser. The photodetector 10 is used to receive the light signal reflected from the target scanning area 230. The photodetector 10 may comprise, for example, an avalanche photodiode. The control system 240 is the control system as in the above embodiments. The laser radar provided by the embodiment of the invention comprises the control system in the embodiment, so that the normal sampling of the output signal of the photoelectric detector can be realized in different environment noise sampling circuits, and the normal work of the laser radar can be ensured.
Alternatively, referring to fig. 6 and 7, the lidar further includes a galvanometer 220, the galvanometer 220 serving as an optical scanning element of the lidar. In fig. 6, an off-axis structure of the receiving and transmitting is taken as an example for illustration, in other embodiments, the lidar may also adopt an on-axis structure, and in this case, the optical signal reflected in the target scanning area 230 is deflected by the galvanometer 220 and then projected to the photodetector 10 by the corresponding mirror. The control system 240 is used to perform control of the photodetector 10 at the beginning or end of each frame of scanning by the galvanometer 220. Because the scanning speed of the slow axis is close to zero when the scanning frame of the laser radar is in the beginning stage and the end stage, a plurality of scanning lines of the fast axis are extruded together and are close to overlapping. The control system 240 controls the photo-detector 10 at the beginning or end of each frame of scanning performed by the galvanometer 220, and the control process of the photo-detector 10 does not have a significant influence on the point cloud output of the lidar. In addition, when the control system 240 performs control of the photodetector 10 at the beginning of each frame scanning by the galvanometer 220, the point cloud data of the scanning frame is generated in the optimal gain state of the photodetector 10, thereby being beneficial to improving the intensity of the signal light. When the control system 240 performs control of the photodetector 10 at the end stage of each frame scanning performed by the galvanometer 220, the point cloud data of the next scanning frame is generated in the optimal gain state of the photodetector 10, thereby facilitating to improve the intensity of the signal light.
Illustratively, referring to fig. 6 and 7, while the control system 240 performs control of the photodetector 10 at the beginning stage of each frame scan by the galvanometer 220, the control system 240 performs control of the photodetector 10 in the first fast axis scanning period of each frame scan. When the control system 240 performs control of the photodetector 10 at the end stage of each frame scanning by the galvanometer 220, the control system 240 performs control of the photodetector 10 in the last fast axis scanning period of each frame scanning (in fig. 7, scanning tracks corresponding to the first fast axis scanning period and the last fast axis scanning period are shown in bold for clarity). Wherein, the fast axis scanning period is the time of one reciprocating motion of the fast axis of the galvanometer 220 in the laser radar. For example, the duration of the fast axis scanning period is about 0.5ms to 1ms, and the control of the photodetector 10 (i.e., adjusting the noise threshold and the signal threshold for sampling the output signal of the photodetector 10, and adjusting the bias voltage of the photodetector 10) may be implemented several hundred times in one fast axis scanning period.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (7)
1. A method of controlling a photodetector, comprising:
acquiring the total current flowing through the photoelectric detector;
acquiring the temperature of the photoelectric detector, and acquiring the dark current of the photoelectric detector according to the temperature of the photoelectric detector and a temperature characteristic curve;
determining the background light intensity received by the photoelectric detector according to the total current and the dark current;
adjusting a noise threshold and a signal threshold for sampling the output signal of the photoelectric detector according to the background light intensity;
after adjusting the noise threshold and the signal threshold for sampling the output signal of the photodetector according to the background light intensity, the method further comprises:
increasing a bias voltage preset step value of the photoelectric detector;
collecting output signals of the photoelectric detector in at least one sampling period;
judging whether the bias voltage of the photoelectric detector reaches breakdown voltage or not according to the output signal of the photoelectric detector, a signal threshold and the noise threshold;
if so, reducing the bias voltage of the photoelectric detector by a preset offset value to obtain an ideal bias voltage of the photoelectric detector;
the judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage according to the output signal of the photoelectric detector, the signal threshold and the noise threshold comprises the following steps:
acquiring the number of pulses with the pulse amplitude between the noise threshold and the signal threshold in the output signal in at least one sampling period;
judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage or not according to the pulse number;
the photoelectric detector is used as a light receiving element of the laser radar, and the control method of the photoelectric detector is executed at the beginning stage or the ending stage of a scanning frame of the laser radar.
2. The method of claim 1, wherein determining whether the bias voltage of the photodetector reaches a breakdown voltage according to the output signal of the photodetector, a signal threshold, and the noise threshold comprises:
obtaining an average value of all the output signals in one sampling period;
and judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage or not according to the average value of the output signals and the noise threshold.
3. The method of claim 1, further comprising, after determining whether the bias voltage of the photodetector has reached a breakdown voltage based on the output signal of the photodetector, a signal threshold, and the noise threshold:
and if the bias voltage does not reach the breakdown voltage, returning to the step of executing the preset step value of the bias voltage for increasing the photoelectric detector.
4. A control system for a photodetector, comprising:
a temperature sensor for detecting a temperature of the photodetector;
the current detection circuit is connected with the photoelectric detector and is used for detecting the total current flowing through the photoelectric detector;
the sampling circuit is connected with the output end of the photoelectric detector and is used for sampling the output signal of the photoelectric detector; and
the controller is respectively electrically connected with the photoelectric detector, the temperature sensor, the current detection circuit and the sampling circuit, acquires the total current of the photoelectric detector through the current detection circuit, acquires the temperature of the photoelectric detector through the temperature sensor, acquires the dark current of the photoelectric detector according to the temperature characteristic curve of the photoelectric detector, determines the background light intensity received by the photoelectric detector according to the total current and the dark current, and adjusts the noise threshold and the signal threshold for sampling the output signal of the photoelectric detector by the sampling circuit according to the background light intensity;
the controller is configured to, after adjusting a noise threshold and a signal threshold of the sampling circuit for sampling the output signal of the photodetector according to the background light intensity,:
increasing a bias voltage preset step value of the photoelectric detector;
collecting output signals of the photoelectric detector in at least one sampling period;
judging whether the bias voltage of the photoelectric detector reaches breakdown voltage or not according to the output signal of the photoelectric detector, a signal threshold and the noise threshold;
if so, reducing the bias voltage of the photoelectric detector by a preset offset value to obtain an ideal bias voltage of the photoelectric detector;
the judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage according to the output signal of the photoelectric detector, the signal threshold and the noise threshold comprises the following steps:
acquiring the number of pulses with the pulse amplitude between the noise threshold and the signal threshold in the output signal in at least one sampling period;
and judging whether the bias voltage of the photoelectric detector reaches the breakdown voltage or not according to the pulse number.
5. The control system of claim 4, further comprising a current limiting resistor, wherein a first end of the current limiting resistor is electrically connected to the photodetector and a second end of the current limiting resistor is electrically connected to the current detection circuit.
6. A lidar, comprising:
the light emitter is used for emitting laser beams to a target scanning area;
a photodetector for receiving the optical signal reflected from the target scanning area; and
a control system as claimed in any one of claims 4 to 5.
7. The lidar of claim 6, further comprising a galvanometer as an optical scanning element of the lidar;
the control system is used for controlling the photoelectric detector at the beginning stage or the ending stage of each frame scanning of the galvanometer.
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| CN113686433B (en) * | 2021-08-23 | 2022-11-18 | 长飞光纤光缆股份有限公司 | Photoelectric detector and erbium-doped optical fiber amplifier based on dark current compensation |
| CN117940799A (en) * | 2021-09-14 | 2024-04-26 | 华为技术有限公司 | Signal processing method and related device |
| CN116930987A (en) * | 2022-04-02 | 2023-10-24 | 上海禾赛科技有限公司 | Laser radar detection method, computer storage medium and laser radar |
| CN114994643B (en) * | 2022-07-18 | 2022-11-15 | 四川吉埃智能科技有限公司 | APD bias voltage adjusting method and circuit in laser ranging |
| WO2024081230A1 (en) * | 2022-10-11 | 2024-04-18 | Zoox, Inc. | Lidar background noise detection and compensation |
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