WO2021243612A1 - 测距方法、测距装置和可移动平台 - Google Patents

测距方法、测距装置和可移动平台 Download PDF

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Publication number
WO2021243612A1
WO2021243612A1 PCT/CN2020/094222 CN2020094222W WO2021243612A1 WO 2021243612 A1 WO2021243612 A1 WO 2021243612A1 CN 2020094222 W CN2020094222 W CN 2020094222W WO 2021243612 A1 WO2021243612 A1 WO 2021243612A1
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Prior art keywords
time
time periods
preset threshold
measurement
count
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PCT/CN2020/094222
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English (en)
French (fr)
Inventor
梅雄泽
马亮亮
许友
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深圳市大疆创新科技有限公司
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Priority to CN202080006252.9A priority Critical patent/CN114402225A/zh
Priority to PCT/CN2020/094222 priority patent/WO2021243612A1/zh
Publication of WO2021243612A1 publication Critical patent/WO2021243612A1/zh

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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
    • 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

Definitions

  • the present invention generally relates to the technical field of laser ranging, and more specifically relates to a ranging method, a ranging device and a movable platform.
  • the laser distance measuring device is an instrument that uses a certain parameter of the modulated laser to measure the distance to the target.
  • the typical ranging methods of laser ranging devices include pulse method and phase method.
  • the pulse method includes emitting a beam or a sequence of short laser pulses to the object to be measured, receiving the laser pulses reflected by the target, and measuring the time interval of the laser beam from launching to receiving, so as to calculate the distance from the laser ranging device to the target. distance.
  • a high-frequency clock is usually used to drive a timer to time the time between sending and receiving pulses. The period of the clock directly determines the accuracy of the measurement, and the hardware cost required to reach the millimeter level measurement is very high.
  • the first aspect of the embodiments of the present invention provides a ranging method, including:
  • the measurement process includes: in a measurement window, transmit an optical pulse signal, receive the return optical pulse signal, convert the return optical pulse signal into an electrical signal, and record multiple measurements in the measurement window
  • the electrical signal triggers the counting of the preset threshold within the time period
  • the receiving time of the return optical pulse signal is determined according to the size of the total count in a plurality of time periods, and the distance of the measured object is calculated according to the interval between the receiving time and the transmitting time of the optical pulse signal.
  • a second aspect of the embodiments of the present invention provides a ranging device, the ranging device includes a transmitting module, a receiving module, a sampling module, an arithmetic module, and a control module, wherein:
  • the control module is used to control the transmitting module, the receiving module, and the sampling module to perform multiple measurement processes, and the measurement process includes: in a single measurement window,
  • the transmitting module is used for transmitting light pulse signals
  • the receiving module is configured to receive the return light pulse signal and convert the return light pulse signal into an electrical signal
  • the sampling module is configured to record the count of the electrical signal triggering a preset threshold in multiple time periods in the measurement window;
  • the arithmetic module is configured to count the counts recorded in the multiple measurement processes to obtain a total count of the preset threshold triggered by the electrical signal in each time period; and according to multiple times The size of the total count of the segment determines the receiving time of the return light pulse signal, and the distance of the measured object is calculated according to the difference between the transmitting time and the receiving time.
  • a third aspect of the embodiments of the present invention provides a movable platform on which a camera and the aforementioned distance measuring device are mounted; the camera performs focusing according to the distance measured by the distance measuring device.
  • a fourth aspect of the embodiments of the present invention provides a movable platform on which a camera and a distance measuring device are mounted, wherein:
  • the camera is used to determine the target according to the field of view picture
  • the distance measuring device is used to determine the target direction according to the position of the target in the field of view picture, and transmit multiple light pulse signals to the target direction, and determine the distance of the target according to the multiple light pulse signals;
  • the camera is also used to focus on the target according to the distance determined by the distance measuring device.
  • the distance measuring method, the distance measuring device and the movable platform according to the embodiments of the present invention can realize a longer measurement distance and higher measurement accuracy at a lower cost.
  • Fig. 1 shows a block diagram of a distance measuring device in an embodiment of the present invention
  • Figure 2 shows a schematic structural diagram of a distance measuring device in an embodiment of the present invention
  • FIG. 3 shows a schematic flowchart of a ranging method according to an embodiment of the present invention
  • Fig. 4 shows a variation curve of the magnitude of noise and the number of statistics according to an embodiment of the present invention
  • FIG. 5 shows the relationship between the signal size obtained from a single measurement and the statistical multiple measurement results with time according to an embodiment of the present invention
  • Fig. 6 is a schematic block diagram of a movable platform according to an embodiment of the present invention.
  • the distance measuring device includes a lidar.
  • the distance measuring device is only used as an example. It can also be applied to this application.
  • the distance measuring device can be used to implement the distance measuring method herein.
  • the distance measuring device can be electronic equipment such as laser radar and laser distance measuring equipment.
  • the distance measuring device is used to sense external environmental information, for example, distance information, orientation information, reflection intensity information, speed information, etc. of environmental targets.
  • the distance measuring device can detect the distance from the probe to the distance measuring device by measuring the time of light propagation between the distance measuring device and the probe, that is, the time-of-flight (TOF).
  • TOF time-of-flight
  • the distance measuring device 100 includes a transmitting module 110, a receiving module 120, a sampling module 130, an arithmetic module 140 and a control module 150.
  • the transmitting module 110 may emit a light pulse sequence (for example, a laser pulse sequence).
  • the receiving module 120 can receive the light pulse sequence reflected by the detected object, that is, obtain the pulse waveform of the echo signal through it, and perform photoelectric conversion on the light pulse sequence to obtain the electrical signal, and then the electrical signal can be processed Output to the sampling module 130.
  • the sampling module 130 may sample the electrical signal to obtain the sampling result.
  • the arithmetic module 140 may determine the distance between the distance measuring device 100 and the detected object, that is, the depth, based on the sampling result of the sampling module 130.
  • the control module 150 can control other circuits. For example, it can control the working time of each circuit and/or set parameters for each circuit.
  • the distance measuring device shown in FIG. 1 includes a transmitting module, a receiving module, a sampling module, and an arithmetic module for emitting a beam for detection
  • the embodiment of the present application is not limited to this, the transmitting module
  • the number of any one of the receiving module, sampling module, and computing module can also be at least two, which are used to emit at least two light beams in the same direction or in different directions; wherein, the at least two light paths can be simultaneous Shooting can also be shooting at different times.
  • the light-emitting chips in the at least two emitting modules are packaged in the same module.
  • each emitting module includes a laser emitting chip, and the dies in the laser emitting chips in the at least two emitting modules are packaged together and housed in the same packaging space.
  • the distance measuring device 100 may also include a scanning module for changing the propagation direction of at least one light pulse sequence (for example, a laser pulse sequence) emitted by the transmitting module to emit it to the field of view. Perform a scan.
  • the scanning area of the scanning module in the field of view of the distance measuring device increases with the accumulation of time.
  • the modules including the transmitting module 110, the receiving module 120, the sampling module 130, and the arithmetic module 140, or the modules including the transmitting module 110, the receiving module 120, the sampling module 130, the arithmetic module 140, and the control circuit 150 may be referred to as the measuring module.
  • the distance module the distance measurement module can be independent of other modules, for example, the scanning module.
  • a coaxial optical path can be used in the distance measuring device, that is, the light beam emitted by the distance measuring device and the reflected light beam share at least part of the optical path in the distance measuring device.
  • the distance measuring device may also adopt an off-axis optical path, that is, the light beam emitted by the distance measuring device and the reflected light beam are respectively transmitted along different optical paths in the distance measuring device.
  • Fig. 2 shows a schematic diagram of an embodiment in which the distance measuring device of the present invention adopts a coaxial optical path.
  • the ranging device 200 includes a ranging module 210, which includes a transmitter 203 (which may include the above-mentioned transmitting module), a collimating element 204, a detector 205 (which may include the above-mentioned receiving module, sampling module, and arithmetic module), and Light path changing element 206.
  • the ranging module 210 is used to emit a light beam, receive the return light, and convert the return light into an electrical signal.
  • the transmitter 203 can be used to emit a light pulse sequence.
  • the transmitter 203 may emit a sequence of laser pulses.
  • the laser beam emitted by the transmitter 203 is a narrow-bandwidth beam with a wavelength outside the visible light range.
  • the collimating element 204 is arranged on the exit light path of the emitter, and is used to collimate the light beam emitted from the emitter 203, and collimate the light beam emitted from the emitter 203 into parallel light and output to the scanning module.
  • the collimating element is also used to condense at least a part of the return light reflected by the probe.
  • the collimating element 204 may be a collimating lens or other elements capable of collimating light beams.
  • the transmitting light path and the receiving light path in the distance measuring device are combined before the collimating element 204 through the light path changing element 206, so that the transmitting light path and the receiving light path can share the same collimating element, so that the light path More compact.
  • the emitter 203 and the detector 205 use their respective collimating elements, and the optical path changing element 206 is arranged on the optical path behind the collimating element.
  • the optical path changing element can use a small-area mirror to transform the light beam.
  • the transmitting light path and the receiving light path are combined.
  • the light path changing element may also adopt a reflector with a through hole, where the through hole is used to transmit the emitted light of the emitter 203 and the reflector is used to reflect the return light to the detector 205. In this way, the shielding of the back light from the support of the small reflector in the case of using the small reflector can be reduced.
  • the optical path changing element deviates from the optical axis of the collimating element 204.
  • the optical path changing element may also be located on the optical axis of the collimating element 204.
  • the distance measuring device 200 further includes a scanning module 202.
  • the scanning module 202 is placed on the exit light path of the distance measuring module 210.
  • the scanning module 202 is used to change the transmission direction of the collimated beam 219 emitted by the collimating element 204 and project it to the external environment, and project the return light to the collimating element 204 .
  • the returned light is collected on the detector 205 via the collimating element 204.
  • the scanning module 202 may include at least one optical element for changing the propagation path of the light beam, wherein the optical element may change the propagation path of the light beam by reflecting, refraction, diffracting the light beam, etc.
  • the optical element includes at least one light refraction element having a non-parallel exit surface and an entrance surface.
  • the scanning module 202 includes a lens, a mirror, a prism, a galvanometer, a grating, a liquid crystal, an optical phased array (Optical Phased Array), or any combination of the foregoing optical elements.
  • at least part of the optical elements are moving.
  • a driving module is used to drive the at least part of the optical elements to move.
  • the moving optical elements can reflect, refract, or diffract the light beam to different directions at different times.
  • the multiple optical elements of the scanning module 202 can rotate or vibrate around a common axis 209, and each rotating or vibrating optical element is used to continuously change the propagation direction of the incident light beam.
  • the multiple optical elements of the scanning module 202 may rotate at different rotation speeds or vibrate at different speeds.
  • at least part of the optical elements of the scanning module 202 may rotate at substantially the same rotation speed.
  • the multiple optical elements of the scanning module may also rotate around different axes.
  • the multiple optical elements of the scanning module may also rotate in the same direction or in different directions; or vibrate in the same direction, or vibrate in different directions, which is not limited herein.
  • the scanning module 202 includes a first optical element 214 and a driver 216 connected to the first optical element 214.
  • the driver 216 is used to drive the first optical element 214 to rotate around the rotation axis 209 to change the first optical element 214.
  • the direction of the beam 219 is collimated.
  • the first optical element 214 projects the collimated beam 219 to different directions.
  • the angle between the direction of the collimated beam 219 changed by the first optical element and the rotation axis 209 changes with the rotation of the first optical element 214.
  • the first optical element 214 includes a pair of opposing non-parallel surfaces through which the collimated light beam 219 passes.
  • the first optical element 214 includes a prism whose thickness varies along at least one radial direction.
  • the first optical element 214 includes a wedge-angle prism, and the collimated beam 219 is refracted.
  • the scanning module 202 further includes a second optical element 215, the second optical element 215 rotates around the rotation axis 209, and the rotation speed of the second optical element 215 is different from the rotation speed of the first optical element 214.
  • the second optical element 215 is used to change the direction of the light beam projected by the first optical element 214.
  • the second optical element 215 is connected to another driver 217, and the driver 217 drives the second optical element 215 to rotate.
  • the first optical element 214 and the second optical element 215 can be driven by the same or different drivers, so that the rotation speed and/or rotation of the first optical element 214 and the second optical element 215 are different, so that the collimated light beam 219 is projected to the outside space.
  • the controller 218 controls the drivers 216 and 217 to drive the first optical element 214 and the second optical element 215, respectively.
  • the rotational speeds of the first optical element 214 and the second optical element 215 can be determined according to the expected scanning area and pattern in actual applications.
  • the drivers 216 and 217 may include motors or other drivers.
  • the second optical element 215 includes a pair of opposed non-parallel surfaces through which the light beam passes. In one embodiment, the second optical element 215 includes a prism whose thickness varies along at least one radial direction. In one embodiment, the second optical element 215 includes a wedge prism.
  • the scanning module 202 further includes a third optical element (not shown) and a driver for driving the third optical element to move.
  • the third optical element includes a pair of opposite non-parallel surfaces, and the light beam passes through the pair of surfaces.
  • the third optical element includes a prism whose thickness varies in at least one radial direction.
  • the third optical element includes a wedge prism. At least two of the first, second, and third optical elements rotate at different rotation speeds and/or rotation directions.
  • the scanning module includes two or three light refraction elements arranged in sequence on the exit light path of the light pulse sequence.
  • at least two of the light refraction elements in the scanning module rotate during the scanning process to change the direction of the light pulse sequence.
  • the scanning path of the scanning module is different at least partly at different moments.
  • the rotation of each optical element in the scanning module 202 can project light to different directions, such as the direction of the projected light 211 and the direction 213, so that the distance measurement device 200 Space to scan.
  • the light 211 projected by the scanning module 202 hits the detection object 201, a part of the light is reflected by the detection object 201 to the distance measuring device 200 in a direction opposite to the projected light 211.
  • the return light 212 reflected by the probe 201 is incident on the collimating element 204 after passing through the scanning module 202.
  • the detector 205 and the transmitter 203 are placed on the same side of the collimating element 204, and the detector 205 is used to convert at least part of the return light passing through the collimating element 204 into electrical signals.
  • an anti-reflection coating is plated on each optical element.
  • the thickness of the antireflection film is equal to or close to the wavelength of the light beam emitted by the emitter 203, which can increase the intensity of the transmitted light beam.
  • a filter layer is plated on the surface of an element located on the beam propagation path in the distance measuring device, or a filter is provided on the beam propagation path for transmitting at least the wavelength band of the beam emitted by the transmitter, Reflect other bands to reduce the noise caused by ambient light to the receiver.
  • the transmitter 203 may include a laser diode through which nanosecond laser pulses are emitted. Further, the distance between the probe 201 and the distance measuring device 200 can be determined according to the received laser pulse. The distance and orientation detected by the distance measuring device 200 can be used for remote sensing, obstacle avoidance, surveying and mapping, modeling, navigation, and the like.
  • the ranging method used by the ranging device generally includes the pulse method and the phase method.
  • the pulse method laser distance measuring device emits a beam or a sequence of short laser pulses to the measured object when it is working, the photoelectric element receives the laser beam reflected by the target, and the timer measures the time interval from the launch to the reception of the laser beam. , So as to calculate the distance from the distance measuring device to the measured object.
  • a high-frequency clock is used to drive the timer to time the time between sending and receiving pulses. The period of the clock directly determines the accuracy of the measurement.
  • the measurement accuracy of the current better distance measuring device can reach ten centimeters. If you want to reach the millimeter level For measurement, the hardware cost required for pulsed ranging is very high.
  • the phase method laser distance measuring device modulates the light intensity of the emitted laser pulse, measures the phase difference between the emitted light and the reflected light when propagating in space to detect the distance, and the accuracy can reach millimeters and micrometers.
  • the rangefinder using a single modulation frequency, it can only distinguish phases within 2 ⁇ , so it is impossible to measure the distance of more than one cycle. For example, when the frequency of the modulation signal is 1MHz, the corresponding range is 150m. If the actual distance value exceeds 150m, the measurement result is still within 150m.
  • the modulation frequency will affect the maximum range of the phase distance measuring device.
  • both the pulse method and the laser distance measuring device using the distance measuring method are limited by the hardware conditions and it is difficult to improve the measurement distance and measurement accuracy at the same time.
  • an embodiment of the present invention provides a distance measurement method, the method includes: repeating multiple measurement processes, the measurement process includes: in a measurement window, transmitting an optical pulse signal, receiving the return optical pulse signal , Converting the return light pulse signal into an electrical signal, recording the count of the electrical signal triggering a preset threshold in a plurality of time periods in the measurement window; counting the counts recorded in the multiple measurement processes to Obtain the total count of the preset threshold triggered by the electrical signal in the multiple measurement windows for each of the time periods; determine the receiving time of the return light pulse signal according to the size of the total count in the multiple time periods, and The distance between the receiving time and the transmitting time of the optical pulse signal is calculated.
  • the distance measurement method of the embodiment of the present invention can achieve a longer measurement distance and higher measurement accuracy at a lower cost within the range of safety regulations.
  • FIG. 3 shows a schematic flowchart of the distance measurement method 300 in an embodiment of the present invention.
  • the ranging method 300 of the embodiment of the present invention includes the following steps:
  • step S310 repeat the measurement process for multiple times, and the measurement process includes: in a measurement window, transmitting an optical pulse signal, receiving a return optical pulse signal, converting the return optical pulse signal into an electrical signal, and recording
  • the electrical signal in the multiple time periods in the measurement window triggers the counting of a preset threshold.
  • the transmitter module and the receiver module are turned on at the same time. It is converted into an electrical signal, and the sampling module records the number of times the electrical signal triggers the preset threshold in each time period in the measurement window.
  • the distance measuring device has multiple transmitting modules and multiple receiving modules, in each measurement window, the corresponding transmitting module and receiving module are turned on at the same time.
  • the receiving module not only includes the return light pulse signal returned by the measured object, but also includes the noise signal.
  • the noise signal and the return light pulse signal are distributed in multiple time periods in the measurement window.
  • the return light pulse signal is weak, and it is difficult to distinguish the return light through a single measurement. Pulse signal and noise signal, therefore, the ranging method of the embodiment of the present invention uses a statistical method to determine the time period where the optical pulse signal is returned.
  • each measurement window after the receiving module converts the received optical signal into an electrical signal, it can also send the electrical signal to the primary or secondary amplifier circuit for amplification, and then send the amplified electrical signal to Into the sampling circuit.
  • the sampling circuit divides the measurement window into multiple time periods and compares the electrical signal with a preset threshold to count the number of times the electrical signal triggers the preset threshold in each time period.
  • the length of the measurement window in each measurement process is the same, and each measurement window is divided into N time periods, where N>1.
  • the sampling module includes a comparator (for example, an analog comparator (COMP), which is used to convert an electrical signal into a digital pulse signal) and a time measurement circuit, via a primary or secondary amplifier circuit
  • a comparator for example, an analog comparator (COMP)
  • COMP analog comparator
  • the amplified electrical signal enters the time measurement circuit after passing through the comparator, and the time measurement circuit counts the number of times.
  • the time measurement circuit may be a time-to-data converter (TDC).
  • TDC can be an independent TDC chip, or based on Field-Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC) or Complex Programmable Logic Device (Complex Programmable Logic Device).
  • FPGA Field-Programmable Gate Array
  • ASIC Application Specific Integrated Circuit
  • Complex Programmable Logic Device Complex Programmable Logic Device
  • the internal delay chain of programmable devices such as CPLD to realize the TDC circuit of time measurement, or the circuit structure of time measurement using high-frequency clock or the circuit structure of time measurement by counting method.
  • the first input terminal of the comparator is used to receive the electrical signal input from the amplifying circuit, and the electrical signal may be a voltage signal or a current signal; the second input terminal of the comparator is used to receive a preset threshold value, which is input to the comparison
  • the electrical signal of the detector is compared with the preset threshold.
  • the output signal of the comparator is connected to TDC.
  • TDC can measure the time information of the output signal edge of the comparator. The measured time is based on the emission time of the optical pulse signal, that is, the time difference between laser signal emission and reception can be measured. In a single measurement, TDC can count whether there is an electrical signal triggering the preset threshold in each time period. If there is a trigger, the count is 1, and if there is no trigger, the count is 0. When there is a 0 to 1 transition in a certain time period, it means that there is a signal rising edge trigger in that time period.
  • the sampling module may also include an analog-to-digital converter (Analog-to-Digital Converter, ADC). After the analog signal input to the sampling module is converted by the ADC, the digital signal can be output to the arithmetic module.
  • ADC Analog-to-Digital Converter
  • the exit direction of the light pulse signal remains unchanged, so as to ensure that the return light pulses returned from the same object are collected during the multiple measurement processes.
  • the measurement method of the embodiment of the present invention is mainly applicable to the situation where the object to be measured is far away or has low reflectivity, that is, the signal-to-noise ratio is low.
  • the measured object is far away or the reflectivity is low
  • the return light pulse energy is low
  • the electrical signal generated after the conversion by the receiving circuit is as large as the noise or even It is less than the noise and the signal-to-noise ratio is low.
  • the measurement process is repeated for multiple times, and the statistical method of multiple measurements is used to improve the signal-to-noise ratio to obtain the distance of the measured object. In this case, obtaining a measurement result through multiple measurements reduces the refresh frequency of the measurement results, but improves the measurement accuracy.
  • the returned laser energy is high after the laser is irradiated to the object, and the pulse generated by the photoelectric sensor is much larger than the noise, and the signal-to-noise ratio is high.
  • the time information of the pulse can be measured directly through the TDC, and the arrival time of the return light pulse signal can be obtained. In this case, there is no need to repeat the measurement process for multiple times, and the correct result can be obtained through one measurement, thereby avoiding reducing the refresh frequency of the measurement result.
  • step S310 before performing step S310, it is first determined whether it is necessary to repeat the measurement process for multiple times.
  • the method for judging whether it is necessary to repeat the measurement process for multiple times includes: comparing the electrical signal with at least two preset thresholds.
  • the preset threshold includes at least a smaller first preset threshold and a larger first preset threshold.
  • the second preset threshold If there is an electrical signal that triggers the second preset threshold in the measurement window, it means that the return light pulse signal is strong. At this time, there is no need to repeat the measurement process for multiple times, and the electrical signal can directly trigger the second preset. Set the threshold time as the receiving time to calculate the distance of the measured object.
  • the electrical signal triggers the first preset threshold, but does not trigger the second preset threshold, in other words, if there is an electrical signal that triggers the first preset threshold in the measurement window, but there is no electrical signal that triggers the second preset threshold , It means that the return light pulse signal is weak. At this time, repeat the measurement process for several times to increase the range.
  • the counting of the electric signal triggering the preset threshold value in the recording multiple time periods described in step S310 is the counting of the electric signal triggering the first preset threshold value.
  • step S310 the number of times of performing multiple measurement processes is fixed or variable. For example, it may be adaptively adjusted according to the confidence of the measurement result. For details, refer to the following.
  • step S320 the counts recorded in the multiple measurement processes are counted to obtain a total count of the preset threshold value triggered by the electrical signal in the multiple measurement windows for each of the time periods.
  • each measurement window is divided into N time periods, then in step S320, the records of each of the first, second, third, ..., N time periods in the multiple measurement windows are The counts are added to obtain the total count of the first, second, third, ..., N time periods of the multiple measurement windows when the electrical signal triggers the preset threshold.
  • Noise signals may appear randomly in each time period.
  • the noise signal of a single measurement has a certain randomness, and a larger noise signal may appear in a single time period.
  • the embodiment of the present invention uses a counting method to count the measurement results.
  • FIG. 5 shows the change curves 501, 502, and 503 of the signal size obtained from the first measurement, the second measurement, and the third measurement with time, and the final statistical results.
  • the size of the return light pulse and the distributed time period are basically fixed, that is, there is basically an electrical signal that triggers the preset threshold in the corresponding time period of each measurement; while the noise signal is received in other time periods. It is random.
  • the first measurement there are electrical signals triggering the first preset threshold Th1 in the T2, T5, and T8 time periods.
  • the count of these time periods is 1, and the other time periods are counted as 0, where the noise signal is received in the T2 and T5 time periods, and the return light pulse signal is received in the T8 time period; in the second measurement, since the receiving time of the noise signal is random, the return light pulse signal The receiving time is fixed.
  • the electrical signal of the noise signal in the time period T1 and T4 triggers the first preset threshold Th1
  • the electrical signal of the return light pulse signal in the time period T8 triggers the first preset threshold Th1, so T1, T4,
  • the count in the T8 period is 1, and the count in other periods is 0;
  • the electrical signal of the noise signal in the T3 period triggers the first preset threshold Th1
  • the electrical signal of the return light pulse signal in the T8 period triggers the first A preset threshold Th1
  • the counts in the T3 and T8 time periods are 1, and the other time periods are counted as 0; and so on, in the T8 time period, basically every measurement can receive the return light pulse signal, while at other times
  • the segment can only receive noise signals randomly.
  • the size of the noise signal in other time periods gradually decreases and tends to be stable, so the statistical result of the signal size in the T8 time period will be higher than that in other time periods.
  • the count of the time period corresponding to the return light pulse signal will be significantly higher than the count of other time periods. Therefore, even if the magnitude of the electrical signal of the return light pulse signal is not enough to trigger the second preset threshold Th2 , The receiving time of the return light pulse signal can also be determined statistically.
  • step S330 the receiving time of the return optical pulse signal is determined according to the size of the total count in multiple time periods, and the measured object is calculated according to the interval between the receiving time and the transmitting time of the optical pulse signal distance.
  • the total count of each time period can be compared separately, and the time period with the largest total count is determined as the receiving time.
  • the time measured by the sampling circuit is based on the emission time of the optical pulse signal. Therefore, after the time period with the most total count is determined, the interval between the reception time and the emission time can be obtained, and the laser signal is from the emission time.
  • the emitted light spot may irradiate more than one object under test. Therefore, in another embodiment, multiple time periods with the largest total count may be determined as the receiving time, and each receiving time may be used separately. Calculate the distance of the measured object to realize the function of measuring the distance of multiple measured objects.
  • the M time periods with the largest total count can be determined as receiving times, where M is a preset value.
  • the number of time periods used to determine the receiving time can also be determined according to the signal-to-noise ratio and the confidence level, see below for details.
  • each return light pulse signal may be randomly distributed in several adjacent time periods, so that the correct time period count decreases, which is equivalent to energy dispersion and a decrease in signal-to-noise ratio. Therefore, as an implementation method, the "sliding window method" can be adopted to treat at least two adjacent time periods as a set of time periods, to count the sum of the total counts of each set of time periods, and to compare the time periods of multiple sets of time periods. According to the sum of the total counts, the receiving time is determined within one or more groups of time periods in which the sum of the total counts is the largest. Of course, in actual calculation, you can also first count the total count of each group of time periods in each measurement window, and then count the sum of the total count of each group of time periods in multiple measurement windows.
  • the first, second, and third time periods in each measurement window can be used as a group
  • the fourth, fifth, and sixth time periods can be used as a group
  • the seventh, eighth, and ninth time periods can be used as a group.
  • Group, and so on that is, each group of time periods includes several different time periods. When dividing in this way, a group of time periods with the highest total count can be determined, and this group of time periods can be regarded as the receiving time of the return light pulse signal.
  • the first, second, and third time periods in each measurement window can be used as a group
  • the second, third, and fourth time periods can be used as a group
  • the third, fourth, and fifth time periods can be used as a group.
  • the return light pulse signal returned by the measured object may not be received during the process of performing multiple measurements.
  • the probability of receiving a noise signal in each time period is basically the same.
  • the total count of each time period is very small, and the signal-to-noise ratio is very low.
  • the signal-to-noise ratio of the time period as the measurement result can be calculated, and the magnitude of the signal-to-noise ratio can be used as the confidence level of the measurement result.
  • the confidence level is higher than the threshold, the measurement result is considered credible.
  • sliding window method when used for statistics, it can be based on the average of the sum of the total counts in one or more groups of time periods with the largest total count and the sum of the total counts of each group of time periods in the measurement window The result of the comparison determines the confidence of the receiving time.
  • the confidence when the confidence is lower than the preset confidence threshold, it is considered that the statistical method of multiple measurements still cannot make the signal-to-noise ratio meet the requirements, so the use of receiving time to calculate the distance of the measured object is abandoned. It can be considered that no object has been measured.
  • the initial measurement result refresh rate is 1KHz
  • the confidence level of the measurement result is lower than the preset confidence threshold. If the confidence level is lower than the preset confidence threshold, add execution The counting of the measurement process, for example, the refresh rate is reduced to 500 Hz. After increasing the number of measurements, the confidence of the measurement result can be calculated again. If the confidence is higher than the confidence threshold, the new receiving time is used to calculate the distance of the measured object. If the confidence is still lower than the confidence threshold, it can continue to decrease Refresh rate until the confidence level is higher than the threshold.
  • the receiving time calculation is abandoned.
  • the distance of the object, at this time it can be considered that no object has been measured.
  • the confidence level of each time period or group of time periods can be calculated separately, and the confidence level is higher than One or more time periods of the confidence threshold, or one or more sets of time periods, and abandoning the time period when the confidence is lower than the confidence threshold to calculate the distance of the measured object.
  • the distance measurement method 300 of the embodiment of the present invention adopts a method of statistically calculating the results of multiple measurements, and can greatly increase the range at a lower cost at the cost of appropriately reducing the result refresh frequency within the safety limit range.
  • a pulse distance measuring device with a range of 20% reflectivity and 300 meters can measure an object with a reflectivity of 20% and 1500 meters after using the distance measuring method of the embodiment of the present invention.
  • the distance measurement method according to the embodiment of the present invention is exemplarily described above.
  • the distance measuring device 100 provided according to an embodiment of the present invention will be described.
  • the distance measurement device 100 according to the embodiment of the present invention is used to implement the distance measurement method 300 according to the embodiment of the present invention described above.
  • the distance measuring device 100 for brevity, only the main structure and functions of the distance measuring device 100 are described below, and some specific details that have been described above are omitted.
  • the distance measuring device 100 includes a transmitting module 110, a receiving module 120, a sampling module 130, an arithmetic module 140, and a control module 150.
  • the control module 150 is used to control the transmitting module 110, the receiving module 120, and the sampling module 130.
  • the measurement process includes: in a measurement window, the transmitting module 110 is used to transmit optical pulse signals; the receiving module 120 is used to receive the return optical pulse signals, and convert the return optical pulse signals into electrical Signal; the sampling module 130 is used to record the counts of the electrical signal triggering a preset threshold in multiple time periods in the measurement window; the calculation module 140 is used to count the counts recorded in multiple measurement processes to obtain each The electrical signal in the time period triggers the total count of the preset threshold, and the receiving time of the return light pulse signal is determined according to the total count of multiple time periods, and the measured object's value is calculated according to the difference between the transmitting time and the receiving time distance.
  • determining the receiving time of the return light pulse signal according to the total counts of multiple time periods may be implemented as: comparing the total counts of multiple time periods; The time period is determined as the receiving time.
  • determining the receiving time of the return optical pulse signal according to the total count of multiple time periods may be implemented as: taking at least two adjacent time periods as a group of time periods, and counting each group of time periods The sum of the total counts; compare the sum of the total counts of multiple groups of time periods, and determine the receiving time within one or more groups of time periods with the largest sum of the total counts.
  • the arithmetic module 140 is further configured to determine the confidence of the receiving time according to the comparison result of the total count in one or more time periods with the largest total count and the average value of the total count.
  • the arithmetic module 140 is further configured to: determine the receiving according to the comparison result of the sum of the total counts and the average value of the sum of the total counts in one or more groups of time periods with the largest total counts. Confidence of time. As an example, when the confidence is lower than the preset confidence threshold, the computing module 140 abandons using the receiving time to calculate the distance of the measured object.
  • control module 150 may also dynamically adjust the number of times the measurement process is performed according to the confidence level. Specifically, it is determined whether the confidence is lower than a preset confidence threshold, and if the confidence is lower than the preset confidence threshold, the number of times of performing the measurement process is increased.
  • the calculation module abandons using the receiving time to calculate the distance of the measured object if the number of times of performing the measurement process reaches the preset maximum number of times, and the confidence level is still lower than the preset confidence level threshold.
  • the preset threshold includes at least a first preset threshold and a second preset threshold, the first preset threshold is less than the second preset threshold, and if the electrical signal triggers the first If a preset threshold value is not triggered, but the second preset threshold value is not triggered, the control module controls to execute the measurement process multiple times; the recording of the electrical signal in a plurality of time periods triggers the counting of the preset threshold value It includes recording the counting of the first preset threshold triggered by the electrical signal in the multiple time periods.
  • the arithmetic module uses the time when the electrical signal triggers the second preset threshold as the receiving time, that is, through a single pass Measure to obtain measurement results without having to perform multiple measurements.
  • a movable platform is also provided.
  • the following describes a schematic block diagram of a movable platform 600 provided by an embodiment of the present invention with reference to FIG. 6.
  • the movable platform includes at least one of an unmanned aerial vehicle, a car, a remote control car, a robot, and a boat.
  • a camera 610 and a distance measuring device 620 are mounted on the movable platform, and the specific details of the distance measuring device 620 can refer to the above distance measuring device 100.
  • the distance measuring device 620 can use the distance measuring method 300 described above to measure the distance of the measured object and send it to the camera 610.
  • the camera 620 focuses on the distance measured by the distance measuring device 620 to collect the measured object. Image. Since the distance measuring device 620 has a higher accuracy and a longer range, the camera 610 can focus more clearly on objects that are farther away.
  • a movable platform is also provided.
  • the movable platform is equipped with a camera 610 and a distance measuring device 620.
  • the camera 610 is used to determine the target according to the field of view picture;
  • the distance measuring device 620 is used to determine the target direction according to the position of the target in the field of view picture, and transmits multiple light pulse signals to the target direction, according to The multiple light pulse signals determine the distance of the target;
  • the camera 610 is also used to focus on the target according to the distance determined by the distance measuring device.
  • the distance measurement device 620 determining the distance of the target according to the multiple optical pulse signals, reference may be made to the distance measurement method 300 above. Since the distance measuring device 620 determines the distance of the target based on multiple light pulse signals, the measured distance of the target is more accurate. Based on the distance measured by the distance measuring device 620, the camera 610 can focus more clearly on objects that are farther away. .
  • the distance measurement method, the distance measurement device and the movable platform count the measurement results of multiple measurement processes to determine the distance of the measured object, without increasing the laser emission power, and within the range of safety regulations , Achieve a longer measurement distance and higher measurement accuracy at a lower cost.
  • the disclosed device and method can be implemented in other ways.
  • the device embodiments described above are merely illustrative.
  • the division of the units is only a logical function division, and there may be other divisions in actual implementation, for example, multiple units or components can be combined or It can be integrated into another device, or some features can be ignored or not implemented.
  • the various component embodiments of the present invention may be implemented by hardware, or by software modules running on one or more processors, or by a combination of them.
  • a microprocessor or a digital signal processor (DSP) may be used in practice to implement some or all of the functions of some modules according to the embodiments of the present invention.
  • DSP digital signal processor
  • the present invention can also be implemented as a device program (for example, a computer program and a computer program product) for executing part or all of the methods described herein.
  • Such a program for implementing the present invention may be stored on a computer-readable storage medium, or may have the form of one or more signals.
  • Such a signal can be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

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Abstract

一种测距方法、测距装置和可移动平台，该方法（300）包括：重复执行多次测量过程，该测量过程包括：在一次测量窗口中，发射光脉冲信号，接收回光脉冲信号，将该回光脉冲信号转换为电信号，记录该测量窗口中多个时间段内电信号触发预设阈值的计数（S310）；对多次该测量过程所记录的计数进行统计，以得到每个时间段在多次测量窗口内电信号触发预设阈值的总计数（S320）；根据多个时间段的该总计数的大小确定回光脉冲信号的接收时间，并根据该接收时间与该光脉冲信号的发射时间之间的间隔计算被测物的距离（S330）。该方法和装置能够以较低的成本实现更远的测量距离和更高的测量精度。

Description

测距方法、测距装置和可移动平台
说明书
技术领域
本发明总体上涉及激光测距技术领域，更具体地涉及一种测距方法、测距装置和可移动平台。
背景技术
激光测距装置是利用调制激光的某个参数实现对目标的距离测量的仪器。激光测距装置的典型测距方法包括脉冲法和相位法两种。
其中，脉冲法包括向被测物发射出一束或一序列短暂的激光脉冲，接收目标反射的激光脉冲，测定激光束从发射到接收的时间间隔，从而计算出从激光测距装置到目标的距离。其中，通常采用高频率的时钟驱动计时器对收发脉冲之间的时间进行计时，时钟的周期直接决定了测量的精度，达到毫米级别的测量所需的硬件成本非常高。
发明内容
在发明内容部分中引入了一系列简化形式的概念，这将在具体实施方式部分中进一步详细说明。本发明的发明内容部分并不意味着要试图限定出所要求保护的技术方案的关键特征和必要技术特征，更不意味着试图确定所要求保护的技术方案的保护范围。
针对现有技术的不足，本发明实施例第一方面提供一种测距方法，包括：
重复执行多次测量过程，所述测量过程包括：在一次测量窗口中，发射光脉冲信号，接收回光脉冲信号，将所述回光脉冲信号转换为电信号，记录所述测量窗口中多个时间段内电信号触发预设阈值的计数；
对多次所述测量过程所记录的所述计数进行统计，以得到每个所述时间段在多次测量窗口内所述电信号触发所述预设阈值的总计数；
根据多个时间段的所述总计数的大小确定回光脉冲信号的接收时间，并根据所述接收时间与所述光脉冲信号的发射时间之间的间隔计算被测物的距 离。
本发明实施例第二方面提供一种测距装置，所述测距装置包括发射模块、接收模块、采样模块、运算模块以及控制模块，其中：
所述控制模块用于控制所述发射模块、所述接收模块以及所述采样模块执行多次测量过程，所述测量过程包括：在一次测量窗口中，
所述发射模块用于发射光脉冲信号；
所述接收模块用于接收回光脉冲信号，并将所述回光脉冲信号转换为电信号；
所述采样模块用于记录所述测量窗口中多个时间段内所述电信号触发预设阈值的计数；
所述运算模块用于对多次所述测量过程所记录的所述计数进行统计，以得到每个所述时间段内所述电信号触发所述预设阈值的总计数；以及根据多个时间段的所述总计数的大小确定回光脉冲信号的接收时间，并根据所述发射时间与所述接收时间的差值计算被测物的距离。
本发明实施例第三方面提供一种可移动平台，所述可移动平台上搭载有相机和上述的测距装置；所述相机根据所述测距装置测得的距离进行对焦。
本发明实施例第四方面提供一种可移动平台，所述可移动平台上搭载有相机和测距装置，其中：
所述相机用于根据视场画面确定目标；
所述测距装置用于根据所述目标在所述视场画面中的位置确定目标方向，并向所述目标方向发射多次光脉冲信号，根据所述多次光脉冲信号确定目标的距离；
所述相机还用于根据所述测距装置确定的距离对所述目标进行对焦。
根据本发明实施例的测距方法、测距装置和可移动平台能够以较低成本实现更远的测量距离和更高的测量精度。
附图说明
图1示出了本发明一实施例中的测距装置的架构框图；
图2示出了本发明一实施例中的测距装置的结构示意图；
图3示出了本发明一实施例的测距方法的示意性流程图；
图4示出了根据本发明一实施例的噪声大小与统计次数的变化曲线；
图5示出了根据本发明一实施例的单次测量以及统计多次测量结果得到的信号大小随时间的变化关系；
图6为根据本发明一实施例的可移动平台的示意性框图。
具体实施方式
为了使得本发明的目的、技术方案和优点更为明显，下面将参照附图详细描述根据本发明的示例实施例。显然，所描述的实施例仅仅是本发明的一部分实施例，而不是本发明的全部实施例，应理解，本发明不受这里描述的示例实施例的限制。基于本发明中描述的本发明实施例，本领域技术人员在没有付出创造性劳动的情况下所得到的所有其它实施例都应落入本发明的保护范围之内。
在下文的描述中，给出了大量具体的细节以便提供对本发明更为彻底的理解。然而，对于本领域技术人员而言显而易见的是，本发明可以无需一个或多个这些细节而得以实施。在其他的例子中，为了避免与本发明发生混淆，对于本领域公知的一些技术特征未进行描述。
应当理解的是，本发明能够以不同形式实施，而不应当解释为局限于这里提出的实施例。相反地，提供这些实施例将使公开彻底和完全，并且将本发明的范围完全地传递给本领域技术人员。
在此使用的术语的目的仅在于描述具体实施例并且不作为本发明的限制。在此使用时，单数形式的“一”、“一个”和“所述/该”也意图包括复数形式，除非上下文清楚指出另外的方式。还应明白术语“组成”和/或“包括”，当在该说明书中使用时，确定所述特征、整数、步骤、操作、元件和/或部件的存在，但不排除一个或更多其它的特征、整数、步骤、操作、元件、部件和/或组的存在或添加。在此使用时，术语“和/或”包括相关所列项目的任何及所有组合。
为了彻底理解本发明，将在下列的描述中提出详细的结构，以便阐释本发明提出的技术方案。本发明的可选实施例详细描述如下，然而除了这些详细描述外，本发明还可以具有其他实施方式。
下面结合附图，对本申请的测距方法、测距装置及可移动平台进行详细说明。在不冲突的情况下，下述的实施例及实施方式中的特征可以相互 组合。
首先参考图1和图2对本发明实施例中的一种测距装置的结构做详细的示例性地描述，测距装置包括激光雷达，该测距装置仅作为示例，对于其他适合的测距装置也可以应用于本申请。该测距装置可以用于执行本文中的测距方法。该测距装置可以是激光雷达、激光测距设备等电子设备。在一种实施方式中，测距装置用于感测外部环境信息，例如，环境目标的距离信息、方位信息、反射强度信息、速度信息等。一种实现方式中，测距装置可以通过测量测距装置和探测物之间光传播的时间，即光飞行时间(Time-of-Flight，TOF)，来探测探测物到测距装置的距离。
为了便于理解，以下将结合图1所示的测距装置100对测距的工作流程进行举例描述。
如图1所示，测距装置100包括发射模块110、接收模块120、采样模块130、运算模块140以及控制模块150。
具体地，发射模块110可以出射光脉冲序列(例如激光脉冲序列)。接收模块120可以接收经过被探测物反射的光脉冲序列，也即通过其获得回波信号的脉冲波形，并对该光脉冲序列进行光电转换，以得到电信号，再对电信号进行处理之后可以输出给采样模块130。采样模块130可以对电信号进行采样，以获取采样结果。运算模块140可以基于采样模块130的采样结果，以确定测距装置100与被探测物之间的距离，也即深度。控制模块150可以实现对其他电路的控制，例如，可以控制各个电路的工作时间和/或对各个电路进行参数设置等。
应理解，虽然图1示出的测距装置中包括一个发射模块、一个接收模块、一个采样模块和一个运算模块，用于出射一路光束进行探测，但是本申请实施例并不限于此，发射模块、接收模块、采样模块、运算模块中的任一种电路的数量也可以是至少两个，用于沿相同方向或分别沿不同方向出射至少两路光束；其中，该至少两束光路可以是同时出射，也可以是分别在不同时刻出射。一个示例中，该至少两个发射模块中的发光芯片封装在同一个模块中。例如，每个发射模块包括一个激光发射芯片，该至少两个发射模块中的激光发射芯片中的die封装到一起，容置在同一个封装空 间中。
一些实现方式中，除了图1所示的电路，测距装置100还可以包括扫描模块，用于将发射模块出射的至少一路光脉冲序列(例如激光脉冲序列)改变传播方向出射，以对视场进行扫描。示例性地，所述扫描模块在测距装置的视场内的扫描区域随着时间的累积而增加。
其中，可以将包括发射模块110、接收模块120、采样模块130和运算模块140的模块，或者，包括发射模块110、接收模块120、采样模块130、运算模块140和控制电路150的模块称为测距模块，该测距模块可以独立于其他模块，例如，扫描模块。
测距装置中可以采用同轴光路，也即测距装置出射的光束和经反射回来的光束在测距装置内共用至少部分光路。例如，发射模块出射的至少一路激光脉冲序列经扫描模块改变传播方向出射后，经探测物反射回来的激光脉冲序列经过扫描模块后入射至接收模块。或者，测距装置也可以采用异轴光路，也即测距装置出射的光束和经反射回来的光束在测距装置内分别沿不同的光路传输。图2示出了本发明的测距装置采用同轴光路的一种实施例的示意图。
测距装置200包括测距模块210，测距模块210包括发射器203(可以包括上述的发射模块)、准直元件204、探测器205(可以包括上述的接收模块、采样模块和运算模块)和光路改变元件206。测距模块210用于发射光束，且接收回光，将回光转换为电信号。其中，发射器203可以用于发射光脉冲序列。在一个实施例中，发射器203可以发射激光脉冲序列。可选的，发射器203发射出的激光束为波长在可见光范围之外的窄带宽光束。准直元件204设置于发射器的出射光路上，用于准直从发射器203发出的光束，将发射器203发出的光束准直为平行光出射至扫描模块。准直元件还用于会聚经探测物反射的回光的至少一部分。该准直元件204可以是准直透镜或者是其他能够准直光束的元件。
在图2所示实施例中，通过光路改变元件206来将测距装置内的发射光路和接收光路在准直元件204之前合并，使得发射光路和接收光路可以共用同一个准直元件，使得光路更加紧凑。在其他的一些实现方式中，也可以是发射器203和探测器205分别使用各自的准直元件，将光路改变元 件206设置在准直元件之后的光路上。
在图2所示实施例中，由于发射器203出射的光束的光束孔径较小，测距装置所接收到的回光的光束孔径较大，所以光路改变元件可以采用小面积的反射镜来将发射光路和接收光路合并。在其他的一些实现方式中，光路改变元件也可以采用带通孔的反射镜，其中该通孔用于透射发射器203的出射光，反射镜用于将回光反射至探测器205。这样可以减小采用小反射镜的情况中小反射镜的支架会对回光的遮挡。
在图2所示实施例中，光路改变元件偏离了准直元件204的光轴。在其他的一些实现方式中，光路改变元件也可以位于准直元件204的光轴上。
测距装置200还包括扫描模块202。扫描模块202放置于测距模块210的出射光路上，扫描模块202用于改变经准直元件204出射的准直光束219的传输方向并投射至外界环境，并将回光投射至准直元件204。回光经准直元件204汇聚到探测器205上。
在一个实施例中，扫描模块202可以包括至少一个光学元件，用于改变光束的传播路径，其中，该光学元件可以通过对光束进行反射、折射、衍射等等方式来改变光束传播路径，例如所述光学元件包括至少一个具有非平行的出射面和入射面的光折射元件。例如，扫描模块202包括透镜、反射镜、棱镜、振镜、光栅、液晶、光学相控阵(Optical Phased Array)或上述光学元件的任意组合。一个示例中，至少部分光学元件是运动的，例如通过驱动模块来驱动该至少部分光学元件进行运动，该运动的光学元件可以在不同时刻将光束反射、折射或衍射至不同的方向。在一些实施例中，扫描模块202的多个光学元件可以绕共同的轴209旋转或振动，每个旋转或振动的光学元件用于不断改变入射光束的传播方向。在一个实施例中，扫描模块202的多个光学元件可以以不同的转速旋转，或以不同的速度振动。在另一个实施例中，扫描模块202的至少部分光学元件可以以基本相同的转速旋转。在一些实施例中，扫描模块的多个光学元件也可以是绕不同的轴旋转。在一些实施例中，扫描模块的多个光学元件也可以是以相同的方向旋转，或以不同的方向旋转；或者沿相同的方向振动，或者沿不同的方向振动，在此不作限制。
在一个实施例中，扫描模块202包括第一光学元件214和与第一光学 元件214连接的驱动器216，驱动器216用于驱动第一光学元件214绕转动轴209转动，使第一光学元件214改变准直光束219的方向。第一光学元件214将准直光束219投射至不同的方向。在一个实施例中，准直光束219经第一光学元件改变后的方向与转动轴209的夹角随着第一光学元件214的转动而变化。在一个实施例中，第一光学元件214包括相对的非平行的一对表面，准直光束219穿过该对表面。在一个实施例中，第一光学元件214包括厚度沿至少一个径向变化的棱镜。在一个实施例中，第一光学元件214包括楔角棱镜，对准直光束219进行折射。
在一个实施例中，扫描模块202还包括第二光学元件215，第二光学元件215绕转动轴209转动，第二光学元件215的转动速度与第一光学元件214的转动速度不同。第二光学元件215用于改变第一光学元件214投射的光束的方向。在一个实施例中，第二光学元件215与另一驱动器217连接，驱动器217驱动第二光学元件215转动。第一光学元件214和第二光学元件215可以由相同或不同的驱动器驱动，使第一光学元件214和第二光学元件215的转速和/或转向不同，从而将准直光束219投射至外界空间不同的方向，可以扫描较大的空间范围。在一个实施例中，控制器218控制驱动器216和217，分别驱动第一光学元件214和第二光学元件215。第一光学元件214和第二光学元件215的转速可以根据实际应用中预期扫描的区域和样式确定。驱动器216和217可以包括电机或其他驱动器。
在一个实施例中，第二光学元件215包括相对的非平行的一对表面，光束穿过该对表面。在一个实施例中，第二光学元件215包括厚度沿至少一个径向变化的棱镜。在一个实施例中，第二光学元件215包括楔角棱镜。
一个实施例中，扫描模块202还包括第三光学元件(图未示)和用于驱动第三光学元件运动的驱动器。可选地，该第三光学元件包括相对的非平行的一对表面，光束穿过该对表面。在一个实施例中，第三光学元件包括厚度沿至少一个径向变化的棱镜。在一个实施例中，第三光学元件包括楔角棱镜。第一、第二和第三光学元件中的至少两个光学元件以不同的转速和/或转向转动。
在一个实施例中，所述扫描模块包括在所述光脉冲序列的出射光路上依次排布的2个或3个所述光折射元件。可选地，所述扫描模块中的至少 2个所述光折射元件在扫描过程中旋转，以改变所述光脉冲序列的方向。
所述扫描模块在至少部分不同时刻的扫描路径不同，扫描模块202中的各光学元件旋转可以将光投射至不同的方向，例如投射的光211的方向和方向213，如此对测距装置200周围的空间进行扫描。当扫描模块202投射出的光211打到探测物201时，一部分光被探测物201沿与投射的光211相反的方向反射至测距装置200。探测物201反射的回光212经过扫描模块202后入射至准直元件204。
探测器205与发射器203放置于准直元件204的同一侧，探测器205用于将穿过准直元件204的至少部分回光转换为电信号。
一个实施例中，各光学元件上镀有增透膜。可选的，增透膜的厚度与发射器203发射出的光束的波长相等或接近，能够增加透射光束的强度。
一个实施例中，测距装置中位于光束传播路径上的一个元件表面上镀有滤光层，或者在光束传播路径上设置有滤光器，用于至少透射发射器所出射的光束所在波段，反射其他波段，以减少环境光给接收器带来的噪音。
在一些实施例中，发射器203可以包括激光二极管，通过激光二极管发射纳秒级别的激光脉冲。进一步地，可以根据接收到的激光脉冲确定探测物201到测距装置200的距离。测距装置200探测到的距离和方位可以用于遥感、避障、测绘、建模、导航等。
测距装置采用的测距方法一般包括脉冲法和相位法两种。其中，脉冲法激光测距装置是在工作时向被测物发射出一束或一序列短暂的激光脉冲，由光电元件接收目标反射的激光束，计时器测定激光束从发射到接收的时间间隔，从而计算出从测距装置到被测物的距离。通过一个高频率的时钟驱动计时器对收发脉冲之间的时间进行计时，时钟的周期直接决定了测量的精度，目前较好的测距装置的测量精度可以达到十厘米，若要达到毫米级别的测量，采用脉冲式测距所需的硬件成本非常高。
相位法激光测距装置是对发射的激光脉冲的光强进行调制，测量发射光和反射光在空间中传播时发生的相位差来检测距离，精度可以达到毫米、微米级。对于采用单一调制频率的测距仪，只能分辨出2π以内的相位，因此无法测得超过一个周期的距离。例如，当调制信号的频率为1MHz时，对应的量程即为150m，如果实际距离值超过150m，则测量结果仍然在 150m之内。调制频率会影响相位式测距装置的最大量程，调制频率越小，则量程越大；然而，当系统测相分辨率一定时，调制频率越小(调制信号周期越大)，则测量精度越低。因此在单一调制频率的情况下，大量程与高精度无法同时满足。
相位法测得的距离L＝c*φ/2π*T/2，其中c为光速，φ为收发脉冲之间的相位差，T为调制信号周期。当发射的激光束功率足够时，量程可达几十公里甚至更远，但大功率激光对人体有伤害，不符合相关使用规范。
由此可见，无论是采用脉冲法还是测距法的激光测距装置，都受到硬件条件的限制而难以同时提高其测量距离和测量精度。
鉴于上述问题的存在，本发明实施例提供一种测距方法，该方法包括：重复执行多次测量过程，所述测量过程包括：在一次测量窗口中，发射光脉冲信号，接收回光脉冲信号，将所述回光脉冲信号转换为电信号，记录所述测量窗口中多个时间段内电信号触发预设阈值的计数；对多次所述测量过程所记录的所述计数进行统计，以得到每个所述时间段在多次测量窗口内所述电信号触发所述预设阈值的总计数；根据多个时间段的所述总计数的大小确定回光脉冲信号的接收时间，并根据所述接收时间与所述光脉冲信号的发射时间之间的间隔计算被测物的距离。通过本发明实施例的测距方法可在安规限制范围内，以较低的成本实现更远的测量距离和更高的测量精度。
下面，参考图3对本发明的测距方法进行描述，其中，图3示出了本发明一个实施例中的测距方法300的示意性流程图。
如图3所示，本发明实施例的测距方法300包括如下步骤：
首先，在步骤S310中，重复执行多次测量过程，所述测量过程包括：在一次测量窗口中，发射光脉冲信号，接收回光脉冲信号，将所述回光脉冲信号转换为电信号，记录所述测量窗口中多个时间段内电信号触发预设阈值的计数。
参照图1所示的测距装置，在每个测量窗口中，发射模块和接收模块同时开启，发射模块发射光脉冲信号，接收模块接收光脉冲信号经被测物反射的回光脉冲信号并将其转换为电信号，采样模块记录该测量窗口中每 个时间段内电信号触发预设阈值的次数。当测距装置具有多个发射模块和多个接收模块时，在每个测量窗口中，相对应的发射模块和接收模块同时开启。
在每次测量过程中，由于受到噪声的影响，接收模块接收到的不止包括被测物返回的回光脉冲信号，还包括噪声信号。噪声信号和回光脉冲信号分布在测量窗口中的多个时间段内，当距离较远或被测物的反射率较低时，回光脉冲信号较弱，难以通过单次测量分辨出回光脉冲信号和噪声信号，因而本发明实施例的测距方法采用统计学的方式确定回光脉冲信号所在的时间段。
示例性地，在每个测量窗口中，接收模块将接收到的光学信号转化为电信号以后，还可以将电信号送入一级或二级放大电路进行放大，之后将放大后的电信号送入采样电路。采样电路将测量窗口划分为多个时间段，并将电信号与预设阈值进行比较，以统计每个时间段内电信号触发预设阈值的次数。示例性地，每次测量过程的测量窗口长度相等，每个测量窗口均被划分为N个时间段，其中N>1。
作为一种实现方式，采样模块包括比较器(例如，可以为模拟比较器(analog comparator，COMP)，用于将电信号转换为数字脉冲信号)和时间测量电路，经由一级或二级放大电路放大后的电信号经所述比较器后进入时间测量电路，由时间测量电路进行次数统计。
其中，时间测量电路可以是时间数字转换器(Time-to-Data Converter，TDC)时。其中TDC可以是独立的TDC芯片，或者是基于现场可编程门阵列(Field－Programmable Gate Array，FPGA)或特定应用集成电路(Application Specific Integrated Circuit，ASIC)或复杂可编程逻辑器件(Complex Programmable Logic Device，CPLD等可编程器件的内部延时链来实现时间测量的TDC电路，或者，采用高频时钟实现时间测量的电路结构或者计数方式实现时间测量的电路结构。
示例性地，比较器的第一输入端用于接收从放大电路输入的电信号，该电信号可以是电压信号或电流信号；比较器的第二输入端用于接收预设阈值，输入到比较器的电信号与预设阈值进行比较运算。比较器的输出信号接TDC，TDC可以测量比较器输出信号沿的时间信息，所测量时间是以 光脉冲信号的发射时间作为参考，也就是可以测量到激光信号从发射到接收之间的时间差。单次测量中，TDC可以统计每个时间段是否有电信号触发预设阈值，有触发则计数为1，没有触发则计数为0。当在某个时间段内存在0到1跳变，表示该时间段存在信号上升沿触发。
作为另一种实现方式，采样模块也可以包括模数转换器(Analog-to-Digital Converter，ADC)。输入到采样模块的模拟信号经过ADC的模数转换之后，可以输出数字信号至运算模块。
在一个实施例中，在所述多次测量过程中，所述光脉冲信号的出射方向保持不变，以确保多次测量过程采集到的是相同被测物返回的回光脉冲。
如上所述，本发明实施例的测量方法主要适用于被测物距离较远或反射率较低、即信噪比较低的情况。当被测物距离较远或反射率较低时，测距装置出射的激光脉冲照射到被测物后，返回的回光脉冲能量低，经过接收电路转换后产生的电信号大小与噪声相当甚至小于噪声，信噪比低，此时重复执行多次测量过程，采用多次测量的统计方法来提高信噪比，以得到被测物的距离。在这种情况下，通过多次测量来得到一次测量结果，降低了测量结果的刷新频率，但提高了测量准确性。
而当被测物体距离较近或反射率较高时，激光照射到物体后，返回的激光能量高，经过光电传感器转换后产生的脉冲远大于噪声，信噪比高。此时可以直接通过TDC测量脉冲的时间信息，获取回光脉冲信号的到达时间。在这种情况下，则无需重复执行多次测量过程，通过一次测量即可得到正确结果，从而避免降低测量结果的刷新频率。
因此，在一个实施例中，在执行步骤S310之前，首先判断是否需要重复执行多次测量过程。
作为示例，判断是否需要重复执行多次测量过程的方法包括：将电信号与至少两个预设阈值进行比较，例如，预设阈值至少包括一个较小的第一预设阈值和一个较大的第二预设阈值，若测量窗口内存在触发第二预设阈值的电信号，则说明回光脉冲信号较强，此时无需重复执行多次测量过程，并可以直接将电信号触发第二预设阈值的时间作为接收时间以用于计算被测物的距离。
若电信号触发第一预设阈值，但不触发第二预设阈值，换句话说，若 测量窗口内存在触发第一预设阈值的电信号，但不存在触发第二预设阈值的电信号，则说明回光脉冲信号较弱，此时重复执行多次测量过程，以提高量程。在该实施例中，步骤S310中所述的记录多个时间段内电信号触发预设阈值的计数为电信号触发第一预设阈值的计数。
在步骤S310中，执行多次测量过程的次数是固定的，也可以是可变的，例如可以根据测量结果的置信度进行自适应的调整，具体参见下文。
在步骤S320，对多次所述测量过程所记录的所述计数进行统计，以得到每个所述时间段在多次测量窗口内所述电信号触发所述预设阈值的总计数。
如上所述，每个测量窗口被划分为N个时间段，则在步骤S320中，将多个测量窗口中第1，2，3，……，N个时间段中每个时间段所记录的计数进行相加，以得到多个测量窗口的第1，2，3，……，N个时间段中电信号触发预设阈值的总计数。
由于噪声的随机性，在单次测量过程中，各个时间段中均有可能随机出现噪声信号。根据统计规律，单次测量的噪声信号具有一定随机性，单个时间段内可能出现较大的噪声信号，但统计次数越多，每个时间段的噪声大小越小，最终趋于稳定，参见图4。当统计次数足够大时，噪声大小的统计结果接近一个稳定值，噪声大小与统计次数的数学模型可表示为：Noise＝Noise0*(N0/N) 1/2，其中N0和N均为统计次数，Noise0是统计次数为N0时的噪声大小。如此，当统计次数足够大时，一定大小的回光脉冲信号叠加在稳定的噪声水平上，能够获得较高的信噪比，从而得到正确结果。
为了便于实现，本发明实施例采用计数的方式对测量结果进行统计。参照图5，其中示出了第一次测量、第二次测量、第三次测量所得的信号大小随时间的变化曲线501、502、503，以及最终的统计结果。对于同一被测物，回光脉冲的大小和所分布的时间段基本固定，即基本每次测量相应时间段内均存在触发预设阈值的电信号；而其他时间段接收到的是噪声信号，其具有随机性。例如，参照图5，在第一次测量中，在T2、T5、T8时间段均有电信号触发第一预设阈值Th1，因此将这几个时间段的计数为1，其他时间段计数为0，其中T2、T5时间段接收到的为噪声信号，T8时 间段接收到的为回光脉冲信号；在第二次测量中，由于噪声信号的接收时间是随机的，而回光脉冲信号的接收时间是固定的，因而在T1、T4时间段噪声信号的电信号触发第一预设阈值Th1，T8时间段回光脉冲信号的电信号触发第一预设阈值Th1，因此将T1、T4、T8时间段的计数为1，其他时间段计数为0；在第三次测量中，T3时间段噪声信号的电信号触发第一预设阈值Th1，T8时间段回光脉冲信号的电信号触发第一预设阈值Th1，因此将T3、T8时间段的计数为1，其他时间段计数为0；以此类推，在T8时间段基本每次测量均能接收到回光脉冲信号，而在其他时间段只能随机地接收到噪声信号。因而随着统计次数的增加，参见图4的曲线，在其他时间段噪声信号的大小逐渐降低并趋于稳定，因而在T8时间段的信号大小的统计结果将高于其他时间段。当体现在计数值上时，回光脉冲信号所对应的时间段的计数将明显高于其他时间段的计数，因此，即使回光脉冲信号的电信号的大小不足以触发第二预设阈值Th2，也能通过统计的方式确定回光脉冲信号的接收时间。
因此，在步骤S330，根据多个时间段的所述总计数的大小确定回光脉冲信号的接收时间，并根据所述接收时间与所述光脉冲信号的发射时间之间的间隔计算被测物的距离。
作为一种实现方式，可以分别对每个时间段的总计数进行比较，并将总计数最多的时间段确定为接收时间。如上所述，采样电路所测量的时间是以光脉冲信号的发射时间作为参考的，因而确定总计数最多的时间段后，可以获得接收时间与发射时间之间的间隔，并根据激光信号从发射到接收之间的时间间隔计算被测物到测距装置的距离，被测物的距离L＝c*T/2，其中c为光速，T为接收时间与发射时间之间的间隔。
此外，由于出射的光斑具有一定大小，可能照射到不止一个被测物上，因而在另一个实施例中，还可以将总计数最多的多个时间段确定为接收时间，分别采用每个接收时间计算得到被测物的距离，以实现测量多个被测物的距离的功能。当确定多个接收时间时，可以将总计数最多的M个时间段确定为接收时间，其中M为预设值。或者，也可以根据信噪比和置信度确定用于确定接收时间的时间段的个数，具体参见下文。
由于采样的随机抖动，多次采样过程中，每次回光脉冲信号可能会随 机分布在几个相邻的时间段，使得正确的时间段计数下降，等效于能量分散，信噪比下降。因而作为一种实现方式，可以采用“滑窗法”，将相邻的至少两个时间段作为一组时间段，统计每组时间段的所述总计数之和，并比较多组时间段的所述总计数之和，在总计数之和最多的一组或多组时间段内确定所述接收时间。当然，在实际计算时，也可以先在每个测量窗口内统计每组时间段的总计数，再统计多个测量窗口内的每组时间段的总计数之和。
其中，作为示例，可以将每个测量窗口内的第1、2、3个时间段作为一组，第4、5、6个时间段作为一组，第7、8、9个时间段作为一组，以此类推，即每组时间段包括若干个不同的时间段。以这种方式进行划分时，可以确定总计数最高的一组时间段，并将该组时间段作为回光脉冲信号的接收时间。
或者，也可以将每个测量窗口内的第1、2、3个时间段作为一组，第2、3、4个时间段作为一组，第3、4、5个时间段作为一组，也就是说，相邻两组时间段之间存在部分重叠。以这种方式进行划分时，可以将每组时间段的总计数拟合得到一条总计数随时间变化的曲线，并将曲线的峰值所对应的时间点作为回光脉冲信号的接收时间。
可以理解的是，在一些情况下，执行多次测量的过程中可能没有接收到被测物返回的回光脉冲信号。当不存在回光脉冲信号时，各个时间段内接收到噪声信号的概率基本相同，多次测量后各个时间段的总计数相差很小，信噪比很低。只有存在回光脉冲信号时，多次测量后与回光脉冲信号对应的时间段内的总计数明显大于其他时间段内的总计数。因此在确定一个或多个时间段以后，可以计算将该时间段作为测量结果的信噪比，信噪比的大小可作为测量结果的置信度。当置信度高于阈值时，才认为测量结果可信。
具体地，可以根据总计数最多的一个或多个时间段内的总计数与总计数的平均值的比较结果计算步骤S330中所确定的接收时间的置信度。具体地，置信度(即信噪比)SNR＝(C-CM)/CM，其中C为作为测量结果的时间段的计数值，CM为所有时间段的计数值的平均值。
类似地，当采用上述“滑窗法”进行统计时，可以根据总计数最多的 一组或多组时间段内的总计数之和与测量窗口内各组时间段的总计数之和的平均值的比较结果确定接收时间的置信度。
在一个实施例中，当置信度低于预设的置信度阈值时，则认为采用多次测量的统计方式仍然不能使信噪比满足要求，因而放弃采用接收时间计算被测物的距离，此时可以认为没有测量到任何物体。
在另一个实施例中，还可以根据置信度动态调整执行所述测量过程的计数，通过增加测量次数来提高置信度，保证测量结果的可靠性。
具体地，假设初始的测量结果刷新率为1KHz，在该刷新率下可以判断测量结果的置信度是否低于预设的置信度阈值，若置信度低于预设的置信度阈值，则增加执行测量过程的计数，例如将刷新率降低至500Hz。增加测量次数后，可以再次计算测量结果的置信度，若置信度高于置信度阈值，则采用新的接收时间计算被测物的距离，若置信度仍低于置信度阈值，则可以继续降低刷新率，直到置信度高于阈值。或者，若执行测量过程的次数达到预设的最高次数，即测量结果的刷新率达到预先设置的下限时，置信度仍低于预设的置信度阈值，则放弃采用所述接收时间计算被测物的距离，此时可以认为没有测量到任何物体。
在一些实施例中，当将总计数最多的多个时间段或多组时间段作为接收时间时，可以分别计算其中每个时间段或每组时间段的置信度，并保留其中置信度高于置信度阈值的一个或多个时间段，或者一组或多组时间段，并放弃采用置信度低于置信度阈值的时间段计算被测物的距离。
综上，本发明实施例的测距方法300通过采用对多次测量结果进行统计的方式，可以在安规限制范围内，以适当降低结果刷新频率为代价，以较低的成本极大地提升量程。实际应用中，量程为20％反射率、300米的脉冲式测距装置，采用本发明实施例的测距方法后可测量到20％反射率、1500米的物体。
以上示例性地描述了根据本发明实施例的测距方法。下面返回图1，描述根据本发明实施例提供的测距装置100。根据本发明实施例的测距装置100用于实现上文中描述的根据本发明实施例的测距方法300。为了简洁，下文中仅对测距装置100的主要结构和功能进行描述，而省略上文中已经描述的部分具体细节。
如图1所示，测距装置100包括发射模块110、接收模块120、采样模块130、运算模块140以及控制模块150，其中，控制模块150用于控制发射模块110、接收模块120以及采样模块130执行多次测量过程，所述测量过程包括：在一次测量窗口中，发射模块110用于发射光脉冲信号；接收模块120用于接收回光脉冲信号，并将所述回光脉冲信号转换为电信号；采样模块130用于记录所述测量窗口中多个时间段内所述电信号触发预设阈值的计数；运算模块140用于对多次测量过程所记录的计数进行统计，以得到每个时间段内所述电信号触发预设阈值的总计数，以及根据多个时间段的总计数的大小确定回光脉冲信号的接收时间，并根据发射时间与接收时间的差值计算被测物的距离。
在一个实施例中，根据多个时间段的所述总计数确定回光脉冲信号的接收时间可以实现为：比较多个所述时间段的所述总计数；将总计数最多的一个或多个时间段确定为所述接收时间。
在一个实施例中，根据多个时间段的所述总计数确定回光脉冲信号的接收时间可以实现为：将相邻的至少两个所述时间段作为一组时间段，统计每组时间段的所述总计数之和；比较多组时间段的所述总计数之和，在总计数之和最多的一组或多组时间段内确定所述接收时间。
在一个实施例中，运算模块140还用于根据总计数最多的一个或多个时间段内的总计数与总计数的平均值的比较结果确定接收时间的置信度。
在一个实施例中，运算模块140还用于：根据所述总计数最多的一组或多组时间段内的所述总计数之和与总计数之和的平均值的比较结果确定所述接收时间的置信度。作为示例，在所述置信度低于预设的置信度阈值时，运算模块140放弃采用所述接收时间计算被测物的距离。
在一个实施例中，控制模块150还可以根据所述置信度动态调整执行所述测量过程的次数。具体地，判断所述置信度是否低于预设的置信度阈值，若所述置信度低于所述预设的置信度阈值，则增加执行所述测量过程的次数。
进一步地，若执行测量过程的次数达到预设的最高次数时，所述置信度仍低于所述预设的置信度阈值，则所述运算模块放弃采用所述接收时间计算被测物的距离。
在一个实施例中，所述预设阈值至少包括第一预设阈值和第二预设阈值，所述第一预设阈值小于所述第二预设阈值，若所述电信号触发所述第一预设阈值，但不触发所述第二预设阈值，则所述控制模块控制执行多次所述测量 过程；所述记录多个时间段内所述电信号触发所述预设阈值的计数包括记录所述多个时间段内所述电信号触发所述第一预设阈值的计数。
在一个实施例中，若所述电信号触发所述第二预设阈值，则所述运算模块将所述电信号触发所述第二预设阈值的时间作为所述接收时间，即通过单次测量获得测量结果，而无需执行多次测量。
根据本发明实施例另一方面还提供了一种可移动平台。下面结合图6描述本发明实施例所提供的可移动平台600的示意性框图。在某些实施方式中，可移动平台包括无人飞行器、汽车、遥控车、机器人、船中的至少一种。如图6所示，可移动平台上搭载有相机610和测距装置620，所述测距装置620的具体细节可以参照上文中的测距装置100。测距装置620可以采用上文所述的测距方法300测得被测物的距离，并发送至相机610，相机620根据所述测距装置620测得的距离进行对焦，以采集被测物的图像。由于测距装置620具有较高的精度和较远的量程，因而相机610可以对更远的物体进行更清晰的对焦。
根据本发明实施例还提供了一种可移动平台。继续参照图6所示，该可移动平台上搭载有相机610和测距装置620。其中，相机610用于根据视场画面确定目标；测距装置620用于根据所述目标在所述视场画面中的位置确定目标方向，并向所述目标方向发射多次光脉冲信号，根据所述多次光脉冲信号确定目标的距离；相机610还用于根据所述测距装置确定的距离对所述目标进行对焦。测距装置620根据多次光脉冲信号确定目标的距离的具体细节可以参照上文中的测距方法300。由于测距装置620根据多次光脉冲信号确定目标的距离，因而测得的目标的距离更为准确，基于测距装置620测得的距离，相机610可以对更远的物体进行更清晰的对焦。
基于上面的描述，根据本发明实施例的测距方法、测距装置和可移动平台统计多次测量过程的测量结果来确定被测物的距离，无需增加激光发射功率，在安规限制范围内，以较低的成本实现了更远的测量距离和更高的测量精度。
尽管这里已经参考附图描述了示例实施例，应理解上述示例实施例仅仅是示例性的，并且不意图将本发明的范围限制于此。本领域普通技术人员可以在其中进行各种改变和修改，而不偏离本发明的范围和精神。所有 这些改变和修改意在被包括在所附权利要求所要求的本发明的范围之内。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，能够以电子硬件、或者计算机软件和电子硬件的结合来实现。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本发明的范围。
在本申请所提供的几个实施例中，应该理解到，所揭露的设备和方法，可以通过其它的方式实现。例如，以上所描述的设备实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个设备，或一些特征可以忽略，或不执行。
在此处所提供的说明书中，说明了大量具体细节。然而，能够理解，本发明的实施例可以在没有这些具体细节的情况下实践。在一些实例中，并未详细示出公知的方法、结构和技术，以便不模糊对本说明书的理解。
类似地，应当理解，为了精简本发明并帮助理解各个发明方面中的一个或多个，在对本发明的示例性实施例的描述中，本发明的各个特征有时被一起分组到单个实施例、图、或者对其的描述中。然而，并不应将该本发明的方法解释成反映如下意图：即所要求保护的本发明要求比在权利要求中所明确记载的特征更多的特征。更确切地说，如相应的权利要求书所反映的那样，其发明点在于可以用少于某个公开的单个实施例的所有特征的特征来解决相应的技术问题。因此，遵循具体实施方式的权利要求书由此明确地并入该具体实施方式，其中权利要求本身都作为本发明的单独实施例。
本领域的技术人员可以理解，除了特征之间相互排斥之外，可以采用任何组合对本说明书(包括伴随的权利要求、摘要和附图)中公开的所有特征以及如此公开的任何方法或者设备的所有过程或单元进行组合。除非另外明确陈述，本说明书(包括伴随的权利要求、摘要和附图)中公开的特征可以由提供相同、等同或相似目的的替代特征来代替。
此外，本领域的技术人员能够理解，尽管在此所述的一些实施例包括其它实施例中所包括的某些特征而不是其它特征，但是不同实施例的特征 的组合意味着处于本发明的范围之内并且形成不同的实施例。例如，在权利要求书中，所要求保护的实施例的任意之一都可以以任意的组合方式来使用。
本发明的各个部件实施例可以以硬件实现，或者以在一个或者多个处理器上运行的软件模块实现，或者以它们的组合实现。本领域的技术人员应当理解，可以在实践中使用微处理器或者数字信号处理器(DSP)来实现根据本发明实施例的一些模块的一些或者全部功能。本发明还可以实现为用于执行这里所描述的方法的一部分或者全部的装置程序(例如，计算机程序和计算机程序产品)。这样的实现本发明的程序可以存储在计算机可读存储介质上，或者可以具有一个或者多个信号的形式。这样的信号可以从因特网网站上下载得到，或者在载体信号上提供，或者以任何其他形式提供。
应该注意的是上述实施例对本发明进行说明而不是对本发明进行限制，并且本领域技术人员在不脱离所附权利要求的范围的情况下可设计出替换实施例。在权利要求中，不应将位于括号之间的任何参考符号构造成对权利要求的限制。本发明可以借助于包括有若干不同元件的硬件以及借助于适当编程的计算机来实现。在列举了若干装置的单元权利要求中，这些装置中的若干个可以是通过同一个硬件项来具体体现。单词第一、第二、以及第三等的使用不表示任何顺序。可将这些单词解释为名称。
以上所述，仅为本发明的具体实施方式或对具体实施方式的说明，本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。本发明的保护范围应以权利要求的保护范围为准。

Claims (26)

  1. 一种测距方法，其特征在于，所述方法包括：
    重复执行多次测量过程，所述测量过程包括：在一次测量窗口中，发射光脉冲信号，接收回光脉冲信号，将所述回光脉冲信号转换为电信号，记录所述测量窗口中多个时间段内电信号触发预设阈值的计数；
    对多次所述测量过程所记录的所述计数进行统计，以得到每个所述时间段在多次测量窗口内所述电信号触发所述预设阈值的总计数；
    根据多个时间段的所述总计数的大小确定回光脉冲信号的接收时间，并根据所述接收时间与所述光脉冲信号的发射时间之间的间隔计算被测物的距离。
  2. 如权利要求1所述的方法，其特征在于，所述根据多个时间段的所述总计数确定回光脉冲信号的接收时间，包括：
    比较多个所述时间段的所述总计数；
    将总计数最多的一个或多个时间段确定为所述接收时间。
  3. 如权利要求1所述的方法，其特征在于，所述根据多个时间段的所述总计数确定回光脉冲信号的接收时间包括：
    将相邻的至少两个所述时间段作为一组时间段，统计每组时间段的所述总计数之和；
    比较多组时间段的所述总计数之和，在总计数之和最多的一组或多组时间段内确定所述接收时间。
  4. 如权利要求2所述的方法，其特征在于，所述方法还包括：
    根据所述总计数最多的一个或多个时间段内的所述总计数与总计数的平均值的比较结果确定所述接收时间的置信度。
  5. 如权利要求3所述的方法，其特征在于，所述方法还包括：
    根据所述总计数最多的一组或多组时间段内的所述总计数之和与总计数之和的平均值的比较结果确定所述接收时间的置信度。
  6. 如权利要求4或5所述的方法，其特征在于，当所述置信度低于预设的置信度阈值时，放弃采用所述接收时间计算被测物的距离。
  7. 如权利要求4或5所述的方法，其特征在于，所述方法还包括：根据所述置信度动态调整执行所述测量过程的次数。
  8. 如权利要求7所述的方法，其特征在于，所述根据所述置信度动态调整执行所述测量过程的次数，包括：
    判断所述置信度是否低于预设的置信度阈值，若所述置信度低于所述预设的置信度阈值，则增加执行所述测量过程的次数。
  9. 如权利要求8所述的方法，其特征在于，所述方法还包括：
    若执行所述测量过程的次数达到预设的最高次数时，所述置信度仍低于所述预设的置信度阈值，则放弃采用所述接收时间计算被测物的距离。
  10. 如权利要求1所述的方法，其特征在于，所述预设阈值至少包括第一预设阈值和第二预设阈值，所述第一预设阈值小于所述第二预设阈值，若所述电信号触发所述第一预设阈值，但不触发所述第二预设阈值，则重复执行多次所述测量过程；
    所述记录多个时间段内所述电信号触发所述预设阈值的计数包括记录所述多个时间段内所述电信号触发所述第一预设阈值的计数。
  11. 如权利要求10所述的方法，其特征在于，所述方法还包括：
    若所述电信号触发所述第二预设阈值，则将所述电信号触发所述第二预设阈值的时间作为所述接收时间。
  12. 如权利要求1所述的方法，其特征在于，在所述多次测量过程中，所述光脉冲信号的出射方向保持不变。
  13. 一种测距装置，其特征在于，所述测距装置包括发射模块、接收模块、采样模块、运算模块以及控制模块，其中：
    所述控制模块用于控制所述发射模块、所述接收模块以及所述采样模块执行多次测量过程，所述测量过程包括：在一次测量窗口中，
    所述发射模块用于发射光脉冲信号；
    所述接收模块用于接收回光脉冲信号，并将所述回光脉冲信号转换为电信号；
    所述采样模块用于记录所述测量窗口中多个时间段内所述电信号触发预设阈值的计数；
    所述运算模块用于对多次所述测量过程所记录的所述计数进行统计，以得到每个所述时间段内所述电信号触发所述预设阈值的总计数；以及根据多个时间段的所述总计数的大小确定回光脉冲信号的接收时间，并根据 所述发射时间与所述接收时间的差值计算被测物的距离。
  14. 如权利要求13所述的测距装置，其特征在于，所述根据多个时间段的所述总计数确定回光脉冲信号的接收时间包括：
    比较多个所述时间段的所述总计数；
    将总计数最多的一个或多个时间段确定为所述接收时间。
  15. 如权利要求13所述的测距装置，其特征在于，所述根据多个时间段的所述总计数确定回光脉冲信号的接收时间包括：
    将相邻的至少两个所述时间段作为一组时间段，统计每组时间段的所述总计数之和；
    比较多组时间段的所述总计数之和，在总计数之和最多的一组或多组时间段内确定所述接收时间。
  16. 如权利要求14所述的测距装置，其特征在于，所述运算模块还用于：
    根据所述总计数最多的一个或多个时间段内的总计数与总计数的平均值的比较结果确定所述接收时间的置信度。
  17. 如权利要求15所述的测距装置，其特征在于，所述运算模块还用于：
    根据所述总计数最多的一组或多组时间段内的所述总计数之和与总计数之和的平均值的比较结果确定所述接收时间的置信度。
  18. 如权利要求16或17所述的测距装置，其特征在于，所述运算模块在所述置信度低于预设的置信度阈值时，放弃采用所述接收时间计算被测物的距离。
  19. 如权利要求16或17所述的测距装置，其特征在于，所述控制模块还用于：根据所述置信度动态调整执行所述测量过程的计数。
  20. 如权利要求19所述的测距装置，其特征在于，所述根据所述置信度动态调整执行所述测量过程的计数，包括：
    判断所述置信度是否低于预设的置信度阈值，若所述置信度低于所述预设的置信度阈值，则增加执行所述测量过程的计数。
  21. 如权利要求20所述的测距装置，其特征在于，若执行所述测量过程的计数达到预设的最高计数时，所述置信度仍低于所述预设的置信度 阈值，则所述运算模块放弃采用所述接收时间计算被测物的距离。
  22. 如权利要求13所述的测距装置，其特征在于，所述预设阈值至少包括第一预设阈值和第二预设阈值，所述第一预设阈值小于所述第二预设阈值，若所述电信号触发所述第一预设阈值，但不触发所述第二预设阈值，则所述控制模块控制执行多次所述测量过程；
    所述记录多个时间段内所述电信号触发所述预设阈值的计数包括记录所述多个时间段内所述电信号触发所述第一预设阈值的计数。
  23. 如权利要求22所述的测距装置，其特征在于，若所述电信号触发所述第二预设阈值，则所述运算模块将所述电信号触发所述第二预设阈值的时间作为所述接收时间。
  24. 如权利要求13所述的测距装置，其特征在于，在所述多次测量过程中，所述光脉冲信号的出射方向保持不变。
  25. 一种可移动平台，其特征在于，所述可移动平台上搭载有相机和如权利要求13-24中任一项所述的测距装置；所述相机根据所述测距装置测得的距离进行对焦。
  26. 一种可移动平台，其特征在于，所述可移动平台上搭载有相机和测距装置，其中：
    所述相机用于根据视场画面确定目标；
    所述测距装置用于根据所述目标在所述视场画面中的位置确定目标方向，并向所述目标方向发射多次光脉冲信号，根据所述多次光脉冲信号确定目标的距离；
    所述相机还用于根据所述测距装置确定的距离对所述目标进行对焦。
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