WO2020220275A1

WO2020220275A1 - Detection circuit, detection method, distance measuring apparatus, and mobile platform

Info

Publication number: WO2020220275A1
Application number: PCT/CN2019/085221
Authority: WO
Inventors: 陈涵; 梅雄泽; 龙承辉
Original assignee: 深圳市大疆创新科技有限公司
Priority date: 2019-04-30
Filing date: 2019-04-30
Publication date: 2020-11-05
Also published as: CN112236687A

Abstract

A detection circuit (130), a detection method, a distance measuring apparatus (200), and a mobile platform. The detection circuit (130) comprises: a comparison unit, used for receiving an electric pulse signal converted from an optical pulse signal, performing a comparison operation between the electric pulse signal and a threshold set, and acquiring time information corresponding to the electric pulse signal, wherein thresholds in the threshold set are classified into a plurality of threshold groups in a descending order, and each threshold group at least comprises one threshold; a determination unit, used for obtaining non-noise time information by means of screening according to the minimum value in the threshold group triggered by the electric pulse signal and a noise level; and a calculation unit, used for calculating pulse information of the electric pulse signal according to the time information obtained by screening. By grouping preset thresholds, a minimum threshold of TDC is optimized, so that under different ambient light and noise levels, a laser distance measuring system can achieve the widest detection range.

Description

Detection circuit, detection method, distance measuring device and mobile platform

Technical field

The invention relates to the technical field of laser radar, in particular to a detection circuit, a detection method, a ranging device, and a mobile platform.

Background technique

The laser ranging system is a perceptual sensor that can obtain three-dimensional information of the scene. Its basic principle is to actively emit a laser pulse signal to the detected object and obtain the reflected pulse signal, according to the time difference between the transmitted signal and the received signal Calculate the depth information of the distance detector of the measured object; obtain the angle information of the measured object relative to the laser ranging system based on the known emission direction of the laser ranging system; combine the aforementioned depth and angle information to obtain a large number of detection points (called Point cloud), based on the point cloud, the spatial three-dimensional information of the measured object relative to the laser ranging system can be reconstructed.

In the existing laser ranging system technology, a certain threshold is usually preset in the laser ranging system. When the optical pulse signal received by the laser ranging system exceeds the threshold, the threshold is triggered by the optical pulse signal to generate Corresponding trigger signal, the threshold is usually fixed, resulting in a mismatch of false alarm rate and range under different ambient light noise levels, which often increases the false alarm rate to an unacceptable level. Therefore, the above-mentioned problems existing at present are improved.

Summary of the invention

The first aspect of the present invention provides a detection circuit, which includes:

The comparing unit is used to receive the electrical pulse signal converted from the optical pulse signal and perform a comparison operation between the electrical pulse signal and a threshold value set, and collect time information corresponding to the electrical pulse signal, wherein the threshold value set Each threshold is divided into multiple threshold groups in descending order, and each threshold group contains at least one threshold;

The judging unit is configured to filter out non-noise time information according to the minimum value in the threshold group triggered by the electrical pulse signal and the noise level;

The calculation unit is configured to calculate the pulse information of the electrical pulse signal according to the filtered time information.

The present invention also provides an optical signal detection method, including:

Receive electrical pulse signals converted from optical pulse signals;

The electrical pulse signal is compared with a threshold value set, and time information corresponding to the electrical pulse signal is collected. Each threshold value in the threshold value set is divided into multiple threshold value groups in ascending order. There is at least one threshold in each threshold group;

Filter out non-noise time information according to the minimum value in the threshold group triggered by the electrical pulse signal and the noise level;

The pulse information of the electrical pulse signal is calculated according to the filtered time information.

The present invention also provides a distance measuring device, including:

Light emitting circuit, used to emit light pulse signals;

A light conversion circuit for receiving at least a part of the laser signal reflected by the object from the laser pulse signal emitted by the light emitting circuit, and converting the received laser signal into an electrical pulse signal;

The aforementioned detection circuit is used to sample the electrical signal from the laser receiving circuit to obtain pulse information of the electrical pulse signal;

The arithmetic circuit is used to calculate the distance between the object and the distance measuring device according to the pulse information.

The present invention also provides a mobile platform, including:

The above-mentioned distance measuring device; and

The platform body, the light emitting circuit of the distance measuring device is installed on the platform body.

Optionally, the mobile platform includes at least one of an unmanned aerial vehicle, a car, and a robot.

The present invention provides the above-mentioned detection circuit, detection method, distance measuring device and mobile platform. The detection circuit can dynamically abandon the low threshold grouping that does not meet the requirements according to the external light noise by grouping preset thresholds to ensure the lowest threshold Always above the noise amplitude, so as to optimize the lowest threshold of TDC so that under different ambient light noise levels, the laser ranging system can reach the widest detection range.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

FIG. 1 is a schematic diagram of the structure of a sampling signal obtained by a time-to-digital conversion method in an embodiment of the prior art;

2 is a flowchart of sampling performed by the detection circuit in an embodiment of the present invention;

3 is a schematic diagram of the structure of the detection circuit for pulse division in an embodiment of the present invention;

4 is a schematic frame diagram of a distance measuring device provided by an embodiment of the present invention;

Fig. 5 is a schematic diagram of an embodiment in which a distance measuring device provided by an embodiment of the present invention adopts a coaxial optical path.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

The detection circuit provided by each embodiment of the present invention may be applied to a distance measuring device, and the distance measuring device may be electronic equipment such as laser radar and laser distance measuring equipment. In one embodiment, 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. In one implementation, 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). Alternatively, the ranging device can also detect the distance from the detected object to the ranging device through other technologies, such as a ranging method based on phase shift measurement, or a ranging method based on frequency shift measurement. There is no restriction.

The distance and azimuth detected by the ranging device can be used for remote sensing, obstacle avoidance, surveying and mapping, modeling, navigation, etc. In one embodiment, the distance measuring device of the embodiment of the present invention can be applied to a mobile platform, and the distance measuring device can be installed on the platform body of the mobile platform. A mobile platform with a distance measuring device can measure the external environment, for example, measuring the distance between the mobile platform and obstacles for obstacle avoidance and other purposes, and for two-dimensional or three-dimensional mapping of the external environment. In some embodiments, the mobile platform includes at least one of an unmanned aerial vehicle, a car, a remote control car, a robot, and a camera. When the ranging device is applied to an unmanned aerial vehicle, the platform body is the fuselage of the unmanned aerial vehicle. When the distance measuring device is applied to a car, the platform body is the body of the car. The car can be a self-driving car or a semi-automatic driving car, and there is no restriction here. When the distance measuring device is applied to a remote control car, the platform body is the body of the remote control car. When the distance measuring device is applied to a robot, the platform body is a robot. When the distance measuring device is applied to a camera, the platform body is the camera itself.

For ease of understanding, the working process of distance measurement will be described as an example in conjunction with the distance measurement device 100 shown in FIG. 4.

As shown in FIG. 4, the distance measuring device 100 may include a transmitting circuit 110, a receiving circuit 120, a detecting circuit 130, and an arithmetic circuit 140.

The transmitting circuit 110 may emit a light pulse sequence (for example, a laser pulse sequence). The receiving circuit 120 can receive the light pulse sequence reflected by the object to be detected, and perform photoelectric conversion on the light pulse sequence to obtain an electrical signal. After processing the electrical signal, the electrical signal can be output to the detection circuit 130. The detection circuit 130 may sample the electrical signal to obtain the sampling result. The arithmetic circuit 140 may determine the distance between the distance measuring device 100 and the detected object based on the sampling result of the detection circuit 130.

Optionally, the distance measuring device 100 may further include a control circuit 150, which can control other circuits, for example, can control the working time of each circuit and/or set parameters for each circuit.

It should be understood that although the distance measuring device shown in FIG. 4 includes a transmitting circuit, a receiving circuit, a detection circuit, and an arithmetic circuit for emitting a beam for detection, the embodiment of the present application is not limited to this, the transmitting circuit The number of any one of the receiving circuit, the detection circuit, and the arithmetic circuit can also be at least two, which are used to emit at least two light beams in the same direction or in different directions respectively; wherein, the at least two light paths can be simultaneous Shooting can also be shooting at different times. In an example, the light-emitting chips in the at least two transmitting circuits are packaged in the same module. For example, each emitting circuit includes a laser emitting chip, and the dies in the laser emitting chips in the at least two emitting circuits are packaged together and housed in the same packaging space.

In some implementation manners, in addition to the circuit shown in FIG. 4, the distance measuring device 100 may further include a scanning module for changing the propagation direction of at least one laser pulse sequence emitted by the transmitting circuit.

Among them, the module including the transmitting circuit 110, the receiving circuit 120, the detection circuit 130, and the operation circuit 140, or the module including the transmitting circuit 110, the receiving circuit 120, the detection circuit 130, the operation circuit 140, and the control circuit 150 may be referred to as the measurement circuit. Distance module, the distance measurement module can be independent of other modules, for example, scanning module.

A coaxial optical path can be used in the distance measuring device, that is, the light beam emitted from the distance measuring device and the reflected light beam share at least part of the optical path in the distance measuring device. For example, after at least one laser pulse sequence emitted by the transmitter circuit changes its propagation direction and exits through the scanning module, the laser pulse sequence reflected by the probe passes through the scanning module and then enters the receiving circuit. Alternatively, 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. 5 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 circuit), a collimating element 204, a detector 205 (which may include the above-mentioned receiving circuit, detection circuit, and arithmetic circuit) 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. Among them, the transmitter 203 can be used to emit a light pulse sequence. In one embodiment, the transmitter 203 may emit a sequence of laser pulses. Optionally, 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.

In the embodiment shown in FIG. 5, 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. In some other implementation manners, the transmitter 203 and the detector 205 may respectively use their own collimating elements, and the optical path changing element 206 is arranged on the optical path behind the collimating element.

In the embodiment shown in FIG. 5, since the beam aperture of the light beam emitted by the transmitter 203 is small, and the beam aperture of the return light received by the distance measuring device is relatively large, the light path changing element can use a small area mirror to The transmitting light path and the receiving light path are combined. In some other implementations, the light path changing element may also use 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 by the bracket of the small mirror in the case of using the small mirror can be reduced.

In the embodiment shown in FIG. 5, the optical path changing element deviates from the optical axis of the collimating element 204. In some other implementation manners, 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.

In an embodiment, 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, refracting, or diffracting the light beam. For example, 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. In an example, at least part of the optical elements are moving. For example, 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. In some embodiments, the multiple optical elements of the scanning module 202 may 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. In one embodiment, the multiple optical elements of the scanning module 202 may rotate at different speeds or vibrate at different speeds. In another embodiment, at least part of the optical elements of the scanning module 202 may rotate at substantially the same rotation speed. In some embodiments, the multiple optical elements of the scanning module may also be rotated around different axes. In some embodiments, 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.

In one embodiment, 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 light beam 219 to different directions. In one embodiment, the angle between the direction of the collimated beam 219 changed by the first optical element and the rotation axis 209 changes as the first optical element 214 rotates. In one embodiment, the first optical element 214 includes a pair of opposed non-parallel surfaces through which the collimated light beam 219 passes. In one embodiment, the first optical element 214 includes a prism whose thickness varies in at least one radial direction. In one embodiment, the first optical element 214 includes a wedge prism, and the collimated beam 219 is refracted.

In one embodiment, 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. In one embodiment, the second optical element 115 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 as to project the collimated light beam 219 to the outside space Different directions can scan a larger space. In one embodiment, 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 may be determined according to the area and pattern expected to be scanned in actual applications. The

drivers

216 and 217 may include motors or other drivers.

In one embodiment, the second optical element 215 includes a pair of opposite non-parallel surfaces through which the light beam passes. In one embodiment, the second optical element 215 includes a prism whose thickness varies in at least one radial direction. In one embodiment, the second optical element 215 includes a wedge prism.

In an embodiment, the scanning module 202 further includes a third optical element (not shown) and a driver for driving the third optical element to move. Optionally, the third optical element includes a pair of opposite non-parallel surfaces, and the light beam passes through the pair of surfaces. In one embodiment, the third optical element includes a prism whose thickness varies in at least one radial direction. In one embodiment, 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 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 space around the distance measuring device 200 is scanned. When 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 an electrical signal.

In one embodiment, an anti-reflection film is plated on each optical element. Optionally, the thickness of the antireflection coating 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.

In an embodiment, 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.

In some embodiments, the transmitter 203 may include a laser diode through which nanosecond laser pulses are emitted. Further, the laser pulse receiving time can be determined, for example, the laser pulse receiving time can be determined by detecting the rising edge time and/or the falling edge time of the electrical signal pulse. In this way, the distance measuring device 200 can calculate the TOF using the pulse receiving time information and the pulse sending time information, so as to determine the distance between the probe 201 and the distance measuring device 200.

In the ranging technology, the lowest threshold on the one hand determines the smallest pulse signal that can be detected, that is, determines the range of the laser ranging system, on the other hand, determines the probability of the detector's false detection of ambient light noise, that is, it determines The false alarm rate of the laser ranging system is improved.

In the ranging system, the threshold used to detect the received pulse signal is usually fixed, resulting in a mismatch of false alarm rate and range under different ambient light noise levels. Taking Figure 1 as an example, if the set threshold 1 is taken as the lowest threshold, an acceptable false alarm rate and range can be obtained in the darkroom environment, but under the sun (the noise level is several times or even ten times that of the darkroom) This increases the false alarm rate to an unacceptable level. Therefore, the set threshold 3 is fixed as the lowest threshold to ensure the false alarm rate and range under the sun, at this time the range of the darkroom will be sacrificed.

In order to increase the range of the laser ranging system as much as possible on the premise that the false alarm rate meets the index, another technique is to dynamically adjust the amplitude of the threshold along with the background light level. Specifically, the lowest threshold is adjusted to the position of the set threshold 1 in the dark room, and the lowest threshold is adjusted to the position of the set threshold 3 in the sun. But this requires a hardware circuit to implement the above-mentioned dynamic adjustment strategy. For high-speed sampling laser ranging systems, a threshold adjustment speed of ms level needs to be reached, which places extremely high requirements on the performance and cost of the hardware circuit.

In order to solve the above problems, the present invention provides a detection circuit. It can be understood that the detection circuit provided by the present invention is not limited to the ranging system described above, and can also be used in ranging systems with other structures or other functions, or in other applications with the same problems or the same requirements. In the system, there is no restriction here.

The detection circuit includes:

The comparing unit is configured to receive the electrical pulse signal converted from the optical pulse signal and perform a comparison operation between the electrical pulse signal and a threshold value set, and collect time information corresponding to the electrical pulse signal, wherein, in the threshold value set Each threshold is divided into multiple threshold groups in ascending order, and each threshold group contains at least one threshold;

Optionally, the comparison unit includes a plurality of time-to-digital converters (Time-to-Digital Converter, TDC), and the plurality of TDCs respectively have different thresholds;

Wherein, the TDC is used to output trigger time information when the received electrical pulse signal triggers a corresponding threshold.

When N thresholds are set in the comparison unit, the number of time information corresponding to the electrical pulse signals collected by the comparison unit is 0-2N. For example, in the case that the electrical pulse signal can trigger all thresholds and only the rising edge information or the falling edge information is collected, the comparison unit can collect N time information, and the electrical pulse signal can trigger all thresholds and collect the rising edge information and the falling edge information. In the case of edge information, the comparison unit can collect 2N time information. However, the time information collected by the comparison unit is not necessarily all triggered by electrical pulse signals, and may also be triggered by noise signals. Therefore, the number of time information output by the comparison unit may be greater than 2N, even in When the number is less than 2N, there may also be time information triggered by noise signals.

Therefore, after the comparison unit collects the time information, the judgment unit filters out the non-noise time information from all the time information collected by the comparison unit, and calculates the electrical pulse based on the filtered time information and the corresponding trigger threshold. The pulse information of the signal. For example, at least one of the waveform, amplitude, and spread of the electrical pulse signal is calculated.

Optionally, in another embodiment of the present invention, multiple different thresholds are set within the dynamic range of the received pulse signal in the comparison unit. For example, 12 thresholds are set in the comparison unit, namely T1, T2,..., T12, and the size of the preset thresholds is T1<T2<...<T12, as shown in Figure 3.

Optionally, in an embodiment of the present invention, each preset threshold in the threshold set is divided into at least two threshold groups in descending order, and each threshold group includes at least one threshold. The threshold values are different between the threshold value groups.

The threshold grouping can be flexibly adjusted according to the designer's classification requirements and the total number of thresholds. In an example, the number of groups depends on the preset number of noise levels. For example, if n levels of noise levels are set according to the light intensity of the use environment, all thresholds in the threshold set can be divided into n threshold groups or n+1 threshold groups when threshold grouping is set. The n threshold groups respectively correspond to each of the preset n noise levels.

Wherein, the noise level in the threshold value group with a larger threshold value is greater than the noise level in the threshold value group with a smaller threshold value, and the minimum threshold value in each threshold value group meets the false alarm rate required by the system under the corresponding noise level.

In one example, 3 levels of noise are preset, corresponding to the strongest natural light noise in summer (for example, con1=100klux), natural light noise under ordinary sunlight (for example, con2=40klux), and common natural light noise at night in the city (for example, con3=1klux). The third gear noise levels con1, con2, and con3 are sequentially reduced. The three threshold values of T3, T2 and T1 are carefully designed according to the level of natural light noise, which can ensure that when the natural light noise is con1, the lowest threshold is set to the false alarm rate that T3 meets the system requirements; when the natural light noise is con2, The lowest threshold is set to the false alarm rate that T2 meets the system requirements; when the natural light noise is con3, the lowest threshold is set to the false alarm rate that T1 meets the system requirements.

Correspondingly, when segmenting the threshold group, there are two optional implementation methods.

In the first implementation manner, the above 12 thresholds are divided into four groups, namely:

CaseA: T4,..., T12, a total of 9 thresholds;

CaseB: T3; a total of 1 threshold;

CaseC: T2; a total of 1 threshold;

CaseD: T1 has 1 threshold.

In the second implementation manner, the above 12 thresholds are divided into three groups, which are divided into:

CaseA: T3,..., T12, a total of 10 thresholds;

CaseB: T2, a total of 1 threshold;

CaseC: T1, a total of 1 threshold.

It should be noted that this grouping example is only exemplary. In actual applications, grouping can be performed as needed. The number of groups is not limited to a certain numerical range, and the number of thresholds contained in each threshold group is not limited to a certain range. A range of values. Generally, a threshold group with a larger threshold has a larger number of thresholds, and a threshold group with a smaller threshold has a smaller number of thresholds.

For example, in the above example, a threshold can be added between T1 and T2, and the added threshold can be grouped with T1 when grouping, or a threshold can be added between T2 and T3, and the threshold can be added during grouping. The added threshold is grouped with T2, or a threshold can be added between T3 and T4, and the added threshold is grouped with T3 when grouping.

In the present invention, grouping by threshold can decouple the collected data and pulse segmentation. After the data is collected, the effective data is filtered out, and the pulse segmentation is performed according to the effective data. If not grouped, the collected data and pulse segmentation are coupled together That is, each TDC does not know how many TDC data it needs to collect, and it needs to perform the cycle of "collection-pulse segmentation-judge whether to discard-judge whether to continue collecting" in real time. The logic to implement in TDC is more complicated.

Wherein, the judging unit determines whether the electrical pulse signal is noise according to the minimum value in the threshold value group triggered by the received electrical pulse signal combined with the noise level, so as to filter out non-noise time information.

In an example, the judging unit is configured to filter time information belonging to non-noise in an order from the largest threshold group to the smallest threshold group. After the judging unit receives all the time information sent by the comparing unit, it first selects the non-noise time information according to the largest threshold group. When it is determined that the non-noise time information cannot be filtered out according to the largest threshold group, then Filter out non-noise time information according to the second largest threshold group, and so on.

For example, in an embodiment of the present invention, the judging unit is configured to determine that the electrical pulse signal is not noise when the minimum value in the maximum threshold group, that is, the first threshold value is triggered by the electrical pulse signal. In this example, since the minimum value in the maximum threshold value group is also relatively large, it is generally determined that the electrical pulse signal is not noise when the first threshold value is triggered by the electrical pulse signal.

Of course, in order to obtain more accurate results, the detection circuit also presets the noise level corresponding to the maximum threshold value group, and the judging unit is also used to compare the noise level with the maximum threshold value when the first threshold value is triggered by the electrical pulse signal. The noise levels corresponding to the groups are compared. When the noise level is less than the noise level corresponding to the first threshold, it is determined that the electrical pulse signal is not noise, and the first threshold is the minimum value in the maximum threshold group.

Wherein, the noise level used for comparison with the preset noise level corresponding to the threshold value group may be measured by a real-time noise measurement device set in the ranging system, for example, an additional setting for receiving noise in the ranging system. The ambient light noise is measured by a photoelectric sensor; or, it can also be measured by using the DC component of the optical signal detected by the detection circuit, which is not limited here.

The judging unit is configured to filter out time information that triggers other threshold groups when there is time information that triggers the first threshold, and then calculate the pulse information of the electrical pulse signal according to the first threshold. When there is no time information that triggers the first threshold, the non-noise time information is filtered from the time information of the second largest threshold group triggered, that is, the time information belonging to the second largest threshold group is filtered out Non-noise time information.

Optionally, the filtering time information belonging to non-noise from the time information of the second largest threshold group triggering includes: when there is time information for triggering the second largest threshold group, and the noise level is less than that corresponding to the second largest threshold group In the case of noise level, it is determined that the electrical pulse signal is not noise.

In turn, when the time information of the second largest threshold group triggered is the time information of noise, then the time information belonging to the non-noise is filtered from the time information of the third largest threshold group triggered, and when there is the time information of the third largest threshold group Time information and when the noise level is less than the noise level corresponding to the third largest threshold group, it is determined that the electrical pulse signal is not noise.

In an embodiment of the present invention, as shown in FIG. 2, in this embodiment, twelve TDCs with different thresholds are set within the dynamic range of the circuit (thresholds are T1, T2,..., T12), and The preset threshold height is T1<T2<...<T12, as shown in Figure 3. Divide these thresholds into four groups. For example, divide the thresholds into CaseA, CaseB, CaseC, and CaseD. CaseA: contains T4,...,T12, a total of 9 thresholds; CaseB: contains T3, a total of 1 threshold; CaseC : Contains 1 threshold for T2; CaseD: Contains 1 threshold for T1. The values of the three thresholds T3, T2 and T1 are designed according to the three noise levels Con1, Con2, and Con3 respectively, that is, when the noise is Con1, the lowest threshold is set to the false alarm rate that T3 meets the system requirements; when the noise is When Con2, the lowest threshold is set to the false alarm rate that T2 meets the system requirements; when the noise is Con3, the lowest threshold is set to the false alarm rate that T1 meets the system requirements.

The determining unit is used to determine that the electrical pulse signal is not noise when there is time information that triggers the minimum threshold T4 in CaseA, and calculate the pulse of the electrical pulse signal according to the time information that triggers the minimum threshold T4 information.

When there is no time information that triggers the threshold in CaseA, the judging unit determines whether there is time information that triggers T3 in CaseB. If it exists, and the measured noise level is less than the time information that triggers the threshold T3 in CaseB. When the noise level is Con1, it is determined that the electrical pulse signal is not noise, and the pulse information of the electrical pulse signal is calculated according to the time information of the trigger T3. When there is time information for triggering T3 but the measured noise level is less than the noise level Con1 corresponding to the time information for triggering T3 in CaseB, it is determined that no non-noise signal is detected.

When there is no time information that triggers the threshold in CaseB, the judging unit determines whether there is time information that triggers T2 in CaseC, if it exists, and the measured noise level is less than that corresponding to the time information that triggers the threshold T2 in CaseC When the noise level is Con2, it is determined that the electrical pulse signal is not noise, and the pulse information of the electrical pulse signal is calculated according to the time information of the trigger T2. When there is time information for triggering T2 but the measured noise level is less than the noise level Con2 corresponding to the time information for T2 in the triggered CaseC, it is determined that no non-noise signal is detected.

When there is no time information that triggers the threshold in CaseC, the judging unit determines whether there is time information that triggers T1 in CaseD, if it exists, and the measured noise level is less than that corresponding to the time information that triggers the threshold T1 in CaseD When the noise level is Con3, it is determined that the electrical pulse signal is not noise, and the pulse information of the electrical pulse signal is calculated according to the time information of the trigger T1. When there is time information for triggering T1 but the measured noise level is less than the noise level Con3 corresponding to the time information for T1 in the triggering CaseD, it is determined that no non-noise signal is detected.

Wherein, the calculation unit is configured to calculate at least one of the waveform, amplitude, and expansion of the electrical pulse signal according to the filtered time information and the corresponding threshold. For example, the calculation unit is configured to restore the electrical pulse signal to a waveform diagram of the light pulse according to the triggered threshold and the time information corresponding to the electrical pulse signal, so as to obtain the waveform, amplitude, and value on the waveform diagram. At least one of the widening.

In an example, in combination with the distance measurement system described in FIGS. 4 and 5, the transmitter 203 emits a light pulse signal at regular intervals, and the light pulse signal to be collected by the detection circuit encounters the object and is reflected back. It must be located after the transmitter emits the optical pulse signal and between the emission of the next optical pulse signal. For the convenience of description, this period of time is taken as the collection time window. Therefore, the whole set of steps of collecting time information-filtering time information belonging to non-noise-calculating pulse information performed by the detection circuit is repeated in each collection time window.

The steps performed by the detection circuit in an acquisition time window will be explained with specific examples in conjunction with FIG. 3.

In an embodiment of the present invention, twelve channels of TDC (T1, T2,..., T12) of different heights are set within the dynamic range of the circuit, and the preset threshold height has T1<T2<...<T12, as shown in the figure 3 shown. The time information is filtered according to the Case A, Case B, Case C, and Case D groups shown in Figure 2.

In one case, within one acquisition time window, the comparison circuit acquires multiple time points as shown in Figure 3. First, use Case A to check whether there is time information for triggering Case A. When it is found, you can select the time information for triggering Case A for calculation. The calculation unit can obtain waveforms such as pulse 3 and pulse 4, pulse 1 and 2 will Filter out as noise.

In another case, within one acquisition time window, the comparison circuit only acquires the 6 time points on the left shown in FIG. 3 (that is, the 6 time points corresponding to pulse 1 and pulse 2 in the figure). In this case, if you cannot find any useful data with Case A and Case B, you can return to case C to check whether there is time information that triggers Case C, and then you can see the 4 time points corresponding to T2. When it is determined that the current noise level is lower than For Con 2 corresponding to T2, pulse 1 and pulse 2 are simulated using these 4 time points.

As shown in Figure 3, two pulses of signal 3 and signal 4 can be detected for CaseA, three pulses of signal 1, signal 2, signal 3 and 4 (fusion) can be detected for CaseB, and signal 1 and signal can be detected for CaseC. There are two pulses in 2 (fusion), signal 3 and 4 (fusion).

Optionally, in another embodiment of the present invention, the judging unit does not start searching from whether the minimum value in the maximum threshold group is triggered by the electrical pulse signal, but the judging unit directly starts from the electrical pulse Among the time information of the largest threshold group triggered by the signal, the non-noise time information is filtered out.

Wherein, when the largest threshold value group triggered by the electrical pulse signal is the largest threshold value group among the plurality of threshold value groups, the judgment is made with reference to the above method, if the largest threshold value group triggered by the electrical pulse signal When it is a threshold value group other than the maximum threshold value group among the plurality of threshold value groups, the judgment unit is configured to compare the noise level with the noise level corresponding to the largest threshold value group triggered by the electrical pulse signal to determine the electrical Whether the pulse signal is noise. When the noise level is less than or equal to the noise level corresponding to the largest threshold group triggered by the electrical pulse signal, the judging unit determines that the electrical pulse signal is not noise; when the noise level is greater than the noise level corresponding to the threshold group , The determining unit determines that the electrical pulse signal is noise.

When the time information of the largest threshold group triggered by the electrical pulse signal is all noise, from the time information of the second largest threshold group triggered by the electrical pulse signal, the time information belonging to non-noise is filtered out . The filtering method is the same as the method for filtering time information belonging to non-noise in the largest threshold group and the second largest threshold group, and will not be repeated here.

In addition, the present invention also provides an optical signal detection method, including:

Step S1: receiving an electrical pulse signal converted from an optical pulse signal;

Step S2: Perform a comparison operation between the electrical pulse signal and a threshold value set, and collect time information corresponding to the electrical pulse signal, wherein each threshold value in the threshold value set is divided into multiple threshold value groups in ascending order , Include at least one threshold in each threshold group;

Step S3: Filter out non-noise time information according to the minimum value in the threshold group triggered by the electrical pulse signal and the noise level;

Step S4: Calculate the pulse information of the electrical pulse signal according to the filtered time information.

Optionally, the filtering out non-noise time information includes:

When the first threshold is triggered by the electrical pulse signal, it is determined that the electrical pulse signal is not noise, and the first threshold is the minimum value in the maximum threshold group.

Optionally, the filtering out non-noise time information includes:

When the first threshold is triggered by the electrical pulse signal and the noise level is less than the noise level corresponding to the first threshold, it is determined that the electrical pulse signal is not noise, and the first threshold is the value in the maximum threshold group. Minimum value.

Optionally, the filtering out non-noise time information includes:

When there is time information that triggers the first threshold, the time information that triggers other threshold groups is filtered out.

Optionally, the filtering out non-noise time information includes:

When there is no time information that triggers the first threshold, the non-noise time information is filtered from the time information of the second-largest threshold group that is triggered.

Optionally, the selection of non-noise time information from the time information of the second-largest threshold group triggering includes:

When there is time information for triggering the second largest threshold group, and the noise level is less than the noise level corresponding to the second largest threshold group, it is determined that the electrical pulse signal is not noise.

Optionally, the filtering out non-noise time information includes:

From the time information of the largest threshold group triggered by the electrical pulse signal, the non-noise time information is filtered out.

Optionally, the filtering out non-noise time information includes:

When the largest threshold value group triggered by the electrical pulse signal is a threshold value group other than the largest threshold value group among the plurality of threshold value groups, the noise level is set to the noise corresponding to the largest threshold value group triggered by the electrical pulse signal Level comparison determines whether the electrical pulse signal is noise.

Optionally, when the noise level is less than or equal to the noise level corresponding to a maximum threshold group triggered by the electrical pulse signal, the determining unit determines that the electrical pulse signal is not noise;

When the noise level is greater than the noise level corresponding to the threshold group, the judgment unit determines that the electrical pulse signal is noise.

Optionally, when it is determined that the time information of the largest threshold group triggered by the electrical pulse signal is all noise, from the time information of the second largest threshold group triggered by the electrical pulse signal, filter out Non-noise time information.

Optionally, the thresholds in the threshold set are divided into at least three threshold groups in descending order.

Optionally, the calculating the pulse information of the electrical pulse signal according to the filtered time information includes:

At least one of the waveform, amplitude, and expansion of the electrical pulse signal is calculated according to the filtered time information and the corresponding threshold.

Among them, step S1 and step S2 can be implemented by the comparison unit in the detection circuit of the foregoing embodiment, step S3 can be implemented by the judgment unit in the detection circuit of the foregoing embodiment, and step S4 can be implemented by the detection circuit of the foregoing embodiment. For the specific implementation and explanation of each step, please refer to the implementation of the comparison unit, judgment unit and calculation unit in the detection circuit, which will not be repeated here.

The present invention provides the above-mentioned detection circuit, detection method, distance measuring device and mobile platform. The detection circuit receives an electrical pulse signal converted from an optical pulse signal and integrates the electrical pulse signal with a preset threshold. Perform a comparison operation, and divide each preset threshold in the preset threshold set into multiple threshold groups in descending order, and each threshold group contains at least one preset threshold; The minimum value in the threshold group triggered by the pulse signal and the noise level determine whether the electrical pulse signal is noise. When the determining unit determines that the electrical pulse signal is not noise, it will be based on the triggered threshold and the electrical The time information corresponding to the pulse signal calculates the pulse information of the electrical pulse signal. By grouping the preset thresholds, the low threshold grouping that does not meet the requirements can be dynamically abandoned according to the external light noise situation, ensuring that the lowest threshold is always above the noise amplitude, so as to optimize the lowest threshold of TDC so that under different ambient light noise levels, laser The ranging system can reach the widest detection range.

The technical terms used in the embodiments of the present invention are only used to describe specific embodiments and are not intended to limit the present invention. In this article, the singular forms "a", "the" and "the" are used to include the plural forms at the same time, unless the context clearly indicates otherwise. Further, the use of "including" and/or "including" in the specification refers to the presence of the described features, wholes, steps, operations, elements and/or components, but does not exclude the presence or addition of one or more Other features, wholes, steps, operations, elements and/or components.

Corresponding structures, materials, actions, and equivalents (if any) of all devices or steps and functional elements in the appended claims are intended to include any structure, material, or action for performing the function in combination with other explicitly required elements. The description of the present invention is given for the purpose of embodiment and description, but is not intended to be exhaustive or to limit the invention to the disclosed form. Without departing from the scope and spirit of the present invention, various modifications and variations will be apparent to those skilled in the art. The embodiments described in the present invention can better reveal the principles and practical applications of the present invention, and enable those skilled in the art to understand the present invention.

The flowchart described in the present invention is only an embodiment, and various modifications and changes can be made to this illustration or the steps in the present invention without departing from the spirit of the present invention. For example, these steps can be performed in a different order, or some steps can be added, deleted or modified. A person of ordinary skill in the art can understand that all or part of the processes for implementing the foregoing embodiments and equivalent changes made in accordance with the claims of the present invention still fall within the scope of the invention.

Claims

A detection circuit, characterized in that the detection circuit includes:

The comparing unit is used to receive the electrical pulse signal converted from the optical pulse signal and perform a comparison operation between the electrical pulse signal and a threshold value set, and collect time information corresponding to the electrical pulse signal, wherein the threshold value set Each threshold is divided into multiple threshold groups in descending order, and each threshold group contains at least one threshold;

The judging unit is configured to filter out non-noise time information according to the minimum value in the threshold group triggered by the electrical pulse signal and the noise level;

The calculation unit is configured to calculate the pulse information of the electrical pulse signal according to the filtered time information.
The detection circuit according to claim 1, wherein the determining unit is configured to determine that the electrical pulse signal is not noise when the first threshold is triggered by the electrical pulse signal, and the first threshold is The minimum value in the maximum threshold group.
The detection circuit according to claim 1, wherein the determining unit is configured to determine when the first threshold is triggered by the electrical pulse signal and the noise level is less than the noise level corresponding to the first threshold The electrical pulse signal is not noise, and the first threshold value is the minimum value in the maximum threshold value group.
The detection circuit according to claim 2 or 3, wherein the determining unit is configured to filter out the time information that triggers other threshold groups when there is time information that triggers the first threshold.
The detection circuit according to any one of claims 2 to 3, wherein the judging unit is configured to filter from the time information that triggers the second largest threshold group when there is no time information that triggers the first threshold Time information that belongs to non-noise.
The detection circuit according to claim 5, wherein the filtering out the non-noise time information from the time information triggering the second largest threshold group comprises:

When there is time information for triggering the second largest threshold group, and the noise level is less than the noise level corresponding to the second largest threshold group, it is determined that the electrical pulse signal is not noise.
The detection circuit according to claim 1, wherein the judgment unit is configured to filter out non-noise time information from the time information of the largest threshold group triggered by the electrical pulse signal.
The detection circuit according to claim 7, wherein when the largest threshold value group triggered by the electrical pulse signal is a threshold value group other than the maximum threshold value group among the plurality of threshold value groups, the judgment unit is configured to The noise level is compared with the noise level corresponding to the largest threshold group triggered by the electrical pulse signal to determine whether the electrical pulse signal is noise.
The detection circuit according to claim 8, wherein when the noise level is less than or equal to the noise level corresponding to the largest threshold group triggered by the electrical pulse signal, the determining unit determines that the electrical pulse signal is not Is noise;

When the noise level is greater than the noise level corresponding to the threshold group, the judgment unit determines that the electrical pulse signal is noise.
The detection circuit according to claim 7, wherein the determining unit is used to determine that the time information of the largest threshold group triggered by the electrical pulse signal is all noise, from the electrical pulse signal From the time information of the second-largest threshold group that is triggered, the time information belonging to non-noise is filtered out.
The detection circuit according to claim 1, wherein the thresholds in the threshold set are divided into at least three threshold groups in descending order.
The detection circuit according to claim 1, wherein the calculation unit is configured to calculate at least one of the waveform, amplitude, and expansion of the electrical pulse signal according to the filtered time information and the corresponding threshold. .
The detection circuit according to claim 1, wherein the comparison unit comprises a plurality of time-to-digital converters, and the plurality of time-to-digital converters respectively have different thresholds;

Wherein, the time-to-digital converter is used to output the triggered time information when the received electrical pulse signal triggers the corresponding threshold.
An optical signal detection method, characterized in that it comprises:

Receive electrical pulse signals converted from optical pulse signals;

The electrical pulse signal is compared with a threshold value set, and time information corresponding to the electrical pulse signal is collected. Each threshold value in the threshold value set is divided into multiple threshold value groups in ascending order. There is at least one threshold in each threshold group;

Filter out non-noise time information according to the minimum value in the threshold group triggered by the electrical pulse signal and the noise level;

The pulse information of the electrical pulse signal is calculated according to the filtered time information.
The detection method according to claim 14, wherein the filtering out non-noise time information comprises:

When the first threshold is triggered by the electrical pulse signal, it is determined that the electrical pulse signal is not noise, and the first threshold is the minimum value in the maximum threshold group.
The detection method according to claim 14, wherein the filtering out non-noise time information comprises:

When the first threshold is triggered by the electrical pulse signal and the noise level is less than the noise level corresponding to the first threshold, it is determined that the electrical pulse signal is not noise, and the first threshold is the value in the maximum threshold group. Minimum value.
The detection method according to claim 15 or 16, wherein the filtering out non-noise time information includes:

When there is time information that triggers the first threshold, the time information that triggers other threshold groups is filtered out.
The detection method according to any one of claims 15 to 16, wherein the filtering out non-noise time information comprises:

When there is no time information that triggers the first threshold, the non-noise time information is filtered from the time information of the second-largest threshold group that is triggered.
The detection method according to claim 18, wherein the filtering out the time information belonging to the non-noise time information triggering the second largest threshold group comprises:

When there is time information for triggering the second largest threshold group, and the noise level is less than the noise level corresponding to the second largest threshold group, it is determined that the electrical pulse signal is not noise.
The detection method according to claim 14, wherein the filtering out non-noise time information comprises:

From the time information of the largest threshold group triggered by the electrical pulse signal, the time information belonging to non-noise is filtered out.
The detection method according to claim 20, wherein the filtering out non-noise time information comprises:

When the largest threshold value group triggered by the electrical pulse signal is a threshold value group other than the largest threshold value group among the plurality of threshold value groups, the noise level is set to the noise corresponding to the largest threshold value group triggered by the electrical pulse signal Level comparison determines whether the electrical pulse signal is noise.
22. The detection method according to claim 21, wherein when the noise level is less than or equal to the noise level corresponding to the largest threshold group triggered by the electrical pulse signal, the determining unit determines that the electrical pulse signal is not noise ；

When the noise level is greater than the noise level corresponding to the threshold group, the judgment unit determines that the electrical pulse signal is noise.
The detection method according to claim 20, wherein when it is determined that the time information of the largest threshold group triggered by the electrical pulse signal is all noise, the second largest one triggered by the electrical pulse signal Among the time information of the threshold group, the non-noise time information is filtered out.
The detection method according to claim 14, wherein the thresholds in the threshold set are divided into at least three threshold groups in descending order.
The detection method according to claim 14, wherein the calculating the pulse information of the electrical pulse signal according to the filtered time information comprises:

At least one of the waveform, amplitude, and expansion of the electrical pulse signal is calculated according to the filtered time information and the corresponding threshold.
A distance measuring device, characterized by comprising:

Light emitting circuit, used to emit light pulse signals;

A light conversion circuit for receiving at least a part of the laser signal reflected by the object from the laser pulse signal emitted by the light emitting circuit, and converting the received laser signal into an electrical pulse signal;

The detection circuit according to any one of claims 1 to 13, which is used to sample the electrical signal from the laser receiving circuit to obtain pulse information of the electrical pulse signal;

The arithmetic circuit is used to calculate the distance between the object and the distance measuring device according to the pulse information.
A mobile platform, characterized in that it includes:

The distance measuring device of claim 26; and

The platform body, the light emitting circuit of the distance measuring device is installed on the platform body.
The mobile platform of claim 27, wherein the mobile platform comprises at least one of an unmanned aerial vehicle, a car, and a robot.