WO2022141468A1 - Detection method for laser radar, computer readable storage medium, and laser radar - Google Patents

Abstract

A detection method for a laser radar (100), a computer readable storage medium, and a laser radar (100). A detection window time of a detection unit (11) comprises multiple integration periods. The detection method for a laser radar (100) comprises: correspondingly selecting any photon number threshold in a first threshold set within each integration period, wherein the first threshold set comprises at least two photon number thresholds, and the photon number thresholds corresponding to at least two integration periods within the detection window time are different (101); when the number of photons received by the detection unit (11) within one integration period is greater than the photon number threshold corresponding to the integration period, the detection unit (11) responding and outputting a sampling signal (102); and fusing the sampling signals within the detection window time to obtain a detection signal (103), wherein the photon number thresholds corresponding to at least two integration periods within the detection window time are different. Objects having different reflectivity can be detected respectively.

Description

Detection method of lidar, computer readable storage medium and lidar technical field

Embodiments of the present invention relate to the technical field of radar, and in particular, to a detection method for a laser radar, a computer-readable storage medium, and a laser radar.

Background technique

Lidar is a radar system that uses lasers to detect the position, speed and other characteristic quantities of the target object. Its working principle is that the transmitting system first transmits the outgoing laser for detection to the target, and then the receiving system receives the echo laser reflected from the target object. , after processing the received echo laser, the relevant information of the target object can be obtained, such as parameters such as distance, azimuth, altitude, speed, attitude, and even shape.

The receiving system can receive the echo laser through the detection array. The detection array is usually composed of a plurality of detectors arranged in an array. Due to the large receiving field of view of the detection array, it is easily affected by interfering light, resulting in the inability of the weak echo laser to respond effectively, which affects the dynamic range of lidar detection. This is the problem that needs to be solved at present.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the main purpose of the embodiments of the present invention is to provide a detection method for a lidar, a computer-readable storage medium and a lidar, which solve the problem of how to improve the dynamic range of the receiving system in the prior art.

The invention provides a detection method for a laser radar, wherein the detection window time includes a plurality of integration periods;

Each integration period corresponds to selecting any one photon number threshold in the first threshold set, wherein the first threshold set includes at least two photon number thresholds;

When the number of photons received by the detection unit in one of the integration periods is greater than the threshold of the number of photons corresponding to the integration period, the detection unit responds and outputs a sampling signal;

Fusing the sampled signals within the detection window time to obtain a detection signal;

Wherein, the photon number thresholds corresponding to at least two of the integration periods within the detection window are different.

Embodiments of the present invention also provide a computer-readable storage medium, where the computer-readable storage medium stores a plurality of instructions, and the instructions are adapted to be loaded by a processor and execute the above method steps.

An embodiment of the present invention also provides a laser radar, where the laser radar includes:

a detection array, comprising a plurality of detection units, the detection units are used for receiving echo laser light;

A processing unit for performing the method steps as described above.

The beneficial effect of the embodiment of the present invention is: the embodiment of the present invention selects different photon number thresholds for at least two integration periods in the detection window time, and when the number of photons received by the detection unit is greater than the photon number threshold corresponding to the integration period, the detection The unit responds and outputs the sampled signal. In the integration period with a large photon number threshold, the detection unit needs to receive more photons to respond, and the integration period can correspond to receiving the echo laser of the object with high reflectivity; correspondingly, in the integration period with a small photon number threshold, The detection unit only needs to receive a small number of photons to respond, and the integration period can correspond to receiving the echo laser of an object with a wider reflectivity range. Since the photon number thresholds corresponding to at least two integration periods in a detection window are different, the detection unit can receive and respond to the echo lasers of objects with different reflectivity, and improve the detection dynamic range of the lidar receiving system.

Description of drawings

One or more embodiments are exemplified by the pictures in the corresponding drawings, and these exemplifications do not constitute limitations of the embodiments, and elements with the same reference numerals in the drawings are denoted as similar elements, Unless otherwise stated, the figures in the accompanying drawings do not constitute a scale limitation.

1 is a structural block diagram of a laser radar provided by an embodiment of the present invention;

2 is a flowchart of a detection method for a lidar provided by an embodiment of the present invention;

FIG. 3 is a flowchart of step 203 of a detection method for a lidar provided by another embodiment of the present invention;

4 is a flowchart of a detection method for a lidar provided by another embodiment of the present invention;

5 is a flowchart of a detection method for a lidar provided by another embodiment of the present invention;

FIG. 6 is a flowchart of a detection method for a lidar provided by another embodiment of the present invention.

The reference numerals in the specific embodiment are as follows:

Lidar 100 , detection array 10 , detection unit 11 , processing unit 20 .

Detailed ways

Embodiments of the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

It should be noted that, unless otherwise specified, the technical or scientific terms used in the present invention should have the usual meanings understood by those skilled in the art to which the present invention belongs.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", " Back, Left, Right, Vertical, Vertical, Horizontal, Top, Bottom, Inside, Outside, Clockwise, Counterclockwise, " The orientation or positional relationship indicated by "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that The device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

In addition, the terms "first", "second", etc. are used for descriptive purposes only, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. In the description of the present invention, "plurality" and "several" mean two or more (including two) unless otherwise expressly and specifically defined.

In the present invention, unless otherwise expressly specified and limited, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection , or integrated; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of the two elements or the interaction relationship between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

In the present invention, unless otherwise expressly specified and limited, a first feature "on" or "under" a second feature may be in direct contact between the first and second features, or the first and second features indirectly through an intermediary touch. Also, the first feature being "above", "over" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is level higher than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

The lidar includes a transmitting system and a receiving system, the transmitting system is used to transmit the outgoing laser, and the receiving system is used to receive the echo laser and output the echo time; wherein, the receiving system includes a detection unit, and the detection unit is used to receive the echo laser and output the detection Signal; the processing unit of the receiving system samples and analyzes the detection signal to obtain the echo time. The detection window of the lidar includes multiple integration periods, and each integration period emits an outgoing laser and receives the echo laser corresponding to the outgoing laser to complete one detection.

The detection unit may be in the form of an array in which the receivers are arranged, such as an APD (Avalanche Photodiode, avalanche photodiode) array, a SiPM (Silicon Photomultipliers, silicon photomultipliers) array, and the like. Existing receivers are extremely sensitive to photons, especially SiPM arrays based on SPADs (Single-photonavalanchediode, single-photon avalanche diodes). The crosstalk and dark count rate problems of SiPM arrays are obvious, and they are easily affected by ambient light. In order to reduce the false alarm rate caused by noise, it is necessary to increase the received photon number threshold of the SiPM array; however, the high photon number threshold makes the echo laser of objects with low reflectivity cannot be effectively received; it is difficult to balance high dynamic range and low false alarm rate.

FIG. 1 is a structural block diagram of a laser radar receiving system provided by an embodiment of the present invention. Referring to FIG. 1 , an embodiment of the present invention provides a lidar 100 , which includes a detection array 10 and a processing unit 20 . Wherein, the detection array 10 includes a plurality of detection units 11, the detection units 11 are used for receiving the echo laser and output sampling signals, and the processing unit 20 is used for processing the sampling signals.

The detection array 10 can be a SiPM array, with p*q pixels that can be individually controlled and output, where p and q are both integers greater than or equal to 1; each pixel includes several SPADs, for example, each pixel includes a*b SPADs . Each pixel of the detection array 10 may be a detection unit that independently receives the echo laser light. The detection array 10 may also receive echoed laser light in rows or columns. If the echo laser is received in columns, each column of pixels forms a detection unit. In addition, each column of pixels can be controlled to operate in sequence, that is, the detection unit is serialized, so as to reduce crosstalk between adjacent columns and reduce power consumption. The same is true for receiving echo lasers in rows, with each row of pixels forming a detection unit. In addition, the detection array 10 can also divide the pixels unevenly according to the detection requirements. For example, several connected pixels can be combined into a whole and controlled in a unified manner, and then several pixels connected as a whole can be regarded as a detection unit . The larger the number of SPADs per pixel, the better the dynamic range against noise interference; however, the size of the SiPM array is limited by the chip size and semiconductor process.

The detection method of the lidar 100 will be described in detail below. 2 is a flowchart of a detection method for a lidar provided by an embodiment of the present invention, and the method includes the following steps:

Step 101 : each integration period corresponds to selecting any photon number threshold in the first threshold set, wherein the first threshold set includes at least two photon number thresholds, and there are at least two photon number thresholds corresponding to two integration periods within the detection window. Thresholds are different.

In an environment with strong background light, the detection unit of LiDAR based on SiPM array is easily disturbed by ambient light, and it is almost impossible to rely on a single pulse to achieve effective detection. Therefore, in the embodiment of the present invention, the detection window of the lidar includes multiple integration periods, each integration period emits an outgoing laser, and receives the echo laser corresponding to the outgoing laser to obtain a sampling signal; The multiple sampled signals obtained are fused to obtain and output a frame of detection signals; the detection probability is improved by means of multiple accumulation. The processing unit processes the sampled signal.

A corresponding photon number threshold is selected for each integration period. When the number of photons received by the detection unit is greater than the photon number threshold corresponding to the current integration period, the detection unit responds and outputs a sampling signal. Under the same emission conditions, the echo laser corresponding to the high reflectivity object is stronger, and the echo laser corresponding to the low reflectivity object is weak, that is, the high reflectivity object returns more photons after reflection, and the low reflectivity object returns. The number of photons returned after reflection is small. If the detection unit sets the same photon number threshold as the condition for responding to the echo laser, the echo laser of the low reflectivity object cannot be effectively received, resulting in missed detection. Compared with using the same photon number threshold, at least two integration periods in the detection window have different photon number thresholds, which can receive more echo lasers from objects with different reflectivity and improve the detection dynamic range.

Exemplarily, the first threshold set includes photon number thresholds A ₁ and A ₂ , and A ₁ >A ₂ , then the number of photons corresponding to the integral period corresponding to the photon number threshold A ₁ is large, and the integral corresponding to the photon number threshold A ₂ The number of photons in the periodic response is small. During the detection process of lidar, the integration period corresponding to the photon number threshold A1 can detect objects in the reflectivity range (R ₂ ～ R ₃ ) _{; the integration period corresponding to the photon number threshold A 2 can} detect a larger reflectivity range ( Objects with R ₁ to R ₃ ), compared with the object reflectivity range (R ₂ to R ₃ ) that can only be detected by the photon number threshold A ₁ , the detection of objects in the reflectivity range (R ₁ to R ₂ ) is increased. Here, R ₁ <R ₂ <R ₃ .

In some embodiments, the photon number thresholds corresponding to each integration period within the detection window time may be different, so that each integration period can detect objects with different reflectivity ranges. Exemplarily, the detection window time includes three integration periods, and the photon number thresholds corresponding to the three integration periods are 12, 9, and 4, respectively. When the integration period of the photon number threshold is 12, the reflectivity range of the object that the detection unit can detect is 80% to 130%; when the photon number threshold is 9, the reflectivity range of the object that the detection unit can detect is 30% to 130%. %; when the photon number threshold is 4, the reflectivity range of the detectable object is 5% to 130%; the reflectivity range of the detectable object is finally 5% to 130%. In some embodiments, the photon number thresholds corresponding to the integration period within the detection window time may be different by at least two, so that objects with different reflectivity ranges can be detected in at least two integration periods. Taking the above embodiment as an example, the detection window time includes 3 integration periods, and the photon number thresholds corresponding to the 3 integration periods are 12, 9 and 9 respectively; the reflectivity of the final detectable object ranges from 30% to 130%. The photon number threshold can also be determined according to the reflectivity of the object to be detected in the integration period. For objects with different reflectivity, the required photon number threshold is different.

Step 102: When the number of photons received by the detection unit in one integration period is greater than the photon number threshold corresponding to the integration period, the detection unit responds and outputs a sampling signal.

Receivers are extremely sensitive to photons, especially SiPM arrays based on the SPAD principle. Theoretically, the SPAD of the detection array receives a photon and can respond and output an induced current. In this way, the noise photons in the environment will frequently trigger the pixel response, causing the false alarm rate of the detection array to be too high. Therefore, a photon number threshold is usually set, and when the number of photons received by the detection unit in the integration period is greater than the photon number threshold, the detection unit responds and outputs a sampling signal. By increasing the photon number threshold of the detection unit, the false alarm rate caused by noise photons can be reduced; however, if the photon number threshold is too high, it is easy to cause the detection unit to miss the normal echo laser. Therefore, the photon number threshold of the detection unit needs to be selected by weighing the two.

Exemplarily, the photon number threshold of the integration period is 12. If the number of photons received by the detection unit in the integration period is greater than or equal to 12, the detection unit will respond and output a sampling signal; If the number of photons is less than 12, the detection unit will not respond and will not output a sampling signal.

Step 103: Fusing the sampled signals within the detection window time to obtain a detection signal.

In this step, all the sampled signals output within the detection window are fused to obtain a complete frame of detection signals within the detection window, and a frame of point cloud images can be obtained according to the detection signals. As mentioned above, at least two integration periods within the detection window have different photon number thresholds, which can receive more echo lasers from objects with different reflectivity; the previous integration period with a high photon number threshold can only detect objects with higher reflectivity However, the echo laser detected by the latter integration period cannot distinguish between objects with high reflectivity and low reflectivity. What are the echo lasers of objects with lower reflectivity. Therefore, part of the signal of the object with higher reflectivity in the sampling signal corresponding to the next integration period is filtered to obtain part of the signal of the object with lower reflectivity; that is, the previous integration is filtered out of the sampling signal of the next integration period The periodic sampling signal can obtain part of the signal of the low reflectivity object. After each sampled signal is subjected to such filtering processing, multiple non-repetitive signals with different reflectivity ranges are obtained; after fusion, a complete frame of detection signal is obtained.

Taking the foregoing embodiment as an example for illustration, the first threshold set includes photon number thresholds A ₁ and A ₂ , and A ₁ >A ₂ , and the first sampling signal output by the first integration period corresponding to the photon number threshold A ₁ can be parsed Objects in the reflectivity range (R ₂ ～ R ₃ ) are obtained; the second sampling signal output by the second integration period corresponding to the photon number threshold A ₂ can be analyzed to obtain objects in a larger reflectivity range (R ₁ ～ R ₃ ), but The sampling signals corresponding to the reflectance range (R ₁ to R ₂ ) and the reflectivity range (R ₂ to R ₃ ) are mixed together and cannot be distinguished. Here, R ₁ <R ₂ <R ₃ . The second sampling signal filters out the first sampling signal, and the obtained partial sampling signal can be analyzed to obtain objects in the reflectivity range (R ₁ -R ₂ ); the first sampling signal and the aforementioned partial sampling signal are fused to obtain the reflectivity range (R ₁ to R ₂ ) signals and reflectance ranges (R ₂ to R ₃ ).

It can be understood that the number of sampled signals output within a detection window is not necessarily equal to the number of integration periods in the detection window. If there is an integration period in which the sampled signal is not output within the detection window, the output will be output within the detection window. The number of sampled signals will be less than the number of integration periods for that detection window time.

The embodiment of the present invention selects different photon number thresholds for at least two integration periods in the detection window time. When the number of photons received by the detection unit is greater than the photon number threshold corresponding to the integration period, the detection unit responds and outputs a sampling signal. In the integration period with a large photon number threshold, the detection unit needs to receive more photons to respond, and the integration period can correspond to receiving the echo laser of the object with high reflectivity; correspondingly, in the integration period with a small photon number threshold, The detection unit only needs to receive a small number of photons to respond, and the integration period can correspond to receiving the echo laser of an object with a wider reflectivity range. Since the photon number thresholds corresponding to at least two integration periods in a detection window are different, the detection unit can receive and respond to echo lasers of objects with different reflectivity, and improve the detection dynamic range of the lidar receiving system.

Another embodiment of the present invention provides a detection method for a laser radar, the method comprising the following steps:

Step 201: each integration period corresponds to selecting any one photon number threshold in the first threshold set; wherein, the first threshold set includes at least two photon number thresholds, and there are at least two photon number thresholds corresponding to two integration periods within the detection window Thresholds are different.

The principle logic of step 201 is similar to that of step 101 .

In some embodiments, the detection window time includes M integration periods, and the first set of thresholds includes A photon number thresholds, where both M and A are positive integers. The photon number threshold in the first threshold set is a positive integer greater than or equal to 1. Exemplarily, taking one pixel as one detection unit as an example, each pixel includes a*b SPADs, where a=4, b=4, and the theoretical photon number threshold can range from 1 to 16 ( That is, A=16), then the photon number thresholds 1-16 can be selected to form the first threshold set. The number of integration periods included in the detection window time should be determined according to the system performance of the lidar, such as ranging distance, hardware operation rate, etc. Exemplarily, the detection window time includes 3 integration periods, that is, M=3. A can be greater than M or less than or equal to M.

The M integration periods traverse the A photon number thresholds in the first threshold set at least once, and select the photon number threshold corresponding to each integration period.

When A>M, each integration period selects a different photon number threshold from the first threshold set, and (A-M) unselected photon number thresholds will remain in the first threshold set. Exemplarily, the first threshold set={2, 4, 7, 9, 12}, A=5, the detection window time includes 3 integration periods, and M=3. In the three integration periods of the first detection window time, three different photon number thresholds, 4, 9, and 12, are selected from the first threshold set as the photon number thresholds for different integration periods; then the remaining two unselected photon number thresholds Threshold, 2 and 7. For the 3 integration periods of the second detection window time, the same 3 photon number thresholds as the first detection window can be selected, 4, 9, and 12, and the remaining 2 and 7 are used as redundancy. The 3 integration periods of the second detection window time can also choose a photon number threshold that is not exactly the same as that of the first detection window, such as 2, 4, and 7, which is convenient for detecting different reflectivity ranges at different detection window times. It will also increase the complexity of the fusion of the sampled signals.

When A=M, the number of integration periods in the detection window time is the same as the number of photon number thresholds in the first threshold set, each integration period corresponds to a photon number threshold, and A photon number thresholds in the first threshold set are traversed. Exemplarily, the first threshold set={4,9,12}, A=3, the detection window time includes 3 integration periods, M=3, and the 3 integration periods of the detection window time are correspondingly selected from the first threshold set 4, 9, and 12 are used as photon number thresholds. All the photon number thresholds in the first threshold set are traversed once in each detection window time, and the detection reflectivity range can be fixedly expanded, and the system setting is relatively simple.

When A<M, the number of integration periods of the detection window time is greater than the number of photon number thresholds of the first threshold set, and at least part of the integration periods will select the same photon number threshold. For simplicity, the M integration periods of the detection window time traverse the A photon number thresholds in the first threshold set multiple times, that is, the A integration periods select the corresponding A photon number thresholds in turn, traverse the first threshold set once, and the remaining (M-A) integration cycles with no photon number threshold selected continue to traverse the first threshold set a second or more times until the corresponding photon number threshold has been selected for each integration cycle. Exemplarily, the first threshold set={4,9}, A=2, the detection window time includes 4 integration periods, M=4; the photon number threshold selected in the first two integration periods is 4, 9. After completing the traversal of the first threshold set once, the photon number threshold has not been selected for the next 2 integration periods; traverse the first threshold set again, and the photon number thresholds selected in the next two integration periods are 4 and 9 of the first threshold set. .

In the above example, A and M have a multiple relationship, M=xA (x is a positive integer), if M=2×A in the above example, it is necessary to traverse the A photons in the first threshold set x times in M integration periods Number threshold, the integration period selects all photon number thresholds in the first threshold set in turn during each traversal. A and M can also be in a non-multiple relationship, for example, M=xA+y, where x and y are both positive integers, and y is less than A, then M integration cycles traverse the photon number threshold of the first threshold set x times, and then sequentially The photon number thresholds of the y first threshold value sets are selected as the photon number thresholds corresponding to the last remaining y integration periods. According to the requirements of the detection reflectivity range, the threshold of the number of photons in the detection window can be set, so as to improve the receiving dynamic range of the detection unit and increase the system adaptability of the lidar.

In some embodiments, the photon number thresholds in the first set of thresholds may be arranged in increasing or decreasing order. For example, the photon number thresholds in the first threshold set include A ₁ , A ₂ and A ₃ , and A ₁ >A ₂ >A ₃ . When the photon number thresholds are arranged in increasing order, the first threshold set={A ₃ ,A ₂ ,A ₁ }; when the photon number thresholds are arranged in decreasing order, the first threshold set={A ₁ ,A ₂ , A ₃ }. As mentioned above, the integration period corresponding to the photon number threshold A1 can detect objects in the reflectivity range (R ₃ -R ₄ ) _{; the integration period corresponding to the photon number threshold A 2 can} detect objects in a larger reflectivity range (R ₂ -R ₄ ) objects; the integration period corresponding to the photon number threshold A3 can detect objects in the maximum reflectivity range (R ₁ -R ₄ ) _; wherein R ₄ >R ₃ >R ₂ >R ₁ . It can be seen from this that the photon number thresholds in the first threshold set are arranged in decreasing order, and the maximum reflectivity range that can be detected by the corresponding integration period is gradually expanded; similarly, the photon number thresholds in the first threshold set are arranged in increasing order, and the corresponding integration period The range of maximum reflectivity that can be detected is gradually reduced. The photon number thresholds are arranged in increasing or decreasing order, and the corresponding photon number thresholds are selected for the integration period in turn. After detection, the fusion processing of subsequent sampling signals can be simplified and the operation rate can be improved.

Preferably, when the number of integration periods of the detection window time is the same as the number of photon number thresholds of the first threshold set, the first integration period of the detection window corresponds to selecting the first photon number threshold in the first threshold set. By analogy, the second integration period of the detection window time corresponds to selecting the second photon number threshold in the first threshold set, until the Mth integration period corresponds to selecting the Mth (M=A) in the first threshold set Photon number threshold, traverse all photon number thresholds once. The integration period of the detection window time and the photon number threshold combined with the first threshold correspond one-to-one in sequence, which can simplify the system design and speed up the operation rate.

Step 202: When the number of photons received by the detection unit in one integration period is greater than the photon number threshold corresponding to the integration period, the detection unit responds and outputs a sampling signal.

Step 202 is similar to step 102 and will not be repeated here.

Step 203: Fusing the sampled signals within the detection window time to obtain a detection signal.

The principle logic of step 203 is similar to that of step 103 .

In some embodiments, as shown in FIG. 3, step 203 further includes:

Step 2031: The i-th integration period of the detection window time outputs the i-th sampling signal, and the j-th integration period adjacent to the i-th integration period outputs the j-th sampling signal; the photon number threshold corresponding to the i-th integration period is greater than the The photon number threshold corresponding to j integration periods; wherein, 1≤i≤M, 1≤j≤M.

The photon number thresholds of the first threshold set are arranged in increasing or decreasing order. Taking the photon number threshold decreasing arrangement as an example, at this time j=i+1, the photon number threshold corresponding to the i-th integration period is larger than the photon number threshold corresponding to the j-th integration period. Therefore, the j-th integration period detects The reflectivity range of the object detected in the ith integration period is greater than the reflectivity range of the object detected in the ith integration period; the reflectivity range of the object detected in the jth integration period can not only cover the reflectivity range of the object detected in the ith integration period, but also Further detection of lower reflectivity objects. Therefore, the j-th sampled signal includes information of the i-th sampled signal. The case where the photon number thresholds of the first threshold set are arranged in increments is similar to that described above, i=j+1, and the jth sampled signal includes the information of the ith sampled signal, which will not be repeated here.

Step 2032: Remove the same information as the ith sampled signal from the jth sampled signal to obtain the jth processed signal.

It can be seen from the foregoing that the jth sampled signal includes the information of the ith sampled signal, and this part of the information is repeated information; in order to obtain the echo signal of the object with lower reflectivity in the jth sampled signal, and then calculate and identify the lower reflectivity from it. For objects with reflectivity, this step removes the information duplicated with the i-th sampled signal in the j-th sampled signal to obtain the j-th processed signal.

The integration period with the largest photon number threshold is the smallest in the detection reflectivity range, and the sampled signal does not need to be deduplicated, and the sampled signal is directly output as the processed signal.

Step 2033: Fusing all the processed signals within the detection window time to obtain a detection signal.

The redundant information is no longer included in the processed signal from which the repeated information is removed. Each processed signal represents the echo signal of a certain segment of the reflectivity range of the object in the entire reflectivity range detected by the lidar, and finally all the processed signals are fused, Get a complete probe signal.

Further description is given by taking the foregoing embodiment in which the threshold value of the number of photons decreases as an example: M=4, the detection window time includes 4 integration periods; the reflectivity range detected by the first integration period is R ₃ -R ₄ , and the second integration period is detected The reflectivity range of R ₂ ～ R 4 is R 2 ～ R ₄ , the reflectivity range detected by the third integration period is R ₁ ～ R ₄ , and the reflectivity range detected by the fourth integration period is R ₀ ～ R ₄ , where R ₀ <R ₁ < R ₂ <R ₃ <R ₄ . The photon number threshold corresponding to the first integration period is the largest, and the first sampling signal is the first processing signal; the second sampling signal of the second integration period removes the same information as the first sampling signal, at this time j=2, i = 1, the second processing signal is obtained, and the reflectivity range of the corresponding detection object is R ₂ ～ R ₃ ; similarly, the third integration period is j=3, i=2, and the third processing signal is obtained after removal processing , the reflectivity range of the corresponding detection object is R ₁ ～ R ₂ ; the fourth integration period is j=4, i=3, and the fourth processing signal is obtained after removal processing, and the reflectivity range of the corresponding detection object is R ₀ to R ₁ .

The first processed signal to the fourth processed signal are spliced and fused to obtain a complete detection signal covering the reflectivity range of R ₀ to R ₄ , and the echo signals of each reflectivity range can be clearly distinguished, which is convenient for calculation and identification. It can produce a variety of objects with different reflectivity and has a large receiving dynamic range.

The embodiment of the present invention selects different photon number thresholds for at least two integration periods in the detection window time. When the number of photons received by the detection unit is greater than the photon number threshold corresponding to the integration period, the detection unit responds and outputs a sampling signal. M integration periods traverse the A photon number thresholds in the first threshold set at least once, select the photon number threshold corresponding to each integration period, expand the reflectivity range of detection, simplify system design, and improve the receiving dynamic range of the detection unit , to increase the applicability of the system. The photon number thresholds in the first threshold set are arranged in an increasing or decreasing order, which simplifies the fusion processing steps of the sampled signals and speeds up the operation rate.

FIG. 4 is a flowchart of a detection method for a lidar provided by another embodiment of the present invention. As shown in FIG. 4, after step 102, the following steps may also be included:

Step 1021: Determine whether the response time of the sampling signal is within the preset time range ΔT of the corresponding integration period. If yes, go to step 1022, otherwise, go to step 1023;

Step 1022: determine that the sampling signal is credible and continue to transmit backwards;

Step 1023: Delete the sampled signal.

During detection, the noise signal brought by ambient light is random, that is, the time when the noise signal appears in the integration period is random. The outgoing laser is emitted in each integration period, and the sampling signal is obtained by receiving the echo laser reflected by the object; the time interval between the emission time and the reception time can be calculated to obtain the distance of the object, so the time interval is linearly related to the distance of the object; due to the emission time It is relatively simple and direct to obtain , which is generally the initial moment of the integration period. The determination of the receiving time is particularly important for the determination of the detection distance. The objects that can be detected by lidar are usually distributed in the range of lidar, and the time range of echo laser in the integration period is relatively stable. Therefore, the reliability of the sampling signal can be judged by the time range in which the sampling signal appears in the integration period, the noise signal can be filtered out, and the detection accuracy can be improved.

The preset time range ΔT is a time range in the integration period, and the preset time range ΔT can be determined according to factors such as the range of the lidar, the response rate of the transmitting system and the receiving system, and the sampling frequency of the receiving system. The sampling signals received in the preset time range ΔT are likely to be normal echoes, so the sampling signals outside the preset time range ΔT are filtered out as noise signals. The response time of the sampling signal is the receiving time confirmed after sampling the echo signal by the sampling device in the integration period. If the response time of the sampled signal is within the preset time range ΔT, the sampled signal is considered to be a normal echo, and the sampled signal is output to the processing unit; if the response time of the sampled signal is outside the preset time range ΔT, then The sampled signal is considered to be a noise signal, and the sampled signal is deleted to prevent the noise signal from interfering with the subsequent signal processing process. Taking an integration period as an example, assuming that the integration period is T and its starting time is T ₀ , the duration of the integration period is T ₀ ～T ₀ +T; the starting time t ₀ of the preset time range ΔT, then The duration of the preset time range in the integration period is t ₀ ˜t ₀ +ΔT, where T ₀ <t ₀ <(t ₀ +ΔT)<(T ₀ +T).

In this embodiment, the reliability of the sampling signal is judged according to the time range of the receiving time of the sampling signal in the integration period. If the receiving time of the sampling signal is outside the preset time range ΔT in the integration period, it is considered as noise. According to this filtering noise signal, the influence of random noise on the lidar system is further reduced, and the accuracy of the system's ambient light immunity is improved.

FIG. 5 is a flowchart of a detection method for a lidar provided by another embodiment of the present invention. As shown in FIG. 5, after step 1022 and step 1023, the following steps may also be included:

Step 1024: Determine whether the number of sampled signals retained within the detection window is greater than the second threshold; if so, go to Step 1025, otherwise, go to Step 1023;

Step 1025: Determine that the sampled signal within the detection window time is credible and continue to transmit it backwards.

On the basis of the previous embodiment, the reliability of the sampled signals in the detection window time can be further judged by the number of reliable sampled signals retained in the detection window time. It can be seen from the foregoing that according to the randomness of the noise signal, the signals outside the preset time range ΔT are considered as noise signals for filtering; but there are still some noise signals that fall within the preset time range ΔT, and this part of the noise signal It cannot be filtered out by the aforementioned methods, so further filtering is required.

The randomness of the noise signal is mainly reflected in: the response time of the noise signal in different integration periods within the detection window time is random; on the contrary, the response time of the normal echo in different integration periods is stable. Therefore, in the M integration periods within a detection window, if the number of response to the sampling signal within the preset time range ΔT is small, it can be considered as a noise signal trigger, and if the number of response to the sampling signal is large, it can be considered that is a normal echo trigger. Based on this, a second threshold may be set, where the second threshold is the number of sampled signals whose response time is within the preset time range ΔT within the detection window. If the number of sampled signals retained within the detection window is greater than the second threshold, it is considered that the number of sampled signals is large, and is triggered by normal echoes, and the sampled signals are output to the processing unit backward; the number of retained sampled signals within the detection window is less than If it is equal to the second threshold, it is considered that the number of sampled signals is small, which is triggered by the noise signal, and the sampled signals are deleted. Of course, multiple second thresholds may also be set to distinguish the number of sampled signals retained within the detection window time. For example, a second upper threshold and a second lower threshold can be set; when the number of sampled signals retained within the detection window is greater than the second upper threshold, it is considered that the number of sampled signals is large; when the number of sampled signals retained within the detection window is greater than If the number is less than the second lower threshold, it is considered that the number of sampled signals is small.

The second threshold may be set according to the number of integration periods of the detection window time. The detection window time includes M integration periods. Exemplarily, the second threshold is M/2; when the number of sampled signals retained within the detection window time is greater than M/2, it is determined that the sampled signals within the detection window time are credible. For example, the detection window time includes 6 integration periods; there are 4 sampled signals retained in the detection window time, which are greater than the second threshold 3, and the sampled signals in the detection window time are credible; the sampled signals retained in the detection window time are only 2, less than the second threshold of 3, the sampling signal within the detection window time is a noise signal triggering unreliable. The second threshold may also be set according to test experience values, noise signal strength, and the like.

In this embodiment, the reliability of the sampling signals within the detection window is judged by the number of sampling signals retained within the detection window, and the sampling signals triggered by noise signals within the preset time range ΔT are filtered out, which further reduces randomness. The impact of noise on the lidar system improves the ambient light immunity and accuracy of the system.

It should be noted that, steps 1024 to 1025 in this embodiment can also be implemented directly after step 102 as an independent embodiment, and it is determined whether the number of sampled signals whose response time is within the preset time range ΔT within the detection window is greater than that of the first Two thresholds, if so, the sampled signal is considered credible, otherwise, the sampled signal is deleted.

FIG. 6 is a flowchart of a detection method for a lidar provided by another embodiment of the present invention. As shown in FIG. 6, after step 102, the following steps may also be included:

Step 1026: Determine whether the number of photons received by the detection unit is less than the third threshold of the number of photons in the previous time period before the start time t ₀ of the preset time range ΔT in the integration period; if so, go to step 1027, otherwise , and execute step 1028;

Step 1027: determine that the sampling signal is credible and continue to transmit backwards;

Step 1028: Delete the sampled signal.

It can be seen from the foregoing that when the number of photons received by the detection unit in one integration period is greater than the threshold of the number of photons corresponding to the integration period, the detection unit responds and outputs a sampling signal. However, the noise signal is random, and the noise photons will be distributed at any time in the integration period, while the distribution of the photons of the echo laser in different integration periods is stable and can be distributed within the preset time range ΔT. If more noise photons are accumulated in the integration period, the integration period will easily meet the requirement of the photon number threshold and output the sampled signal, but the response time of the sampled signal cannot truly reflect the receiving time of the echo laser, which affects the distance of the processing unit. Interference with solving and object recognition. Therefore, it is necessary to discriminate the integration period of this part of the accumulated noise photons, which causes the detection unit to saturate and output the sampling signal, and filter out the sampling signal that causes interference.

In the integration period, the time period before the start time t ₀ of the preset time range ΔT is the previous time period. Set the third photon number threshold. In an integration period, if the number of photons received by the detection unit in the previous time period is less than the third photon number threshold, the number of noise photons accumulated in the integration period is less, and the output sampling signal is mainly It is triggered by the echo laser, and the sampling signal is considered to be a normal echo and is credible, and the sampling signal is output to the processing unit backward; if the number of photons received by the detection unit in the previous time period is greater than or equal to the third photon number threshold, then There are many noise photons accumulated in this integration period, and the output sampling signal is mainly triggered by noise photons. The sampling signal is considered unreliable, and the sampling signal is deleted to avoid interference to the processing of the processing unit.

The preset time range ΔT is a time range in the integration period, and the preset time range ΔT can be determined according to factors such as the range of the lidar, the response rate of the transmitting system and the receiving system, and the sampling frequency of the receiving system.

The third photon number threshold may be determined according to the number of SPADs included in the detection unit. Exemplarily, taking one pixel as one detection unit as an example, each pixel includes a*b SPADs, where a=4, b=4, the detection unit includes 16 SPADs, and the theoretical value of the photon number threshold is The range can be 1-16. The third photon number threshold can be set to half the number of SPADs, 8; it can also be set to any ratio based on experience. The third photon number threshold may also be determined according to the photon number threshold corresponding to the current integration period. Taking the above example as an example, the photon number threshold of the current integration period is 10, that is, the detection unit outputs a sampling signal when the number of photons received is greater than 10. At this time, the third photon number threshold can be set as half of the photon number threshold corresponding to the current integration period, 5; an arbitrary ratio can also be set according to experience. The third photon number threshold may also be determined or adjusted according to factors such as the sensitivity of the detection unit, the sampling frequency, the response rate of the receiving system, and the like.

In this embodiment, by setting the third photon number threshold, the integration period with more accumulated noise photons is identified, and the sampling signal that causes interference is filtered out, which can further reduce the interference caused by random noise to the lidar system, and improve the system reliability. Ambient light immunity and accuracy.

It should be noted that the examples of steps 1021 to 1023, the examples of steps 1024 to 1025, the examples of steps 1021 to 1025, and the examples of steps 1026 to 1028 can be implemented directly after step 102 as independent examples, or at least two examples can be selected. The various embodiments are implemented in sequence after step 102 . Implementing the foregoing embodiments after step 102 alone can satisfy the requirement of filtering out noise interference, simplify the detection method, and speed up the processing rate. Implementing at least two of the foregoing embodiments in sequence after step 102 can remove as many noise interferences as possible from multiple aspects and improve the signal-to-noise ratio and accuracy of the system.

An embodiment of the present invention further provides a computer-readable storage medium, where the computer-readable storage medium stores a plurality of instructions, and the instructions are adapted to be loaded by a processor and execute the detection of the lidar according to any of the above embodiments method steps.

An embodiment of the present invention further provides a laser radar, where the laser radar includes: a transmitting system and a receiving system; a transmitting system for transmitting outgoing laser light; and a receiving system for performing any one of claims 1-8 method steps.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. The scope of the invention should be included in the scope of the claims and description of the present invention. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any manner. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims (10)

1. A detection method for lidar, characterized in that the detection window time includes a plurality of integration periods;

   Each integration period corresponds to selecting any one photon number threshold in the first threshold set, wherein the first threshold set includes at least two photon number thresholds;

   When the number of photons received by the detection unit in one of the integration periods is greater than the threshold of the number of photons corresponding to the integration period, the detection unit responds and outputs a sampling signal;

   Fusing the sampled signals within the detection window time to obtain a detection signal;

   Wherein, the photon number thresholds corresponding to at least two of the integration periods within the detection window are different.
2. The method of claim 1, wherein the detection window time includes M integration periods, and the first threshold set includes A photon number thresholds, wherein M and A are both positive integers , A≤M;

   Each of the integration periods corresponds to selecting any photon number threshold in the first threshold set, including:

   The M integration periods traverse the A photon number thresholds in the first threshold set at least once, and select the photon number threshold corresponding to each integration period.
3. The method of claim 2, wherein the photon number thresholds in the first threshold set are arranged in an increasing or decreasing order.
4. The method according to claim 3, wherein, when A=M, the first integration period of the detection window time corresponds to selecting the first photon number threshold in the first threshold set.
5. The method according to claim 1, wherein when the number of photons received by the detection unit in one of the integration periods is greater than the threshold of the number of photons corresponding to the integration period, the detection unit responds and outputs a After sampling the signal, it also includes:

   Determine whether the response time of the sampling signal is within the preset time range ΔT of the corresponding integration period;

   If so, determine that the sampled signal is credible and continue to transmit backwards;

   If not, delete the sampled signal.
6. The method according to claim 5, characterized in that judging whether the response time of the sampling signal is within a preset time range ΔT of the corresponding integration period; if so, determining that the sampling signal is credible And continue to pass backward; if not, after deleting the sampling signal, it also includes:

   judging whether the number of the sampled signals retained within the detection window time is greater than a second threshold;

   If so, determine that the sampled signal within the detection window time is credible and continue to transmit backwards.
7. The method according to claim 1, wherein when the number of photons received by the detection unit in one of the integration periods is greater than the threshold of the number of photons corresponding to the integration period, the detection unit responds and outputs a After sampling the signal, it also includes:

   Determine whether the number of photons received by the detection unit is less than a third photon number threshold in the previous time period before the start time t ₀ of the preset time range ΔT in the integration period;

   If so, determine that the sampled signal is credible and continue to transmit backwards;

   If not, delete the sampled signal.
8. The method according to any one of claims 3 to 7, wherein the fusing the sampled signals within the detection window time to obtain the detection signal comprises:

   The i-th integration period of the detection window time outputs the i-th sampling signal, and the j-th integration period adjacent to the i-th integration period outputs the j-th sampling signal; the i-th integration period outputs the j-th sampling signal; The photon number threshold corresponding to the integration period is greater than the photon number threshold corresponding to the jth integration period; wherein, 1≤i≤M, 1≤j≤M;

   Remove the same information as the i-th sampled signal from the j-th sampled signal to obtain the j-th processed signal;

   The detection signal is obtained by fusing all the processed signals within the detection window time.
9. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a plurality of instructions, and the instructions are adapted to be loaded by a processor and execute the method steps according to any one of claims 1-8 .
10. A laser radar, characterized in that the laser radar includes a transmitting system and a receiving system;

    the emission system, used for emitting outgoing laser light;

    The receiving system is configured to perform the method steps according to any one of claims 1-8.

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