Laser radar control method and laser radar

Abstract

The present invention provides a control method for a laser radar, comprising: S101: transmitting a pulse sequence encoded with a time interval; S102: receiving a radar echo, wherein the radar echo includes an echo pulse sequence corresponding to the pulse sequence; S103: sampling the echo pulse sequence with a sampling period T, wherein the time interval encoding is configured according to the sampling period T, so that for each echo pulse in the echo pulse sequence, the time difference between the sampling moment of the sampling point in the echo pulse and the center position of the echo pulse is not completely the same as the time difference of other echo pulses; S104: selecting the maximum value of the pulse amplitudes corresponding to the sampling points as the peak value of the echo pulse sequence.

Description

Technical Field

[0001] The present invention generally relates to the field of laser detection technology, and in particular to a control method for a laser radar and a laser radar. Background Art

[0002] In a lidar based on time-of-flight ranging, a laser transmitting circuit emits narrow-pulse laser pulses. These pulses strike and reflect off objects. The lidar uses the time difference between the narrow-pulse laser echo signal and the emitted laser pulse to determine the distance to the surrounding object using the formula d = c * t / 2, where c is the speed of light and t is the time of flight. Reflectivity is also a key measurement parameter for lidar, and determining the peak value of the echo pulse is crucial for calculating reflectivity. To obtain the peak value of the narrow-pulse laser echo signal, a high-speed analog-to-digital converter (ADC) is typically used to sample the laser echo signal. The sampling rate of high-speed ADCs used in lidars typically ranges from 500Msps to 1Gsps. This increased sampling rate also significantly increases circuit power consumption. This increased circuit power consumption typically results in increased heat generation. In lidar applications, due to the large number of components packed into a relatively small space, this increased heat generation is extremely detrimental to system operation.

[0003] The contents of the background technology section are merely technologies known to the public and do not necessarily represent the existing technologies in this field. Summary of the Invention

[0004] In view of at least one drawback of the prior art, the present invention provides a control method for a laser radar, comprising:

[0005] S101: transmitting a pulse sequence encoded with time intervals;

[0006] S102: Receive a radar echo, where the radar echo includes an echo pulse sequence corresponding to the pulse sequence;

[0007] S103: Sampling the echo pulse sequence at a sampling period T, wherein the time interval encoding is configured according to the sampling period T, so that for each echo pulse in the echo pulse sequence, a time difference between a sampling moment of a sampling point in the echo pulse and a center position of the echo pulse is not completely the same as the time differences of other echo pulses;

[0008] S104: Selecting the maximum value of the pulse amplitudes corresponding to the sampling points as the peak value of the echo pulse sequence.

[0009] According to one aspect of the present invention, the step of transmitting a pulse sequence encoded with a time interval includes: transmitting N pulses encoded with a time interval, wherein the time interval between the i+1th pulse and the first pulse is: Ti=ki*T+i / N*T, wherein, i=1,2,...N-1, ki is an integer greater than or equal to 1, and ki+1 is greater than ki, and T is the sampling period.

[0010] According to one aspect of the present invention, the sampling period T is greater than or equal to 10 nanoseconds.

[0011] According to one aspect of the present invention, the control method further includes: S105: calculating the reflectivity of the target object according to the peak value of the echo pulse sequence.

[0012] According to one aspect of the present invention, the step of calculating the reflectivity of the target object based on the peak value of the echo pulse sequence includes:

[0013] obtaining the energy of the echo pulse sequence according to the peak value of the echo pulse sequence;

[0014] The reflectivity is calculated based on the relationship between the energy of the echo pulse sequence and the energy of the transmitted pulse sequence.

[0015] According to one aspect of the present invention, step S102 further includes:

[0016] sequentially measuring the pulse width of each pulse in the echo pulse sequence that crosses the threshold according to the amplitude threshold;

[0017] According to the pulse width threshold, an echo pulse sequence including a pulse with a pulse width smaller than the pulse width threshold is removed from the radar echo.

[0018] According to one aspect of the present invention, the amplitude threshold is a fixed value, or changes according to changes in the external environment.

[0019] According to one aspect of the present invention, the step of sequentially measuring the pulse width of each pulse in the echo pulse sequence according to the amplitude threshold comprises:

[0020] The echo pulse sequence is input into the positive phase terminal of the comparator, and the amplitude threshold is input into the negative phase terminal of the comparator. When the comparison result of the amplitude of each pulse in the echo pulse sequence and the amplitude threshold is flipped for the first time, a first moment is obtained through a time-to-digital converter; when the comparison result of the amplitude and the amplitude threshold is flipped for the second time, a second moment is obtained through the time-to-digital converter, and the interval between the second moment and the first moment is the pulse width of the threshold crossing.

[0021] The present invention also provides a laser radar, comprising:

[0022] a transmitting unit configured to transmit a pulse sequence encoded with time intervals;

[0023] a receiving unit configured to receive a radar echo, wherein the radar echo includes an echo pulse sequence corresponding to the pulse sequence;

[0024] a sampling unit, receiving the radar echo from the receiving unit, and configured to sample the echo pulse sequence at a sampling period T, wherein the time interval encoding is configured according to the sampling period T, so that for each echo pulse in the echo pulse sequence, a time difference between a sampling moment of a sampling point in the echo pulse and a center position of the echo pulse is not completely the same as the time differences of other echo pulses;

[0025] The signal processing unit is coupled to the sampling unit and is configured to select the maximum value of the pulse amplitudes corresponding to the sampling points as the peak value of the echo pulse sequence.

[0026] According to one aspect of the present invention, the transmitting unit is configured to transmit N pulses encoded with time intervals, wherein the time interval between transmitting the i+1th pulse and the first pulse is: Ti=ki*T+i / N*T, wherein i=1,2,...N-1, ki is an integer greater than or equal to 1, and ki+1 is greater than ki, and T is the sampling period.

[0027] According to one aspect of the present invention, the sampling period T is greater than or equal to 10 nanoseconds.

[0028] According to one aspect of the present invention, the signal processing unit is configured to calculate the reflectivity of the target object according to the peak value of the echo pulse sequence.

[0029] According to one aspect of the present invention, the signal processing unit is configured to: obtain the energy of the echo pulse sequence according to the peak value of the echo pulse sequence; and calculate the reflectivity according to the relationship between the energy of the echo pulse sequence and the energy of the transmitted pulse sequence.

[0030] According to one aspect of the present invention, the sampling unit is configured to: measure the pulse width of each pulse in the echo pulse sequence that crosses the threshold in sequence according to the amplitude threshold; and remove the echo pulse sequence including pulses with a pulse width less than the pulse width threshold from the radar echo according to the pulse width threshold.

[0031] According to one aspect of the present invention, the amplitude threshold is a fixed value, or changes according to changes in the external environment.

[0032] According to one aspect of the present invention, the sampling unit further includes a comparator and a time-to-digital converter, and the sampling unit is configured to:

[0033] Each pulse in the echo pulse sequence is input into the positive phase terminal of the comparator, and the amplitude threshold is input into the negative phase terminal of the comparator. When the comparison result of the amplitude of each pulse in the echo pulse sequence with the amplitude threshold is flipped for the first time, a first moment is obtained through a time-to-digital converter; when the comparison result of the amplitude with the amplitude threshold is flipped for the second time, a second moment is obtained through the time-to-digital converter, and the interval between the second moment and the first moment is the pulse width of the threshold crossing.

[0034] The preferred embodiment of the present invention provides a control method and a laser radar, which uses medium and low-speed analog-to-digital converters to interleave sampling of the laser radar's echo pulse sequence, thereby obtaining the peak value of the echo pulse sequence in a low-power mode, and calculating the reflectivity of the target object based on the peak value of the echo pulse sequence, avoiding the influence of heat generated by the high-speed analog-to-digital converter on the laser radar, reducing system power consumption, and at the same time, multi-pulse detection improves the anti-interference ability of the laser radar system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 Schematically shows a laser radar emitting a pulse sequence coded at time intervals;

[0037] Figure 2 Schematically illustrates the sampling of the laser radar's echo pulse train using a medium- and low-speed analog-to-digital converter;

[0038] Figure 3A An embodiment of sampling a laser radar echo pulse sequence using a medium- and low-speed analog-to-digital converter is schematically shown;

[0039] Figure 3B Another embodiment of sampling the laser radar echo pulse sequence using a medium- and low-speed analog-to-digital converter is schematically shown;

[0040] Figure 4 A control method for a laser radar according to a preferred embodiment of the present invention is shown;

[0041] Figure 5 Schematically showing that a transmitter of a laser radar according to a preferred embodiment of the present invention performs time interval encoding on a transmission pulse sequence according to a sampling period;

[0042] Figure 6 The abnormally broadened echo pulse waveform is schematically shown;

[0043] Figure 7Schematically illustrates the process of filtering noise according to an amplitude threshold and obtaining the pulse width of each pulse in an echo pulse sequence according to a preferred embodiment of the present invention;

[0044] Figure 8 Schematically shows the internal structure of a sampling unit according to a preferred embodiment of the present invention;

[0045] Figure 9 A laser radar according to a preferred embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0046] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0047] In the description of the present invention, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," "counterclockwise," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for the purpose of facilitating the description of the present invention and simplifying the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of the aforementioned features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0048] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, removable, or integral connections; mechanical, electrical, or intercommunication connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0049] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may also include the first and second features not being in direct contact but being in contact via another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or diagonally above the second feature, or may simply mean that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or diagonally above the second feature, or may simply mean that the first feature is at a lower level than the second feature.

[0050] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0051] The following describes embodiments of the present invention in conjunction with the accompanying drawings. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0052] In order to improve the anti-interference ability, current laser radar usually adopts the time interval coding of the transmitter, such as Figure 1 As shown, each pulse is emitted in the form of a pulse sequence, which includes multiple narrow pulses (such as laser pulses with a half-width less than 5ns), and the time interval ΔT of the multiple narrow pulses in the pulse sequence is controlled. 1、 ΔT2……ΔT N When the time intervals of multiple narrow pulses in the received radar echo signal match the transmitted pulse sequence, it is determined to be the received signal of this laser radar. In this way, the anti-crosstalk capability of the laser radar is improved.

[0053] In the prior art, a high-speed analog-to-digital converter (e.g., a sampling rate of 500Msps-1Gsps) is usually used to perform high-speed sampling on the radar echo signal, fit the full pulse waveform, and obtain the pulse peak value. If a medium- or low-speed analog-to-digital converter (sampling rate less than 100Msps, e.g., 50Msps-100Msps) is directly used to sample the radar echo pulse, if the sampling interval T of the medium- or low-speed analog-to-digital converter is not compatible with the echo pulse interval, it is likely that the pulse peak information cannot be obtained. Figure 2As shown, for example, if a 100Msps analog-to-digital converter is used to sample the echo pulse sequence, the sampling interval T is 10ns (i.e., 1 / 100Msps). Assuming that the number of single pulses in the pulse sequence is 4, the half-maximum width of a single pulse is 5ns, and the single-pulse time interval is also 10ns, then no waveform information can be obtained when sampling at 0, 10ns, 20ns, 30ns...

[0054] When the echo pulse interval and the sampling interval T are adapted, for example, by setting the time intervals between the multiple pulses of the transmitted pulse sequence, each pulse in the echo pulse sequence (its peak value) is located at a different position in each sampling period, that is, for each echo pulse in the echo pulse sequence, the pulse amplitude corresponding to the sampling point in the echo pulse is not completely the same as the pulse amplitude corresponding to the sampling point in other echo pulses, then the peak information can be obtained after multiple samplings. Figure 3A 、 Figure 3B As shown in the figure, a medium-to-low-speed analog-to-digital converter (100Msps) is used to sample the echo pulse sequence. Assuming that the corresponding sampling interval T is 10ns, the number of single pulses in the pulse sequence is still 4, the half-maximum width of a single pulse is 5ns, and each pulse in the echo pulse sequence is located at a different position in the sampling period, different pulse amplitudes can be obtained by sampling at 0, 10ns, 20ns, 30ns..., among which the maximum value is close to the peak value, and the more pulses in the pulse sequence, the closer the maximum value is to the peak value.

[0055] Since the pulse time intervals in the same laser radar transmit pulse sequence and the echo pulse sequence match, the time interval of the transmit pulse sequence can be provided according to the sampling requirements of the echo pulse sequence.

[0056] The present invention utilizes the multi-pulse anti-interference characteristics of laser radar, combines with medium and low speed analog-to-digital converters, and performs interleaved sampling on the laser echo pulses. Finally, the peak value of the narrow pulse can be obtained through the medium and low speed analog-to-digital converters. Figure 4 As shown, the present invention provides a control method 10 of a laser radar, comprising:

[0057] In step S101, a pulse sequence encoded with time interval is transmitted. The transmitting end encodes the pulse sequence with time interval, and the transmitting time interval is ΔT 1、 ΔT2……ΔT N-1 Multiple pulses.

[0058] In step S102, a radar echo is received. The radar echo includes an echo pulse sequence corresponding to the transmitted pulse sequence. A received radar echo signal is identified as a received signal from the current lidar only when the time intervals between multiple pulses in the echo match the transmitted pulse sequence. This improves the radar's ability to resist crosstalk.

[0059] In step S103, the received echo pulse sequence is sampled with a sampling period T, wherein the time interval coding of the transmitting end is configured according to the sampling period T, so that for each echo pulse in the echo pulse sequence, the time difference between the sampling moment of the sampling point in the echo pulse and the center position of the echo pulse (the moment corresponding to the peak) is not exactly the same as the time difference of other echo pulses. If the distribution of the sampling points in each echo pulse is the same, the following may occur: Figure 2 The situation shown in the figure results in the medium and low speed analog-to-digital converter not being able to sample any echo information. If a certain rule is used to encode the time interval of the transmitted pulse sequence at the transmitting end, when sampling the radar echo pulse, the distribution of multiple sampling points in multiple echo pulses is different, such as Figure 3A 、 Figure 3B As shown, the acquired echo pulse peak value is relatively accurate.

[0060] In step S104: the maximum value among the pulse amplitudes corresponding to the multiple sampling points is selected as the peak value of the echo pulse sequence.

[0061] According to a preferred embodiment of the present invention, the step of transmitting a pulse sequence encoded with time intervals in the control method 10 comprises:

[0062] Transmit N pulses coded by time intervals, where the time interval between the i+1th pulse and the first pulse is: T i =k i *T+i / N*T, where i=1,2,...N-1,k i is an integer greater than or equal to 1, and k i+1 Greater than k i , T is the sampling period.

[0063] like Figure 5 As shown, the number of pulses in the laser radar pulse sequence is N, the sampling interval of the medium-speed analog-to-digital converter is T, and the time interval between the i+1th (i=1, 2, ... N-1) pulse in the control pulse sequence and the first pulse in the pulse sequence is T i =k i *T+i / N*T, where i=1,2,...N-1,k i is an integer greater than or equal to 1, and k i+1 Greater than k i .

[0064] For example, the time interval between the second pulse and the first pulse is T1, T1 = k1*T+1 / N*T, for example, k1 = 1;

[0065] The time interval T2 between the third pulse and the first pulse is T2 = k2*T+2 / N*T, for example, k2 = 2, or k2 = 3, as long as k2 is greater than k1;

[0066] The time interval T between the N-1th pulse and the 1st pulse N-2 , T N-2 =k N-2 *T+(N-2) / N*T;

[0067] The time interval T between the Nth pulse and the first pulse N-1 , T N-1 =k N-1 *T+(N-1) / N*T.

[0068] The time interval between two adjacent pulses in the transmitted pulse sequence is an integer multiple of the sampling period T plus 1 / N*T. The medium-speed analog-to-digital converter uniformly samples the echo pulse sequence with the sampling period T, so that the offset time of the sampling point in a single echo pulse relative to each sampling moment is 1 / N*T, that is, each sampling corresponds to a different position of a single echo pulse waveform.

[0069] Taking the transmission pulse sequence including 4 single pulses as an example, according to the above relationship T i =k i *T+i / N*T is T i =k i *T+i / 4*T, then the time interval between the second pulse and the first pulse is T1=T+1 / 4T, k1=1. The time interval between the third pulse and the first pulse is T2=2T+1 / 2T, k2=2. The time interval between the fourth pulse and the first pulse is T3=3T+3 / 4T, k3=3. At this time, the echo pulse sequence corresponds to Figure 3A The situation shown; the time interval between the fourth pulse and the first pulse can also be T3 = 4T + 3 / 4T, k3 = 4, and k3 is greater than k2. At this time, the echo pulse sequence corresponds to Figure 3B The situation shown.

[0070] According to a preferred embodiment of the present invention, in the control method 10, the sampling period T is greater than or equal to 10 nanoseconds (ie, the sampling rate is less than or equal to 100 Msps). Preferably, the laser radar uses a medium- or low-speed analog-to-digital converter for sampling.

[0071] According to a preferred embodiment of the present invention, the control method 10 further includes:

[0072] In step S105 , the reflectivity of the target object is calculated based on the peak value of the echo pulse sequence.

[0073] Since the energy of the transmitted pulse is known, the relationship between the peak value of the echo pulse sequence and the energy of the echo pulse sequence can be established, and then the reflectivity of the target object can be calculated based on the relationship (e.g., ratio) between the energy of the echo pulse sequence and the energy of the transmitted pulse sequence. The relationship between the peak value of the echo pulse sequence of the laser radar and the energy of the echo pulse sequence can be measured by a calibration station. For example, by replacing a reflector with a known reflectivity, fixing the luminous intensity, and the energy of the echo pulse sequence corresponding to the peak value of the echo pulse sequence is proportional to the reflectivity of the reflector. According to a preferred embodiment of the present invention, the peak value of the echo pulse sequence can be obtained by the control method 10, and then the energy of the echo pulse sequence is calculated based on the peak value of the echo pulse sequence. Thereafter, the reflectivity of the target object is calculated based on the relationship between the energy of the echo pulse sequence and the energy of the transmitted pulse sequence.

[0074] It is easy for those skilled in the art to understand that calculating the time of flight (TOF) based on the sampling points corresponding to the peak values of the echo pulse sequence and then obtaining the distance between the target object and the laser radar is also within the scope of protection of the present invention.

[0075] According to a preferred embodiment of the present invention, step S102 further includes:

[0076] sequentially measuring the pulse width of each pulse in the echo pulse sequence that crosses the threshold according to the amplitude threshold;

[0077] Based on the pulse width threshold, echo pulse trains including pulses with pulse widths less than the pulse width threshold are removed from the radar echoes. Generally, when the pulse widths of multiple pulses in a transmitted pulse train are the same, the pulse widths of multiple pulses in the corresponding echo pulse train are also the same. Therefore, the pulse width of a pulse in an echo pulse train can be measured to determine the pulse width of the pulses in the echo pulse train. This pulse width can then be compared with the pulse width threshold to remove echo pulse trains with pulse widths that do not exceed the pulse width threshold.

[0078] When the laser radar echo pulse signal is not saturated, the pulse width and the energy of the echo pulse usually meet a certain relationship, and the reflectivity can be calculated based on the pulse width. However, in cases of oblique incidence (such as the light spot projected onto the ground), drag point (such as the light spot projected onto two objects very close to each other), and long distance, the pulse broadening is abnormal and the peak value is reduced. Using the pulse width to calculate the reflectivity will bring about a large deviation (such as Figure 6 To ensure that the laser radar can accurately obtain reflectivity in all situations, in step S102 of control method 10: after receiving the laser radar echo pulse, a time-to-digital converter (TDC) is used to obtain the leading and trailing edges that cross the threshold to determine the pulse width. When the pulse width is greater than a certain threshold (e.g., 10ns), steps S103 and S104 of control method 10 are executed to obtain the peak value, and then the reflectivity of the target object is calculated.

[0079] like Figure 7 As shown, a time-to-digital converter is used to obtain the leading and trailing edges that cross the threshold to determine the pulse width, which can filter out the noise signal in the echo waveform and obtain the pulse width that crosses the threshold. The waveform after noise filtering is classified according to the pulse width. For the case of an echo pulse sequence with a pulse width greater than a certain threshold, the peak value obtained in steps S103 and S104 of the present application is used to calculate the reflectivity of the target object. For a normally widened echo pulse sequence, the reflectivity of the target object is calculated according to the conventional method.

[0080] like Figure 8 As shown, according to a preferred embodiment of the present invention, the input of a time-to-digital converter (TDC) is connected to a comparator. The radar echo pulse train is synchronously fed into the positive phase terminal of the comparator, and the amplitude threshold is fed into the negative phase terminal of the comparator. When the comparison result of the amplitude of each pulse in the echo pulse train and the amplitude threshold flips for the first time, the time-to-digital converter obtains a first moment; when the comparison result of the amplitude and the amplitude threshold flips for the second time, the time-to-digital converter obtains a second moment. The interval between the second moment and the first moment is the pulse width at which the threshold was crossed. The amplitude threshold can be set to a fixed value or to vary with ambient light noise. When the amplitude threshold varies with ambient light noise, it can be provided by the medium- or low-speed analog-to-digital converter used in control method 10.

[0081] Although the resolution of the time-to-digital converter is inconsistent with that of the medium- and low-speed analog-to-digital converter, the flipping moment of the time-to-digital converter relative to the sampling moment of the medium- and low-speed analog-to-digital converter is an absolute value that can be calculated through clock design. The leading edge moment and trailing edge moment obtained using the time-to-digital converter can be converted to the corresponding position or adjacent position of the sampling of the medium- and low-speed analog-to-digital converter.

[0082] According to a preferred embodiment of the present invention, Figure 9 As shown, the present invention further provides a laser radar 20 , comprising: a transmitting unit 21 , a receiving unit 22 , a sampling unit 23 and a signal processing unit 24 .

[0083] The transmitting unit 21 is configured to transmit a pulse sequence coded with a time interval. The transmitting end is coded with a time interval, and the transmitting time interval is ΔT1, ΔT2...ΔT N Multiple pulses.

[0084] Receiving unit 22 is configured to receive radar echoes, which include an echo pulse sequence corresponding to the transmitted pulse sequence. A received radar echo signal is identified as a received signal from the laser radar only when the time intervals between multiple pulses in the received radar echo signal match the transmitted pulse sequence. This improves the laser radar's ability to resist crosstalk.

[0085] The sampling unit 23 receives the radar echo pulse sequence from the receiving unit 22 and is configured to sample the received echo pulse sequence with a sampling period T, wherein the time interval coding of the transmitting end is configured according to the sampling period T, so that for each echo pulse in the echo pulse sequence, the time difference between the sampling moment of the sampling point in the echo pulse and the center position of the echo pulse (the moment corresponding to the peak) is not completely the same as the time difference of other echo pulses (or optionally, for each echo pulse in the multiple echo pulses, the pulse amplitude corresponding to the sampling point in the echo pulse is not completely the same as the pulse amplitude corresponding to the sampling point in other echo pulses). If the distribution of the sampling points in each echo pulse is the same, it may cause the medium and low speed analog-to-digital converter to fail to sample any echo information. If a certain rule is used to perform time interval coding on the transmitting end of the transmitting pulse sequence, so that when the radar echo pulse sequence is sampled, the distribution of multiple sampling points in multiple echo pulses is different, then the acquired echo pulse peak value is relatively accurate.

[0086] The signal processing unit 24 is coupled to the sampling unit 23 and is configured to select the maximum value of the pulse amplitudes corresponding to the sampling points as the peak value of the radar echo pulse sequence.

[0087] According to a preferred embodiment of the present invention, the transmitting unit 21 is configured to transmit N pulses encoded with time intervals, wherein the time interval between transmitting the i+1th pulse and the first pulse is: T i =k i *T+i / N*T, where i=1,2,...N-1,k i is an integer greater than or equal to 1, and k i+1 Greater than k i , T is the sampling period.

[0088] The time interval between two adjacent pulses in the transmitted pulse sequence is an integer multiple of the sampling period T plus 1 / N*T. The medium-speed analog-to-digital converter uniformly samples the echo pulse sequence with the sampling period T, so that the offset time of the sampling point in a single echo pulse relative to each sampling moment is 1 / N*T, that is, each sampling corresponds to a different position of a single echo pulse waveform.

[0089] According to a preferred embodiment of the present invention, the sampling period T of the sampling unit 23 is greater than or equal to 10 nanoseconds (ie, the sampling frequency is less than or equal to 100 Msps). Preferably, the sampling unit 23 includes a medium- to low-speed analog-to-digital converter.

[0090] According to a preferred embodiment of the present invention, the signal processing unit 24 is configured to calculate the reflectivity of the target object according to the peak value of the echo pulse sequence.

[0091] Because the energy of the transmitted pulse is known, a relationship between the peak value of the echo pulse sequence and the energy of the echo pulse sequence can be established, and the reflectivity of the target object can be calculated based on the energy of the echo pulse sequence and the energy of the transmitted pulse sequence. According to a preferred embodiment of the present invention, the signal processing unit 24 is configured to calculate the energy of the radar echo pulse sequence based on the peak value of the radar echo pulse sequence, and then calculate the reflectivity of the target object based on the relationship between the energy of the radar echo pulse sequence and the energy of the transmitted pulse sequence.

[0092] According to a preferred embodiment of the present invention, the sampling unit 23 is configured to: measure the pulse width of each pulse in the echo pulse sequence that exceeds the threshold in sequence according to the amplitude threshold; and remove the echo pulse sequence including pulses with a pulse width less than the pulse width threshold from the radar echo according to the pulse width threshold.

[0093] According to a preferred embodiment of the present invention, Figure 8 As shown, the sampling unit 23 includes a comparator 231, a time-to-digital converter 232, and a medium-speed analog-to-digital converter 233. The sampling unit 23 is configured to input the echo pulse sequence into the positive phase terminal of the comparator 231 and the amplitude threshold into the negative phase terminal of the comparator 231. When the comparison result of the amplitude of each pulse in the echo pulse sequence with the amplitude threshold flips for the first time, the time-to-digital converter 232 obtains a first moment; when the comparison result of the amplitude with the amplitude threshold flips for the second time, the time-to-digital converter 232 obtains a second moment. The interval between the second moment and the first moment is the pulse width that crosses the threshold.

[0094] The time-to-digital converter 232 is used to obtain the leading and trailing edges that cross the threshold to determine the pulse width. The noise signal in the echo waveform can be filtered out, and the pulse width that crosses the threshold can be obtained. The waveform after noise filtering is classified according to the pulse width. For the case of an echo pulse sequence with a pulse width greater than a certain threshold, the peak value obtained in steps S103 and S104 of the present application is used to calculate the reflectivity of the target object. For a normally widened echo pulse sequence, the reflectivity of the target object is calculated according to the conventional method.

[0095] According to a preferred embodiment of the present invention, the amplitude threshold can be set as a fixed value or change with the ambient light noise. When the amplitude threshold changes with the ambient light noise, it can be provided by the medium-low speed analog-to-digital converter 233 of the sampling unit 23.

[0096] The preferred embodiment of the present invention provides a control method and a laser radar, which uses medium and low-speed analog-to-digital converters to perform interleaved sampling on the echo pulse sequence, thereby obtaining the peak value of the echo pulse sequence in a low-power mode, and calculating the reflectivity of the target object based on the peak value of the echo pulse sequence, avoiding the influence of heat generated by the high-speed analog-to-digital converter on the laser radar, reducing system power consumption, and at the same time, multi-pulse detection improves the anti-interference ability of the laser radar system.

[0097] The preferred embodiment of the present invention utilizes a low- to medium-speed analog-to-digital converter (under 100Msps) to obtain pulse peak values. Compared to the traditional method of using a high-speed analog-to-digital converter (1Gsps) to fully sample the echo signal, the power consumption is approximately 1 / 10. Even considering the back-end time-to-digital converter (TDC), the power consumption can be reduced to approximately 1 / 3 of the traditional method, which is very beneficial for LiDAR operation. The present invention uses the echo pulse peak value to calculate reflectivity. Compared to the traditional method of calculating reflectivity based on pulse width, this method greatly improves reflectivity accuracy in LiDAR applications with abnormal pulse broadening, such as oblique incidence and drag points.

[0098] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for controlling a laser radar, comprising: S101: transmitting a pulse sequence encoded with time intervals; S102: Receive a radar echo, where the radar echo includes an echo pulse sequence corresponding to the pulse sequence; S103: Sampling the echo pulse sequence at a sampling period T, wherein the time interval encoding is configured according to the sampling period T, so that for each echo pulse in the echo pulse sequence, a time difference between a sampling moment of a sampling point in the echo pulse and a center position of the echo pulse is not completely the same as the time differences of other echo pulses; S104: selecting the maximum value of the pulse amplitudes corresponding to the sampling points as the peak value of the echo pulse sequence; S105: Calculating the reflectivity of the target object according to the peak value of the echo pulse sequence.

2. The control method according to claim 1, wherein the step of transmitting a pulse sequence encoded with time intervals comprises: Transmit N pulses coded by time intervals, where the time interval between the i+1th pulse and the first pulse is: T i =k i *T+i / N*T, where i=1,2,...N-1,k i is an integer greater than or equal to 1, and k i+1 Greater than k i , T is the sampling period. 3 . The control method according to claim 1 , wherein the sampling period T is greater than or equal to 10 nanoseconds.

4. The control method according to claim 1 , wherein the step of calculating the reflectivity of the target object according to the peak value of the echo pulse sequence comprises: obtaining the energy of the echo pulse sequence according to the peak value of the echo pulse sequence; The reflectivity is calculated based on the relationship between the energy of the echo pulse sequence and the energy of the transmitted pulse sequence.

5. The control method according to claim 1 or 2, wherein step S102 further comprises: sequentially measuring the pulse width of each pulse in the echo pulse sequence that crosses the threshold according to the amplitude threshold; According to the pulse width threshold, an echo pulse sequence including a pulse with a pulse width smaller than the pulse width threshold is removed from the radar echo. The control method according to claim 5 , wherein the amplitude threshold is a fixed value or changes according to changes in external environment.

7. The control method according to claim 5, wherein the step of sequentially measuring the pulse width of each pulse in the echo pulse sequence at the threshold value according to the amplitude threshold value comprises: The echo pulse sequence is input into the positive phase terminal of the comparator, and the amplitude threshold is input into the negative phase terminal of the comparator. When the comparison result of the amplitude of each pulse in the echo pulse sequence and the amplitude threshold is flipped for the first time, a first moment is obtained through a time-to-digital converter; when the comparison result of the amplitude and the amplitude threshold is flipped for the second time, a second moment is obtained through the time-to-digital converter, and the interval between the second moment and the first moment is the pulse width of the threshold crossing.

8. A laser radar comprising: a transmitting unit configured to transmit a pulse sequence encoded with time intervals; a receiving unit configured to receive a radar echo, wherein the radar echo includes an echo pulse sequence corresponding to the pulse sequence; a sampling unit, receiving the radar echo from the receiving unit, and configured to sample the echo pulse sequence at a sampling period T, wherein the time interval encoding is configured according to the sampling period T, so that for each echo pulse in the echo pulse sequence, a time difference between a sampling moment of a sampling point in the echo pulse and a center position of the echo pulse is not completely the same as the time differences of other echo pulses; The signal processing unit is coupled to the sampling unit and configured to select the maximum value of the pulse amplitudes corresponding to the sampling points as the peak value of the echo pulse sequence, and calculate the reflectivity of the target object according to the peak value of the echo pulse sequence.

9. The laser radar according to claim 8, wherein the transmitting unit is configured to transmit N pulses encoded with time intervals, wherein the time interval between transmitting the i+1th pulse and the first pulse is: T i =k i *T+i / N*T, where i=1,2,...N-1,k i is an integer greater than or equal to 1, and k i+1 Greater than k i , T is the sampling period.

10. The laser radar as described in claim 8 or 9, wherein the sampling period T is greater than or equal to 10 nanoseconds.

11. The laser radar as claimed in claim 8, wherein the signal processing unit is configured to: obtain the energy of the echo pulse sequence based on the peak value of the echo pulse sequence; and calculate the reflectivity based on the relationship between the energy of the echo pulse sequence and the energy of the transmitted pulse sequence.

12. The laser radar as claimed in claim 8 or 9, wherein the sampling unit is configured to: measure the pulse width of each pulse in the echo pulse sequence that crosses the threshold in sequence according to the amplitude threshold; and remove the echo pulse sequence including pulses with a pulse width less than the pulse width threshold from the radar echo according to the pulse width threshold.

13. The laser radar as claimed in claim 12, wherein the amplitude threshold is a fixed value or changes according to changes in the external environment.

14. The laser radar according to claim 12, wherein the sampling unit further comprises a comparator and a time-to-digital converter, and the sampling unit is configured to: The echo pulse sequence is input into the positive phase terminal of the comparator, and the amplitude threshold is input into the negative phase terminal of the comparator. When the comparison result of the amplitude of each pulse in the echo pulse sequence and the amplitude threshold is flipped for the first time, a first moment is obtained through a time-to-digital converter; when the comparison result of the amplitude and the amplitude threshold is flipped for the second time, a second moment is obtained through the time-to-digital converter, and the interval between the second moment and the first moment is the pulse width of the threshold crossing.

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