CN111427025A - Laser radar and ranging method of laser radar - Google Patents
Laser radar and ranging method of laser radar Download PDFInfo
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- CN111427025A CN111427025A CN202010037802.5A CN202010037802A CN111427025A CN 111427025 A CN111427025 A CN 111427025A CN 202010037802 A CN202010037802 A CN 202010037802A CN 111427025 A CN111427025 A CN 111427025A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
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Abstract
The invention discloses a laser radar and a ranging method of the laser radar, wherein the laser radar comprises the following components: the pulse method distance measuring unit is used for transmitting a first transmitting laser beam with a first frequency and receiving a corresponding first echo laser beam; the first distance calculating unit is connected with the laser beam transmitting and receiving unit and is used for calculating a first measuring distance according to the time of the laser beam transmitting and receiving unit; the phase method distance measuring unit is used for transmitting a second transmitting laser beam with a second frequency and receiving a corresponding second echo laser beam; the second distance resolving unit is connected with the second distance resolving unit and is used for determining the length of the redundant ruler under the phase method according to the phase difference of the laser beams transmitted and received by the second distance resolving unit and the second frequency; the data processing unit is respectively connected with the first distance resolving unit and the second distance resolving unit; the data processing unit is used for determining the whole ruler number based on the phase method according to the first measuring distance and the length of the residual ruler, and determining the actual measuring distance by combining the first measuring distance, the second measuring distance and the residual ruler. The large distance can be measured quickly and effectively with high precision.
Description
Technical Field
The embodiment of the invention relates to the technical field of laser radars, in particular to a laser radar and a ranging method of the laser radar.
Background
The laser radar is a radar system that emits a laser beam to detect a characteristic quantity such as a position and a velocity of a target object. Based on different distance measurement principles, the distance measurement method of the laser radar can comprise a phase distance measurement method (also called as a phase method) and a pulse distance measurement method (also called as a pulse method), and the laser radars based on the two different distance measurement principles have respective advantages and disadvantages and respective application fields. The phase method is high in ranging precision and can reach the level of 1 millimeter, different 'measuring scales' need to be switched in different measuring ranges, and strong light interference resistance is relatively weak. The method for realizing the distance measurement (such as Time of flight (TOF)) by the pulse distance measurement method is relatively simple, the precision can reach about 3 centimeters, the strong light interference is resisted, and the error magnitude is less influenced by the range.
In general, the phase ranging method is that a range finder (including a laser radar) modulates the intensity of laser light, and a measured distance is determined by measuring a phase delay. The principle is shown in fig. 1. The relationship between the round trip time of the ranging light and the phase change of the light wave is as follows:
ω - -modulating the angular frequency of the lightwave;
n- - - - - - -number of integers long;
in the formula (I), the compound is shown in the specification,
less than one wavelength of the phase mantissa.
Based on this, the periodic signal cannot distinguish the integer period N, and the measuring tape must ensure that N is zero. So the measuring distance is mainly determined by the measuring rule and the precision is determined by
And (6) determining. Therefore, at least different frequencies are needed to measure the same distance, and three or even more frequencies are needed to be used for measurement in the practical application process, so that the measurement timeliness is greatly reduced, and the number of points measured per second is small. Therefore, the factors such as measuring range and measuring precision need to be comprehensively considered by singly utilizing the phase method for measuring distance, the multi-frequency measuring mode with more than two frequencies can solve the problem of contradiction between the measuring range and the measuring ruler, but the time required by measurement is reduced, and the effectiveness is greatly reduced。
And the laser radar for realizing the distance measurement based on the single pulse TOF (time of flight) principle has a relatively simple implementation mode, can quickly complete the distance measurement process, but the precision is usually limited to about 3 cm.
In conclusion, the existing laser radar technology cannot rapidly and effectively realize the purpose of ensuring higher measurement precision while measuring a larger range.
Disclosure of Invention
The embodiment of the invention provides a laser radar and a ranging method of the laser radar, which combine the advantages of wide range of pulse ranging and high precision of phase ranging, thereby being beneficial to quickly and effectively realizing the measurement of a large range and ensuring higher measurement precision.
In a first aspect, an embodiment of the present invention provides a laser radar, including:
the pulse method distance measuring unit is used for transmitting a first transmitting laser beam with a first frequency to a target scanning area and receiving a first echo laser beam reflected by an object in the target scanning area;
the first distance calculating unit is connected with the pulse method distance measuring unit and used for calculating to obtain a first measuring distance according to the time for the pulse method distance measuring unit to receive and transmit the laser beam;
the phase method distance measuring unit is used for transmitting a second transmitting laser beam with a second frequency to a target scanning area and receiving a second echo laser beam reflected by an object in the target scanning area;
the second distance resolving unit is connected with the phase method distance measuring unit and used for determining the length of the redundant ruler under the phase method according to the phase difference of the laser beams transmitted and received by the phase method distance measuring unit and the second frequency; and
the data processing unit is respectively connected with the first distance calculating unit and the second distance calculating unit; the data processing unit is used for determining the number of the whole ruler based on a phase method according to the first measuring distance and the length of the residual ruler; the data processing unit is further used for determining an actual measurement distance according to the whole ruler number, the length of the residual ruler and the first measurement distance.
In an embodiment, the data processing unit is further configured to, when a deviation between the full scale number and a rounded value of the full scale number is within a preset deviation range, round the full scale number, determine a second measurement distance in the phase method by combining the length of the rest scale, and use the second measurement distance as the actual measurement distance.
In an embodiment, the data processing unit is further configured to take the first measured distance as an actual measured distance when a deviation between the full size number and a rounded value of the full size number is not within a preset deviation range.
In one embodiment, the first distance solution unit and the second distance solution unit are both integrated within the data processing unit; or
The first distance calculating unit and the pulse method ranging unit are integrated into a module, and the second distance calculating unit and the phase method ranging unit are integrated into a module.
In one embodiment, the first frequency is greater than the second frequency.
In one embodiment, the transmissions of the pulse method ranging unit and the phase method ranging unit are coaxial and the reception is coaxial, or the transmissions of the pulse method ranging unit and the phase method ranging unit are coaxial and the reception is off-axis.
In an embodiment, the lidar further comprises a transmitting optical unit; the transmitting optical unit comprises a first reflector and a first half mirror;
the transmitting end of the pulse method distance measuring unit comprises a first laser transmitter and a first transmitting lens group; the first emission lens group is used for focusing and collimating the light beam emitted by the first laser emitter into a first initial light beam;
the transmitting end of the phase method distance measuring unit comprises a second laser transmitter and a second transmitting lens group; the second emission lens group is used for focusing and collimating the light beam emitted by the second laser emitter into a second initial light beam;
the first initial beam passes through the first half mirror after being reflected by the first reflector to form a first emitted laser beam, and the second initial beam passes through the first half mirror to form a second emitted laser beam coaxial with the first emitted laser beam after being reflected by the first half mirror; or
The first initial beam is reflected by the first half mirror to form a first emitted laser beam, and the second initial beam is reflected by the first reflector and then passes through the first half mirror to form a second emitted laser beam coaxial with the first emitted laser beam.
In an embodiment, the receiving end of the pulse-method distance measuring unit includes a first receiving lens set, a first optical filter and a first photoelectric receiving device sequentially arranged along the transmission direction of the first echo laser beam;
the first receiving lens group is used for focusing the first echo laser beam, the first optical filter is used for filtering an interference signal in the first echo laser beam, and the first photoelectric receiving device is used for converting the first echo laser beam into a pulse current signal;
the receiving end of the phase method distance measuring unit comprises a second receiving lens group, a second optical filter and a second photoelectric receiving device which are sequentially arranged along the transmission direction of the second echo laser beam;
the second receiving lens group is used for focusing the second echo laser beam, the second optical filter is used for filtering interference signals in the second echo laser beam, and the second photoelectric receiving device is used for converting the second echo laser beam into a continuous current signal.
In one embodiment, the first echo laser beam and the second echo laser beam are received through the same receiving window; or
And the first echo laser beam and the second echo laser beam are received through different receiving windows, and the different receiving windows are respectively positioned at two sides of a transmitting window of the laser radar.
In a second aspect, an embodiment of the present invention further provides a ranging method for a laser radar, where the ranging method for the laser radar includes:
calculating according to the time of the pulse method distance measurement unit for receiving and transmitting the laser beam to obtain a first measurement distance;
determining the length of the margin ruler under the phase method according to the phase difference of the laser beams transmitted and received by the phase method distance measuring unit and the second frequency; wherein the second frequency is the frequency of the laser beam emitted by the phase method ranging unit;
determining the whole ruler number based on the phase method according to the first measuring distance and the length of the excess ruler; and
and determining the actual measuring distance according to the whole ruler number, the length of the residual ruler and the first measuring distance.
The laser radar provided by the embodiment of the invention comprises a pulse method ranging unit, a first receiving unit and a second receiving unit, wherein the pulse method ranging unit is used for transmitting a first transmitting laser beam with a first frequency to a target scanning area and receiving a first echo laser beam reflected by an object in the target scanning area; the first distance calculating unit is connected with the pulse method distance measuring unit and used for calculating to obtain a first measuring distance according to the time for the pulse method distance measuring unit to receive and transmit the laser beam; the phase method distance measuring unit is used for transmitting a second transmitting laser beam with a second frequency to the target scanning area and receiving a second echo laser beam reflected by an object in the target scanning area; the second distance resolving unit is connected with the phase method distance measuring unit and used for determining the length of the residual ruler under the phase method according to the phase difference of the laser beams transmitted and received by the phase method distance measuring unit and the second frequency; the data processing unit is respectively connected with the first distance calculating unit and the second distance calculating unit; the data processing unit is used for determining the whole ruler number based on the phase method according to the first measuring distance and the length of the residual ruler; the data processing unit is also used for determining the actual measurement distance according to the whole ruler number, the length of the residual ruler and the first measurement distance, so that the advantages of large range of pulse method distance measurement and high precision of single-frequency phase method distance measurement are combined, the large range can be measured quickly and effectively, and meanwhile, high measurement precision is ensured.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description will be given below of the drawings required for the embodiments or the technical solutions in the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a distance measurement principle of a laser radar based on phase method distance measurement;
FIG. 2 is a schematic structural diagram of a lidar according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of another lidar provided by an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a transmitting end of a laser radar according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of another transmitting end of the lidar provided by the embodiment of the invention;
FIG. 6 is a schematic view of a window distribution of a lidar according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a receiving end of a laser radar according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of another receiving end of the lidar provided by the embodiment of the present invention;
FIG. 9 is a schematic view of another window distribution of a lidar according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of another receiving end of a lidar according to an embodiment of the present invention;
fig. 11 is a flowchart illustrating a ranging method of a laser radar according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The improvement points of the embodiment of the invention are as follows: through integrating pulse method range unit and phase method range unit in laser radar, can utilize pulse range method and the respective advantage of phase distance method, when realizing measuring great range fast effectively, ensure higher measurement accuracy to be favorable to promoting laser radar's performance index.
The laser radar and the ranging method of the laser radar according to the embodiment of the present invention are exemplarily described below with reference to fig. 2 to 11.
Referring to fig. 2, the laser radar 10 includes: the pulse method ranging unit 110, the first distance calculating unit 131, the phase method ranging unit 120, the second distance calculating unit 141 and the data processing unit 130; the pulse method distance measuring unit 110 is configured to emit a first emitted laser beam with a first frequency to a target scanning area and receive a first echo laser beam reflected by an object in the target scanning area, and the first distance calculating unit 131 is connected to the pulse method distance measuring unit 110 and configured to calculate a first measured distance according to a time for the pulse method distance measuring unit 110 to receive and transmit the laser beam. The phase method distance measuring unit 120 is configured to emit a second emission laser beam with a second frequency to the target scanning area and receive a second echo laser beam reflected by an object in the target scanning area, and the second distance calculating unit 141 is connected to the phase method distance measuring unit 120 and configured to determine the length of the scale under the phase method according to the phase difference between the laser beam transmitted and received by the phase method distance measuring unit 120 and the second frequency. The data processing unit 130 is connected with the first distance calculating unit 131 and the second distance calculating unit 141, respectively; the data processing unit 130 is used for determining the number of the whole rulers based on the phase-based method according to the first measuring distance and the length of the remainder ruler; the data processing unit 130 is further configured to determine an actual measurement distance according to the number of full rulers, the length of the remainder ruler, and the first measurement distance.
In one embodiment, the first frequency is a high frequency, the second frequency is a low frequency, or the first frequency is greater than the second frequency and the difference between the two frequencies is at least greater than the identification capability of the lidar, so as to ensure that the laser beams of the two frequencies can be correctly received and correctly identified. By setting the second frequency to be a relatively small frequency, the phase method distance measurement can be ensured to have high precision.
When the laser radar is used for ranging, phase method ranging and pulse method (namely TOF (time of flight) ranging are fused, actual ranging distance can be determined according to a first ranging distance measured by the pulse method and a length of a scale obtained by phase method measurement, and the number of the scales determined by the pulse method and the length of the scale, so that high-precision measurement can be realized while measurement effectiveness is guaranteed, and the requirement on the scale in the phase method measurement process can be reduced.
In an embodiment, the first distance calculating unit 131 may determine a time difference between the first emitting laser beam time and the received first echo laser beam time, and further determine the measured distance according to the speed of light, so as to obtain the first measured distance D1.
The second distance calculating unit 141 may determine a phase difference between the second transmitting laser beam and the second received echo laser beam according to the phase of the second transmitting laser beam and the phase of the second received echo laser beam, and further obtain the length a of the redundant ruler by combining the second frequency. Specifically, the formula for calculating the excess length a is as follows:
wherein the content of the first and second substances,
the residual phase of the less than full periodic wave can be obtained by reading the phase of the laser beam transmitted and received by the phase-method distance measuring unit 120 according to the second distance calculating unit 141, wherein L is the length of the measuring tape, and the calculation formula is as follows:
where c represents the speed of light and f represents the second frequency both the second frequency and the speed of light are known and therefore the tape length L is also known fixedly and the remainder length a can be calculated.
In one embodiment, the data processing unit 130 may determine the integer size amount according to the following equation:
N×L+a＝D1
in the above equation, D1 is the distance of TOF ranging, and N is the full scale number. In the above formula, the sum of the left side is the result of the phase method distance measurement, and the right side is the result of the TOF distance measurement. In the case of no error, the measurement results are closer, only because there is some deviation in the measurement accuracy of the two. Therefore, the two can be made equal to obtain the integer number N.
Further, the data processing unit 130 determines the calculated full scale number N, and if the deviation between the full scale number N and the rounded value is within the preset deviation range, it indicates that the phase method measurement is an effective measurement, so that the full scale number N can be rounded and substituted into the left side of the above equation to obtain a second measurement distance under the phase method, and the measurement distance is used as an actual measurement distance. If the deviation between the full scale number N and the rounded value is not within the preset deviation range, the phase method measurement is represented as an invalid measurement, and the first measurement distance D1 is taken as the actual measurement distance.
Illustratively, the predetermined deviation range between the number of integers and their rounded values may be ± 0.05. For example, if the calculated number of measuring rulers is 1.01, the rounding value thereof is 1, and the deviation between the two is 0.01, and the deviation is within ± 0.05 of the preset deviation range, the measured distance of the phase method calculated by the rounding value of the number of the whole rulers can be directly output as an actual result; for example, if the calculated number of scales is 4.96 and the rounding value is 5, and the deviation between the two is-0.04, which is within the preset deviation range ± 0.05, the measured distance by the phase method calculated by rounding the number of scales can be directly output as an actual result. If the calculated number of the full scales is 4.7, 9.5, etc., the rounding value of 4.7 is 5, the deviation between the two is-0.3, the rounding value of 9.5 is 10, and the deviation between the two is-0.5, both of which exceed the preset deviation range +/-0.05, the first measured distance is taken as the actual measured distance.
In other embodiments, the preset deviation range may also be set according to the requirement of the laser radar 10, which is neither described nor limited in this embodiment of the present invention.
According to the laser radar, the phase method and the pulse TOF ranging method are fused, the number of the whole scales in ranging of the phase method can be determined, and then ranging under the phase method is obtained according to the number of the whole scales and the length of the rest scale, so that the result has high precision. In addition, the whole ruler number N can be obtained by a fusion method, so that the phase method distance measurement process is not limited by the length of the measuring ruler, a smaller measuring ruler can be selected for realization, and the measuring result can be ensured to have enough precision. Meanwhile, the laser radar integrates pulse TOF ranging and adopts the integration algorithm, so that the phase method ranging unit can finish measurement only by emitting a laser beam with one frequency.
Compared with the conventional phase method distance measurement, in order to realize long distance measurement and high precision, a proximity method is generally used, in which when the distance measurement is longer than a basic measuring tape (i.e., a precise measuring tape), one or more auxiliary measuring tapes (also called rough measuring tapes) are used, so that distance values measured by the measuring tapes are combined to obtain single and precise distance information. The distance measuring method needs to emit a plurality of laser beams with different frequencies, the measuring time is long, the timeliness is low, and the number of points measured per second is small. The laser radar in the embodiment can well overcome the problems, greatly reduces the time required by measurement, greatly improves the timeliness, and thoroughly solves the problem of contradiction between the measuring range and the measuring ruler.
The laser radar can output the result under the pulse TOF ranging as an actual result when the integral measurement is determined to be invalid, the accuracy of the output is reduced, the laser radar can be ensured to have correct ranging result output, and the defect of poor anti-interference performance when a single phase method is used for ranging can be overcome. In general, the single phase method distance measurement has high precision and can reach millimeter level, but has weak strong light resistance, is interfered by strong light when being used in a strong light environment, and can not work normally. Laser radar in the present case then can solve this problem well, because TOF range finding can anti highlight interference, even if under the highlight environment, if judge that the phase method is measured for invalid measurement, also can export the range finding result of TOF to ensure that laser radar can normally work.
In the above, the fusion manner of the pulse method distance measurement data obtained by the first distance calculating module 131 and the phase method distance measurement redundant scale data obtained by the second distance settlement module 141 is shown only by way of example. In other embodiments, the pulse method distance measurement data and the phase method distance measurement residual scale data may be fused in other manners known to those skilled in the art to obtain the actual measurement distance, which is not limited in the embodiment of the present invention.
In an embodiment, referring to fig. 3, the first distance solution unit 131 and the second distance solution unit 141 are both integrated within the data processing unit 130.
In other embodiments, the first distance calculating unit 131 and the pulse method ranging unit 110 may be integrated into a module, and the second distance calculating unit 141 and the phase method ranging unit 120 may be integrated into a module; or adopt other integrated mode of setting that technical staff in the field can know, can set up according to laser radar 10's actual demand to reduce laser radar 10's the quantity of structural division, thereby be favorable to improving its integrated level, be favorable to reducing laser radar 10's whole volume, realize its miniaturized design.
In one embodiment, referring to fig. 4 or 5, the pulse method ranging unit 110 is coaxial with the transmission of the phase method ranging unit 120. That is, the first emission laser beam 100 emitted from the emission end of the pulse method ranging unit 110 and the second emission laser beam 200 emitted from the emission end of the phase method ranging unit 120 are coaxially arranged.
So set up, can make first transmission laser beam 100 and second transmission laser beam 200 realize synchronous detection in time and space, two detecting beam shine in same direction at the same moment promptly to realize the first measuring distance that pulse method range finding obtained and the excess ruler length that single-frequency phase method range finding obtained synchronous in time and space, and then guarantee to survey the accuracy.
Illustratively, the coaxial arrangement of the first and second emitted laser beams 100 and 200 may be implemented in any manner known to those skilled in the art, and the embodiment of the present invention is not limited thereto. Hereinafter, based on fig. 4 and 5, an exemplary explanation is made in conjunction with the first mirror and the first half mirror.
In an embodiment, with continued reference to fig. 4 and 5, the lidar 10 further includes a transmitting optical unit including a first mirror 123 and a first half mirror 113;
the transmitting end of the pulse method distance measuring unit 110 includes a first laser transmitter 111 and a first transmitting lens group 112; the first emission lens group 112 is used for focusing and collimating the light beam emitted by the first laser emitter 111 into a first initial light beam 101; the transmitting end of the phase distance measuring unit 120 includes a second laser transmitter 121 and a second transmitting lens group 122; the second emission lens group 122 is used for focusing and collimating the light beam emitted by the second laser emitter 121 into a second initial light beam 201; the first initial beam 101 is reflected by the first mirror 123 and then passes through the first half mirror 113 to form a first emitted laser beam 100, and the second initial beam 201 is reflected by the first half mirror 113 to form a second emitted laser beam 200 coaxial with the first emitted laser beam 100, as shown in fig. 5; or the first initial beam 101 is reflected by the first half mirror 113 to form the first emitted laser beam 100, and the second initial beam 201 is reflected by the first mirror 123 and then passes through the first half mirror 113 to form the second emitted laser beam 200 coaxial with the first emitted laser beam 100, as shown in fig. 4.
In this way, a coaxial arrangement of the first emitted laser beam 100 and the second emitted laser beam 200 can be achieved.
Meanwhile, the first emission lens group 112 focuses and collimates the light beam emitted by the first laser emitter 111, which is beneficial to improving the optical density of the first emitted laser beam 100, so that the measurement accuracy of the pulse method distance measurement unit 110 is improved; similarly, the light beam emitted by the second laser emitter 121 is focused and collimated by the second emitting lens group 122, which is beneficial to improving the optical density of the second emitted laser beam 200, thereby being beneficial to improving the measurement accuracy of the phase method distance measuring unit 120; further, it is advantageous to improve the measurement accuracy of the remote measurement of the laser radar 10.
Meanwhile, in the structure of the laser radar 10 shown in fig. 4 and 5, the first reflecting mirror 123 is used for reflecting the light beam, and the first half mirror 113 is used for selectively reflecting and transmitting the light beam, so that the first emission laser beam 100 and the second emission laser beam 200 are coaxially arranged, the overall structure of the laser radar 10 is simpler, the overall size of the laser radar 10 is reduced, and the miniaturization design of the laser radar is realized.
In fig. 4 and 5, the first and second emitting lens groups 112 and 122 are exemplarily shown to include two convex lenses, respectively. In the actual product structure of the laser radar 10, on the premise that the focusing and collimation of the light beam can be realized, the transmitting lens groups may be further configured to be other lenses or lens group structures known to those skilled in the art, which is not limited in the embodiment of the present invention.
In one embodiment, the first laser transmitter 111 of the transmitting end of the pulse method ranging unit 110 includes a pulse laser diode, and the second laser transmitter 121 of the transmitting end of the phase method ranging unit 120 includes a continuous laser diode; wherein, the wave band range of the pulse laser diode is different from that of the continuous laser diode.
Therefore, the laser signals of the pulse method distance measuring unit 110 and the phase method distance measuring unit 120 do not interfere with each other, thereby facilitating the simultaneous measurement of the same distance by the pulse method and the single-frequency phase method.
Illustratively, the duty cycle of a pulsed laser diode is less than 1 ‰, the instantaneous power may be several tens of watts (e.g., 30W or 50W), and the emission time within one cycle may be several nanoseconds (e.g., 2ns or 3 ns); the peak power of a continuous laser diode may be a few milliwatts (e.g., 2mW or 3 mW).
In other embodiments, the working parameters of the pulse laser diode and the continuous laser diode may also be set according to the requirements of the laser radar 10, which is neither described nor limited in this embodiment of the present invention.
In the above, with reference to fig. 4 to fig. 5, the structure of the transmitting end of the laser radar 10 is exemplarily described, in other embodiments, the transmitting end of the laser radar 10 may further include other optical elements or electrical elements known to those skilled in the art, which is neither described nor limited in this embodiment of the present invention.
The structure of the receiving end of the laser radar 10 is exemplarily described below with reference to fig. 6 to 10. The receiving end of the laser radar 10 may be provided with a receiving window, that is, the receiving axes of the pulse method ranging unit and the phase method ranging unit are shown in fig. 6, 7 and 8; two receive windows, the receive off-axis of the pulse method ranging unit and the phase method ranging unit, may also be provided, as shown in fig. 9 and 10.
In one embodiment, with reference to fig. 2 and fig. 6, the receiving end of the pulse-method ranging unit 110 receives the first echo laser beam 300, and the receiving end of the phase-method ranging unit 120 receives the second echo laser beam 400; wherein the first echo laser beam 300 and the second echo laser beam 400 coaxially enter the same receiving window 500.
Thus, the number of receiving windows of the laser radar 10 is small, the degree of integration is high, and the appearance is simple.
The first echo laser beam 300 and the second echo laser beam 400 enter the same receiving window 500 and are split, received and processed separately, which is described in the following with reference to fig. 7 and 8.
It should be noted that fig. 6 only exemplarily shows that the transmission window 150 and the reception window 500 are disposed adjacent to each other on the left and right sides, and in other embodiments, the relative position relationship between the transmission window 150 and the reception window 500 may also be set according to the requirements of the laser radar 10, which is not limited in this embodiment of the present invention.
Alternatively, in an embodiment, with reference to fig. 2 and 9, the receiving end of the pulse-method ranging unit 110 receives the first echo laser beam 300, and the receiving end of the phase-method ranging unit 120 receives the second echo laser beam 400; the first echo laser beam 300 and the second echo laser beam 400 enter different receiving windows respectively and independently, which are respectively shown as a first receiving window 510 and a second receiving window 520, and the bright receiving windows are respectively located at two sides of the transmitting window 150 of the laser radar 10.
In this way, the pulse method ranging unit 110 and the phase method ranging unit 120 can receive the return light signal independently, the optical system is relatively simple, the intensity of the return light signal is relatively strong, and the ranging accuracy is high, which is exemplarily described below with reference to fig. 10.
In an embodiment, the laser radar 10 further includes a transmitting window 150, and the first receiving window 510 and the second receiving window 520 are symmetrically disposed on two sides of the transmitting window 150.
In this way, the distance between the first receiving window 510 and the second receiving window 520 of the laser radar 10 is large, the mutual interference between the first echo laser beam 300 and the second echo laser beam 400 is small, and the ranging accuracy is high. Meanwhile, the laser radar 10 is symmetrical in structure, and is designed and manufactured conveniently.
It should be noted that fig. 9 only exemplarily shows that the first receiving window 510 and the second receiving window 520 are separately disposed on two opposite sides of the transmitting window 15, and in other embodiments, the relative position relationship between the first receiving window 510, the second receiving window 520 and the transmitting window 150 may also be set according to the requirement of the laser radar 10, which is not limited in this embodiment of the present invention.
In an embodiment, with reference to fig. 9 and 10, the receiving end of the pulse-based ranging unit 110 includes a first receiving lens set 132, a first optical filter 134 and a first photoelectric receiving device 136 sequentially disposed along the transmission direction of the first echo laser beam 300; the first receiving lens set 132 is configured to focus the first echo laser beam 300, the first filter 134 is configured to filter an interference signal in the first echo laser beam 300, and the first photoelectric receiving device 136 is configured to convert the first echo laser beam 300 into a pulse current signal; the receiving end of the phase method distance measuring unit 120 includes a second receiving lens group 142, a second optical filter 144 and a second photoelectric receiving device 146 sequentially arranged along the transmission direction of the second echo laser beam 400; the second receiving lens group 142 is configured to focus the second echo laser beam 400, the second optical filter 144 is configured to filter an interference signal in the second echo laser beam 400, and the second photoelectric receiving device 146 is configured to convert the second echo laser beam 400 into a continuous current signal.
Thus, the receiving end of the pulse-method distance measuring unit 110 can receive the first echo laser beam 300, and the receiving end of the phase-method distance measuring unit 120 can receive the second echo laser beam 400; and the integral intensity of the return light signal is higher, and the interference signal is smaller, thereby being beneficial to improving the accuracy of distance measurement.
In an embodiment, with reference to fig. 6 and 7, in a configuration where the first echo laser beam 300 and the second echo laser beam 400 coaxially enter the same receiving window 500: the receiving end of the pulse method distance measuring unit 110 further includes a second half mirror 138, and the receiving end of the phase method distance measuring unit 120 further includes a second mirror 148; the second half mirror 138 is used for reflecting the first echo laser beam 300 in the echo signal to be detected and for transmitting the second echo laser beam 400 in the echo signal to be detected; the second mirror 148 is used to reflect the second echo laser beam 400.
In this way, the first echo laser beam 300 and the second echo laser beam 400 in the echo signal can be split by the second half mirror 138 and processed separately to obtain the first measurement distance and the second measurement distance.
In an embodiment, with reference to fig. 6 and 8, in a configuration where the first echo laser beam 300 and the second echo laser beam 400 coaxially enter the same receiving window 500: the receiving end of the pulse method distance measuring unit 110 further comprises a second reflecting mirror 148, and the receiving end of the phase method distance measuring unit 120 further comprises a second half mirror 138; the second half mirror 138 is used for reflecting the second echo laser beam 400 in the echo signal to be detected and for transmitting the first echo laser beam 300 in the echo signal to be detected; the second mirror 148 is used to reflect the first echo laser beam 300.
In this way, the first echo laser beam 300 and the second echo laser beam 400 in the echo signal can be split by the second half mirror 138 and processed separately to obtain the first measurement distance and the second measurement distance.
The operation principle of the receiving end is exemplarily explained based on fig. 7.
Referring to fig. 7, the receiving end of the laser radar 10 is composed of the first photo-receiving device 136 and the second photo-receiving device 146 and the optical elements associated therewith to form two receiving sets, which are respectively shown as the receiving end of the pulse method ranging unit 110 and the receiving end of the phase method ranging unit 120, and the two receiving sets can exchange positions (as shown in fig. 8). The receiving end of the pulse-method distance measuring unit 110 corresponds to a receiving group of the waveband laser return light of the light source at the transmitting end of the pulse-method distance measuring unit 110, the receiving end of the phase-method distance measuring unit 120 corresponds to a receiving group of the waveband laser return light of the light source at the transmitting end of the phase-method distance measuring unit 120, and sensitive wavebands of the receiving end can be respectively screened through the optical filters (including the first optical filter 134 and the second optical filter 144) so as to improve the signal-to-noise ratio. In other embodiments, the front and rear positions of the optical filter and the receiving lens set (including the first receiving lens set 132 and the second receiving lens set 142) in the optical path may be replaced, or an optical filter with the same parameters may be added to the front of the receiving lens set, which is not limited in the embodiments of the present invention.
For example, referring to fig. 7, the return light signal includes a high-frequency pulse laser and a low-frequency phase modulation laser, after the return light signal passes through the second half mirror 138, half of the return light signal passes through the first receiving lens set 132 to be focused, that is, the first receiving lens set 132 focuses the return light signal (i.e., the first return laser beam 300) of the pulse-method distance measuring unit 110, and then after the first return laser beam 300 passes through the first optical filter 134, both the natural light in the wavelength band of the light source of the non-pulse-method distance measuring unit 110 and the return light of the phase-method distance measuring unit 120 are filtered, and only the return light signal of the light source of the pulse-method distance measuring unit 110 reaches the photosensitive device (i.e., the first photoreceiving device 136). The light return signal of the light source of the pulse method ranging unit 110 is converted into a pulse current signal through the first photoelectric receiving device 136, and is processed by software and hardware of the pulse TOF distance calculating module (i.e., the first distance calculating unit 131) to obtain measurement data of the pulse TOF, i.e., the first measurement distance. Meanwhile, half of the return optical signal containing the pulse and phase modulated light passes through the second half mirror 138 to reach the second reflecting mirror 148, and then passes through the second receiving mirror group 142 and the second optical filter 144, and only the laser echo signal of the wavelength band corresponding to the light source of the pulse method ranging unit 120 remains. The light return signal of the pulse method distance measuring unit 120 is converted into a continuous current signal through the second photoelectric receiving device 138, and the signal is processed by software and hardware of the phase method distance dissociation calculation module (i.e., the second distance calculating unit 141) to obtain measurement data of a single-frequency phase method, that is, the length of the redundant ruler for measuring distance by the phase method is obtained.
The distance accuracy of the measurement data of the pulse TOF can be controlled to be about plus or minus 3cm and contains range information, and the accuracy of the phase method can be controlled to be in the millimeter level but does not contain complete range information (because the distance measurement formula of the phase method is as follows)
Whereby light emitting at only one frequency cannot determine the value of N). In the embodiment of the invention, high-precision complete measurement information can be obtained by fusing the range information of the pulse TOF and the high-precision redundant scale length information of the single-frequency phase method distance measurement, so that the fast and effective measurement of a large range of high-precision distance information is realized.
On the basis of the above embodiment, the embodiment of the invention also provides a ranging method of the laser radar. The ranging method of the laser radar can be implemented by any of the laser radars provided in the above embodiments, and therefore, the ranging method of the laser radar also has the beneficial effects of the laser radar in the above embodiments, and the same points can be understood by referring to the explanation of the laser radar in the above description, and are not repeated herein.
For example, referring to fig. 11, the ranging method of the laser radar may include:
s610, calculating according to the time of the pulse method distance measuring unit for receiving and sending the laser beam to obtain a first measuring distance.
For example, the step may include the first distance calculating unit calculating the first measured distance using the time of transmitting and receiving the laser beam of the pulse method ranging unit.
And S620, determining the length of the margin ruler under the phase method according to the phase difference of the laser beams transmitted and received by the phase method distance measuring unit and the second frequency.
Wherein the second frequency is the frequency of the laser beam emitted by the phase method distance measuring unit
For example, the step may include calculating the stub length of the phase method using the phase difference between the laser beam transmitted and received by the phase method distance measuring unit and the second frequency using the second distance calculating unit.
And S630, determining the whole ruler number based on the phase method according to the first measuring distance and the length of the redundant ruler.
Illustratively, this step may include calculating the scale number based on the scale length of the phase method, the remainder length, and the first measured distance of the impulse method range.
And S640, determining the actual measuring distance according to the number of the whole scales, the length of the rest scale and the first measuring distance.
For example, the step may include determining whether a difference between the full size amount and the rounded value is within a preset deviation range; if yes, calculating the actual measurement distance based on the number of the measuring tapes after the rounding, the length of the measuring tapes and the length of the rest tapes; and if not, taking the first measurement distance as the actual measurement distance.
Thus, in the distance measurement method provided by the embodiment of the present invention, the first measurement distance obtained by the pulse method distance measurement and the length of the residual ruler obtained by the phase method distance measurement are subjected to data fusion, the number of complete measurement rulers can be calculated, and the number of measurement rulers is rounded, so that an N0 value is obtained, the N0 value is brought back to the left side of the formula, and a more accurate actual measurement distance can be obtained based on the determined number of measurement rulers and the accurate measurement ruler precision, so that high-precision complete measurement information is obtained.
In other embodiments, other manners known to those skilled in the art may also be adopted to fuse the first measurement distance and the length of the redundant scale under the phase method, which is neither described nor limited in this embodiment of the present invention.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A lidar, comprising:
the pulse method distance measuring unit is used for transmitting a first transmitting laser beam with a first frequency to a target scanning area and receiving a first echo laser beam reflected by an object in the target scanning area;
the first distance calculating unit is connected with the pulse method distance measuring unit and used for calculating to obtain a first measuring distance according to the time for the pulse method distance measuring unit to receive and transmit the laser beam;
the phase method distance measuring unit is used for transmitting a second transmitting laser beam with a second frequency to a target scanning area and receiving a second echo laser beam reflected by an object in the target scanning area;
the second distance resolving unit is connected with the phase method distance measuring unit and used for determining the length of the redundant ruler under the phase method according to the phase difference of the laser beams transmitted and received by the phase method distance measuring unit and the second frequency; and
the data processing unit is respectively connected with the first distance calculating unit and the second distance calculating unit; the data processing unit is used for determining the number of the whole ruler based on a phase method according to the first measuring distance and the length of the residual ruler; the data processing unit is further used for determining an actual measurement distance according to the whole ruler number, the length of the residual ruler and the first measurement distance.
2. The lidar of claim 1, wherein the data processing unit is further configured to, when a deviation between the full scale number and a rounded value of the full scale number is within a preset deviation range, round the full scale number, determine a second measured distance in a phase method by combining the remaining scale length, and use the second measured distance as an actual measured distance.
3. The lidar of claim 2, wherein the data processing unit is further configured to take the first measured distance as an actual measured distance when a deviation between the full-scale quantity and a rounded value of the full-scale quantity is not within a preset deviation range.
4. The lidar of claim 1, wherein the first and second distance solution units are each integrated within the data processing unit; or
The first distance calculating unit and the pulse method ranging unit are integrated into a module, and the second distance calculating unit and the phase method ranging unit are integrated into a module.
5. The lidar of claim 1, wherein the first frequency is greater than the second frequency.
6. The lidar of claim 1, wherein the transmissions of the pulse method ranging unit and the phase method ranging unit are coaxial and receive coaxial, or wherein the transmissions of the pulse method ranging unit and the phase method ranging unit are coaxial and receive off-axis.
7. The lidar of claim 1, further comprising a transmit optical unit; the transmitting optical unit comprises a first reflector and a first half mirror;
the transmitting end of the pulse method distance measuring unit comprises a first laser transmitter and a first transmitting lens group; the first emission lens group is used for focusing and collimating the light beam emitted by the first laser emitter into a first initial light beam;
the transmitting end of the phase method distance measuring unit comprises a second laser transmitter and a second transmitting lens group; the second emission lens group is used for focusing and collimating the light beam emitted by the second laser emitter into a second initial light beam;
the first initial beam passes through the first half mirror after being reflected by the first reflector to form a first emitted laser beam, and the second initial beam passes through the first half mirror to form a second emitted laser beam coaxial with the first emitted laser beam after being reflected by the first half mirror; or
The first initial beam is reflected by the first half mirror to form a first emitted laser beam, and the second initial beam is reflected by the first reflector and then passes through the first half mirror to form a second emitted laser beam coaxial with the first emitted laser beam.
8. The lidar of claim 7, wherein the receiving end of the pulse-method distance measuring unit comprises a first receiving lens set, a first optical filter and a first photoelectric receiving device, which are sequentially arranged along the transmission direction of the first echo laser beam;
the first receiving lens group is used for focusing the first echo laser beam, the first optical filter is used for filtering an interference signal in the first echo laser beam, and the first photoelectric receiving device is used for converting the first echo laser beam into a pulse current signal;
the receiving end of the phase method distance measuring unit comprises a second receiving lens group, a second optical filter and a second photoelectric receiving device which are sequentially arranged along the transmission direction of the second echo laser beam;
the second receiving lens group is used for focusing the second echo laser beam, the second optical filter is used for filtering interference signals in the second echo laser beam, and the second photoelectric receiving device is used for converting the second echo laser beam into a continuous current signal.
9. The lidar of claim 8, wherein the first echo laser beam and the second echo laser beam are received through a same receive window; or
And the first echo laser beam and the second echo laser beam are received through different receiving windows, and the different receiving windows are respectively positioned at two sides of a transmitting window of the laser radar.
10. A ranging method of a laser radar, comprising:
calculating according to the time of the pulse method distance measurement unit for receiving and transmitting the laser beam to obtain a first measurement distance;
determining the length of the margin ruler under the phase method according to the phase difference of the laser beams transmitted and received by the phase method distance measuring unit and the second frequency; wherein the second frequency is the frequency of the laser beam emitted by the phase method ranging unit;
determining the whole ruler number based on the phase method according to the first measuring distance and the length of the excess ruler; and
and determining the actual measuring distance according to the whole ruler number, the length of the residual ruler and the first measuring distance.
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