CN113030908A

CN113030908A - Laser radar system

Info

Publication number: CN113030908A
Application number: CN201911252523.4A
Authority: CN
Inventors: 马宏
Original assignee: Juexin Electronics Wuxi Co ltd
Current assignee: Juexin Electronics Wuxi Co ltd
Priority date: 2019-12-09
Filing date: 2019-12-09
Publication date: 2021-06-25

Abstract

The invention provides a laser radar system, which comprises a laser transmitting module, a laser receiving module and a laser receiving module, wherein the laser transmitting module is used for transmitting a detection laser beam; a first reflection unit for receiving and changing a transmission direction of the detection laser beam emitted from the laser emission module; the second reflection unit is used for reflecting the detection laser beam reflected by the first reflection unit to a target to be detected and receiving and reflecting an echo signal reflected by the target to be detected; the laser receiving module is used for receiving and processing the echo signal transmitted by the second reflecting unit; the first reflection unit is located between the second reflection unit and the laser receiving module, and the effective reflection area of the first reflection unit is smaller than that of the second reflection unit. The invention makes up the defect of a non-coaxial laser radar that a short-distance optical detection blind area exists, and can ensure higher signal-to-noise ratio during short-distance detection.

Description

Laser radar system

Technical Field

The invention relates to the technical field of laser radars, in particular to a laser radar system.

Background

The laser radar is an active detection system, and the working principle of the active detection system is that a laser signal is actively transmitted to a target to be detected, the laser signal reflected back by the target is received, and the information of the target to be detected is obtained by comparing and analyzing the characteristics of the transmitted and received signals.

At present, many laser radars realize detection of information such as target distance and contour based on a pulse time of flight (PTOF) ranging principle. Due to the structural design problems of an optical path and a system, many two-dimensional or three-dimensional laser radar systems based on the PTOF principle have the problems of large close-distance blind area, incapability of transmitting power supply and signals through cables and the like. To reduce the near dead zone, some systems have addressed this by adding a compensating mirror, which is typically placed near or in close proximity to the receiver lens, which tends to have a lower signal-to-noise ratio at near distances. In order to solve the problems of power supply and signal transmission, some systems adopt wireless power supply and signal transmission, the power supply efficiency is low, a wireless power supply module is complex, and the cost is increased; there are also solutions using slip ring transmission, but the lifetime of the lidar is limited due to the high wear.

It is necessary to improve the optical path system of the existing laser radar to make up for the deficiencies of the prior art.

Disclosure of Invention

The invention aims to solve the technical problem that a laser radar adopting a non-coaxial light path in the prior art has a short-distance detection blind area.

In order to solve the above technical problems, the present invention discloses a laser radar system, comprising a laser emitting module, a first reflecting unit, a second reflecting unit and a laser receiving module,

the laser emission module is used for emitting a detection laser beam;

the first reflection unit is used for receiving and changing the transmission direction of the detection laser beam emitted from the laser emission module;

the second reflection unit is used for reflecting the detection laser beam reflected by the first reflection unit to a target to be detected, and receiving and reflecting an echo signal reflected by the target to be detected so as to be received by the laser receiving module;

the laser receiving module receives and processes the echo signal transmitted by the second reflecting unit;

the first reflection unit is located between the second reflection unit and the laser receiving module, and the effective reflection area of the first reflection unit is smaller than that of the second reflection unit.

Further, the reflection surface of the first reflection unit is opposite to the reflection surface of the second reflection unit.

Further, the laser receiving module comprises a receiving mirror group and a detector, and the receiving mirror group is positioned between the detector and the first reflecting unit;

the receiving mirror group is used for converging the echo signals reflected by the second reflecting unit;

the detector is used for receiving and processing the echo signals converged by the receiving mirror group.

Further, the centers of the first reflection unit, the second reflection unit, the receiving mirror group and the detector are coaxial, the common axis of the centers is the central axis of the lidar system, and the laser beam reflected by the first reflection unit is incident on the second reflection unit along the direction of the central axis.

Furthermore, the laser radar system further comprises a driving mechanism, wherein the driving mechanism is connected with the second reflecting unit and used for driving the second reflecting unit to rotate around the central axis.

Further, the second reflecting unit rotates around the central axis counterclockwise or clockwise, and the rotation angle is 0-360 degrees.

Preferably, an angle of 45 ° is formed between a normal direction of a mirror surface of the first reflecting unit and an incident direction of the detection laser beam, and an angle of 45 ° is formed between a normal direction of a mirror surface of the second reflecting unit and the detection laser beam reflected from the first reflecting unit.

Further, the laser emission module comprises a laser and a beam collimator disposed in front of the laser, the beam collimator disposed near the first reflection unit,

the laser is used for emitting the detection laser beam, and the beam collimator is used for collimating the laser beam emitted by the laser and enabling the laser beam to be incident into a three-dimensional space.

Further, the response wavelength of the detector is matched with the output wavelength of the laser.

Furthermore, the laser receiving module further comprises a filtering unit, the filtering unit is arranged between the detector and the receiving lens group, the filtering unit is used for filtering optical signals outside a preset wavelength range and transmitting the echo signals converged by the receiving lens group,

the transmission center wavelength of the filter unit is matched with the output wavelength of the laser, and the transmission bandwidth of the filter unit is matched with the line width of the laser.

By adopting the technical scheme, the laser radar system has the following beneficial effects:

1) the laser radar system is provided with the first reflecting unit, the second reflecting unit, the receiving mirror group and the detector which are coaxial in center, and ensures that laser beams are always incident on the second reflecting unit along the central axis direction of the system, thereby avoiding the short-distance scanning blind area caused by non-coaxial, and ensuring higher signal-to-noise ratio during short-distance detection;

2) according to the laser radar system, 360-degree scanning can be realized only by rotating the second reflecting unit, and other parts are kept fixed, so that the scanning is more stable, and the power supply of a laser, the signal output of a detector and other parts can be realized through conventional wired cables without adopting a slip ring or wireless mode, so that the service life of the system is longer, and the power consumption and the cost are lower;

3) the laser radar system of the invention completely adopts conventional optical elements, and does not need to process special-shaped structural elements or open holes on the lens or the reflecting unit, thereby not only having small processing and adjusting difficulty, but also reducing the manufacturing cost.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic diagram of a lidar system according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a second reflection unit of a lidar system according to an embodiment of the present invention rotated a first angle about its optical axis;

the system comprises a laser emitting module 1, a laser 11, a beam collimator 12, a first reflecting unit 2, a second reflecting unit 3, a laser receiving module 4, a receiving lens group 41, an optical filter 42, a light filter 43, a detector and a target to be detected 5.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the invention. In the description of the present invention, it is to be understood that the terms "upper", "lower", "top", "bottom", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein.

In order to solve the technical problem of the prior art that a laser radar adopting a non-coaxial light path has a short-distance detection blind area, the invention provides a laser radar system, and particularly, referring to fig. 1 and 2, the laser radar system comprises a laser emitting module 1, a first reflecting unit 2, a second reflecting unit 3 and a laser receiving module 4,

the laser emitting module 1 is used for emitting a detection laser beam;

the first reflection unit 2 is used for receiving and changing the transmission direction of the detection laser beam emitted from the laser emission module 1;

the second reflecting unit 3 is configured to reflect the detection laser beam reflected by the first reflecting unit 2 onto the target 5 to be detected, and receive and reflect an echo signal reflected by the target 5 to be detected, so that the echo signal is received by the laser receiving module 4;

the first reflection unit is located between the second reflection unit and the laser receiving module, a reflection surface of the first reflection unit is opposite to a reflection surface of the second reflection unit, and an effective reflection area of the first reflection unit is smaller than that of the second reflection unit.

Specifically, the laser receiving module 4 comprises a receiving mirror group 41 and a detector 43,

the receiving mirror group 41 is used for converging the echo signals reflected by the second reflecting unit 3;

the detector 43 is configured to receive and process the echo signal collected by the receiving mirror group 41, and specifically, the detector 43 is configured to convert the echo signal into an electrical signal after receiving the echo signal collected by the receiving mirror group 41.

The centers of the first reflection unit 2, the second reflection unit 3, the receiver group 41 and the detector 43 are coaxial, the common axis of the four centers is the central axis of the lidar system, and the laser beam reflected by the first reflection unit 2 is incident on the second reflection unit 3 along the direction of the central axis. The photosensitive surface of the detector 43 is located at the focal plane of the receiving mirror group 41.

Preferably, the first reflection unit 2 and the second reflection unit 3 may be mirrors, and a high-reflectivity film layer may be plated on the reflection surface of the mirrors to improve reflectivity. Preferably, the projection length of the reflection surface of the first reflection unit 2 in the horizontal plane is longer than the length of the receiving mirror group 41, and the projection length of the reflection surface of the second reflection unit 3 in the horizontal plane is shorter than the length of the receiving mirror group 41.

It can be understood that, under the condition of short distance, the light beam converged by the receiving lens group enters the region beyond the effective area of the detector, so that a blind zone appears at the short distance, and by the above structure, especially by arranging the first reflecting unit 2, the second reflecting unit 3, the receiving lens group 41 and the detector 43 with coaxial centers, the laser beam is ensured to enter the second reflecting unit 3 along the central axis direction of the system all the time, the non-coaxial short-distance scanning blind zone is avoided, the defect of the non-coaxial laser radar that the short-distance optical detection blind zone exists is effectively overcome, and the high signal-to-noise ratio during the short-distance detection can be ensured.

In some embodiments, it is preferable that an angle of 45 ° is formed between the normal direction of the mirror surface of the first reflection unit 2 and the incident direction of the detection laser beam, and an angle of 45 ° is formed between the normal direction of the mirror surface of the second reflection unit 3 and the detection laser beam reflected from the first reflection unit, and at this time, the scanning of the target 5 to be measured at the position shown in fig. 1 is implemented.

Further, in some embodiments, the lidar system further includes a driving mechanism, the driving mechanism is connected to the second reflecting unit 3, and the second reflecting unit 3 rotates around the central axis, preferably, the rotation around the central axis is 0 ° to 360 °. For example, when the second reflecting unit 3 rotates around the central axis by a first angle, preferably 180 °, the second reflecting unit 3 rotates to the position shown in fig. 2, and the scanning of the target 5 to be measured at the position shown in fig. 2 is realized. It will be appreciated that the target 5 to be measured at the position shown in fig. 1 and the target 5 to be measured at the position shown in fig. 2 are only exemplary fixed positions, and that in the rotation process of the second reflecting unit 3 from the position of fig. 1 to the position of fig. 2, the lidar performs scanning of the target 5 to be measured at each position passed by during the rotation process, and that this embodiment can perform 180 ° scanning, and similarly, when the second reflecting unit 3 is rotated again to the position of fig. 1 in the same rotation direction, 360 ° scanning can be performed. Further, the rotation direction of the second reflection unit 3 rotating counterclockwise in fig. 2 is only a preferable way, and in other implementable schemes, the second reflection unit may also rotate clockwise.

Further, in the rotating process of the second reflecting unit 3, the laser emitting module 1, the first reflecting unit 2 and the laser receiving module 4 are fixed with the laser radar body and are kept immovable relative to the body. It can be understood that 360-degree scanning can be realized by arranging the second reflecting unit 3 to rotate around the rotating mechanism, other parts are all kept fixed, and not only is the scanning more stable, but also the power supply of the laser 11, the signal output of the detector 43 and other parts can be realized by conventional wired cables without adopting a slip ring or a wireless mode, so that the system has longer service life and lower power consumption and cost.

Further, the laser emitting module 1 comprises a laser 11 and a beam collimator 12, the beam collimator 12 is arranged in front of the laser 11, the beam collimator 12 is arranged near the first reflecting unit 2,

the laser 11 is used for emitting the detection laser beam, the beam collimator 12 is used for collimating the laser beam emitted by the laser 11 and is incident to a three-dimensional space, and the beam collimator 12 can reduce the divergence angle of the detection laser beam.

In some embodiments, the response wavelength of the detector 43 is matched with the output wavelength of the laser 11, and preferably, the detector 43 can convert the received echo signal into an electrical signal output. The detector 43 may be an Avalanche Photodiode (APD) or other type of detector. The laser may be a Laser Diode (LD), or a Vertical Cavity Surface Emitting Laser (VCSEL), or other types of lasers. The output wavelength of the laser 11 may be 905nm or 1550 nm. It will be appreciated that the output wavelength of the laser 11 shown is only a preferred option and in other implementations, suitable wavelengths may be provided as desired.

Further, the laser receiving module 4 further includes a filtering unit 42, the filtering unit 42 is disposed between the detector 43 and the receiving lens group 41, the filtering unit 42 is configured to filter out optical signals outside a preset wavelength range and transmit the echo signals collected by the receiving lens group 41, the filtering unit 42 is disposed in front of the detector 43 along a transmission path of the echo signals and configured to filter stray light and improve a signal-to-noise ratio, and preferably, the filtering unit 42 may be an optical filter.

In some embodiments, the filter unit 42 has a transmission center wavelength matched to the output wavelength of the laser 11, and the filter unit 42 has a transmission bandwidth matched to the linewidth of the laser 11.

In some embodiments, the lidar system may further include a data processing module, and the processing module is connected to the detector 43 and configured to calculate a distance from the target 5 to be measured to the lidar system according to the received signal.

Specifically, with reference to fig. 1 and fig. 2, the operation principle of the lidar system is as follows: the detection laser beam emitted by the laser 11 is collimated by the beam collimator 12 into a laser beam with a divergence angle of milliradian (mrad) order, and is irradiated on the target 5 to be detected in a three-dimensional space, and is subjected to diffuse reflection on the surface of the target 5 to be detected, wherein a part of diffuse reflection light is received by the laser radar, is reflected to the laser receiving module 4 by the second reflecting unit 3, and then reaches the detector 43 after sequentially passing through the receiving mirror group 41 and the filtering unit 42, and is converted into an electric signal by the detector 43 for processing. And the data processing module of the laser radar calculates the distance from the target 5 to be detected to the laser radar according to the time difference between the emission and the reception of the laser signal, so as to realize the detection of the target 5 to be detected.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A laser radar system is characterized by comprising a laser emitting module, a first reflecting unit, a second reflecting unit and a laser receiving module,

the laser emission module is used for emitting a detection laser beam;

2. The lidar system of claim 1, wherein a reflective surface of the first reflective element is opposite a reflective surface of the second reflective element.

3. The lidar system of claim 1, wherein the laser receiving module comprises a receiver mirror group and a detector, the receiver mirror group being located between the detector and the first reflection unit;

4. The lidar system of claim 3, wherein centers of the first reflecting unit, the second reflecting unit, the receiver group, and the detector are coaxial, a common axis of the centers is a central axis of the lidar system, and the laser beam reflected by the first reflecting unit is incident on the second reflecting unit along the direction of the central axis.

5. The lidar system of claim 4,

the laser radar system further comprises a driving mechanism, wherein the driving mechanism is connected with the second reflecting unit and used for driving the second reflecting unit to rotate around the central axis.

6. The lidar system of claim 5, wherein the second reflecting unit rotates counterclockwise or clockwise about the central axis by an angle of 0 ° to 360 °.

7. The lidar system of claim 1,

an angle of 45 degrees is formed between the normal direction of the mirror surface of the first reflection unit and the incidence direction of the detection laser beam, and an angle of 45 degrees is formed between the normal direction of the mirror surface of the second reflection unit and the detection laser beam reflected from the first reflection unit.

8. The lidar system of claim 1,

the laser emission module comprises a laser and a beam collimator arranged in front of the laser, the beam collimator being arranged close to the first reflection unit,

9. The lidar system of claim 8,

the response wavelength of the detector is matched with the output wavelength of the laser.

10. The lidar system of claim 8,

the laser receiving module also comprises a filtering unit which is arranged between the detector and the receiving lens group and is used for filtering optical signals outside a preset wavelength range and transmitting the echo signals converged by the receiving lens group,