CN113030989A

CN113030989A - Laser radar based on DMD

Info

Publication number: CN113030989A
Application number: CN201911252530.4A
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 discloses a laser radar based on DMD, comprising: the transmitting module and the galvanometer module are sequentially arranged along a transmitting light path; the emission module is used for emitting a detection light beam to a target to be detected; the galvanometer module is used for deflecting and emitting the detection light beam so as to scan the target to be detected; the receiving lens module, the DMD module, the convergent lens module and the detector are sequentially arranged along a receiving light path; the receiving lens module is used for receiving an echo light beam reflected by the detection light beam through the target to be detected; the DMD module receives the echo light beam reflected by the galvanometer module and transmits the echo light beam to the convergent lens module; the convergent lens module converges the echo light beam reflected by the DMD module; the detector receives and processes the echo light beams converged by the converging lens module. By adopting the invention, the scanning frequency and the angular resolution are improved; the signal to noise ratio is improved, so that remote detection is realized; and cost saving.

Description

Laser radar based on DMD

Technical Field

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

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) distance measurement principle, and have wide application prospects in the fields of automatic driving, topographic mapping, road detection, mine field detection, urban three-dimensional modeling and the like.

In order to obtain three-dimensional information of a target, the lidar is required to scan in both the horizontal direction and the vertical direction. At present, most commercial products adopt a plurality of lasers and a plurality of detectors, realize multi-line scanning through the control of a precise mechanical mechanism, and improve the resolution ratio of the laser radar by increasing the number of the lasers and the detectors. Although this system solution can achieve a large detection distance, the high cost makes it difficult to be applied in a large scale.

Therefore, there is an urgent need to improve the optical path system of the laser radar, and a laser radar optical path system with high resolution, low cost and long enough detection distance is provided to make up for the deficiencies of the prior art.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: a novel lidar system with longer detection range, higher resolution and lower cost is provided.

In order to solve the technical problem, the invention discloses a laser radar based on a DMD, which comprises:

the transmitting module and the galvanometer module are sequentially arranged along a transmitting light path; the emission module is used for emitting a detection light beam to a target to be detected; the galvanometer module is used for deflecting and reflecting the detection light beam so as to scan the target to be detected;

the receiving lens module, the DMD module, the convergent lens module and the detector are sequentially arranged along a receiving light path; the receiving lens module is used for receiving an echo light beam reflected by the detection light beam through the target to be detected; the DMD module receives the echo light beam reflected by the galvanometer module and transmits the echo light beam to the convergent lens module; the convergent lens module converges the echo light beam reflected by the DMD module; the detector receives and processes the echo light beams converged by the converging lens module.

Further, the DMD module includes a plurality of micromirror units,

the micro mirror unit deflects around the axis of the micro mirror unit according to the deflection of the galvanometer module so that the echo light beam is emitted to the convergent lens module.

Furthermore, the DMD module further includes a control unit for controlling the deflection of the micromirror unit.

Further, the galvanometer module comprises a one-dimensional galvanometer and/or a two-dimensional galvanometer.

Furthermore, the surface of the reflector of the galvanometer module is plated with a film layer, and the reflection wavelength range of the film layer is matched with the output wavelength of the emission module.

Further, the transmitting module comprises a laser and a beam collimation unit;

the laser is used for providing a detection beam;

and the beam collimation unit is used for collimating the detection beam emitted by the laser.

Further, the laser includes a laser diode, a fiber laser, or a vertical cavity surface emitting laser.

Further, the center of the DMD module and the center of the detector are respectively disposed at object-image conjugate positions with respect to the converging lens module.

Further, the detector comprises an avalanche photodiode or a single photon counter.

Furthermore, the laser radar also comprises an optical filter, and the transmission center wavelength and the transmission bandwidth of the optical filter are matched with the output wavelength and the line width of the emission module.

By adopting the technical scheme, the invention has the following beneficial effects:

1) according to the laser radar system, scanning can be achieved without a mechanical scanning mechanism, and based on the scheme, the laser radar system can be used for manufacturing a two-dimensional laser radar and a three-dimensional laser radar, and can achieve high scanning frequency and angular resolution.

2) The laser radar system can control the instantaneous field angle of the system to be very small at any time, so that the entering of ambient stray light is reduced, the signal to noise ratio is improved, and the long-distance detection is realized.

3) The laser radar system does not need a complex and precise mechanical scanning mechanism, and can realize high-resolution scanning only by adopting one laser emitting module and one detector, so the cost is greatly reduced.

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 optical path system according to the present disclosure;

FIG. 2 is a schematic diagram illustrating a deflection state of the DMD module according to the present invention;

FIG. 3 is a schematic view of another deflection state of the DMD module of the present invention;

FIG. 4 is a schematic view of another deflection state of the DMD module of the present invention;

fig. 5 is a schematic view illustrating another deflection state of the DMD module according to the present invention.

The following is a supplementary description of the drawings: 1-a transmitting module; 101-a laser; 102-a beam collimation module; 2-a galvanometer module; 3-a receive lens module; 4-a DMD module; 401-micro mirror unit; 5-a converging lens module; 6-an optical filter; 7-a detector; 8-a first direction; 9-second direction.

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.

Example (b):

as shown in fig. 1, an embodiment of the present invention provides a DMD-based lidar including: the device comprises a transmitting module 1, a galvanometer module 2, a receiving lens module 3, a DMD module 4, a converging lens module 5 and a detector 7;

after the detection light beam is emitted by the emission module 1, the detection light beam is deflected and reflected by the galvanometer module 2 to scan a target to be detected; the echo light beams reflected by scanning are received and converged by the receiving lens module 3 and then are emitted to the DMD module 4; the DMD module 4 can deflect the echo light beams reflected back in different directions and angles, and the reflected echo light beams are emitted to the convergent lens module 5 for convergence, and finally emitted to the detector 7 for processing. Wherein the content of the first and second substances,

the emitting module 1 is used for emitting a detection light beam to a target to be detected.

In some embodiments, the transmission module 1 comprises a laser 101 and a beam collimation unit 102;

the laser 101 is used for providing a detection beam;

the beam collimation unit 102 is configured to collimate the probe beam emitted by the laser 101.

It is understood that the wavelength of the laser light output by the laser 101 may be 905nm or 1550nm, which is commonly used, and other suitable wavelengths may be used. The beam collimating unit 102 collimates the probe beam emitted from the laser 101, and can reduce the divergence angle of the beam, so devices having the same or similar functions all belong to the protection scope of the embodiment of the present invention.

Further, the laser 101 may be a Laser Diode (LD), a fiber laser, a Vertical Cavity Surface Emitting Laser (VCSEL), or other types of lasers.

And the galvanometer module 2 is used for deflecting and reflecting the detection light beam so as to scan the target to be detected after the detection light beam is emitted in different directions and angles.

It can be understood that the galvanometer module 2 can deflect in different directions and at different angles, so that the probe beam can be emitted in the direction and at the angle required by scanning to scan the target to be detected.

In some embodiments, the galvanometer module 2 is a one-dimensional galvanometer. The one-dimensional galvanometer can scan along a certain direction, so that the two-dimensional laser radar function is realized.

In other embodiments, the galvanometer module 2 is a two-dimensional galvanometer. The two-dimensional galvanometer can scan along two orthogonal directions, so that the three-dimensional laser radar function is realized.

In some embodiments, the mirror surface of the galvanometer module 2 is coated with a high-reflectivity film layer to improve reflectivity. The reflection wavelength range of the film layer is matched with the output wavelength of the emission module 1 so as to output the detection light beam emitted by the emission module 1, and therefore the target to be detected is scanned.

The receiving lens module 3 is configured to receive an echo light beam reflected by the target to be detected from the probe light beam. The receiving lens module 3 can also converge the echo light beam to the DMD module 4.

Further, the receiving lens module 3 may be an aspheric lens, or a combination of multiple lenses which are optimized to achieve a converging function.

The DMD module 4, i.e., a digital micromirror device, is configured to change the direction of the echo light beam according to the deflection direction and the deflection angle of the galvanometer module 2. It will be appreciated that the range of reflected wavelengths of the DMD module 4 matches the output wavelength of the laser 101.

In some embodiments, the DMD module 4 includes a plurality of micromirror cells 401,

the micromirror unit 401 is deflected around the axis of the micromirror unit 401 according to the deflection of the galvanometer module 2 to direct the echo light beam to the converging lens module 5.

Further, the DMD module 4 is disposed at the focal plane position of the receiving lens module 3.

Further, the DMD module 4 further includes a control unit for controlling the deflection of the corresponding micro-mirror unit 401.

In some embodiments, the micro mirror cells 401 form a two-dimensional array, and each of the micro mirror cells 401 may deflect about its own axis.

At any time during the scanning process of the galvanometer module 2, at least one micro-mirror cell 401 has a deflection state different from that of the other micro-mirror cells 401. For example,

if only one micromirror cell 401 is in the ON state and the other micromirror cells 401 are in the OFF state, the ON state is the active operating state of micromirror cell 401;

alternatively, if only one micromirror cell 401 is in the OFF state and the other micromirror cells 401 are in the ON state, the OFF state is the active operating state of micromirror cell 401.

The choice of the two states depends on the relative position and layout of the DMD module 4 and the converging lens module 5. When the micromirror unit 401 is in the ON state to reflect the echo light beam to the condensing lens module 5, the effective operating state of the micromirror unit 401 is the ON state, and vice versa. That is, the selection of the effective operating state depends on the state in which the echo light beam can be reflected to the converging lens module 5.

Further, different deflection directions and deflection angles of the galvanometer module 2 correspond to the switching states of different micro-mirror units 401 on the DMD module 4; by changing the on-off state of different micromirror units 401 on the DMD module 4, the target reflected light reflected in different directions within the field of view can be converged on the detector 7.

The converging lens module 5 is used for converging the echo light beam passing through the DMD module 4.

Further, the converging lens module 5 may be an aspheric lens, or a combination of multiple lenses which are optimized to achieve the converging function.

And the detector 7 is used for receiving the echo light beams converged by the converging lens module 5 and converting the echo light beams into electric signals to be output.

Further, the response wavelength of the detector 7 is matched to the output wavelength of the laser 101.

Further, the detector 7 may be an Avalanche Photodiode (APD), but also other types of detectors 7 are possible.

In some embodiments, the center of the DMD module 4 and the center of the detector 7 are placed at conjugate positions with respect to the object image of the converging lens module 5, respectively.

In some embodiments, the lidar further comprises an optical filter 6, wherein the transmission center wavelength and the transmission bandwidth of the optical filter 6 are matched with the output wavelength and the line width of the emission module 1; the optical filter 6 is used for filtering stray light and improving the signal to noise ratio.

In order to make the implementation process more intuitive, the following is further explained with reference to the accompanying drawings.

Referring to fig. 1, the detection beam emitted by the laser 101 is collimated into a detection beam with a divergence angle of mrad magnitude by the beam collimating unit 102, and the detection beam irradiates on the reflecting surface of the galvanometer module 2 and is reflected to the target to be measured; the probe beam is diffusely reflected on the target surface, and a part of the diffusely reflected light is received by the receiving lens module 3 and converged on a micromirror unit 401 of the DMD module 4 located at the image plane position. The converged light is reflected by the micromirror unit 401, converged again by the converging lens module 5, and received by the detector 7 after passing through the filter 6.

In the working process of the laser radar shown in fig. 1, the galvanometer module 2 continuously scans along two orthogonal directions, so that the position of the detection beam irradiated on the target to be detected continuously changes; meanwhile, the direction of the echo light beam reflected from the target to be measured and received by the receiving lens module 3 is also changed in real time; therefore, the position of the light spot on the DMD module 4 after the echo light beam is converged by the receiving lens module 3 is also changed.

Specifically, assume at t₁At the moment, the echo beam reflected from the target to be measured is incident on the receiving lens module 3 along the first direction 8, and the position of the convergent light spot is P₁(as shown in fig. 2). The deflection state of the corresponding micromirror unit 401, i.e. the light spot P, is controlled by the control unit in the DMD module 4₁The corresponding micromirror unit 401 is controlled such that only P₁The corresponding one of the micromirror cells 401 at the spot location deflects to an active operating state (e.g., ON state) and the other micromirror cells 401 are in an inactive operating state (e.g., OFF state). At the position ofThe micromirror unit 401 in the active working state reflects the echo beam and then converges the reflected echo beam to the P of the detector 7 through the converging lens module 5₁In the' position, the other micromirror units 401 do not contribute to the reflection of the echo light beam.

Then at t₂At the moment, the echo beam reflected from the target to be measured is incident on the receiving lens module 3 along the second direction 9, and the position of the convergent light spot is P₂(as shown in fig. 3). The deflection state of the corresponding micromirror unit 401, i.e. the light spot P, is controlled by a control unit in the DMD module 4₂The corresponding micromirror unit 401 is controlled such that only P₂The corresponding one of the micromirror cells 401 at the spot location deflects to an active operating state (e.g., ON state) and the other micromirror cells 401 are in an inactive operating state (e.g., OFF state). The micromirror unit 401 in the active working state reflects the echo beam and then converges the reflected echo beam to P of the detector 7 through the converging lens module 5₂In the' position, the other micromirror units 401 do not contribute to the reflection of the echo light beam. In this way, the deflection state of the micro mirror unit 401 on the DMD module 4 is changed in real time according to the deflection angle of the galvanometer module 2, so as to realize target detection of different directions in the laser radar field of view.

It should be noted that fig. 2 and 3 are schematic diagrams, and not all micromirror units 401 are shown, and in practice, many more micromirror units 401 may be included in DMD module 4, such as 854 × 480, 1280 × 800, and other specifications.

And the data processing module of the laser radar calculates the distance from the target to the laser radar according to the time difference between the emission and the reception of the detection light beam. With the high-speed deflection of the galvanometer module 2 and the real-time adjustment of the DMD module 4, a large amount of point cloud data with a certain field angle in the vertical direction and the horizontal direction can be obtained, and the three-dimensional detection of the target in the space is realized.

In the above discussion, the case where only one micromirror unit 401 is in an active operating state at the same time is explained; in practical applications, the DMD module 4 may drive a plurality of micromirrors to work effectively at the same time according to the condition of the echo beam, as will be explained below:

as shown in fig. 1, 4 and 5, the optical path layout of the lidar is the same as that described above, i.e., the optical path structure shown in fig. 1, but the DMD module 4 is different in the deflection state and the control mode. Specifically, at any time during the operation of the laser radar, the number of the micro-mirror units 401 in the effective operation state on the DMD module 4 is greater than one, and fig. 4 shows one possible operation manner of the DMD module 4, where four adjacent micro-mirror units 401 are in the effective operation state at any time. Fig. 5 shows another possible way of operating DMD module 4, with five adjacent micromirror cells 401 in active operating state at any time. With reference to these two modes of operation, more similar modes of operation can also be derived.

In the embodiment of the invention, the galvanometer is adopted to realize three-dimensional scanning in the vertical direction and the horizontal direction, the scanning speed is high, and the angular resolution is high. Meanwhile, only one or a few micro-mirror units 401 are in an effective working state at any moment, and the size of each micro-mirror unit 401 is only in a micron order, so that the instantaneous field angle of the system can be controlled to be very small, the entering of ambient stray light can be greatly reduced, the signal-to-noise ratio is improved, and remote detection is realized. The system does not need a complex and precise mechanical scanning mechanism, so that the system has simpler structure, more stable work and longer service life. In addition, in the laser radar, three-dimensional high-resolution scanning can be realized by only adopting one laser emitting module 1 and one detector 7, so that the cost is greatly reduced.

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 DMD-based lidar comprising:

the transmitting module (1) and the galvanometer module (2) are sequentially arranged along a transmitting light path; the emission module (1) is used for emitting a detection light beam to a target to be detected; the galvanometer module (2) is used for deflecting and reflecting the detection light beam so as to scan the target to be detected;

the receiving lens module (3), the DMD module (4), the convergent lens module (5) and the detector (7) are sequentially arranged along a receiving light path; the receiving lens module (3) is used for receiving an echo light beam reflected by the detection light beam through the target to be detected; the DMD module (4) receives the echo light beam reflected by the galvanometer module (2) and transmits the echo light beam to the convergent lens module; the convergent lens module (5) converges the echo light beam reflected by the DMD module (4); the detector (7) receives and processes the echo light beams converged by the converging lens module (5).

2. The DMD based lidar according to claim 1, wherein: the DMD module (4) comprises a plurality of micromirror units (401),

the micromirror unit (401) deflects around the axis of the micromirror unit (401) according to the deflection of the galvanometer module (2) to direct the echo light beam to the converging lens module (5).

3. The DMD based lidar according to claim 2, wherein: the DMD module (4) further comprises a control unit for controlling the deflection of the respective micromirror cell (401).

4. The DMD based lidar according to claim 1, wherein: the galvanometer module (2) comprises a one-dimensional galvanometer and/or a two-dimensional galvanometer.

5. The DMD based lidar according to claim 1, wherein: the surface of the reflector of the galvanometer module (2) is plated with a film layer, and the reflection wavelength range of the film layer is matched with the output wavelength of the emission module (1).

6. The DMD based lidar according to claim 1, wherein: the transmission module (1) comprises a laser (101) and a beam collimation unit (102);

the laser (101) for providing a probe beam;

the beam collimation unit (102) is used for collimating the detection beam emitted by the laser (101).

7. The DMD based lidar according to claim 6, wherein: the laser (101) comprises a laser diode, a fiber laser, or a vertical cavity surface emitting laser.

8. The DMD based lidar according to claim 1, wherein: the center of the DMD module (4) and the center of the detector (7) are respectively arranged at the conjugate position of the object image relative to the convergent lens module (5).

9. The DMD based lidar according to claim 1, wherein: the detector (7) comprises an avalanche photodiode or a single photon counter.

10. The DMD based lidar according to claim 1, wherein: the laser radar also comprises an optical filter (6), and the transmission center wavelength and the transmission bandwidth of the optical filter (6) are matched with the output wavelength and the line width of the emission module (1).