CN113721220A - Method for realizing two-dimensional optical scanning by single-degree-of-freedom rotation - Google Patents
Method for realizing two-dimensional optical scanning by single-degree-of-freedom rotation Download PDFInfo
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- CN113721220A CN113721220A CN202010445339.8A CN202010445339A CN113721220A CN 113721220 A CN113721220 A CN 113721220A CN 202010445339 A CN202010445339 A CN 202010445339A CN 113721220 A CN113721220 A CN 113721220A
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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
- G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
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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
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
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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
- G01S7/4816—Constructional features, e.g. arrangements of optical elements of receivers alone
Abstract
The invention relates to a method for realizing two-dimensional optical scanning by single-degree-of-freedom rotation, which is characterized in that a core device is a multi-surface reflector with N reflecting surfaces, the relative angles of each reflecting surface and a rotating shaft are different, the multi-surface reflector rotates around a fixed shaft, and an incident beam irradiates to the multi-surface reflector at a certain angle and then is reflected to different directions of a space to realize two-dimensional optical scanning. According to the invention, two-dimensional optical scanning can be realized only through single free rotation, the system structure can be simplified, the reliability and the stability can be improved, and the cost can be reduced.
Description
Technical Field
The invention relates to the technical field of optics, in particular to a method for realizing two-dimensional optical scanning by single-degree-of-freedom rotation.
Background
The optical scanning system mainly comprises a light source for emitting light beams and a light beam deflection unit, can deflect the light beams emitted by the light source and enable the light beams to fall on a preset scanning line or surface in sequence, and is mainly applied to devices such as laser printers, laser welding machines, laser marking machines, laser engraving machines, high-speed cameras, projectors, movie projectors, laser radars and the like.
The beam deflection unit mainly has a mechanical type, a micro electro mechanical system (MEMES) type, and an Optical Phased Array (OPA) type according to a difference in a beam scanning manner.
In mechanical or MEMS scanning, generally, a single degree of freedom motion can only achieve one-dimensional optical scanning, for example, a linear one-dimensional scanning of a light beam within a certain angle range can be achieved by a rotation or reciprocation of a light source, a rotation or reciprocation of a mirror, or the like; two-dimensional optical scanning can be realized only by the movement of two degrees of freedom, for example, two-stage reflection in which two reflecting mirrors respectively rotate or reciprocate, a MEMS optical galvanometer, and the like can realize two-dimensional scanning of a light beam in a certain spatial range. However, the two-dimensional mechanical scanning method is always accompanied by unbalanced reciprocating motion, such as reciprocating swing within a certain angle range, and such a structure is often poor in reliability and short in service life. In addition, the MEMS optical galvanometer scheme also has a problem of limited receiving aperture, and in some applications requiring receiving echo signals, such as laser radar, a higher signal-to-noise ratio cannot be obtained, so that a longer detection distance cannot be obtained.
In the OPA-type scanning, the exit angle of the light beam is changed by adjusting the phase difference of each emission unit in the light emitting array. Optical phased arrays are generally used to achieve beam-directed scanning by strictly controlling the phase of the optical phased array through an electrical signal, and therefore may also be referred to as electronic scanning technology. However, this technology is far from mature at present and cannot meet the requirement of long distance due to the limited power.
Disclosure of Invention
Based on the above problems, the present invention aims to provide a method for realizing two-dimensional optical scanning by single-degree-of-freedom rotation, which has the following main advantages: 1) two-dimensional optical scanning can be realized only by using rotation with single degree of freedom, so that the system structure is greatly simplified, and the complexity is reduced; 2) when the single-degree-of-freedom rotation is constant, the whole scanning system is in a balanced state, the reliability is high, and the service life is long; 3) in the application of needing to receive echo signals, the scanning method can realize coaxial emission and light beam recovery, and the light receiving aperture is far larger than that of an MEMS optical galvanometer scheme.
According to a first embodiment of the present invention, there is provided a method for realizing two-dimensional optical scanning by single-degree-of-freedom rotation, including an optical emission unit and an optical reflection unit, wherein: the optical emission unit comprises a light source for generating emergent light, and the emergent light is transmitted along an emission path and reflected by the optical reflection unit; the optical reflection unit includes a polygon mirror rotatable about a main axis to direct the outgoing light toward a surrounding environment.
According to a first embodiment of the present invention, the optical emission unit includes a light source for generating outgoing light, which can emit natural light or laser light of various wavelengths.
Preferably, the laser emitting unit includes an emitting lens for collimating the outgoing light generated by the light source. The emission lens is capable of collimating the optical magnification of the outgoing light generated by the light source to reduce the divergence of the outgoing light, i.e., to reduce the width of the outgoing light in the first and second directions of its beam cross-section.
According to a first embodiment of the present invention, the optical reflection unit includes a polygon mirror having N surfaces, each of which has a different relative angle with respect to the rotation axis, the polygon mirror rotates around a fixed axis, and an incident light beam is emitted at a certain angle to the polygon mirror and then reflected in different directions of a space, thereby performing two-dimensional optical scanning. Multiple scans of the light beam can be realized within 360 degrees of a circle, the times are equal to the number N of the surfaces of the reflecting mirror, and the scanning pattern is N scanning lines.
According to a second embodiment of the present invention, there is provided a laser radar including a laser transmitting unit, and a laser receiving unit, wherein: the laser emission unit comprises a laser light source for generating emergent light, and the emergent light is transmitted along an emission path and passes through the laser transmission unit; the laser transmission unit comprises a spectroscope, a multi-surface reflector and a focusing lens, guides the emergent light to the surrounding environment, collects the reflected light reflected by one or more objects of the surrounding environment and guides the reflected light to the laser receiving unit along a receiving path; wherein the polygon mirror is rotatable about the main axis; the laser receiving unit includes a laser detector configured to detect reflected light transmitted along a receiving path; wherein in the laser transmission unit, an emission path of the emitted light and a reception path of the reflected light at least partially coincide.
According to a second embodiment of the present invention, the laser emitting unit includes a laser light source for generating an outgoing light, which can emit laser light of various wavelengths, such as 905nm or 1550 nm. Preferably, the laser emitting unit uses laser with the wavelength of 1550nm, and the 1550nm detector uses indium gallium arsenide compound and other materials instead of silicon. This has the advantage that the liquid in the human eye is opaque at 1550nm and therefore light cannot reach the retina at the back of the eye. This means that the laser can be operated at higher power levels to increase the laser detection range without posing a safety risk to the eye.
According to a second embodiment of the present invention, the laser transmission unit includes a beam splitter that partially passes the outgoing light from the laser emission unit, and partially reflects the reflected light reflected by one or more objects in the surrounding environment along the reception path and then guides the reflected light toward the laser reception unit. Therefore, the emitting path of the emergent light and the receiving path of the reflected light are completely coaxially arranged, which is beneficial to eliminating optical errors in a paraxial light path, improving the precision of laser ranging and simplifying the structural design.
According to a second embodiment of the present invention, the laser transmission unit includes a polygon mirror scanning structure composed of N surfaces, each of which has a different relative angle with respect to the rotation axis, the polygon mirror rotates around a fixed axis, and the incident laser is emitted at a certain angle to the polygon mirror and then reflected to different directions in space, thereby implementing two-dimensional laser scanning. The laser can be scanned for multiple times within 360 degrees of a circle, the times are equal to the number N of the surfaces of the reflecting mirror, and the scanning pattern is N scanning lines.
Preferably, the value of N is 4 or 5, the value of N affecting the horizontal (detectable angle of the direction of rotation about the rotation axis of the N-mirror) detectable angle of the lidar. Under the condition that the circumferential spacing angles of the N mirrors are uniform, when N is 4, the maximum detectable angle of a single laser radar is 180 degrees; when N is 5, the detectable angle of the single lidar is 144 °. The reasonable arrangement of a plurality of the laser radars can realize 360-degree detection through cooperative work.
According to a second embodiment of the present invention, the laser receiving unit includes a laser detector for converting the received reflected light into an electric signal, thereby obtaining distance information traveled by the light beam. The laser detector can be an Avalanche Photodiode (APD), a Photodiode (PIN) and a single photon detector (SPAD) of silicon or indium gallium arsenide, wherein the silicon APD is used for detecting 905nm laser, and the indium gallium arsenide APD is used for detecting 1550nm laser. Preferably, the laser detector is an indium gallium arsenide APD, as described above, the 1550nm laser is selected to operate at a higher power level to improve the laser detection range.
Preferably, the laser emitting unit includes an emitting lens for collimating the outgoing light generated by the laser light source, and/or the laser receiving unit includes a receiving lens for focusing the reflected light from the external object. The emission lens is capable of collimating the optical magnification of the outgoing light generated by the laser light source to reduce the divergence of the outgoing light, i.e., to reduce the width of the outgoing light in the first direction and the second direction of the beam cross-section thereof. The receiving lens is capable of focusing the optical magnification of the reflected light to reduce the divergence of the reflected light, i.e., to reduce the width of the reflected light in the first and second directions of its beam cross-section, thereby enabling more efficient detection.
According to a third embodiment of the present invention, there is provided a laser radar including a laser transmitting unit, and a laser receiving unit, wherein: the laser emission unit comprises a laser light source for generating emergent light, and the emergent light is transmitted along an emission path and passes through the laser transmission unit; the laser transmission unit comprises a spectroscope, a multi-surface reflector and a focusing lens, guides the emergent light to the surrounding environment, collects the reflected light reflected by one or more objects of the surrounding environment and guides the reflected light to the laser receiving unit along a receiving path; wherein the polygon mirror is rotatable about the main axis; the laser receiving unit includes a laser detector configured to detect reflected light transmitted along a receiving path; wherein in the laser transmission unit, an emission path of the emitted light and a reception path of the reflected light at least partially coincide.
According to a third embodiment of the present invention, the laser emitting unit includes a laser light source for generating an emitting light, the emitting light can emit laser light of a plurality of wavelengths, such as 905nm or 1550nm, and the emitting laser light is a linear laser light having a certain divergence angle in a certain direction, and the direction and the rotation axis of the polygon mirror are in the same plane. Preferably, the laser emitting unit uses a laser having a wavelength of 1550 nm.
According to a third embodiment of the present invention, the laser transmission unit includes a beam splitter that partially passes the outgoing light from the laser emission unit, and partially reflects the reflected light reflected by one or more objects in the surrounding environment along the reception path and guides the reflected light toward the laser reception unit. Therefore, the emitting path of the emergent light and the receiving path of the reflected light are basically coaxially arranged, which is beneficial to eliminating optical errors existing in a paraxial light path, improving the precision of laser ranging and simplifying the structural design.
According to a third embodiment of the present invention, the laser transmission unit includes a polygon mirror scanning structure composed of N surfaces, the relative angle between each reflection surface and the rotation axis is different, the polygon mirror rotates around the fixed axis, and the incident linear laser is emitted to the polygon mirror at a certain angle and then reflected to different directions in space, thereby implementing two-dimensional laser scanning. Can realize the multiple scanning to linear laser in 360 of a week, the number of times equals the face number N of speculum, and the scanogram has certain width's scanning area for N, and the divergence angle of the reasonable design incident linear laser and the relative angle of every face of polygon mirror and rotation axis can make N scanning areas connect into a whole scanning face without gapped ground.
Preferably, the value of N is 4 or 5, the value of N affecting the horizontal (detectable angle of the direction of rotation about the rotation axis of the N-mirror) detectable angle of the lidar. Under the condition that the circumferential spacing angles of the N mirrors are uniform, when N is 4, the maximum detectable angle of a single laser radar is 180 degrees; when N is 5, the detectable angle of the single lidar is 144 °. The reasonable arrangement of a plurality of the laser radars can realize 360-degree detection through cooperative work.
Preferably, the divergence angle of the exiting laser light is between 5 and 60 degrees, the magnitude of the divergence angle affecting the vertical detectable angle of the lidar. In the case where N scan bands are connected in series, the vertical detectable angle of the lidar is equal to the divergence angle of the exiting laser light multiplied by N.
According to a third embodiment of the present invention, the laser receiving unit includes a laser detector for converting the received reflected light into an electric signal, thereby obtaining distance information traveled by the light beam. The laser detector can be a linear array of silicon or indium gallium arsenic Avalanche Photodiode (APD), and comprises M APD units, and the linear laser is matched with the APD units, so that the distance information of M points can be obtained at one time.
Preferably, the laser receiving unit includes a receiving lens for focusing reflected light from an external object. The receiving lens may have an optical magnification capable of focusing the reflected light to reduce the divergence of the emitted light, i.e., to reduce the widths of the reflected light in the first and second directions of its beam cross-section, thereby achieving more efficient detection.
Drawings
FIG. 1 illustrates a method for two-dimensional optical scanning with single degree of freedom rotation according to the present invention; wherein, the laser emitting unit 1, the polygon mirror 2, the emitting path L1 and the rotating direction R1 are the rotating directions of the rotating shaft of the polygon mirror.
Fig. 2 shows an optical path structure of a laser radar according to a second embodiment of the present invention; the laser system comprises a 1-laser emitting unit, a 2-spectroscope, a 3-multi-surface reflector, a 4-laser receiving unit, an L1-emitting path, an L2-receiving path and an R1-multi-surface reflector rotating shaft rotating direction.
Fig. 3 shows an optical path structure of a laser radar according to a third embodiment of the present invention; the laser system comprises a 1-laser emitting unit, a 2-spectroscope, a 3-multi-surface reflector, a 4-laser receiving unit, an L1-emitting path, an L2-receiving path and an R1-multi-surface reflector rotating shaft rotating direction.
The specific implementation mode is as follows:
the invention is further illustrated with reference to the following figures and examples.
Fig. 1 shows a method for realizing two-dimensional optical scanning by single-degree-of-freedom rotation implemented according to the method of the invention.
In the first exemplary embodiment of the present invention, the optical emission unit 1 and the optical reflection unit — the polygon mirror 2 are mainly included. The optical emission unit 1 continuously emits light of a specific wavelength, which is emitted to the outside via reflection by the polygon mirror 3.
The optical emission unit 1 includes a light source, such as a Light Emitting Diode (LED), a laser driver, a laser diode, or the like, to generate an outgoing light along an emission path L1. According to a first exemplary embodiment of the present invention, the LED emits continuous white light.
According to a first embodiment of the invention, the optical reflection unit comprises a polygon mirror 2 which can change the spatial orientation of the outgoing light in one or more directions to achieve a two-dimensional scanning of the light beam. According to an exemplary embodiment of the present invention, the polygon mirror 2 may be a four-sided mirror, each of which has a different angle with respect to the rotation axis, for example, may be +12 degrees, +6 degrees, -6 degrees and-12 degrees, respectively, and the polygon mirror may be rotated around the rotation axis at a certain speed (for example, 200 revolutions/second), the reflection of each of the faces may change the spatial orientation of the outgoing light in the horizontal direction, and the different faces may change the spatial orientation of the outgoing light in the vertical direction. Therefore, four one-dimensional scanning lights which scan left and right in the horizontal direction can be generated, the horizontal scanning angle is +/-180 degrees, and the four scanning lights are distributed at equal intervals. Thereby, the one-dimensional scanning light can be further converted into the two-dimensional scanning light, thereby realizing two-dimensional optical scanning in a certain spatial range.
Fig. 2 shows the structure of the light path of a lidar in a second embodiment of the method according to the invention. The lidar is configured to acquire lattice data of a surrounding environment of the motor vehicle. The processor (such as an on-board computer) of the motor vehicle can receive the dot matrix data, analyze and process the dot matrix data, thereby realizing specific functions of the processor, acquiring the conditions of the surrounding environment of the vehicle, outputting specific control strategies according to the specific functions, and controlling the vehicle to perform functions of steering, speed changing, starting and stopping and the like, thereby realizing intelligent driving without driver intervention.
In the second exemplary embodiment of the present invention, the laser radar may include a laser emitting unit 1, a laser transmitting unit-beam splitter 2 and a polygon mirror 3, and a laser receiving unit 4. The laser emission unit 1 continuously emits pulsed exit light which enters the surroundings of the motor vehicle via a laser transmission unit spectroscope 2 and a polygon mirror 3. The outgoing light is projected at a reflective surface of an object in the surrounding environment and reflected light is generated. The reflected light returns to the interior of the laser radar via the laser transmission unit, the polygon mirror 3 and the spectroscope 2, and is received and detected by the laser receiving unit 4. By measuring the time difference Δ t between the emission of the laser pulse and the reception of the reflected light pulse, the distance d of the reflecting surface can be obtained as C ·Δt/2(C is the speed of light).
The laser emitting unit 1 includes a laser light source including, for example, a laser driver and a laser diode to generate outgoing light along an emission path L1, the emission path L1 being shown in solid lines in the figure. According to a second exemplary embodiment of the present invention, the laser continuously emits laser light in the form of pulses at a specific frequency (e.g., 125 kHz). According to a second exemplary embodiment of the present invention, the laser light source generates outgoing light having a wavelength of about 1550 nm.
According to a second embodiment of the invention, the laser transmission unit comprises a polygon mirror 3 which can change the spatial orientation of the outgoing light in one or more directions to achieve a scanning of the surroundings. According to a second exemplary embodiment of the present invention, the polygon mirror 3 may be a four-sided mirror, each of which has a different angle with respect to the rotation axis, for example, may be +12 degrees, +6 degrees, -6 degrees and-12 degrees, respectively, and the polygon mirror may be rotated around the rotation axis at a certain speed (for example, 200 revolutions/second), the reflection of each of the faces may change the spatial orientation of the outgoing light in the horizontal direction, and the different faces may change the spatial orientation of the outgoing light in the vertical direction. Therefore, four one-dimensional scanning lights which scan left and right in the horizontal direction can be generated, the horizontal scanning angle is +/-180 degrees, and the four scanning lights are distributed at equal intervals. Therefore, the four-wire laser radar is obtained only by using the rotation with single degree of freedom and a single laser light source, and the detection and measurement of the surrounding environment can be realized in a certain space range.
The outgoing light, the spatial orientation of which is changed, then leaves the laser transmission unit along emission path L1 into the surroundings, where diffuse reflection takes place at the reflective surfaces of one or more objects of the surroundings. The reflected light from the surroundings partly returns along a receiving path L2 to the laser transmission unit, which receiving path L2 is shown in the figure with a dashed line, which in turn directs the reflected light along a receiving path L2 towards the laser receiving unit 4. Specifically, the polygon mirror 3 and the beam splitter 2 of the laser transmission unit can change the spatial orientation from the reflected light and guide the reflected light toward the laser reception unit 4 along the reception path L2.
As can be seen from fig. 1, in the laser transmission unit, the emission path L1 of the emitted light and the reception path L2 of the reflected light at least partially coincide. Due to such a light path structure design, the laser transmission unit can provide a common space for the transmission path L1 and the reception path L2, so that the outer size and manufacturing cost of the laser radar can be further reduced. In addition, the emitting path L1 of the emergent light and the receiving path of the reflected light are basically coaxially arranged in the laser transmission unit, which is beneficial to eliminating the optical error in the paraxial light path, improving the precision of laser ranging and simplifying the structural design.
The laser light receiving unit 4 comprises a laser light detector for receiving and detecting reflected light transmitted along the receiving path L2 reflected by one or more objects of the surrounding environment. The laser detector is, for example, an Avalanche Photodiode (APD). Alternatively, the laser detector may be any optical sensor capable of converting a received optical signal into an electrical signal.
The reflected light transmitted along the receive path L2 may have a greater divergence due to the diffuse reflection of the outgoing light at the reflective surfaces of the one or more objects. In order to allow more reflected light to reach the laser light detector, the laser receiving unit 4 may include a receiving lens having an optical power for focusing the reflected light, reducing the divergence of the reflected light, i.e., reducing the width of the reflected light in the first direction and the second direction of the beam cross-section thereof. Advantageously, the receiving lens is designed such that the reflected light is focused at the laser detector of the laser receiving unit 4.
The laser radar comprises a main circuit board P0, and electrical components such as a processor, a memory, an I/O interface and the like can be carried on the main circuit board P0. The laser light source is electrically connected to the laser circuit board P1, and the circuit carried on the laser circuit board P1 is adapted to drive the laser light source. The laser detector is electrically connected to a detector circuit board P2, and circuitry carried on the detector circuit board P2 is adapted to receive and transmit output signals from the detector. The laser circuit board P1 and the detector circuit board P2 are both disposed parallel to each other and are vertically terminated to the main circuit board P0 on the same side, and the main circuit board P0 can be electrically connected to the laser circuit board P1 and the detector circuit board P2, whereby the processor can control the laser light source to emit light in pulses and process the output signals from the detectors to generate and output dot matrix data representing the surrounding environment.
Fig. 3 shows the structure of the light path of a lidar in a third embodiment of the method according to the invention. The lidar is configured to acquire lattice data of a surrounding environment of the motor vehicle. The processor (such as an on-board computer) of the motor vehicle can receive the dot matrix data, analyze and process the dot matrix data, thereby realizing specific functions of the processor, acquiring the conditions of the surrounding environment of the vehicle, outputting specific control strategies according to the specific functions, and controlling the vehicle to perform functions of steering, speed changing, starting and stopping and the like, thereby realizing intelligent driving without driver intervention.
In the third exemplary embodiment of the present invention, the laser radar may include a laser emitting unit 1, a laser transmitting unit-beam splitter 2 and a polygon mirror 3, and a laser receiving unit 4. The laser emission unit 1 continuously emits pulsed exit light which enters the surroundings of the motor vehicle via a laser transmission unit spectroscope 2 and a polygon mirror 3. The outgoing light is projected at a reflective surface of an object in the surrounding environment and reflected light is generated. The reflected light returns to the interior of the laser radar via the laser transmission unit, the polygon mirror 3 and the beam splitter 2, and is received and detected by the laser receiving unit 4. By measuring the time difference Δ t between the emission of the laser pulse and the reception of the reflected light pulse, the distance d of the reflecting surface can be obtained as C ·Δt/2(C is the speed of light).
The laser emitting unit 1 includes a laser light source including, for example, a laser driver and a laser diode, and generates linear laser-emitted light having a certain divergence angle along an emission path L1, the emission path L1 being shown by a solid line in the drawing. According to the third exemplary embodiment of the present invention, the laser continuously emits laser light in the form of pulses having a divergence angle of 12 degrees in one direction at a specific frequency (e.g., 125kHz), and the direction is adjusted to be in the same plane as the rotation axis of the polygon mirror 3. According to an exemplary embodiment of the present invention, the laser light source generates outgoing light having a wavelength of about 1550 nm.
According to one embodiment of the invention, the laser transmission unit comprises a polygon mirror 3 which can change the spatial orientation of the outgoing light in one or more directions to enable scanning of the surroundings. According to an exemplary embodiment of the present invention, the polygon mirror 3 may be a four-sided mirror, each of which has a different angle with respect to the rotation axis, for example, may be +12 degrees, +6 degrees, -6 degrees and-12 degrees, respectively, and the polygon mirror may be rotated around the rotation axis at a certain speed (for example, 200 revolutions/second), the reflection of each of the faces may change the spatial orientation of the outgoing light in the horizontal direction, and the different faces may change the spatial orientation of the outgoing light in the vertical direction. Therefore, four laser scanning bands with divergence angles of 12 degrees in the horizontal direction can be generated, the horizontal scanning angle is +/-180 degrees, the four scanning bands are sequentially connected, and the vertical scanning angle is +/-24 degrees. Therefore, two-dimensional surface scanning of laser can be realized only by using rotation with single degree of freedom and a single laser light source, and detection and measurement of the surrounding environment are realized in a certain spatial range.
The outgoing light, the spatial orientation of which is changed, then leaves the laser transmission unit along emission path L1 into the surroundings, where diffuse reflection takes place at the reflective surfaces of one or more objects of the surroundings. The reflected light from the surroundings partly returns along a receiving path L2 to the laser transmission unit, which receiving path L2 is shown in the figure with a dashed line, which in turn directs the reflected light along a receiving path L2 towards the laser receiving unit 4. Specifically, the polygon mirror 3 and the beam splitter 2 of the laser transmission unit can change the spatial orientation from the reflected light and guide the reflected light toward the laser reception unit 4 along the reception path L2.
As can be seen from fig. 1, in the laser transmission unit, the emission path L1 of the emitted light and the reception path L2 of the reflected light at least partially coincide. Due to such a light path structure design, the laser transmission unit can provide a common space for the transmission path L1 and the reception path L2, so that the outer size and manufacturing cost of the laser radar can be further reduced. In addition, the emitting path L1 of the emergent light and the receiving path of the reflected light are basically coaxially arranged in the laser transmission unit, which is beneficial to eliminating the optical error in the paraxial light path, improving the precision of laser ranging and simplifying the structural design.
The laser light receiving unit 4 comprises a laser light detector for receiving and detecting reflected light transmitted along the receiving path L2 reflected by one or more objects of the surrounding environment. The laser detector may be a linear array of silicon or indium gallium arsenide Avalanche Photodiode (APD), which includes M APD units, such as a 128-line indium gallium arsenide APD array, and the linear laser is used to cooperate with the above-mentioned linear laser to obtain distance information of 128 points at one time. Alternatively, the laser detector may be any optical sensor capable of converting a received optical signal into an electrical signal.
The reflected light transmitted along the receive path L2 may have a greater divergence due to the diffuse reflection of the outgoing light at the reflective surfaces of the one or more objects. In order to allow more reflected light to reach the laser light detector, the laser receiving unit 4 may include a receiving lens having an optical power for focusing the reflected light, reducing the divergence of the reflected light, i.e., reducing the width of the reflected light in the first direction and the second direction of the beam cross-section thereof. Advantageously, the receiving lens is designed such that the reflected light is focused at the laser detector of the laser receiving unit 4.
The laser radar comprises a main circuit board P0, and electrical components such as a processor, a memory, an I/O interface and the like can be carried on the main circuit board P0. The laser light source is electrically connected to the laser circuit board P1, and the circuit carried on the laser circuit board P1 is adapted to drive the laser light source. The laser detector is electrically connected to a detector circuit board P2, and circuitry carried on the detector circuit board P2 is adapted to receive and transmit output signals from the detector. The laser circuit board P1 and the detector circuit board P2 are both disposed parallel to each other and are vertically terminated to the main circuit board P0 on the same side, and the main circuit board P0 can be electrically connected to the laser circuit board P1 and the detector circuit board P2, whereby the processor can control the laser light source to emit light in pulses and process the output signals from the detectors to generate and output dot matrix data representing the surrounding environment.
Further features of the invention can be found in the claims, the drawings and the description of the drawings. The features and feature combinations mentioned above in the description and further features and feature combinations described in the figures and/or shown in the figures alone are used not only in the respectively indicated combination but also in other combinations or alone without departing from the scope of the invention. Details of the invention which are not explicitly shown and explained in the figures, but which are present from the explained details and can be produced by individual feature combinations, are hereby included and disclosed. Accordingly, details and combinations of features not owned by the originally formed independent claims should also be considered disclosed.
Claims (11)
1. A method for realizing two-dimensional optical scanning by single-degree-of-freedom rotation is characterized by comprising an optical transmitting unit and an optical transmission/reflection unit;
the optical emission unit and the optical transmission/reflection unit are sequentially arranged along a light propagation path;
the optical emission unit is used for emitting light beams;
the relative positions of the emission unit and the optical transmission/reflection unit are fixed.
2. A two-dimensional optical scanning method according to claim 1, wherein said optical emission unit comprises a light emitting diode, a laser comprising a semiconductor laser, a single wavelength fiber laser, or a multi-wavelength fiber laser.
3. A two-dimensional optical scanning method according to claim 1, wherein said laser light emitting unit includes an emission lens;
the emission lens may collimate an optical magnification of outgoing light generated by the light source to reduce a divergence of the outgoing light.
4. A two-dimensional optical scanning method according to claim 1, wherein said optical transmission/reflection unit is a polygon mirror;
the multi-surface reflector is provided with N reflecting surfaces distributed around a rotating shaft, and the relative angle of each reflecting surface and the rotating shaft is different and can rotate around a fixed shaft.
5. Lidar characterized in that it is implemented based on a two-dimensional optical scanning method as claimed in claims 1-4.
6. The lidar of claim 5, comprising a laser transmitter unit, and a laser receiver unit.
7. The lidar of claim 5, wherein the laser emitting unit is a point light source, a line light source, or a surface light source.
8. The lidar of claim 5, wherein the laser transmission unit comprises a beam splitter;
the beam splitter may partially pass the outgoing light from the laser emitting unit, and partially reflect reflected light reflected by one or more objects in the surrounding environment along a receiving path and guide the reflected light toward the laser receiving unit.
9. The lidar of claim 5, wherein the laser receiving unit comprises a laser detector;
the laser detector may convert the received reflected light into an electrical signal, thereby obtaining distance information traveled by the light beam.
The laser detector comprises a silicon or indium gallium arsenide Avalanche Photodiode (APD), or any optical sensor capable of converting a received optical signal to an electrical signal;
the avalanche photodiode can be a single diode, and can also be a linear array or an area array.
10. The lidar of claim 5, wherein the laser receiving unit comprises a receiving lens;
the acceptance lens may focus reflected light from an external object.
11. Lidar according to claim 5, wherein in the laser transmission unit, a transmission path of the outgoing light and a reception path of the reflected light at least partially coincide.
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