CN109444848B - Scanning device and scanning method thereof, and laser radar - Google Patents
Scanning device and scanning method thereof, and laser radar Download PDFInfo
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- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 7
- 229910052700 potassium Inorganic materials 0.000 claims description 7
- 239000011591 potassium Substances 0.000 claims description 7
- OBTSLRFPKIKXSZ-UHFFFAOYSA-N lithium potassium Chemical compound [Li].[K] OBTSLRFPKIKXSZ-UHFFFAOYSA-N 0.000 claims description 4
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- 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
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Abstract
A scanning device, a scanning method thereof and a laser radar are provided, wherein the scanning device comprises: a first scanning unit, adapted to make a first deflection of the propagation direction of an incident light beam to form an emergent light beam, wherein the first scanning unit changes the deflection angle of the first deflection by rotating or swinging; and the second scanning unit is positioned in the optical path of at least one of the incident light beam and the emergent light beam, and when the incident light beam or the emergent light beam transmits through the second scanning unit, the second scanning unit enables the transmission direction of the transmitted light beam to generate second deflection based on the electro-optical effect. The scanning device can realize delay angle compensation, effectively shorten single detection time, effectively improve scanning frequency and be favorable for realizing high scanning frequency and high coherence efficiency.
Description
Technical Field
The invention relates to the field of laser detection, in particular to a scanning device and a scanning method thereof, and a laser radar.
Background
Laser radar is a range finding sensor commonly used, has characteristics such as detection range is far away, resolution ratio is high, receive environmental disturbance little, and the wide application is in fields such as intelligent robot, unmanned aerial vehicle, unmanned driving. In recent years, the automatic driving technology has been rapidly developed, and the laser radar has become indispensable as a core sensor for distance sensing.
Currently, most lidar systems scan the outgoing beam by means of a continuous rotation or a back-and-forth oscillation. In the laser radar of the receiving and transmitting common path, a scanning device not only needs to realize the scanning of the emergent light beam, but also needs to realize the collection of the echo light beam formed by the reflection of the target to be detected. Due to the continuous rotation of the scanning device, after the light beam is reflected by the target, the angle of the scanning device when receiving the echo light beam is different from the angle of the scanning light beam when emitting, namely the scanning device generates a delay angle.
The size of the delay angle is related to the distance of the target to be measured. In particular, in the laser radar based on coherent detection, coherent detection of the laser radar is implemented based on a coherent signal between a local oscillator light and an echo light formed by reflection of a target to be detected, and a signal-to-noise ratio of the coherent signal is proportional to a wavefront matching degree between the local oscillator light and the echo light. Therefore, in order to improve the coherence efficiency between the local oscillator light and the echo light to ensure the signal-to-noise ratio of the coherent signal, angle compensation is required to suppress the decrease in coherence efficiency caused by the delay angle.
However, in the prior art, the laser radar system capable of realizing angle compensation often has the problem of too low scanning frequency.
Disclosure of Invention
The invention aims to provide a scanning device, a scanning method thereof and a laser radar, which can improve the scanning frequency of the laser radar while ensuring the angle compensation effect.
To solve the above problems, the present invention provides a scanning device, comprising:
a first scanning unit, adapted to make a first deflection of the propagation direction of an incident light beam to form an emergent light beam, wherein the first scanning unit changes the deflection angle of the first deflection by rotating or swinging; and the second scanning unit is positioned in the optical path of at least one of the incident light beam and the emergent light beam, and when the incident light beam or the emergent light beam transmits through the second scanning unit, the second scanning unit enables the transmission direction of the transmitted light beam to generate second deflection based on the electro-optical effect.
Optionally, the second scanning unit includes an electro-optical crystal, and the electro-optical crystal is at least one of a linear electro-optical crystal and a nonlinear electro-optical crystal.
Optionally, the electro-optic crystal is a nonlinear electro-optic crystal; the quadratic electro-optical coefficient of the electro-optical crystal is in the order of 10-14m2/V2To 10-15m2/V2Within the range.
Optionally, the electro-optic crystal includes: at least one of potassium tantalate niobate crystal, potassium lithium tantalate niobate crystal, and potassium sodium tantalate niobate crystal.
Optionally, the first scanning unit changes the propagation direction of the outgoing light beam in a swinging manner, and the first scanning unit includes: at least one of a galvanometer and a galvanometer; the first scanning unit changes the propagation direction of the outgoing light beam by rotating, and the first scanning unit includes: and (5) rotating the mirror.
Optionally, the first scanning unit has a first reflecting surface swinging around a first scanning axis; the second scanning unit includes: a first electro-optic crystal, the second deflection comprising the first electro-optic crystal rotating the transmitted light beam about a first deflection axis; the first deflection axis is parallel to the first scanning axis.
Optionally, the first scanning unit has a first reflecting surface swinging around a first scanning axis and a second reflecting surface swinging around a second scanning axis, and the first scanning axis is not parallel to the second scanning axis; the ratio of the swing frequency of the first reflecting surface to the swing frequency of the second reflecting surface is less than or equal to a preset value; the second scanning unit includes: the first electro-optical crystal and the second electro-optical crystal are sequentially arranged along the light path, and the second deflection comprises that the first electro-optical crystal enables the transmitted light beam to rotate around a first deflection shaft; the second electro-optic crystal rotates the transmitted light beam about a second deflection axis; the first yaw axis is non-parallel to the second yaw axis; the first deflection axis is parallel to the first scanning axis; the second deflection axis is parallel to the second scanning axis.
Optionally, the first scanning unit has a first reflecting surface swinging around a first scanning axis and a second reflecting surface swinging around a second scanning axis, and the first scanning axis and the second scanning axis are perpendicular to each other; the ratio of the swing frequency of the first reflecting surface to the swing frequency of the second reflecting surface is greater than a preset value; the second scanning unit includes: a first electro-optic crystal, the second deflection comprising the first electro-optic crystal rotating the transmitted light beam about a first deflection axis; the first deflection axis is parallel to the first scanning axis.
Optionally, the second scanning unit has an input surface for receiving the light beam to enter; the light beam is projected perpendicularly to the input face.
Optionally, the second scanning unit includes an electro-optical crystal; the electro-optic crystal receives a modulation voltage to effect the second deflection; the modulation voltage is less than 100V.
Optionally, the outgoing light beam is suitable for forming a scanning light beam outgoing from the scanning device, and the scanning light beam is reflected by the target to be detected to form an echo light beam; collecting the echo light beams to form collecting light beams; the collecting light beam is deflected by the first scanning unit and the second scanning unit to form a signal light beam; the collection beam is co-incident with the incident beam.
Optionally, the first scanning unit changes the size of the deflection angle of the first deflection through continuous rotation or oscillation.
Correspondingly, the present invention further provides a scanning method of a scanning device, where the scanning device is the scanning device of the present invention, and the scanning method includes:
first deflecting the incident light beam with the first scanning unit to form an emergent light beam; rotating or swinging the first scanning unit to change the size of the deflection angle of the first deflection; and providing a modulation voltage to the second scanning unit, and enabling the propagation direction of the light beam transmitted through the second scanning unit to generate second deflection based on the electro-optical effect so as to compensate the delay angle.
Optionally, the deflection angle of the second deflection is changed periodically; the variation period of the second deflection angle is an electro-optic deflection period; and in the electro-optical deflection period, the deflection angle of the second deflection is linearly changed.
Optionally, the deflection angle of the second deflection is changed periodically; the variation period of the second deflection angle is an electro-optic deflection period; the second scanning unit comprises an electro-optical crystal; and in the electro-optical deflection period, the modulation voltage makes the refractive index of the electro-optical crystal linearly change along with time.
Optionally, the second scanning unit includes a quadratic electro-optical crystal; the square of the modulation voltage varies linearly with time during the electro-optical deflection period.
Optionally, the first scanning unit rotates or swings continuously; the deflection angle of the first deflection varies continuously.
In addition, the present invention also provides a laser radar including: the invention relates to a scanning device.
Optionally, the laser radar is a coherent laser radar.
Compared with the prior art, the technical scheme of the invention has the following advantages:
in the technical scheme of the invention, the first scanning unit enables the propagation direction of the incident light beam to generate first deflection and changes the propagation direction of the emergent light beam in a rotating or swinging mode; the second scanning unit secondarily deflects a propagation direction of the transmitted light beam based on an electro-optical effect to compensate for the delay angle. The deflection angle of the second deflection is equal to the delay angle generated in the single detection process, and the deflection directions are opposite, so that the delay angle can be compensated in the single detection process by the second deflection of the light beam, the light path from the incident light beam to the emergent light beam can be kept unchanged by the first deflection and the second deflection, and the light path from the light beam received by the scanning device to the light path from the light beam emitted by the scanning device is further kept unchanged; moreover, since the electro-optical effect has a high response rate to a change in the electrical signal, and thus the change in the propagation direction of the light beam in the second deflection has a high response rate to the electrical signal, the second scanning unit can realize delay angle compensation at a faster speed. Therefore, the technical scheme of the invention can effectively shorten the time of single detection, is beneficial to improving the scanning frequency and is beneficial to realizing the compromise of high scanning frequency and high coherence efficiency on the premise of ensuring the delay angle compensation effect, namely maintaining the light path unchanged.
In the alternative of the invention, the electro-optic crystal is a nonlinear electro-optic crystal; the quadratic electro-optical coefficient of the electro-optical crystal is in the order of 10-14m2/V2To 10-15m2/V2Within the range; for example, at least one of potassium tantalate niobate crystals, potassium lithium tantalate niobate crystals, and potassium sodium tantalate niobate crystals. The larger the electro-optic coefficient of the electro-optic crystal is, the more the electro-optic coefficient of the electro-optic crystal isUnder the same voltage, the larger the refractive index change of the electro-optical crystal is, so that the electro-optical crystal with a larger electro-optical coefficient is arranged in the second scanning unit, the larger refractive index change can be realized by using a smaller voltage, and the deflection angle of the second deflection is larger, so that the modulation voltage for realizing the electro-optical effect can be effectively reduced by adopting the electro-optical crystal with the large electro-optical coefficient, and the aim of low voltage and high frequency can be achieved on the premise of ensuring the delay angle compensation.
In the alternative scheme of the invention, the position of the electro-optical crystal in the second scanning unit is reasonably set according to the scanning direction and the scanning speed of the first scanning unit, so that the deflection direction of the second deflection is matched with the deflection direction of the first deflection, the deflection direction of the second deflection is parallel to the deflection direction of the first deflection, the influence of the second deflection on the transmission direction of the emergent light beam can be effectively enhanced, the deflection angle of the transmission direction of the formed scanning light beam is enlarged, the scanning light beam with a larger deflection angle can be formed by a smaller voltage, the modulation voltage applied to the electro-optical crystal can be effectively reduced, and the aim of low-voltage high-frequency scanning is favorably fulfilled.
In an alternative aspect of the invention, the modulation voltage is less than 100V. The modulation voltage is controlled, the control voltage of the scanning device can be effectively reduced, the purpose of low-voltage high-frequency scanning is facilitated, and the technical requirement of the vehicle-mounted laser radar is met.
In an alternative aspect of the present invention, the first scanning unit reflects the incident light beam to form the emergent light beam; the second scanning unit is located on a light path of the incident light beam, namely the first scanning unit carries out first deflection on the incident light beam deflected in the second direction to form the emergent light beam, and the deflection angle of the incident light beam in the second deflection process can be amplified in the first deflection process, so that the emergent light beam with a larger deflection angle can be formed by a smaller deflection angle of the second deflection, and further the scanning light beam with a larger deflection angle can be obtained, the voltage required by the electro-optic effect can be effectively reduced, the aim of realizing low-voltage high-frequency scanning is facilitated, and the technical requirements of the vehicle-mounted laser radar can be favorably met.
Drawings
FIG. 1 is a schematic diagram of an optical path structure of a first embodiment of a scanning device according to the present invention;
FIG. 2 is a schematic diagram of an optical path structure of a second embodiment of the scanning device according to the present invention;
FIG. 3 is a timing diagram of signals used in an embodiment of a scanning method according to the present invention;
fig. 4 is a graph of deflection angle of the first deflection, deflection angle of the second deflection, and scan angle versus time in the embodiment of the scanning method shown in fig. 3.
Detailed Description
As can be seen from the background art, the lidar system capable of implementing angle compensation in the prior art has a problem of too low scanning frequency. The reason for the problem of too low scanning frequency is analyzed by combining a method for realizing angle compensation by a laser radar system:
in the existing laser radar, methods for suppressing the delay angle are mainly divided into two types: step-and-scan and local angle compensation. Step scanning refers to using a discontinuous scanning mode, and the scanning device is kept unchanged in a single detection process until the next detection. Specifically, the conventional laser radar performs scanning by using an electro-optical device such as a stepping motor or a liquid crystal optical waveguide.
The local angle compensation means that the direction of the local oscillation light is adjusted in real time by using another reflecting device while the scanning device scans so as to ensure the wave front matching of the local oscillation light and the signal light; the reflecting device adjusts the local oscillator light direction in real time, which is usually realized by means of a servo motor.
No matter in a stepping scanning mode or a local angle compensation mode, in the technical scheme of considering both angle compensation and scanning, the scanning frequency is limited by the frequency of the existing motor, so that the defect that single detection time is long and is mostly in millisecond order appears.
Particularly, in the field of automatic driving, the technical requirements of the frame frequency and the spatial resolution of the laser radar are high, the single detection time is short, and most of the detection time is several microseconds, so that the traditional stepping motor or servo motor cannot meet the requirements, and the problems of too low scanning frequency and too long single detection time occur.
To solve the above technical problem, the present invention provides a scanning device, including:
a first scanning unit adapted to first deflect the propagation direction of an incident light beam to form an emergent light beam, the first scanning unit changing the propagation direction of the emergent light beam by rotating or oscillating; and the second scanning unit is positioned in the optical path of at least one of the incident light beam and the emergent light beam, and when the incident light beam or the emergent light beam transmits through the second scanning unit, the second scanning unit enables the transmission direction of the transmitted light beam to generate second deflection based on the electro-optical effect. The scanning device can not only realize the delay angle compensation in the single detection process, but also effectively shorten the single detection time, effectively improve the scanning frequency and be beneficial to realizing the high scanning frequency and the high coherence efficiency.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, there is shown a schematic diagram of the optical path structure of a first embodiment of the scanning device of the present invention.
The scanning device 100 includes:
a first scanning unit 110, said first scanning unit 110 being adapted to first deflect the propagation direction of an incident light beam 121 to form an emergent light beam 119, said first scanning unit 110 changing the propagation direction of said emergent light beam 119 by rotating or oscillating; and a second scanning unit 120, where the second scanning unit 120 is located in an optical path of at least one of the incident light beam 121 and the emergent light beam 119, and when the incident light beam 121 or the emergent light beam 119 transmits through the second scanning unit 120, the second scanning unit 120 generates a second deflection on a propagation direction of the transmitted light beam based on an electro-optical effect.
The deflection angle of the second deflection is equal to the delay angle generated in the detection process, and the deflection direction is opposite, so that the delay angle can be compensated in a single detection process by the second deflection of the light beam, and the light path of the incident light beam 121 deflected to the emergent light beam 119 can be kept unchanged by the first deflection and the second deflection, thereby ensuring that the light path of the light beam received by the scanning device 100 and the light path of the light beam emitted from the scanning device 100 are kept unchanged.
Also, since the electro-optical effect has a high response rate to a change in the electrical signal, and thus the change in the propagation direction of the light beam in the second deflection has a high response rate to the electrical signal, the second scanning unit 120 can implement the delay angle compensation at a faster speed.
Therefore, the scanning device 100 can effectively shorten the time of single detection, which is beneficial to increasing the scanning frequency and realizing the compromise of high scanning frequency and high coherence efficiency on the premise of ensuring the delay angle compensation effect, i.e. maintaining the light path unchanged.
As shown in fig. 1, in the present embodiment, the scanning device 100 receives the initial light beam 138 generated by the transceiver 130 to form the incident light beam 121.
In this embodiment, the transceiver 130 and the scanning device 100 are transceivers and scanning devices in a coherent laser radar, and therefore the transceiver 130 is a coherent transceiver to obtain advantages of high angular resolution, high distance resolution, strong anti-interference capability, and the like. There is also provided a beam splitting means (not shown) in the optical path between the light source (not shown) generating the light beam and the scanning means 100, said beam splitting means being arranged to form a local oscillator beam for coherent detection. Specifically, the formation of the local oscillator beam is not limited in the present invention.
It should be noted that the scanning device 100 may further include other optical components, such as a stop, a lens, or a lens group, which are not shown in fig. 1, to receive the initial light beam 138 to form the incident light beam 121.
The first scanning unit 110 first deflects the propagation direction of the incident light beam 121 to form an emergent light beam 119, and changes the deflection angle of the first deflection in a rotating or swinging manner, so as to form emergent light beams 119 with different propagation directions.
In this embodiment, the first scanning unit 110 changes the propagation direction of the outgoing light beam 119 in a swinging manner, and the first scanning unit 110 includes: at least one of a galvanometer and a galvanometer.
Specifically, the first scanning unit 110 includes: a galvanometer. The galvanometer has the characteristics of high precision, high speed and high integration level, so that the first scanning unit 110 is set as the galvanometer, which not only can effectively improve the scanning frequency of the scanning device 100, but also can effectively control the integration level and the optical path precision of equipment.
The first scanning unit 110 reflects the incident light beam 121 to form the emergent light beam 119. Specifically, as shown in fig. 1, the first scanning unit 110 includes a one-dimensional galvanometer. The first scanning unit 110 has a first reflective surface (not shown) swinging around a first scanning axis 117. The incoming light beam 121 is reflected on the first reflective surface to form the outgoing light beam 119.
It should be noted that, in the present embodiment, the way of setting the first scanning unit 110 as a galvanometer is only an example. In other embodiments of the present invention, the first scanning unit may be further configured as a swing mirror. In addition, in other embodiments of the present invention, the first scanning unit changes the propagation direction of the outgoing light beam by rotating, and the first scanning unit includes: and (5) rotating the mirror.
With the swing of the first reflection surface, the incident angle of the incident light beam 121 on the first reflection surface changes, and the reflection angle of the formed emergent light beam 119 changes, that is, the deflection angle of the first deflection changes with the swing of the first reflection surface, so that the propagation direction of the formed emergent light beam 119 changes.
In this embodiment, the first scanning unit 110 changes the deflection angle of the first deflection by continuous rotation or oscillation. The first scanning unit 110 is continuously rotated or swung to change the deflection angle of the first deflection, so that the rotation or swing of the first scanning unit 110 is prevented from being limited by the motor frequency, and conditions are created for shortening the single detection time and improving the scanning frequency.
Specifically, as shown in fig. 1, the first reflective surface continuously swings around the first scanning axis 117, the incident angle of the incident light beam 121 on the first reflective surface continuously and periodically changes, and the reflection angle of the emergent light beam 119 also periodically and continuously changes.
The second scanning unit 120 is located on an optical path of at least one of the incident light beam 121 and the emergent light beam 119, and the second scanning unit 120 is adapted to transmit the incident light beam 121 or the emergent light beam 119 and deflect the propagation direction of the transmitted light beam for a second time based on an electro-optical effect to compensate for a delay angle.
The deflection angle of the second deflection is equal to the delay angle, and the direction is opposite, so that the delay angle can be compensated in a single detection process; in a single detection process, the first deflection and the second deflection can maintain the optical path of the incident light beam 121 deflected to the emergent light beam 119 unchanged, thereby ensuring that the optical path of the light beam received by the scanning device 100 and the optical path of the light beam emitted from the scanning device 100 are maintained unchanged.
It can be seen that, although the magnitude of the deflection angle of the first deflection changes with the rotation or swing of the first scanning unit 110, and the magnitude of the deflection angle of the second polarization changes based on the electro-optical effect in the second scanning unit 120, the combined angle of the first deflection and the second deflection is maintained constant in a single detection process, that is, the deflection angle between the incident light beam 121 to the emergent light beam 119 is maintained constant, that is, the equivalent optical path of the scanning device 100 is maintained constant; therefore, in a single detection process, the optical path of the light beam received from the scanning device 100 and the optical path of the light beam emitted from the scanning device 100 are maintained constant, and the propagation direction of the light beam emitted from the scanning device 100 is maintained constant.
As shown in fig. 1, in this embodiment, during a single detection process, the first deflection and the second deflection can maintain the optical path between the initial beam 138 and the scanning beam 190 unchanged, and ensure that the propagation direction of the scanning beam 190 is constant.
Also, the second deflection occurs based on the electro-optical effect, and thus the change of the propagation direction of the light beam in the second deflection has a high response rate to the electrical signal, and the second scanning unit 120 can implement the delay angle compensation at a faster speed. The rapid delay angle compensation makes it possible to shorten the time for maintaining the equivalent optical path of the scanning device 100 unchanged, and makes it possible to maintain the equivalent optical path of the scanning device 100 unchanged from the motor frequency limitation, thereby facilitating the shortening of the single detection time, the improvement of the scanning frequency, and the realization of the compromise of the high scanning frequency and the high coherence efficiency.
In this embodiment, the first scanning unit 110 changes the deflection angle of the first deflection by continuous rotation or oscillation. Therefore, the scanning device 100 can get rid of the limitation of the frequency of the motors such as the servo motor and the stepping motor to the scanning frequency, and is beneficial to realizing the compatibility of high scanning frequency and high coherence efficiency.
Specifically, the electro-optic Effect refers to a phenomenon that the refractive index of a substance changes due to an external electric field, and the electro-optic Effect includes Pockels Effect (Pockels Effect) and Kerr Effect (Kerr Effect). Wherein, the phenomenon that the refractive index changes in direct proportion to the first power of the external electric field intensity is the Pockels effect or the linear electro-optic effect; the phenomenon in which the refractive index changes in proportion to the square of the applied electric field strength is the kerr effect or the quadratic electro-optic effect.
The electro-optic effect has a higher response rate to the change of the electrical signal, and thus the deflection angle of the second deflection has a higher response rate to the electrical signal, so that the second scanning unit 120 can implement delay angle compensation at a faster speed; therefore, the scanning device 100 can effectively shorten the time of single detection on the premise of ensuring the delay angle compensation effect, i.e. maintaining the light path unchanged, thereby being beneficial to improving the scanning frequency and realizing the compromise of high scanning frequency and high coherence efficiency.
Wherein the second scanning unit 120 includes an electro-optical crystal, and the electro-optical crystal is at least one of a linear electro-optical crystal and a nonlinear electro-optical crystal. Specifically, the incident light beam 121 undergoes a second deflection during transmission through the electro-optic crystal.
It should be noted that the second scanning unit 120 has an input surface for receiving the incident light beam; the light beam is projected perpendicularly to the input face. The light beam is made to vertically enter, so that the light path of the scanning device 100 can be effectively simplified, and the difficulty in adjusting the light path is favorably reduced.
In this embodiment, the electro-optic crystal is a nonlinear electro-optic crystal; the quadratic electro-optical coefficient of the electro-optical crystal is in the order of 10-14m2/V2To 10-15m2/V2Within the range. Wherein the electro-optic crystal comprises: at least one of potassium tantalate niobate crystal, potassium lithium tantalate niobate crystal, and potassium sodium tantalate niobate crystal.
The electro-optical crystal with a larger electro-optical coefficient is arranged in the second scanning unit 120, so that the larger the electro-optical coefficient of the electro-optical crystal is, the larger the change of the refractive index of the electro-optical crystal is under the same voltage, the larger the change of the refractive index can be realized by a smaller voltage, and the larger the deflection angle of the second deflection is, that is, the smaller the voltage required by the electro-optical crystal with a larger electro-optical coefficient is to realize the deflection at the same angle, so that the adoption of the electro-optical crystal with a large electro-optical coefficient can effectively reduce the voltage required for ensuring the compensation effect of the delay angle, that is, maintaining the optical path unchanged, thereby achieving the purposes of low voltage and high frequency.
In this embodiment, the electro-optic crystal is potassium tantalate niobate. The potassium tantalate niobate crystal is the crystal with the largest quadratic electro-optic coefficient known at present. The electro-optic crystal is set as the potassium tantalate niobate crystal, so that the required voltage can be effectively reduced under the condition of generating the same deflection angle, and the scanning effect of low voltage and high frequency is achieved.
In this embodiment, the second scanning unit 120 is located in the optical path of the incident light beam 121, and the first scanning unit 110 performs a first deflection on the incident light beam 121 subjected to the second deflection to form the emergent light beam 119.
In this embodiment, the second scanning unit 120 is disposed on the optical path of the incident light beam 121, which is only an example. In other embodiments of the present invention, the second scanning unit may also be disposed on the optical path of the outgoing light beam. The incident light beam forms the emergent light beam after being subjected to first deflection, and the emergent light beam transmits through the second scanning unit; during transmission through the second scanning unit, the outgoing beam is subjected to a second deflection to form the scanning beam and to achieve delay angle compensation.
As shown in fig. 1, the first scanning unit 110 includes a galvanometer, and the first scanning unit 110 forms the outgoing light beam 119 by reflecting the incident light beam 121 by a first reflecting surface oscillating around a first scanning axis 117. Accordingly, the second scanning unit 120 includes: a first electro-optic crystal 129, the second deflection comprising the first electro-optic crystal 129 rotating the transmitted beam about a first deflection axis; the first deflection axis is parallel to the first scanning axis 117.
The first deflection axis is parallel to the first scanning axis 117, the first scanning axis 117 is perpendicular to an incident plane (the incident plane is a plane formed by incident light and a normal at an incident point) during the second deflection of the light beam, so that the deflection direction of the first deflection can be matched with the deflection direction of the second deflection, and the incident light beam 121, the incident light beam 121 subjected to the second deflection and the emergent light beam 119 are coplanar. By the method, the influence of the second deflection on the propagation direction of the emergent light beam 119 can be effectively enhanced, the emergent light beam 119 with large angle change can be obtained through small voltage, the required voltage can be effectively reduced, and the purpose of low-voltage high-frequency scanning can be realized.
Specifically, the first electro-optic crystal 129 is wedge-shaped, and has a first right-angle surface (not shown) and a second right-angle surface (not shown) perpendicular to each other, and a first inclined surface (not shown) connecting the first right-angle surface and the second right-angle surface and opposite to the first right-angle surface. The first right-angle surface faces the transceiver 130, and the incident light beam 121 is perpendicularly projected to the first right-angle surface; the second right-angle surface is arranged parallel to the incident light beam 121; the incident light beam 121 is refracted on the first inclined surface, undergoes a second deflection, and exits from the first electro-optic crystal 129.
As shown in fig. 1, the scanning device 100 receives the initial light beam 138 generated by the transceiver 130 to form the incident light beam 121; the incident light beam 121 transmits the first electro-optical crystal 129 in the second scanning unit 120, and is projected to the first scanning unit 110 after the second deflection. Therefore, the second scanning unit 120 is located on the optical path between the first scanning unit 110 and the transceiver 130.
It should be noted that the second scanning unit 120 generates a second deflection of the transmitted light beam based on the electro-optical effect, and the second scanning unit 120 includes an electro-optical crystal; the electro-optic crystal receives a modulation voltage to effect the second deflection. Wherein the modulation voltage is less than 100V. The modulation voltage is controlled, so that the voltage of the scanning device 100 is reduced, the purpose of low-voltage high-frequency scanning is achieved, and the technical requirement of the vehicle-mounted laser radar is met.
Therefore, the scanning apparatus 100 may further include: a control unit (not shown in the figure) adapted to provide a modulation voltage to the electro-optical crystal to achieve the electro-optical effect. The control unit is connected to the second scanning unit 120 and adapted to provide the modulation voltage to the second scanning unit 120, so that the second scanning unit 120 performs a second deflection on the transmitted light beam based on the electro-optical effect.
In addition, in this embodiment, the control unit may be further connected to the first scanning unit 110, and the control unit is further adapted to control the rotation or swing of the first scanning unit 110 to obtain a higher scanning frequency and angular resolution.
With continued reference to FIG. 1, the emergent beam 119 is adapted to form a scanning beam 190 that emerges from the scanning device 100, and the scanning beam 190 is reflected off of an object (not shown) to be detected to form an echo beam (not shown).
In this embodiment, the scanning device 100 is applied to a coherent laser radar of a transmitting-receiving common path, and the scanning device 100 is further adapted to receive an echo light beam to form a signal light beam; the transceiver 130 is further adapted to receive the signal beam for coherent detection.
Therefore, the echo beam is collected to form a collecting beam (not shown); the collecting light beam is deflected by the first scanning unit 110 and the second scanning unit 120 to form a signal light beam (not shown); the collection beam is co-incident with the incident beam 121.
It should be noted that the scanning device 100 may further include other optical elements, such as a stop, a lens, or a lens group, which are not shown in fig. 1, and collect the echo light beam to form the collected light beam, and the collected light beam is deflected by the first scanning unit 110 and the second scanning unit 120 to form a signal light beam exiting toward the transceiver 130; the transceiver 130 receives the signal beam and performs coherent detection by combining with the local oscillator beam.
Since the second deflection can realize the compensation of the delay angle, the first deflection and the second deflection can ensure that the optical path of the light beam received by the scanning device 100 and the optical path of the light beam emitted from the scanning unit are kept unchanged, and therefore, the optical path of the echo light beam deflected to the signal light beam is also kept unchanged; and the optical path of the light beam received by the scanning device and the optical path of the light beam emitted from the scanning unit are also maintained unchanged during the process that the scanning light beam 190 is reflected to form the echo light beam.
Therefore, the optical paths from the initial beam 138, to the incident beam 121, to the emergent beam 119, to the scanning beam 190, to the echo beam, to the collecting beam and to the signal beam are always maintained constant during a single probing process, and thus it can be seen that although the deflection angle of the first deflection and the deflection angle of the second deflection are both changed, the equivalent optical path of the scanning apparatus 100 is always maintained constant during a single probing process, i.e. the scanning apparatus 100 is equivalent to scanning in a step-wise manner.
The scanning device 100 is utilized for scanning, so that the delay angle can be effectively reduced, the adverse effect of the delay angle is inhibited, the problem of reduction of the coherence efficiency caused by the delay angle is favorably solved, the limitation of the frequency of motors such as servo motors or stepping motors on the scanning frequency can be eliminated, the time of single detection is favorably shortened, the scanning frequency is favorably improved, and the high scanning frequency and the high coherence efficiency are favorably realized.
Referring to fig. 2, there is shown a schematic diagram of the optical path structure of a second embodiment of the scanning device of the present invention.
The present embodiment is the same as the previous embodiment, and the description of the present invention is omitted. The present embodiment is different from the previous embodiments in that the first scanning unit (not shown) has a first reflecting surface (not shown) swinging around a first scanning axis 217x and a second reflecting surface (not shown) swinging around a second scanning axis 217y, and the first scanning axis 217x is not parallel to the second scanning axis 217 y.
In this embodiment, the first scanning unit is at least one of a two-dimensional galvanometer and two one-dimensional galvanometers, so as to control the complexity of the optical system and simultaneously realize scanning of targets in different ranges.
In addition, the swing rate of the first reflecting surface is close to the swing rate of the second reflecting surface, and the ratio of the swing frequency of the first reflecting surface to the swing frequency of the second reflecting surface is less than or equal to a preset value (for example, the preset value may be set to a value of about 1). A delay angle problem occurs in both a first scanning direction in which scanning is performed by swinging the first reflecting surface and a second scanning direction in which scanning is performed by swinging the second reflecting surface.
As shown in fig. 2, the second scanning unit 220 includes: a first electro-optic crystal 229a and a second electro-optic crystal 229b disposed along the optical path, the second deflection comprising the first electro-optic crystal 229a rotating the transmitted beam about a first deflection axis 229 ax; the second electro-optic crystal 229b rotates the transmitted beam about a second deflection axis 229 by; the first deflection axis 229ax is non-parallel to the second deflection axis 229 by; the first deflection axis 229ax is parallel to the first scan axis 217 x; the second deflection axis 229by is parallel to the second scanning axis 217 y. In this embodiment, the first scanning axis 217x and the second scanning axis 217y are perpendicular to each other, and therefore the first deflection axis 229ax and the second deflection axis 229by are also perpendicular to each other.
Having the first deflection axis 229ax parallel to the first scan axis 217 x; the second deflection axis 229by is made parallel to the second scanning axis 217y, that is, the first scanning axis 217x is perpendicular to the incident plane of the light beam transmitting the first electro-optical crystal 229a, and the second scanning axis 217y is perpendicular to the incident plane of the light beam transmitting the second electro-optical crystal 229a, so that the directions of the second deflection and the first deflection can be matched, thereby achieving the purposes of enhancing the second deflection influence and expanding the deflection angle, further achieving the effect of forming a larger deflection angle with a smaller voltage, being beneficial to reducing the modulation voltage, and being beneficial to realizing low-voltage high-frequency scanning.
In this embodiment, the first electro-optic crystal 229a and the second electro-optic crystal 229b are both wedge-shaped, and the first electro-optic crystal 229a and the second electro-optic crystal 229b are disposed perpendicular to each other.
Specifically, the first electro-optic crystal 229a has a first right-angle surface (not shown) and a second right-angle surface (not shown) perpendicular to each other, and an inclined surface (not shown) connecting the first right-angle surface and the second right-angle surface and opposite to the first right-angle surface; the second electro-optic crystal 229b has a first right-angle surface (not shown) and a second right-angle surface (not shown) perpendicular to each other and an inclined surface (not shown) connecting the first right-angle surface and the second right-angle surface and opposite to the first right-angle surface.
The first right-angle face of the first electro-optic crystal 229a and the first right-angle face of the second electro-optic crystal 229b are parallel to each other; the second right-angle surface of the first electro-optic crystal 229a is perpendicular to the second right-angle surface of the second electro-optic crystal 229 b; the slope of the first electro-optic crystal 229a is parallel to the first scanning axis 217 x; the slope of the second electro-optic crystal 229b is parallel to the second scanning axis 217 y.
In this embodiment, the fact that the swing speed of the first reflection surface is close to the swing speed of the second reflection surface is only an illustrative example. In other embodiments of the present invention, the first scanning unit may further perform scanning in a fast-slow axis manner, that is, a difference between a swing speed of the first reflecting surface and a swing speed of the second reflecting surface is relatively large. Specifically, a ratio of the wobble frequency of the first reflection surface to the wobble frequency of the second reflection surface is greater than a preset value (for example, the preset value may be set to a relatively large value such as 5, 8, 10, 20, 50).
According to the principle of occurrence of the delay angle, although the delay angle problem occurs in both the first scanning direction in which scanning is performed by swinging the first reflecting surface and the second scanning direction in which scanning is performed by swinging the second reflecting surface, the delay angle problem in the first scanning direction is much more serious than the delay angle problem in the second scanning direction, that is, in this case, the delay angle problem mainly occurs in the first scanning direction.
Therefore, when the first scanning unit scans in a fast-slow axis manner, the second scanning unit includes: a first electro-optic crystal, the second deflection comprising the first electro-optic crystal rotating the transmitted light beam about a first deflection axis; the first deflection axis is parallel to the first scanning axis. When scanning is carried out in a fast and slow axis mode, the problem of the delay angle in the first scanning direction is solved by the first electro-optical crystal, so that the adverse effect of the delay angle can be properly improved, the structure of an optical system can be simplified, the integration level can be improved, the cost can be reduced, and the realization of the compromise between the performance and the cost is facilitated.
The invention also provides a scanning method of the scanning device.
It should be noted that the scanning method is a scanning method based on the scanning device of the present invention. Referring to fig. 3 in combination, fig. 3 shows a timing diagram of signals used in an embodiment of the scanning method of the present invention.
It should be noted that the scanning device used in the scanning method is the scanning device of the present invention. Therefore, referring to fig. 1 in combination, a schematic diagram of an optical path structure of a scanning apparatus 100 used in the embodiment of the scanning method shown in fig. 3 is shown. Since the adopted scanning device 100 is the scanning device of the present invention, the specific technical solution of the scanning device 100 refers to the foregoing embodiment of the scanning device 100, and the detailed description of the present invention is omitted here.
The scanning method comprises the following steps: first deflecting the incident light beam 121 with the first scanning unit 110 to form an emergent light beam 119; the first scanning unit 110 is rotated or swung to change the magnitude of the deflection angle of the first deflection.
With combined reference to fig. 3(a), fig. 3(a) shows a schematic diagram of a pulse sequence of the incident light beam 121, where the abscissa is time t and the unit is × 10-3s; the ordinate represents the intensity of the incident beam 121.
In this embodiment, the scanning method is applied to a coherent laser radar that scans with light pulses. The incident light beam 121 is therefore a pulsed signal.
As shown in fig. 1 and fig. 3, after the transceiver 130 generates the optical pulse signal, the initial light beam 138 is received by the scanning device 100 to form the incident light beam 121, the incident light beam 121 is deflected by the scanning device 100 to form an emergent light beam 119, and then a scanning light beam 190 is formed and emitted from the scanning device 100; the scanning beam 190 is an echo beam formed by the reflection of a target to be detected; the echo beam is collected and deflected by the scanning device 100 to form a signal beam, which is received by the transceiver 130. The process from emission to reception of a light pulse is a single detection process.
As shown by the graph 31 in fig. 3(a), at ta、tbAnd tcGenerating an optical pulse signal at each time; t is taTime to tbTime t andbtime to tcThe time interval between the moments is the scanning time, and in this embodiment, the scanning times are equal.
When the first scanning unit 110 rotates or swings, the deflection angle of the first deflection of the light beam changes accordingly. In this embodiment, as the first reflection surface swings along the first scanning axis 117, the incident angle of the incident beam 121 on the first reflection surface changes, and accordingly, the reflection angle of the formed emergent beam 119 changes, so as to form the scanning beam 190 with a changed propagation direction.
As shown in fig. 3(C), fig. 3(C) shows graphs of the first deflection angle and the second deflection angle, respectively, with respect to time in the embodiment of the scanning method shown in fig. 1. In the figure, the abscissa represents time; the ordinate indicates the beam deflection angle and the graph 33 indicates the deflection angle versus time for the first deflection.
In this embodiment, the rotation or oscillation of the first scanning unit 110 is continuous, that is, the first scanning unit 110 rotates or oscillates continuously, that is, as shown in fig. 1, the first reflective surface oscillates continuously around the first scanning axis 117. The deflection angle of the first deflection thus varies continuously.
Specifically, during the first deflection, the deflection angle of the incident light beam 121 is a sinusoidal function with respect to time, namely:
where f is a frequency of the first reflecting surface oscillating around the first scanning axis 117 in the first scanning unit 110,
is the initial phase of the first reflecting surface, and A is the amplitude of the oscillation angle of the first reflecting surface.
Since the incident light beam 121 is a pulse light beam, the scanning time is less than the swing period of the first scanning unit 110, and therefore there are N detections in each swing period of the first scanning unit 110, so the scanning time is: 1/Nf, the angle range swept by the scanning beam 190 emitted from the scanning device 100 during the nth detection is:
on the other hand, in the embodiment, the scanning method is applied to the laser radar with a transceiver common path, and the scanning device 100 is further adapted to receive the echo beam to form a signal beam, so that the size of the angle swept by the scanning beam 190, that is, the delay angle generated in the nth detection process, is:
according to the reason generated by the delay angle, the size of the delay angle is related to the distance of the target to be measured; in the actual detection process, the position of the target to be detected at the beginning of each detection is unknown, so that the angle compensation of the target to be detected cannot be realized, and therefore, in order to solve the problem of the delay angle, the compensation needs to be started at the same time of the detection, that is, the optical path of the light beam received by the scanning device 100 and the optical path of the light beam emitted from the scanning unit 100 are kept unchanged in the whole time range of each detection process.
The scanning method further comprises: the modulation voltage is supplied to the second scanning unit 120 to cause the propagation direction of the light beam transmitted through the second scanning unit 120 to be second deflected based on the electro-optical effect to compensate for the delay angle.
Therefore, the second scanning unit 120 deflects the transmitted light beam by a second deflection angle during the nth detection:
it follows that the deflection angle of the second deflection varies periodically; the period of change of the second deflection angle is an electro-optical deflection period, and as shown in fig. 3(C), a graph 34 represents the relationship between the deflection angle of the second deflection and time, and the electro-optical deflection period refers to the time between the deflection angles of the second deflections being zero values two adjacent times. The fact that the deflection angle of the second deflection is zero means that the angle deflection due to the electro-optical effect is zero, and the angle deflection due to other optical effects such as refraction and reflection is not taken into account.
Specifically, in this embodiment, the electro-optical deflection period is equal to the scanning time, so as to ensure that the deflection angles of the scanning beam 190 and the echo beam are kept constant in the whole time range of each detection.
In this embodiment, the scanning device 100 is suitable for performing uniform scanning, the scanning angular velocity of the scanning beam is uniform, and the variation of the deflection angle of the first deflection is uniform. Since the scan time is: 1/Nf, therefore, during the nth detection in each oscillation period of the first scanning unit 110, the rate of change of the deflection angle of the second deflection is:
it can be seen that, as shown by the graph 34 in fig. 3(C), the deflection angle of the second deflection is related to time by:
in this embodiment, in the electro-optical deflection period, the deflection angle of the second deflection changes linearly. The linear change of the deflection angle of the second deflection can not only ensure the compensation effect of the delay angle and improve the coherence efficiency, but also has simple change rule of the light path and lower scanning control difficulty, thereby being beneficial to improving the precision of the light path setting.
Specifically, the second scanning unit 120 includes an electro-optical crystal, and the modulation voltage is applied to the electro-optical crystal to cause an electro-optical effect of the electro-optical crystal. As shown in fig. 1, in the second scanning unit 120, the first electro-optical crystal 129 is wedge-shaped, and the incident light beam 121 is refracted at the surface of the first electro-optical crystal 129 when transmitting through the first electro-optical crystal 129, so as to realize the second deflection.
In combination with the principle of refraction of light, it is known that the modulation voltage causes the refractive index of the electro-optic crystal to change linearly with time during the electro-optic deflection period.
Referring collectively to fig. 3(B), fig. 3(B) shows a graph of modulation voltage versus time for an embodiment of the scanning method shown in fig. 1. In the figure, the abscissa represents time; the ordinate represents the square magnitude of the modulation voltage, and the plot 32 represents the modulation voltage received by the second scanning unit 120 versus time.
Therefore, as shown by a graph 32 in fig. 3(B), the modulation voltage varies periodically, and the variation period of the modulation voltage is equal to the electro-optical deflection period, that is, the variation period of the modulation voltage, the electro-optical deflection period, and the scanning time are all equal.
In this embodiment, the second scanning unit 120 includes a quadratic electro-optic crystal, i.e., the first electro-optic crystal 129 is a quadratic electro-optic crystal. And in the electro-optical deflection period, the modulation voltage makes the refractive index of the electro-optical crystal linearly change along with time.
According to the kerr effect, the refractive index of the first electro-optic crystal 129 is related to the modulation voltage by:
the deflection angle of the second deflection of the incident light beam 121 in relation to the applied voltage is:
where L denotes an optical path length of a light beam in the first electro-optical crystal 129, d denotes a thickness of the first electro-optical crystal 129, and V denotes a voltage applied to the first electro-optical crystal 129.
Therefore, in each variation period, the square of the modulation voltage varies linearly with time, i.e. the modulation voltage is linearly related to the square root of time, i.e. the square of the modulation voltage varies linearly with time during the electro-optical deflection period.
Referring to fig. 4 in combination, a deflection angle of the first deflection, a deflection angle of the second deflection, and a scan angle versus time in the embodiment of the scanning method shown in fig. 3 are shown.
Wherein the abscissa represents time in a unit of × 10-3s; the ordinate represents the beam deflection angle. Graph 51 represents the deflection angle of the first deflection versus time; graph 52 shows the deflection angle of the second deflection versus time; plot 53 represents the resultant angular scan curve after the first deflection and the second deflection.
As shown in FIG. 4, since the deflection angle of the second deflection is equal to the formed delay angle and opposite to the deflection direction, the second deflection can compensate the delay angle in a single detection process, so that the scanning curve of the combined angle can be kept constant in the electro-optical deflection period (such as t in FIG. 4)1And t2Shown by the line 53 therebetween), that is, there is no or little angular difference between the formed scanning beam and the echo beam formed by reflection from the target. The scanning method based on the scanning apparatus 100 can effectively suppress the adverse effect of the delay angle and can improve the coherence efficiency.
On the other hand, the second deflection is realized based on the electro-optic effect, and the speed of the scanning method for compensating the delay angle is related to the corresponding speed of the electro-optic effect on the electric signal, so that the scanning method can break through the limitation of the motor frequency on the scanning frequency, and the scanning method can effectively shorten the time of single detection, effectively improve the scanning frequency and be beneficial to realizing the compromise of high scanning frequency and high coherence efficiency on the premise of ensuring the effect of compensating the delay angle.
Setting the oscillation frequency of the first reflecting surface in the first scanning unit 110 to 1kHz (that is, setting the oscillation frequency of the galvanometer to 1kHz), and setting the scanning range to 30 °; taking a laser radar with a range of 300m as an example, the single detection time is 2 μ s, and the magnitude of the delay angle generated by the first scanning unit 110 is about: 30 ° × 1kHz × 2 μ s ═ 0.06 °. The second scanning unit 120 therefore only needs to achieve an angular compensation of 0.06 ° within 2 μ s, i.e. the electro-optical deflection period is 2 μ s and the frequency is: 1/2 μ s-500 kHz.
It should be noted that the scanning method is applied to a coherent laser radar, and the laser radar may also use continuous light to scan, and perform the above angle compensation in the time period of each detection, where the time period of each detection is the reciprocal of the repetition frequency of the detection.
In addition, the present invention also provides a laser radar including: the invention relates to a scanning device.
Specifically, the laser radar includes: the scanning device is the scanning device of the invention. Therefore, the specific technical solution of the scanning device refers to the embodiments of the scanning device. The present invention will not be described herein.
In some embodiments of the invention, the lidar is a coherent lidar, that is, the lidar is a coherent detection based lidar. The laser radar realizes scanning detection based on coherent signals between local oscillator light and echo light formed by reflection of a target to be detected, and has the advantages of high angular resolution, high distance resolution, strong anti-interference capability and the like.
The scanning device of the laser radar is the scanning device of the invention; the first deflection and the second deflection can ensure that the optical path of the light beam received by the scanning device and the optical path of the light beam emitted from the scanning unit are kept unchanged in the whole time range of each detection, and the scanning device 100 is equivalent to scanning in a stepping mode. Therefore, the scanning device 100 is used for scanning, so that the influence of the delay angle on the coherence efficiency can be effectively suppressed, the problem of the delay angle is favorably solved, and the coherence efficiency is favorably improved.
On the other hand, due to the high-speed response of the electro-optic effect to the change of the electric signal, the high response rate of the change of the second deflection angle can realize delay angle compensation at a higher speed, so that the time of single detection is favorably shortened and the scanning frequency is favorably improved under the condition of ensuring that the light path is unchanged.
Therefore, the laser radar can effectively shorten the time of single detection, is beneficial to improving the scanning frequency and is beneficial to realizing the consideration of high scanning frequency and high coherence efficiency on the premise of ensuring the delay angle compensation effect, namely maintaining the light path unchanged.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (19)
1. A scanning device, comprising:
a first scanning unit, adapted to make a first deflection of the propagation direction of an incident light beam to form an emergent light beam, wherein the first scanning unit changes the deflection angle of the first deflection by rotating or swinging;
it is characterized in that the method also comprises the following steps:
the second scanning unit is positioned in the optical path of at least one of the incident light beam and the emergent light beam, and when the incident light beam or the emergent light beam transmits through the second scanning unit, the second scanning unit enables the transmission direction of the transmitted light beam to generate second deflection based on the electro-optic effect so as to compensate for a delay angle;
the outgoing light beam is adapted to form a scanning light beam outgoing from the scanning device, which scanning light beam is reflected by the object to be detected to form an echo light beam.
2. The scanning device of claim 1, wherein the second scanning unit comprises an electro-optic crystal, the electro-optic crystal being at least one of a linear electro-optic crystal and a non-linear electro-optic crystal.
3. The scanning device of claim 2, wherein the electro-optic crystal is a non-linear electro-optic crystal; the quadratic electro-optical coefficient of the electro-optical crystal is in the order of 10-14m2/V2To 10-15m2/V2Within the range.
4. The scanning device of claim 2, wherein the electro-optic crystal comprises: at least one of potassium tantalate niobate crystal, potassium lithium tantalate niobate crystal, and potassium sodium tantalate niobate crystal.
5. The scanning device according to claim 1, wherein the first scanning unit changes the propagation direction of the outgoing light beam by oscillating, the first scanning unit comprising: at least one of a galvanometer and a galvanometer;
the first scanning unit changes the propagation direction of the outgoing light beam by rotating, and the first scanning unit includes: and (5) rotating the mirror.
6. The scanning device according to claim 5, wherein the first scanning unit has a first reflecting surface oscillating about a first scanning axis;
the second scanning unit includes: a first electro-optic crystal, the second deflection comprising the first electro-optic crystal rotating the transmitted light beam about a first deflection axis;
the first deflection axis is parallel to the first scanning axis.
7. The scanning device according to claim 5, wherein the first scanning unit has a first reflecting surface oscillating about a first scanning axis and a second reflecting surface oscillating about a second scanning axis, the first scanning axis being non-parallel to the second scanning axis;
the ratio of the swing frequency of the first reflecting surface to the swing frequency of the second reflecting surface is less than or equal to a preset value;
the second scanning unit includes: the first electro-optical crystal and the second electro-optical crystal are sequentially arranged along the light path, and the second deflection comprises that the first electro-optical crystal enables the transmitted light beam to rotate around a first deflection shaft; the second electro-optic crystal rotates the transmitted light beam about a second deflection axis; the first yaw axis is non-parallel to the second yaw axis;
the first deflection axis is parallel to the first scanning axis;
the second deflection axis is parallel to the second scanning axis.
8. The scanning device according to claim 5, wherein the first scanning unit has a first reflecting surface oscillating about a first scanning axis and a second reflecting surface oscillating about a second scanning axis, the first scanning axis and the second scanning axis being perpendicular to each other;
the ratio of the swing frequency of the first reflecting surface to the swing frequency of the second reflecting surface is greater than a preset value;
the second scanning unit includes: a first electro-optic crystal, the second deflection comprising the first electro-optic crystal rotating the transmitted light beam about a first deflection axis; the first deflection axis is parallel to the first scanning axis.
9. The scanning device according to claim 1, wherein the second scanning unit has an input surface on which the light beam is incident; the light beam is projected perpendicularly to the input face.
10. The scanning device of claim 1, wherein the second scanning unit comprises an electro-optic crystal; the electro-optic crystal receives a modulation voltage to effect the second deflection; the modulation voltage is less than 100V.
11. The scanning device of claim 1, wherein the echo beam is collected to form a collection beam;
the collecting light beam is deflected by the first scanning unit and the second scanning unit to form a signal light beam;
the collection beam is co-incident with the incident beam.
12. The scanning device according to any one of claims 1 to 11, wherein the first scanning unit changes the magnitude of the deflection angle of the first deflection by continuous rotation or oscillation.
13. A scanning method of a scanning apparatus according to claim 1, the scanning method comprising:
first deflecting the incident light beam with the first scanning unit to form an emergent light beam;
rotating or swinging the first scanning unit to change the size of the deflection angle of the first deflection;
and providing a modulation voltage to the second scanning unit, and enabling the propagation direction of the light beam transmitted through the second scanning unit to generate second deflection based on the electro-optical effect so as to compensate the delay angle.
14. The scanning method according to claim 13, wherein the deflection angle of the second deflection is changed periodically; the variation period of the second deflection angle is an electro-optic deflection period;
and in the electro-optical deflection period, the deflection angle of the second deflection is linearly changed.
15. The scanning method according to claim 13, wherein the deflection angle of the second deflection is changed periodically; the variation period of the second deflection angle is an electro-optic deflection period;
the second scanning unit comprises an electro-optical crystal, and the refractive index of the electro-optical crystal is linearly changed along with time by the modulation voltage in the electro-optical deflection period.
16. The scanning method of claim 15, wherein the second scanning unit comprises a quadratic electro-optic crystal;
the square of the modulation voltage varies linearly with time during the electro-optical deflection period.
17. The scanning method according to any one of claims 13 to 16, wherein the first scanning unit is continuously rotated or oscillated;
the deflection angle of the first deflection varies continuously.
18. A lidar, comprising:
a scanning device according to any one of claims 1 to 12.
19. The lidar of claim 18, wherein the lidar is a coherent lidar.
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| CN110376567B (en) * | 2019-08-16 | 2020-09-18 | 上海禾赛光电科技有限公司 | Laser radar and transmitting device thereof |
| CN110967680B (en) * | 2019-12-18 | 2022-09-27 | 中国科学院半导体研究所 | Composite structure rotating mirror for three-dimensional scanning and laser radar applying same |
| CN111025737B (en) * | 2019-12-23 | 2021-11-23 | 中国兵器装备研究院 | Electric scanning continuous light beam orientation device |
| CN114442104A (en) * | 2020-10-30 | 2022-05-06 | 苏州镭智传感科技有限公司 | Coherent laser radar |
| CN114787657A (en) * | 2020-12-31 | 2022-07-22 | 深圳市大疆创新科技有限公司 | Detection device, unmanned aerial vehicle, and control method and device of detection device |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007271997A (en) * | 2006-03-31 | 2007-10-18 | Mitsubishi Electric Corp | Ir/laser common-use optical system device |
| CN104635212A (en) * | 2007-08-16 | 2015-05-20 | 罗伯特·博世有限公司 | Monostatic multi-beam radar sensor for motor vehicles |
| CN105120188A (en) * | 2015-10-08 | 2015-12-02 | 杭州虹视科技有限公司 | Laser scanner and laser display system |
| CN107422473A (en) * | 2017-08-31 | 2017-12-01 | 南京理工大学 | MEMS micromirror two-dimensional scan for laser radar collimates optical transmitting system |
| CN108562887A (en) * | 2018-04-27 | 2018-09-21 | 北京工业大学 | A kind of multi-wavelength laser radar based on wavelength-division multiplex |
Family Cites Families (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4380391A (en) * | 1980-09-30 | 1983-04-19 | The United States Of America As Represented By The Secretary Of The Army | Short pulse CO2 laser for ranging and target identification |
| JP3483303B2 (en) * | 1994-06-21 | 2004-01-06 | 株式会社トプコン | Rotary laser device |
| DE10112833C1 (en) * | 2001-03-16 | 2003-03-13 | Hilti Ag | Method and device for electro-optical distance measurement |
| US7522642B2 (en) * | 2006-03-29 | 2009-04-21 | Amo Development Llc | Method and system for laser amplification using a dual crystal Pockels cell |
| JP5130810B2 (en) * | 2007-07-13 | 2013-01-30 | 沖電気工業株式会社 | Optical deflector |
| US20090190463A1 (en) * | 2008-01-30 | 2009-07-30 | Jds Uniphase Corporation, | Optical pick-up unit with two-mirror phase shifter |
| US8054464B2 (en) * | 2010-01-25 | 2011-11-08 | Sigma Space Corp. | Polarization switching lidar device and method |
| DE102011005746A1 (en) * | 2011-03-18 | 2012-09-20 | Robert Bosch Gmbh | Measuring device for multi-dimensional measurement of a target object |
| CN202199930U (en) * | 2011-06-15 | 2012-04-25 | 中科中涵激光设备（福建）股份有限公司 | Laser scanning device for processing micro-circular aperture based on electro-optical effect |
| WO2016025502A1 (en) * | 2014-08-11 | 2016-02-18 | Gerard Dirk Smits | Three-dimensional triangulation and time-of-flight based tracking systems and methods |
| CN107430193B (en) * | 2014-12-22 | 2020-08-07 | 特林布尔有限公司 | Distance measuring instrument |
| WO2016169871A1 (en) * | 2015-04-22 | 2016-10-27 | Trinamix Gmbh | Detector for an optical detection of at least one object |
| CN105241374B (en) * | 2015-10-16 | 2017-10-03 | 哈尔滨工程大学 | The common orthogonal carrier frequency digital holographic detection device in road of dual wavelength and detection method |
| EP4194888A1 (en) * | 2016-09-20 | 2023-06-14 | Innoviz Technologies Ltd. | Lidar systems and methods |
| JP6587599B2 (en) * | 2016-12-02 | 2019-10-09 | オムロンオートモーティブエレクトロニクス株式会社 | Object detection device |
| CN207336754U (en) * | 2017-10-19 | 2018-05-08 | 北京万集科技股份有限公司 | Laser radar scanning system and vehicle |
| CN207675932U (en) * | 2017-11-14 | 2018-07-31 | 北京万集科技股份有限公司 | MEMS galvanometers synchronizing device based on laser radar and laser radar |
| CN108445469A (en) * | 2018-05-11 | 2018-08-24 | 天津大学 | A kind of rotating mirror scanning device and method of multi-line laser radar |
-
2018
- 2018-10-25 CN CN201811254267.8A patent/CN109444848B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007271997A (en) * | 2006-03-31 | 2007-10-18 | Mitsubishi Electric Corp | Ir/laser common-use optical system device |
| CN104635212A (en) * | 2007-08-16 | 2015-05-20 | 罗伯特·博世有限公司 | Monostatic multi-beam radar sensor for motor vehicles |
| CN105120188A (en) * | 2015-10-08 | 2015-12-02 | 杭州虹视科技有限公司 | Laser scanner and laser display system |
| CN107422473A (en) * | 2017-08-31 | 2017-12-01 | 南京理工大学 | MEMS micromirror two-dimensional scan for laser radar collimates optical transmitting system |
| CN108562887A (en) * | 2018-04-27 | 2018-09-21 | 北京工业大学 | A kind of multi-wavelength laser radar based on wavelength-division multiplex |
Non-Patent Citations (2)
| Title |
|---|
| A preliminary comparison of Na lidar and meteor radar zonal winds during geomagnetic quiet and disturbed conditions;G.Kishore Kumar;《Journal of Atmospheric and Solar-Terrestrial Physics》;20180331;70-79 * |
| 相位编码合成孔径激光雷达关键技术研究;李飞;《中国博士学位论文全文数据库 信息科技辑》;20161115;I136-5 * |
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