Beam-steering device particularly for lidar systems
A beam-steering engine, comprising an optical element switchable between a first operational mode and a second operational mode, in the first operational mode of the optical element the beam-steering engine is configured to output an input light beam incident on the beam-steering engine along a first propagation direction and in the second operational mode of the optical element the beam-steering engine is configured to output the input light beam incident on the beam-steering engine along a second propagation direction. A transition of the optical element between the first and second operational modes is characterized by a transition time period that varies with a temperature of the optical element. The beam-steering engine further includes a device to control a temperature of the solid-state optical element to maintain the transition time period below a certain limit.
1. A LIDAR apparatus for scanning a scene, comprising:
a. a transmitter stage for generating a light beam,
b. a receiver stage,
c. a beam-steering engine configured to steer the light beam to scan at least a portion of the scene, the beam-steering engine including:
i. a first steering stage to steer the light beam in a first steering range by performing a continuous angular deflection of the light beam within the first steering range,
ii. a second steering stage to steer the light beam in a second steering range by performing a stepwise angular deflection of the light beam within the second steering range, wherein the second steering stage includes a light-transmissive heating layer, a polarization selector, and a polarization grating, the light-transmissive heating layer configured to be sandwiched between the polarization selector and the polarization grating and configured to heat both the polarization selector and the polarization grating.
2. The LIDAR apparatus as defined in claim 1 , wherein the second steering stage is located downstream the first steering stage, wherein the second steering stage steers the light beam initially steered by the first steering stage.
3. The LIDAR apparatus as defined in claim 1 , wherein the first steering stage includes an optical component that is continuously moveable to produce the continuous angular deflection of the light beam.
4. The LIDAR apparatus as defined in claim 3 , wherein the optical component is a mirror.
5. The LIDAR apparatus as defined in claim 4 , wherein the first steering stage includes a Micro-Electro-Mechanical System (MEMS) responsive to a steering signal to continuously move the mirror to produce the continuous angular deflection of the light beam.
6. The LIDAR apparatus as defined in claim 1 , wherein the second steering stage is responsive to a steering signal to deflect the light beam in a step selected among a finite number of steps in the second steering range.
7. The LIDAR apparatus as defined in claim 1 , wherein the polarization grating is a liquid crystal polarization grating.
8. The LIDAR apparatus as defined in claim 1 , wherein the second steering stage is configured to alter a polarization of the input light beam and alter a propagation angle thereof.
9. The LIDAR apparatus as defined in claim 1 , wherein the polarization selector is configured to alter a handedness of a circular polarization of an incident light beam.
10. The LIDAR apparatus as defined in claim 1 , wherein the second steering range is defined between a first light beam propagation direction and a second light beam propagation direction at an angle with relation to the first light beam propagation direction, the second steering range being configured such that the light beam is displaced from the first light beam propagation direction to the second light beam propagation direction in a single discrete step.
11. The LIDAR apparatus as defined in claim 1 , wherein the second steering range is defined between a first light beam propagation direction and a second light beam propagation direction at an angle with relation to the first light beam propagation direction, the second steering range being configured such that the light beam is displaced from the first light beam propagation direction to the second light beam propagation direction in multiple discrete steps that define at least a third light propagation direction angularly spaced from the first and second light beam propagation direction and residing therebetween.
12. The LIDAR apparatus as defined in claim 1 , wherein the LIDAR apparatus further comprises a controller configured to generate a succession of switching commands that are applied to the second steering stage.
13. The LIDAR apparatus as defined in claim 12 , wherein each two switching commands of the succession of switching commands include a dwell time interval.
14. The LIDAR apparatus as defined in claim 13 , wherein the dwell time interval varies based on an order of the two switching commands.
15. A method for scanning a scene, comprising:
providing a LIDAR apparatus including:
a. a transmitter stage for generating a light beam,
b. a receiver stage,
c. a beam-steering engine configured to steer the light beam to scan at least a portion of the scene,
scanning the scene using the beam-steering engine by (i) steering the light beam in a first steering range by performing a continuous angular deflection of the light beam within the first steering range; and (ii) steering the light beam in a second steering range by performing a stepwise angular deflection of the light beam within the second steering range, wherein the second steering stage includes a light-transmissive heating layer, a polarization selector, and a polarization grating, the light-transmissive heating layer configured to be sandwiched between the polarization selector and the polarization grating to heat both the polarization selector and the polarization grating;
sensing an optical return with the receiver stage; and
generating an output conveying a three-dimensional (3D) representation of the scene.
16. The method as defined in claim 15 , wherein the second steering stage is located downstream the first steering stage, wherein the second steering stage steers the light beam initially steered by the first steering stage.
17. The method as defined in claim 15 , wherein the first steering stage includes an optical component that is continuously moveable to produce the continuous deflection of the light beam.
18. The method as defined in claim 17 , wherein the optical component is a mirror.
19. The method as defined in claim 17 , wherein the first steering stage includes a Micro-Electro-Mechanical System (MEMS) responsive to a steering signal to continuously move the mirror to produce the continuous deflection of the light beam.
20. The method as defined in claim 15 , wherein the second steering stage is responsive to a steering signal to deflect the light beam in a step selected among a finite number of angular steps in the second steering range.