Patent Application
20210405161
Light detection and ranging (LIDAR) is a technology that measures a distance to an object by projecting a laser toward the object and receiving the reflected laser. As a method of measuring a distance in the LIDAR technology, a time of flight (TOF) which uses a flight time of laser light, a triangulation method which calculates a distance according to a position of a received laser according to a position of a received laser, and the like are used. The triangulation method measures a distance with respect to a wide range at once mainly by using a flash laser, but has low accuracy, therefore LIDAR, to which the TOF method capable of performing relatively high definition/high resolution measurement with respect to a long distance, is used as a distance sensor for autonomous vehicles which have recently taken center stage as a significant application field for LIDAR.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other features, details, utilities, and advantages of the claimed subject matter will be apparent from the following, more particular written Detailed Description of various implementations as further illustrated in the accompanying drawings and defined in the appended claims.
Various implementations of a LiDAR system disclosed herein include two laser sources configured to generate a first laser beam and a second laser beam, a first vertically scanning mirror configured to rotate about a first axis, a second vertically scanning mirror configured to rotate about a second axis, wherein the first axis and second axis are parallel to each other, and a polygonal mirror configured to rotate around a third axis, wherein the third axis is orthogonal to each of the first axis and the second axis, wherein the first vertical scanning mirror is configured to direct the first laser beam towards the polygonal mirror and the first vertical scanning mirror is configured to direct the first laser beam towards the polygonal mirror.
These and various other features and advantages will be apparent from a reading of the following Detailed Description.
A further understanding of the nature and advantages of the present technology may be realized by reference to the figures, which are described in the remaining portion of the specification.
In mechanically scanning LiDAR for automotive applications, achieving large detection range, field of view, high density scanning, and low cost is not trivial. The design of the mechanically scanning LiDAR disclosed herein allows for the use of simple and few components alongside a large collection aperture to meet all the above metrics. Additionally, the design is quite compact, in the sense that much of the cross-sectional area is well-utilized.
One or more implementations disclosed herein provide mechanically scanning LiDARs of two laser emitters, two optical detectors, two collection lenses, two vertically scanning mirrors, and one horizontally rotating mirror. In one implementation, each laser is directed into the scanning mirrors, leading it to raster across a field of view as the mirrors articulate. Objects which reflect light in the field of view bounce scattered light back towards the device, which are de-scanned by reflection off the same scanning mirrors in reverse order, and then collected and focused down to the detector via the collection lens. By relating the generation of light at the laser to the time it was received by the detector, the mechanically scanning LiDAR allows users to estimate the distance of the object in the field of view. Repeating this over different mirror positions allows users to build map surrounding environment in 3D fashion.
Two-dimensional mechanically scanning LiDAR at large scanning field-of-views with high frame rates, large scanning densities, long range, and eye-safe are typically difficult to achieve. The disclosed mechanically scanning LiDAR overcome the normal obstacles of using expensive galvanometer mirrors or many laser emitters and detectors by incorporating a fast rotational mirror, and a cheap, slow vertically scanning mirror. Having two passive optical mirrors allows the mechanically scanning radars to cut the number of laser emitters and detectors to two of each. The operational simplicity of the mirrors also allows for cheap manufacture and reliable design. Furthermore, the optical components of the mechanically scanning LiDAR disclosed herein are placed in a compact design to facilitate integration into larger systems. As opposed to a micro electromechanical system (MEMS) based or other small-aperture based scanning systems, the mechanically scanning LiDARs disclosed herein allows for a large collection aperture, thus enabling long range. While this mechanically scanning LiDAR disclosed herein can be scaled arbitrarily, in one implementation, the mechanically scanning LiDARs disclosed herein have an aperture of approximate 1-5 cm{circumflex over ( )}2, however wider apertures may be provided in alternative implementations.
The technology disclosed herein provides various implementations of mechanically scanning LiDAR. One implementations of such mechanically scanning LiDAR includes a rotationally-scanning mirror, two vertically scanning mirrors, a laser source, a collection lens, and a detector. For the following figures elements that are configured in substantial symmetry, such symmetric components are referred to by “a” and “b” with respect to the reference numeral. When referred to such symmetric components together, the reference numeral is used to refer to both of such symmetric components. Thus, for example, laser sources 110a and 110b may be referred to together as laser sources 110, detectors 112a and 112b may be referred to together as detectors 112, etc.
After reflection from the vertical scanning mirrors 104, the light beam 120 then bounces off the rotationally scanning mirror 102. The rotationally scanning mirror 102 may be in the shape of a polygon with n sides. In
Due to contributions of both mirrors, the laser light beam therefore scans in two largely independent dimensions, allowing for a raster scan across the field of view of the mechanically scanning LiDAR 100. The light beam 120 reflected from the rotationally scanning mirror 102 is shown by 122, which after colliding with an object 160 may back scatter towards the mechanically scanning LiDAR 100. The back scattered light beam 132 reflects off of the rotationally scanning mirror 102 and the galvo mirror 104 towards collection lens 114. The collection lens 114 focuses the backscattered light beam 132 towards a detector 112. Note that the detector 112 may be one of a single element detector or a multiple element detector.
The rotationally scanning mirror 102 maybe rotating at a speed in the range of 10 to 30 revolutions per minute (RPM). On the other hand, the galvo mirror 104 may rotate at similar speed, however, it does not revolve completely around its axis. Assuming that not too much time has passed, the backscattered light beam 132 which makes it to the mechanically scanning LiDAR 100 then reflects off the rotationally scanning mirror 102, followed by the vertically scanning mirror 104, and eventually travels through the collection lens 114. In the implementation disclosed in
It is understood that the actual implementation of the mechanically scanning LiDAR 100 need not fit the precise geometric configuration as pictured in
In one or more of the implementations disclosed above, the laser sources and the detector/collection lens pair are roughly aligned or imaged (via auxiliary mirrors) into the same optical axis. However, this can happen after the collection lens as shown in
Furthermore, a number of alternative mechanical enumerations may be used. For example, the auxiliary mirrors could be mechanically combined with the laser, the auxiliary mirrors could be mechanically combined into the collection lens, and the laser could be mechanically combined into the collection lens. Yet alternatively, the form of the laser beam (such as 120, 220, etc.) may also vary in alternative implementations. For example, the laser sources 110, 210, etc., may be semiconductor laser source with single mode, multi-mode, or multi-emitter, a fiber laser, a diode-pumped solid state (DPSS) laser, an optically pumped surface-emitting laser (OPSEL), etc.
The above specification, examples, and data provide a complete description of the structure and use of example embodiments of the disclosed technology. Since many embodiments of the disclosed technology can be made without departing from the spirit and scope of the disclosed technology, the disclosed technology resides in the claims hereinafter appended. Furthermore, structural features of the different embodiments may be combined in yet another embodiment without departing from the recited claims.
