Lidar device

Abstract

The present invention relates to a lidar device (1) for detecting an environment of a vehicle, the lidar device comprising: a transmitting unit (10) for emitting laser beams (20), wherein the transmitting unit (10) includes a beam deflection unit (18) designed to direct the emitted laser beams (20) in different directions in order to scan the environment, and a receiving unit (12) for receiving laser beams (22) reflected by the environment, wherein the receiving unit (12) includes a detector (28) designed to convert the received laser beams (22) into electrical signals; According to the invention, the receiving unit (12) has a parabolic mirror (24) by means of which the received laser beams (22) are collected and reflected to a light-sensitive detector surface (32) of the detector (28)

Description

[0001] The present invention relates to a lidar device according to the preamble of claim 1.

[0002] A generic lidar device is used to detect the surroundings of a vehicle. Such a lidar device has a transmitting unit for emitting laser beams, wherein the transmitting unit includes a beam deflection unit configured to direct the emitted laser beams in different directions to scan the surroundings. A generic lidar device further has a receiving unit for receiving laser beams reflected by the surroundings, wherein the receiving unit includes a detector configured to convert the received laser beams into electrical signals.

[0003] Using such a known lidar device, vehicles can scan their surroundings and, in particular, detect objects in that environment. If an emitted laser beam is reflected back to the lidar device from such an object in the environment, the distance between the lidar device and the object can be determined based on the travel time. The corresponding laser beams are emitted as short pulses, and by emitting them in different directions, an area of ​​the environment can be scanned or sampled. The reflection points in the environment that reflect the laser beam from the lidar device are combined into a lidar point cloud, which serves as a representation of the environment and is stored, for example, in a vehicle's computer and continuously refreshed through the cyclical scanning process.

[0004] In known lidar devices, a further beam deflection unit is provided in the receiving unit, which also scans the environment synchronously with the first beam deflection unit of the transmitting unit and feeds the laser beams reflected by the environment to the detector.

[0005] The use of two beam deflection units makes conventional lidar devices complex, expensive, and error-prone. Such beam deflection units typically use macroscopic mechanically rotating mirrors. As an alternative to macroscopic rotating mirrors, MEMS-based (MEMS: Micro-Electro-Mechanical System) beam deflection units are also used. Such MEMS lidar systems use millimeter-sized semiconductor mirrors to direct the laser beam in different directions. However, even such a system is complex and ultimately relies on mirrors that must be moved.

[0006] It is therefore the object of the present invention to provide a lidar device with reduced complexity.

[0007] This object is achieved by a lidar device according to the characterizing part of claim 1.

[0008] In a lidar device according to the invention, the receiving unit comprises a parabolic mirror, by means of which the received laser beams are collected and reflected to a light-sensitive detector surface of the detector. A parabolic mirror has the shape of a paraboloid of revolution.

[0009] This offers the advantage that the receiving unit can be constructed without moving parts. The parabolic mirror efficiently collects laser beams reflected from the environment and focuses them onto the light-sensitive detector surface of the detector, where they are converted into electrical signals. The parabolic mirror does not need to be moved, which significantly simplifies the construction of a lidar device according to the invention. The spatial resolution can be obtained by taking into account the solid angle at which the transmitting unit emits the laser beams and when. The evaluation electronics can therefore assume that, except for the travel times, laser beams received at the same time were also reflected back from this solid angle. The spatial resolution of the detector can, but does not necessarily have to, be evaluated for the spatial resolution.

[0010] Further preferred embodiments of the present invention emerge from the subclaims.

[0011] In a preferred embodiment of the invention, the parabolic mirror is oriented with an opening in the direction of the solid angle into which the emitted laser beams are directed during scanning. The opening is preferably designed, both in terms of its dimensions and its orientation, so that the parabolic mirror can collect and focus laser beams from as many of the expected incident directions as possible. The expected incident directions can, in particular, include the emission directions realized during scanning. The parabolic mirror is, in particular, arranged such that its axis of symmetry is aligned parallel to an axis that extends from the transmitting unit to a center of the detection range of the lidar device.

[0012] A particularly preferred embodiment of the present invention results in a lidar device in which the parabolic mirror is not moved relative to the transmitting unit during scanning.

[0013] The detector surface of the detector can be arranged at a first focal point of the parabolic mirror, in which received laser beams incident parallel to a symmetry axis of the parabolic mirror are focused.

[0014] In another particularly preferred embodiment of a lidar device according to the invention, the detector surface forms a plane that (preferably additionally) contains several focal points of the parabolic mirror, in which received laser beams that are not incident parallel to the parabolic mirror's axis of symmetry are focused. Light that is not incident on a parabolic mirror parallel to the axis of symmetry is not collected at the focal point for parallel-axis light, but rather at different focal points depending on the incident angle relative to the parabolic mirror's axis of symmetry, which form a focal line in a two-dimensional section. Such focal lines are also called caustics. Caustics for parabolic mirrors are known and can be determined, for example, through simulations.Therefore, a fundamental idea of ​​the present invention is to exploit the property of parabolic mirrors, whereby the focal point of incident light rays is located at a fixed position depending on the angle of incidence (but independent of the point of incidence of the light rays on the parabolic mirror). The focal points for different angles of incidence are known from corresponding caustics and represent moving points for varying angles of incidence. The detector (e.g., a detector chip) can thus be designed to contain several or as many expected focal points as possible (depending on the variance of the angles of incidence).It should be noted that corresponding caustics for a three-dimensional case represent not only focal lines but focal surfaces and that an ideal detector would therefore have a curved detector surface in which all possible or as many focal points as possible are taken into account.

[0015] According to the present invention, a flat detector surface can be used, which is preferably oriented such that a surface normal of the detector surface is parallel to a symmetry axis of the parabolic mirror. This represents a compromise, but reduces the complexity of the detector surface. Laser beams focused at focal points that do not lie on the detector surface can also be detected, albeit less efficiently. Certain components are lost.

[0016] Alternatively, a detector surface can also be a curved surface, which then includes multiple focal points of the parabolic mirror, into which received laser beams that are not incident parallel to a symmetry axis of the parabolic mirror are focused. The shape of such a curved surface can be determined, for example, by a simulation in which parallel beams of light strike the parabolic mirror at different angles of incidence and are reflected by it. The multitude of correspondingly determined focal points results in the ideal curved surface of the detector, to which a real detector surface can be approximated. An ideal detector surface can, for example, be partially banana-shaped.

[0017] In a further preferred embodiment of the present invention, the detector surface has an extension of 0.5 cm to 2.5 cm in at least one direction, preferably in two mutually orthogonal directions. This means that the detector surface is advantageously not that of a more or less point-shaped sensor, but rather that of an area detector, which offers the advantage that, with an increasing surface area, more focal points can be detected by laser beams that are not incident parallel to the axis of symmetry of the parabolic mirror.

[0018] Preferably, a detector is designed as a one-dimensional line sensor or as a two-dimensional array sensor. A particularly preferred embodiment of the invention is one in which the detector is designed as a charge-coupled device (CCD) sensor. While CCD sensors with a flat light-sensitive surface have been known for some time, curved CCD sensors, for example, with spherically curved, concave CCD chips, are now also available on the market. Such a curved CCD sensor can be optimized to fit the focal surfaces or caustics of a parabolic mirror of a lidar device according to the invention. Its surface can thus follow the focal points of the parabolic mirror for laser beams with different angles of incidence.

[0019] In the following, the invention is explained in more detail using the attached figure as an example.

[0020] It shows: Fig. 1: a lidar device according to the invention with a parabolic mirror.

[0021] Fig. Figure 1 schematically shows a lidar device 1 according to the invention, which has a transmitting unit 10 and a receiving unit 12. The transmitting unit 10 contains, in a known manner, a light source 14, for example, containing at least one laser diode, which emits laser beams 16. These beams impinge on a beam deflection unit 18, which deflects the emitted laser beams 16 so that emitted laser beams 20 leave the lidar device 1 at different angles and cyclically scan the surroundings of the lidar device 1 (or a vehicle in which the lidar device 1 is installed). The emitted laser beams 20 pass through a transparent pane 30, which covers the lidar device 1 and thus protects its components from environmental influences.

[0022] The emitted laser beams 20 strike an object (not shown in detail) in the vicinity of the lidar device 1 and are reflected back by it. Such reflected laser beams pass through the transparent pane 30 of the lidar device 1 as received laser beams 22 and strike a parabolic mirror 24, which is provided in the receiving unit 12 according to the invention. In contrast to the beam deflection unit 18, the parabolic mirror 24 is fixedly arranged in the receiving unit 12, and the receiving unit 12 also has no other moving parts, which significantly distinguishes it from the receiving units of known lidar devices. In known lidar devices, another beam deflection unit would be provided in the receiving unit, for example, like the beam deflection unit 18 of the transmitting unit 10.

[0023] The parabolic mirror 24 collects the received laser beams 22 and focuses them onto a focal point on a detector surface 32 of a detector 28. However, since the schematically illustrated received laser beams 22 do not impinge parallel to an axis of symmetry 34 of the parabolic mirror 24, they are reflected as laser beams 26 by the parabolic mirror 24 and focused onto a focal point that does not correspond to the focal point for incident radiation parallel to the axis. The focal point lies on the axis of symmetry 34 and preferably on the detector surface 32. Therefore, the detector 28 is advantageously not designed as a point detector, but as a flat CCD chip. The detector surface 32 is designed and arranged such that it contains multiple focal points for received laser beams 22 with different angles of incidence.

[0024] In the schematic representation of the Fig.In Figure 1, the detector 28 and, with it, the detector surface 32 are shown as a planar detector 28. Depending on the determined caustics or focal surfaces for such a parabolic mirror 24, the detector surface 32 can also be curved in various directions, at least approximately matching the determined focal surfaces of the parabolic mirror 24. This offers the advantage that additional focal points from additional directions of incidence can lie directly on the detector surface 32, so that the laser beams 22 received from different directions can be converted into electrical signals even more efficiently. List of reference symbols 1 Lidar device 10 transmitter unit 12 Receiving unit 14 Light source 16 emitted laser beams 18 Beam deflection unit 20 emitted laser beams 22 received laser beams 24 parabolic mirrors 26 reflected laser beams 28 detector 30 transparent discs 32 detector area 34 axis of symmetry

Claims

[1] Lidar device (1) for detecting the surroundings of a vehicle, the lidar device comprising: a transmitting unit (10) for emitting laser beams (20), wherein the transmitting unit (10) includes a beam deflection unit (18) configured to direct the emitted laser beams (20) in different directions to scan the environment, and a receiving unit (12) for receiving laser beams (22) reflected from the environment, wherein the receiving unit (12) includes a detector (28) configured to convert the received laser beams (22) into electrical signals; characterized by , that: the receiving unit (12) has a parabolic mirror (24) by means of which the received laser beams (22) are collected and reflected to a light-sensitive detector surface (32) of the detector (28). [2] Lidar device (1) according to claim 1, characterized by , that the parabolic mirror (24) is oriented with an opening in the direction of the solid angle into which the emitted laser beams (20) are directed during scanning. [3] Lidar device (1) according to any one of the preceding claims, characterized by , that the parabolic mirror (24) is not moved relative to the transmitting unit (10) during scanning. [4] Lidar device (1) according to any one of the preceding claims, characterized by , that the detector surface (32) is arranged in a first focal point of the parabolic mirror (24), in which received laser beams (22) that are incident parallel to an axis of symmetry (34) of the parabolic mirror (24) are focused. [5] Lidar device (1) according to any one of the preceding claims, characterized by, that the detector surface (32) is a plane which includes several focal points of the parabolic mirror (24) in which received laser beams (22) which do not occur parallel to an axis of symmetry (34) of the parabolic mirror (24) are focused. [6] Lidar device (1) according to claim 5, characterized by , that a surface normal of the detector surface (32) is aligned parallel to the axis of symmetry (34) of the parabolic mirror (24). [7] Lidar device (1) according to any one of the preceding claims 1 to 4, characterized by that the detector surface is a curved surface which includes several focal points of the parabolic mirror in which received laser beams that do not occur parallel to an axis of symmetry of the parabolic mirror are focused. [8] Lidar device (1) according to any one of the preceding claims, characterized by, that the detector surface (32) has an extent of 0.5 cm to 2.5 cm in at least one direction, preferably in two directions orthogonal to one another. [9] Lidar device (1) according to any one of the preceding claims, characterized by , that the detector (28) is configured as a one-dimensional line sensor or as a two-dimensional array sensor. [10] Lidar device (1) according to any one of the preceding claims, characterized by , that the detector (28) is designed as a CCD sensor.

Images