Lidar sensor and method for optically scanning an environment

Abstract

Lidar sensor (1) comprising at least one transmitting unit (S1-S4) and at least one receiving unit (E1-E4), wherein the transmitting unit (S1-S4) is configured to swivel a light signal in a horizontal direction, wherein the light signal is positioned at an angle α to a ground surface (5), wherein the transmitting unit (S1-S4) and the receiving unit (E1-E4) are designed as a single assembly (2) and the lidar sensor (1) has an adjustment device (3) designed such that the assembly (2) can be tilted by at least an angle β in the vertical direction, characterized by the fact that the lidar sensor (1) has at least two transmitting units (S1-S4) and receiving units (E1-E4), wherein the light signals of the transmitting units (S1-S4) are positioned at different angles (α, 2·α, 3·α, 4·α) to the ground surface (5), and wherein the at least two transmitting units (S1-S4) and receiving units (E1-E4) are designed as one assembly (2) to which the adjustment device (3) is jointly assigned.

Description

[0001] The invention relates to a lidar sensor and a method for optically scanning an environment.

[0002] Lidar (Light Detection and Ranging) sensors are used to detect objects and their distance. A preferred application for such lidar sensors is in automotive engineering. Various designs are available.

[0003] For example, designs are known where multiple transmitters are used, their light beam being deflected 360° horizontally by a rotating mirror. The transmitters are oriented vertically at different angles to a floor surface. The horizontal area scanned by the light beam can also be called the scan plane. Instead of a rotating mirror, MEMS or solid-state lidar systems are also known, where the horizontal swiveling motion is implemented differently. Such a lidar system with up to 64 transmitters is known from WO 2011 / 146523 A2 or WO 2008 / 008970 A2. However, such systems are currently very expensive and complex. Commercially available lidar sensors therefore often only have four scan planes.

[0004] From DE 10 2014 104 027 A1, an optoelectronic device for acquiring object information from a monitored area is known, comprising a light receiver, a receiving optic associated with the light receiver which has an adaptive lens with variable tilt, and an evaluation unit for generating the object information from a received signal of the light receiver. The evaluation unit is designed to move the adaptive lens into several different tilt positions and thereby acquire additional object information from an enlarged monitored area.

[0005] From DE 10 2011 001 387 A1, an optical scanning system is known in which the transmitters are relocated when emitting the test light beams and / or the receivers are relocated when receiving the measuring light beams in order to scan a horizontal area, thus eliminating the need for rotating mirrors. The relocation can be achieved, for example, by pivoting or tilting.

[0006] Other systems are known from DE 11 2012 001 708 T5, DE 10 2004 014 041 A1 and US 5 552 893 A.

[0007] DE 10 2013 007 961 A1 describes an optical measuring system for a vehicle. To increase the sensed area, an optical measuring system for a vehicle is provided, comprising a plurality of light sources for illuminating the area to be sensed and at least one sensor operating according to the time-of-flight principle, the sensor interacting with a wide-angle lens. It is provided that at least one light source from the plurality of light sources is directed in a first direction and at least one light source from the plurality of light sources is directed in a second direction.

[0008] The invention is based on the technical problem of creating a lidar sensor by means of which an increased number of scan planes can be easily realized, as well as providing a method for optically scanning an environment using such a lidar sensor.

[0009] The solution to the technical problem is achieved by a lidar sensor having the features of claim 1 and a method having the features of claim 6. Further advantageous embodiments of the invention are set forth in the dependent claims.

[0010] The lidar sensor comprises at least one transmitter and one receiver. The transmitter is configured to pivot a light signal horizontally, with the light signal being angled relative to a ground surface. The transmitter and receiver are integrated as a single unit. The lidar sensor features an adjustment mechanism that allows the unit to be tilted vertically by at least one angle. The number of possible tilt positions of the adjustment mechanism allows for an increase in the number of scan planes. The advantage of such a vertical adjustment mechanism is its relative robustness and simple design. The adjustment mechanism can be configured as a swivel / rotation module or as a linear actuator, where the linear movement is converted into a small rotational angle via a suitable gearbox.Piezoelectric actuators are particularly suitable for this purpose, as they can be controlled very easily with high accuracy.

[0011] In principle, the lidar sensor can be designed with a single transmitter and receiver unit. However, this limits the measurement frequency. For example, if the measurement time for one scan plane is T0 and 20 scan planes are to be implemented, the measurement time for the entire detection range increases twentyfold. In addition, the adjustment time of the positioning mechanism must also be taken into account.

[0012] According to the invention, the lidar sensor therefore has at least two transmitting units and receiving units, wherein the light signals of the transmitting units are positioned at different angles to the ground surface. For each specific task, a suitable compromise must be achieved between the number of transmitting units and the number of angular positions (scan planes), and thus the measurement time. Preferably, the lidar sensor has at least four transmitting units.

[0013] In principle, each component consisting of a transmitter and a receiver can have its own adjustment mechanism, allowing all transmitters to be controlled independently. However, this results in a correspondingly high complexity for the adjustment mechanisms. According to the invention, therefore, at least two transmitters and receivers are designed as a single component unit to which a common adjustment mechanism is assigned. More preferably, all transmitters and receivers are designed as a single component unit to which a common adjustment mechanism is assigned.

[0014] In another embodiment, the adjustment device is designed to tilt the assembly into several angles in the vertical direction.

[0015] In one embodiment, the light beams from the transmitting units define an opening angle in the vertical direction, and the adjustment device is designed to tilt the assembly by at least this opening angle. If, for example, the assembly can be tilted by the opening angle or multiples thereof, the overall opening angle can be increased accordingly. For instance, if the opening angle of four transmitting units in a starting position is 4° and the adjustment device can be tilted by 4° in each of four different positions relative to the previous position, an overall opening angle of 20° can be achieved.

[0016] Alternatively, the light beams from adjacent transmitters can define a partial opening angle, with the adjustment device designed to tilt the unit by at least a fraction of this partial opening angle. This increases the resolution and also slightly enlarges the overall opening angle. For example, if the partial opening angle between two transmitters is 1° and the adjustment device has three angular positions, the unit will be tilted by 1 / 3° in the second position and by 2 / 3° in the third position relative to its initial position.

[0017] The invention is explained in more detail below with reference to preferred embodiments. The figures show: Fig. 1 a schematic representation of a lidar sensor in a first position and Fig. 2 A schematic representation of a lidar sensor in a second position.

[0018] In the Fig. Figure 1 is a schematic representation of a lidar sensor 1. The lidar sensor 1 comprises four transmitting units S1 to S4 and four receiving units E1 to E4, which are combined into a single assembly 2. The assembly 2 is connected to an adjustment device 3, by means of which the assembly 2 can be tilted vertically. Furthermore, the lidar sensor 1 has a control unit 4, which controls the transmitting units S1-S4, receiving units E1-E4, and the adjustment device 3. A light signal from the first transmitting unit S1 is directed at an angle α to a ground surface 5. Similarly, the light signal from the second transmitting unit S2 is directed at an angle of 2α to the ground surface 5, and finally, the light signal from the fourth transmitting unit S4 is directed at an angle of 4α to the ground surface 5. It should be noted that the angles of the light signals do not necessarily have to be multiples of α.It is also possible that these differ by a fixed angular distance Δα, i.e., α, α+Δα, α+2Δα, and α+3Δα. In this first position, the vertical opening angle γ of the lidar sensor is 4α.

[0019] To determine the total opening angle γ ges To increase the Lidar sensor 1, the assembly 2 of the Lidar sensor 1 is tilted vertically by the angle β using the adjustment device 3 (see. Fig. 2) As a result, the sensor units S1-S4 are now positioned at angles α+β, 2α+β, 3α+β, and 4α+β, respectively, relative to the base surface 5. If β=4α is chosen, the total opening angle γ increases. ges to 2·γ. If the assembly 2 is then tilted vertically by a further angle β using the adjusting device 3 and the measurement is repeated, the total opening angle γ increases. ges on 3·φ and so on.

[0020] With four transmitting units S1-S4 with an opening angle 4·α and an adjustment device 3 that can be tilted by a total of 4·β, a total of 20 scan planes result with a total opening angle γ. ges =5 γ=20α. For this, the measurement time has increased fivefold, whereby the time for the tilting by the actuating device 3 must also be taken into account.

[0021] Alternatively, the adjustment device 3 can primarily be used to increase the resolution. This will be briefly explained by way of example. The angle between light beams from two adjacent transmitting units S1-S4 (e.g., between S2 and S3) is α. β can now be chosen as a fraction of α. If the adjustment device 3 is capable of assuming a total of five positions (90°, 90°-β, 90°-2β, 90°-3β, and 90°-4β), then β is chosen to be β = α / 5.

Claims

[1] Lidar sensor (1) comprising at least one transmitting unit (S1-S4) and at least one receiving unit (E1-E4), wherein the transmitting unit (S1-S4) is configured to pivot a light signal in a horizontal direction, wherein the light signal is directed at an angle α to a ground surface (5), wherein the transmitting unit (S1-S4) and the receiving unit (E1-E4) are designed as a single assembly (2) and the lidar sensor (1) has an adjustment device (3) designed such that the assembly (2) can be tilted by at least an angle β in the vertical direction, characterized by , that the lidar sensor (1) has at least two transmitting units (S1-S4) and receiving units (E1-E4), wherein the light signals of the transmitting units (S1-S4) are positioned at different angles (α, 2·α, 3·α, 4·α) to the ground surface (5), and wherein the at least two transmitting units (S1-S4) and receiving units (E1-E4) are designed as one assembly (2) to which the adjustment device (3) is jointly assigned. [2] Lidar sensor according to claim 1, characterized by , that all transmitting units (S1-S4) and receiving units (E1-E4) are designed as a single assembly (2) to which a single adjustment device (3) is assigned. [3] Lidar sensor according to any of the preceding claims, characterized by , that the adjusting device (3) is designed to tilt the assembly (2) into several angles β in the vertical direction. [4] Lidar sensor according to one of claims 1 to 3, characterized by , that the light beams of the transmitting units (S1-S4) define an opening angle γ in the vertical direction, wherein the adjusting device (3) is designed to tilt the assembly (2) at least by the opening angle γ. [5] Lidar sensor according to any one of claims 1 to 4, characterized by , that the light beams of adjacent transmitting units (S1-S4) define a partial opening angle α, wherein the adjusting device (3) is designed to tilt the assembly (2) by at least a fraction of the partial opening angle α. [6] Method for optically scanning an environment using a lidar sensor (1) according to claim 1, characterized by , that a first series of measurements is carried out in a first position of the assembly (2), the actuating device (3) moves the assembly (2) into at least a second position in which the assembly (2) is tilted by a vertical angle β, and then at least one series of measurements is carried out in the second position.

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