DE102017209294A1 - lidar - Google Patents

Abstract

A lidar sensor comprises a multi-beam light source for emitting light rays; a receiving optics for collecting incident light rays; a directional filter; and a light detector having at least one sensor associated with one of the light sources.

Description

The invention relates to a LiDAR sensor. In particular, the invention relates to a multi-beam LiDAR sensor.

State of the art

A LiDAR sensor includes a light source, a light detector, and a processing device. The light source emits light in a predetermined spatial area where an object can reflect the light toward the detector. The processing device determines a distance between the LiDAR sensor and the object on the basis of a signal propagation time (Time of Flight, TOF) or on the basis of a Frequency Modulated Continuous Wave (FMCW) signal. A single-beam system uses a laser as the light source, a multi-beam system includes a light source that emits multiple laser beams simultaneously.

To cover large horizontal detection angles between 150 ° and 360 °, a mechanical laser scanner is generally used in which the propagation direction of the laser beams is changed by means of a movable mirror. In a rotating mirror laser scanner whose maximum detection angle is limited to about 150 °, only a motor-driven deflection mirror rotates. For larger detection ranges up to 360 °, all electro-optical components of the LiDAR sensor are mounted on a motor-driven turntable or rotor.

For imaging an incident laser beam onto the light detector, simple optics with few lenses are typically used, which typically have insufficient imaging property to generate sufficient imaging on the detector side. In addition, the aperture of such a system is limited technically and due to the image, which is why an aperture of more than about 800 mm ^{2 is} hardly achievable.

An object underlying the present invention is to provide an improved LiDAR sensor. The invention achieves this object by means of the subject matter of the independent claim. Subclaims give preferred embodiments again.

Disclosure of the invention

A LiDAR sensor comprises a multi-beam light source for emitting light rays; a receiving optics for collecting incident light rays; a directional filter; and a light detector having at least one sensor associated with one of the light sources.

Usually, the light detector comprises a plurality of sensors, each sensor being associated with one of the light sources. Preferably, as many sensors as light sources are provided. The association between sensors and light sources can be bijective.

In particular, the receiving optics may have a large aperture in order to also receive a weak reflection of an emitted light beam on an object and to focus it in a focused manner onto the light detector. The aperture can be chosen freely over a wide range and in particular more than about 800 mm ² . As a result, the receiving optics can be designed to be bright, in order to reliably detect even a faint or distant reflection of a light beam. A detection range can thereby be increased. An accuracy of the LiDAR sensor, in particular with regard to its image sharpness or resolution, can be improved.

It is particularly preferred that the receiving optics comprise a reflective element. The reflective element may in particular comprise a mirror system with one or more mirrors, a prism or another element in which a total reflection of light takes place. In particular, the receiving optics may comprise folded optics in which a light beam is deflected in such a way that an optical path through the receiving optics is significantly longer than its size.

A reflective receiving optics is usually limited in angle, so it may be poorly suited for a multi-beam LiDAR sensor, especially if this is to be used to cover a relatively large vertical angle range of up to about 8 ° or even more. However, in conjunction with the directional filter, despite the aberrations of the reflective element, it can be ensured that a light beam associated with a first sensor of the light detector does not fall, or only diminishes, to a second sensor which is adjacent to the first sensor. Losses in the light passing through the directional light amount can be compensated in particular by a large aperture of the receiving optics. Thus, an improved image sharpness or resolution can be realized. By a corresponding optical design of the receiving optics, the signal dynamics can be limited. The receiving optics can be realized compactly and with only a few elements. The reflective element can have a low temperature dependence, so that the receiving optics can be improved in terms of temperature stability.

In a particularly preferred embodiment, the directional filter is integrated with the reflective element. As a result, a robust receiving optics, for example for use of the LiDAR sensor on a motor vehicle, can be provided. The directional filter may be formed, for example, on or in a prism or a concave mirror element.

In general, the directional filter may comprise a pinhole or a coating of a transparent element. Both variants can be easily integrated with the reflective element. For this purpose, the directional filter can be arranged in particular when a light beam emerges from an optically denser medium than air. The pinhole may, for example, comprise a plastic or metal part which carries as many recesses as light beams and sensors are provided. The recesses may be introduced, for example by means of punching. The position of each recess defines the direction of an incident light beam. Light that does not fall from the predetermined direction through the recess does not hit the sensor of the associated light detector.

The LiDAR sensor may further include imaging optics arranged to image the plane of the directional filter onto the light detector. In this case, an aperture of the imaging optics may be small, in particular substantially smaller than the aperture of the receiving optics, as a result of which the imaging optics can be realized inexpensively and arranged in a space-saving manner. In a preferred embodiment, the imaging optics have an imaging factor not equal to one. In other words, the imaging optics can be set up with little effort to realize an optical enlargement or reduction. The optics can be improved so adapted to a predetermined light detector, the number and arrangement of light sensors usually can not be changed. Thereby, a wide variety of existing light sensors with the described optics can be used to provide an improved lidar sensor.

It is particularly preferred that the imaging optics comprise a first and a second element, between which light beams can propagate. The division into two parts makes it possible to better control imaging properties of the imaging optics. In particular, the elements may be designed and arranged such that the light beams propagate between them substantially parallel to one another. In the area between the two elements of the imaging optics, an optical filter can then easily be arranged which, for example, keeps unwanted extraneous light away from the light detector. The optical filter may in particular be a narrow-band frequency filter. The interference immunity of the LiDAR sensor can thereby be improved.

list of figures

• 1 einen mehrstrahligen Lidarsensor in einer ersten Ausführungsform;
• 2 einen mehrstrahligen Lidarsensor in einer zweiten Ausführungsform;
• 3 eine schematische Darstellung eines Lidarsensors mit einer Abbildungsoptik; und
• 4 beispielhafte Richtungsfilter für einen mehrstrahligen Lidarsensor darstellt.

The invention will now be described in more detail with reference to the attached figures, in which:

• 1 a multi-beam lidar sensor in a first embodiment;
• 2 a multi-beam lidar sensor in a second embodiment;
• 3 a schematic representation of a Lidarsensors with an imaging optics; and
• 4 represents exemplary directional filter for a multi-beam Lidarsensor.

1 shows a multi-beam LiDAR sensor (or: lidar sensor) 100 in a first embodiment. The LiDAR sensor 100 includes a multi-beam light source 105 , which send out several coherent light beams 110 is set up, a receiving optics 115 for collecting light rays 110 attached to an object 120 (not shown), a directional filter 125 and a light detector 130 with several sensors 135 , In addition, a processing device is preferred 140 provided on the basis of emitted and received light, the distance between the LiDAR sensor 100 and the object 120 to determine.

The illustrated receiving optics 115 is preferably formed as a folded optic and comprises in the illustrated embodiment one or more mirror elements 145 to collect and direct the incoming light. A folded optics is designed to make the length of an optical path, along which light moves through the optics, longer than the distance along the optical axis of the optics. Usually, the folded optic comprises at least one reflective surface. Often, the light is reflected multiple times within the optic, allowing it to travel a portion of the path through the optic, counter to the direction from the entrance to the exit of the optic. Shown is an example of a receiving optics 115 with a primary and a secondary mirror element 145 , which can each be shaped so that a predetermined optical imaging takes place. For example, at least one of the mirror elements 145 be spherical or parabolic. Incident light becomes on the surface of the primary mirror element 145 reflects and falls back on the secondary mirror element 145 where it is reflected again. Both mirror elements 145 can bundle the incident light rays or On the output side they steer to a narrower area than an entrance area, through which they enter the optics.

In the beam path after the receiving optics 115 is a directional filter 125 which is adapted to selectively irradiate incident light rays on only one of the sensors on the basis of their incident direction 135 forward. Light which does not come from a predetermined direction is preferably absorbed or, in another embodiment, completely or partially reflected. Preference is given to many sensors 135 at the light detector 130 provided as light rays 110 simultaneously from the light source 105 can be sent out. At the light detector 130 are preferably just as many light sensors 135 educated. The number of light sensors 135 can also be different from the number of light rays 110 in particular, fewer light sensors can be 135 be used, one after the other by means of different light beams 110 is illuminated. The arrangement of the light sensors 135 can the arrangement of the light source 105 Corresponding light rays correspond. This arrangement can be one or two-dimensional. The sensors 135 are usually designed as photosensitive semiconductors and can be designed to detect light of a predetermined wavelength range in which the wavelength emitted by the light source is located.

The direction filter 125 can be used to make an angle-related, relatively large error of the receiving optics 115 to compensate. By retaining light that does not have a predetermined direction, the portions of the light that are due to an aberration of the receiving optics 115 go back, be excluded from further processing. The attenuating effect of the directional filter 125 on the incident light can be compensated by an aperture of the receiving optics 115 is chosen correspondingly large. This can still be ensured that sufficient light on the light sensors 135 falls in order to provide reliable proof.

Before the received light from the directional filter 125 on the light detector 130 it may be an imaging optic 150 go through to focus the light rays on the light detector 130 to improve. The imaging optics can be made adjustable. Optionally, the imaging optics is arranged to image the light rays on the light detector 130 to enlarge or reduce. As below with reference to 3 will be explained in more detail, includes the imaging optics 150 preferably one or more refractive elements, in particular lenses.

2 shows a multi-beam LiDAR sensor 100 in a second embodiment. Unlike the in 1 illustrated embodiment is here the optical system 115 preferably designed in one piece. In particular, the optical system 115 formed in the manner of an inverted telescope and be made for example of glass or plastic. In this case, a material with high refractive index can be used to the optical system 115 and thus the entire LiDAR system 100 improved compact build.

In a further variant, the directional filter 125 directly on or in the receiving optics 115 attached, integrated with it or be integral with it. For example, the directional filter 125 be formed as a coating of the material from which the receiving optics 115 is formed. In a preferred embodiment, the directional filter comprises 125 as below with reference to 4 will be described in more detail, a pinhole, for example, by gluing, vapor deposition or otherwise on the receiving optics 115 is appropriate.

3 shows a schematic representation of a LiDAR sensor 100 by type 1 or 2 , with an imaging optics 150 , The imaging optics 150 comprises at least one refractive element 205 , which may be formed in particular as a lens. In the illustrated preferred embodiment, there is a first refractive element 205 and a second refractive element 210 intended. The refractive elements 205 . 210 are preferably designed and arranged against each other, that incident light rays 110 between them are essentially parallel to each other.

It is further preferred that in the space between the refractive elements 205 . 210 an optical filter 215 is provided to allow only such light to happen, which originally from the light source 105 was sent out. For this purpose, the optical filter can be designed in particular as a bandpass filter. That from the light source 105 emitted light ideally has a very narrow wavelength range. The optical filter 215 Accordingly, it can be made very narrow band to pass only those light whose wavelength corresponds to the wavelength of the emitted light.

4 shows exemplary directional filters 125 for a multi-beam LiDAR sensor 100 , The illustrated directional filters 125 are designed as pinhole. An embodiment a is arranged for three light beams, an embodiment b for nine light beams, an embodiment c for sixteen light beams, and an embodiment d for twenty-five light beams. The direction filter 125 each includes an opaque material 405 For example, a metal sheet in which so many recesses 410 are provided, such as rays through the directional filter 125 to be let through. A position of each recess 410 corresponds to a direction from the light through the directional filter 125 can fall. Light coming from a different direction on the material 405 it is absorbed or reflected by it.

Claims (8)

Lidar sensor (100) comprising: - A multi-beam light source (105) for emitting light beams (110); - Receiving optics (115) for collecting incident light beams (110); a directional filter (125); and - A light detector (130) with at least one sensor associated with one of the light sources (105). Lidar sensor (100) after Claim 1 wherein the receiving optics (115) comprises a reflective element. Lidar sensor (100) after Claim 2 , wherein the directional filter (125) is designed to be integrated with the reflective element. The lidar sensor (100) of any one of the preceding claims, wherein the directional filter (125) comprises a pinhole. The lidar sensor (100) of any one of the preceding claims, further comprising imaging optics (150) arranged to image the plane of the directional filter (125) onto the light detector (130). Lidar sensor (100) after Claim 5 , wherein the imaging optics (150) has a mapping factor not equal to one. Lidar sensor (100) after Claim 5 or 6 wherein the imaging optics (150) comprises a first (205) and a second element (210) between which light beams (110) can propagate. Lidar sensor (100) after Claim 7 , wherein the light beams (110) between the two elements (205, 210) extend substantially parallel to each other and in this area an optical filter (215) is arranged.

Images