DE102014118055A1 - Transmitting device, receiving device and object detection device for a motor vehicle and method for this - Google Patents

Abstract

The invention relates to a transmitting device 12 and a receiving device 14 for an object detection device 10 for a motor vehicle, with a movable micromirror 20. The transmitting device 12 has two or more light sources 16a, 16b, each light source 16a, 16b being arranged in such a way to transmit a transmitted light beam 18a-18c towards the micromirror 20 at a predefined angle 36a-36c. The predefined angles 36a-36c are different from each other here. The receiving device 14 comprises at least one receiver 26, in particular at least one diode, for receiving the light 28 of a plurality of reflected or scattered transmitted light beams 18a-18c of the transmitting device 12.
Furthermore, the invention relates to an object detection device 10 with a transmitting device 12 and a receiving device 14 and a method for this.

Description

The invention relates to a transmission device for object detection for a motor vehicle according to the preamble of claim 1, a receiving device for object detection for a motor vehicle according to the preamble of claim 8, an object detection device for object detection according to the preamble of claim 11 and a method for detecting objects according to the The preamble of claim 12.

In the prior art, object detection devices are known which are integrated into a motor vehicle and serve to scan the surroundings of the motor vehicle (so-called scanning).

With these devices, a transmitted light beam is emitted and the reflected or backscattered light is reflected or scattered back at a point where the transmitted light beam strikes an object. The properties of the reflected or backscattered light change as a result of the reflection, the change being dependent on the object, in particular its surface, as well as the distance of the object and other parameters.

The change in the transmitted light beam is possible by comparing the properties with the received reflected or backscattered light in an evaluation unit. This makes it possible to deduce the properties of the object on which the transmitted light beam was reflected or scattered.

Laser-based systems are known under the name "Lidar" ("light detection and ranging"). Laser scanners operate according to the light transit time principle, wherein laser pulses are emitted and the light reflected by a target object in the surroundings of the vehicle is detected. Known laser scanners have an optical transmitting device for emitting electromagnetic radiation and an optical receiving device for receiving reflected beams and for providing an electrical received signal dependent on the received beams. The transmitting device is assigned a deflecting mirror, which deflects the emitted laser pulses in such a way that a scanning of the entire field of view takes place within a certain scanning angle range. Per scanning angle while a laser pulse is emitted. In the same angular step, the reflected beams are received by means of the optical receiver and a corresponding electrical reception signal is provided. If echoes or pulses are detected in the received signal, these are fundamentally due to reflections of the emitted beams to target objects in the environment. The time between sending and receiving the echo is proportional to the distance to the object. From the transit time measurement, the distance for the angular step is determined.

To expand the field of view of the laser scanner, the deflection by means of a micromirror, so-called "MEMS" known. The micromirror consists in the so-called MEMS technology of small individual elements, each having a reflective surface. Continuous movement of the micromirror allows an extended field of view of the sensor to be scanned.

An optoelectronic object detection device for motor vehicles with a micromirror ("MEMS") is known, for example, in US Pat DE 10 2012 025 281 A1 disclosed.

As is known, the micromirror must be pivotable for as large an angle as possible in order to divert the transmitted light beam to the largest possible area in which objects are to be detected. By limiting the pivoting angle of the micromirror, therefore, the range of object detection is limited.

Devices are known from the prior art which can be used with the aid of lenses, e.g. Meniskuslinsen, enlarge the range of object detection by the transmitted light beam is deflected by the lens in the edge regions disproportionately to the mirror movement. However, such lenses are very expensive because they must be made very precisely.

The present invention is therefore based on the object to enlarge the area in which objects can be detected, in which case a meniscus lens or the like should be dispensed with.

The invention solves this problem by a device for detecting objects for a motor vehicle according to claim 1, a receiving device for object detection for a motor vehicle according to claim 8, an object detection device for object detection according to claim 11 and a method for detecting objects according to claim 12.

The invention is used in particular for a vehicle or is used in vehicles and for this purpose according to a first aspect comprises a transmitting device. The transmitting device comprises a movable micromirror and two or more light sources. Thus, therefore, two, three four or more light sources are possible.

The light sources are arranged in particular at predefined angles to the micromirror, so that they can each transmit a transmitted light beam at the predefined angle in the direction of the micromirror. The predefined angles of the transmitted light beams also differ from each other, so they are different.

The predefined angles are e.g. each defined as an angle which occurs between the exit direction of the transmitted light beam of a light source and an elongated imaginary line of a stationary part of the micromirror or an imaginary straight line passing through a stationary part of the micromirror. Here, the same elongated imaginary straight line of the fixed part of the micromirror or the same imaginary straight line passing through a stationary part of the micromirror is used to define all predefined angles.

Because of the differing predefined angles, the angles of incidence of the transmitted light beams of the light sources therefore differ in each position of the micromirror. Thus, e.g. a light source arranged such that the transmitted light beam in relation to a transmitted light beam of a further light source substantially flatter hits the micromirror.

This makes it possible to send transmitted light beams in a much larger area with constant amplitude of the pivoting movement of the micromirror without the use of lenses. In order to proceed with the preceding example, both of the transmitted light beams may be deflected into areas whose size is limited in each case by the amplitude of the pivoting movement of the micromirror, but these areas differ from one another, e.g. overlap only in a small area of their respective areas. In any case, the resulting entire area in which the transmitted light beams are deflected or sent is larger than one of the individual areas.

According to a first embodiment, the light sources are independently of each other e.g. controllable with a control device. According to a particularly preferred embodiment, the light sources can be connected and disconnected independently of each other.

Thus, it is possible e.g. sequentially switch on only a first light source, while the other light source or the other light sources are turned off. Thus, the transmitted light beam of this light source can be guided by the pivoting movement of the micromirror into a first range defined by the predefined angle of the transmitted light beam.

With a non-selective receiving device, the reflected or scattered light can then be received and assigned exactly to the first area.

In the next step, then e.g. a second light source is turned on while the first light sources or all other light sources are switched off. Thus, the transmitted light beam of the second light source can also be directed by the pivoting movement of the micromirror into a second range defined by the predefined angle of the transmitted light beam.

With the receiving device, the reflected or scattered light can then be received and assigned exactly to the second region, which is different from the first region.

Thus, objects in several subareas of the environment, which together give a larger total area compared to the area of the prior art, can be detected in a simple manner with the invention.

According to a further embodiment, at least one light source comprises a laser. Accordingly, one, several or all light sources each comprise a laser. The laser is e.g. a semiconductor laser. A laser is particularly well suited to transmit light beams with well-defined properties, e.g. a defined wavelength.

According to a further embodiment, at least two light sources are formed with a stack laser. A stack laser is also referred to as a laser stack or stacked laser and is made up of a plurality of individual lasers, which in turn are e.g. made of so-called. Laser bars are produced. By the use of stacking lasers a favorable realization of several lasers on a small installation space can be realized.

According to a further embodiment, the transmitting device comprises three light sources. The light sources have predefined angles so that the transmitted light beams of adjacent lasers have different predefined angles that differ in a range of 25 to 35 degrees or substantially 30 degrees. With such an arrangement of the light sources, a large area can preferably be scanned or scanned with a comparatively small deflection of the micromirror. According to a further embodiment of the invention, the difference in the angle of the transmitted light beams is chosen to be less than 36 degrees.

According to a further embodiment, the light sources each have an encoder. With The coder is coded for the transmitted light beam of the light source. An encoding is effected in particular by the modulation of the transmitted light beam or of the light of the transmitted light beam. During modulation, a defined characteristic is impressed on the transmitted light beam of the light source, for example with a modulator. This can be, for example, a temporal or spatial amplitude or phase variation.

By coding or modulation of the transmitted light beams on and off one or more light sources is no longer necessary because the scattered or reflected light on the object is clearly attributable to a transmitted light beam. The speed during scanning or scanning of the environment is thereby increased.

According to a further embodiment, the encoder is set up to encode the transmitted light beam with a PN code, which is also called a pseudo noise code, or a PRN code, which is also called a pseudo random noise code. Examples of such codes are the MLS code, the Gold code or the Barker code whose coding algorithms can be found in the general technical literature. Such codes are particularly well-suited for digital coding, so that also a modulation of a single parameter of the light in a simple manner - e.g. can be coded with two values of a parameter in the manner of a digital coding.

According to a further embodiment, the individual codes of the selected encoding method or the coding for the individual light sources are generated via feedback shift registers or by using different seed values.

According to a second aspect, the invention comprises a receiving device for object detection for a motor vehicle. The receiving device comprises at least one receiver which, according to a preferred embodiment, is a diode, in particular a photodiode. The receiving device is set up to receive a plurality of reflected or scattered transmitted light beams of a transmitting device according to one of the preceding embodiments.

By means of the receiving device, an evaluation of the objects in the environment by comparison of the received reflected or scattered light with the emitted transmitted light beams is possible.

According to one embodiment, the receiving device comprises at least one decoder. The decoder is arranged to decode the received transmitted light beams, that is the received reflected or scattered light. For this, the decoder comprises e.g. a correlator that correlates the received light with the individual codes with which the transmitted light beams have been coded or modulated. Thus, the received light or the received transmitted light beam can be assigned to exactly one light source, and thus to the area of this light source.

According to a further embodiment of the receiving device, the decoder is arranged to decode the received transmitted light beam or the received light with the PN code or PRN code, in particular the MLS code, Gold Code or Barker code. For this purpose, the code selected in the transmitting device is also used in the receiving device for decoding, e.g. in the correlation, used.

In addition, the invention comprises an object detection device with a transmission device according to one of the preceding embodiments of the transmission device and a reception device according to one of the preceding embodiments of the transmission device.

According to one embodiment, the object detection device has a control device or drive device which serves to control or pivot the micromirror and acts on a drive device of the micromirror.

Furthermore, the invention comprises a method for object detection, wherein with two or more light sources of the transmitting device, which are each arranged at a predefined angle to a micromirror, in each case a transmitted light beam is emitted in the direction of a micromirror. In this case, the light sources are arranged at different predefined angles with respect to the micromirror.

The transmitted light rays, which are deflected by the micromirror, are emitted to the environment as well as objects in the environment and reflected or scattered by the objects. The light reflected or scattered by the environment and the objects is received by the receiving device with at least one receiver, e.g. at least one diode - preferably a photodiode - includes.

According to one embodiment of the method, the transmitted light beams are each coded with an encoder before being emitted into the environment or onto objects. For this purpose, the transmitted light beams are each modulated, for example. In addition, the scattered or reflected received light is decoded with a decoder. The decoding takes place, for example, by correlation of the scattered or reflected received light with a comparison signal of the encoder. Furthermore, the received light is thus assigned to a light source.

Further embodiments of the invention will become apparent from the illustrated with reference to the drawings embodiments. Show it:

1 an embodiment of the invention,

2a deflected transmitted light rays with a micromirror in a first position,

2 B deflected transmitted light rays with a micromirror in a second position and

3 the steps of an embodiment of the method and

4 an embodiment of a decoder.

1 shows an embodiment of the object detection device 10 , The object detection device 10 comprises a transmitting device 12 and a receiving device 14 ,

The transmitting device 12 has two light sources 16a . 16b on, with each of which a transmitted light beam 18a . 18b is produced. The light sources 16a . 16b send the respectively generated transmitted light beam with different predefined angles to a micromirror 20 , These are the light sources 16a . 16b at different predefined angles to the micromirror 20 arranged. The micromirror 20 exists according to the so-called MEMS technology of small individual elements, each having a reflective surface.

The micromirror 20 is so to the light sources 16a . 16b arranged that the transmitted light rays 18a . 18b directly on the micromirror 20 meet, according to further embodiments, one or more deflection mirrors between the light sources 16a . 16b and the micromirror 20 are arranged so that the transmitted light beams 18a . 8b on the micromirror 20 be steered over the deflecting mirror.

The micromirror 20 is movable about a first axis parallel to the plane of the drawing and about a second axis perpendicular to the plane of the drawing. The transmitted light rays 18a . 18b be through the micromirror 20 therefore distracted to different points of the environment.

The movement of the micromirror, which is also called "MEMS", can be controlled via a control device. This control device is associated with the object detection device. The control device controls the micromirror such that it is pivotable in at least one horizontal and one vertical direction. The controller is further configured to move the micromirror so that the transmitted light beams are steerable to all points of a predefined grid having a predefined number of rows and columns.

The light sources 16a . 16b each further comprise a laser 22a . 22b each one of the transmitted light beams 18a and 18b produce. The lasers 22a . 22b Here are laser diodes and are each using a coder 24a . 24b driven. The encoders 24a . 24b supply the laser diodes with a modulated operating current, so that the light of the transmitted light rays 18a . 18b is modulated. Thus, due to the coding of the transmitted light beams 18a . 18b the transmitted light rays 18a . 18b clearly distinguishable.

The receiving device has a diode 26 on, which is a photodiode here. With the diode 26 becomes light 28 received, the reflected or backscattered transmitted light beams 18a . 18b equivalent. The received light, ie in particular a signal derived therefrom, is stored in a decoder 30 correlated with a signal selected according to the coding method. Thus, then the received light in an evaluation device 32 exactly a transmitted light beam 18a . 18b and thus the area in which the transmitted light beam 18a . 18b was sent to be assigned.

2a shows a micromirror 20 in a first position and three transmitted light beams 18a to 18c on the micromirror 20 meet with different angles according to an embodiment of the invention and are therefore deflected at a different angle. For this purpose, three light sources not shown in different predefined angles to the micromirror 20 arranged. In the alternative, a straight line 34 represented by the micromirror 20 runs. The transmitted light rays 18a to 18c have different predefined angles 36a to 36c to the straight line, with the angles around here 30 Different from each other.

In 2a the transmitted light beam hits 18a at an angle of 7.5 degrees to the mirror plane of the micromirror 20 on the micromirror 20 , Accordingly, the exit angle corresponds to 7.5 degrees. As already described above, the transmitted light beams 18a to 18c different angles, each differing by 30 degrees. Accordingly, the transmitted light beam 18c an angle α of 22.5 degrees to the normal 37 of the micromirror 20 on.

In 2 B is now the micromirror 20 in a second position opposite 2a shown, wherein the transmitted light beams 18a to 18c as well as the straight line 34 are fixed. So, too the predefined angles 36a to 36c the same as in 2a , The second position of the micromirror 20 deviates from the first position by 15 degrees, which is therefore the deflected transmitted light beams 18a to 18c have changed by 30 degrees. Thus, an area of the present arrangement of 90 degrees is scannable, scannable or illuminable while the micromirror 20 only pivoted 15 degrees. Accordingly, despite a small deflection of the micromirror 20 a comparatively large range can be scanned, scanned or illuminated.

In 2 B thus meets the transmitted light beam 18a now with an angle of 22 , 5 degrees to the mirror plane of the micromirror 20 on the micromirror 20 , Accordingly, the exit angle also corresponds to 22.5 degrees. As already described above, the transmitted light beams 18a to 18c different angles, each differing by 30 degrees. Accordingly, the transmitted light beam 18c now an angle α of 7.5 degrees to the normal 37 of the micromirror 20 on.

3 shows the steps of an embodiment of the method. First, in a coding step 38 the drive current of several lasers encodes so in a subsequent transmission step 40 several transmitted light beams 18a to 18c on a micromirror 20 sent out and over this in a deflection step 42 with an adjustable angle of the micromirror 20 be distracted to an environment. In a reflection step or scattering step 44 become the transmitted light rays 18a to 18c reflected and / or scattered by the environment.

In a reception step 46 the reflected and / or scattered light is received and in a Dokodierschritt 48 with several signals, each derived from the coding, with which the transmitted light beams 18a to 18c coded, correlated.

4 shows an embodiment of a decoder. First, the reflected light 28 with a receiver 30 receive. The signal obtained therefrom is then provided with a signal processing circuit 50 , For example, an analog-to-digital converter, which here is for example a 1-bit ADC, in a bit stream 52 converted and three correlators 54a to 54c fed. Each correlator will also receive one additional signal, each with a code 56a to 56c is formed and each corresponds to a reference signal supplied. In the correlators 54a to 54c becomes the bitstream 52 each correlated with one of the reference signals. At the output of the correlators, a signal is then output in each case that one of the transmitted light beams 18a to 18c is assigned and describes a measure of the reflected or scattered light that has been reflected or scattered by the respective transmitted light beam to the environment.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102012025281 A1 [0007]

Claims (13)

Transmitting device for object detection for a motor vehicle with a movable micromirror ( 20 ), characterized in that the transmitting device ( 12 ) two or more light sources ( 16a . 16b ), each light source ( 16a . 16b ) is arranged in each case, a transmitted light beam ( 18a - 18c ) and is arranged to transmit the transmitted light beam ( 18a - 18c ) at a predefined angle ( 36a - 36c ) in the direction of the micromirror ( 20 ), the predefined angles ( 36a - 36c ) are different from each other. Transmitting device according to claim 1, characterized in that the light sources ( 16a . 16b ) can be controlled independently, in particular switched on and off. Transmitting device according to claim 1 or 2, characterized in that at least one light source ( 16a . 16b ) a laser ( 22a . 22b ), in particular a semiconductor laser. Transmitting device according to one of the preceding claims, characterized in that at least two light sources ( 16a . 16b ) comprise a staple laser, wherein a staple laser in particular comprises at least two laser bars. Transmitting device according to one of the preceding claims, characterized in that the transmitting device ( 12 ) three light sources ( 16a . 16b ), wherein the predefined angles ( 36a - 36c ) of the transmitted light beams ( 18a - 18c ) of adjacent light sources ( 16a . 16b ) differ in a range of 25 to 35 degrees or substantially 30 degrees from each other. Transmitting device according to one of the preceding claims, characterized in that the light sources ( 16a . 16b ) one encoder each ( 24a . 24b ), the encoder ( 24a . 24b ), the transmitted light beam ( 18a - 18c ), in particular by modulation, so that each transmitted light beam ( 18a - 18c ) one of the light sources ( 16a . 16b ) is assignable. Transmitter according to Claim 6, characterized in that the encoder ( 24a . 24b ), the transmitted light beam ( 18a - 18c ) with a PN code or PRN code, in particular an MLS code, Gold Code or Barker code. Receiving device for object detection for a motor vehicle, characterized in that the receiving device ( 14 ) at least one recipient ( 26 ), in particular at least one diode, for receiving the reflected or scattered light (US Pat. 28 ) of several reflected or scattered transmitted light beams ( 18a - 18c ) a transmitting device ( 12 ) according to one of the preceding claims. Receiving device according to claim 8, characterized in that the receiving device ( 14 ) at least one decoder ( 30 ), wherein the decoder ( 30 ), the received reflected or scattered light ( 28 ), in particular by correlation, so that the received reflected or scattered light ( 28 ) one of the light sources ( 16a . 16b ) is assignable. Receiving device according to claim 8 or 9, characterized in that the decoder ( 30 ), the received reflected or scattered light ( 28 ) with a PN code or PRN code, in particular an MLS code, Gold code or Barker code to decode. Object detection device for object detection, characterized in that the object detection device ( 10 ) a transmitting device ( 12 ) according to one of claims 1 to 7 and a receiving device ( 14 ) according to any one of claims 8 to 10. Method for detecting objects with a transmitting device ( 12 ) according to one of claims 1 to 7 and a receiving device ( 14 ) according to one of claims 8 to 10, characterized in that with two or more light sources ( 16a . 16b ) of the transmitting device ( 12 ) each arranged to receive a transmitted light beam ( 18a - 18c ) at a predefined angle ( 36a - 36c ) towards a micromirror ( 20 ), the predefined angles ( 36a - 36c ) are different from each other, and the transmitted light beams ( 18a - 18c ) from the micromirror ( 20 ) are redirected to an environment and the light reflected or scattered by the environment ( 28 ) from the receiving device ( 14 ) with at least one receiver ( 26 ), in particular at least one diode. Method according to claim 12, characterized in that the light sources ( 16a . 16b ) one encoder each ( 24a . 24b ), the transmitted light beams ( 18a - 18c ) each with the encoder ( 24a . 24b ), in particular by modulation, and the receiving device ( 14 ) at least one decoder ( 30 ), wherein the received reflected or scattered light ( 28 ) with the decoder ( 30 ), in particular by correlation, and thus the received reflected or scattered light ( 28 ) a transmitted light beam ( 18a - 18c ) one of the light sources ( 16a . 16b ).

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