WO2016116302A1

WO2016116302A1 - Device and method for detecting objects for a motor vehicle

Info

Publication number: WO2016116302A1
Application number: PCT/EP2016/050283
Authority: WO
Inventors: Thomas Schuler
Original assignee: Valeo Schalter Und Sensoren Gmbh
Priority date: 2015-01-22
Filing date: 2016-01-08
Publication date: 2016-07-28
Also published as: DE102015100910A1

Abstract

The invention relates to a device and to a method for detecting objects for a motor vehicle, said device comprising a transmitting apparatus (12) for producing at least one transmission light beam (18). The invention further relates to a motor vehicle having such a device. Furthermore, the transmission light beam (18) is emitted into the environment by means of the transmitting apparatus (12). In addition, the transmitting apparatus (12) is designed to emit the transmission light beam (18) for a duration before the transmission light beam (18) is emitted again for a next duration. In addition, the invention comprises a receiving apparatus (14) for receiving the light (28) reflected by the environment and to convert the received light (28) into a reception signal (32). The device also comprises an evaluating apparatus (30), by means of which a progression of the amplitudes (36, 38) of the reception signal (32) or of a signal derived therefrom during each duration is determined and the duration is varied in accordance with the progression of the amplitude (36, 38).

Description

Device and method for detecting objects for a motor vehicle

The invention relates to a device for detecting objects for a motor vehicle according to the preamble of claim 1 and a method for detecting objects for a motor vehicle according to the preamble of claim 10 and a motor vehicle according to claim 11.

In the prior art, object detection devices are known which are integrated into a motor vehicle and serve to sense the environment of the motor vehicle. The scanning is also 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.

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 means for emitting electromagnetic radiation and an optical receiving means for receiving reflected rays. With the

Receiving device, the received light is also converted into a dependent of the received beams and the received light electrical received signal.

The transmitting device is associated with a deflection mirror, which the

deflected emitted laser pulses so that a scan 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. Are echoes, or pulses, in the Detected received signal, so these are basically due to reflections of the emitted rays to target objects in the area. 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 extend the field of view of the laser scanner, the deflection is known by means of a micromirror, so-called "MEMS." The micromirror consists of so-called MEMS technology of small individual elements, each having a reflective surface Field of view of the sensor to be scanned.

An optoelectronic object detection device for motor vehicles with a

Micromirror ("MEMS") is disclosed for example in DE 10 2012 025 281 A1.

Furthermore, LED sensors are known which work with the transit time method, which is also called TOF (time of flight). For this purpose, the environment is illuminated by means of a light pulse, and the sensor measures the time it takes the light to reach the object and back again. The time required is directly proportional to the distance. The principle corresponds to the laser scanning, whereby an entire environment is recorded at once and does not have to be scanned. A micromirror is therefore not necessary.

In these methods, it is known that the receiving device in addition to the

reflected or scattered light also receives light from other light sources that are not from the transmitted light beam. This causes a noise in the received signal, so that the useful signal of interest in the noise is difficult to detect. Therefore, e.g. in US Pat. No. 7,917,320 B1 proposed to emit a plurality of light pulses with the same scanning angle and to receive the received signal of all the light pulses. This eliminates random noise in the signal, which improves the signal-to-noise ratio.

However, the disadvantage of averaging is the amount of time it takes to perform the 1024 samples referred to as an example. Therefore, it is also proposed in US Pat. No. 7,917,320 B1 to reduce the latency ("Response Time") by making the number N of the measurements, which is averaged, dependent on the distance of a viewed object from the sensor. The determination of the distance is not easy, however, since the distance must be known in advance and kept up-to-date about a tracking method.

In addition, when using LED TOF sensors often to improve the ratio between useful signal and noise, an accumulation of the sampled signal is performed. The summation of the complete number of scans, however, takes a long time.

The object of the present invention is therefore to shorten the sampling time of the entire field of view and to realize a known state of the art easier

Find process.

The object is achieved according to the invention by a device, in particular a laser scanner or LED sensor, for detecting objects for a motor vehicle according to claim 1. The object is also achieved by a method for detecting objects for a motor vehicle according to claim 10 and a motor vehicle according to claim 1 1.

The invention is for a vehicle and includes for this a method and a

Device for detection or detection of objects. For this purpose, the invention has a transmitting device with which at least one transmitted light beam is emitted. The transmitted light beam is in particular a laser beam of a laser or a light pulse of an LED sensor. An LED sensor illuminates the scene to be measured by means of

Light emitting diodes and detected by the receiving device reflected light. The scene is illuminated several times with a certain number and thus scanned. Accordingly, the term transmitted light beam in the following includes a focused beam but also the scattered light emitted by an LED.

In this case, the transmitting device is set up to transmit the transmitted light beam for a period of time before the transmitted light beam is transmitted again for a next period of time. Furthermore, a receiving device is provided for receiving the light reflected from the surroundings. With the receiving device, moreover, the received light is converted into a received signal.

According to the invention, the periods of time during which the transmitted light beam is transmitted can be varied. For this purpose, an evaluation device is provided. The evaluation device is set up to determine a progression of the amplitude of the received signal or of a signal derived therefrom during each time duration. The received signal is formed, in particular, from an electrical signal which corresponds to the received light.

Accordingly, during a period in which the transmitted light beam is transmitted, the course of the amplitude of the received signal is continuously determined. With this curve of the amplitude of the received signal then the respective time period is in

Dependence of the course of the amplitude of the respective time period varies.

Thus, if a clear wanted signal next to the noise signal is already recognizable, which can be recognized by a clear curve of the amplitude in the current useful signal, the current time duration can be shortened, thereby shortening the entire sweep. For example, thus is one

Refresh rate of 30Hz can be realized.

According to one embodiment, the device corresponds to a laser scanner and comprises a deflecting mirror with which the transmitted light beam is deflected. Of the

Deflection mirror is movable, so that the transmitted light beam is deflected in dependence of the movement of the deflection mirror. The deflection mirror can be a micromirror, so-called "MEMS." A control device serves to move the micromirror.

The control device controls the micromirror, which will also be called mirror for short. The mirror is pivotable with the control device at least in a horizontal and a vertical direction.

The control device is further configured to move the deflection mirror so that the transmitted light beam can be deflected at different scanning angles, which are also referred to simply as directions. According to this embodiment, the transmitting device is arranged to emit the transmitted light beam in a first direction for a period of time before the transmitted light beam is emitted in a next direction for a next period of time.

According to a first advantageous embodiment, at least one time period is defined as a time range between a start time and an end time. The starting time corresponds to the time from which the transmitted light beam is transmitted again after a previous period of time. The end time corresponds to the point in time at which the transmitted light beam is switched off briefly, in order then to be transmitted again in the following period of time.

The evaluation device is further configured to determine the end time as the time at which a threshold value is determined by a curve of the amplitude of the

Received signal is exceeded or reached. Accordingly, a course of the amplitude in the received signal can be seen, which is exceeded by reaching or reaching the

Threshold value is assigned to a useful signal against the noise, so already the next sampling angle can be illuminated and it is therefore determined this time as the end time.

According to a further embodiment, the transmitting device is set up to transmit the transmitted light beam pulsed. In addition, the receiving device is set up to convert the reflected light of each pulse into a sub-signal and to determine the received signal of one of the time periods from the sub-signals of the respective time duration, in particular by accumulation, ie by adding up the sub-signals of the respective time duration.

Thus, during a period of time, that is, while the transmitted light beam is transmitted in the same direction, a plurality of pulsed transmitted light beams are emitted. The reflected light of each pulse is determined as a sub-signal and the sub-signals superimposed, summed. The accumulated sub-signals then yield the received signal whose course of the amplitude is determined. The superimposition advantageously raises random values of

Noise while reinforcing values of the useful portion. Exceeding the threshold value can then take place after the accumulation of several partial signals.

According to a further embodiment, the transmitting device is set up to transmit the transmitted light beam at a frequency in the range of 75 kHz to 125 kHz or in the range of 95 kHz to 105 kHz or substantially 100 kHz. This frequency can be generated by transmitting devices without having to use particularly expensive special light sources, while at the same time a complete scanning step can be carried out in a time which is sufficient for further processing.

According to another embodiment, a maximum period of time is defined. Furthermore, the evaluation device is set up to determine the time of reaching the maximum time duration as the end time when reaching the maximum time duration.

Accordingly, the time duration is thus limited by a maximum period of time. Accordingly, if the signal-to-noise ratio remains poor, that is to say the course of the amplitude is below a threshold value, the direction or the scanning angle of the transmitted light beam is changed when the maximum time duration has been reached. This prevents the

The transmitted light beam does not stay on for an infinitely long time if the signal-to-noise ratio remains poor and a useful signal is not extractable.

According to a further embodiment, the maximum time duration is determined as the or at least the duration in which 512, 1024 or 2048 pulsed transmitted light beams are transmitted at the selected transmission frequency of the transmitting device. The maximum duration is thus easily definable with a digital counter.

According to a further embodiment, the threshold value is adjustable, whereby an adaptation to changing noise is possible by disturbing light in the environment. According to a specific embodiment, the device is arranged to switch off the transmitted light beam for the duration of the setting of the threshold value, to detect noise values in the received signal and to set the threshold value to a value above the maximum noise value. As a result, a useful signal that is received in a next lighting step can be distinguished from the noise. According to a further embodiment, the transmitting device has a laser for generating the transmitted light beam and an adjustable micromirror, in particular a MEMS mirror, in order to move the transmitted light beam in different directions in the

Send environment. A laser is particularly well suited to transmit light beams with well-defined properties, e.g. a defined wavelength, and can produce together with a micro mirror in a small installation space a transmitted light beam and emit it in different directions.

According to an alternative embodiment, the transmitting device has one or more light-emitting diodes (LED) or a laser diode.

Furthermore, the invention comprises a motor vehicle with a device according to one of the embodiments for carrying out the method according to one of the embodiments.

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

Fig. 1 shows an embodiment of the device and

Fig. 2a to c received with a receiving device received signals.

Fig. 1 shows an embodiment of an object detection device 10. The

Object detection device 10 comprises a transmitting device 12 and a

Receiving device 14.

The transmitting device 12 has a light source 16 with which a transmitted light beam 18 is generated. In the exemplary embodiment shown, the light source 16 is a laser and transmits the generated transmitted light beam 18 to a micromirror 20. For this purpose, the light source 16 is arranged at a predefined angle to the micromirror 20. The micromirror 20 according to the so-called MEMS technology consists of small individual elements, each of which has a reflective surface.

The micromirror 20 is arranged relative to the light source 16 in such a way that the transmitted light beam 18 strikes the micromirror 20 directly, wherein, according to further exemplary embodiments, one or more deflection mirrors are arranged between the light source 16 and the micromirror 20 are arranged so that the transmitted light beam 18 is directed to the micromirror 20 via the deflection 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 beam 18 is thus deflected by the micromirror 20 in different directions of the environment. This direction can also be referred to as a scanning angle.

A control device 22 serves to move the micromirror 20, which is also called "MEMS" mirror. The control device 22 controls the micromirror 20 so that it can be swiveled in at least one horizontal and one vertical direction.

The light source 16 here corresponds to a laser which generates the transmitted light beam 18. The laser here comprises one or more laser diodes. The light source 16 is connected to a control device 22, so that the light source 16 is controlled by the control device 22 and by driving a pulsed transmitted light beam 18 with a frequency, e.g. 100 kHz is sent out. The controller 22 is also configured to turn off the light source.

The transmitting device 12 is further arranged to direct the transmitted light beam 18 in each case for a period of time in one direction with the micromirror 20 before the transmitted light beam 18 is directed in the next direction for a next period of time. For this purpose, the control device 22 controls the micromirror 20 after a period of time, so that it moves. After expiration of the next period of time, the micromirror 20 is driven again for the next movement.

In a further, not shown embodiment is the

Object detection device 10 designed as an LED sensor and includes one or more light-emitting diodes (LED) for illuminating the scene to be measured. The scene to be measured is illuminated many times, for example with a number of 512, 1024 or 2048 illuminations.

The receiving device 14 has a diode 26, which is a photodiode here. With the diode 26 light 28 is received, which corresponds to the reflected or backscattered by the environment transmitted light beam 18. The received light 28, is connected to the diode 26 and their wiring converted into an electrical signal. The electrical signal is then fed to an evaluation device 30.

In the evaluation device 30, the electrical signals which are generated from the reflected light 28 of the pulses of the transmitted light beam 18 or the number of illuminations of a period of time are referred to as partial signals and summed up. The accumulated signal then corresponds to a received signal.

Before summing up each new or a next partial signal is in the

Evaluation device 30 checks whether the curve of the amplitude in the received signal exceeds a threshold value. If the threshold value is exceeded, the current time is determined as the end time of the current time duration and the totalization is aborted. The control device 22 is connected via a connection with the

Evaluation device 30 instructed to deflect the transmitted light beam 18 in the next direction.

FIG. 2a shows a received signal 32a corresponding to a single partial signal of a period of time. Thus, the received light corresponding to a pulse of a transmission light beam 18 is represented by the reception signal 32a. Further, a threshold 34 is shown. The course of the amplitude of the received signal 32a does not exceed the threshold value 34. Thus, the current time is not considered to be the end time, and the micromirror 20 remains in the current position.

FIG. 2b shows a later point in time in FIG. 2a. Here, eight partial signals are added up and give the received signal 32b. Although it is already the course of the amplitudes 36 and 38 to recognize, which stands out against the noise, but this is not yet clearly recognizable as a useful signal. The course of the amplitude 36, 38 of the received signal 32b thus exceeds the

Threshold 34 still not. Thus, the current time is not considered as the end time and the micromirror 20 remains in the current position.

Again a later time of the same period of time from Figs. 2a and 2b is shown in Fig. 2c. In FIG. 2c, 16 partial signals are now added up and produce the received signal 32c. The course of the amplitude 36 of the received signal 32a

now exceeds the threshold 34. Thus, the current time as Considered end time of the time period and the micromirror 20 is now adjusted, so that the transmitted light beam 18 is emitted in the following in a next direction.

Claims

claims

1 . Device for detecting objects for a motor vehicle, comprising

Transmission device (12) for generating at least one transmitted light beam (18) and for emitting the transmitted light beam (18) into the environment, wherein the

Transmitting device (12) is arranged to emit the transmitted light beam (18) for a period of time before the transmitted light beam (18) is sent out again for a next period of time, and receiving means (14) for receiving the reflected light from the environment (28) and the Converting the received light (28) into an electrical signal from which a received signal (32) can be determined,

characterized in that

the device comprises an evaluation device (30) which is set up to determine a progression of the amplitude (36, 38) of the received signal (32) or of a signal derived therefrom during the time duration and the time duration as a function of the course of the amplitude (36, 38) to vary.

2. Apparatus according to claim 1,

characterized in that

at least one time period is defined as the time interval between a start time and an end time and the evaluation device (30) is set up to determine the end time as a function of the time or as the time at which a threshold value (34) is determined by the amplitude (36, 38 ) of the received signal (32) is reached or exceeded.

3. Apparatus according to claim 1 or 2,

characterized in that

the transmitting device (12) is set up to transmit the transmitted light beam (18) pulsed, ie with a plurality of pulses, per time duration and the receiving device (14) is set up, the reflected light (28) of each pulse of the respective one

To convert each time period into a sub-signal of the respective time duration and to determine the received signal (32) from the sub-signals of the respective time period, in particular by accumulation.

4. Device according to one of the preceding claims

characterized in that

the transmitting device (12) is arranged to transmit the transmitted light beam (18) pulsed at a frequency in the range of 75 kHz to 125 kHz or in the range of 95 kHz to 105 kHz or substantially 100 kHz.

5. Device according to one of the preceding claims,

characterized in that

a maximum period of time is defined, and the evaluation device (30) is set up, upon reaching the maximum time duration by one of the time periods, to determine the time of reaching the maximum time duration as the end time of the time duration.

6. Apparatus according to claim 5,

characterized in that

the maximum period of time is determined as the duration of the transmission of 512, 1024 or 2048 pulsed transmitted light beams (18) with the selected

Transmitting frequency of the transmitting device (12) corresponds.

7. Device according to one of the preceding claims,

characterized in that

the threshold value (34) is adjustable.

8. Apparatus according to claim 7,

characterized in that

the device is arranged to turn off the transmit light beam (18) for the duration of the threshold (34) adjustment, noise values in

Receive signal (32) to detect and set the threshold (34) to a value above the maximum noise value or to the maximum noise value.

9. Device according to one of the preceding claims,

characterized in that

the transmitting device (12) comprises a laser for generating the transmitted light beam (18) and a deflecting mirror, in particular an adjustable micromirror (20), comprises the transmitting light beam (18) in different directions in the

Send environment or the transmitting device one or more

Having light-emitting diodes or laser diodes for generating transmitted light beams.

10. A method for detecting objects for a motor vehicle, wherein with a

At least one transmitted light beam (18) is generated and emitted into the environment, wherein the transmitted light beam (18) is emitted for a period of time before the transmitted light beam (18) is transmitted again for a next period of time, and with a receiving device (14 ) the light (28) reflected by the environment is received and the received light (28) is converted into an electrical signal from which a received signal (32) can be determined,

characterized in that

an evaluation of an amplitude (36, 38) of the received signal (32) or a signal derived therefrom is determined during the time period with an evaluation device (30) and the time duration is varied as a function of the course of the amplitude (36, 38).

1 1. Motor vehicle with a device according to one of claims 1 to 9.