DE102017126388A1 - Method for determining at least one free space in a monitoring area of a distance measuring device, distance measuring device and driver assistance system - Google Patents

Abstract

A method is described for determining at least one free space (42) in a monitoring area (14) of a distance measuring device (12), in particular of a vehicle (10), a distance measuring device (12) and a driver assistance system (20). In the method, transmission signals (32) are sent to the monitoring area (14), received signals (34) are received from the monitoring area (14) and ambient information is determined from the received signals (34) from which at least one free space (42) is determined. The environmental information is characterized by a distance-dependent amplitude curve (36) that depends on distances from a reference range of the rangefinder device (12). The amplitude profile is compared in terms of amplitude with a free space threshold, which is set or predetermined in terms of amplitude below a predefinable detection threshold for determining target signals. With the smallest distance in which the amplitude curve is in amplitude above the free space threshold, an outer boundary (46) of the at least one free space (42) is defined.

Description

Technical area

• - bei dem Sendesignale in den Überwachungsbereich gesendet werden,
• - Empfangssignale aus dem Überwachungsbereich empfangen werden
• - und aus den Empfangssignalen Umgebungsinformationen ermittelt werden, aus denen wenigstens ein Freiraum ermittelt wird.

The invention relates to a method for determining at least one free space in a monitoring area of a distance measuring device, in particular of a vehicle

• in which transmission signals are sent to the surveillance area,
• - Receive signals are received from the surveillance area
• - And from the received signals environmental information are determined from which at least one free space is determined.

• - wenigstens einen Sender zum Senden von Sendesignalen in den Überwachungsbereich,
• - wenigstens einen Empfänger zum Empfangen von Empfangssignalen aus dem Überwachungsbereich
• - und wenigstens eine Steuer- und/oder Auswerteeinrichtung zur Steuerung des wenigstens einen Senders und des wenigstens einen Empfängers und/oder zur Auswertung von Empfangssignalen,
• - wobei die wenigstens eine Steuer- und/oder Auswerteeinrichtung Mittel aufweist zur Ermittlung wenigstens eines Freiraums im Überwachungsbereich aus den Empfangssignalen.

Furthermore, the invention relates to a distance measuring device for monitoring a monitoring area, in particular of a vehicle, on objects, the distance measuring device having

• at least one transmitter for transmitting transmission signals to the surveillance area,
• at least one receiver for receiving received signals from the surveillance area
• and at least one control and / or evaluation device for controlling the at least one transmitter and the at least one receiver and / or for evaluating received signals,
• - Wherein the at least one control and / or evaluation means comprises means for determining at least one free space in the monitoring area from the received signals.

• - wenigstens eine elektronische Steuereinrichtung zur Steuerung von Funktionseinrichtungen des Fahrzeugs abhängig von Umgebungsinformationen, welche durch wenigstens eine Entfernungsmessvorrichtung bereitgestellt werden,
• - und wenigstens eine Entfernungsmessvorrichtung zur Ermittlung von Umgebungsinformationen aus einem Überwachungsbereich, wobei die wenigstens eine Entfernungsmessvorrichtung aufweist
• - wenigstens einen Sender zum Senden von Sendesignalen in den Überwachungsbereich,
• - wenigstens einen Empfänger zum Empfangen von Empfangssignalen aus dem Überwachungsbereich und
• - wenigstens eine Steuer- und/oder Auswerteeinrichtung zur Steuerung des wenigstens einen Senders und des wenigstens einen Empfängers und/oder zur Auswertung von Empfangssignalen,
• - wobei die wenigstens eine Steuer- und/oder Auswerteeinrichtung Mittel aufweist zur Ermittlung wenigstens eines Freiraums im Überwachungsbereich aus den Empfangssignalen.

Moreover, the invention relates to a driver assistance system of a vehicle having at least one distance measuring device

• at least one electronic control device for controlling functional devices of the vehicle depending on environmental information provided by at least one distance measuring device,
• - And at least one distance measuring device for determining environmental information from a monitoring area, the at least one distance measuring device
• at least one transmitter for transmitting transmission signals to the surveillance area,
• at least one receiver for receiving received signals from the surveillance area and
• at least one control and / or evaluation device for controlling the at least one transmitter and the at least one receiver and / or for evaluating received signals,
• - Wherein the at least one control and / or evaluation means comprises means for determining at least one free space in the monitoring area from the received signals.

State of the art

From the DE 100 49 229 A1 For example, a method is known, in particular for improving the responsiveness of vehicles or vehicle drivers when danger occurs in traffic. In the method, the lying in the direction of travel of a vehicle vehicle environment is examined for a free driving space. At least the location parameters of the free travel area are made available to a system or a person for further processing.

The invention has for its object to design a method, a distance measuring device and a driver assistance system of the type mentioned, in which an accuracy and / or reliability of the free space determination can be improved.

Disclosure of the invention

• - die Umgebungsinformationen durch einen entfernungsabhängigen Amplitudenverlauf charakterisiert werden, der von Entfernungen von einem Referenzbereich der Entfernungsmessvorrichtung abhängig ist,
• - der Amplitudenverlauf amplitudenmäßig mit einer Freiraumschwelle verglichen wird, welche amplitudenmäßig unterhalb einer vorgebbaren Detektionsschwelle zur Ermittlung von Zielsignalen eingestellt oder vorgegeben wird,
• - mit der kleinsten Entfernung, in der der Amplitudenverlauf amplitudenmäßig oberhalb der Freiraumschwelle liegt, eine äußere Grenze des wenigstens einen Freiraums definiert wird.

This object is achieved in that

• the environmental information is characterized by a distance-dependent amplitude characteristic, which depends on distances from a reference range of the distance-measuring device,
• the amplitude profile is compared in terms of amplitude with a free space threshold, which is set or specified in terms of amplitude below a predefinable detection threshold for determining target signals,
• - With the smallest distance in which the amplitude curve is in amplitude above the free space threshold, an outer boundary of the at least one free space is defined.

According to the invention, therefore, an amplitude-related detection threshold is predetermined, which may be so high that correspondingly stronger detections can be identified as target signals. The detection threshold can advantageously be specified such that increases in the amplitude profile that result from reflections of the transmission signals on real target objects are above the detection threshold. With the detection threshold, so can an appropriate false detection rate be achieved. Furthermore, a free space threshold is defined, which lies below the detection threshold. With the free space threshold, according to the invention, even smaller increases in amplitude can be detected, which can result in particular from weak reflections on real objects. In this way it can be ensured that even objects with weak reflections can be detected and no object for determining the free space is overlooked. The outer limit of the free space is thus determined by the safety of the reference range of the distance measuring device closest to the amplitude increase, which are above the free space threshold. Thus, on the whole, it can be ensured that the free space is even more likely to be free of any objects. The free space determination can be performed in this way more accurate and reliable.

A free space is part of the corresponding surveillance area, which is extremely likely to be free of objects. To be considered free space, the distance dependent amplitude must be below the free space threshold.

The outer boundary of the free space describes the end of the free space away from the reference area. An inner boundary of the free space can accordingly describe the end of the free space facing the reference area.

The reference range of the distance measuring device may be a reference point, a reference line or a reference surface to which the distances can be referred. The reference range may be defined by the position of a transmitter and / or a receiver of the rangefinder.

Advantageously, the free space threshold can be fixed prior to commissioning of the distance measuring device or adjusted during operation. The free space threshold can be specified in particular during a calibration of the removal device. During operation, the free space threshold can be adjusted according to the environmental conditions and / or the operating conditions. Thus, overall, reliability and accuracy of free space determination can be improved.

By means of the invention it is also possible to detect objects in which it is difficult or impossible to detect whether they are static or dynamic. In particular, the invention can also be used to detect objects which move on a trajectory tangent to the reference region. Such objects may be susceptible to false detections, in particular due to noise or interference from other sources, which without the invention would be detected with little probability as detections associated with real objects. The invention enables the identification of false detections. In particular, according to the invention, such false detections that have arisen due to accumulation from previous measurement cycles in a map and / or detections that have been erroneously classified as static can be identified. Furthermore, it can be detected by means of the invention whether an object originally recognized as static, in particular a stationary pedestrian, a parked vehicle or the like, has moved.

The invention can be used in a vehicle, in particular a motor vehicle. Advantageously, the invention can be used in a land vehicle, in particular a passenger car, truck, a bus, a motorcycle or the like, an aircraft and / or a watercraft. The invention can also be used in autonomous or at least partially autonomous vehicles.

In a vehicle recognized free spaces can be identified as free and / or parking spaces. Knowledge of open spaces can improve the responsiveness of vehicles or vehicle drivers when traffic hazards occur. In particular, in combination with a driver assistance system so the driving safety and / or driving comfort can be improved.

Standing or moving objects, in particular vehicles, persons, obstacles, road bumps, in particular potholes or stones, roadway boundaries, free spaces, in particular parking spaces, or the like, can be detected as ambient information with the distance measuring device.

The detection device may advantageously be connected to or part of at least one electronic control device of the vehicle, in particular a driver assistance system and / or a chassis control and / or a driver information device and / or a parking assistance system or the like. In this way, the object data detected by the detection device, in particular the distance, orientation and / or relative speed of an object relative to the vehicle, transmitted to the control device and for influencing driving functions, in particular the speed, a brake function, a steering function, a chassis control and / or an output of a warning and / or warning signal, in particular for the driver or the like.

In an advantageous embodiment of the method, the free space threshold can be adjusted depending on a noise of the amplitude curve. In this way, the free space threshold can be adapted to the noise component in the amplitude curve. The free space threshold can be chosen to be above a maximum noise. Thus, an overall accuracy of the method can be improved.

In a further advantageous embodiment of the method, the free space threshold can be set or specified with an offset function starting from the detection threshold. In this way, the free space threshold can be coupled with the already predetermined detection threshold.

In a further advantageous embodiment of the method, an offset function can be preset or set constant over at least part of the amplitude curve and / or can be variably set or adjusted at least over part of the amplitude profile. The offset function can be set constant at least over part of the amplitude curve. The offset function can have a constant value over the entire amplitude curve. Thus, a calculation effort can be reduced accordingly. Alternatively or additionally, the offset function can be variably set or adjusted at least over part of the amplitude curve. In this way, the offset function can be adjusted individually in particular to the noise and / or the course of the detection threshold.

In a further advantageous refinement of the method, an offset function can be preset or set in terms of amplitude to be constant or variable over at least part of the amplitude profile and / or can be preset or set at least over a part of the amplitude curve in a constant or variable manner. In this way, the offset function can be better adapted in particular to the noise and / or the detection threshold. Overall, the offset function can be chosen so that an improvement in the accuracy and reliability of the free space determination is achieved.

Advantageously, the offset function can be constant in terms of amplitude and / or time over at least part of the amplitude profile. This makes it easier to specify the offset function.

Advantageously, the offset function can be variable in amplitude and / or time over at least part of the amplitude curve. Thus, the offset function can be adapted to an amplitude-related and / or temporal course, in particular of the detection threshold, the noise and / or the amplitude profile of the surroundings information.

In a further advantageous embodiment of the method, at least one free space can be defined as a spatially one-dimensional distance, as a two-dimensional area or as a three-dimensional volume. In this way, depending on the application and arrangement of the distance measuring device in each case the most suitable free space information can be obtained.

Advantageously, at least one free space can be specified as a two-dimensional surface via an azimuth angle or an elevation angle or as a three-dimensional volume via azimuth and elevation. At least one free space can be defined as a vertical or horizontal section or as a spatial section. At least one free space can be defined two-dimensionally as a circular sector or three-dimensionally as a spherical sector.

In a further advantageous embodiment of the method, distances, directions and / or speeds of any objects relative to the reference range of the distance measuring system can be determined from the environmental information. In this way, a location, in particular a distance and a direction, and / or a movement of a possible object relative to the reference range of the distance measuring device can be determined. Thus, detected objects can also be identified as static or dynamic, in particular on the basis of the speed information. This allows more accurate statements about the free space.

In a further advantageous embodiment of the method, at least one radar system, a LiDAR system, an ultrasound system or another type of distance measuring system can be used to determine the environmental information. With such distance measuring systems, a monitoring area can be precisely and quickly monitored for objects. Such distance measuring systems work without contact.

Advantageously, a scanning, in particular scanning, measuring system can be used for the distance measuring device. With such measuring systems, a monitoring area can be scanned accordingly.

In a further advantageous embodiment of the method, the environmental information can be determined from the received signals by means of at least one Fourier transformation. Using the Fourier transform, a Amplitude curve can be determined in a so-called distance gate Dopplertor matrix. Any objects in the surveillance area may be represented in such a range gate doppler gate matrix by corresponding target signals in the form of amplitude peaks. From the corresponding distance values of the target signals, a distance of a corresponding object to the reference range of the distance measuring device can be determined. From the Doppler values corresponding relative velocities can be determined.

To be considered free space, the intensities of the corresponding range cells obtained from the Fourier transform of the received signals must be below the free space threshold.

Advantageously, the free space threshold can be predetermined or adjusted depending on a noise of the amplitude curve in the Doppler and / or distance dimension. In this way, the accuracy and / or reliability of the free space determination can be further improved.

Advantageously, at least one multidimensional discrete Fourier transformation, in particular at least one two-dimensional or three-dimensional Fourier transformation, can be performed. Advantageously, a fast Fourier transform (FFT) can be performed.

In particular, radar signals can be reshaped using Fourier transforms.

In a further advantageous embodiment of the method, an inner limit of the free space can additionally be specified or set. With the inner boundary, a distance of an opening of the free space from the reference range of the removal device can be predetermined. The clearance is between the inner border and the outer border. In this way, signals having their local origin between the reference range of the distance device and the inner limit of the free space may be disregarded in the clearance determination. Such signals may be caused by reflections on static objects relative to the reference range of the rangefinder. In particular, by specifying the inner boundary of the free space reflections on a bumper of the own vehicle can be disregarded.

Advantageously, the inner boundary may lie behind a near zone of the distance measuring device. In this way, any objects in the vicinity can be disregarded in the free space determination.

Advantageously, the inner limit can be set at a distance of approximately between 10 cm and 1 m from the reference range of the distance measuring device.

The object is further achieved in the distance measuring device according to the invention in that the control and / or evaluation device comprises means for performing the method according to the invention.

Advantageously, the control and / or evaluation device may comprise means for carrying out at least one multi-dimensional discrete Fourier transformation of the received signals.

The object is also achieved in the driver assistance system according to the invention in that the control and / or evaluation device has means for carrying out the method according to the invention.

Incidentally, the features and advantages shown in connection with the method according to the invention, the distance measuring device according to the invention and the driver assistance system according to the invention and their respective advantageous embodiments apply mutatis mutandis and vice versa. The individual features and advantages can, of course, be combined with one another, whereby further advantageous effects can be achieved that go beyond the sum of the individual effects.

list of figures

• 1 ein Kraftfahrzeug in einer Fahrsituation in der Draufsicht, mit einem Fahrerassistenzsystem und bespielhaft vier Radarsystemen zu Überwachung jeweiliger Überwachungsbereiche;
• 2 eine Funktionsdarstellung des Kraftfahrzeugs mit dem Fahrerassistenzsystem und einem der Radarsysteme aus der 1;
• 3 ein Entfernungstor-Amplituden-Diagramm, in dem ein Amplitudenverlauf einer Radarmessung mit einem der Radarsysteme aus der 1 gezeigt ist.

Further advantages, features and details of the invention will become apparent from the following description in which an embodiment is explained in detail in the invention with reference to the drawing. The person skilled in the art will expediently also individually consider the features disclosed in the drawing, the description and the claims in combination and combine these into meaningful further combinations. It show schematically

• 1 a motor vehicle in a driving situation in plan view, with a driver assistance system and exemplary four radar systems for monitoring respective monitoring areas;
• 2 a functional representation of the motor vehicle with the driver assistance system and one of the radar systems of the 1 ;
• 3 a distance-gate amplitude diagram in which an amplitude characteristic of a radar measurement with one of the radar systems from the 1 is shown.

In the figures, the same components are provided with the same reference numerals.

Embodiment (s) of the invention

In the 1 is a motor vehicle 10 shown in the form of a passenger car in a driving situation in plan view. The car 10 has four exemplary identical radar systems 12 , The radar systems 12 are exemplary at the four corners of the motor vehicle 10 arranged. With the radar systems 12 can each surveillance areas 14 in the direction of travel 16 diagonally in front and diagonally behind the motor vehicle 10 on objects 18 monitored. The radar systems 12 can also be found elsewhere on the motor vehicle 10 be arranged and oriented differently. There may also be more or fewer than four radar systems 12 be provided. At the objects 18 they may be, for example, other vehicles, people, obstacles, road bumps, such as potholes or stones, roadway boundaries or the like. In the 1 and 2 are some examples of some objects 18 indicated.

Every radar system 12 is designed for example as a frequency-modulated continuous wave radar. Frequency-modulated continuous wave radars are also referred to in the art as FMCW (Frequency Modulated Continuous Wave) radars. With the radar system 12 For example, a distance, a direction and a speed of the object 18 relative to a reference point of the motor vehicle 10 be determined. Reference point, for example, the position of a transmitter 26 of the radar system 12 on the motor vehicle 10 his.

The radar systems 12 are part of a driver assistance system 20 or at least be associated with it. In the 2 is a functional diagram of the driver assistance system 20 , Some exemplary components of the motor vehicle 10 and one of the radar systems 12 shown. With the driver assistance system 20 For example, a driver of the motor vehicle 10 get supported. For example, the motor vehicle 10 using the driver assistance system 20 at least partially autonomous driving, on or off parking. With the driver assistance system 20 can driving functions of the motor vehicle 10 For example, an engine control, a brake function or a steering function, influences or hints or warning signals are issued. This is the driver assistance system 20 with functional facilities 22 regulating and / or controlling connected. In the 2 are exemplary two functional devices 22 shown. At the functional facilities 22 it may be, for example, an engine control system, a brake system, a steering system, a landing gear control or a signal output system.

The driver assistance system 20 has an electronic control device 24 on, with the appropriate electronic control signals to the functional facilities 22 transmitted and / or received and processed by them.

Every radar system 12 includes, for example, a transmitter 26 , an electronic control and evaluation device 28 and a receiver 30 ,

Each control and evaluation device 28 is signal technology with the control device 24 connected. With the control device 24 can depend on environmental information provided with the radar systems 12 be determined, driving functions of the motor vehicle 10 be controlled / regulated.

For the invention, it is not essential whether electrical / electronic control and / or evaluation devices, such as the control device 24 , the control and evaluation equipment 28 , an engine control unit of the motor vehicle 10 or the like, integrated in one or more components or groups of components or at least partially realized as a decentralized components or groups of components.

With every transmitter 26 can send signals 32 for example, with constantly changing frequency in the appropriate monitoring area 14 be sent. The transmission signals 32 may be attached to objects 18 reflected and as corresponding received signals 34 to the recipient 30 sent back and received with this. From the received signals 34 is with the control and evaluation 28 the distance, the direction and the speed of the object 18 relative to the motor vehicle 10 , respectively to the reference point.

The process of obtaining environmental information from the appropriate surveillance area 14 will be exemplified below using one of the radar systems 12 explained.

With the control and evaluation device 28 becomes the transmitter 26 controlled so that transmission signals 32 in the surveillance area 14 be sent. The transmission signals 32 are generated by way of example from frequency-modulated continuous-wave signals.

With the appropriate receiver 30 if available on the object 18 reflected echoes of the transmitted signals 32 as received signals 34 received and if necessary in one with the control and evaluation 28 brought usable shape. In addition or if no object 18 can exist with the receiver 30 False detections, for example in the form of noise or possibly interference from other sources, as received signals 34 from the surveillance area 14 be received.

The one with the receiver 30 Received signals received 34 be with appropriate resources of the control and evaluation 28 subjected to a two-dimensional fast Fourier transform. The result of the Fourier transformation results for the transformed received signals 34 an amplitude course 36 , In the 3 is an example of a distance gate amplitude diagram of the amplitude curve 36 shown in the range gate dimension. The amplitude curve 36 is dependent on a distance to the reference point.

From the result of the two-dimensional discrete Fourier transformation go target signals 38a of physically existing targets and their respective amplitudes as peaks. The amplitude curve 36 characterizes the intensity of a possible target signal 38a or if in the appropriate surveillance area 14 is located, just noise.

A target object is an area of an object 18 , on the transmission signal 32 can be reflected. Multiple targets can be from the same object 18 or from different objects 18 originate. In the range gate-doppler dimension, the range gates correspond to so-called "range bins" or pitch intervals. The Doppler doors correspond to so-called relative speed gates or "Doppler bins".

To the destination signals 38a of physically existing targets in the amplitude history 36 to be able to identify the amplitude curve 36 with a predetermined detection threshold 40 compared. The detection threshold 40 is in the 3 exemplified as a constant amplitude. The detection threshold 40 For example, before starting up the radar system 12 specified and stored during test measurements. The detection threshold 40 is chosen so that only target signals 38a of real target objects whose amplitudes are correspondingly large, above the detection threshold 40 lie and therefore be recognized. From the target signals 38a may be a distance, a velocity and / or a direction of the respective target objects relative to the reference point of the radar system 12 be determined.

To have a free space 42 to determine which is a driving or parking space for the motor vehicle 10 is below the detection threshold in terms of amplitude 40 a free space threshold 44 specified. In the in 3 The embodiment shown is the free space threshold 44 by way of example by a constant amplitude offset 48 opposite the detection threshold 40 reduced. The amplitude offset 48 is chosen so that the free space threshold 44 above the noise 50 lies, so that noise 50 not falsely as a target signal 38a or 38b is identified.

The amplitude curve 36 becomes with the free space threshold 44 compared. If available, possible target signals 38b determines their amplitudes over the free space threshold 44 and below the detection threshold 40 lie. The possible destination signals 38b are for easier discrimination of the above-mentioned target signals 38a with the reference number 38b Provided. The possible destination signals 38b For example, they may be due to weak reflections on target objects or signal noise. Target objects, which are the possible target signals 38b are for the sake of simpler distinctness in the 1 as black dots with the reference numerals 18b Provided. The possible destination signals 38b are compared with the detection threshold 40 not detected because their reflections are too weak. By using the free space threshold 44 ensures that even very weak reflections of possible targets to determine the free space 42 can be used.

The smallest distance 52 in which the amplitude course 36 above the open space threshold 44 lies, is called outer boundary 46 of the open space 42 Are defined.

Due to the opening angle of the radar system 12 has the freedom 42 depending on the orientation of the radar system 12 exemplary in the 1 the shape of a circular sector. In the in the 1 The embodiment shown is the free space 42 shown as a two-dimensional area in azimuth. Alternatively or additionally, by a corresponding configuration and / or orientation of the radar system 12 the free space 42 also be defined in the elevation direction or as a three-dimensional volume.

Optionally, in addition, an inner limit 54 for the free space 42 be specified. This is in the 1 as an example in the open space 42 shown in the direction of travel 16 front left radar system 12 is determined. The inner border 54 can close the radar system 12 . for example, at distances of about 20 cm to 50 cm from the radar system 12 , spared. In this area, for example, the bumper of the vehicle 10 be arranged, which falsely as relative to the motor vehicle 10 static object would be detected.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 10049229 A1 [0004]

Claims (12)

Method for determining at least one free space (42) in a monitoring area (14) of a distance measuring device (12), in particular of a vehicle (10), in which transmitting signals (32) are sent to the monitoring area (14), receiving signals (34) from the monitoring area (14) are received - and from the received signals (34) environment information is determined from which at least one free space (42) is determined, characterized in that - the environmental information is characterized by a distance-dependent amplitude curve (36) of distances from a The amplitude profile (36) is compared in terms of amplitude with a free space threshold (44), which is set or predetermined in amplitude below a predefinable detection threshold (40) for determining target signals (38a), with the smallest Distance (52), in which the amplitude curve (3 6) in terms of amplitude above the free space threshold (44), an outer boundary (46) of the at least one free space (42) is defined. Method according to Claim 1 , characterized in that the free space threshold (44) is adjusted depending on a noise (50) of the amplitude profile (36). Method according to Claim 1 or 2 , characterized in that the free space threshold (44) with an offset function (48) starting from the detection threshold (40) is set or predetermined. Method according to Claim 3 , characterized in that an offset function (48) at least over a part of the amplitude curve (36) is constantly preset or adjusted and / or at least over a part of the amplitude curve is variably set or adjusted. Method according to Claim 3 or 4 , characterized in that an offset function (48) at least over a part of the amplitude curve (36) is set or adjusted in amplitude constant or variable and / or at least over a part of the amplitude curve (36) temporally constant or variable predetermined or adjusted. Method according to one of the preceding claims, characterized in that at least one free space (42) is defined as a spatial one-dimensional distance, as a two-dimensional surface or as a three-dimensional volume. Method according to one of the preceding claims, characterized in that from the environmental information distances, directions and / or speeds of any objects (18) relative to the reference range of the distance measuring system (12) are determined. Method according to one of the preceding claims, characterized in that at least one radar system (12), a LiDAR system, an ultrasound system or a different distance measuring system is used to determine the environmental information. Method according to one of the preceding claims, characterized in that the environmental information is determined by means of at least one Fourier transformation from the received signals (34). Method according to one of the preceding claims, characterized in that in addition an inner boundary (54) of the free space (42) is set or adjusted. Distance measuring device (12) for monitoring a monitoring area (14) in particular of a vehicle (10) on objects (18), wherein the distance measuring device (12) comprises - at least one transmitter (26) for transmitting transmission signals (32) into the monitoring area (14 ), - at least one receiver (30) for receiving received signals (34) from the monitoring area (14) - and at least one control and / or evaluation device (28) for controlling the at least one transmitter (26) and the at least one receiver ( 30) and / or for evaluation of received signals (34), - wherein the at least one control and / or evaluation device (28) comprises means (for determining at least one free space 42) (in the monitoring area 14) (from the reception signals 34), characterized in that the control and / or evaluation device (28) has means for carrying out the method according to one of the preceding claims. Driver assistance system of a vehicle (10) with at least one distance measuring device (12) comprising - at least one electronic control device (24) for controlling functional devices (22) of the vehicle (10) depending on environmental information provided by at least one distance measuring device (12), and at least one distance measuring device (12) for detecting environmental information from a monitoring area (14), wherein the at least one distance measuring device (12) - at least one transmitter (26) for transmitting transmission signals (32) into the monitoring area (14), - at least one receiver (30) for receiving received signals (34) from the monitoring area (14), and at least one control and / or evaluation device (28) for controlling the at least one transmitter (26) and the at least one receiver (30) and / or for evaluating received signals (34), - wherein the at least one control and / or evaluation device (28) comprises means for determining at least one free space (42) in the monitoring area (14) from the received signals (34), characterized in that the control and / or evaluation device (28) comprises means for performing the method according to one of Claims 1 to 10 ,

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