DE102017126388B4 - 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

Method for determining at least one free space (42) in a monitoring area (14) of a distance measuring device (12), in particular a vehicle (10) - in which transmission signals (32) are sent into the monitoring area (14), - receiving signals (34) from the monitoring area (14) are received and environmental information is determined from the received signals (34), 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), which is based on distances from a Reference range of the distance measuring device (12) is dependent, - the amplitude curve (36) is compared in amplitude with a free space threshold (44) which is set or specified in amplitude below a predeterminable detection threshold (40) for determining target signals (38a), - with the smallest Distance (52) in which the amplitude curve (36) is in terms of amplitude ig above the free space threshold (44), 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

• - where transmit signals are sent into the surveillance area,
• - Received signals are received from the monitoring area
• and environmental information is determined from the received signals, 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.

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

• - At least one transmitter for sending transmission signals into 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 device has 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.

The invention also 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 information about the surroundings, which are 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 having
• - At least one transmitter for sending transmission signals into the surveillance area,
• - At least one receiver for receiving 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 device has 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 a method is known, in particular for improving the reactivity of vehicles or vehicle drivers when a danger occurs in traffic. In the method, the vehicle surroundings in the direction of travel of a vehicle are examined for a free driving space. At least the location parameters of the free driving space are made available to a system or a person for further processing.

The invention is based on the object of designing a method, a distance measuring device and a driver assistance system of the type mentioned at the outset, in which the 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.

According to the invention, this object is achieved in that

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

According to the invention, a detection threshold in terms of amplitude is specified which can be so high that correspondingly stronger detections can be identified as target signals. The detection threshold can advantageously be predefined in such a way that increases in the amplitude curve that result from reflections of the transmitted signals on real target objects are above the detection threshold. With the detection threshold, an appropriate false detection rate can be achieved be achieved. Furthermore, a free space threshold is defined which is below the detection threshold. According to the invention, the free space threshold can also be used to detect lower amplitude increases, which in particular can result from weak reflections on real objects. In this way, it can be ensured that objects with weak reflections can also be detected and that no object is overlooked for determining the free space. To be on the safe side, the outer limit of the free space is therefore determined by the amplitude increase which is closest to the reference area of the distance measuring device and which is above the free space threshold. In this way, it can be ensured overall that the free space is even more likely to be free of any objects. The free space determination can be carried out more precisely and reliably in this way.

A free space is a part of the corresponding monitoring area that is extremely likely to be free of objects. In order to be considered as free space, the distance-dependent amplitude must be below the free space threshold.

The outer limit of the free space describes the end of the free space that is remote from the reference area. An inner boundary of the free space can correspondingly describe the end of the free space facing the reference area.

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

Advantageously, the free space threshold can be preset in a fixed manner before the distance measuring device is put into operation, or it can be set during operation. The clearance threshold can in particular be specified when calibrating the removal device. During operation, the clearance threshold can be adapted accordingly to the ambient conditions and / or the operating conditions. In this way, the reliability and accuracy of the free space determination can be improved overall.

With the aid of the invention, it is also possible to detect objects for which it is difficult or impossible to detect whether they are static or dynamic. In particular, objects can also be recognized with the invention which move on a trajectory that is tangential with respect to the reference area. Such objects can be susceptible to false detections, in particular due to noise or interference from other sources, which without the invention would only be detected with a low probability as detections belonging to real objects. The invention enables false detections to be identified. In particular, according to the invention, false detections can be identified which have arisen through accumulation from previous measurement cycles in a map, and / or detections which have been incorrectly classified as static. Furthermore, it can be recognized with the aid of the invention whether an object originally recognized as static, in particular a standing pedestrian, a parked vehicle or the like, has moved.

The invention can be used in a vehicle, in particular a motor vehicle. The invention can advantageously be used in a land vehicle, in particular a passenger car, truck, bus, 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 the case of a vehicle, recognized free spaces can be identified as free driving spaces and / or parking spaces. Knowledge of free spaces can improve the ability of vehicles or vehicle drivers to react to hazards in traffic. In particular in combination with a driver assistance system, driving safety and / or driving comfort can be improved.

With the distance measuring device, stationary or moving objects, in particular vehicles, people, obstacles, uneven road surfaces, in particular potholes or stones, road boundaries, open spaces, in particular parking spaces, or the like, can be recorded as environmental information.

The detection device can advantageously be connected to 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, or be part of such. In this way, the object data recorded with the detection device, in particular the distance, orientation and / or relative speed of an object relative to the vehicle, can be transmitted to the control device and used to influence driving functions, in particular the speed, a braking function, a steering function, a chassis control and / or an output of an information and / or warning signal, in particular for the driver or the like, can be used.

In an advantageous embodiment of the method, the clearance threshold can be set as a function of noise in 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 so that it is above a maximum noise. In this way, the accuracy of the method can be improved overall.

In a further advantageous embodiment of the method, the clearance threshold can be set or specified with an offset function based on the detection threshold. In this way, the clearance threshold can be coupled with the detection threshold that is already specified.

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

In a further advantageous embodiment of the method, an offset function can be specified or set constant or variable in amplitude at least over part of the amplitude curve and / or specified or set constant or variable over time at least over part of the amplitude curve. 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 selected so that an improvement in the accuracy and reliability of the free space determination is achieved.

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

The offset function can advantageously be variable in terms of 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 profile, in particular the detection threshold, the noise and / or the amplitude profile of the environmental information.

In a further advantageous embodiment of the method, at least one free space can be defined as a spatially one-dimensional path, 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, the most suitable free space information can be obtained.

Advantageously, at least one free space can be specified as a two-dimensional area 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 area 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 area of the distance measuring device can be determined. In this way, detected objects can also be identified as static or dynamic, in particular on the basis of the speed information. This allows more precise 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 some other type of distance measuring system can be used to determine the environmental information. With such distance measuring systems, a monitoring area can be monitored precisely and quickly for objects. Such distance measuring systems work without contact.

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

In a further advantageous embodiment of the method, the information on the surroundings can be determined from the received signals with the aid of at least one Fourier transformation. Using the Fourier transform, a Amplitude curve can be determined in a so-called distance gate Doppler gate matrix. Any objects in the monitoring area can be represented in such a range gate-Doppler gate matrix by corresponding target signals in the form of amplitude peaks. A distance between a corresponding object and the reference area of the distance measuring device can be determined from the corresponding distance values of the target signals. Corresponding relative speeds can be determined from the Doppler values.

In order to be considered as free space, the intensities of the corresponding distance cells, which are obtained from the Fourier transformation of the received signals, must be below the free space threshold.

The free space threshold can advantageously be specified or set as a function of noise in the amplitude profile in the Doppler and / or distance dimension. In this way, the accuracy and / or reliability of the free space determination can be further improved.

At least one multi-dimensional discrete Fourier transformation, in particular at least one two-dimensional or three-dimensional Fourier transformation, can advantageously be carried out. A fast Fourier transformation (FFT) can advantageously be carried out.

With the help of Fourier transformations, radar signals in particular can be converted accordingly.

In a further advantageous embodiment of the method, an inner limit of the free space can additionally be specified or set. With the inner limit, a distance of a start of the free space from the reference area of the removal device can be specified. The free space is between the inner limit and the outer limit. In this way, signals that have their local origin between the reference area of the distance device and the inner limit of the free space can be disregarded when determining the free space. Such signals can be produced by reflections on objects that are static relative to the reference area of the distance measuring device. In particular, by specifying the inner limit of the free space, reflections on a bumper of one's own vehicle can be disregarded.

The inner limit can advantageously lie behind a close range of the distance measuring device. In this way, any objects in the close range can be disregarded when determining the free space.

The inner limit can advantageously be specified at a distance of approximately between 10 cm and 1 m from the reference area of the distance measuring device.

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

The control and / or evaluation device can advantageously have means for performing 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.

In addition, 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 configurations apply mutually and vice versa. The individual features and advantages can of course be combined with one another, whereby further advantageous effects can arise that go beyond the sum of the individual effects.

Figure list

• 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 emerge from the following description, in which an exemplary embodiment of the invention is explained in more detail with reference to the drawing. The person skilled in the art will expediently also consider the features disclosed in combination in the drawing, the description and the claims individually and combine them into meaningful further combinations. It show schematically

• 1 a motor vehicle in a driving situation in plan view, with a driver assistance system and, for example, four radar systems for monitoring the respective monitoring areas;
• 2 a functional representation of the motor vehicle with the driver assistance system and one of the radar systems from 1 ;
• 3 a range gate amplitude diagram in which an amplitude curve 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 symbols.

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, for example, four identical radar systems 12th . The radar systems 12th are exemplary at the four corners of the motor vehicle 10 arranged. With the radar systems 12th can respective monitoring areas 14th in the direction of travel 16 diagonally in front of and diagonally behind the motor vehicle 10 on objects 18th to be monitored. The radar systems 12th can also be used in other places on the vehicle 10 be arranged and oriented differently. There can also be more or less than four radar systems 12th be provided. With the objects 18th it can be, for example, other vehicles, people, obstacles, uneven roads, for example potholes or stones, road boundaries or the like. In the 1 and 2 are examples of some objects 18th indicated.

Any radar system 12th is designed, for example, as a frequency-modulated continuous wave radar. Frequency-modulated continuous wave radars are also known as FMCW (Frequency modulated continuous wave) radars in specialist circles. With the radar system 12th can for example be a distance, a direction and a speed of the object 18th relative to a reference point of the motor vehicle 10 be determined. The reference point can, for example, be the position of a transmitter 26th of the radar system 12th on the motor vehicle 10 his.

The radar systems 12th are part of a driver assistance system 20th or can at least be connected to this. In the 2 is a functional diagram of the driver assistance system 20th , some exemplary components of the motor vehicle 10 and one of the radar systems 12th shown. With the driver assistance system 20th can for example be a driver of the motor vehicle 10 get supported. For example, the motor vehicle 10 using the driver assistance system 20th Drive, park or leave a parking space at least partially autonomously. With the driver assistance system 20th can drive functions of the motor vehicle 10 , for example a motor control, a braking function or a steering function, influenced or instructions or warning signals are output. The driver assistance system is for this purpose 20th with functional devices 22nd regulating and / or controlling connected. In the 2 are exemplary two functional devices 22nd shown. With the functional devices 22nd it can be, for example, an engine control system, a braking system, a steering system, a chassis control or a signal output system.

The driver assistance system 20th has an electronic control device 24 on, with the corresponding electronic control and regulation signals to the functional devices 22nd can be transmitted and / or received and processed by them.

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

Every control and evaluation device 28 is signaling with the control device 24 connected. With the control device 24 can depend on environmental information that comes with the radar systems 12th are determined, driving functions of the motor vehicle 10 controlled / regulated.

It is not essential for the invention whether electrical / electronic control and / or evaluation devices, such as the control device, for example 24 , the control and evaluation devices 28 , an engine control unit of the motor vehicle 10 or the like, integrated in one or more components or component groups or at least partially implemented as decentralized components or component groups.

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

The procedure for determining environmental information from the corresponding surveillance area 14th is shown below using one of the radar systems as an example 12th explained.

With the control and evaluation device 28 becomes the sender 26th driven so that transmit signals 32 in the monitoring area 14th be sent. The broadcast signals 32 are generated, for example, from frequency-modulated continuous wave signals.

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

The one with the recipient 30th received signals 34 are made with appropriate means of the control and evaluation device 28 subjected to a two-dimensional fast Fourier transform. The result of the Fourier transformation results for the transformed received signals 34 an amplitude curve 36 . In the 3 is an example of the amplitude curve in a range gate amplitude diagram 36 shown in the distance gate dimension. The amplitude curve 36 depends on a distance to the reference point.

Target signals emerge from the result of the two-dimensional discrete Fourier transformation 38a of physically existing target objects and their respective amplitudes emerge as peaks. The amplitude curve 36 characterizes the intensity of any target signal 38a or, if in the relevant monitoring area 14th is just noise.

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

To the target signals 38a of physically existing target objects in the amplitude curve 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 shown by way of example as a constant amplitude. The detection threshold 40 can, for example, before commissioning the radar system 12th can be specified and saved for 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 are therefore recognized. From the target signals 38a can be a distance, a speed and / or a direction of the corresponding target objects relative to the reference point of the radar system 12th be determined.

About a free space 42 to determine which is the driving space or parking space for the motor vehicle 10 is suitable in terms of amplitude below the detection threshold 40 a free space threshold 44 given. In the in 3 The embodiment shown is the clearance threshold 44 for example a constant amplitude offset 48 compared to the detection threshold 40 decreased. The amplitude offset 48 is chosen so that the clearance threshold 44 above the noise 50 lies so that noise 50 not mistakenly used as a target signal 38a or 38b is identified.

The amplitude curve 36 becomes with the free space threshold 44 compared. If there are any possible target signals 38b determined whose amplitudes are above the free space threshold 44 and below the detection threshold 40 lie. The possible target signals 38b are for easier differentiation from the target signals mentioned above 38a with the reference number 38b Mistake. The possible target signals 38b can for example result from weak reflections from target objects or from signal noise. Target objects, which are the possible target signals 38b produce, are in the 1 as black dots with the reference symbols 18b Mistake. The possible target signals 38b are compared with the detection threshold 40 not captured because their reflections are too weak. By using the clearance threshold 44 it ensures that even very weak reflections from possible target objects to determine the free space 42 can be used.

The smallest distance 52 , in which the amplitude curve 36 above the free space threshold 44 is called the outer limit 46 of free space 42 Are defined.

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

An inner limit can also be optionally added 54 for the free space 42 can be specified. This is in the 1 for example with the free space 42 shown with the one in the direction of travel 16 front left radar system 12th is determined. The inner limit 54 can the close range of the radar system 12th , for example at distances of about 20 cm to 50 cm from the radar system 12th , leave out. In this area, for example, the bumper of the vehicle 10 be arranged which is incorrectly considered relative to the motor vehicle 10 static object would be detected.

Claims (12)

Method for determining at least one free space (42) in a monitoring area (14) of a distance measuring device (12), in particular a vehicle (10) - in which transmission signals (32) are sent into the monitoring area (14), - receiving signals (34) from the monitoring area (14) are received - and environmental information is determined from the received signals (34), 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), which is based on distances from a Reference range of the distance measuring device (12) is dependent, - the amplitude curve (36) is compared in amplitude with a free space threshold (44) which is set or specified in amplitude below a predeterminable detection threshold (40) for determining target signals (38a), - with the smallest Distance (52) in which the amplitude curve (36) amplit udeniform above the free space threshold (44), an outer boundary (46) of the at least one free space (42) is defined. Procedure according to Claim 1 , characterized in that the free space threshold (44) is set as a function of a noise (50) of the amplitude curve (36). Procedure according to Claim 1 or 2 , characterized in that the clearance threshold (44) is set or specified with an offset function (48) based on the detection threshold (40). Procedure according to Claim 3 , characterized in that an offset function (48) is constantly specified or set over at least part of the amplitude curve (36) and / or is variably specified or set at least over part of the amplitude curve. Procedure according to Claim 3 or 4th , characterized in that an offset function (48) is specified or set constant or variable in amplitude at least over part of the amplitude curve (36) and / or is specified or set constant or variable over time at least over part of the amplitude curve (36). Method according to one of the preceding claims, characterized in that at least one free space (42) is defined as a spatially one-dimensional path, as a two-dimensional area or as a three-dimensional volume. Method according to one of the preceding claims, characterized in that distances, directions and / or speeds of any objects (18) relative to the reference area of the distance measuring system (12) are determined from the environmental information. Method according to one of the preceding claims, characterized in that at least one radar system (12), a LiDAR system, an ultrasound system or some other type of distance measuring system is used to determine the environmental information. Method according to one of the preceding claims, characterized in that the information about the surroundings is determined from the received signals (34) with the aid of at least one Fourier transformation. Method according to one of the preceding claims, characterized in that an inner limit (54) of the free space (42) is additionally specified or set. Distance measuring device (12) for monitoring a monitoring area (14), in particular of a vehicle (10), for objects (18), the distance measuring device (12) having 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), - the at least one control and / or evaluation device (28) having means for determining at least one free space (42) in the monitoring area (14) from the received signals (34), thereby characterized in that the control and / or evaluation device (28) has means for carrying out the method according to one of the preceding claims. A driver assistance system of a vehicle (10) having at least one distance measuring device (12) - 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 determining environmental information from a monitoring area (14), the at least one distance measuring device (12) having at least a transmitter (26) for sending transmission signals (32) into the monitoring area (14), - at least one receiver (30) for receiving reception 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), - the at least one control and / or evaluation device (28) having 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) has means for performing the method according to one of the Claims 1 to 10 .

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