Method for determining distances of objects captured by at least one camera using at least one time-to-collision

Abstract

A method (28) for determining distances (d) of objects relative to at least one predetermined reference point is described. In the method (28), at least one object is at least partially detected using at least one camera, in particular at least one vehicle camera of a vehicle. At least one distance (d) of at least part of the at least one detected object relative to the at least one reference point is determined using object data (BD t1 , BD t2 , BD t3 ) of at least one detected object is determined. At least one time-to-collision value (TTC post(t2) , TTC pre(t2) ) is carried out using at least part of the object data (BD t1 , BD t2 , BD t3 ) is determined. At least one change in velocity (Δv(t3, t1)) of the camera, in particular at least one change in speed of the vehicle, is determined. The at least one distance (d) of the at least part of the detected object (22) relative to the at least one reference point (26) is determined using the at least one time-to-collision variable (TTC post(t2) , TTC pre(t2) ) and at least one change in speed (Δv(t 3, t1)) of the camera, in particular the at least one speed change of the vehicle (10).

Description

Technical FieldThe invention relates to a method for determining distances of objects relative to at least one predefined reference point, in which at least one object is detected at least partially using at least one camera, in particular at least one vehicle camera of a vehicle, and at least one distance of at least one part of the at least one detected object relative to the at least one reference point is determined using object data of the at least one detected object determined using the at least one camera, in particular the at least one vehicle camera.The invention further relates to a camera, in particular a vehicle camera for a vehicle, which has at least one part of means for carrying out a method for determining distances of objects relative to at least one predefined reference point.Furthermore, the invention relates to a driver assistance system having at least one vehicle camera, which has at least one part of means for carrying out a method for determining distances of objects relative to at least one predefined reference point.The invention also relates to a vehicle having at least one vehicle camera, which has at least one part of means for carrying out a method for determining distances of objects relative to at least one predefined reference point.Prior ArtUS 2014 / 0324297 A1 discloses a collision avoidance apparatus for a vehicle. The collision avoidance device includes a measurement unit, a vehicle speed sensor, a yaw rate sensor, a steering angle sensor, an electronic control unit, and an actuator. The measurement unit is configured to measure the movement of an obstacle (e.g., an oncoming vehicle) located in front of or behind the vehicle. A radar device can be used as the measuring unit. In addition, cameras can also be used as the measuring unit. When an obstacle in front of the vehicle is detected, the measurement unit calculates a distance between the vehicle and the obstacle and a relative speed of the vehicle with respect to the obstacle, and transmits the calculated distance to the electronic control unit.The object of the invention is to design a method, a camera, in particular a vehicle camera, a driver assistance system and a vehicle of the type mentioned at the beginning, in which the determination of distances can be carried out more efficiently with available data, in particular object data determined with the camera, in particular the vehicle camera.Disclosure of the InventionAccording to the invention, the object is achieved in the method in that at least one time-to-collision variable is determined using at least a part of the object data determined with the camera, in particular the vehicle camera, at least one speed change of the camera, in particular at least one speed change of the vehicle, is determined, and the at least one distance of the at least one part of the detected object relative to the at least one reference point is determined using the at least one time-to-collision variable and the at least one speed change of the camera, in particular the at least one speed change of the vehicle.According to the invention, the at least one time-to-collision variable and the at least one speed change are used to determine the at least one distance. The at least one time-to-collision variable is determined using object data that are determined with a camera, in particular the vehicle camera. In this way, no separate distance measurement is required for determining the at least one distance. The distance can thus be ascertained efficiently using the data present from the at least one camera, in particular the at least one vehicle camera. From object data which are determined with the vehicle camera, in particular, time-to-collision variables can be determined very accurately.The camera, in particular the vehicle camera, can be arranged on or in a vehicle. Scenes in a monitored zone can be optically captured by the camera, in particular the vehicle camera. Advantageously, the camera, in particular the vehicle camera, can have an image recording device, in particular a camera chip. In this way, objects in the monitored zone can be optically detected.The time-to-collision is known to be the time until the camera, in particular the vehicle, collides with the at least one object. The time-to-collision can also be abbreviated as "TTC".Advantageously, the camera, in particular the vehicle camera, can be oriented in the direction of travel of the vehicle. In this way, a monitoring area in front of the vehicle in the direction of travel can be monitored for objects, in particular other vehicles. Alternatively or additionally, at least one camera, in particular at least one vehicle camera, can be oriented differently. In this way, monitoring areas can also be monitored next to or behind the vehicle.Advantageously, the distance can be the minimum distance of the at least one detected object relative to the at least one reference point. Advantageously, the distance of the part of the at least one object closest to the at least one reference point can be determined. In this way, time-to-collision quantities for the collision of the vehicle with the closest parts of the object can be determined.Advantageously, the at least one reference point can be predefined with respect to the at least one camera, in particular the at least one vehicle camera, and / or with respect to the vehicle. In this way, the at least one distance can be specified with respect to the camera, in particular the vehicle camera, or with respect to the vehicle.Advantageously, the at least one reference point can lie in a camera chip of the camera, in particular of the vehicle camera. Alternatively or additionally, the at least one reference point can lie in an origin of a coordinate system of the camera, in particular of the vehicle camera. In this way, the at least one distance can be determined directly with respect to the camera chip or to the origin of the coordinate system.Alternatively or additionally, the at least one reference point can lie in an origin of a coordinate system of the vehicle. In this way, the at least one distance may be more easily used for autonomous or semi-autonomous control of the driving functions of the vehicle.The invention can be used in connection with vehicle cameras of vehicles. An essential functional feature of a vehicle is its ability to move. Vehicles may be motor vehicles. The invention can advantageously be used in land vehicles, in particular passenger cars, trucks, buses, motor cycles, drones, mobile robots, mobile machines, in particular construction or transport machines, such as cranes, excavators or the like, aircrafts, in particular flying drones, and / or (sub) water drones, in particular (sub) water drones. The invention may also be used with vehicles that may be operated autonomously or semi-autonomously. However, the invention is not limited to vehicles. It can also be used in stationary operation, in particular in road traffic, for example traffic monitoring or the like.The camera, in particular the vehicle camera, can be used for detecting stationary or moving objects, in particular vehicles, persons, animals, plants, obstacles, ground, lanes, unevenness in the lane, in particular pinholes or stones, lane boundaries, (lane) markings, (traffic) signs, free spaces, in particular parking spaces, precipitation or the like, and / or movements and / or gestures.In an advantageous embodiment of the method, at least two time-to-collision variables at different times can be used to determine the at least one distance. In this way, a change in the time-to-collision variable can be used for determining the at least one distance. Thus, the at least one distance can be determined more accurately.In a further advantageous embodiment of the method, the at least one change in speed can be determined between two times, in particular between times at which a time-to-collision variable is determined in each case, and / or the at least one change in speed can be determined by means of at least one path length measurement.The determination of the at least one speed change between two points in time enables the determination of an average speed change. The determination of the at least one speed change between points in time at which a time-to-collision variable is determined in each case makes it possible to assign the speed change to the corresponding time-to-collision variables.The change in speed can be determined very accurately by means of path length measurements.Advantageously, the change in speed can be determined using path length measuring devices of the vehicle. In this way, devices present in any case in the vehicle, in particular speed sensors or the like, can be used. The speed change can advantageously also be determined by means of the camera, in particular the vehicle camera. In this way, it is possible to reduce the outlay on required apparatuses.In a further advantageous embodiment of the method, at least one time-to-collision variable can be a time-to-collision and / or at least one time-to-collision variable can be an inverse time-to-collision.The use of the time-to-collision as the time-to-collision variable can be effected directly without further conversion.By using the inverse time-to-collision as the time-to-collision quantity, the at least one distance can be calculated more easily. Thus, in particular, division by zero can be avoided in the calculation of the at least one distance.In a further advantageous embodiment of the method, the at least one distance of at least a part of the detected object can be determined from a product with the speed change and a quotient which, as divisor, comprises a difference of a minuend which contains a time-to-collision variable before a defined point in time and a subtrahend which contains a time-to-collision variable after the defined point in time. In this way, the distance of the at least one part of the object can be calculated by means of algorithms from the speed change and the time-to-collision variables.Advantageously, the defined time can be defined on the basis of the measurements with the camera, in particular the vehicle camera. In this way, a correlation can be established between the definition of the time-to-collision variables and the image acquisition with the camera, in particular the vehicle camera.In a further advantageous embodiment of the method, the minuend may contain the inverse time-to-collision before the defined time and the subtrahend may contain the inverse time-to-collision after the defined time or the minuend may contain the time-to-collision before the defined time and the subtrahend may contain the time-to-collision after the defined time. In this way, a change in the time-to-collision or the inverse time-to-collision before the defined time and after the defined time can be taken into account for determining the distance of the at least one part of the object. Thus, the distance of at least a portion of the object can be determined more accurately.In a further advantageous embodiment of the method, the subtrahend can be a product with a scaling factor of the camera, in particular of the vehicle camera. In this way, properties of a receiving device, in particular of a camera chip, of the camera, in particular of the vehicle camera, can be additionally taken into account. In this way, the accuracy in determining the distance of the at least part of the object can be further improved.In a further advantageous embodiment of the method, the quotient can contain as a dividend a time interval with the defined point in time. In this way, the duration of the time interval which contains the defined time can additionally be taken into account. Thus, the accuracy of determining the distance of the at least part of the object can be further improved.Advantageously, the at least one distance can be calculated from the times-to-collision as time-to-collision variables according to the following formula: wherein d is the distance, Δv(t 3, t 1) the speed change between an earlier point in time t 1 before the defined point in time t 2 and a later point in time t 3 after the defined point in time t 2, TTC post(t2) the time-to-collision as time-to-collision variable after the defined point in time t 2, ttc_ner 9_die Time-To-Collision as Time-To-Collision variable before the defined time t 2 and S c,post(t2) are a scaling factor of the camera, in particular of the vehicle camera, after the defined time t 2.In this case, S c,post(t2) is the relative change in size of the object in the image of the camera with respect to the time between the defined time t 2 and the later time t 3, that is to say after the defined time t 2. The index "c" refers to the camera (camera), in particular vehicle camera.Advantageously, the speed change Δv(t 3, t 1) can be determined in the direction perpendicular to an image plane of the camera, in particular of the vehicle camera. In this way, a mounting direction of the camera, in particular the installation direction of the vehicle camera in a vehicle, can also be taken into account. Accordingly, the distance d is determined in the direction perpendicular to the image plane of the camera, in particular of the vehicle camera. The image plane of the camera, in particular of the vehicle camera, can be predefined in particular by the plane of a camera chip of the camera, in particular of the vehicle camera.Alternatively, the at least one distance can advantageously be calculated using the following inverse times-to-collision as time-to-collision variables:Where d is the distance, Δv(t 3, t 1) the change in speed between the earlier time t 1 and the later time t 3, invTT post(t2) the inverse time-to-collision as the time-to-collision variable after the defined time t 2, invTT pre(t2) the inverse time-to-collision as the time-to-collision variable before the defined time t 2, and S c,post(t2) the scaling factor of the camera, in particular of the vehicle camera. In this way, in the difference, divisions by zero can be avoided.In a further advantageous embodiment of the method, the change in speed of the camera, in particular the change in speed of the vehicle, can be determined by means of at least one path length measurement, in particular by means of at least one path length measurement between at least two points in time at which in each case at least one time-to-collision variable is determined. In this way, the speed change can be assigned to a time interval between the at least two points in time. Thus, the determination of the distance of the object can be further improved.The speed change can advantageously be determined by means of at least one path length measurement between at least two times at which at least one time-to-collision variable is determined in each case. In this way, the speed change can be better assigned to the time-to-collision variables.In a further advantageous embodiment of the method, the at least one time-to-collision variable can be determined from at least one rate of change of an image variable of at least a part of the object captured by the camera, in particular the vehicle camera. In this way, the at least one time-to-collision variable can be determined directly from image data of the detected object.Advantageously, in order to determine a rate of change of an image size of at least part of the captured object, a plurality of prominent points of the captured object image can be tracked over a plurality of image sequences (frames). In this way, the rate of change can be determined more efficiently.Advantageously, at least one scale-invariant feature transformation can be carried out for determining distinctive points. In this way, the prominent points can be determined by means of an algorithm. A scale-invariant feature transformation is referred to in English as a scale-invariant feature transformation (SIFT).In a further advantageous embodiment of the method, at least one sequential Monte Carlo method, in particular a Kalman filter or the like, and / or at least one scale-invariant feature transformation can be used to determine the at least one time-to-collision variable. In this way, statistical fluctuations, in particular noise, can be compensated for during the detection of the at least one object using the camera, in particular the vehicle camera. Thus, the accuracy of the at least one time-to-collision variable can be improved. This leads to an improvement in the determination of the distance from objects.Furthermore, the object is achieved according to the invention in the case of the camera, in particular the vehicle camera, in that the camera, in particular the vehicle camera, has at least some of means for carrying out the method according to the invention.Advantageously, the means for carrying out the method for determining distances of objects can have at least one optical receiving device, in particular at least one camera chip. The optical receiving device can be used to determine image data which characterize a scene optically captured by the vehicle camera. If an object is located in the scene, the image data contains object data. Object data is image data relating to the detected object. These can be, in particular, image sizes which characterize the extent of at least a part of the detected object.Furthermore, the means for carrying out the method comprise at least one processing device, in particular an electronic processing device, such as a processor, for processing the image data. In this way, further information and data can be obtained from the image data. Advantageously, the electronic processing device can have at least one processor. Algorithms, in particular software programs, can be executed with a processor.Furthermore, the means for carrying out the method can have algorithms, in particular software programs, databases and the like. The algorithms can be used to process the image data, in particular the object data. In particular, the time-to-collision variables can thus be determined. Further, the time-to-collision quantities may be processed in conjunction with the speed changes.Advantageously, the means for carrying out the method can be implemented by software and / or hardware. By software, the method can be more easily integrated into already existing hardware, such as processors or the like.Furthermore, the object is achieved according to the invention in the driver assistance system in that the driver assistance system has at least one part of means for carrying out the method according to the invention.The driver assistance system has at least one vehicle camera. At least one monitoring area in the vicinity of the vehicle and / or within the vehicle can be monitored by the at least one vehicle camera. In this case, image data characterizing a scene in the monitored zone can be determined using the at least one vehicle camera.The driver assistance system has at least some of the means for carrying out the method according to the invention. Advantageously, at least one vehicle camera of the vehicle can have at least a part of the means for carrying out the method according to the invention. Since the at least one vehicle camera is part of the driver assistance system, the part of the means of the at least one vehicle camera for carrying out the method according to the invention is therefore also part of the driver assistance system, that is to say also part of the means of the driver assistance system for carrying out the method according to the invention.Advantageously, the at least one part of the means for carrying out the method according to the invention can be realized exclusively in the at least one vehicle camera. Alternatively, the at least one part of the means for carrying out the method according to the invention can be realized in the driver assistance system, but outside the at least one vehicle camera. Alternatively, at least a part of the means for carrying out the method according to the invention can be implemented in the at least one vehicle camera and a part of the means for carrying out the method according to the invention can be implemented in the driver assistance system outside the at least one vehicle camera.The explanation in the last two paragraphs applies accordingly to the vehicle which has at least one driver assistance system and / or at least one vehicle camera. The means of the at least one driver assistance system and / or the at least one camera are accordingly part of the means of the vehicle.Furthermore, the driver assistance system can have at least one control unit. With the at least one control unit, functions of the driver assistance system and or of the at least one vehicle camera and / or of the vehicle, in particular driving functions, can be controlled autonomously or semi-autonomously. Image data, in particular object data, obtained with the at least one vehicle camera can be transmitted to the at least one control unit. In this way, the functions of the vehicle camera and / or of the vehicle can be controlled using the data obtained with the at least one vehicle camera.In addition, the object is achieved in the case of the vehicle according to the invention in that the vehicle has at least some of means for carrying out the method according to the invention.The vehicle has at least one vehicle camera. At least one monitoring area in the environment of the vehicle and / or within the vehicle can be monitored by the vehicle camera.The vehicle may advantageously have at least one driver assistance system. The at least one vehicle camera can be part of the at least one driver assistance system or can be implemented separately therefrom. With the driver assistance system, functions of the vehicle, in particular driving functions, can be operated autonomously or semi-autonomously. Data obtained with the at least one vehicle camera can be used with the driver assistance system.Moreover, the features and advantages shown in connection with the method according to the invention, the vehicle camera according to the invention, the driver assistance system according to the invention and the vehicle according to the invention and their respective advantageous embodiments apply correspondingly and vice versa. The individual features and advantages can of course be combined with one another, wherein further advantageous effects can be obtained which go beyond the sum of the individual effects.Brief Description of the DrawingsFurther advantages, features and details of the invention will become apparent from the following description in which exemplary embodiments of the invention are explained in more detail with reference to the drawings. The person skilled in the art will expediently also consider the features disclosed in the drawing, the description and the claims in combination individually and summarize them to form meaningful further combinations. They show schematically FIG. 1 shows a vehicle having a driver assistance system, which has a vehicle camera, a control unit and a path length measuring device; FIG. 2 shows a flow diagram of a method according to a first exemplary embodiment for determining the distance of an object detected with the vehicle camera from FIG. 1 ; FIG. 3 shows a flow diagram of a method according to a second exemplary embodiment for determining the distance of an object detected with the vehicle camera from FIG. 1 ;In the figures, identical components are provided with identical reference numerals.Embodiment(s) of the InventionFIG. 1 shows a vehicle 10 in the form of a passenger car in a side view. The vehicle 10 has a driver assistance system 12. The driver assistance system 12 comprises, by way of example, a vehicle camera 14, a control unit 16 and a path length measuring device 30.The vehicle camera 14 is configured as a so-called window camera. The in-vehicle camera 14 is disposed on the inner side of the windshield of the vehicle 10. The vehicle camera 14 is directed into a monitoring area 18. The monitoring region 18 is located in front of the vehicle 10 in the direction of travel 20 of the vehicle 10. A plurality of vehicle cameras 14 can also be arranged at different locations and / or with different alignments on the vehicle 10.A scene in the monitored zone 18 can be optically captured by the vehicle camera 14. For example, objects 22 which are located in the monitoring region 18 can be optically detected. In this case, light reflected at the object 22 is received by a camera chip of the vehicle camera 14. FIG. 1 shows an example of an object 22 onto which the vehicle 10 is driving.The vehicle camera 14 is connected to the control unit 16 for the purposes of data transmission and control. Data which are obtained with the vehicle camera 14 can be transmitted to the control unit 16 via the connection.The data obtained with the vehicle camera 14 and transmitted to the control unit 16 can be object data, such as distances d from objects 22 detected with the vehicle camera 14 to a predefined reference point 26.The predefined reference point 26 can be located, for example, in the coordinate system of the camera chip of the vehicle camera 14. Alternatively, the reference point 26 may be located at the origin of a vehicle coordinate system of the vehicle 10 and / or of the vehicle camera 14.The distance d is the minimum distance of the object 22 optically captured with the vehicle camera 14-provided this is completely captured-or of the captured part of the object 22 relative to the reference point 26.Functions, for example driving functions, of the vehicle 10 can also be controlled autonomously or semi-autonomously using the data obtained and transmitted by the vehicle camera 16 using the control unit 16.The vehicle 10 has means for carrying out a method 28 for determining distances d from objects 22 to the reference point 26.By way of example, all means for carrying out method 28 are implemented as part of vehicle camera 14. The means are implemented in software and hardware. The means for carrying out the method can comprise, inter alia, the camera chip of the vehicle camera 14, electronic processing devices, such as, for example, one or more processors, electronic storage media, such as, for example, memory chips, analog-to-digital converters, software programs, control and evaluation devices and interfaces for connections to other devices of the vehicle 10, for example to the control unit 16 and the path length measuring device 30.For example, the path length measuring device 30 of the vehicle 10 is connected via an interface of the vehicle camera 14. With the path length measuring device 30, measurements of the path travelled by the vehicle 10 can be carried out.Alternatively, a part of the means for carrying out the method 28 can also be implemented outside the vehicle camera 14, for example in the control unit 16 and / or another device of the vehicle 10.Method 28 for determining distance d according to a first exemplary embodiment is explained below with reference to a flow chart shown in FIG. 2.In a measurement step 32, a camera measurement is carried out with the vehicle camera 14 at three different successive points in time t 1, t 2 and t 3 in each case. In this case, the first time t 1 is before the second time t 2 and the third time t 3 is after the second time t 2. The entire measurement time interval can be defined via the second time t 2 so that the second time t 2 can also be referred to as a "defined time.".If an object 22 is located in the monitoring area 18, the image data BD t1 for the time t 1, the image data BD t2 for the time t 2 and the image data BD t3 for the time t 3 are determined for the detected object 22. The image data BD t1, BD t2 and BD t3 are, for example, measurement data which characterize the respective image of the object 22, which is imaged onto the camera chip at the corresponding points in time t 1, t 2 and t 3 respectively.In a collision determination step 34, a time-to-collision TTC pre(t2) before the second time t 2 and a time-to-collision TTC post(t2) after the second time t 2 are determined from the image data BD t1, BD t2 and BD t3 and the corresponding ratios of the times t 1, t 2 and t 3 respectively. The time-to-collision TTC pre(t2) and the time-to-collision TTC post(t2) are time-to-collision quantities, respectively.To determine the time-to-collision TTC pre(t2) and the time-to-collision TTC post(t2) a sequential Monte Carlo method, for example a Kalman filter, and / or scale-invariant feature transformation can be carried out, for example.The time-to-collision TTC pre(t2) and the time-to-collision TTC post(t2) are calculated by way of example according to the following formulae:In this case, S c( t 1, t 2) is the scaling factor of the vehicle camera 10 in the time interval between the first time t 1 and the second time t 2. S c( t 2, t 3) is the scaling factor of the vehicle camera 10 in the time interval between the second time t 2 and the third time t 3. The scaling factors S c can be determined, for example, from the image sizes of the image of the object 22, which is recorded with the camera chip, at the corresponding points in time t 1 and t 2 or t 2 and t 3 respectively.With a path length measurement 36 with the aid of the path length measuring device 30, the path length covered by the vehicle 10 between the first time t 1 and the third time t 3 is determined. The path length measurement 36 can be carried out parallel to the measurement step 32.In a step 38, a change in speed Δv(t 3, t 1) of the vehicle camera 14 between the first time t 1 and the third time t 3 is determined from the data of the path length measurement 36.The change in speed Δv(t 3, t 1) is determined, for example, in the direction perpendicular to an image plane of the vehicle camera 14. Accordingly, the distance d is determined in the direction perpendicular to the image plane of the vehicle camera 14. The image plane of the vehicle camera 14 is predefined, for example, by the plane of the camera chip of the vehicle camera 14. If the image plane of the vehicle camera 14 extends in the direction of travel 20 of the vehicle 10, the change in speed Δv(t 3, t 1) can also be determined from a change in speed of the vehicle 10. In this case, the speed change of the vehicle 10 may also be directly used as the speed change Δv(t 3, t 1) of the in-vehicle camera 14.The change in speed Δv(t 3, t 1) and the time-to-collision TTC pre(t2) before the defined second time t 2 and the time-to-collision TTC post(t2) after the defined second time t 2 are fed to a distance calculation step 40. In the distance calculation step 40, the distance d is calculated according to the following formula:According to this formula, the distance d is calculated from a product with the speed change Δv(t 3, t 1), namely half the speed change Δv(t 3, t 1), and a quotient which contains as divisor a difference of a minuend which contains the time-to-collision TTC post(t2) before the defined second time t 2, namely the reciprocal of the time-to-collision TTC post(t2), and a subtrahend which contains the time-to-collision TTC pre(t2) after the defined second time t 2, namely, the reciprocal of the time-to-collision TTC pre(t2), is determined. The subtrahend is a product with the scaling factor S c,post(t2) of the vehicle camera 14, namely the product of the time-to-collision TTC pre(t2) and the scaling factor S c,post(t2) after the defined second time t 2. The quotient contains as a dividend the time interval (t 3- t 1) with the defined second time t 2.The distance d is transmitted to the control unit 16 of the driver assistance system 12. The controller 16 uses the distance d to autonomously or semi-autonomously operate the driving functions of the vehicle 10.FIG. 3 shows the method 28 for determining the distance d according to a second exemplary embodiment. Those elements which are similar to those of the first embodiment of FIG. 2 are provided with the same reference numerals. In contrast to the first exemplary embodiment from FIG. 2, in the second exemplary embodiment, in the collision determination step 34, instead of the time-to-collision TTC pre(t2) before the defined second time t 2 and the time-to-collision TTC post(t2) after the defined second time t 2 the inverse time-to-collision invTT pre(t2) before the defined second time t 2 and the inverse time-to-collision invTT post(t2) after the defined second time t 2 are determined. The inverse time-to-collision invTT pre(t2) and the inverse time-to-collision invTT post(t2) are time-to-collision quantities, respectively.The following relationship exists between the respective time-to-collision TTC, which is used in the first exemplary embodiment according to FIG. 2, and the corresponding inverse time-to-collision invTT:In the distance calculating step 40, the distance d is calculated according to the following formula:According to this formula, the distance d is determined from a product with the speed change Δv(t 3, t 1), namely half the speed change Δv(t 3, t 1), and a quotient which contains as divisor a difference of a minuend which contains the inverse time-to-collision invTT post(t2) before the defined second time t 2 and a subtrahend which contains the inverse time-to-collision invTT pre(t2) after the defined second time t 2. The subtrahend is a product with the scaling factor S c( t 2, t 3) of the vehicle camera 14, namely the product of the inverse time-to-collision invTT pre(t2) after the defined second time t 2 and the scaling factor S c( t 2, t 3). The quotient contains as a dividend the time interval (t 3- t 1) with the defined second time t 2.In the described exemplary embodiments of the method 28, the change in speed Δv(t 3, t 1) can also be determined in another manner instead of using a path length measurement by means of the path length measuring device 30. For example, means of the vehicle camera 14 can also be used to determine the speed change Δv(t 3, t 1).References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedUS 2014 / 0324297 A1

[0005]

Claims

Method (28) for determining distances (d) of objects (22) relative to at least one predetermined reference point (26), in which at least one object (22) is detected at least partially using at least one camera (14), in particular at least one vehicle camera (14) of a vehicle (10), and at least one distance (d) of at least one part of the at least one detected object (22) relative to the at least one reference point (26) is determined using object data (BD t1, BD t2, BD t3) of the at least one detected object (22) determined using the at least one camera (14), in particular the at least one vehicle camera (14), characterized in that at least one time-to-collision variable (TTC post(t2), TTC pre(t2); invTT post(t2), invTT p-re(t2)) is determined using at least a part of the object data (BD t1, BD t2, BD t3) determined with camera (14), in particular with the vehicle camera (14), at least one change in speed (Δv(t 3, t 1)) of the camera (14), in particular at least one change in speed (Δv(t 3, t 1)) of the vehicle (10), and the at least one distance (d) of the at least one part of the detected object (22) relative to the at least one reference point (26) is determined using the at least one time-to-collision variable (TTC post(t2), TTC pre(t2); invTT post(t2), invTT p-re(t2)) and the at least one change in speed (Δv(t 3, t 1)) of the camera (14), in particular the at least one change in speed (Δv(t 3, t 1)) of the vehicle (10).Method according to Claim 1, characterized in that at least two time-to-collision variables (TTC post(t2), TTC pre(t2); invTT post(t2), invTT pre(t2)) at different times (t 1, t 3) are used to determine the at least one distance (d).Method according to Claim 1 or 2, characterized in that the at least one change in speed (Δv(t 3, t 1)) between two times (t 1, t 3), in particular between times at which a time-to-collision variable (TTC post(t2), TTC pre(t2); invTT post(t2), invTT pre(t2)) is determined in each case, is determined, and / or the at least one change in speed (Δv(t 3, t 1)) is determined by means of at least one path length measurement (36).Method according to one of the preceding claims, characterized in that at least one time-to-collision variable (TTC post(t2), TTC pre(t2)) is a time-to-collision and / or at least one time-to-collision variable (invTT post(t2), invTT pre(t2)) is an inverse time-to-collision.Method according to one of the preceding claims, characterized in that the at least one distance (d) of at least part of the detected object (22) consists of a product with the speed change (Δv(t 3, t 1)) and a quotient which contains as divisor a difference of a minuend which contains a time-to-collision variable (TTC post(t2); invTT post(t2)) before a defined time (t 2) and a subtrahend which contains a time-to-collision variable (TTC pre(t2); invTT pre(t2)) after the defined time (t contains 2).Method according to claim 5, characterised in that, wherein the inverse time-to-collision (invTT post(t2)) is contained in the minuend before the defined time instant (t 2) and the inverse time-to-collision (invTT pre(t2)) is contained in the subtrahend after the defined time instant (t 2) or the time-to-collision (TTC post(t2)) is contained in the minuend before the defined time instant (t 2) and the time-to-collision (TTC pre(t2)) is contained in the subtrahend after the defined time instant (t 2).Method according to Claim 5 or 6, characterized in that the subtrahend is a product with a scaling factor (S c) of the camera (14), in particular of the vehicle camera (14).Method according to one of Claims 5 to 7, characterized in that the quotient contains as a dividend a time interval (t 3- t 1) with the defined time (t 2).Method according to one of the preceding claims, characterized in that the change in speed (Δv(t 3, t 1)) of the camera (14), in particular the change in speed (Δv(t 3, t 1)) of the vehicle (10), is determined by means of at least one path length measurement (36), in particular by means of at least one path length measurement (36) between at least two points in time (t 1, t 3), at which in each case at least one time-to-collision variable (TTC post(t2), TTC pre(t2); invTT post(t2), invTT pre(t2)) is determined.Method according to one of the preceding claims, characterized in that the at least one time-to-collision variable (TTC post(t2), TTC pre(t2); invTT post(t2), invTT pre(t2)) is determined from at least one rate of change of an image size of at least part of the object (22) captured by the camera (14), in particular the vehicle camera (14).Method according to one of the preceding claims, characterized in that at least one sequential Monte Carlo method, in particular a Kalman filter or the like, and / or at least one scale-invariant feature transformation is used for determining the at least one time-to-collision variable (TTC post(t2), TTC pre(t2); invTT post(t2), invTT pre(t2)).Camera, in particular a vehicle camera (14) for a vehicle (10), which has at least one part of means for carrying out a method (28) for determining distances (d) of objects (22) relative to at least one predefined reference point (26), characterized in that the camera (14), in particular the vehicle camera (14), has at least one part of means for carrying out the method (28) according to one of Claims 1 to 11.Driver assistance system (12) having at least one vehicle camera (14) which has at least some of means for carrying out a method (28) for determining distances (d) of objects (22) relative to at least one predefined reference point (26), characterized in that the driver assistance system (12) has at least some of means for carrying out the method (28) according to one of Claims 1 to 11.Vehicle (10) having at least one vehicle camera (14) which has at least one part of means for carrying out a method (28) for determining distances (d) of objects (22) relative to at least one predefined reference point (26), characterized in that the vehicle (10) has at least one part of means for carrying out the method (28) according to one of Claims 1 to 11.

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