CN114575685B

CN114575685B - Automobile door handle false touch prevention method and system based on vision

Info

Publication number: CN114575685B
Application number: CN202210244816.3A
Authority: CN
Inventors: 陈立里; 袁丹寿; 张祺
Original assignee: Hozon New Energy Automobile Co Ltd
Current assignee: Hozon New Energy Automobile Co Ltd
Priority date: 2022-03-14
Filing date: 2022-03-14
Publication date: 2023-05-16
Anticipated expiration: 2042-03-14
Also published as: CN114575685A

Abstract

The invention provides a vision-based automobile door handle false touch prevention method and system. The false touch prevention method comprises the following steps: collecting an analysis image of a user in the vehicle through a camera in the vehicle, wherein the analysis image comprises an image of the palm of the user; determining a first position of a palm of a user in an automobile space according to the analysis image or parameters of the analysis image and an in-automobile camera; acquiring a second position of the automobile door handle in the automobile inner space; determining a spatial distance d between the second location and the first location within the automotive space; and monitoring the relation between the space distance D and the threshold D, and executing the false touch prevention reaction operation when the space distance D is smaller than the threshold D. The vision-based automobile door handle false touch prevention method and system can intelligently judge the situation that the door handle is touched by mistake in the environment in the automobile and make corresponding reactions, and improve the intelligent and safety of automobile use.

Description

Automobile door handle false touch prevention method and system based on vision

Technical Field

The invention mainly relates to the field of automobile intelligence, in particular to a vision-based automobile door handle false touch prevention method and system.

Background

Although in the prior art, automatic locking of a door handle of an automobile in a driving process is a common safety guarantee measure, the door handle of the automobile is not automatically locked after the automobile is started aiming at some special automobile types, or the automatic locking of the door handle is not very effective or has an obstacle in application in combination with other intelligent operation designs in the automobile because of the limitation of some use scenes.

In addition, aiming at some special in-car users such as young children, the phenomenon that the door handle is tampered with due to curiosity often exists in the running process of the car, and if the car is not yet unlocked for automatic locking or fails in the automatic locking process, hidden danger is brought to the safety of passengers in the car. Therefore, the door handle safety problem in the automobile driving process is still not intelligent enough and perfect enough by comprehensively considering all automobile types and applicable scenes of different users.

Disclosure of Invention

The invention aims to solve the technical problem of providing a vision-based automobile door handle false touch prevention method and system, which can intelligently judge the condition that a door handle is touched by mistake in an environment in an automobile and make corresponding reactions, thereby improving the intelligent and safety of automobile use.

In order to solve the technical problems, the invention provides an automobile door handle false touch prevention method based on vision, which comprises the following steps:

collecting an analysis image of a user in the vehicle through a camera in the vehicle, wherein the analysis image comprises an image of the palm of the user;

determining a first position of the palm of the user in the automobile space according to the analysis image or parameters of the analysis image and the in-automobile camera;

acquiring a second position of an automobile door handle in the automobile inner space;

determining a spatial distance d between the second location and the first location within the automotive space; and

and monitoring the relation between the space distance D and a threshold D, and executing false touch prevention reaction operation when the space distance D is smaller than the threshold D.

In an embodiment of the present invention, the in-vehicle camera includes a monocular camera or a binocular camera, wherein when the in-vehicle camera is a monocular camera, the first position of the user palm is determined according to the depth of the user palm obtained by the monocular camera and internal parameters and external parameters of the monocular camera; and when the in-vehicle camera is a binocular camera, determining the first position of the palm of the user according to the analysis image.

In one embodiment of the present invention, the vehicle space has a three-dimensional coordinate system including an x-axis, a y-axis, and a z-axis, the first position has coordinates of (x 1, y1, z 1), the second position has coordinates of (x 2, y2, z 2), and the space distance d satisfies the formula

Wherein A, B and C are constants.

In one embodiment of the invention, both B and C are 0.

In an embodiment of the invention, the threshold D ranges between 0 and 50 cm.

In an embodiment of the present invention, the analysis image further includes a facial image of the user, and the method further includes, after collecting the analysis image including the facial image of the user in the vehicle by the in-vehicle camera, determining a user type according to the analysis image, and setting different corresponding thresholds D according to different user types.

In one embodiment of the present invention, the relationship between the spatial distance D and the product d×e of the threshold D and the line of sight factor E is monitored, and when the spatial distance D is smaller than d×e, an anti-false touch reaction operation is performed, and the method further includes obtaining the eyebrow coordinates of the user and determining the visibility theta of the eyes of the user at any moment according to the eyebrow coordinates,

the E is assigned an alpha value when the visibility theta is greater than an upper visibility limit;

the E is assigned beta when the visibility theta is less than a lower visibility limit; and

and when the visibility theta is greater than or equal to the lower visibility limit and less than or equal to the upper visibility limit, the E is ((theta-25)/99 x alpha+ (99- (theta-25))/99 x beta).

In an embodiment of the present invention, when the user type is a first user type, the alpha is set to be a constant 1, and the beta is any constant between more than 1 and less than 10; and when the user type is a second user type, setting the alpha as a constant 1, and setting the beta as any constant greater than 0 and less than 1.

In one embodiment of the invention, the false touch prevention operation includes sounding an alarm and/or locking the automobile door handle.

In order to solve the technical problem, the invention also provides an automobile door handle anti-false touch system based on vision, which comprises: a memory for storing instructions executable by the processor; and the processor is used for executing the instruction to realize the vision-based automobile door handle false touch prevention method.

A computer readable medium storing computer program code which, when executed by a processor, implements the vision-based automotive door handle anti-false touch method described above.

Compared with the prior art, the invention has the following advantages: according to the invention, through an image processing means, the space distance between the palm of a user and the automobile door handle is analyzed, and after the space distance is smaller than a preset threshold value, the automobile door handle can be automatically locked or an alarm can be sent out, so that intelligent false touch prevention of the automobile inner door handle is realized; particularly, after key points are set on the whole body and/or the face of a user in the vehicle, the key points are modeled, so that subsequent judgment errors caused by back and forth vibration in the running process of the vehicle are avoided; in addition, the invention can also set different thresholds for different user types, thereby more pointedly preventing dangerous accidents, providing protection for drivers and in-car users for safe travel and reducing loss of lives and properties.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the invention. In the accompanying drawings:

FIG. 1 is a schematic flow chart of a vision-based anti-false touch method for an automobile door handle according to an embodiment of the invention;

fig. 2 and 3 are schematic diagrams of a vision-based method for preventing an automobile door handle from being touched by mistake according to an embodiment of the present invention; and

fig. 4 is a system block diagram of a vision-based anti-false touch system for an automobile door handle according to an embodiment of the present invention.

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are used in the description of the embodiments will be briefly described below. It is apparent that the drawings in the following description are only some examples or embodiments of the present application, and it is obvious to those skilled in the art that the present application may be applied to other similar situations according to the drawings without inventive effort. Unless otherwise apparent from the context of the language or otherwise specified, like reference numerals in the figures refer to like structures or operations.

As used in this application and in the claims, the terms "a," "an," "the," and/or "the" are not specific to the singular, but may include the plural, unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that the steps and elements are explicitly identified, and they do not constitute an exclusive list, as other steps or elements may be included in a method or apparatus.

The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present application unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

In the description of the present application, it should be understood that, where azimuth terms such as "front, rear, upper, lower, left, right", "transverse, vertical, horizontal", and "top, bottom", etc., indicate azimuth or positional relationships generally based on those shown in the drawings, only for convenience of description and simplification of the description, these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present application; the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In addition, the terms "first", "second", etc. are used to define the components, and are merely for convenience of distinguishing the corresponding components, and unless otherwise stated, the terms have no special meaning, and thus should not be construed as limiting the scope of the present application. Furthermore, although terms used in the present application are selected from publicly known and commonly used terms, some terms mentioned in the specification of the present application may be selected by the applicant at his or her discretion, the detailed meanings of which are described in relevant parts of the description herein. Furthermore, it is required that the present application be understood, not simply by the actual terms used but by the meaning of each term lying within.

It will be understood that when an element is referred to as being "on," "connected to," "coupled to," or "contacting" another element, it can be directly on, connected or coupled to, or contacting the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly on," "directly connected to," "directly coupled to," or "directly contacting" another element, there are no intervening elements present. Likewise, when a first element is referred to as being "electrically contacted" or "electrically coupled" to a second element, there are electrical paths between the first element and the second element that allow current to flow. The electrical path may include a capacitor, a coupled inductor, and/or other components that allow current to flow even without direct contact between conductive components.

Referring to fig. 1, an embodiment of the present invention provides a vision-based method 10 for preventing a door handle from being touched by mistake (hereinafter referred to as "method 10 for preventing a touch by mistake") of an automobile, which can intelligently determine the situation that the door handle is touched by mistake in an environment in an automobile and make a corresponding reaction, thereby improving the intelligence and safety of the use of the automobile. Fig. 1 of the present application uses a flowchart to illustrate operations performed by a system according to embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in order precisely. Rather, the various steps may be processed in reverse order or simultaneously. At the same time, other operations are added to or removed from these processes.

According to fig. 1, the false touch prevention method 10 includes the following steps.

And step 11, acquiring an analysis image of a user in the vehicle through a camera in the vehicle, wherein the analysis image comprises an image of the palm of the user. For example, in order to obtain an image of the palm portion of the user, the position of the camera in the vehicle may be prevented from being at a suitable position in front of the seat of the user in the vehicle, and in practical application, the position of the camera in the vehicle may be selected according to different vehicle types and requirements, which is not limited by the present invention.

Step 12 is to determine a first position of a palm of a user in a vehicle space according to the analysis image or parameters of the analysis image and the in-vehicle camera.

In different embodiments of the invention, the in-vehicle camera comprises a monocular or binocular camera, which means that with different types of cameras the way in which the first position of the user's palm in the vehicle space is obtained in this step 12 may be different. When the in-vehicle camera is a monocular camera, the first position of the user palm needs to be determined according to the depth of the user palm obtained by the monocular camera and the internal parameters and the external parameters of the monocular camera, and the specific determination mode can be executed by referring to the common method of calibrating the monocular camera and acquiring the world coordinates of a certain point in the photographed image in the prior art, and the method is not the focus of the invention and is not expanded in detail here. On the other hand, when the camera in the vehicle is a binocular camera, the first position of the palm of the user can be directly determined according to the analysis image, which means that the binocular camera can be used for easily acquiring the first position of the palm of the user, and the speed of image information processing is increased.

With further reference to FIG. 1, step 13 is to obtain a second position of the door handle within the interior space of the vehicle. As mentioned above, the order of the steps in the anti-false touch method 10 of fig. 1 of the present invention may be changed and adjusted, and in some embodiments of the present invention, the second position of the door handle in the vehicle space obtained in this step 13 may be placed in the first step or configured as a preset parameter in the corresponding module of the vehicle machine that performs the subsequent operation.

Step 14 is determining a spatial distance d between the second location and the first location within the automotive space.

For example, referring to FIG. 2, in some embodiments of the present invention, the vehicle space has a three-dimensional coordinate system including an x-axis, a y-axis, and a z-axis, the first position P1 where the palm is located has coordinates of (x 1, y1, z 1), the second position where the door handle is located has coordinates of (x 2, y2, z 2), and the space distance d satisfies the formula

Wherein A, B and C are constants.

In some embodiments of the present invention, A, B and C may have different values to adapt to different application scenarios. For example, in general, A, B and C can be respectively taken as 1, and then the method is converted into a commonly used method for measuring and calculating the distance between two points in a space. However, in some instances, if considering the usage habits of different users, such as users in the passenger cabin often need to manually open the storage box located in front of the passenger seat during the driving of the automobile, then both B and C are set to 0, and a is set to 1 or other constant greater than zero, which means that in such instances, the distance between the palm and the door handle in the y-axis and z-axis will not affect the measurement of the distance between the palm and the door handle, but only consider the distance between the palm and the door handle in the x-axis, so on. For example, different constant settings may embody different modes of this function, allowing the user to freely choose when turning on this function.

Finally, referring to fig. 1, step 15 is to monitor the relationship between the space distance D and the threshold D, and execute the false touch reaction prevention operation when the space distance D is smaller than the threshold D.

Illustratively, the threshold D may be selected in the range of 0-50 cm, considering the scenario in which the inventive approach is typically applicable. The anti-false touch reaction operation comprises sounding alarm and/or locking the automobile door handle, specifically, sounding alarm can be connected with a loudspeaker in the automobile in a signal mode, locking the door handle can be connected with a mechanical or electrical switch for controlling locking of the door handle in the automobile, and different anti-false touch reaction operations can be correspondingly designed and improved in the automobile according to different requirements in the practical process, so that technical difficulties do not exist in realization.

The method for preventing the false touch described with reference to fig. 1 can intelligently judge the condition that the door handle is touched by mistake in the environment in the automobile and make corresponding reactions, thereby improving the intelligent and safety of the automobile. On this basis, in some embodiments of the present invention, the anti-false touch method of the present invention may also have a more intelligent function. For example, in some instances, the analysis image acquired in step 11 as shown in fig. 1 also contains a facial image of the user. In such an example, the false touch preventing method of the present invention further includes, based on the steps shown in fig. 1, after the step 11 is performed to collect the analysis image including the face image of the user in the vehicle through the in-vehicle camera, determining the user type according to the analysis image, and setting different corresponding thresholds D according to different user types. For example, for dangerous people such as young children who easily touch the car door by mistake, the threshold D can be set to be larger, and for adults, the threshold D can be set to be smaller, so that universality and intelligence of the scheme of the invention are improved.

More preferably, in some embodiments of the present invention, step 15 shown in FIG. 1 may be further optimized. In these embodiments, specifically, the relationship between the spatial distance D and the product d×e of the threshold D and the line of sight factor E is monitored, and when the spatial distance D is smaller than d×e, the false touch reaction preventing operation is performed. In particular, the line-of-sight factor E can be understood as a correction parameter for the threshold value D. In such an example, the false touch preventing method further includes the step of acquiring the eyebrow coordinates of the user and determining the visibility theta of the user's eyes at any time according to the eyebrow coordinates. Wherein E is assigned an alpha value when the visibility theta is greater than the upper visibility limit; e is assigned beta when the visibility theta is less than the lower visibility limit; and when the visibility theta is greater than or equal to the lower visibility limit and less than or equal to the upper visibility limit E is ((theta-25)/99 x alpha+ (99- (theta-25))/99 x beta).

More specifically, as shown in fig. 3, a schematic diagram of an embodiment of the present invention using a line of sight factor E is shown. According to fig. 3, the normal angle fov of the human eye is known to be 124 degrees and when focused about 1/5 of the normal angle, i.e. 25 degrees. Then in the embodiment shown in fig. 3, the upper limit of visibility is set to 124 degrees and the lower limit of visibility is set to 25 degrees. Thus, when the visibility theta of the human eye at any time is greater than 124 degrees, the human eye is considered not to be concentrated on the door handle, the risk is low, and the sight line factor at the moment is set to be alpha. When the visibility theta is smaller than 25 degrees, the attention of the eyes is considered to be focused on the door handle, the danger of opening the door handle is high, and the sight line factor is set to be beta. If the visibility of the human eye is detected to be between 25 degrees and 124 degrees, the line-of-sight factor E is calculated using the above formula.

Further description is given of the problem of the values of alpha and beta. When the user type is the first user type (such as a child), alpha is set to be a constant 1, and beta is any constant between more than 1 and less than 10, whereby the threshold D can be adjusted to be larger by the line-of-sight factor when the user is a child or the like who is more likely to be mistakenly touched with the door handle. On the other hand, when the user type is the second user type (e.g., adult), alpha is set to be constant 1 and beta is any constant greater than 0 and less than 1, whereby the threshold D can be adjusted to be smaller by the line-of-sight factor when the user is an adult or the like who is less likely to be mistakenly touched with respect to the door handle. Therefore, the scheme can be comprehensively applied to different application scenes.

An embodiment of the present invention also proposes a vision-based automotive door handle anti-false touch system 40 as shown in fig. 4. According to fig. 4, a vision-based automotive door handle anti-false touch system 40 may include an internal communication bus 41, a Processor (Processor) 42, a read-only memory (ROM) 43, a Random Access Memory (RAM) 44, and a communication port 45. When applied to a personal computer, the vision-based automotive door handle anti-false touch system 40 may also include a hard disk 46.

The internal communication bus 41 may enable data communication between components of the vision-based automotive door handle anti-false touch system 40. Processor 42 may make the determination and issue a prompt. In some embodiments, processor 42 may be comprised of one or more processors. The communication port 45 may enable the vision-based automotive door handle anti-false touch system 40 to communicate data with the outside. In some embodiments, the vision-based automotive door handle anti-false touch system 40 may send and receive information and data from a network through the communication port 45.

The vision-based automotive door handle anti-false touch system 40 may also include various forms of program storage units and data storage units, such as a hard disk 46, read-only memory (ROM) 43 and Random Access Memory (RAM) 44, capable of storing various data files for computer processing and/or communication, and possible program instructions for execution by the processor 42. The processor executes these instructions to implement the main part of the method. The result processed by the processor is transmitted to the user equipment through the communication port and displayed on the user interface.

In addition, another aspect of the present invention provides a computer readable medium storing computer program code which, when executed by a processor, implements the vision-based automotive door handle anti-false touch method described above.

While the basic concepts have been described above, it will be apparent to those skilled in the art that the above disclosure is by way of example only and is not intended to be limiting. Although not explicitly described herein, various modifications, improvements, and adaptations of the present application may occur to one skilled in the art. Such modifications, improvements, and modifications are intended to be suggested within this application, and are therefore within the spirit and scope of the exemplary embodiments of this application.

Meanwhile, the present application uses specific words to describe embodiments of the present application. Reference to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic is associated with at least one embodiment of the present application. Thus, it should be emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various positions in this specification are not necessarily referring to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of the present application may be combined as suitable.

Some aspects of the present application may be performed entirely by hardware, entirely by software (including firmware, resident software, micro-code, etc.) or by a combination of hardware and software. The above hardware or software may be referred to as a "data block," module, "" engine, "" unit, "" component, "or" system. The processor may be one or more Application Specific Integrated Circuits (ASICs), digital Signal Processors (DSPs), digital signal processing devices (DAPDs), programmable Logic Devices (PLDs), field Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or a combination thereof. Furthermore, aspects of the present application may take the form of a computer product, comprising computer-readable program code, embodied in one or more computer-readable media. For example, computer-readable media can include, but are not limited to, magnetic storage devices (e.g., hard disk, floppy disk, tape … …), optical disk (e.g., compact disk CD, digital versatile disk DVD … …), smart card, and flash memory devices (e.g., card, stick, key drive … …).

The computer readable medium may comprise a propagated data signal with the computer program code embodied therein, for example, on a baseband or as part of a carrier wave. The propagated signal may take on a variety of forms, including electro-magnetic, optical, etc., or any suitable combination thereof. A computer readable medium can be any computer readable medium that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code located on a computer readable medium may be propagated through any suitable medium, including radio, cable, fiber optic cable, radio frequency signals, or the like, or a combination of any of the foregoing.

Likewise, it should be noted that in order to simplify the presentation disclosed herein and thereby aid in understanding one or more inventive embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof. This method of disclosure, however, is not intended to imply that more features than are presented in the claims are required for the subject application. Indeed, less than all of the features of a single embodiment disclosed above.

In some embodiments, numbers describing the components, number of attributes are used, it being understood that such numbers being used in the description of embodiments are modified in some examples by the modifier "about," approximately, "or" substantially. Unless otherwise indicated, "about," "approximately," or "substantially" indicate that the number allows for a 20% variation. Accordingly, in some embodiments, numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and employ a method for preserving the general number of digits. Although the numerical ranges and parameters set forth herein are approximations that may be employed in some embodiments to confirm the breadth of the range, in particular embodiments, the setting of such numerical values is as precise as possible.

While the present application has been described with reference to the present specific embodiments, those of ordinary skill in the art will recognize that the above embodiments are for illustrative purposes only, and that various equivalent changes or substitutions can be made without departing from the spirit of the present application, and therefore, all changes and modifications to the embodiments described above are intended to be within the scope of the claims of the present application.

Claims

1. The automobile door handle false touch prevention method based on vision is characterized by comprising the following steps of:

2. The method of claim 1, wherein the in-vehicle camera comprises a monocular camera or a binocular camera, wherein,

when the in-vehicle camera is a monocular camera, determining the first position of the user palm according to the depth of the user palm obtained by the monocular camera and the internal parameters and the external parameters of the monocular camera;

and when the in-vehicle camera is a binocular camera, determining the first position of the palm of the user according to the analysis image.

3. Such asThe method of claim 1, wherein the automotive space has a three-dimensional coordinate system including an x-axis, a y-axis, and a z-axis, the first location has coordinates of (x 1, y1, z 1), the second location has coordinates of (x 2, y2, z 2), and the spatial distance d satisfies the formula

Wherein A, B and C are constants.

4. A method according to claim 3, wherein B and C are both 0.

5. The method according to any one of claims 1 to 4, wherein the threshold D ranges between 0 and 50 cm.

6. The method of claim 1, wherein the analysis image further comprises a facial image of the user, the method further comprising determining a user type from the analysis image after acquiring the analysis image of the user in the vehicle including the facial image by the in-vehicle camera, and setting different corresponding thresholds D according to different user types.

7. The method of claim 6, wherein the relationship between the spatial distance D and the product D.E of the threshold D and the line of sight factor E is monitored, and when the spatial distance D is less than D.E, an anti-false touch response operation is performed, the method further comprising obtaining the user's eyebrow coordinates and determining the visibility theta of the user's eye at any time based on the eyebrow coordinates, wherein,

8. The method of claim 7, wherein,

when the user type is a first user type, setting the alpha as a constant 1, and the beta as any constant between more than 1 and less than 10; and

when the user type is a second user type, the alpha is set to be a constant 1, and the beta is any constant greater than 0 and less than 1.

9. The method of claim 1, wherein the anti-false touch response operation comprises sounding an alarm and/or locking the automobile door handle.

10. A vision-based automotive door handle false touch prevention system, comprising:

a memory for storing instructions executable by the processor; and a processor for executing the instructions to implement the method of any one of claims 1-9.

11. A computer readable medium storing computer program code which, when executed by a processor, implements the method of any of claims 1-9.