BE1023596B1 - INTERACTIVE SYSTEM BASED ON MULTIMODAL GESTURES AND METHOD USING SINGLE DETECTION SYSTEM - Google Patents

Abstract

This document describes a method and system for enabling efficient and complementary natural multimodal management-based interaction with a computerized system that displays visual feedback information on a graphical user interface on an interaction surface. The interaction surface is located within the truncated cone of an imaging device comprising a single detection system. The system uses the only sensing system to detect touch gesture interactions with the interaction surface and three-dimensional non-touch gesture interactions in areas or volumes above the interaction surface performed by the hands of an user. The two types of interaction are contextually associated with an interaction command controlling the computerized system when the gesture has been detected. The system includes a projection system to display the graphical user interface and visual feedback on the interaction surface.

Description

INTERACTIVE SYSTEM BASED ON MULTIMODAL GESTURES AND METHOD USING A SINGLE SYSTEM OF

DETECTION

Field of the invention

The present invention relates to or relates to multimodal human-computer interactive system enhancements and particularly relates to a method and a system for providing two complementary modes of interaction using a single detection means, for example, a system. three-dimensional imaging system exploited for the recognition of gestures, the two interaction modes being respectively touch gesture interactions and interactions of non-tactile three-dimensional gestures.

Prior art of the invention

Conventional human-computer interfaces include control system hardware interfaces such as keyboards, mice, remote control, tablets, touch screens and pointing devices. With such interfaces, a physical action must be performed on the hardware device itself, for example, touch, move, hold, point, squeeze, click, or even a plurality of these actions together, sequentially or simultaneously, in a manner made possible through these device interfaces so that control commands, such as triggered binary events or continuous values, can be sent to a computer system with which the interface is intended to interact.

The computer system often includes a graphical user interface (GUI) having windows, buttons and other components or elements, all together called parameters, which are displayed on screens to provide a visual feedback to a user as a function of triggered and executed control commands; they are designed according to the usability and ergonomics of conventional human-computer hardware interfaces and the two-dimensional capabilities of consumer display systems. For example, operating systems basically have two-dimensional GUI windows that often include scrollbars to allow browsing of multimedia content such as a map, an image, or a text box that is potentially larger than the image displayed in the area delimited by the actual size of the display screen. Interaction with the scrollbars is optimized to use a wheel on a hardware mouse device or by combining a movement of the mouse cursor with a click-hold action. In addition, conventional GUIs often include two-dimensional buttons on which a user clicks with mouse buttons to zoom in and out of the GUI content when the mouse cursor representation points to the specifically determined button area. .

In addition, conventional two-dimensional GUIs may also include map navigation GUI interactions that typically require a combined click with continuous mouse movement to scroll the map as a function of mouse movement or to change a map. map area to another.

More recently, conventional two-dimensional GUIs have been developed to be operated by multi-touch and / or tactile control interfaces such as multi-touch surface display screens. Control commands for these second-generation touch gesture-based interfaces have been designed to allow a user to interact, click, scroll, or zoom in and out using at least a portion of a hand, for example a finger, and can be based on different types of hardware technologies such as capacitive, resistive, infrared grid, based on optical imaging, dispersive signals or acoustic waves.

More recently, a third generation of control system interfaces has become available. This generation includes contactless interaction systems. These systems can also be based on a capacitive motion tracking sensor and include a system including electrodes and interface electronics. The main advantage of using such capacitive sensors over existing control systems is that they consume little power, provide easy integration and are low cost. However, capacitive sensors only allow very close contactless interactions, for example at a distance between 0 cm and 10 cm from the plane of the electrodes, with the ability to distinguish and follow a very limited number of points of interest or extremities at the same time, such as human fingers, typically only one or two. These capacitive motion tracking sensors are commonly associated with another interaction system of the first or second generation of control interfaces, for example a touch screen system, to enable tactile and non-tactile gesture interactions or without touching. However, such sensors are not complementary enough to be used effectively to combine a recognition of tactile and non-tactile three-dimensional gestures where the control gestures are performed in the air by a user, for example, using both hands and a plurality of fingers, for example 6, at distances varying between 0 cm and 150 cm from an interaction surface.

This third generation of non-contact interaction systems may also be based on an imaging system, for example, two-dimensional or three-dimensional camera devices, for sequentially capturing images of a scene over time and a method for determining three-dimensional gestures made by a user in the captured scene. Such contactless interaction systems conform to use in combination with existing conventional hardware interfaces, such as touchscreen displays, or possibly only by triggering the same control commands as said conventional hardware interfaces but from a set of recognized three-dimensional gestures, namely static poses or dynamic poses, in the images of the scene captured sequentially.

Such a multimodal interaction system using a non-tactile gesture recognition system of a 3D camera combined with another interactive system of a hardware device is described in WO-A-2013/104681. WO-A-2013/104681 discloses a novel handheld wireless remote control device system. It can be used to provide conventional hardware-based remote control signals for interacting with a computer system in association with three control signals based on three-dimensional gestures provided by the gesture recognition system. The hand-held wireless remote control device includes a housing having a detection unit and having at least one control button that is capable of generating or triggering a control signal for the associated computer system. The computerized system uses the information obtained from the control device together with the information obtained from a gesture recognition system in a multimodal manner to resolve any ambiguity due, for example, to the occlusion of the hand performing the gesture. or hand outside the field of view of the imaging system associated with the computerized system and to trigger interactions with the gesture-based interaction system. Multimodally operated, the two different interaction systems are used effectively in combination and each delivers signals to be used to enhance the signals of the other, thereby enabling enhanced human-computer interaction that can not be provided. if only one of the two interaction systems is used.

Another non-contact interaction system that uses a video camera and a computer screen system is disclosed in WO-A-99/40562. The system includes a touch screen type data entry system determined from video images including data relating to objects approaching the computer screen. The video camera system is mounted above the computer screen to monitor the area immediately in front of the screen. Image processing allows the detection and tracking of a user's hand or pen in the foreground of the screen using common background removal techniques. A calibration process is used in which calibration points are positioned to cover most of the screen, the calibration process generating screen spatial coordinates by transforming virtual space coordinates of the screen. hand position followed using such means as linear interpolation and linear extrapolation.

In WO-A-02/03316, a passive capacitive touch screen is associated with at least one stereo vision camera based on a contactless interaction system. The low-resolution, low temperature, humidity sensitive, low-resolution capacitive touch system data is enhanced by the information retrieved by the camera. The stereo vision camera based on a contactless interaction system comprises at least two cameras with overlapping fields of view that encompass the surface of the capacitive touch screen. Cameras acquire images of the touch surface from different locations and determine the exact location of the pointer to the touch surface when that pointer is captured in images acquired by the cameras. A calibration routine is used to facilitate the determination of the position of the object using triangulation and taking into account deflection angles of the camera with respect to the touch surface. This makes it possible to better determine if a pointer is in contact with the touch surface at a given point or if it is hovering over the touch surface.

While the existing human-computer interactive systems allow multimodal interactions based on tactile interfaces and contactless three-dimensional gesture interfaces by associating at least two detection systems having different technologies, for example a capacitive touch screen associated with a control system. recognition of three-dimensional touch-free gestures exploited using depth information from a 3D camera, there is as yet no solution to allow tactile multimodal interfaces based on contactless three-dimensional gestures, accurate, reliable, efficient and cost-effective for control a computer system in the same way as a system using a combination of different existing technologies.

In addition, the integration of two detection systems with different technologies with a graphical user interface is still constrained by one of the technologies. For example, when using a capacitive display screen to enable touch gesture interaction, the screen used has the main graphical user interface and, adding another graphical user interface that, for example, may have Extensibility properties, such as a projection system, need to add complexity and cost to the existing system. In the same way, the combination of a plurality of display screens with a plurality of detection systems does not provide a complete system that is versatile and embeddable, thus allowing the interactive system to be operated anywhere and on any surface.

Last but not least, as the integration of a plurality of detection systems is constrained and complicated by the display system required by one of the detection systems, the integration of natural interactions into using a combination of tactile and non-tactile three-dimensional gestures to naturally exploit the human-machine (or computer) multimodal interface tends to be quite limited in terms of application, usability and ergonomics in the interaction process . Summary of the invention

It is therefore an object of the present invention to provide a versatile multimodal interaction system that overcomes the problems associated with using a plurality of detection systems to enable reliable, simple and usable multimodality. The present invention includes, in particular, a novel method for using a single detection system, either alone or in combination with a single versatile display system, to provide an interactive system based on tactile and non-tactile gestures having a user interface. graphic, the method being sufficiently versatile and ergonomic to be operated on different interaction surfaces that may be different from that imposed by the unique detection system itself.

Therefore, an object of the present invention is also to provide a novel natural multimodal interaction system in which different modes of interaction can be easily associated or combined with each other, either sequentially or simultaneously, to enable human interaction. computer using at least a portion of at least one hand of a user, or other object, while being sufficiently versatile to allow human-computer natural interactions using at least two parts of either one or two hands or more than one or multiple users.

Therefore, an object of the present invention is, in particular, to provide a versatile system for interacting with a graphical user interface, the system comprising: a display system for displaying a graphical user interface on an interaction surface, a three-dimensional imaging system operated to at least track at least a portion of at least one object or at least one hand of a user within its truncated cone, and a computer system configured to control the system display and the three-dimensional imaging system and to determine gesture-based interaction controls based on data produced by the three-dimensional imaging system.

The present interactive system is furthermore advantageously characterized in that the display surface for displaying the graphical user interface is located in a part of the truncated cone of the imaging system and is also substantially aligned thereon. to minimize the problem and the calibration constraints. The term "substantially aligned" as used herein refers to the perspective of the display or the interaction surface from the point of view of the camera, i.e., the XY plane of the interaction surface is in a predetermined angular range with respect to the XY plane of the imaging system, for example between 0 and 45 degrees.

Advantageously when considering embedded systems, the display system will include a projector element located on the same side of the interaction surface on which the graphical user interface is displayed as the three-dimensional imaging device.

When considering interaction surfaces such as desks, tables, or windows, the interactive system will preferably be configured so that the three-dimensional imaging system and the projector element are located on opposite sides of the surface of the image. the interaction on which the graphical user interface is projected. The interaction surface will preferably be operable to diffuse radiation having a wavelength in a range that substantially corresponds to the visible portion of the electromagnetic spectrum, and to transmit radiation having a wavelength in a range that substantially corresponds to to the infrared part of the electromagnetic spectrum with limited diffusion, the transmission coefficient of the interaction surface being greater than 50% with limited diffusion of less than 20 degrees in the IR domain.

Therefore, another object of the present invention is to provide a method to be implemented by the interactive system, the method being stored in a non-temporary computer medium and being implemented as executable instructions by the interactive system.

The method provides tactile and non-tactile multimodal interactions for controlling the computer system in which said tactile and non-tactile multimodal interactions are detected and recognized using data information from a single detection system. The unique detection system is preferably a three-dimensional imaging device, and the method comprises the steps of: detecting and tracking at least a portion of at least one object within the truncated cone of a three-dimensional imaging device; initiating the interaction by determining whether said at least a portion of said at least one tracked object performs at least one of: a predetermined touch gesture on a predetermined interactive area on the interaction surface and a predetermined non-touch three-dimensional gesture in a volume interactive interactive along a normal vector axis of a predetermined interactive area; interacting with the computerized system by detecting and recognizing the gestures made by said at least a portion of said at least one object within the truncated cone of the three-dimensional imaging device, and the detected and recognized gestures being at least one of a predetermined tactile gesture on the predetermined interactive area of the interaction surface and a predetermined non-tactile three-dimensional gesture in the predetermined interactive volume along a vector axis normal to a predetermined interactive area.

Advantageously, the detection of the execution of a touch gesture on a predetermined interactive area of the interaction surface corresponds to the fact of detecting when the said at least part of the said at least one tracked object is positioned in three-dimensional space. at the same place in the space as the predetermined interactive area on the interaction surface.

In a preferred embodiment, detecting whether a tactile gesture has been made may correspond to determining when the distance from the interaction surface of said at least a portion of said at least one tracked object in three-dimensional space. is less than a predetermined threshold.

Similarly, the method includes determining whether a multi-touch gesture is performed by detecting when the positions of at least two portions of said at least one tracked object in space reach at least two predetermined interactive areas belonging to the surface. interaction.

The method further comprises determining interaction control commands of touch gestures as a function of successive positions and durations of at least one of: a touch gesture and a multi-touch gesture.

In addition, the method also includes detecting non-tactile three-dimensional gesture interactions and determining control commands contextually as a function of the three-dimensional gesture performed by said at least a portion of said at least one tracked object. Contextually we mean when, for how long and where in space with respect to the zones and interaction volumes of the interaction surface.

In a preferred embodiment, the method further comprises the step of terminating gesture-initiated interaction when a predetermined event is triggered, said predetermined event being at least one of: the flow of a period predetermined time, the recognition of a predetermined tactile gesture on the interaction surface, the recognition of a predetermined three-dimensional non-tactile gesture in the truncated cone of the three-dimensional imaging device and an output of said at least one object of a predetermined interactive volume in the three-dimensional space.

The method may utilize at least a first detected portion and followed by at least a first object to initiate an interaction and at least a second detected and followed portion of the at least one first object to effect the interaction. The method may also sequentially use a single detected portion followed by an object to initiate the gesture interaction and the actual gesture interaction. The method may also use a plurality of objects detected and followed by one or more objects to determine either tactile gestures, multi-touch gestures and three-dimensional gestures, the three-dimensional gestures being static, for example, a hand pose, or dynamic, for example a gesture of the hand with change of at least the arrangement in space of at least a detected portion and followed on the hand.

Advantageously, the method comprises displaying a predetermined visual feedback on a graphical user interface on at least a portion of the interaction surface, said visual feedback being relative to at least one of: the position of said at least one a part of said at least one object and recognized gestures of said at least part of said at least one object being tracked.

An object of the present invention is in particular to provide a method in which interaction with the graphical user interface displayed on the interaction surface further comprises accomplishing the steps of: - determining the position in space and the topology of the interaction surface using the three-dimensional imaging device; determining a predetermined set of interactive areas on the interaction surface as a function of its topology and size; and associating with each interactive area at least one touch gesture interaction control.

More advantageously, the method further comprises the steps of: associating with the predetermined set of interactive areas of at least one interactive volume, each interactive volume being located above said interactive area along a normal vector to this interactive area; and associating each interactive volume with a predetermined three-dimensional non-tactile gesture interaction control.

And finally, the method comprising displaying a predetermined visual feedback on a graphical user interface on the interaction surface according to any one of the preceding embodiments which may further be implemented using at least one of a part of a user's body, a desktop tray, a wall, a translucent infrared surface and an object, the graphical user interface being projected onto the interaction surface.

Brief description of the drawings

For a better understanding of the present invention, reference will now be made, by way of example only, to the accompanying drawings in which:

FIG. 1 shows a schematic side view of an interactive system according to the present invention, the interactive system comprising an interaction surface on which a graphical user interface is projected, an additional display screen and projection detection elements. and depth with an upper mounting assembly;

Figure 2 shows a schematic front view of the interactive system of Figure 1;

Fig. 3 shows a plan view of a surface associated with the interactive system of Figs. 1 and 2 in which the interactive area is embedded in the surface of the interaction surface;

Figure 4 shows four different positions of a tracking element used to control a three-dimensional interaction using the interactive system of the present invention, where the position of a tracked element is determined as a function of the interaction surface and where the four different positions respectively determine a touch gesture interaction control and three three-dimensional gesture interaction controls;

Fig. 5 shows an embodiment of the interactive system of the present invention in which a color diffusing surface displays a back-projected graphical user interface and the first-hand tactile interaction of a first hand is used in combination with an interaction of three-dimensional gesture of a second hand followed; and Fig. 6 shows another embodiment of the interactive system of the present invention wherein a color diffusing surface displays a back-projected graphical user interface and a multipoint touch gesture interaction of at least two parts of a first hand followed. is used adjacent to another single-point touch interaction determined by a portion of a second hand followed.

Description of the invention

The present invention will be described in connection with particular embodiments and with reference to certain drawings but the invention is however not limited thereto. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes.

The present invention provides a method and system for enabling interactions based on tactile and non-tactile multimodal human gestures with a computer system having at least one graphical user interface (GUI) displaying visual feedback information. The graphical user interface may display parameters such as buttons to be pressed, scrollbars, buttons to rotate, pointers, windows, multimedia content or any other parameter among those known to those skilled in the art. Control commands may be associated with each displayed parameter to operate the interactive system. Each control command can be associated with a trigger event controlled by the detection and recognition of at least one predetermined specific gesture.

A predetermined specific gesture may be a tactile or non-tactile human gesture. Interactions based on tactile gestures form a first mode of multimodal gesture interaction and interactions based on non-tactile gestures form a second mode of multimodal gesture interaction. The combined use of the two modes of interaction, sequentially or simultaneously, forms an interactive system based on multimodal gestures to be exploited from information data obtained from a single detection system.

For example, a predetermined specific gesture may be a three-dimensional gesture based on a one-handed pose followed where a three-dimensional point cloud (3D) of that hand captured by the imaging system has a specific arrangement corresponding to a specific pose. Detection of this pose is performed using classifiers and machine learning techniques for image processing and computer vision. Any of a neural network, an SVM classifier, or a Random Forest classifier (or other appropriate classifiers) works well, i.e., at a detection rate greater than 85%, with a set of predefined three-dimensional gestures and appropriate descriptors.

The predetermined specific gesture may be a three-dimensional gesture based on a movement of a hand followed where a 3D point cloud of that hand captured by the imaging system, or at least one associated point of interest, such as, without however, to be limited to this, a point corresponding to a palm center point or a fingertip, demonstrates the execution of a specific dynamic motion in space, whose associated three-dimensional path is statistically analyzed to determine, from a set of descriptors, the form that has been realized. Each form can be associated with a three-dimensional gesture. For example, if the movement of a moving hand moves circularly within a predetermined area in the truncated cone of the imaging system, a circle-like gesture can be detected. It should be noted that the quality of the descriptors is decisive. A relevant high quality object descriptor may be its average velocity over time, a set of positions where the motion as demonstrated is a change of direction along one of the axes of a coordinate system, the acceleration, duration, movement size, etc.

Three-dimensional gestures based on motion and three-dimensional gestures based on a pose are jointly referred to hereinafter as three-dimensional gesture. They can be performed and therefore detected at the same time and, therefore, they can trigger a control command if the interactive system allows it. In practice, the selection of one or the other is predetermined specifically for each type of interaction. For example, a hand moving rapidly from left to right in the scene may trigger a right "scan" control command if the application allows it. In such a case, for example, multimedia content may be replaced by other content. In another example, if the detection of a three-dimensional gesture of "capture" based on a pose is performed at a specific location on a representation of a scrollbar or a button of the graphical user interface (GUI) and that this "grabbing" gesture is maintained while the hand position moves along the GUI scrollbar axis, the scrollbar or button representation will move and the displayed content , like a map, will scroll accordingly until the "capture" gesture is detected as released or no longer performed.

The detection of the execution of a tactile gesture is done with respect to a predetermined interactive zone on the interaction surface. Multipoint gestures are determined in the same way but relate to a plurality of interactive areas of the interaction surface. Detection includes tracking a three-dimensional position, relative to time or over time, of at least a portion of at least one tracked object. It further comprises the step of continuously determining the distance of each part followed by the object, which may be the tip of a finger of a hand, with respect to the predetermined closest interactive zone on the surface of 'interaction. It further comprises the step of triggering the touch gesture event or the multipoint touch gesture at each interactive area where at least a portion of the tracked object has its distance from the interactive area below a predetermined threshold, for example, the threshold may be 0.1 mm, or if the distance is zero (0). Each single touch gesture triggers a control command based on the interactive area with which it is associated or to which it belongs.

For example, a simultaneous control using multi-touch gestures can be enabled with a GUI displaying a keyboard in which three simultaneous touch gestures on the GUI and their associated interactive zones correspond to the "CTRL" button, the "ALT" button and the "ALT" button. LED ", and when done together, activate a control command to display a new menu.

Simultaneous control using a combination of at least two gestures of the same mode or different modes is also possible, for example, a multipoint touch control performed with one hand while the other hand performs a three-dimensional movement-based gesture. Sequential combinations of different modes of gesture interaction may also be permitted.

The present invention is characterized in that it uses an interaction system comprising only a detection system as a data information provider by means of calculation or processor which determines the two different modes of interaction, namely the Interactions of tactile gestures and interactions of non-tactile gestures. The interactions of non-tactile gestures can also be called "contactless gestures", "three-dimensional gestures (3D)" or "three-dimensional gestures (3D) non-tactile".

As described above, the displayed GUI may include a plurality of parameters that may be contextually associated with at least one interaction control means. An interaction control means is a computerized system instruction that will perform a predetermined calculation when it is triggered. The result of the predetermined calculation may optionally be provided as feedback information according to the return means of the computerized system, using at least the graphic visual feedback of the GUI, and possibly audio returns, if an audio rendering system is included in the system. multimodal interactive system. For example, a button on a user interface may be associated with a "close window" operation or a "play multimedia" action that the computer system will perform. If a user interaction triggers the start of this operation, the computerized system will close the open windows and render it on the GUI and launch the media player generating audio feedback through an audio system, while the GUI will display and refresh the status of a progress bar of the media player.

Each parameter will be controlled by a user interaction that may be associated with at least one predetermined interactive area on the surface of the interaction surface with which the user is expected to interact.

Each interactive zone thus defined is intended to be used with tactile gesture interactions. Preferably, the area associated with a parameter will be of a size corresponding to the rendered representation of this parameter on the interaction surface. This prevents triggering an interaction based on a gesture, which belongs to a neighboring parameter, if the parameters are too close to each other. However, for ease-of-use purposes, some parameters may contextually have an interactive area of different size (either smaller or larger) than their graphical representation on the interaction surface.

Similarly, each parameter, or a sub-parameter of this parameter that will be controlled by the user interactions can be associated with at least one predetermined interactive volume, i.e., a three-dimensional interactive area whose position is preferably above the interactive area a visual feedback made on the interaction surface. The size, position, and shape of the interactive volume can be contextually predefined depending on the interaction supported by the application. Interactive volume controls are preferably intended for use with three-dimensional gesture interactions.

For example, an interactive volume can be associated with the volume control of an audio system. The interactive volume can be located above a speaker representation displayed on the GUI. When the user performs a tactile interaction, using at least a portion of his hand, with the interactive area on the interaction surface associated with the speaker representation, the interactive area having the size of the representation of loudspeaker. speaker, the computer system receives the instruction that a volume control interaction begins. The movement of the user's hand as a result of the tactile interaction constitutes a continuous three-dimensional gesture interaction control for which the distance between at least a portion of the hand, for example, the predetermined palm or finger, and the area of the interactive area determines the value of the adjustment (or control) parameter of the audio volume, i.e., the further the hand is distant (or elevated) from the interaction surface, the greater the audio volume is high, and the closer the hand is (or lower) to the interaction surface, the lower the volume.

In a further embodiment, the audio volume value may be continuously adjusted as a function of the movement of the hand until the hand exits an interactive volume associated with the interactive zone, and therefore the audio volume control. In another embodiment, the audio volume may be continuously adjusted as a function of the distance from the hand to the interaction surface and set after a predetermined period of time. In another preferred embodiment, the audio volume may be continuously adjusted as a function of the distance from the hand to the interaction surface and fixed when the hand followed, within the interactive volume, performs a predetermined three-dimensional gesture, namely a static gesture or a pose, such as a gesture of "pinching" or "seizure", where predetermined fingers, for example, but not limited to, the index and the thumb, are detected as s' approaching each other below a predetermined distance threshold. In one embodiment, the distance threshold can be as low as 1 mm.

In this last example, it will be understood that the representation of the speaker on the GUI is a GUI parameter in an interactive zone associated with a start interaction operation of the "audio volume control" triggered when a touch interaction is detected and that the volume interaction is associated with an activated "audio value control" sub-parameter as a function of the detection of a predetermined subsequent three-dimensional gesture interaction.

As described herein, the invention includes a method comprising tracking at least a portion of at least one object within the truncated cone of the three-dimensional imaging system. The object can be a hand and part of the object can be a finger or a fingertip. It will be appreciated that the detection and tracking of points of interest is not the object of the present invention and that several techniques can be applied to achieve a similar required input. For example, as soon as the interactive system configuration is set, a static background learning technique can be applied to record the background of a captured scene, and a rearward elimination technique. plane, such as a morpho-mathematical depth image subtraction, can be applied at runtime to dissociate, frame by field, moving objects of interest in the foreground of a captured scene from the static background. With respect to the acquisition of a depth map of the imaging sensor device, a 3D point cloud of a user's hand can be obtained. A cluster-constrained 3D clustering technique can then be applied to the foreground points corresponding to the hand and an adjacency graph used to determine extremes by detecting which clusters are connected to only one other cluster. The identification and tracking of objects, or portions of objects, can be efficiently performed using classification techniques, such as the Random Forest classifier, if applied to properly segmented data using, for example, a mix of K-averaged clustering and leader-follower. Combining background removal with clustering and classifier techniques provides a way to detect, track, and identify each part of a known object with known or learned 3D shapes for use in interaction.

If the interaction method is compatible with any type of display system having at least one display screen, a plurality of displays may be used in combination, such as, for example, as shown in Fig. 1 where a display Conventional display 110 such as an LCD screen is associated with an interaction surface 120 on which a GUI can be displayed using projection means. Gesture-based interactions may allow a user to transfer parameters, such as multimedia content, from the GUI of one display screen to the GUI of the other. Specifically, the transfer control may be triggered after a touch gesture has been detected at the location where the parameter was displayed on a first GUI, initiating the interaction that can then be enabled and performed by detecting the completion of the interaction. a sequence of "drag-and-drop" gestures toward the second GUI to which the content parameter will be transferred.

In a preferred embodiment of the present invention, the GUI is displayed using a single display system due to the use of the projection means, such as a projector or pico-projector, which provides visual feedback. to the user during the interaction. This is illustrated in Figures 5 and 6 below and described with reference thereto.

The projection can be performed on a wide variety of surfaces and materials. The term "surface" as used herein refers to any surface on which images can be projected. Suitable surfaces include, but are not limited to, screens, flat surfaces, curved surfaces, and transparent surfaces.

In the simplest embodiment of the present invention, the GUI may be projected onto a desktop flatbed or flat wall that will be used as a display medium defining the human-computer interaction surface. However, the GUI can also be projected onto non-planar surfaces, such as an object having circular shapes, for example a balloon, or a part of a user's body, such as a forearm or the inner part of a palm of a hand.

In a preferred embodiment, the hardware used as a display screen and interaction surface may exhibit substantial scattering properties for electromagnetic radiation having wavelengths in the visible (human) portion of the electromagnetic spectrum . Substantial diffusion properties mean that the material diffuses at least ten percent (10%) of the incident light to allow adequate rendering of the visual feedback to be displayed. The light energy emitted by the projection system can be adapted accordingly.

Preferably, electromagnetic radiation belonging to the incident light beam having a wavelength range between 400 nm and 680 nm can be scattered in a "lambertian" manner, that is to say in a homogeneous manner for all angles of possible reflection when the user is on the same side of the interaction surface as the projection means or for all possible transmission angles when the user is on the opposite side of the interaction surface to that of the projection means .

Lambertian reflectance is a property that defines an ideal "matte" or diffuse reflection surface, and the apparent brightness of such a surface for an observer is the same regardless of the viewer's angle of view. the luminance of the surface is isotropic and the luminous intensity obeys Lambert's law of cosine.

In an even more preferred embodiment of the present invention, the electromagnetic radiation of the incident beam of projected light having a wavelength greater than 680 nm, i.e., in the infrared range, may be transmitted with a high transmission coefficient (eg greater than 20%) and no substantial diffusion, ie, within a solid angle of less than 20 degrees when the user is positioned on the opposite side of the interaction surface with respect to the three-dimensional camera. When the user is positioned on the same side of the interaction surface as the three-dimensional camera, material with a low infrared reflectance (IR) ratio of less than 20% is preferred while having a substantial high diffusion rate. more than 60 degrees of solid angle to avoid specular IR reflection in the imaging system that is capable of destroying the reliability of the depth measurement values.

The present system for enabling interactions based on tactile and non-tactile multimodal human gestures with a computerized system is characterized in that it comprises a single detection system. The only detection system as used herein as a data information provider comprises a three-dimensional detection system, for example a three-dimensional detection system may be an imaging system or a three-dimensional (3D) camera. Preferably, the present interactive computer system based on multimodal tactile and non-tactile human gestures will make use of a 3D camera using the IR lighting of the scene to obtain better depth measurements. A passive 3D IR camera, such as a 3D camera with stereo vision or structured light, may be appropriate with the computerized system, however, 3D cameras based on active lighting, such as depth detection cameras or flight time (ToF) are preferred. Even better, the imaging system may further incorporate a 3D camera together with a color camera of similar or higher resolution. The depth detection camera or ToF and the color camera each have a truncated cone that at least overlap each other and that will capture the entire interaction surface in which movements and gestures of at least a part of at least one hand or object can be detected, tracked and used to determine control parameters of the projected GUI.

The term "truncated cone" as used herein refers to the field of view of the imaging element, for example, a conical volume extending from a lens to a surface. to a view of an image projected from a projector, for example, a cone extending from the projector lens to a surface In each case, the area on the surface can be defined by an ellipse, a circle or a rectangle, if the projection is collimated in the same way.

The terms "three-dimensional camera", "depth-sensing camera" or "flight-time camera (ToF)" as used herein refer to a video camera or a camera that provides three-dimensional coordinates for each pixel in an image of a captured scene. Two of the dimensions (X and Y) are determined by an X-Y plane that is normal to an axis of the camera, and the third dimension (Z) is a distance from the pixel of the camera to the imaged surface. Such a camera produces a three-dimensional point cloud where each point in the cloud corresponds to a pixel having three-dimensional coordinates. The 3D point cloud or corresponding depth map provides values correlated with the camera coordinate system and correlated with the interaction surface (or global) coordinate system when a calibration method of the state of the art is used to apply a transformation matrix to project data values from one coordinate system into the other.

In addition, the terms "color camera" or "RGB camera" as used herein refer to a video camera or a camera that provides color images of a captured scene. Such a camera produces a two-dimensional color image for each pixel in the captured scene. The color camera and the three-dimensional camera associate each depth measurement value (if there is reference to the camera's coordinate system) or 3D point (if there is reference to the global coordinate system) to a color when state-of-the-art image recording techniques are used. In one embodiment, the imaging system includes at least one three-dimensional camera for extracting depth information from the scene and a color camera of a higher resolution. The higher resolution of the color detection unit that gives an image of the same scene as the depth detection unit can be used for the precise location and determination of touch gestures on an interaction surface displaying the graphical user interface. Conventional image recording techniques may be used to associate each depth detector pixel with each color detector pixel, the higher resolution of the color detection unit being used to refine raw XY positions obtained from the camera at lower resolution depth detection to provide a more accurate XY position on the display surface which is also of high resolution.

The present invention will now be described in more detail hereinafter with reference to Figs. 1 to 6 which relate to specific embodiments encompassing the scope of the present invention.

The method of the present invention includes detecting the execution of a touch gesture with respect to a predetermined interactive area on the interaction surface. It also includes a step of predetermining the interactive areas contextually with a graphical user interface to be displayed and the control commands allowed to interact with it. During a preliminary step, the interaction surface is detected and at least one of its position, shape and topology, that is to say the modeling of the surface is recorded.

According to the system operating the method, the detection of the interaction surface can be performed once, for example, at the start of the interactive system based on multimodal gestures when the interaction surface is fixed, that is to say , non-mobile, and of a known form, such as a flat panel, a desk or a surface, the detection process can be performed manually or automatically. When the interaction surface is able to move and have a variable shape, for example when the interaction surface is a forearm of a user, the detection must be performed automatically in real time.

In a first embodiment in which the detection is carried out manually with a static flat surface disposed in the space in the system so that its surface is inside the truncated cone of the imaging system, the user of the The interactive system may, in a first step, use a simple sheet of white paper placed on top of the surface, the size of which is defined to be the size of the interaction surface. The white sheet of paper reflects the IR illumination of an active IR depth-detecting camera, for example a three-dimensional ToF camera. However, if the IR reflection property of the surface, without the white paper sheet, is strong enough, that is to say at least 20% of the incident light, the white paper sheet is not mandatory.

In a second step, the distance from the designated interaction area to the detection system is measured using the detection system. The acquired depth data may be used in a third step using computer vision methods to determine a plane in the 3D data set, the 3D point cloud, or the acquired depth map. Plan detection methods, such as conventional plane adjustment algorithms, for example 3D least squares plane for example, Ransac or any other method based on linear algebra can be used. The input required to determine the geometric properties of the plane must include at least four points distributed over the surface of the interaction surface. Preferably, if these points are limited to the number of four, they should be chosen as the corners of the interaction surface. Once the plane is determined, each of its points can be located as a function of their distance from the imaging system, and as a function with respect to any point within the truncated cone of the imaging system. Depth measurements, providing actual distance measurements, can be used as criteria for determining thresholds to be used for gesture recognition purposes in a subsequent step.

Similarly, the same steps of detecting and determining the interaction surface can be performed automatically with a static flat surface disposed in the space in the system so that its surface is inside the truncated cone of the system. imaging. As illustrated in FIG. 3, the flat interaction surface may comprise a set of four highly reflective points in the IR illumination which replace the at least four points measured on the white paper sheet of the manual detection and determination steps, each point being again located in a corner of an area defined to be the interaction surface.

In another manual implementation of the detecting step and determining the interaction surface, the set of four points that are highly reflective to the IR illumination may not be on the interaction surface. The user will use his fingers to locate sequentially in time the four corners of the interaction surface. The imaging system will additionally be activated to detect and track a specific fingertip and sequentially record the three-dimensional position in the space of each of the four corners.

In any of the implementations previously described, a deflection of, for example, 3 mm, may be applied in the vertical direction (Z) along a normal to the plane of the interaction surface.

This provides compensation for the accuracy problems of depth measurements of the 3D imaging device, and to ensure that a moving object that is detected to be almost in contact with the interaction zone is ie, for example, at a distance of 2 mm, may still be able to trigger a touch gesture event if possible.

In another embodiment of the present invention where the three-dimensional position of the projector is known with respect to the position of the three-dimensional camera, for example if they are both on the same side of the interaction zone, and they are statically incorporated into a hardware system, such as a laptop, a headset or embedded in smart glasses, adjusting the projection parameters, namely focus, keystone distortion, zooming, and GUI model size can be automatically modified by extracting the distance, topology and geometric information relating to a potentially moving interaction surface to fit the rendering of the graphical user interface template size. This can be done by restoring geometric distortion using triangulation methods.

Detection and determination of the interaction surface and those of the display surface can be performed continuously even when the display surface can move with respect to time. For example, when the display surface is a specific object or part of a user's body, for example the forearm or the inner part of a palm, and if the three-dimensional camera and the projector are mounted on a helmet or in smart glasses, the use of image processing means such as pattern recognition techniques or classifiers, provides reliable detection and tracking of the forearm used as a surface interaction in three-dimensional space. The position and orientation of the forearm tracked can further be determined by gradually accumulating a topological model of the moving object tracked using any of the simultaneous location and mapping algorithm (SLAM) of the state of the technique, the topological model being a three-dimensional representation of the interaction surface, the exact position and orientation of the representation being determined from frame to frame, and any position of the display surface may be to be determined using simple three-dimensional geometric calculations such as triangulation.

Referring first to Figure 1, a schematic side view of an interactive system 100 according to the present invention is shown. The system 100 includes a screen 110 positioned on a surface 120 and an imaging unit 130 associated with the screen 110. The screen 110 may be any suitable screen that can be connected to a data source (not shown) for display images. The imaging unit 130 is positioned to have a truncated cone 140 that extends to the support surface 120.

In the embodiment shown in Fig. 1, the imaging unit 130 is mounted directly on the screen 110. However, it will be readily appreciated that the imaging unit 130 may be mounted of any other suitably so that it has the same truncated cone 140 but is either incorporated or mounted separately from the screen. In addition, the screen 110 is shown supported by the surface 120. Again, it will be appreciated that the screen can be supported in other ways.

Figure 2 shows a schematic front view of the interactive system 100. The imaging unit 130 includes three separate imaging elements 150, 160, 170. Although the imaging elements 150, 160, 170 are shown integrated in a single imaging unit 130, it will be appreciated that each of these elements can be located individually with respect to the screen 110 and with respect to the surface 120 while providing the same functionality as will be described in more detail below. The imaging element 150 may comprise a color or RGB camera that captures two-dimensional color images of a scene within its truncated cone 180 (indicated by two dot-dot-dot lines) . The imaging element 150 produces images that are used for image recording with images of the imaging element 170, both of which are in the interactive system of the present invention, and as described in detail. more detailed below. The imaging element 170 may include a depth-detecting camera or ToF that captures three-dimensional images of a scene within its truncated cone 190 (indicated by two dashed-dot-line lines). The images produced by the imaging element 170, when processed, provide three-dimensional position information for objects within its truncated cone 190 that can be used for interaction with a user interface. graph (GUI) projected on the surface 120 as will be described in more detail below. The imaging element 160 includes a projector that is connected to the computer system. It can project the same images supplied to the screen 110 on the surface 120. The imaging element 160 projects the images in a truncated cone 200 (indicated by two dashed lines). In one embodiment, the projected images are color images including a GUI with at least one parameter that is displayed on the surface 120.

As shown in FIG. 2, there is an overlap, on the surface 120, of the truncated cones 180, 190, 200 of each of the imaging elements 150, 160, 170.

Figure 3 illustrates a plan view of the surface 120 showing areas within the truncated cones of the imaging elements 150, 170 with the area 200 on which the imaging element 160 projects images. As shown, each zone is framed by the same type of line as in FIG. 2 and comprises, for example, a rectangle. Naturally, depending on the particular imaging elements, the truncated cones may be different, for example, an ellipse or a circle.

As shown in FIG. 3, an area 210 is common to the truncated cones 180, 190, 200. An interactive area or region 220 is also shown within the common area 210. The interactive area or region does include a volume extending from the interaction surface in one direction to the ToF imaging system. Once the interactive system has been calibrated, the movement of any object within the interactive region 220 can be used to control an image on the screen.

In one embodiment of the present invention in which a flat surface such as a desk top is used as the interaction surface, the calibration of the interactive region 220 is performed by defining a subset of four points 220A, 220B, 220C, 220D which correspond to the corners of a rectangle on the surface inside the common area. The calibration process may be a preliminary step in which a user can only perform the placement of at least a portion of at least one hand, for example a finger, in each of the corners sequentially for define the interactive area on the surface 120 on which a graphical user interface (GUI) is projected by the imaging element or projector 160. In the calibration process, the position of the finger in the three-dimensional space is recorded sequentially for each of the four points and a plane is determined as being the area delimited by the four points by geometric calculations. Any position belonging to the surface thus determined, that is to say having the same height as this surface and horizontal and vertical coordinates within the limits of the surface, constitutes points which form an interaction surface and its interactive zone. associated.

In another embodiment of the present invention in which a flat surface, such as a desktop tray, is used as the interaction surface, the calibration of the interactive region 220 can be performed in line with an automated process at the same time. start-up. The automated process may include detecting, using pattern recognition techniques, the pattern of four self-adhesive thumbnails previously pasted on the interaction surface so as to physically determine its boundaries. Pattern recognition can include the use of one of the shape, color and texture of the four self-adhesive thumbnails. Once the thumbnails are detected with each imaging system, the calibration includes transforming the position data of each imaging system into position data of another imaging system. For example, horizontal X and vertical Y data of the color camera can be projected into the coordinate system of the three-dimensional camera using ordinary image recording transformation models, such as a simple linear transformation or preferably splines in thin plate or surface, multiquadratic transformations.

The respective XY positions of the color camera, the 3D camera and the projector are recorded relative to each other so that any XY position of a parameter of any of these systems can be associated with depth information. . The combination of a two-dimensional (2D) X-Y coordinate of a parameter with a third coordinate relative to the depth information forms a 3D coordinate. Therefore, the calibration allows each parameter of the imaging system 130 to be associated with a three-dimensional position in space and a color with respect to any position on the determined interaction surface that makes part of the interactive zone 220.

As described above, in one embodiment of the present invention, the GUI may include at least one portion above which a movement of an object with respect thereto in a direction perpendicular to the plane of the surface 120 can control a parameter, for example, an audio volume control. Figure 4 shows an example of the implementation of a volume control which will be described in more detail below. The identification of an object within the interactive region 220 is determined using the imaging element 170, i.e., the depth detection camera or ToF. A three-dimensional point cloud is processed first to identify the object and then to follow its movement from one frame to another. Object tracking provides the interaction that is used to control the GUI; Movement of the object 240 away from the surface 120 in the direction perpendicular thereto is followed to provide control signals to the volume controller.

More specifically, a portion 230 of the GUI, that is to say an interactive zone corresponding to the position of a parameter of the GUI, can be considered as a controller and, when an object 240, such as a finger or hand, is brought into contact with the surface on the part and moved away in a direction of the surface 120 on which the GUI is projected in a predetermined direction, the controller is activated to change the volume level associated with a projected image . At the position represented by 0%, the volume is at 0 or off. When the object 240 is moved from the 0% position to a first predetermined distance from the portion 230, the volume is increased to 25% of the maximum volume. When the object 240 is moved at a second predetermined distance from the portion 230, the volume is increased to 50% of the maximum volume. When the object is moved a third predetermined distance from the portion 230, the volume is increased to the maximum volume. Of course, although only three levels are shown in Figure 4 as an example, it will be appreciated that any appropriate number of levels may be implemented in accordance with other predetermined distances from the surface.

Although the movement of an object in a direction perpendicular to the surface is described, it will be appreciated that other movements with respect to the surface may also be used to control the GUI, for example dynamic motion, such as a rotation, which can be detected when considering a user's hand as a function of the change of position of a set of at least three points of interest, which may be the tip of the thumb, the tip of the index and the middle of the wrist. Detection and tracking of points of interest may be performed by a variety of methods, such as an analysis of major components, on the hand-detection mask or other suitable end.

In Fig. 5, an embodiment of the interactive system of the present invention includes a back-projection display diffusing colors of the graphical user interface using a projector 160. An interaction surface 120 is used for tactile gesture interactions. in a contextally predetermined interaction zone 230a of first-hand tactile gestures 240a followed in combination with a determined interaction of three-dimensional gestures by a second hand 240b followed and occurring in an interaction volume of a predetermined size which extends along a normal to the interaction surface 120 on a second contextally determined interaction zone 230b, the tracking using a front-end depth-sensing camera 170 located above the interaction surface 120 and on the side opposite to the projector with respect to the interaction surface 120.

In the embodiment illustrated in FIG. 5, the interaction surface must have specific properties with respect to light. It must broadcast wavelengths in the visible part of the electromagnetic spectrum so that the projected graphical user interface can be seen by the user, while being transparent to the IR to avoid saturation or disruption of depth measurements on IR sensors when using an active depth-detecting IR camera, such as a 3D ToF camera, due to specular or strong reflections of the material of which the interaction surface is made.

Such photonic properties for such a surface are difficult to obtain, and some solutions may be provided. These include, but are not limited to, the use of a glass window or polycarbonate window having a surface on which a coating can be applied. The coating may consist of zinc sulfide pigment particles (ZnS) or zinc sulfate particles (ZnSO4) in a proportion of 10% of the substance used to apply the coating. Barium sulphate pigment (BaSO4) may also be suitable, being considered as the best light scatterer of the visible spectrum, and since it does not introduce chromatic aberrations when it is used as a substrate since it reflects homogeneously the wavelengths in the visible part of the electromagnetic spectrum lambertian way.

One embodiment will include a coating on a glass or polycarbonate window that is printed with the substance to form a coating material grid on the window. The pitch between the tiny areas coated on the window as well as their size and arrangement can be adjusted according to the expected color diffusion properties.

In Fig. 6, an embodiment of the interactive system of the present invention includes a back-projection display diffusing colors of the graphical user interface using a projector 160. A determined interaction surface 120 is used for gesture interactions. tactile in interacting zones of contextually predetermined interaction of tactile gestures. A first hand 240c followed performs an interaction of a single touch gesture while a second hand 240d followed performs an interaction of touch gestures multipoint on two different interaction zones 230, tracking using a depth detection camera 170 with a truncated cone 140 located above the interaction surface 120.

A more preferred embodiment more suitable for robust and powerful multi-touch gestures would be to have the imaging detection device on the opposite side of the user's side from the interaction surface. Such an embodiment would provide a system where the main interacting parts of a user's hand for tactile gestures, i.e. fingertips are never masked.

Although the present invention has been described with reference to specific embodiments, it will be appreciated that the invention is not limited to such embodiments and that the invention may be implemented otherwise.

Claims (18)

CLAIMS: A multimodal tactile and non-tactile interaction method with a computer system in which said tactile and non-tactile multimodal interaction is performed using data information from a single detection system, the only detection system being a device three-dimensional imaging, the method comprising the steps of: a) detecting and tracking at least a portion of at least one object within the truncated cone of a three-dimensional imaging device; b) initiating the interaction by determining whether said at least a portion of said at least one tracked object performs at least one of: a predetermined touch gesture on a predetermined interactive area of an interaction surface and a predetermined non-touch three-dimensional gesture in a predetermined interactive volume on the vector axis normal to a predetermined interactive area; c) interacting with the computerized system by detecting and recognizing the gestures made by said at least a portion of said at least one object within the truncated cone of the three-dimensional imaging device, the detected and recognized gestures being at least one of: a predetermined touch gesture on a predetermined interactive area of the interaction surface and a predetermined non-touch three-dimensional gesture in a predetermined interactive volume on the vector axis normal to an interactive area. The method of claim 1, wherein detecting the execution of a touch gesture on a predetermined interactive area of the interaction surface is to detect when said at least a portion of said at least one tracked object is positioned in the three-dimensional space at the same location in the space as the predetermined interactive area on the interaction surface. The method of claim 1 or 2, wherein detecting whether a touch gesture has been executed is determined when the distance from the interaction surface of said at least a portion of said at least one tracked object, in the three-dimensional space is less than a predetermined threshold. The method according to any one of claims 1 to 3, wherein determining a multi-touch gesture is performed when the positions of at least two portions of said at least one object tracked in space reach at least two areas. predetermined interactive features belonging to the interaction surface. The method of any one of claims 1 to 4, further comprising the step of determining gesture interaction controls as a function of successive positions and the duration of at least one of: a touch gesture and a multi-touch gesture. The method of any one of claims 1 to 5, further comprising the step of determining non-tactile three-dimensional gesture interaction controls as a function of the three-dimensional gesture performed by said at least a portion of said at least one object. The method of any one of claims 1 to 6, wherein step c) comprises the step of terminating the interaction when a predetermined event is triggered, said predetermined event comprising at least one of: flow of a predetermined period of time, recognition of a predetermined tactile gesture on the interaction surface, recognition of a predetermined three-dimensional non-tactile gesture in the truncated cone of the three-dimensional imaging device and an output of said at least one object of a predetermined interactive volume in the three-dimensional space. The method of claim 7 wherein step b) comprises using a first portion detected and followed by said at least one object, and step c) comprises using a second detected portion and followed by said at least one object. The method of claim 7, wherein steps b) and c) are sequentially controlled using a single detected portion followed by an object. The method of any one of claims 1 to 9, which further comprises displaying a predetermined visual feedback on a graphical user interface on at least a portion of the interaction surface, the visual feedback relating to at least one of: the position of said at least a portion of said at least one object and recognized gestures of said at a portion of said at least one tracked object. The method of claim 10, wherein the interaction with the graphical user interface displayed on the interaction surface further comprises accomplishing the steps of: - d) determining the position in the space and the topology of the interaction surface using the three-dimensional imaging device; e) determining a predetermined set of interactive areas on the interaction surface as a function of its topology and size; and f) associating with each interactive area at least one tactile gesture interaction control. The method of claim 11, further comprising the steps of: g) associating with the predetermined set of interactive areas, at least one interactive volume, each interactive volume being located above said interactive area along the interactive area; a vector normal to this interactive zone; and h) associating with each interactive volume a predetermined three-dimensional non-tactile gesture interaction control. The method of claim 11 or 12, wherein the interaction surface is at least one of: a portion of a user's body, a desktop tray, a wall, a translucent infrared surface, and an object, the graphical user interface being projected onto the interaction surface. A system for interacting with a graphical user interface, the system comprising: - a display system for displaying the graphical user interface on the interaction surface; a three-dimensional imaging system operated to at least follow at least a portion of at least one hand of a user within its truncated cone; and a computer system configured to control the display system and the three-dimensional imaging device, and to determine gesture-based interaction controls using data produced by the three-dimensional imaging device; the system being characterized in that the display surface for displaying the graphical user interface comprises at least a portion of the truncated cone of the three-dimensional imaging device and is substantially aligned therewith. The system of claim 14, wherein the display system comprises a projector element that is located on the same side of the interaction surface on which the graphical user interface is displayed as the three-dimensional imaging device. The system of claim 14, wherein the three-dimensional imaging system and the projector element are located on opposite sides of the interaction surface on which the graphical user interface is projected, the interaction surface being exploitable. for diffusing radiation having a wavelength in a range substantially corresponding to the visible portion of the electromagnetic spectrum and for transmitting radiation having a wavelength in a range substantially corresponding to the infrared portion of the electromagnetic spectrum with limited diffusion , the transmission coefficient of the interaction surface being greater than 50% and the limited diffusion being less than 20 degrees. 17. System according to any one of claims 14 to 16, which is operable to implement the method of any one of claims 1 to 13. 18. Non-temporary computer support usable for storing executable instructions for implementing the method according to any one of claims 1 to 13.