WO2011117505A2

WO2011117505A2 - Interactive device that can adapt to ambient light conditions

Info

Publication number: WO2011117505A2
Application number: PCT/FR2011/050504
Authority: WO
Inventors: Frédéric GUERAULT; Régis LE BRAS; Rachid Guerchouche
Original assignee: Intui Sense
Priority date: 2010-03-25
Filing date: 2011-03-14
Publication date: 2011-09-29
Also published as: FR2958010B1; EP2550583A2; WO2011117505A3; FR2958010A1

Abstract

The invention relates to a method for controlling the power of a light source of a device comprising an interactive facade, on the basis of images captured by the facade. The invention also relates to designing and adapting a device such as an interactive display case or vending machine using said method.

Description

Interactive device adaptable to the conditions of

ambient brightness

The invention relates to any device comprising an interactive or tactile facade allowing a user to interact directly on said facade to obtain a service. The invention relates more specifically, but in a non-limiting manner, vending machines food (snacking in English terminology), hot or cold beverages. It also concerns interactive panels or windows for delivering location, price and other information.

Automatic distribution is a privileged channel for the food industry. In particular, it allows substantial margins. To maximize the attractiveness of such distributors, manufacturers have chosen to equip the main facade of said dispensers with a touch screen, sometimes even large. The objective is to allow a playful use of the distributor and to deliver additional information on the products. A second objective aims at facilitating the adaptation of the distributors to the products delivered, the evolution of the prices etc. However, this solution proves to be expensive because of the cost of a touch screen. Manufacturers or operators of such distributors who have opted for this solution must also deal with the fragility of this type of screens. Indeed, a screen can be quickly scratched or broken according to the use that is made of it. A distributor is then out of service, causing high maintenance costs.

For applications remote from the agri-food distribution, interactive facades have been created using the technique of stereovision in particular. This technique consists of providing around a generally translucent wall, sensors, a lit or backlit frame to detect a finger by example, or more generally a pointer, near said translucent wall. Using known methods, such as triangulation for example, it is possible to know precisely the position of the pointer on the wall. Actions may be preprogrammed for a particular position of said pointer to trigger a generally informative service. There are mainly applications in the field of showcases or interactive totems.

To date, this type of interactive facade has not been applied to the field of distribution. Even if this technique would solve the problem of lack of robustness raised by the use of touch screens, the integration of an interactive facade in a beverage vending machine, for example, causes other difficulties.

First, such devices are arranged in varied environments: indoor or outdoor, bright or dark spaces, etc. The ambient light conditions, due to direct exposure to sunlight, to more or less sustained lighting, have particularly negative consequences for such a device - such as a food vending machine for example.

Indeed, if it is exposed in full sun, even though the distributor has an internal light source to illuminate the content offered for sale, it may be very difficult to collect certain items or information posted through the facade. A user may be hesitant to make a purchase. He may also make a selection error because of his limited visual abilities. Conversely, if a similar distributor is placed in a very dimly lit room, a too strong light source may be perceived as aggressive and dissuasive for a buyer. The power of the light source of certain distributors is thus set "at the factory" to an average power that may be suitable for average or nominal conditions of ambient light. The use of these is therefore relative in more extreme light conditions at the expense of the operator's turnover.

Moreover, the brightness to which an interactive facade is exposed, can cause a malfunction of the detection mechanism. Indeed, the sensor or sensors of an interactive facade may be saturated in the presence of particularly intense lighting caused by excessive sunlight, for example. In addition, the presence of shadows due to objects or a person approaching a facade can greatly alter the detection capabilities of the facade.

To combat this inconvenience, the interactive façades of totems or known interactive windows have a dedicated lighting. This lighting is generally in the form of light-emitting diodes located around the frame of the facade, particularly near the sensor or sensors. In an attempt to combat the phenomenon of direct sunlight, most interactive façades use sensors sensitive only to the near infrared. Thus the spectral band located outside the near infrared is filtered. For example, the document US2005 / 277071A1 discloses an interactive table having a wall and an image sensor sensitive only to near-infrared radiation to provide an image of said wall and to allow the detection of a pointer in the vicinity of it. The table operates a video projector to deliver content through the wall. The disadvantages of this type of façade are however numerous. First, the spectral band is impoverished compared to that delivered by a sensor working in the field of the visible. Detection capabilities are therefore lower. In addition, the costs are greatly increased: the sensors are much more expensive than standard sensors and the light sources dedicated to the illumination of the frame, such as infrared diodes are also more expensive than diodes emitting in the visible.

The invention makes it possible to meet all the disadvantages raised by the known solutions. Among the many advantages provided by the invention, we can mention that the invention allows:

to use interactive facades working in the visible, so more precise and inexpensive, including in the field of automatic food distribution;

to reduce or even eliminate light sources dedicated to illuminating the frame of the interactive facades;

optimize the detection capacity of said facades including in extreme ambient light conditions;

to maximize the attractiveness of the devices by regulating the light source dedicated to the illumination of contents, whatever said ambient light conditions, etc.

To this end, it is in particular and first of all provided a device comprising:

an interactive facade in the form of a wall surrounded by a frame, said frame comprising a matrix image sensor for providing an image of said frame and allowing the detection of a pointer near the wall; a light source emitting radiation visible to the human eye for illuminating said facade and / or a visible content therethrough. ;

According to the invention, such a device is arranged for:

a part of the light delivered by the light source illuminates the frame of the interactive facade for the matrix image sensor to deliver an image of said illuminated frame;

comprise means for regulating the power of the light source by exploiting an image of the frame delivered by the matrix image sensor.

According to an advantageous embodiment, such a device may comprise means for directing a portion of the light delivered by the light source to the frame of the interactive facade to illuminate it.

It may also be provided that the means for regulating the power of the light source of the device further regulate the exposure of the sensor.

According to a preferred embodiment, the means for regulating a device according to the invention translate all or part of the image delivered by the sensor in the form of a histogram in gray level.

In this case, said means for regulating can calculate the absolute central moment of the histogram for estimating ambient lighting conditions.

They can further calculate a sampling average of the histogram to estimate the ability of the interactive facade to detect a pointer near the wall. According to a second object, the invention provides, to solve the known drawbacks, a method for adapting a device comprising:

an interactive facade in the form of a wall surrounded by a frame, said frame including at least one matrix image sensor for providing an image of said frame and allowing the detection of a pointer near the wall;

- A light source emitting radiation visible to the human eye to illuminate said facade and / or visible content through said facade.

Such a method comprises a step for arranging the device for:

a part of the light delivered by the light source illuminates said frame; said device comprises means for regulating the power of the light source by exploiting a partial image of the frame delivered by the matrix image sensor.

According to a third object, the invention provides a method for regulating the power of a light source - emitting radiation visible to the human eye - of a device according to the invention, said method being implemented by the means for regulating said device. Such a method comprises:

a step for estimating the light intensity delivered by the light source on the basis of a partial image of the frame delivered by a sensor of the interactive facade;

a step for:

i. increase the power of the light source as long as said intensity the estimated luminous value is less than a predetermined optimum value;

ii. decreasing the power of said light source as said estimated light intensity is greater than said predetermined optimum value.

According to an alternative embodiment, it is provided that the method may comprise a step for estimating, together with the estimate of the light intensity delivered, an ability to detect a pointer on the basis of an image delivered by a frame sensor. of the interactive facade.

Other features and advantages will emerge more clearly on reading the following description and on examining the figures that accompany it, among which:

- Figure 1 shows an interactive facade according to the state of the art;

FIG. 2 presents two examples of images obtained by means of a matrix image sensor according to the state of the art;

FIG. 3 describes a known functional system making it possible, from an interactive facade, to detect a pointer close to it;

- Figures 4, 5 and 6 respectively show three types of device adapted to host an interactive facade according to the invention;

FIGS. 7a to 7d each show the translation of an image obtained by a matrix image sensor, in the form of a histogram according to the invention;

- Figure 8 illustrates a calibration step according to the invention;

FIG. 9 is a block diagram of an interactive device according to the invention; - Figure 10 describes alternative embodiments of a method for controlling a light source of an interactive device according to the invention. Figure 1 allows to present an interactive facade 10 used in an interactive totem for example. One could consider integrating such a facade in a device in the form of a vending machine drinks for example. The facade comprises a wall 14, generally translucent, surrounded by a frame 15. On the upper part 11 of the frame are arranged 3 matrix image sensors 12a, 12b and 12c. Each provides a two-dimensional image of a region of the frame 15, called region of interest. FIG. 2 makes it possible, by way of example, to illustrate two respectively polygonal 15a and rectangle 15b images captured using sensors 12a and 12b whose respective fields of view 12v and 12w do not alone make it possible to embrace the entire wall 14 of the facade.

To illuminate the frame and allow the capture of an image of good quality, in connection with Figure 1, a known facade 10 comprises one or more light source (s) dedicated (s) for this purpose. Thus, for example, four light-emitting diodes 13a, 13b, 13c and 13d are placed in close proximity to the image sensors. Generally, identical diodes are also arranged all around the frame, especially if the surface of the facade is important. For the reasons explained above, the sensors of the interactive facades are sensitive mainly in the near infrared to reduce the sensitivity to variations in ambient brightness. In this case, the diodes emit according to these same wavelengths. The arrangement of the sensors 12a, 12b and 12c makes it possible to make the wall 14 touch. Thus, as soon as a pointer, such as a hand 20, approaches the wall, it is captured by one or more image sensors of the facade 10.

FIG. 3 illustrates a functional diagram of a device comprising an interactive facade. Thus a processing unit 30 exploits a set 21 of two-dimensional points u and v resulting from images 15a, 15b and 15c respectively taken by the sensors 12a, 12b and 12c. From information 23 delivered during a calibration step, and from the assembly 21, the means 30 implement a triangulation function to determine the three-dimensional position x, y and z of a pointer in the vicinity of the wall of a facade. To implement a triangulation function, it is necessary that at least two sensors can capture said pointer. According to the techniques of the prior art, an intense and inhomogeneous illumination of the wall related to excessive sunlight, for example, can greatly reduce the detection and positioning capability of a pointer. Indeed, the shadow carried by a pointer or by any object close to the wall can lead to inadvertent detection.

Figures 4 to 6 describe three examples of devices likely to host an interactive facade.

According to Figure 4, a device la, distributor of food (snacking), has an interactive facade 10 through which we guess racking 6 for accommodating sandwiches and / or other sweets. A coin 3 allows to receive the coins of a buyer. A receptacle 4 is provided to restore the excess of money. A salvage zone 5 of a purchased item allows the buyer to collect the expected item. To highlight the items and appeal to the customer, a light source 2 is intended to illuminate the content of the device. A parameterization step made it possible to define zones L1 to L16 at the wall of the facade 10. Thus, when a hand approaches the wall, a triangulation mechanism - as shown in connection with FIG. is implemented by a processing unit (not shown in FIG. 4) of the device 1a. It makes it possible to determine the position of the pointer with respect to said zones L1 to L16. By means of a prior association of said areas L1 to L16 and predefined actions, the device triggers the distribution of an item whose rack or display has been "pointed" by a customer.

FIG. 5 makes it possible to present an alternative device comprising an interactive facade. This is a lb vending machine of hot or cold beverages. The surface of the interactive facade 10 may be smaller in size than those of the facade of the dispenser described above. The interaction zone delimited by the interactive frontage 10 of the dispenser 1b can be customized, for example with stickers. Zones L1 to L16 may be predefined. Each can be dedicated to a product indication (instant coffee, coffee beans, etc.) or preparation (adding milk, sugar, etc.). When a customer's hand points to a predefined area of the interactive facade, the interactive facade captures an image and the device 1b determines the position of the customer's finger. The recovery space 5 makes it possible to dispense the beverage thus prepared, after payment via the coin mechanism 3 associated with the receptacle 4 for the surplus of money. To make the interaction zone attractive, a light source 2 is provided to illuminate the interaction zone.

FIG. 6 presents a device of the "interactive showcase" type whose purpose is to deliver information: geographical positioning, plan of subway, jukebox etc. As well as the devices la and lb, the device may comprise means for making a payment (coin mechanism 3 and coin receptacle 4). It also includes an interactive facade, generally large, which can cover a full flat screen 7 on which information is displayed. The active face 7a of the screen 7 (as opposed to its rear face 7b) faces the translucent wall of the interactive facade 10. A light source 2 diffuses light on the frame of the facade to backlight and thus highlight the latter. A user can point to an area of said facade and control the display of information on the screen 7. It can still, or alternatively, collect a product, such as a digital medium for example, via a distribution receptacle. 5. We could also imagine that the device is a food distributor in the same way as the device la. According to this variant, the products are not directly visible on their display. Visual information (photo (s), video (s), composition, etc.) and / or advertising is presented to potential buyers. Whatever the device considered, it can be implanted in an environment where the brightness can be variable or extreme under normal and average conditions for which the manufacturer and / or the operator of said device has / have based the parameterization .

The invention aims to design or adapt devices comprising an interactive facade to eliminate the disadvantages related in particular to the environment. In the case of a device designed according to the invention, it also reduces manufacturing costs (suppression of light sources). on the facade, use of sensitive sensors in the visible, etc. ).

FIG. 9 illustrates a block diagram of a device according to the invention.

Such a device - which may be similar to the devices 1a, 1b or the previously described - has an interactive facade of which a matrix image sensor 12 is shown. This sensor delivers one or more images relating to a region of interest (part of the frame surrounding the wall of the facade). The device further comprises a light source 2. The latter is used, as for devices 1a, 1b or 1c, to illuminate the contents of the device and / or the interaction zone. The invention provides that part of the light delivered by said source 2 is used to detect a pointer. Thus, depending on the configuration of the device, it may be necessary to provide the latter with means (reflector (s) for example) to direct said portion of the light to the frame of the facade. According to the invention, the interactive facade - as illustrated in FIG. 1 - may be devoid of dedicated light sources (diodes 13a to 13d, for example). Indeed according to the invention, the source 2 may be sufficient alone to illuminate or backlight the frame of the facade. In addition, according to the invention, the sensor 12 of the facade can work in the visible - unlike most sensors working in the near infrared. Thus, the invention makes it possible to greatly reduce the costs inherent to the interactive facade used. A device according to the invention further comprises means 33 for regulating the power of the light source. Said means 33 may consist of a processing unit 30, responsible for detecting a pointer and for triggering an action, as described with reference to FIG. adapted to further regulate the light output. To control said means 33, the device (or its processing unit) further comprises means 31 for analyzing a two-dimensional image delivered by the sensor 12. This image may be similar to the images 15a and 15b presented in connection with FIG. 2. The means 31 may analyze the entirety of an image or a portion Ai thereof. Thus, FIG. 2 illustrates several examples of portions A1 to A6. Whether an image is considered in its entirety or in part, the invention provides that the analysis performed by said means 31 may consist of translating all or part of an image in the form of a histogram in gray level. Gray is known for its sensitivity to changes in ambient light conditions. It is therefore a particularly relevant choice for implementing the invention. However, this one would not be limited by the choice of this hue.

FIG. 7a illustrates an example of translation in the form of a histogram 16 of a captured image. Such a histogram can be defined as a discrete function that associates with each intensity value, a number p of pixels taking said value. Several intensity values can be grouped into a single class to better understand a distribution of the intensities of an image. Thus, FIG. 7a shows a histogram for which 256 intensity values are represented on an abscissa axis. On the ordinate, the number p of pixels per intensity value appears. FIG. 7a also makes it possible to illustrate the possibility of grouping the intensity values into five classes z ₀ to z ₄ respectively from 0 to 50, 51 to 101, 102 to 152, 153 to 203, 204 to 255. Different measurements are applicable on such a histogram. The invention provides according to a first mode of realization of calculating the sampling mean μ (Mean Sample Value - MSV according to English terminology). This value makes it possible to estimate the capacity, for a given exposure of a sensor 12, to be able to detect a pointer near the wall of the interactive facade.

For a zone ζ ₂ ·, the means 31 calculate the sum x _{i =} p (j) where j is the intensity value in the class z _i j≡ _Zi

considered. The sampling mean μ is then

4

Σ (i + i) X _i

calculated by μ = ^{1 = 0} .

Σ Xi

i = 0

Alternatively, the invention provides that such an average is not calculated directly on an image 15a or 15b as described in Figure 2. According to this embodiment the invention provides to translate in the form of a histogram each portion A _k (Al to A6, for example, in connection with Figure 2).

The means 31 then calculate for each image portion A _k , then an average MSV μ ^1ί

such as average sampling

based on an image of n portions Ao to A _n _i is then

1 nl _k

equal to μ = - Σ μ.

n k = o

According to the invention, it is possible to limit the values of

. By way of example, μ may thus vary between 1 to 5.

So a value of μ:

close to 5 represents an overexposed image for which the sensor 12 is saturated (FIG. 7d); close to 1 represents an underexposed (or even totally dark) image (Figure 7b).

Figures 7b, 7c and 7b respectively illustrate the translation in the form of a gray scale histogram of an underexposed, normal or overexposed image.

In order for a sensor to deliver an image from which a pointer can be detected or positioned, it must not be saturated. The brightness must be otherwise sufficient. We can therefore define, within the meaning of the invention, an interval of values [¾, _e ] for which detection is possible, thus represents the lower bound of said interval and μ _β , the upper bound.

The image, therefore the histogram and finally the value μ or the range of values [¾, _e ] depend on the exposure parameter of the sensor that delivered said image. We will later name "exposure" to that parameter. We consider that, according to a first embodiment of the invention, the exposure of the sensor is set to a mean value.

A device according to the invention comprising means 30, 31 and 32 able to regulate the power of the light source 2 can therefore estimate the ability to detect a pointer, for example using the calculation of the MSV sampling mean . The invention would not be limited to this single example of calculation. Any other method, allowing such an estimate, is within the scope of the present invention.

To optimize the ability of the device to detect a pointer near an interactive facade regardless of the ambient brightness, the means 31 may control means 33 for regulating the power of the light source of the device - intended to illuminate the contents of this device. last - to respectively increase or decreasing said power according to whether the calculated value μ becomes close to or μ _β .

A second objective of the invention consists in exploiting a captured image, from the interactive facade, for detection purposes in order to estimate a lighting level of the content of the device and thus be able to regulate said light source in order to optimize the visibility of the articles and / or information available through the interactive facade. This objective remains compatible and complementary to maintaining the ability to detect (or to distinguish a pointer from the frame).

The invention thus provides for estimating the light intensity delivered by the light source of the device from image (s) delivered (s) by an image sensor of an interactive facade.

According to a first embodiment, the processing unit 30 of a device according to the invention can calculate 31 an absolute central moment δ of a gray level histogram, such as the histogram 16 presented in FIG. . For this, the means 31 can calculate the average of the histogram, t

being the number of possible intensities (t = 256 in FIG. 7a).

The absolute central moment δ is therefore obtained by

In a variant, the invention provides that such an absolute central moment is not calculated directly on an image 15a or 15b - as described in FIG. 2. According to this embodiment, the invention provides for the translation into the form of a histogram each portion A _k (Al to A6, for example, in connection with Figure 2). The means 31 then calculate for each portion k

of image A _k p = - 1-- ^f Σ ^_1 ip () then the absolute central moment

7 = 0

The absolute central moment, based on an image of n

1 nl _k

portions A ₀ to A _n _i, is then equal to δ = - Σδ.

nk = o

The value δ can vary from 0 to <5 _max . δ close to 0 represents a captured region that is totally underexposed or completely dark. Conversely, δ close to <5 _max represents a totally overexposed captured region, for which the sensor having delivered the image must be totally saturated.

The absolute central moment of a histogram resulting from a captured image is thus representative of the lighting of the distributor highlighting its content.

Translating the human eye to determine a range of values for which a person clearly distinguishes the content of a device through an interactive facade is subjective.

Also the invention provides a calibration step during which such a device is positioned under average ambient light conditions, for which - and for an exposure of a given sensor, an interval of values [<¾, < 5 _e ]. <¾ and δ _e respectively denote the absolute central moment within or beyond which the content of the device is no longer easily and agreeably distinguished. According to the invention, it is possible to define an optimum value δ _ορ such that δ _ορ = ^e , for which the illumination delivered by the light source of the device added to the illumination ambient allows a perfect visibility of the content through the interactive facade.

The captured image, the resulting histogram, the δ value or the range of values [<¾, <5 _e ] and therefore δ _ορ depend on the exposure parameter of the sensor. We consider that according to a first embodiment of the invention, the exposure of the sensor is initialized to an average value.

According to an alternative embodiment, the invention provides that it is possible to regulate the exposure of a sensor. Thus, in connection with FIG. 9, means 32 are provided for modifying this parameter.

The calibration step therefore consists in determining, for an exposure value Ei, the values ° op or even FIG. 8 illustrates an exemplary result obtained at the end of a calibration step.

FIG. 8 presents the values of δΐ, δί and δ _ορ for an exposure Ei between a minimum value Ei and a maximum value E _m . Three curves are thus described by said FIG. 8. It may therefore be noted that, for a given exposure value Ei, the content is sufficiently illuminated as long as the value δ ¹ remains between the value <¾ and δ _e '. In addition, we can notice that the means 31 of the device can estimate that the lighting conditions, in particular due to a fluctuating ambient brightness, become less than the optimal lighting conditions associated with the value o _o ^l _pt if <¾ << 5 ^z <(5 ^. Conversely, said means 31 may judge that said lighting conditions become more intense as the optimal lighting conditions if δ ¹ ρ ₀ <δ ¹ _<δ β ^1. the invention thus provides that means 31, via the means 33, can regulate the power of the light source according to the estimate of the variation of ambient brightness.

Thus a device according to the invention can automatically:

- Increase the power of the light source if said estimated light intensity is less than the optimum value;

- Decrease the power of said light source if said estimated light intensity is greater than said optimum value.

According to an alternative embodiment, the means 31 may further automatically regulate the exposure of a sensor of the interactive facade. For this, they exploit the estimation of the ability to detect a pointer, defined for example by the value μ.

A device according to the invention can thus automatically increase or decrease the exposure Ei of the sensor if the sampling mean μ ¹ is not within the predetermined interval.

For this, the means 31 can exploit the value of the calculated absolute central moment δ ¹ . If the latter is less than the predetermined value δ _ορ , it is a sign of a drop in ambient brightness. On the other hand, if said calculated absolute central moment δ ¹ is greater than the predetermined value δ _ορ , this shows an increase in ambient luminosity. It therefore seems appropriate to increase the exposure of the sensor in the first case and reduce it in the second.

The invention thus makes it possible to control the power of the light source or even the exposure of a sensor to ambient light conditions. Thanks to the invention, the capabilities of a device to detect a pointer and to allow the separate observation of a content through an interactive facade are maximized.

The invention provides that the values - such as <¾,

<¾ '^ opt f4> ^or obtained during the calibration of an interactive device can be stored by storage means coupled to the means 31 so that the latter can exploit said values to regulate the power of the light source or even the exposure of a sensor to ambient light conditions.

According to one embodiment, the invention provides that alert means 35 may be activated by means 31 for regulating the light source. Thus, said activation can be controlled if μ reaches the values and / or μ _β , synonymous with a loss of ability to properly detect a pointer. The activation can be alternatively controlled, if δ reaches the values <¾ and / or δ _β , synonymous with a lighting of the inappropriate content.

Any other threshold could be used to trigger said alert means 35.

The invention also relates to a device comprising an interactive facade comprising a plurality of sensors. In this case, according to a preferred embodiment, the power of the light source of the device is regulated on the basis of images delivered by a single sensor. This one usually has a central field of vision with regard to the facade. In the same way, the exposure of all the sensors can be enslaved on the basis of said images delivered by said selected sensor. Alternatively, the exposure of said sensors can be regulated independently of each other. FIG. 10 makes it possible to describe various embodiments of a method for regulating a light source of a device according to the invention. Such a method is implemented by the processing unit of said device.

Such a method starts at 100. It comprises a first step 101 of analyzing an image delivered by an image sensor of the interactive facade. This results, for example, in translating said image into a gray-scale histogram. A step 102 is then followed to estimate the light intensity delivered by the light source - or the ability to provide a pleasant and distinct observation of the content. This step may consist in calculating an absolute central moment δ of said histogram.

A method according to the invention thus comprises a step for:

increasing, at 105, the power of the light source as, at 103, said estimated light intensity is less than a predetermined optimum value;

decreasing, in 107, the power of said light source as, at 103, said estimated light intensity is greater than said predetermined optimum value.

The invention provides that one can increase said power as, at 104, a maximum value P _max of the power is not reached. Conversely, it can be expected that one can reduce said power as, in 106, a minimum value P _m i _n of the power is not reached. According to such a method, the power of the light source is kept constant, if the ambient light conditions are close to the brightness conditions used to calibrate (for a given sensor exposure value) the device. According to an alternative embodiment, such a method for regulating the power of the light source of a device according to the invention makes it possible to regulate the exposure parameter Ei of the sensor (s) of the interactive facade.

Thus, such a method comprises a step 201 for estimating an ability to detect a pointer. This step may consist in calculating a sampling mean μ of a histogram resulting from an image delivered by a sensor of the interactive facade.

According to this embodiment, the method comprises a step for:

increasing, in 203, the exposure of the sensor as long as, in 202, the sampling mean μ is not included in a range, the values and μ _β being predetermined for the current exposure of the sensor;

or decrease, at 205, the exposure of the sensor as long as, in 204, the sampling mean is not included in said interval

According to a preferred embodiment, the exposure of the sensor is increased if the ambient light conditions are estimated to decrease with respect to the nominal conditions (for example, if the calculated absolute central moment δ is less than the predetermined value δ _ορ ). Said exposure is, however, decreased if the ambient light conditions are estimated to be more intense with respect to the nominal conditions (for example, if said calculated absolute central moment δ is greater than the predetermined value δ _ορ ). Any other embodiment to enslave the power of the light source or even the exposure of the sensors could be considered to design a device according to the invention. All that is needed is for the regulation to be based on estimates based on images captured using the interactive facade.

Claims

Device (la, lb, le) comprising:

an interactive facade (10) in the form of a wall (14) surrounded by a frame (15), said frame including a matrix image sensor (12, 12a, 12b, 12c) for providing an image (15a, 15b, 15c) of said frame and allowing the detection of a pointer (20) near the wall;

a light source (2) emitting visible radiation for the human eye to illuminate said facade and / or a visible content therethrough;

characterized in that the device is arranged for:

a part of the light delivered by the light source (2) illuminates the frame (15) of the interactive facade so that the matrix image sensor (12, 12a, 12b, 12c) delivers an image (15a, 15b, 15c) of said frame thus illuminated;

comprising means (30, 31, 33) for regulating (30, 31) the power of the light source by exploiting an image (41, 15a, 15b, 15c) of the frame delivered by the matrix image sensor .

Device according to the preceding claim, characterized in that it comprises means for directing a portion of the light delivered by the light source (2) to the frame (15) of the interactive facade to illuminate it. Device according to claims 1 or 2, characterized in that the means for regulating (30, 31) the power of the light source further regulate (32) the exposure of the sensor.

Device according to any one of the preceding claims, characterized in that the means for regulating translate all or part (15a, 15b, Al, ..., A6) of the image delivered by the sensor in the form of a histogram ( 16) in gray level.

Device according to the preceding claim, characterized in that the means for controlling calculate the absolute central moment δ of the histogram (16) to estimate the ambient lighting conditions.

Device according to claims 4 or 5, characterized in that the means for controlling calculate a sampling mean μ of the histogram (16) to estimate the ability of the interactive facade to detect a pointer near the wall.

Device according to claims 5 or 6 characterized in that the means for regulating (30, 31) trigger (46) alert means (35) when the calculated absolute central moment δ reaches a predetermined threshold. Device according to claims 6 or 7 characterized in that the means for regulating (30, 31) trigger (46) alert means (35) when the sampling mean μ reaches a predetermined threshold.

Device according to any one of the preceding claims, characterized in that the interactive facade comprises a plurality of sensors and in that the means for regulating regulate the power of the light source from an image delivered by one of said sensors. 10. Device according to claims 9 and 3, characterized in that the means for regulating regulate the exposure of each sensor of the facade.

A method for adapting a device comprising: an interactive facade (10) in the form of a wall (14) surrounded by a frame (15), said frame comprising at least one matrix image sensor (12, 12a, 12b, 12c) for providing an image (15a, 15b, 15c) of said frame and for detecting a pointer (20) near the wall;

a light source (2) emitting radiation visible to the human eye for illuminating said facade and / or a visible content through said facade; characterized in that the method comprises a step for arranging the device (la, lb, le) for:

a part of the light delivered by the light source (2) illuminates said frame (15); said device comprises means (30, 31, 33) for regulating the power of the light source (2) by exploiting a partial image of the frame delivered by the matrix image sensor (12, 12a, 12b, 12c).

A method for regulating the power of a light source (2) - emitting visible radiation for the human eye - from a device (1a, 1b, 1c) according to any one of claims 1 to 10, said method being implemented by the means for regulating said device and being characterized in that it comprises:

a step (101, 102) for estimating the light intensity delivered by the light source on the basis of a partial frame image delivered by a sensor of the interactive facade;

a step for:

i. increasing (104, 105) the power of the light source as long as (103) said estimated light intensity is less than a predetermined optimum value;

ii. decreasing (106, 107) the power of said light source as long as (103) said estimated light intensity is greater than said predetermined optimum value. Method according to the preceding claim characterized in that it comprises a step (201) for estimating, together with the estimate of the light intensity delivered, an ability to detect a pointer on the basis of an image delivered by a sensor of the frame of the interactive facade.

Process according to claims 12 or 13, characterized in that:

the step step (102) for estimating the light intensity delivered by the source comprises calculating the absolute central moment δ of a resulting histogram (16) (101) of an image delivered by a sensor of the interactive facade;

and in that :

i. the step of increasing (104, 105) the power of the light source is performed as long as (103) said calculated absolute central moment δ is less than a predetermined value δ _ορ , said optimum moment;

ii. the step of decreasing (106, 107) the power of said light source is performed as long as (103) said calculated absolute central moment δ is greater than said predetermined value δ _0Ό .

Process according to Claims 13 or 14, characterized in that:

step (201) for estimating an ability to detect a pointer is to calculate a sampling mean μ of a resulting histogram (16) (101) of an image delivered by a sensor of the interactive facade; and that said method comprises a step for:

i. increasing (203) the exposure of the sensor as long as (202) the sampling mean μ is not in a range μ ₁₎ , μ

e the values and μ _β being predetermined for a given sensor exposure, if the calculated absolute central moment δ is less than the predetermined value δ _ορ ;

decreasing (205) the exposure of the sensor as long as (204) the sampling mean μ is not within said interval if said

absolute central moment δ calculated greater than the predetermined value δ

16. The method of claim 14 or 15 characterized in that it comprises a prior calibration step for determining the predetermined value δ _ορ said optimum moment, for a given sensor exposure.

17. Method according to the preceding claim characterized in that the prior calibration step further allows to determine the interval μ _ύ , μ

e predetermined for a given sensor exposure.