# Patent

## Title
Partial detect mode

## Abstract

The disclosure relates to a touch sensitive system comprising a touch sensitive panel defining a touch surface, a plurality of emitters configured to emit light into the panel for propagation in the panel, a plurality of detectors configured to detect the light propagating in the panel, a plurality of distributed control devices each configured to control operation of a segment of emitters and detectors, a main control unit configured to control the distributed control devices. The touch sensitive system is configured to be set in a partial detect mode in which mode a first of the distributed control devices is configured to be active and to control a first emitter to emit light in a partial region of the panel coincident with a partial area of the touch surface. The touch sensitive system is further configured to detect a predetermined gesture on the partial area of the touch surface, generate a gesture signal indicating the predetermined gesture, and activate a feature of the touch sensitive system in accordance with the predetermined gesture. The disclosure also relates to a method in connection with the touch sensitive system.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of Swedish patent application No. 1350870-0, filed 12 Jul. 2013.
FIELD OF THE INVENTION
The present invention relates to low power functions in a touch system to e.g. start up the system according to the preamble of the independent claim. In particular, the touch system includes distributed control devices configured to control emission and detection of light.
BACKGROUND OF THE INVENTION
Touch sensing systems (“touch systems”) are in widespread use in a variety of applications. Typically, the touch systems are actuated by a touch object such as a finger or stylus, either in direct contact, or through proximity (i.e. without contact), with a touch surface. Touch systems are for example used as touch pads of laptop computers, in control panels, and as overlays to displays on e.g. hand held devices, such as mobile telephones. A touch panel that is overlaid on or integrated in a display is also denoted a “touch screen”. Many other applications are known in the art. To an increasing extent, touch systems are designed to be able to detect two or more touches simultaneously, this capability often being referred to as “multi-touch” in the art.
There are numerous known techniques for providing multi-touch sensitivity, e.g. by using cameras to capture light scattered off the point(s) of touch on a touch panel, or by incorporating resistive wire grids, capacitive sensors, strain gauges, etc into a touch panel.
WO2011/028169 and WO2011/049512 disclose multi-touch systems that are based on frustrated total internal reflection (FTIR). Light sheets are coupled into a panel to propagate inside the panel by total internal reflection (TIR). When an object comes into contact with a touch surface of the panel, the propagating light is attenuated at the point of touch. The transmitted light is measured at a plurality of outcoupling points by one or more light sensors. The signals from the light sensors are processed for input into an image reconstruction algorithm that generates a 2D representation of interaction across the touch surface. This enables repeated determination of current position/size/shape of touches in the 2D representation while one or more users interact with the touch surface. Examples of such touch systems are found in U.S. Pat. No. 3,673,327, U.S. Pat. No. 4,254,333, U.S. Pat. No. 6,972,753, US2004/0252091, US2006/0114237, US2007/0075648, WO2009/048365, US2009/0153519, WO2010/006882, WO2010/064983, and WO2010/134865.
An overall goal for the touch system is to consume less energy to save resources and reduce costs. For example, when the system is not used it can be in a power saving mode or an idle mode in which modes the system is configured to use less power than in a normal mode. Such a system is disclosed in e.g. WO2011/028170 which uses a less number of emitters/detectors in power saving or idle mode than in a normal detect mode to save power. When an interaction on the touch surface is detected, the system is turned into normal mode.
The touch technology is now being implemented into consumer products such as smartphones and laptops. These products commonly have a limited access to power, e.g. battery, and new challenges are approached when integrating the touch system into the often smaller products. An ASIC (Application Specific Integrated Circuit) has been developed to which a limited number of emitters and detectors are connected. By using ASICs the touch system can be made smaller and use less energy. The whole touch system comprises a plurality of ASIC blocks with connected emitters and detectors.
The need for power saving solutions is however still present. The system needs to monitor when to change mode from a power saving or idle mode to a normal mode and this monitoring uses power. A common used approached is to have a button to activate the touch system. A mechanical part is thus sensitive to mechanical failure.
From US2012/0191993 a system and method is known for reducing power consumption in an electronic device such as a mobile phone having a touch-sensitive display. The system comprises a touch panel controller, which may have resource constraints compared to a main processor, for preliminary gesture recognition to transition the electronic device from sleep mode to full power mode. The touch panel controller consumes less power than the main processor and power can thus be saved.
It is an object of the present invention to provide a low power function which takes advantage of a distributed control structure of the touch system.
SUMMARY OF THE INVENTION
According to a first aspect, the object is at least partly achieved by a touch sensitive system according to the first independent claim. The system comprises a touch sensitive panel defining a touch surface, a plurality of emitters configured to emit light into the panel for propagation in the panel and a plurality of detectors configured to detect the light propagating in the panel. The system further comprises a plurality of distributed control devices each configured to control operation of a segment of emitters and detectors, and a main control unit configured to control the distributed control devices.
The touch sensitive system is configured to be set in a partial detect mode in which mode a first of the distributed control devices is configured to be active and to control a first emitter to emit light in a partial region of the panel coincident with a partial area of the touch surface. The touch sensitive system is further configured to detect a predetermined gesture on the partial area of the touch surface; generate a gesture signal indicating the predetermined gesture, and activate a feature of the touch sensitive system in accordance with the predetermined gesture.
As only a subset of the distributed control devices, e.g. one or two, are used in the partial detect mode, power consumption can be kept very low. As less power is used, one control device can be used for both emitting and detecting at the same time as fewer disturbances will be introduced into the control device during detection. In a normal operation, a distributed control device is used for only emitting or detection at the same time to not compromise any detection results, as currents necessary for emitting light otherwise might disturb the detection result.
According to one embodiment, the main control unit is configured to be set in a low power mode when the touch sensitive system is set in the partial detect mode. The main control unit is normally the most power demanding unit in the system. If the touch sensitive system is not used, it can save energy by setting itself in a partial detect mode in which mode the main control unit is set in a low power mode and only a subset of the distributed control devices are active. When the main control unit is in the low power mode, most or all of the functions of the main control unit are disabled and do not consume any energy.
According to one embodiment, each distributed control device comprises a processing unit and a computer readable storage medium. Thus, each distributed control device has the possibility to store operational instructions and to act independently from the main control unit.
According to one embodiment, the distributed control devices are grouped into at least one group. All the distributed control devices may be grouped into the same group, and then there is only one group. Instead, the distributed control devices may be divided into two or more groups. According to one embodiment, the distributed control devices in each group are connected in series. By having the distributed control devices connected in series, the need for separate cables between each distributed control device and the main control unit is obviated. Thus, space can be saved and less cable length is needed. Disturbances may be introduced by cables, and if they are made shorter then disturbances can be reduced. It follows that the control devices in a group communicate in a serial way. According to one embodiment, only one of the distributed control devices in each group is operatively connected directly to the main control unit. This control device will then act as a master over the other distributed control devices in the same group. Only one interface from the main control unit to each master is then needed. The interface may e.g. include one or several cables.
According to one embodiment, a second of the distributed control devices is configured to be active in the partial detect mode, wherein the first and the second distributed control devices are grouped into the same group. With this configuration it is possible to have e.g. a partial area in a corner of the touch surface and energy is saved compared to having all the distributed control devices active.
According to another embodiment, the first distributed control device is configured to detect a predetermined gesture and to generate a gesture signal. The first distributed control device may thus independently emit light in the partial area and also detect a gesture in the same area.
According to one embodiment, the second distributed control device is configured to detect the predetermined gesture and to generate the gesture signal. Thus, the first and the second distributed control device may be configured to cooperate in the partial detect mode to detect a gesture.
According to one embodiment, the partial area is a corner of the touch surface. According to another embodiment, the partial area is an area of the touch surface with a size adapted to the size of an area of a fingerpad. Thus, only a limited area of the touch surface has to be sensitive to touches.
According to one embodiment, the first emitter is configured to emit light along a detection line being reflected in the partial area of the touch surface. Thus, the partial area will be sensitive to a gesture. The first emitter may e.g. be configured to emit light along a detection line that hits a central point of the dedicated partial area. If the partial area is small enough, the user will be guided to touch the partial area and then attenuate the light, even if light is emitted along only one detection line.
According to one embodiment, the first emitter is configured to emit light in a predetermined emission angle α adapted to a distance between the first emitter and the partial area such that the emitted light is reflected in a certain area of the partial area. Thus, a dedicated area for detecting a touch and/or gesture is covered.
According to one embodiment, the first distributed control device is configured to control the first emitter to emit light with an energy adapted to the partial detect mode. As the distance that has to be covered by the emitted light is short, the light can be emitted with less energy than in a normal mode and still be used for detecting a touch.
The predetermined gesture may be characterized by a touch of a touching object at the partial area.
According to one embodiment, the main control unit is configured to activate a feature of the touch sensitive system in response to receiving a gesture signal. For example, activate a feature comprises changing the mode of the touch sensitive system from the partial detect mode to a normal mode, wherein the main control unit is configured to change mode from the power saving mode to a normal mode. Thus, the main control unit may be waken up when a predetermined gesture is detected.
According to another embodiment, a remaining of the distributed control devices which were not active in the partial detect mode are configured to be activated in response to receiving a gesture signal, or an activation signal. Thus, the first or the second of the distributed control devices may wake up the other distributed control devices such that the touch sensitive system may detect a touch over the whole touch surface.
According to one embodiment, the touch sensitive system is based on Frustrated Total Internal Reflection, FTIR.
According to a second aspect, the object is at least partly achieved by a method for activating a feature of a touch sensitive system. The touch sensitive system comprises a touch sensitive panel defining a touch surface and a main control unit configured to control a plurality of distributed control devices each configured to control operation of a segment of emitters and detectors, wherein each emitter is configured to emit light into the panel for propagation in the panel and each detector is configured to detect the light propagating in the panel. The method comprising:

    
    
        setting the touch sensitive system in a partial detect mode in which mode a first of the distributed control devices is active;
        controlling a first emitter to emit light in a partial region of the panel coincident with a partial area of the touch surface;
        detecting a predetermined gesture in the partial area of the touch surface;
        generating a gesture signal indicating the predetermined gesture;
        activating a feature of the touch sensitive system in accordance with the predetermined gesture.
    
    


According to one embodiment, the method comprises setting the main control unit in a low power mode when the touch sensitive system is set in the partial detect mode.
According to one embodiment, the method comprises controlling the first emitter to emit light with an energy adapted to the partial detect mode.
According to one embodiment, the distributed control devices are grouped into at least one group. The method may comprise setting the touch sensitive system in a partial detect mode in which mode also a second of said distributed control devices is active, wherein the first and the second distributed control device belongs to the same group. The second distributed control device may then perform the steps of detecting a predetermined gesture and generating a gesture signal.
According to another embodiment, the first distributed control device performs the steps of detecting a predetermined gesture and generating a gesture signal.
According to another embodiment, the method comprises if a predetermined gesture is detected, activating a remaining of the distributed control devices which were not active in the partial detect mode.
According to one embodiment, the method comprising sending the gesture signal to the main control unit and activating a feature comprises changing the mode of the touch sensitive system from the partial detect mode to a normal mode.
According to a third aspect the object is at least partly achieved by a computer-readable medium comprising computer instructions configured to cause a processor to execute the method according to any of the steps as herein described.
Preferred embodiments are set forth in the dependent claims and in the detailed description.



SHORT DESCRIPTION OF THE APPENDED DRAWINGS
Below the invention will be described in detail with reference to the appended figures, of which:
FIG. 1A illustrates a side view of a touch arrangement based on FTIR.
FIG. 1B illustrates a touch sensitive system based on FTIR according to some embodiments of the invention.
FIG. 1C illustrates a touch sensitive system based on FTIR according to some other embodiments of the invention.
FIG. 2 illustrates a control device according to some embodiments of the invention.
FIGS. 3-4 are schematic views of different embodiments of the invention.
FIG. 5 illustrates how emitted light is reflected in a partial area of the touch surface.
FIGS. 6A-6B are showing emitters emitting light with various emitting angles.
FIG. 7 is a flowchart of a method for activating a feature of a touch sensitive system.



DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
FIG. 1A-1B illustrates a side view and a top view of an example embodiment of a touch-sensitive system 1 that is based on the concept of FTIR (Frustrated Total Internal Reflection), also denoted “FTIR system”. The touch arrangement 11 operates by transmitting light inside a touch sensitive panel 2, from light emitters 4 to light sensors or detectors 5, so as to illuminate a touch surface 3 from within the panel 2. The panel 2 is made of solid material in one or more layers and may have any shape. The panel 2 defines an internal radiation propagation channel, in which light propagates by internal reflections. In the example of FIG. 1A, the propagation channel is defined between two boundary surfaces 12, 13 of the panel 2, where a top surface 12 allows the propagating light to interact with touching objects 14, 15 and thereby defines the touch surface 3. This is achieved by injecting the light into the panel 2 such that the light is reflected by total internal reflection (TIR) in the touch surface 3 as it propagates through the panel 2. The light may be reflected by TIR in the bottom surface 13 or against a reflective coating thereon. It is also conceivable that the propagation channel is spaced from the bottom surface 13, e.g. if the panel 2 comprises multiple layers of different materials. The panel 2 may be designed to be overlaid on or integrated into a display device or monitor.
The system 1 allows one or several objects 14, 15 that is brought into close vicinity of, or in contact with, the touch surface 3 to interact with the propagating light at the point of touch. In this interaction, part of the light may be scattered by the object 14, 15, part of the light may be absorbed by the object 14, 15, and part of the light may continue to propagate in its original direction across the panel 2. Thus, the touching object 14, 15 causes a local frustration of the total internal reflection, which leads to a decrease in the energy (power/intensity) of the transmitted light, as indicated by the thinned lines downstream of the touching objects 14, 15 in FIG. 1A. If two objects 14 and 15 happen to be placed after each other along a light path i from an emitter 4 to a detector 5, part of the light will interact with both these objects 14, 15. Provided that the light energy is sufficient, a remainder of the light will interact with both objects 14, 15 and an output signal will be generated that allows both interactions (touch inputs) to be identified. The output signal is received to a distributed control device 6, which may process the output signal before it is sent to a main control unit 8. Here, another distributed control device 6 controls the emitter 4 to emit light into the panel 2.
The emitters 4 are distributed along the perimeter of the panel 2 to generate a corresponding number of light sheets inside the panel 2. Each emitter 4 generates a beam of light that expands in the plane of the panel 2 while propagating in the panel 2. Each beam propagates from one or more entry or incoupling points on the panel 2. The detectors 5 are distributed along the perimeter of the panel 2 to receive the light from the emitters 4 at a number of spaced-apart outcoupling points on the panel 2. It should be understood that the incoupling and outcoupling points merely refer to the position where the beam enters and leaves, respectively, the panel 2. Thus, one emitter/detector may be optically coupled to a number of incoupling/outcoupling points in the panel 2. The emitters 4 and detectors 5 may be implemented in a printed circuit board (PCB) around the periphery of the panel 2. As illustrated in FIGS. 1B and 1C, the emitters 4 and detectors 5 distributed around the panel 2 are divided into segments 7, where the emitters 4 and detectors 5 in each segment 7 are electrically connected to a distributed control device 6. The emitters 4 and detectors 5 may be equally divided into the segments 7, such that each segment 7 includes the same number of emitters 4 and detectors 5. The touch sensitive system 1 thus comprises a plurality of distributed control devices 6 each configured to control operation of a segment 7 of emitters 4 and detectors 5.
Each emitter 4 is configured to emit light in any of the visible, infrared or ultraviolet spectral regions. Each detector 5 is configured to receive the light and generate a light signal in any of these regions.
The distributed control devices 6 can be divided into one or several groups. In FIG. 1B, all the distributed control devices 6, here a number of eight, are grouped into the same group. In FIG. 1C, the eight distributed control devices 6 are instead divided in a first and a second group 27, 28, with two control devices 6 in the first group 27 and six in the second group 28. The control devices 6 can be divided into more groups if appropriate. The distributed control devices 6 in each group are preferably connected in series to minimize the need for cables, and communicate serially with each other. One distributed control device 6 in each group is operatively connected directly to a main control unit 8 and this control device 6 is a master over the other distributed control devices 6 in the group. One purpose of dividing the distributed control devices 6 into several groups is to be able to limit the number of control devices 6 that are active.
The main control unit 8 is configured to control the distributed control devices 6 via the control device 6 acting as master, here called “master”. The master may be configured to send an activation signal to the remaining distributed control devices 6 which are not active to thereby activate them. The activation signal may include a synchronisation signal to synchronize processor clocks in the distributed control devices 6. In this way the control devices 6 will operate in the same time frame such that they can operate in synchronization.
The control devices 6 control the emitters 4 and the detectors 5 according to one or several schemes. The control devices 6 are acting according to the same scheme such that all the emitters 4 and detectors 5 around the panel 2 are acting in common. According to one embodiment, a segment 7 of emitters 4 and detectors 5 is chosen such that the emitters 4 and the detectors 5 in the segment 7 do not need to emit and detect at the same time. This is advantageous, as detection values and/or signals in a control device 6 might become disturbed by disturbances introduced by large currents in the control device 6 when light is controlled to be emitted by the same. For example, if the panel 2 has a rectangular shape, the emitters 4 and detectors 5 in a segment 7 may be distributed along only one of the sides of the panel 2 as illustrated in FIGS. 1B and 1C. Then the emitters 4 and the detectors 5 in a segment 7 do not have to emit and detect at the same time to cover the touch surface 3.
In FIG. 1B, a first distributed control device 9 of the distributed control devices 6 is operatively connected directly to the main control unit 8. The first control device 9 is thus the master. The remaining distributed control devices 6 are connected in series to the first control device 9. In a partial detect mode which will be explained in the following, it is in this embodiment only the first distributed control device 9 that is active.
In FIG. 1C, the first group 27 includes the first and a second distributed control device 9, 26. In the figure it is illustrated that it is the first control device 9 that is operatively connected to the main control unit 8, and the first control unit 9 is thus the master. One of the first and second control device 9, 26 is configured to control one or several connected emitters 4 to emit light, and the other one of the first and second control device 9, 26 is configured to detect the emitted light via one or several detectors 5. The other one of the distributed control devices 9, 26 is then configured to detect the predetermined gesture and to generate the gesture signal. In the second group 28 another distributed control device 6 is the master, and the remaining control devices 6 in the second group 28 are connected in series to the master. The master is operatively connected directly to the main control unit 8. In partial detect mode, both the first and the second distributed control devices 9, 26 are active, while the distributed control devices 6 in the second group 28 are not active. It is understood that the distributed control devices 6 may be divided into more groups and that more than one group may be active at the same time. For example, the distributed control devices 6 may be divided into a further third group, similar to the first group, with two distributed control devices 6. Then, in partial detect mode, the distributed control devices 6 in the first and the third groups may be active, while the remaining control devices 6 in the second group are not active.
The group or groups that are active may then sense touches on one or several partial areas 22 of the touch surface 3. Thus, energy can be saved compared to having all the distributed control devices 6 activated.
In FIG. 2 an example of a distributed control device 6 is illustrated. In one implementation the control device 6 is an integrated circuit such as an ASIC (Application Specific Integrated Circuit). The ASICs are then integrated in a PCB (Printed Circuit Board) around the periphery of the panel 2 together with the emitters 4 and detectors 5. The control device 6 comprises a processing unit 16 and a computer readable storage medium 17. The processing unit 16 may be a computer programmable unit (CPU) of 1-100 MIPS (Million instructions per second), preferably 10-50 MIPS. The computer readable storage medium 17 may have a storage capacity of 1-64 KB, preferably 8-50 KB. The processing unit 16 is connected to an emitter control unit 20 configured to control the 1-K emitters 4 in a segment 7 to emit light according to a scheme. Alternatively the control unit 20 is integrated in the processing unit 6. The processing unit 16 is further connected to a detector control unit 19 configured to control the 1-N detectors 5 in the same segment 7. Light from the panel 2 is detected by one or several detectors 5 in the same segment 7 and received to the detector control unit 19 where a light signal is created. The detector control unit 19 is connected to an analogue to digital (A/D) converter unit 18 where the light signal is digitalized into light data before it is received to the processing unit 16. The light data may be processed before it is sent as one or several output signals or as light data to the main control unit 8. For example, the control device 6 may be configured to compensate the received light for ambient light. The control device 6 may store an ambient background profile of the light data, and compensate the light data with the ambient background profile. The ambient background profile may be continuously updated.
If the distributed control device 6 is not a master, the output signal(s) are sent to the main control unit 8 via the master and via intermediate distributed control device 6, if any. The distributed control device 6 in FIG. 2 is a master and is thus operatively connected directly to the main control unit 8, here via a signal line. Signal lines may also go to and from the distributed control device 6 to the other distributed control devices 6.
One or several schemes can be loaded into the computer readable storage medium 17 as computer instructions operable to cause the processing unit 16 to perform various operations. For example, at start up of the touch sensitive system 1, the main control unit 8 may be configured to send one or several schemes to the distributed control devices 6, whereby the one or several schemes are loaded into their respective computer readable storage medium 17. Light is emitted and detected with a certain frame rate which can be adapted to the partial detect mode. Within a frame light is both emitted and detected.
The touch sensitive system 1 is configured to be set in a partial detect mode. In the partial detect mode, the first 9 of the distributed control devices is configured to be active. This mode may be initiated when there has been no touch on the touch surface 3 for a certain time, or if a user actively sets the system 1 in the mode by e.g. interacting with the touch surface 3 in a certain way. The main control unit 8 may be configured to be set in a low power mode when the touch sensitive system 1 is set in the partial detect mode. When the touch sensitive system 1 is set in a partial detect mode, the main control unit 8 may be configured to send a partial detect mode signal to the first control unit 9, which in response deactivates the other distributed control devices 6. Preferably the first control unit 9 also deactivates the emitters 4 and detectors 5 connected to the first control unit 9 which are not used in the partial detect mode. If more than one group, the main control unit 8 may be configured to send a partial mode signal to each of the masters of the control devices 6, which in response will deactivate or activate the control devices 6 in its group according to predefined rules for the partial detect mode. For example, a second distributed control device 26 belonging to the same group as the first distributed control device 9 may be configured to also be active in the partial detect mode. Any of the activated first or second distributed control devices 9, 26 may be configured to generate a gesture signal 21.
In FIG. 3 one embodiment is shown where a first emitter 10 is located close to a corner of the panel 2. An area of the touch surface 3 limited by the corner defines a partial area 22, here in the shape of a triangle. The partial area 22 is thus a corner of the touch surface 3. The first emitter 10 is connected to the first distributed control device 9, and the first emitter 10 is configured to be controlled by the same. In the partial detect mode the first distributed control device 9 is configured to control the first emitter 10 to emit light in a partial region of the panel 2 coincident with the partial area 22 of the touch surface 3. The first distributed control device 9 is further electrically connected to a segment 7 of emitters 4 and detectors 5. At least one detector 5 in the segment 7 has an optical path to the panel 2 such that a detection line is defined from the first emitter 10 to the detector 5. According to one embodiment a plurality of detectors 5 are used to detect the light emitted from the first emitter 10 along a plurality of detection lines to cover a larger partial area 22. Thus, in the partial detect mode, the first distributed control device 9 controls the first emitter 10 to emit light into the panel 2, and the light is detected by one or several of the detectors 5 and sent to the processing unit 16 (FIG. 2) of the first distributed control device 9. If a user makes a predetermined gesture on the partial area 22, this gesture can be detected by the processing unit 16 by analysing the light received from the detector(s) 5.
The segment 7 of emitters 4 and detectors 5 are located along a first side of the panel 2, and the first emitter 10 is located along a second side at an angle to or parallel to the first side. The first and second side are according to one embodiment arranged perpendicular to each other. The partial area 22 is here limited by the first and second sides. The first emitter 10 may be an extra emitter 10 not being one of the number of emitters 4 and detectors 5 belonging to the segment 7. In the figure only a first emitter 10 is illustrated, but it is understood that the embodiment may encompass a plurality of first emitters 10, e.g. two or three, also connected to the first distributed control device 9 and configured to emit light in the partial region of the panel 2 coincident with the partial area 22 of the touch surface 3. It is also understood that the first emitter 10 instead may be one of the emitters 4 in the segment 7 located along the first side of the panel 2, and that one or several detectors 5 may be located along the second side of the panel 2. The one or several detectors 5 located along the second side of the panel 2 may be extra detectors that are only used in partial detect mode.
Instead of using only one distributed control device 6 as in FIG. 3, the configuration of a first group 27 of two distributed control devices 6 illustrated in FIG. 1C can be used. Then, the first emitter 10 (or several first emitters 10) may be controlled by the first distributed control device 9, and the detectors 5 may be controlled by the second distributed control device 26.
In FIG. 4 a further embodiment of the touch system 1 is shown where a first emitter 10 is located close to a partial area 22 of the touch surface 3, here in the shape of a circle 22. The partial area 22 may have any other size, such as rectangular, triangular etc. The partial area 22 may be an area of the touch surface 3 with a size adapted to the size of an area of a fingerpad. The size of the partial area 22 may be large enough such that a touch of a fingerpad can be detected, but small enough such that the area for detection becomes limited. The first emitter 10 is connected to the first distributed control device 9, and the first emitter 10 is configured to be controlled by the same. In the figure the panel 2 is shown where part of the upper surface 12 and part of the touch surface 3 are being covered with a filter, e.g. black colour, here illustrated in a lattice to be able to illustrate components of the system 1.
As in the embodiment illustrated in FIG. 3, in the partial detect mode, the first distributed control device 9 is configured to control the first emitter 10 to emit light in the partial region of the panel 2 coincident with the partial area 22 of the touch surface 3. The first distributed control device 9 is also electrically connected to a segment 7 of emitters 4 and detectors 5. According to one embodiment, at least one detector 5 in the segment 7 has an optical path to the panel 2 such that light emitted along a detection line from the first emitter 10 will be detected by the detector 5. The detector 5 is then configured to detect light reflected both in a main touch surface 24 and light reflected in the partial area 22. A plurality of detectors 5 may be used to detect the light emitted from the first emitter 10. Thus, in the partial detect mode, the first distributed control device 9 controls the first emitter 10 to emit light into the panel 2 in the partial region of the panel 2 coincident with the partial area 22. The light is detected by one or several of the detectors 5 whereby at least one light signal is generated indicating the detected light. The light signal is then sent to the processing unit 16 (FIG. 2) of the first distributed control device 9. If a user makes a predetermined gesture on the partial area 22, this gesture can be detected by the processing unit 16 by analysing the light signal received from the detector(s) 5.
It is also understood that the first emitter 10 instead may be one of the emitters 4 in the segment 7, and that one or several extra detectors may be located on the opposite side of the partial area 22 where the first emitter 10 now is located in FIG. 4.
The partial area 22 of the touch surface 3 is according to one embodiment marked-up on the touch surface 3 such that it is obvious for the user where to make a gesture. The area 22 may e.g. be marked with the text “ON”, with a line surrounding the area 22 or with another marking.
The predetermined gesture may be characterized by a touch of a touching object 14 at the partial area 22. Other more complex gestures may be defined, e.g. a touch and a pressure, or dragging the touching object 14 a small distance. The touching object 14 may be a finger or a pointing device. Any of the active control devices 6, e.g. the control device 6 detecting the light, is configured to analyse the detected light after it has been digitalized and to determine if a predetermined gesture has been detected. If the predetermined gesture is a single touch the analysis may be performed by comparing the signal level of the received light with a previously determined signal level of the received light. If an attenuation of the light can be determined, a touch has been detected. In this case it is not necessary to extract any details such as the position etc of the touch, as the first control device 9 only emits light to the partial area 22. Thus, the analysis can be kept relatively simple and energy saving. The received light is preferably also compensated for ambient light. This can be made by determining an ambient profile of the light and compensating the received light with the ambient light profile. The ambient light profile may be determined by the control device 6, or may be a previously ambient light profile determined by the main control unit 8. The ambient light profile is preferably continuously updated. The control device 6 detecting the light may be configured to detect more advanced gestures such as a pressure, or a dragging touch. In the Swedish application 1251014-5 it is explained how a pressure of a touch can be determined in an FTIR-system, and the context of the application is hereby incorporated by reference. In this application it is also explained how a pattern of a touch can be determined by establishing a trace of the touch. The trace comprises e.g. positions and an identity for the touch. As long as the touching object 14 touches the touch surface 3, positions for the touching object 14 with the same identity can be detected. When the touching object 14 is lifted from the touch surface 3 there will not be any more positions with this identity. The trace will show a pattern, which can be compared with patterns identifying predetermined gestures. If a time aspect is introduced, a velocity for the trace can also be determined to distinguish a gesture.
For detecting a touch on the main touch surface 24 in a normal mode, the signal to noise ratio




  s
  n




preferably should be as large as possible to be able to retrieve desired information from the touch. In a partial detect mode, the signal to noise ratio can be lower as less information has to be retrieved about the touch. For example, the emitted light can be emitted with a lower intensity, and/or the ambient light compensation can be made in a simpler way than in a normal mode.

If a predetermined gesture on the partial area 22 of the touch surface 3 is detected, the control unit detecting the light is configured to generate a gesture signal indicating the predetermined gesture. The gesture signal can be sent to the main control unit 8 whereby the main control unit 8 is configured to activate a feature of the touch sensitive system 1. To activating a feature may then comprise changing the mode of the touch sensitive system 1 from the partial detect mode to a normal mode, wherein the main control unit 8 is configured to change mode from the power saving mode to a normal mode. Thus, the main control unit 8 can be activated by making a gesture in the partial area 22.
To activate a feature may instead comprise sending the gesture signal to the remaining distributed control devices 6 not being active in partial detect mode, whereby the remaining distributed control devices 6 are configured to be activated. If the distributed control devices 6 are grouped into different groups, the gesture signal may be sent via the main control unit 8 to the remaining distributed control devices. The gesture signal may have the same content as the previously mentioned activation signal, and will then synchronize processor clocks in the distributed control devices 6. The distributed control devices 6 will then control their respective emitters 4 to emit light and their respective detectors 5 to detect light such that one or several touches can be detected over the whole touch surface 3. The system 1 may now await a touch on the main touch surface 24 before the main control unit 8 is activated. As the distributed control devices 6 may be configured to make some analysis of the detected light, a single touch may e.g. be detected by the distributed control devices 6. If an interaction, i.e. a touch on the main touch surface 24 that affects a detected parameter, is detected, this information is distributed to the master of the group which then will send a wake-up signal indicating the touch data to the main control unit 8 which will activate the same.
It is of course possible to simultaneously activate the distributed control devices 6 and the main control unit 8. This can be accomplished by sending the gesture signal to both the distributed control devices 6 and to the main control unit 8.
If the touch sensitive panel 2 is overlaid on or integrated into a display device, the gesture in the partial area 22 may invoke a feature visible on the display device. This feature may include showing a graphical item on a graphical user interface, GUI, of the display device, such as a “menu”, or initiating the function of “return” and thus go to a higher level in the GUI-environment or return to a previous shown view. To invoke these features, the main control unit 8 has to be involved and be configured to communicate with the display device. Thus, the gesture signal may both wake up the main control unit 8 and invoke a feature visible on the display device. Different gestures can be used to invoke different features visible on the display device.
In FIG. 5 it is illustrated how light is emitted into the touch sensitive panel 2 such that light is reflected to the touch surface 3 whereby a touching object 14 has a chance to attenuate the light. The first emitter 10 is thus configured to emit light along a detection line being reflected in the partial area 22 of the touch surface 3. A detection line is defined as a path of the light emitted from an emitter 10 and detected by a detector 5. If several first emitters 10 and/or several detectors are used, more detection lines can be had on the partial area 22. The touch surface 3 is here partly covered with a filter, e.g. black colour, which is removed in the partial area 22.
In FIGS. 6A-6C it is illustrated that the placement of the first emitter 9 in relation to the partial area 22 may have an impact on how large part of the partial area 22 that will be covered by the emitted light. The first emitter 10 may emit light in an emission angle α. The further away the first emitter 10 is located from the partial area 22, the greater the energy of the emitted light has to be to reach the detector 5 also after it has become attenuated. However, the further away from the partial area 22, the smaller the size of the emission angle α to cover the same partial area 22, thus the light can be emitted with less energy. This relationship is illustrated in FIGS. 6A and 6B, where in FIG. 6A the first emitter 10 is located a first distance from the partial area 22, and the emission angle is small to cover the partial area 22. In FIG. 6B the first emitter 10 is located a second distance from the partial area, where the second distance is smaller than the first distance, and the emission angle α here has to be greater to cover the same partial area 22 as in FIG. 6A.
If the partial area 22 has a size that is small enough such that a fingerpad touching the partial area 22 always will cover at least half the area 22, the emission angle α can be kept small such that the centre of the area 22 is covered, but not the whole partial area 22. This embodiment is illustrated in FIG. 6C, where the first emitter 10 is placed close to the partial area 22 and emits light in a small emission angle α such that the centre of the partial area 22 will be covered by the emitted light. Thus, the first emitter 10 is configured to emit light in a predetermined emission angle α adapted to a distance between the first emitter 10 and the partial area 22 such that the emitted light is reflected in a certain area of the partial area 22. If a greater emission angle α is used, more detectors 5 or a detector 5 covering a larger area may be used to detect light from the wider angle α.
As the distance between the first emitter 10 and the detector 5 is small, the energy of the emitted light can be kept small compared to the energy needed for emitting light over the main touch surface 24. The first distributed control device 9 may thus be configured to control the first emitter 10 to emit light with an energy adapted to the partial detect mode. The energy of the emitted light may be predetermined, or may be adapted during running.
The first distributed control device 9 may be configured to regulate the energy transmitted by the first emitter 10, such that the received energy by the detector 5 is sufficient to be able to determine a touch in the dedicated area. This can be done be comparing the present signal to noise ratio with a predetermined signal to noise ratio necessary for detecting a gesture, e.g. a touch, and regulate the energy of the light to an appropriate level based on the result of the comparison. This may be advantageous e.g. if the first emitter 10 has been previously used for emitting light over the main touch surface 24 and now shall be used in the partial detect mode, and/or if the partial area 22 comprises e.g. contaminations on the surface 3 which disturb the propagating light. Light can then be emitted into the panel 2 with an optimal amount of energy for detecting a touch in the partial area 22 such that energy can be saved.
A method for activating a feature of the described touch sensitive system 1 will know be described with reference to the flowchart in FIG. 7. The method comprises setting the touch sensitive system 1 in a partial detect mode in which mode a first 9 of the distributed control devices 6 is active (A1). As explained with the system 1, instead two or three first distributed control devices 9 may be activated in partial detect mode. When setting the touch sensitive system 1 in the partial detect mode, the main control unit 8 may simultaneously be set in a low power mode to save energy. A first emitter 10 is controlled to emit light in a partial region of the panel 2 coincident with a partial area 22 of the touch surface 3 (A2). The first emitter 10 may be configured to emit light with an energy adapted to the partial detect mode. A user then makes a predetermined gesture on the partial area 22, and the method continues with detecting the predetermined gesture in the partial area 22 (A3). A gesture signal 21 is then generated indicating the predetermined gesture (A4) and thereafter a feature of the touch sensitive system 1 is activated in accordance with the predetermined gesture (A5). The steps A4 and A5 may include sending the gesture signal 21 to the main control unit 8 and activating a feature comprises changing the mode of the touch sensitive system 1 from the partial detect mode to a normal mode. The steps A4 and A5 may instead or also include activating the other distributed control devices 6 if a predetermined gesture is detected.
The distributed control devices are divided into at least one group. The step A1 of the method may comprise setting the touch sensitive system 1 in a partial detect mode in which mode also a second 26 of the distributed control devices 6 is active, wherein the first and the second distributed control devices 9, 26 belongs to the same group. The second distributed control device 26 may then perform the steps of A3 of detecting a predetermined gesture and A4 of generating a gesture signal.
Instead, the first distributed control device 9 may perform the steps of detecting a predetermined gesture (A3) and generating a gesture signal (A4).
The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

## Claims

1. A touch sensitive system comprising:
a touch sensitive panel defining a touch surface;
a plurality of emitters configured to emit light across the touch surface;
a plurality of detectors configured to detect the light;
a plurality of distributed control devices, wherein each of the plurality of distributed control devices is configured to control operation of a respective segment of the plurality of emitters and the plurality of detectors;
a main control unit connected with the plurality of distributed control devices;
wherein during a partial detect mode, a first subset of said plurality of distributed control devices are activated and wherein the first distributed control device in the first subset is configured to control a first set of emitters to emit light across a partial area of said touch surface; and
wherein the first distributed control device is further configured to:
detect a predetermined gesture on the partial area of said touch surface; and
generate a gesture signal indicating the predetermined gesture,


wherein a remaining set of distributed control devices which were not active in the partial detect mode are configured to be activated in response to receiving the gesture signal.

2. The touch sensitive system according to claim 1, wherein said main control unit connected to the plurality of distributed control devices is set in a low power mode when the touch sensitive system is set in said partial detect mode.

3. The touch sensitive system according to claim 1, wherein each distributed control device comprises a processing unit and a computer readable storage medium.

4. The touch sensitive system according to claim 1, wherein the distributed control devices are grouped into at least one group.

5. The touch sensitive system according to claim 4, wherein the distributed control devices in each group are connected in series.

6. The touch sensitive system according to claim 4, wherein only one distributed control device in each group is operatively connected directly to the main control unit.

7. The touch sensitive system according to claim 4, wherein a second of the distributed control devices is configured to be active in the partial detect mode, wherein the first and the second distributed control devices are grouped into the same group.

8. The touch sensitive system according to claim 7, wherein the second distributed control device is configured to detect a predetermined gesture and to generate a gesture signal.

9. The touch sensitive system according to claim 1, wherein the first distributed control device is configured to detect a predetermined gesture and to generate a gesture signal.

10. The touch sensitive system according to claim 1, wherein the partial area is a corner of the touch surface.

11. The touch sensitive system according to claim 1, wherein the partial area is an area of the touch surface with a size adapted to the size of an area of a fingerpad.

12. The touch sensitive system according to claim 1, wherein the first emitter is configured to emit light along a detection line being reflected in the partial area of the touch surface.

13. The touch sensitive system according to claim 1, wherein the first emitter is configured to emit light in a predetermined emission angle a adapted to a distance between the first emitter and the partial area such that the emitted light is reflected in a certain area of the partial area.

14. The touch sensitive system according to claim 1, wherein the first distributed control device is configured to control the first emitter to emit light with an energy adapted to the partial detect mode.

15. The touch sensitive system cording to claim 1, wherein said predetermined gesture is characterized by a touch of a touching object at the partial area.

16. The touch sensitive system according to claim 1, wherein the main control unit connected to the plurality of distributed control devices activates a feature of the touch sensitive system in response to receiving a gesture signal.

17. The touch sensitive system according to claim 16, wherein activate a feature comprises changing the mode of the touch sensitive system from said partial detect mode to a normal mode, wherein the main control unit is connected to the plurality of distributed control devices to chance mode from said power saving mode to a normal mode.

18. The touch sensitive system according to claim 1, wherein said touch sensitive system is based on Frustrated Total Internal Reflection, FTIR.

19. A method for activating a feature of a touch sensitive system comprising a plurality of distributed control devices connected with a main control unit, the method comprising:
emitting light from a plurality of emitters across a touch surface;
detecting the emitted light at a plurality of detectors;
controlling, with the plurality of distributed control devices, operation of the plurality of emitters and the plurality of detectors;
activating a first subset of the plurality of distributed control devices in a partial detect mode;
detecting, with a first distributed control device, a predetermined gesture on a partial area of said touch surface; and
generating, with the first distributed control device in the first subset, a gesture signal indicating the predetermined gesture;
wherein a remaining set of distributed control devices which were not active in the partial detect mode are activated in response to receiving the gesture signal.