GB2505661A - Force sensitive touch screen using strain gauges - Google Patents

Abstract

An electronic device for receiving force touch-based control input, using at least one layer of material with a number of strain gauges. The strain gauges being configured to obtain location-based and pressure-based data indicative of touch on the touch-sensitive input area, and a computing entity configured to determine an occurrence of a touch implied by, pressure point or points on the touch-sensitive area engendered by the user of the device by finger, stylus or by a similar means. The strain gauges may be inserted into a molded tablet, mobile or other device, or be printed by inkjet printing in a laminated arrangement.

Description

USER INTERFACE FOR TOUCH-BASED CONTROL INPUT AND

RELATED METHOD OF MANUFACTURE

FIELD OF THE INVENTION

Generally the present invention concerns electronic devices and related user interfaces. Particularly, however not exclusively, the invention relates to user interfaces (U I), user input devices for force touch based control in-corporating pressure induced deformation sensing technology.

BACKGROUND

User interfaces (UI) of electronic devices such as computers including desktop, laptop and palmtop devices have developed tremendously since the advent of the era of modern computing. Simple switches, buttons, and knobs have been in many cases replaced by keyboard, keypad, mouse, speech recognition input, touch display and related UI means like touch- pad. Such more modern UT alternatives can provide the users of the asso-ciated devices with somewhat bearable user experience after a typically extensive adoption period.

In particular, touch surfaces such as touch pads and touch screens un- doubtedly form the de facto' UI of modern smartphones, tablets and sup-plementary UT of many desktop computers as well. The touch displays may generally apply of a number of different technologies for implement- ing the touch-sensitive functionality. Among various other potential op-tions, e.g. capacitive, resistive, infrared, optical imaging (camera-based), FTIR (frnstrated total internal reflection), acoustic, and hybrid solutions are feasible.

However, many of the above mentioned touch surface technologies, espe-cially the resistive touch screen, require various layers and substrates, which affect the visibility and light transmission of the screen. This de-creases the user experience considerably compared to what it would be without any or at least substantial number of layers on top of a plain dis-play. This also limits the capabilities of the screen and is a drawback for manufacturers who aim to improve the performance of touch displays in terms of resolution and brightness.

Other options, such as capacitive touch screen, require the desired input object to be conductive or have a di&ectric different than that of air. This limits the capabilities and applicability of the screen, as the input gestures shall thus be done almost exclusively by hand. Further on, this technology practically dismisses the ability to sense different pressures inflicted by a touch. Also some other technologies are limited to the extent that they on-ly function with a certain type of stylus.

Some of the mentioned technologies, such as acoustic and optical touch screens, are suitable only for devices of certain size. This is undesirable, as many modern applications would benefit from scalable screens to fit for different needs and designs.

Technologies, such as the infrared touch screen, are ftirther limited by their resolution due to their spacing of touch sensing elenients. This be-conies niore difficult a setback as more accuracy, which depends on the resolution, is needed.

Further on, many of the discussed technologies are prone to breakage due to sensitivity to external impacts. To overcome this, some manufacturers have implemented a stronger type of protective glass on the outer surface of the screen. This construction however increases the weight as well as the price of the device and doesn't necessarily solve the problem since many of the components may still be exposed or attached to the outer sur-face and impacts inflicted on the overlaying glass may actually be spread on to the components, which may result to the failure of components.

Further on, some touch screen technologies don't allow protection from dust and moisture. This also limits the working conditions and hence the

applicability of the touch screen device.

Still further, many a time the constniction of the touch screen becomes complex. For this reason there is a need for a simple design that enables quick and cost-efficient manufacturing, of the touch surface device.

Strain gauges have been previously used th a number of contexts. Devices which measure defonnation with a strain gauge have been set forth.

SUMMARY OF THE INVENTION

The objective of the embodiments of the present invention is to at least al- leviate one or more of the aforesaid drawbacks evident in the prior art ar- rangements particularly in the context of force touch-based user input ar- rangernents. The objective is generally achieved with a device and a corre-sponding method of manufacture in accordance with the present invention.

The device may be utilized for simpler buttons and 2D touch displays as well as for a technological implementation option to be exploited in con-nection with 3D gesture tracking and position tracking.

In accordance with one aspect of the present invention an electronic de-vice, such as a cell phone, a PDA, a tablet, a desktop computer, a laptop computer, a wristop computer, or a user input device for such, capable of receiving force touch-based control input, comprises a protective entity including a predetermined touch-sensitive input area and comprising at least one layer of material with a number of strain gauges embedded therein, the protective entity and the strain gauges being configured to obtain location-based and pressure-based data indicative of touch on the touch-sensitive input area, and a computing entity configured to determine, on the basis of the obtained data, an occurrence of a touch implied by the pressure point or points, such as location and pressure thereof, on the touch-sensitive area engen-dered by the user of the device by finger, stylus or by a similar means.

Optionally, the computing entity may be configured to determine the loca-tion(s) by substantially determining at least indications of force vectors, preferably along the lines between said strain gauges, on the basis of the obtained data.

Aiii embodiment of the computing entity, such as at least one processor, microcontroller, a plurality of at least functionally connected processing devices, or a similar entity, may indeed be configured to determine the lo-cation of the pressure point or points on the basis of the data indicative of touch on the touch-sensitive input area defined on the surface of the pro- tective entity. Indication of touch pressures or forces may also be deter-mined. Optionally the computing entity is further configured to derive the control input, such as a nunTher of instructions regarding pointer move-ment and/or location selection, relative to a target application, such as an active application running on the electronic device, on the basis of the de- termination result. Yet, the computing entity may be configured to pro- vide the determined or derived data forward towards a number of other en-tities.

In one embodiment, the protective entity comprises an overlay, such as film or sheet including, preferably optically transmissive, material that may be placed, on a light-emissive area such as that of a display panel.

The protective entity comprises strain gauges that can be placed on the pe- riphery area of the established touch input device to improve light trans-mission of the center area perpendicular to the light emitting device under the touch input device. The protective entity may thus simultaneously act as a screen cover and input device for the display. The protective entity may comprise or substantially consist of plastic and/or glass, for instance.

The protective entity may be provided with desired properties in terms of touch feel, flexibility, transparency, hardness, scratch-resistance, anti-glare treatment, filtering properties, etc. Preferably the protective entity is optically substantially transparent rela-tive to predetermined wavelengths such as visible light to be emitted by a light emitting device such as a display panel for enabling flawless lighting of the touch input device as well as viewing experience, or at least the por- tion of the protective entity covering the emissive area of the panel is pref-erably such. The protective entity may be a single layer film comprising the strain gauges and electronics embedded therein. Alternatively the pro- tective layer may be at least partially provided with a multi-part or multi- layer overlay containing e.g. multiple overlay layers, such as a thin sub-strate for accommodating elements such as strain gauges and a thicker protective outer layer such as a front glass or plastic layer in immediate contact with the environment. Therefore, the embedded strain gauges may be substantially sandwiched between the multiple layers. The layers are preferably attached, optionally by lamination, together.

Regarding more specific material examples, the overlay, or the protective entity in general, may include e.g. PC (polycarbonate), PMMA (polyme- thyl methacrylate), PA (polyarnide, nylon), COC (cyclo olefin copoly-mer), and/or COP (cyclo olefin polymer). A piece of any aforesaid and/or other material, e.g. a sheet or film with desired dimensions, may be posi-tioned and secured onto the display to establish the protective overlay thereon. The piece may contain a number of recesses, cavities, or holes for accommodating various elements such as the strain gauges, electronic cir-citits, conductors, etc. In tIjrther, either supplementary or alternative, embodiments the protective entity comprises an overlay, such as a sheet or film, optionally non- transmissive material, wherein strain gauges are embedded into the pe-riphery area and/or in the touch area of the protective entity. Such overlay can be used as an input device such as a touch pad, keyboard or similar aggregate of buttons and/or touch control surface. The protective entity may comprise plastic and/or glass, for instance. The protective entity may be provided with desired properties in terms of touch feel, flexibility, transparency, hardness, scratch-resistance, anti-glare treatment, filtering properties, etc. In one other, either supplementary or alternative, embodiment the protec- tive entity comprises a frame structure and a number of strain gauges em-bedded therein at least partially surrounding an interface device such as a display panel or at least a portion thereof The frame may preferably be used as housing for different devices. Material(s) used in the touch input field and in the frame may differ from the material(s) used in the periphery area. Optionally the frame may be used as an input field on the sides of the device, to control the said device, wherein it protects the device at the same time. The protective entity fianie is attached to the inner touch sur-face area by mechanical means such as screwing and/or soldering and/or gluing or said surfaces can be attached together by laminating or molding in a manufacturing process at least partially common with the protective entity. The screen cover of the display may be considered to form a part of the protective entity.

In various embodiments, the protective entity may be releasably integrated with another element or device such as a controlling device or a display device or it may be alternatively irremovably integrated with said device.

Integration may be done either directly or via an intermediate element such as a common housing. Different lamination, molding, gluing and e.g. mechanical fixing elements (screws, bolts, hooks etc.) may have been ap-plied for the desired type and degree of integration.

In further, either supplementary or alternative, embodiments the electronic device is configured to apply the protective entity and the strain gauge(s) embedded therein to implement touch-sensing. The strain gauge(s) are po- sitioned so that pressure inflicted on the protective entity can be recog-nized. E.g. static or dynamic threshold values, such as lower threshold values, may be utilized to separate the elevated pressure indicative of touch on the input area from other pressure deviations detected. Also tem-poral monitoring iriay be applied in a sense that static, i.e. lasting over a predetermined period, pressure on a certain location iriay be classified as probable non-touch, for example. This might take place when a person is carrying the device of the present invention in his pocket and introduces pressure to the input area accidentally, for instance. In case at least three strain gauges are used, preferably substantially positioned to the far edges of the protective entity and optionally evenly spread, it is possible to de-termine a force touch engendered between them by measuring the amount andlor direction of strain each strain gauge goes through. Information is sent from the strain gauges to a CPU or other computing entity that further on uses triangulation or similar technique(s) to position the pressure point or points. Information shared between the strain gauges or intermediate el- ements and the CPU may be transferred by wire or wirelessly. Additional-ly adding more strain gauges and improving their positions so that they are spread evenly, in relation to the touch sensing area, in the protective entity increases the input device's accuracy and reaction speed.

Optionally the device may be configured to implement force touch sensing by a protective entity with only one strain gauge embedded therein. In this embodiment the protective entity mostly coarsely calculates the location of an input but focuses on determining the pressure of the touch engen- dered. This enables different configurations such as linking different pres-sures to correspond different commands.

The force touch input may comprise pointing with any object capable of engendering pressure on a surface, most common such objects including finger and stylus among various other objects. The location and the nature of the touch, i.e. the duration and/or pressure, engendered on the contact area, may be configured as different commands according to predeter-mined rules in converting die force touch into a control input.

Further, the strain gauges may be provided with support electronics and/or other electronics such as conductors, electrical components, chips, etc. op-tionally also embedded in the protective element. They may be printed on a substrate by utilizing a selected printing technique, or attached as ready- made entities, e.g. SMT (surface-mount technology) and/or flip chip enti-ties, to the substrate by e.g. glue or other adhesive.

In a further, either supplementary or alternative, embodiment the touch in-put device utilizes vibration to implement tactile feedback. The device comprises at least one piezoelectric actuator or vibration motor embedded into the protective entity.

In a further, either supplementary or alternative, embodiment the touch in- put device utilizes touchiess gesture tracking. The device comprises, pref- erably at least one light emitter, and at least one camera entity. Said cam-era entities are aligned as to image objects in front of the display panel.

Said light emitters ifluminate the potential imaging target such as a finger or a hand of a user hovering in front of the display panel and the emitted light may be then at least partially reflected to camera entities capable of capturing it and forming a related image. Optionally the device may com- prise at least one camera entity and use ambient and/or natural light to il-luminate said imaging targets in front of the display. The monitored space (dimensions) may be case-specifically determined.

The emitters may include optoelectronic components such as LEDs (light emitting diode) or OLEDs (organic LED), for example. Such elements may be formed utilizing a feasible printed electronics technology. Alterna-tively or additionally, SMT technology may be applied.

In another aspect, a control input module for receiving and forwarding force touch-based control input from a user, comprises at least one protective entity including a predetermined touch-sensitive in-pitt area and comprising at least one layer of material with a number of strain gauges substantially embedded therein, and an output interface, such as a connector or a plurality of conductors, at least functionally connected with the strain gauges and configured to pro- vide related location-based and pressure-based data to an external compu-ting entity for the determination of the location of pressure point or points on the touch-sensitive area engendered by the user via finger, stylus or a similar means.

In one embodiment, the output interface may contain a wireless output in-terface such as a wireless transmitter or transceiver.

An electronic device, such as a hand-held terminal, tablet, laptop computer or a desktop computer, may incorporate the control input module.

In a further aspect of the present invention, a method for manufacturing an electronic device for user input acquisition, such as a pressure sensitive input device, comprises embedding a number of strain gauges in the mate-rial of a protective entity in the periphery region around a predetermined active, force-touch -sensitive area, which is preferably sufficiently optical- ly transparent, elastic, tough and scratch-resistant, said active area deEm-ing a pressure sensitive area, via the embedded strain gauges, for deriving control input on the basis of the pressure and preferably location of a touch engendered by a user of the device.

In one embodiment the protective element is manufactured by injection molding so that the strain gauges and e.g. the necessary electrical wiring are embedded inside the protective entity. The thickness of the protective entity as well as the installation depth of the said strain gauges and elec-tronics in the protective entity may be varied according to the application so that they may form a part of the surface or be completely embedded in-side the protective entity. This enables customization of the toughness, elasticity, transparency, etc., of the device as a whole as well as customi-zation of the maintenance capabilities and protection of said embedded electronic components. Embedding the strain gauges completely inside the protective entity provides better protection for the strain gauges and other electronic components. Optionally leaving the strain gauges andior other components to the surface provides less protection but enables the mainte-nance of said components.

In further, either supplementary or alternative, embodiments the protective entity is manufactured by laminating, i.e., attaching layers together. Strain gauges and other electronic components e.g. wiring, LEDs and cameras are printed or otherwise formed on a layer and then a new layer is attached on top of them. Printing said components may be achieved by flexog-raphy, gravure, offset, lithography, inkjet and/or screen printing. The amount of the layers may vary according to the required attributes such as transparency and toughness of the protective entity.

In further, either supplementary or alternative, embodiments the strain gauges and other electronic components e.g. wiring, LEDs and cameras are embedded into the protective entity by in-mold labeling.

In further, either supplementary or alternative, embodiments the strain gauges and other electronic components e.g. wiring, LEDs and cameras are embedded into the protective entity by in-mold decoration.

In further, either supplementary or alternative, embodiments the protective layer may be made porous so that the strain gauges and other electronic components e.g. wiring, LEDs and cameras may be inserted in the associ-ated recesses. These recesses are then filled with a substance according to the material(s) used to make the protective entity. This enables easier and more customizable way to insert the strain gauges into the protective enti-ty.

The previously presented considerations concerning the various embodi-ments of the electronic device or related module may be flexibly applied to the embodiments of the method mutatis mutandis and vice versa, as be-ing appreciated by a skilled person.

As briefly reviewed hereinbefore, the utility of the different aspects of the present invention arises from a plurality of issues depending on each par- ticular enibodinient. The manufacturing costs for producing the touch in- put device in accordance with the present invention to enable force touch -based sensing may be kept low due to rather extensive use of affordable and easily obtainable materials, components, and process technology. The provided force touch sensing -based input device is scalable from small buttons to hand-held mobile devices to larger applications. The feasible process technology also provides for rapid industrial scale manufacturing of the arrangement in addition to mere prototyping scenarios.

The arrangement may be kept thin, light, and energy conserving in order to suit most use scenarios with little modifications to the surrounding ele- ments and designs. The obtained integration level is very high. The pro-tective entity may be made robust towards external impacts. This will in turn offer better protection for the components, i.a. strain gauges. The pro-tective entity may, in particular, comprise optically transmissive material that sufficiently passes the incident light through away from the possible emitters. In some embodiments, the protective element or a portion thereof may be specifically configured for light guiding purposes.

Yet, the touch input device suits particularly well various industrial appli- cations including e.g. industrial automation/electronics control apparatus- es, as it may provide hermetical and dust repelling isolation from the hos-tile use environment with e.g. humid and/or dusty air.

The expression "a number of' may herein refer to any positive integer starting from one (1). The expression "a plurality of' may refer to any positive integer starting from two (2), respectively.

Different embodiments of the present invention are also disclosed in the attached dependent claims.

BRIEF DESCRIPTION OF THE RELATED DRAWINGS

Next, the embodiments of the present invention are more closely reviewed with reference to the attached drawings, wherein Fig. 1 illustrates the basic concept of the present invention via one embod-iment thereof 1*I Fig. 2 illustrates the concept of the present invention via four further em-bodiments thereof Fig. 3 depicts a configuration of an embodiment of the invention to obtain information of the touch engendered on the touch surface.

Fig. 4 is a flow diagram disclosing an embodiment of a method in accord-ance with the present invention.

Fig. 5 is a flow diagram disclosing another embodiment of a method in accordance with the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

With reference to Figure 1, an axonometric view 102 of an embodiment of the suggested solution with force sensing function is shown. The electron- ic device or module may comprise various additional elements, either in- tegrated or separate, in addition to the disclosed ones. As being appreciat-ed by skilled readers, also the configuration of the disclosed elements may differ from the explicitly depicted one depending on the requirements of each intended use scenario wherein the present invention may be capital-ized.

The strain gauge arrangement, which may be implemented as a touch sur- face input device or module, comprises a protective entity 110 for ac-commodating predeteniiined electronics such as a number of strain gauges 106a, 106b, 106c, 106d, which are full bridge strip strain gauges for cx-ample, and optionally other components such as cameras, light emitters, conductors, control chips, memory, etc. (not shown in the picture). In the case of multiple strain gauges, the strain gauges may be mutually different in terms of such properties as bridge construction, axial strain sensing, strip size, material, etc. The protective entity 110 may comprise a touch area 108 of a preferred size. The touch area 108 may be manufactured separately from the frame 104 or it may be manufactured andlor integrated at least partially in the same manufacturing process as the frame 104. The touch area 108 may al- so comprise same or different substances than the rest of the protective en- tity 110. The touch area 108 may be attached to the frame 104 by mechan- ical means such as, screwing, soldering, welding and/or gluing or the sur-faces may be attached together in at least partially same manufacturing process. The integration of the touch area 108 and frame area 104 may be releasable or irremovable, based on the attachment method used.

A computing entity 112 may be arranged to the electronic device. It may be integrated with the protective entity 110, optionally embedded in the frame 104 thereof, for instance. Particularly, in connection with a module-type of embodiment, an external computing entity 112 may be exploited, in which case the computing entity 112 may be disposed at an apparatus configured to receive strain gauge-based data from the module for analy-sis. Wireless or wired data transfer may be applied.

Figure 2 illustrates four alternative cross-sectional side views 202a, 202b, 202c, 202d of the corresponding four alternative embodiments of the sug-gested input device.

In the embodiment of view 202a the protective entity 210 may comprise undivided sheet and/or undivided film or optionally a number of sheets andlor films attached together. A number of strain gauges 206a, 206b are at least partially embedded inside the protective entity 210, potentially to- gether with desired supportive elements, such as wires, conductors, com-puting entities 111cc processors, etc. The protective entity 210 may comprise multiple materials or it may be made of the same material throughout. Said protective entity 210 may hence be heterogeneous or homogeneous. Such protective entity 210 and strain gauge 206a, 206b configuration may be used for example as a touch pad and can therefore be used without a display or similar device. A touch object 220, such as finger or stylus, more thoroughly reviewed hereinlater, depicts the input signal engender on the surface of the protective entity.

For a bare input device embodiment, the protective entity needn't to be transparent, and therefore it is preferable that the materials chosen for this construction of the protective entity are scratch-resistant, flexible and/or lightweight prior to transparent. More specific material options are dis-closed hereinlater.

In the embodiment of view 202b the protective entity 204 comprises two or more initially separate areas attached together. A number of strain gauges 206a, 206b are embedded into the periphery, i.e. the aforemen-In Ii tioned frame 204 of the protective entity 210 and the touch input area - containing element 208, such as a display panel with a cover layer, is posi- tioned inside the protective entity frame 204. The frame 204 may be re- leasably integrated with the touch input element 208 or it may be alterna-tively irremovably integrated with said element. Different mechanical means as well as manufacturing means such as lamination, molding, glu-ing and e.g. mechanical fixing elements (screws, bolts, hooks etc.) may be applied for the desired type and degree of integration.

The embodiment of view 202b can il1deed be used with a display device so that the display panel replaces the touch input element 208. Herein the frame may be made to cover at least partially the sides of the display panel wherein it may function as a protective cover as well as an input area for the display panel.

In the embodiment of view 202c the protective entity is disposed upon a display device 218. The protective entity 210 covers at least the whole top area of the display panel 218, but optionally and/or additionally other sides as well. The protective entity may be disposed upon the display pan-el 218 fixedly or releasably. For instance, gluing, lamination, molding, or mechanical fixing means (screws, bolts, fingers, etc.) may be applied. The protective entity 210 protects the underlying display electronics and op-tional other elements with a flat overall structure.

Optionally, the protective entity 210 may be made bigger than the under-lying display panel 218. In this embodiment the protective entity 210 may be similar to the one disclosed in view 202b so that it has two separate ar-eas wherein the touch area 208 at least partially covers the display and the periphery area, i.e. the area that comprises the strain gauges and optional supportive elements, extends over the display panel 218. Herein the center touch area 208 is also preferably homogenous so that it comprises one film or sheet. Also, the material(s) of the touch area 208 covering the dis-play panel is sufficiently transparent from the standpoint of flawless light emission and sufficiently flexible from the standpoint of inputting touch commands effortlessly. The periphery area that contains the strain gauges and related electronics needn't to be transparent or homogenous. There-fore said periphery area can act as housing for the strain gauges 206a, 206b and other supportive elements as well as a cover for the display pan- ci 218, as the periphery area can be made out of tough and/or durable ma-terial.

The protective entity 210 may optionally be the same size as the underly-ing display panel 218. Herein the whole protective entity 210 is preferably made homogenous throughout, i.e. of the same film or sheet, and of said sufficiently transparent material. The strain gauges 206a, 206b are prefer-ably placed into the far edges of the protective entity 210 to eliminate their interference with the light emitted from the display panel 218 and/or into the display panel 218, from an ambient light source, for example. The strain gauges 206a, 206b are preferably also made of transparent material, which further on increases the homogeneity of the protective entity 210 in terms of optical transparency. Sufficiently transparent strain gauges 206a, 206b may enable a matrix array positioning of the strain gauges into the protective entity 210, for improved touch sensing, for example.

In the embodiment of view 202d the protective entity 210 comprises one or more material(s) and one or more layer(s) wherein essentially one strain gauge 206 has been embedded. This kind of construction can be applied into any surfaces and devices, e.g. the ones that utilize aggregate of but-tons.

The device of view 202d isn't capable of accurately registering location (there's only one strain gauge, which provides mostly coarse location de- termination) but it may calculate the pressure engendered on it. This ena- bles different configurations such as linking different pressures to corre- spond different commands. This may be utilized preferably, but not exclu-sively, for devices where the output of input commands can be monitored, for example in a lifting operation of a crane or similar linear and/or non-linear movement. Herein the button can be configured to control linear single direction movement of an object wherein the pressure applied on the button can be configured to change the movement speed of the object.

Other similar linear and unidirectional processes may be performed as well with the single strain gauge construction.

The single strain gauge protective entity may also be configured with oth- er such devices in order to control more complicated processes. For exam- ple, two single strain gauge buttons can be used to move an object bi-directionally, whereas a larger aggregate of buttons will enable operation in even more dimensions.

Further on, this kind of one strain gauge application may be utilized on various surfaces to sense forces engendered on the surface, which the pro-tective entity is disposed on, regardless of the location of the impact. Such applications may include sensing vibration of a device, sensing an impact inflicted on the device, etc. In all of the abovementioned embodiments the configuration of the strain gauges such as the number, type, positioning, alignment thereoL may be determined according to use case -specific objectives. In the shown case four strain gauges have been located on the four corners of the rectangular protective entity's far periphery area. The strain gauges however, could be also located in some alternative maimer, e.g. placed inside the protective entity evenly in a matrix sequence or on one same side of the display area, and/or the amount of strain gauges could be greater depending on the em-bodiment. Through increase of the number of strain gauges, more accurate gesture tracking results may be generally obtained, but the complexity and size of the solution respectively increases, and vice versa.

In all above mentioned embodiments, integration, between the touch area and the periphery area and/or the protective entity upon the display panel, may be performed so that at least one further, protective layer is laminat-ed, molded or otherwise disposed onto the electronics on the substrate, where the provided layer, or the material forming the layer, preferably adapts to the surface contours of the substrate provided with the strain gauges. Alternatively or additionally the layer may contain pre-formed re- cesses for (enabling) accommodating elements on the substrate. Accord-ingly, the overlay structure at least partially embeds the strain gauges and potentially other desired elements.

The protective entity may be substantially flat or contain substantially flat portion(s). In some embodiments the protective entity may be at least par- tially curved or contain curved shape(s) e.g. at the edges. Yet, the protec-tive entity may contain concave or convex shape(s), for instance.

The shape of the protective entity may be defined on the basis of the used manufacturing method and desired target shape(s). The illustrated, howev-er merely exemplary, overlay arrangement and/or elements thereof has/have substantially a rectangular (cuboid), substantially flat, shape, which works particularly well with roll-to-roll manufacturing methods and with typical display applications, but also e.g. round(ed) and/or thicker shapes are possible and achievable via proper cutting, for instance.

Figure 3 illustrates the process of determining location and pressure of a force touch 322 engendered on the touch surface 308. In the embodiment of view 302a four strain gauges 306a, 306b, 306c, 306d have been embed-ded into the protective entity 310. When pressure is engendered to a point on the surface of the protective entity the surface bends. Said bending is then measured relative to the strain gauges.

In the case of four strain gauges, the strain gauges 306a, 306b, 306c, 306d are preferably placed in the far corners of the rectangular protective entity, so that the touch area covers as big an area of the protective entity 310 as possible. However, also other configurations are possible. There are then two diagonals 324a, 324b; one for each pair of the strain gauges 306a, 306b, 306c and 306d. These diagonal lines 324a, 324b depict the bending of the surface relative to the strain gauges 306a, 306b, 306c, 306d and the force vector components 322a, 322b engendered on said lines 324a and 324b.

View 302b and 302c illustrate the resultant forces 322a, 322b engendered on the lines 324a, 324b between the strain gauges 306a, 306b, 306c, 306d and force components 326a, 326b, 326c, 326d distributed on the strain gauges 306a, 306b, 306c, 306d. Using information of the forces sensed in the strain gauges, the location and pressure of the touch 322 can be calcu-lated by a CPU or other computing entity. The location and pressure data measured may be farther on used by the computing entity to determine what command was intended by the input.

It should be noted that this kind of pressure-location -sensing can be achieved with at least three strain gauges. Two strain gauges can be there-fore used to measure pressure and its location on a line between said strain gauges. One strain gauge configuration can be used to detect pressure en-gendered on protective entity and coarse location awareness.

The meaning of an input signal may be different for different embodi-ments. For example for a single button embodiment the command may be programmed to be interpreted as a simple on/off -command. However, in the button embodiment this input may be further on more comprehensive as the amount of pressure can be interpreted as a command in itself, re-gardless of the location. Therefore two force touches engendered on the same point may be configured to mean different commands depending on the pressure of the touch. It is therefore important to notice that the input device may be configured not only to determine the input signal command by the location, but from the pressure engendered as well, which can be very big an advantage especially when using the device without an output device.

It should also be noted that according to the method of measuring pressure and its location on a protective entity, greater accuracy can be achieved by utilizing more strain gauges. Herein it is important to notice that better placing of strain gauges relative to other strain gauges' locations leads to greater accuracy, reliability and operating speed. In order to achieve some features such as multi touch, it is preferable to place strain gauges evenly throughout the whole protective entity.

Further on, the input commands engendered on the device may be multi-touch commands such as taps made by a plurality of fingers. As said, this can be made possible only by using a plurality of strain gauges to sense a number of simultaneous touches and to determine the location of each touch. When multi-touch sensing is required, a more comprehensive posi-tioning of the strain gauges is needed. In some embodiments it may be an advantage to place strain gauges in the center of the touch area as well.

Even further, to enable even more commands, the computing entity shall also measure the time that the strain gauges 326a, 326b, 326c, 326d un-dergo stress, i.e. the time that the pressure is engendered on the point 322 on the touch area 308, to determine force touch -based conmiands de-pendent of the time. For example, touch-wise equal, temporally different commands, may be configured to mean different inputs.

Tn all of the abovementioned embodiments, the input signal, engendered by a user of the input device, can be made by applying pressure to a point on the protective entity. The force touch input commands can be made with any object capable of conveying pressure on the surface of the pro-tective entity; such objects include stylus, finger and similar objects. The input device may be of any size but for the sake of accuracy these exam-pies are presented.

Figure 4 is a flow diagram of one feasible embodiment for manufacturing the solution of the present invention.

At 402, referring to a start-up phase, the necessary tasks such as material, component and tools selection and acquisition take place. In determining the suitable strain gauges and other elements/electronics, specific care must be taken that the individual elements and material selections work together and survive the selected manufacturing process of the overall ar-rangement, which is naturally preferably checked up-front on the basis of the manufacturing process vs. component data sheets, or by analyzing the produced prototypes, for example.

At 404, a first layer of material, chosen in the start-up phase, is cut to the right size and cleaned. Preferable materials used in the layers are de-scribed hereinlater.

At 406, a decision between the use of ready-made strain gauges and the use of strain gauges made specifically for this construction is made.

At 408a, a decision of using ready-made strain gauges is made.

At 41 Oa, ready-made strain gauges and other electronics are attached on the surface of the layer. Attaching may be done by introducing adhesive epoxy to the surface wherein the strain gauge is to be attached and apply- ing pressure until strain gauge sticks to the layer. Both conductive (for en-abling electrical contact) and non-conductive (for mere fixing) adhesives may be utilized. Such elements are preferably selected so as to withstand the pressure and temperature of the utilized protective entity-establishing lamination process. Alternatively or additionally, the enclosing material layer may be established by applying a sheet or film of swtable material, e.g. glass or plastic material, which is disposed onto the substrate and, for example, glued and/or otherwise fixed thereto. The materials, such as the materials utilized in the protective element, may include epoxy and/or sol-gel or colTesponding, potentially molded, materials.

At 408b, an optional decision of not Lising the ready-made strain gauges is made.

At 4lOb, strain gauges and other supportive elements are printed on the layer. Feasible printing techniques for providing printed electronics may include screen printing, rotary screen printing, gravure printing, flexog-raphy, ink-jet printing, tampo printing, etching (111cc with PWB-substrates, printed wiring board), transfer-laminating, thin-film deposition, etc. For instance, in the context of conductive pastes, silver-based PTF (Polymer Thick Film) paste could be utilized for screen printing the desired circuit design on the substrate. Also e.g. copper or carbon-based PTF pastes may be used. Alternatively, copper/aluminum layers may be obtained by etch-ing. In a thither alternative, conductive LTCC (low temperature co-fired ceramic) or IITCC (high temperature co-fired ceramic) pastes may be sin-tered onto the substrate. One shall take into account the properties of the substrate when selecting the material for conductors. For example, sinter-ing temperature of LTCC pastes may be about 850 to 900°C, which may require using ceramic substrates. Further, silver/gold-based nanoparticle inks could be used for producing the conductors.

The paste/ink shall be preferably selected in connection with the printing technique and the substrate material because different printing techniques require different rheological properties from the used ink/paste, for in-stance. Further, different printing technologies provide varying amounts of ink/paste per time unit, which often affects the achievable conductivity figures.

At 412, a number of layers are arranged onto the electronics attached on the first layer. The amount of these layers may be decided according to the features desired of the device such as stiffness and hardness. The layers may also include different materials so that different layers provide differ-ent features, such as in an embodiment wherein the layers connected with the supportive elements are conductive and the surface layer is noncon-ductive and wear-resistant for example. Attaching the layers together may be done with silicone or acrylic-based pressure-sensitive adhesives, which are optically clear and provide a permanent bond to the substrate upon completion of curing in l2-24 hours. Optionally, polyethylene thermal bond adhesive may be used.

At 414, the temperature and the pressure of the packet are raised in order to tighten the packet and activate the adhesive. A person skilled in the art may determine applicable heat and pressure parameters case specifically depending on the materials and e.g. intended use of the suggested solution.

At 416, the laminated protective entity is let to cool down so that the adhe- sive hardens and the layers and the electronics embedded therein stick to-gether. Laminate may be ready to use after 15-30 minutes but in many cases 24 hours or more should be preferred for a better end result.

At 418, the method execution is ended. Further actions such as strain gauge configurationlcalibration may take place.

Figure 5 is a flow diagram of another feasible embodiment for rnanuf'ac-turing the solution of the present invention.

At 502, referring to a start-up phase, the necessary tasks such as material, component and tools selection and acquisition take place. In determining the suitable strain gauges and other elements/electronics, specific care must be taken that the individual elements and material selections work together and survive the selected manufacturing process of the overall ar-rangement, which is naturally preferably checked up-front on the basis of the manufacturing process vs. component data sheets, or by analyzing the produced prototypes, for example.

At 504, strain gauges, ready-made or printed, as well as desired other elec-tronic components are placed into the insert. The strain gauges and the other components may be provided on a substrate, on which they are pro- duced by printing for example, or they can be placed into the insert in pre-ferred positions without a substrate. Such substrate may comprise PC, PET andlor PVC film, for example. The provided material and the used at-tachrnent method shall be preferably selected such that the electronics on the substrate remain unharmed during the process, while the provided ma-terial is properly attached to the substrate.

Considering the process parameters and set-tip, few further guidelines can be given as mere examples as being understood by the skilled persons.

When the substrate is PET and the plastics to be, for example, over-molded thereon is PC, the temperature of the melted PC may be about 280 to 320°C and mold temperature aboLit 20 to 95°C, e.g. about 80°C. The used substrate (film) and the process parameters shall be preferably select-ed such that the substrate does not melt and remains substantially solid durhig the process. The substrate shall be positioned in the mold such that it remains properly fixed. Likewise, the preinstalled electronics shall be at-tached to the substrate such that they remain static during the molding.

At 506, granules of plastic material are poured into the device. The mate-rial is then heated until molten, and is then force injected into the mold, wherein it sets around the supportive elements. Material used is chosen accordingly to the desired features.

At 508, the molten material inserted illto the mold is kept under a pressure so that the mold becomes even.

At 510, the mold is et to coot down.

At 512, the finished product is taken out of the mold.

At 514, the method execution is ended. Further actions such as strain gauge configurationlcalibration may take place.

In both of the above mentioned methods, the layer material of the laminat-ing method as well as the granular material of injection molding, materials may include, for example, polymers such as PC (polycarbonate), PET (polyethylene terephthalate), PMMA (polyrnethyl methacrylate), PA pol-yamide, nylon), COC (cyclo olefin copolyrner), and/or COP (cyclo olefrn polymer), PIFE (polytetrafluoroethylene) andlor PVC (polyvinyl chlo- ride). Alternatively or additionally, the material may include glass. An ap-plicable layer material shall be generally selected such that the desired flexibility, robustness, and other reqLrirernents like adhesion properties in view of the electronics and the adjacent materials, or e.g. in view of avail-able manufacturing techniques, are met.

The strain gauges used are preferably, however not necessarily, the types that are sensitive to both longitudinal and transverse tension and coinpres-sion. Said strain gauges comprise preferably thin strips of metallic alloy film deposited by gluing or printing on a nonconducting material. Option-ally metallic wiring deposited on a nonconducting material can be also used among other potential alternatives.

The strain gauge unit may comprise mid be configured with a Wheatstone bridge circuit with a combination of four active gauges (full bridge), two gauges (half bridge), or, less commonly, a single gauge (quarter bridge).

In the half and quarter circuits, the bridge is completed with precision re- sistors. For higher accuracy the full bridge is preferred. As stress is ap- plied to the bonded strain gauge, resistive change takes place and unbal-ances the Wheatstone bridge. This results in a signal output, related to the stress value. When at least three strain gauges around a point or a number of points experience deformation, as a result of pressure inflicted on the point(s), a CPU is able to determine the location and pressure of the point(s) using the information of measured electrical resistance change in each of the strain gauges.

Regarding more specific material examples, the strain gauges, may in- clude Platinum (Pt 100%), Platinum-Iridium (Pt 95%, Ir 5%), Platinum-Tungsten (Pt 92%, W 8%), Isoelastic (Fe 55.5°A, Ni 3694), Cr 8°A, Mn 0.5%), Constantan/Advance/Copel (Ni 45%, Cu 55%), Nichrome V (Ni 80%, Cr 20%), Karma (Ni 74%, Cr 20%, Al 3%, Fe 3%), Armour D (Fe 70%, Cr 20%, Al 0%), Monel (Ni 67%, Cu 33%), Manganin (Cu 84%, Mn 12%, Ni 4%), Nickel (Ni 100%), Indium oxide (In2O3) and/or Indium tin oxide (1n203 90%, Sn02 10%). The nonconducting base material cx- amples may include conductive polymer poly (3,4-ethylen dioxythio- phene) oxidized with polystyrene sulfonated acid (PEDOT:PSS), polyi-mide (P1) and/or glass-fiber-reinforced epoxy-phenolic.

In case a display panel is provided, the panel incorporates the necessary electronics for providing the desired control, lighting and image estab-nfl Li lishment elements. The pane] may be manufactured in connection with the rest of the device or provided as at least partially ready-made element. The panel may include a number of layers some of which have electrical andlor optical function and some of which are mainly protective, for cx-ample. In some embodiments, the device could include multiple display panels optionally located adjacent to each other.

The display panel 218 may include an LCD (liquid crystal display), LED (light-emitting diode) or plasma display, for instance. So-called flat dis-play technologies such as the aforementioned LCD or LED are in typical applications preferred but in principle other technologies such as CRT (cathode ray tube) are feasible in the context of the present invention as well.

The optional substrate for the strain gauges and other supportive elements may also be preconditioned prior to and/or during the illustrated pro-cessing phases. Said substrate may be preconditioned to increase adhesion with other materials such as laminated, glued or injection-molded cover plastics, for example.

The use of advantageously flexible materials preferably enables carrying out at least some of the method items by roll-to-roll methods, which may provide additional benefits time-, cost-and even space-wise considering e.g. transportation and storage. In roll-to-roll, or reel-to-reel', methods the desired elements, such as optical and/or electrical ones, may be deposited on a continuous roll' substrate, which may be both long and wide, ad- vancing either in constant or dynamic speed from a source roll, or a plural- ity of source rolls, to a destination roll during the procedure. Thus the sub-strate may thus comprise multiple products that are to be cut separate later.

The roll-to-roll manufacturing advantageously enables rapid and cost ef- fective manufacturing of products also in accordance with the present in-vention. During the roll-to-roll process several material layers may be joined together on the fly', and the aforesaid elements such as electronics may be structured on them prior to, upon, or after the actual joining in-stant. The source layers and the resulting band-like aggregate entity may be further subjected to various treatments during the process. Layer thick-nesses (thinner layers such as films' are generally preferred in facilitating roll-to-roll processing) and optionally also other properties should be se-lected so as to enable roll-to-roll processing to a preferred extent.

The scope of the invention is determined by the attached claims together with the equivalents thereof The skilled persons will again appreciate the fact that the disclosed embodiments were constructed for illustrative pur-poses only, and the innovative fulcrum reviewed herein will cover further embodiments, embodiment combinations, variations and equivalents that better suit each particular use case of the invention.

Claims (22)

1. C I aims 1. An electronic device (102, 202a, 202b, 202c, 202d, 302a) for re-ceiving force touch-based control input, comprising a protective entity (110) including a predetermined touch-sensitive input area (108) and comprising at least one layer of material with a number of strain gauges (106a, 106b, 106c, 106d) embedded therein, the protective entity (110) and the strain gauges (106a, 106b, 106c, 106d) being config-ured to obtain location-based and pressure-based data indicative of touch (322) on the touch-sensitive input area (108), and a computing entity (112) configured to determine, on the basis of the ob-tained data, an occurrence of a touch implied by pressure point or points on the touch-sensitive (108) area engendered by the user of the device by finger, stylus or by a similar means (210).
2. 2. The device of claim I, wherein the protective entity (210) compris- es an overlay, such as film or sheet including, preferably optically trans-missive, material that may be placed, on a light emitting area such as that of a display panel (218) and further the periphery region (204) supplied with strain gauges (206a, 206b, 206c, 206d) embedded into the protective entity (210), said protective entity (210) comprising optionally scratch re-sistant plastic and/or glass.
3. 3. The device of any preceding claim, wherein the protective entity (210) comprises an overlay, such as a sheet or film, optionally non-transmissive material, wherein strain gauges (206a, 206b, 206c, 206d) are embedded into the periphery area (204) and/or in the touch area 208 of the protective entity (2W), said protective entity (210) comprising optionally scratch resistant plastic and/or glass nuterial.
4. 4. The device of any preceding claim, wherein the protective entity 210 comprises a frame structure (204) supplied with strain gauges (206a, 206b, 206c, 206d) embedded into the protective entity (210) and an over-lay (208), made of different or same material as the frame material (204), attached to the surrounding frame material, that is optionally scratch re-sistant plastic and/or glass.
5. 5. The device of any preceding claim, configured to determine the lo-cation of the pressure point or points or derive related control input through force touch sensing incorporating utilization of data by a number of strain gauges (326a, 326b, 326c, 326d) indicative of force touch (322).
6. 6. The device of claim 5, wherein the computing entity (112) is con-figured to determine the location or derive the control input through force touch sensing, incorporating utilization of a singular strain gauge data (326) indicative of force touch (322) to indicate simple onloff command.
7. 7. The device of claim 5, wherein the computing entity (112) is con-figured to determine the location or derive the control input through force touch sensing, incorporating utilization of two strain gauges' data (326a, 326b) indicative of force touch (322) to indicate a command.
8. 8. The device of claim 5, wherein the computing entity (112) is con-figured to determine the location or derive the control input through force touch sensing incorporating utilization of at least three strain gauges' data (326a, 326b, 326c) indicative of force touch (322) to indicate complex multi-touch commands.
9. 9. The device of any preceding claim, configured to produce vibration as tactile feedback incorporating utilization of at least one piezoelectric actuator embedded into the protective entity (110).
10. 10. The device of any preceding claim, wherein at least one camera is embedded inside the protective entity (110), which is preferably optically substantially transparent material and is provided optionally by over-molding or laminating.
11. 11. The device of any preceding claim, comprising at least one light emitter, such as LED (light-emitting diode) or OLED (organic LED), for illuminating predetermined region or direction substantially in front of the display panel (218).
12. 12. The device of any preceding claim, comprising a number of camera entities, wherein the computing entity (112) is configured to derive the control input through tracking of touchless gestures incorporating utiliza-tion of said number of camera entities and related image data.
13. 13. Use of the device of any of claims 1-12 iii iiriplementing a mobile tenninal, personal digital assistant, c-book reader, wristop, desktop or lap-top computer, tablet computer, television monitor, industrial or automotive touch surface.
14. 14. Use of the device of any of claims 1-12 in implementing a touch input surface, optionally a touchpad or a touch button.
15. 15. Use of the device of any of claims 1-12 in implementing a touch display.
16. 16. A method for manufacturing an electronic device for user input ac-quisition, such as a pressure sensitive input device, comprising embedding a number of strain gauges (410a, 4 lOb, 412, 504,506) in the material of a protective entity in the periphery region around a predetermined active, force-touch -sensitive area, said active area defining a pressure sensitive area, via the embedded strain gauges, for deriving control input on the ba-sis of the pressure and preferably location of a touch engendered by a user of the device thereon.
17. 17. The method of claim 16, wherein at least one strain gauge is manu-factured by inkjet printing (4 lOb).
18. 18. The method of any of claims 16-17, wherein at least portion of the protective entity is manufactured by injection iriolding (502-514) so that the strain gauges are embedded inside the protective entity (504,506).
19. 19. The method of any of claims 16-18, wherein at least portion of the protective entity is manufactured by laminating (402-418) so that the strain gauges are embedded in between the layers.
20. 20. The method of claim 18, wherein one or more strain gauges are printed on one of the laminating layers, which is made of nonconducting material, suitable for carrying strain gauges (41 Oa, 41 Ob, 412).
21. 2 L The method of any of claims 16-20, wherein one or more strain gauges are embedded into the protective entity by in-mold labeling.
22. 22. The method of any of claims 16-21, wherein one or more strain gauges are embedded into the protective entity by in-mold decoration.