Patent Description:
In existing electronic devices with a display, the display can be of a touch sensitive type to allow input via a pressing force on the display. The existing touch sensitive displays have components formed in the display to allow the electronic device to sense a pressing force on the display. A drawback of existing force-sensing technologies on displays is an increased product cost. Also, the components included in existing force sensitive displays cause the display module to be thicker as additional force sensing layer needs to be implemented in the display.

Hence, there is a need for an improved electronic device with a force sensitive display.

<CIT> discloses a touch screen system comprising acoustic transmitters and receivers receiving acoustic waves transmitted by the transmitters. A touch pressure of a user's touch is determined by the determination of the attenuation of the acoustic waves.

<CIT> discloses a ontroller including an adjustable gain amplifier and a control circuit. The adjustable gain amplifier has an input, an output, and a gain control terminal, and receives a first signal representative of an acoustic signal on a touch screen on the input terminal and delivers an amplified version of the first signal on the output terminal. The gain control terminal receives a control signal that varies the gain of the amplifier. The control circuit includes an analog to digital converter that receives a portion of the amplified first signal and outputs a digital signal representative thereof. The control circuit includes a processing element that is electrically coupled to the ADC and receives the digital signal. The processing element compares the digital signal to a preslected value and determines the difference if any between the digital signal and the preselected value. If the difference exceeds a preselected limit, the control circuit delivers a control signal to the control input of the amplifier.

It is an object of the present invention to provide an improved electronic device having a force sensitive display.

It is provided an electronic device comprising:.

the lowpass filter is configured to have a passband that is below any frequency generated by the audio generator such that no signals generated by the audio signal generator are comprised in the output signal.

The low-passed signal can be used to determine a pressing force on the display and to thereby implement a force sensitive functionality in the electronic device without the need for any additional electronic components such as the use of force sensitive displays. Instead the audio actuator can be used to generate a voltage signal that can be used to sense a pressure on the screen after low-pass filtering of the voltage signal. Hereby there is no need for a pressure sensitive display with force sensing layer(s) integrated in the display.

In accordance with a second implementation, the electronic device is provided with a frame and a suspension member. The display is then attached to the frame via the suspension member. Hereby a suspended display can be achieved. This can make the voltage signal generated by the audio actuator less sensitive to where on the display the pressing force is applied. Thus, in particular if the display is relatively small, such on a smart phone, there can be large differences in the signal generated by the audio actuator depending on if a user applies a force close to the rim of the display or if the force is applied in the middle of the display. This problem can be alleviated by suspending the display in a frame whereby there can be a more linear movement of the display in response to a pressing force on the display.

The detected low pass filtered signal can then be used as an input signal to control the electronic device or to read input from a user.

In accordance with another implementation, the force detection unit is further configured to determine a time during which a force is applied to the display based on the output signal from the lowpass filter. Hereby the electronic device can be made to distinguish between different pressing force inputs based on for how long the pressing force is applied to the screen. Hereby a user is enabled to input different control commands by varying the time during which a pressing force is applied to the display.

In accordance with another implementation, the force detection unit is further configured to determine a magnitude of a force applied to the display based on the output signal from the lowpass filter. Hereby the electronic device can be made to distinguish between different pressing force inputs based on the magnitude of the pressing force applied to the screen.

Hereby a user is enabled to input different control commands by varying the magnitude at which a pressing force is applied to the display.

Since the lowpass filter is configured to have a passband that is below any frequency generated by the audio generator, it can be ensured that only signals resulting from a pressing force are output from the lowpass filter. Thus, there is no risk that signals the audio generator generates will be used as a signal indicating a pressing force of the display.

In accordance with another implementation, the electronic device can further comprise a tactile feedback actuator located behind the display. Hereby it is made possible to provide tactile feedback to a user of the electronic device. For example, when input of commands or text is made via the display the user can get a feedback from the touch sensitive display to enhance correct input by providing a feedback that makes it easier to for example enter double commands or no command at all.

In accordance with another implementation, at least two audio actuators are provided. By providing multiple audio actuators, it is made possible to use the different output signals from the different audio actuators to determine where on the display the pressing force is applied. Depending on the number of audio actuators provided it can become possible to determine the location on the pressing force with varying precision. Typically, the larger number of audio actuators used the higher precision in a determination on where the pressing force is applied can be achieved.

The electronic device can advantageously be a mobile phone.

The invention also extends to a method for detecting a pressing force on a display using the device above and to a computer program product for implementing the method.

The invention will now be described in more detail, by way of example, and with reference to the accompanying drawings, in which:.

The invention will now be described in detail hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

To provide an easy to implement and cost-efficient display that is capable of providing touch-sensitive input, an audio actuator connected to the display can be used to provide a voltage signal when a force is applied to the display.

As has been realized, an audio display, i.e. a display used as an audio radiating membrane, will have some electro-mechanical transducer component behind display causing a mechanical vibration for transmitting audio via the display. The transducer also referred to audio actuator will transform an electrical alternating current, AC, audio signal to a mechanical vibration causing an acoustical audio signal transmitted via the display. Typically, such an audio actuator is formed by an electro-dynamic (coil + magnet) element or a piezo-electric element. The audio actuator also works in the other direction, i.e. it will transform a mechanical force on the display to electrical signal. By using this property of the audio actuator connected to a display working as a membrane, it is made possible to implement a touch sensitive display in an electronic device without the use of a conventional touch sensitive display having components integrated in the display. This will be particularly useful when the electronic device is provided with an audio display, in which case there is no need for any expensive additional components since the basic components are already in place for implementing the audio display. Thus, no additional force-detecting components are then required. A force applied to the display can then be detected by detecting a voltage signal generated by the audio actuator from a force applied to the display.

In <FIG>, the components used in an exemplary implementation in an electronic device <NUM> are depicted. The electronic device <NUM> comprises an audio codec <NUM> to generate a signal to be output via an audio display of the electronic device <NUM>. The signal generated by the audio codec <NUM> can be output to an audio actuator <NUM> via a digital to analogue D/A converter <NUM> and power amplifier <NUM>. The audio actuator is connected to a display <NUM>. The display <NUM> acts as a membrane that vibrates in response to the signal received from the audio actuator <NUM>.

The audio actuator <NUM> is also connected to output a signal in response to a force on the display <NUM>. The output from the audio actuator <NUM> is connected to an output for a signal generated by a force of the display <NUM>. In accordance with some embodiments, the signal from the audio actuator <NUM> is provided to a force detection unit also referred to as detector <NUM>. The detector <NUM> is configured to determine a pressing force on the display <NUM> based on the signal generated by the audio actuator connected to the display <NUM>. In accordance with one embodiment, the signal from the audio actuator <NUM> is made to pass a low pass filter <NUM> before being provided to the detector <NUM>. By letting the signal from the audio actuator pass a low pass filter <NUM> before reaching the detector <NUM>, there is no risk that a signal for driving the display as an audio display will be interpreted as a pressing force on the display. However, in embodiments where there is no audio display such a low pass filter <NUM> typically need not be used. The low pass filter can have a pass band up to about <NUM> or any other frequency that efficiently filters out any signals generated to drive the audio display. Other filter configurations are possible that filter out only signals generated by a pressing force such as a pass-band filter with a suitable pass band to filter out signals resulting from a pressing force on the display <NUM>. Thus, audio actuators typically only have one pair of connectors (plus and minus). Both the audio drive signal from the amplifier <NUM> and the voltage signal received back from a pressing force will typically be applied together in same electrical connection lines. As audio electrical signal and the voltage signal typically are in different frequency ranges, it is possible to filter actuator electrical AC voltage to separate audio signal and voltage created by finger-pressing. Audio signal frequency range is typically about <NUM>-<NUM><NUM>. As an example, a typical finger pressing time is about <NUM> seconds which equals <NUM> frequency. The frequencies related to finger pressing may thus differ from typical audio signal frequencies by orders of magnitude, so audio signal and pressing force voltage signal can be separated from each other with a relatively simple filter structure as set out above.

When in use, the electronic device <NUM> can both generate an audio output A1 via the audio display <NUM> and also receive a mechanical pressing force input F1. Any type of audio actuator can be used, such as electro-dynamic (magnet + coil) actuator, piezo-electric actuator or electro-active polymer actuator. All are originally designed to transform electrical AC signal to mechanical vibration A1, but they also work backwards transforming mechanical finger-pressing movement F1 to electrical voltage.

The received pressing force can be processed by the electronic device to detect various input signals to the electronic device as will be described below.

In <FIG> the electronic device <NUM> is seen in a cross-sectional view from the side. The electronic device <NUM> can have a frame <NUM>. The display <NUM> can be attached to the frame <NUM>. In accordance with some embodiments, the display <NUM> is attached to the frame via suspension members <NUM>. Hereby a suspended display can be achieved. This can make the voltage signal generated by the audio actuator less sensitive to where on the display the pressing force is applied. For example, if the display is relatively small such on a smart phone, there can be large differences in the signal generated by the audio actuator depending on if a user applies a force close to the rim of the display or if the force is applied in the middle of the display. By suspending the display <NUM> in the frame <NUM>, a more linear movement of the display in response to a pressing force can be achieved.

In accordance with some embodiments multiple, i.e. at least two, audio actuators are provided. By providing multiple audio actuators, it is made possible to use the different output signals from the different audio actuators to determine where on the display the pressing force is applied. Depending on the number of audio actuators provided it can become possible to determine the location on the pressing force with varying precision. Typically, the larger number of audio actuators used the higher precision in a determination on where the pressing force is applied can be achieved. For example, two audio actuators can be used wherein when a mobile phone is held towards the ear, only an upper-half actuator is used to create a close to ear functionality. By driving both audio actuators, a handsfree loudspeaker mode can be implemented. When having two audio actuators, can enable detection of a finger-pressing force separately for upper and lower half of display. In other implementations additional audio actuators can be provided. For example, <NUM> audio actuators, one of each corner of display can be used. This will also allow a more accurate force detection from a wider display area when detecting the voltage signal of several audio actuators instead of just one audio actuator.

Above, the different components such as low-pass filter and force detection unit are presented as individual blocks. In some implementations these components can be integrated in an audio actuator system configured to monitor an audio actuator displacement This monitoring of the audio actuator displacement can use the same audio display system functionality as the audio display when the audio display comprises a system for sensing actuator displacement compared to center/rest position.

In <FIG>, a flowchart illustrating some steps performed in an electronic device <NUM> when a mechanical force is applied to the display <NUM> connected to the audio actuator <NUM> is shown. First, in a step <NUM> a signal from the audio actuator <NUM> is output Next, in a step <NUM>, the output signal is lowpass filtered in the lowpass filter <NUM>. The signal from the lowpass filter <NUM> is received by a detector <NUM> and the signal received by the detector is used to detect a pressing force on the display in a step <NUM>. In accordance with some embodiments, it is determined in a step <NUM>, a time during which a force is applied to the display based on the output signal from the lowpass filter. In accordance with some embodiments, it is determined in a step <NUM>, a magnitude of a force applied to the display based on the output signal from the lowpass filter. By determining time and magnitude of the input signal the electronic device is enabled to differentiate between different types of input from a user. In case multiple, i.e. at least two, audio actuators are provided in the electronic device, a determination of where on the display the force is applied is performed based on the output signal from the at least two audio actuators in a step <NUM>.

The signal detected can be used in later processing for determining an input command or some other input from a user pressing on the display <NUM>. Using the device as set out herein it is made possible to implement force sensing without additional pressing sensors built into the display. This will save product cost and reduce the size of the product. When in use, the electronic device <NUM> can both generate an audio output A1 via the audio display <NUM> and also receive a mechanical pressing force input F1. Any type of audio actuator can be used, such as electro-dynamic (magnet + coil) actuator, piezo-electric actuator or electro-active polymer actuator. All are originally designed to transform electrical AC signal to mechanical vibration A1, but they also work backwards transforming mechanical finger-pressing movement F1 to electrical voltage.

Above, the different components such as low-pass filter and force detection unit are presented as individual blocks. In some implementations these components can be integrated in an audio actuator system configured to monitor an audio actuator displacement. This monitoring of the audio actuator displacement can use the same audio display system functionality as the audio display when the audio display comprises a system for sensing actuator displacement compared to center/rest position.

In <FIG>, a flowchart illustrating some steps performed in an electronic device <NUM> when a mechanical force is applied to the display <NUM> connected to the audio actuator <NUM> is shown. First, in a step <NUM> a signal from the audio actuator <NUM> is output. Next, in a step <NUM>, the output signal is lowpass filtered in the lowpass filter <NUM>. The signal from the lowpass filter <NUM> is received by a detector <NUM> and the signal received by the detector is used to detect a pressing force on the display in a step <NUM>. In accordance with some embodiments, it is determined in a step <NUM>, a time during which a force is applied to the display based on the output signal from the lowpass filter. In accordance with some embodiments, it is determined in a step <NUM>, a magnitude of a force applied to the display based on the output signal from the lowpass filter. By determining time and magnitude of the input signal the electronic device is enabled to differentiate between different types of input from a user. In case multiple, i.e. at least two, audio actuators are provided in the electronic device, a determination of where on the display the force is applied is performed based on the output signal from the at least two audio actuators in a step <NUM>.

Claim 1:
An electronic device (<NUM>) comprising:
- a display (<NUM>) working as a membrane;
- an audio actuator (<NUM>) connected to the display (<NUM>) and wherein the audio actuator (<NUM>) is an electro-mechanical transducer configured to transform an electrical alternating current audio signal to mechanical vibration and a mechanical force applied to the display to an electrical signal, wherein the audio actuator (<NUM>) is configured to generate a voltage signal from a pressing force on the display (<NUM>);
- an audio signal generator (<NUM>) connected to the audio actuator (<NUM>), wherein the audio actuator (<NUM>) is configured to make the display (<NUM>) vibrate in accordance with an audio signal generated by the audio signal generator (<NUM>),
- a lowpass filter (<NUM>) configured to filter the voltage signal to generate an output signal by filtering out the audio signal,
and
- a force detection unit (<NUM>) connected to the lowpass filter (<NUM>), wherein the force detection unit (<NUM>) is configured to determine if a is force applied to the display (<NUM>) based on the output signal from the lowpass filter (<NUM>); and wherein
the lowpass filter (<NUM>) is configured to have a passband that is below any frequency generated by the audio generator (<NUM>) such that no signals generated by the audio signal generator (<NUM>) are comprised in the output signal.