Patent Application
20130106759
This disclosure generally relates to detecting an interaction with an object.
An array of conductive drive and sense electrodes may form a mutual-capacitance touch sensor having one or more capacitive nodes. An intersection of a drive electrode and a sense electrodes in the array may form a capacitive node. At the intersection, the drive and sense electrodes may come near each other, but they do not make electrical contact with each other. Instead, the sense electrode is capacitively coupled to the drive electrode. A pulsed or alternating voltage applied to the drive electrode may induce a charge on the sense electrode, and the amount of charge induced may be susceptible to external influence (such as a touch by or the proximity of an object). When an object touches or comes within proximity of the drive and sense electrodes, a change in capacitance may occur at that capacitive node and a controller may measure the change in capacitance as a change in voltage. By measuring changes in voltage throughout the array, the controller may determine the position of the touch or proximity on the touch sensor.
An array of conductive electrodes of a single type (e.g. drive) may form a self-capacitance touch sensor. Each of the conductive electrodes in the array may form a capacitive node, and, when an object touches or comes within proximity of the electrode, a change in self-capacitance may occur at that capacitive node and a controller may measure the change in capacitance as a change in voltage or a change in the amount of charge needed to raise the voltage by a pre-determined amount. As with a mutual-capacitance touch screen, by measuring changes in voltage throughout the array, the controller may determine the position of the touch or proximity on the touch sensor.
In a touch-sensitive display application, a touch sensor may enable a user to interact directly with what is displayed on a display underneath the touch sensor, rather than indirectly with a mouse or touchpad. A touch sensor may be attached to or provided as part of, for example, a desktop computer, laptop computer, tablet computer, personal digital assistant (PDA), smartphone, satellite navigation device, portable media player, portable game console, kiosk computer, point-of-sale device, or other suitable device. A control panel on a household or other appliance may include a touch sensor.
[10] Controller 102 may be coupled to touch sensor 104 through one or more sense lines Y and one or more drive lines X. In particular embodiments, touch sensor 104 may be a mutual-capacitance touch sensor 104 that includes an array of drive electrodes and sense electrodes coupled to one of corresponding drive lines X and sense lines Y, respectively. Each intersection of a drive electrode and sense electrode forms a capacitive node. In other particular embodiments, the touch sensor may be a self-capacitance touch sensor. The self-capacitance touch sensor includes one or more electrodes each coupled to one of corresponding sense line Y. Self-capacitance touch sensor detects a presence of an object as an interaction between an object (not shown) and an electric field generated by one or more electrodes of self-capacitance touch sensor.
Controller 102 may detect and process a change in capacitance to determine the presence and location of a touch or proximity input. Controller 102 may then communicate information about the touch or proximity input to one or more other components (such one or more central processing units (CPU) or digital signal processors (DSP)) of a device, which may respond to the touch or proximity input by initiating a function of the device (or an application running on the device) associated with it. Controller 102 may be one or more integrated circuits (ICs), such as for example general-purpose microprocessors, microcontrollers, programmable logic devices or arrays, application-specific ICs (ASICs). Although this disclosure describes and illustrates a particular controller in the example system, this disclosure contemplates any suitable controller in the example system.
Drive-line function generator 106 may be configured to communicate a drive signal to touch sensor 104 through drive lines X. In particular embodiments, the drive signal may be a function pattern, e.g., trapezoid or sinusoid, with an associated frequency. A trapezoidal function pattern may utilize a slew rate limiter (not shown), while a sinusoidal pattern may prevent the function pattern from causing harmonic distortion. In other particular embodiments, Drive-line function generator 106 may be configured to modify the frequency associated with the generated function pattern.
The drive signal may induce charge on one or more sense electrodes. The amount of charge induced on one or more sense electrodes may be susceptible to external influence (such as a touch by, the proximity of an object, or noise sources). Example noise sources may comprise radiation sources or electrical chargers that emit signals over a relatively wide spectrum of frequencies during charging. As an example and not by way of limitation, power chargers for smart phones may introduce noise to touch sensor 104 of a smart phone during charging. Additional induced charge from noise sources may corrupt the signal indicative of the change in capacitance on sense lines Y of touch sensor 104. In some cases, noise on the signal indicative of the change in capacitance may register a false “touch” indicating an interaction between touch sensor 104 and an object regardless of whether the object is actually present.
Bandpass filter 108 may be coupled to touch sensor 104 through sense lines Y. Signals from touch sensor 104 may be transmitted to bandpass filter 108 through sense lines Y. As discussed above, an output signal from touch sensor 104 may include the signal indicative of the change in capacitance with a frequency associated with the function pattern, as well as a wide-band noise component. Bandpass filter 108 may be configured to pass components of an input signal within a range centered about a center frequency or passband, while attenuating components of the signal outside the passband. As an example and not by way of limitation, the center frequency may be determined by a configuration of a resistor/capacitor array or a switch cap filter of bandpass filter 108. In particular embodiments, bandpass filter 108 may have a programmable passband. Bandpass filter 108 may be configured to synchronize the center frequency with a drive-line function pattern frequency. By attenuating components of the signal outside the passband of bandpass filter 108, components of example system 100 downstream of bandpass filter 108 may receive a substantially noise-free passband signal indicative of the change in capacitance of touch sensor 104.
Amplitude detector 114 may be coupled to an output of bandpass filter 108. The output of bandpass filter 108 may include components of the passband signal from touch sensor 104 within a range of the center frequency of bandpass filter 108. Amplitude detector 114 may sample the passband signal from bandpass filter 108 and communicate a voltage corresponding to a peak amplitude of the passband signal. Amplitude detector 114 may also store the peak amplitude, and if the amplitude of the passband signal increases above the stored peak amplitude, the output voltage of amplitude detector 114 may increase to the new peak amplitude. In particular embodiments, amplitude detector 114 may include a diode coupled in series with a capacitor. In other particular embodiments, the peak voltage of the passband signal may be an indicator of a quality of the passband signal. Although this disclosure describes and illustrates a particular arrangement of particular components for amplitude detector 114, this disclosure contemplates any suitable arrangement of any suitable components for amplitude detector 114.
Analog-to-digital converter 112 may be configured to receive and sample the peak amplitude of the passband signal from amplitude detector 114. ADC 112 quantizes the analog signal from amplitude detector 112 to generate a digital representation of the analog signal. Processing unit 110 receives the digital representation of the signal from ADC 112. Processing unit 110 may be configured to filter or further process, e.g., shape, the digital representation from ADC 112. Processing unit 110 may be further configured to control generation of the function pattern by drive-line function generator 106 or program the center frequency of bandpass filter 118. In particular embodiments, a signal from processing unit 110 may configure a resistor/capacitor array or a switching frequency of a switch cap filter to program the center frequency of bandpass filter 108. In other particular embodiments, processing unit 110 may include a CPU or DSP configured to process the digital representation from ADC 112 or control generation of the function pattern by drive-line function generator 106.
In particular embodiments, the periodic signal transmitted to mixer 124 may be synchronized with the drive-line function pattern generated by drive-line function generator 106. As an example and not by way of limitation, the drive-line function pattern may be simultaneously transmitted to mixer 124 and drive lines X. Components of the signal outside the passband, defined by the periodic signal transmitted to mixer 124, may be substantially attenuated.
stylus 122 may provide input to touch sensor 104. In particular embodiments, stylus 122 may be an “active” stylus 122 configured to generate a function pattern with an associated frequency. The function pattern of the stylus 122 may interact with touch sensor 104 through capacitive coupling between the stylus 122 and capacitive nodes of touch sensor 104. The frequency of the function pattern generated by stylus 122 may be different than the associated frequency of the function drive-line function pattern. The function pattern generated by stylus 122 may induce an output signal having a frequency associated with the stylus 122 function pattern and indicative of a change in capacitance caused by interaction between touch sensor 104 and stylus 122. Processing unit 110 may configure drive-line function generator 106 to transmit a periodic signal with the stylus 122 function pattern frequency to mixer 124. Since the frequency of the function generator 106 function pattern may be different than the frequency of the stylus 122 function pattern, mixer 124 may separate signals caused by interaction between touch sensor 104 and stylus 122 from signals caused by interaction between touch sensor 104 and an object based on the frequency transmitted to mixer 124. Therefore, signals caused by interaction between touch sensor 104 and stylus 122 may be detected by amplitude detector 114 without synchronization between stylus 122 and touch sensor 104 or processing unit 110. In particular embodiments, processing unit 110 may instruct drive-line function generator 106 to alternately transmit the periodic signal corresponding to the stylus 122 function pattern and the periodic signal corresponding to the drive-line function pattern. Processing unit 110 may receive input from either stylus 122 or an object (e.g., finger) and mixer 124 may filter out each input based on the frequency of the periodic signal at a given time.
In other particular embodiments, each drive line X of touch sensor 104 may receive a drive-line function pattern with a unique frequency transmitted by drive-line function generator 106 over a relatively short period of time. A periodic signal having each of the unique frequencies of the drive-line function patterns may be transmitted to mixer 124 and the signal from all sense lines Y may be scanned simultaneously. By adjusting the passband of mixer 124 to each unique frequency, controller 102 may differentiate each a passband signal component associated with each sense line Y. Simultaneously scanning all sense lines Y may significantly decrease the scan time of example system 120.
As described above, amplitude detector 114 may receive a filtered signal from mixer 124 containing components from the interaction between touch sensor 104 and an object or a component from interaction between touch sensor 104 and stylus 122. Amplitude detector 114 may sample the passband signal and transmit the peak amplitude of passband signal to ADC 112. The filtered signal from mixer 124 may be converted to a digital representation by ADC 112 and the digital representation transmitted to processing unit 110 for processing.
In other particular embodiments, the bandpass filter may be synchronized to another predetermined frequency in response to noise at the initial predetermined frequency. Step 204 receives a change of capacitance signal from an interaction between an object and the touch sensor. In particular embodiments, the interaction may be capacitive coupling between a stylus transmitting a function pattern at a second predetermined frequency and the touch sensor. In other particular embodiments, the change of capacitance signal includes components introduced by a noise source. At step 206, components of the signal outside the predetermined frequency may be filtered. In particular embodiments, a passband of the bandpass filter may be defined through the predetermined frequency of the drive-line function pattern or the predetermined frequency of the stylus function pattern. In other particular embodiments, filtering may be through a periodic signal predetermined frequency transmitted to a mixer coupled to the sense lines of the touch sensor. At step 208, the passband signal may be communicated to a processor, at which point the method may end. Although this disclosure describes and illustrates particular steps of the method of
Herein, reference to a computer-readable storage medium encompasses one or more non-transitory, tangible computer-readable storage media possessing structure. As an example and not by way of limitation, a computer-readable storage medium may include a semiconductor-based or other IC (such, as for example, a field-programmable gate array (FPGA) or an ASIC), a hard disk, an HDD, a hybrid hard drive (HHD), an optical disc, an optical disc drive (ODD), a magneto-optical disc, a magneto-optical drive, a floppy disk, a floppy disk drive (FDD), magnetic tape, a holographic storage medium, a solid-state drive (SSD), a RAM-drive, a SECURE DIGITAL card, a SECURE DIGITAL drive, or another suitable computer-readable storage medium or a combination of two or more of these, where appropriate. Herein, reference to a computer-readable storage medium excludes any medium that is not eligible for patent protection under 35 U.S.C. § 101. Herein, reference to a computer-readable storage medium excludes transitory forms of signal transmission (such as a propagating electrical or electromagnetic signal per se) to the extent that they are not eligible for patent protection under 35 U.S.C. § 101. A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate.
Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context.
This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.
