Patent Application
20160231854
A touch panel is a human machine interface (HMI) that allows an operator of an electronic device to provide input to the device using an instrument such as a finger, a stylus, and so forth. For example, the operator may use his or her finger to manipulate images on an electronic display, such as a display attached to a mobile computing device, a personal computer (PC), or a terminal connected to a network. In some cases, the operator may use two or more fingers simultaneously to provide unique commands, such as a zoom command, executed by moving two fingers away from one another; a shrink command, executed by moving two fingers toward one another; and so forth.
A touch screen is an electronic visual display that incorporates a touch panel overlying a display to detect the presence and/or location of a touch within the display area of the screen. Touch screens are common in devices such as all-in-one computers, tablet computers, satellite navigation devices, gaming devices, media devices, and smartphones. A touch screen enables an operator to interact directly with information that is displayed by the display underlying the touch panel, rather than indirectly with a pointer controlled by a mouse or touchpad. Capacitive touch panels are often used with touch screen devices. A capacitive touch panel generally includes an insulator, such as glass, coated with a transparent conductor, such as indium tin oxide (ITO). As the human body is also an electrical conductor, touching the surface of the panel results in a distortion of the panel's electrostatic field, measurable as a change in capacitance.
A fingerprint sensor is an electronic device used to capture a digital image of a fingerprint pattern (e.g., a live scan of a fingerprint). The live scan can be utilized to create a biometric template, which can be stored and utilized for matching purposes.
In embodiments, an apparatus includes a controller configured to operatively couple to a sensor (e.g., a touch panel sensor, a fingerprint sensor). The sensor includes a plurality of drive electrodes and a plurality of sense electrodes. Nodes (“pixels”) are formed at the intersections of the plurality of drive electrodes and the sense electrodes. The controller includes output circuitry operatively coupled to the plurality of drive electrodes. The output circuitry is configured to generate unique drive signals to drive corresponding drive electrodes of the sensor. The controller also includes input circuitry operatively coupled to the sense electrodes. The input circuitry is configured to measure mutual-capacitance formed at each intersection of the plurality of drive electrodes and the plurality of sense electrodes to create an image of one or more objects proximate to the sensor.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The detailed description is described with reference to the accompanying figures. The use of the same reference numbers in different instances in the description and the figures may indicate similar or identical items.
Overview
Typically, measuring the mutual capacitance at the intersection of transmitter and receiver lines on a touch sensor is to scan one row at a time down the sensor. If the touch sensor has to update at 100 frames per second (fps) and if there are 50 rows to scan in each frame, then each row has only 200 μs (1/[(100 fps)(50 rows)]. In some measuring methods, multiple rows are driven at the same time. After the driving waveforms have propagated through the sensor pathways, the waveforms can be summed together at the input circuitry (e.g., a receiver) of the sensor.
Orthogonality of various drive signals can be used by a receiver to identify the change in each of the drive signals to determine how the impedances changed at each intersection. In the case of a touch sensor or a fingerprint sensor, each drive line of the sensor is driven by a drive signal having its own orthogonal signal. The signals can run continuously during the frame time, and the result is that the entire touch screen or fingerprint sensor is actively measuring capacitance changes.
In embodiments, an apparatus includes a controller configured to operatively couple to a sensor (e.g., a touch panel sensor, a fingerprint sensor). The sensor includes a plurality of drive electrodes and a plurality of sense electrodes. Nodes (“pixels”) are formed at the intersections of the plurality of drive electrodes and the sense electrodes. The controller includes output circuitry operatively coupled to the plurality of drive electrodes. The output circuitry is configured to generate unique drive signals to drive corresponding drive electrodes of touch panel sensor. The controller also includes input circuitry operatively coupled to the sense electrodes. The input circuitry is configured to measure the mutual-capacitance formed at each intersection of the plurality of drive electrodes and the plurality of sense electrodes to create an image of the object on the sensor. Additionally, further signal processing of the image can determine the location of a finger or unique characteristics associated with a fingerprint (e.g., unique ridge patterns, etc.) For example, as described above, each drive signal may have a frequency characteristic orthogonal to the frequency characteristics of other drive signals.
Thus, the receiver can measure the amplitude and/or the phase delay of the signals in order to determine how the impedance has changed along the path from the transmitter (e.g., output circuitry) to the receiver (e.g., input circuitry). Measurements are averaged together for greater accuracy.
Example Implementations
In a specific implementation, the sensor 102 is a transparent panel positioned in front of or within a display device, such as a liquid crystal display, cathode ray tube, plasma displays, or the like. However, in other implementations, the display device and the touch panel sensor may be distinct (i.e., touch panel sensor is not positioned in front of the display device). The row and the column traces can be formed from a transparent conductive material, such as Indium Tin Oxide (ITO) or Antimony Tin Oxide (ATO), although other transparent and non-transparent materials, such as copper or silver, may be used. In some implementations, the row and the column traces can be perpendicular to each other such that the row and column traces define a coordinate system and each coordinate location comprises a capacitor formed at the intersection 118 of the row and column traces, as described in greater detail herein. In other implementations, other non-Cartesian orientations are also possible. As described above, the sensor system 100 is configured to detect touch events (e.g., fingerprints, palm), stylus events, and hover events.
The controller 108 is configured to interface with the sensor 102 to stimulate the sensor 102 (e.g., stimulate the drive lines) and to detect (e.g., read) the change in capacitance from the sense lines. In one or more implementations, the controller 108 comprises application specific integrated circuitry (ASIC) that is configured to drive the drive lines 110 (e.g., drive channels, drive electrodes). In an implementation, the controller 108 may comprise firmware and/or ASIC that provides processing functionality to the system 100.
As shown in
The frequency generator 122 is configured to generate a unique signal for each respective drive line 110. For example, the frequency generator 122 is configured to generate a first signal for a first drive line 110 and configured to generate a second signal for a second drive line 110 (and so forth). In an implementation, the frequency generator 122 generates a signal having orthogonal frequency characteristics with respect to an adjacent signal. For example, a first signal driving a first drive line 110 may have orthogonal frequency characteristics with respect to a second signal that is driving a second drive line 110 (where the second drive line 110 is directly adjacent to the first drive line 110).
Each intersection 118 of the drive lines 110 (e.g., rows) and the sense lines 112 (e.g., columns) represents a pixel that has a characteristic mutual-capacitance. A grounded object (e.g., a finger, a stylus, etc.) that moves towards a corresponding pixel 118 may shunt an electric field present between the corresponding row and column intersection, which causes a decrease in the mutual-capacitance at that location. During operation, each row (or column) may be sequentially charged by driving (via the sensor drivers) the corresponding drive line 110 with a predetermined voltage signal having a waveform corresponding to a particular frequency characteristic. The capacitance of each intersection 118 is measured. That is, the sensing circuitry 106 is configured to measure capacitive coupling of the drive signals between the drive lines 110 and the sense lines 112 to determine the capacitance of an object with respect to each node (e.g., an intersection 118 pixel).
The controller 108 is configured to cause the frequency generator 122 to generate the drive signals for scanning (e.g., measure or determine the change in capacitance within) the sensor 102. For example, the controller 108 is configured to cause the output circuitry 104 to output signals having a predefined frequency characteristic (e.g., generate an output signal occurring within a predefined range of frequencies). The sensing circuitry 106 is configured to monitor (e.g., determine) the charge transferred in a given time to detect changes in capacitance at each node. The positions within the sensor 102 where the capacitance changes occur and the magnitude of those changes are used to image fingers and/or palms proximate (e.g., over) the sensor 102.
In some implementations, the sensing circuitry 106 (e.g., a receiver) may include low pass filters 128 (e.g., anti-alias filters) communicatively connected to respective sense lines 112. The low pass filters 128 are connected to respective buffers 130, and the buffers 130 are communicatively connected to respective analog-to-digital converters (ADCs) 132. The sensing circuitry 106 also includes a fast Fourier transform module 134, which is communicatively connected to the ADCs 132. The fast Fourier transform module 134, which computes the discrete Fourier transform in an efficient manner, converts the time data from the ADCs into its corresponding frequency representation. The fast Fourier transform module 134 is communicatively coupled to a capacitance measurement module 134. The drive signals contain unique frequencies, and the capacitance measurement module 134 monitors the changes in the amplitude of those frequencies to determine if the mutual capacitance has changed at any pixels on the sensor. Typically, the capacitance measurement module 134 determines a base measurement of the mutual capacitances when there is no object proximate to the sensor 102. A change in the mutual capacitance from the base measurement might indicate that an object is proximate (e.g., over, on, etc.) to the screen. Since there is usually a great deal of noise in the environment, the challenge is to decide whether the change in mutual capacitance is due to an object or noise.
The buffers 126 are configured to buffer the signal generated by the sensor DACs 124 and outputs the buffered drive signal to the sensor 102 (e.g., drive the drive lines 110 of the sensor 102). The DACs 124 are configured to convert the respective signal received from the frequency generator 122 to a corresponding analog signal. In implementations, the sensor DACs 124 may generate a signal having waveform characteristics represented by the equation:
A1·sin(ωt), EQN. 1,
where A1 represents the amplitude of the signal, ω represents the angular frequency of the signal, and t represents time. As described above, each DAC 124 generates a unique signal for the respective drive line. For example, the DAC 124 may generate a signal having orthogonal frequency characteristics with respect to the adjacent drive signals. In some implementations, the sensor DACs 124 may be configured to output sine waves. However, in other implementations, the sensor DACs 124 may be configured to output other signals having other waveform characteristics, such as square waves, wavelets, and so forth.
In one or more implementations, the system 100 is configured to measure a change in mutual-capacitance (CM). The mutual-capacitance (CM) is capacitance that occurs between two charge-holding objects (e.g., conductors). In this instance, the mutual-capacitance is the capacitance between the drive lines 110 and the sense lines 112 that comprise the sensor 102.
In some implementations, as shown in
In one or more implementations, as shown in
In one or more implementations, a stylus device may be utilized to write text, draw objects, select objects, manipulate objects move objects, etc. on the screen (see
In implementations, the sensor 102 may be initially in touch detection mode (e.g., touch scan mode), as shown in
After the stylus device transmits the sync signal, it transmits data representing identity information, the state of the buttons associated with the stylus, battery level, tilt, and/or the pressure associated with the stylus device (see
Since the stylus device transmits and does not have a receive capability, the stylus device does not phase lock to an external signal. Therefore, the controller 108 can phase lock to the stylus device whenever the stylus device is present so that the controller 108 switches its transmitters to receivers in the part of the period when the stylus device is transmitting. The stylus device circuitry may have a phase locking method to align the timing of the controller with that of the stylus. Nevertheless, there may be some error between the timing of the controller 108 and the stylus device. Thus, some buffer period between the stylus scan and touch scan might be necessary. For example,
Although the subject matter has been described in language specific to structural features and/or process operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.
This application claims priority to U.S. Provisional Patent Application No. 62/112,778, filed on Feb. 6, 2015 and entitled “ORTHOGONAL FREQUENCY DIVISION SCANNING METHOD FOR SENSORS,” which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62112778 | Feb 2015 | US |
