This Application is directed, in general, to a single-touch mutual capacitive sensing and, more specifically, to a single touch mutual capacitive sensing that uses a tapered capacitive sensing pattern.
Mutual capacitive sensing can be generally defined as wherein an object (finger, conductive stylus) alters the mutual coupling between row and column electrodes, which are typically scanned sequentially.
Coupled to the row electrodes 105 and the column electrodes 140, there are bond pads 105a-105c for the sensor (row electrode) 105, and bond pads 150a-152c for the various column electrodes 140, electrode sets 140a-140c, respectively. Basically, the FPCB 153 is bonded to the edge of sensor glass that contains the sensing network 100. A representative “X and Y” matrix is formed by 3 columns 105a, 105b and 105c, with 3 rows of electrodes 150, 151, and 152.
These bond pads 105a-105c and 150a-152c are coupled to a top metal layer 140 of a flexible printed circuit board (FPCB) layer 153. The various bond pads are coupled to the top metal layer of FPC 150 with a bonding material, and therefor coupled to the capacitive sensor circuit 115.
Sets of bonding pad sets are themselves coupled together on the bottom metal layer 180 of the flex FPCB 153 (to be illustrated later) after passing through bonding materials, the lower layer metal of FPCB 160 and vias on the lower FPCB level 160. The sensor (row) electrodes 105 and the column electrodes 140 are themselves embedded in a level of Indium Tin Oxide (ITO) , as will be illustrated in prior art FIG. 1Bii.
However, not all electrodes are shorted together: the corresponding bond pads 105a, 105b and 105c are not shorted together, and each has its own independent path to the capacitive sensor circuit 115. However, bond pads 150a, 150b and 150c are shorted, together so therefore their corresponding electrodes are shorted. Bond pads 151a/b/c are shorted to one another, and bond pads 152a/b/c are shorted to one another, but no shorting in between bond pad sets 150, 151, and 152 occurs on the bottom metal layer 180 of the FPCB 153.
The effect of the coupling on the second level is to create a “matrix” or “array” that simulates a 3-D that can read simultaneous multiple touches. As a conductive digit (such as a thumb) is brought closer to the electrodes, the capacitance between row electrodes 105 and column electrodes 140 will be modulated, which will be measured by the capacitive sensor circuit 115, and then the position of the touch will be calculated by the position processor 117.
Prior Art
A transparent cover of glass or polymer (“polymer”) 120 is a protective overlay. An optical clear adhesive (“OCA”) 129 is mounted beneath the polymer 120. A layer of ITO 123, used for the electrodes, is coupled beneath the OCA 123, and a substrate for ITO 124 is coupled beneath the ITO 123.
As is illustrated, the bonding material 105a-105c, and 150a-152c are coupled between the ITO 123 and the lower layer metal 150 on FLEX PCB 160. Coupled to the lower metal layer 160 is the dielectric substrate of flex PCB 153, and coupled to that, is the upper layer metal on flex PCB 180. The interconnections of the various sets of the electrodes occur on this upper level.
However, as appreciated by the inventor of the present application, there are drawbacks with this design. The sensing network 100 required a high bonding pad counts. For example, twelve bonding pads are required for a 3×3 mutual capacitance array, and sixty bonding pads are required by 5×10 mutual capacitance array. This high count of bonding pads is a significant disincentive for design, due to such drawbacks as problems with yield with bonding pads. Moreover, the routing of the array requires the upper metal level 180, an additional cost factor.
It would be advantageous to have a single touch sensor that addresses at least some of these drawbacks.
A first aspect provides a single touch mutual capacitive sensing that uses a tapered capacitive sensing pattern comprising a plurality of receiving electrode sets, each of the plurality of receiving electrodes being defined by a coupled intersecting diagonal bar; a plurality of sets of transmitting electrodes, each set of the transmitting electrodes having: at least a first electrode on a first side of its corresponding receiving electrode, and a second electrode on a second side of its corresponding receiving electrode; and a first AC signal generator to generate a signal on the plurality of electrode sets of transmitting electrodes to be received by the receiving electrodes.
A second aspect provides a system, comprising: a plurality of receiving electrode sets, each of the plurality of receiving electrodes being defined by a coupled intersecting diagonal bar; a plurality of sets of transmitting electrodes, each set of the transmitting electrodes having: at least a first electrode on a first side of its corresponding receiving electrode, and a second electrode on a second side of its corresponding receiving electrode; and a first AC signal generator to generate a signal on the plurality of electrode sets of transmitting electrodes to be received by the receiving electrodes; and a second AC signal generator to generate a signal on the first of the plurality of sets of transmitting electrodes to be received by the receiving electrodes.
A third aspect provides a system, comprising: a plurality of receiving electrode sets, each of the plurality of receiving electrodes being defined by a coupled intersecting diagonal bar; a plurality of sets of transmitting electrodes, each set of the transmitting electrodes having: at least a first electrode on a first side of its corresponding receiving electrode, and a second electrode on a second side of its corresponding receiving electrode; a first AC signal generator means to generate a signal on the plurality of electrode sets of transmitting electrodes to be received by the receiving electrodes, wherein the transmitting and receiving electrodes are tapered.
Generally, a “tapered” sensing pattern is used, such as disclosed in
Use of a transmit and receive sensor path in this configuration allows for the sensing of a touch with only a single FPCB layer, and with less bond pads, as compared to the prior art mutual capacitive sensing, as will be described below.
Turning to
The transmit ITO strip 230 has individual sets of individual transmit strips 231, 233, etc. each of a different length that also correspond to the diagonal intersecting path, as does its corresponding transmit ITO strip 240. The transmit electrode strips alternate with the receive electrode strips.
Each of the transmit paths are coupled to its own respective transmit bond pad 252, 254, etc. and each receive electrode path are coupled to its own respective receive bond pad 258 etc. Although not illustrated for a sake of clarity, each transmit sensor or receive sensor path is coupled to its own bond pad.
In one aspect, all transmit bond pads are then coupled to a first AC signal generator 260. In a further aspect, as illustrated, alternating transmit bond pads are then coupled to the first AC signal generator 260 and a second AC signal generator 262, respectively.
In a first aspect, AC signals used for generating a signal for determining a mutual conductance are transmitted in sequence, not in parallel, so no need to differentiate them. In the alternative aspect, a parallel scan occurs on the pads with the first and second AC signal generators generating different AC signals, which is then distinguished by the receive sensor circuit 270.
The receive pad 258, etc. are each coupled to a receive sensor circuit 270, which measures the combined received capacitive signal from both the first and second transmit path, and the touch processor 280, which takes the measurements from the receive sensor circuit 270, and then determines a position of the touch.
For example, referring to the system 200, there are illustrated three different potential touch areas that occur at different locations on the part of a capacitive touch screen that corresponds to TX3 and TX4: touch area one, touch area two, and touch area three.
At touch area 1, the strength first AC signal of TX3/RX2 will higher than the signal strength from TX4/RX2, whereas at location 2, it is vice versa. At location three, this ratio is about unity. Therefore, the value of this ratio can be used to determine the location of finger touch.
There are numerous advantages to this “tapered design.” As is illustrated, each section of a screen only requires three bond pads: two transmit bond pads and a receive bond pad. On a typical design, this is a significant reduction of bond pads. As shown in
Moreover, the electrodes are not directly coupled to each other. In the prior art, the electrodes were coupled to each other on the second FPCB. However, in the tapered mutual capacitance sensing system 200, there is no need of a second FPCB for this routing. Advantageously, the mutual capacitive system 200 allows for the omission of the FCPC, yet allows for a sensing of a position of a tapered capacitive mutual touch on a pad.
Furthermore, compared to the prior art system 100, the electrodes do not merely perform the function that they performed separately in the prior art. In the prior art, the electrodes were shorted into an x-y matrix. Here, the tapered electrodes are not shorted, yet they are still capable of a determination of a position of a touch without the shorting that occurs from creating an array, something that did not occur in the prior art.
As is illustrated, the system 200 has a plurality of receiving electrode sets, for example, 221, 222 and 223, 224, each of the plurality of receiving electrodes being defined by a coupled intersecting diagonal bar 219; a plurality of sets of transmitting electrodes, for example, 231, 233, 251, and 252, and each set of the transmitting electrodes having: at least a first electrode on a first side of its corresponding receiving electrode, and a second electrode on a second side of its corresponding receiving electrode; and a first AC signal generator to generate a signal on the plurality of electrode sets of transmitting electrodes to be received by the receiving electrodes.
The additional circuitry (AC generation etc.) is not shown in this figure for an ease of illustration.
As is illustrated for a 5 by 10 array, the prior art mutual sensing 100 used 60 bonding pads, wherein the tapered system 200 uses 20. Moreover, the bigger the touch panel, the more benefit we will see on bonding pads reduction, as there is a linear increase of bonding pads per additional segment, but a bigger screen use a power of two exponential increase in bonding pads. Moreover, prior art mutual sensing 100 required at least two layers of a flexible printed circuit board, whereas the single touch tapered mutual capacitive system 200 is enabled with only a single layer FPCB.
Number | Date | Country | Kind |
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PCT/CN2013/078603 | Jul 2013 | CN | national |