Force sensor apparatus and keyboard

Abstract

To provide a force sensing apparatus, a keyboard, and a method of manufacturing a force sensing apparatus.SOLUTION: A disclosed force sensing apparatus includes drive lines and sensing lines arranged to provide intersections, each of the intersections defining a sensel, each sensel being configured to exhibit a variable resistance response in dependence on a magnitude of a force applied to the sensel. The sensels are grouped in multiple sensel groups and each of the sensels in a sensel group is configured to exhibit a variable resistance response within a group resistance range. The group resistance range of first multiple sensel groups is different to the group resistance range of further multiple sensel groups. The force sensing apparatus includes control modules, each of the control modules connected to a corresponding sensel group and configured to output a force signal indicative of a force applied to a sensel in the corresponding sensel group.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to force sensing, and in particular to a force sensing device configured to sense a force applied to one or more keys of a keyboard. The present invention also relates to a keyboard and a method of manufacturing a force sensing keyboard. [Background technology]

[0002] Force sensing technology can be used in electronic devices to create input devices into the electronic device that are dependent on the amount of force applied to an input element, such as a key on a keyboard. For example, a light press on a key can result in a different input than a heavier press on the same key.

[0003] Such "force-enabled" keyboards include a membrane with a matrix structure, with keys positioned at the intersections of the matrix. Variations in the keys can result in varying force sensitivity of those keys. For example, different key cap sizes, shapes, and locations on the keyboard can change the force response of those keys. Achieving uniform force sensitivity across a keyboard employing force sensing technology can be challenging. Examples disclosed herein aim to solve this problem in the art. Summary of the Invention [Means for solving the problem]

[0004] Aspects and embodiments of the present invention provide a force sensing device, a keyboard, and a method for manufacturing a force sensing device.

[0005] In accordance with the present disclosure, there is provided a force sensing device, the device comprising: a plurality of drive lines and a plurality of sensing lines arranged to provide a plurality of intersections, each of the plurality of intersections defining a sensel, each sensel configured to exhibit a variable resistance response in response to a magnitude of force applied to the sensel; The multiple sensor cells are grouped into multiple sensor groups, each of the sensels in the sensor group is configured to exhibit a variable resistance response within a group resistance range; a group resistance range of the first plurality of sensor groups is different from a group resistance range of the further plurality of sensor groups; Further, the system includes a plurality of control modules, each of the plurality of control modules connected to a corresponding sensor group and configured to output a force signal indicative of a force applied to a sensor in the corresponding sensor group, and each of the plurality of control modules is tuned to operate within a group resistance range of the corresponding sensor group.

[0006] At least one of the plurality of sensor groups includes a plurality of sensors.

[0007] A variable resistance response within the group resistance range may correspond to forces applied to the sensors within a force signal range of operation of the sensors in the sensor group, and a first force signal range of a first sensor group may differ from further force signal ranges of further sensor groups.

[0008] Each of the sensors in a sensor group may have a sensor size within the size range of the group sensors, and may thereby be configured to exhibit a variable resistance response within the group resistance range.

[0009] The force sensing device may further include a plurality of key caps, each of which may be disposed adjacent a corresponding sensor of the plurality of sensors and configured to exert a corresponding force on the adjacent corresponding sensor when a force is applied to the key cap. In some examples, the key cap may correspond to the plurality of sensors.

[0010] Each of the sensels in the sensel group may have a corresponding keycap having one or more of a keycap size within the size range of the group keycaps and a keycap dome characteristic within the dome characteristic range of the group keycaps, thereby configured to exhibit a variable resistance response within the group resistance range.

[0011] At least two of the keycaps having corresponding sensors of the first sensor group may be separated, and at least one keycap having at least one corresponding sensor from a further sensor group is positioned between the at least two keycaps having corresponding sensors of the first sensor group.

[0012] Each of the plurality of control modules may be configured to convert analog force sensor signals from the sensors in the corresponding sensor group into digital output signals representative of force signals indicative of forces applied to the sensors. Each of the plurality of control modules may include an analog-to-digital converter configured to convert analog force sensor signals from the sensors in the corresponding sensor group into digital output signals, and a group resistance range of each of the plurality of control modules may correspond to a dynamic range of the analog-to-digital converter.

[0013] Each of the plurality of control modules may be configured to provide a signal gain for force sensor signals received from sensors in a corresponding sensor group according to a group resistance range.

[0014] Each of the plurality of control modules may comprise an input amplifier configured to receive force sensor signals received from sensors in a corresponding sensor group, and a gain resistor coupled to the input amplifier, the gain resistor configured to provide a signal gain. The input amplifier may be configured to operate over a particular range of resistance values, and the control module comprises the gain resistor, thereby having a signal range adjusted to the group resistance range of the corresponding sensor group. The gain resistor may be configured to operate over a particular range of resistance values, and the control module comprises the gain resistor, thereby having a signal range adjusted to the group resistance range of the corresponding sensor group.

[0015] Each of the plurality of control modules may include an offset resistor configured to limit an upper resistance of a group resistance range.

[0016] The input amplifier may comprise a transimpedance amplifier.The gain resistor may comprise a high-resolution digitally controlled resistor array.

[0017] The force sensing device may include a resistive ink material disposed at intersections between drive lines and sense lines to form sensors. The resistive ink material may include a resistive ink layer having a first surface and a second opposing surface, the resistive ink layer sandwiched between a plurality of drive lines on the first surface and a plurality of sense lines on the second surface.

[0018] The number of sensors in a sensor group may be equal to the number of drive lines for that sensor group. Each sensor group may be associated with a dedicated sensing line connected to a dedicated control module for that sensor group. The total number of drive lines for the force sensing device may be equal to the number of sensors in the sensor group having the maximum number of sensors among all sensor groups.

[0019] In one aspect, a keyboard is provided that includes a force-sensing device as disclosed herein. The keyboard includes a plurality of key caps, each associated with at least one corresponding sensor. The keyboard may include one or more sensor groups corresponding to a plurality of alphabetic character keys, a plurality of numeric keys, a plurality of keys in a numeric keypad area, a plurality of function keys, and a plurality of modifier keys.

[0020] In one aspect, a method of manufacturing a force sensing device is provided, the method comprising: Providing a plurality of drive lines; Providing a plurality of sensing lines; arranging a plurality of drive lines and a plurality of sensing lines to provide a plurality of intersections, each of the plurality of intersections defining a sensor, each sensor configured to exhibit a variable resistance response depending on a magnitude of force applied to the sensor; grouping the plurality of sensor cells into a plurality of sensor cell groups, each of the sensor cells in the sensor cell group being configured to exhibit a variable resistance response within a group resistance range, the group resistance range of a first sensor cell group being different from the group resistance range of a further sensor cell group; providing a plurality of control modules; and connecting each of the plurality of control modules to a corresponding sensor group, each of the plurality of control modules being adjusted to operate within a group resistance range of the corresponding sensor group, and each of the plurality of control modules being configured to output a force signal indicative of a force applied to a sensor in the corresponding sensor group. [Brief description of the drawings]

[0021] Example embodiments are further described below with reference to the accompanying drawings. [Figure 1] 1 illustrates an electronic device with a keyboard including a plurality of keys, according to examples disclosed herein. [Diagram 2] 1 illustrates a plurality of drive lines and a plurality of sensing lines forming a force sensing matrix according to an example disclosed herein. [Figure 3a] An example of a keyboard key layout is shown below. [Figure 3b] An example of sensor assignment to individual keys is shown below. [Figure 3c] An example of sensors assigned to keys is shown below. [Figure 4a] 1 illustrates an example keyboard key layout with one sensor group illustrated, according to an example disclosed herein. [Figure 4b] 1 shows an example keyboard key layout where every key is assigned to an individual sensor group, according to an embodiment disclosed herein. [Figure 4c] 13 illustrates a representation of some of the sensors assigned to grouping keys according to an example disclosed herein. [Diagram 5] 1 shows a schematic diagram of a force sensing device, according to an example disclosed herein. [Figure 6] 1 shows an example controller including three drive outputs and three sense inputs connected to respective groups of sense cells according to examples disclosed herein. [Figure 7a] An example of the relationship between resistance and force for a typical sensor is shown below. [Figure 7b] 13 illustrates the relationship between resistance and force sensing range for multiple sensor groups according to examples disclosed herein. [Figure 8] 8 illustrates an example method 800 for manufacturing a force sensing device, according to examples disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Force sensing technology can be used in electronic devices to enable input devices to be electronic devices that depend on the amount of force applied to an input element, such as a keyboard key. Such "force-enabled" keyboards include a membrane with a matrix structure, with keys positioned at the intersections of the matrix. Variations in the keys can result in changes in the force sensitivity of those keys. For example, different key cap sizes, shapes, and locations on the keyboard can change the force response of those keys. Due to these variations, it is difficult to achieve uniform force sensitivity across a keyboard that employs force sensing technology.

[0023] Conventional methods of connecting the keyboard membrane of a force-enabled keyboard to the output electronics create challenges for the force measurement system, making it difficult to achieve a uniform force experience across a complete force-enabled keyboard (e.g., a force sensing resistor (FSR) based membrane keyboard).

[0024] The examples disclosed herein aim to overcome this problem by dividing the membrane into sections and grouping FSR sensors (e.g., sensing elements located at matrix intersections of the membrane) that operate over similar resistance ranges and connecting them to separate dedicated input channels of the overall measurement system. The measurement electronics for each sensor group can then be tuned to the characteristics of the sensors (and keys) in that particular group. These techniques can be particularly useful in combination with measurement systems employing transconductance amplifier input front ends, which allow hardware tuning for both the upper and lower limits of the input resistance range of each dedicated input channel. Other measurement systems, such as systems employing voltage divider inputs, can also be used in combination with the examples disclosed herein.

[0025] 1 illustrates an example of an electronic device 101, shown as a personal computer, with a keyboard 103 and a display 102. The keyboard 103 includes a number of keys 104 configured to interact with a keyboard membrane. Pressure or force applied to the keys 104 of the keyboard 103 provides input to the electronic device 101, for example, to control an application running on the electronic device 101 or to control other functions of the device 101. In an FSR keyboard 103, keys can be pressed with different pressures / forces to provide different inputs. Such a keyboard 103 can be used, for example, to control gaming applications, productivity applications, or other applications or software.

[0026] 2 illustrates an example of a sensing array 200 that may be used in a keyboard membrane. The sensing array 200 comprises a plurality of conductive rows 202 and a plurality of conductive columns 204. A drive control unit 206 is configured to sequentially apply voltages to the plurality of conductive columns 204, also known as drive lines, causing current to flow through the drive lines 204. The sensing array 200 further comprises a sensing control unit 208 configured to receive outputs from the plurality of conductive rows 202, also known as sensing lines. The outputs may be received in analog form and converted to a digital output, if desired, using an analog-to-digital converter or the like.

[0027] 2, the sensing array 200 includes a plurality of sensing elements 210 disposed at each intersection between the drive lines 204 and the sensing lines 202. Each sensing element 210 includes a material that exhibits a variable resistance in response to an applied force. Each sensing element 210 is positioned to correspond to one of a plurality of keys of the keyboard 103 such that when a force or pressure is applied to the key (and thus to the corresponding sensing element 210), the electrical resistance of the sensing element 210 decreases, causing a current to flow through the sensing element 210 and the intersection, which is detected by the sensing control unit 208.

[0028] The sensing element may include, for example, a resistive ink such as a quantum tunneling material, such as that sold under the trademark "QTC" by the applicant's Peratec Holdco Limited.

[0029] In some examples, the rows 202 are disposed on an upper conductive layer and the columns 204 are disposed on a lower conductive layer, respectively, with a sensing layer therebetween that defines sensing elements 210 associated with the rows and / or columns. When pressure is applied, the sensing layer 210 is compressed in contact with the opposing conductive layer, decreasing the resistance of the sensing layer. Thus, the resistance of each sensing element 210 depends on the applied force or area, such as the level of force applied to a key of the keyboard 103.

[0030] Thus, in use, each drive line 204 can be driven by the drive control unit 206 such that when a corresponding sensing element 210 is activated due to an applied force, current flows through the sensing line 204 to the sensing control unit 208. While the illustrated example 200 can be used in a keyboard having a keyboard membrane, other examples can be used in other configurations where there are multiple keys or sensing locations within the membrane.

[0031] FIG. 3a shows an example of a layout of keys 302 (keycaps) on a keyboard 300. The illustrated example is a QWERTY keyboard 300, but other keyboards (e.g., as standalone hardware or as part of a laptop or other portable electronic device), keypads (e.g., numeric keypads, or dedicated key arrays (e.g., as part of a security input device)) can also be used with the examples disclosed herein. FIG. 3b shows that each key 302 can have a unique key identifier 304 (reference number in this example). For example, in this example, the space bar key 302a has reference number "61" and the left arrow key 302b has reference number "79". FIG. 3b can be considered to show key sense mapping for the keyboard because each unique key identifier 304 is associated with a dedicated sensel, as shown in FIG. 3c.

[0032] FIG. 3c shows an example of the assignment of sensors of a force sensing matrix 350 (also called a force keyboard membrane 350, as shown in FIG. 2) to individual keys of the keyboard 300. In this example, each key corresponds to an individual dedicated sensor. Each number in the matrix 350 corresponds to a particular key 302 in the keyboard layout 300. Shown are sensor 306a for the space bar 302a (assigned unique key identifier "61") and sensor 306b for the left arrow key 302b (assigned unique key identifier "79").

[0033] In this example, every key 302 has a dedicated sensor 306, and a controller (not shown) for the keyboard 300 is connected to the matrix 350 using 18 drive outputs 310 (y0-y17) shown along the horizontal direction and 8 sense inputs 312 (x0-x7) shown along the vertical direction. For example, the spacebar sensor cell 306a is located at (x7,y10) and the left arrow key sensor cell 306b is located at (x7,y14).

[0034] This force sensitive keyboard 300 can have problems due to the different force responses of the keys 302. For example, the space bar 302a, which is assigned to sensor 61, shares a controller input channel, i.e., sensing line x7, with the left arrow key, which is assigned to sensor "79" on the same sensing line x7. However, these two keys have significantly different FSR sensor responses due to the large difference in keycap size. Therefore, connecting both of them to the same sensor line, and thus to the same controller, means that the connected controller needs to operate over a relatively wide response range and be able to handle the forces applied (and the varying resistance caused by pressing) of both the larger space bar and the smaller left arrow key (as well as other keys connected to the same sensing line 312). This means that the resolution of the force detection is reduced, since the range of the control electronics needs to be able to receive a wide range of force inputs from the various keys on that sensing line.

[0035] 4a-4c show an example of a keyboard key layout 400, where a single key group 408a is illustrated. The keyboard key layout 400 has all keys assigned to individual key groups 408a-d (or "segments", corresponding to sensor groups), with an indication of a portion of the sensors 406 assigned to group 1 grouped keys 408a. FIGS. 4a and 4b show a keyboard 400 with any of the force sensing devices disclosed herein, where the keyboard 400 includes a plurality of key caps, each associated with a corresponding sensor 414, as shown in FIG. 4c. In some examples, a key cap may be associated with a plurality of sensors. Thus, the force sensing device disclosed herein may include a plurality of key caps, each of which may be considered to be located adjacent a corresponding sensor of the plurality of sensor 414. Each of the plurality of key caps may be configured to exert a corresponding force on an adjacent corresponding sensor when a force is applied to the key cap.

[0036] FIG. 4a shows the layout of keys (keycaps) on a keyboard 400, with one key group marked as key group 408a. Every key in key group 408a has at least one corresponding sensor in a sensor group 406 of an associated FSR matrix or membrane, as shown in FIG. 4c. That key group 408a is connected to a dedicated controller (not shown) configured to operate within the electronic parameters of the keys in that group. The keys are grouped such that they have similar force sensing characteristics, and electronic parameters, so that the associated controller can be tuned or configured to work specifically for that key group. In this example, all the keys in the group have similar sizes and key shapes, and exhibit similar force response characteristics when pressed.

[0037] FIG. 4b shows an example of multiple key groups 408a-408d (actually there are eight groups marked as #1-#8, but in FIG. 4b not all are marked with reference numbers 408a-d for clarity). In this example, all the keys on the keyboard 400 are located in one key group 408a-408d. The keys are grouped to have a similar force response, for example because all the keys in key groups 408a-d have similar keycap sizes. For example, in group #1 408a, this includes the function keys along the top of the keyboard, which are all equally sized. Key group #5 includes the Tab, Caps, Backspace, Enter, and the "0" key on the numeric keypad, which are all equally sized. The space bar is in a single key group (group #8) because there are no other keys of an equivalent size to the space bar. The space bar has a different force response than all the other keys on the keyboard 400. As such, it has a key group that is the only key in the group. Thus, the illustrated keyboard 400 includes sensor groups corresponding to a number of alphabetic character keys, a number of numeric keys, a number of keys in the numeric keypad area, a number of function keys, and a number of modifier keys. In other examples, a keyboard may include any one or more of these key types.

[0038] 4c shows an example assignment of sensors 414 in sensor group 406, which corresponds to key group #1 408a. Each number in matrix 450 corresponds to a particular key in group #1 408a of keyboard layout 400. It will be understood that the keys in the other key groups #2-#8 also have at least one corresponding sensor 414 in matrix 450, but only those for key group #1 408a are shown here.

[0039] Each keycap group 408a-d includes keycaps with similar keycap sizes, thereby avoiding a mix of keycaps with different force sensitivities that share the same sensing input line 412 of the controller. Thus, each of the keycaps corresponding to a sensor in a sense group 406 (and in the corresponding key group 408a-d) can have a keycap size within the group keycap size range, and thereby be said to be configured to exhibit a variable resistance response within the group resistance range. The group resistance range can be thought of as the range of resistance from the minimum resistance to the maximum resistance that a key in the associated key group can provide when pressed.

[0040] In some examples, it may be the dome characteristics of the keycap that are considered when grouping together keycaps having similar force responses. For example, a rectangular shaped keycap may provide a different force response than a round dome shaped keycap, even if they are of comparable size. Thus, each of the sensels in a sensel group may have a corresponding keycap having one or more keycap sizes within the group keycap size range and keycap dome characteristics within the group keycap dome characteristic range, thereby being configured to exhibit a variable resistance response within the group resistance range.

[0041] In some examples, each of the sensors 414 in a sensor group 406 may have a sensor size within a group sensor size range, thereby configured to exhibit a variable resistance response within a group resistance range. In some examples, each of the sensors 414 in a sensor group 406 may have a sensor size within a group sensor sensitivity range, thereby configured to exhibit a variable resistance response within a group resistance range according to a particular sensitivity requirement. For example, higher force resolution can be achieved for a particular sensor group (e.g., a sensor group used to control a particular sensitive function, such as zooming in / out, image processing parameter adjustment, precision movement of a controlled element such as a marker on a display screen, or motion control of a remote device) that can be grouped according to this particular sensing requirement.

[0042] In this example, the maximum number of keys in a key group is 20 (group #1 408a), and to accommodate this, two additional drive lines 410, y18 and y19, are included, in this example, with an individual drive line 410 for each sensor 414 in the sensor group 406. Thus, in this example, each sensor group 406 (for the corresponding key group 408a-d) has a corresponding number of drive lines 410 that is at least equal to the maximum number of keys in the key group (and thus the maximum number of sensor cells 414 in the sensor group 406). Thus, the number of sensors in a sensor group may be equal to the number of drive lines 410 for that sensor group. All sensor cells 414 in a group 406 are connected to the same sense line 412 (x0 in this example) and to a control module for the sense line. In other words, each sensor group 406 may be associated with a dedicated sense line 412 that is connected to a dedicated control module for that sensor group 406.

[0043] In different examples, the number of drive lines 410 and sense lines 412 can be balanced to accommodate, for example, hardware costs, available routing space, scan speed, and the degree of segmentation (i.e., number of key groups 408a-d) desired for a particular controller system. For example, rather than including an additional drive line to accommodate the number of sense cells in a sense cell group to connect to a single corresponding sense line as in FIG. 4c, an additional sense line can be included such that a group of, for example, 20 sense cells is formed with, for example, two groups of 10 sense cells, each of the two groups having a separate sense cell line and associated control module (thereby adding a sense line to accommodate the group rather than two drive lines). Other combinations of drive / sense lines can be envisioned to accommodate the sense cell groups.

[0044] Figure 4a shows an example of a keyboard where there is one sensor group with multiple sensors, and Figure 4b shows an example of a keyboard where there are multiple sensor groups each containing multiple sensors. Where there is at least one sensor group containing one or more sensors, it will be understood that keyboards and force sensing devices including different combinations of numbers of sensor groups with one or more sensors within a group can be envisioned within the scope of the present disclosure.

[0045] A variable resistance response within the group resistance range of the sensor group 406 can correspond to a force applied to the sensor cells 414 within a force signal range of operation of the sensors in the sensor group 406. For example, the sensors 414 in the sensor group 406 can detect a force sensing signal in a range of 60 grams to 150 grams. The first force signal range of the first sensor group can be different from the further force signal range of the further sensor group. For example, the further force signal range of the further sensor group can be in a range of 90 grams to 180 grams. The individual force signal ranges of the multiple sensor groups can partially overlap in some examples. The individual force signal ranges of the multiple sensor groups can be different or non-overlapping in some examples.

[0046] In some examples, at least two of the keycaps with corresponding sensors of the first sensor group may be separated, and at least one keycap with at least one corresponding sensor from a further sensor group is positioned between at least two keycaps with corresponding sensors of the first sensor group. In the example of FIG. 4b, it can be seen that the left shift key of group #6 is physically separated from the right shift key, which is also in group #6, and the character key of group #4 is placed between these two keys in group #6. In this example, the keys in group #5 are also physically separated from each other, and the keys assigned to other groups are placed between the keys of group #5. In other examples, the keys in a group may be physically placed together without any intervening keys of other groups between the keys of the group, as shown, for example, by the keys of groups #1 and #4 in FIG. 4b.

[0047] The force sensing device 500 may comprise a resistive ink material disposed at the intersections between the drive lines 410 and the sense lines 412 to form sensors. Such resistive ink material is thus disposed at a layer or series of intersection locations between a layer formed by the array of drive lines 410 and a layer formed by the array of sense lines 412, forming a sandwich structure with the resistive ink material between the two arrays of lines. That is, the resistive ink material may comprise a resistive ink layer having a first surface and a second opposing surface, the resistive ink layer being sandwiched between a plurality of drive lines 410 on the first surface and a plurality of sense lines 412 on the second surface.

[0048] FIG. 4c may be considered to illustrate a matrix portion 450 of the force sensing device 500 shown in FIG. 5. The matrix portion 450 includes a plurality of drive lines 410 and a plurality of sense lines 412 arranged to provide a plurality of intersections. Each of the plurality of intersections defines a sensor cell 414, with each sensor cell 414 configured to exhibit a variable resistance response in response to a magnitude of force applied to the sensor cell 414. The plurality of sensor cells 414 are grouped into a plurality of sensor cell groups 406, with each of the sensor cells 414 within the sensor cell group 406 configured to exhibit a variable resistance response within a group resistance range. The group resistance range of the first plurality of sensor cell groups 406 is different from the group resistance range of the further plurality of sensor cell groups. The force sensing device also includes a plurality of control modules, as described in connection with FIG. 5 and FIG. 6.

[0049] FIG. 5 illustrates a force sensing device 500 as disclosed herein. The force sensing matrix portion 450 of the force sensing device 500 is as described in connection with FIGS. 4a-4c. Also illustrated are a plurality of control modules 550a-c, which may be part of the control circuit controller 550. Each of the plurality of control modules 550a-c is connected to a corresponding group of sensor cells 408a-c in the force sensing matrix portion 450. Each of the plurality of control modules 550a-c is configured to output a force signal indicative of a force applied to a sensor in the corresponding group of sensor cells 408a-c. Each of the plurality of control modules 550a-c is tuned to operate within the group resistance range of the corresponding group of sensor cells 408a-c. The control modules 550a-c are described in more detail in connection with FIG. 6.

[0050] 6 shows an example of a controller 550 connected to a force sensing matrix 450 with three drive output lines 410a-c and three sense input lines 412a-c connected to respective sensor groups 408a-c. In this example, example features of the controller 550 with three control modules 550a-c are now described. FIG. 6 may be considered to show a controller front end 550 with three drive output lines 410a-c and three sense input lines 412a-c.

[0051] Each control module 550a-c includes an input from a sense line 412a-b of the FSR 450 connected to a negative input of an input amplifier 552a-c. The input amplifier 552a-c may comprise a transimpedance amplifier (TIA) 552a-c. The positive input of the input amplifier 552a-c is connected to a reference TREF+ 558a-c via a power supply. As shown, each of the plurality of control modules 550a-c may include an input amplifier 552a-c configured to receive a force sensor signal received from a sensor in a corresponding sensor group 408a-c, and a gain resistor Rg 556a-c connected to the input amplifier 552a-c. The gain resistor Rg 556a-c is configured to provide a signal gain.

[0052] The offset resistors Ro 554a-c are connected between the inputs from the sense lines 412a-c and the TREF+ 558a-c. Thus, each of the plurality of control modules 550a-c may include an offset resistor Ro 554a-c as shown. The offset resistors Ro 554a-c may be configured to limit the upper resistance of the group resistance range.

[0053] Gain resistors Rg 556a-c are connected between the inputs from the sense lines 412a-c and the TIA output voltages VOUT 560a-c. Thus, each of the plurality of control modules 550a-c can be configured to provide signal gain for the force sensor signals received from the sensors in the corresponding sensor group according to a group resistance range, for example, via the gain resistors Rg 556a-c. The gain resistors Rg 556a-c may comprise high-resolution digitally controlled resistor arrays in some examples.

[0054] Each TIA 552a-c output provides an output voltage VOUT 560a-c that is provided as an input to an analog-to-digital converter (ADC) 562a-c, which is itself connected to a reference voltage VREF+ 564a-c.

[0055] The conversion of the force-sensing resistor (FSR) sensor resistance to voltage via the input amplifiers 552a-c is given by the TIA resistance configurations Ro 554a-c, Rg 556a-c and TREF+ 558a-c and the drive output voltage. The TIAs 552a-c output a voltage VOUT 560a-c which is further converted to a digital code via the ADCs 562a-c and their reference configurations VREF+ 564a-c. Each sense input has its own separate offset resistor Ro 554a-c and gain resistor Rg 556a-c configuration to allow operation over different FSR sensor resistance ranges. Thus, sensing membranes can be arranged such that similar key and FSR characteristics can be grouped together and connected to the same TIA 552a-c inputs.

[0056] In such an arrangement, each of the plurality of control modules 550a-c is configured to convert analog force sensor signals from the sensing lines 412a-c from the sensors in the corresponding sensor group 408a-c into digital output signals representative of force signals indicative of forces applied to the sensors. For example, as shown, each of the plurality of control modules can include an analog-to-digital converter 562a-c configured to convert analog force sensor signals from the sensors in the corresponding sensor group 408a-c into digital output signals. The group resistance range of each of the plurality of control modules 550a-c can correspond to the dynamic range of the analog-to-digital converter 562a-c.

[0057] The input amplifiers 552a-c can be configured to operate over a particular range of resistance values ​​so that the control modules 550a-c, including the gain resistors Rg 556a-c, have a signal range tuned to the group resistance range of the corresponding sensor group. The gain resistors Rg 556a-c can be configured to operate over a particular range of resistance values ​​so that the control modules 550a-c, including the gain resistors Rg 556a-c, have a signal range tuned to the group resistance range of the corresponding sensor group.

[0058] FIG 7a shows an example of resistance vs. force for a group of multiple sensor cells, with the overall FSR resistance range shown for all sensors in the group. FIG 7b shows resistance vs. force sensing range for a group of multiple sensor cells (each sensor cell group has a corresponding group resistance range 758a-c) according to an example disclosed herein. FIGs 7a and 7b show applied force 702 along the horizontal axis plotted against FSR resistance 704 on the vertical axis.

[0059] As shown in Figure 7a, without resistance range optimization, the controller outputs FSR resistance data over the entire resistance operating range of the sensor 708. This operating range 708 can be referred to as the non-optimized ADC range 708 for a circuit that includes an output ADC such as that shown in Figure 6, and will be large (and therefore lower resolution compared to the techniques described below).

[0060] However, in force-enabled keyboard applications, the ADC range available for each sensor will often not need to cover the entire resistance range of all sensors present. The resistance may be limited to the activation threshold of the FSR sensor upon dome collapse. For example, this may be around 60 grams to 70 grams (when the keycap is depressed enough to be detected). The lower resistance limit is given by the maximum force the user applies to the key at maximum applied force, which is typically around 400 grams to 500 grams.

[0061] This operation is illustrated in Figure 7a, where the ADC dynamic range 708 for detecting force input to any key on the keyboard is shown along the FSR resistance axis 704, and the application range 706 (i.e., the range of forces a user can apply to the keyboard keys) is shown along the force axis 702. In this example, force-resistance curves 710a-c for three theoretical key groups are shown, which means that in an example without key grouping (i.e., without sensor grouping) as discussed above, the ADC dynamic range 708 needs to be sufficient to cover all of the possible force responses for all of the key groups. In this example, the ADC dynamic range 708 is considered to be the range without key or sensor grouping (i.e., without keyboard segmentation).

[0062] In Fig. 7b, the operation is illustrated where ADC dynamic ranges 758a-c for detecting force input to any key of the corresponding key group on the keyboard are shown along the FSR resistance axis 704, and the application ranges 756 corresponding to those key groups (i.e., the range of forces a user can apply to the keys of that group of the keyboard) are shown along the force axis 702. In this example, force-resistance curves 710a-c for three theoretical key groups are shown. For example, curve 710a shows the force response characteristic of group #1 shown in Fig. 4b, curve 710b shows the force response characteristic of group #2 shown in Fig. 4b, and curve 710c shows the force response characteristic of group #3 shown in Fig. 4c. Of course, this diagram is schematic and the actual force response curves for a particular key may differ depending on the characteristics of the key and the sensor.

[0063] In this example, where there is grouping of keys in key groups, with dedicated control modules tuned to the force response characteristics of the keys in each particular group, the ADC dynamic range 758a-c (i.e., "group resistance range") for each key group is individual (i.e., tuned) to the possible force responses for each of the separate key groups. Thus, it can be seen that using the examples disclosed herein (where keys are grouped into key groups having similar force response characteristics), one can improve (i.e., increase) the ADC resolution obtained by tuning the electrical characteristics of the ADC of the control module connected to a particular key group to the force response characteristics of the keys in that key group. Each ADC need only operate over a smaller resistance range 758a-c for the connected sensor group, thereby increasing the sensing resolution for that key group.

[0064] Thus, this approach can advantageously increase sensitivity to force input by adjusting the characteristics of a control module connected to a particular key group to the force response characteristics of the keys in that group, thereby providing resistance values ​​within the group resistance range for that key group. Furthermore, this approach can advantageously reduce problems such as consistency in force response between different keys and low response yield due to control electronics not being optimized such that the keys provide smaller output signals when force is applied to them, thus improving the user experience. Furthermore, the examples disclosed herein allow flexibility in the mechanical integration and layout of keycap sensors, thereby providing an improved force sensing force sensing device, which can be a constraint on circuit and force sensing membrane design.

[0065] It will be understood that where a Key Group is discussed, the discussion also applies to the corresponding Sensel Group, and where a Sensel Group is discussed, the discussion also applies to the corresponding Key Group.

[0066] FIG. 8 illustrates an example method 800 for manufacturing a force sensing device according to examples disclosed herein. The method 800 includes providing (802) a plurality of drive lines, providing (804) a plurality of sensing lines, and arranging (806) the plurality of drive lines and the plurality of sensing lines to provide a plurality of intersections, each of the plurality of intersections defining a sensor, each sensor configured to exhibit a variable resistance response in response to a magnitude of force applied to the sensor, grouping (808) the plurality of sensor groups, each of the sensor groups configured to exhibit a variable resistance response within a group resistance range, the group resistance range of a first sensor group being different from the group resistance range of a further sensor group, providing (810) a plurality of control modules, connecting (812) each of the plurality of control modules to a corresponding sensor group, each of the plurality of control modules tuned to operate within the group resistance range of the corresponding sensor group, each of the plurality of control modules configured to output a force signal indicative of the force applied to a sensor in the corresponding sensor group.

[0067] The method further includes providing a plurality of keycaps and placing each of the plurality of keycaps adjacent to at least one corresponding sensor of the plurality of sensors such that when a force is applied to a keycap, a corresponding force is applied to the adjacent corresponding at least one sensor. The method further includes providing a housing, assembling the plurality of sensors and the plurality of control modules within the housing, and placing the plurality of keycaps on a surface of the housing to form a keyboard device, such as keyboard 103,400.

[0068] Throughout the description and claims of this specification, the terms "comprise", "comprises" and variations thereof mean "including but not limited to" and are not intended to exclude, and do not exclude, other moieties, additives, ingredients, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification should be understood to contemplate the plural as well as the singular unless the context otherwise requires.

[0069] It should be understood that features, integers, properties, compounds, chemical moieties or groups described in connection with a particular aspect, embodiment or example of the invention are applicable to other aspects, embodiments or examples described herein, unless incompatible therewith. All of the features disclosed herein (including the accompanying claims, abstract and drawings) and / or all of the steps of the methods or processes so disclosed may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any of the foregoing embodiments. The invention extends to any novel feature, or any novel combination of features disclosed herein (including the accompanying claims, abstract and drawings) or any novel feature, or any novel combination of steps of the methods or processes so disclosed.

[0070] It will be understood that various changes or modifications can be made to the present invention without departing from the scope of the invention.

Claims

1. 1. A force sensing device, comprising: a plurality of drive lines and a plurality of sensing lines arranged to provide a plurality of intersections, each of the plurality of intersections defining a sensor, each sensor configured to exhibit a variable resistance response in response to a magnitude of force applied to the sensor; The multiple sensor cells are grouped into multiple sensor groups, each of the sensels in the sensor group is configured to exhibit a variable resistance response within a group resistance range; a group resistance range of the first plurality of sensor groups is different from a group resistance range of the further plurality of sensor groups; The force sensing device further comprises a plurality of control modules, each of the plurality of control modules connected to a corresponding sensor group and configured to output a force signal indicative of a force applied to a sensor in the corresponding sensor group, and each of the plurality of control modules is tuned to operate within a group resistance range of the corresponding sensor group.

2. The force sensing device of claim 1 , wherein a variable resistance response within a group resistance range corresponds to forces applied to sensors within a force signal range of operation of sensors in the sensor group.

3. 3. A force sensing device as claimed in claim 1 or 2, wherein each of the sensors in a sensor group has a sensor size within the size range of the group sensors and is thereby configured to exhibit a variable resistance response within the group resistance range.

4. It also has multiple key caps, Each of the plurality of keycaps is disposed adjacent to a corresponding one of the plurality of sensors; A force sensing device according to any one of claims 1 to 3, configured to exert a corresponding force on an adjacent corresponding sensor when a force is applied to the keycap.

5. Each of the sensors in the sensor group has a corresponding keycap; The key cap is Keycap sizes within the group keycap size range, and having one or more of the keycap dome characteristics within the group keycap dome characteristic range; 5. A force sensing device as claimed in claim 4, whereby it is configured to exhibit a variable resistance response within the group resistance range.

6. At least two of the keycaps having corresponding sensors of the first group of sensors are separated; 6. A force sensing device according to claim 4 or 5, wherein at least one keycap having at least one corresponding sensor from the further sensor group is positioned between at least two keycaps having corresponding sensors of the first sensor group.

7. 7. A force sensing device as described in any one of claims 1 to 6, wherein each of the plurality of control modules is configured to convert analog force sensor signals from sensors in a corresponding sensor group into digital output signals representative of force signals indicative of forces applied to the sensors.

8. each of the plurality of control modules includes an analog-to-digital converter configured to convert analog force sensor signals from the sensors in the corresponding sensor group into digital output signals; 8. The force sensing device of claim 7, wherein a group resistance range of each of the plurality of control modules corresponds to a dynamic range of the analog-to-digital converter.

9. A force sensing device according to any preceding claim, wherein each of the plurality of control modules is configured to provide a signal gain of force sensor signals received from sensors in a corresponding sensor group according to a group resistance range.

10. Each of the plurality of control modules includes an input amplifier configured to receive force sensor signals received from sensors in a corresponding sensor group; A force sensing device according to any preceding claim, comprising: a gain resistor connected to the input amplifier, the gain resistor being configured to provide a signal gain.

11. 11. The force sensing device of claim 10, wherein the force sensing device is one or more of the following: The input amplifier is configured to operate over a specific range of resistance values, and the control module includes a gain resistor so that it has a signal range adjusted to the group resistance range of the corresponding sensor group. The gain resistors are configured to operate over a specific range of resistance values, and the control module includes gain resistors that have a signal range adjusted to the group resistance range of the corresponding sensor group.

12. A force sensing device according to any preceding claim, wherein each of the plurality of control modules comprises an offset resistor configured to limit an upper resistance of a group resistance range.

13. A force sensing device according to any preceding claim, comprising a resistive ink material located at an intersection between a drive line and a sensing line, forming a sensor.

14. the resistive ink material includes a resistive ink layer having a first surface and a second opposing surface; 14. The force sensing device of claim 13, wherein the resistive ink layer is sandwiched between a plurality of drive lines on the first surface and a plurality of sensing lines on the second surface.

15. the number of sensors in a sensor group is equal to the number of drive lines of the sensor group; A force sensing device according to any preceding claim, wherein each group of sense cells is associated with a dedicated sensing line connected to a dedicated control module for that group of sense cells.

16. A keyboard comprising the force sensing device according to any one of claims 1 to 15, The keyboard comprises a plurality of keycaps each associated with at least one corresponding sensor.

17. 17. The keyboard of claim 16, wherein the keyboard includes one or more sensor groups corresponding to: -Multiple alphabetic keys -Multiple number keys - Multiple keys in the numeric keypad area -Multiple function keys - Multiple modifier keys

18. providing a plurality of drive lines; providing a plurality of sensing lines; arranging a plurality of drive lines and a plurality of sensing lines to provide a plurality of intersections, each of the plurality of intersections defining a sensor, each sensor configured to exhibit a variable resistance response depending on a magnitude of force applied to the sensor; grouping the plurality of sensor cells into a plurality of sensor cell groups, each of the sensor cells in the sensor cell group being configured to exhibit a variable resistance response within a group resistance range, the group resistance range of a first sensor cell group being different from the group resistance range of a further sensor cell group; providing a plurality of control modules; and connecting each of a plurality of control modules to a corresponding group of sensor cells, each of the plurality of control modules being tuned to operate within a group resistance range of the corresponding group of sensor cells, and each of the plurality of control modules being configured to output a force signal indicative of a force applied to a sensor in the corresponding group of sensor cells.

19. providing a plurality of key caps; 20. The method of claim 18, further comprising the steps of: disposing each of the plurality of keycaps adjacent to at least one corresponding sensor of the plurality of sensors such that when a force is applied to the keycap, a corresponding force is applied to the at least one adjacent corresponding sensor.

20. providing a housing; assembling a plurality of sensor modules and a plurality of control modules within a housing; and disposing a plurality of keycaps on a surface of the housing to form a keyboard device.

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