BRIEF DESCRIPTION OF THE DRAWINGS
Further details and advantages of the present invention will be apparent from the following detailed description of several not limiting embodiments with reference to the attached drawings, wherein:
FIG. 1 is a schematic cross sectional view of capacitive pressure and proximity sensor according to a first embodiment;
FIG. 2 is a schematic cross sectional view of an input device according to a second embodiment;
FIG. 3 is an illustration of different examples of electrically insulating patterns;
FIGS. 4
a and 4b are cross sectional views of a touchpad having keypad functionality;
FIGS. 5
a and 5b are cross sectional views of an alternative touchpad having keypad functionality;
FIGS. 6
a and 6b are cross sectional views of yet another example of a touchpad having keypad functionality;
FIGS. 7
a-7c are illustrations of a touchpad with keypad functionality, in which the keys are arranged along a straight line;
FIGS. 8
a-8e are illustrations of an input device implemented as a linear slider;
FIGS. 9
a-9d are illustrations of an input device implemented as a circular slider;
FIGS. 10
a-10d are illustrations of variants of an alternative embodiment of a touchpad;
FIGS. 11
a-11b are cross-sectional schematic views of yet another example of an input device.
DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 shows a data input device 10, comprising a capacitive proximity and pressure sensor 12 of film-type construction. The capacitive proximity and pressure sensor 12 comprises first and second carrier layers in the form of the first and second carrier films 16, 18, made of substantially flexible, electrically insulating material, such as e.g. PET, PEN, PI or the like. A spacer 20 is sandwiched between the first and second carrier films 16, 18 so as to keep them apart from one another. The spacer 20 is also be made of a substantially flexible, electrically insulating material, e.g. a double-sided adhesive. The spacer 20 is provided with an opening 14 therein, which delimits an active zone of the pressure sensor 10. In the active zone 14, the first carrier foil 16 carries a first capacitor electrode 22 on the side directed towards the second carrier film 18, while the second carrier foil 18 carries a second capacitor electrode 24 on the side directed towards the first carrier film 16. The first and second capacitor electrodes 22, 24 are formed from conductive material (e.g. silver ink) applied directly on the first and second carrier films 16, 18, respectively. The second capacitor electrode has formed thereon a layer 26 of electrically insulating material (dielectric, e.g. PET, PEN, PI, etc.).
The right-hand side of FIG. 1 shows a control circuit 28 connected to the first and second capacitor electrodes 22, 24 by leads 30, 32. The control circuit 28 comprises a microprocessor, an application-specific integrated circuit (ASIC) or a programmable chip, configured so as to operate in at least a first and a second mode of operation. The control circuit determines, while in the first mode of operation, a quantity indicative of a capacitance between the first capacitor electrode and ground and, while in the second mode of operation, a quantity indicative of a capacitance between the first capacitor electrode and the second capacitor electrode.
The first mode of operation is associated to sensing the proximity of an object to be sensed, e.g. of a user's finger 34. In the first mode of operation the control circuit keeps the first and second electrodes essentially at the same electric potential so that the electric field substantially cancels between the first and second electrodes. The second electrode 24 thus acts as a driven shield for the first electrode 22 and the sensitivity of the latter is directed away from the second electrode 24. If an oscillating voltage is applied to the first capacitor electrode an oscillating electric field to ground is built up. The object to be sensed modifies the capacitance between the first capacitor electrode and ground, which is sensed by the control circuit 28. It should be noted that in the first mode of operation detecting the proximity of the object to be does not require the object touching or being in contact with the proximity and pressure sensor 12.
The second mode of operation is associated with sensing pressure exerted on the sensor by some kind of actuator, such as e.g. the user's finger or stylus. In the second mode of operation, the control circuit essentially determines the capacitance of the capacitor formed by the first and the second capacitor electrodes 22, 24. It is well known that the capacitance of a capacitor depends upon the distance between its electrodes. In the illustrated case, the distance between the first and second capacitor electrodes decreases with increasing pressure exerted upon the pressure sensor by the user. As a consequence, the capacitance between the capacitor electrodes increases, which is detected by the control circuit 28.
FIG. 2 shows a variant of the proximity and pressure sensor of FIG. 1. The construction is the same, except that the first capacitor electrode 22, like the second capacitor electrode 24, has formed thereon a layer 26 of electrically insulating material. Those skilled will appreciate that patterning one of the electrically insulating layers 26 allows tailoring the response of the proximity and pressure sensor in the second mode of operation. As long as the electrically insulating layers are spaced from one another (i.e. for low pressures exerted by the user) the pattern has no significant influence on sensor response. However, as the pressure increases the electrically insulating layers come into contact and a contact surface forms. A patterned insulating layer results in that the minimum distance between the first and second electrodes is varying on the contact surface. Accordingly, the capacitance increase is different from the case where the insulating layers are uniform. Examples of patterned insulating layers are shown in FIG. 3.
In FIGS. 4a-4b, elements similar to elements of FIG. 1 have been attributed the same reference numeral as the corresponding element of FIGS. 1 and 2, preceded by a prefix according to the number of the drawing.
FIGS. 4
a and 4b show a cross section of a touchpad 412 having keypad functionality. The touchpad 412 comprises a laminated structure of a first carrier film 416, a second carrier film 418 and a spacer 420, sandwiched between the first and second carrier films so as to keep them spaced apart. The spacer 420 has a matrix-like arrangement of openings 414 therein, which define keys of the touchpad 412. To each key is associated a pair of a first capacitor electrode 422 and a second capacitor electrode 424 arranged on the first and second carrier films 416, 418, respectively. Each first capacitor electrode 422 is arranged opposite its second-capacitor-electrode counterpart 424, with respect to the associated opening 414 of the spacer 420. The touchpad 412 further comprises a control circuit (not shown, for the sake of clarity of the drawings), which determines, in a first mode of operation, a quantity indicative of capacitance between individual ones of the first capacitor electrodes 422 and ground and, in a second mode of operation, a quantity indicative of a capacitance between individual ones of the first capacitor electrodes 422 and the associated ones of the second capacitor electrodes 424.
In FIG. 4a, a user's finger 434 lightly touches the first carrier film 416. The force exerted is not sufficient to cause significant bending of the first carrier film 416 in the region of a key. The position of the user's finger 434 is detected by determining, for each one of the first capacitor electrodes 422, the quantity indicative of capacitive coupling between this electrode 422 and ground. The position may e.g. be computed as the centroid of the positions of the first capacitor electrodes 422, weighed with the corresponding quantity indicative of capacitance. The first mode of operation is suitable, for instance, when the user controls a cursor (e.g. on the display of an appliance) with the touchpad 412.
In FIG. 4b, the user presses down the first carrier film 416, so that it bends into an opening 414 of the spacer 420 and the distance between the corresponding first and second capacitor electrodes 422, 424 decreases. This causes the capacitance between these capacitor electrodes to go up, which can be detected in the second mode of operation of the touchpad 412. The second mode of operation is, therefore, associated to actuation of a key of the touchpad 412, e.g. by a user's finger 434 or a stylus.
In operation, the first and second modes of operation are carried out in alternance, i.e. the touchpad 412 is switched, more or less periodically, from the first mode of operation to the second mode and inversely. It should be noted that, in the second mode of operation, the touchpad does not need to determine the quantity indicative of capacitance for each key. Indeed, it is considered advantageous if the latter is determined only with respect to that key or those keys in the neighborhood of which the position of the user's finger 434 has been detected when the touchpad 412 operated in the first mode of operation.
FIGS. 5
a and 5b show a cross section of an alternative touchpad 512 having keypad functionality. The touchpad 512 comprises a first carrier film 516, a second carrier film 518 and a spacer 521, sandwiched between the first and second carrier films 516, 518 so as to keep them spaced apart. The spacer 521 is made of an electrically insulating, compressible foam material, e.g. polyurethane foam or the like. The first and second carried films 516, 518 have capacitor electrodes 522, 524 applied on the surfaces that face the spacer 521. Each first capacitor electrode 522 is arranged on the first carrier film opposite a second capacitor electrode 524 on the second carrier film, with respect to the spacer 521. Each pair of opposite first and second capacitor electrodes defines a key of the touchpad 512. The latter further comprises a control circuit (not shown), which determines, in a first mode of operation, a quantity indicative of capacitance between individual ones of the first capacitor electrodes 522 and ground and, in a second mode of operation, a quantity indicative of a capacitance between individual ones of the first capacitor electrodes 522 and the associated ones of the second capacitor electrodes 524.
In FIG. 5a, a user's finger 534 lightly touches the first carrier film 516. The force exerted is not sufficient to cause significant bending of the first carrier film 516 in the region of a key. The position of the user's finger 534 is detected by determining, for each one of the first capacitor electrodes 522, the quantity indicative of capacitive coupling between this electrode 522 and ground. As in the previous example, the position may e.g. be computed as the centroid of the positions of the first capacitor electrodes 522, weighed with the corresponding quantity indicative of capacitance. The first mode of operation is suitable, for instance, when the user controls a cursor (e.g. on the display of an appliance) with the touchpad 512.
In FIG. 5b, the user presses on the first carrier film 516, so that the underlying spacer 521 is compressed, whereby the distance between a pair of first and second capacitor electrodes 522, 524 decreases. This causes the capacitance between these capacitor electrodes to go up, which can be detected in the second mode of operation of the touchpad 512. The second mode of operation is, therefore, associated to actuation of a key of the touchpad 512, e.g. by a user's finger 534 or a stylus.
Operation of the touchpad 512 is similar to the previous example: the first and second modes of operation are carried out in alternance, i.e. the touchpad 512 is switched, more or less periodically, from the first mode of operation to the second mode and inversely. In the second mode of operation, it is considered advantageous if the quantity indicative of capacitance between a first and a second capacitor electrode 522, 524 is determined only with respect to that key or those keys in the neighborhood of which the position of the user's finger 534 has been detected when the touchpad 512 operated in the first mode of operation.
FIGS. 6
a and 6b illustrate that it is also possible to combine the embodiments of the preceding examples within a single touchpad. The touchpad 612 comprises a first carrier film 616, a second carrier film 618 and a first spacer 620, sandwiched between the first and second carrier films 616, 618 so as to keep them spaced apart. The spacer 620 has a matrix-like arrangement of openings 614 therein, which define keys of the touchpad 612. To each key is associated a pair of a first capacitor electrode 622 and a second capacitor electrode 624 arranged on the first and second carrier films 616, 618, respectively. Each first capacitor electrode 622 is arranged opposite its second-capacitor-electrode counterpart 624, with respect to the associated opening 614 of the spacer 620. Some of the openings (middle keys in FIGS. 6a and 6b) in spacer 620 are filled with electrically insulating, compressible foam material 621, e.g. polyurethane foam or the like. The spacer 620 is made, in this example, from a flexible material, which has substantially lower compressibility than the foam material 621. The haptic properties of keys with foam material 621 differ from those without the foam material. Similarly, their capacitance as a function of pressure behaves differently. Nevertheless, operation of touchpad 621 is analogous to operation of touchpads 412 and 512.
FIGS. 7
a-7c show a touchpad 712 with keypad functionality, in which the keys are arranged along a straight line (a curve would also be feasible). FIG. 7a shows the layout of the keys, FIGS. 7b and 7c show cross-sectional views of the touchpad 712. The touchpad 712 comprises a laminated structure of a first carrier film 716, a second carrier film 718 and a spacer 720, sandwiched between the first and second carrier films so as to keep them spaced apart. The spacer 720 has openings 714 therein, which are arranged along a line and which define the keys of the touchpad 712. To each key is associated a first capacitor electrode 722 arranged on the first carrier film 716. A common second capacitor electrode 724 extends over all the keys of the touchpad 712. The touchpad 712 further comprises a control circuit (not shown), which determines, in a first mode of operation, a quantity indicative of capacitance between individual ones of the first capacitor electrodes 722 and ground and, in a second mode of operation, a quantity indicative of a capacitance between individual ones of the first capacitor electrodes 722 and the common second capacitor electrode 724.
In FIG. 7b, a user's finger 734 lightly touches the first carrier film 716. The force exerted is not sufficient to cause significant bending of the first carrier film 716 in the region of a key. The position of the user's finger 734 is detected by determining, for each one of the first capacitor electrodes 722, the quantity indicative of capacitive coupling between this electrode 722 and ground. The position may e.g. be computed as the centroid of the positions of the first capacitor electrodes 722, weighed with the corresponding quantity indicative of capacitance. The first mode of operation is suitable, for instance, when the user controls a cursor (e.g. on the display of an appliance) with the touchpad 712.
In FIG. 7c, the user presses down the first carrier film 716, so that it bends into an opening 714 of the spacer 720 and the distance between the corresponding first electrode 722 and the second capacitor electrode 724 decreases. This causes the capacitance between these capacitor electrodes to go up, which can be detected in the second mode of operation of the touchpad 712. The second mode of operation is, therefore, associated to actuation of a key of the touchpad 712, e.g. by a user's finger 734 or a stylus.
In operation, the first and second modes of operation are carried out in alternance, i.e. the touchpad 712 is switched, more or less periodically, from the first mode of operation to the second mode and inversely. It should be noted that, in the second mode of operation, the touchpad does not need to determine the quantity indicative of capacitance for each key. Indeed, it is considered advantageous if the latter is determined only with respect to that key or those keys in the neighborhood of which the position of the user's finger 734 has been detected when the touchpad 712 operated in the first mode of operation.
FIGS. 8
a-8c show possible layouts of a slider 812, FIGS. 8d and 8e show cross-sectional views thereof. The slider 812 comprises a laminated structure of a first carrier film 816, a second carrier film 818 and a spacer 820, sandwiched between the first and second carrier films so as to keep them spaced apart. The spacer 820 has an opening 814 therein, which extends, in this case, along a straight line (a curvilinear course is possible, see FIGS. 9a-9d). The opening 814 defines the active zone of the slider 812. The first carrier film 816 has first capacitor electrodes arranged thereon in the active zone, the second carrier film has a common second capacitor electrode 824 applied thereon in the active zone. The first capacitor electrodes 822 are arranged in facing relationship to the second capacitor electrode 824. The second capacitor electrode has a thin dielectric layer 826 arranged thereon, which prevents short-circuits between the first capacitor electrodes 822 and the second capacitor electrode 824, if they are brought closer to one another by a compressive force acting on the slider 812.
In FIG. 8d, a user's finger 834 lightly touches the first carrier film 816. The force exerted is not sufficient to cause significant bending of the first carrier film 816 in the region of the active zone. In FIG. 8e, however, the user presses down the first carrier film 816, so that it locally bends into the opening 814 of the spacer 820 and the distance between the first electrodes 822 and the second capacitor electrode 824 decreases at the point where the force is applied.
In the sliders of FIGS. 8a and 8b, the first capacitor electrodes 822 are separately connected to a control circuit (not shown). Accordingly, these sliders are able to detect the position of the user's finger 834 (in the first and the second mode of operation). In the first mode of operation, the control circuit determines, for each one of the first capacitor electrodes 822, the quantity indicative of capacitive coupling between this electrode 822 and ground. The said position may e.g. be computed as the centroid of the positions of the first capacitor electrodes 822, weighed with the corresponding quantity indicative of capacitance. In the second mode of operation, a quantity indicative of a capacitance between single ones of the first capacitor electrodes 822 and the common second capacitor electrode 824 can be detected. As can be seen, operation of the slider 812 as shown in FIGS. 8a and 8b is similar to operation of the keypad 712.
In the slider of FIG. 8c, the first capacitor electrodes are not separately connected to the control circuit. Instead, there are three groups of first capacitor electrodes 822. The first capacitor electrodes 822 of each group are conductively interconnected. Along the active zone, a first capacitor electrode of the first group is followed by one of the second group, which is, in turn, followed by one of the third group, after which the succession starts again with a first capacitor electrode of the first group. A slider as shown in FIG. 8c is not capable of detecting (absolute) position of the user's finger 834 or stylus. Nevertheless, such slider can detect movement of the user's finger 834 or stylus (in both modes of operation). In the first mode of operation, when the user's finger 834 moves from the left to the right, the succession of the groups of first capacitor electrodes that have increased capacitive coupling to ground is 2-3-1 (and cyclically continued). When the user's finger 834 moves from the right to the left, the succession of the groups of first capacitor electrodes that have increased capacitive coupling to ground is 3-2-1 (and cyclically continued). In the second mode of operation, the direction of movement can be determined from the succession of the groups of first capacitor electrodes that have increased capacitive coupling to the second capacitor electrode. Of course, in the second mode of operation, the amount of force exerted upon the slider can also be detected. For instance, if the quantity indicative of capacitance exceeds a predetermined threshold, some switching action may be triggered.
Given the reduced number of external connectors, the slider of FIG. 8c is particularly interesting if the absolute position needs not to be known, e.g. for navigating though list-based menus (scrolling through a list of items displayed and selecting an item to enter a sub-menu or start a certain function). The action of selecting an item from the list can e.g. take place when the user presses on the slider with a force that causes the quantity indicative of capacitance between the first and second capacitor electrodes to exceed the predetermined threshold.
FIGS. 9
a-9d show circular sliders 912. The sliders of FIGS. 9a and 9b are configured for detecting position (sliders with keypad functionality); those of FIGS. 9c and 9d are analogous to the linear slider of FIG. 8c.
FIGS. 10
a-10c show schematic top views, FIG. 10d a schematic cross-sectional view of variants of an alternative embodiment of a touchpad 1012. The touchpad 1012 has a plurality of first elongated capacitor electrodes 1022 applied on the first carrier film 1016 and a plurality of second elongated capacitor electrodes 1024 applied on the second carrier films 1018. The first capacitor electrodes 1022 are arranged opposite the second capacitor electrodes with respect to an opening 1014 in spacer 1020, which is sandwiched between the carrier films 1016, 1018. The first capacitor electrodes 1022 extend crosswise to the second capacitor electrodes 1024. In the shown embodiment, the angle between any one of the first capacitor electrodes and any one of the second capacitor electrodes is 90°; it should, however, be noted that this angle could also be different from 90°, e.g. between 30° and 90°. The second capacitor electrodes 1024 are covered with a thin dielectric layer, which prevent a short-circuit when the first and second capacitor electrodes 1022, 1024 are brought closer together at the location where a compressive force acts on the touchpad 1012. The touchpad 1012 is connected to control circuit (not shown), which determines, while in the first mode of operation, a quantity indicative of capacitance between individual ones of the first capacitor electrodes 1022 and ground and, while in the second mode of operation, a quantity indicative of a capacitance between individual ones of the first capacitor electrodes 1022 and individual ones of the second capacitor electrodes 1024.
In the touchpads of FIGS. 10a and 10b, the capacitor electrodes 1022 and 1024 are separately connected to a control circuit (not shown). Accordingly, these touchpads are able to detect the position of the user's finger 1034 (with respect to one dimension in the first mode of operation and with respect to two dimensions in the second mode of operation). In the first mode of operation, the control circuit determines, for each one of the first capacitor electrodes 1022, the quantity indicative of capacitive coupling between this electrode 1022 and ground. The position may e.g. be computed as the centroid of the positions of the first capacitor electrodes 1022, weighed with the corresponding quantity indicative of capacitance. It should be noted that in first mode of operation, the position of the user's finger 1034 is detected in the direction perpendicular to the direction along which the first capacitor electrodes extend. In the second mode of operation, the control circuit determines, for each one of the first capacitor electrodes 1022, the quantity indicative of capacitance between this electrode 1022 and each one of the second capacitor electrodes 1024. The position of the user's finger (the point of application of the force) is obtained from those first and second electrodes, which show maximum capacitive coupling.
In FIG. 10c, the first and the second capacitor electrodes 1022 and 1024 are not separately connected to the control circuit. Instead, there are three groups of first capacitor electrodes 1022 and three groups of second capacitor electrodes 1024. The capacitor electrodes of each group are conductively interconnected. Along the direction perpendicular to the first capacitor electrodes, a first capacitor electrode of the first group is followed by one of the second group, which is, in turn, followed by one of the third group, after which the succession starts again with a first capacitor electrode of the first group. The second capacitor electrodes are arranged analogously. A touchpad as shown in FIG. 10c is not capable of detecting (absolute) position of the user's finger 1034 or stylus. Nevertheless, such touchpad can detect movement of the user's finger 1034 or stylus. In the first mode of operation, when the user's finger 1034 moves perpendicular to the first capacitor electrodes, the succession of the groups of first capacitor electrodes which have increased capacitive coupling to ground is 2-3-1 (and cyclically continued) or 3-2-1 (and cyclically continued), depending on the direction of the movement. In the second mode of operation, the direction of the movement perpendicular to the first capacitor electrodes can be determined from the succession of the groups of first capacitor electrodes which have increased capacitive coupling to the second capacitor electrodes. Likewise, the direction of the movement perpendicular to the second capacitor electrodes can be determined from the succession of the groups of second capacitor electrodes which have increased capacitive coupling to the first capacitor electrodes. Of course, in the second mode of operation, the amount of force exerted upon the touchpad can also be detected. For instance, if the quantity indicative of capacitance exceeds a predetermined threshold, some switching action may be triggered.
FIGS. 11
a and 11b show yet another alternative embodiment of an input device including a proximity and pressure sensor 1112. The capacitive proximity and pressure sensor 1112 comprises a first carrier layer in the form of a substantially rigid cover 1116 and a second carrier layer in the form of a substrate 1118. The rigid cover 1116 includes a plurality of component layers, such as a protective hard plastic 1116a, a double-sided adhesive 1116b and a flexible thermoplastic film 1116c. A pivot 1123 is sandwiched between the first and second carrier layers 1116, 1118. The capacitive proximity and pressure sensor 1112 comprises electrode pairs diametrically opposed with respect to the pivot 1123. Each electrode pair comprises a first capacitor electrode 1122 arranged on the first carrier layer 1116 (on the side directed towards the second carrier layer 1118) and a second capacitor electrode 1124 on the second carrier layer 1118 (on the side directed towards the first carrier layer 1116). The first and second capacitor electrodes 1122, 1124 are formed from conductive material (e.g. silver ink) applied directly on the first and second carrier layers, respectively. A spacer 1121 made of electrically insulating foam material is arranged between the first and second capacitor electrodes of a pair.
The first and second capacitor electrodes 1122, 1124 are connected to a control circuit (not shown). The control circuit determines, while in the first mode of operation, a quantity indicative of a capacitance between the first capacitor electrodes and ground and, while in the second mode of operation, a quantity indicative of a capacitance between the first capacitor electrode and the second capacitor electrode of each pair.
The first mode of operation is associated to sensing the proximity of an object to be sensed, e.g. of a user's finger 1134. In the first mode of operation the control circuit keeps the first and second electrodes essentially at the same electric potential so that the electric field substantially cancels between the first and second electrodes. The second electrodes 1124 thus act as driven shields for the respective first electrodes 1122 and the sensitivity of the latter is directed away from the respective second electrode 1124. If an oscillating voltage is applied to the first capacitor electrode, an oscillating electric field to ground is built up. The object to be sensed modifies the capacitance between the first capacitor electrode and ground, which is sensed by the control circuit 1128.
The second mode of operation is associated with sensing pressure exerted on the sensor by some kind of actuator, such as e.g. the user's finger 1134 or stylus. In the second mode of operation, the control circuit essentially determines the capacitance of the capacitor formed by the first and the second capacitor electrodes 1122, 1124. In the embodiment of FIGS. 11a and 11b, pressure exerted on the proximity and pressure sensor 1112 by the user causes the first carrier layer to tilt, whereby the first and second capacitor electrodes of a first pair get closer together (right-hand side in FIG. 11b) and those of a second pair are moved away from one another (left-hand side in FIG. 11b). When the user stops pressing on the sensor, the foam spacers 1121 bring the first carrier layer back into the neutral position.
Patent Application
20080018611
