Touchpad with capacitive force sensing

#Touchpads seemingly are the de facto industry-standard pointing device built into portable computing devices (e.g., laptops, netbooks, notebooks, etc.). Typically, a touchpad (i.e., trackpad) has a small, flat, touch-sensitive surface area that senses the position of a user's finger (or fingers) on its surface to provide on-screen navigation, cursor movement, application control, and/or other user-interactive input to a computing device. Conventionally, touchpads work by sensing the changes in an electrical field using, for example, capacitance or conductance (i.e., resistance).

#Capacitive touchpads (e.g., projected or surface capacitive) primarily detect location on the two-dimensional surface of the touchpad of the user's touch. This location may be called the “X/Y position” herein. Due to the nature of the technology, sensor designs, and environmental conditions, the “touch threshold” can vary quite widely.

#FIG. 1 illustrates a conventional touchpad scenario 100, which shows a user's finger 102 hovering over a cross-section of a user-interactive portion 104 of a conventional touchpad. This portion 104 includes a touchsurface 106 and a conventional capacitive touch sensor 108. A region of varying capacitance (i.e., “circuit”) 110 lies between the finger 102 and the capacitive touch sensor 108. Typically, the finger 102 is determined to have “touched” the touchsurface 106 when the capacitance of the circuit 110 exceeds a given threshold, as measured by the sensor 108.

#FIG. 1 is elevation view that illustrates a conventional touchpad scenario with a conventional capacitive touch sensor.

#FIG. 2 is an elevation view that illustrates a first implementation of a capacitive force-sensing touchpad configured in accordance with the techniques described herein.

#FIG. 3 is an elevation view that illustrates a second implementation of a capacitive force-sensing touchpad configured in accordance with the techniques described herein.

#The Detailed Description references the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

#Described herein are techniques related to a touchpad with capacitive force sensing. As described herein, one or more of the exemplary force-sensing touchpads offer new approaches in determining the X/Y position of a user's finger touching the touchsurface of the touchpad. These new approaches include a determination of the X/Y position of the user's finger touch on the touchsurface by using one or more capacitive force-sensors. In addition, these new approaches also determine the force of the user's finger press on the touchsurface using one or more capacitive force-sensors. The force of the finger press moves the touchsurface in a “Z” direction (e.g., down) and thus the determination of that force equates to a detection of the “Z position” of the user's finger. Therefore, collectively, the new approaches described herein determine the X/Y/Z position of user's finger on the touchsurface of the exemplary force-sensing touchpad.

#Furthermore, the described exemplary force-sensing touchpad may offer active tactile feedback (i.e., haptics) to the user's finger touching the touchsurface of the touchpad. Such feedback may be provided to enhance the illusion of pressing a displayed button on an on-screen user-interface (UI) of a computer display.