The invention relates generally to the field of touch detection. More particularly, the present invention is directed in one exemplary aspect to providing a stylus adapted for use with a capacitive touch sensor panel optimized for finger detection.
According to the patent, methods and apparatus adapted to ensure that contact from a stylus will be detected on a low resolution touch sensor panel irrespective of the location of the region of contact upon the touch surface. In some embodiments, a metallic or otherwise conductive disk may be attached to one end of the stylus. The disk may be sized so as to guarantee sufficient electrical interaction with at least one sensory element of the touch sensor panel. In some embodiments, the stylus may be powered so as to provide a stimulus signal to the capacitive elements. Optionally, one or more force and/or angle sensors disposed within the stylus can supply additional data to the touch panel.
Here's Apple's background and summary of the invention: "Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
"Touch sensor panels are typically fabricated as one or more layers of thin film deposited and patterned into conductive regions upon at least one layer of a transparent substrate. The conductive regions include a number of capacitive elements arranged into a plurality of rows and columns. When a user's finger contacts a specific region of the touch surface, the approximate location of the user's finger can be determined based upon analysis of one or more sensed signals.
"A low resolution array of row and column elements is usually sufficient for finger detection. This is because the width of the typical human finger is relatively large (roughly 10 mm) in relation to at least one dimension of a capacitive element. Therefore, if it is known in advance that the touch sensor panel will primarily be driven by finger input, fewer capacitive elements can be built into the touch sensor panel. Additionally, the rows and columns can be separated at a greater distance.
"However, when a stylus is subsequently employed on a touch sensor panel optimized for finger input, the stylus's small tip can often contact a region of the touch surface that is between adjacent capacitive elements (e.g., as between adjacent column sensors). Since the tip of the stylus is not sufficiently wide so as to guarantee the level of electrical interaction necessary for it to be sensed by at least one capacitive element, many situations exist where the touch sensor panel will not be able to identify an input even if the stylus is making contact with the touch surface.
"In many conventional touch sensor panels, capacitive elements are arranged into a plurality of rows and columns so as to service an entire region of a touch surface. By analyzing the state of each column sensor after a particular row has been driven, a centroid can be calculated indicating the approximate position of a contacting entity upon the touch surface.
"In many cases, however, the small tip of a stylus will contact a region of the touch surface that is between adjacent sensors (for example, as in certain low resolution touch sensor panels that are adapted for finger input). Without sufficient electrical interaction with at least one sensory element, a centroid may not be properly identified, and hence the input will not be recognized. Various embodiments of the present invention therefore ensure that contact from the stylus will be detected on a low resolution touch sensor panel irrespective of the location of the region of contact upon the touch surface.
"In some embodiments, a metallic or otherwise conductive disk may be attached to one end of the stylus. The disk may be sized so as to guarantee sufficient electrical interaction with at least one sensory element of the touch sensor panel. In some embodiments, the disk may be attached to one end of the stylus via a pivotal connector. This increases the likelihood that the disk will remain flush with the touch surface as the user applies different combinations of directional forces to the stylus.
"In some embodiments, the stylus may be powered so as to provide a stimulus signal to the capacitive elements. In this manner, the capacitive elements do not need to be driven continuously within a host device. Optionally, one or more force and/or angle sensors disposed within the stylus can supply additional data to the touch panel. This additional data can be used for selecting various features in an application executing on the host device (e.g., selecting various colors, brushes, shading, line widths, etc.)."
The inventor is John G. Elias. The graphic below illustrates an exemplary stylus adapted for use with a host device according to one embodiment of the present invention.
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