| 摘要 |
<p>Power management is provided in a user operated data input device (eg an optical mouse) utilizing proximity sensing and switching between three or more power states. Switching between the power states occurs based upon the presence or absence of input activity, and an operation instrumentality ( e.g., a hand) in close proximity to or contact with the device. Capacitive proximity sensing is carried out by detecting a relative change in the capacitance of a "scoop" capacitor formed by a conductor and a surrounding ground plane. A state transition (e.g., from low to high, or high to low) of the input threshold switch is detected and a value (Touch Val) indicative of a number of cycles of charge transfer required to reach the state transition is determined. The presence or absence of an object or body portion in close proximity to or contact with a device can be determined by comparing Touch Val with a predetermined threshold value (TouchOff). TouchOff can be adjusted to take into account environmentally induced (non-touch related) changes in the capacitance of the scoop capacitor. In an optical surface tracking cursor control device embodiment, switching to and from a BEACON state, which provides a reduced flash rate of a surface illuminating light source, is carried out based upon a detected presence or absence of a trackable surface.</p> |
