Wireless optical input devices are well known in the art. A typical optical input device uses a light source to illuminate a portion of a navigation surface and a sensor to generate digital images from the light that is reflected off the navigation surface. In general, an optical input device tracks the relative movement between a navigation surface and the input device, multiple frames of digital image data of the illuminated navigation surface are captured by the sensor and successive digital images are subsequently processed and further translated as a cursor movement on the input device.
As the wireless input devices are becoming more popular, power saving has become one of the critical considerations in the design of an energy efficient wireless input device. It is desired to reduce the power consumption of a wireless input device during operation in order to increase the battery life of the device. Additionally, prolonging the battery life may reduce the adverse impact on the environment associated with the disposal of used batteries.
One of the methods that is commonly adopted to improve the energy efficiency of a wireless input device is to put the input device into a rest mode when it is inactive or stays idle for a predetermined period of time. When an input device is in the active mode, the input device operates at full operational capacity. On the other hand, when the device is in a rest mode, portions of the device circuitry are normally rendered inactive, thus, reducing the power consumption. However, in a conventional design, even when the input device is in the rest mode, a wake up detector on the input device may still be in operation, whereby the wake up detector is configured to trigger the input device to periodically check the sensor in order to monitor for movement and immediately wake up the input device if movement is detected. Hence, the input device is periodically being switched to active mode even though it is in an idle state. As a result, much of the supposedly inactivated device circuitry is being activated during the wake up detection operation. Therefore, the input device is actually consuming considerable battery power even though it is in a rest mode while inactive.
In general, during a typical wake up detection operation, the whole image data on the sensor array may be processed by the input device during the motion detection. However, since the computed motion data would not be outputted by the sensor to facilitate any navigation operation during a wake up detection operation. Therefore, an accurate motion data computation is actually not critical and may be unnecessary during the wake up detection operation. Accordingly, there is no need to process the whole image data on the sensor array during waking up detection operation and consuming battery power unnecessarily.
Throughout the description and figures, similar reference numbers may be used to identify similar elements.