| 摘要 |
A hall element and a magnet are extensively used for making a focus due to size reductions in digital cameras. The magnet is normally attached to a lens while the hall element is fixed to a moving path of the lens, and an output voltage of the hall element, which is a magnetic sensor, varies when a position of the lens changes due to a movement of the lens. The position of the lens is detected by detecting the variation in the output voltage. When a direction of gravity applied to a camera changes in a conventional position detection scheme, the distance difference between the hall element and the magnet occurs and this is called a heading error, so even when the lens is in a same position, the output voltage of the hall element varies due to the heading error. A more accurate focusing function cannot be performed due to an error caused by the heading error, and an objective of the present invention is to reduce the inaccuracy caused by the heading error. Conventional schemes apply a constant bias to the hall element regardless of the heading error, thereby generating the output voltage error of the hall element, but the present invention adjusts the bias applied to the hall element in such a manner that the output voltage error of the hall element can be minimized. |
