Voice coil motor (VCM) is the mainstream technology to linearly drive a lens to achieve autofocus function of a camera module of a mobile phone. Various VCM designs have been invented to provide such lens driving capability. For most of the VCMs design, there is one serious problem which has still no effective solution since VCM has been applied as a lens driving apparatus of a camera module. This problem is known as the dust particle problem. Due to the very simple structure of a camera module, the VCM or lens driving apparatus is directly mounted on a PCB board, on which an imaging sensor is mounted. As a result, the VCM or lens driving apparatus directly faces the imaging sensor. If any dust particle can go through the VCM or lens driving apparatus, it will fall onto the surface of the imaging sensor. This will cause an image defect because a dark spot will be formed on the image. Therefore, camera module manufacturers all assemble the camera module in a precisely controlled clean room to avoid dust particle contamination during assembly. However, after the assembly process, the camera module will be installed into a mobile phone and go to the end user. In normal application environment, the atmosphere outside the camera module could be very dusty. Dust particles can pass through the VCM and falls onto the imaging sensor surface due to the tiny gap between the moving part and the stationary part, which is the lens holder and the base (and/or casing) respectively. This dust particle issue has been one of the major quality problems to all the VCM manufacturers and camera module manufacturers. Some VCM manufacturers have been losing money due to the cost increased by the failure caused by dust particles. Therefore, it is very important to have some kinds of mechanisms to prevent dust particle contamination.
The above description of the background is provided to aid in understanding the dust-free lens driving apparatus, but is not admitted to describe or constitute pertinent prior art to the dust-free lens driving apparatus, or consider the cited documents as material to the patentability of the claims of the present application.