The Driving & Controlling Of Digital Camera Lens

Technology advances with CCD, like increased resolution at lower manufacturing costs, have fueled the growth in the electronic imaging industry. Combined with Hi-tech, the electronic product DSC(Digital Still Camera), is also rapidly developing in the last 10 years. Due to the resolution of CCD improving from dozens thousand pixels to nearly ten mega pixels, the image quality of DSC is extremely improved and compared to the traditional film camera. With the mature of technology and lower cost, DSC has become photograph lovers'first option.With the popularization of DSC, it is the image quality that can assure a producer's competitiveness. However, the key part that influences the image quality is the lens, that's because it will do complicated movement. So it is very important to study the accurately controlling of lens.This dissertation depicts the whole structure and the basic principle of the driving & controlling of digital still camera's lens system. Mainly include:1) The whole structure of DSC and the basic principle of embedded system are depicted. The DSC studied is based on the Zoran structure which uses COACH, i.e. Camera On A Chip, as the central controlling chip, which controls the camera's movement by firmware. The chip COACH, which is highly integrated and strongly functioned, is the camera's digital signal processor, and supplies a number of application program interfaces to operate the hardware layer. The application layer of the system is HCE, i.e. Host COACH Embedded, which supplies a message based loop structure, in which all tasks are executed.2) The hardware structure and controlling principle of lens are depicted. The lens of camera is driven by a chip, also a programmable device, in which there are 8 status registers that are used to set the input/output mode of the chip. The driver IC receives instructions and executes them. Since the lens system is a close loop system, there are in the lens positioning sensors which generate feedback signals, according to which the lens is accurately controlled by COACH.3) Several engineering problems about controlling & calibrating of lens are analyzed and solved. One case is that when camera is abnormally powered off before restarted, the lens is blocked and can not move again. Another is that the auto focus steps fluctuate, this leads to blurry images. The third case is how to optimize the calibration process of M-Shutter.