Study And Implementation On Auto-focusing System With High Sensitivity

Currently, electronic information technology develops rapidly, network technologycontinues to mature, the scope of digital images and digital video applications becomes more andmore wide. In the field of consumer electronics digital cameras, digital cameras and other videosurveillance security field, the field of defense forces in the military field, the field of agriculture,forestry fire monitoring, industrial production, auto-focus technology as a key technologybecomes more and more popular. In recent years, research of auto-focus technology based ondigital image processing has some achievement. However, because of the imaging target’scomplexity and variability of imaging conditions, auto-focus technology meets lots of tests andreveals a number of problems. On the side of selecting the algorithm, we need to considerchoosing the right image clarity-evaluation function, the window area and the motor searchingalgorithm. In fact, we should consider how to improve the sensitivity and real-time of auto-focussystem. These are the problems to be solved.Firstly, the paper analyzes the background and significance of the topic, and introduces thedevelopment of the auto-focusing technique at home and abroad. Then the paper analyzes theprinciples of auto-focus and traditional auto-focus technology and auto-focus technology basedon digital image. Then the paper analyzes how the image clarity-evaluation function, the windowarea and the motor searching algorithm affect the auto-focus system’s sensitivity. The paperanalyzes some selection methods, and in order to ensure the real time of auto-focusing, selectsthe central region of the focusing window. Aiming at that the image clarity evaluation functionsensitivity is not high enough, and it has large computation and other issues, on the basis ofcomparison of the six traditional image clarity evaluation function and three image clarityevaluation functions which have been improved by other people, we propose a new image clarityevaluation function. This function is been improved based on the traditional Brenner function.Through simulation, improved image clarity evaluation function has a single peak which isstrong, clear and high spirits, a small amount of computation, stability and other characteristics.The paper builds a PC-based auto-focusing system to do the auto-focusing experiment inorder to verify the correctness of the algorithm. The hardware frame of autofocus experimentalplatform includes lens, the CCD image sensor, the image acquisition card and DC motor drivingboard. The results of Auto-focus experiments show that this method focusing effect, with highfeasibility, provides solutions for practical engineering applications.