The Study On Image Auto-focus System With Segmented Strategy

This paper relies on "11th Five-Year key projects of National Science andTechnology Support Program.The research which is called " the research anddevelopment of the secondary ion mass spectrometry’s main technology and keycomponents " is led by the China Academy of Geological Sciences. For the needshigh precision and high anti-interference ability of the image focusing system,thispaper has designed the hardware and software systems and made the research andpractical application.The autofocus system key technologies is consisted of two parts: Focusingevaluation function and focusing control strategy.Focusing evaluation function iscalculated the current image clarity and defines whether the system is focused.Focusing control strategy is the way of control camera lens.It is based on thecalculated value of the current focus of the evaluation function to determine thedirection of movement and range of camera lens.The two parts of the focusing systemis closely combines.This paper has studied and improved two aspects which isaccuracy and anti-jamming and developed the segmented focus strategy of digitalimage.The entire focusing process is divided into two phases: when the system isaway from focal point,using the SMD and Differential accumulation strategy infocusing to accelerate the speed of focus;when the camera lens is close to the focalpoint, using the laplace focusing evaluation function which is improved and themethod of two pionts-direction judgment in elaborate adjusting.Beside,we use theimage segmentation method to capture the target part of the image.Finally applyingthe genetic algorithms to amend the parameters of the traditional focus evaluationfunction.,So that it can adjust the parameters when the environmental changes.The method improves the accuracy of the autofocus system, enhanced theanti-jamming of auto-focus system. It can be applicated in the situation which needshigh accuracy and exist high external interference.