The Study On Image Processing Based Auto-focus Method And Its System Realization

It is a crucial influencing factor for measurement precision to obtain definite images in the photogrammetry systems of range and railway geometry parameters measurement. Traditional optical measurement imaging device take a manual focusing method to get definite images, which does not work effectively and can be disturbed easily by various arbitrary factors. With this method, focusing system of imaging device can not guarantee the definition of target images in the whole process of the measurement. And the precision and reliability of these data, which analyze from poor precision images, will be influenced inevitably.After the current situation of auto-focusing method in home and abroad being introduced, the characteristic and principle of the method based on image processing is analyzed systematically in the paper, and then according to the principle of videometrics, we design the rapid auto-focusing system based on image processing. Two key techniques of this focusing system are investigated: moving object tracking and the choice of auto-focusing algorithm. Comparing with data analysis by experiment, two modified algorithms are presented in this paper: algorithm of rapid auto focusing combining roughly focusing and fine focusing; Mean Shift tracking algorithm with adaptive tracking window, and the software of the system is written by the Visual C++ programme language. Selecting the apt device depending on the requisition of system design, the rapid auto-focusing system based on image processing is built.In the video-metric system for railway geometry parameters measurement, for the negative influence of atmospheric turbulence, Image definition of Near-ground Moving object Under turbulent flow condition make random agitation, which leading to the problem of auto-focusing failure. This paper take part in the amelioration work of the video-metric system and propose a new auto-focusing algorithm: focusing by ratio. This method realize focusing for moving object by using the proportional relations between zoom and focus, which need not to calculate the definition of each image. Via the experiments of the auto-focusing system outdoor, the result proves the feasibility of the auto-focusing method for the Near-ground moving targets.