基于阈值的调焦方向判断方法

Direction judgment method for autofocus based on threshold

为了克服局部峰值对方向判断的影响,同时又拥有比较高的实时性,提出了一种基于阈值的调焦方向判断方法。它通过区域判断阈值将调焦曲线分为靠近峰值和远离峰值2类区域。在靠近峰值的区域,通过比较相邻2个采样点的调焦评价函数值得到正确的调焦方向;在远离峰值的区域,当调焦评价函数值进行差分累加后的累加值的绝对值大于差值累积阈值时,通过判断累加值的符号得到正确的调焦方向。实验结果表明,所提出的调焦方向判断方法可以有效地克服局部峰值的影响而保证100%的方向判断正确率,同时拥有较高的方向判断速度。

In order to eliminate the negative effect of local peaks on the direction judgment and also maintain high real time characteristic,a direction judgment method for autofocus based on thresholds is proposed in this paper.According to the proposed direction judgment method,the autofocus curve is divided into two zones based on the threshold of zone judgment：one is the zone near the peak and the other is the zone far from the peak.In the near peak zone,the correct autofocus direction is determined by comparing the focus values of two points sampled at a fixed step.In the zone far from the peak,the right direction can be obtained from the sign of the accumulated difference value when the absolute value of the accumulated difference value of the focus values of adjacent points is larger than the threshold of accumulated difference values.Research results show that the proposed direction judgment method for autofocus can not only judge the correct direction with the correct rate of 100% due to eliminating the negative effect of local peaks,but also keep a high speed in direction judgment process.