基于MTF的十字线目标自动调焦算法

An Auto-focusing Algorithm of Cross-line Target Based on MTF

十字线目标作为调焦系统中的常见目标,其调焦精度是影响调焦系统测量结果的关键因素。传统的调焦函数在灵敏度和实时性方面不能完全满足自动调焦要求。基于调制传递函数(modulation transfer function,MTF)的自动调焦算法通过连续测量多幅图像在固定频率下的MTF值绘制调焦曲线,得到调焦曲线的唯一极值点即正焦位置;在Matlab运行环境下,与现有算法进行比较,结果表明,基于数字图像MTF的调焦函数可实现单张图片的清晰度值计算仅用0.01 s,该算法实时性更好、灵敏度更高,具有应用价值。

The cross-line target is the common target in focusing systems.Its focusing accuracy is the key factor affecting measurement results.The traditional focusing function can’t fully meet the requirements in terms of sensitivity and real-time performances.The focusing curve is drawn by continuously measuring MTF values of multiple images at fixed frequencies with the automatic focusing evaluation function based on MTF(modulation transfer function),and the focus position is gotten at the only extreme point of the focusing curve.In the Matlab environment,the result shows that the focusing function based on the MTF of the digital image can only use 0.01 s to calculate the definition value of a single image.The algorithm has the better real-time performance,higher sensitivity and application value.