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摄像镜头的自动聚焦可分为有源方式和无源方式两种。前者普遍采用红外线发射和接收的办法,这种方法有利于拍摄较暗的或对比度很低的景物,但对远距离的被摄物,则聚焦精度要降低,拍摄较远的被摄物,由于红外线的反射被吸收会产生虚假动作。后者通常采用主透镜拍摄景物,对被摄景物作对比度检测,亦能取得较理想的聚焦效果。目前,有一些摄录像机已经将有源和无源这两种自动聚焦方式融为一体,以求达到更佳的自动聚焦效果。一、有源自动聚焦原理有源外测距自动聚焦控制系统运用红外线反射所形成的三角测距原理,如图1所示。
Camera lens autofocus can be divided into two kinds of active mode and passive mode. The former generally uses infrared emission and reception, this method is conducive to shooting dark or very low contrast scene, but for long-range subjects, the focus is to reduce the accuracy of shooting subjects farther, as a result of Infrared reflection is absorbed will produce false movements. The latter usually uses the main lens to take pictures of the scenery, and contrasts the detected scenery for better contrasting effect. At present, some camcorders have integrated the two types of autofocus, active and passive, in order to achieve better autofocus. First, the principle of active auto-focus Active outer distance auto-focus control system uses the infrared reflection formed by the triangulation principle, shown in Figure 1.