Autofocusing imaging system based on laser ranging and a retina-like sample

A novel autofocusing method combining active and passive techniques is proposed to improve autofocusing performance. The proposed method is divided into coarse and fine autofocusing stages. First, a laser ranging finder viewed as the active technique is used to obtain a reasonable initial position of the compensating lens group during the coarse autofocusing stage. Second, a retina-like sampling method is used to decrease the volume of processing data during the fine autofocusing stage. We developed a prototype and performed comparative experiments using different targets based on the proposed method and the traditional passive method (TPM). Under optical power of 9×, the TPM consumed 2.5 s, while the proposed method performed at 1.3 s. The comparative experiments also showed that the proposed method exhibited a better anti-interference property than the traditional method.