An adaptive depth of field imaging system for micromanipulation

Vision-based techniques used in automatic micromanipulation are limited by small depth of field (DOF) because of high magnification and big numerical aperture of optical system. This paper proposed a new adaptive DOF image system which can adaptively adjust DOF during micromanipulation while maintaining high resolution of the images. The proposed system uses a spatial light modulator instead of fixed phase mask to make flexible wave-front coding, which can change the DOF during micro manipulation. An DOF-extension scheme is proposed based on the depth information of micro objects, which is estimated by the stereo vision method. The large DOF in the coarse assembly and high resolution in the fine assembly are achieved. The image qualities of multi micro objects in different depths are improved during the micromanipulation process. Experiment results show the feasibility of the proposed system in the micromanipulation application.