A method for obtaining object defocus information in the RC observation mode.

The micro-operation robot is widely used in micro-manipulations of biological cells in biological and medical experiments. It plans and controls micro-effector movement based on image feedback information to achieve micro-operations. However, the displacement information of the micro-effector on the x-y plane can be obtained from the image, but not the position information of the micro-effector in the z-axis direction. This makes the micro-effector movement in the z-axis direction discontinuous, which is time-consuming and reduces operational efficiency. In this study, starting from the optical imaging principle of Robert Hoffman modulation contrast method (RC), we propose a defocus detection method for the RC observation mode of an optical microscope. Our method can determine the direction of defocus, which is not available in previous defocusing detection methods. Utilizing this method, we achieve rapid focus for the micro-effector while it is moving along the z-axis direction.