Precise 3D displacement measurement by using a monocular micro-vision system containing liquid tunable lens

This paper proposes a precise 3-D displacement measurement method by using a monocular micro-vision system containing liquid tunable lens. Firstly, the configuration of the monocular micro-vision system containing liquid tunable lens is introduced, and the corresponding depth measurement model is established. In order to achieve precise spatial 3D measurement, a detection algorithm framework integrating depth estimation based on autofocus and template matching based on affine transformation is proposed. In the experimental study, in order to improve the measurement effect, the relationship between the equivalent current and temperature of the liquid lens was calibrated, and the focus clarity evaluation function was screened. In addition, the measurement accuracy of the proposed visual 3D displacement measurement method is evaluated using an ultra-precision positioning platform. The experimental results show that the system can effectively measure spatial 3D displacement, and the corresponding depth measurement resolution is better than 10 μm within the measurement depth range of 3.9 mm.