Integrated optical system for high-precision and decoupled 6DOF motion measurement of miniature actuators

The multi-degree-of-freedom (MDOF) motion accuracy of voice coil motors (VCMs) in smartphone lens modules directly impacts imaging quality. Existing six-degree-of-freedom (6DOF) measurement methods are difficult to apply in this scenario due to large target volumes, insufficient measurement ranges, or severe coupling between DOF. This paper proposes a high-precision, with relatively large measurement ranges, 6DOF measurement system based on a compact cross-shaped ring reflector target. By employing a separated optical measurement principle and co-optical path multiplexing, the system is divided into three optical subsystems, achieving a compact optical path with no significant coupling crosstalk between each DOF. Experiments show that the system has better resolution than 0.8 µm, 1 µm, 0.0004°, 0.005° within the measurement range of <i>X</i>- and <i>Y</i>-axis displacement of ±1<i>m</i><i>m</i>, <i>Z</i>-axis displacement of ±2<i>m</i><i>m</i>, <i>R</i><i>X</i> and <i>R</i><i>Y</i> angles of ±1^∘, and <i>R</i><i>Z</i> angle of ±5^∘, respectively. It is suitable for high-precision position measurement of tiny structures.