Precision positioning measurement sensor based on the integration of confocal techniques and three-degree-of-freedom geometric measurement

For the fields of optical imaging and focal plane measurement and adjustment in optical processing, this paper proposes a compact three-degree-of-freedom measurement sensor suitable for high-precision positioning of small measurement surfaces. The advantage of the measurement sensor is that it effectively combines multi-degree-of-freedom geometric measurement with confocal measurement, achieving multi-degree-of-freedom measurement by the correspondence between the position of the measured surface and the position of the laser spot on the camera and achieving high-precision, large-range Z-axis axial measurement by confocal technology and triangular light measurement. In addition, compared with traditional multi-degree-of-freedom methods, the measurement points of the sensor are small, and no special target is required. The measurement optical path design was maximized for reuse, and the structure was compact and widely applicable. Simultaneously, the theoretical principles of three-degree-of-freedom simultaneous measurement are described in detail. The experimental validation shows that the sensor achieves angular resolutions better than 0.02° over a range of ±2.5° for pitch and yaw. For the Z-axis, a resolution of 20 nm is achieved for a 4 μm range and a resolution of 500 nm over a 1 mm range. In multi-DOF coupled measurements, angle and displacement errors remain within 5%.