A novel simple and low cost 4 degree of freedom angular indexing calibrating technique for a precision rotary table

For calibrating an angular rotary table, either a high precision standard table or a laser interferometer and related optics are normally employed at high cost. This paper establishes a novel, simple and low cost technique to calibrate the 4-degrees-of-freedom (DOF) errors of a rotary table (three angular position errors and one linear position error) for a 360° full circle by employing one reference rotary table, one 1 dimensional (1D) grating and two 2 dimensional (2D) position-sensing-detectors (PSD). With this technique, no highly accurate reference rotary table, but with good repeatability is needed. After two full circle tests, the 4-DOF errors of both the target rotary table and the reference rotary table could be obtained. The system calibration, stability test, system verification and full circle test were completed. The angular stability of this system was less then 2 arc sec, while the displacement stability was less than 1.2 μm.