| 摘要 |
PCT No. PCT/GB91/00968 Sec. 371 Date Jan. 27, 1992 Sec. 102(e) Date Jan. 27, 1992 PCT Filed Jun. 17, 1991 PCT Pub. No. WO91/19958 PCT Pub. Date Dec. 26, 1991.A rotable object table which has a stator (112) a rotor (114), and positioning servo and measuring system (16). The system (16) is calibrated using an angular interferometer and an intermediate table having stator 122 and rotor 124. Values of angular displacement of stator 124 are determined by the interferometer by solving 3 orthogonal simultaneous equations derived from the equation R+Ro=K sin ( THETA - THETA o), and are compared with corresponding angular displacement as determined by the system (16).
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