POSITIONING APPARATUS

摘要

A positioning device (11) comprises a stationary frame (2), and at least two scales (20, 30) for measuring the location of the platform with respect to the frame, the scales having mutually different pitches (Pl; P2), and respective scanners (23, 33) providing respective scanner output signals (SM l, SM2)- A controller (6) receiving both scanner output signals is capable to uniquely calculate the position (X) of the platform with respect to the frame in a measuring range (MR) that is larger than the largest of said two pitches (Pl; P2).