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 (P1; P2), and respective scanners (23, 33) providing respective scanner output signals (SM 1, 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 (P1; P2).