| 摘要 |
<p>A scale (10) is fixed to one part of the apparatus (12), and a read head (14) is relatively movable on the other part of the apparatus. Incremental scale marks (34, 35, 42, 44) are regularly spaced along the scale (10) and are counted in a counter (28) to give an indication of relative position of the scale and read head. The marks may for example be recorded magnetically. Some scale marks (34, 42, 44) are distinguishable from the others (35), e.g. by having different amplitudes (L1, L2). Positioning information can then be encoded in a binary word (40). This can either be absolute position values, or error correction information.</p> |
