| 摘要 |
<p>An encoder for measuring for position of an object, comprising a light source, and a scale (1) and readhead arranged for relative movement therebetween, the scale (1) including an optical feature (2) and the readhead comprising an optical detector (7), wherein in use the light source illuminates a region of the scale (1) and the readhead determines the presence of the feature (2) in that region using a phase contrast technique.</p> |
