| 摘要 |
The position measuring device includes a light source (L), two gratings (1,2) and several photodetectors (D0,D1,D2). The light from the source is modulated, dependent on position, by the gratings. These gratings are movable relative to each other in the measuring direction and have determined division periods. Light beam bundles deflected at least one of the gratings interfere with each other. The photodetectors detect position dependent signals phase shifted relative to each other. At least one of the gratings (1) has at least three regions (B) arranged one after the other in the measuring direction (X), in each period oriented in the measurement direction. These regions run perpendicular to the measurement direction. Each region has different direction selective properties. Each signal beam bundle taken from these regions strike an associated photodetector which are arranged transversal to the measurement direction. |
