| 摘要 |
PURPOSE:To obtain the quantity of transmission of an index scale plate which is at the same level with other signal layers even if the slit shape of the index scale plate side is different by setting the track width ratio of an absolute value signal layer and a reference-signal provided absolute value signal layer to 1:n (n: integer). CONSTITUTION:The signal layer of a main scale plate 1 consists of three tracks of absolute value signal layers (ZS) 6-8, and the part of a reference-signal provided track 7a is a reference signal layer part 7. The slit shape of the index scale plate 2 consists of a main signal layer 2a and ZSs 2b-2d as shown in a figure (b) and the part of the layer 2c outputs both a reference signal and an absolute value signal. The outputs of the ZSs 6-8 can be increased in the light transmission area of slits even when the slits are in the same shape by making the track width l2 of said signal layer 7 larger than the width l1 of other tracks. For example, when the light transmission part slit width of the layers 2b and 2d (or 2c) is 40T (T: nontransmission part slit width) or 20T (in total), the light transmission area is 1:2, but the same area is obtained by doubling the width of only the layer 2c, thereby obtaining output pulses of the same level.
|
