| 摘要 |
PURPOSE:To detect the absolute value of a displacement variable from an original point to a detecting position with high resolution by reading out absolute addresses in a subscale section corresponding to the pitch of a main scale where the detecting position exists and adding the reading values of both the scales. CONSTITUTION:The main scale 10 consists of an optical scale and a reading head having an index scale and a photoelectric converter is arranged oppositely to the main scale 10 to extract the change of light quantity as an electric signal. The subscale 12 has a binary code pattern and consists of a line A and lines B, C, D which form dark and bright patterns of which pitches are successively multiplied by 2<n> of the pitch of the line A. The darkness and brightness of the pattern are detected as electric signals '0' and '1' by the reading head having photoelectric conversion elements inherent to respective lines which are arrayed on one direction rectangular to the displacement direction, converted into a binary value on the basis of the combination of '0' and '1' on the lines A-D and then converted into a decimal value to obtain the absolute position from the original point of the scale 12.
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