| 摘要 |
PROBLEM TO BE SOLVED: To reduce an interpolation error caused by an contaminated area or a junction area on a main scale by increasing the number of slit groups and elaborating the arrangement thereof on an index scale. SOLUTION: On the index scale 4N (N is an integer not less than two), slit groups for obtaining four kinds of displacement signals having phases different from each other are arranged in a matrix, thereby allowing the slit groups for obtaining the four kinds of displacement signals to be arranged in any row and allowing the slit groups for obtaining the four kinds of displacement signals to be equally arranged adjacent to each other from at any point of observation. COPYRIGHT: (C)2007,JPO&INPIT
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