| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection type encoder based on three-lattice theory capable of detecting an origin position precisely. SOLUTION: A photodiode group 5 for detecting the origin position is formed in a moving grating board 6 of this projection type linear encoder 1, and a reflecting grating group 8 for detecting the origin position is formed in a reflecting grating board 9. The photodiode group 5 for detecting the origin position includes photodiodes 5Z, 5Z1, 5Z', 5Z1' arrayed according to an array pattern patternized using random numbers, and the reflecting grating group 8 for detecting the origin position includes a reflecting grating 81 and a non-reflecting grating 82 wider than gratings for detecting A and B phase signals arrayed according to an array pattern patternized using random numbers. The origin position of the moving grating board 6 is detected precisely based on a differential signal between the photodiode 5Z and the photodiode 5Z', and based on a differential signal between the photodiodes 5Z1, 5Z1' different by 90°from their phases. COPYRIGHT: (C)2004,JPO
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