| 摘要 |
PROBLEM TO BE SOLVED: To enhance angle resolution for a rotary encoder utilizing a moire inference fringe. SOLUTION: This encoder is provided with a rotary FZP array 11 wherein plural rotary FZPs 111a having the same focal distance are arranged inside the first circumferential part 11a of a rotary disk 10 at pesrcibed spacing, and wherein rotary FZPs 111b, 111c having the same focal distance within the same circumferential part are arranged in at least one circumferential part in an inner side of the first circumferential part 11a to interpolate a space between the rotary FZPs 111a, LEDs 14, 15 for emitting parallel beams from a direction orthogonal to the rotary FZP array, plural fixed FZPs 122a-122c arranged in a row to correspond to the circumferntial parts in a radial direction of the rotary disk 10 by the same number as the number of the circumfernetial parts in an incident position of transmitted beams in the rotary FZPs, and different slightly in their focal distances from the focal distances of the rotary FZPs in the circumferential parts corresponding thereto, and two-split PDs 16a-16c arranged in a position where a moire FZP generated by moire intefernce between the rotary FZPs and the fixed FZPs coverges the emitted beams.
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