Using nano-imprint technology we have developed a rotary diffraction grating scale, which is used for micro rotary encoding. The off-center error between the center of the trough-hole for a rotational axis and the center of the high-precision micro-pattern on the periphery of the scale is less than 3 µm because we are able to shape the through-hole and the grating pattern simultaneously. The use of nano-imprinting is epoch-making, in view of the traditionally poor centering precision of grating scale through-holes fabricated using the conventional photolithography coupled with machining of the through-hole.
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