WAVEPLATE ELEMENT AND OPTICAL PICKUP DEVICE

摘要

There is provided a waveplate element capable of mitigating performance degradation due to incident angle dependency even when the waveplate element is used in an optical system in which convergent light or divergent light is incident. The waveplate (10) has a periodic uneven structure having a structural pitch P shorter than a used wavelength ?. The periodic uneven structure is divided into at least first to third areas (11, 12, 13) along a diving line drawn perpendicular to a fast axis in a plane constituted by the fast axis and a slow axis, wherein the first area has a periodic uneven structure different from those of the second and third areas disposed on mutually opposite sides of the first area.