To manufacture a half wavelength plate by effectively utilizing even a crystal wafer being not capable of satisfying the standards due to variations of polishing processing while realizing a polarization conversion element using the half wavelength plate with low cost and high performance.
A laminated wavelength plate unit includes a wavelength plate unit 20A and a wavelength plate unit 20B and gives a phase difference Γ to light having a wavelength λ as a whole so as to rotate a polarization plane thereof. The wavelength plate unit 20A includes: a crystal wavelength plate 30A for giving a phase difference Γ1±a taking a phase error a into account; and a phase difference adjusting element 40A being laminated on the crystal wavelength plate 30A and canceling the phase error a so as to correct a phase difference of the wavelength plate unit 20A to be Γ1. The wavelength plate unit 20B includes: a crystal wavelength plate 30B for giving a phase difference Γ2±b taking a phase error b into account; and a phase difference adjusting element 40B being laminated with respect to the crystal wavelength plate 30B and canceling the phase error b so as to correct a phase difference of a whole of the wavelength plate unit 20B to be Γ2.
SAKURAI MAKOTO
Osamu Suzawa
Kazuhiko Miyasaka