Patent ID: 7855834

Claim:
A multilayered phase difference plate formed by bonding a first phase difference plate and a second phase difference plate together, the first and second phase difference plates being a plurality of quartz crystal plates, wherein: an optical axis azimuth θa of the first phase difference plate, an optical axis azimuth θb of the second phase difference plate, and an angle α formed by the optical axis azimuths θa and θb have a relation of θb=θa+α, 0°<θa<45°, and 40°<α<50°, and a deviation amount of a phase difference of the first and the second phase difference plates satisfies the formula: ΔΓ ⁢ ⁢ b = cos - 1 ⁡ ( 1 - ( 1 - cos ⁡ ( 4 ⁢ θ ⁢ ⁢ a ) ) ⁢ ( 1 - cos ⁢ ⁢ ΔΓ ⁢ ⁢ a ) ( 1 - cos ⁢ ⁢ 4 ⁢ ( α - θ ⁢ ⁢ a ) ) ) , where Γa represents the phase difference of the first phase difference plate and is assumed to be 180°, ΔΓa represents the deviation amount of the phase difference Γa from a design target value, Γb represents the phase difference of the second phase difference plate and is assumed to be 180°, and ΔΓb represents the deviation amount of the phase difference Γb from a design target value.