Patent ID: 7936508

Claim:
A laminated wave plate that functions as a half-wave plate as a whole by laminating together a first wave plate having a phase difference Γ 11 with respect to a wavelength λ and a second wave plate having a phase difference Γ 22 with respect thereto in such a manner that their optical axes intersect, the laminated wave plate comprising: when an in-plain azimuth angle of the first wave plate is set to be θ 3 ; an in-plain azimuth angle of the second wave plate is set to be θ 4 ; and a phase difference of the second wave plate with respect to a wavelength λ 1 is set to be Γ 211 , while a phase difference thereof with respect to a wavelength λ 2 is set to be Γ 222 and the wavelength λ 1 is less than the wavelength λ 2 , the laminated wave plate is formed to satisfy following formulas (4) to (7): Γ11=360°+360°×2 ×n (4); Γ22=180°+360° ×n (5); cos 2θ3=1−(1−cos ΔΓ2)/{2(1−cos ΔΓ2)} (6); and θ4=45°±10 (7), in which n is a natural number starting with 1; and ΔΓ 2 =(Γ 222 −Γ 211 ) /2.