Patent ID: 8000208

Claim:
A laminated wave plate corresponding to a plurality of wavelengths including at least two wavelengths of λ A and λ B , and including a first wave plate disposed on an incident side and a second wave plate disposed on an emitting side, the first wave plate and the second wave plate being laminated in such a manner that their optical axes are intersected each other, the laminated wave plate satisfying the following equations from (1) to (5): Γ A1 =360°+360°×2 N A (1); Γ A2 =180°+360°× N A (2); Γ B1 =360°×2 N B (3); Γ B2 =360°× N B (4); and N B =(Δ n B/Δ n A )×(λ A /λ B )×(0.5+ N A ) (5), wherein N A is a positive integer Γ A1 is a phase difference of the wavelength λ A at the first wave plate, Γ A2 is a phase difference of the wavelength λ A at the second wave plate, Γ B1 is a phase difference of the wavelength λ B at the first wave plate, Γ B2 is a phase difference of the wavelength λ B at the second wave plate, θ 1 is an in-plane azimuth of the first wave plate, θ 2 is an in-plane azimuth of the second wave plate, Δn A is a birefringent difference that is a difference (ne A -no A ) between a normal ray refractive index no A and an abnormal ray refractive index ne A of the wavelength λ A , and Δn B is a birefringent difference that is a difference (ne B -no B ) between a normal ray refractive index no B and an abnormal ray refractive index ne B of the wavelength λ B , under conditions of θ 1 =−21°, and θ 2 =45°.