Patent ID: 8031401

Claim:
A wavelength plate in which a first wavelength plate of a phase difference Γ 1 with respect to light of a wavelength λ and a second wavelength plate of a phase difference Γ 2 with respect to the light of the wavelength λ are arranged such that their optical axes cross each other, wherein with respect to linearly polarized light of a plurality of wavelength bands λ 1 , λ 2 , λ 3 which are different from each other and that passes through the first and second wavelength plates, a polarization plane of the incident linearly polarized light is converted to linearly polarized light rotated by a predetermined rotation angle, and the light is emitted, the relationship of the wavelength bands λ 1 , λ 2 , λ 3 satisfies λ1<λ2<λ3, the phase difference Γ 1 is 360° of a high-order mode, and the phase difference Γ 2 is 180° of a high-order mode, the wavelength λ is a wavelength included in any of the wavelength bands λ 1 , λ 2 , λ 3 , when an angle between the optical axis of the first wavelength plate and the polarization plane of the incident linearly polarized light is taken to be an optical axis direction angle θ 1 , and an angle between the optical axis of the second wavelength plate and the polarization plane of the incident linearly polarized light is taken to be an optical axis direction angle θ 2 , the optical axis direction angle θ 1 and the optical axis direction angle θ 2 satisfy −26°≦θ1≦−6° or −31°≦θ1≦−11° 35°≦θ2≦55°.