Laminated half-wave plate, polarizing converter, polarized light illumination device and light pickup device
View Patent ↗First and second wave plates using quartz crystal having birefringence are laminated together in such a manner that their optical axes intersect to form a laminated wave plate functioning as a half-wave plate as a whole. Phase differences of the first and the second wave plates relative to an ordinary ray and an extraordinary ray with respect to a predetermined wavelength λ are set to be Γ 1 and Γ 2 , an order of a high-mode order is set to be a natural number n, whereby the high-order mode laminated half-wave plate is formed so as to satisfy: Γ 1 =180°+360°×n; and Γ 2 =180°+360°×n.
1. 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.
2. The laminated wave plate according to claim 1 , wherein
n=4; and
θ 3 =−16° or −21° are set.
3. The laminated wave plate according to claim 1 , wherein
n=5; and
θ 3 =−16° or −21° are set.