Laminated wave plate, optical pickup device, polarization converter, and projection display apparatus

A laminated wave plate comprising a first wave plate with a phase difference of Γ1=180° with respect to a designed wavelength λ0 and a second wave plate with a phase difference of Γ2=180°, in which the first wave plate and the second wave plate are arranged and laminated so that optical axes thereof intersect each other,

• wherein when in-plane bearing angles of optical axes of the first and second wave plates are represented by θ1 and θ2, an angle formed by a polarization direction of the linearly-polarized beam incident on the laminated wave plate and a polarization direction of a linearly-polarized beam output from the laminated wave plate is represented by φ, and an optical axis adjustment amount is represented by a, the following expressions are satisfied:
• θ2=θ1+φ/2;
• θ1=φ/4+a;
• θ2=3φ/4−a;
• and
• θ<a≦amax,
• wherein the maximum value amax of the optical axis adjustment amount satisfies the following expressions in the designed wavelength range of 400≦λ0≦490 nm:
• amax=A0+A1·φ+A2·φ2+A3·φ3+A4·φ4+A5·φ5;
• A0=0.00001548;
• A1=0.0427887;
• A2=−0.000385;
• A3=1.723×10−6;
• A4=−4.19×10−9;
• and
• A5=4.086×10−12,
• satisfies the following expressions in the designed wavelength range of 490≦λ0≦520 nm:
• amax=A0+A1·φ+A2·φ2+A3·φ3+A4·φ4+A5·φ5+A6·φ6+A7·φ7;
• A0=0.00006705;
• A1=17.699248;
• A2=−0.16963;
• A3=0.0006754;
• A4=−1.4×10−6;
• A5=1.68×10−9;
• A6=−1.1×10−12;
• and
• A7=2.72×10−16, and
• satisfies the following expressions in the designed wavelength range of 520≦λ0≦800 nm:
• amax=A0+A1·φ+A2·φ2+A3·φ3+A4·φ4+A5·φ5+A6·φ6;
• A0=0.00003014;
• A1=5.4681617;
• A2=−0.038557;
• A3=0.0001094;
• A4=−1.56×10−7;
• A5=1.106×10−10;
• and
• A6=−3.13×10−14.

A laminated wave plate comprising a first wave plate with a phase difference of Γ1=180° with respect to a designed wavelength λ0 and a second wave plate with a phase difference of Γ2=180°, in which the first wave plate and the second wave plate are arranged and laminated so that optical axes thereof intersect each other, the laminated wave plate converting an incident linearly-polarized beam into a linearly-polarized beam obtained by rotating a polarization plane of the incident linearly-polarized beam by a predetermined angle of 90° and outputting the converted linearly-polarized beam,

• wherein when in-plane bearing angles formed by the polarization plane of the incident linearly-polarized beam and optical axes of the first and second wave plates are represented by θ1 and θ2, the following expressions are satisfied:
• 22.5°<θ1<45.0°;
• and
• 45.0°<θ2<67.5°.