US 6,982,772 B2
Quarter wavelength plate and projection type video display device using same
Kazuo Shikita, Tokyo (Japan); Tsutomu Nakashima, Tokyo (Japan); and Nobuyuki Kimura, Tokyo (Japan)
Assigned to Hitachi, Ltd., Tokyo (Japan)
Filed on Jan. 31, 2003, as Appl. No. 10/356,294.
Claims priority of application No. 2002-022683 (JP), filed on Jan. 31, 2002.
Prior Publication US 2003/0174290 A1, Sep. 18, 2003
Int. Cl. G02F 1/1335 (2006.01)
U.S. Cl. 349—117 3 Claims
OG exemplary drawing
 
1. A quarter wavelength plate used in a projection type video display device comprising:
a first optically anisotropic crystal having a first thickness; and
a second optically anisotropic crystal having a second thickness,
wherein the first and second optically anisotropic crystals adhered to each other such that phase delay axes thereof are oriented substantially orthogonal to each other,
wherein said quarter wavelength plate having a thickness in a range of 0.1 mm to 0.5 mm,
wherein a difference between the first and second thicknesses is in a range of 10 μm to 20 μm, inclusive.