Patent ID: 7148946

Claim:
An optical device comprising a laminate of cholesteric liquid-crystal layers in which circularly polarized light having a specific rotative direction is selectively reflected according to wavelength ranges, wherein all wavelength ranges of circularly polarized light beams that are selectively reflected are not in a visible light region, wherein one of said cholesteric liquid-crystal layers transmits left-handed circularly polarized light having a wavelength that is not in a visible light region, and another of said cholesteric liquid-crystal layers transmits right-handed circularly polarized light having a wavelength that is not in a visible light region wherein the optical device exhibits index anisotropy of nx≈ny>nz in which nz is a refractive index in a direction of a Z axis indicating a direction of a thickness of said optical device, nx is a refractive index in a direction of an X axis indicating one direction in a plane perpendicular to the Z axis, and ny is a refractive index in a direction of a Y axis indicating a direction perpendicular to the Z and X axes.