US 2004/0165126 A1 · Multi-layer diffraction type polarizer and liquid crystal element

Abstract

A multi-layer diffraction type polarizer and a liquid crystal element capable of realizing a stable high extinction ratio is provided. Further, a liquid crystal element is obtained, which can rotate the polarization direction maintaining high linearity of output light when linearly polarized light is incident. A multi-layer diffraction type polarizer is formed by laminating at least two polarizing diffraction gratings each having a birefringent material which straightly transmits incident light having a first polarization direction without functioning as a diffraction grating, and diffracts incident light having a second polarization direction perpendicular to the first polarization direction by functioning as a diffraction grating. Further, in order to realize an optical attenuator having a high extinction ratio even at low voltage, a phase plate made of an organic thin film is provided to cancel the retardation of the liquid crystal cell remaining when the voltage is applied. Further, in order to rotate the polarization direction of a linearly polarized incident light, the liquid crystal cell is provided with a λ/4 phase plate comprising an organic thin film.

Claims12

Dependent claims

A multi-layer diffraction type polarizer comprising a lamination of at least two polarizing diffraction gratings each comprising a birefringent material, wherein the diffraction gratings each straightly transmits incident light having a first polarization direction without functioning as a polarizer, and diffracts incident light having a second polarization direction perpendicular to the first polarization direction by functioning as a polarizer.

A liquid crystal element comprising:

a liquid crystal cell comprising transparent substrates having electrodes and a liquid crystal layer sandwiched between them, the liquid crystal cell having a retardation value for a linearly polarized light having a wavelength of λ incident and transmitting through the liquid crystal cell, the retardation value changing from R1 to R2 (R1>R2>0) when the voltage applied between the electrodes is changed from V1 to V2 (V1≠V2) ;
and
a phase plate having a retardation value R for a linearly polarized light having a wavelength of λ, the retardation value R satisfying a relation R+Rv=m×λ (m:
integer) with a retardation value Rv generated by the voltage satisfying R1≧Rv≧R2.

1 more element

A liquid crystal element having a λ/4 phase plate, comprising:

a liquid crystal cell comprising substrates having electrodes and a liquid crystal layer sandwiched between them, the liquid crystal cell having a retardation value changeable for linearly polarized incident light having a wavelength of λ depending on the magnitude of a voltage applied between the electrodes;
and
a λ/4 phase plate producing a phase-shift corresponding to a retardation value of substantially λ/4 for the linearly polarized incident light, the λ/4 phase plate having an organic thin film and the alignment of molecules constituting the organic thin film is in parallel with the plane of the phase plate;
wherein the fast axis direction of the phase plate is at an angle of about 45° to the fast axis direction of the liquid crystal cell.

1 more element

Dependencies are inferred from the claim text.

Multi-layer diffraction type polarizer and liquid crystal element

Life of this patent

Multi-layer diffraction type polarizer and liquid crystal element

Life of this patent

Abstract

Claims12