Polarization Compensator for Tilted Optical Surfaces
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Solution Overview
Problem
Optical systems face challenges in precisely controlling the state-of-polarization (SOP) over a range of ray angles and positions due to polarization nonuniformity caused by reflecting or absorbing surfaces, leading to polarization distortion and reduced display contrast in applications like liquid crystal displays and polarization-based lenses.
Innovation Solution
The use of an optical component comprising an anisotropic material with a thickness-direction retardation and absorption, along with a Z-Partial-Polarizer (ZPP) that selectively transmits p-polarized light less than s-polarized light, and a compensator that includes cross-linked reactive mesogens, homeotropically aligned liquid crystals, or oriented nano-structures to manage diattenuation and retardation, thereby maintaining polarization uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light passes through reflecting or absorbing surfaces at non-zero angles of incidence, then the optical system can function over a range of angles, but polarization distortion increases and display contrast deteriorates
Solution Approach 1:
The patent introduces a polarization compensator that applies a compensating polarization effect in advance to counteract the expected polarization distortion from tilted surfaces. The compensator is designed with specific optical properties (retardation and absorption) that pre-compensate for the diagonal polarization ellipse that will be induced by the tilted dielectric surface, thereby preventing contrast deterioration before it occurs.
Solution Approach 2:
The patent changes the optical parameters of the compensator material, specifically using anisotropic materials with controlled retardation (Rth) and absorption coefficients. By adjusting these parameters, the compensator can independently control the real and imaginary parts of the complex refractive index difference, enabling precise compensation of polarization distortion across different incidence angles.
2Manufacturing precision
If the state-of-polarization is precisely controlled to maintain display contrast, then contrast ratio is maintained, but the system becomes sensitive to angle-dependent polarization distortion
Solution Approach 1:
The patent introduces a polarization compensator as an intermediary element between the light source and the tilted dielectric surface. This compensator mediates the polarization state by applying a controlled transformation that counteracts the harmful angle-dependent polarization distortion, allowing the system to maintain precise polarization control without being sensitive to incidence angle variations.
3Ease of manufacture
If conventional isotropic dielectric surfaces are used, then the optical system is simple to manufacture, but polarization distortion increases with angle of incidence
Solution Approach 1:
The patent uses composite material structures, specifically anisotropic materials with controlled optical properties, to create the polarization compensator. These composite materials combine specific crystalline or molecular structures that provide the desired retardation and absorption characteristics, enabling polarization compensation while maintaining manufacturing feasibility through established anisotropic material fabrication techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces polarization distortion and enhances contrast and uniformity of the polarization pupil map, maintaining high contrast ratios even at varying incidence angles, thereby improving the performance of optical systems.
Implementation Method 1
an anisotropic material with an optic-axis substantially normal to the substrate, a thickness-direction retardation (Rth), and a thickness-direction absorption
Implementation Method 2
The absorption of light at normal incidence may be 0e−κdsin2θ
Implementation Method 3
the Fresnel equations give the transmission/reflection of light polarized parallel (P) and perpendicular (S) to the plane of incidence (POI)
Implementation Method 4
a Z-Partial-Polarizer (ZPP), wherein the ZPP transmits p-polarized light less than s-polarized light in a manner that substantially reduces the polarization distortion produced by diattenuation
Implementation Method 5
The compensator may include a homeotropically aligned liquid crystal
Implementation Method 6
The compensator may include a cross-linked reactive mesogen
Data Source
AI summary
In polarization-based optical systems, preserving a state-of-polarization (SOP) over a prescribed range of incidence angles and wavelengths may be necessary. Optical materials with local normal tilted with respect to an incident ray can introduce an undesirable polarization nonuniformity that can be substantially corrected using a compensator as disclosed herein. The compensator may include a uniaxial retarder and a z-partial polarizer (ZPP). The ZPP may include a uniaxial material with an absorption axis normal to the substrate.