Liquid Crystal Projector Contrast via Pre-Tilt Alignment
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Solution Overview
Problem
Existing projection display apparatuses using vertically aligned liquid crystals struggle to achieve high contrast due to unknown alignment conditions for liquid crystal molecules, which affect the bright and dark states, leading to suboptimal image quality.
Innovation Solution
A projection display apparatus is designed with a reflective liquid crystal display device and a wire grid polarizing beam splitter, where liquid crystal molecules are aligned with a pre-tilt angle and specific azimuthal angles (42 to 48 degrees) to optimize brightness and contrast, and a phase compensator is used to enhance contrast by adjusting the phase of reflected light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If vertically aligned liquid crystal molecules are used to achieve faster response time and higher contrast, then response speed is improved, but alignment control becomes difficult leading to disclination and image quality deterioration
Solution Approach 1:
The patent applies pre-tilt angles to the liquid crystal molecules before voltage application. This preliminary alignment configuration prevents disclination when voltage is applied, as the molecules already have a controlled inclination rather than being perfectly perpendicular. This resolves the contradiction by preparing the molecules in advance to respond to voltage without forming defects.
Solution Approach 2:
The patent modifies the alignment parameters of liquid crystal molecules by introducing specific pre-tilt angles (θp) and controlling azimuthal angles (ψ). By changing these physical parameters from perfect vertical alignment to controlled tilted alignment, the system achieves both fast response and reliable alignment control without disclination.
2Stability of the object's composition
If pre-tilt angle is applied to liquid crystal molecules to prevent disclination, then alignment stability is improved, but contrast ratio deteriorates due to retardation
Solution Approach 1:
The patent optimizes the pre-tilt angle parameter to a specific range (75-85 degrees) and controls the azimuthal angle parameter to balance two competing requirements: sufficient pre-tilt to prevent disclination but not so large as to cause excessive retardation. This parameter optimization resolves the contradiction between alignment stability and contrast ratio.
Solution Approach 2:
The patent applies different alignment conditions to different regions of the liquid crystal layer by controlling the pre-tilt and azimuthal angles locally at the molecule level. This allows molecules to have the precise orientation needed for stable alignment while minimizing the overall retardation effect on contrast.
3Illumination intensity
If wire grid polarizing beam splitter is used to achieve high contrast, then contrast ratio is improved, but device complexity increases
Solution Approach 1:
The patent replaces traditional polarizing beam splitters with wire grid structures that can be integrated directly onto the substrate. This substitution maintains the high contrast ratio function while reducing mechanical complexity and enabling planar integration with the liquid crystal display device.
Solution Approach 2:
The patent combines the polarizing beam splitting function with the wire grid structure, merging multiple optical functions into a single integrated component. This reduces the number of separate optical elements needed in the system, thereby reducing overall device complexity while maintaining high contrast performance.
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
The solution achieves higher contrast ratios and maintains high brightness levels in the bright state while minimizing brightness in the dark state, improving overall image quality by optimizing liquid crystal alignment conditions.
Implementation Method 1
The liquid crystal display devices utilize the double refraction of liquid crystal molecules to control the transmission of the light passing therethrough.
Implementation Method 2
a wire grid formed on the polarizing separative plane and being in parallel to the first substrate, whereby the polarizing beam splitter allows only a first polarized light component of incident illuminating light to be transmitted therethrough
Implementation Method 3
a phase compensator is used to enhance contrast by adjusting the phase of reflected light
Data Source
AI summary
A projection display apparatus comprises a reflective LC display device and a polarizing beam splitter having a polarizing separative plane and wired grids. The LC molecules of the device are aligned such that i) a segment on a second subtracted, produced by projecting a major axis of each LC molecule perpendicularly onto the second substrate, makes an angle of 42 to 48 degrees counterclockwise or counterclockwise in relation to a direction of a straight line on the second substrate, formed by projecting each wire grid perpendicularly onto the second substrate and ii) of both ends of the segment, one end meeting an end of each LC molecule, which is positioned nearer to the second substrate than the other end, is positioned nearer to an intersection at which a plane including the polarizing separative plane and a plane including the second substrate mutually intersects, than the other end of the segment.