Reflection Projector Optical Alignment for Contrast Stability
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Solution Overview
Problem
Reflection type liquid crystal projectors face a deterioration in contrast ratio due to deviations in the rotational angle of optical elements, such as the liquid crystal panel or wire grid element, leading to an increased ratio of polarized light for reversed images, which affects image quality.
Innovation Solution
A projector configuration is implemented with specific rotational angle settings for the transmission axes of polarizing plates and the wire grid element, ensuring that the rotational angles φ0 to φ3 satisfy certain equations, thereby maintaining a contrast ratio of 80% or more of the maximum value, preventing noticeable deterioration in contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the alignment axis of the liquid crystal layer is deviated from the predetermined direction due to manufacture error, then the manufacturing process is simpler and faster, but the contrast ratio of the projected image deteriorates
Solution Approach 1:
The patent applies parameter changes by introducing specific rotational angle ranges (φ0 to φ3) for the transmission axes of optical elements relative to the alignment axis of the liquid crystal layer. These angular parameters are optimized to satisfy specific mathematical relationships, allowing the system to maintain high contrast ratio even when the alignment axis deviates from the ideal predetermined direction, thus accommodating manufacturing variations without sacrificing image quality
Solution Approach 2:
The patent implements preliminary action by pre-calculating and pre-setting the optimal rotational angles for the transmission axes of the incident-side polarizing plate, wire grid element, and exit-side polarizing plate during the design and manufacturing phase. These pre-determined angular configurations ensure that even with alignment deviations, the optical paths are correctly oriented to maintain contrast ratio, eliminating the need for post-manufacturing adjustment or image processing compensation
2Reliability
If optical compensation plates are added to remove refractive index anisotropy, then the refractive index becomes isotropic, but the device complexity increases
Solution Approach 1:
Instead of adding optical compensation plates to address refractive index anisotropy, the patent changes the angular parameters (rotational angles φ0 to φ3) of the existing optical elements. By optimizing these rotational angles, the patent achieves proper light modulation and maintains contrast ratio without introducing additional optical components, thus improving optical performance while avoiding increased device complexity
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 specified rotational angle settings in the projector configuration effectively suppress the deterioration of the contrast ratio, ensuring high-quality image display and improving the yield ratio of the liquid crystal panel, thus reducing manufacturing costs and avoiding the need for image processing or optical compensation.
Implementation Method 1
an incident-side polarizing plate which is disposed at a position at which light emitted from the illumination optical system is incident and through which polarized light parallel to a transmission axis passes
Implementation Method 2
a wire grid element which is disposed at a position at which the light emitted from the illumination optical system and passing through the incident-side polarizing plate is incident, through which polarized light parallel to a transmission axis passes, and from which polarized light perpendicular to the transmission axis is reflected
Implementation Method 3
a reflection type liquid crystal panel which is disposed at a position at which the light emitted from the illumination optical system and passing through the wire grid element is incident
Implementation Method 4
the light incident on the liquid crystal panel is modulated and reflected by the liquid crystal panel
Implementation Method 5
an exit-side polarizing plate which is disposed at a position at which light reflected by the wire grid element in the light modulated and reflected by the liquid crystal panel and incident on the wire grid element is incident and through which polarized light parallel to a transmission axis passes
Data Source
AI summary
When axes are projected to a reference surface perpendicular in the thickness direction of a liquid crystal layer, a rotational angle φ0 of an alignment axis of a liquid crystal layer from a reference direction on the reference surface, a rotational angle φ1 of a transmission axis of an incident-side polarizing plate from the reference direction, a rotational angle φ2 of a transmission axis of a wire grid element from the reference direction, and a rotational angle φ3 of a transmission axis of an exit-side polarizing plate from the reference direction satisfy all the equations below:44°≦φ0-φ2<45° or 45°<φ0-φ2≦45°f1≦φ1≦f2, where f1=0.191×φ22+0.986×φ2−14.435 and f2=0.191×φ22+0.986×φ2+14.435, and g1≦φ3−90°≦g2, where g1=0.064×φ23+0.841×φ22+1.525×φ2−1.46 and g2=0.064×φ23−0.841×φ22+1.525×φ2+1.46.