Waveplate Compensation in Polarization Conversion Systems
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Solution Overview
Problem
In projection systems, particularly stereoscopic projection systems, the decreasing throw ratio leads to larger component sizes for polarization conversion systems, making them less cost-effective and manufacturable, and resulting in reduced brightness and increased leakage and ghosting in 3D imagery due to polarization state distortion at mirrors.
Innovation Solution
A polarization conversion system incorporating a polarizing beam splitter, optical stacks with rotators, polarizers, polarization switches, and quarter wave retarders, which separate incoming light into orthogonal polarization states and utilize waveplate compensation to maintain linear polarization, reducing distortion and enhancing contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the throw ratio is decreased to achieve shorter projection distance, then the projection system becomes more compact and adaptable, but the component size for the polarization conversion system increases, resulting in reduced manufacturing cost-effectiveness and higher system complexity
Solution Approach 1:
The polarization conversion system is divided into separate optical stacks for different polarization states (S-polarized and P-polarized light paths), allowing independent optimization of each stack's components including waveplates, polarizers, and projection elements, thereby managing overall system complexity while achieving compact throw ratio
Solution Approach 2:
The system uses polarization dimension (orthogonal S and P polarization states) to create separate optical paths that can be independently controlled and optimized, enabling compact design by utilizing the polarization degree of freedom rather than requiring separate physical systems for different projection distances
2Adaptability or versatility
If the throw ratio is decreased to achieve shorter projection distance, then the projection system becomes more compact, but the brightness of the projected image decreases and leakage and ghosting in 3D imagery increase
Solution Approach 1:
The system dynamically adjusts polarization state parameters using waveplates and polarizers in each optical stack to maintain optimal brightness and minimize leakage/ghosting effects across different throw ratios, with the first and second quarter wave retarders having orthogonal optic axis orientations to compensate for polarization distortion
Solution Approach 2:
The polarization conversion system incorporates feedback mechanisms through the interaction of polarized light with the PBS and optical stacks, where the polarization state is continuously maintained and corrected to ensure consistent brightness and minimal ghosting across varying projection conditions
3Adaptability or versatility
If the throw ratio is decreased to achieve shorter projection distance, then the projection system becomes more compact, but polarization state distortion at mirrors increases, resulting in reduced image quality
Solution Approach 1:
Waveplates and polarizers are introduced as intermediary optical elements between the light source and projection elements to compensate for polarization distortion caused by mirrors, with the first and second quarter wave retarders serving as mediators to restore the correct polarization state after reflection
Solution Approach 2:
The first and second quarter wave retarders are configured with asymmetric orthogonal optic axis orientations relative to the vertical axis, creating asymmetric compensation that specifically addresses the polarization distortion introduced by the mirror reflection geometry in compact throw ratio systems
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 provides a brighter 3D image with reduced leakage and ghosting by maintaining polarization purity and contrast, even in systems with smaller throw ratios, through the use of waveplate compensation and orthogonal quarter wave retarders.
Implementation Method 1
a polarizing beam splitter (PBS) operable to receive incoming light and separate the incoming light into a first light bundle with a first state of polarization (SOP) and a second light bundle with a second state of polarization (SOP) and the first SOP orthogonal to the second SOP
Implementation Method 2
a first quarter wave retarder operable to receive the first light bundle from the mirror and a second quarter wave retarder operable to receive the first light bundle from the lens set
Implementation Method 3
a reflector operable to receive the first light bundle from the first optical stack
Data Source
AI summary
Three dimensional projection systems may be single projector or multiple projector systems. These 3D projection systems may include a one or more polarization conversion systems (PCS). Each PCS may be designed for relatively small throw ratios and thus, may be designed to accommodate the small throw ratios. Each PCS may include a polarizing beam splitter, a first optical stack, a reflector and a second quarter wave retarder. The first optical stack may include a rotator, a polarizer, a polarization switch and a first quarter wave retarder. Each PCS may receive light from a respective projector, and the PBS in each PCS may direct the light toward the first optical stacks. The light may be converted to a different polarization state as it passes through the first optical stack. The converted light may then be re-directed by a reflecting element to a second quarter wave retarder. The second quarter wave retarder may convert linearly polarized light to circularly polarized light.