Polarization Conversion Stack for Efficient 3D Display Light
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Solution Overview
Problem
Existing pixel array display systems face inefficiencies in providing linearly polarized light for 3D displays, as adding a polarizer to the projection lens discards half of the modulated light, increasing cost and complexity, and maintaining polarization state across optical elements is costly and complex.
Innovation Solution
A spatially distributed multiple emitter discrete illumination source with a separate collimator for each emitter, directing collimated light onto an optical homogenizer, which then modulates light onto a polarization conversion stack with alternating beamsplitter polarizers and rotators, converting unpolarized light to polarized light efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polarizer is added to the projection lens to provide polarized light, then the polarization function is achieved, but half of the modulated light is discarded and cost and complexity increase
Solution Approach 1:
The system segments the illumination source into multiple discrete emitters arranged in a specific spatial pattern. Each emitter is independently imaged onto the polarization conversion stack, allowing selective polarization conversion only for the necessary light paths rather than polarizing all light through a traditional polarizer that would block 50% of the light.
Solution Approach 2:
A polarization conversion stack is introduced as an intermediary component between the pixel array and the projection lens. This stack includes polarization converters that actively convert the polarization state of light from the discrete emitters, replacing the passive polarizer approach and enabling more efficient light utilization.
2Reliability
If a polarizer is added to the projection lens to provide polarized light, then the polarization function is achieved, but cost and complexity of the illumination source increase
Solution Approach 1:
The illumination source is segmented into multiple discrete emitters with specific spatial relationships, eliminating the need for a single complex polarized illumination source. Each emitter can be independently controlled and imaged, simplifying the overall system architecture while achieving the polarization function through the conversion stack.
Solution Approach 2:
The system replaces the mechanical/optical approach of using a polarized illumination source with a field-based approach using polarization conversion. The polarization state is converted through optical elements (beam splitters, wave plates) rather than relying on the illumination source itself to provide polarized light, reducing complexity at the source.
3Reliability
If a polarized illumination source is used to maintain polarization state, then polarization is maintained, but all optical elements must maintain polarization state which adds cost and complexity
Solution Approach 1:
Instead of maintaining polarization state throughout the entire optical path from the illumination source, the system inverts the approach by using unpolarized or partially polarized illumination and actively converting the polarization state at the projection stage. This reverses the traditional workflow and reduces the polarization maintenance requirements for intermediate optical elements.
Solution Approach 2:
The polarization conversion stack acts as an intermediary that handles polarization conversion at a specific point in the optical path. This localized conversion approach means that optical elements before the stack do not need to maintain polarization state, reducing their complexity requirements while still achieving the desired polarized output.
4Reliability
If traditional polarizer methods are used, then polarized light is provided, but optical efficiency is poor due to light discarding
Solution Approach 1:
The system changes the parameter of polarization conversion from a passive filtering process (polarizer that blocks 50% of light) to an active conversion process using polarization converters. This parameter change in the conversion mechanism enables more efficient light utilization while maintaining the polarized light output requirement.
Solution Approach 2:
The polarization conversion stack serves as an intermediary that efficiently converts polarization states without the light loss inherent in traditional polarizer methods. By using beam splitters and wave plates in combination, the system can redirect and convert light paths to achieve polarization conversion with minimal light discarding.
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 configuration provides a polarized light output suitable for 3D displays with improved optical efficiency, reducing waste and complexity by ensuring all light is imaged onto the first beamsplitter polarizers, thus maintaining polarization effectively.
Implementation Method 1
first beamsplitter polarizers and second beamsplitter polarizers combined with polarization rotators, so that an image of the emitters of the illumination source is formed at entrance surfaces of the polarization conversion stack. Unpolarized light entering the first beamsplitter polarizers may be converted to polarized light.
Implementation Method 2
first beamsplitter polarizers and second beamsplitter polarizers combined with polarization rotators
Data Source
AI summary
A pixel array display system which has an illumination source with a plurality of emitters in a sparse array, collimators in front of the emitters, a condenser lens downstream of the collimators, an optical homogenizing element downstream from the condenser lens, a relay lens downstream from the optical homogenizing element, a pixel array downstream from the relay lens, a rear group of lens elements of a projection lens downstream from the pixel array, a polarization converter stack downstream from the rear group of lens elements and a front group of lens elements of the projection lens downstream from the polarization converter stack, so that light from the emitters is imaged onto input apertures of the polarization converter stack.