Polarizing Illuminator Light Recycling Waveguide
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Solution Overview
Problem
Existing polarization recycling methods for visual display systems, such as near-eye displays, suffer from inefficient light utilization due to random propagation of recycled light and multiple passes through the recycling system, leading to energy loss and reduced efficiency in illuminating liquid crystal display panels.
Innovation Solution
A polarizing illuminator configuration that includes a light source, a reflective polarizer, and a quarter-wave plate, which collimates unpolarized light and efficiently recycles it through a well-defined path, allowing a single pass for polarization conversion and improved light utilization, with the reflective polarizer transmitting a first portion in one polarization state and reflecting a second portion in an orthogonal state, ensuring effective illumination of spatial light modulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If scatterer-based polarization recycling methods are used, then light can be recycled, but light utilization efficiency is reduced due to random propagation and multiple passes
Solution Approach 1:
The patent introduces a waveguide as an intermediary structure to channel and direct the recycled light in a controlled manner. The waveguide replaces random scatterer-based recycling with guided propagation, ensuring light follows a defined path from the reflective polarizer back to the liquid crystal display panel, thereby improving light utilization efficiency while maintaining system compactness.
Solution Approach 2:
The patent changes the propagation parameter of recycled light from random (scatterer-based) to guided and controlled (waveguide-based). By confining light within the waveguide structure, the system achieves predictable single-pass recycling behavior, improving both efficiency and reducing the complexity associated with managing random light paths.
2Productivity
If multiple passes through the recycling system are used, then more light can be recycled, but energy loss increases due to repeated polarization conversion
Solution Approach 1:
The patent enables light to skip unnecessary multiple passes by using the waveguide to directly return recycled light to the display panel after a single polarization conversion at the reflective polarizer. This single-pass approach rushes the light through the recycling process efficiently, avoiding the energy losses that would accumulate with multiple passes while still achieving high recycling rates.
3Volume of moving object
If a compact light source is used, then the display device is smaller and lighter, but illumination efficiency is reduced due to geometrical constraints
Solution Approach 1:
The patent addresses geometrical constraints by introducing the waveguide dimension, which allows light to propagate in a controlled spatial path that overcomes the limitations of compact packaging. The waveguide provides an additional spatial dimension for light management, enabling efficient illumination despite the small form factor of the display device.
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 enhances light utilization efficiency and wall plug efficiency by ensuring that a significant portion of recycled light is directed efficiently to specific pixels, improving the overall performance of visual display systems by maintaining more than 50% optical power in a single pass, compared to scatterer-based methods.
Implementation Method 1
a lens, a quarter-wave plate (QWP), and a reflective polarizer. The assembly is configured such that the lens collimates unpolarized light emitted by the light source to provide a collimated beam
Implementation Method 2
The reflective polarizer receives the collimated beam transmits a first portion of the collimated beam in a first polarization state, and reflects a second portion of the collimated beam in a second, orthogonal polarization state
Implementation Method 3
The QWP is disposed between the light source and the reflective polarizer to convert the second portion to the first polarization state after the second portion is reflected by the reflector
Implementation Method 4
The second portion propagates back through the lens, gets focused by the lens onto the reflector, gets reflected by the reflector, propagates again through the lens, and gets re-collimated by the lens
Data Source
AI summary
A polarizing illuminator with light recycling includes a light source and a reflector disposed proximate one another. An assembly including a lens, a quarter-wave plate, and a reflective polarizer is configured to redirect the light at unwanted polarization back to the specific location of the reflector, which reflects the light back through the quarter-wave plate, enabling the light to be recycled. The lens collimates both the transmitted and the recycled light portions, providing well-defined light beams. The configuration allows the recycled light beam to be collimated and to propagate in a pre-determined direction, allowing targeted focusing of the recycled light onto pixels of a spatial light modulator.