Projection Light Source Polarization Layout for Speckle Reduction
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Solution Overview
Problem
Speckle patterns occur due to coherent light emitted from solid-state light source elements, which are not effectively reduced by polarization multiplexing methods that rely on uniform polarization ratios.
Innovation Solution
A light source device with a configuration that includes multiple solid-state light sources emitting linearly polarized light, utilizing half mirrors to separate and redirect light into different optical paths, combined using polarized light combination mirrors, and adjusted by retardation plates to achieve alternate point image arrangements, effectively increasing the number of light beams and reducing speckles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If polarization multiplexing is used to reduce speckles, then speckle reduction is achieved, but the method is ineffective for solid-state light sources with uniform polarization
Solution Approach 1:
The patent changes the polarization parameter of light beams by introducing a retardation plate that converts linearly polarized light into circularly polarized light. This parameter transformation enables the light to interact differently with the half mirror, allowing separation into multiple optical paths even when the original light source has uniform polarization, thereby resolving the ineffectiveness of traditional polarization multiplexing for solid-state light sources.
Solution Approach 2:
The patent introduces a retardation plate as an intermediary element between the light source and the half mirror. This intermediary component transforms the polarization state of the light, enabling subsequent separation by the half mirror into multiple optical paths. The retardation plate acts as a mediator that makes the uniform polarization light compatible with the polarization-based separation mechanism.
2Object-affected harmful factors
If multiple optical paths are created to reduce speckles, then speckle reduction is achieved, but the device complexity increases
Solution Approach 1:
The patent segments the single optical path into multiple optical paths (first optical path and second optical path) by using a half mirror to separate the light based on polarization state. This segmentation creates multiple independent light beams that can be recombined later, reducing speckle patterns while maintaining a relatively simple overall structure through systematic division of the optical path.
3Quantity of substance
If light is separated into multiple optical paths, then the number of light beams increases, but the polarization ratios become greatly different
Solution Approach 1:
The patent applies parameter change by using a retardation plate to transform the polarization state of separated light beams. The retardation plate converts linearly polarized light into circularly polarized light, which then interacts with the half mirror to produce multiple light beams with more uniform polarization ratios, resolving the issue of greatly different polarization ratios that would otherwise result from simple polarization separation.
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 described configuration significantly reduces speckle patterns by doubling or quadrupling the effective number of light beams through optical path manipulation and polarization conversion, enhancing light source multiplexing.
Implementation Method 1
a half mirror that reflects and transmits emitted light from the first light source and separates the emitted light into first light traveling to a first optical path and second light traveling to a second optical path
Implementation Method 2
a polarized light combination mirror that transmits and reflects light in accordance with type of polarization, and combines the first light and the second light
Implementation Method 3
a retardation plate that is disposed on the second optical path and converts the second light into second linear polarization inclined with respect to the first linear polarization
Data Source
AI summary
A light source device includes: a first light source that emits light of first linear polarization; a half mirror that separates emitted light from the first light source into first light traveling to a first optical path and second light traveling to a second optical path; a polarized light combination mirror that combines the first light and the second light; an optical path change element that is disposed on the second optical path and reflects the second light and guides the second light to the polarized light combination mirror; and a retardation plate that is disposed on the second optical path and converts the second light into second linear polarization inclined with respect to the first linear polarization. The optical path change element is disposed such that point images of the first light and point images of the second light on the polarized light combination mirror are alternately arranged.