Half Wave Plate Positioning in Illuminator Optical Path
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Solution Overview
Problem
Existing projection-type display apparatuses face challenges in reducing the size of the light source apparatus while maintaining even illumination, as the placement of a retardation film between lenses and a dichroic mirror increases the apparatus size, and using multiple light sources can lead to color unevenness due to varying polarization rotation efficiency.
Innovation Solution
The illuminator design incorporates a half wave plate positioned between two lenses of an afocal system, with two solid-state light sources arranged perpendicularly to the optical axis, allowing for reduced size and improved polarization efficiency by minimizing the variation in polarization rotation across different angles of incidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retardation film is disposed between lenses and a dichroic mirror to control polarization, then polarization control is achieved, but the apparatus size increases
Solution Approach 1:
The patent extracts the retardation film from its conventional position between lenses and the dichroic mirror, and relocates it to a position between the first lens and the second lens in the afocal system. This extraction and relocation reduces the overall apparatus size while maintaining the polarization control function.
Solution Approach 2:
The patent changes the spatial arrangement by moving the retardation film to a different location in the optical path (between lenses rather than between lenses and dichroic mirror), effectively utilizing space more efficiently and reducing the apparatus volume.
2Illumination intensity
If multiple light sources are used to provide high-luminous illumination, then luminous flux is improved, but color unevenness occurs due to varying polarization rotation efficiency
Solution Approach 1:
The patent positions the retardation film at a specific location between the first lens and the second lens where the light flux diameter is reduced. This local positioning ensures that the polarization rotation efficiency is optimized and minimized variation across different angles of incidence, thereby maintaining color uniformity even when multiple light sources are used.
Solution Approach 2:
The patent changes the parameter of light flux diameter by utilizing the afocal system to reduce the diameter before the retardation film. This parameter change (reduced diameter) leads to more consistent polarization rotation efficiency across multiple light sources, suppressing color unevenness while maintaining high luminous flux.
3Reliability
If the light flux diameter is reduced to improve polarization control, then polarization rotation efficiency is improved, but the angle of incidence varies greatly causing color unevenness
Solution Approach 1:
The patent uses an adjustable retardation film that can be rotated to change its orientation. This dynamic adjustment allows optimization of the polarization rotation efficiency while compensating for variations in angle of incidence, thereby maintaining color uniformity across the illumination field.
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 enables a compact illuminator that suppresses color unevenness and maintains high luminous flux, enhancing the quality and compactness of the projection-type display apparatus.
Implementation Method 1
The half wave plate transmits the first light and converts the first light into a second light containing both the first polarized light component and a second polarized light component having a polarization direction perpendicular to a polarization direction of the first polarized light component
Data Source
AI summary
An illuminator includes a first light source, a second light source, a first lens on which light emitted from the first and second light sources is incident, a second lens disposed in a downstream of the first lens, and a half wave plate. The first lens, the second lens and the half wave plate are arranged along a first axis. The first light source and the second light source are arranged along a plane perpendicular to the first axis. The half wave plate is disposed in the optical axis between the first lens and the second lens, the half wave plate being disposed in a position close to the second lens.