Projection Display Polarization Splitter for Contrast Ratio
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Solution Overview
Problem
The use of wavelength selective retardation films in projection display apparatuses leads to a decrease in contrast ratio due to the difficulty in controlling polarization direction rotation across all primary colors, causing unintended leakage of light into reflective light modulators.
Innovation Solution
A projection display apparatus design that eliminates or reduces the need for wavelength selective retardation films by using a polarization splitter with two incident surfaces, allowing light in one wavelength band to enter as first polarized light and the other two bands to enter as orthogonal polarized light, thereby guiding each wavelength band directly to corresponding reflective light modulators without the need for narrow band retardation films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wavelength selective retardation films are used to separate light into three primary colors, then color separation is achieved, but contrast ratio decreases due to unintended light leakage
Solution Approach 1:
The patent divides the color separation function into two independent stages: first, a broadband retardation film performs preliminary polarization rotation for all wavelengths; second, wavelength-specific polarization splitters separate each primary color. This segmentation eliminates the need for complex narrow-band selective films, preventing light leakage while achieving accurate color separation and maintaining high contrast ratio.
Solution Approach 2:
The patent introduces a broadband retardation film as an intermediary component that performs initial polarization rotation before light enters the polarization splitters. This intermediary element simplifies the overall system by handling the common polarization transformation for all wavelengths, allowing subsequent wavelength-specific splitters to focus only on directional separation, thereby improving contrast ratio.
2Adaptability or versatility
If wavelength selective retardation films are used to rotate polarization direction selectively, then color separation is enabled, but device complexity increases
Solution Approach 1:
The patent segments the polarization control function into two distinct components: a broadband retardation film that handles wavelength-independent polarization rotation, and wavelength-specific polarization splitters that handle directional separation. This segmentation replaces the complex narrow-band selective films with simpler, more modular components, reducing overall device complexity while maintaining full color separation capability.
Solution Approach 2:
The patent changes the operational parameters of the retardation film from narrow-band selective rotation to broadband rotation. By using a retardation film that operates across all visible wavelengths rather than being tuned to specific bands, the system simplifies the optical path and reduces the number of specialized components needed, thereby reducing device complexity.
3Measurement precision
If narrow band retardation films are used for wavelength-specific polarization rotation, then precise color separation is achieved, but manufacturing difficulty increases
Solution Approach 1:
The patent segments the wavelength-selective function into two manageable parts: a broadband retardation film with straightforward manufacturing specifications, and separate polarization splitters for each primary color. This segmentation avoids the need to manufacture complex narrow-band selective films with precise wavelength control, making the overall system easier to produce while maintaining precise color separation through the combination of components.
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 design enhances contrast ratio by preventing unintended light leakage, simplifies optical design, and reduces the number of components, leading to improved luminance uniformity and contrast in projected images.
Implementation Method 1
a first polarization splitter that guides the light in the first wavelength band outputted from the color separator to the first reflective light modulator; a second polarization splitter that guides the light in the second wavelength band outputted from the color separator to the second reflective light modulator and guides the light in the third wavelength band outputted from the color separator to the third reflective light modulator
Data Source
AI summary
A first projection display apparatus includes a color separator (41A) that has first and second incident surfaces (S1a and S1b), and allows light in first to third wavelength bands to pass therethrough or reflects the light in the first to third wavelength bands; first to third reflective light modulators (15); a first polarization splitter (12G); a second polarization splitter (12RB); and a projection optical system (19). Light in at least one of the first to third wavelength bands enters the first incident surface of the color separator as first polarized light, and light in the other wavelength bands enters the second incident surface of the color separator as second polarized light orthogonal to the first polarized light.