Wavelength Selection Filter Reduces Planar Reflection Light in Projection Displays
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Solution Overview
Problem
Current projection image display apparatuses face inefficiencies in light collection due to unnecessary light entering the projection lens, which reduces image quality and light utilization efficiency, especially when using a small F-number illumination system.
Innovation Solution
Incorporating a wavelength selection filter, such as a color filter, that reflects unwanted light components, like flat-face reflection light, thereby preventing them from entering the projection lens and improving the transmission efficiency of effective luminous flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a metal plate is used to block unnecessary light, then unnecessary light is shielded, but effective light is also blocked resulting in decreased light-collecting efficiency
Solution Approach 1:
The patent applies local quality by using a wavelength selection filter with spatially varying transmission characteristics. The filter allows different wavelength ranges to pass through different regions, selectively blocking only the unnecessary light (short wavelength components) while preserving effective light (long wavelength components). This resolves the contradiction by achieving localized spectral filtering rather than uniform blocking.
Solution Approach 2:
The patent changes the parameter of light wavelength selection by introducing a wavelength selection filter that selectively transmits long wavelength light while blocking short wavelength light. This parameter-based differentiation allows the system to distinguish between necessary and unnecessary light components, enabling selective blocking without compromising overall light-collecting efficiency.
2Productivity
If a small F-number illumination system is used, then light-collecting efficiency is improved, but unnecessary light enters the projection lens reducing image quality
Solution Approach 1:
The wavelength selection filter acts as an intermediary component between the illumination system and the projection lens. It mediates the light path by selectively filtering out unnecessary short wavelength components while allowing effective long wavelength components to pass through. This intermediary function enables the system to maintain small F-number illumination for high efficiency while preventing unnecessary light from degrading image quality.
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 use of a color filter as a wavelength selection filter enhances light utilization efficiency by blocking unnecessary light while maintaining high transmittance for effective light, resulting in improved image quality and reduced light quantity loss.
Implementation Method 1
the wavelength selection filter reflects a light wavelength component that will be planar reflection light after being reflected on the base and entering the incident port of the projection lens
Implementation Method 2
These mirrors are driven to switch, based on an image signal, between the ON state for reflecting a light entering from a light source toward the incident port of the projection optical system and the OFF state for reflecting a light entering from the light source in a direction other than the incident port
Data Source
AI summary
The projection image display apparatus of the disclosure includes a light source, a projection optical system that projects light entering an incident port, an optical modulator element, and wavelength selection filter. The optical modulator element includes multiple mirrors on its base. These mirrors are driven to switch, based on an image signal, between the ON state for reflecting a light entering from a light source toward the incident port of the projection optical system and the OFF state for reflecting a light entering from the light source in a direction other than the incident port of the projection optical system. In light entering from the light source to irradiate the optical modulator element, the wavelength selection filter reflects a light wavelength component that will be planar reflection light after being reflected on the base and entering the incident port of the projection lens.