Projection Display Filter Spectral Control
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Solution Overview
Problem
Projection-type image display devices using blue laser light and yellow phosphor suffer from a biased color gamut towards the yellow side and reduced brightness due to the inclusion of unnecessary wavelength bands, which affects the white balance and overall image quality.
Innovation Solution
A filter with dielectric multilayered films is introduced to reflect a portion of the blue illumination light and attenuate the unnecessary wavelength band between the red and green bands, enhancing color purity and maintaining brightness by adjusting the spectral transmittance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a filter is used to remove unnecessary wavelength bands between red and green bands, then color gamut is expanded, but brightness of the image decreases
Solution Approach 1:
The patent extracts and removes only the unnecessary wavelength bands between red and green using a filter, while preserving the essential red, green, and blue wavelength bands. This selective extraction approach expands color gamut by eliminating color-interfering wavelengths while maintaining sufficient brightness by keeping the useful spectral components intact.
2Manufacturing precision
If a filter is used to remove unnecessary wavelength bands, then color purity is improved, but white balance deviates
Solution Approach 1:
The patent applies local quality by using a filter with specifically designed spectral characteristics that target only the unnecessary wavelength bands between red and green. The filter's transmittance is locally optimized to block harmful wavelengths while maintaining high transmittance in the red, green, and blue regions, thus improving color purity without disrupting white balance.
3Productivity
If blue laser light and yellow phosphor are used as illumination sources, then red and green light images are generated, but color gamut is biased to yellow side
Solution Approach 1:
The patent converts the harmful effect of yellow phosphor's broad spectrum emission (which causes yellow bias) into a benefit by using a filter to remove the unnecessary intermediate wavelengths. The filter transforms the problematic broadband yellow light into useful narrowband red and green components, eliminating the yellow bias while maintaining the efficiency of phosphor-based light generation.
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 filter effectively expands the color gamut while minimizing the decrease in brightness and maintaining optimal white balance, ensuring a balanced and vibrant image display.
Implementation Method 1
A filter with dielectric multilayered films is introduced to reflect a portion of the blue illumination light
Implementation Method 2
A filter with dielectric multilayered films is introduced to reflect a portion of the blue illumination light and attenuate the unnecessary wavelength band
Implementation Method 3
the yellow phosphor is irradiated with a laser beam from the blue laser light source, and thereby converts energy of the irradiated laser beam into yellow light with a wavelength band including a red band and a green band
Data Source
Figure 1
Figure 2A~3
Figure 4~5
AI summary
A projection-type image display device (100) includes a light source (1), a phosphor (2), and a filter (50). The light source (1) emits a first blue illumination light (Ba). The phosphor (2) generates a first yellow illumination light (Ya) of a first wavelength band, which includes a component of a red band and a component of a green band, from a part of the first blue illumination light (Ba), and reflects a second blue illumination light (Bb) and the first yellow illumination light (Ya). The filter (50) reflects, to the phosphor side, a third blue illumination light (Bc) that is a part of the second blue illumination light (Bb) reflected by the phosphor, and attenuates a component of a second wavelength band of the first yellow illumination light (Ya), which is narrower than the first wavelength band. The phosphor also generates a second yellow illumination light (Yb) from the third blue illumination light (Bc) reflected by the filter.