Projector Color Gamut Expansion via Dual Threshold Optical Filters
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Solution Overview
Problem
Projectors using phosphors face challenges in expanding color gamut without reducing luminance, as existing filter configurations either widen the attenuation wavelength region, leading to reduced luminance, or narrow it, resulting in insufficient attenuation and color gamut narrowing due to color mixing.
Innovation Solution
A projector design incorporating a first filter and a second filter, both insertably and removably positioned on the optical paths of green and red light, respectively, with specific threshold settings to attenuate light in the dimming wavelength region, allowing for expanded color gamut while minimizing luminance reduction, and storing them in an overlapping manner to reduce projector size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a filter is insertably and removably disposed upstream of the second dichroic mirror to attenuate light in the yellow wavelength region, then the color gamut can be expanded, but the luminance of the projection image is reduced
Solution Approach 1:
The patent divides a single filter function into two separate filters: a first filter disposed on the optical path of green light and a second filter disposed on the optical path of red light. Each filter independently attenuates light in the yellow wavelength region, allowing for precise control of color separation while minimizing overall luminance loss. This segmentation enables the system to achieve color gamut expansion without the severe luminance penalty of a single comprehensive filter.
Solution Approach 2:
The patent applies different filtering characteristics to different optical paths based on local requirements. The first filter on the green light path and the second filter on the red light path have differently positioned threshold wavelengths, creating localized attenuation zones that precisely target yellow light contamination in each color channel while preserving the luminance of transmitted colors. This local quality approach optimizes the balance between color purity and brightness.
2Adaptability or versatility
If the wavelength region to be attenuated is widened to sufficiently reduce yellow light, then the color gamut expands, but the luminance is reduced
Solution Approach 1:
The patent changes the parameter of threshold wavelength positioning for the two filters to optimize performance. The first filter has its threshold wavelength positioned to attenuate yellow light while transmitting green, and the second filter has its threshold positioned to attenuate yellow light while transmitting red. By independently optimizing these threshold parameters for each color path, the system achieves sufficient yellow light attenuation for color gamut expansion while minimizing luminance loss in the transmitted color regions.
3Illumination intensity
If the wavelength region to be attenuated is narrowed to maintain luminance, then the color mixing is reduced, but the color gamut is narrowed due to insufficient attenuation
Solution Approach 1:
The patent segments the attenuation function across two filters with different threshold wavelengths, allowing each filter to operate with a narrower, more precise attenuation band. This segmentation enables sufficient yellow light rejection in each color channel without requiring either filter to have an excessively broad attenuation range, thereby maintaining luminance while achieving the necessary color separation for gamut expansion.
4Volume of moving object
If filters are stored in an overlapping manner, then the projector size is reduced and filter switching is simplified, but the filter insertion and removal mechanism becomes more complex
Solution Approach 1:
The patent merges the storage spaces for the first and second filters into a single overlapping storage region. Both filters are stored in the same physical space when not in use, eliminating the need for separate storage compartments. This merging approach reduces the overall projector volume and simplifies the filter switching mechanism by using a single insertion/removal path for both filters, despite the added complexity of coordinating their simultaneous movement.
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 solution effectively expands the color gamut while maintaining image luminance, and by storing filters in an overlapping configuration, it reduces the projector's size and simplifies the filter switching mechanism, compared to separate filter insertion and removal configurations.
Implementation Method 1
a first filter that is insertably and removably provided on an optical path of the third color light; and a second filter that is insertably and removably provided on an optical path of the fourth color light, wherein a wavelength of the third color light is shorter than a wavelength of the fourth color light, the first filter attenuates light at a wavelength exceeding a first threshold set in an dimming wavelength region
Implementation Method 2
the second filter attenuates light at a wavelength equal to or less than a second threshold set in the dimming wavelength region
Implementation Method 3
The phosphor converts a portion of incident excitation light to fluorescence at a wavelength different from the excitation light. The fluorescence and another portion of the excitation light are emitted as illumination light from the phosphor
Data Source
AI summary
A projector includes: an illumination device; first color separation device that separates first and second color light from light emitted from the illumination device; second color separation device that separates third and fourth color light from the second color light; plurality of light modulation devices that modulate the lights separated by the first and second devices; projection optical device that projects an image based on the modulated lights; first and second filters provided on optical paths of the third and fourth color lights, respectively. A wavelength of the third color light is shorter than that of the fourth. The first filter attenuates light at a wavelength exceeding a first threshold set in a dimming wavelength region between a wavelength region of the third and fourth color lights. The second filter attenuates light at a wavelength equal to or less than a second threshold set in the dimming wavelength region.