Spatially Varying Reflector PSF Control for Display Color Fringing
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Solution Overview
Problem
Current light sources for displays, such as LCDs, suffer from undesirable Point Spread Functions (PSFs) that result in optical artifacts, color fringing, and uneven luminance, which affect display quality and contrast.
Innovation Solution
The implementation of a spatially varying compensation mechanism using reflectors with holes, absorptive or reflective dots, and color-specific filters positioned around light sources to modify the PSF, allowing for control over the light distribution to reduce tails, sharpen the PSF, and eliminate fringing effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a standard reflector is used to illuminate the spatial modulator, then the backlight provides sufficient luminance, but optical artifacts and color fringing occur due to undesirable PSF tails
Solution Approach 1:
The reflector is designed with spatially varying properties: different regions of the reflector have different reflectance values and spectral characteristics. Specifically, the reflector includes regions with higher reflectance and regions with lower reflectance, and color-specific filters are positioned at different locations to address color fringing in different areas. This local differentiation allows the reflector to suppress PSF tails and color fringing while maintaining overall luminance.
Solution Approach 2:
The reflector's optical parameters are varied spatially across its surface. The reflectance parameter changes from region to region, with some areas having high reflectance and others having low reflectance. Additionally, the spectral properties are modified through color-specific filters that absorb certain wavelengths in specific locations. These parameter changes enable control over the PSF shape and color uniformity.
2Illumination intensity
If the reflector uses high reflectance to maintain luminance, then brightness is sufficient, but color uniformity deteriorates due to color fringing
Solution Approach 1:
Color-specific filters are positioned at specific locations on the reflector where color fringing occurs. These filters have spectral characteristics tailored to absorb the fringing colors (e.g., cyan filters to absorb red fringing, magenta filters to absorb green fringing, yellow filters to absorb blue fringing). This localized color correction maintains overall luminance while improving color uniformity.
Solution Approach 2:
The color-specific filters on the reflector convert the harmful effect of color fringing into a beneficial outcome by selectively absorbing the fringing colors. The filters are positioned to intercept the fringing light paths and absorb the unwanted colors, thereby converting the color uniformity problem into a solution that enhances display quality.
3Ease of manufacture
If the reflector structure is simplified, then manufacturing is easier, but the ability to control PSF and compensate for spatial variations is reduced
Solution Approach 1:
The reflector is segmented into multiple functional regions with distinct properties. Different segments have different reflectance values and spectral characteristics. This segmentation allows the reflector to perform multiple functions (luminance maintenance, PSF tail suppression, color fringing correction) simultaneously. The segmented design can be implemented using standard manufacturing techniques by applying different coatings or filters to different regions.
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 approach enhances luminance and color uniformity across the display, reduces optical artifacts, and maintains contrast by controlling the PSF, resulting in improved display performance and reduced color fringing.
Implementation Method 1
The type of reflection can range from specular (glossy, mirror-like reflection) to Lambertian (diffuse spreading, paper-like reflection) and/or a combination of these two types of reflection
Implementation Method 2
The light source may comprise, for example, red, green, and blue LEDs and the filters comprise yellow, magenta, and cyan filters. The filters may be, for example, spatially varied and positioned to absorb red, green, and blue fringing of the light source
Data Source
AI summary
A Point Spread Function (PSF) of a light source is controlled by the provision of a PSF modifier on a reflector at or near the light source. The modifier may be a gradient or spatially varying application of any of transmission holes, filters, and absorptive dots. The invention may be applied to displays (e.g., backlighting of displays), and arrangement of the modifiers may include patterns that vary according to artifacts occurring in the display. The PSF modifier may flatten, remove, or increase tails, or mitigate fringing colors or patterns. In backlight arrays, the PSF modifier may be similar for all centrally located light sources, and exhibit differences when applied to light sources near edges or other anomalies in the backlight or surrounding structure.