Dual LCD Panel Image Display Device Black Lifting Prevention
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Solution Overview
Problem
Liquid crystal display (LCD) devices suffer from a low contrast ratio due to 'black lifting' and difficulty in reproducing dynamic ranges of natural images, particularly in high luminance regions, leading to issues with gray level linearity and color reproducibility.
Innovation Solution
An image display method using a dual LCD panel setup where an RGB image is processed to generate a black-and-white image with adjusted luminance, utilizing a look-up table for gray level conversion and high luminance region expansion to improve contrast and prevent black lifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single LCD panel is used for image display, then the device structure is simple, but the contrast ratio is low due to black lifting and the dynamic range reproduction is poor
Solution Approach 1:
The patent divides the display system into two separate LCD panels: a front panel for color display and a rear panel for luminance control. This segmentation allows independent optimization of each panel's function, with the rear panel specifically dedicated to controlling black levels and contrast, thereby resolving the contradiction between simple structure and high contrast ratio.
Solution Approach 2:
The rear LCD panel acts as an intermediary layer between the backlight and the front display panel. It modulates the luminance of light passing through it to prevent black lifting, effectively mediating the interaction between the backlight and the front panel to achieve improved contrast ratio without significantly complicating the overall device structure.
2Manufacturing precision
If gamma correction is applied to improve gray level linearity, then the gray level display is improved, but the high luminance region reproduction is limited and color fidelity is reduced
Solution Approach 1:
The patent separates the display functions into two panels: the front panel handles color information and the rear panel handles luminance information. This allows gamma correction to be applied independently to the luminance channel without compromising color fidelity, as each panel can be optimized for its specific function without information loss.
Solution Approach 2:
The patent applies different processing to different regions of the luminance signal. The rear panel specifically targets the low luminance region to prevent black lifting while preserving the high luminance region information, applying local quality improvement rather than uniform processing across the entire luminance range.
3Manufacturing precision
If two LCD panels are used to improve contrast ratio, then the black lifting is prevented, but the device complexity increases and alignment precision becomes difficult to maintain
Solution Approach 1:
The patent merges the luminance control function of the rear panel with the color display function of the front panel in a single display assembly. The two panels are optically aligned and work together as an integrated system, reducing the overall device complexity compared to having separate display systems while maintaining the contrast ratio improvement benefits.
4Length of stationary object
If the rear LCD panel is positioned close to the backlight unit, then the device thickness is reduced, but the images from the two panels are misaligned due to physical parallax
Solution Approach 1:
The patent employs asymmetric positioning of the two LCD panels relative to each other and the backlight unit. The panels are arranged at specific angles and distances that compensate for parallax effects, creating an asymmetric optical path that maintains image alignment while minimizing device thickness. This asymmetric arrangement allows the panels to be positioned close together without suffering from severe misalignment.
Data Source
AI summary
Disclosed is a method of displaying an image using an image display device including a front LCD panel and a rear LCD panel overlapping each other that may include displaying an RGB image in the front LCD panel; generating a black-and-white image having a luminance value adjusted by a pixel by signal-processing the RGB image, and displaying the black-and-white image in the rear LCD panel.