Backlight Luminance Control for Aspect Ratio Mismatch
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Solution Overview
Problem
Conventional liquid crystal display devices face challenges in maintaining display quality when the aspect ratio of input image data differs from the display screen's aspect ratio, leading to image non-display areas and inadequate backlight luminance control, resulting in unnatural video displays, especially for high-definition formats like 4K2K.
Innovation Solution
The device includes a control system that adjusts image data by adding dummy pixels, divides the image into sections, and compensates luminance distribution to ensure proper backlight control across the display area, using a backlight unit with multiple LEDs arranged in a matrix pattern to maintain image quality by setting luminance signals based on average luminance levels and reference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If image data is displayed without aspect ratio adjustment, then the original image quality is preserved, but image non-display areas occur in edge regions when the aspect ratio differs from the display screen
Solution Approach 1:
The control device performs preliminary aspect ratio adjustment on the image data before display, detecting the aspect ratio of input image data and comparing it with the display screen's aspect ratio. When they differ, the control device adjusts the image data in advance by adding dummy pixels to fill edge areas, ensuring that the entire display screen is utilized without black borders or non-display areas.
2Device complexity
If backlight luminance is uniformly controlled across the display screen, then the control complexity is reduced, but display quality becomes unnatural in regions where image data is not displayed
Solution Approach 1:
The control device implements local backlight luminance control by dividing the display screen into multiple regions and independently adjusting backlight intensity for each region. In edge regions where dummy pixels are added due to aspect ratio differences, the control device reduces backlight luminance locally to match the reduced image data luminance, preventing unnatural brightness in areas without actual image content.
3Manufacturing precision
If backlight luminance is increased in edge areas to compensate for missing image data, then display uniformity is improved, but power consumption increases
Solution Approach 1:
The control device dynamically changes backlight luminance parameters based on the actual image content and aspect ratio. When image data has a different aspect ratio than the display screen, the control device reduces backlight luminance in edge regions where dummy pixels are added, rather than increasing it. This parameter adjustment maintains display uniformity by matching backlight intensity to actual image content, avoiding unnecessary power consumption in areas without real image data.
Data Source
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AI summary
The present invention relates to a liquid crystal display device including a liquid crystal display panel and a backlight unit having light sources arranged in back of the liquid crystal display panel. Image data obtained by adding a dummy image to a periphery of inputted image data is divided into blocks which correspond to positions of LEDs. A light-emitting luminance of an LED in an image display area, in which an image corresponding to the inputted image data is displayed, is determined in accordance with a maximum value among gradation values of pixels included in a block corresponding to the LED. A light-emitting luminance of an LED in an image non-display area, in which an image corresponding to the dummy image data is displayed, is determined in accordance with an average luminance level of some of small blocks which are adjacent to the block corresponding to the LED in the image non-display area, the small blocks being obtained by further dividing a block of the image display area adjacent to the block corresponding to the LED. According to the present invention, in a case where an aspect ratio of the inputted image data is different from that of the liquid crystal display panel, display quality in a border area of the image display area and the image non-display area can be improved.