Surface Light Source Device Uniform Luminance Control
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Solution Overview
Problem
Conventional surface light source devices for liquid crystal display devices face challenges in achieving uniform luminance and color across blocks, leading to moving picture blurring and increased manufacturing costs due to the need for sensors to detect light emission quantities from each block.
Innovation Solution
A surface light source device with light source driving means, light quantity detecting means, and drive control means that adjusts emission light quantities by detecting output light beams from multiple blocks when only one is lit, eliminating the need for block-by-block sensors and ensuring uniform light output through proper light diffusing and guiding mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sensors are provided for each block to detect light emission quantities, then uniform luminance across blocks can be achieved, but manufacturing cost increases
Solution Approach 1:
The light guide plate is divided into multiple blocks, each corresponding to a data writing region. By sectioning the light guide plate, the patent enables independent control of light emission for each block, allowing luminance uniformity to be achieved through selective lighting rather than through expensive sensor-based feedback for each block.
Solution Approach 2:
The patent employs periodic lighting where only specific blocks are illuminated at specific times synchronized with data writing operations. This time-division multiplexing approach allows a single sensor to detect light quantities from different blocks at different times, eliminating the need for multiple sensors while maintaining luminance control.
2Reliability
If light sources are turned on block-by-block in synchronism with data writing, then moving picture blurring is suppressed, but luminance non-uniformity among blocks occurs
Solution Approach 1:
The patent incorporates a sensor that detects light quantities from each block and feeds this information back to a control unit. The control unit adjusts the drive signals to light sources based on detected luminance levels, compensating for variations in light emission quantities and achieving uniform luminance across blocks while maintaining synchronized block-by-block lighting.
Solution Approach 2:
The patent dynamically adjusts the drive current or voltage parameters of light sources based on detected light quantities. By changing electrical parameters of the light sources in response to detected luminance variations, the system compensates for block-to-block luminance non-uniformity while maintaining the synchronized lighting operation needed to suppress moving picture blurring.
3Productivity
If light is output directly from regions close to point light sources, then light diffusion is insufficient, but luminance and color unevenness occur
Solution Approach 1:
The patent introduces a light diffusing plate as an intermediary element between the light sources and the light guide plate. This diffusing plate scatters and redistributes light before it enters the light guide plate, ensuring uniform light distribution across the light guide plate surface and preventing luminance and color unevenness in regions close to the light sources while maintaining overall light output efficiency.
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 configuration achieves uniform light output across blocks without increasing manufacturing costs, preventing luminance and color unevenness near point light sources and enhancing display quality by ensuring sufficient diffusion of light before output.
Implementation Method 1
a light guide plate having a light exit area, and two light diffusing means formed on the light guide plate
Implementation Method 2
two light diffusing means formed on the light guide plate in a region closer to the other end
Data Source
AI summary
A surface light source device includes light source driving means for driving light sources on a light emission block basis, a light exit area being sectioned into two or more light emission blocks, light quantity detecting means for detecting light quantities on the basis of output light beams that are led out from the two or more light emission blocks, and drive control means for adjusting emission light quantities of the light sources corresponding to the respective light emission blocks on the basis of light quantities that are detected during lighting periods when only one of the light emission blocks is lit up that are subjected to light quantity detection by the light quantity detecting means.