Backlight Calibration for LCD Uniformity
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Solution Overview
Problem
Existing LED backlight systems for LCDs face challenges in ensuring uniformity of color and brightness due to variations in intrinsic characteristics among LEDs, leading to spatial non-uniformity, which current optical feedback control systems fail to address effectively by only monitoring and adjusting the backlight unit as a whole rather than individual LEDs.
Innovation Solution
A backlight calibration apparatus comprising photo-sensors, a controller, a driving circuit, and a processing unit that measures and adjusts the light output of each LED or group of LEDs to achieve uniform lighting conditions, using a method that involves measuring light conditions, comparing with predefined settings, and calculating adjustments to drive LEDs for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical feedback control is used to monitor and adjust the backlight unit as a whole, then color and brightness variation over temperature and time is minimized, but spatial non-uniformity due to variation of characteristics on individual LEDs cannot be solved
Solution Approach 1:
The backlight unit is divided into multiple independently controllable LED regions or individual LEDs. The feedback control system measures light output from each segment separately using photo-sensors and adjusts each segment's driving current independently through the driving circuit, thereby resolving spatial non-uniformity while maintaining overall color and brightness stability
Solution Approach 2:
Different regions of the backlight unit are provided with locally optimized driving parameters based on their specific characteristics. The system measures and adjusts each LED or LED group individually, applying local compensation for variations in color and brightness characteristics, thus achieving uniformity across the entire backlight while accounting for local differences
2Manufacturing precision
If individual driving on each light source is implemented to achieve uniform lighting conditions, then spatial non-uniformity is reduced, but device complexity increases due to additional control requirements
Solution Approach 1:
The driving circuit is designed to perform multiple functions: it can drive individual LEDs independently for calibration, drive groups of LEDs for regional adjustment, and maintain overall backlight operation. This multi-functionality reduces the need for separate dedicated control circuits for each LED, thereby managing complexity while achieving individual LED control
Solution Approach 2:
A feedback control loop is established where photo-sensors measure the light output from each LED or LED group, the measured values are compared against target values, and the driving circuit automatically adjusts individual LED driving currents based on the feedback signals. This closed-loop feedback system automates the calibration process, reducing the complexity of manual adjustment while achieving uniform lighting
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 enables precise calibration of individual LEDs, reducing spatial non-uniformity and ensuring consistent color and brightness across the backlight unit, thereby improving the overall display quality of LCDs by addressing the intrinsic variations in LEDs.
Implementation Method 1
at least one photo-sensor adapted to measure the light emitted by the backlight unit
Data Source
AI summary
Methods and apparatuses for backlight calibration are described. The apparatus 100 comprises a backlight unit 102 comprising a plurality of light sources 120, at least one photo-sensor 103 adapted to measure the light emitted by the backlight unit 102, a photo-sensor controller 112 coupled to the photo-sensor 103 for controlling the photo-sensor(s) 103, a backlight driving circuit 104 coupled to the light sources 120 for providing individual driving on each light source, a signal generator 114 coupled to the photo-sensor controller 112 and the backlight driving circuit 104 for controlling the operation timing of photo-sensors 103 and each of the light source 120 such that lighting conditions from each of the light source can be acquired, and a processing unit 111 coupled to the photo-sensor 103 and the backlight driving circuit 104 for analyzing the measurement data from the photo-sensors 103 and providing an adjustment signal to the backlight driving circuit 104 to achieve uniform lighting conditions of the backlight unit 102. Also described is a method comprising the steps of providing saved settings for backlight driver, providing a modified timing sequence to backlight driver and photo sensor 202, measuring light conditions of each individual light source or each individual group of light sources in backlight unit 203, comparing measurement data with predefined light conditions 205, calculating the adjustment required on backlight drivel to achieve desired light conditions, and saving calculated adjustment as new settings for backlight driver 207.