LED Display Calibration via Photo-Sensitivity Measurement
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Solution Overview
Problem
LED displays using arrays for illumination face challenges in maintaining uniform brightness and color over time due to variations in LED light output and wavelength, requiring frequent recalibration, which is costly and time-consuming, especially in large installations like billboards and stadium displays.
Innovation Solution
The use of photo-sensitivity measurements to infer and correct for variations in LED optical output power and peak wavelength by adjusting drive current correction factors, allowing for uniform intensity and color across LED arrays through calibration during production and periodic recalibration using a consistent light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LED arrays are used for display applications, then energy efficiency and lifetime are improved, but variations in light output and wavelength among individual LEDs cause non-uniform brightness and color
Solution Approach 1:
The patent applies preliminary action by measuring the optical characteristics (light output and wavelength) of each individual LED during the manufacturing process and storing these measurements in a lookup table. Based on these pre-measured characteristics, correction factors are calculated and applied to the drive current of each LED before the display is deployed. This preliminary calibration eliminates the need for post-installation recalibration and ensures uniform brightness and color across the entire LED array, resolving the uniformity issue while maintaining the energy efficiency benefits of LED technology.
2Area of stationary object
If LED displays are installed in large installations like billboards and stadium displays, then display coverage and visibility are improved, but recalibration becomes costly and time-consuming
Solution Approach 1:
The patent implements preliminary action by performing complete optical measurements and calculations of correction factors for each LED during manufacturing, storing all necessary calibration data in a lookup table within the display controller. This pre-calibration approach ensures that when the display is installed, no field recalibration is needed. The system automatically uses the pre-stored correction factors to drive each LED with the appropriate current, maintaining uniform performance across large installations without requiring time-consuming recalibration operations.
Solution Approach 2:
The patent applies self-service by designing the system to automatically apply correction factors from the lookup table without requiring external intervention or recalibration equipment. The display controller autonomously reads the pre-stored optical characteristics and correction factors for each LED and adjusts the drive current accordingly. This self-calibrating capability eliminates the need for technicians to perform manual recalibration of large displays, significantly reducing maintenance time and costs while preserving the large display coverage capability.
3Manufacturing precision
If LED arrays are calibrated during production, then initial uniformity is improved, but degradation over time requires periodic recalibration
Solution Approach 1:
The patent applies preliminary action by measuring and storing the optical characteristics of each LED at multiple time points during aging tests, and using this historical data to predict future degradation patterns. Correction factors are pre-calculated to compensate for expected degradation over the display's operational lifetime. This approach maintains long-term performance stability by proactively accounting for aging effects before they manifest as visible non-uniformity, reducing or eliminating the need for periodic recalibration while preserving initial uniformity.
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 method significantly reduces the need for frequent recalibration by LED billboards and stadium displays, maintaining uniformity and reducing operational costs by automating the adjustment of LED arrays, ensuring consistent performance over their lifespan.
Implementation Method 1
the photo-sensitivity of each LED is measured, and the measured photo-sensitivity is used to infer the variations
Data Source
AI summary
Display calibration systems and related methods are disclosed that use photo-sensitivity of LEDs to correct for variations between LEDs during initial production and over lifetime for display systems. The display devices include arrays of LEDs and use photo-sensitivity of the LEDs to correct for variations between LEDs. Such LED arrays can produce images directly as in LED billboards and sports arena scoreboards, and smaller Organic LED (OLED) displays, or can produce the backlight for LCD screens for instance. Variations in LED brightness and color can be compensated for in order for such a display to have uniform color and brightness. This compensation is performed in the embodiments disclosed by measuring the signal induced on each LED by uniform incident light as a measurement of the photo-sensitivity of the LEDs.