Self-luminous Display Device Luminance Control for Image Persistence
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Solution Overview
Problem
Self-luminous display devices using organic EL elements face image persistence issues due to deteriorating luminance characteristics when a voltage is continuously applied, leading to reduced luminance and persistence phenomena, especially in pixels with high luminance frequency.
Innovation Solution
A self-luminous display device with a data calculation section that calculates luminance data in blocks, a resampling section that adjusts the data in larger blocks, and a scaling section that generates control data to flexibly manage video signal luminance, preventing image persistence by controlling current levels and pixel luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If voltage is continuously applied to organic EL elements to maintain display operation, then the display can function continuously, but luminance characteristics deteriorate and image persistence occurs
Solution Approach 1:
The patent applies periodic action by using alternating voltage to drive the organic EL elements instead of continuous direct current. The display device alternates between displaying image signals and blanking periods, during which compensation signals are applied to maintain luminance characteristics. This periodic operation prevents the cumulative degradation that occurs with continuous voltage application, thereby resolving the contradiction between continuous operation and luminance reliability.
Solution Approach 2:
The patent changes the electrical parameters applied to the organic EL elements by switching between different voltage patterns (image signal voltage during display, compensation voltage during blanking). The compensation signal adjusts the accumulated charge in the pixel circuit, effectively resetting the luminance characteristics. This parameter change prevents luminance degradation while maintaining continuous display operation.
2Illumination intensity
If current amount is increased to improve luminance in high luminance frequency pixels, then brightness is enhanced, but image persistence phenomenon worsens
Solution Approach 1:
The patent extracts and separately handles the compensation function from the main image display function. During blanking periods, compensation signals are applied specifically to pixels that have accumulated excessive charge, without affecting the overall image luminance. This separation allows high luminance pixels to be compensated individually, removing the image persistence effect while preserving the desired luminance levels.
Solution Approach 2:
The patent applies local quality by providing differentiated compensation to different pixel regions based on their individual luminance accumulation. The compensation signal is calculated and applied selectively to specific pixel circuits that exhibit image persistence, rather than uniformly to all pixels. This localized approach corrects luminance degradation in high-frequency pixels without reducing the luminance of other pixels.
3Reliability
If luminance control is applied to the entire screen, then image persistence is suppressed, but flexible luminance control for specific regions is lost
Solution Approach 1:
The patent segments the screen into individual pixel circuits, each capable of independent compensation. The compensation signal is calculated and applied at the pixel level rather than as a uniform screen-wide adjustment. This segmentation allows selective luminance control for specific regions or pixels that require it, while maintaining overall image persistence suppression across the entire display.
Solution Approach 2:
The patent implements dynamic luminance control by adjusting compensation signals in real-time based on the actual luminance accumulation in each pixel circuit. The compensation amount and timing are dynamically adapted to the displayed content and pixel usage patterns, providing flexible region-specific control while maintaining image persistence suppression throughout the screen.
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 effectively suppresses image persistence by dynamically adjusting luminance across the screen, preventing luminance degradation and maintaining image quality by controlling current levels and pixel luminance, thereby enhancing display performance.
Implementation Method 1
An organic EL element changes from a ground state to an excited state when energy is received by electrodes, and discharges the energy of a difference when returning from the excited state to the ground state
Data Source
AI summary
Provided is a self-luminous display device including a data calculation section configured to calculate, by using a supplied video signal, data relating to a luminance amount accumulated in a unit of a first block in a target region for luminance control in a screen on which a plurality of pixels are arranged in a matrix, each of the pixels including a light emitting element which emits light by itself according to a current amount, a resampling section configured to resample the data relating to the luminance amount in the target region, in a unit of a second block, the data relating to the luminance amount being calculated by the data calculation section, the second block being larger than the first block, and a scaling section configured to generate data for luminance control in the target region by scaling the data resampled by the resampling section.