OLED Luminance Correction via Periodic Detection Frames
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Solution Overview
Problem
Organic electroluminescence (EL) displays face issues with variation in light-emission characteristics over time, leading to image persistence and uneven luminance, as the voltage-current characteristics of OLED elements deteriorate, requiring frequent measurement to maintain accurate image display.
Innovation Solution
Implementing a display system where frames are classified into detection and non-detection frames, with increased power supply voltage and scanning frequency during detection frames, and varying light emission intensity and power supply voltage to maintain equivalent luminance across all frames, using a display scanning circuit and a detection scanning circuit to execute characteristic detection during blanking periods or on a scanning line-by-scanning line basis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measurement of OLED elements is executed for all frames, then detection precision of voltage-current characteristics is improved, but luminance intensity of the screen deteriorates and flicker occurs
Solution Approach 1:
The patent implements periodic measurement by alternating between measurement frames and non-measurement frames. In measurement frames, all OLED elements are measured for voltage-current characteristics, while in non-measurement frames, normal display operation continues without measurement. This periodic alternation ensures that measurement precision is maintained over time while preventing continuous measurement from causing luminance deterioration and flicker.
Solution Approach 2:
The patent segments the frame structure into distinct measurement periods and non-measurement periods. Each frame is divided into a light emission period for image formation and a measurement period for characteristic detection. This segmentation allows the system to allocate specific time slots for measurement without compromising overall display performance and luminance stability.
2Measurement precision
If measurement period is extended to cover entire frame, then detection precision is improved, but image formation time is reduced causing luminance deterioration
Solution Approach 1:
The patent segments each frame into distinct functional periods: a light emission period for image formation and a measurement period for characteristic detection. By separating these functions into non-overlapping time slots, the system ensures that image formation receives sufficient time while still allowing comprehensive measurement to occur during dedicated measurement periods.
Solution Approach 2:
The patent implements periodic measurement where comprehensive measurement of all OLED elements is performed in alternating frames rather than continuously in every frame. This periodic approach allows full measurement cycles to occur without permanently reducing the light emission period, as non-measurement frames restore full image formation time.
3Measurement precision
If all frames are used for measurement alternately, then detection precision is improved, but screen luminance deteriorates and flicker occurs
Solution Approach 1:
The patent implements periodic measurement by alternating between measurement frames and non-measurement frames. This alternation ensures that measurement precision is maintained over time while preventing continuous measurement from causing luminance deterioration and flicker.
Solution Approach 2:
The patent incorporates feedback mechanisms where measurement results from voltage-current characteristic detection are used to adjust drive signals for OLED elements. This feedback loop compensates for individual element variations and aging effects, maintaining uniform luminance across the screen while enabling comprehensive measurement.
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 approach allows for natural image display by minimizing the impact of detection on luminance, ensuring equivalent luminance across frames and reducing the appearance of image persistence, while maintaining accurate gradation and power efficiency.
Implementation Method 1
organic electroluminescence (EL) displays
Data Source
AI summary
In an organic EL display, correction is made for a difference in screen luminance between the case of measuring characteristics of OLED elements, and the case of not measuring the characteristics of the OLED elements. A data line for feeding image data items, and a detection line for measuring the characteristics of the OLED elements are connected to respective pixels. Detection of the characteristics of the OLED elements is executed by utilizing a specified period of a frame period. Because an image-displaying period is limited in a frame where measurement of the characteristics of the OLED element 11 is executed, the luminance undergoes deterioration. In order to prevent the deterioration of the luminance, an analog-to-digital converter ADC causes γ characteristic of the OLED elements in the frame where measurement of the characteristics of 11 is executed to be varied by the agency of a signal from a timing controller Tcon to the analog-to-digital converter ADC, thereby increasing luminance intensity of light emission of the OLED elements.