OLED Pixel Self-Calibration Using Light-Receiving Subpixels
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Solution Overview
Problem
Display apparatuses using organic electroluminescence (EL) devices face issues with non-lighting pixels due to manufacturing defects, leading to reduced yield and difficulty in correcting luminance variations between pixels, especially after shipment, and require multiple image captures to identify defects.
Innovation Solution
A display apparatus with a structure incorporating light-emitting and light-receiving devices per pixel, utilizing a correction circuit to calculate and store correction data via a quadratic expression, allowing for luminance correction without additional image captures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image capturing with external camera is used to identify defective pixels, then defective pixels can be detected, but the number of image captures increases and it is difficult to correct luminance variations after shipment
Solution Approach 1:
The patent extracts the light-receiving function from a separate inspection device and integrates it directly into each pixel structure. Each pixel includes a light-receiving device that measures luminance locally, eliminating the need for external camera-based inspection and multiple image captures while enabling post-shipment correction of luminance variations.
Solution Approach 2:
The pixel structure is designed with multi-functionality: each pixel contains both light-emitting devices for display and light-receiving devices for luminance measurement. This universal design allows the same pixel structure to serve both display and self-inspection functions, enabling defective pixel detection and luminance correction without additional external equipment.
2Reliability
If peripheral pixel correction algorithm is applied, then black dot defects can be corrected, but relative variation in luminance between pixels cannot be corrected
Solution Approach 1:
The patent implements feedback by using light-receiving devices in each pixel to measure actual luminance values, which are then used to calculate correction values. These correction values are stored and applied to adjust video data, creating a closed-loop system that continuously compensates for luminance variations and ensures uniform display quality.
Solution Approach 2:
The patent changes the approach from fixed correction algorithms to dynamic parameter adjustment. Correction values are calculated based on measured luminance parameters from light-receiving devices, and these parameters are stored for ongoing adjustment of video data, enabling precise correction of luminance variations across different pixels.
3Measurement precision
If control circuit with external compensation is used, then defective pixels can be identified, but correction requires additional external equipment and cannot address post-shipment variations
Solution Approach 1:
The patent merges the light-receiving devices with the pixel structure itself, combining display and measurement functions in a single integrated unit. This eliminates the need for separate external compensation circuits and equipment, reducing device complexity while maintaining defective pixel identification accuracy and enabling post-shipment correction capabilities.
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 method effectively corrects luminance variations between pixels post-shipment by using a correction table based on calculated coefficients, reducing the need for multiple image captures and enhancing display quality.
Implementation Method 1
each pixel includes a first subpixel including a light-emitting device and a second subpixel including a light-receiving device
Data Source
AI summary
A novel correction method for a display apparatus is provided. A correction circuit of the display apparatus obtains offset corresponding to a current flowing through a second subpixel when a first subpixel is not lit. The correction circuit of the display apparatus obtains, for each pixel, correction output data, obtained by correcting, with the offset, data corresponding to a current flowing through each of the second subpixels in sequentially supplying correction video data to the first subpixels and stores the correction video data and the correction output data corresponding to the correction video data in a memory circuit. The correction circuit of the display apparatus calculates coefficients obtained when a relation between the correction video data and the correction output data corresponding to the correction video data is approximated by a quadratic expression and stores the coefficients in the memory circuit. The correction circuit of the display apparatus stores a correction table that is created on the basis of the correction output data and the coefficients, in the memory circuit. The correction circuit of the display apparatus corrects display video data in accordance with the correction table.