Chromaticity Adjustment for LED Displays Using Rank-Based Correction
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Solution Overview
Problem
Current liquid crystal display devices face challenges in chromaticity adjustment due to large chromaticity unevenness in white LEDs, leading to increased manufacturing costs and reduced throughput, as they require extensive measurement and correction of γ characteristics for each device, and the use of specialized color sensors and circuits, which can result in device upsizing and higher costs.
Innovation Solution
A method for chromaticity adjustment that involves measuring chromaticity coordinates, determining if correction is needed, and applying pre-stored correction data to adjust the gray-scale signal for red, green, and blue pixels independently, using a drive circuit to correct the γ characteristic and bring the display within tolerance, even with large LED unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If extensive measurement and correction of γ characteristics is performed for each device, then chromaticity tolerance is improved, but manufacturing time increases significantly
Solution Approach 1:
The chromaticity correction is segmented into two parts: (1) common correction data that applies to all devices of the same LED rank, and (2) individual device measurement and selection. This segmentation allows most correction to be done once per rank rather than for each individual device, significantly reducing manufacturing time while maintaining chromaticity tolerance
Solution Approach 2:
Correction data is prepared in advance for each LED rank based on typical characteristics. During manufacturing, devices are simply measured and matched to the appropriate pre-prepared correction data, eliminating the need for extensive real-time correction calculations and reducing manufacturing throughput requirements
2Manufacturing precision
If color sensors and correction circuits are added to each device, then chromaticity adjustment precision is improved, but device complexity increases
Solution Approach 1:
The complex color sensor and correction circuit components are extracted from the display device itself and relocated to the manufacturing/test equipment. The display device only needs simple chromaticity measurement capability, while the heavy correction processing is done externally during manufacturing, reducing device complexity
Solution Approach 2:
Instead of using physical color sensors in each device, the invention uses a camera to capture optical images and converts these images into chromaticity data through software processing. This copying approach eliminates the need for complex physical sensors and circuits in the display device
3Manufacturing precision
If only LEDs with small chromaticity unevenness are used, then chromaticity tolerance is improved, but manufacturing cost increases due to LED ranking
Solution Approach 1:
The invention changes the approach from selecting LEDs based on narrow chromaticity parameters to using wide chromaticity correction data tables that accommodate large LED variations. By preparing comprehensive correction data for each LED rank, the system can use lower-cost LEDs with larger chromaticity variations while still achieving required display chromaticity tolerance
Solution Approach 2:
The invention converts the harmful effect of large LED chromaticity variations into a manageable parameter by creating rank-based correction systems. LEDs with large variations are not discarded but instead assigned appropriate correction data, turning what was previously a defect into a controllable characteristic that can be compensated through software
Data Source
AI summary
Provided is a method of chromaticity adjustment of a display device including a drive circuit for generating a gray-scale signal corresponding to a video signal input from an external portion and supplying the gray-scale signal to a plurality of pixels, the method including: measuring chromaticity coordinates of an image displayed on the display device; determining whether the measured chromaticity coordinates are chromaticity coordinates within a first region that does not need a chromaticity correction or chromaticity coordinates within a second region that needs the chromaticity correction; determining, if the measured chromaticity coordinates are the chromaticity coordinates within the second region, which of a plurality of correction regions obtained by dividing the second region the chromaticity coordinates fall within; correcting the gray-scale signal corresponding to the video signal by using a chromaticity correcting portion corresponding to the determined one of the plurality of correction regions; and performing corrected image display.