Distributed Measurement Units for Inter-Chip Correction in Display Apparatus
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Solution Overview
Problem
Variations in capacitance of capacitors in current measurement circuits within semiconductor chips lead to inaccurate current measurement in organic EL display apparatuses, resulting in luminance differences and challenges in achieving high image quality due to uncompensated variations in element characteristics among semiconductor chips.
Innovation Solution
An active matrix display apparatus with distributed measurement units across multiple semiconductor chips, utilizing inter-chip correction data to compensate for capacitance variations, and storing data for image signal correction, ensuring uniformity across the display unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current measurement circuits including operational amplifiers and capacitors are used to measure currents flowing through pixel circuits, then current measurement capability is provided, but variation of capacitance of the capacitor occurs due to variation in semiconductor process, leading to measurement inaccuracy
Solution Approach 1:
The patent changes the measurement approach from direct current measurement using capacitive circuits to voltage measurement using resistive voltage divider circuits. This parameter change from capacitive to resistive measurement eliminates the capacitance variation problem caused by semiconductor process variations, as resistors exhibit much better process stability and lower variation compared to capacitors in standard semiconductor manufacturing.
2Area of stationary object
If multiple semiconductor chips are used to provide current measurement circuits across the display apparatus, then measurement coverage is improved, but variation of characteristics among semiconductor chips causes luminance differences at boundaries
Solution Approach 1:
The patent uses voltage measurement as a copy or proxy for current measurement. By measuring voltage across a known resistance (the pixel circuit's effective resistance), the system indirectly obtains current information without the instability of direct capacitive current measurement. This copied measurement approach is more stable across semiconductor chips and eliminates luminance differences at chip boundaries.
3Loss of information
If image signal correction is performed based on inaccurate current measurement results, then compensation for element characteristic variations is attempted, but the correction accuracy is limited by measurement errors
Solution Approach 1:
The patent replaces the mechanical/electrical capacitive measurement system with an electronic voltage measurement system. By substituting the capacitive current measurement mechanism with a resistive voltage measurement mechanism, the system achieves higher measurement precision and more accurate image signal correction for compensating element characteristic variations.
Data Source
AI summary
In a data line drive/current measurement circuit, m measurement units are disposed in a plurality of semiconductor chips such that the m measurement units are distributed among the plurality of semiconductor chips. A display apparatus includes transistors such that one transistor is provided for two adjacent semiconductor chips. Inter-chip correction data indicating a variation among the semiconductor chips in terms of characteristics of elements in the measurement units is determined based on a result of a current measurement performed for the same transistor using measurement units disposed in different semiconductor chips. The inter-chip correction data is stored in a storage unit and is used in correcting an image signal. The inter-chip correction data may be determined based on a result of measuring a current flowing through a common cathode of organic EL elements for each semiconductor chip. Thus, a variation in the characteristic of the element among the semiconductor chips is compensated for and high image quality is achieved in displaying.