Organic EL Pixel Inspection via Periodic Reverse Bias Imaging

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing methods for inspecting organic electroluminescence display devices fail to accurately detect defective pixels due to light emission states changing over time, leading to potential defects being missed during the inspection process.

Innovation Solution

A method involving repeated imaging of pixels under a reverse bias voltage, identifying light emitting points with luminance greater than or equal to a threshold intensity, and determining a pixel as defective only if the same point is identified multiple times, with the threshold intensity set based on average luminance from simultaneous light emission across all pixels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a single imaging is performed to detect defective pixels, then the inspection time is short, but defective pixels may be missed due to changing light emission states

Engineering Contradiction:

Improveinspection speedVSAvoiddefect detection accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The inspection method performs multiple imaging operations at different time points during the light emission period. By periodically capturing images at intervals, the system ensures that defective pixels exhibiting transient light leakage are detected even if their emission state changes over time. This periodic imaging approach balances inspection speed with reliable defect detection.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The inspection process maintains continuous monitoring of light emission by performing multiple imaging operations throughout the entire light emission period. Rather than a single discrete measurement, the continuous imaging sequence ensures that transient defects are captured, maintaining both thoroughness and efficiency in the inspection process.

Inventive Principle:

Principle #20Continuity of useful action

2Reliability

If multiple imaging operations are performed to ensure defect detection, then detection accuracy improves, but inspection time increases

Engineering Contradiction:

Improvedefect detection accuracyVSAvoidinspection time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Instead of continuous imaging which would be time-consuming, the method uses periodic imaging at strategically selected time points during the light emission period. This approach captures transient defects while maintaining reasonable inspection time by imaging at intervals rather than continuously.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The method performs a limited number of imaging operations (more than one but not exhaustive continuous imaging) to achieve sufficient detection accuracy. By performing partial imaging at key moments during the emission period, the system achieves adequate defect detection without the time cost of exhaustive continuous monitoring.

Inventive Principle:

Principle #16Partial or excessive action

3Device complexity

If a fixed threshold is used for identifying light emitting points, then the identification process is simple, but accurate detection of defective pixels is difficult due to varying light emission intensities

Engineering Contradiction:

Improvethreshold setting complexityVSAvoidlight leakage detection precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The threshold for identifying light emitting points is not fixed but is dynamically determined based on the actual light emission characteristics observed during imaging. By adjusting the threshold parameter according to the measured luminance distribution and emission intensity variations, the system achieves precise defect detection while accounting for natural variations in light emission.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The threshold setting incorporates feedback from the actual imaging results and light emission measurements. The system analyzes the luminance data from multiple images and adjusts the threshold accordingly, ensuring that the threshold adapts to the specific emission characteristics of the display device being inspected, thereby improving detection precision.

Inventive Principle:

Principle #23Feedback

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 ensures that defective pixels are reliably detected, preventing their escape and enabling the manufacture of high-quality organic EL display devices with increased accuracy.

Implementation Method 1

imaging the pixels for a predetermined time with a reverse bias voltage being applied to the pixels; identifying light emitting points which produce, in the imaging, luminance of light leakage

Methodology Applied

Scientific EffectLight emission: Luminescence

Data Source

PatentUS8687874B2Method of inspecting organic electroluminescence display device

Publication Date: 2014.04.01 MAGNOLIA BLUE CORP

AI summary

A method of inspecting an organic electroluminescence (EL) display device which includes pixels each of which includes an organic electroluminescence (EL) element includes: imaging the pixels for a predetermined time with a reverse bias voltage being applied to the pixels; identifying light emitting points which produce, in the imaging, light leakage that is greater than or equal to threshold intensity, the light emitting points being located within the pixels; and determining that a pixel including one light emitting point is a defective pixel when, after plural iterations of the imaging and the identifying, the light emitting point is identified in twice or more in the plural iterations of the identifying.