Mura Effect Measurement Using Luminance Standard Deviation
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Solution Overview
Problem
The Mura effect in displays, characterized by non-homogeneous backlight illumination, is currently evaluated subjectively, leading to inconsistent assessments among observers, necessitating an objective method for measuring luminance and color level variations.
Innovation Solution
A method involving point-by-point luminance measurement of displays after warming, with points selected at specific intervals on parallel vertical lines, followed by numerical processing using polynomial fitting and standard deviation calculations to determine objective Mura effect levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If subjective evaluation by naked eye is used, then evaluation process is simple, but measurement precision and reliability are poor
Solution Approach 1:
The patent replaces the human visual system (mechanical/biological) with an automated optical measurement system consisting of a luminance meter, controller, and processing unit. The controller automatically controls the luminance meter to measure luminance at multiple predetermined positions, and the processing unit objectively calculates Mura effect levels using standard deviation and maximum difference computations, eliminating subjective human evaluation.
2Measurement precision
If point-by-point luminance measurement is performed, then measurement precision improves, but measurement time increases
Solution Approach 1:
The patent performs preliminary actions by pre-determining the measurement positions and intervals before actual measurement. The controller is programmed with predetermined positions based on display characteristics, and the measurement process automatically proceeds through these pre-planned positions, eliminating the need for manual position selection during measurement and reducing overall measurement time.
Solution Approach 2:
The measurement system uses periodic action by measuring luminance at regularly spaced intervals across the display. The controller automatically moves the luminance meter through predetermined positions at fixed intervals, creating a systematic periodic measurement pattern that ensures comprehensive coverage while maintaining efficient measurement speed.
3Measurement precision
If display is measured immediately after powering on, then measurement time is reduced, but measurement accuracy decreases due to thermal instability
Solution Approach 1:
The patent applies preliminary action by requiring the display to undergo a warm-up period before measurement begins. The controller is programmed to wait for a predetermined time interval after power-on before starting luminance measurements, allowing the display to reach thermal stability and ensuring accurate measurements of the actual operating conditions.
Data Source
AI summary
Present invention describes a method of measuring the luminance level in a display for Mura effect level measurement, comprising the steps of: measuring the luminance of the display in a calculated number of points on parallel vertical lines on the display, and in a steady state condition of luminance; comparing the measured luminance with nominal values to obtain a standard deviation from the nominal value.