Backlight Control Synchronization for Display Ghost Reduction

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Solution Overview

Problem

Existing display devices using PWM dimming and blinking backlight control suffer from 'ghost' and 'leading edge' phenomena, which degrade moving image display performance due to improper synchronization of backlight illumination and liquid crystal state transitions.

Innovation Solution

A display device with control means that synchronizes backlight illumination and extinction with frame updates, ensuring the backlight starts to illuminate after the liquid crystal state has transitioned and ends illumination before the next frame update, thereby reducing ghost and leading edge effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the backlight starts to illuminate before the liquid crystal state completes transition, then the display can show the current frame earlier, but ghost phenomenon occurs where the previous frame reflects on the display image

Engineering Contradiction:

Improveframe display speedVSAvoidghost phenomenon

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The backlight controller delays the backlight illumination start time point to occur after the liquid crystal state has completed its transition. This preliminary completion of the liquid crystal transition before backlight illumination prevents the ghost phenomenon while still maintaining efficient frame display timing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from the liquid crystal response time characteristics to dynamically adjust the backlight illumination timing. By monitoring when the liquid crystal state completes transition, the backlight controller optimizes the illumination start time to avoid ghost while maximizing display speed.

Inventive Principle:

Principle #23Feedback

2Duration of action of moving object

If the backlight illumination end time point is delayed with respect to vertical synchronization signal, then the current frame can be illuminated longer, but leading edge phenomenon occurs where the subsequent frame reflects on the display image

Engineering Contradiction:

Improvebacklight illumination durationVSAvoidleading edge phenomenon

Core Design Contradiction:

Duration of action of moving objectVSObject-affected harmful factors

Solution Approach 1:

The backlight controller advances the backlight illumination end time point to occur before the liquid crystal state begins transition to the subsequent frame. This preliminary completion of illumination before the next frame's liquid crystal transition prevents the leading edge phenomenon while maintaining adequate illumination duration.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from the vertical synchronization signal and liquid crystal transition timing to dynamically adjust the backlight illumination end time. By monitoring when the subsequent frame's liquid crystal transition begins, the controller optimizes the illumination end time to prevent leading edge while maximizing illumination duration.

Inventive Principle:

Principle #23Feedback

3Illumination intensity

If the backlight illumination period is extended to improve visibility, then moving image visibility improves, but overlap between backlight illumination period and liquid crystal transition period increases causing ghost and leading edge

Engineering Contradiction:

Improvemoving image visibilityVSAvoidimage reflection from liquid crystal transition

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The backlight controller sets the illumination period boundaries based on preliminary completion of liquid crystal transitions. The illumination starts after the current frame's liquid crystal transition completes and ends before the subsequent frame's liquid crystal transition begins, preventing image reflection while maintaining visibility.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously adjusts the backlight illumination period based on feedback from liquid crystal transition timing and vertical synchronization signals. This dynamic adjustment ensures the illumination period is optimized for visibility while avoiding overlap with liquid crystal transition periods that would cause ghost and leading edge phenomena.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9959814B2Display device and display method

Publication Date: 2018.05.01 EIZO CORP

AI summary

Provided is a display device and display method that can improve the moving image display performance. A display device includes a display panel and a backlight for the display panel. The display device also includes control means configured to output a control signal for controlling illumination and extinction of the backlight, to the backlight in synchronization with start of update of a frame on the display panel and update means configured to update a frame in each predetermined period in order to change one image displayed on a screen of the display panel. The control means outputs a control signal for controlling the backlight so that the backlight starts to illuminate after the update means starts to update one frame and ends illumination at the time point when the update means starts to update a frame subsequent to the one frame or after the time point.