AMOLED Display Refresh Rate Control for Ghost Image Mitigation

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Solution Overview

Problem

Displays operating at low refresh rates experience poor image transitions due to the hysteresis effect of thin-film transistors, leading to noticeable 'ghost images' when switching between images, which can be distracting for users.

Innovation Solution

Implementing a display system that temporarily increases the refresh rate to a higher threshold rate for the initial frames of a new image and then reverts to the lower power-saving rate, allowing sufficient frames to render the image with intended luminance values, thereby mitigating the hysteresis effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the display operates at a low refresh rate to save power, then power consumption is reduced, but image transitions become poor and ghost images appear

Engineering Contradiction:

Improvepower consumptionVSAvoidimage transition quality

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The display driver dynamically adjusts the refresh rate based on the type of content being displayed. When a new image is detected, the refresh rate is temporarily increased to a high refresh rate for initial frames, then transitions to a low refresh rate for subsequent frames, optimizing both power consumption and image quality at different times

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the refresh rate parameter from a fixed low value to a variable value that switches between high and low based on frame conditions. This parameter change allows the display to adapt to different display scenarios, reducing ghost images during transitions while maintaining power efficiency during stable displays

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the display uses a high refresh rate to improve image transitions, then ghost images are reduced, but power consumption increases

Engineering Contradiction:

Improveimage transition qualityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The display of each frame is segmented into different refresh rate phases: initial frames are displayed at high refresh rate to establish proper luminance values, while subsequent frames use low refresh rate. This segmentation allows the system to apply high refresh rate only when necessary, reducing overall power consumption

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of maintaining high refresh rate for all frames, the system applies high refresh rate partially - only for the initial frames of each new image - which is sufficient to prevent ghost images without the continuous power cost of high refresh rate operation

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS12148382B2Image change sequence to prevent optical artifacts in low refresh rate AMOLED displays

Publication Date: 2024.11.19 GOOGLE LLC

AI summary

A first image is rendered on an active area of an OLED display panel with a first refresh rate that is below a threshold refresh rate and, subsequent to rendering the first image with the first refresh rate, a second image that is different from the first image is rendered on the active area, where the rendering of the second image includes rendering a number of initial frames of the second image at a second refresh rate that is at or above the threshold refresh rate. After rendering the number of initial frames of the second image at the second refresh rate, additional frames of the second image on the active area are rendered with the first refresh rate, where the number of initial frames is greater than 1.