Flicker Artifact Reduction in Rolling Shutter Cameras

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Solution Overview

Problem

Light flicker caused by alternating current power frequency results in noticeable artifacts in captured images, particularly in rolling shutter cameras, where exposure times not set to integer multiples of the power frequency period lead to constrained exposure times and noticeable flicker artifacts in video frames.

Innovation Solution

A method to determine the power frequency and magnitude and phase of flicker fluctuations in ambient light, allowing for adjustment of images to reduce or remove flicker artifacts without limiting exposure time to integer multiples of the power frequency period, using an image processor with flicker reduction logic to process images and adjust for flicker based on these determinations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If exposure time is set to integer multiples of the power frequency period, then flicker artifacts are reduced, but exposure time flexibility is lost

Engineering Contradiction:

Improveflicker artifactsVSAvoidexposure time flexibility

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent applies preliminary action by estimating the flicker magnitude and phase before adjusting the image. The system performs flicker analysis and calculates correction parameters in advance, then uses these pre-computed values to remove flicker artifacts from the captured image, allowing flexible exposure times without being constrained to integer multiples of the power frequency period

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes parameters by estimating the flicker magnitude and phase from the captured image and using these estimated parameters to adjust and remove flicker artifacts. This approach transforms the fixed exposure time constraint into a flexible parameter that can be adjusted while still achieving flicker reduction through post-processing

Inventive Principle:

Principle #35Parameter changes

2Speed

If exposure time is reduced below 1/(2f) period, then capture speed increases, but flicker artifacts become more noticeable

Engineering Contradiction:

Improvecapture speedVSAvoidflicker artifacts

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful flicker effect into a beneficial estimation opportunity. By analyzing the flicker pattern in the captured image, the system estimates the magnitude and phase of the flicker, then uses this information to remove artifacts. This allows the use of short exposure times for high-speed capture while still achieving flicker reduction through the estimation and correction process

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-affected harmful factors

If conventional flicker reduction methods are used, then flicker artifacts are reduced, but additional processing time is required

Engineering Contradiction:

Improveflicker artifactsVSAvoidprocessing time

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The patent applies self-service by having the captured image itself provide the information needed for flicker correction. The system estimates flicker magnitude and phase directly from the captured image data, then uses this self-derived information to remove artifacts. This eliminates the need for separate reference measurements or additional processing steps, reducing overall processing time

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS7561190B2Method and system to reduce flicker artifacts in captured images

Publication Date: 2009.07.14 IMAGINATION TECH LTD

AI summary

In one embodiment, a method for controlling artifacts in an image due to a presence of flicker in ambient light is provided. The method comprises determining a power frequency for the ambient light; determining a magnitude and phase of flicker fluctuation in the image due to the flicker; and adjusting the image for the flicker fluctuation based on the power frequency, magnitude, and phase.