Hysteresis Gain Calculation for Image Flicker Suppression

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Solution Overview

Problem

Conventional auto white balance (AWB) processing for moving images results in flickering due to frame-by-frame changes in white balance gains, making the image difficult to view, and existing techniques do not effectively address this issue while reducing processing load and cost.

Innovation Solution

An image processing apparatus and method that calculates a hysteresis gain based on multiple frames, locks it during a specified period, and adjusts it using a correction hysteresis gain after unlocking, with a weight-based calculation to minimize flickering and adapt to changing light conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If white balance gain is calculated for each frame individually, then the white balance can adapt quickly to changing light conditions, but the color and brightness of the image change for each frame causing flickering

Engineering Contradiction:

Improvewhite balance adaptation speedVSAvoidimage color and brightness stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The system pre-calculates and stores the hysteresis gain Gh based on multiple previous frames before the current frame arrives. When processing the current frame, this pre-computed hysteresis gain is applied to suppress flickering, allowing the white balance to adapt to light changes while maintaining stability through advance preparation of correction values.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The hysteresis gain Gh serves as an intermediary between the rapidly changing scene white balance gains and the final applied white balance correction. It mediates the transition by smoothing out frame-to-frame variations while still responding to genuine light source changes, thus resolving the contradiction between adaptation speed and stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If WB gain is fixed without periodic AWB processing, then processing load is reduced, but the system cannot adapt to scene changes

Engineering Contradiction:

Improveprocessing load reductionVSAvoidscene change adaptation

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The system continuously monitors the scene by calculating white balance gains from incoming frames and uses this feedback to update the hysteresis gain. The feedback mechanism compares current frame statistics with historical data, enabling the system to adapt to scene changes while maintaining lower processing loads by only performing full AWB processing when necessary rather than every frame.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Instead of performing complete AWB processing every frame, the system uses periodic updates of the hysteresis gain based on accumulated frame statistics. This periodic action reduces processing load while still capturing scene changes over time, balancing computational efficiency with adaptability.

Inventive Principle:

Principle #19Periodic action

3Stability of the object's composition

If hysteresis gain is used to suppress flickering, then image stability improves, but the response to light source changes becomes slower

Engineering Contradiction:

Improveimage flicker suppressionVSAvoidlight source change response

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The hysteresis gain calculation dynamically adjusts its behavior based on the characteristics of incoming frames. When significant light source changes are detected through frame comparison, the system increases the weight of recent frames in the hysteresis calculation, enabling faster response. During stable conditions, it emphasizes historical data for smoother suppression, thus adapting the response speed dynamically to scene conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the parameters of the hysteresis gain calculation, specifically the weighting factors applied to different frames in the history, based on detected scene conditions. By adjusting these parameters dynamically, the system can switch between prioritizing stability (during normal conditions) and prioritizing response speed (during light source transitions), resolving the contradiction between suppression effectiveness and response agility.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10021362B2Image processing apparatus, non-transitory computer-readable medium storing computer program, and image processing method using hysteresis to calculate gain

Publication Date: 2018.07.10 OLYMPUS CORPORATION(JP)

AI summary

An image processing apparatus includes an AWB gain calculation section that calculates a WB gain Gs and a hysteresis gain Gh for every frame, a WB correction section that performs WB correction using Gh, a control section that causes the WB correction section to perform the WB correction using a fixed gain Gf during lock of white balance, and a gain adjustment section that weights and adds a WB gain Gs(n) and a correction hysteresis gain Gh′(n−1) to calculate a correction hysteresis gain Gh′(n) after unlock of the white balance, and the control section causes the WB correction section to perform WB correction for a frame n using Gh′(n).