Dynamic Focus Window Compensation for Hand Jitter

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Solution Overview

Problem

Existing auto-focusing methods in digital cameras may fail to accurately determine the optimal focus position due to camera movement, shaking, or jittering during the focusing process, leading to inconsistent image areas being captured and potentially incorrect lens positioning.

Innovation Solution

The method involves obtaining multiple image frames with dynamically adjusted focus windows using motion vectors to ensure that each frame captures the same target image portion, identifying the frame with the most contrast, and focusing the camera using the corresponding lens position, thereby mitigating the effects of camera movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If continuous image capture is performed during auto-focusing, then contrast levels can be continuously monitored, but camera movement and hand jitter cause the focus window to capture different image areas, leading to inaccurate focus determination

Engineering Contradiction:

Improvefocus determination accuracyVSAvoidimage area consistency

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The system performs preliminary actions by capturing multiple image frames before final focus determination. These pre-captured frames are used to calculate motion vectors that predict camera movement, allowing the system to compensate for jitter and maintain consistent focus window positioning throughout the auto-focusing process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by continuously monitoring contrast levels and using this information to adjust the focus window position based on calculated motion vectors. The feedback loop ensures that even when camera movement occurs, the system can correct the focus window positioning to maintain accurate focus determination

Inventive Principle:

Principle #23Feedback

2Device complexity

If the focus window remains fixed during auto-focusing, then the measurement process is simple, but camera movement causes the window to capture different image portions, preventing optimal focus position identification

Engineering Contradiction:

Improvefocus window managementVSAvoidfocus position identification

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The system transitions from a static focus window to a dynamic one that automatically adjusts its position based on calculated motion vectors. This dynamic adjustment ensures the focus window continues to capture the same image portion even when the camera moves during auto-focusing, significantly improving focus position identification reliability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system replaces mechanical adjustment of the focus window with computational methods. Instead of physically moving the focus window, the system calculates motion vectors from image frames and uses these vectors to computationally adjust the focus window position, achieving the same effect with simpler, more reliable mechanisms

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If multiple image frames are captured and processed, then motion compensation can be performed, but the processing time and computational load increase

Engineering Contradiction:

Improvemotion compensation accuracyVSAvoidauto-focusing duration

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system captures more image frames than strictly necessary for minimal motion compensation. This excessive sampling provides redundant information that improves the accuracy of motion vector calculation, allowing for more precise focus window adjustment and better overall focus determination

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system changes the parameter of focus window position dynamically based on motion vectors calculated from multiple image frames. By adjusting the focus window position parameter in response to detected camera movement, the system maintains measurement precision while managing processing time through efficient motion compensation algorithms

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7634187B2Dynamic auto-focus window selection that compensates for hand jitter

Publication Date: 2009.12.15 QUALCOMM INC

AI summary

The invention relates to methods and devices for mitigating and/or minimizing effects of hand jitter or shaking during an auto-focusing process of an image-capturing device. In order to more accurately focus a lens for capturing a digital image, the lens is moved between a minimum and maximum position (along an axis) while capturing sample image frames using a focus window at various lens positions. Improved auto-focusing is achieved by dynamically adjusting the relative position of the focus window for each image frame to cover substantially the same image portion of the target image. By adjusting the focus window for each image frame to cover substantially the same image portion of the target image, variations from shaking may be minimized, thereby improving auto-focusing.