Auto Focus Area Determination Using Face Size in Digital Images
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Solution Overview
Problem
Digital image processing devices face accuracy issues with auto focusing due to the inclusion of background high-frequency components and face shape information, leading to back-focusing when the face area detection includes background or face shape details.
Innovation Solution
A method and apparatus that dynamically determine the auto focus area based on the size information of a face in a digital image processing device, where the processor detects a face area, determines the focus area, and sets focus accordingly, using pre-set reference values for size and ratio criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the AF function sets focus based on the face area detected through Face Detection, then the auto focusing function operates automatically without user operation, but the accuracy of AF is reduced due to back-focusing caused by background high frequency information or face shape information in the detected face area
Solution Approach 1:
The patent segments the detected face area into multiple sub-regions and selectively determines focus areas based on specific criteria. Instead of using the entire face area for focus determination, the system divides it and identifies sub-regions that meet predetermined conditions (such as excluding regions with high frequency components from background or face shape information), thereby resolving the contradiction between automatic operation and focus accuracy.
2Area of stationary object
If the face area detected through FD function includes background or face shape information, then the face detection covers the complete facial region, but back-focusing occurs due to high frequency information in the included areas
Solution Approach 1:
The patent applies local quality by treating different sub-regions of the face area differently. Instead of uniformly using the entire face area for focus determination, the system evaluates each sub-region individually and selects only those sub-regions that meet predetermined conditions for focus area determination. This allows the system to maintain comprehensive face area coverage for detection while excluding problematic local regions that cause back-focusing.
Data Source
AI summary
Various embodiments of the present disclosure provide a method and apparatus for dynamically determining an auto focusing (AF) area according to a size information of a face in a digital image processing device. An embodiment of the disclosure provides a digital image processing device including a camera and a processor configured to detect a face area in a preview image obtained by the camera, obtain a size of the face area, determine a focus area based on the size of the face area, and set focus based on the focus area.