Mobile Camera Lens Travel Paths for Accurate Face Focusing
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Solution Overview
Problem
Existing mobile terminals struggle to accurately focus on faces at distances of two to three meters due to small detected face regions, leading to blurred images as the lens moves to the infinity focus position without determining the extreme focus point, resulting in unclear photographs.
Innovation Solution
A method involving a preset travel path for the lens that starts at a first position and ends at a second position close to the far focus position, avoiding direct movement to infinity, with the lens moving along this path to ensure clear focusing on the face region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lens moves to the far focus position (infinity) during focusing, then the focusing range is extended, but the face region becomes too small to achieve accurate focus when the object is 2-3 meters away
Solution Approach 1:
The patent changes the lens travel endpoint parameter from infinity (far focus position) to a finite distance (second position close to far focus position). This parameter modification allows the face region to maintain sufficient size in the detection area while still achieving focus at 2-3 meter distances, resolving the contradiction between focus range and face region size.
Solution Approach 2:
The patent dynamically adjusts the lens travel path based on detected face region characteristics. When face region area is small, the system modifies the focusing behavior by limiting the lens movement to a preset travel path that ends at the second position rather than continuing to infinity, thereby adapting the focusing process to maintain optimal face region visibility.
2Reliability
If the lens travels to the far focus position, then the infinity focus is achieved, but the focusing time increases and the extreme focus point cannot be determined
Solution Approach 1:
The patent pre-calculates and stores a preset travel path that ends at the second position (close to far focus position) rather than requiring the lens to travel all the way to infinity. This preliminary preparation of the travel path allows the system to achieve accurate focus at 2-3 meter distances without unnecessary extended travel, reducing focusing time while maintaining reliability.
Solution Approach 2:
The patent applies partial action by limiting the lens travel to only the necessary extent (to the second position) rather than performing the complete travel to infinity. This partial travel is sufficient to achieve the required focus accuracy for distant objects while avoiding the time loss associated with excessive lens movement.
3Area of stationary object
If the face region is small in the detection area, then the detected area is reduced, but the Focus Value calculation becomes flat without strong downward trend
Solution Approach 1:
The patent modifies the focus detection parameter by changing the lens endpoint from infinity to the second position. This parameter change ensures that the face region maintains adequate size in the detection area, producing a Focus Value curve with strong downward trend that enables precise determination of the extreme focus point, thereby resolving the contradiction between focus area size and detection precision.
Data Source
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AI summary
The present disclosure relates to a focusing control method and device, a computer storable medium and a mobile terminal, the method comprising: entering a photo-taking preview mode and identifying whether there is a face region in a preview window; acquiring a preset travel path of a lens matched with the face region when the area of an existing face region is less than a preset value, the start point of the preset travel path being a first position, the ending point thereof being a second position close to the far focus position, and the first position not coinciding with the second position; and according to the preset travel path, controlling a motor to drive the lens to move along an optical axis between the first position and the second position so as to complete focusing of the face region.