Autofocus Lens Step Segmentation for Precision and Speed
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Solution Overview
Problem
Conventional autofocus methods, such as hill climbing, are time-consuming and may fail to capture a sharp image in a timely manner due to the need to move the lens through multiple steps to find the optimal focal position, leading to delays in image capture.
Innovation Solution
An autofocus method and device that divide lens steps into areas based on capturing mode settings, using a combination of first and second area decisions with threshold values and various search methods to quickly identify the lens step with the highest focal value, allowing for precise and fast autofocus adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lens is moved through multiple steps to find the optimal focal position using hill climbing method, then the focus precision is improved, but the autofocus time increases
Solution Approach 1:
The patent divides the lens movement range into multiple search areas (first search area, second search area, third search area) with different search strategies. The first search area uses a coarse search with larger step sizes, the second search area uses a medium search with moderate step sizes, and the third search area uses a fine search with small step sizes. This segmentation allows the system to quickly locate the general focus region and then progressively refine the focus precision without unnecessarily scanning the entire lens range, thereby reducing total autofocus time while maintaining focus precision.
Solution Approach 2:
The patent implements dynamic adjustment of search step sizes based on the current search area and focal value changes. In earlier search areas, larger step sizes are used to cover more ground quickly, while in later search areas, smaller step sizes are used to achieve precise focus. The search algorithm dynamically adapts the search strategy based on the detected focal value trends, switching between different search modes (coarse search, medium search, fine search) to optimize the balance between speed and precision throughout the autofocus process.
2Manufacturing precision
If the number of lens steps is increased to achieve better focus, then the image quality is improved, but the autofocus execution time increases
Solution Approach 1:
The patent performs preliminary actions by first identifying the approximate focus region using a coarse search with larger step sizes before committing to a full precision search. The system evaluates focal values at multiple preview points to determine which area is most likely to contain the optimal focus position. This preliminary assessment allows the system to concentrate subsequent search efforts only in the most promising regions, avoiding unnecessary searches in areas unlikely to yield the optimal focus, thereby improving both image quality and execution speed.
Solution Approach 2:
The patent applies different search qualities to different regions of the lens movement range. Instead of uniformly applying high-precision searching across the entire range, the system identifies specific local areas (first search area, second search area, third search area) and applies appropriately tailored search strategies to each. The fine search with small step sizes is applied only in the final search area where precise focus is critical, while coarser searches are used in earlier areas. This local differentiation of search quality optimizes the balance between image quality and search efficiency.
Data Source
AI summary
The present invention relates to an autofocus device, and to a method therefor, whereby the delay necessary for auto focus can be reduced according to circumstances and a clear image of a subject can be obtained in a timely fashion by suitably adjusting the precision and speed of autofocus, as auto focus settings are differently applied in accordance with the photography mode when autofocus is being implemented in a camera. To this end, the autofocus method according to an embodiment of the present invention comprises: a step of inputting a photography mode for a subject; a step of deciding which auto focus setting corresponds to the input photography mode; a step of determining the lens step with the highest focal value among lens steps set according to the distance of the subject and the lens on the basis of the auto focus setting decided upon; and a step of moving the lens to the determined lens step.