Autofocus Control for Image Sensors During Video Capture
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Solution Overview
Problem
Conventional auto focus control methods for digital cameras, particularly those using contrast detection, are inefficient and take too long to achieve focus, especially when switching between still and moving picture pick-up modes.
Innovation Solution
The implementation of an image sensing apparatus with separate auto focus control units for still and moving picture pick-up, allowing for a narrower focus lens movement range during still picture pick-up, thereby reducing the time required for auto focus operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the focus lens is moved across the full movable range to ensure comprehensive focus coverage, then the reliability of focus acquisition is improved, but the time required for auto focus operation increases
Solution Approach 1:
The system performs preliminary actions by continuously executing moving picture pick-up processes that maintain focus lens movement within a limited range. This preliminary focus maintenance allows the focus lens to be positioned near the optimal focus point before still picture pick-up, eliminating the need for extensive lens movement and reducing auto focus operation time while ensuring reliable focus acquisition.
Solution Approach 2:
The system dynamically adjusts the focus lens movement range based on the pick-up mode. During moving picture pick-up, the lens moves within a limited range to maintain readiness. When still picture pick-up is requested, the system determines whether full-range movement is necessary based on current lens position and focus conditions, optimizing the balance between reliability and speed.
2Productivity
If separate auto focus control units are implemented for still and moving picture pick-up, then the productivity of focus operations is improved, but the device complexity increases
Solution Approach 1:
The auto focus control function is segmented into distinct control units: a first auto focus control unit for moving picture pick-up and a second auto focus control unit for still picture pick-up. Each unit is optimized for its specific function, allowing independent optimization of control strategies without interfering with the other mode, thereby improving overall productivity while maintaining manageable complexity through functional separation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly shortens the time needed for auto focus operations by limiting focus lens movement during still picture pick-up, enhancing the efficiency of the auto focus process.
Implementation Method 1
an image sensor which senses an object image which is incident through a focus lens
Data Source
AI summary
When the start of still picture AF operation is designated during moving picture pick-up/recording, the current position of an AF lens is acquired, and the AF lens is moved by X addresses from the lens position. The AF lens is moved to the Yth address in an opposite direction from the lens position to which the AF lens has been moved by X addresses, and an AF evaluation value is detected for each address. Whether the peak value of the AF evaluation value has been detected is determined. If so, whether the peak value is larger than the threshold is determined. If the peak value is determined larger, the AF lens is-moved to a lens position at which the peak value has been obtained. Hence, still picture AF operation can be performed within a short time during moving picture pick-up/recording.