Auto-Focus Sensor Exposure Control for Wide Dynamic Range
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Solution Overview
Problem
Conventional autofocus systems in digital cameras face challenges in dynamically adjusting exposure times of focus state detection sensor elements (FDels) based on scene content, leading to potential saturation and suboptimal focus state information, especially in scenes with varying brightness.
Innovation Solution
The method involves dynamically setting the exposure time of FDels to either long-exposure or short-exposure mode based on the detected brightness of a selected region of interest, allowing for adaptive auto-focusing by switching between modes to prevent saturation and optimize focus state information capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the exposure time of focus state detection sensor elements (FDels) is fixed, then the device complexity is reduced, but the measurement precision of focus state information deteriorates in scenes with varying brightness
Solution Approach 1:
The patent implements dynamic exposure time adjustment for FDels based on scene brightness conditions. The system switches between long-exposure mode and short-exposure mode depending on whether the scene is bright or dark, making the exposure time a variable parameter rather than a fixed value. This dynamic adaptation resolves the contradiction by allowing the system to maintain simple operation in uniform conditions while achieving high measurement precision in varying brightness scenarios.
Solution Approach 2:
The patent changes the exposure time parameter of FDels according to scene brightness. By adjusting this critical parameter based on detected light conditions, the system optimizes focus state information capture without requiring complex structural modifications. The parameter change approach allows the same hardware to adapt to different lighting conditions, resolving the precision-complexity tradeoff.
2Measurement precision
If long-exposure mode is used for FDels, then the focus state information capture in dark regions is improved, but saturation occurs in bright regions leading to loss of information
Solution Approach 1:
The system dynamically selects between long-exposure and short-exposure modes based on scene brightness detection. In dark regions, long-exposure mode is activated to improve signal capture, while in bright regions, short-exposure mode prevents saturation. This dynamic mode switching resolves the information loss problem by adapting exposure characteristics to local scene conditions.
Solution Approach 2:
The patent applies different exposure time characteristics to different regions of the scene. By detecting scene brightness and selectively applying long-exposure or short-exposure modes, the system creates locally optimized capture conditions. This local quality approach ensures that each region receives the appropriate exposure treatment, preventing information loss while maintaining measurement precision.
3Loss of information
If short-exposure mode is used for FDels, then saturation in bright regions is prevented, but the focus state information capture in dark regions deteriorates
Solution Approach 1:
The system dynamically adjusts exposure mode based on scene conditions. When bright regions are detected, short-exposure mode is activated to prevent saturation. When dark regions dominate, long-exposure mode is selected to improve signal capture. This dynamic adaptation resolves the contradiction by allowing the system to optimize for the dominant scene condition while minimizing the adverse effects on the other condition.
Solution Approach 2:
The patent changes the exposure time parameter based on scene brightness detection. By adjusting this parameter dynamically, the system prevents saturation in bright conditions while maintaining adequate signal capture in dark conditions. The parameter change strategy allows the system to adapt to varying scene characteristics without hardware modifications.
4Adaptability or versatility
If adaptive exposure time adjustment is implemented for FDels, then the wide dynamic range performance is improved, but the device complexity increases
Solution Approach 1:
The patent achieves wide dynamic range performance by changing the exposure time parameter based on scene brightness. This parameter-based approach provides adaptability without requiring complex structural modifications. The system uses simple brightness detection and conditional parameter adjustment to achieve versatile performance across different lighting conditions.
Solution Approach 2:
The patent achieves wide dynamic range performance by changing the exposure time parameter based on scene brightness. This parameter-based approach provides adaptability without requiring complex structural modifications. The system uses simple brightness detection and conditional parameter adjustment to achieve versatile performance across different lighting conditions.
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 enables the capture of focus state information with a wide dynamic range, improving autofocus performance by adjusting exposure times according to scene conditions, thereby enhancing image focus across bright and dark regions.
Implementation Method 1
Each of the picture elements and each of the focus state detecting (sensing) elements (FDels) includes a photodiode
Data Source
AI summary
A method and apparatus performing scene-adaptive auto-focusing for image capture with a variable-focus lens. The array of color pixels includes a array of half-covered light sensors to obtain lens-focus state information. The exposure time of the plurality of partially-covered light sensors is dynamically selected as long-exposure or short-exposure, based upon a current measurement of a property (e.g., brightness, or color-specific brightness) of a selected region of interest within a scene to be captured by the array. Then, focus state information corresponding to the selected region of interest is obtained by capturing light from the selected region of interest with first and second partially-covered light sensors. The exposure time of the partially-covered light sensors can be changed based on whether the brightness is greater than a predetermined threshold value.