Adaptive Line Sensor Accumulation for Flicker Light Focus Detection
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Solution Overview
Problem
Conventional focus detection systems under flicker light sources face challenges in obtaining stable focus detection results due to varying light intensity, leading to unstable defocus distribution information and reduced accuracy in object positioning and size determination.
Innovation Solution
A focus detection apparatus with a determination unit to identify flicker light sources and a controller that adjusts the accumulation period of line sensors based on signal thresholds and maximum accumulation periods, ensuring optimal focus detection even under flicker light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If accumulation period is shortened to suppress increase in accumulation period in dark area, then productivity is improved, but measurement precision deteriorates because signal amount becomes small
Solution Approach 1:
The patent applies dynamics by making the accumulation period adjustable and adaptive rather than fixed. The control unit dynamically sets different accumulation periods for different line sensors based on their signal amounts and flicker conditions, allowing the system to optimize between speed and accuracy for each sensor individually.
Solution Approach 2:
The patent changes the accumulation period parameter based on signal amount and flicker detection results. By modifying this key parameter adaptively, the system can extend accumulation time for sensors with weak signals to improve precision while maintaining short accumulation times for sensors with strong signals to preserve productivity.
2Measurement precision
If accumulation period is extended to obtain sufficient signal amount, then measurement precision is improved, but productivity deteriorates because overall focus detection period increases
Solution Approach 1:
The patent segments the focus detection process by independently controlling accumulation periods for different line sensors rather than using a single uniform period. This allows each sensor to have optimized accumulation time based on its specific conditions, resolving the contradiction between precision and productivity at the system level.
Solution Approach 2:
The patent applies local quality by assigning different accumulation periods to different line sensors based on their local conditions (signal amount, flicker presence). Sensors in dark areas with weak signals receive extended accumulation periods, while sensors in bright areas maintain shorter periods, optimizing both precision and productivity locally.
3Productivity
If accumulation timing is set to peak light intensity, then productivity is improved by obtaining sufficient signal quickly, but measurement precision deteriorates due to unstable defocus distribution information under flicker
Solution Approach 1:
The patent uses feedback by detecting flicker in the light source and using this information to adjust accumulation timing and periods. The control unit monitors light intensity variations and modifies accumulation strategies accordingly, ensuring stable defocus distribution information while maintaining productivity.
Solution Approach 2:
The patent performs preliminary action by detecting the presence of flicker light sources before conducting focus detection. This advance detection allows the system to pre-adjust accumulation periods and timing for all line sensors, preventing instability in defocus distribution information while maintaining efficient signal acquisition.
4Productivity
If maximum accumulation period is set short to reduce overall detection time, then productivity is improved, but measurement precision deteriorates because focus detection cannot be performed in low contrast areas
Solution Approach 1:
The patent makes the maximum accumulation period dynamic and sensor-specific rather than a fixed system-wide parameter. The control unit adjusts each line sensor's accumulation period based on its signal amount and flicker conditions, allowing sensors in low contrast areas to use extended periods while maintaining short periods for other sensors, thus preserving overall productivity.
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
The solution enables stable and accurate focus detection by adjusting sensor accumulation periods, reducing the impact of flicker light sources and improving defocus distribution information, thus enhancing the accuracy of object positioning and size determination.
Implementation Method 1
line sensors corresponding to the AF frames 702 and 704 directly receive light from this flicker light source
Data Source
AI summary
A focus detection apparatus comprises: a determination unit that determines whether a flicker light source is included in focus detection areas; a plurality of sensors for focus detection that correspond to the focus detection areas, and accumulate electric charges corresponding to received light; and a controller that controls accumulation in the sensors. The controller monitors a signal that is based on electric charges accumulated in the sensors, and performs first control for stopping accumulation in a sensor in which the signal has exceeded a predetermined threshold value, and second control for stopping accumulation in a sensor which continues accumulation of electric charges when a maximum accumulation period has reached. The controller sets the maximum accumulation period based on a determination result by the determination unit and the accumulation period of a first sensor in which the first control is performed first.