Focus Detection Device Adaptive Filter Switching
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Solution Overview
Problem
Existing focus detection devices using phase difference AF methods face challenges in achieving rapid focus detection, especially with low contrast subjects or moving subjects, as they require significant time for data accumulation and may fail to detect focus in high-speed or low-contrast scenarios.
Innovation Solution
The focus detection device employs a combination of differential filters with different frequency bands, spatial addition of pixel data, and adaptive adjustment of focus detection areas and exposure settings to enhance contrast and reliability, reducing the need for time-series data addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time series addition of focus detection pixel data is performed continuously until data level reaches threshold value, then focus detection reliability is improved, but focus detection time becomes excessively long
Solution Approach 1:
The patent changes the frequency band parameter of differential filters based on detected contrast values. When contrast is low, it switches to a lower frequency band filter to enhance detection capability without requiring extensive time series addition, thus resolving the contradiction between reliability and time consumption.
Solution Approach 2:
Instead of continuously adding time series data until threshold is reached, the patent performs partial addition based on contrast evaluation. It determines whether time series addition is necessary by evaluating contrast values, and only performs addition when needed, reducing unnecessary processing time while maintaining detection reliability.
2Object-affected harmful factors
If differential filter for high frequency band is used, then noise reduction is improved, but focus detection capability deteriorates in low contrast scenarios
Solution Approach 1:
The patent dynamically switches between high frequency band and low frequency band differential filters based on real-time contrast value evaluation. This dynamic adaptation allows the system to use high frequency filtering for noise reduction when contrast is sufficient, and switch to low frequency filtering when contrast is low, maintaining both noise reduction and detection capability.
Solution Approach 2:
The frequency band parameter of the differential filter is changed based on contrast conditions. The system selects appropriate filter characteristics (high frequency for noise reduction, low frequency for low contrast enhancement) to optimize both noise filtering and focus detection capability under different imaging conditions.
3Reliability
If focus detection area is widened to improve detection capability, then focus detection reliability is improved, but processing complexity increases
Solution Approach 1:
The patent segments the focus detection process into multiple stages: contrast evaluation, filter selection, and focus detection execution. By dividing the detection area into different processing paths based on contrast values, it manages complexity through structured segmentation rather than uniform processing of the entire area.
Solution Approach 2:
The system performs focus detection on partial areas based on contrast evaluation. When contrast is sufficient, it uses standard detection areas; when contrast is low, it selectively expands detection areas only where needed, rather than always processing the entire area, thus managing complexity efficiently.
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 reduces the time required for focus detection, improves precision, and enables focus detection in scenarios where traditional methods fail, particularly with low contrast or moving subjects by increasing the contrast value of focus detection pixel data.
Implementation Method 1
an image sensor that subjects light flux from an imaging optical system to photoelectric conversion using a plurality of pixels, and outputs an imaging signal
Data Source
AI summary
A focus detection device, comprising an image sensor that outputs an imaging signal, and one or more processors constructed in hardware, the processor performing focus detection using a phase difference detection method based on the imaging signal, wherein the focus detection performs first focus detection based on a signal that has been obtained by subjecting the imaging signal to first filter processing, performs second focus detection based on a signal that has been obtained by subjecting the imaging signal to second filter processing if reliability of the first focus detection is lower than a specified value, and if it is determined that reliability of the second focus detection is lower than a specified value executes third focus detection based on a picture signal that has been obtained by adding a plurality of imaging signals that have been obtained at different times.