Dynamic Line Addition for Focus Detection Noise Reduction
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Solution Overview
Problem
Existing imaging apparatuses face challenges in accurately performing focus detection while minimizing noise in the image signal, as exposure setting values often compromise either focus detection or image resolution, particularly in low-light conditions and when the exposure setting is inappropriate for focus detection.
Innovation Solution
An imaging apparatus with a focus detection unit using phase difference detection, an addition unit for combining pixel outputs, and a defocus amount calculation unit, where the line addition range in the focus detection area is dynamically controlled based on exposure settings and shooting conditions to optimize focus detection accuracy and maintain vertical resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If line addition processing is performed to reduce noise in focus detection, then focus detection accuracy is improved, but vertical resolution of the photographic subject deteriorates
Solution Approach 1:
The patent applies local quality by performing line addition processing selectively only in the focus detection area rather than across the entire image sensor output. The addition unit adds lines within the bounded focus detection area to reduce noise for phase difference detection, while the imaging unit preserves the original high-resolution data for the photographic subject. This localized application of noise reduction maintains vertical resolution in the main image while improving focus detection accuracy.
2Manufacturing precision
If exposure setting value is optimized for imaging, then image quality is improved, but focus detection may fail due to inappropriate exposure settings
Solution Approach 1:
The patent segments the image sensor output into distinct focus detection area and imaging area. The focus detection unit processes only the focus detection area through phase difference detection, while the imaging unit processes the imaging area for final image output. This segmentation allows independent optimization of processing parameters for each function, enabling focus detection to use noise-reduced processed data while imaging maintains high resolution, thus ensuring both focus detection reliability and image quality.
3Device complexity
If the image sensor is used for both focus detection and imaging, then device complexity is reduced, but exposure setting control becomes difficult
Solution Approach 1:
The patent implements dynamic control of the addition range setting unit based on shooting conditions. The addition range is adjusted according to the F value (aperture setting) and other shooting parameters, allowing the system to adaptively optimize the balance between noise reduction and resolution preservation. This dynamic adjustment simplifies operation by automatically adapting exposure and processing settings for dual-purpose use of the image sensor without requiring manual configuration.
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 highly accurate focus detection with reduced noise in the image signal, preventing deterioration of vertical resolution by adjusting the line addition range according to exposure settings and lens diaphragm size, thereby improving focus detection precision.
Implementation Method 1
an image sensor including a plurality of pixels each having a photoelectric conversion portion
Data Source
AI summary
An imaging apparatus performs a focus detecting operation with an image sensor including a photoelectric conversion portion that has a pupil-dividing function. The imaging apparatus increases a line addition number according to a target exposure value corresponding to a pixel dynamic range that is variable depending on an exposure setting value. Thus, the imaging apparatus can reduce the amount of noise and can suppress the dispersion of focus detection result. Further, the imaging apparatus changes the line addition number according to a lens diaphragm aperture size, a defocus amount, or a pixel signal reading mode. Thus, the imaging apparatus can secure the resolution in the vertical direction and can prevent the detection accuracy from deteriorating even in a case where a photographic subject is obliquely positioned in a focus detection area.