Adaptive A/D Conversion for Phase-Difference Autofocus
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Solution Overview
Problem
Existing image capturing apparatuses using the imaging plane phase difference method face challenges in achieving high-speed pixel signal readout while maintaining focus detection accuracy, as lowering A/D conversion resolution to speed up the process compromises defocus amount detection accuracy.
Innovation Solution
An image capturing apparatus with a pixel array, a readout unit, and an A/D conversion unit that switches between two resolution modes based on the pixel signal, allowing for high-speed readout while maintaining accurate focus detection by using a first mode for lower resolution and a second mode for higher resolution A/D conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If A/D conversion resolution is lowered to speed up the conversion process, then readout speed is improved, but defocus amount detection accuracy deteriorates
Solution Approach 1:
The A/D conversion unit dynamically switches between first resolution mode and second resolution mode based on the pixel signal characteristics. When the pixel signal indicates sufficient light intensity, the unit operates in first resolution mode for high-speed conversion. When the pixel signal indicates insufficient light intensity, the unit switches to second resolution mode to maintain detection accuracy, thus adaptively resolving the speed-accuracy contradiction
Solution Approach 2:
The invention changes the resolution parameter of A/D conversion based on imaging conditions. By adjusting the resolution parameter dynamically - using lower resolution (first resolution) when conditions permit and higher resolution (second resolution) when needed - the system optimizes both readout speed and detection accuracy according to actual signal characteristics
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 high-speed pixel signal readout while preserving focus detection accuracy, improving the balance between readout speed and detection precision.
Implementation Method 1
photoelectric conversion is performed on a pair of subject images formed by light beams that have passed through two different areas (hereinafter, referred to as pupil areas) in an exit pupil of an imaging optical system, using a plurality of pixels for focus detection provided on an image sensor
Data Source
AI summary
An image capturing apparatus is provided with a pixel array that has a plurality of image forming pixels and a plurality of focus detection pixels, a readout unit that reads out a pixel signal from the pixel array, an A/D conversion unit that has a first mode for A/D converting the pixel signal read out by the readout unit with a first resolution and a second mode for A/D converting the pixel signal read out by the readout unit with a second resolution that is higher than the first resolution, and a control unit that switches between the first mode and the second mode in accordance with the pixel signal read out from the pixel array.