Phase-Difference Focus Detection in Thinned-Out Image Sensors
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Solution Overview
Problem
Conventional image capturing apparatuses face challenges in detecting focus using phase-difference detection pixels, especially when pixel signals are thinned out for live view display, leading to loss of pixel data and flawed images.
Innovation Solution
An image capturing apparatus with an image sensor, focus detection pixels, readout means, and switching means that allows for focus detection using phase-difference detection even when pixel signals are thinned out, by selecting appropriate pairs of focus detection pixels and adjusting gain levels to maintain image signal continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel signals are thinned out for live view display, then display performance is improved, but focus detection capability deteriorates due to loss of pixel data
Solution Approach 1:
The image sensor is segmented into different pixel types: focus detection pixels (first and second types) and image forming pixels. This segmentation allows simultaneous optimization for both focus detection and image formation, resolving the contradiction by dedicating specific pixels to each function while allowing the system to operate in different modes.
Solution Approach 2:
The focus detection pixels serve multiple functions: they can be used for phase-difference focus detection when all pixels are read out, and their data can be interpolated to maintain image quality when thinning out occurs. This multi-functionality ensures focus detection capability is maintained regardless of thinning-out status.
2Measurement precision
If focus detection pixels are arranged in the image sensor, then focus detection precision is improved, but image continuity deteriorates due to data loss at pixel positions
Solution Approach 1:
Different regions of the image sensor have different qualities and functions. Focus detection pixels are strategically positioned to provide phase-difference information, while image forming pixels provide continuous image data. The interpolation process restores local quality by generating missing image data from neighboring pixels, maintaining overall image continuity.
Solution Approach 2:
Interpolation processing acts as an intermediary mechanism that bridges the gap created by focus detection pixels. By calculating pixel values at focus detection pixel positions based on neighboring image forming pixels, the interpolation process restores image continuity and eliminates the discontinuity caused by the presence of focus detection pixels.
3Measurement precision
If pairs of focus detection pixels are selected for phase-difference detection, then focus detection accuracy is improved, but adaptability deteriorates when thinning-out is applied
Solution Approach 1:
The system dynamically adapts its focus detection pixel selection based on the thinning-out status. When thinning-out is applied, the control unit selects different pairs of focus detection pixels compared to when all pixels are read out. This dynamic adaptation maintains focus detection accuracy across different operating conditions.
Solution Approach 2:
The system changes operational parameters (which specific focus detection pixel pairs are used) based on the thinning-out condition. By adjusting the selection of focus detection pixel pairs according to the readout mode, the system maintains focus detection accuracy while adapting to different display requirements.
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
Enables accurate focus detection in both thinning-out and non-thinning-out scenarios, ensuring continuous image quality and maintaining focus detection capabilities during live view display.
Implementation Method 1
an image sensor including a plurality of image forming pixels which photoelectrically convert an object image formed via an imaging lens to generate an image signal, and a plurality of focus detection pixels which are discretely arranged among the plurality of image forming pixels
Data Source
AI summary
An image capturing apparatus comprising an image sensor including image forming pixels each of which generates a signal for image generation, and focus detection pixels each of which generates a signal for phase difference detection, readout means for reading out the signal of each pixel of the image sensor, focus detection means for detecting a focus by a phase-difference detection method using the signals for phase difference detection from the focus detection pixels, and switching means for switching a combination of the focus detection pixels to be used for focus detection by the focus detection means between a case in which the readout means reads out the signals of the pixels of the image sensor after thinning-out and a case in which the readout means reads out the signals of the pixels of the image sensor without thinning-out.