Focus Detection Pixel Layout Switching for Phase Error Reduction
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Solution Overview
Problem
Existing image sensor technologies face challenges in reducing focus detection errors due to focus detection pixels receiving light fluxes from different portions of a subject image, leading to phase shift inconsistencies and increased error probabilities.
Innovation Solution
An image-capturing apparatus with an image sensor that arranges pairs of focus detection pixels at a predetermined pitch, where the layouts of the first and second focus detection pixels are switched in adjacent pairs perpendicular to the phase difference detection direction, allowing detection of focusing status using phase differences between image waveforms from these pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus detection pixels are arranged with light-receiving units divided in two, then phase difference detection function is achieved, but light-receiving efficiency lowers resulting in narrower dynamic range and lower S/N ratio
Solution Approach 1:
The pixel array is segmented into three distinct types: first focus detection pixels with first microlenses, second focus detection pixels with second microlenses, and image capturing pixels with third microlenses. This segmentation allows each pixel type to have optimized light-receiving characteristics for its specific function, resolving the contradiction between achieving phase difference detection and maintaining light-receiving efficiency.
Solution Approach 2:
Different microlenses are designed with different local qualities: the first and second microlenses have different focal lengths or aperture diameters compared to the third microlenses. This local differentiation optimizes light-receiving efficiency for both focus detection and image capturing functions simultaneously.
2Measurement precision
If pairs of focus detection pixels are spaced apart to detect phase difference, then focus detection function is achieved, but focus detection error occurs at higher probability due to receiving light fluxes from different portions
Solution Approach 1:
The first and second focus detection pixels are designed as copies with identical structures and positions, but with different microlens characteristics. This copying approach ensures that both pixels receive light fluxes from the same portions of the subject image, eliminating the error caused by receiving light from different portions while maintaining phase difference detection capability.
3Measurement precision
If focus detection pixels are arranged at predetermined pitch, then phase difference detection is enabled, but image information corresponds to defective pixels requiring interpolation
Solution Approach 1:
The image-capturing apparatus is designed with multi-functionality: it can perform both phase difference detection using the first and second focus detection pixels, and capture high-quality images using all pixels including the third image capturing pixels. The different microlens types enable each pixel to contribute to its designated function without requiring interpolation, as the focus detection pixels are now valid light-receiving pixels with optimized 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 reduces focus detection errors by ensuring consistent phase shifts and improving the accuracy of focus detection across different subject patterns, enhancing the reliability of image capture.
Implementation Method 1
a plurality of pixels which photoelectrically convert a subject image
Implementation Method 2
detection means for detecting, based on a phase difference between a first image waveform and a second image waveform obtained from the first focus detection pixels and the second focus detection pixels, respectively, a focusing status of the lens
Data Source
AI summary
In an image sensor having a plurality of pixels which photoelectrically convert a subject image, a plurality of pairs of focus detection pixels including first focus detection pixels (SHA) and second focus detection pixels (SHB) are arranged while being distributed. The layouts of the first focus detection pixel (SHA) and the second focus detection pixel (SHB) are switched in pairs of focus detection pixels adjacent in the focus detection direction. Focus detection is performed using image waveforms obtained from the first focus detection pixel (SHA) and the second focus detection pixel (SHB) whose layouts are switched. This reduces focus detection errors generated when the pixels included in the pairs of focus detection pixels receive light fluxes from different portions of the subject.