Pupil-Divided Focus Detection Pixels for Low Luminance Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image capturing apparatuses face challenges in achieving accurate focus detection due to low luminance corresponding to focus detection portions, making it difficult to reliably detect object luminance distributions.
Innovation Solution
An image capturing apparatus with an image sensor featuring pupil-divided focus detection portions, where first and second focus detection pixels are used to generate composite and coupled signals, allowing for the calculation of defocus amounts in the image forming optical system, thereby improving focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pupil-divided focus detection pixels are used, then phase-difference focus detection capability is improved, but luminance corresponding to focus detection portions decreases
Solution Approach 1:
Each focus detection pixel is divided into multiple pupil-divided light receiving portions (e.g., left and right portions). This segmentation allows each portion to receive light from a specific pupil region, enabling phase-difference focus detection while maintaining sufficient luminance through signal composition across multiple pixels.
Solution Approach 2:
Signals from multiple focus detection pixels with the same pupil division are composited (added together) to generate a single focus detection signal. This merging process increases the effective luminance and signal-to-noise ratio, compensating for the reduced luminance in individual pupil-divided portions.
2Measurement precision
If focus detection pixels are arranged between image sensing pixels, then phase-difference detection is enabled, but image sensing pixels are reduced at those positions
Solution Approach 1:
The focus detection pixels serve dual purposes: they perform phase-difference focus detection through their pupil-divided light receiving portions, and their composited signals can be used to reconstruct image information through interpolation. This multi-functionality reduces the impact of having fewer dedicated image sensing pixels.
Solution Approach 2:
Image information at positions where focus detection pixels are arranged is generated by interpolating from peripheral image sensing pixels. This copying approach allows the system to recover image data without requiring dedicated image sensing pixels at every position.
3Device complexity
If contrast detection method is used, then image sensor can serve as focus detection sensor, but high-speed focus adjustment is not achieved
Solution Approach 1:
The patent replaces the mechanical hill-climbing approach of contrast detection with a computational phase-difference detection method. By using pupil-divided pixels and calculating defocus amounts directly from signal differences, the system eliminates the need for iterative mechanical adjustments, achieving high-speed focus adjustment while maintaining sensor integration.
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 enhances focus detection capability and accuracy by effectively utilizing composite and coupled signals from pupil-divided focus detection pixels, even when luminance is low, ensuring reliable detection of object luminance distributions.
Implementation Method 1
an image sensor having a plurality of pupil-divided focus detection portions each made up of a first focus detection pixel and second focus detection pixel
Data Source
AI summary
An image capturing apparatus includes an image sensor, composition unit, coupling unit, and arithmetic unit. The image sensor has a plurality of pupil-divided focus detection portions each formed from a first focus detection pixel and second focus detection pixel. The composition unit composites signals output from the first focus detection pixels to obtain a first composite signal, and composites signals output from the second focus detection pixels to obtain a second composite signal in each of sections assigned to the image sensor to include a plurality of focus detection portions. The coupling unit couples first composite signals to obtain a first coupled signal, and couples second composite signals to obtain a second coupled signal in the plurality of sections. The arithmetic unit calculates the defocus amount of an image forming optical system on the basis of the first and second coupled signals.