Focus Detection Apparatus Saturated Pixel Handling
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Solution Overview
Problem
Existing focus detection methods using phase difference methods with image pickup elements suffer from reduced accuracy due to saturated pixels, which can result in erroneous focus shift calculations when correlation waveforms are calculated in regions including saturated pixels.
Innovation Solution
A focus detection apparatus that calculates correlation data between first and second pixels sharing a microlens, detects saturated pixels, and performs addition processing using correlation data from ranges with fewer saturated pixels to determine defocus amounts, thereby reducing the impact of saturated pixels on focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If correlation waveforms are calculated in regions including saturated pixels, then focus detection can be performed using all pixel data, but focus detection accuracy deteriorates due to erroneous focus shift calculations
Solution Approach 1:
The patent extracts and identifies saturated pixels through saturation detection, then excludes them from the correlation waveform calculation. By removing only the problematic saturated pixel data while retaining valid pixel data, the system maintains processing efficiency while improving focus detection accuracy.
Solution Approach 2:
The patent applies different processing quality to different regions: saturated pixels are excluded from correlation calculation while non-saturated pixels are included. This local differentiation ensures that only reliable data contributes to the focus detection, maintaining overall processing productivity while improving local measurement precision.
2Productivity
If all pixel data is used for correlation calculation, then processing efficiency is maintained, but image signal accuracy is reduced due to saturation effects
Solution Approach 1:
The system extracts saturated pixels from the total pixel data through saturation detection, then removes them from the correlation waveform calculation. This selective extraction maintains processing efficiency by working with only the necessary valid data while improving image signal accuracy.
Solution Approach 2:
Instead of processing all pixel data (excessive action), the system processes only the valid non-saturated pixel data (partial action). This partial processing approach achieves sufficient accuracy without the harmful effects of including saturated pixels, balancing productivity and precision.
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 improves the signal-to-noise ratio and allows for accurate defocus amount calculation even when saturated pixels are present, enhancing focus detection accuracy.
Implementation Method 1
an image pickup element including a plurality of first pixels and a plurality of second pixels, each pair of the first and second pixels sharing one microlens
Data Source
AI summary
A focus detection apparatus performs focus detection by a phase difference method using an image pickup element including first and second pixels, the focus detection apparatus includes a correlation data calculator which calculates correlation data between pixel data obtained from the first pixels and the second pixels in ranges of image data, a detector which detects a saturated pixel having a level of at least a predetermined value in each of the ranges, an adding processor which performs an addition processing of the correlation data calculated in each of the ranges based on a detection result, and a defocus amount calculator which calculates a defocus amount based on a result of the addition processing, and the adding processor performs the addition processing using correlation data obtained from a first range in which the number of the saturated pixels is less than a predetermined number.