Focus Detection Pixel Defect Handling via F-Number Adaptation
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Solution Overview
Problem
Existing image pickup apparatuses face challenges in accurately performing focus detection due to defective pixels in focus detection pixel groups, especially when the F-number is high, leading to rough sample pitch and potential changes in the desired focusing region.
Innovation Solution
An image pickup apparatus that includes a focus detector capable of utilizing defective pixels within a certain F-number range for focus detection, and when the F-number exceeds this range, it performs focus detection without using the defective pixel's signal, ensuring accurate focus detection even with defective pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If focus detection pixels are discretely aligned on the image pickup surface, then the device complexity is reduced, but the measurement precision deteriorates due to rough sample pitch making it difficult to accurately correct defective pixel outputs
Solution Approach 1:
The patent changes the parameter of F-number to dynamically adjust focus detection strategy. When F-number is within usable range, defective pixels are utilized; when F-number exceeds usable range, defective pixels are excluded. This parameter-based adaptation resolves the contradiction by optimizing measurement precision according to optical conditions while maintaining the simple discrete pixel arrangement structure.
2Measurement precision
If defective pixels are excluded from focus detection, then the measurement precision is maintained, but the reliability deteriorates due to reduced number of usable focus detection pixels
Solution Approach 1:
The patent implements a dynamic focus detection system that adapts pixel selection based on F-number conditions. The system dynamically switches between including and excluding defective pixels according to the usable F-number range, optimizing both precision and reliability for different optical conditions rather than using a static exclusion approach.
Solution Approach 2:
By using F-number as a control parameter, the system determines whether to include defective pixels in focus detection. This parameter-driven approach allows the system to maintain reliability by utilizing more pixels when optical conditions permit, while preserving precision when conditions require stricter selection.
3Reliability
If focus detection is performed using signals from defective pixels at high F-numbers, then the reliability is improved by using more pixels, but the measurement precision deteriorates due to rough sample pitch
Solution Approach 1:
The patent uses F-number as a threshold parameter to control pixel selection. By comparing the current F-number against a predetermined usable F-number range, the system intelligently decides whether to include defective pixels, thereby preventing precision deterioration at high F-numbers while maintaining reliability when conditions are favorable.
Solution Approach 2:
The system incorporates feedback through the F-number condition check to determine pixel utilization. This feedback mechanism ensures that defective pixels are only used when optical conditions (F-number) support accurate focus detection, automatically preventing precision loss while maximizing pixel utilization for reliability.
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 apparatus effectively uses defective pixels to maintain focus detection accuracy, preventing errors in high spatial frequency objects and ensuring the desired focusing region is maintained, even when defective pixels are present.
Implementation Method 1
a plurality of image pickup pixels that perform photoelectric conversion of light obtained from an image pickup lens to generate an image of an object
Implementation Method 2
a plurality of focus detection pixels that receive light passing through a part of an area of an exit pupil of the image pickup lens
Data Source
AI summary
An image pickup apparatus having an image pickup element with a plurality of image pickup pixels and a plurality of focus detection pixels, a focus detector performing a focus detection based on the output from the focus detection pixels corresponding to a focus detection area, and a setter configured to set a usable F-number based on stored information of a defective pixel that exists in the focus detection pixels. When the defective pixel exists in the focus detection pixels corresponding to the focus detection area, if an F-number is within the usable F-number, the focus detector performs focus detection by using the output from the defective pixel, and if the F-number is out of the usable F-number, the focus detector performs focus detection without using such output.