Image Sensor Focus Detection to Cut AF Calculation Time Lag
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Solution Overview
Problem
The existing imaging plane phase difference AF method experiences prolonged calculation times when increasing the number of phase difference pixels, leading to a time lag between exposure and focus control, while compromising on accuracy and reliability.
Innovation Solution
An image sensor with a hybrid automatic focus system that combines contrast AF and imaging plane phase difference AF methods, utilizing a dual focus detection approach with a first and second focus detector to generate focus detection data, and adding these data to the captured image signal for efficient focus control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of phase difference pixels is increased to improve AF calculation accuracy and reliability, then the measurement precision and reliability improve, but the calculation time is prolonged
Solution Approach 1:
The patent segments the focus detection process into two distinct methods: contrast AF method and imaging plane phase difference AF method. Each method processes different aspects of focus detection, allowing the system to distribute computational load and achieve accurate focus detection without requiring all pixels to be processed through the more computationally intensive phase difference method.
2Reliability
If the number of phase difference pixels is increased to improve AF calculation reliability, then the reliability improves, but the time lag between exposure and focus control increases
Solution Approach 1:
The patent implements a dynamic focus detection system that adaptively selects between contrast AF and imaging plane phase difference AF methods based on current imaging conditions. This dynamic selection allows the system to maintain high reliability by using phase difference method when conditions favor it, while reducing time lag by switching to contrast method when speed is prioritized, thus dynamically optimizing the balance between reliability and response time.
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 configuration ensures high accuracy and reliability of phase difference AF calculations while reducing the time lag between exposure and focus control, even with an increased number of phase difference pixels, by performing simplified and detailed phase difference AF calculations based on reliability determination.
Implementation Method 1
a plurality of unit pixels for converting an optically formed subject image into an image signal
Data Source
AI summary
An image sensor outputs captured image data by discriminating whether to add a result of an imaging plane phase difference AF calculation to a top of the captured image data or whether to add the result to an end of the captured image data, thus reducing a time lag between exposure and focus position movement.