Image Capture Autofocus Control via Dynamic Frame Rate Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image capture systems using phase-difference detection methods for autofocus are affected by vignetting, which deteriorates focus detection accuracy, especially at larger defocus amounts, due to varying output waveforms and reduced contrast.
Innovation Solution
An image capture apparatus and method that adjusts the frame rate based on the defocus amount, increasing the frame rate when the defocus amount exceeds a threshold to improve focus detection speed and accuracy, and maintaining the original frame rate when the defocus amount is within the threshold to conserve power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frame rate is increased to improve focus detection speed and accuracy during high defocus conditions, then the focus detection accuracy is improved, but the power consumption increases
Solution Approach 1:
The frame rate is made dynamic rather than fixed. The control unit adjusts the frame rate based on the detected defocus amount, using a higher frame rate when defocus is large and a lower frame rate when defocus is small or the subject is in focus, thereby optimizing both detection accuracy and power consumption
Solution Approach 2:
The frame rate parameter is changed based on the defocus amount. When the defocus amount exceeds a threshold, the frame rate is increased to improve detection accuracy; when the defocus amount is within the threshold, the frame rate is reduced to conserve power
2Speed
If the frame rate is continuously increased to improve focus detection speed, then the focus detection speed is improved, but the power consumption increases
Solution Approach 1:
The frame rate is dynamically adjusted based on the detection needs. During active focus adjustment with large defocus amounts, the frame rate is increased to improve detection speed. When the subject is in focus or focus adjustment is not needed, the frame rate is reduced to conserve power
Solution Approach 2:
The frame rate parameter is changed according to the defocus amount threshold. When defocus exceeds the threshold, a higher frame rate is used for faster detection; when within threshold, a lower frame rate is used to reduce power consumption
3Measurement precision
If the frame rate is increased to capture phase-difference signals more frequently, then the focus detection accuracy is improved, but unnecessary power consumption occurs when in-focus
Solution Approach 1:
The frame rate parameter is adjusted based on the defocus amount. When the defocus amount is large (exceeding threshold), the frame rate is increased to improve detection accuracy. When the defocus amount is small (within threshold), indicating the subject is in focus, the frame rate is reduced to avoid unnecessary power consumption
Data Source
AI summary
If it is determined that an imaging optical system is not in an in-focus state, an interval for obtaining a phase-difference signal is set to a second time interval that is faster than a first time interval when a defocus amount that is obtained using the phase-difference signal that is output from an image sensor is a predetermined threshold or more, and the interval for obtaining a phase-difference signal is set to the first time interval when the defocus amount is less than the predetermined threshold.