Hybrid AF Controller Switching Phase Difference to TV-AF
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Solution Overview
Problem
Conventional hybrid AF methods in image-pickup apparatuses often result in overshooting or temporary stops of the focus lens, leading to reduced image quality and increased focusing time due to lower accuracy in phase difference detection compared to TV-AF, and parallax issues with external phase difference detection methods causing incorrect focus positions.
Innovation Solution
An image-pickup apparatus with a controller that performs first focus control based on a focus evaluation signal and second focus control based on phase difference, stopping or switching from second focus control to first focus control when a predetermined change is detected in the focus evaluation signal, ensuring smooth and accurate in-focus state achievement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase difference detection method is used for quick focusing, then focusing speed is improved, but focusing accuracy deteriorates causing overshooting or temporary stops
Solution Approach 1:
The patent segments the focusing process into two distinct phases: first using phase difference detection to rapidly move the focus lens near the in-focus position, then switching to TV-AF method to precisely reach the exact in-focus position. This segmentation allows each method to operate in its optimal performance range without interference.
Solution Approach 2:
The patent implements dynamic switching between two focus control methods based on real-time focus evaluation signals. The system transitions from phase difference AF to TV-AF when the focus lens approaches the in-focus position, optimizing both speed and accuracy at different stages of the focusing process.
2Speed
If external phase difference detection method is used, then focusing speed is improved, but parallax causes incorrect focus positions
Solution Approach 1:
The patent uses focus evaluation signals as feedback to monitor the actual focus state during phase difference detection. When the focus lens approaches the in-focus position, the system detects changes in the focus evaluation signal and switches to TV-AF method to correct any parallax-induced positioning errors, ensuring accurate focus.
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 enables smooth and accurate focus control, preventing overshooting and temporary stops, thereby improving image quality and reducing focusing time in hybrid AF systems.
Implementation Method 1
an image-pickup element photoelectrically converting an object image
Implementation Method 2
a light-receiving sensor outputting a signal in accordance with a phase difference between a pair of object images
Data Source
AI summary
An image-pickup apparatus includes an image-pickup element photoelectrically converting an object image, a light-receiving sensor outputting a signal in accordance with a phase difference between a pair of object images, and a controller performing first focus control of controlling drive of a focus adjusting member based on a focus evaluation signal representing a contrast state of a video signal produced with the image-pickup element and second focus control of controlling drive of the focus adjusting member based on the signal in accordance with the phase difference. The controller stops the second focus control or switches focus control from the second focus control to the first focus control in response to a predetermined change found in the focus evaluation signal during the second focus control. The apparatus is capable of achieving an in-focus state smoothly and accurately with a hybrid AF.