Camera Autofocus Lens Position Association
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Solution Overview
Problem
Existing camera systems with interchangeable lenses face challenges in achieving high accuracy for autofocus operations using contrast systems, as they often rely on phase difference detection systems for correction, which may not improve the accuracy of focusing information itself obtained in the contrast system.
Innovation Solution
A camera system with an interchangeable lens that includes a signal generating portion for periodic timing signals, an imaging device for generating image data, an evaluation value calculating portion for autofocus, and a body control portion that associates the focus lens position with the calculated evaluation value to control the autofocus operation, allowing for improved accuracy in autofocus operations by switching between control modes to detect reverse rotations of the focus lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase difference detection system is used for autofocus, then high-speed focusing is achieved, but detection accuracy is insufficient
Solution Approach 1:
The patent implements a feedback mechanism where the contrast detection result is used to correct the phase difference detection focusing control information. The system continuously monitors the contrast evaluation value and adjusts the focus position accordingly, creating a closed-loop control system that improves detection accuracy while maintaining the high-speed advantage of phase difference detection.
Solution Approach 2:
The patent introduces the contrast detection system as an intermediary to bridge the gap between phase difference detection and final focus determination. The contrast evaluation acts as a mediator that verifies and refines the focus position suggested by phase difference detection, combining the speed of one method with the accuracy of another.
2Measurement precision
If contrast system is used for autofocus, then highly-accurate focus judgment is achieved, but focusing speed is reduced
Solution Approach 1:
The patent applies preliminary action by using phase difference detection to obtain an initial focus position estimate before performing contrast detection. This pre-positioning reduces the search range for contrast optimization, allowing the system to achieve high accuracy without the time penalty of exhaustive contrast search from all possible positions.
Solution Approach 2:
The patent implements a hybrid approach where phase difference detection provides the primary focusing action for most situations, and contrast detection is applied partially or selectively to verify and refine the focus position. This partial application of contrast detection maintains accuracy while minimizing its impact on focusing speed.
3Measurement precision
If focusing control information from phase difference detection is corrected by contrast system, then focusing accuracy is improved, but the accuracy of focusing information obtained in contrast system itself is not improved
Solution Approach 1:
The patent replaces the traditional mechanical focus adjustment mechanism with an information-based control system. Instead of relying solely on mechanical position feedback, the system uses optical information (contrast evaluation of captured images) to determine and control focus position, substituting mechanical measurement with optical measurement for improved accuracy.
Data Source
AI summary
In a camera system according to the present invention, a lens controller obtains an exposure synchronizing signal that is generated by a camera controller from a camera body, causes a configuration formed of a first encoder, a second encoder and a counter to detect the position of a focus lens according to the obtained exposure synchronizing signal, and notifies the camera body of the detected position of the focus lens. The camera controller associates the position of the focus lens or the mechanism member obtained from the lens controller with an AF evaluation value based on the exposure synchronizing signal, and controls an autofocus operation of the camera system based on the position and AF evaluation value that are associated with each other. With this configuration, it is possible to improve the accuracy of an autofocus operation with a contrast system.