Auto-Focus Control Using Variable Lens Step Size
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image capture devices using combined phase difference AF and contrast AF methods face delays in focus control completion, leading to slower autofocus speeds.
Innovation Solution
An image capture device with first and second signal detection units that determine the focus control method and adjust the arbitrary movement distance based on detection signals, allowing for faster focus control by selecting between phase difference AF and contrast AF methods dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If focus control is performed using contrast AF method from the beginning, then focusing speed is improved, but focusing accuracy and reliability deteriorate when phase difference AF could provide sufficient defocus amount
Solution Approach 1:
The patent dynamically switches between phase difference AF and contrast AF methods based on real-time evaluation of defocus amount reliability. The focus control method adapts its approach by determining whether to use phase difference information or contrast information depending on the imaging conditions, thereby optimizing both speed and reliability adaptively
Solution Approach 2:
The patent changes the control parameter from fixed method selection to variable method selection based on defocus amount reliability. By evaluating the reliability of defocus amount calculated through phase difference AF and adjusting the focus control strategy accordingly, the system achieves optimal performance across different shooting conditions
2Reliability
If focus control switches to contrast AF method when phase difference AF reliability is low, then focusing accuracy is improved, but time until focus control completion increases
Solution Approach 1:
The patent applies partial phase difference AF action by using only the defocus amount information when its reliability is sufficient, and supplementing with contrast AF only when necessary. This partial use of phase difference information reduces the overall focus control time while maintaining accuracy when conditions permit
Solution Approach 2:
The system performs self-evaluation of defocus amount reliability and automatically adjusts the focus control method without external intervention. The focus control determination unit assesses the current imaging conditions and selects the appropriate AF method, enabling the system to serve itself in optimizing focus performance
3Reliability
If combined phase difference AF and contrast AF methods are used, then focusing accuracy is improved, but system complexity increases
Solution Approach 1:
The imaging element serves multiple functions by acting as both a phase difference detection unit and a contrast detection unit. The same imaging element can operate in different modes depending on the focus control method selected, eliminating the need for separate detection hardware and reducing system complexity
Solution Approach 2:
The focus control determination unit acts as an intermediary that evaluates defocus amount reliability and mediates between phase difference AF and contrast AF methods. This intermediary component simplifies the overall system architecture by providing a unified decision-making mechanism rather than requiring complex parallel processing of both methods simultaneously
Data Source
AI summary
Provided are an image capture device and a focus control method capable of performing auto-focus (AF) at high speed by reducing time until a focus control is completed even when a focus control based on a phase difference AF method and a focus control based on a contrast AF method are used in combination. A digital camera performs a correlation operation of two images captured by a pixel pair P1, performs a correlation operation of two images captured by a pixel pair P2, and determines reliability of correlation operation results based on information generated from the two correlation operation results. When the reliability is low, the digital camera performs the contrast AF. Here, the digital camera variably controls a movement step (arbitrary distance) when moving a focus lens in a predetermined range to calculate a contrast value, according to the height of the reliability.