Hybrid Phase-Difference and Contrast Focus Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing focus adjustment methods in imaging apparatuses, such as single-lens reflex cameras, face challenges in accurately determining the focusing position and direction, especially during live view photography, leading to inefficient and sometimes erroneous focusing, particularly in moving image photography where continuous focusing is required.
Innovation Solution
A focus adjustment apparatus that combines imaging surface phase-difference AF and contrast AF, using a control unit to selectively utilize detection results from both methods based on conditions, ensuring appropriate focus lens driving by integrating phase difference and contrast information for reliable focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase-difference detection method is used for focus adjustment during live view photography, then focusing speed is improved, but focusing accuracy deteriorates when the focus lens is far from the in-focus position
Solution Approach 1:
The patent combines phase-difference detection method and contrast detection method into a hybrid focus adjustment system. The control unit selects which method to use based on the absolute value of the correlation change amount, thereby merging the advantages of both methods: phase-difference detection provides fast focusing when accurate, while contrast detection ensures accuracy when phase-difference detection becomes unreliable.
Solution Approach 2:
The patent changes the detection method parameter based on the correlation change amount threshold. When the absolute value of the correlation change amount exceeds the threshold, contrast detection is used; otherwise, phase-difference detection is used. This dynamic parameter change allows the system to adapt to different focusing conditions and maintain both speed and accuracy.
2Measurement precision
If contrast detection method is used for focus adjustment, then focusing accuracy is improved, but focusing speed deteriorates and unfavorable behavior occurs
Solution Approach 1:
The patent applies contrast detection method partially, only when the absolute value of the correlation change amount exceeds the threshold. In other cases, the faster phase-difference detection method is used. This partial application of contrast detection avoids its speed disadvantages while maintaining its accuracy benefits in appropriate situations.
3Speed
If phase-difference detection method is used, then focusing speed is improved, but reliability of focus detection deteriorates due to asymmetric image signals
Solution Approach 1:
The patent uses the correlation change amount as feedback to determine whether to trust the phase-difference detection results. When the correlation change amount is within the threshold, phase-difference detection is reliable and is used. When it exceeds the threshold, the system switches to contrast detection, thereby using feedback to maintain reliability.
4Device complexity
If a single focus detection method is used, then device complexity is reduced, but adaptability to different photographing situations deteriorates
Solution Approach 1:
The patent makes the focus adjustment system universal by incorporating both phase-difference detection and contrast detection capabilities. The control unit automatically selects the appropriate method based on the photographing situation, as indicated by the correlation change amount. This multi-functionality allows the system to adapt to various conditions without requiring separate systems for different situations.
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 approach enhances the accuracy and speed of focusing operations by appropriately selecting between phase-difference and contrast AF results, reducing the likelihood of erroneous focusing and improving focus tracking during live view and moving image photography.
Implementation Method 1
an imaging unit configured to receive and photoelectrically convert a light flux passed through a photographing optical system including a focus lens
Data Source
AI summary
A focus adjustment apparatus includes an imaging unit, a first detection unit, a second detection unit, and a control unit. The imaging unit receives and photoelectrically converts a light flux passed through a photographing optical system including a focus lens. The first detection unit detects a phase difference between a pair of image signals output from the imaging unit. The second detection unit detects contrast information from a signal output from the imaging unit. The control unit controls driving of the focus lens based on a detection result of at least one of the first detection unit and the second detection unit. If the detection result of the first detection unit satisfies a first condition, the control unit controls driving of the focus lens by using the detection result of the first detection unit, and changes the first condition according to the contrast information detected by the second detection unit.