Hybrid Phase Contrast Autofocus Control for Camera Dead Zones
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Solution Overview
Problem
Existing camera focus systems, particularly those using phase difference AF and contrast AF, face challenges in quickly focusing on objects across the entire field of view due to dead zones in phase difference AF and long focusing times with contrast AF, especially when objects are far out of focus or moving quickly.
Innovation Solution
A camera system employing a first focus detection device for phase difference-based defocus amount calculation and a second focus detection device for high-frequency component analysis, with distinct areas of focus control, allowing for faster focusing by utilizing both methods in their respective zones and controlling the optical system based on detection results from the first focus detection device when the object is in a phase difference AF dead zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase difference AF is used for focus detection, then focusing speed is improved, but dead zones are generated in the focus detection area
Solution Approach 1:
The patent combines phase difference AF and contrast AF into a hybrid focus detection system. The phase difference AF provides fast initial focusing, while contrast AF covers the dead zones and confirms final focus accuracy. This merging allows the system to leverage the speed advantage of phase difference AF while eliminating its coverage limitations through contrast AF supplementation.
2Measurement precision
If contrast AF is used for focus detection, then focus detection accuracy is improved, but focusing time increases
Solution Approach 1:
The system performs preliminary focusing using phase difference AF to quickly bring the lens close to the correct focus position before engaging contrast AF for final precision adjustment. This preliminary action eliminates the need for contrast AF to scan the entire focus range, significantly reducing the time penalty while maintaining accuracy.
Solution Approach 2:
The focus detection process is segmented into two stages: coarse adjustment using phase difference AF and fine adjustment using contrast AF. Each method is applied to the portion of the task where it excels, with phase difference AF handling the bulk of the focusing distance and contrast AF handling only the final precision positioning.
3Adaptability or versatility
If the AF lens moving range is increased to cover the entire photographing field, then focus coverage is improved, but resolution and AF precision decrease
Solution Approach 1:
The patent implements dynamic focus detection method selection based on object position. When objects are in the dead zone area, the system automatically switches to or supplements with contrast AF. This dynamic adaptation allows full field coverage without permanently compromising precision, as each detection method is applied where it maintains optimal performance.
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 focusing speed and precision by allowing the camera to quickly focus on objects regardless of their position within the viewfinder, reducing the time required to adjust focus and increasing operational efficiency.
Implementation Method 1
a first focus detection device which obtains a defocus amount from a phase difference of an object image and detects a focus on the basis of the defocus amount
Implementation Method 2
a second focus detection device which detects the focus in accordance with a magnitude of a high-frequency component in an output image signal
Data Source
AI summary
This invention can increase the focusing speed and quickly focus a camera to an object regardless of the position of the object within the field of the viewfinder. When the position of a main object falls within a range in which phase difference AF is impossible, the lens scan range of contrast AF is determined by referring to distance measurement information of phase difference AF near the main object or immediately preceding distance measurement information of phase difference AF. The scan range of contrast AF is narrowed to increase the focusing speed.