Autofocus Control Using Parallax Detection for Moving Objects
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Solution Overview
Problem
Conventional autofocus systems using contrast AF methods are slow and struggle to quickly focus on moving objects with telephoto lenses, as they require time to adjust focus after the object enters the field of view and may lose the object during autofocusing, leading to blurred images.
Innovation Solution
An image capturing apparatus with a focus detector that uses parallax image signals from a second image capturer with a wider angle of field to perform focus detection and control the first image capturer, allowing for high-speed autofocus by calculating object distance using two image capturing optical systems with overlapping fields of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a contrast AF method is used for autofocus, then focusing accuracy is improved, but processing speed deteriorates
Solution Approach 1:
The system performs preliminary focus detection using the second image capturer with wider angle of view to acquire object distance information before the object enters or while it is in the narrow field of view of the first image capturer. This preliminary action provides initial focus position data that accelerates the subsequent contrast AF process, resolving the contradiction between accuracy and speed.
Solution Approach 2:
The second image capturer acts as an intermediary device that provides distance information to the focus detector, which then guides the focus control of the first image capturer. This intermediary system enables the main imaging system to start with pre-calculated focus positions rather than searching from scratch, achieving both speed and accuracy.
2Measurement precision
If a telephoto lens is used to capture moving objects, then image quality is improved, but the ability to track and focus on moving objects deteriorates
Solution Approach 1:
The second image capturer with wider angle of view performs preliminary detection of moving objects and calculates their distance before the object enters or while it is in the narrow field of view of the telephoto lens. This allows the focus control to be pre-positioned, enabling the telephoto lens to capture high-quality images without losing track of fast-moving objects.
Solution Approach 2:
The system uses a second image capturer with a different field of view dimension (wider angle) to supplement the first image capturer's narrow telephoto view. This dimensional complementarity allows the system to maintain both wide-area tracking capability and high-magnification imaging capability simultaneously.
3Measurement precision
If the field of view is narrowed for telephoto imaging, then image detail is improved, but the ability to locate and focus on objects deteriorates
Solution Approach 1:
The second image capturer with wider angle of view performs preliminary object location and distance measurement before the object enters or while it is in the narrow field of view of the telephoto lens. This preliminary detection resolves the difficulty of locating objects in the narrow field of view while maintaining the detailed imaging capability of the telephoto lens.
Solution Approach 2:
The second image capturer serves as an intermediary detection system that expands the effective detection range. It provides object location and distance information that guides the first image capturer's focus control, enabling the narrow-field system to benefit from wide-field detection capabilities.
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
Enables rapid and accurate autofocus on moving objects, reducing the likelihood of capturing blurred images by acquiring object distance information over a wider field of view and focusing the main image capturer before the object moves out of the imaging field.
Implementation Method 1
a focus detector configured to perform focus detection based on a plurality of parallax image signals obtained via a second image capturer with an angle of field that is wider than an angle of field of a first image capturer
Data Source
AI summary
An image capturing apparatus (1) includes a focus detector (21) that performs focus detection based on a plurality of parallax image signals obtained via a second image capturer (110) with an angle of field that is wider than an angle of field of a first image capturer (100), and a controller (30, 41) that performs focus control of the first image capturer (100) based on an output signal from the focus detector (21).