Focus Detection Device Dynamic Pixel Selection
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Solution Overview
Problem
Existing focus detection systems in imaging devices face challenges in maintaining high accuracy due to variations in exit pupil distance with image height and lens type, leading to decreased focus detection precision.
Innovation Solution
A focus detection device that includes an imaging unit with first and second pixels for focus detection, an input unit for receiving information on image plane position and exit pupil distance, a selection unit to choose between focus detection methods based on input signals, and a focus detection unit that performs the selected focus detection, with the interchangeable lens outputting information on exit pupil distance to the camera body for accurate pixel pair selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single type of AF pixel pair is used for focus detection, then the device structure is simple, but focus detection accuracy decreases when exit pupil distance varies with image height and lens type
Solution Approach 1:
The patent implements dynamic selection of AF pixel pairs based on real-time exit pupil distance measurements. The system automatically switches between different AF pixel pair types (first, second, third) depending on the detected exit pupil distance, which varies with image height and lens characteristics. This dynamic adaptation resolves the contradiction by maintaining high focus detection accuracy across varying conditions without requiring a completely complex static structure
Solution Approach 2:
The patent changes the operational parameters of the focus detection system by selecting different AF pixel pairs based on the exit pupil distance parameter. When exit pupil distance exceeds a threshold, the system switches to a first AF pixel pair; when it falls within a specific range, it uses a second AF pixel pair; and when it falls below another threshold, it employs a third AF pixel pair. This parameter-based selection mechanism maintains measurement precision while managing device complexity through intelligent control
2Measurement precision
If multiple types of AF pixel pairs are prepared for different exit pupil distances, then focus detection accuracy is maintained across varying conditions, but the device complexity and control difficulty increase
Solution Approach 1:
The patent implements a feedback mechanism where the exit pupil distance is continuously measured and used to control the selection of AF pixel pairs. The measurement unit detects the exit pupil distance, and this measurement feedbacks to the control unit, which then selects the appropriate AF pixel pair type. This closed-loop feedback system automates the selection process, reducing control complexity while maintaining high measurement precision across varying exit pupil distances
Solution Approach 2:
The focus detection system performs self-service by automatically selecting the appropriate AF pixel pair based on the measured exit pupil distance without requiring manual intervention. The control unit autonomously determines which AF pixel pair type (first, second, or third) to use based on the current exit pupil distance conditions, thereby maintaining measurement precision while simplifying the control interface and reducing operational complexity
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
The system achieves highly accurate focus detection by selecting the appropriate AF pixel pair based on exit pupil distance changes, ensuring consistent precision across different lenses and image heights.
Implementation Method 1
an imaging unit having a first pixel and a second pixel each of which receives light transmitted through an optical system and outputs signal used for focus detection
Data Source
AI summary
A focus detection device includes: an imaging unit having a first pixel and a second pixel each of which receives light transmitted through an optical system and outputs signal used for focus detection; an input unit to which first information regarding a position on an image plane and an exit pupil distance of the optical system is input; a selection unit that selects a first focus detection based on the signal having been output from the first pixel or a second focus detection based on the signal having been output from the second pixel, based on the first information having been input to the input unit; and a focus detection unit that performs the first focus detection or the second focus detection based on a selection by the selection unit.