Camera Autofocus Area Selection for Face Detection
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Solution Overview
Problem
Conventional cameras using phase difference detecting methods for autofocus face difficulties in selecting an optimal focusing area for face detection, especially in monocular reflex type cameras, as the arrangement of focusing areas is restrictive and not well-suited for face detection processing.
Innovation Solution
A camera system comprising a face detecting section, a focusing section, and an area specifying section that dynamically adjusts the focusing area based on the size and position of the face within the image plane, using multiple optional areas with varying densities to optimize autofocus performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a phase difference detecting method is used for autofocus, then high speed AF is achieved, but the constitution is unsuitable for face detection processing
Solution Approach 1:
The patent implements dynamic switching between two autofocus methods (phase difference detecting method and contrast detecting method) based on the detection state of the face. When a face is detected, the system switches to contrast detecting method which is suitable for face detection; when no face is detected, it uses phase difference detecting method for high speed AF. This dynamic adaptation resolves the contradiction between speed and face detection suitability.
2Device complexity
If the focusing area arrangement is fixed for phase difference detecting method, then device complexity is reduced, but adaptability to different face detection states is restricted
Solution Approach 1:
The patent employs multiple sets of focusing areas (first focusing areas and second focusing areas) that can be dynamically selected based on face detection results. The system can switch between different focusing area arrangements depending on whether a face is detected and its size, enabling adaptability without requiring a completely complex flexible arrangement system.
Solution Approach 2:
The patent divides the focusing area into multiple distinct sets (first focusing areas for general use, second focusing areas for face detection). This segmentation allows the system to select the appropriate set based on detection state, providing adaptability while maintaining manageable complexity through organized separation of functions.
3Device complexity
If the focusing area is fixed, then device complexity is reduced, but autofocus accuracy for different face sizes is compromised
Solution Approach 1:
The patent implements dynamic selection of focusing areas based on the detected face size. When a face of a certain size is detected, the system selects appropriate focusing areas from the available sets to optimize autofocus accuracy for that specific face size. This dynamic adjustment maintains AF accuracy across different shooting scenarios without requiring overly complex focusing area management.
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 efficient autofocus control by selecting the appropriate focusing area, ensuring optimal focus on the face regardless of its size or position, thereby improving autofocus accuracy and adaptability to different shooting scenarios.
Implementation Method 1
the focusing section obtains the image phase difference amount of a pair of images based on luminous flux having passed through a shooting lens in each of the optional areas
Data Source
AI summary
A camera is provided with a face detecting section, a focusing section, an area specifying section, and a controlling section. The face detecting section detects a face area within a shooting image plane. The focusing section has plural optional areas within the shooting image plane. Further, the focusing section obtains an image phase difference amount of a pair of images based on luminous flux having passed through a shooting lens in each of the optional areas. The area specifying section specifies a focusing area from among the optional areas corresponding to the face area. Further, the area specifying section changes a method of specifying the focusing area in accordance with the size of the face area. The controlling section performs a focusing operation of the shooting lens on the basis of the image phase difference amount in the focusing area.