Autofocus Control for Moving Subjects Using Region Segmentation
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Solution Overview
Problem
Conventional autofocus techniques face challenges in maintaining focus on moving subjects and correctly identifying the intended subject, often resulting in the subject going out of focus or an obstacle being inadvertently focused on, especially when the subject is small or moving swiftly.
Innovation Solution
An imaging apparatus that divides the image signal into multiple regions, detects defocus amounts in each region, and controls the focus lens based on overlapping regions to ensure accurate focus on the intended subject without precise setting of the autofocus frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If arbitrary selection AF is used to focus on a specific subject, then the user can select a desired subject, but the subject cannot be brought into focus when it falls outside the AF frame due to small size or fast movement
Solution Approach 1:
The image capturing screen is divided into multiple regions: the user-designated AF frame region and a subject detection region that extends beyond the AF frame. This segmentation allows the system to independently process focus information from different areas, enabling reliable focus on subjects that may be partially outside the AF frame while maintaining user control over the primary focus area.
Solution Approach 2:
A subject detection function acts as an intermediary between the user's AF frame selection and the actual focus execution. This intermediary detects subjects within the extended region and provides focus information, bridging the gap between user intent and accurate focus acquisition for subjects that are small or moving rapidly.
2Ease of operation
If subject recognition function is used to automatically detect subjects, then focusing can be simplified, but another subject unintended by the user may be recognized and focused on
Solution Approach 1:
Different regions of the image capturing screen are assigned different functions: the AF frame region responds to user selection for manual subject choice, while the extended subject detection region automatically detects subjects. This local differentiation allows the system to combine automatic detection capabilities with user control, ensuring that the intended subject is focused on while benefiting from automated assistance.
Solution Approach 2:
The system provides visual feedback by displaying both the AF frame and subject detection region, allowing the user to verify which subject will be focused on. This feedback mechanism enables the user to confirm that the detected subject matches their intent before focus execution, preventing unintended subject focus while maintaining ease of operation.
3Measurement precision
If the AF frame is kept small for precise subject selection, then user control is improved, but the subject easily falls outside the frame when moving swiftly
Solution Approach 1:
The focus detection area is segmented into the user-controlled AF frame and an automatically monitored extended region. This segmentation allows the AF frame to remain small for precise user selection while the extended region provides a safety buffer that detects subjects even when they move outside the AF frame, maintaining continuous focus reliability.
Solution Approach 2:
The subject detection region extends beyond what is strictly necessary for the user's selected AF frame, performing an 'excessive' detection action in surrounding areas. This partial extension beyond the minimum required area ensures that moving subjects are detected and tracked even when they temporarily exit the AF frame, maintaining focus reliability without compromising user control.
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 allows for accurate focus on a subject without precise framing, effectively maintaining focus on moving subjects and preventing obstacles from being inadvertently focused on, improving the reliability of autofocus in dynamic imaging scenarios.
Implementation Method 1
an image sensor that photoelectrically converts a subject image formed via the imaging optical system into an imaging signal
Data Source
AI summary
An apparatus includes a device that acquires an image signal by photoelectrically converting a light beam of a subject that has entered via an optical system including a focus lens, a setting unit that sets a first region in the image signal, a focus detection unit that detects a defocus amount for each divided region of a region in the image signal, a detection unit that detects a second region as a region of a specific subject, based on the image signal, and a control unit that controls the focus lens based on the defocus amount of the divided region included in the second region if the first region and the second region overlap, and controls the focus lens based on the defocus amount of the divided region included in the first region if the first region and the second region do not overlap.