Focus Detection Apparatus with Dual-Mode Correction for Lens Positioning
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Solution Overview
Problem
Conventional focus detection systems in single-lens reflex cameras face challenges in accurately determining the in-focus position due to environmental and manufacturing errors, requiring repetitive operations for focus adjustment and distinguishing between focus states in captured images.
Innovation Solution
An image capturing apparatus with a detection unit for defocus value, first and second calculation units for obtaining correction values, and a controller to move the focus lens based on stored values, allowing user selection in one mode and automated focus adjustment in another, with the second mode enabling larger correction value increments for improved focus state differentiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the imaging lens is driven within a predetermined range to automatically calculate AF correction value, then automation is improved, but the ability to distinguish focus states deteriorates
Solution Approach 1:
The system dynamically adjusts the lens driving range based on the selected mode. In first mode, the lens is driven within a predetermined range for automated calculation. In second mode, the lens is driven over a wider range than the predetermined range to capture multiple focus states, enabling better differentiation while maintaining automation through user guidance.
Solution Approach 2:
The system changes the operating parameters by offering two distinct modes with different lens driving ranges. The first mode uses a limited predetermined range for subtle adjustments, while the second mode expands the range to capture broader focus variations, allowing the system to adapt to different user needs and imaging conditions.
2Measurement precision
If the user manually selects focus shift amount, then precision is improved, but operation complexity increases
Solution Approach 1:
The system provides partial automation by allowing users to select between two modes. In first mode, users directly select focus shift amounts from predetermined options, providing precision without requiring complex manual operations. In second mode, the system performs excessive action by automatically capturing multiple images at different focus positions, reducing user burden while maintaining correction capability.
Solution Approach 2:
In the second mode, the system performs self-service by automatically moving the lens to multiple positions, capturing images, and presenting them to the user for selection. This eliminates the need for users to manually adjust and capture multiple images, simplifying operation while maintaining the ability to achieve precise focus correction.
3Measurement precision
If multiple images are captured at different focus positions, then focus state differentiation is improved, but time consumption increases
Solution Approach 1:
The system performs preliminary action by pre-defining multiple focus positions and automatically moving the lens to these positions before capturing images. This preparation eliminates the need for users to manually adjust focus during image capture, reducing time consumption while ensuring that multiple distinct focus states are captured for accurate differentiation.
Solution Approach 2:
The system uses periodic action by automatically moving the lens between predetermined focus positions in a systematic sequence, capturing images at each position. This structured approach ensures comprehensive coverage of focus states while minimizing total capture time through efficient positioning and automated sequencing.
Data Source
AI summary
A detection unit detects a defocus value, a correction value for shifting an in-focus position that is based on the defocus value is obtained by first or second method and stored in a memory. A controller controls to move a focus position to a lens position obtained from the defocus value and the stored correction value. The first mode is to make a user select an amount for shifting the focus position, and the correction value is obtained according to the selection. In the second mode, imaging and detection of the defocus value are performed at each of different focus positions, and the correction value is obtained from a defocus value corresponding to selected one of obtained images. A minimum unit of the correction value in the second mode is larger than that in the first mode.