Focus Detection Apparatus Using Dual Correction Methods
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Solution Overview
Problem
Conventional focus detection systems in single-lens reflex cameras face challenges in accurately detecting the in-focus position due to environmental and manufacturing errors, requiring repeated operations for micro adjustments and resulting in inconsistent correction values between different focus adjustment methods.
Innovation Solution
A focus detection apparatus and method that utilizes a focus detection unit to detect defocus values, with two calculation methods to obtain correction values, a conversion unit to unify these values, and a control unit to adjust the focus lens, allowing users to select images for precise focus adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If phase difference detection method is used to detect focus state, then focus detection function is provided, but measurement precision deteriorates due to environmental influence and manufacturing error
Solution Approach 1:
The patent implements a feedback mechanism where the detected defocus value is used to calculate a correction value, which is then applied to adjust the focus lens position. This closed-loop feedback system continuously refines the focus detection accuracy by using the initial detection result to generate a correction that compensates for environmental and manufacturing errors, thereby improving the measurement precision of the in-focus position.
2Measurement precision
If user performs manual micro adjustment to correct focus, then measurement precision improves, but loss of time increases due to repeated operations
Solution Approach 1:
The patent enables the system to perform self-service by automatically calculating the correction value based on the detected defocus value and controlling the focus lens to the corrected position. This eliminates the need for the user to manually perform repeated image capturing and checking operations, while still achieving accurate focus adjustment through the automated calculation and execution of the correction value.
3Adaptability or versatility
If different methods are used to calculate correction value, then adaptability improves, but device complexity increases due to multiple calculation units
Solution Approach 1:
The patent implements universality by designing a unified calculation unit that can perform multiple calculation methods for obtaining correction values. Instead of creating separate dedicated units for each calculation method, the single calculation unit is designed to handle various calculation approaches (such as using defocus values from different image pairs or different computational algorithms), thereby achieving adaptability while avoiding the complexity of multiple specialized units.
Data Source
AI summary
A focus detection unit detects a defocus value, and a correction value for shifting an in-focus position based on the defocus value is obtained by a first method or by a second method. The correction value obtained by the second method is converted to a correction value of the first method by changing units, and the correction value obtained by the first method or the converted correction value is stored in a storage unit. A control unit controls driving of a focus lens to a lens position based on a value obtained by correcting the defocus value by the stored correction value. In the second method, a user selects one of a plurality of images obtained by driving the focus lens, and the correction value is calculated based on the defocus value of the selected image.