Imaging Optical System Autofocus Aberration Correction
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Solution Overview
Problem
Conventional autofocus methods, such as contrast AF and phase-difference AF, struggle to accurately correct focus detection errors caused by optical aberrations like astigmatism, chromatic aberration, and spherical aberration, as they do not adequately consider the focus condition of the photographic image or the frequency components involved.
Innovation Solution
A focus adjustment device and method that obtain correction values from aberration information and focus detection information to accurately correct autofocus results, using a combination of phase-difference and contrast detection methods, and control the position of the focusing lens to improve focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional autofocus methods (contrast AF or phase-difference AF) are used, then the device complexity is low, but the measurement precision of focus detection is insufficient due to optical aberrations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values for various aberration conditions (astigmatism, chromatic aberration, spherical aberration) and focus detection frequencies before actual autofocus operation. When autofocus is performed, the system simply retrieves and applies the appropriate pre-computed correction value based on detected conditions, avoiding complex real-time calculations while achieving high precision focus detection correction
Solution Approach 2:
The patent introduces an intermediary correction value that mediates between the raw autofocus detection result and the final accurate focus position. This correction value, derived from aberration information and focus detection frequency, acts as a bridge to compensate for systematic errors without requiring fundamental changes to the autofocus detection mechanism itself
2Measurement precision
If correction values are obtained from aberration information and focus detection information, then the measurement precision of focus detection is improved, but the loss of time increases due to additional processing steps
Solution Approach 1:
The patent pre-computes correction values for various combinations of aberration types (astigmatism, chromatic aberration, spherical aberration) and focus detection frequencies, storing them in advance. During actual autofocus operation, the system only needs to identify the current conditions and retrieve the corresponding pre-computed correction value, significantly reducing processing time compared to real-time calculation
Solution Approach 2:
The patent applies partial action by selectively applying correction based on the detected aberration type and frequency conditions. Rather than always applying full correction processing, the system adjusts the level of correction based on the specific situation, reducing unnecessary processing steps when aberrations are minimal or when conditions match pre-stored correction profiles
Data Source
AI summary
A focus adjustment device obtains a correction value for correcting a result of autofocus, from aberration information regarding at least one of an astigmatism, a chromatic aberration, and a spherical aberration of an imaging optical system, and focus detection information regarding the autofocus. The focus adjustment device then controls a position of a focusing lens that the imaging optical system has, based on a result of the autofocus corrected using the correction value. By correcting the result of the autofocus while considering at least a focus condition of a photographic image, a focus detection error caused by an aberration of the optical system can be accurately corrected.