Imaging Autofocus Lens Chromatic Aberration Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chromatic aberration in imaging apparatus lenses leads to focal deviation and image blurring, particularly at the edge portions of the subject, resulting in reduced image quality due to incorrect focus determination.
Innovation Solution
The imaging apparatus includes a movable lens for focus adjustment and an imaging element for photoelectric conversion, with a control unit that calculates and corrects focal deviations caused by chromatic aberration using positional information from a correction table, ensuring the focus lens is adjusted to the in-focus position while revising the correction amount to suppress edge coloring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus adjustment is performed by alignment with the G component to achieve just focus position, then the focal position is accurately determined, but chromatic aberration causes coloring on edge portions and reduces image quality
Solution Approach 1:
The patent changes the parameter used for focus determination from contrast-based AF evaluation to defocus amount calculation based on blur circle diameter. By measuring the actual blur circle size formed on the imaging element and comparing it to the acceptable circle of confusion, the system determines focus position without being affected by chromatic aberration-induced coloring, thus resolving the contradiction between accurate focus positioning and edge coloring.
2Reliability
If contrast AF method is used to determine focus position, then the AF evaluation value is maximized, but the determined position corresponds to where focus lacks sharpness and chromatic aberration is not present, resulting in blurred images
Solution Approach 1:
The patent replaces the contrast-based optical evaluation method with a geometric optics calculation approach. Instead of relying on contrast maximization which is affected by chromatic aberration, the system calculates defocus amount by measuring blur circle diameter and comparing it to the acceptable circle of confusion, substituting the mechanical/optical contrast evaluation with a geometric calculation that directly addresses focus sharpness.
3Measurement precision
If correction table is used to adjust focus lens position for chromatic aberration, then focal deviation is corrected, but edge coloring may still occur due to incomplete suppression of chromatic aberration effects
Solution Approach 1:
The patent extracts the essential focus determination criterion from the problematic contrast-based system. By isolating the blur circle diameter measurement and comparing it independently to the acceptable circle of confusion threshold, the system separates focus positioning from chromatic aberration effects, taking out the focus determination function from the contrasting evaluation that causes edge coloring.
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 solution effectively prevents focal deviation and suppresses edge coloring, thereby maintaining image quality by accurately adjusting the focus lens position and revising the correction amount within the depth of focus.
Implementation Method 1
an imaging element configured to perform photoelectric conversion upon reception of light from the subject
Data Source
AI summary
An imaging apparatus includes an autofocus function, and performs focus adjustment by displacing a focus lens to an in-focus opposition. A focal correction calculation unit calculates a focal correction amount using at least one type of information selected from the diaphragm information used for exposure adjustment, positional information for the zoom lens, and positional information for the focus lens. The focal correction amount is further revised, and processing is executed to suppress coloring on the subject image resulting from chromatic aberration. The correction amount after revision is sent to a focal adjustment unit and the focal lens is driven and controlled by the lens control unit.