Autofocus Control Using Pupil Division for Speed and Precision
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Solution Overview
Problem
Existing autofocus systems in digital cameras often fail to achieve sufficient focusing precision and have limitations in the range of focus adjustment, leading to difficulties in obtaining a sharply focused image, especially when the focus point exceeds a certain range.
Innovation Solution
An image pickup apparatus that simultaneously employs phase difference AF and contrast AF by using pupil division means to restrict light from specific exit pupil areas, allowing for precise focus evaluation through correlation and contrast calculations, and decides focus positions based on the structure of the image pickup element and pupil division.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase difference AF control is used, then high-speed focus adjustment can be attained, but sufficient focusing precision cannot always be obtained
Solution Approach 1:
The patent combines phase difference AF control and contrast AF control into a unified autofocus system. The control unit selectively uses phase difference information for high-speed focus adjustment and contrast information for precise focus determination, merging the advantages of both methods to achieve both high speed and high precision focus adjustment.
2Measurement precision
If contrast AF control is used, then exact focus adjustment can be attained, but focus adjustment speed is reduced
Solution Approach 1:
The system uses phase difference AF control to perform preliminary focus adjustment that brings the focus close to the optimal position quickly. Then contrast AF control is applied for fine-tuning to achieve exact focus. This preliminary action reduces the range over which contrast evaluation must be performed, thereby maintaining speed while achieving precision.
3Adaptability or versatility
If focus evaluation range is extended beyond limitation, then more focus positions can be evaluated, but normal image acquisition becomes difficult
Solution Approach 1:
The control unit dynamically adjusts the focus evaluation range based on the current focus position and the limitations of the image pickup element. When the focus position approaches the limitation range, the system adapts by adjusting evaluation parameters or switching between phase difference and contrast AF methods, maintaining reliable image acquisition across a broader focus range.
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 enables high-speed and high-precision autofocus by selectively using phase difference and contrast AF, maintaining high AF precision and allowing for faster in-focus control operations.
Implementation Method 1
an image pickup element for photoelectrically converting an optical image of an object which enters through the photographing lens and outputting an image signal
Data Source
AI summary
An image pickup apparatus which can perform an AF of a high speed and a high focusing precision by simultaneously realizing a phase difference AF and a contrast AF, decides arrange where a contrast evaluation can be performed on the basis of a correspondence relation between each pixel of an image pickup element which is restricted by pupil division means provided for restricting light of an optical image of an object which enters each pixel of the image pickup element to light from a specific exit pupil area of a photographing lens and the specific exit pupil area of the photographing lens, and decides a focus evaluation value of the object in accordance with the decided range from a contrast focus position or a correlation focus position.