Auto Focus Evaluation Using Horizontal and Vertical Contrast Analysis
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Solution Overview
Problem
Conventional digital photographing apparatuses face challenges in achieving exact auto focusing, particularly for patterns with contrast distributed in both horizontal and vertical directions, as they rely solely on horizontal AF evaluation values, which can lead to inaccurate focus adjustment.
Innovation Solution
The apparatus calculates both horizontal and vertical AF evaluation values and uses them to drive the focus lens in alternating directions, ensuring accurate focus detection by interpolating peak values from stored image signals, allowing for precise focus adjustment regardless of contrast distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only horizontal AF evaluation values are used for focus adjustment, then the device complexity is reduced and processing speed is improved, but measurement precision deteriorates for patterns with vertical contrast distribution
Solution Approach 1:
The patent segments the AF evaluation process into two independent directional components: horizontal AF evaluation and vertical AF evaluation. Each direction processes image data independently using dedicated evaluation units, allowing the system to handle different contrast distributions without increasing overall system complexity. This segmentation enables accurate focus detection for various pattern orientations while maintaining modular processing architecture.
2Measurement precision
If both horizontal and vertical AF evaluation values are calculated, then focus detection accuracy for all patterns is improved, but processing time increases
Solution Approach 1:
The patent implements periodic alternation between horizontal and vertical AF evaluation operations. Rather than simultaneously computing both directions continuously, the system periodically switches between horizontal evaluation mode and vertical evaluation mode, utilizing the same processing resources for both directional assessments. This periodic action reduces cumulative processing time while ensuring both directional contrast distributions are evaluated for accurate focus detection.
3Adaptability or versatility
If vertical image signals are read and processed, then AF evaluation completeness is improved for vertical patterns, but processing complexity increases
Solution Approach 1:
The patent designs the vertical AF evaluation unit to use the same fundamental processing architecture as the horizontal evaluation unit, making the processing system universal. Both horizontal and vertical evaluators employ identical contrast calculation algorithms and peak detection methods, differing only in the directional arrangement of pixel data. This multi-functionality approach allows the system to adapt to various pattern orientations without requiring fundamentally different processing pathways, thereby limiting complexity increase.
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 method enables precise auto focusing for images with patterns lacking horizontal contrast, improving focus detection accuracy and capturing quality by utilizing both horizontal and vertical AF evaluation values.
Implementation Method 1
an imaging device comprising a plurality of photoelectric converting units for converting image light from a subject into an electric signal to generate an image signal
Data Source
AI summary
A digital photographing apparatus and a method of controlling the digital photographing apparatus are provided. The digital photographing apparatus stores an image signal in a memory at the same time with the calculation of a horizontal AF evaluation value with respect to the image signal, and calculates a vertical AF evaluation value by using the stored image signal. Accordingly, exact AF detection may be performed with respect to images of all patterns.