Phase Difference AF Reliability Determination Using Correlation Amount Comparison
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Solution Overview
Problem
The phase difference auto-focus (AF) method in imaging devices is slow due to the time required for frequency analysis, which prolongs the time to achieve focus on a subject, especially when high-frequency patterns are present in the image.
Innovation Solution
An imaging device with a focusing control method that uses a pair of signal detection units to perform correlation operations and determine the reliability of focusing control based on phase difference AF, allowing for faster determination by comparing correlation amounts between detection signal groups from differently arranged phase difference detection pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency analysis is performed to determine reliability of phase difference AF, then measurement precision is improved, but time consumption increases
Solution Approach 1:
The patent segments the imaging pixels into multiple groups based on their positional relationships, creating first pairs and second pairs of pixel groups. This segmentation allows parallel processing of correlation operations on different pixel groups, reducing the overall computation time while maintaining reliable focus determination through multiple comparison pathways.
Solution Approach 2:
The patent performs correlation operations on multiple pixel groups in advance and stores the results. By pre-calculating correlation amounts for different pixel group configurations before final reliability determination, the system reduces the time needed for actual focus decision-making, as the computational work is already completed and ready for immediate use.
2Speed
If phase difference AF method is used for focusing control, then focusing speed is improved, but reliability is reduced when high frequency patterns are present
Solution Approach 1:
The patent implements a feedback mechanism where correlation operation results from multiple pixel group pairs are continuously monitored and used to dynamically determine reliability. When high frequency patterns are detected through correlation analysis, the system can identify this condition and adjust its focus determination strategy accordingly, providing feedback that maintains reliability while preserving the speed advantages of phase difference AF.
Solution Approach 2:
The patent changes the parameter being analyzed from direct frequency domain analysis to spatial domain correlation operations. By performing correlation operations on detection signal groups from differently arranged pixel pairs and comparing correlation amounts, the system transforms the problem into a form that is less sensitive to high frequency patterns, thereby maintaining reliability without sacrificing the speed of phase difference AF.
3Measurement precision
If multiple pixel groups are processed for reliability determination, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the reliability determination process with the existing phase difference AF processing pipeline. By integrating correlation operations into the standard focus control flow and using the same detection signal groups already captured for phase difference measurement, the system achieves improved measurement precision without adding separate dedicated hardware or processing pathways, thus avoiding significant increases in device complexity.
Data Source
AI summary
The present invention provides an imaging device and a focusing control method capable of performing reliability determination of a phase difference AF at high speed. A phase difference AF processing unit (19) performs a correlation operation with respect to detection signal groups in first pairs P1, and performs a correlation operation with respect to detection signal groups in second pairs P2. A system control unit (11) compares a difference between a first correlation amount M1 which is a minimum correlation amount between the detection signal groups in the first pairs P1, among obtained results of the correlation operation with respect to the first pairs P1 and a second correlation amount M2 which is a minimum correlation amount between the detection signal groups in the second pairs P2, among obtained results of the correlation operation with respect to the second pairs P2 with a threshold value TH, to thereby determine a reliability of a focusing control based on the phase difference AF method.