Autofocus Mode Selection Based on Subject Size
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Solution Overview
Problem
The phase difference AF mode in imaging apparatuses with solid-state imaging devices may result in reduced autofocus precision when the AF region is narrowed, leading to focus blurring of the main subject due to high-frequency background elements.
Innovation Solution
An imaging apparatus with a solid-state imaging device that includes a size identification unit to determine the image size of the main subject, an AF region setting unit to adjust the autofocus region based on the image size, and an AF mode selector to switch between phase difference and contrast AF modes depending on the image size, ensuring accurate focus on the main subject.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the AF region is narrowed to prevent background focus, then the harmful effect of back focus is reduced, but the AF precision deteriorates
Solution Approach 1:
The patent dynamically adjusts the AF region size based on the detected subject size. When a small subject is detected, the AF region is narrowed to prevent background focus. When a large subject is detected, the AF region is expanded to maintain sufficient phase difference detection pixels and preserve AF precision. This dynamic adaptation resolves the contradiction by making the AF region flexible rather than fixed.
Solution Approach 2:
The patent changes the parameter of AF region size according to the subject size condition. By modifying this parameter dynamically, the system prevents background focus when appropriate while maintaining AF precision when needed, thus resolving the technical contradiction between preventing back focus and maintaining measurement precision.
2Productivity
If the phase difference AF mode is continuously adopted for fast focus adjustment, then the shutter chance is improved, but the AF precision may not be acquired when the subject size and AF region relationship is inappropriate
Solution Approach 1:
The patent introduces dynamic mode selection based on subject size detection. Instead of continuously using phase difference AF mode, the system switches to contrast AF mode when the subject is small and the AF region would be narrowed, thereby preventing focus blurring. This dynamic strategy maintains high shutter chance while ensuring AF precision in appropriate conditions.
Solution Approach 2:
The patent changes the operating mode parameter (phase difference AF vs. contrast AF) based on the relationship between subject size and AF region. This parameter change ensures that the system maintains both productivity (shutter chance) and measurement precision (AF precision) by selecting the appropriate mode for each shooting scenario.
3Object-affected harmful factors
If the AF region is narrowed to exclude high-frequency background elements, then the harmful effect of background focus is reduced, but the number of phase difference detection pixels decreases
Solution Approach 1:
The patent dynamically adjusts the AF region size based on subject detection. When a small subject is detected, the AF region is narrowed to exclude background elements. When a large subject is detected, the AF region is expanded to include sufficient phase difference detection pixels. This dynamic adjustment resolves the contradiction between excluding background and maintaining pixel quantity.
Solution Approach 2:
The patent changes the AF region size parameter according to subject size conditions, thereby dynamically controlling the number of phase difference detection pixels included. This parameter change allows the system to prevent background focus while maintaining sufficient pixel quantity for accurate focus detection when appropriate.
Data Source
AI summary
An imaging apparatus with a solid-state imaging device having phase difference detection pixels arranged on a light receiving surface acquires the size of a main subject image by identifying the main subject image picked on the light receiving surface of the solid-state imaging device, sets an AF region subjected to autofocus processing in accordance with an image size, and selects a phase difference AF mode (step S32) or a contrast AF mode (step S31) depending on whether the image size is larger than a required size (step S23) as a mode used for the autofocus processing.