Autofocus Area Selection Stability in Image Pickup Apparatus
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Autofocusing systems in image pickup apparatuses frequently change the selected autofocus area due to measurement errors, leading to unstable exposure control and user discomfort, especially when subjects are at close distances to each other.
Innovation Solution
An image pickup apparatus with light receiving means, acquiring means, determining means, and selecting means that continuously select the previously determined autofocus area as the focusing target when no scene change is detected, using focusing information and defocus amount calculations to stabilize autofocus area selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If autofocus area selection is performed based on distance measurement, then the nearest subject can be brought into focus, but the selected AF area changes frequently due to measurement errors when subjects are at close distances
Solution Approach 1:
The system performs preliminary actions by continuously monitoring scene parameters (brightness, contrast, color) before making AF area selection decisions. By detecting scene changes in advance through parameter comparison between current and previous frames, the system can maintain the currently selected AF area when no actual scene change occurs, preventing frequent switching due to measurement errors while still responding to genuine subject changes.
2Reliability
If the selected AF area changes frequently to track the nearest subject, then focusing accuracy is maintained, but exposure control becomes unstable and user experience deteriorates
Solution Approach 1:
The system implements feedback mechanisms by continuously comparing scene parameters (brightness, contrast, color) between current and previous frames. This feedback loop allows the system to distinguish between actual scene changes requiring AF area switching and mere measurement fluctuations, thereby maintaining focusing accuracy while stabilizing the selected AF area to prevent user discomfort from frequent changes.
3Measurement precision
If distance measuring sensor measurement accuracy is improved, then nearest subject selection becomes more accurate, but the frequent switching due to measurement errors still occurs when subjects are at similar distances
Solution Approach 1:
By performing preliminary scene change detection through parameter comparison before finalizing AF area selection, the system prevents unnecessary switching caused by measurement errors. This preliminary check saves time by avoiding repeated AF area changes and refocusing operations when subjects are at similar distances, while still maintaining accurate nearest subject selection when genuine scene changes occur.
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 suppresses undesired changes in the selected autofocus area, providing stable exposure control and reducing user frustration by maintaining focus on the originally selected subject even when subjects are at close distances.
Implementation Method 1
light receiving means for performing photoelectric conversion of a subject image introduced through an imaging lens
Data Source
AI summary
In an image pickup apparatus, a light receiving unit produces a first signal at a first timing and a second signal at a second timing later than the first timing. First and second parameters for detecting a scene change are acquired based on the first and second signals, respectively. The presence or the absence of a scene change is determined based on both the parameters. The apparatus further includes a selecting unit configured to select a focusing target AF area from among a plurality of AF areas, and a focusing control unit configured to execute focusing control by using focusing information with respect to the AF area selected by the selecting unit. When the determining unit determines that the scene change is not present, the selecting unit selects the AF area having been selected at the first timing, as the focusing target AF area, at the second timing continuously.