Contrast AF Focus Control with Motion Region Exclusion
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Solution Overview
Problem
Existing image pickup apparatuses face challenges in maintaining focus accuracy when a moving object is present, as conventional contrast AF methods can be influenced by motion, leading to potential focus loss and decreased detection accuracy.
Innovation Solution
An image pickup apparatus with a contrast AF section that acquires multiple images while changing the focus position, detects motion in each region, and excludes regions with significant motion from the contrast evaluation calculation, using a correction coefficient to adjust the contrast evaluation value based on the area of the calculation target region and the excluded region, ensuring accurate focus adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contrast AF is performed using all regions in the image, then focus detection can be performed across the entire field of view, but moving objects cause focus loss and decreased detection accuracy
Solution Approach 1:
The image is divided into multiple regions, and motion detection is performed for each region. Regions with motion exceeding a threshold are identified and excluded from contrast evaluation calculations. This segmentation approach allows the system to maintain focus detection in stationary regions while avoiding interference from moving objects.
Solution Approach 2:
Regions containing moving objects are extracted and separated from the calculation target regions. By removing these problematic regions from the contrast evaluation process, the system ensures that focus detection is performed only on stationary areas, thereby maintaining accuracy and preventing focus loss.
2Measurement precision
If motion regions are excluded from contrast evaluation, then focus detection accuracy is maintained, but the calculation target region area decreases
Solution Approach 1:
A correction coefficient is calculated based on the ratio of the calculation target region area to the total image area. This correction coefficient compensates for the reduced calculation area by adjusting the contrast evaluation value, ensuring that focus detection accuracy is maintained even when moving object regions are excluded from calculations.
3Measurement precision
If multiple frames are acquired for contrast AF, then focus position can be determined through contrast evaluation, but processing time increases
Solution Approach 1:
Motion detection is performed in advance on acquired image frames to identify regions containing moving objects before contrast evaluation begins. This preliminary motion detection allows the system to pre-determine which regions should be excluded from contrast calculations, streamlining the subsequent focus detection process and reducing overall processing time.
Data Source
AI summary
An image pickup apparatus is provided with: an objective optical system; an image pickup device; a contrast AF section adjusting a focus so that a peak value of a contrast evaluation value of an image is taken; an amount-of-motion detecting section detecting, from a plurality of time-series images, amounts of motion of the subject; and a control section controlling the contrast AF section so as to calculate another contrast evaluation value in a region where a region to be excluded where an amount of motion is equal to or larger than a threshold is excluded from a calculation target region, and the contrast AF section corrects the other contrast evaluation value based on an area of the calculation target region and an area of the region where the region to be excluded is excluded from the calculation target region.