Focus Area Shaping for Low Light Autofocus Accuracy
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Solution Overview
Problem
In low brightness conditions, digital single lens reflex cameras face challenges in focusing on subjects at varying distances due to far and near focus detection competition, leading to undesirable results such as subjects being out of focus or the background being in focus instead.
Innovation Solution
A focus adjustment apparatus and method that includes a focus lens, a focus lens driver, an image pickup unit, a determiner, a focus area setting unit, and a lens controller, which sets a focus area with a narrow upper part width and adjusts the focus accordingly to prioritize the subject in low brightness scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the focus area is enlarged in low brightness conditions, then more subjects can be detected, but far and near focus detection competition occurs leading to focusing errors
Solution Approach 1:
The focus area is segmented into multiple sub-areas, with different weighting applied to different regions. The lower part of the focus area (where the subject is more likely to be located) is given higher weight, while the upper part (where background subjects and light sources are more likely to be) is given lower weight. This segmentation allows the system to process information from the entire enlarged focus area while prioritizing the subject region.
Solution Approach 2:
Different regions within the focus area are assigned different qualities or weights. The lower region is assigned higher quality/weight for focus detection, while the upper region is assigned lower quality/weight. This local differentiation enables the system to emphasize the subject region while still utilizing the enlarged focus area for low brightness detection.
2Quantity of substance
If the focus area includes both near and far subjects, then more information is captured, but the contrast value may not match the in-focus position
Solution Approach 1:
The focus detection process is segmented into weighted sub-areas, allowing the system to capture information from both near and far regions while giving different importance to each region. This enables quantity of information capture without compromising focus position accuracy.
Solution Approach 2:
The system performs partial focus detection by emphasizing certain regions (lower part) over others (upper part). Rather than treating all regions equally, it applies partial action with higher weight to the subject-likely region, ensuring accurate focus detection even when the focus area encompasses multiple depth planes.
3Illumination intensity
If dot light sources are included in the focus area, then brightness detection is improved, but the maximum contrast value does not match the in-focus position
Solution Approach 1:
The focus area is segmented to separate regions likely to contain subjects from regions likely to contain light sources. By applying different weights to different segments, the system can utilize brightness information from light sources without allowing them to dominate the contrast calculation and cause focus errors.
Solution Approach 2:
Different local regions are assigned different qualities in the focus detection process. Regions in the lower part of the focus area (subject regions) are assigned higher quality/weight, while regions in the upper part (light source regions) are assigned lower quality/weight. This local quality differentiation allows brightness detection improvement while maintaining contrast value accuracy for subject focus.
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
Effectively focuses on the desired subject even in low brightness conditions by minimizing the influence of background subjects and dot light sources, reducing far and near focus competition, and ensuring the subject is in focus.
Implementation Method 1
an image pickup unit for generating an image signal by converting image light incident through the focus lens into an electrical signal
Data Source
AI summary
Focus adjustment apparatus and methods for effectively auto-focusing on a subject by adaptively changing a shape of a focus area according to a determined image condition, and in particular, setting the focus area in a shape of which a width of an upper part is narrow according to the condition.