Auto Focus Window Brightness Detection for Off-Center Subjects
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Solution Overview
Problem
Image capturing devices, such as cameras, struggle to perform Auto Focus (AF) functions on subjects not located in the central area of the image, and they fail to effectively focus in low-light environments without a flash.
Innovation Solution
An image capturing device equipped with an image sensor, a flash unit, and a controller that divides the image into windows, determines the brightest window, and sets an AF detection area centered on that window, enabling AF functionality even when the subject is not in the image center, especially in low-light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the AF function is performed centering on the central area of an image, then the focus accuracy in the central area is improved, but the device cannot perform AF on subjects located outside the central area
Solution Approach 1:
The image is divided into multiple regions (e.g., central area and peripheral areas) with different AF detection capabilities. The controller selectively activates AF detection in different regions based on subject location, allowing both central and peripheral subjects to be focused on accurately.
Solution Approach 2:
The AF detection area is dynamically adjusted based on the detected subject position. When a subject is detected outside the central area, the AF detection region is shifted or expanded to cover the subject location, enabling accurate focus adjustment regardless of subject position.
2Illumination intensity
If the flash unit is enabled in dark environments, then the brightness for AF detection is improved, but the device may incorrectly identify bright background areas as subjects
Solution Approach 1:
Different regions of the image are assigned different brightness thresholds for AF detection. The controller adjusts the brightness criterion based on the local characteristics of each region, allowing accurate subject identification in both bright and dark areas without being misled by uniformly bright backgrounds.
Solution Approach 2:
The controller continuously monitors the brightness distribution across the image and adjusts the AF detection parameters based on feedback from the overall image characteristics. This prevents misidentification of bright areas by adapting the detection threshold to the specific scene conditions.
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
Enables accurate Auto Focus on subjects regardless of their location within the image and allows for effective focus in dark environments with low illumination by using the flash unit to determine the subject's position based on brightness values.
Implementation Method 1
an image sensor for generating an image by capturing a subject through a lens
Implementation Method 2
a flash unit for generating a flash of light while the image sensor is capturing the image
Data Source
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AI summary
An apparatus and a method for automatically adjusting a focus in an image capturing device are provided. The method includes generating an image by capturing a subject through a lens when a flash unit is enabled, dividing the image into a plurality of windows, determining a brightest window from among the plurality of windows, and setting an Auto Focus (AF) detection area for performing an AF function centering on the determined window.