White Balance Control Device Face Region Skin Color Correction
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Solution Overview
Problem
Conventional automatic white balance control methods inaccurately determine skin color as white, especially under varying light conditions, leading to miscorrection of human skin color and decreased accuracy in color temperature information, particularly when face detection is incorrect or unreliable.
Innovation Solution
A white balance control device and method that computes a first white balance correction value, detects face regions, determines if the corrected image signal falls into a skin color region, and adjusts the white balance using a second correction value based on the relationship between the face region and skin color signals, while modifying the correction value according to capture information to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the white detection region is expanded to accommodate skin color under fluorescent light, then the ability to detect white balance under high color temperature light is improved, but skin color is mistakenly determined as white leading to incorrect white balance correction
Solution Approach 1:
The patent divides the color evaluation space into multiple distinct regions: a white color region and a skin color region. By segmenting the detection space rather than using a single unified region, the system can accurately distinguish between white objects and skin tones under fluorescent lighting, preventing miscorrection while maintaining adaptability to different light sources.
Solution Approach 2:
The patent applies different detection criteria and region definitions for different lighting conditions. Under fluorescent light, the system uses specific color evaluation value ranges that are optimized for detecting white objects while excluding skin color regions. This localized optimization for specific lighting conditions enables accurate white balance correction without mistakenly correcting skin tones.
2Measurement precision
If the white detection region is narrowed to avoid mistakenly determining skin color as white under sunlight, then the accuracy of white balance correction is improved, but the ability to detect white color under fluorescent light deteriorates
Solution Approach 1:
The patent dynamically adjusts the white detection region based on the detected lighting conditions. The system determines whether the scene is under sunlight or fluorescent light by analyzing color evaluation values, and then adapts the detection region parameters accordingly. This dynamic adaptation allows the system to maintain high accuracy under sunlight while preserving the ability to detect white objects under fluorescent light.
Solution Approach 2:
The patent changes the parameters defining the white detection region according to lighting conditions. By modifying the color evaluation value thresholds and region boundaries based on whether the scene is under sunlight or fluorescent light, the system optimizes its detection accuracy for each lighting type without compromising performance in other conditions.
3Measurement precision
If face detection is used to exclude face regions from white balance detection, then the accuracy of white balance correction is improved by avoiding skin color miscorrection, but the reliability of face detection affects the stability of the correction process
Solution Approach 1:
The patent incorporates feedback mechanisms that continuously monitor the detection results and adjust the white balance correction process accordingly. When face regions are detected and excluded, the system uses feedback to verify that the correction is achieving the desired effect on skin tones while maintaining accuracy on actual white objects. This feedback loop compensates for potential inaccuracies in face detection by adapting the correction process in real-time.
Data Source
AI summary
A first white balance correction value is computed by detecting white pixels from an image. A determination is made as to whether or not a corrected image signal in the face region falls into a second color signal region surrounding a first color signal region that represents a skin color if white balance of the image signal in the face region is corrected based on the first white balance correction value. When it is determined that the corrected image signal of the face region falls into the second color signal region, a second white balance correction value for correcting the image signal is computed based on relationships between the corrected image signal of face region and the first color signal region. The computed second white balance correction value is modified based on information obtained when the image was captured.