Hybrid Webcam Exposure Control Using Face and Background ROIs
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Solution Overview
Problem
Existing webcam systems face issues with over- or underexposure of a user's face due to mean weightage auto exposure algorithms, which fail to accurately adjust exposure levels when the user's position or background lighting changes, leading to user dissatisfaction during videoconferencing.
Innovation Solution
A hybrid face detection auto exposure system that uses a webcam's hardware microcontroller to detect a user's face and background regions of interest, adjusting exposure settings based on both face and background lighting changes, avoiding unnecessary adjustments by setting a brightness threshold for the background region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If mean weightage auto exposure algorithm is used to adjust exposure levels, then overall image brightness is improved, but face exposure accuracy deteriorates when user position or background lighting changes
Solution Approach 1:
The patent divides the image into multiple regions of interest (ROIs), including a face region and a background region. By segmenting the image, the system can independently analyze and adjust exposure for different areas, allowing the face to maintain accurate exposure while the background provides contextual lighting information, thereby resolving the contradiction between overall brightness and face exposure accuracy.
Solution Approach 2:
The patent applies different exposure adjustment strategies to different regions of the image. The face region receives targeted exposure correction based on detected facial brightness, while the background region provides lighting context. This local differentiation ensures that the face maintains optimal exposure quality even when overall image brightness changes due to background lighting variations.
2Measurement precision
If face detection auto exposure system adjusts exposure based on face location, then face exposure accuracy is improved, but unnecessary exposure fluctuations occur when user changes position
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors both face region brightness and background region brightness. The system uses this feedback to distinguish between legitimate exposure adjustments (when background lighting changes) and unnecessary adjustments (when only face position changes). By requiring consistent brightness changes in both regions before triggering exposure adjustment, the system maintains face exposure accuracy while preventing unnecessary fluctuations.
Solution Approach 2:
The patent performs preliminary analysis of background lighting conditions before adjusting exposure. By first detecting and analyzing the background region brightness, the system determines whether a proposed exposure adjustment is necessary. This preliminary action prevents unnecessary exposure changes when the user simply changes position, while still allowing accurate exposure adjustment when actual lighting changes occur.
3Speed
If exposure adjustment is triggered by any brightness change in face region, then face exposure responsiveness is improved, but exposure stability deteriorates due to minor brightness variations
Solution Approach 1:
The patent changes the threshold parameter for triggering exposure adjustments. Instead of responding to any brightness change in the face region, the system requires brightness changes to exceed a predetermined threshold. This parameter modification maintains responsive exposure adjustment for significant lighting changes while filtering out unnecessary adjustments for minor brightness variations, thereby balancing responsiveness and stability.
Data Source
AI summary
A webcam includes a hardware microcontroller and a memory device. The hardware microcontroller executes program code of a hybrid face detection auto exposure module to detect a user's face within an image captured by the webcam and define a first image region of interest of the image that includes the user's face with the second image region of interest of the image including a background of the image, executes program code of a lighting detection module to detect brightness levels of the user's face within the first image region of interest and brightness levels in the second image region of interest, and executes program code of a hybrid face detection auto exposure module to determine if a background brightness change threshold level is exceeded and to automatically adjust an exposure setting for the first image region of interest of the image captured by the webcam when the threshold is exceeded.