Automatic Exposure Control Using Luminance Sub-Range Mapping
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Solution Overview
Problem
Existing automatic exposure control methods fail to accurately determine exposure compensation values, particularly in scenes with varying lighting conditions such as back-lighting, strong front-lighting, and dark situations, leading to misjudgments and incorrect exposure adjustments.
Innovation Solution
An automatic exposure control method using a coordinate system with sub-ranges for different exposure compensation values, where bright and dark area ratios are calculated to determine the image's position, allowing for appropriate exposure value adjustments based on corresponding sub-ranges, and incorporating a lookup table for precise exposure compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a general-purpose light-metering method is used, then the exposure control process is simple, but the accuracy of exposure compensation is insufficient under varying lighting conditions
Solution Approach 1:
The image frame is divided into multiple smaller element blocks, and each block is further divided into a plurality of sub-blocks. The luminance is calculated separately for each sub-block, and then the sub-blocks are classified into principal object regions and background regions based on their luminance values. This segmentation allows the system to accurately distinguish between different lighting conditions and apply appropriate exposure compensation.
Solution Approach 2:
Different regions of the image are treated differently based on their luminance characteristics. The system calculates the average luminance of sub-blocks in the principal object region and background region separately, and applies different exposure compensation strategies to each region. This local quality approach enables accurate exposure control under varying lighting conditions without requiring complex overall processing.
2Reliability
If the image frame is divided into principal object region and background region based on luminance, then the exposure control for backlighting scenes is improved, but misjudgement occurs when the principal object position changes
Solution Approach 1:
The image frame is divided into multiple smaller element blocks, and each block is further divided into a plurality of sub-blocks. This multi-level segmentation ensures that even when the principal object position changes, the system can accurately identify the new principal object region and background region based on luminance characteristics, preventing misjudgement.
Solution Approach 2:
The system calculates the average luminance of sub-blocks and uses this information to classify regions into principal object and background regions. This feedback mechanism allows the system to dynamically adjust its classification based on the actual luminance distribution in the image, ensuring accurate identification even when object positions change.
3Ease of manufacture
If the average luminance of the entire frame is used for exposure control, then the processing is simple, but the exposure compensation is incorrect for scenes with strong front lighting
Solution Approach 1:
The image frame is divided into multiple smaller element blocks, and each block is further divided into a plurality of sub-blocks. The luminance is calculated separately for each sub-block, and then the sub-blocks are classified into principal object regions and background regions. This segmentation allows the system to distinguish between scenes with strong front lighting and other lighting conditions, applying appropriate exposure compensation without overly complex processing.
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
This method effectively prevents misjudgments in exposure adjustments across various lighting conditions, ensuring proper exposure compensation and maintaining pre-established exposure values for normal lighting scenes, resulting in clearer and more realistic images.
Implementation Method 1
an image sensor, which is a two-dimensional array device formed by a plurality of photo-diodes and which converts a detected optical intensity into an electronic signal
Data Source
AI summary
An automatic exposure control method and compensation apparatus are disclosed. It includes a coordinate system having sub-ranges with different corresponding exposure compensation values. It includes the setting of bright and dark regions threshold values and the calculation of the ratios of the pixel count in an image where the luminance of each pixel is higher than the bright area threshold value for obtaining a bright area ratio, and also includes the calculation of the ratio of the pixel count in an image where the luminance of each pixel is lower than the dark area threshold value for obtaining a dark area ratio. Afterwards, the image position in the coordinate system is determined. When the image position in the coordinate system is fallen inside one of the sub-ranges, the corresponding exposure compensation value of the sub-range where the image is located is given to compensate the exposure value of the image.