Camera Clamp Circuit Switching Between Partial Black Areas
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Solution Overview
Problem
Conventional electronic cameras experience fluctuations in clamp levels due to differences between preliminary feeding and optical black levels, leading to inefficiencies in the clamping process.
Innovation Solution
An electronic camera system that includes evaluators for assessing luminance in specific image areas, a damper for precise clamping, and a switcher to alternate between partial black areas based on evaluation values, ensuring high-precision clamping by adjusting for potential blooming effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If clamp timing is switched between optimal black period and preliminary feeding period based on level difference, then the clamping process can adapt to different lighting conditions, but the clamp level fluctuates due to the level difference between preliminary feeding level and optical black level
Solution Approach 1:
The patent divides the optical black area into multiple partial black areas (first partial black area and second partial black area) corresponding to different regions of the effective area. Each partial black area is used for clamping in specific situations: the first partial black area is used when blooming occurs in the second partial black area, and vice versa. This local differentiation allows the system to maintain stable clamp levels by selecting the appropriate regional reference based on actual imaging conditions.
2Device complexity
If a single black area is used for clamping, then the device complexity is low, but the clamping precision deteriorates when blooming occurs in certain regions
Solution Approach 1:
The optical black area is segmented into multiple partial black areas (first partial black area and second partial black area), each serving as a clamping reference for specific regions. The switcher selectively chooses which partial black area to use based on blooming detection, thereby maintaining high clamping precision without requiring complex additional hardware.
Solution Approach 2:
The system dynamically switches between different partial black areas for clamping based on real-time evaluation of luminance levels and detection of blooming conditions. The switcher changes the clamping reference from the first partial black area to the second partial black area (or vice versa) depending on which region is experiencing blooming, making the clamping process adaptive to changing imaging conditions.
3Device complexity
If clamp level is fixed, then the device complexity is reduced, but the clamping accuracy deteriorates when blooming occurs in different regions of the image sensor
Solution Approach 1:
The clamp level is made dynamic by implementing a switching mechanism that selects between different partial black areas based on blooming detection. The switcher monitors luminance levels in different regions and automatically switches the clamping reference to an unaffected region when blooming occurs, thereby maintaining high clamping accuracy without requiring manual intervention or complex calibration procedures.
Data Source
AI summary
An electronic camera includes a CCD imager. A first specific evaluation area is assigned to one end in a horizontal direction of an effective area formed on an imaging surface, and a second specific evaluation area is assigned to the other end in a horizontal direction of the effective area. Also, a first clamp area is assigned in an optical black area in vicinity of the first specific evaluation area, and a second clamp area is assigned in an optical black area in vicinity of the second specific evaluation area. A luminance evaluation circuit obtains a first luminance evaluation value with respect to the first specific evaluation area and obtains a second luminance evaluation value with respect to the second specific evaluation area. In addition, a clamp circuit performs a clamping process on a raw image signal taking note of the first clamp area or the second clamp area. A CPU switches the area to be noted for the clamping process between the first clamp area and the second clamp area based on the first luminance evaluation value and the second luminance evaluation value.