Auto White Balance Gain Table Switching for Strobe Color Accuracy
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Solution Overview
Problem
Existing auto white balance control methods in image pickup apparatuses fail to accurately maintain proper white balance when strobe light is used in conjunction with external light sources other than sunlight, leading to color reproduction issues in recorded images.
Innovation Solution
An image pickup apparatus with a light emitting unit, amplifying units, and a control unit that detects the light source and adjusts gains for each color component to ensure accurate white balance, even during strobe light emission, by referencing pre-stored gain tables and varying gain settings based on detected light source types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If auto white balance control is performed using conventional methods during strobe light emission, then white balance is automatically obtained, but color reproduction becomes inaccurate when external light sources other than sunlight are present
Solution Approach 1:
The patent applies parameter changes by switching between different gain tables (first gain table for non-strobe conditions, second gain table for strobe conditions) based on the detected light source type. This allows the system to adjust gain parameters dynamically to match the specific lighting conditions, resolving the contradiction between automated white balance control and accurate color reproduction under varied lighting.
Solution Approach 2:
The system dynamically selects and switches between different gain tables based on real-time detection of the light source type during strobe emission. This dynamic adaptation enables the white balance control to respond to changing lighting conditions, maintaining both automation and color accuracy simultaneously.
2Reliability
If gain setting is performed based on sun light assumptions during strobe emission, then white balance is maintained for sunlight conditions, but color accuracy deteriorates when external light sources other than sunlight are present
Solution Approach 1:
The patent employs feedback by detecting the actual light source type during strobe emission and using this information to select the appropriate gain table. This feedback mechanism ensures that the gain settings accurately reflect the actual lighting conditions rather than relying on assumptions, thereby maintaining both white balance stability and color reproduction accuracy.
Solution Approach 2:
The system changes gain parameters by selecting different gain tables based on detected light source type. When strobe light is detected with external lighting, the second gain table is applied, which provides corrected gain values suitable for those conditions, thus maintaining color accuracy while preserving white balance stability.
3Device complexity
If a single gain table is used for all imaging conditions, then device complexity is reduced, but white balance accuracy deteriorates under different light sources during strobe emission
Solution Approach 1:
The patent applies segmentation by dividing the gain table into multiple versions (first gain table for non-strobe conditions, second gain table for strobe conditions) based on imaging mode. This segmentation allows each gain table to be optimized for its specific condition, improving white balance accuracy without requiring a completely separate system for each mode.
Solution Approach 2:
The control unit serves multiple functions by detecting light source type, determining imaging conditions, and selecting appropriate gain tables. This multi-functionality reduces overall device complexity by consolidating control logic in a single unit rather than requiring separate mechanisms for each function.
Data Source
AI summary
An electronic still camera has first and second gain controller circuits and a gain storage memory. The gain storage memory includes a first gain table for storing gains for an R amplifier and a B amplifier of the first gain controller circuit; and a second gain table for storing gains for an R amplifier and a B amplifier of the second gain controller circuit, during auto white balance control using light emission of a strobe. The gains of the second gain table are sequentially set to the second gain controller circuit to carry out white detection. Based on a result of the detection, a gain to be set to the first gain controller circuit is selected from the first gain table, and the selected gain is set to the first gain controller circuit.