Digital Camera White Balance Calibration Using Single Illumination Source
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Solution Overview
Problem
The existing methods for digital camera white balance calibration are time-consuming and costly due to the need for individual testing and calibration of each camera module under various light sources, as gain adjustments are specific to each light source and require multiple tests.
Innovation Solution
A method that allows for initial white-balance calibration of digital camera modules using a single reference illumination source, enabling the determination of fixed scale factors for various illumination sources, which can be applied across different modules, reducing the need for multiple tests and saving time and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If each digital camera module is individually tested and calibrated under multiple light sources to achieve accurate white balance, then the manufacturing precision and reliability are improved, but the calibration time and production cost increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing gain adjustment scaling factors for multiple light sources in a lookup table during manufacturing. Instead of performing time-consuming individual calibration tests under each light source, the system pre-computes the necessary gain adjustments and stores them for rapid retrieval during operation, significantly reducing calibration time while maintaining accuracy
Solution Approach 2:
The patent implements universality by creating a single calibration apparatus that can determine gain adjustment scaling factors for multiple different light sources (incandescent, fluorescent, LED, etc.) using one illumination source. The lookup table stores universal calibration data applicable to various light sources, eliminating the need for separate calibration processes for each light type
2Adaptability or versatility
If individual calibration under each light source is performed, then the adaptability to different illumination conditions is improved, but the device complexity and production cost increase
Solution Approach 1:
The patent applies parameter changes by storing pre-calculated gain adjustment scaling factors for multiple light sources in a lookup table. The system retrieves appropriate calibration parameters based on the detected light source type, enabling adaptable calibration without requiring complex real-time adjustment mechanisms or multiple calibration apparatuses
Solution Approach 2:
The patent introduces an intermediary lookup table that maps light source types to their corresponding gain adjustment scaling factors. This intermediary structure simplifies the calibration process by providing a direct mapping between illumination source and calibration parameters, avoiding complex calculation or multiple calibration procedures
3Reliability
If multiple light sources are used for calibration testing, then the reliability of white balance across different conditions is improved, but the quantity of testing resources and time required increases
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing gain adjustment scaling factors for multiple light sources in a lookup table during manufacturing. Instead of performing time-consuming individual calibration tests under each light source, the system pre-computes the necessary gain adjustments and stores them for rapid retrieval during operation, significantly reducing calibration time while maintaining accuracy
Solution Approach 2:
The patent applies segmentation by separating the calibration data for different light sources into distinct entries in a lookup table. Each light source type (incandescent, fluorescent, LED, etc.) has its pre-calculated gain adjustment scaling factors stored separately, allowing efficient retrieval and application without processing all calibration data simultaneously
Data Source
AI summary
A method includes determining white balance calibration color ratios for a plurality of illumination sources by using a representative camera of a given type to establish a set of ratios. Because the ratios are fixed for the given camera type, a plurality of cameras of the type may store the fixed ratios, and calibrate by measuring only the reference illumination source. Later white balancing is achieved by using the measured reference illumination source color ratios and the stored fixed ratios as scaling factors to map from the reference illumination source to any other illumination source. The method includes an off-line advance calibration procedure to obtain the fixed ratios, an on-line per camera calibration procedure to obtain color ratios for the reference source, and subsequent white balancing which uses the fixed ratios/scaling factors and the reference source color ratios.