Digital Camera White Balance Correction for Mixed Strobe and Ambient Lighting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digital cameras struggle to maintain consistent white balance in photographs taken with partial strobe illumination, as the color balance of strobe light often differs from ambient lighting, leading to discordant appearances in images.
Innovation Solution
A method is implemented to generate a blended image by combining a strobe image and an ambient image using color correction factors and histogram factors, aligning and blending pixels to achieve consistent white balance across regions illuminated by both light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a digital camera uses a strobe to illuminate the subject in low-light conditions, then the exposure level is improved, but the color balance becomes discordant between strobe-illuminated and ambient-illuminated regions
Solution Approach 1:
The patent segments the image processing into two distinct pathways: one for strobe-illuminated regions and one for ambient-illuminated regions. By separating the white balance processing for these two light sources, the system can apply different color correction factors to each region, thereby maintaining color balance consistency within each region while allowing the overall image to contain both types of illumination.
Solution Approach 2:
The patent applies local quality by determining whether each pixel or region is primarily illuminated by the strobe or by ambient light, and then applying the appropriate white balance correction. This localized approach ensures that each region receives the correct color correction for its specific illumination source, resolving the color balance discordance while preserving the benefits of strobe illumination.
2Measurement precision
If a digital camera applies white balance compensation for ambient illumination, then the color accuracy of ambient regions is improved, but the strobe-illuminated regions become color-distorted
Solution Approach 1:
The patent segments the white balance processing by creating separate correction pathways for strobe and ambient illumination. Pixels are classified into those primarily illuminated by the strobe and those by ambient light, with different white balance compensation applied to each segment. This segmentation allows each region to achieve color accuracy appropriate to its illumination source while maintaining overall image consistency.
Solution Approach 2:
The patent introduces an intermediary classification mechanism that determines the primary illumination source for each pixel. This intermediary step acts as a mediator between the two white balance correction systems, routing each pixel to the appropriate correction pathway and ensuring that color consistency is maintained across regions with different illumination sources.
3Device complexity
If a digital camera uses a single set of gain values for all regions, then the device complexity is reduced, but the color balance cannot be properly corrected for mixed illumination sources
Solution Approach 1:
The patent implements dynamic white balance correction by determining the primary illumination source for each pixel and applying the appropriate correction factors. Rather than using a static single set of gain values, the system dynamically selects between strobe-based and ambient-based white balance corrections on a pixel-by-pixel basis. This dynamic approach maintains adaptability to mixed illumination while managing complexity through efficient pixel classification.
Solution Approach 2:
The patent creates a universal white balance processing system that can handle multiple illumination sources through a single integrated algorithm. The system universally processes all pixels through the same classification and correction framework, adapting to whichever illumination source is primary for each pixel. This multi-functional approach allows the camera to properly correct color balance for mixed illumination without requiring separate processing pipelines for different lighting scenarios.
Data Source
AI summary
A technique for generating a digital photograph comprises blending two related images, each sampled according to a different illumination environment. The two related images are blended according to a blend surface function that includes a height discontinuity separating two different blend weight regions. Color consistency between the two related images is achieved by spatial color correction prior to blending. The technique enables a digital camera to generate a strobe image having an appearance of consistent color despite discordant strobe and ambient scene illumination.