Digital Watermark Encoding for Low Reflectance Backgrounds
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Solution Overview
Problem
Existing digital watermarking technologies face challenges in efficiently embedding and detecting imperceptible signals in images and physical objects, particularly in environments with low reflectance backgrounds, where traditional red LED scanners struggle to detect encoded signals.
Innovation Solution
The method involves determining the reflectance difference between a target color and a substrate at a machine-vision wavelength to optimize signal robustness and visibility, using a Digimarc Barcode solution that selectively modulates package design colors or adds ink to enhance detectability by red LED scanners, and employing a DB Score to evaluate color suitability for encoded signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional red LED scanners are used to detect encoded signals, then the detection process is simple and cost-effective, but the detection reliability fails in environments with low reflectance backgrounds
Solution Approach 1:
The patent changes the wavelength parameter of the detection light from traditional red LED (around 660nm) to green LED (around 530nm). This parameter change exploits the fact that green light has higher reflectance from typical packaging materials and products, thereby improving detection reliability in low reflectance environments without requiring complex hardware modifications
Solution Approach 2:
The patent introduces an intermediary processing step that calculates a synthetic reflectance value by combining reflectance measurements from multiple wavelength channels (including green and red). This intermediary calculation creates a composite signal that compensates for low reflectance in individual channels, enabling reliable detection even when individual wavelength reflectance is low
2Reliability
If digital watermarking is applied to enhance signal robustness, then the encoded signal becomes more reliable, but the visibility to human viewers increases making it perceptible
Solution Approach 1:
The patent applies digital watermarking selectively in specific color channels (particularly in the green channel which is less sensitive to human vision) rather than uniformly across all channels. By concentrating the watermarking effort in locally optimized channels, the patent achieves signal robustness while minimizing overall visual perceptibility
Solution Approach 2:
The patent utilizes color channel transformations and selective modulation of color values to embed the encoded signal. By manipulating color in a way that exploits human color perception characteristics (where certain chrominance variations are less noticeable), the patent achieves robust encoding while maintaining visual imperceptibility under normal viewing conditions
3Measurement precision
If reflectance difference is optimized for machine-vision detection, then the detectability by scanners improves, but the color accuracy for human viewing may be compromised
Solution Approach 1:
The patent separates the optimization goals into different color channels and processing stages. Reflectance optimization for machine vision is applied independently to specific channels (particularly green and luminance channels), while color accuracy is maintained in other channels. This segmentation allows each channel to be optimized for its specific function without compromising overall color fidelity
Solution Approach 2:
The patent transforms the color representation from standard color spaces to a custom color space optimized for machine vision detection. By defining new color parameters that prioritize reflectance characteristics important for scanner detection while maintaining a reversible transformation, the patent achieves both machine-vision detectability and color accuracy preservation
Data Source
AI summary
This disclosure relates to advanced image signal processing technology including encoded signals and digital watermarking. One implementation is directed to a method comprising: obtaining data representing a color area; determining that the data representing the color area, or information obtained by using the data representing the color area, indicates that the color area comprises a reflectivity of 15 percent (%) or less at or around 660 nm; generating an encoded signal, the encoded signal comprising a pattern including signal elements at various spatial locations corresponding to the color area; generating holes in the color area according to the pattern, said generating holes yield an encoded color area; and selecting a fill color for placement within the holes of the encoded color area, said selecting utilizing an encoded signal error that is associated with the color area, the fill color, and a reflectance difference at or around 660 nm between the color area and the fill color, said selecting also utilizing a color error that is associated with the color area, the fill color, and the reflectance difference. Of course, other implementations, methods, packages, systems and apparatus are described in this patent document.