US Patent 11354767 Signal encoding for physical objects including dark ink

This disclosure relates to advanced image signal processing technology including encoded signals and digital watermarking. One implementation is directed a printed object comprising: a substrate comprising a first area; a first colored ink or design printed within the first area, the first colored ink or design comprising a spectral reflectivity of less than or equal to 20% at or around 660 nm; a colored ink mixture printed over the first colored ink or design at a first plurality of spatial locations within the first area, the colored ink mixture printed such that the first area comprises a second plurality of spatial locations without the colored ink mixture, the colored ink mixture comprising opaque white ink and a first colorant, wherein the color ink mixture comprises a spectral reflectivity greater than the first colored ink or design at or around 660 nm, and wherein colored ink mixture comprises a spectral reflectivity less than the first colored ink or design in the range of 495 nm-570 nm; in which the first plurality of spatial locations is arranged in a pattern conveying an encoded signal, and in which the first colored ink or design and the colored ink mixture comprise a spectral reflectivity difference at or around 660 nm in a difference range of 8%-30%. Of course, other objects, methods, packages, labels, containers, systems and apparatus are described in this patent document.