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.
1. 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 colored ink mixture comprises a spectral reflectivity greater than the first colored ink or design at or around 660 nm, and wherein the 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%.
2. The printed object of claim 1 in which the colored ink mixture comprises opaque white ink and a plurality of colorants including the first colorant.
3. The printed object of claim 2 , in which the plurality of colorants comprises Lithol Rubine, and the first colorant comprises Carbazole Violet.
4. The printed object of claim 3 in which the colored ink mixture comprises by weight or volume 30%-42% Lithol Rubine, 8%-22% Carbazole Violet and 44%-56% Opaque White.
5. The printed object of claim 4 in which the first colored ink or design comprises a color selected from the color group consisting of: PANTONE 357 C, PANTONE 2945, and PANTONE Violet.
6. The printed object of claim 4 in which the first colored ink or design comprises a color selected from the color group consisting of: PANTONE 357 C, PANTONE 2945, PANTONE Violet and a Cyan/Magenta/Yellow combination.
7. The printed object of claim 3 in which the colored ink mixture comprises by weight or volume 36% Lithol Rubine, 14% Carbazole Violet and 50% Opaque White.
8. The printed object of claim 1 in which the first colorant comprises Lithol Rubine.
9. The printed object of claim 8 in which the volume of weight ratio for the colored ink mixture comprises 24%-32% Lithol Rubine and 68%-76% opaque white.
10. The printed object of claim 8 in which the volume or weight ratio for the colored ink mixture comprises 78% opaque white and 22% Lithol Rubine.
11. The printed object of claim 1 in which the difference range comprises 12%-25%.
12. The printed object of claim 1 in which the first colored ink or design and the colored ink mixture comprise a spectral reflectivity difference of 12%-30% at 670 nm±10 nm.
13. The printed object of claim 1 in which the encoded signal comprises a sparse mark and carries a plural bit payload.
14. The printed object of claim 1 in which at or around 660 nm comprises a spectral range of 620 nm-700 nm.
15. An image processing method comprising:
obtaining optically captured imagery representing a printed object, the imagery captured by a scanner including a peak illumination at or around 660 nm, the printed object comprising a substrate comprising a first area, and 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, and 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 colored ink mixture comprises a spectral reflectivity greater than the first colored ink or design at or around 660 nm, and wherein the 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, the encoded signal comprising a plural-bit payload, 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%;
processing the captured imagery to decode the plural-bit payload from the encoded signal;
outputting the plural-bit payload.
16. The image processing method of claim 15 , in which the colored ink mixture comprises Lithol Rubine, and the first colorant comprises Carbazole Violet.
17. The image processing method of claim 16 in which the colored ink mixture comprises by weight or volume 30%-42% Lithol Rubine, 8%-22% Carbazole Violet and 44%-56% Opaque White.
18. The image processing method of claim 17 in which the first colored ink or design comprises a color selected from the color group consisting of: PANTONE 357 C, PANTONE 2945, and PANTONE Violet.
19. The image processing method of claim 15 in which the colored ink mixture comprises by weight or volume 36% Lithol Rubine, 14% Carbazole Violet and 50% Opaque White.
20. The image processing method of claim 15 in which the first colored ink or design and the colored ink mixture comprise a spectral reflectivity difference of 12%-30% at 670 nm±10 nm.
21. The image processing method of claim 15 in which the encoded signal comprises a sparse mark.
22. The image processing method of claim 15 in which the first colored ink or design comprises a color selected from the color group consisting of: PANTONE 357 C, PANTONE 2945, PANTONE Violet, and a Cyan/Magenta/Yellow combination.