HP INCFollow


One of the applications of printers with white inks is to print on a transparent substrate and cover it

with white, so that the image, printed in mirror image, is seen through the substrate on a white

background. An unmirrored image can be printed on the other side, allowing for an image on both sides

of the substrate. This is referred to as a (three‐layer) sandwich mode.

To reduce translucency, a variation is the five‐layer sandwich mode, in which the middle white layer is

replaced by another sandwich of white, black and white.

Depending on the hardware, in particular the carriage layout, this can be printed in a single job: so this

has to print the first image in mirror image, then cover it with white, optionally a layer of black and

another layer of white, and finally print the second image.

To do this, you need (logical) pens of all fluids needed for the first image at the bottom of your carriage,

which passes over the image first, after that a pen with white ink, and finally another set of pens for the

second image.

We describe an approach in which each physical trench (nozzle array) of a given colorant in a given pass

only has to print the data of a single image plane, and mask it with a single mask. It is described how two

image planes and two masks can be encoded in a single one, enabling the three layer mode with a single

trench, and five layer with just two trenches, at the cost of a reduced bit depth of each image.

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