Dot-on-dot printing halftone graininess reduction via sequential color conversion

The patent divides the printing process into separate passes for different color groups (e.g., CMYK and RGB). Each pass uses its own optimized half-toning screen, allowing each screen to be designed for optimal dot distribution without compromise. This segmentation resolves the contradiction by maintaining simple individual processes while achieving high overall image quality through multiple specialized passes.

The patent applies inverted screens strategically to specific color groups (e.g., using inverted CMYK screen for one pass and regular RGB screen for another pass, or vice versa). This selective inversion prevents overlapping droplets in specific color combinations while avoiding the dot clumping problem that would occur if inversion were applied uniformly to all colors. The contradiction is resolved by applying the inversion principle selectively rather than universally.

The patent introduces a temporal dimension by using multiple printing passes with different screen configurations. Instead of trying to solve the dot-on-dot problem within a single spatial plane (which causes graininess and Moiré), the solution moves to multiple temporal layers where each pass handles specific color groups with optimized screens. This dimensional transition from single-plane to multi-pass approach resolves the contradiction by eliminating harmful dot-on-dot printing without generating artifacts.

The patent changes the correlation parameter between screens for different color groups. Instead of using completely uncorrelated screens (which cause random dot patterns) or identical screens (which cause aligned dot patterns), the invention uses screens with controlled partial correlation - screens that are related but not identical, creating a balance where dots are sufficiently distributed without complete alignment. This parameter adjustment resolves the contradiction between preventing dot alignment and maintaining image uniformity.