Halftone Processing Apparatus for Consistent Dot Density
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Solution Overview
Problem
Existing image processing technologies for printing fail to accurately express print image densities due to differences in driving signals for isolated and consecutive dots, leading to inconsistent dot densities in printed images.
Innovation Solution
An image processing apparatus and method that perform a halftone process to generate processed image data, calculating corrected tone values and error values for pixels, and determining dot values based on threshold comparisons, allowing for appropriate dot formation status and density expression by distinguishing between isolated and consecutive dots using different density values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different driving signals are used for isolated dots and consecutive dots to ensure reliable dot formation, then dot formation reliability is improved, but dot density consistency deteriorates
Solution Approach 1:
The patent applies local quality by using different driving signals for different dot types (isolated vs. consecutive dots) based on their local formation conditions. The controller selectively applies first driving signals for isolated dots and second driving signals for consecutive dots, allowing each dot type to be optimized for its specific formation context while maintaining overall density consistency through error diffusion compensation.
Solution Approach 2:
The patent changes the driving signal parameters (pulse width, amplitude, or frequency) depending on the dot formation context. By adjusting these parameters dynamically based on whether a dot is isolated or consecutive, the system achieves reliable dot formation while compensating for density variations through the error diffusion process.
2Manufacturing precision
If error diffusion is applied uniformly to all pixels, then overall image quality is improved, but local density accuracy for different dot types deteriorates
Solution Approach 1:
The patent implements local quality by performing error diffusion processing separately for different dot types. Error values are calculated and distributed differently for isolated dots versus consecutive dots, allowing each dot type to maintain its local density accuracy while contributing to the overall image quality through the error diffusion mechanism.
Data Source
AI summary
The present invention provides an image processing apparatus that includes a processor. The processor is configured to calculate a corrected tone value of a target pixel using a tone value of the target pixel and an error value of a previously processed pixel; determine a dot value of the target pixel by comparing the corrected tone value with a threshold value; calculate an error value of the target pixel using the corrected tone value and a first density value when the dot value indicates to form a dot and the dot to be formed is a first dot formed in isolation; and calculate an error value of the target pixel using the corrected tone value and a second density value when the dot value indicates to form a dot and the dot to be formed is a second dot formed at a particular location in consecutive dots.