Halftone Dot Pattern Design for Laser Print Stability
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Solution Overview
Problem
High frequency or stochastic halftone screens used in laser printers can appear unstable or noisy due to irregular dot spacing, affecting the quality of printed images.
Innovation Solution
Generating non-printing halftone dots with a lower frequency and larger size, and connecting printing halftone dots with lines to create a higher frequency pattern, which reduces toner density and improves toner distribution, thereby stabilizing the print output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high frequency or stochastic halftone screens are used, then image detail and resolution are improved, but the printed output appears unstable or noisy
Solution Approach 1:
The patent divides the halftone screen into two distinct frequency components: a high-frequency component that provides image detail and a low-frequency component that provides stability. This segmentation allows each frequency to serve its specific function without the drawbacks of using a single high-frequency screen alone.
Solution Approach 2:
The patent creates a composite halftone screen by superimposing two different frequency patterns (high-frequency and low-frequency screens) to form a single combined screen. This composite structure combines the advantages of both frequencies: the high-frequency component provides image detail while the low-frequency component provides print stability and reduces noise.
2Measurement precision
If smaller halftone dot sizes are used to maintain appearance at each color level, then image quality is improved, but the amount of toner used is reduced which can affect coverage
Solution Approach 1:
The patent changes the frequency parameter of the halftone screen by introducing a low-frequency component in addition to the high-frequency component. This parameter change allows smaller dots to be used for image quality while the low-frequency pattern ensures adequate toner distribution and coverage across the printed area.
3Measurement precision
If stochastic patterns with irregular dot spacing are used, then image realism is improved, but the appearance becomes noisy and unstable in laser printers
Solution Approach 1:
The patent segments the stochastic pattern into two frequency components, allowing the high-frequency stochastic element to provide realism while the low-frequency element suppresses the noisy appearance that occurs in laser printing.
Solution Approach 2:
The patent combines a stochastic high-frequency pattern with a regular low-frequency pattern to create a composite screen that maintains the realism benefits of stochastic screening while eliminating the noisy appearance through the stabilizing low-frequency component.
Data Source
AI summary
A special-purpose image processor can convert an electronic file into a bitmap by generating printing halftone dots within the bitmap based on locations of colors within the electronic file, and generating non-printing dots within the bitmap. A printing apparatus can print the bitmap, by not print marking materials where the non-printing dots are positioned within the bitmap. The special-purpose image processor can generate the non-printing dots within the bitmap by increasing the size of the printing halftone dots until they contact one another, or generating printing lines that connect the printing halftone dots to each other within the bitmap. Also, the special-purpose image processor can generate, as each printing halftone dot, a higher frequency pattern of printing dots, where the non-printing dots are generated to have a lower frequency pattern relative to that higher frequency.