Dot Dispersion Control via Threshold Matrix Correction and Error Diffusion
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Solution Overview
Problem
Existing image forming technologies face challenges in achieving well-dispersed distributions of dots with different densities per unit area, leading to deteriorated image quality due to the restriction of quantization error reflection to unprocessed pixels, resulting in poor dispersion and graininess.
Innovation Solution
An image forming apparatus and method that utilize a first dot formation determining section for dither method-based dot formation, a second dot formation determining section for error diffusion-based dot formation, and a calculating section to correct and reflect the threshold value matrix, ensuring proper dot placement and dispersion by controlling the position of dots and preventing interference between different dot types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If quantization error reflection is restricted to unprocessed pixels only, then the processing complexity is reduced, but the dot dispersion deteriorates and image quality worsens
Solution Approach 1:
The patent implements feedback by allowing processed pixels to reflect their quantization errors back to influence subsequent dot formation decisions. The error diffusion mechanism continuously feeds back error information from already-processed pixels to the current processing position, enabling dynamic adjustment of dot placement based on accumulated errors from all previously processed pixels, not just unprocessed ones.
Solution Approach 2:
The patent performs preliminary error accumulation by maintaining running error values for all pixels throughout the processing sequence. Before making a dot formation decision at any position, the system has already accumulated error information from all previously processed pixels, allowing the current decision to be informed by the complete error history rather than being restricted to future unprocessed pixels only.
2Ease of manufacture
If high density dots are determined by dither method and low density dots by error diffusion method, then dot formation is simplified, but the interference between different dot types causes poor dispersion
Solution Approach 1:
The patent merges the dither method and error diffusion method into a unified processing framework. Both methods operate simultaneously within the same error diffusion loop, sharing the same error accumulation and feedback mechanism. The quantization error from high density dot decisions (dither) is immediately fed into the error diffusion process that governs low density dot formation, creating a coordinated interaction between the two dot types rather than independent processing.
Solution Approach 2:
The quantization error serves as an intermediary that mediates between high density dot formation (dither method) and low density dot formation (error diffusion method). The error value acts as a communication channel between the two processes, allowing the decision to form a high density dot to directly influence subsequent low density dot placement decisions through the error feedback mechanism, thereby coordinating their interactions.
Data Source
AI summary
An image forming apparatus, for forming an image with plural types of dots having different densities per unit area in a same hue, including: a section to compare between a pixel value of a target pixel and a value of a prescribed threshold value matrix, and to determine, based on the comparison, whether to form a first type of dot at a position corresponding to the target pixel; a section for calculating a corrected threshold value matrix from the prescribed threshold value matrix; a section for calculating a second determining condition by reflecting the corrected threshold value matrix; and a section for determining whether to form the second type of dot, based on a target pixel value added an error with an error diffusion process and the second determining condition, at the position where the first type of dot has been determined not to be formed.