Adaptive Threshold Block Processing for Back Surface Noise Removal
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in efficiently removing back surface noise from scan images of duplex-printed documents, leading to deteriorated image quality and increased processing time due to the need for large memory and inaccurate background color treatment.
Innovation Solution
An image forming apparatus and control method that divides the document into block units, using an adaptive threshold to compensate background color data based on brightness and color difference histograms, allowing for accurate removal of back surface noise and reduced processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If brightness checking is performed one by one for entire scan data to set background color threshold, then background color treatment accuracy is improved, but memory capacity requirement increases and processing time increases
Solution Approach 1:
The patent divides the entire scan data into multiple blocks, and performs brightness checking and threshold setting for each block separately. This segmentation allows the processing to be distributed across multiple smaller units, reducing the memory capacity required to store entire scan data while maintaining accurate background color treatment for each region.
Solution Approach 2:
The patent performs preliminary brightness checking and threshold setting for each block before final image processing. By preparing block-specific thresholds in advance, the system avoids the need to check entire scan data sequentially, significantly reducing processing time while maintaining accuracy.
2Productivity
If uniform background color treatment is applied to entire document based on initial scanning, then processing time is reduced, but image quality deteriorates due to inaccurate treatment
Solution Approach 1:
The patent applies different background color treatment thresholds to different blocks of the document based on local characteristics. Each block undergoes independent brightness analysis to determine its specific threshold, ensuring that the background color treatment is accurately adapted to local variations in the document while maintaining efficient processing.
3Measurement precision
If large memory capacity is allocated to store scan data for comprehensive brightness checking, then background color threshold accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments scan data into smaller blocks that can be processed with limited memory capacity. By handling one block at a time rather than storing and processing entire scan data, the system achieves accurate threshold setting without requiring large memory resources, thus reducing device complexity and cost.
Data Source
AI summary
An image forming apparatus and a control method thereof include an adaptive threshold, which can be adapted for every block dividing an entire scanned region of a document, is set. A brightness value of original brightness data of the document is disregarded, and is substituted by a brightness value of background color data corresponding to the block, by use of a brightness threshold and a color difference threshold set as the adaptive threshold based on difference between brightness of the blocks and difference between color differences of the blocks. Accordingly, there is no problem of back surface noise such that an undesired object of a back surface of the duplex-printed document appears on a scan image in scanning a front surface of the document.