Mask Processor Sheet Edge Detection for Oblique Alignment
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in preventing colored materials from adhering to the outer periphery of print sheets, particularly when the sheets are not aligned correctly, leading to image quality degradation.
Innovation Solution
An image forming apparatus equipped with a conveying belt, a print engine, an image sensor, and a mask processor that sets a mask area based on the shape of the print sheet, performing mask processing on the outer periphery to prevent ink from being deposited outside the sheet boundaries, even when the sheet is positioned obliquely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mask processing is performed based on simple sheet detection, then processing speed is maintained, but image quality degrades when sheets are obliquely positioned
Solution Approach 1:
The patent performs preliminary detection of the sheet's long-edge direction before mask processing. The detection unit identifies the sheet orientation in advance, and the mask processing unit uses this information to rotate or adjust the mask area accordingly. This preliminary action ensures accurate mask alignment with obliquely positioned sheets without adding complex real-time adjustment mechanisms during the printing process.
Solution Approach 2:
The patent replaces complex mechanical adjustment mechanisms with image processing algorithms. Instead of physically rotating masks or adjusting mechanical components to match sheet orientation, the system uses software-based detection of sheet direction and applies corresponding transformations to the mask area in the digital domain, simplifying the overall system while maintaining precision.
2Reliability
If the mask area is expanded to cover oblique sheets, then ink adhesion prevention improves, but image quality degrades due to excessive masking
Solution Approach 1:
The patent applies mask processing with locally adjusted parameters rather than a uniform approach. The mask processing unit determines the sheet's long-edge direction and applies masking specifically along the detected edges at appropriate distances. This local quality approach ensures that masking is applied precisely where needed to prevent ink adhesion while avoiding excessive masking that would degrade image quality in other areas.
Solution Approach 2:
The patent dynamically changes mask parameters based on detected sheet orientation. The mask distance from sheet edges and the angular orientation of the mask area are adjusted according to the detected long-edge direction of oblique sheets. This parameter adaptation ensures optimal masking effectiveness for preventing ink adhesion while maintaining image quality by avoiding over-masking.
3Measurement precision
If sheet detection sensitivity is increased, then sheet boundary detection accuracy improves, but false detection increases leading to processing errors
Solution Approach 1:
The detection unit employs feedback mechanisms to verify sheet boundary detections. After initial detection of potential sheet edges, the system performs verification checks to confirm whether detected boundaries are genuine or false detections. This feedback loop allows the system to maintain high detection sensitivity for accurate sheet boundary identification while filtering out false detections that would lead to processing errors.
Solution Approach 2:
The patent implements preliminary anti-action by establishing detection thresholds and validation criteria before final sheet boundary determination. The system预先 sets criteria for what constitutes a valid sheet boundary detection, preventing false detections from triggering erroneous mask processing. This preliminary anti-action against false detections maintains measurement precision while preserving detection reliability.
Data Source
AI summary
A mask processor sets a mask area based on a shape of a print sheet read by an image sensor, masks an outer peripheral portion of a print image using the mask area, and causes a print engine to form a mask-processed print image. The mask processor (a) identifies a pixel in which the print sheet is detected in a line image obtained from an output of the image sensor, (b) detects a sub-scanning-direction reference position corresponding to an edge of the print sheet based on the number of pixels in which the print sheet is detected, and (c) sets a linear edge of the mask area at a line spaced apart by a specific number of offset lines from a line where the sub-scanning-direction reference position is detected toward a center of the print sheet.