Pattern-Light Sheet Surface Identification for Asperity Detection
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Solution Overview
Problem
Existing sheet identification techniques in image forming apparatuses struggle with low accuracy in detecting asperities due to the need for shallow light incident angles, which results in dark images with asperity shadows being buried in noise.
Innovation Solution
A sheet identification device that projects pattern light onto the sheet surface to capture an identification image, allowing for the identification of asperity information based on the deformation and distortion of the pattern light, thereby improving accuracy without requiring shallow light angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light incident angle is made shallow to increase sensitivity to asperities, then the sensitivity to asperities is improved, but the overall image becomes dark and asperity shadows are buried in noise
Solution Approach 1:
The invention segments the illumination into multiple discrete light sources positioned at different angles and locations. Instead of using a single shallow-angle light source that creates dark images, multiple light sources illuminate different regions of the sheet surface, segmenting both the illumination task and the resulting image data. This allows the system to maintain sensitivity to asperities while avoiding overall image darkness.
Solution Approach 2:
The invention transitions from a single-angle illumination approach to multi-angle illumination, adding the dimension of angular diversity. By illuminating the sheet surface from multiple different angles simultaneously, the system captures asperity information from various perspectives, maintaining sensitivity while ensuring adequate overall illumination and preventing shadow burial in noise.
2Measurement precision
If oblique light irradiation is used to detect shadow images of asperities, then asperity detection capability is improved, but the detection accuracy varies depending on fiber direction
Solution Approach 1:
The invention segments the detection task by using multiple light sources positioned at different angles relative to the sheet conveying direction. Each light source illuminates from a different angular position, and the imaging apparatus captures images from multiple angles. This segmentation of the detection process ensures that asperities are detected consistently regardless of fiber direction, as the multi-angle approach averages out directional biases.
Solution Approach 2:
The invention deliberately uses asymmetric illumination angles positioned at specific orientations (e.g., ±45 degrees) relative to the conveying direction. This asymmetric multi-angle approach is designed to counteract the asymmetric effect of fiber direction on detection accuracy. By illuminating from multiple asymmetric angles, the system compensates for fiber-direction-dependent variations and achieves consistent detection accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the accuracy of identifying asperities on the sheet surface by providing a bright identification image, enabling improved image processing conditions and quality.
Implementation Method 1
the surface roughness of the sheet is estimated by detecting a shadow image caused by the asperities on the surface of the sheet from the image of the irradiation region
Implementation Method 2
an area sensor that reads the irradiation region as an image
Data Source
AI summary
A sheet identification device includes an acquisition portion and an asperity identification portion. The acquisition portion acquires an identification image (Im1). The identification image (Im1) is an image of an identification region (R1) of the surface (A1) of a sheet (Sh1) on which image formation or image reading is performed. The identification region (R1) is a region on which pattern light (P1) is projected of the surface (A1) of the sheet (Sh1). The asperity identification portion identifies asperity information on the asperities on the surface (A1) of the sheet (Sh1), based on the identification image (Im1).