Window Soiling Check Using Combined Spectral Channels
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Solution Overview
Problem
Current methods for checking window soiling in measuring apparatuses for sheet material are unreliable, as they fail to detect 'dark soiling' and only partially detect 'light soiling', leading to incorrect classification of sheet material as faulty.
Innovation Solution
Combining multiple spectral channels to evaluate temporal variations in intensity, using a combined spectral channel to differentiate between soiling types, and employing statistical evaluations like standard deviation and average value quotients to identify dark soiling, which is not recognized by existing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the window is cleaned frequently to maintain measurement accuracy, then the reliability of sheet material checking is improved, but the throughput of the apparatus is reduced due to interruptions
Solution Approach 1:
The soiling check is performed in advance during gaps between sheet material measurements, allowing the system to detect window soiling before it significantly degrades measurement accuracy. This preliminary detection enables proactive scheduling of cleaning operations during natural interruptions, rather than waiting for accuracy degradation to trigger urgent cleaning that would interrupt throughput.
Solution Approach 2:
The system continuously monitors window soiling levels and provides feedback about the window condition state. This feedback mechanism allows the system to adaptively determine when cleaning is necessary based on actual soiling levels rather than fixed schedules, optimizing the balance between maintaining measurement reliability and maximizing throughput by cleaning only when necessary.
2Device complexity
If the threshold-based soiling check method is used, then the device complexity is kept low, but the measurement precision of soiling detection is insufficient leading to false classifications
Solution Approach 1:
The system transitions from single-threshold intensity comparison to multi-threshold classification with three distinct soiling level categories (first, second, and third levels). This dimensional expansion in the evaluation criteria enables more precise differentiation of soiling severity, allowing the system to distinguish between minor soiling that tolerable and severe soiling requiring immediate cleaning, thereby reducing false classifications while maintaining relatively simple device architecture.
3Ease of operation
If the intensity comparison method is used for soiling check, then the ease of operation is maintained, but the reliability of soiling detection is insufficient to distinguish dark soiling from low intensity areas
Solution Approach 1:
The detection area is divided into multiple y-positions along the transport direction, with each position independently evaluated for soiling. This segmentation allows the system to create a spatial map of window soiling, distinguishing between localized dark soiling on the window and uniformly low intensity areas. The segmented approach maintains operational simplicity while significantly improving detection reliability through position-specific analysis.
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
This approach provides a more reliable soiling check by distinguishing between light and dark soiling, reducing incorrect classifications and enabling more accurate window cleaning, thus improving the throughput of sheet material checking apparatuses.
Implementation Method 1
illuminated on one or both surfaces so as to detect by means of a measuring apparatus the light remitted by the sheet material and/or the light transmitted by the sheet material
Implementation Method 2
detect by means of a measuring apparatus the light remitted by the sheet material
Implementation Method 3
a window is arranged which is transmissive to the wavelengths to be detected
Implementation Method 4
a window is arranged which is transmissive to the wavelengths to be detected, and which prevents mechanical damage or a soiling of sensitive components
Implementation Method 5
a soiling of the window along the transport direction of the sheet material can lead to stripes on an image detected of the sheet material
Implementation Method 6
a soiling of the window along the transport direction of the sheet material can lead to stripes on an image detected of the sheet material
Data Source
AI summary
A method for checking the soiling of the windows of a measuring apparatus for checking sheet material, includes having at least two sensor rows oriented transversally to the transport direction of the sheet material. Each of the sensor rows detects the light emanating from the sheet material in a certain spectral channel. For checking the soiling of the window the sensor rows detect the light at several detection times at which no sheet material is present in the capture area of the sensor rows. At least two of the spectral channels are combined with each other and the temporal variation of the intensities of the combined spectral channel is evaluated for the purpose of the soiling check. A small temporal variation of the intensity of the combined spectral channel is employed as an indicator for the presence of a soiling of the window.