Scanner Imaging Assembly Dust Streak Reduction
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Solution Overview
Problem
Scanners often produce poor images due to dust accumulation, which appears as spots or streaks, reducing efficiency and requiring re-scanning of original documents, especially when using movable heads or guides like black foam rollers that become less effective over time.
Innovation Solution
A scanning system with a lens having a recess outside the depth of focus and a guide with portions outside the depth of field, combined with air movement to prevent debris settlement, ensuring clear image capture and reducing the impact of dust and debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a guide (such as black foam or rubber roller) is used to guide documents toward the glass plate, then document guidance and positioning are improved, but dust accumulation on the guide reduces image quality over time
Solution Approach 1:
The guide is positioned outside the depth of field of the imager, moving the guide from the focal plane to a different spatial dimension. This allows the guide to remain functional for document guidance while its dust accumulation no longer appears in the focused image, effectively resolving the contradiction between guidance functionality and image quality.
Solution Approach 2:
The guide is extracted from the depth of field region, separating its function (document guidance) from the imaging region. By positioning the guide outside the focal plane, the harmful effect of dust on the guide is extracted from the image formation process, allowing the guide to perform its function without degrading image quality.
2Stability of the object's composition
If a stationary head scanner is used where the item travels past the head, then scanning stability is improved, but dust shows up as elongated streaks along the document length
Solution Approach 1:
The imager is positioned such that the dust particles in the document path are outside the depth of field. By changing the spatial relationship between the imager, document path, and focal plane, dust particles appear blurred or invisible while the document remains in focus, eliminating streak artifacts while maintaining scanning stability.
Solution Approach 2:
The imaging system has different focus characteristics at different depths. The document plane is sharply focused while regions containing dust particles (outside the document plane) are intentionally kept out of focus. This local differentiation of focus quality allows stable scanning without dust streaks appearing in the final image.
3Manufacturing precision
If the guide is positioned within the depth of field to ensure proper document alignment, then document positioning accuracy is improved, but dust on the guide becomes visible in the image
Solution Approach 1:
The guide is repositioned from within the depth of field to outside the depth of field along the optical axis. This dimensional relocation maintains the guide's ability to position documents accurately (since positioning occurs in the lateral directions) while removing the guide and its dust from the focal plane, preventing dust visibility in the image.
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
The system effectively minimizes the appearance of dust and debris in scanned images, maintaining image quality and reducing the need for re-scanning by keeping the guide and lens surfaces clear, thus enhancing scanning efficiency.
Implementation Method 1
Airflow is generated, the airflow being blown into the convey pass from a location upstream in a conveying direction compared to a location of the image sensor
Data Source
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AI summary
A system for processing document to scan the documents to obtain optical image data representing the document is provided. The system (10) includes elements that reduce or eliminate the effects of debris that can create streaks in the scanned images. One element is a recess (174) in the lens (170) through which an imaging device (60) scans the document. Another element is a guide (80) having an opening (84) opposing the lens (70, 170) of the imaging device (60). The opening (84) reduces or eliminates light reflecting off the guide back to the imaging device so that the area around the document is scanned as black.