Three-Edge Sheet Registration for Duplex Image Alignment
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Solution Overview
Problem
Existing sheet registration methods fail to adequately align front and back side images on non-rectangular sheets, particularly trapezoid-shaped sheets, leading to misalignment issues in the final printed product.
Innovation Solution
A method for registering sheets that involves determining the relative orientations of three different edges, aligning one lateral edge with a predetermined direction on both passes, and adjusting the printing of the second image based on these orientations to ensure alignment, using a sensor assembly and actuator assembly to correct for deviations in edge parallelism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single edge is detected for sheet registration, then the registration process is simple, but misalignment between front and back side images occurs on non-rectangular sheets
Solution Approach 1:
The patent divides the sheet edge detection into multiple segments by detecting three different edges (first longitudinal edge, second longitudinal edge, and lateral edge) instead of a single edge. This segmentation allows the system to capture the geometric characteristics of non-rectangular sheets and calculate orientation deviations, thereby achieving precise alignment on both front and back sides without excessive complexity.
Solution Approach 2:
The patent transitions from one-dimensional single edge detection to two-dimensional multi-edge detection by incorporating lateral edge detection alongside longitudinal edge detection. This dimensional expansion enables the system to determine the sheet's geometric shape and orientation deviations, solving the misalignment problem on non-rectangular sheets.
2Adaptability or versatility
If the sheet is flipped for duplex printing, then both sides can be printed, but the reference edge changes position causing misalignment
Solution Approach 1:
The patent implements a feedback mechanism where the detected geometric parameters (orientations of three edges) are used to calculate orientation deviations, and these deviations are then applied to adjust the printing positions on the back side. This feedback loop ensures that even after flipping, the images on both sides remain precisely aligned by compensating for the changed reference edge position.
Solution Approach 2:
The patent changes the printing parameters (position offsets) based on the detected geometric parameters of the sheet. By calculating orientation deviations from the three-edge detection and applying these as correction parameters to the back side printing positions, the system maintains alignment precision despite the sheet being flipped for duplex printing.
3Ease of operation
If traditional registration methods are used on trapezoid-shaped sheets, then the process is straightforward, but rotational and lateral misalignment occurs
Solution Approach 1:
The patent performs preliminary detection of three different edges and calculation of their orientations before the actual printing process. This preliminary action captures the sheet's geometric characteristics and calculates orientation deviations in advance, allowing the system to pre-determine the correct printing positions and offsets, thereby achieving precise alignment on trapezoid-shaped sheets without complicating the operation.
Data Source
Figure 1A~3
Figure 4A~4B
Figure 4C~4D
AI summary
When duplex printing non-rectangular sheets of printable media, said sheets require proper registration to prevent misalignment of front and back images. The present invention proposes to ensure this by: - determining relative orientations of three different edges of a sheet being transported towards print station on a first pass; - registering the sheet on the first pass by aligning one of said edges with respect to a predetermined alignment direction; - printing a first image on a first side of the registered sheet; - flipping the sheet on a second pass; - registering the flipped sheet by aligning one of said edges with respect to a predetermined alignment direction; and - printing a second image on a second side of the registered, flipped sheet aligned with the first image based on the determined relative orientations.