Inkjet Printer Skew Correction via Image Weighting
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Solution Overview
Problem
Conventional inkjet printing apparatuses face challenges in fully inhibiting positional deviations due to skewing and transport speed errors, leading to suboptimal print quality, as they rely on nozzle-by-nozzle shifting which is insufficient for non-integral skew amounts and temperature-induced transport roller expansion.
Innovation Solution
An image processing apparatus and method that utilize a reference and target print head system with recording position acquisition, positional deviation calculation, and interpolation-based image conversion, applying weights to correct for skew and transport direction deviations, employing Sinc or exponential window functions to ensure accurate alignment and minimize print quality degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If shifting process is performed on a nozzle-by-nozzle basis according to skew amount, then correction can be applied to each recording element, but sufficient correction cannot be achieved when skew amount is not an integral multiple of nozzle interval, resulting in residual positional deviation
Solution Approach 1:
The patent transitions from discrete nozzle-by-nozzle shifting (1D discrete correction) to continuous image data shifting in both width and transport directions (2D continuous correction). By treating the correction as a two-dimensional spatial transformation rather than one-dimensional discrete nozzle adjustment, the system achieves sub-nozzle precision correction for arbitrary skew amounts.
Solution Approach 2:
The patent changes the correction parameter from discrete nozzle shift amounts (integral multiples of nozzle interval) to continuous image data shift amounts (arbitrary real values). This parameter change enables correction of non-integral skew amounts by applying fractional pixel shifts through image processing techniques.
2Manufacturing precision
If transport speed is detected using a rotary encoder on the transport roller, then timing of ink droplet dispensing can be adjusted, but transport roller expansion due to heat causes detection errors, resulting in positional deviation in the transport direction
Solution Approach 1:
The patent replaces the mechanical transport speed detection system (rotary encoder on transport roller) with an optical/image-based measurement system. By using recorded image positions to calculate actual transport distance and speed, the system eliminates mechanical detection errors caused by roller expansion while maintaining synchronization between ink dispensing and substrate transport.
3Manufacturing precision
If image data is shifted to correct skew, then positional deviation can be reduced, but boundaries between corrected and uncorrected regions may become conspicuous, potentially degrading print quality
Solution Approach 1:
The patent applies different correction strategies to different regions of the image data based on local requirements. Image data in regions requiring correction is shifted according to calculated skew amounts, while regions not requiring correction or adjoining corrected regions undergo minimal or no shifting. This localized approach maintains positional accuracy where needed while preserving print quality by avoiding conspicuous boundaries.
Data Source
AI summary
An image processing apparatus for a printing apparatus. The image processing apparatus includes a recording position acquiring device for acquiring recording positions of a reference image printed by a reference print head and a target image printed by a target print head, a positional deviation amount calculating device for calculating a deviation amount due to a skew with respect to the recording positions of the reference image and the target image, and a positional deviation interpolation image converting device, when there is a remainder of the deviation amount and the predetermined intervals, for adding a weight based on the remainder, and adding a smaller weight than the weight to the reference image or the target image without a remainder and adjoining the reference image or the target image with the remainder, thereby converting the image into a width direction positional deviation interpolation image.