Inkjet Recording Position Error Measurement Using Signal Segmentation
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Solution Overview
Problem
Existing techniques for detecting defective nozzles in inkjet recording systems, particularly with full-line heads, face challenges when using a reading apparatus with a resolution lower than the recording resolution, leading to inaccuracies in recording position error measurement and image quality issues due to streaky artifacts.
Innovation Solution
A method involving a recording position error measurement apparatus and method that uses a test pattern with line-shaped patterns recorded by the recording elements, where a read image signal is acquired and processed to identify recording position errors, even with a reading apparatus of lower resolution, by dividing pixel series into sequences, calculating prediction signals, determining threshold values, and comparing change signals to specify recording position errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a reading apparatus with lower resolution than recording resolution is used, then device complexity and cost are reduced, but measurement precision of recording position error deteriorates
Solution Approach 1:
The patent segments the read image signal into multiple pixel series, each corresponding to a specific nozzle group. By analyzing position errors in each segmented series separately and then synthesizing the results, the system achieves high measurement precision even with lower reading resolution. This segmentation allows the system to extract precise position information from each nozzle group's pixel series without requiring the reading apparatus to have recording-level resolution.
Solution Approach 2:
The patent transforms the position error measurement problem from direct spatial measurement in the image domain to frequency domain analysis. By converting pixel series to frequency spectra and analyzing spectral characteristics, the system can determine recording position errors with high precision. This dimensional transformation from spatial to frequency domain enables accurate measurement despite the limitations of lower reading resolution.
2Device complexity
If conventional detection methods are used with lower resolution reading apparatus, then device complexity is reduced, but reliability of defective nozzle detection deteriorates due to streaky artifacts
Solution Approach 1:
The patent implements a feedback mechanism where the analyzed recording position error information is used to correct the image data before recording. The system continuously monitors position errors through test pattern analysis and uses this feedback to adjust subsequent recording operations, thereby eliminating streaky artifacts and improving image quality. This closed-loop feedback ensures reliable defective nozzle detection and correction.
Solution Approach 2:
The patent changes the analysis parameters by examining multiple pixel series at different positions and comparing their spectral characteristics. By analyzing the frequency spectra of multiple pixel series and identifying anomalies in specific frequency components, the system can reliably detect defective nozzles even with lower reading resolution. This parameter-based analysis approach transforms the detection problem into a spectral comparison task that is more robust to resolution limitations.
3Manufacturing precision
If high precision recording position error measurement is achieved, then image quality improves, but device complexity increases due to sophisticated signal processing requirements
Solution Approach 1:
The patent employs self-service principles where the test pattern itself serves as the measurement reference. By recording a known test pattern and analyzing its actual recorded form, the system uses the pattern's inherent structure to determine position errors without requiring external high-precision measurement equipment. The pixel series from the read image contain the necessary information for self-diagnosis of recording position errors.
Solution Approach 2:
The patent replaces complex mechanical measurement systems with signal processing-based detection. Instead of using high-precision optical measurement equipment or mechanical gauges to measure recording position errors, the system uses digital signal processing of the read image data. By converting spatial information into frequency domain analysis, the system achieves high measurement precision through computational methods rather than mechanical means, thereby reducing overall device complexity.
Data Source
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AI summary
A recording position error measurement apparatus includes a read image signal acquisition means (136, 290) and a signal processing means (372, 380) having: a dividing means (372, 380) which divides pixel series of the read image signal into sequences having different remainder values so as to generate image signals of the respective sequences; a prediction signal generation means (372, 380) which calculates regular prediction signals which are predicted with respect to the respective sequences, according to the read image signal; a threshold value determination means (372, 380) which determines tone value differences corresponding to respective distances representing recording position errors from the prediction signals, and which determines threshold values corresponding respectively to the recording position errors, from the tone value differences; a change signal calculation means (372, 380) which calculates a change signal indicating a difference between the prediction signal and the image signal of each of the sequences; and an error distance calculation means (372, 380) which specifies the recording position errors of the plurality of recording elements in the recording head according to comparing the change signal with each of the threshold values.