Dr. Ahmed H. Eid Profile

Dr. Ahmed H. Eid

Software Engineer

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Publications (9)

Proceedings Article | 8 February 2015 Paper

Photoconductor surface modeling for defect compensation based on printed images

Ahmed Eid, Brian Cooper

Proceedings Volume 9396, 93960H (2015) https://doi.org/10.1117/12.2081428

KEYWORDS: Expectation maximization algorithms, Printing, Photoresistors, Wavelets, Image filtering, Image processing, Optical filters, Manufacturing, Imaging arrays, Sensors

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Proceedings Article | 3 February 2014 Paper

Automated measurement of printer effective addressability

Brian Cooper, Ahmed Eid, Edward Rippetoe

Proceedings Volume 9016, 901607 (2014) https://doi.org/10.1117/12.2037407

KEYWORDS: Printing, Error analysis, Scanners, Detection and tracking algorithms, Statistical analysis, Image segmentation, Visualization, Image resolution, Modulation transfer functions, MATLAB

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When evaluating printer resolution, addressability is a key consideration. Addressability defines the maximum number of spots or samples within a given distance, independent of the size of the spots when printed. Effective addressability is the addressability demonstrated by the final, printed output. It is the minimum displacement possible between the centers of printed objects. In this paper, we present a measurement procedure for effective addressability that offers an automated way to experimentally determine the addressability of the printed output. It requires printing, scanning, and measuring a test target. The effective addressability test target contains two types of elements, repeated to fill the page: fiducial lines and line segments. The fiducial lines serve as a relative reference for the incremental displacements of the individual line segments, providing a way to tolerate larger-scale physical distortions in the printer. An ordinary reflection scanner captures the printed test target. By rotating the page on the scanner, it is possible to measure effective addressability well beyond the scanner’s sampling resolution. The measurement algorithm computes the distribution of incremental displacements, forming either a unimodal or bimodal histogram. In the latter case, the mean of the second (non-zero) peak indicates the effective addressability. In the former case, the printer successfully rendered the target’s resolution, requiring another iteration of the procedure after increasing the resolution of the test target. The algorithm automatically estimates whether the histogram is unimodal or bimodal and computes parameters describing the quality of the measured histogram. Several experiments have refined the test target and measurement procedure, including two round-robin evaluations by the ISO WG4 committee. Results include an analysis of approximately 150 printed samples. The effective addressability attribute and measurement procedure are included in ISO/IEC TS 29112, a technical specification that describes the objective measurement of printer resolution for monochrome electrophotographic printers.

Proceedings Article | 3 February 2014 Paper

On the analysis of wavelet-based approaches for print mottle artifacts

Ahmed Eid, Brian Cooper

Proceedings Volume 9016, 901609 (2014) https://doi.org/10.1117/12.2041035

KEYWORDS: Wavelets, Image filtering, Spatial frequencies, Image analysis, Image quality, Standards development, Image quality standards, Image processing, Bandpass filters, Linear filtering

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Proceedings Article | 4 February 2013 Paper

On the analysis of wavelet-based approaches for print grain artifacts

Ahmed Eid, Brian Cooper, Edward Rippetoe

Proceedings Volume 8653, 86530K (2013) https://doi.org/10.1117/12.2000378

KEYWORDS: Wavelets, Halftones, Image filtering, Image analysis, Image quality, Standards development, Image quality standards, Spatial frequencies, RGB color model, Contrast sensitivity

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Grain is one of several attributes described in ISO/IEC TS 24790, a technical specification for the measurement of image quality for monochrome printed output. It defines grain as aperiodic fluctuations of lightness greater than 0.4 cycles per millimeter, a definition inherited from the latest official standard on printed image quality, ISO/IEC 13660. Since this definition places no bounds on the upper frequency range, higher-frequency fluctuations (such as those from the printer’s halftone pattern) could contribute significantly to the measurement of grain artifacts. In a previous publication, we introduced a modification to the ISO/IEC 13660 grain measurement algorithm that includes a band-pass, wavelet-based, filtering step to limit the contribution of high-frequency fluctuations. This modification improves the algorithm’s correlation with the subjective evaluation of experts who rated the severity of printed grain artifacts. Seeking to improve upon the grain algorithm in ISO/IEC 13660, the ISO/IEC TS 24790 committee evaluated several graininess metrics. This led to the selection of the above wavelet-based approach as the top candidate algorithm for inclusion in a future ISO/IEC standard. Our recent experimental results showed r² correlation of 0.9278 between the wavelet-based approach and the subjective evaluation conducted by the ISO committee members based upon 26 samples covering a variety of printed grain artifacts. On the other hand, our experiments on the same data set showed much lower correlation (r²= 0.3555) between the ISO/IEC 13660 approach and the same subjective evaluation of the ISO committee members. In addition, we introduce an alternative approach for measuring grain defects based on spatial frequency analysis of wavelet-filtered images. Our goal is to establish a link between the spatial-based grain (ISO/IEC TS 24790) approach and its equivalent frequency-based one in light of Parseval’s theorem. Our experimental results showed r² correlation near 0.99 between the spatial and frequency-based approaches.

Proceedings Article | 2 February 2012 Paper

A linear filter design technique for equalizing document scanners

Ahmed Eid

Proceedings Volume 8295, 82950X (2012) https://doi.org/10.1117/12.908441

KEYWORDS: Scanners, Optical filters, Image filtering, Linear filtering, Spatial frequencies, Signal attenuation, Nonlinear filtering, Image quality, Image processing, Measurement devices

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Proceedings Article | 4 February 2011 Paper

Descreening using segmentation-based adaptive filtering

Mohamed Ahmed, Ahmed Eid

Proceedings Volume 7870, 78700E (2011) https://doi.org/10.1117/12.872516

KEYWORDS: Image segmentation, Halftones, Nonlinear filtering, Digital filtering, Image filtering, Linear filtering, Scanners, Image classification, Image quality, Light scattering

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Proceedings Article | 25 January 2011 Paper

Window-based spectral analysis of color halftone screens

Ahmed Eid, Brian Cooper, Edward Rippetoe

Proceedings Volume 7866, 78661G (2011) https://doi.org/10.1117/12.872542

KEYWORDS: Halftones, Raster graphics, Optical inspection, Visualization, Moire patterns, Spatial frequencies, Printing, Error analysis, Inspection, Superposition

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Proceedings Article | 28 January 2008 Paper

Characterization of mottle and low-frequency print defects

Ahmed Eid, Brian Cooper, Edward Rippetoe

Proceedings Volume 6808, 680809 (2008) https://doi.org/10.1117/12.766785

KEYWORDS: Printing, Wavelets, Visualization, Halftones, Spatial frequencies, Quality systems, Statistical analysis, Humidity, Coating, Image filtering

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Proceedings Article | 29 January 2007 Paper

A unified framework for physical print quality

Ahmed Eid, Brian Cooper, Ed Rippetoe

Proceedings Volume 6494, 64940C (2007) https://doi.org/10.1117/12.707186

KEYWORDS: Printing, Wavelets, Statistical analysis, Visualization, Signal detection, Quality measurement, Calibration, Interference (communication), Analytical research, Quality testing methods

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Showing 5 of 9 publications

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