Abstract

The ordered-dither halftoning technique which reproduces continuous tones with spatially encoded binary imaging elements uses the digital halftone screen. The effect at the microstructural level of four screens on tone reproduction, spatial signal reproduction, and quantization noise is evaluated by measuring the tone reproduction curve (TRC), the two-dimensional Fourier transform of a constant density patch, the degree of harmonic distortion (THD), the system Modulation Transfer Function (MTF), and the Wiener Spectrum (WS) produced by each screen. The applicablity of these five conventional image evaluation metrics on binary output is also evaluated. Spatial averaging is done to convert the binary output to a more linear form. The TRCs were found to be identical with a full output average reflectance range and a contrast of 1.0/255.0. The curves were step-wise linear, displaying 65 reproducible average reflectance levels. Fourier analysis of the binary structure showed that aliasing was likely to occur with the Diamond Dot and Bryngdahl screens, while aliasing from the Bayer and Allebach screens was unlikely. The THD plots showed that the Diamond Dot screen produced the highest degree of non-linearity, followed by Bryngdahl. The Bayer and Allebach screens produced the lowest THD. The line edge derivative approach to determining MTF did not yield useful MTF results for the halftoned forms. The Weiner spectrum for the Diamond Dot and Bryngdahl screens contained components at the halftone cell frequency, while the spectrum for the Bayer and Allebach screens contained components at much higher frequencies. Using these results, it was concluded that all the traditional metrics are valid for binary output except the line edge derivative approach for the MTF which did not yield the traditional MTF.

Library of Congress Subject Headings

Computer graphics--Technique--Evaluation; Image processing--Digital techniques--Evaluation

Publication Date

3-1-1989

Document Type

Thesis

Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)

Advisor

Engeldrum, Peter

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: T385 .E445 1989

Campus

RIT – Main Campus

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