Shinichi Inoue*, , Norimichi Tsumura#, and
Yoichi Miyake#
Department of Information and Image Sciences,
Chiba University, Inage-ku, Chiba, Japan
* Process Development Laboratory, Corporate
Research Center, Mitsubishi Paper Mills Limited
# Department of Information and Computer
Sciences, Chiba University
J. Image Science and Technology Vol.41 No.
6 pp.657-661(1997)
Abstract
Image quality of hardcopy is significantly
influenced by paper characteristics. Light
scattering phenomena in paper produce optical
dot gain, which has a large influence on
the tone reproduction characteristics of
halftone images. Light scattering phenomena
in paper can be represented by the modulation
transfer function (MTF) of paper. However,
little has been reported on techniques for
measuring the MTF of paper. In this study,
a new technique for measuring MTF of paper
is proposed. We have developed a modified
microdensitometer to project a sinusoidal
test pattern on sample paper. The reflection
density distribution of the projected sinusoidal
test pattern was measured by the microdensitometer,
and the MTFs of various types of papers obtained.
The point spread function (PSF) of paper
was calculated by the Fourier transform of
the measured MTF. The PSF could be expressed
by an exponential function. The obtained
PSFs were applied to a model to predict reflection
density of the halftone image. This result
showed that the predicted density is approximately
the same as the measured density in the halftone
image and the estimated optical dot gain
is well correlated to the measured optical
dot gain.