Numerical Evaluation of Banding Patterns in the Context of Human Visual System Noise Sensitivity.

1
Numerical Evaluation of Banding Patterns in the
Context of Human Visual System Noise Sensitivity.

• Submitted as a final study towards the degree of
• Master of Science in Interdisciplinary Studies
• in the Tel-Aviv University by
• Alex Braginsky

2
Banding phenomena definition

• Banding pattern is an image that has a noisy
  oriented structure.
• Banding pattern appears is printouts due to
  mechanical and other malfunctions of industrial
  printers.
• Banding pattern visibility should be checked
  during quality assessment of industrial printers.

3
Banding images example
4
Objectives of the study

• Visual system sensitivity to banding patterns
• Development of quality criterion for banding
  patterns in printouts in the context of visual
  system sensitivity.
• Development of an automatic tool for printout
  quality classification in terms of the visibility
  of banding patterns.

5
Sensitivity to banding

• Visual sensitivity was measured in a series of
  psycho-physical experiments.
• The experiments resulted in contrast sensitivity
  curves for banding patterns.
• The curve describe the visual sensitivity as a
  function of spatial frequency band in which
  banding pattern energy is concentrated.
• The curves are obtained for horizontal, vertical
  and diagonal orientation of the pattern

6
Sensitivity curves for banding of the three
orientations.
0.25-0.5
4-8
32-50
0.5-1
1-2
2-4
8-16
16-32
spatial frequency, cpd
Averaged experimental sensitivity curves
horizontal marked with circles, vertical with
x and diagonal with diamonds.
7
Analysis

• Human vision is less sensitive to stochastic
  stimulus than to periodic one.
• It is also less sensitive to changes in frequency
  content of the noisy stimuli.
• Peak of the sensitivity is located at different
  spatial frequencies for periodic and stochastic
  stimuli.

8
sinusoidal
banding
9
Quality criterion for banding patterns.
Criterion. Contrasts in different frequency
bands weighted according to visual sensitivity.
Visual system is sensitive to contrast
The sensitivity depends on the frequency content
of the banding pattern.
10

-
quality group
1
An example screen of the evaluation tool

-
quality group
2

-
quality group
3

-
quality group
4
11
Evaluation tool

• inputs digitized images
• calculates weighted contrasts of banding pattern
  of the image
• classifies images in terms of quality groups

12
Summary of the tool.

• Tool performance was checked on images
  preliminary classified by experts in indigo.
• The tool is not bounded to any amount of quality
  classes.
• With database growth, objective classification
  may be obtained (in terms of quality groups
  description).

13
Summary and conclusion

• Sensitivity to banding patterns was established
  in a series of experiments.
• The sensitivity to banding differs from that to
  periodic patterns.
• Banding printout quality evaluation S/W was
  suggested, based on the above experimental data.