1. INTERMEDIATE LEVELS
A quantized or digitized image can appear as a contone image if the human visual system is unable to resolve between the tone steps or if it simply is not concerned about the discrete nature of the image. Tne number of tone levels needed in an image is depending on the eye’s ability to distinguish between tone levels.
”A few intermediate levels can provide a substantial improvement”

2. Human vision -Contrast sensitivity function (CSF)
~30cycles/deg for 20/20 vision
-Sensitive for disturbances with
mm wavelength for normal reading distance
-Perceptible luminance modulation
~200 tone levels
For normal reading distance

3. MULTILEVEL HALFTONE SCREEN
Uniform quantizer

4. MULTILEVEL HALFTONE SCREEN
Non-uniform quantizer

5. MULTILEVEL SCREEN OPTIMIZATION
Theoretical upper limit of possible tone level combinations for a cell with
Np number of pixels
gmax tone levels per pixel

6. MULTILEVEL SCREEN OPTIMIZATION
In practice,
the distinguishable levels are much lower because of redundancy in tone level arrangements the difference between some levels is too small to be resolved visually

7. REDUNDANCY
2x2 Trilevel Halftone cells – 15 Reflectances

8. REDUNDANCY
2x2 Trilevel Halftone cells – 9 Unique Reflectances

9. REDUNDANCY
Ravg = 0.25

10. OPTIMIZATION TRC ~ optical density out vs. optical density in
Performance evaluation RMS-fit to 45° line

11. OPTIMIZATION Density is not linear to human visual perception
Solution, a more linear measure of brightness response
Munsell value L
for Ravg> 0.05

12. OPTIMIZATION

13. OPTIMIZATION

14. MULTILEVEL
STOCHASTIC SCREEN – USE GENERIC APPROACH TO CREATE BNM DITHER MATRIX
ERROR DIFFUSION – REPLACE THRESHOLD WITH QUANTIZER AND DIFFUSE THE QUANTIZATION ERROR
COLOR HALFTONING - COLOR SCREEN SUPERIMPOSITION CAN BE USED DIRECTLY METHOD FOR ERROR DIFFUSION (OSTROMOUKHOV…)

15. HIGH-ADRESSABILITY

16. INKJET MULTIPLE DROPLETS MULTIPLE NOZZLES – DIFFERENT ORIFICES
MULTIPLE INKJET HEADS – DIFFERENT INKS
USE SATELLITE DROPLETS
COMBINATIONS OF 1-4