1. Dr. Engr. Sami ur Rahman Digital Image Processing Lecture 2: Visual System

2. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 2 Courtesy Brian Mac Namee Gonzalez and Woods

3. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 3 Human Visual System The best vision model we have! Knowledge of how images form in the eye can help us with processing digital images.

4. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 4 Structure Of The Human Eye  Cornea and sclera: covering the optic globe

5. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 5 Structure Of The Human Eye Choroid: Providing nutrition

6. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 6 Structure Of The Human Eye Lens: Focuses light from objects onto the retina

7. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 7 Structure Of The Human Eye Retina: Covered with light receptors called cones (6-7 million) and rods (75-150 million)

8. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 8 Structure Of The Human Eye Cones: Concentrated around the fovea, very sensitive to colour Rods: More spread out and are sensitive to low levels of illumination

9. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 9 Distribution of rods and cones in the retina

10. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 10 Image Formation In The Eye  Muscles within the eye can be used to change the shape of the lens allowing us focus on objects that are near or far away  An image is focused onto the retina causing rods and cones to become excited which ultimately send signals to the brain

11. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 11 Brightness Adaptation & Discrimination  The human visual system can perceive approximately 10 10 different light intensity levels  However, at any one time we can only discriminate between a much smaller number – brightness adaptation  Similarly, the perceived intensity of a region is related to the light intensities of the regions surrounding it

12. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 12 Brightness Adaptation & Discrimination

13. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 13 Brightness Adaptation & Discrimination (cont…)

14. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 14 Brightness Adaptation & Discrimination (cont…) An example of simultaneous contrast

15. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 15 Optical Illusions (cont…) Stare at the cross in the middle of the image and think circles

16. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 16 Optical Illusions (cont…) Our visual systems play lots of interesting tricks on us

17. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 17 Optical Illusions (cont…)

18. University Of Malakand | Department of Computer Science | UoMIPS | Dr. Engr. Sami ur Rahman | 18 Thanks for your attention