1. The Visual System and Visual Performance

2. 2 Electromagnetic Spectrum

3. 3 The Visible Spectrum

4. 4 Anatomy of the Eye Illustration by Mark Ericksen, St. Luke’s Cataract and Laser Center, StLukesEye.com

5. 5 The Eye (2) ● Cornea – Protection – Focusing ● Aqueous Humor – Shape – Nutrition ● Iris – Light control – Focusing

6. 6 The Eye (3) ● Lens – Focusing – Accommodation ● Vitreous Humor – Shape ● Retina – Rods: black & white, night vision – Cones: color, day vision – Fovea: sharpest vision (concentration of cones)

7. 7 The Eye (4) ● Optic Nerve – Nerve signals to brain – Optic Disk: blind spot ● Eye Muscles – Eye movement – Convergence

8. 8 Visual Performance ● Brightness ● Visual Angle ● Visual Acuity ● Color ● Visual Field

9. 9 Brightness ● Relative amount of light reflected from an object produces a sensation of lightness or brightness. ● Brightness is related to the luminance of light as well as a subjective response to color

10. 10 Luminous Intensity

11. 11 Luminous Flux

12. 12 Illuminance

13. 13 Illuminance v. Luminance ● Illumination/Illuminance: The amount of light striking any point on the inside surface of a sphere surrounding the light source (Luminous flux/unit area) – Foot candle: 1 lumen/square foot – Lux: 1 luman/square meter ● Luminance: The amount of light per unit area leaving (reflected from) a surface – Foot Lamberts: 1 lumen/square foot – Candelas/square meeter

14. 14 Luminance Note: 1 foot-Lambert (ft-L) = 0.929 mL, so 1 ft-L ~ 1 mL.

15. 15 Luminance (2) ● Threshold of detectability 1 x 10 -6 mL ● Threshold of pain 3 x 10 4 mL ● Limits to discriminability 3 - 4 levels

16. 16 Visual Angle (minutes of arc)

17. 17 Visual Angle of Familiar Objects ObjectDistanceVisual Angle Sun 93,000,000 mi30’ Moon240,000 mi30’ Quarterarm’s length2° Quarter90 yd1’ Quarter3 mi1” Lowercase pica typereading distance13’

18. 18 Cumulative Probability of Detection

19. 19 Variation in Visual Performance Across the Retina

20. 20 Minimum Separable Acuity ● Also called gap resolution ● Smallest space eye can detect between parts of a target (visual object).

21. 21 Minimum Separable Acuity as Function of Contrast

22. 22 Minimum Perceptible Acuity ● Also called spot detection. ● Eye’s ability to detect smallest possible target.

23. 23 Minimum Perceptible Acuity as Function of Contrast and Background Luminance

24. 24 Vernier Acuity ● Smallest lateral displacement of one line from another that can be detected.

25. 25 Vernier Acuity as Function of Background Luminance

26. 26 Color ● Attributes – hue: red, green, blue … – saturation: vividness of hue – brightness: luminance ● Relative discrimination – thousands of distinct colors ● Absolute discrimination – 24 distinct colors – recommended: 9

27. 27 Visual Field

28. 28 Visual Impairments Myopia :Nearsightedness Hyperopia :Farsightedness Presbyopia :Loss of accommodation Night Blindness :Reduced rod vision Color Blindness :Inability to discriminate Tunnel Vision : Reduced field of view

29. 29 Other Factors Affecting Visual Performance ● Contrast: optimum level exists ● Illumination: optimum level exists ● Time: positive relationship ● Luminance Ratio: see contrast

30. 30 Other Factors Affecting Visual Performance (2) ● Glare: negative relationship ● Movement: negative relationship ● Age: negative relationship ● Drugs: some drugs impair vision

31. 31 Supplementary Slides Cockpit Display of Traffic Information

32. A Cockpit Multifunction Display (MFD) e.g., the Garmin GMX200 (see https://buy.garmin.com/shop/shop.do?pID=6422#)https://buy.garmin.com/shop/shop.do?pID=6422

33. N E N S W SLEAN R LBQPMBMP T 00 8 BL Y 50 nm

34. N E N S W SLEAN R LBQPMBMP T 3152Q +12 00 8 BL Y FDX145 -10 UPS483 +6 6034A -3 50 nm 3152Q 12.2 nm 106 kt +1220