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The Visual System and Visual Performance

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Presentation on theme: "The Visual System and Visual Performance"— Presentation transcript:

1 The Visual System and Visual Performance

2 The Visible Spectrum

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

4 The Eye (2) Cornea Aqueous Humor Iris Protection Focusing Shape
Nutrition Iris Light control vision.ppt

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

6 The Eye (4) Optic Nerve Eye Muscles Nerve signals to brain
Optic Disk: blind spot Eye Muscles Eye movement Convergence vision.ppt

7 NEAR AND FARSIGHTED EYE
vision.ppt

8 DENSITY OF RODS AND CONES
vision.ppt

9 Visual Performance Brightness Visual Angle Visual Acuity Color
Visual Field vision.ppt

10 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 vision.ppt

11 Luminous Intensity vision.ppt

12 Luminous Flux vision.ppt

13 Illuminance vision.ppt

14 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 vision.ppt

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

16 Luminance (2) Threshold of detectability Threshold of pain
1 x mL Threshold of pain 3 x 10 4 mL Limits to discriminability 3 - 4 levels vision.ppt

17 Lightness vision.ppt

18 Lightness vision.ppt

19 Contrast Sensitivity the luminance of pixels is varied sinusoidally in the horizontal direction. The spatial frequency increases exponentially from left to right. The contrast also varies logarithmically from 100% at the bottom to about 0.5% at the top. The luminance of peaks and troughs remains constant along a given horizontal path through the image. If the detection of contrast was dictated solely by image contrast, the alternating bright and dark bars should appear to have equal height everywhere in the image. However, the bars seem to be taller in the middle of the image. vision.ppt

20 Visual Angle (minutes of arc)
Visual Angle = tan-1 H/D vision.ppt

21 Visual Angle of Familiar Objects
Object Distance Visual Angle Sun 93,000,000 mi 30’ Moon 240,000 mi 30’ Quarter arm’s length 2° Quarter 90 yd 1’ Quarter 3 mi 1” Lowercase pica type reading distance 13’ vision.ppt

22 Cumulative Probability of Detection
vision.ppt

23 vision.ppt

24 Acuity vision.ppt

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

26 Minimum Separable Acuity as Function of Contrast
vision.ppt

27 Minimum Perceptible Acuity
Also called spot detection. Eye’s ability to detect smallest possible target. vision.ppt

28 Minimum Perceptible Acuity as Function of Contrast and Background Luminance
vision.ppt

29 Vernier Acuity Smallest lateral displacement of one line from another that can be detected. vision.ppt

30 Vernier Acuity as Function of Background Luminance
vision.ppt

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

32 HUE vision.ppt

33 Absolute discrimination 0
vision.ppt

34 vision.ppt

35 Absolute discrimination 1
vision.ppt

36 vision.ppt

37 Absolute discrimination 2
vision.ppt

38 Relative discrimination
vision.ppt

39 List of colors http://en.wikipedia.org/wiki/List_of_colors vision.ppt
Shades of blue Alice blue Azure Baby blue Blue Cerulean Cerulean blue Chinese blue Cobalt blue Columbia blue Cornflower blue Dark blue Denim Dodger blue Indigo International Klein Blue Light blue Midnight blue Navy blue Periwinkle Persian blue Powder blue Prussian blue Royal blue Sapphire Steel blue Ultramarine Air Force blue Egyptian blue Electric blue Maya Blue Medium blue Sky blue vision.ppt

40 Visual Field

41 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 vision.ppt

42 Other Factors Affecting Visual Performance
Contrast: optimum level exists Illumination: optimum level exists Time: positive relationship Luminance Ratio: see contrast vision.ppt

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

44 • vision.ppt

45 vision.ppt

46 vision.ppt

47 vision.ppt

48 vision.ppt

49 vision.ppt

50 vision.ppt

51 vision.ppt

52 vision.ppt

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