CS349 - Implementing User Interfaces - Spring 2010

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1. Assignment 4.

Lecture 33 - Display Properties

Human Vision

Eye & Brain

Optics of the Eye

• cornea, lens, retina
• iris
• need to think in terms of angles

Photoreceptors

• two types of photoreceptor
  • rods: large, fast, sensitive
  • cones: small, slow
• three types of cone
  • L: long wavelength, red
  • M: medium wavelength, green
  • S: short wavelength, blue
• fovea (only cones) versus periphery (mainly rods)
  • vision is active, seeking information
  • saccades between fixations, which are 100 msec to a few sec in length
• function over about ten orders of magnitude of illumination

Psychophysical Properties

Spatial Acuity

Cone mosaic

• cones gather light from a finte area
• cones are spaced by about 0.008 degrees in the fovea

At the optometrist

• 20/20 vision means being able to see a gap of

At the psychophysicist

Hyperacuity

The cone mosaic is not ordered, but random.

• phase processing is possible
• much finer resolutions, not limited by receptor size
• another order of magnitude in resolution.

Temporal Acuity

Eye integrates over a temporal window

`Full Size' Displays

Display Types

Serial versus Parallel Displays

Reflective versus Self-Luminous

Resolution

Temporal

Spatial

Small Displays

Apple Retina Display

• the display of the iPhone 4
• liquid crystal, backlit with LED backlight
  • not OLED, Why?
• 3" by 2" (75mm by 50mm)
• 960 by 640 pixels
• 326 pixels per inch
  • 13 pixels per mm
  • "Apple engineers developed pixels so small a mere 78 micrometers across that the human eye can't distinguish individual pixels."
• roughly 200 mm viewing distance
  • pixel spacing is 0.022 degrees
  • under optimal resolution we can resolve things down to 0.005 degrees
    • Viewing distance assumed above must be 70mm
  • with hyperacuity the same test gives a viewing distance of 7mm.

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