Vision and Colour Flashcards
(10 cards)
Vision and Colour
- Physiology of the Eye
- Light Sensing
- Visual System
- Foveal and Peripheral Vision
- Eye and Head Movement
- Binocular Vision
- Colour perception
Physiology of the Eye
- Iris controls light coming in
(pupil size) - Lens transmits incoming light
to the retina, adapting to
focus nearer/farther - Retina: layer of
photoreceptors (light sensors)
Fovea: are of highest density on the retina
Retina: Photoreceptor layer
Types of Photoreceptor
* Rods – Sensitive to light intensity
* Cones – Sensitive to light frequencies
* Central retina (fovea): only cones
* High density: perception of form
* Peripheral retina: more rods
* light detection, motion detection
Colour Sensitivity – Distribution of Cones
- Cones differ in their sensitivity to light of
different wavelengths - Short (S): most sensitive to blue light
- Medium (M): most sensitive to green light
- Long (L): most sensitive to red light
- There are about 10 times more L and M cones
than S cones in the retina - Higher sensitivity for red and green than
blue
Colour Vision - Anomalies
- Protanopia: missing L cones,
less sensitivity for red - Deuteranopia: missing M cones
- Tritanopia: missing S cones
- Red/green deficiency quite
common: 8% of male
population
Eye Movement – Fixation and Saccades
Fixations are moments when the eyes stop to focus on an object, aligning it with the fovea to capture detail. They need to last at least 200ms to gather enough information.
Saccades are rapid eye movements that shift focus from one point to another. They last about 20–30ms for small shifts, with a maximum of 3–4 fixations per second.
Binocular Vision – Conceptual Models
Cyclopean model
* Signals from both eyes are fused in a single canvas of vision
- Binocular model
- Two cameras at an offset from
each other - IPD = Inter-pupillary distance
Vergence-Accommodation Reflex
- Vergence
- Eyes rotate in head so the lines
of sight converge for a fixation - Depends on distance of object
- Accommodation
- Eye lenses change shape to
focus on an object - Conflicting cues in 3D display
- Fixed focal plane, on which
disparate images are shown
Visual-Vestibular Interaction
The vestibular system detects head movement, while optical flow (motion patterns on the retina) comes from self-motion. These visual and vestibular signals are combined to help us perceive motion and navigate. When they conflict, it can lead to simulator sickness
HSV – Hue, Saturation, Value
Hue
* where it appears on the spectrum
* consistent ordering
* Saturation (or Chroma)
* Purity of the colour
* Range from grey to pure
* Lightness
* Intensity
* Range from light/pale to dark
