Vision and Colour

What are Interaction Techniques?

• method that enable users to complete a task on a digital/physical product

• includes the input actions a user takes and the system's corresponding feedback

• combining hardware and software

What does the Iris do?

controls light coming in - linked to pupil size

What does the Lens do?

transmits incoming light to the retina, adapting to focus nearer/father

What is the Retina?

layers of photoreceptors

What is a Photoreceptor?

light sensor

What are the Types of Photoreceptor?

rods - sensitive to light intensity

cones - sensitive to light frequencies - create colour perceptions, 3 different types

What is the Fovea?

area of highest density on the retina

only cones

What is the Peripheral Retina?

has more rods

light detection, motion detection

What are the different types of Cones?

• short - most sensitive to blue

• medium - most sensitive to green

• long - most sensitive to red

about 10x more medium and long than short in the retina

• higher sensitivity for red and green than blue

What happens to the Signals obtained by Cones?

combined into 3 opponent channels

• lightness - adding up intensity values

• red-green contrast

• yellow-blue contrast

What are the different types of Colour Blindness?

• protanopia - missing L cones - less sensitivity for red

• deuteranopia - missing M cones

• tritanopia - missing S cones

• red/green deficiency common 8% of males

What is Foveal Vision?

1-2 degrees in visual field

high resolution and colour sensitivity

perception of detail - reading, object recognition etc

What is Peripheral Vision?

wide field-of-view, up to 200 degrees horizontally

detection of stimuli - motion, salient features

What is a Fixation?

aligning objects in the visual field with fovea to access detail for at least 200ms to have sufficient time for extraction of information

What is a Saccade?

fast ballistic movement from one fixation to the next object of interest

20-30ms for small shifts

What is Viewing Range?

comfortable eye-in-head positions

max 20 degrees to the left/right

up to 30 degrees down from the head centre

What is Eye-Head Coordination?

head movement supports vision, to have wider coverage

larger gaze shifts are a combination of eye saccade and head movement

What is the Cyclopean Model?

signals from both eyes are fused in a single canvas of vision

What is the Binocular Model?

2 cameras at an offset from each other

IPD - inter pupillary distance

What is Binocular Disparity?

left and right eye differ in viewing angle towards an object of interest

difference in the images seen by each eye - caused by parallax

provides a depth queue

What is the Vergence-Accommodation Reflex?

eyes rotate in head so lines of sight coverage for fixation

depends on distance of object

eye lens change on distance of object

What is a Visual-Vestibular Interaction?

vestibular system senses motion of the head in space

self-motion induces optical flow - patterns of motion across the retina

visual-vestibular information is integrated for perception of self-motion and navigation

How do we perceive Colour?

the perceptual system interprets the signals from the photoreceptors