Chapter 2: Visual Sensory System

Visual properties of light waves

Amplitude & Wavelength

Amplitude =

Brightness

Wavelength =

Color/hue

Illumination

Light hitting a surface

Luminance

Light reflecting off a surface

Accommodation definition

Ciliary muscles changing lens shape to focus images on the retina

Ciliary muscle state

Distant & Close vision

Distant vision

Muscles relax (lens flattens)

Close vision

Muscles contract (lens rounds, causes fatigue)

Myopia physical cause

Inability to flatten the lens enough, often due to an elongated eye

Presbyopia definition

Age-related farsightedness caused by the lens losing flexibility

Rods

Dim light, peripheral vision

Cones

Color, fine detail, central fovea

Purkinje Shift

Switch from cone to rod vision at night; shorter wavelengths (blues/greens) look brighter

Dark Adaptation HF application

Red cockpit lights are used because rods are insensitive to long wavelengths, preserving night vision

Most common color vision deficiency

Deuteranomaly (green weak), affecting 6% of males

Visual Search formula variables: \(T = (N \times I) / 2\)

\(T\) = total search time; \(N\) = number of objects; \(I\) = inspection time per object

Pop-out Effect

Parallel search triggered by highly unique visual features, minimizing search time

Signal Detection Matrix

Hit vs. False Alarm

Hit Alarm

Signal present, response “Yes”

False Alarm

Signal absent, response “Yes”