IMEN 315 인간공학
4. Visual Sensory Systems
THE STIMULUS: LIGHT
 the visual stimuli as a wave of electromagnetic energy (fig 4.1a)
 visible range of wavelength from 400nm (blue-violet) to 700 nm (red)
 a given light stimulus characterized by hue, saturation, brightness
 the source of light by luminous intensity/flux (candela)
 illumination – the lighting quality of a given working environment (fig 4.2)
 illuminance (照度), luminance (輝度)
 Reflectance (%) = luminance (FL) / illuminance (FC)
THE RECEPTOR SYSTEM
 schematic view of the eyeball (fig 4.3)
The Lens
 corona  pupil  lens (accommodation)  retina
 myopia (근시), presbyopia (노안)
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IMEN 315 인간공학
The Visual Receptor System
 the image may be characterized by its intensity (luminance), wavelengths,
and size (visual angle)
 VA = 5.7 * 60* (H/D)
 two types of receptor cells (rods and cones)
1. location – cones for fovea (2°of VA) and rods for periphery
2. acuity – motion in the periphery
3. sensitivity – advantage of rods in sensitivity
4. color sensitivity – rods are color blind
5. adaptation – temporary blindness, glare
6. differential wavelength sensitivity – cones are generally sensitive to all
wavelengths while rods are insensitive long lengths
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BOTTOM-UP VS. TOP-DOWN PROCESSING
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DEPTH PERCEPTION
 depth cues (fig 4.7)
 accommodation, binocular convergence, binocular disparity – inherent in
the physiological structure (bottom-up processing)  only effective for
judging distance, slant, and speed for objects within a few meters
 linear perspective, relative size, interposition, light and shading, textual
gradients (density) – based on experience (top-down processing) Where’s Wally?
 motion parallax
VISUAL SEARCH AND DETECTION
Eye Movements
 pursuit movement – constant velocity to follow targets
 saccadic movements – abrupt and discrete movements: initiation latency,
movement time, destination [dwell: duration (information content, ease of
information extraction) and UFOV (foveal region, 2 degrees of VA)]
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IMEN 315 인간공학
Visual Search
The serial Search Model
 T= NT/2
 typical search pattern – top to bottom, left to right
 random (non-exhaustive) search
Conspicuity
 bottom-up influence
 parallel processing
Expectancies
 top down processing – based on prior knowledge (experience)
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Detection
Signal Detection Theory
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IMEN 315 인간공학
Sensitivity and Response Bias
 sensitivity (d’) – how good an operator is at discriminating the signal from
the noise
 response bias (response criterion, beta) – expectancy, payoff
 ROC (receiver operating characteristic) curve
higher sensitivity
conservative
Interventions
 A C: instructions, incentives
 A B: training, visual template
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brightness
hue
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