4. visual sensory systems

산업경영공학과

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 )



The Visual Receptor System the image may be characterized by its intensity (luminance), wave-

lengths, 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 periphery2. acuity – motion in the periphery3. sensitivity – advantage of rods in sensitivity4. color sensitivity – rods are color blind5. adaptation – temporary blindness, glare6. differential wavelength sensitivity – cones are generally sensitive to all

wavelengths while rods are insensitive long lengths



BOTTOM-UP VS. TOP-DOWN PROCESSING



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)

motion parallax

VISUAL SEARCH AND DETECTIONEye 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)]

Where’s Wally?

http://en.wikipedia.org/wiki/File:MartinHandfordWally&Friends.PNG



Visual SearchThe serial Search Model T= NT/2 typical search pattern – top to bottom, left to right random (non-exhaustive) search

Conspicuity bottom-up influence parallel processingExpectancies top down processing – based on prior knowledge (experience)



DetectionSignal Detection Theory



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

Interventions A C: instructions, incentives A B: training, visual template

higher sensitivity

conservative



hue

brightness

4. visual sensory systems

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