数字图像处理第二章.ppt

DigitalImageProcessing2DigitalImageFundamentals1

PreviewThemechanicsofthehumanvisualsystem.Light,othercomponentsoftheelectromagneticspectrum,andtheirimagingcharacteristics.Imagingsensorsandhowtheyareusedtogeneratedigitalimages.Theconceptsofuniformimagesamplingandgray-levelquantization.Somebasicrelationshipsbetweenpixels.Theconditionsforlinearoperations.2

2.1ElementsofvisualPerceptionStructureofthehumaneye(FIGURE2.1)CorneaIrisCiliarybodyCiliarymuscleCiliaryfiberAnteriorchamberLensVisualaxisRetinaScleraChoroidBlindspotFoveaNervesheathVitreoushumor角模虹膜睫状体睫状肌睫状小带前房晶状体视轴视网膜巩膜脉络膜盲点中央凹神经和鞘玻璃体3

2.1ElementsofvisualPerceptionBlindspotConesRodsNumbersofrodsorconespermm2Degreesfromvisualaxis(centeroffovea)杆状细胞圆锥细胞FIGURE2.2Distributionofrodsandconesintheretina.4

2.1ElementsofvisualPerceptionImageinformationintheeyeFIGURE2.3Graphicrepresentationoftheeyelookingatapalmtree.PointCistheopticalcenterofthelens.5

2.1ElementsofvisualPerceptionBrightnessadaptationHumaneyecanadapt1010levelsoflightintensity.Objectivebrightnessmeanstheintensityasperceivedbythehumanvisualsystem.Humanvisualfeatureisalogfunction.Lambert—TheunitofbrightnessAdaptationrangeScotopicPhotopicGlarelimitScotopicthresholdSubjectivebrightnessLogofintensity(mL)6

2.1ElementsofvisualPerceptionBrightnessadaptationInphotopicvision,therangeisabout106.Thevisualsystemcannotoperateoverthewholerangeatthesametime.Brightnessadaptationlevel,e.g,Ba.LowestbrightnessBb.AdaptationrangeScotopicPhotopicGlarelimitScotopicthresholdSubjectivebrightnessLogofintensity(mL)Lambert—Theunitofbrightness7

2.1ElementsofvisualPerceptionBrightnessdiscriminationThequantityΔIc/IiscalledtheWeberratio.LogΔIc/I8

ActualilluminationPerceivedbrightness2.1ElementsofvisualPerceptionMachbandsFIGURE2.7(a)Anexampleshowingthatperceivedb