大学物理实验报告英文版--全息照相

physicallabreport:HolographyWriter:[Backgrounds]Lightsareelectromagneticwaves.Amonochromaticopticalwavecanbemathematicallyexpressedasawaveequation:2cos()rxAtwhereAistheamplitudeand)2(rtcarriesphaseinformation.Thewayweviewanygivenobjectistoobservethebrightness(amplitude),color(wavelength),andshape/distance(phase).Aconventionalphotographrecordsthefocusedimageofanobjectonaphotographicfilmorplate.Ahologramisaphotographicrecordingofanopticalinterferencepattern.Theamplitudeandphaseoflightcomingfromtheobjectarestoredinthehologram.Thephaseinformationenablesustoreconstructtheoriginalwavefrontandhenceobtainathree-dimensionalimageinspace.Theholographyyouexperienceinthislabwillconsistoftwosteps,a)recording:theamplitudeandphaseinformationofanobjectisrecordedonafilm,b)viewing:illuminatingthefilmtoreconstructtheobjectthatwasbeingfilmed.Thisexperimentusesa658nmdiodelaserasasourceofcoherentlightwhichirradiatestheobjects,andalsoprovidesareferencebeamofuniformamplitudeandphase.[Process]1.RecordingAttheverybeginning,wepreparelightpathaccordingtoFig.First,wehaveadarkenvironment.Thenweadjustthepathlengthofthereferenceandobjectbeam,sothatthepathdifferenceissmall.Then,weadjustthedevicessothatboththeobjectandreferencebeamsareirradiatingthefilmareauniformly.Teachertoldusthattheratiobetweentheobjectandreferencebeamsshouldbetterbebetween1:1to1:10.Thenmypartnerkeepadjustingtheopticstilltheseconditionsaremet.Successfullywegetanopticalfilm(wrappedinblackpaper)andmountitontotheholder.Then,weexposethefilmtolightforabout0.5second,thendismountthefilm.Figure1:recordingofahologram2.FilmdevelopmentAftergettingafilm,wetakeittothedarkroomtodevelop.Therearethreebathbasins:developer,stopbath(water),andfixer.Accordingtotheinstructor,weimmersethefilmintodevelopmentliquid.Mypartnerflipthefilmupanddownwiththetweezersandwewaittillthegray-scaleissimilartothecoloronthebottomofthebasin.Thisusuallytakes2minutesand25seconds.Later,werinsethefilminthewaterbasinfor25seconds,andwetakeittothefixer.Iimmerseitinthefixerfor3minutes.Wetakethefilmtotheviewingroomanddrythefilm.3.ViewingTheprincipletoreconstructimagefromahologramisvialightdiffraction.Ifalaserbeamirradiatesontothefilmexactlyliketheobjectbeam,diffractionwillhappenonthepatternrecordedonthehologram.Seefigurebelow.Figure2:illustrationofimagereconstructioninhologram..Weareallexcitedtogetreadytoviewthefilm.Beforeviewing,wehaveahighexpectationaboutit.WeUseaviewingbeamtoirradiatethefilm.Afterhavingmadesuretheemulsionsideisfacingthebeam,weadjustourviewingangleontheothersideofthefilmtoobserveanexpected3-Dimageoftheobject.HOWEVERunfortunately,weareunluckytofindtheimage.Nomatterwhatanglewetry,wecan’tfindit.Wesupposeitisbecausetheangleistoolargetofind.Sowetryonceagain,LUCKLY,wefinallyfindthe3-Dimage!-------Alovelywhitehorse!![Feeling]Inthisexperiment,wehaveadeepimpressionofthe3-Dimage.Ithinkthisexperienceisveryunforgettable.Indeed,thisiswherephysicsisattractivetous.