Dab tsi yog qhov kev soj ntsuam ntau ntawm lub teeb tsom iav thiab electron microscope
Cov qauv ntawm optical microscope Lub optical microscope feem ntau yog tsim los ntawm ib theem, lub condenser illumination system, lub hom phiaj lens, eyepiece thiab ib tug focusing mechanism. Cov theem yog siv los tuav cov khoom kom pom. Lub tshuab tsom tuaj yeem raug tsav los ntawm lub pob qhov rooj tsom kom ua rau theem nce thiab nqis rau kev hloov kho ntxhib thiab kev kho kom zoo, kom cov khoom pom tau tuaj yeem tsom thiab pom meej meej.
Nws cov txheej txheej sab saud tuaj yeem raug txav mus los thiab tig rau hauv lub dav hlau kab rov tav, thiab qhov pom pom feem ntau yog hloov kho rau qhov chaw ntawm qhov pom. Lub teeb tsom teeb pom kev zoo yog tsim los ntawm lub teeb ci thiab lub teeb condenser lens. Lub luag haujlwm ntawm lub condenser lens yog kom mloog ntau lub teeb lub zog rau qhov pom. Cov yam ntxwv spectral ntawm lub illuminator yuav tsum tau yoog rau kev ua haujlwm ntawm lub receiver ntawm lub tshuab tsom.
Lub hom phiaj lens yog nyob ze ntawm cov khoom pom thiab yog lub lens uas paub txog qhov kev nthuav dav thawj zaug. Ob peb lub hom phiaj lo ntsiab muag nrog qhov sib txawv magnifications yog ntsia rau ntawm lub hom phiaj lens converter tib lub sij hawm, thiab lub hom phiaj lens nrog cov magnifications sib txawv tuaj yeem nkag mus rau txoj kev kho qhov muag los ntawm kev tig lub converter. Qhov loj ntawm lub hom phiaj lens feem ntau yog 5 txog 100 zaug. Lub hom phiaj lens yog ib qho khoom siv kho qhov muag uas ua lub luag haujlwm txiav txim siab zoo ntawm cov duab hauv lub tshuab tsom.
Feem ntau siv cov hom phiaj achromatic uas tuaj yeem kho chromatic aberration rau ob xim ntawm lub teeb; zoo dua lub hom phiaj apochromatic uas tuaj yeem kho chromatic aberration rau peb xim ntawm lub teeb; tuaj yeem xyuas kom meej tias tag nrho cov duab dav hlau ntawm lub hom phiaj lens yog lub dav hlau, txhawm rau txhim kho qhov pom ntawm lub hom phiaj tiaj tiaj nrog cov duab zoo nkauj marginal. Lub hom phiaj ua kua dej yog feem ntau siv rau hauv lub hom phiaj lub hom phiaj siab, uas yog, qhov ntsuas qhov ntsuas ntawm 1 tau sau nruab nrab ntawm qhov chaw qis ntawm lub hom phiaj lo ntsiab muag thiab sab saud ntawm daim ntawv kuaj.
5 los yog li ntawd, nws tuaj yeem txhim kho qhov kev daws teeb meem ntawm kev soj ntsuam microscopic. Lub eyepiece yog lub lens nyob ze ntawm tib neeg lub qhov muag kom ua tiav qib ob, thiab qhov loj ntawm daim iav feem ntau yog 5 txog 20 zaug. Raws li qhov loj ntawm qhov kev pom uas tuaj yeem pom, eyepieces tuaj yeem muab faib ua cov eyepieces zoo tib yam nrog lub ntsej muag me me thiab cov qhov muag loj (los yog lub qhov muag dav) nrog rau qhov pom loj dua.
Ob qho tib si theem thiab lub hom phiaj lens yuav tsum muaj peev xwm txav tau txheeb ze rau qhov kho qhov muag axis ntawm lub hom phiaj lens kom ua tiav kev ua kom pom tseeb thiab tau txais cov duab meej. Thaum ua hauj lwm nrog lub hom phiaj magnification siab, qhov tso cai tsom ntau yam yog feem ntau me dua li micron, yog li lub tshuab tsom iav yuav tsum muaj qhov tseeb micro-focusing mechanism. Qhov txwv ntawm microscope magnification yog qhov ua tau zoo, thiab qhov kev daws teeb meem ntawm lub tshuab tsom xam yog hais txog qhov tsawg kawg nkaus ntawm ob lub ntsiab lus uas tuaj yeem ua kom pom tseeb ntawm lub tshuab tsom.
Kev daws teeb meem thiab kev nthuav dav yog ob qhov sib txawv tab sis muaj feem xyuam nrog cov ntsiab lus. Thaum tus lej aperture ntawm lub hom phiaj xaiv lub lens tsis loj txaus, uas yog, qhov kev daws teeb meem tsis siab txaus, lub tshuab ntsuas ntsuas tsis tuaj yeem paub qhov txawv ntawm cov qauv zoo ntawm cov khoom. Lub sijhawm no, txawm tias qhov kev nthuav dav yog nce ntau dhau, tsuas yog ib daim duab nrog cov qauv loj tab sis cov ntsiab lus tsis meej tuaj yeem tau txais. , hu ua ineffective magnification.
Ntawm qhov tod tes, yog tias qhov kev daws teeb meem tau ua tau raws li qhov yuav tsum tau ua thiab qhov kev nthuav dav tsis txaus, lub tshuab tsom iav muaj peev xwm daws tau, tab sis cov duab me me dhau los ua kom pom tseeb ntawm tib neeg lub qhov muag. Yog li ntawd, txhawm rau muab kev ua si tag nrho rau kev daws lub zog ntawm lub tshuab tsom iav, tus lej aperture yuav tsum sib haum nrog tag nrho qhov loj ntawm lub tshuab tsom. Lub condensed illumination system muaj kev cuam tshuam zoo rau kev ua haujlwm ntawm lub tshuab tsom iav, tab sis nws kuj yog qhov txuas uas yooj yim saib los ntawm cov neeg siv.
Nws txoj haujlwm yog los muab kev pom zoo txaus thiab teeb pom kev zoo ntawm cov khoom nto. Lub beam los ntawm lub condenser yuav tsum muaj peev xwm sau lub aperture lub kaum sab xis ntawm lub hom phiaj lens, txwv tsis pub lub siab tshaj plaws daws teeb meem uas lub hom phiaj lens tuaj yeem ua tiav tsis tuaj yeem siv tag nrho. Rau lub hom phiaj no, lub condenser yog muab nrog qhov sib txawv aperture diaphragm zoo ib yam li hauv lub hom phiaj kev yees duab, thiab qhov loj ntawm qhov aperture tuaj yeem hloov kho kom haum rau lub teeb pom kev zoo kom haum rau lub kaum sab xis ntawm lub hom phiaj.
Los ntawm kev hloov txoj kev teeb pom kev zoo, koj tuaj yeem tau txais cov kev soj ntsuam sib txawv xws li cov ntsiab lus tsaus nti ntawm qhov ci ci tom qab (hu ua lub teeb pom kev zoo) lossis cov khoom ci ci ntawm qhov tsaus ntuj (hu ua tsaus nti teeb pom kev zoo), thiaj li nrhiav tau zoo dua nyob rau hauv ntau qhov xwm txheej. thiab saib cov microstructure. Electron microscope yog ib qho cuab yeej uas hloov lub teeb beam thiab optical lens nrog electron beam thiab electron lens raws li lub hauv paus ntsiab lus ntawm electron optics, kom cov qauv zoo ntawm cov teeb meem tuaj yeem pom nyob rau hauv qhov loj heev.
Kev daws lub zog ntawm lub tshuab ntsuas hluav taws xob yog qhia los ntawm qhov tsawg tshaj plaws ntawm qhov deb ntawm ob lub ntsiab lus uas nws tuaj yeem daws tau. Hauv xyoo 1970s, qhov kev daws teeb meem ntawm kev xa hluav taws xob hluav taws xob microscopes yog li ntawm 0.3 nanometers (qhov kev daws teeb meem ntawm tib neeg lub qhov muag yog li 0.1 hli). Tam sim no qhov siab tshaj plaws magnification ntawm electron microscope yog ntau tshaj 3 lab lub sij hawm, thiab qhov siab tshaj plaws magnification ntawm optical microscope yog hais txog 2000 lub sij hawm, yog li cov atoms ntawm tej yam hnyav hlau thiab cov txheej txheem zoo atomic lattice nyob rau hauv crystals yuav ncaj qha soj ntsuam los ntawm electron microscope.
Nyob rau hauv 1931, Knorr-Bremse thiab Ruska nyob rau hauv lub teb chaws Yelemees tau hloov ib tug high-voltage oscilloscope nrog ib tug txias-cathode tawm electron qhov chaw thiab peb electron lo ntsiab muag, thiab tau ib tug magnified duab ntau tshaj kaum lub sij hawm, uas tau lees tias muaj peev xwm ntawm magnifying imaging los ntawm ib tug electron microscope. . . Xyoo 1932, tom qab Ruska txoj kev txhim kho, kev daws teeb meem ntawm lub tshuab hluav taws xob hluav taws xob tau mus txog 50 nanometers, uas yog kwv yees li kaum npaug ntawm lub zog daws teeb meem ntawm lub tshuab ntsuas qhov muag thaum lub sijhawm ntawd, yog li lub tshuab hluav taws xob hluav taws xob pib nyiam tib neeg cov kev xav.
Hauv xyoo 1940s, Hill hauv Tebchaws Meskas tau siv tus kws kho mob astigmatist los them nyiaj rau kev sib hloov asymmetry ntawm lub lens electron, uas ua rau muaj kev cuam tshuam tshiab hauv kev daws lub zog ntawm lub tshuab ntsuas hluav taws xob thiab maj mam mus txog qib niaj hnub. Nyob rau hauv Tuam Tshoj, ib tug kis tau tus mob electron microscope tau ntse tsim nyob rau hauv 1958 nrog ib tug daws teeb meem ntawm 3 nanometers, thiab nyob rau hauv 1979 nws tau ua nrog ib tug daws teeb meem ntawm 0.
3nm loj electron microscope. Txawm hais tias qhov kev daws teeb meem ntawm electron microscopes yog qhov zoo dua li ntawm optical microscopes, nws yog ib qho nyuaj rau kev soj ntsuam cov kab mob uas muaj sia nyob vim tias electron microscopes yuav tsum ua haujlwm nyob rau hauv lub tshuab nqus tsev, thiab irradiation ntawm electron beams kuj yuav ua rau hluav taws xob puas tsuaj rau cov qauv lom. Lwm yam teeb meem, xws li kev txhim kho qhov ci ntawm rab phom electron thiab qhov zoo ntawm lub lens electron, kuj yuav tsum tau kawm ntxiv.
Lub zog daws teeb meem yog qhov taw qhia tseem ceeb ntawm electron microscopy, uas muaj feem xyuam rau qhov xwm txheej lub khob hliav qab thiab lub wavelength ntawm electron beam dhau los ntawm cov qauv. Lub wavelength ntawm pom lub teeb yog li ntawm 300 mus rau 700 nanometers, thaum lub wavelength ntawm lub electron beam muaj feem xyuam rau lub accelerating voltage. Thaum qhov ntsuas hluav taws xob nrawm yog 50-100 kV, lub teeb hluav taws xob hluav taws xob wavelength yog li 0.
0053 rau 0.0037 nm. Txij li thaum lub wavelength ntawm lub electron beam yog ntau me dua lub wavelength ntawm pom lub teeb, txawm yog hais tias lub khob hliav qab ntawm lub electron beam tsuas yog 1 feem pua ntawm cov optical microscope, lub zog daws teeb meem ntawm ib tug electron microscope tseem nyob deb superior rau qhov ntawd. ntawm ib qho optical microscope. Lub tshuab ntsuas hluav taws xob muaj peb ntu: lub lens raj, lub tshuab nqus tsev thiab lub hwj huam mov txee.
Lub lens chim feem ntau suav nrog cov phom hluav taws xob, lub lens electron, cov qauv tuav, fluorescent screen thiab lub koob yees duab mechanism, uas feem ntau yog sib sau ua ke rau hauv lub tog raj kheej los ntawm sab saum toj mus rau hauv qab; lub tshuab nqus tsev yog tsim los ntawm cov tshuab nqus tsev twj tso kua mis, diffusion twj tso kua mis thiab lub tshuab nqus tsev vacuum, thiab lwm yam. Lub raj xa hluav taws xob txuas nrog lub lens chim; lub hwj chim mov txee yog tsim los ntawm high-voltage generator, ib tug excitation tam sim no stabilizer thiab ntau yam kev hloov kho thiab tswj units.
Lub lens electron yog qhov tseem ceeb tshaj plaws ntawm electron microscope chim. Nws siv lub spatial hluav taws xob teb los yog magnetic teb uas yog symmetrical rau lub axis ntawm lub lens chim rau khoov lub electron trajectory rau lub axis los tsim tsom. Nws muaj nuj nqi zoo ib yam li cov iav convex lens kom pom cov nqaj, yog li nws hu ua electron. lens. Niaj hnub nimno electron microscopes feem ntau siv electromagnetic lo ntsiab muag, uas tsom cov electrons los ntawm ib tug muaj zog magnetic teb generated los ntawm ib tug ruaj khov DC excitation tam sim no los ntawm ib tug coil nrog ib tug ncej khau.
Cov phom hluav taws xob yog ib qho khoom siv uas muaj tungsten filament kub cathode, kab sib chaws thiab cathode. Nws tuaj yeem tso tawm thiab tsim cov kab hluav taws xob nrog lub nrawm nrawm, yog li qhov ruaj khov ntawm qhov nrawm nrawm tsis tsawg dua 1/10,000. Electron microscopes tuaj yeem muab faib ua kis tau tus mob electron microscopes, scanning electron microscopes, reflection electron microscopes thiab emission electron microscopes raws li lawv cov qauv thiab siv.
Kev xa cov tshuab hluav taws xob siv hluav taws xob feem ntau siv los soj ntsuam cov khoom siv zoo uas tsis tuaj yeem paub qhov txawv ntawm cov tshuab microscopes; scanning electron microscopes yog siv los soj ntsuam cov morphology ntawm cov khoom nto, thiab tseem tuaj yeem ua ke nrog X-ray diffractometers lossis electron zog spectrometers los tsim electrons. Microprobes rau kev tsom xam ntawm cov khoom muaj pes tsawg leeg; Emission Electron Microscopy rau kev kawm ntawm tus kheej-emitting electron nto.
Qhov projection electron microscope muaj npe tom qab lub teeb hluav taws xob nkag mus rau cov qauv thiab tom qab ntawd siv lub lens electron los ua duab thiab nthuav dav. Nws txoj kev kho qhov muag zoo ib yam li lub tshuab kho qhov muag. Hauv lub tshuab ntsuas hluav taws xob no, qhov sib piv ntawm cov duab cov ntsiab lus yog tsim los ntawm kev tawg ntawm cov kab hluav taws xob los ntawm cov atoms ntawm cov qauv. thinner los yog tsawg dua qhov chaw ntawm cov qauv, cov kab hluav taws xob hluav taws xob tawg tsawg dua, yog li cov hluav taws xob ntau dhau los ntawm lub hom phiaj aperture, koom nrog hauv cov duab, thiab zoo li ci dua hauv daim duab.
Conversely, thicker los yog denser qhov chaw ntawm cov qauv tshwm darker nyob rau hauv daim duab. Yog hais tias tus qauv yog tuab heev los yog tuab heev, qhov sib piv ntawm daim duab yuav deteriorate los yog txawm yuav puas los yog puas los ntawm absorbing lub zog ntawm lub electron beam. Sab saum toj ntawm kis tau tus mob electron microscope raj yog ib rab phom electron. Cov electrons raug tso tawm los ntawm tungsten filament kub cathode thiab dhau los ntawm thawj thiab thib ob condensers los tsom rau cov kab hluav taws xob.
Tom qab dhau los ntawm cov qauv, cov kab hluav taws xob tau teeb tsa rau ntawm daim iav nruab nrab los ntawm lub hom phiaj lens, thiab tom qab ntawd nthuav tawm cov kauj ruam dhau los ntawm daim iav nruab nrab thiab daim iav projection, thiab tom qab ntawd muab duab rau ntawm lub vijtsam fluorescent lossis cov duab thaij duab qhuav. Daim iav nruab nrab feem ntau yog kho qhov excitation tam sim no, thiab qhov magnification tuaj yeem hloov pauv tsis tu ncua los ntawm kaum tawm mus rau ntau pua txhiab zaus; los ntawm kev hloov lub focal ntev ntawm daim iav nruab nrab, cov duab electron microscope thiab electron diffraction dluab tuaj yeem tau txais ntawm qhov me me ntawm tib cov qauv. .
Txhawm rau kawm cov qauv hlau tuab dua, Fab Kis Dulos Electron Optics Laboratory tau tsim lub tshuab hluav taws xob ultra-high voltage electron microscope nrog qhov nrawm nrawm ntawm 3500 kV. Lub teeb hluav taws xob ntawm lub tshuab hluav taws xob scanning tsis dhau los ntawm cov qauv, tab sis tsuas yog scans thiab ua rau cov khoom siv hluav taws xob thib ob ntawm cov qauv. Ib tug siv lead ua scintillation tso rau ib sab ntawm cov qauv tau txais cov khoom siv hluav taws xob thib ob thiab hloov kho qhov siv hluav taws xob ntawm lub teeb duab raj tom qab kev nthuav dav, yog li hloov qhov ci ntawm qhov screen ntawm lub raj duab.
Lub deflection yoke ntawm daim duab tube khaws cia synchronously nrog lub electron beam ntawm tus qauv nto, yog li ntawd lub fluorescent screen ntawm daim duab raj qhia cov duab topographic ntawm tus qauv nto, uas yog zoo ib yam li lub hauv paus ntsiab lus ua hauj lwm ntawm industrial TV. Qhov kev daws teeb meem ntawm lub tshuab ntsuas hluav taws xob ntsuas hluav taws xob feem ntau yog txiav txim siab los ntawm txoj kab uas hla ntawm lub teeb hluav taws xob ntawm cov qauv saum npoo.
Qhov kev nthuav dav yog qhov piv ntawm qhov ntsuas amplitude ntawm daim duab raj mus rau qhov ntsuas amplitude ntawm tus qauv, uas tuaj yeem hloov pauv tsis tu ncua los ntawm kaum tawm mus rau ntau pua txhiab zaus. Scanning electron microscope tsis xav tau cov qauv nyias nyias; daim duab muaj zog peb-dimensional nyhuv; Nws tuaj yeem txheeb xyuas qhov sib xyaw ntawm cov teeb meem siv cov ntaub ntawv xws li cov khoom siv hluav taws xob thib ob, cov hluav taws xob nqus hluav taws xob thiab X-rays tsim los ntawm kev sib cuam tshuam ntawm cov kab hluav taws xob nrog cov teeb meem.
Cov phom electron thiab condenser ntawm scanning electron microscope yog roughly tib yam li cov kis tau tus mob electron microscope, tab sis nyob rau hauv thiaj li yuav ua kom lub electron beam thinner, lub hom phiaj lens thiab astigmatism yog ntxiv nyob rau hauv lub condenser lens, thiab ob txheej ntawm kev sib nrig sib. perpendicular scanning kuj tau nruab rau hauv lub hom phiaj lens. coil. Cov qauv chamber nyob rau hauv lub hom phiaj lens tsev cov qauv theem uas tuaj yeem txav tau, tig thiab tilted.
