01
Taw qhia
Optical detection technology plays lub luag haujlwm tseem ceeb hauv laser ultrasonic kuaj (LUT) thiab muaj qhov zoo dua li cov tshuaj piezoelectric sensors. Tsis yog-kev tiv thaiv kev kho qhov muag tsis cuam tshuam nrog thaj chaw ultrasonic thiab tso cai rau cov ntsiab lus tshawb pom kom txav mus sai nrog qhov tseeb ntawm qhov tseeb. Optical detection npog ntau zaus nyob rau hauv siab -frequency bands, ua rau nws muaj peev xwm txheeb xyuas thiab txheeb xyuas ultrasonic tsis. Hauv qhov sib piv, piezoelectric sensors ntsib cov teeb meem hauv kev tshawb pom siab -ntau zaus teeb liab vim muaj kev txwv ntawm cov khoom siv. Txawm li cas los xij, qhov rhiab heev ntawm kev kuaj pom qhov muag tau txo qis thaum cuam tshuam nrog cov khoom tawg. Cov nyhuv ntawm ultrasonic nthwv dej ntawm lub teeb beam tuaj yeem raug faib ua kev siv zog thiab theem lossis zaus hloov kho. Vim yog lub teeb ntau zaus ntawm lub teeb, photodetectors tam sim no tsis tuaj yeem ntsuas cov theem ntawm lub teeb ncaj qha thiab tsuas tuaj yeem ntes lub teeb siv. Yuav kom tau txais cov ntaub ntawv theem ntawm lub teeb beam, beam yuav tsum tau hloov pauv hloov cov ntaub ntawv theem mus rau hauv cov ntaub ntawv siv zog, uas yog tom qab ntawd rov qab los ntawm demodulation.
02
Kev siv zog siv tshuab
Intensity modulation techniques tau txais qhov chaw vibration thiab cov ntaub ntawv hloov chaw los ntawm kev saib xyuas qhov hloov pauv ntawm lub teeb siv. Txoj hauv kev no feem ntau suav nrog cov twj tso kua mis- cov txheej txheem sojntsuam, cov txheej txheem kho qhov muag pom, thiab cov txheej txheem ntog qhov sib txawv. Lub twj tso kua mis- cov txheej txheem sojntsuam yog siv los ua tus yam ntxwv ultrafast dynamics thiab micro- rau nanoscale acoustic teb. Raws li tau piav qhia hauv daim duab 1, lub hauv paus ntsiab lus suav nrog kev siv siab - lub zog twj tso kua mis lub teeb los ua kom lub zog hloov pauv hloov pauv hloov pauv lossis siab - zaus ultrasonic pulses hauv cov khoom, ua raws li kev ntsuas nrog lub teeb pom kev uas muaj lub sijhawm tswj tau qeeb. Refractive Performance index cuam tshuam los yog hloov pauv los ntawm ultrasound hloov cov yam ntxwv ntawm lub teeb tsom teeb. Los ntawm kev kho lub sijhawm ncua ntawm ob lub pulses siv lub tshuab txhais lus, lub kaw lus tuaj yeem sau cov kev hloov pauv hloov pauv ntawm ultrasound ntawm picosecond lossis femtosecond scale. Optical deflection cov tswv yim pom cov geometric tilts hauv zos uas tshwm sim los ntawm qhov chaw acoustic nthwv dej. Thaum lub ultrasound dhau los ntawm qhov ntsuas pom, me ntsis qaij ntawm qhov chaw ua rau spatial deflection ntawm lub teeb pom kev zoo. Los ntawm kev qhia txog kev cuam tshuam ntawm lub cev mus rau hauv txoj kev kho qhov muag, angular displacements tau hloov mus rau hauv lub teeb siv zog hloov pauv tau txais los ntawm tus ntes. Qhov zaus ntawm cov kev hloov pauv no ncaj qha qhia txog lub cev yam ntxwv ntawm qhov chaw acoustic nto. Cov txheej txheem deg grating diffraction yog tsim rau cov chaw nrog ntu ntu microstructures. Raws li ultrasound propagates, nws feem ntau ua rau hloov me ntsis rau lub grating, uas nyob rau hauv lem hloov lub kaum sab xis thiab lub zog faib ntawm lub diffracted beams. Los ntawm kev saib xyuas cov kev hloov pauv ntawm qhov sib txawv ntawm qhov sib txawv ntawm qhov kev txiav txim tshwj xeeb, lub kaw lus tuaj yeem rho tawm cov ntaub ntawv hloov pauv ntawm qhov chaw nyob ntawm sub-nanometer theem.
03
Phase Modulation thiab Fabry-Perot Interferometry
Theem modulation tshuab siv lub hauv paus ntsiab lus cuam tshuam ntawm coherent lub teeb los hloov cov theem hloov modulated los ntawm ultrasonic vibrations rau hauv variations nyob rau hauv qhov siv ntawm kev cuam tshuam fringes. Cov thev naus laus zis no feem ntau ua tiav nanometer- theem precision lossis qis dua. Interferometric detection tuaj yeem muab faib ua kev siv - teeb pom kev cuam tshuam thiab tus kheej - siv cuam tshuam. Kev siv - lub teeb cuam tshuam suav nrog xoom- txoj hauv kev- cuam tshuam sib txawv thiab heterodyne cuam tshuam, thaum tus kheej - cov txheej txheem siv suav nrog kev cuam tshuam qeeb, hloov kho holographic cuam tshuam, thiab kev tshawb pom laser tawg. Hauv theem demodulation schemes, Fabry-Perot interferometer yog cov txheej txheem tseem ceeb rau laser ultrasonic nrhiav kom tau. Txoj kev no ua tiav coherent superposition ntawm ntau kab teeb los ntawm cov kab noj hniav resonant tsim los ntawm ob lub iav tsom iav heev (Daim duab 2). Thaum cov kev sojntsuam lub teeb nqa qhov chaw vibration theem cov ntaub ntawv nkag mus rau hauv cov kab noj hniav, cov kab teeb pom kev ntau zaus ntawm daim iav, ua rau cov kev cuam tshuam ntawm qhov sib txawv heev. Thaum ultrasonic-induced displacement ua rau ib lub sij hawm hloov, lub resonance mob drifts, ua rau ua heev linear fluctuations nyob rau hauv kis los yog reflected lub teeb siv. Piv nrog rau cov pa Michelson interferometers, Fabry-Perot interferometers qhia tau siab dua rau ib puag ncig kev vibrations thiab muaj ntau dua optical collimation, ua rau muaj kev nkag siab zoo dua thaum cuam tshuam nrog qhov ntxhib ntawm cov khoom siv dav hlau loj. Los ntawm kev tswj cov kab noj hniav ntev nrog piezoelectric ceramics, lub kaw lus tuaj yeem kaw qhov chaw ua haujlwm ntawm thaj chaw rhiab tshaj plaws ntawm kev cuam tshuam nkhaus, ua kom siab -linearity extraction ntawm qaug zog acoustic vibration signals. Tsis tas li ntawd, adaptive holographic interferometers siv photorefractive crystals dynamically sau cov qauv cuam tshuam, cia li them nyiaj rau wavefront distortions tshwm sim los ntawm ib puag ncig cuam tshuam los yog complex deg morphologies, txhim kho system stability nyob rau hauv hnyav industrial puag ncig. Laser scattering nrhiav tshuab ntes cov ntaub ntawv kev vibration los ntawm kev tshuaj xyuas cov kev hloov pauv hloov pauv ntawm speckle teb kev faib tawm. Txawm hais tias nws qhov kev daws teeb meem tsis txaus ntseeg me ntsis tsis zoo rau cov txheej txheem interferometric ntshiab, nws muaj lub zog ruaj khov thaum tuav cov khoom tsis ua tiav, tawg tawg heev, ua ib qho kev sib txuas ntxiv los ua cov khoom siv dav hlau dav dav (raws li qhia hauv daim duab 3). Heterodyne interferometers tsim cov cim ntaus cim los ntawm kev qhia qhov sib txawv ntawm qhov sib txawv, ua haujlwm zoo txog DC teeb liab drift teeb meem thiab txhim kho kev ntsuas qhov tseeb hauv qhov chaw muaj zog.
04
Cov ntsiab lus
Lub hauv paus ntsiab lus kho qhov muag pom ntawm laser ultrasonic kuaj tsim ib qho kev ua tiav los ntawm kev hloov dua siab tshiab ntawm lub cev lub zog rau lub teeb liab theem demodulation. Kev siv thev naus laus zis kev siv tshuab, nrog nws cov qauv kev nkag siab thiab qhov tseeb- lub sijhawm teb, ua lub luag haujlwm tseem ceeb hauv kev saib xyuas cov txheej txheem ceev thiab micro-nano tus yam ntxwv. Phase modulation thev naus laus zis, sawv cev los ntawm Fabry-Pérot interferometers, kov yeej cov kev txwv ntawm tsis yog- tiv tauj nrhiav kom paub txog qhov rhiab heev thiab kev daws teeb meem los ntawm cov txheej txheem optical coherence. Qhov no tsis yog tag nrho - hom kev kuaj xyuas tsis yog tsuas yog hais txog cov teeb meem ntawm kev ntsuam xyuas online ntawm cov khoom nkhaus nyuaj tab sis kuj tseem muab kev txhawb nqa tseem ceeb theoretical thiab txoj hauv kev rau kev saib xyuas kev noj qab haus huv ntawm cov ntaub ntawv thoob plaws hauv lawv lub neej.
