▁principle ▁is ▁based ▁on ▁the ▁Do pp ler ▁effect , ▁which ▁occurs ▁when ▁light ▁is ▁back - sc atter ed ▁from ▁a ▁v ibr ating ▁surface . ▁▁ ▁Both ▁velocity ▁and ▁disp lacement ▁can ▁be ▁determined ▁by ▁analyz ing ▁the ▁optical ▁signals ▁in ▁different ▁ways . ▁A ▁sc anning ▁las er ▁v ib rom eter ▁integr ates ▁computer - control led ▁X , Y ▁sc anning ▁mirror s ▁and ▁a ▁video ▁camera ▁inside ▁an ▁optical ▁head . ▁ ▁The ▁las er ▁is ▁sc anned ▁point - by - point ▁over ▁the ▁test ▁object ' s ▁surface ▁to ▁provide ▁a ▁large ▁number ▁of ▁very ▁high ▁spatial ▁resolution ▁measurements . ▁ ▁This ▁sequ entially ▁measured ▁v ibration ▁data ▁can ▁be ▁used ▁to ▁calculate ▁and ▁visual ize ▁animated ▁def lection ▁shapes ▁in ▁the ▁relevant ▁frequency ▁bands ▁from ▁frequency ▁domain ▁analysis . ▁Alternatively , ▁data ▁can ▁be ▁acquired ▁in ▁the ▁time ▁domain ▁to , ▁for ▁example , ▁generate ▁anim ations ▁showing ▁wave ▁propag ation ▁across ▁structures . ▁ ▁In ▁contrast ▁to ▁contact ▁meas uring ▁methods , ▁the ▁test ▁object ▁is ▁una ffect ed ▁by ▁the ▁v ibration ▁meas uring ▁process . ▁▁ ▁V ib rom etry ▁covers ▁a ▁huge ▁range ▁of ▁applications ▁such ▁as ▁the ▁study ▁of ▁micro struct ures ▁moving ▁only ▁a ▁few ▁pm ▁at ▁frequencies ▁up ▁to ▁ 3 0   M Hz , ▁all ▁the ▁way ▁up ▁to ▁the ▁inten se ▁dynamics ▁occurr ing ▁in ▁Formula ▁ 1 ▁engines ▁with ▁v ibration ▁veloc ities ▁approaching ▁ 3 0   m / s . ▁