使用Dark-field和MIX观测的观测和测量示例

在拉曼显微镜中，样品观察的质量对于确定合适的测量点至关重要。NRS系列拉曼光谱仪可用于各种类型的观测：明场（外延照明）、明场（透射照明）、Dark-field、MIX、偏振和差分干涉。Observation and Measurement examples using2/4Application NoteDark-field and MIX observation Observation and Measurement examples using Dark-field and MIX observation I n trod u c t ion I n Raman m ic r oscopy， the qu a lity o f samp l e observ a t i on is essent i al f or id en tifying sui t a b le measurement p oints . T h e NRS Se ri es of Raman spect r omete r s ca n be u sed with variou s types of obse r vat i o n： Bright-f i e l d (epi-illumi n ation)， Bright-f i e l d (tr ans m i t t e d i l lumi n atio n )， Dark -f i e ld ， MIX， Po l ar i z e d a n d Differ e ntial Int er f er e n c e . This applicat i o n note introduc e s two o f these met h od s ： Dark -fi e l d and MIX observat i on， wh i ch a r e r ecommend e d for observat i o n of colored and hete r oge n eous samp l es. What i s Dark-field observation? Bright -f ield observation is mos t com m on， a n d uses light i rradiated f rom t h e center o f the objective l e n s， and the r ef l ected l igh t i s collected. Da r k-f ield observation differs i n that the lig ht is ir r ad i ated f r om ou t side of the object i ve lens by us i ng r ing -i llumi n ation， a n d th e scat tere d ligh t and diffract e d light ar e collect e d . This r e s ul ts in obs e rvat i on of t he scatt er ed and diffracted ligh t reflected f ro m the sa m ple in a dar k f ield of view. Advantage #1 Observation of colored sample I n Da r k-field observat i on， the color (except f o r b l ac k ) o f the samp l e can be obse r ved clea r ly. Since t h e background will become dark， black samples ca n be d i fficu l t to observe. Advantage #2 Observation of heterogeneous sample Dark-f i e l d obse r vat i o n i s very effective for obse r ving h eterogeneo u s samples (severa l 10 nm). Although Different i al I n t er fe r ence obs e r vat i o n is often u s e d for th is type of sample (s e veral n m)， its obs er vat i on f i lter has to be removed when per f or m ing the measureme nt ， because of the di ff erence between th e optical path for observat i on and that for Raman meas u rement. On t he ot h e r hand， Da r k-field observation enables Rama n measurement with the same objective lens without c h a ngi n g f il te r s. Ap p l i cat i on L i b ra r y： jasco i nc.co m /ap p licat i ons What i s MIX observation? MIX obse r v a tion is the at tr ac t i ve tec h nique co m bi n ing both “Br i ght -fi e l d ” a n d “Dar k-fi e l d”o b servation， a n d offers excel l ent observat i o n of images b y ut i lizing the unique adva n tages of both m ethods. Especially， MI X mode observation can be u s e d to o b s e rve b la c k samp l e s， wh i ch th e Dark-f ield o b s e rvation i s n ot we l l sui te d to. Figure 1. Exa m p l e s o f s a m ple o bserv atio n (Brig h t-f i eld， D ar k-f ie l d a n d M I X ) Expe r imen t al Observation method Dark -f i e l d and MIX obse r vat i o n are per f ormed us i ng a dedicated objec t i ve l e n s with LED i ll uminat i o n ar r anged in a ring *.Since t h e o b jective lens and the illu m inat i on can be mo un ted/dismounted easily， other observat i on methods such as the Bright -f i e ld can b e e as i ly e xchanged. I n add i tion， t he dir e c t i on of i l l u mi na t i on for Dark -f ield observat i on can be changed，and t he target in th e o b served image can be selective l y emphas i zed . * Dark-f i e l d and MIX observat i o n o n ly work with a dedicated object i ve revolver (facto r y option only). 28600 M ary's C ou r t， East on ， MD 21601 USA JS.CO An NRS-4500 Raman spectromete r (Figure 2) was used for th i s measurement， and p ar t icles i n a vitami n capsule were observed usi n g Dark-f i e l d and MIX modes. Using Dark-f i e l d mode t h e white a n d yellow p a r t i c l es cou l d be clear l y i dent i fied a g ai nst a da r k bac k ground， a n d i n MIX mode the white and yellow partic l es co u ld be clear l y i dent if ied against a br i ght background (F i gur e 3). Th e se p artic l e s we re measured at a p propriat e e xcitat i o n wav e l e ngths (white ： 532 n m，yellow： 785 n m )， a n d a da t a b ase searc h was perfo rm ed o n the o b ta i ned spect r a. From the result of the database search ， t h e white partic l es were ide nt i f ied as vita m i n C， and yel l ow part i cles as vitami n B2. Iden t ifyi n g t he color when o b se r vi n g t he sampl e provides addi ti onal us e ful infor m at i on about t h e compo n e n ts and t h e i r correla t io n with t he o b tained Raman spectra . Figure 2. NRS-4500R a m a n spectro m e ter Figure 3. Ra m an mea s ur em e nt of m ult i vi t am in O b s e r v a ti on i m ag e (l ef t )， Ram a n s pect ra a nd d a t a base s e arch re sult s (r i g ht) Using Dark-field and MIX observation modes， it is possible to more clearly observe the color and surface heterogeneity such as sample color， surface scratches/defects， and shapes that were difficult to see with conventional observation methods. Enhancement of observation helps with better identi f ication of the measurement point， and enables faster，more reliable measurement of spectral data. These observation modes are recommended for the following sample types . -Color information on fabrics， particles， printing etc. - Heterogeneous information on rocks and minerals， scratches on color panels etc. 28600 M ary's C ou r t， East on ， MD 21601 USA JS.CO System Configuration Model Description Part Number Main Unit NRS-4500-532 Raman Spectrometer 7118-JO51A Options RMIX4 MIX observation unit(Factory Option) 7118-J255A LMPLFLN20xBD Objective lens， x20， for Dark-field(Vis range) 1108-0134 7118-J201A 785 nm laser upgrade package(Factory Option)