Name: high-speed optical diagnostics of a supersonic ping-pong cannon
Uploaded: 2023-03-24T13:10:00
Description: Watch this Scientific Journal Video about High-Speed Optical Diagnostics of a Supersonic Ping-Pong Cannon at JoVE.com

Detta arbete stöds av NSF Division of Undergraduate Education (utmärkelse # 2021157) som en del av IUSE: EHR-programmet

1. Byggande och montering av pingiskanonen (PPC)
<ol><li>Montera alla komponenter i PPC enligt figur 1.</li>
	<li>Sätt in två akrylfönster med hög klarhet i kanonens sidor för att möjliggöra optisk sondering över kanonens inre.<ol><li>Borra två 1/2 i hål genom motsatta sidor av PVC nära kanonens utgång.</li>
		<li>Förbered två 1/8 i tjocka akrylfönster med en lasergraver. Ladda ner de tre kompletterande svg-filerna. Det finns tre filer märkta "JoVE_Acryl...

<ol>
	<li>Peterson, R. W., Pulford, B. N., Stein, K. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+ping-pong+cannon:+A+closer+look.">The ping-pong cannon: A closer look.</a> The Physics Teacher. 43 (1), 22-25 (2005).</li><li>Olson, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+shock+waves+in+expansion+tube+accelerators.">The role of shock waves in expansion tube accelerators.</a> American Journal of Physics. 74 (12), 1071-1076 (2006).</li><li>Cockman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+vacuum+bazooka.">Improved vacuum bazooka.</a> The Physics Teacher. 41 (4), 246-247 (2003).</li><li>Ayars, E., Buchholtz, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+vacuum+cannon.">Analysis of the vacuum cannon.</a> American Journal of Physics. 72 (7), 961-963 (2004).</li><li>Thuecks, D. J., Demas, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+the+effect+of+air-intake+aperture+size+in+the+ping-pong+ball+cannon.">Modeling the effect of air-intake aperture size in the ping-pong ball cannon.</a> American Journal of Physics. 87 (2), 136-140 (2019).</li><li>Liepmann, H. W., Roshko, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Elements of gas dynamics. , (1957).</li><li>Settles, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Schlieren and shadowgraph techniques. , (2001).</li><li>Geisert, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+single+mirror+schlieren+optical+system.">A single mirror schlieren optical system.</a> American Journal of Physics. 52 (5), 467 (1984).</li><li>French, R. M., Gorrepati, V., Alcorta, E., Jackson, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mechanics+of+a+ping-pong+ball+gun.">The mechanics of a ping-pong ball gun.</a> Experimental Techniques. 32 (1), 24-30 (2008).</li><li>French, M., Zehrung, C., Stratton, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+supersonic+ping-pong+gun.">A supersonic ping-pong gun.</a> arXiv. , (2013).</li><li>French, F., Choudhuri, R., Stratton, J., Zehrung, C., Huston, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modular+supersonic+ping-pong+gun.">A modular supersonic ping-pong gun.</a> arXiv. , (2018).</li><li>Fredrick, C. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complementary+studies+on+supersonic+nozzle+flow:+heterodyne+interferometry,+high-speed+video+shadowgraphy,+and+numerical+simulation.">Complementary studies on supersonic nozzle flow: heterodyne interferometry, high-speed video shadowgraphy, and numerical simulation.</a> WIT Transactions on Modelling and Simulation. 59, 223-234 (2015).</li></ol>

Vi har presenterat en metod för konstruktion av en PPC och en SSPPC tillsammans med optisk diagnostik för mätning av kulhastigheter och för karakterisering av chockutbredning nära kanonens utgång. Standard PPC är konstruerad med en 2 m sektion av 1,5 i schema 80 PVC-rör. Röret är utrustat med flänsar i varje ände, snabbkopplade vakuumbeslag och akrylfönster nära utgången för laserdiagnostik. En detaljerad schematisk bild av PPC visas i figur 1. Före avfyrning sätts en pingi...

PPC är en populär fysikdemonstration som används för att visa det enorma lufttrycket som människor ständigt utsätts för 1,2,3,4,5. Demonstrationen innebär placering av en pingisboll i en sektion av röret som har en innerdiameter som är ungefär lika med kulans diameter. Röret förseglas i varje ände med tejp och evakueras till ett inre tryck på mindre än 2 Torr. Tejpen i ena änden av röret punkteras, vilket gör att luft kan komma in i kanonen och får bollen att uppleva toppaccelerationer på cirka 5 000 g. Kulan, som accelereras av enbart atmosfärstryck, lämnar kanonen med en hastighet av cirka 300 m / s efter att ha rest 2 m.
Även om PPC vanligtvis drivs som en enkel demonstration av atmosfärstryck, är det också en apparat som uppvisar komplex kompressibel flödesfysik, vilket har resulterat i många öppna studentprojekt. Bollens dynamik påverkas av sekundära faktorer som väggfriktion, läckage av luft runt bollen och bildandet av chockvågor av den accelererande bollen. Den betydande accelerationen av bollen introducerar en kompressionsvåg med stor amplitud som färdas ner i röret framför bollen. Dessa kompressioner färdas snabbare än den lokala ljudhastigheten, vilket resulterar i en brantning av kompressionsvågen och slutligen bildandet av en chockvåg6. Tidigare arbete har studerat den snabba uppbyggnaden av tryck vid rörets utgång på grund av reflektionerna av chockvågen mellan bollen och rörets tejpade utgång och den resulterande lossningen av tejpen före utgången av bollen2. Höghastighetsvideo med en spegel schlieren-bildteknik har avslöjat bandets svar på de reflekterande chockvågorna och den slutliga lossningen av tejpen vid utgången av PPC 7,8 (Video 1). Således fungerar PPC både som en enkel demonstration av lufttryck som fascinerar publik i alla åldrar och som en anordning som uppvisar komplex vätskefysik, som kan studeras i detalj i en laboratorieinställning.
Med standard PPC begränsas pingisbollhastigheterna av ljudets hastighet. Denna grundläggande version av PPC omfattas av detta dokument, tillsammans med en modifierad kanon som används för att öka bollen till supersoniska hastigheter. I tidigare arbete av French et al. har supersoniska pingisbollhastigheter uppnåtts genom att använda tryckdrivet flöde genom ett konvergerande-divergerande munstycke 9,10,11. SSPPC som presenteras här använder ett trycksatt (driv) rör för att ge en större tryckskillnad på pingiskulan än vad som tillhandahålls av atmosfärstryck ensam. Ett tunt polyestermembran används för att separera drivröret från det evakuerade (drivna) röret som innehåller kulan. Detta membran brister under tillräckligt gagetryck (vanligtvis 5-70 psi, beroende på membranets tjocklek), vilket accelererar pingisbollen till hastigheter upp till Mach 1,4. Den supersoniska pingisbollen producerar en stående chockvåg, vilket kan ses med hjälp av höghastighets skugggrafavbildningstekniker 7,12 (Video 2).
En HeNe-laser med låg effekt (klass II) används för att utföra optiska diagnostiska studier på kanonens prestanda. HeNe-laserstrålen är uppdelad i två banor, med en väg som passerar genom en uppsättning akrylfönster nära kanonens utgång och den andra vägen som korsar precis förbi kanonens utgång. Varje bana avslutas på en fotomottagare, och signalen visas på ett dubbelkanals oscilloskop. Oscilloskopspåret som registrerats under avfyrningen av kanonen avslöjar information om både hastigheten på den accelererade pingisbollen och det komprimerbara flödet och chockvågorna som föregår kulans utgång från kanonen. Hastigheten på pingisbollen med en diameter på 40 mm vid varje strålplats är direkt relaterad till den tid då kulan blockerar strålen. En känslig "knivkant" stötdetekteringsinställning uppnås genom att täcka hälften av detektorn med en bit svart elektrisk tejp och placera kanten på tejpen i mitten av strålen2. Med denna inställning är små avböjningar av He-Ne-laserstrålen, som produceras av det komprimerbara flödesinducerade indexet för brytningsgradienter, tydligt synliga som spänningsspikar på oscilloskopspåret. Chockvågorna som färdas mot kanonutgången och de reflekterade chockvågorna avböjer strålen i motsatta riktningar och identifieras därför av antingen en positiv eller negativ spänningsspets.
Här ger vi instruktioner för konstruktion och användning av en optimerad PPC och SSPPC, samt optiska diagnostiska tekniker (figur 1, figur 2 och figur 3). De optiska diagnostiska teknikerna och mätningarna har utvecklats genom tidigare års studie 1,2.

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high-speed optical diagnostics of a supersonic ping-pong cannon

Den traditionella pingiskanonen (PPC) är en pedagogisk apparat som skjuter en pingisboll ner i ett evakuerat rör till nästan ljudhastigheter med enbart atmosfärstryck. SSPPC, en förstärkt version av PPC, uppnår supersoniska hastigheter genom att accelerera bollen med större än atmosfärstryck. Vi tillhandahåller instruktioner för konstruktion och användning av en optimerad PPC och SSPPC.
Optisk diagnostik implementeras i syfte att undersöka kanondynamiken. En HeNe-laser som skickas genom två akrylfönster nära rörets utgång avslutas på en fotomottagarsensor. En mikroprocessor mäter den tid som strålen hindras av pingisbollen för att automatiskt beräkna bollens hastighet. Resultaten presenteras omedelbart på en LCD-skärm. 
En optisk knivkantsinställning ger ett mycket känsligt sätt att upptäcka chockvågor genom att skära av en bråkdel av HeNe-strålen vid sensorn. Chockvågor orsakar brytningsinducerade avböjningar av strålen, som observeras som små spänningsspikar i den elektriska signalen från fotomottagaren. 
De metoder som presenteras är mycket reproducerbara och erbjuder möjlighet till vidare undersökning i laboratoriemiljö.

Här tillhandahåller vi instruktioner för konstruktion och användning av en PPC och en SSPPC, tillsammans med implementeringen av optisk diagnostik för chockkarakterisering och hastighetsmätningar. Representativa experimentella resultat tillhandahålls också. De färdiga systemen för PPC och SSPPC, tillsammans med nödvändiga tillbehör, visas i figur 1 och figur 2. SSPPC är en förstärkt version av PPC, där en drivande, trycksatt rörsektion är ansl...

Watch this Scientific Journal Video about High-Speed Optical Diagnostics of a Supersonic Ping-Pong Cannon at JoVE.com

High-Speed Optical Diagnostics of a Supersonic Ping-Pong Cannon

Vi beskriver en metod för konstruktion av en supersonisk pingiskanon (SSPPC) tillsammans med optiska diagnostiska tekniker för mätning av kulhastigheter och karakterisering av utbredande chockvågor under avfyrningen av kanonen.

Höghastighets optisk diagnostik av en supersonisk ping-pong-kanon

The traditional ping-pong cannon (PPC) is an educational apparatus that launches a ping-pong ball down an evacuated pipe to nearly sonic speeds using ...

Vi tillhandahåller instruktioner för att konstruera och driva en supersonisk pingiskanon tillsammans med optiska diagnostiska tekniker för att mäta kulhastigheter och detektera chockvågor. Den optiska knivseggen är mycket känslig för små, traversa avböjningar av en laserstråle och ger ett sätt att upptäcka chockvågor associerade med kanonen. För att börja, driva fotomottagarna och lasermodulen genom att ansluta dem till en 15 volt strömbegränsad strömförsörjning och laserströmförsörjning.Anslut sedan fotomottagarna till oscilloskopets två kanaler med BNC-kablar. För optisk diagnostisk inställning, placera lasern vinkelrätt mot den tillverkade kanonen med den första strålen som passerar genom akrylfönstren inuti röret och den andra strax utanför kanonutgången. Placera svart elektrisk tejp över hälften av fotomottagarsensorn och skapa en inställning för detektering av knivkantchocker.För att undvika klippning, justera strålpositionen på kniveggen så att baslinjespänningen är ungefär 50% av det maximala. Justera sedan inställningarna på oscilloskopet för att samla in 20 miljoner datapunkter. Använd den horisontella skalningsknappen för att ställa in datainsamlingshastigheten till 500 megahertz.Vrid avtryckarratten för att lösa ut med en spänning något under den inställda baslinjen som erhållits från fotomottagaren. Innan du avfyrar PPC, använd öron- och ögonskydd. Sätt in en pingiskula i kanonens utgång och blås lätt i kanonens ände tills den träffar vakuumbeslaget nära röringången.Försegla kanonens utgångsfläns och akryllock med två bitar fyrkantig tejp. Se till att laserstrålen är centrerad på knivseggen, avtryckaren är korrekt placerad och fångstbehållaren är säker. Slå på vakuumpumpen för att evakuera röret till ett reducerat absolut tryck på mindre än två Torr.När ett tillräckligt vakuum har uppnåtts, använd en bredhuvudspets för att punktera tejpen vid ingången. Stäng av vakuumpumpen efter avfyrning och ta bort eventuell kvarvarande tejp från utgångsflänsen och akryllocket. För att avfyra supersonisk PPC, stäng ventilen som ansluter drivröret till luftkompressorn och fyll luftkompressortanken.Blås bollen, som tidigare visats. Efter tätning av den supersoniska PPC-utgångsflänsen, sätt in ett tunt förskuret polyestermembran mellan två gummipackningar och placera dem mellan kanonens drivare och drivna sektioner. Anslut de två sektionerna med fyra kamklämmor.När trycket har minskat i röret, släpp trycket från luftkompressorn in i drivröret, så att trycket kan öka tills membranet brister och tryckluften i drivröret fyller det evakuerade drivna röret. Stäng av luftkompressorn och vakuumpumpen efter den supersoniska PPC-avfyrningen. Ta bort det spruckna polyestermembranet och tejpen från kanonen.Den förökande chockvågen, reflekterad under hela kanonavfyrningsprocessen, representerades av en spänningsförändring med avseende på tid. En positiv eller negativ spik visar chockvågens riktning i signalen, och hastigheten beräknades genom kvadratpulsbredden, som producerades av kulan som skar av strålen. En mikroprocessor användes för att bearbeta signalen från strålen som korsar rörets inre för att automatiskt beräkna och visa kulhastigheten nära kanonutgången.Oscilloskopspåren demonstrerade dubbelkanalsavfyrningen av supersonisk PPC. Det övre spåret representerar strålen som korsar kanonens inre, nära utgången. Medan det nedre spåret motsvarar strålen som korsar pingisbollbanan efter att ha lämnat kanonen.En avstängningssignal indikerade att bollen passerade och hindrade varje stråle. Diagrammet över tryckskillnad kontra Mach-tal avslöjade att 0,001 och 0,002 tum tjocka membran brister vid tillräcklig tryckskillnad för att accelerera pingisbollen till supersonisk hastighet. Bollhastigheten var genomgående större än Mach 1.3 med ett 0.002 tum tjockt membran.Den presenterade supersoniska pingiskanonen och den optiska diagnostiken kommer att öka kanonens värde, både som demonstrationsanordning och som apparat för uppföljande laboratorieexperiment.

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Unit 1

Kinematics of a Particle

SCIENTISTS IN ACTION

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

Konstruktion och test av Knappceller av litiumjonbatterier

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime.  Lithium ion ...

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

Tillverka Metamaterial med den metod fiberdragning

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

Optisk fångst av nanopartiklar

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses triangulation between matching points in two views of the same scene at different angles to compute depth.&#160;However, unlike a stereo-based method, DFP uses a digital video projector to replace one of the cameras1. The projector rapidly projects a known sinusoidal pattern onto the subject, and the surface of the subject distorts these patterns in the camera&#8217;s field of view. Three distorted patterns (fringe images) from the camera can be used to compute the depth using triangulation.
Unlike other 3D measurement methods, DFP techniques lead to systems that tend to be faster, lower in equipment cost, more flexible, and easier to develop.&#160;DFP systems can also achieve the same measurement resolution as the camera.&#160;For this reason, DFP and other digital structured light techniques have recently been the focus of intense research (as summarized in1-5). Taking advantage of DFP, the graphics processing unit, and optimized algorithms, we have developed a system capable of 30&#160;Hz 3D video data acquisition, reconstruction, and display for over 300,000 measurement points per frame6,7.&#160;Binary defocusing DFP methods can achieve even greater speeds8.
Diverse applications can benefit from DFP techniques. Our collaborators have used our systems for facial function analysis9, facial animation10, cardiac mechanics studies11, and fluid surface measurements, but many other potential applications exist.&#160;This video will teach the fundamentals of DFP techniques and illustrate the design and operation of a binary defocusing DFP system.

This video describes the fundamentals of digital fringe projection techniques, which provide dense 3D measurements of dynamically changing surfaces.&#160;It also demonstrates the design and operation of a high-speed binary defocusing system based on these techniques.

Högupplöst, hög hastighet, tredimensionell video Imaging med Digital Fringe Projection Tekniker

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses ...

Construction of a High Resolution Microscope with Conventional and Holographic Optical Trapping Capabilities

High resolution microscope systems with optical traps allow for precise manipulation of various refractive objects, such as dielectric beads 1 or cellular organelles 2,3, as well as for high spatial and temporal resolution readout of their position relative to the center of the trap. The system described herein has one such "traditional" trap operating at 980 nm. It additionally provides a second optical trapping system that uses a commercially available holographic package to simultaneously create and manipulate complex trapping patterns in the field of view of the microscope 4,5 at a wavelength of 1,064 nm. The combination of the two systems allows for the manipulation of multiple refractive objects at the same time while simultaneously conducting high speed and high resolution measurements of motion and force production at nanometer and piconewton scale.

The system described herein employs a traditional optical trap as well as an independent holographic optical trapping line, capable of creating and manipulating multiple traps. This allows for the creation of complex geometric arrangements of refractive particles while also permitting simultaneous high-speed, high-resolution measurements of the activity of biological enzymes.

Konstruktion av en högupplöst mikroskop med konventionella och holografiskt optiskt fångstmetoder Capabilities

High resolution microscope systems with optical traps allow for precise manipulation of various refractive objects, such as dielectric beads 1 or cellular ...

High-speed Particle Image Velocimetry Near Surfaces

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. 
Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (&gt; 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows.
A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included.

A procedure for studying transient flows near boundaries using high-resolution, high-speed particle image velocimetry (PIV) is described here. PIV is a non-intrusive measurement technique applicable to any optically accessible flow by optimizing several parameter constraints such as the image and recording properties, the laser sheet properties, and analysis algorithms.

High-speed Particle Image Velocimetry Nära Ytor

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The ...

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

Visualisering av High Speed ​​Liquid Jet Impac på en rörlig yta

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and&#160;limits the&#160;resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

Tillverkning och drift av en Nano-optisk Transportband

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

Writing Bragg Gratings in Multicore Fibers

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

We describe a technique for inscribing identical fiber Bragg gratings into each core of a multicore fiber. This is achieved by introducing an additional surface into the optical path to mitigate lensing by the curved surface of the fiber cladding.

Skriva Bragg-gitter i multicore Fibrer

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong ...

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

We present a compact reflection digital holographic system (CDHM) for inspection and characterization of MEMS devices. A lens-less design using a diverging input wave providing natural geometrical magnification is demonstrated. Both static and dynamic studies are presented.

Kompakt Lens mindre Digital Holographic Mikroskop för MEMS inspektion och karakterisering

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and ...