Digital Holographic Interferometry - A New Method for Measuring Polymerization Shrinkage of Composite Materials

Polimerizacija kompozitnih materijala smatra se iznimno važnim čimbenikom dugotrajnosti kompozitnog ispuna. Kakvoća polimerizacije utječe na fizičko-mehanička svojstva, stabilnost boje, volumetrijske promjene restoracije te na biokompatibilnost samoga materijala. Neizbježna posljedica stvrdnjavanja kompozitnih materijala jest polimerizacijsko skupljanje. Iznos polimerizacijskoga skupljanja do sada se je mjerio s viπe različitih postupaka. Digitalna holografska interferometrija, opisana u ovome radu, jedini je postupak koji omogućuje da se izravno prati polimerizacijsko skupljanje u svakoj sekundi osvjetljavanja kompozitnog materijala. Vrijednosti polimerizacijskoga skupljanja dobivene ovim postupkom u okviru su veličina polimerizacijskoga skupljanja izmjerenih drugim postupcima.Polymerization of composite filling is considered to be an important factor in achieving longevity of the restorative treatment. Quality of the polymerization influences physico-mechanical characteristics, color stability, volumetric changes of restoration and biocompatibility of the material itself. Polymerization shrinkage is an unavoidable consequence of setting of the composite material. So far, it has been measured by several different methods. Digital holographic interferometry, a method described in this study, is the only procedure that enables direct monitoring of the polymerization shrinkage for every second of polymerization of the composite material. Values of the polymerization shrinkage obtained by this method correspond with the values obtained by other methods

Optimiziranje korelacijskih filtara prema faznim prostornim svjetlosnim modulatorima

Correlation filters (CFs) are designed for pattern recognition tasks, taking into account the implementation of possibilities of available spatial light modulators (SLMs). Commercially available SLMs have the amplitude and phase responses that cannot be independently controlled. Furthermore, the phase modulation curves of such SLMs generally cannot cover the desired (0, 2π) interval. Therefore, previous filter designs include the SLM contraints as starting point for designing the CFs. Here we start with previously designed and calculated CFs and propose an optimum mapping of such CF values to the values constrained by the modulation properties of arbitrary SLM, in order to achieve a maximum intensity of the output correlation peak. Optimization procedure, achieved by the variation of a phase shift parameter, is discussed theoretically and numerically.Na razvoj korelacijskih filtara utječu potrebe raspoznavanja uzoraka kao i mogućnosti upotrebe dostupnih prostornih svjetlosnih modulatora. Tržišno dostupni prostorni svjetlosni modulatori imaju amplitudne i fazne odzive koji se ne mogu neovisno definirati. Štoviše, njihova fazna značajka najčešće ne obuhvaća željeni interval (0, 2π). Zbog toga su prijašnji pristupi uzimali u obzir ograničenja prostornih svjetlosnih modulatora kao početnu točku u razvoju korelacijskih filtara. Ovdje polazimo od već izračunatih i razvijenih korelacijskih filtara i predlažemo optimalno preslikavanje tih vrijednosti u vrijednosti dozvoljene modulacijskim svojstvima proizvoljnog prostornog svjetlosnog modulatora, sa ciljem dobivanja maksimalnog intenziteta izlaznog korelacijskog signala. Optimiziranje dobiveno varijacijom parametra faznog pomaka obrađuje se teorijski i numerički

Quantum holography with single-photon states

The retrieval of the phase with single-photon states is a fundamental and technical challenging endeavor. Here we report the first experimental realization of hologram recordings with heralded single-photon illumination and continuous observation of photon statistics. Thereby, we demonstrate the basic principle of holography with single-photon states which cannot be described with the classical wave theory. Under conditions with illumination more than 200 times weaker than the noise of the detector, a hologram (interferogram) recorded with a heralded single-photon source revealed an object not visible with non-heralded illumination and slightly higher intensity. The dramatic improvement in retrieval of amplitude and phase information achieved with the heralded single-photon source can be explained by the strong suppression of noise due to the nonclassical temporal correlation between twin photons and the small coincidence time window. The method could be useful for recording and retrieving of amplitude and phase information in the presence of strong noise, for covert imaging, and for imaging of photosensitive biological and material samples.Comment: 20 pages, 6 figures, 2 table

Primjena korelatora s preklopljenim fourierovim transformatima i panelima s tekućim kristalima za raspoznavanje klinastog pisma

An optoelectronic joint transform correlator system for recognizing cuneiform inscription signs is described. Real-time correlation experiments are carried out with the help of liquid crystal television (LCTV) type of addressable spatial light modulators. The in-class and out-of-class sensitivities as well as the effects of preprocessing of input signals taken from an original clay tablet are discussed.Opisana je primjena optoelektroničkog korelatora s preklopljenim Fourierovim transformatima na problem raspoznavanja znakova klinastog pisma. Provedeni su korelacijski eksperimenti u realnom vremenu uz pomoć adresabilnih prostornih modulatora svjetlosti s tekućim kristalima. Raspravljane su korelacijske osjetljivosti objekata unutar i izvan definirane klase te utjecaj prethodne obrade ulaznih signala uzetih s originalne glinene pločice

Linearity and Optimum-Sampling in Photon-Counting Digital Holographic Microscopy

In the image plane configurations frequently used in digital holographic microscopy (DHM) systems, interference patterns are captured by a photo- sensitive array detector located at the image plane of an input object. The object information in these patterns is localized and thus extremely sensitive to phase errors caused by nonlinear hologram recordings (grating profiles are either square or saturated sinusoidal) or inadequate sampling regarding the information coverage (undersampled around the Nyquist frequency or arbitrarily oversampled). Here, we propose a solution for both hologram recording problems through implementing a photon-counting detector (PCD) mounted on a motorized XY translation stage. In such a way, inherently linear (because of a wide dynamic range of PCD) and optimum sampled (due to adjustable steps) digital holograms in the image plane configuration are recorded. Optimum sampling is estimated based on numerical analysis. The validity of the proposed approach is confirmed experimentally

Influence of Polymerization Light Intensity on the Polymerization Shrinkage of Composite Materials (Part III)

Kompozitni materijali skupljaju se tijekom procesa polimerizacije što umanjuje njihovu kliničku vrijednost. Modifikacija u sastavu kompozitnoga materijala i tehnika aplikacije kompozita pokazale su se nedostatnima za kompenzaciju polimerizacijskoga skupljanja, pa se je zato pokušalo s modifikacijom polimerizacijskih programa. Polimerizacijski programi nižega intenziteta omogućit će dužu pregelacijsku fazu i time uvelike smanjiti ukupan iznos skupljanja. Svrha rada bila je odrediti polimerizacijsko skupljanje Tetric Ceram (Vivadent, Schaan, Liechtenstein) i Filtek Z 250 (3M Dental Products, St. Paul, MN) kompozitnoga materijala postupkom digitalne holografske interferometrije. Uzorci kompozitnih materijala polimerizirani su trima programima različita intenziteta (srednji, eksponencijski i standardni) Elipar Trilight halogene žarulje (ESPE, Seefeld, Germany). Najviše vrijednosti polimerizacijskoga skupljanja zabilježene su kod polimerizacijskoga programa s najjačim intenzitetom svjetla.Composite materials shrink during the polymerization process which lessens their clinical value. Modifications of composition of the composite material and application technique proved inadequate for compensation of polymerization shrinkage, and therefore modification of polymerization modes was attempted. The polymerization modes of lower intensities will enable prolongation of the pre-gelation phase and consequently greatly decrease the total amount of shrinkage. The purpose of the study was to determine the polymerization shrinkage of Tetric Ceram (Vivadent, Schaan, Liechtenstein) and Filtek Z 250 (3M/ESPE Dental Products, St Paul, MN) composite materials by digital holographic interpherometry. Samples of the composite material were polymerized by three modes of various intensities (medium, exponential and standard) Elipar Trilight halogen curing unit (3M/ESPE, Seefeld, Germany). Highest values of the polymerization shrinkage were recorded for the polymerization mode with highest light intensity

Dimensional Changes of Glass Ionomers and a Giomer during the Setting Time

Svrha: Cilj ovoga rada bio je postupkom digitalne laserske interferometrije odrediti dimenzijske promjene konvencionalnih staklenoionomernih cementa, smolom modificiranog staklenoionomernog cementa i giomera tijekom stvrdnjivanja materijala. Također se želio odrediti utjecaj različitih programa (visoki, postupni, niski) polimerizacijskog uređaja proizvedenog na temelju svjetlećih dioda (LED) na dimenzijske promjene svjetlom polimerizirajućih materijala. Materijali i postupci: Određeno je linearno skupljanje konvencionalnih staklenoionomernih cementa (K SIC) Fuji IX Extra (F9E), Fuji IX Fast (F9F), Ketac Molar Aplicap (KM) i Ketac Molar Quick Aplicap (KMQ), zatim smolom modificiranog staklenoionomernog cementa (SM SIC) Fuji II LC (F2LC) te giomera Beautifil II (B2). Svi ispitani materijali bili su nijanse A3, a svi staklenoionomerni cementi kapsulirani. Uzorci diskoidnog oblika (n = 10, d = 10 mm, h = 0,85 mm) pripremljeni su prema uputama proizvođača za svaki ispitani materijal i svaki polimerizacijski program (za svjetlom polimerizirajuće materijale). Svjetlosno polimerizirajući uzorci polimerizirani su LED uređajem za polimerizaciju (Bluephase G2, Ivoclar-Vivadent, Schaan, Lihtenštajn). Dimenzijske promjene tijekom stvrdnjivanja zabilježene su u stvarnom vremenu. Rezultati su analizirani ANOVA-om, a Tukeyjev post hoc test korišten je za višestruke usporedbe (α < 1 %). Rezultati: Svi ispitani materijali imali su početnu ekspanziju i naknadno skupljanje. KM i KMQ značajno su se manje skupljali od SM SIC-a polimeriziranog bilo kojim od triju polimerizacijskih programa. B2 se manje skupljao od F2LC-a. Zaključak: Stupanj polimerizacijskog skupljanja SM SIC-a može utjecati na trajnost restauracija.Objectives: The aim of this study was to evaluate dimensional changes of conventional glass ionomer cements, resin-modified glass-ionomer cement, and a giomer during the setting time using digital laser interferometry. Additionally, the influence of different curing modes (“high”, “soft”, and “low”) of a light-emitting diode (LED) curing unit on dimensional changes was evaluated. Materials and methods: Linear curing shrinkage of conventional glass ionomer cements (CGICs): Fuji IX Extra (F9E), Fuji IX Fast (F9F), Ketac Molar Aplicap (KM), Ketac Molar Quick Aplicap (KMQ), resin-modified glass ionomer cement (RM GIC): Fuji II LC (F2LC) and giomer: Beautifil II (B2) was analyzed. All tested materials were of shade A3, while all of the GIC were encapsulated. Discoid specimens (n=10, d=10 mm, h=0.85 mm) were prepared for each tested material and each curing mode (for light-curable materials) according to the manufacturer’s instructions. Light-curable specimens were cured with LED curing unit (Bluephase G2, Ivoclar-Vivadent, and Schaan, Liechtenstein). Dimensional changes during curing were recorded in real-time. The results were analyzed by ANOVA, and Tukey post hoc test was used for multiple comparisons (α < 1%). Results: All tested materials showed an initial setting expansion and a subsequent setting shrinkage. KM and KMQ had significantly lower setting shrinkage than RM GIC polymerized using any of the three curing modes. B2 showed lower shrinkage compared to F2LC. Conclusions: The extent of curing shrinkage in RM GIC measured in this study can affect longevity of restorations