Relevant bibliographies by topics / Laser contrast

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Laser contrast'

Author: Grafiati
Published: 4 June 2021
Last updated: 17 February 2022

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Journal articles on the topic "Laser contrast"

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Yuxuan Ma, Yuxuan Ma, Fei Meng Fei Meng, Yan Wang Yan Wang, Aimin Wang Aimin Wang, and Zhigang Zhang Zhigang Zhang. "High contrast linking six lasers to a 1 GHz Yb:fiber laser frequency comb." Chinese Optics Letters 17, no. 4 (2019): 041402. http://dx.doi.org/10.3788/col201917.041402.

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Stanhewicz, Anna E., Sara B. Ferguson, Rebecca S. Bruning, and Lacy M. Alexander. "Laser-Speckle Contrast Imaging." JAMA Dermatology 150, no. 6 (June 1, 2014): 658. http://dx.doi.org/10.1001/jamadermatol.2013.7937.

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Torrisi, Lorenzo. "Laser contrast and other key parameters enhancing the laser conversion efficiency in ion acceleration regime." EPJ Web of Conferences 167 (2018): 02002. http://dx.doi.org/10.1051/epjconf/201816702002.

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Measurements of ion acceleration in plasma produced by fs lasers at intensity of the order of 1018 W/cm2 have been performed in different European laboratories. The forward emission in target-normal-sheath-acceleration (TNSA) regime indicated that the maximum energy is a function of the laser parameters, of the irradiation conditions and of the target properties.In particular the laser intensity and contrast play an important role to maximize the ion acceleration enhancing the conversion efficiency. Also the use of suitable prepulses, focal distances and polarized laser light has important roles. Finally the target composition, surface, geometry and multilayered structure, permit to enhance the electric field driving the forward ion acceleration.Experimental measurements will be reported and discussed.
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Angelov, Nikolay, Lybomir Lazov, and Edmunds Teirumnieks. "INFLUENCE OF THE OVERLAP COEFFICIENT ON THE CONTRAST IN LASER MARKING OF C110W STEEL." ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 3 (June 16, 2021): 15–19. http://dx.doi.org/10.17770/etr2021vol3.6599.

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The laser marking process by melting samples of C110W carbon tool steel was studied. The experiments were performed with a fiber laser and a CuBr laser. A field of squares is marked in a raster method for different values of the overlap coefficient and power density. The contrast of the marking is determined on each marked square. From the obtained experimental data, graphs of the dependence of the contrast on the overlap coefficient for three power densities were drawn. The obtained results for the two lasers are compared and the influence of the wavelength is indirectly analysed. The working intervals of the overlap coefficient for the studied power densities for the two lasers at which the optimal contrast in the processing zone is obtained are determined.
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Geri, George A., and Logan A. Williams. "Perceptual assessment of laser-speckle contrast." Journal of the Society for Information Display 20, no. 1 (2012): 22. http://dx.doi.org/10.1889/jsid20.1.22.

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Paramsothy, Sudarshan, and Rupert W. L. Leong. "Fluorescein contrast in confocal laser endomicroscopy." Nature Reviews Gastroenterology & Hepatology 7, no. 7 (July 2010): 366–68. http://dx.doi.org/10.1038/nrgastro.2010.83.

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Glückstad, Jesper, Darwin Palima, Peter John Rodrigo, and Carlo Amadeo Alonzo. "Laser projection using generalized phase contrast." Optics Letters 32, no. 22 (November 2, 2007): 3281. http://dx.doi.org/10.1364/ol.32.003281.

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Penide, J., F. Quintero, A. Riveiro, A. Fernández, J. del Val, R. Comesaña, F. Lusquiños, and J. Pou. "High contrast laser marking of alumina." Applied Surface Science 336 (May 2015): 118–28. http://dx.doi.org/10.1016/j.apsusc.2014.10.004.

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Zhao, Yuemei, Kang Wang, Weitao Li, Huan Zhang, Zhiyu Qian, and Yangyang Liu. "Laser speckle contrast imaging system using nanosecond pulse laser source." Journal of Biomedical Optics 25, no. 05 (May 25, 2020): 1. http://dx.doi.org/10.1117/1.jbo.25.5.056005.

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Li, Chun Ling. "Contrast Prediction for Laser Direct Part Marked Data Matrix Symbols on Titanium Alloy Substrates." Advanced Materials Research 941-944 (June 2014): 2161–64. http://dx.doi.org/10.4028/www.scientific.net/amr.941-944.2161.

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To establish a mathematical relationship between Nd:YAG laser parameters and the qualities of laser direct marked Data Matrix symbols on titanium alloys, multiple linear regression analyses were performed based on orthogonal experiment results. According to the analysis results, the paper developed a prediction model to estimate the contrasts of laser direct marked Data Matrix symbols (i.e. Symbol Contrast). The prediction model was statistically analyzed by regression analysis and multi-factor analysis of variance (ANOVA). The predicted symbol contrasts were compared with the experimental values and they were close. The multiple linear regression analyses results showed that the developed prediction model was extremely significant and could be used to estimate the symbol contrast in laser direct part marking.
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Dissertations / Theses on the topic "Laser contrast"

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Sun, Shen. "Laser Doppler imaging and laser speckle contrast imaging for blood flow measurement." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604304.

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The two blood flow imaging techniques, laser Doppler blood flow imaging (LDI) and laser speckle contrast blood flow imaging (LSCI), are well established and broadly applied in medical research. They are similar as both detect and process a fluctuating interference (speckle) pattem. However, the difference between processing algorithms provides different imaging characteristics. LDI can provide accurate, quantitative blood flow measurement which is seldom achieved by LSCI. Nevertheless, the fast imaging speed and simple instrumental setup provided by LSCI overcome some of the limitations ofLDI. With the development of high frame rate cameras full field LDI is now feasible and with the development of new processing algorithms LSCI is now providing more accurate quantitative information. It is therefore important to compare the performance of these two techniques. A full-field LDI system based on an FPGA (Field Programmable Gate Array) coupled with a high-speed CMOS (Complementary Metal-Oxide-Semiconductor) camera chip has been developed which provides blood flow images with flexible frame rates and spatial resolution. When a high spatial resolution is required, 1280xl024-pixel blood flow images were obtained by processing up to 2048 samples at O.2fps (frame per second). Altematively, a maximum of 15.5fps was achieved by reducing the resolution and sampling points to 256x256 pixels and 128 samples respectively. As a generic full-field LDI system, several parts of the system (memory unit, processing unit) can be simply updated or transplanted to another platform. The resource usage is optimized by utilizing a mixture of fixed and floating-pointing implementations, and the imaging speed is maximised because of the design of streamline structure which enables continuous input of data. Images were obtained of rotating diffusers at different rotation velocities and the system provides a linear relationship with velocity. Human blood flow images are also demonstrated both of the finger and of a healing wound. The author-designed LDI system was then applied to a high-spatial resolution flow imaging application in which the mixture of water and polystyrene micro spheres was pumped through a micropipette (diameter = 250llm) with controlled velocities, and the resulting flow was imaged and processed. The accurate, high-spatial resolution flow measurement was demonstrated by the resulting flow images which are of size 1280x 1 024 pixels and obtained by processing 2048 samples at each pixel. Besides the LDI system, a novel LSCI system has been developed on the same platform, establishing a unique LDI and LSCI hybrid system. By developing the LSCI method with equivalent exposures, the LDI data can be analysed using LSCl processing, enabling a truly fair comparison of these two methodologies. For comparison, measurements were carried out on a rotating diffuser that simulates the human tissue with controlled parameters. Although LDI and LSCI are qualitatively similar, the lack of quantitative blood flow measurement ofLSCI was recognized from the comparison since LSCI is exposure time dependent and unable to linearly detect the velocity changes. 11 To improve the linearity and accuracy ofLSCI measurement, multi-exposure laser speckle contrast imaging (MLSCI) has been introduced. However this increases image acquisition time as consecutive images at different exposure times need to be acquired. On the basis of the novel LSCI method, a new MLSCI scheme has been invented. The advantage of the MLSCI is that each frame is exposed with a fixed duration and various exposure times are alternatively achieved by accumulating several successive frames. In this way, the requirement to obtain a wide range of exposure times from consecutive images is overcome. This reduces image acquisition time as it depends on the longest exposure time rather than the sum of all exposures. From measurements of a rotating diffuser, the MLSCI was demonstrated to be capable of quantitatively measuring flow changes as in LDI. III
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Song, Lipei. "Endoscopic laser speckle contrast analysis for tissue perfusion." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/10923.

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Laser speckle contrast analysis (LASCA), as a method of measuring blood flow speed and tissue perfusion, is a full field imaging technique requiring simple configurations and data processing, which is important for the application in real time in vivo. But LASCA is sensitive to changes in environmental factors. The application in vivo is also limited to superficial detection due to the limitation of the light penetration depth. Therefore this thesis aims to develop an endoscopic LASCA system to extend the access to internal detection and explore the relationship between the contrast and experimental parameters. Firstly the relationship between the contrast and speckle size, flow mode, quantity of stationary scatterers and the signal intensity were investigated. Theoretical models for the relationship between the contrast and the mean intensity of the speckle pattern were deduced and the correction methods were introduced to correct the contrast bias due to the intensity difference. Then a flexible single wavelength endoscopic laser speckle contrast analysis system (ELASCA) was developed using a leached fibre image guide (LFIG). A Butterworth filter and defocus were used to remove the fibre pattern to retrieve the contrast images. This system and the data processing methods were used on a customized phantom demonstrating that this ELASCA system can detect the flow speed changes in an imaging domain. Afterwards a dual-wavelength ELASCA was developed for functional imaging of the blood circulation. The test on a human fingertip and rabbit uterine blood vessels show that this system can monitor the change of blood flow speed and the oxygen saturation introduced by occlusion, in addition to the cardiac pulse and respiration rate. Then a novel application of LASCA to visualize the ultrasound pressure field and the propagation of the shear wave is presented for the application of locating area of interest (AOI) and detecting tissue variation.
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Flacco, Alessandro. "Experimental study of proton acceleration with ultra-high intensity, high contrast laser beam." École polytechnique, 2010. http://www.theses.fr/2008EPXX0071.

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La production de faisceaux énergétiques d'ions/protons avec des impulsions laser à intensités relativistes (I>10^{18}W/cm^2) a reçu, au cours des dernières années, un intérêt croissant parmi les scientifiques travaillant dans les domaines de l'optique, de la physique des plasmas et des accélérateurs. Une fraction des électrons est chauffée à haute température lors de l'interaction entre une impulsion laser femtoseconde et un plasma surdense. Les ions et les protons sont extraits et accélérés par la séparation de charge qui est produite pendant l'expansion du plasma. Les résultats présentés dans ce manuscrit décrivent la réalisation d'expériences d'accélération d'ions avec un système laser à haute puissance et à haut contraste (XPW). Deux expériences préparatoires sont réalisées, afin d'étudier l'interaction entre le piédestal d'une impulsion laser et une cible. L'expansion d'un plasma créé par laser à intensité moyenne est mesurée par interférométrie; l'évolution de la longueur de son gradient de densité est déduite par les cartes de densité électronique, mesurées à différents instants. La variation de la réflectivité absolue d'une cible mince d'aluminium est mise en corrélation avec la température électronique afin de contrôler le débouché du choc produit par le laser. La corrélation entre les deux expériences est finalement utilisée pour définir le conditions optimales pour l'accélération des protons. Des expériences d'accélération de protons avec un laser à haut contraste, la construction et la validation d'un spectromètre (Galette a Micro-canaux et Parabole Thomson), ainsi que des autres détails sur le montage sont présentés. Les résultats ainsi obtenus montrent que l'amélioration du contraste permet d'utiliser des cibles plus minces et de produire des conditions d'interaction plus stables et contrôlables. Des faisceaux des protons ayant énergie cinétique supérieure à 4MeV sont produits, avec une stabilité tir à tir meilleure de 4% rms. L'accélération des protons avec deux impulsions laser confirme que l'absorption d'énergie laser est augmentée dans le cas des cibles pre-chauffées par une impulsion laser avec les bons paramètres
The production of energetic proton/ion beams with laser pulses at relativistic intensities (I>10^{18}W/cm^2) has received, in the past few years, increasing interest from the scientific community in plasma, optics and accelerator physics. A fraction of electrons is heated to high temperature during the ultrafast interaction between a femtosecond laser pulse and an overdense plasma. Ions and protons are extracted and accelerated by the charge separation set up during the expansion of the plasma. The results presented in this manuscript report on the realization of ion acceleration experiments using a high contrast (XPW) multi-terawatt laser system. Two preparatory experiments are set up, aiming to study the pedestal of a laser pulse interacting with the target. The expansion of a plasma created by a laser at moderate intensity is measured by interferometry; the evolution of the density gradient length is deduced from the electron density maps at different moments. The variation of the absolute reflectivity of a thin aluminium foil is correlated to the electron temperature and is used to monitor the arrival time of the laser produced shock. The crossing between the two experiments is finally used to define the optimum condition for proton acceleration. Proton acceleration experiments with high contrast laser are reported, including the construction and the validation of a real-time, single shot ion spectrometer (Micro-channel Plate and Thomson Parabola), and other details of the realised setup. The obtained results show that the increased contrast enables the use of thinner targets and the production of more stable and controllable interaction conditions. Proton beams with kinetic energy higher than 4 MeV are produced, with a shot-to-shot stability better than 4% rms. Proton acceleration experiment with two laser beams confirms that the laser energy absorption is enhanced when the target is pre-heated by a laser pulse with proper parameters
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Apeland, Knut Øyvind. "Reduction of speckle contrast in HDTV laser projection display." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-8943.

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Abstract In this thesis the focus has been on laser speckle. It is done in collaboration with poLight. They are developing a projector, where laser light is the source of illumination. In such projectors, laser speckle degrades the image quality. The aim of this project is to construct a speckle reduction device to be used in the laser projector. The theory covers a description of laser speckle, how to reduce the speckle contrast, and five methods to so. We explain why speckle arises and which parameters we can manipulate to reduce the speckle contrast. The five speckle reduction methods included in this thesis are; vibrating diffuser, slowly moving diffuser, Hadamard matrices, scattering tube, and vibrating mirror. Large vibrational motions are unwanted, considering the size of the device, generation of noise, and problems with alignment of the optical components in the projector that this would lead to. The quality of the laser beam is prominent in order to produce a sharp image, thus the use of diffusers with large scattering angles is not a good solution. The scattering tubes, designed by poLight, are tubes filled with micro pearls in a polymer gel. The size of the pearls decides the nature of the scattering. Larger pearls will give less back scattering and more light transmitted in the forward direction. If the tubes are rotated in a well balanced device we can avoid generating vibrations. The Hadamard matrices is the only one of the five methods which is not based on a motion. The challenge is to find a SLM to implement the matrices. It requires a low response time in order to present enough matrices during the exposure time of the eye. The laboratory setup we use to measure the speckle contrast is an improved version of the setup constructed in the specialisation project. A screen was removed from the old setup, and the speckle is now imaged directly from the speckle reduction device. The measured speckle reduction is thus due to the device alone, and not affected by the screen. The results were reproducible and in agreement with what we expected. We implemented a vibrating diffuser, both the single and the slowly moving. A piece cut from a plastic bag and some Scotch Magic tape were used as diffusers. The tape is the strongest diffuser and gives the lowest speckle contrast, however, it also has the largest scattering angle. The single tape diffuser reduced the speckle contrast to $C = 0.112$. With two tape difusers in series the intensity in the images becomes too low to exploit the dynamic range of the CCD sensor. The result is a higher calcualted speckle contrast with two diffusers, $C=0.131$, even though it ought to be smaller. We tested five prototypes of the scattering tube with different concentrations. The tube with the highest concentration has the highest speckle reduction abilities. It also has the strongest scattering effect. The scattering is less than with the tape diffuser, and so is the speckle reduction. The speckle contrast is reduced to $C=0.320$ when the tube is rotated, and to $C=0.389$ when it is vibrated. The tubes was also tested in series with a ground glass. The ground glass acted as a second diffuser. In this setting, vibration and rotation of the tubes reduced the speckle contrast equally, $C approx 0.283$ From the measured speckle contrast of the diffusers and tubes in stationary conditions, a polarization analysis should show a depolarization of the laser beam. This were the case only for the plastic diffuser. It is assumed that the error lays with the polarization analysis. There should be a depolarization in the tape and a partial depolarization in the tubes. A calculation of the speckle size was performed as well. Based on the theory we expected the size of the speckle grains to be $sigma_s = 37.77~mu m$. From the Fourier analysis of a speckle image from the setup we calculated the speckle size to be $sigma_s = 5.35$~mm, which is approximately 140 times bigger. The expected speckle size is too small, because we did not take into account a small magnification in the setup. The Fourier analysis of discrete and limited sets of data points is probably the main explanation of the difference, but a more thorough study is needed.

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Young, Anthony M. "Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami153256524246362.

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Li, Sinan. "Laser speckle contrast detection of acoustic radiation force response." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/34931.

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Light and ultrasound are both non-ionizing radiations, ideal for biomedical applications. Recent studies on combining ultrasound and light for biomedical imaging show new promises in improving imaging quality and/or providing complementary imaging contrast. Among a variety of the imaging modalities that simultaneously use ultrasound and light, this work focuses on optical detection of tissue responses to acoustic radiation force (ARF). The applications include optical shear wave elastography and ultrasound modulated optical tomography. The first half of the thesis provides a systematic study on tracking shear waves in optical turbid media using CCD-based laser speckle contrast analysis. The theory, simulation and experiment are developed and cross-validated. The simulation quantitatively relates CCD speckle contrast signal with shear waves, providing useful information to understand the underlying physics. In addition, multiple shear waves are tracked using laser speckle contrast detection. Results show that two counter-propagating shear waves produce a modulation pattern in the optical signal, and the modulation pattern was suggested by simulation as a result of the dual shear wave interference. Shear wave speed measurements in phantoms suggest that the dual shear wave approach is more accurate than the single shear wave approach as that the standard deviation of the speed measurement is reduced by a factor of at least 2. The the dual shear wave approach also provides a reduced boundary effect. Both factors suggest that the dual shear wave approach should improve the accuracy of elasticity measurements. In the second half of the thesis, instead of detecting ARF response in the late phase, the study is motivated by detecting ARF response in the early stage for enhancement of ultrasound modulation of light. A pilot study on incorporating perfluorocarbon-based phase change contrast agent with ultrasound modulated optical tomography is explored. To understand the phase transition process, a quantitative measurement of acoustic nanodroplet vapourisation is developed. A preliminary result also showed that a single ultrasound burst can simultaneously vaporise the nanodroplets and sonify the converted microbubbles to provide additional ultrasound modulation of light. This additional light modulation was shown to increase the laser speckle contrast signal detected on a CCD camera.
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Floquet, Vincent. "Génération d’ions rapides par impulsions laser ultra intenses et ultra courtes." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112269/document.

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Pour accélérer des ions/protons il est possible d'utiliser une impulsion laser de courte durée temporelle (quelques dizaines de femtosecondes) focalisée sur quelques micromètres sur une cible solide (aluminium, carbone, plastique...). L'intensité du champ électromagnétique atteinte sur cible (> 1018 W.cm-2) nous permet de former un plasma chaud et dense. La dynamique des électrons de ce plasma génère des champs électriques intenses aux interfaces plasma-vide par séparation de charge. Ce champ électrique est alors responsable de l'accélération des ions situés sur la couche superficielle des cibles où se sont déposés des polluants organiques (dont des protons). Ce mécanisme d'accélération connu sous le nom de Target Normal Sheath Acceleration (TNSA), a constitué l'objet des travaux exposés dans cette thèse.Nos efforts au cours des différentes campagnes expérimentales se sont concentrés sur l'augmentation de l'énergie maximale des protons. En effet, les applications potentielles des particules de hautes énergies requièrent des énergies de l'ordre de la centaine de MeV. Pour ce faire, nous avons étudié différentes configurations permettant l'augmentation du couplage entre une impulsion laser et un plasma, ceci afin de transmettre avec le meilleur rendement possible, l'énergie du laser aux ions accélérés. C'est principalement en utilisant des configurations particulières de cibles (cibles avec microsphères, réseaux, cibles en mousses) que nous avons procédé. Des expériences utilisant une pré-impulsion comme contrôle de l'expansion du plasma ont également été réalisée. Du point de vue des applications et utilisations des ions accélérés, une étude des matériaux de fluorescence (CdWO4) a été menée dont le but était d'explorer le dépôt d'énergie des ions dans la matière, à des débits de flux jusqu'alors inaccessible avec les accélérateurs conventionnels
Accelerating ions/protons can be done using short laser pulse (few femtoseconds) focused on few micrometers area on solid target (carbon, aluminum, plastic...). The electromagnetic field intensity reached on target (1019 W.cm-2) allows us to turn the solid into a hot dense plasma. The dynamic motion of the electrons is responsible for the creation of intense static electric field at the plasma boundaries. These electric fields accelerate organic pollutants (including protons) located at the boundaries. This acceleration mechanism known as the Target Normal Sheath Acceleration (TNSA) has been the topic of the research presented in this thesis.The goal of this work has been to study the acceleration mechanism and to increase the maximal ion energy achievable. Indeed, societal application such as proton therapy requires proton energy up to few hundreds of MeV. To proceed, we have studied different target configurations allowing us to increase the laser plasma coupling and to transfer as much energy as possible to ions (target with microspheres deposit, foam target, grating). Different experiments have also dealt with generating a pre-plasma on the target surface thanks to a pre-pulse. On the application side, fluorescent material such as CdWO4 has been studied under high flux rate of protons. These high flux rates have been, up to now, beyond the conventional accelerators capabilities
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Lifjeld, Anders. "Reduction of speckle contrast in laser based HDTV projection displays." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9636.

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In this assignment the theoretical background for the nature of speckle is presented and practical work was done to reduce the speckle effect in a display system based on a laser source. This was done without any picture modulators, or any kind of line scan or flying spot scanning. Work was done to find the right setup to be able to as easy as possible characterize the statistics of the speckle in an image. A still image of an expanded laser spot worked as an image. A series of test sets were carried out to address the different factors which could make a difference on the speckle contrast and their role in such systems.

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Stuart, Nicholas. "Generation of high-contrast, terawatt to petawatt OPCPA laser pulses." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/51098.

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Laser-matter experiments using >10^18 W cm^2 focused light intensities from terawatt to petawatt peak-power laser systems are highly sensitive to the optical noise sources that are generated and amplified in conjunction with the primary high-power laser pulse. This limits the temporal intensity contrast, the signal to noise of the primary pulse intensity in time. This thesis presents a detailed investigation into the noise sources that degrade the contrast of high-power laser pulses created for laser-matter interaction experiments. To achieve this, a high-contrast multi-terawatt peak-power laser system, named Cerberus, has been developed to deliver up to 5 J, 500 fs pulses (10 TW) using an optical parametric chirped pulse amplification (OPCPA) front-end and Nd:Glass laser rod power amplifiers. To compliment this study, >10^10 dynamic range diagnostics have been developed that measure these noise sources in the presence of the intense primary pulse. Parametric fluorescence noise from parametric amplifiers was measured with a diagnostic able to observe the real-time seeded OPCPA fluorescence noise emission and determined the fluorescence emission to be directly linked to the level of pump-depletion, with a ~500 times contrast enhancement from the undepleted to maximum pump depletion modes of operation. A combination of picosecond-pumped OPCPA and nanosecond-pumped OPCPA amplifiers effectively suppresses the longer timescale parametric fluorescence to >10^8-10^10 contrast. A scanning third-order autocorrelator diagnostic (TOAD) was developed to characterise the compressed pulses emitted from a range of mode-locked laser oscillator sources and the compressed high-power laser pulses from major laser laboratories in the UK. We found the commonly used chirped pulse amplification architecture limits the temporal contrast from formation of an incoherent noise pedestal that can extend many hundred of picoseconds before the arrival of the primary laser pulse. We also observed non-linear generation of pre-pulses from internal reflections inside parallel-faced OPCPA crystals incident with long duration pump pulses.
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Arnesson, Fredrik. "How to run a semiconductor diode laser in a stable way." Thesis, Umeå universitet, Institutionen för fysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-56794.

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Interferometry and holography are two well-known methods for measuring distances, positions, vibrations, index of refraction etc. In these methods a coherent light source is used to create interference between different parts of the light. Since the wavelength of the light is used as reference it is possible to achieve very good accuracy in the measurements. The need of small and cheap light sources for these applications is large and an interesting alternative would be to use ordinary semiconductor diode lasers. These are unfortunately not designed to give sufficiently good coherence. In this Master Thesis work investigations of how the coherence of semiconductor diode lasers is affected by changes in temperature, injection current and between different individuals are performed. A Michelson interferometer is used to create an interference pattern where the contrast then can be analyzed. The contrast is related to the coherence of the laser, i.e., good coherence will give high contrast. The results show that in order to drive the laser in a stable way it is better to hold the temperature constant and varying the injection current until the wanted output power is achieved instead of doing the opposite. The results also indicate that the best coherence is achieved for low temperatures (around 10 OC) and high injection currents (around 80 mA). During these conditions a contrast of 70 % -80 % is achieved. The result of this Master Thesis work gives a hint on how to run a semiconductor diode laser in a stable way.
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Books on the topic "Laser contrast"

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Klett, Zachary G. The correlation between objective lens opacity and laser interferometric contrast sensitivity in the cataract patient. [New Haven: s.n.], 1989.

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Rousseau, Jean-Jacques. The social contract and other later political writings. Cambridge, U.K: Cambridge University Press, 1997.

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DeFigueiredo, Rui J. P. A contribution to laser range imaging technology: NASA contract final report. [Houston, Tex.?]: Research Institute for Computing and Information Systems, University of Houston-Clear Lake, 1991.

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Chromatography: Concepts and contrasts. New York: Wiley, 1988.

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M, Miller James. Chromatography: Concepts and contrasts. 2nd ed. Hoboken, N.J: Wiley, 2005.

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Rosenthal, Carolyn J. Intergenerational solidarity in later life: Ethnic contrasts in Jewish and Anglo families. Toronto: Programme in Gerontology, University of Toronto, 1986.

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Hart, Oliver. Agreeing now to agree later: Contracts that rule out but do not rule in. Cambridge, MA: National Bureau of Economic Research, 2004.

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Hart, Oliver D. Agreeing now to agree later: Contracts that rule out but do not rule in. Cambridge, Mass: National Bureau of Economic Research, 2004.

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Office, General Accounting. Strategic Defense Initiative Program: Zenith Star space-based chemical laser experiment : report to the Honorable J. Bennett Johnston, U.S. Senate. Washington, D.C: U.S. General Accounting Office, 1989.

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United States. Congress. Senate. Committee on Foreign Relations. Environmental treaties: Treaty doc. 103-4 ... Treaty doc. 103-5 ... Treaty doc. 103-9 ... Treaty doc. 103-8 ... Treaty doc. 103-10 ... : hearing before the Committee on Foreign Relations, United States Senate, One Hundred Third Congress, first session, October 26, 1993. Washington: U.S. G.P.O., 1994.

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Book chapters on the topic "Laser contrast"

1

Briers, J. David, Paul M. McNamara, Marie Louise O'Connell, and Martin J. Leahy. "Laser Speckle Contrast Analysis (LASCA) for Measuring Blood Flow." In Microcirculation Imaging, 147–63. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527651238.ch8.

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Kazmi, S. M. Shams, Lisa M. Richards, and Andrew K. Dunn. "Cerebral Blood Flow Imaging with Laser Speckle Contrast Imaging." In Neurovascular Coupling Methods, 287–305. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-0724-3_15.

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Jacques, Steven L. "Confocal Laser Scanning Microscopy Using Scattering as the Contrast Mechanism." In Handbook of Coherent-Domain Optical Methods, 1157–71. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-5176-1_28.

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Doucet, Michel, Mélanie Leclerc, Francis Picard, and Keith K. Niall. "Brightness and Contrast of Images with Laser-Based Video Projectors." In Vision and Displays for Military and Security Applications, 27–48. New York, NY: Springer New York, 2010. http://dx.doi.org/10.1007/978-1-4419-1723-2_3.

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Ceccotti, Tiberio, Anna Lévy, and Philippe Martin. "Laser-Driven Ion Generation with Short, Intense, and High Contrast Pulses." In Springer Series in Chemical Physics, 187–207. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03825-9_10.

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Jayanthy, A. K., N. Sujatha, and M. Ramasubba Reddy. "Laser Speckle Contrast Imaging for Perfusion Monitoring in Burn Tissue Phantoms." In IFMBE Proceedings, 443–46. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-21729-6_113.

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Winship, Ian R. "Laser Speckle Contrast Imaging to Measure Changes in Cerebral Blood Flow." In Methods in Molecular Biology, 223–35. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-0320-7_19.

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Aldibaja, Mohammad, Noaki Suganuma, Keisuke Yoneda, Ryo Yanase, and Akisue Kuramoto. "Supervised Calibration Method for Improving Contrast and Intensity of LIDAR Laser Beams." In Lecture Notes in Electrical Engineering, 210–18. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-90509-9_12.

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Yanovsky, V., V. Chvykov, G. Kalinchenko, P. Rousseau, T. Planchon, T. Matsuoka, A. Maksimchuk, et al. "Ultra-high intensity-High Contrast 300-TW laser at 0.1 Hz repetition rate." In Springer Series in Chemical Physics, 750–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-95946-5_243.

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dos Santos, Gustavo Sato, Efthymios Maneas, Daniil Nikitichev, Anamaria Barburas, Anna L. David, Jan Deprest, Adrien Desjardins, Tom Vercauteren, and Sebastien Ourselin. "A Registration Approach to Endoscopic Laser Speckle Contrast Imaging for Intrauterine Visualisation of Placental Vessels." In Lecture Notes in Computer Science, 455–62. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-24553-9_56.

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Conference papers on the topic "Laser contrast"

1

Ushenko, Alexander G., and Serhiy B. Yermolenko. "Fine polarization structure of laser speckles." In Phase Contrast and Differential Interference Contrast Imaging Techniques and Applications, edited by Maksymilian Pluta and Mariusz Szyjer. SPIE, 1994. http://dx.doi.org/10.1117/12.171880.

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Tychinsky, Vladimir P. "Phase-laser microscope with the factor-of-ten enhanced resolution over classical limit." In Phase Contrast and Differential Interference Contrast Imaging Techniques and Applications, edited by Maksymilian Pluta and Mariusz Szyjer. SPIE, 1994. http://dx.doi.org/10.1117/12.171890.

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Chang, Tsu-Chi, Ehsan Hashemi, Åsa Haglund, Shuo-Yi Kuo, and Tien-Chang Lu. "GaN vertical-cavity surface-emitting laser with a high-contrast grating reflector." In High Contrast Metastructures VII, edited by Connie J. Chang-Hasnain, Fumio Koyama, Weimin Zhou, and Andrei Faraon. SPIE, 2018. http://dx.doi.org/10.1117/12.2289318.

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Pirotta, Stefano, Ngoc-Linh Tran, Giorgio Biasiol, Paul Crozat, Jean-Michel Manceau, Adel Bousseksou, and Raffaele Colombelli. "Room-temperature fast amplitude modulator of mid-IR free-space laser beams (Conference Presentation)." In High Contrast Metastructures IX, edited by Connie J. Chang-Hasnain, Weimin Zhou, and Andrei Faraon. SPIE, 2020. http://dx.doi.org/10.1117/12.2546303.

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Lyon, Richard G. "NASA High Contrast Imaging for Exoplanets." In Laser Science. Washington, D.C.: OSA, 2008. http://dx.doi.org/10.1364/ls.2008.stub3.

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Gebski, M., M. Marciniak, M. Dems, M. Wasiak, J. A. Lott, and T. Czyszanowski. "Monolithic high-index-contrast grating VCSELs." In 2016 International Conference Laser Optics (LO). IEEE, 2016. http://dx.doi.org/10.1109/lo.2016.7549725.

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Tang, Yunxin, Chris J. Hooker, Bryn Parry, Oleg Chekhlov, Steve Hawkes, Klaus Ertel, Rajeev Pattathil, and John L. Collier. "Contrast Enhancement for Astra-Gemini Laser." In High Intensity Lasers and High Field Phenomena. Washington, D.C.: OSA, 2012. http://dx.doi.org/10.1364/hilas.2012.ht1c.2.

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Yuan, Shuai, Andrew K. Dunn, and David A. Boas. "Calibration in laser speckle contrast imaging." In Biomedical Topical Meeting. Washington, D.C.: OSA, 2006. http://dx.doi.org/10.1364/bio.2006.me32.

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Karagodsky, Vadim, Forrest Sedgwick, and Connie J. Chang-Hasnain. "New Physics of Subwavelength High Contrast Gratings." In Quantum Electronics and Laser Science Conference. Washington, D.C.: OSA, 2011. http://dx.doi.org/10.1364/qels.2011.qthd2.

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Nikawa, K., and S. Inoue. "Various Contrasts Identifiable From the Backside of a Chip by 1.3μm Laser Beam Scanning and Current Change Imaging." In ISTFA 1996. ASM International, 1996. http://dx.doi.org/10.31399/asm.cp.istfa1996p0387.

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Abstract We can identify various contrasts by scanning an 1.3 um laser beam from the backside of a chip and displaying current changes as brightness changes on a CRT, because the 1.3 um laser beam generates no OBIC signal and can penetrate P- Si substrate with little intensity degradation. The contrasts we have confirmed up to now are: (1) Current pass contrast at Al lines caused by OBIRCH, (2) Defect contrast at Al interconnects caused by OBIRCH, (3) Current pass contrast at a poly Si lines caused by OBIRCH, (4) Parasitic MIM (metal-insulator-metal) contrast caused by temperature dependence of MIM current, (5) Schottky-barrier contrast caused by internal photoemission.
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Reports on the topic "Laser contrast"

1

Higginson, Drew Pitney. Ultra-High-Contrast Laser Acceleration of Relativistic Electrons in Solid Targets. Office of Scientific and Technical Information (OSTI), January 2013. http://dx.doi.org/10.2172/1059459.

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Campbell, Benjamin, and Jeremy Andrew Palmer. Investigation of temporal contrast effects in femtosecond pulse laser micromachining of metals. Office of Scientific and Technical Information (OSTI), June 2006. http://dx.doi.org/10.2172/887259.

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Kemp, Gregory Elijah. Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions. Office of Scientific and Technical Information (OSTI), January 2013. http://dx.doi.org/10.2172/1092502.

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White, W. E., A. Sullivan, D. F. Price, R. Trebino, K. DeLong, and J. Heritage. Production of high contrast ultrashort laser pulses for short scale length plasma experiments. Office of Scientific and Technical Information (OSTI), July 1994. http://dx.doi.org/10.2172/10196585.

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Dykes, Jim. Psychophysical Test of Contrast Acuity to Aid Operational Effectiveness of Aircrew Laser Eye Protection (LEP). Fort Belvoir, VA: Defense Technical Information Center, August 2005. http://dx.doi.org/10.21236/ada438158.

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Ellison, Chad M., Matthew J. Perricone, Kevin M. Faraone, and Jerome T. Norris. Pulse shaping effects on weld porosity in laser beam spot welds : contrast of long- & short- pulse welds. Office of Scientific and Technical Information (OSTI), October 2007. http://dx.doi.org/10.2172/921738.

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Hart, Oliver, and John Moore. Agreeing Now to Agree Later: Contracts that Rule Out but do not Rule In. Cambridge, MA: National Bureau of Economic Research, March 2004. http://dx.doi.org/10.3386/w10397.

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Cram, Jana, Mary Levandowski, Kaci Fitzgibbon, and Andrew Ray. Water resources summary for the Snake River and Jackson Lake Reservoir in Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway: Preliminary analysis of 2016 data. National Park Service, June 2021. http://dx.doi.org/10.36967/nrr-2285179.

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This report summarizes discharge and water quality monitoring data for the Snake River and Jackson Lake reservoir levels in Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway for calendar year 2016. Annual and long-term discharge summaries and an evaluation of chemical conditions relative to state and federal water quality standards are presented. These results are considered provisional, and may be subject to change. River Discharge: Hydrographs for the Snake River at Flagg Ranch, WY, and Moose, WY, exhibit a general pattern of high early summer flows and lower baseflows occurring in late summer and fall. During much of 2016, flows at the Flagg Ranch monitoring location were similar to the 25th percentile of daily flows at that site. Peak flows at Flagg Ranch were similar to average peak flow from 1983 to 2015 but occurred eleven days earlier in the year compared to the long-term average. Peak flows and daily flows at the Moose monitoring station were below the long-term average. Peak flows occurred four days later than the long-term average. During summer months, the unnatural hydro-graph at the Moose monitoring location exhibited signs of flow regulation associated with the management of Jackson Lake. Water Quality Monitoring in the Snake River: Water quality in the Snake River exhibited seasonal variability over the sampling period. Specifically, total iron peaked during high flows. In contrast, chloride, sulfate, sodium, magnesium, and calcium levels were at their annual minimum during high flows. Jackson Lake Reservoir: Reservoir storage dynamics in Jackson Lake exhibit a pattern of spring filling associated with early snowmelt runoff reaching maximum storage in mid-summer (on or near July 1). During 2016, filling water levels and reservoir storage began to increase in Jackson Lake nearly two weeks earlier than the long-term average and coincident with increases in runoff-driven flows in the Snake River. Although peak storage in Jackson Lake was larger and occurred earlier than the long-term average, minimum storage levels were similar to the long-term average.
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Guidati, Gianfranco, and Domenico Giardini. Joint synthesis “Geothermal Energy” of the NRP “Energy”. Swiss National Science Foundation (SNSF), February 2020. http://dx.doi.org/10.46446/publication_nrp70_nrp71.2020.4.en.

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Near-to-surface geothermal energy with heat pumps is state of the art and is already widespread in Switzerland. In the future energy system, medium-deep to deep geothermal energy (1 to 6 kilometres) will, in addition, play an important role. To the forefront is the supply of heat for buildings and industrial processes. This form of geothermal energy utilisation requires a highly permeable underground area that allows a fluid – usually water – to absorb the naturally existing rock heat and then transport it to the surface. Sedimentary rocks are usually permeable by nature, whereas for granites and gneisses permeability must be artificially induced by injecting water. The heat gained in this way increases in line with the drilling depth: at a depth of 1 kilometre, the underground temperature is approximately 40°C, while at a depth of 3 kilometres it is around 100°C. To drive a steam turbine for the production of electricity, temperatures of over 100°C are required. As this requires greater depths of 3 to 6 kilometres, the risk of seismicity induced by the drilling also increases. Underground zones are also suitable for storing heat and gases, such as hydrogen or methane, and for the definitive storage of CO2. For this purpose, such zones need to fulfil similar requirements to those applicable to heat generation. In addition, however, a dense top layer is required above the reservoir so that the gas cannot escape. The joint project “Hydropower and geo-energy” of the NRP “Energy” focused on the question of where suitable ground layers can be found in Switzerland that optimally meet the requirements for the various uses. A second research priority concerned measures to reduce seismicity induced by deep drilling and the resulting damage to buildings. Models and simulations were also developed which contribute to a better understanding of the underground processes involved in the development and use of geothermal resources. In summary, the research results show that there are good conditions in Switzerland for the use of medium-deep geothermal energy (1 to 3 kilometres) – both for the building stock and for industrial processes. There are also grounds for optimism concerning the seasonal storage of heat and gases. In contrast, the potential for the definitive storage of CO2 in relevant quantities is rather limited. With respect to electricity production using deep geothermal energy (> 3 kilometres), the extent to which there is potential to exploit the underground economically is still not absolutely certain. In this regard, industrially operated demonstration plants are urgently needed in order to boost acceptance among the population and investors.
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