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  • Conference Proceeding  (118)
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  • Conference Proceeding  (118)
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  • 1
    Language: English
    In: 07 January 2014, Vol.9016, pp.901603-901603-12
    Description: This paper presents secondary Standard Quality Scale (SQS2) rankings in overall quality JNDs for a subjective analysis of the 3 axes of noise, amplitude, spectral content, and noise type, based on the ISO 20462 softcopy ruler protocol. For the initial pilot study, a Python noise simulation model was created to generate the matrix of noise masks for the softcopy ruler base images with different levels of noise, different low pass filter noise bandwidths and different band pass filter center frequencies, and 3 different types of noise: luma only, chroma only, and luma and chroma combined. Based on the lessons learned, the full subjective experiment, involving 27 observers from Google, NVIDIA and STMicroelectronics was modified to incorporate a wider set of base image scenes, and the removal of band pass filtered noise masks to ease observer fatigue. Good correlation was observed with the Aptina subjective noise study. The absence of tone mapping in the noise simulation model visibly reduced the contrast at high levels of noise, due to the clipping of the high levels of noise near black and white. Under the 34-inch viewing distance, no significant difference was found between the luma only noise masks and the combined luma and chroma noise masks. This was not the intuitive expectation. Two of the base images with large uniform areas, ‘restaurant’ and ‘no parking’, were found to be consistently more sensitive to noise than the texture rich scenes. Two key conclusions are (1) there are fundamentally different sensitivities to noise on a flat patch versus noise in real images and (2) magnification of an image accentuates visual noise in a way that is non-representative of typical noise reduction algorithms generating the same output frequency. Analysis of our experimental noise masks applied to a synthetic Macbeth ColorChecker Chart confirmed the color-dependent nature of the visibility of luma and chroma noise.
    Keywords: Engineering
    ISBN: 9780819499332
    ISBN: 0819499331
    ISSN: 0277786X
    E-ISSN: 1996756X
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - eBooks
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  • 2
    Language: English
    In: Proceedings of SPIE, 23 January 2012, Vol.8293(1), pp.829302-8293012
    Description: The I3A Camera Phone Image Quality (CPIQ) initiative aims to provide a consumer-oriented overall image quality metric for mobile phone cameras. In order to achieve this goal, a set of subjectively correlated image quality metrics has been developed. This paper describes the development of a specific group within this set of metrics, the spatial metrics. Contained in this group are the edge acutance, visual noise and texture acutance metrics. A common feature is that they are all dependent on the spatial content of the specific scene being analyzed. Therefore, the measurement results of the metrics are weighted by a contrast sensitivity function (CSF) and, thus, the conditions under which a particular image is viewed must be specified. This leads to the establishment of a common framework consisting of three components shared by all spatial metrics. First, the RGB image is transformed to a color opponent space, separating the luminance channel from two chrominance channels. Second, associated with this color space are three contrast sensitivity functions for each individual opponent channel. Finally, the specific viewing conditions, comprising both digital displays as well as printouts, are supported through two distinct MTFs.
    Keywords: Engineering
    ISSN: 0277-786X
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - eBooks
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  • 3
    Language: English
    In: 18 January 2013, Vol.8653, pp.86530E-86530E-10
    Description: In this paper we address the problem of Image Quality Assessment of no reference metrics, focusing on JPEG corrupted images. In general no reference metrics are not able to measure with the same performance the distortions within their possible range and with respect to different image contents. The crosstalk between content and distortion signals influences the human perception. We here propose two strategies to improve the correlation between subjective and objective quality data. The first strategy is based on grouping the images according to their spatial complexity. The second one is based on a frequency analysis. Both the strategies are tested on two databases available in the literature. The results show an improvement in the correlations between no reference metrics and psycho-visual data, evaluated in terms of the Pearson Correlation Coefficient.
    Keywords: Engineering
    ISBN: 9780819494269
    ISBN: 0819494267
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - eBooks
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  • 4
    Language: English
    In: Proceedings of SPIE, 17 January 2010, Vol.7529(1), pp.752904-7529012
    Description: Imaging systems in camera phones have image quality limitations attributed to optics, size, and cost constraints. These limitations generally result in unwanted system noise. In order to minimize the image quality degradation, nonlinear noise cleaning algorithms are often applied to the images. However, as the strength of the noise cleaning increases, this often leads to texture degradation. The Camera Phone Image Quality (CPIQ) initiative of the International Imaging Industry Association (I3A) has been developing metrics to quantify texture appearance in camera phone images. Initial research established high correlation levels between the metrics and psychophysical data from sets of images that had noise cleaning filtering applied to simulate capture in actual camera phone systems. This paper describes the subsequent work to develop a texture-based softcopy attribute ruler in order to assess the texture appearance of eight camera phone units from four different manufacturers and to assess the efficacy of the texture metrics. Multiple companies participating in the initiative have been using the softcopy ruler approach in order to pool observers and increase statistical significance. Results and conclusions based on three captured scenes and two texture metrics will be presented.
    Keywords: Engineering
    ISBN: 9780819479228
    ISSN: 0277-786X
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - eBooks
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  • 5
    Language: English
    In: 07 May 2013, Vol.8780, pp.878006-878006-7
    Description: The Diode Pumped Optical Laser Experiments (DiPOLE) project at Central Laser Facility (CLF) is aimed at the development of scalable diode pumped, cryogenic gas cooled, multi-slab Yb:YAG amplifiers. Optimized designs for amplifiers capable of generating kJ pulse energies at multi-Hz repetition rate have been finalised and development of a scaled-down 10J, 10Hz prototype is currently underway at the CLF. We report on the recent results obtained on a 4-pass bowtie as well as 6-pass image relaying multi-pass setup for the DiPOLE amplifier. Additionally, Preliminary results for the amplifier performance with uniform doping (3 × 2at%) compared to gradient doping (2 × 1at% + 2 × 2at%) at cryogenic temperatures, confirms the multi-slab gradient doped design adopted for DiPOLE amplifier.
    Keywords: Engineering
    ISBN: 9780819495822
    ISBN: 0819495824
    ISSN: 0277786X
    E-ISSN: 1996756X
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - eBooks
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  • 6
    Language: English
    In: Proceedings of SPIE, 02 February 2010, Vol.7527(1), pp.75270Z-75270Z-12
    Description: Human observers are able to make fine discriminations of surface gloss. What cues are they using to perform this task? In previous studies, we identified two reflection-related cues-the contrast of the reflected image (c, contrast gloss) and the sharpness of reflected image (d, distinctness-of-image gloss)--but these were for objects rendered in standard dynamic range (SDR) images with compressed highlights. In ongoing work, we are studying the effects of image dynamic range on perceived gloss, comparing high dynamic range (HDR) images with accurate reflections and SDR images with compressed reflections. In this paper, we first present the basic findings of this gloss discrimination study then present an analysis of eye movement recordings that show where observers were looking during the gloss discrimination task. The results indicate that: 1) image dynamic range has significant influence on perceived gloss, with surfaces presented in HDR images being seen as glossier and more discriminable than their SDR counterparts; 2) observers look at both light source highlights and environmental interreflections when judging gloss; and 3) both of these results are modulated by surface geometry and scene illumination.
    Keywords: Engineering
    ISBN: 9780819479204
    ISSN: 0277-786X
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - eBooks
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  • 7
    Language: English
    In: 2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC, May 2013, pp.1-1
    Description: Summary form only given. The next generation of ultra-intense laser facilities, currently being developed in European projects such as HiPER [1] and ELI [2], require the development of a laser amplifier technology capable of producing kJ-level pulses with nanosecond duration. These will need to operate at multi-Hz repetition rate and high wall-plug efficiency, which is only possible using diode-pumped solid-state laser (DPSSL) technology. The DiPOLE project at the Central Laser Facility (CLF) is developing a scalable and efficient high pulse energy DPSSL architecture based on a cryogenic gas cooled, multi-slab ceramic Yb:YAG amplifier concept, capable of generating kJ pulse energies. To test the viability of this concept, a scaled-down prototype amplifier has been built, designed to deliver 10 J pulses at 10 Hz repetition rate with an optical-to-optical (η〈sub〉o-o〈/sub〉) efficiency of 25% [4]. Recently, a new multi-pass relay-imaging extraction architecture, including spatial filtering, has been installed that allows up to eight passes through the amplifier head. This has enabled more efficient extraction at higher coolant temperatures, where gain is lower and the impact of ASE is reduced [4], as well as improving the spatial quality of the output beam.In this paper we report details of the new multi-pass architecture and present recent performance results for amplification of ns-pulses at 1030 nm in a six-pass configuration, operating at a coolant temperature of 125 K. In this configuration we have measured up to 9.5 J at 1 Hz and 7.4 J at 10 Hz, corresponding to Ko-o efficiencies of 24% and 23%, respectively, for seed energies of approximately 20 mJ. The measured dependence of conversion on pulse repetition frequency (PRF) is shown in Fig. 1 and Fig. 2. A preliminary assessment of output energy stability has also been undertaken at 10 Hz where stable operation has been achieved for periods of over 5 minutes with a measured rms variation in output energy of 0.7%. It has been found that insufficient isolation between amplifier stages has a detrimental impact on output stability. Low frequency modulation in the output energy is observed but this is directly related to the temperature stability of the gas cooling system.These results confirm the validity of the amplifier design concept and give confidence that the target specification will be reached once greater seed energy is available and round trip losses are reduced further.
    Keywords: Laser Excitation ; Semiconductor Lasers ; Cryogenics ; Gas Lasers ; Laser Stability ; Thermal Stability
    Source: IEEE Conference Publications
    Source: IEEE Xplore
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  • 8
    Language: English
    In: 03 March 2015, Vol.9343, pp.93431N-93431N-8
    Description: A high average power cryogenically-cooled diode-pumped solid-state laser system for Hilase centre in Czech Republic is being developed by Central Laser Facility at Rutherford Appleton Laboratory, England in collaboration with Hilase team. The system will deliver pulses with energy of 100 J at 10 Hz repetition rate and will find applications in research and industry. The laser medium and other elements of the system are subject to heavy thermal loading which causes serious optical aberrations and degrade the output beam quality. To meet the stringent laser requirements of this kWclass laser, it is necessary to implement adaptive optics system, which will correct for these aberrations. During our research the sources of aberrations have been identified and analyzed. Based on this analysis, a suitable adaptive optics system was proposed. After finalizing numerical models, simulations and optimizations, the adaptive optics system was developed, characterized and installed in a cryogenically-cooled multi-slab laser system running up to 6 J and 10 Hz. The adaptive optics system consists of 6x6 actuator bimorph deformable mirror and wavefront sensor based on quadriwave lateral shearing interferometry operated in closed loop. The functionality of the system was demonstrated at full power.
    Keywords: Engineering
    ISBN: 9781628414332
    ISBN: 1628414332
    ISSN: 0277786X
    E-ISSN: 1996756X
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - eBooks
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  • 9
    Language: English
    In: 2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC, May 2013, pp.1-1
    Description: Summary form only given. Over the last few decades the cost reductions and performance increase of diode laser technology has advanced to the point that it has now become a very attractive and generic means of driving laser systems. Diode pumped technology has found widespread uptake in the industrial sector - multi kW CW powers are routine and a wide variety of low energy pulsed systems have been reported - many are commercially available. However the development of pulsed diode pumped systems capable of operating at mutli kW and higher average power levels with very high pulse energy (100'sJ - kJ's) has been very limited.In this presentation I will report on the development of a new diode pumped high energy laser concept at the Rutherford Appleton Laboratory (RAL). Known as "DiPOLE", it has been developed to be an intrinsically scalable system, providing a high average power basis for energetic pulse production from Joules to kiloJoules. Based on large aperture ceramic Yb:YAG configured in a novel geometry and operated at cryogenic temperatures it is a concept that is, in principle, scalable from the Joule level to the multi kiloJoule level. A prototype system, operating at close to 10 J / 10 Hz has been constructed, and a 100 J / 10 Hz version is under development. The DiPOLE architecture is being developed, in part, to capitalize on the applications potential of high peak power (~PW+ level) lasers but operating high average power levels (multi kW). This offers a truly exciting opportunity for both new scientific advance and, possibly of more relevance in today's climate, of new, emergent commercial and industrial applications. Today's generally flashlamp pumped high peak power lasers can be unique, super bright, super fast sources of very energetic electrons, protons, neutrons, X-Rays, g-Rays, THz radiation etc. and thus offer a significant applications potential. In some areas it's fair to say they offer a possible capability that cannot be achieved with conventional non-laser based source technology. Certainly, driving high peak powers lasers with diode technology offers an efficient, compact and reliable route for such an applications environment to develop Thus, in addition to DiPOLE, I will touch on achievements in our development of the associated high peak power technology necessary for applications, highlighting our plans at RAL for their combination, and finally consider some of the downstream applications opportunities we are working on.
    Keywords: Power Lasers ; Semiconductor Lasers ; Laser Excitation ; Pump Lasers ; Laser Theory ; Laboratories
    Source: IEEE Conference Publications
    Source: IEEE Xplore
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  • 10
    Language: English
    In: 01 January 2010
    Description: In this work a novel aerosol method, derived form the batch Reduction/Expansion Synthesis (RES) method, for production of nano / micro-scale metal particles from oxides and hydroxides is presented. In the Aerosol-RES (A-RES) method, an aerosol, consisting of a physical mixture of urea and metal oxide or hydroxides, is passed through a heated oven (1000 C) with a residence time of the order of 1 second, producing pure (zero valent) metal particles. It appears that the process is flexible regarding metal or alloy identity, allows control of particle size and can be readily scaled to very large throughput. Current work is focused on creating nanoparticles of metal and metal alloy using this method. Although this is primarily a report on observations, some key elements of the chemistry are clear. In particular, the reducing species produced by urea decomposition are the primary agents responsible for reduction of oxides and hydroxides to metal. It is also likely that the rapid expansion that takes place when solid/liquid urea decomposes to form gas species influences the final morphology of the particles.
    Keywords: Aerosols ; Alloys ; Decomposition ; Expansion ; Hydroxides ; Metals ; Mixtures ; Morphology ; Nanostructures ; Oxides ; Particle Size ; Particles ; Production ; Reduction ; Synthesis ; Urea
    Source: SciTech Connect (U.S. Dept. of Energy - Office of Scientific and Technical Information)
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