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  • SPIE Digital Library  (32)
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  • SPIE Digital Library  (32)
  • arXiv  (1)
  • 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: 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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  • 8
    Language: English
    In: 15 February 2018, Vol.10511, pp.105110X-105110X-7
    Description: The HiLASE “Bivoj” laser system developed at CLF Rutherford Appleton Laboratory in collaboration with HiLASE team as DiPOLE100 was relocated to Dolni Brezany near Prague, Czechia at the end of 2015 and fully re-commissioned at the end of 2016. In 2016, the system demonstrated average output power of 1kW generating pulses of 105 J at 10 Hz repetition rate for the first time in the world. Since then the system has been subjected to several testing campaigns in order to determine some of its key characteristics. Beam quality, wavefront quality, pointing stability, energy stability and experience with long term operation of 1 kW laser are presented. In addition, depolarization effects have been detected inside the main amplifier. Details on these results along with numerical simulations are presented.
    Keywords: Engineering
    ISBN: 9781510615076
    ISBN: 1510615075
    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: Proceedings of SPIE, 01 December 1993, Vol.2060(1), pp.225-236
    Description: In computer vision, one of the major problems is how to identify an observed object in an image by comparing it to a set of models in a library. The comparison is made using a shape metric which measures the similarity between different shapes. The observed object is classified as the library object with which it minimizes the shape metric. This paper looks at algorithms for efficiently searching a geometric library to identify an observed object in the image. All objects are modeled as points and (epsilon) -congruence is used as the shape metric. Algorithms are presented for searching two classes of geometric libraries, ordered linear libraries and convex linear libraries. The complexity of the algorithms is expressed in terms of the number of objects in the library, the size of the objects, the error in the optimal match, and the geometric structure.
    Keywords: Engineering
    ISBN: 9780819413253
    ISSN: 0277-786X
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  • 10
    Language: English
    In: Proceedings of SPIE, 25 October 1994, Vol.2277(1), pp.2-11
    Description: An algorithm has been developed for the automatic identification of human faces. Because the algorithm uses facial features restricted to the nose and eye regions of the face, it is robust to variations in facial expression, hair style and the surrounding environment. The algorithm uses coarse to fine processing to estimate the location of a small set of key facial features. Based on the hypothesized locations of the facial features, the identification module searches the database for the identity of the unknown face. The identification is made by matching pursuit filters. Matching pursuit filters have the advantage that they can be designed to find the differences between facial features needed to identify unknown individuals. The algorithm is demonstrated on a database of 172 individuals.
    Keywords: Engineering
    ISBN: 9780819416018
    ISSN: 0277-786X
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