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We study how to build optimal light-field or plenoptic models. We quantify geometric errors in light-field representations and show how geometric error bounds directly affect rendering artifacts. Artifacts depend on how the light-field is parameterized, stored, reconstructed and rendered. We present the rendering artifacts and relate them to the presence of geometric errors in the four most common light-field implementations. We show how to optimize a light-field model. We take an arbitrary bounded object and construct the best possible representation using each of the four parameterizations. The best representation has the least geometric error bounds. We use two geometric errors, a positional and a directional error. We also quantify pixelation artifacts. Our analysis is useful to decide how to build a light-field model. It helps select a parameterization, build an optimal representation, and choose the samplings of the parameter spaces so that geometric errors and rendering artifacts are minimized.

We propose and experimentally demonstrate a novel concept to spatially resolve the chemical composition of complex biological samples by pixelation within a micro total analysis system (μTAS) platform. The device we developed images samples of interest by discretising targeted areas into droplets suspended in a two-phase microflow. These droplets are transferred from parallel to serial mode for data readout in a similar fashion to a CCD camera, thus referred as “microfluidic imaging”. Three major process steps are conducted within the device: (i) parallel pixelation and uptake of the sample (ii) sample transfer from parallel to serial mode into a microchannel for individual analysis and (iii) image generation. This microfluidic pixelation method is a technique suitable for obtaining non-averaged data from heterogeneous specimen. The concept attempts to reduce arduous preparation steps, allowing high throughput while retaining the spatial information.

We proposed the direct deposition of CsI(Tl) scintillator layer with pixelated structure on a CMOS image sensor (CIS) in order to improve the spatial resolution. CMOS sensors developed for test have a 128×128 photodiode array with 50 μm pixel pitch and integrated readout-electronics including a 10 bit pipe-lined ADC. CsI(Tl) layer has thickness of 50 μm. The modulation transfer function, the noise power spectrum, and the detective quantum efficiency of pixelated and non-pixelated CsI(Tl) X-ray image sensors (XIS) were estimated with a 50 kVp X-ray beam. At 10% of modulation transfer function (MTF), the spatial resolution of pixelated and non-pixleated XIS are about 8 and 6 lp/mm, respectively. It implies that pixelation enhances the spatial resolution by reducing the lateral light diffusion. Though the NPS of pixelated XIS was slightly higher than the non-pixelated XIS, its detective quantum efficiency (DQE) values were much better than non-pixelated XIS especially at high spatial frequencies.

Isotropic light spread in the scintillator film decreases the spatial resolution of scintillator-based digital X-ray imaging systems such as digital radiography and mammography. Pixelation of the scintillator film could be a good solution to overcome this limitation. This has been demonstrated with pixilated CsI:Tl layers which was made by thermal evaporation process on a pre-patterned substrate or which was post-patterned by laser after preparation. Additionally, in order to minimize cross-talk between pixels and to maximize light collection efficiency, a reflection material can be coated on the top and side surfaces of each pixilated scintillator block. In This paper, several materials such as Al, and quarter-wave multilayer reflector with SiO2 and TiO2 were considered as the reflector materials of pixilated CsI:Tl scintillator blocks. Through a serious of simulations given below on these simple 2-dimensional scintillator blocks coated by a reflector, reflectivity, cross-talk, and modulation transfer fu...

Weak gravitational lensing is a promising probe of dark matter and dark energy requiring accurate measurement of the shapes of faint, distant galaxies. Such measures are hindered by the finite resolution and pixel scale of typical cameras. On the other hand, as imaging telescopes are practically limited to a fixed number of pixels and operational life-span, so the survey area increases with pixel size. We investigate the optimum choice of pixel scale in this trade-off for a space-based mission, using the full engineering model and survey strategy of the proposed SuperNova/Acceleration Probe as an example. Our methodology is to simulate realistic astronomical images of known shear and to evaluate the surface density of sources where the shear is accurately recovered using the Rhodes, Refregier, & Groth algorithm in the context of the derived dark matter power spectrum. In addition to considering single exposures, we also examine the benefits of sub-pixel dithering. Although some of our results depend upon the adopted shape measurement method, the relative trends, particularly those involving the surface density of resolved galaxies, are robust. Our approach provides a practical counterpart to studies which consider the effects of pixelation from analytic principles, which necessarily assume an idealized shape measurement method. We find that the statistical error on the mass power spectrum is minimized with a pixel scale equal to 75-80% of the FWHM of the point-spread function, and that dithering is marginally beneficial at larger pixel scales., 17 pages, 12 figures, submitted for publication to PASP

A method was developed to assist in the photo-identification of individual grey seals (Halichoerus grypus). Fixed reference points of the eye and ear were used to define a rectangular area of pelage on the seal's head, termed the identifier patch (IP). Extracted IPs were converted to binary masks, and the percentage of black pixelation within each mask was evaluated. Multiple images of the same head profile gave masks with similar patterns and percentage of black pixelation (mean standard deviation 3.3% (±1.6%)). The low level of ‘within seal’ variability enabled ‘between seal’ images to be separated on the basis of percentage of black pixelation. Subsequent matching was achieved by eye using the mask pattern to complete the identification process. Successful matching of seal images, collected two years and nine months apart, at a North Wales field site was accomplished using this method. Pattern-matching trials using 88 untrained volunteers showed the extracted black and white mask to be a superior visual cue for separating individual seals compared to straightforward inspection of photographs. All volunteers identified a greater number of correct matches using the mask-matching method. This method shows promise in providing a cheap and accessible system to order and search image databases.

An X-ray imaging detector consisting of a silicon charge coupled device (CCD) and pixel structured scintillator was developed to improve spatial resolution. The pixelated structure reduces spreading of scintillation light through the scintillator by providing air gap between scintillator pixels, and increased spatial resolution by reducing the cross-talk between CCD pixels. The modulation transfer functions (MTF) of the non-pixelated and pixilated scintillator detector were compared. The improvement in spatial resolution was evaluated by both computational simulation and experimental measurement of MTF; both results showed coincidence.

By using an fiber bundle endomicroscope to transmit the image, image quality is typically degraded by pixelation artifacts due to the spacing between individual fiber core in the liber bundle. Generally7 a personal computer is required to remove these artifacts in real-time which making the overall system bulky and cost In this work, we proposed a method of fast image processing to eliminate pixelation artifacts and enhancing signal to noise of acquire images. The computation was implemented on an embedded system in order to prototype a truly affordable portable imaging system for a remote clinic. The calculation technique to implement real-time display involves a convolution of a square point spread function separated into two one-dimensional arrays with no floating point An averaged processing time of 13 millisecond is achieved from this method, which is foster than a standard Gaussian filtering method of an OpenCV library version 3.0 by a factor of 50.

Current high-resolution scintillators are fabricated using mechanical pixelation technique. However the fabrication cost of finely pitched scintillator arrays together with their lack of flexibility to accommodate new depth of interaction designs has remained a significant issue with mechanical pixelation. Another pitfall of mechanically pixelated scintillators is their relatively large inter-pixel gaps that adversely affect their sensitivity to the incident gamma-ray. The main objective of our ongoing efforts is to fabricate high-spatial resolution and high sensitivity PET detectors with depth of interaction (DOI) capability and single-side readout in a cost-effective manner using laser-induced optical barriers (LIOB) technique. We have simulated the behavior of simple optical barriers in LYSO:Ce crystal using the DETECT simulation code. We have also created optical barriers with different size and barrier density in LYSO:Ce at various depths up to 20 mm to form pixel-like shapes similar to mechanically pixelated crystals. In order to process 20mm thick crystals we corrected for laser beam defocusing effect and its adverse effect on laser energy density which results in smaller barrier size and reflectivity. The fabrication time for 10x10x1 and 10x10x20 mm3 LYSO crystals (with lmm pixels) was similar to 8 and 95 minutes respectively.

Disordered optical fibers show novel waveguiding properties that can be used for various device applications, such as beam-multiplexed optical communications and endoscopic image transport. The quality of the transported image is shown to be comparable with or better than some of the best commercially available multicore image fibers with less pixelation and higher contrast. Progress and results, as well as ongoing efforts on the design, fabrication, and characterization of the disordered optical fibers will be discussed.

The accurate determination of the local impulse response and the covariance in voxels from penalized maximum likelihood reconstructed images requires performing reconstructions from many noise realizations of the projection data. As this is usually a very time-consuming process, efficient analytical approximations based on the Fisher information matrix (FIM) have been extensively used in PET and SPECT to estimate these quantities. For 3D imaging, however, additional approximations need to be made to the FIM in order to speed up the calculations. The most common approach is to use the local shift-invariant (LSI) approximation of the FIM, but this assumes specific conditions which are not always necessarily valid. In this paper we take a single-pinhole SPECT system and compare the accuracy of the LSI approximation against two other methods that have been more recently put forward: the non-uniform object-space pixelation (NUOP) and the subsampled FIM. These methods do not assume such restrictive conditions while still increasing the speed of the calculations considerably. Our results indicate that in pinhole SPECT the NUOP and subsampled FIM approaches could be more reliable than the LSI approximation, especially when a high accuracy is required.

This paper presents a robust and blind digital image watermarking technique to achieve copyright protection. In order to protect copyright material from illegal duplication, various technologies have been developed, like key-based cryptographic technique, digital watermarking etc. In digital watermarking, a signature or copyright message is secretly embedded in the image by using an algorithm. In our paper, we implement that algorithm of digital watermarking by combining both DWT and SVD techniques. Initially, we decompose the original (cover) image into 4 sub-bands using 2-D DWT, and then we apply the SVD on each band by modifying their singular values. After subjecting the watermarked image to various attacks like blurring, adding noise, pixelation, rotation, rescaling, contrast adjustment, gamma correction, histogram equalization, cropping, sharpening, lossy compression etc, we extract the originally inserted watermark image from all the bands and compare them on the basis of their MSE and PSNR values. Experimental results are provided to illustrate that if we perform modification in all frequencies, then it will make our watermarked image more resistant to a wide range of image-processing attacks (including common geometric attacks), i.e. We can recover the watermark from any of the four sub-bands efficiently.

You now have enough of the WatchFaces API code in place to be able to test your Java code, which means that this is going to be a busy chapter. You’ll learn how to get the emulators working, test the code, and make any additions, and after you have a working vector watch face application, you’ll then look at how to incorporate a BitmapDrawable asset to create a background image for the watch face application. Most watch face designs will utilize a combination of bitmap assets and vector drawing code to create a design.

In order to produce bright images, projectors have large apertures and hence narrow depths of field. In this paper, we present methods for robust scene capture and enhanced image display based on projection defocus analysis. We model a projector's defocus using a linear system. This model is used to develop a novel temporal defocus analysis method to recover depth at each camera pixel by estimating the parameters of its projection defocus kemel in frequency domain. Compared to most depth recovery methods, our approach is more accurate near depth discontinuities. Furthermore, by using a coaxial projector-camera system, we ensure that depth is computed at all camera pixels, without any missing parts. We show that the recovered scene geometry can be used for refocus synthesis and for depth-based image composition. Using the same projector defocus model and estimation technique, we also propose a defocus compensation method that filters a projection image in a spatially-varying, depth-dependent manner to minimize its defocus blur after it is projected onto the scene. This method effectively increases the depth of field of a projector without modifying its optics. Finally, we present an algorithm that exploits projector defocus to reduce the strong pixelation artifacts produced by digital projectors, while preserving the quality of the projected image. We have experimentally verified each of our methods using real scenes.

Matching the emotional expressions of pairs of face photos was slower with pixelated and blurred photos than with original, untransformed photos. Matching the identities of the same face pairs was unaffected by pixelation and blurring. Because pixelation and blurring degrade higher spatial frequencies carrying edge-based information that define feature shape more than lower frequencies carrying configural properties, these findings converge with findings for line drawings and negative photos in showing that expression and face recognition processes differ in their reliance on edge-based and configural information.

This paper presents a novel FPGA-based architecture for the Speeded-Up Robust Feature (SURF) extractor. By leveraging the inherent parallelism of the SURF algorithm, we designed a fully pipelined architecture implemented on the FPGA fabric of a Xilinx Zynq-7020 device (XC7Z020CLG484-1). Compared with other high-performing SURF designs in the literature, our implementation achieved the highest frame rate (131.36 fps) while compactly fitting on a single device and consuming only 0.608 Watts of average power. An experimental platform featuring a 640×480 resolution camera was used to compare the proposed design with OpenSURF, a widely used open-source C++ library, running on a high-end Intel i7 processor. Our system achieved real-time performance independent of the number of interest points extracted from the targeted image, and consistently outperformed the SURF software baseline, reaching a maximum speedup of 15. An extensive analysis was conducted to prove that the performance of our proposed architecture was as robust as the SURF algorithm to image transformations (rotation and scaling) and image distortions (blurring and pixelation), demonstrating that interest-point repeatability was maintained under varying viewing conditions.

Modern astronomical catalogs and sky surveys, that contain billions of objects, belong to the “big data” data class. Existing available services have limited functionality and do not include all required and available catalogs. The software package ACrId (Astronomical Cross Identification) for cross-matching large astronomical catalogs, which uses an sphere pixelation algorithm HEALPix, ReiserFS file system and JSON-type text files for storage, has been developed at the Research Institution “Mykolaiv Astronomical Observatory”

We report a new scintillator based on a transparent ceramic of Lu 2 O 3 :Eu. The material has an extremely high density of 9.4 g/cm 3 , a light output comparable to CsI:Tl, and a narrow band emission at 610 nm that falls close to the maximum of the response curve of CCDs. Pixelation of the scintillator to prevent lateral spread of light enhances the spatial and contrast resolution, providing imaging performance that equals or surpasses all other currently known scintillators. Upon further development of readout technologies to take full advantage of its transparency, the new scintillator should play a major role in digital radiographic systems.

The key to reaching SPECT's full diagnostic potential lies in optimizing the imaging geometry to maximize the system geometric efficiency (SGE) at a given resolution. The optimal geometry differs for different imaging applications, for different imaging tasks within a single application, and for different patients. The C-SPECT cardiac SPECT/Tct platform unifies innovative sub-systems in a cardiocentric system. These components enable the use of a large curved detector to acquire up to 17 simultaneous minified projections from a small field of view (FOV). C-SPECT's cost-effective modular NaI (Tl) detector relies on pixelation to yield high intrinsic spatial resolution for projection minification, and to eliminate unusable edge areas of the modules. The detector arc is matched by the slit-slat collimator capable of switching between several resolution/sensitivity and FOV modes without disturbing the patient. This supports patient positioning and adaptive imaging operations and optimizes the imaging geometry for a given patient. The high SGE for cardiac imaging is augmented by additional functionality achieved with minimal costs. The multiple simultaneous projections, combined with the small FOV, provide sufficient angular sampling without system motion. This enables dynamic imaging to be performed in the high sensitivity collimator mode. We present preliminary imaging results obtained with a section of the C-SPECT lab-prototype, which includes 3 of the ultimate 14 detector modules and a corresponding section of the collimator arc capable of two resolution/sensitivity/FOV modes. These results, combined with Monte Carlo simulations and analytic predictions, demonstrate the validity and feasibility of the C-SPECT approach to advancing the capabilities of SPECT cardiac imaging.

A major limitation of the currently available small animal PET and SPECT imaging is their relatively low sensitivity to the incident gamma rays. While providing high spatial resolution utilizing finely pitched scintillator arrays has been explored, the cost of array fabrication has been an issue. Moreover, high sensitivity has been traded off for high spatial resolution since fabrication of scintillator arrays with small pixel cross-section and large thickness can be challenging and cost-prohibitive. The currently used mechanical pixelation of scintillators results in relatively large inter-pixel gaps and hence low packing fraction and sensitivity. We control the light spread in scintillators using a novel technique called Laser-Induced Optical Barriers (LIOB). In this work we are reporting on manipulation of scintillation light spread and hence improving pixel separation in LYSO:Ce arrays fabricated by LIOB technique as well as pixelation of CsI:Tl to 0.625×0.625×5 mm3 and 1×1×10 mm3 pixels with 100% process yield.

One of the most common topologies for the scintillator crystals used in gamma radiation detectors for PET scanners is pixelation. The size of these pixels, the crystal surface treatment and the reflector thickness inserted between crystals directly affects the energy and the spatial resolution as well as the sensitivity of the detector. The fabrication of pixels is laborious, complex and expensive. Here we investigate the possibility of creating pixels within monolithic LYSO scintillators crystals using the proven technique of sub-surface laser engraving with a Nd:YAG laser. To evaluate possible designs considering the limitations of the engraving procedure, we used the simulation software GAMOS to analyze the light propagation inside the crystals engraved with a variety of patterns. We carried out different experimental procedures, including microscopy and laser reflectometry to assess the relative reflective quality of the engraved surfaces. We compared the results of different engraving procedures to a reference reflector commonly used in this type of pixelated crystal matrices. We have configured different engraved surfaces with variable transparency in several pixel geometries including depth-of-interaction encoding patterns. Our results demonstrate that pixels engraved with this method can also be configured to compensate for the multiplexed readout penalties, and at the same time preserve the detector performance requirements. Such modifications of the engraving pattern takes place at practically no cost and constitute a highly promising solution for industrial fabrication, reducing substantially the cost of the detector.

The quality of super-resolution images obtained by single-molecule localization microscopy (SMLM) depends largely on the software used to detect and accurately localize point sources. In this work, we focus on the computational aspects of super-resolution microscopy and present a comprehensive evaluation of localization software packages. Our philosophy is to evaluate each package as a whole, thus maintaining the integrity of the software. We prepared synthetic data that represent three-dimensional structures modeled after biological components, taking excitation parameters, noise sources, point-spread functions and pixelation into account. We then asked developers to run their software on our data; most responded favorably, allowing us to present a broad picture of the methods available. We evaluated their results using quantitative and user-interpretable criteria: detection rate, accuracy, quality of image reconstruction, resolution, software usability and computational resources. These metrics reflect the various tradeoffs of SMLM software packages and help users to choose the software that fits their needs.

Visual privacy in video-based applications such as surveillance, assisted living or home monitoring is a highly active research topic. It is critical to protect the privacy of monitored people without severely limiting the utility of the system. We present a resource-aware cartooning privacy protection filter which converts raw images into abstracted frames where the privacy revealing details are re-moved. Cartooning can be applied either to entire images or pre-selected sensitive regions of interest. We provide an adaptation mechanism to our cartooning technique where the operator can easily change the filter intensity. The feasibility of this new approach is demonstrated by its deployment to real-world embedded smart cameras. We evaluate privacy protection and utility of cartooning with the PEViD data set and compare it with the two widely-used privacy filters: blurring and pixelation.

Radio spectrum is a limited natural resource. Most spectrum resources are assigned in the form of licenses, but the actual usage of most spectrum bands is limited. Market mechanisms to trade unused spectrum resources is a promising approach to mitigate the spectrum crunch. An extremely flexible approach to this, the spectrum micro-trading pixelation model, has been proposed to trade spectrum on the micro-scale in frequency, time and geography. In this paper we implement this model in a simulator and evaluate its performance in the spatial dimension using different pixel sizes and auction models. Some surprising findings are presented; the auction that assign spectrum to the bidders willing to pay the most does not provide service to most customers, does far from optimally maximize spectrum utilization, and gives far lower profit to the spectrum broker facilitating the market. Furthermore, we demonstrate the critical tradeoff between spectrum exploitation efficiency, allocation overhead and geographical pixel sizes in the market.

A fiber bundle is widely used for endoscopic imaging due to its direct image delivery capability. However, there exists an inevitable pixelation artifact, which limits spatial resolution to the diameter of individual fibers. In this Letter, we present a method that can eliminate this artifact and achieve diffraction-limited spatial resolution. We exploited the binary control of a digital micromirror device to measure a transmission matrix of a fiber bundle and to subsequently control mode mixing among individual fibers. In doing so, we achieved a 22 kHz scanning rate of a diffraction-limited focused spot and obtained fluorescence endoscope imaging (58 μm×58 μm) with near video-rate (10.3 Hz) acquisition. Our study lays a foundation for developing an ultrathin and high-resolution microendoscope.

The world of insects displays myriad hues of coloration effects produced by elaborate nano-scale architectures built into wings and exoskeleton. For example, we have recently found many weevils possess photonic architectures with cubic lattices. In this talk, we will present high-resolution three-dimensional reconstructions of weevil photonic structures with diamond and gyroid lattices. Moreover, by reconstructing entire scales we found arrays of single-crystalline domains, each oriented such that only selected crystal faces are visible to an observer. This pixel-like arrangement is key to the angle-independent coloration typical of weevils—a strategy that could enable a new generation of coating technologies.

Coherent fiber bundles with high core density give both flexibility and high resolution to microscopy. Despite of these advantages, fiber bundles inevitably have uncovered region between adjacent cores. The region results in structural artifact known as pixelation effect. Many kinds of image processing techniques have been introduced to remove this pixelation artifact such as frequency domain filter and Gaussian filter. However, these methods fundamentally have limitation because they use the information of adjacent pixels to make up for these uncovered area; therefore, they cannot avoid blurring effect as a result. To overcome this problem, we introduce spatial compound imaging method to overcome this pixelation artifact. The method uses multiple frames taken with small deviation of position. Some parts of these images include information which is devoid of in other images. The total amount of information increase as more images are added up and we can expect the improvement of resolution in the final images. At the same time, the duplicated parts among these images can be averaged to improve SNR ratio. For these improvements, we essentially need sophisticated registration algorithm. The pixelation artifact is troublesome again in registration process because its structural artifacts are strong features shared with whole images. However, we can solve this problem by using reference image and divide the sample images into two parts: effective and ineffective regions. We used effective regions for registration. We used USAF target to evaluate our method and we could get a result that SNR and resolution are both critically increase.

Light fields are a computational photography technique which allow features like refocusing and novel view synthesis. The previous work in light fields either have sampling bias or have a very complex acquisition setup. Here, we acquire a light field using a simple cylindrical arrangement of cameras. Our acquisition setup is simpler to implement where there is need to capture a large field of view. The parameterization we present uniformly samples the environment in the horizontal direction. Zooming options provided in traditional cameras either tend to change the relative sizes of the objects in an image(optical zoom) or introduce pixelation effect(digital zoom). We propose as well as demonstrate an approach that we have named “true zoom” that produces a significantly superior and realistic zooming effect.

Photopolymers are often used as a base of holographic memories displays. Recently the capacity of photopolymers to record diffractive optical elements (DOE’s) has been demonstrated. To fabricate diffractive optical elements we use a hybrid setup that is composed by three different parts: LCD, optical system and the recording material. The DOE pattern is introduced by a liquid crystal display (LCD) working in the amplitude only mode to work as a master to project optically the DOE onto the recording material. The main advantage of this display is that permit us modify the DOE automatically, we use the electronics of the video projector to send the voltage to the pixels of the LCD. The LCD is used in the amplitude-mostly modulation regime by proper orientation of the external polarizers (P); then the pattern is imaged onto the material with an increased spatial frequency (a demagnifying factor of 2) by the optical system. The use of the LCD allows us to change DOE recorded in the photopolymer without moving any mechanical part of the set-up. A diaphragm is placed in the focal plane of the relay lens so as to eliminate the diffraction orders produced by the pixelation of the LCD. It can be expected that the final pattern imaged onto the recording material will be low filtered due to the finite aperture of the imaging system and especially due to the filtering process produced by the diaphragm. In this work we analyze the effect of the visibility achieved with the LCD and the high frequency cut-off due to the diaphragm in the final DOE recorded into the photopolymer. To simulate the recording we have used the fitted values parameters obtained for PVA/AA based photopolymers and the 3 dimensional models presented in previous works. This work was supported by the Ministerio de Economía y Competitividad of Spain under projects FIS2011-29803-C02-01 and FIS2011-29803-C02-02 and by the Generalitat Valenciana of Spain under project PROMETEO/2011/021 and ISIC/2012/013.

A new technology is being proposed as a solution to the problem of unintentional facial detection and recognition in pictures in which the individuals appearing want to express their privacy preferences, through the use of different tags. The existing methods for face de-identification were mostly ad hoc solutions that only provided an absolute binary solution in a privacy context such as pixelation, or a bar mask. As the number and users of social networks are increasing, our preferences regarding our privacy may become more complex, leaving these absolute binary solutions as something obsolete. The proposed technology overcomes this problem by embedding information in a tag which will be placed close to the face without being disruptive. Through a decoding method the tag will provide the preferences that will be applied to the images in further stages.

Comunicación presentada al "ICDSC 2014" celebrado en Venecia 8Italia) del 4 al 7 de Noviembre de 2014, Privacy awareness constitutes a critical aspect for smart camera networks. An ideal awless protection of sensitive information would boost their application scenarios. How- ever, it is still far from being achieved. Numerous chal- lenges arise at di erent levels, from hardware security to subjective perception. Generally speaking, it can be stated that the closer to the image sensing device the protection measures take place, the higher the privacy and security at- tainable. Likewise, the integration of heterogeneous camera components becomes simpler since most of them will not require to consider privacy issues. The ultimate objective would be to incorporate complete protection directly into a smart image sensor in such a way that no sensitive data would be delivered o -chip while still permitting the tar- geted video analytics. This paper presents a 320 240-px prototype vision sensor embedding processing capabilities useful for accomplishing this objective. It is based on re- con gurable focal-plane sensing-processing that can provide programmable obfuscation. Pixelation of tunable granular- ity can be applied to multiple image regions in parallel. In addition to this functionality, the sensor exploits recon g- urability to implement other processing primitives, namely block-wise high dynamic range, integral image computation and Gaussian ltering. Its power consumption ranges from 42.6mW for high dynamic range operation to 55.2mW for integral image computation at 30fps. It has been fabricated in a standard 0.18 m CMOS process.

Comunicación presentada al "ICDSC 2014" celebrado en Venecia (Italia) del 4 al 7 de Noviembre de 2014, Privacy concerns are hindering the introduction of smart camera networks in prospective application scenarios like retail analytics, factory monitoring or elderly care. The idea of networked cameras pervasively collecting data gen- erates social rejection in the face of sensitive information being tampered by hackers or misused by legitimate users. New strategies must be developed in order to ensure pri- vacy from the very point where sensitive data are generated: the sensors. Protection measures embedded on-chip at the front-end sensor of each network node signi cantly reduce the number of trusted system components as well as the im- pact of potential software aws. In this demonstration, we present a full-custom QVGA vision sensor that can be re- con gured to implement programmable pixelation of image regions at the focal plane. In particular, we show on-the- y focal-plane face obfuscation supported by the Viola-Jones frontal face detector provided by OpenCV

The shape of a focus-modulated point spread function (PSF) is used as a quick visual assessment tool of aberration modes in the PSF. Further analysis in terms of shape moments can permit quantifying the modal coefficients with an accuracy comparable to that of typical wavefront sensors. In this letter, the error of the moment-based wavefront sensing is analytically described in terms of the pixelation and photon/readout noise. All components highly depend on the (unknown) PSF shape, but can be estimated from the measured PSF sampled at a reasonable spatial resolution and photon count. Numerical simulations verified that the models consistently predicted the behavior of the modal estimation error of the moment-based wavefront sensing., Comment: 5 pages, 3 figures

Visual access to physically inaccessible parts has become the forefront of research and development in medical diagnostics tools and procedures. Flexible and thin endoscopes with fiber bundle as an image conduit serves this purpose. However, when the light passes through the core of the fiberlet, it is blocked by the inter fiberlet gap. This structural limitation creates special honeycomb like pattern overlaying the image captured with the image fiber assisted probes, known as the comb structure or fiber pixelation. It obstructs the perception of the original image sacrificing resolution and contrast and inhibits the use of object recognition and tracking algorithms. Generally, comb structure removal or depixelation methods are employed to remove honeycomb pattern from an image. In the recent past, several depixelation techniques have been proposed albeit using different set of pixilated images by different researchers. It is quite difficult to make a comparison of their performances based on such images, as they adopt different images for different particular framework of their study. In this context, a basic database of such images is the need of the hour to meet the growing diagnostic needs in the medical and industrial arena. This paper in this context proposes and details a Comb Structure Affected Image database (CSAI) to meet the objective. Images are generated considering the image fiber specifications and the characteristics at different targeted optical imaging modalities delineated by resolution scales. The proposed database is designed to have a set of synthetically generated pixelated images of test patterns of different scales, sizes and shapes. Published version

Current performance measures for infrared imagers are applicable to linear mechanically scanned systems but not to those with focal plane arrays of detector elements, because these are nonlinear due to aliasing. The performance of an imager affects the ability of an observer to perform perception tasks using it. Psychophysical trials have been undertaken in an attempt to identify more appropriate performance measures. Simple shapes degraded by various degrees of Gaussian blurring and pixelation were selected at random and displayed on a computer monitor. A correlation has been found between the probability of recognition of an image and a quantity called ‘recognition contrast’ (C R). This is related to the shape observed and a template of the equivalently degraded alternative shape most similar to it. This quantity C R was refined following trials in which spatial noise was added to Gaussian blurred images. C R is calculated from information about each of the two images and is directly proportion...

Two experiments are reported that assess how well the identity of highly familiar (famous) faces can be masked from short naturalistic television clips. Recognition of identity was made more difficult by either pixelating (Experiment 1) or blurring (Experiment 2) the viewed face. Participants were asked to identify faces from both moving and static clips. Results indicated that participants were still able to recognize some of the viewed faces, despite these image degradations. In addition, moving images of faces were recognized better than static ones. The practical and theoretical implications of these findings are discussed. Copyright (C) 2001 John Wiley & Sons, Ltd.

Consider digitising a binary pattern on a regular lattice, so that each “face” or pixel of the lattice is given just one of the two colours in the pattern. If the pixelation algorithm is symmetric, meaning that a pixel which straddles the boundary between two colours inherits the colour that predominates in that particular face, then the systematic errors in pixel counts are generally small. However, they can be significant for asymmetric pixelations. In this paper we provide explicit corrections for systematic errors in area estimates based on asymmetric pixelation algorithms. The corrections are derived by interpreting systematic error as the bias in a statistical estimation problem, and arguing that the pattern was placed into the lattice in a stochastically uniform way. We suggest two sorts of correction: first, a “local” adjustment based on tracking the boundary and accumulating small amendments along the way; and secondly, a “global” correction based on parametric knowledge of the type of shape that is being digitised.

We developed an X-ray imaging detector consisting of a silicon charge coupled device and pixel structured CsI(Tl) scintillator in previous research. Scintillator pixelation for minimizing the spread of scintillation light enhanced spatial resolution. In this study, we investigated the effect of pixel size on spatial resolution using DETECT97 simulation and obtained the measured modulation transfer functions (MTFs) of pixelated CsI(Tl) scintillators. The size of a pixel is controlled by the pattern on glass substrate in the fabricating process.

Photo-asymmetric synthesis of pentahelicenes have been carried out in liquid crystals. The objective of this investigation is to study the feasibility of using polyhelicenes as tunable chiral materials in the color pixelation of reflective cholesteric displays (RCDs). Since the pitch of a cholesteric liquid crystal phase can be changed by the addition of a small amount of chiral compounds, in-situ photo-asymmetric synthesis in display cells provides a valuable method in the modification of liquid crystal properties. We describe herein attempts to use linearly//circularly polarized light to modify the pitch and hence, the color of a RCD.

A novel method is outlined which allows measurement of the amplitude of oscillation of a sinusoidal sound field and the mean flow using particle image velocimetry. The method involves simplifying the interrogation area in such a way that the autocorrelation function contains four significant peaks. The accuracy is of the order of half pixel resolution, once a constant offset related to the non-continuous nature of the probability function of a sine wave is taken into account. This constant, which originates from the pixelation of the image, is shown to be 0.85 pixels.

Note-taking applications today have features that imitate the behavior of real handwriting such as smooth strokes, responsive interface, and stroke thinning. However, the problem is that the writing tools of these applications do not fully simulate the feel of their real counterpart. Some of these applications have flaws like unnatural pen thinning effect, pixelation of strokes, and lack of highlighter blending. To solve these, an iPad application with a custom smooth writing algorithm was developed. It was compared to five commercially available note-taking programs in the App Store.

To achieve high spatial resolution required in nuclear imaging, scintillation light spread has to be controlled. This has been traditionally achieved by introducing structures in the bulk of scintillation materials; typically by mechanical pixelation of scintillators and fill the resultant inter-pixel gaps by reflecting materials. Mechanical pixelation however, is accompanied by various cost and complexity issues especially for hard, brittle and hygroscopic materials. For example LSO and LYSO, hard and brittle scintillators of interest to medical imaging community, are known to crack under thermal and mechanical stress; the material yield drops quickly with large arrays with high aspect ratio pixels and therefore the pixelation process cost increases. We are utilizing a novel technique named Laser Induced Optical Barriers (LIOB) for pixelation of scintillators that overcomes the issues associated with mechanical pixelation. In this technique, we can introduce optical barriers within the bulk of scintillator crystals to form pixelated arrays with small pixel size and large thickness. We applied LIOB to LYSO using a high-frequency solid-state laser. Arrays with different crystal thickness (5 to 20 mm thick), and pixel size (0.8×0.8 to 1.5×1.5 mm 2 ) were fabricated and tested. The width of the optical barriers were controlled by fine-tuning key parameters such as lens focal spot size and laser energy density. Here we report on LIOB process, its optimization, and the optical crosstalk measurements using X-rays. There are many applications that can potentially benefit from LIOB including but not limited to clinical/pre-clinical PET and SPECT systems, and photon counting CT detectors.