Search

In recent years, the development of computational imaging technology provides a new method for the realization of non-scanning super-resolution imaging. In this paper, a pixel super-resolution algorithm based on Fourier ptychographic technology is proposed, and the corresponding integrated and systematic programmable aperture coded super-resolution imaging system is constructed. By modulating the intensity with the coded aperture mask, utilizing different system point spread functions to obtain multiple samples of the original scene, and finally adopting sparse optimization iterative algorithm to reconstruct the original image, the result of super- resolution imaging is more than 3.5 times of Nyquist sampling frequency. In this tutorial, the proposed new super-resolution photoelectric imaging technology innovatively adopts the approach of coded aperture to realize image super-resolution imaging and effectively solve image pixelation. High-resolution images beyond the spatial resolution of the detector are obtained without any physical moving device or scanning mechanism. Compared with the traditional micro-scanning technology, it not only improves the reliability and stability of the system but also greatly reduces the cost and volume weight of the system.

Layout features become highly susceptible to lithography process fluctuations due to the widening subwavelength lithography gap. Problematic layout patterns incur poor printability even if they pass design rule checking. These hotspots should be detected and removed at early design phases to improve manufacturability. While existing studies mainly focus on hotspot detection and pattern classification, hotspot pattern library generation is rarely addressed in literature but crucial to the effectiveness and efficiency of hotspot detection. For an advanced process, in addition to yield-limiting patterns inherent from old processes and computation intensive lithography simulation, defect silicon images (SEM images) inspected from test wafers provide more realistic process-dependent hotspots. For facilitating hotspot pattern library generation, we raise a pattern matching problem of searching design layout patterns that may induce problematic SEM images. The key challenge is the various shape distortions between an SEM image and corresponding design layouts. Directly matching either feature points or shapes of both is thus not applicable. We observe that even with shape distortions, matched design layouts and the SEM image have similar density distribution. Therefore, in this paper, we propose an efficient multilevel pixilation framework to seek layout clips with similar density distribution from coarse- to finegranularities to an SEM image. The proposed framework possesses high parallelism. Our results show that the proposed method can effectively and efficiently identify matched layout pattern candidates.

Pixelation, blur and additional noise of imaging system limit the resolution of final images acquired. Many pixel superresolution algorithms have been applied to enhance the resolution of imaging system by merging a sequence of lowresolution holograms with different type of imaging system, for example by shifting illumination source or using wavelength scanning. Most of these pixel super-resolution imaging systems can only be implemented to single-layer sample. For multi-layer imaging system and volumetric imaging scenarios, the relative displacement of various sample at different layers will disturb each other. Herein, we report a portable, cost-effective, lensless wide-filed digital in-line holographic microscopy imaging system based on in-line hologram segmentation and pixel super-resolution algorithm, which can separate target sample from the background and improve the resolution of the sample. We demonstrated the effectiveness of our system with numerical simulation and experiment with volumetric sample. In numerical simulation, we applied a very simple two-layer sample model that samples in two layers have various moving speed and directions and also did the volumetric imaging experiment with cuvette containing algae floating in. In our system, the sensor captured a sequence of low-resolution diffraction patterns. The target sample mix with background disturbance, which will invalidate the direct pixel super-resolution technique. We applied segmentation algorithm to the reconstructed images from holograms, separating target sample from background and generating a sequence of sub-images containing only target sample with same resolution and numerical aperture as original holograms. Finally the enhanced resolution reconstructed image of target sample was obtained with pixel super-resolution algorithm, which can go beyond pixel limitation and get sub-pixel perspective microscopy. This imaging system has the advantages of wide-field, portable and lensless.

Pixelated Cadmium Zinc Telluride (CdZnTe) detectors are currently flying on the Nuclear Spectroscopic Telescope ARray (NuSTAR) NASA Astrophysics Small Explorer. While the pixel pitch of the detectors is ≈ 605 μm, we can leverage the detector readout architecture to determine the interaction location of an individual photon to much higher spatial accuracy. The sub-pixel spatial location allows us to finely oversample the point spread function of the optics and reduces imaging artifacts due to pixelation. In this paper we demonstrate how the sub-pixel information is obtained, how the detectors were calibrated, and provide ground verification of the quantum efficiency of our Monte Carlo model of the detector response.

X-ray diffraction is known to be an effective technique for illicit materials detection in baggage screening, as it can reveal molecular structural information of any solid substances but also of liquids, aerosols and gels. Some X-ray diffraction systems using 2D pixelated spectrometric detectors, such as CdZnTe detectors, are then able to perform 3D baggage scanning in time compatible with bag throughput constraints of airports. However, X-ray diffraction systems designed for baggage screening generally suffer from poor photon count statistics and bad spatial resolution, because of the tight collimations and the small scattering angle. To improve these factors, techniques of sub-pixelation can be implemented in CdZnTe detectors. Indeed, sub-pixelation enables to open the collimation without angular resolution degradation and also to segment the inspected volume in several sub-volumes, inducing a better spatial resolution in the X-ray beam direction. In this paper, we present some experiments demonstrating the interest of sub-pixelation within CdZnTe detectors for X-ray diffraction imaging systems. In particular, an experimental demonstration is presented with a 2D XRD image of a realistic baggage performed with only one single pixel from our own CdZnTe based imager.

The limited space-bandwidth-product of microscopy systems in general forces users to sacrifice either resolution or field-of-view (FOV). Here we introduce a wide-field and high-resolution imaging method that uses a stack of out-of-focus images of the specimen to increase the space-bandwidth-product of lens-based microscopes. Although modern microscope objective-lenses are designed for high-resolution imaging and can achieve a relatively large FOV, often the active area of the imager chip sets a limitation. To best utilize the full field-of-view of an objective-lens in our microscope, we first added a demagnification camera adaptor (e.g., 0.35×) to match the CCD sensor chip active area to the FOV of a 10X objective-lens (~5 mm2) that has an NA of 0.3. This demagnification, while increasing the FOV, downgrades the image resolution and results in pixelation. We illustrate that this spatial undersampling can be overcome through an iterative pixel super-resolution algorithm that uses a stack of out-of-focus images of the sample to restore a high-resolution image across a large FOV. We demonstrated the success of this approach using a resolution test-target and showed that our technique reduces the number of measurements required to achieve the same effective space-bandwidth-product using e.g., lateral scanning and digital stitching of different FOVs. Phase retrieval capability of this approach is also demonstrated by reconstructing unstained Papanicolaou (Pap) smear samples without the need for phase-contrast objective-lenses. This technique might be useful to maximize the throughput of lens-based optical imaging systems and inspire new microscopy designs that utilize auto-focusing steps to increase resolution.

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.

High power LEDs were introduced in automotive headlights in 2006-2007, for example as full LED headlights in the Audi R8 or low beam in Lexus. Since then, LED headlighting has become established in premium and volume automotive segments and beginning to enable new compact form factors such as distributed low beam and new functions such as adaptive driving beam. New generations of highly versatile high power LEDs are emerging to meet these application needs. In this paper, we will detail ongoing advances in LED technology that enable revolutionary styling, performance and adaptive control in automotive headlights. As the standards which govern the necessary lumens on the road are well established, increasing luminance enables not only more design freedom but also headlight cost reduction with space and weight saving through more compact optics. Adaptive headlighting is based on LED pixelation and requires high contrast, high luminance, smaller LEDs with high-packing density for pixelated Matrix Lighting sources. Matrix applications require an extremely tight tolerance on not only the X, Y placement accuracy, but also on the Z height of the LEDs given the precision optics used to image the LEDs onto the road. A new generation of chip scale packaged (CSP) LEDs based on Wafer Level Packaging (WLP) have been developed to meet these needs, offering a form factor less than 20% increase over the LED emitter surface footprint. These miniature LEDs are surface mount devices compatible with automated tools for L2 board direct attach (without the need for an interposer or L1 substrate), meeting the high position accuracy as well as the optical and thermal performance. To illustrate the versatility of the CSP LEDs, we will show the results of, firstly, a reflector-based distributed low beam using multiple individual cavities each with only 20mm height and secondly 3x4 to 3x28 Matrix arrays for adaptive full beam. Also a few key trends in rear lighting and impact on LED light source technology are discussed.

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 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.

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.

The emerging technique of three-dimensional (3D) printing provides a simple, fast, and flexible way to fabricate structures with arbitrary spatial features and may prove useful in the development of standardized, phantom-based performance test methods for biophotonic imaging. Acrylonitrile Butadiene Styrene (ABS) is commonly used in the printing process, given its low cost and strength. In this study, we evaluate 3D printing as an approach for fabricating biologically-relevant optical phantoms for hyperspectral reflectance imaging (HRI). The initial phase of this work involved characterization of absorption and scattering coefficients using spectrophotometry. The morphology of phantoms incorporating vessel-like channels with diameters on the order of hundreds of microns was examined by microscopy and OCT. A near-infrared absorbing dye was injected into channels located at a range of depths within the phantom and imaged with a near-infrared HRI system (650-1100 nm). ABS was found to have scattering coefficients comparable to biological tissue and low absorption throughout much of the visible and infrared range. Channels with dimensions on the order of the resolution limit of the 3D printer (~0.2 mm) exhibited pixelation effects as well as a degree of distortion along their edges. Furthermore, phantom porosity sometimes resulted in leakage from channel regions. Contrast-enhanced channel visualization with HRI was possible to a depth of nearly 1 mm – a level similar to that seen previously in biological tissue. Overall, our ABS phantoms demonstrated a high level of optical similarity to biological tissue. While limitations in printer resolution, matrix homogeneity and optical property tunability remain challenging, 3D printed phantoms have significant promise as samples for objective, quantitative evaluation of performance for biophotonic imaging modalities such as HRI.

Pixelation problem of textures in Virtual Reality can be resolved by using theory of J.A. Wheeler, affirming that our consciousness densely interacts with the objective world even in a very large scale. Despite of uncertainty with correctness of this hypothesis to the real world, this idea looks very attractive for computer based virtual worlds modeling as a method of local environment detailing just "when we are looking."© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Columnar CsI(Tl) screens are now routinely used for digital x-ray imaging in a wide variety of applications such as mammography, dental radiography, and non-destructive testing. While commercially available CsI(Tl) screens exhibit excellent properties, it is possible to significantly improve their performance. Here, we report on a new design of a columnar CsI(Tl) screen. Specifically, columnar CsI(Tl) screens were subjected to mechanical pixelation for minimizing the long range spread of scintillation light within the film, thus enhancing spatial and contrast resolution, and increasing the detective quantum efficiency (DQE(f)) of the digital imaging detector. To date we have fabricated up to 200 μm thick pixelated CsI(Tl) screens for mammography, and characterized their performance using a CCD camera. This paper presents a comparison of the new pixelated CsI(Tl) screens, conventional columnar CsI(Tl) screens, and Gd 2 O 2 S(Tb) screens. The data show that pixelated screens substantially improve the DQE(f) of the digital imaging system.

While many HMD designs exhibit see-through capability and a relatively narrow field of view (FOV), the HMD design presented int his paper is purposely immersive since it seeks operational roles requiring anthropomorphic telepresence, which seeks to procure its operator the impression of being at a remote location. This technology is applicable in situations where it is deemed too expensive and/or hazardous to send an operator on site. The HMD developed for this purpose exhibits SVGA resolution, and achieves a FOV of approximately 84 degrees through compact 6-element eyepieces. It is color and stereo capable, and the usual degradation in effective resolution due to RGB triads from conventional composite color display devices is circumvented by the use of a sequential color technique, which yields a very acceptable image quality with acceptable pixelation, in spite of the high FOV. Several add-ons to this HMD, greatly enhancing its capabilities, have also been developed and will be described briefly; they include translucentgraphical overlays, an embryo of real-time video CODEC technology that could enable fully digitized visual telepresence at acceptable bandwidths, the associated robotics complementing the HMD and enabling actual telemanipulations, and finally, a time delay (in static environments) and motion compensation algorithm.

Flexible micro-endoscopes with dimensions of as small as 1.0 mm in outer diameter and as long as 3.0 m in length produce images that have a 'honeycomb' pattern due to the spaces between the individual collection optical fibers contained in the imaging conduit. This pattern is found to exhibit a definable spatial frequency that is discrete from that of the desired information or the actual images of interest. By applying a filter and by sharpening the contrast between adjacent pixels, it was possible to remove the honeycomb pattern without significant degradation to the visual quality of the image. The technique described employs Fourier analysis to analyze the image so as to define the 'noise' component. Then a discrete band-reject frequency filter was applied to both the original and sharpened images, resulting in the effective removal of the honeycomb pattern. The advantages and limitations of the image processing technique are discussed.

We introduce a pattern matching algorithm and a bitmap reconstruction method used in document image compression. This pattern matching algorithm uses the cross entropy between two patterns as the criterion for a match. We use a physical model which is based on the finite resolution of the scanner to estimate the probability values used in cross entropy calculation. The matching algorithm is enhanced by the bitmap reconstruction method which infers a good high resolution image form a series of poor low resolution images. This bitmap reconstruction method is based on the naive image averaging method, but it uses a preprocessing smoothing filter and it is done in a higher resolution than the original image. Experimental results show that this pattern matching algorithm and this bitmap reconstruction method compare favorably to previous techniques.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The application of recent computer technology of the National Center for Missing and Exploited Children (NCMEC) has provided the means to age progress faces of long term missing children. In the thousands of cases of missing children that have disappeared for two or more years, there is a particular priority to identify and recover these children. It is apparent that long term solutions to this problem lie in the realm of technology. One of the areas is the computerized aging of children's faces. Forensic artists working with this new technology help this goal become a reality. When imaging a child's face, the forensic artist must consider using photographs of the biological family at an age consistent with the age of the missing child. With these pictures, a reasonable likeness can be produced using computer technology. This image can aid law enforcement, child find and social service agencies and the public in their search for the missing child. Unique features of the system provide for the stretching, merging, pixelation and refining of a completed progression. A knowledge of the steps of facial growth and anatomy is necessary to achieve an accurate image. Future developments in age progression and facial reconstruction may be in the realm of morphing technology. Application of this technology is being tested to provide a more accurate image for investigative use.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The correction of phase aberrations in optical systems using an adaptive liquid crystal phase screen having 64 X 64 pixels is considered. These adaptive components have advantages over deformable mirror systems in that liquid crystal technology is relatively inexpensive and large pixelation densities can be achieved. In particular we address the application of these devices to astronomical adaptive optics. A simulator of the phase correction plate at work using time changing distorted wave fronts is described. Preliminary measurements of the optical flatness and response times of the prototype device are discussed.

Replication in the output plane of an optical correlator, due to pixelation of the Fourier plane filter, can lead to false correlation signals. This paper suggests randomization of the pixel positions of the Fourier plane filter as a solution, and demonstrates its effectiveness through computational simulations and optical correlation experiments using a custom made SLM.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Electronic image projection systems generally suffer from dark grid (pixelation) or scan line structures which become more noticeable as the image is expanded. Since these structures represent a high spatial frequency error in the image, appropriate spatial filtering can be used to reduce this error and increase image fidelity. A new, transparent spatial filter is introduced and demonstrated to depixelize the image produced by a liquid crystal video projector. Various filter design and fabrication guidelines to achieve the best apparent image are also discussed.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Focal plane arrays (FPA) of CdHgTe detectors have been incorporated successfully into infrared imagers with sensitivities in either the 3-5 µm or 8-14 µm bands. Whilst it has been possible to obtain good imagery with minimal fixed pattern noise using digital non-uniformity correction electronics, these imagers suffer from problems caused by the sampling of the scene by the FPA; in particular, aliasing results in the obscuration of high frequency detail in the scene and its appearance at lower frequencies below the Nyquist frequency. It is demonstrated how microscanning may be used to reduce these sampling effects and in addition, ways of improving the ease of viewing of the final image by reducing the degree of pixelation are discussed.