Wide Illumination Research Articles

A 128$\,\times$128 1.5% Contrast Sensitivity 0.9% FPN 3 µs Latency 4 mW Asynchronous Frame-Free Dynamic Vision Sensor Using Transimpedance Preamplifiers

Dynamic Vision Sensors (DVS) have recently appeared as a new paradigm for vision sensing and processing. They feature unique characteristics such as contrast coding under wide illumination variation, micro-second latency response to fast stimuli, and low output data rates (which greatly improves the efficiency of post-processing stages). They can track extremely fast objects (e.g., time resolution is better than 100 kFrames/s video) without special lighting conditions. Their availability has triggered a new range of vision applications in the fields of surveillance, motion analyses, robotics, and microscopic dynamic observations. One key DVS feature is contrast sensitivity, which has so far been reported to be in the 10-15% range. In this paper, a novel pixel photo sensing and transimpedance pre-amplification stage makes it possible to improve by one order of magnitude contrast sensitivity (down to 1.5%) and power (down to 4 mW), reduce the best reported FPN (Fixed Pattern Noise) by a factor of 2 (down to 0.9%), while maintaining the shortest reported latency (3 μs) and good Dynamic Range (120 dB), and further reducing overall area (down to 30 × 31 μm per pixel). The only penalty is the limitation of intrascene Dynamic Range to 3 decades. A 128 × 128 DVS test prototype has been fabricated in standard 0.35 μm CMOS and extensive experimental characterization results are provided.

Tips in ophthalmic photography

Dear Editor, We congratulate Mahesh et al., for their article on “video indirect ophthalmoscopy using handheld video camera.”[1] Documentation of clinical findings is a crucial part of an ophthalmologist's work and is important for communication with col-leagues and patients. The quality of an image depends as much as on the photographer's knowledge of the anatomy and physiology of the eye, as it does on photographic techniques and technology. In this regard, we would like to describe certain techniques in anterior segment photography which would greatly enhance the quality of the images obtained using an inexpensive personal digital camera. The settings we recommend for external photography (for lids and adnexal structures) are: Most cameras have “auto focus” mode and the system automatically adjusts to select the best focus. For clinical photography it is better to switch off the auto focus mode and to select “central focus” mode. Flash is optional, depending on ambient lighting. It is better to capture he image with and without flash and choose the better one later. ISO settings should be set as “auto” unless the photographer is experienced with different ISO speeds of camera. An important setting is the “macro mode” function denoted by “flower symbol” [Fig. 1]. It allows the camera to focus on objects as close as 2-4 inches.[2] With this, finer details of lid and adnexal lesions like surface irregularity, vascularity, and pigmentation can be documented, preserving clarity even on zooming. With the same technique gross details of the anterior segment can also be photographed. Proper focus is obtained by pressing the shutter button halfway, then adjusting the camera to obtain clear focus as seen on the LCD viewfinder. On obtaining clear focus, the yellow-colored rectangle will change to green in the LCD viewfinder. Figure 1: Photograph showing “macro mode” in the cameraFor slit-lamp photography of the anterior segment, the digital camera should be placed in one of the slit-lamp oculars after adjusting focus. Cameras with 3 megapixel (MP) resolution cater to most of our needs in obtaining clinical photographs. Higher resolution cameras (>3 MP) are not required for this purpose. Choose cameras with the objective piece protruding out so that it can snugly fit into slit-lamp oculars. Settings recommended are centre focus, macro mode, flash off, auto ISO. Camera focus can be adjusted by depressing shutter halfway down until the green box appears. Yellow box indicates that the camera has to be repositioned to obtain better focus. Most anterior segment photographs require an external light source which is usually provided by ambient room lighting. Without an external light source, the camera makes poor choice regarding exposure, resulting in the image being too dark or too bright. However, for ocular findings like keratic precipitates, iris transillumination defects, or lens opacities, external light source is not necessary. Anterior segment photographs are obtained better with wide illumination with diffuser on. Good-quality photographs make scientific publications more convincing. They can also be used as evidence in medico-legal cases. Techniques of obtaining clinical photographs should be part of resident training. This method may help ophthalmologists working in resource-constraint situations to document ophthalmic findings without expensive photography equipments.

RADAR IDENTIFICATION OF HOSTILE FIRE BY MEANS OF THE ELECTROMAGNETIC COMPLEX NATURAL RESONANCES OF PROJECTILES

The authors discuss and demonstrate the feasibility of using ultra wide band microwave radar to detect and identify small arms flre. Detection and tracking is by standard radar techniques, but identiflcation is carried out by exciting the projectiles Complex Natural Resonances and using this aspect independent information to assign a caliber to the incoming projectiles. The typical sizes of small arms projectiles (calibers 5.56mm through to 13mm) imply that ultra wide band illumination in the microwave region of the spectrum between 1.5{5.5GHz is required to excite these object's fundamental resonances. The authors give a discussion of the efiects of motion on the quality of the complex natural resonance data obtainable and present both simulated and laboratory data for the radar cross section of three difierent caliber projectiles (5.56mm, 7.62mm and 13mm).

An Improved Multi-Exposure Image Fusion Algorithm

An improved Multi-Exposure image fusion scheme is proposed to fuse visual images for wide range illumination applications. While previous image fusion approaches perform the fusion only concern with local details such as regional contrast and gradient, the proposed algorithm takes global illumination contrast into consideration at the same time; this can extend the dynamic range evidently. Wavelet is used as Multi-Scale analysis tool in intensity fusion. For color fusion, HSI color model and weight map based method is used. The experimental results showed that the proposed fusion scheme has significant advantages in dynamic range, regional contrast and color saturation.

Multichannel routing of diffraction-inhibited beams in two-dimensional photonic crystals

We show that two rows of photonic lattices on each side of a narrow diffraction-inhibited beam are sufficient for confinement, enabling the launching of multi-beams with an interval of one lattice constant for independent propagation. A few integrated photonic circuit building blocks including arbitrary angle bends, power splitter and intersection are designed to realize flexible controls of the diffraction-inhibited beams. In addition, under wide beam illumination, incident beam power is well separated by the lattices rows, facilitating the simultaneous excitation of multiple diffraction-inhibited beams. These novel effects and building blocks offer exceptional opportunities for multichannel photonic routing.

Material classification of nanoparticles by focused beam scattering

Advanced science and technology frequently encounters the need to detect particles in the micrometer and nanometer range of a given composition. While the scattering process of light by small particles is well documented, most conventional analytic methods employ wide illumination of large ensembles of particles. With such an approach, no information can be obtained about single particles due to their weak interaction. In this paper, we show that single particles can be classified with respect to their material composition by analyzing the scattering pattern of a focused Gaussian beam.

Technical Note: A fast laser‐based optical‐CT scanner for three‐dimensional radiation dosimetry

To introduce a novel laser-based optical-CT scanner for the readout of three-dimensional (3D) radiation dosimeters. The scanner employs a diode laser, a cylindrical lens, a motorized linear rail, a rotation stage, and a charge-coupled device camera. The scanner operates in a translate-rotate fashion and may be set up in two configurations depending on the orientation of the cylindrical lens. The attenuation coefficient versus dose response was determined for a normoxic N-vinylpyrrolidone based polymer gel dosimeter. Cylindrical dosimeters, 2 cm diameter, were homogenously irradiated to known doses up to 60 Gy using a 6 MV linear accelerator. For a test irradiation, a 5 cm diameter dosimeter was irradiated along its cylindrical axis using a rectangular 1 cm x 1 cm irradiation beam. The dose readout of this scanner was compared to the corresponding readout of a common wide illumination and area detector optical-CT scanner. The attenuation coefficient versus dose response of the laser-based system was found to be linear up to 60 Gy (r2 = 0.997) compared to the wide field illumination based optical-CT scanner, which exhibits linearity up to 32 Gy (r2 = 0.996). The noise in the reconstructed attenuation coefficient maps was +/- 7.2 x 10(-2) mm(-1) versus +/- 9.5 x 10(-3) mm(-1) for the laser-based system and the wide field illumination system, respectively. We have developed a novel laser-based optical-CT scanner, which is capable of generating fast 3D dosimetric data using a scattering polymer gel dosimeter. Our data demonstrate that the dose readout of this scanner preserves the advantage of existing laser-based optical-CT scanners in providing measurements, which are minimally affected by scattered light. For accurate reconstruction of the attenuation coefficients, noise reduction techniques need to be applied.

Thyroid-stimulating hormone (thyrotropin)-secretion pituitary adenoma in an 8-year-old boy: case report

In this report, an extremely rare case of pediatric thyrotropin-secreting pituitary macroadenoma (TSHoma) is described. An 8-year-old boy, complaining of unsteady gait, was suspected of endocrinopathy because of emaciation and muscle weakness of the legs. Endocrinological work-up established a diagnosis of hyperthyroidism due to syndrome of inappropriate secretion of TSH. Magnetic resonance imaging showed a pituitary macroadenoma with suprasellar and sphenoidal extension without cavernous sinus invasion. He underwent an endoscopic endonasal transsphenoidal adenomectory due to the diagnosis of TSHoma. The adenoma was soft and it was totally removed. Histopathological staining confirmed diagnosis of TSHoma. Postoperative evaluation revealed a subnormal level of TSH (from 13-21 to 0.03 micro U/ml), normalization of alpha-subunit (from 10.0 to 0.09 ng/ml), and as a result, hypothyroidism. The boy left the hospital with oral levothyroxine that continued until 12 months of discharge. The present 8-year-old case is the youngest case to the best of our knowledge based on a bibliographical search. Reasons for endocrinological remission following adenomectomy are (1) correct diagnosis without delay: lack of cavernous sinus invasion, (2) soft and non-fibrous adenoma tissue, and (3) endoscopic technique with wide vision and illumination: safe even for a 8-year-old child. Early recognition/detection and pituitary-conserving adenomectomy can cure TSHoma and avoid long-term medical therapy and/or irradiation, which contribute to the best interests of patients with TSHoma.

Effect of illumination intensity on cell parameters of a silicon solar cell

The effect of illumination intensity P in on the cell parameters of a silicon solar cell has been investigated based on one diode model. The variation of slopes of the I–V curves of a cell at short circuit and open circuit conditions with intensity of illumination in small span of intensity has been applied to determine the cell parameters, viz. shunt resistance R sh , series resistance R s , diode ideality factor n and reverse saturation current I 0 of the cell. The dependence of cell parameters on intensity has been investigated for a fairly wide illumination intensity range 15–180 mW/cm 2 of AM1.5 solar radiations by dividing this intensity range into a desirable number of small intensity ranges for measurements of the slopes of the I–V curves at short circuit and open circuit conditions. Initially R sh increases slightly with P in and then becomes constant at higher P in values. However, R s , n and I 0 all decrease continuously with P in , but the rate of decrease of each of these becomes smaller at higher P in values. Theoretical values of open circuit voltage V oc , curve factor CF and efficiency η calculated using the cell parameters determined by the present method match well with the corresponding experimental values.

Micropatterned single lens for wide-angle light-emitting diodes

This work presents a simple and effective method for a wide-angle light-emitting diode module by using a single lens corrugated with micropattern arrays. Impinged onto the micropattern arrays of a curved surface, light undergoes an enhancement of the illumination angle due to omnidirectional diffraction. A hemispherical dome lens with micropattern arrays is microfabricated by a reconfigurable microtemplating and a replica molding method. Depending on the micropattern size, the experimental and simulation results show the micropatterned single lens has the wide illumination angle as well as the high extraction efficiency of an incoming LED light source, compared with a conventional dome lens.

Wide-Beam X-Ray Source Target Thermal Management Simulation Using Inner Jet Cooling

A wide-beam area X-ray source has been proposed as a practical replacement for synchrotron sources in clinical DEI applications. Due to a wide X-ray illumination area, a decrease in X-ray flux is expected and thus high electron beam currents up to 3A are considered. To ensure the target performance without deterioration, melting, cracking, or even evaporation, an active cooling system is required for the target block in order to remove the heat and allow for sufficient scanning time. In this study, jet cooling of the target back is investigated for a prototype proof-of-principle target. The prototype target was simulated with the transient k-ɛ turbulence multiphysics model in ANSYS CFX. The simulations were conducted at a heat flux of 1.8×107 W/m2, consistent with values anticipated for a full scale target. The simulation results show that the target temperature exceeds the copper melting point in 2 seconds at inlet velocities below 2 m/s. Also, critical heat flux calculations show that a 1.5 m/s inlet velocity at atmospheric pressure is a lower limit for prevention of target burnout using water as a coolant. Inlet velocities in excess of 2 m/s allows for steady-state operation while satisfying all thermal design constraints.

Multi-Spectral Imaging by Optimized Wide Band Illumination

We present a novel active imaging approach that uses optimized wide band filtered illumination to obtain multi-spectral reflectance information. Our optimization algorithm utilizes light source and camera spectral information in order to maximize the signal strength and the robustness to noise. Through the use of active wide band illumination, our system can obtain material reflectance information in the presence of moderate (indoor) unknown ambient illumination. Our method is very simple and does not require special equipment. It can be used by photographers to obtain material properties in uncontrolled environment and to synthesize captured scenes under arbitrary illumination.

Light intensity enhancement by diffracting structures in solar cells

A simplified three-dimensional study is presented of the light confinement, that is, of the enhancement of the Poynting vector of the electromagnetic radiation of the light inside a solar cell absorbing the light weakly when diffracting structures are used. The model is based on the theory of periodic radiation arrays and is easily applied to one- and two-dimensional diffraction gratings. Realistically wide illumination bundles are considered. The extended nature of illumination severely limits the enhancement capabilities of diffraction structures. Results are compared to those of the more widely used Lambertian light confinement.

Characterization and Simple Fixed Pattern Noise Correction in Wide Dynamic Range “Logarithmic” Imagers

Wide dynamic range logarithmic imagers can render naturally illuminated scenes while preserving detail and contrast information at a lower cost than high dynamic range linear sensors. However, the quality of the output is severely degraded by fixed pattern noise (FPN). Although previous FPN correction techniques can eliminate the dominant additive form of this noise, the contrast threshold of the imager over a wide illumination range is poor compared to the human visual system. In this paper, it is shown that a four-parameter model fits the measured characteristic response of wide dynamic range pixels over 11 decades of input current. A comparison of the responses of 200 pixels shows that there are significant variations in all four parameters. A procedure is described that allows the four pixel parameters to be obtained from the response of each pixel to five input currents. However, a much simpler procedure is shown to correct FPN, leading to a contrast threshold comparable to the human visual system over the five decades required to image wide-dynamic-range, naturally illuminated scenes.

Lighting facilities of wide span tunnel illumination

Lighting facilities of wide span tunnel illumination

A novel adaptive logarithmic digital pixel sensor

A major problem associated with complementary metal-oxide-semiconductor and charge couple device imagers is their limited dynamic range (DR), typically 60-70 dB. This falls far short of covering the wide illumination ranges found in natural scenes (typically 120-140 dB). Biological retinas are known to feature adaptive, logarithmic-type responses enabling them to cover a very wide DR, without compromising the resolution. This letter presents a novel way to realize such an adaptive logarithmic response by combining a digital time domain vision sensor and a simple adaptive digital quantizer. This letter presents the theory and experimental results for an adaptive logarithmic response sensor featuring over 100-dB DR

A New Dimming Algorithm for the Electrodeless Fluorescent Lamps

In this paper, a new dimming algorithm for the electronic ballast of an electrodeless fluorescent lamp is proposed. The proposed method is based on the burst dimming method that controls the duty ratio for the two switches of the electronic ballast by intermittently modulated pulse signal. This paper presents a fully digital circuit using an erasable programmable logic device (EPLD). To verify the validity of the proposed method, the implemented control circuit was applied to the electronic ballast for a 100 W electrodeless fluorescent lamp. As a result, a dimming method with a wide illumination range from 5 to 100% was obtained.

Phased-array transmitters for GPR surveys

The antennas commonly used in ground penetrating radar surveys have wide illumination, but limited spatial resolution. To overcome this limitation, we propose the use of phased-array transmitters, which allow us to direct the electromagnetic energy. We first perform a theoretical analysis to determine the influence of the number of antennas, the antenna spacing and the phase shifts between antennas. This analysis is useful to define the direction of the main lobe of the radiation pattern and its width. The simulations, which show the versatility of using phased arrays as compared to a single antenna, have been done to determine the best array parameters to image a given interface. On the basis of these simulations, we acquired common-receiver gathers with two single 100 MHz antennas to simulate a single survey involving 21 phase-shifted transmitter antennas and a single-receiver antenna. We have improved the signal-to-noise ratio, and the lateral coherence of the reflection events, and obtained a greater penetration depth as a consequence of the energy focusing.

Ray Differentials and Multiresolution Geometry Caching for Distribution Ray Tracing in Complex Scenes

Abstract When rendering only directly visible objects, ray tracing a few levels of specular reflection from large, low‐curvaturesurfaces, and ray tracing shadows from point‐like light sources, the accessed geometry is coherentand a geometry cache performs well. But in many other cases, the accessed geometry is incoherent and a standardgeometry cache performs poorly: ray tracing of specular reflection from highly curved surfaces, tracing rays thatare many reflection levels deep, and distribution ray tracing for wide glossy reflection, global illumination, widesoft shadows, and ambient occlusion. Fortunately, less geometric accuracy is necessary in the incoherent cases.This observation can be formalized by looking at the ray differentials for different types of scattering: coherentrays have small differentials, while incoherent rays have large differentials. We utilize this observation to obtainefficient multiresolution caching of geometry and textures (including displacement maps) for classic and distributionray tracing in complex scenes. We use an existing multiresolution caching scheme (originally developed forscanline rendering) for textures and displacement maps, and introduce a multiresolution geometry caching schemefor tessellated surfaces. The multiresolution geometry caching scheme makes it possible to efficiently render scenesthat, if fully tessellated, would use 100 times more memory than the geometry cache size.

On the Spectral Dimensionality of Subject Colors

Three dimensions of aperture color do not suffice some professional applications of color imaging. To improve metameric and low-illumination subject colors, a fourth spectral channel in color films and the multi-spectral systems in the electronic imaging are designed. To evaluate the dimensionality, a mathematical simulation has been performed on the base of the optical mechanism for single-pigment intrareceptor color opponency, which explained color phenomena, inconsistent with the common RGB-cones opponency models. Recent data on the two anatomical parts of outer segment of rod or cone and the spectra of long-living photoproducts at the human body temperature allowed to detect five spectral ranges independently affecting color hues within a wide illumination range. The rhodopsin partial receptors (505 and 535 nm) in the rod perform the yellow-blue separation in the two differential sensitivity ranges parted by the neutral point of protanope or deuteranope at 495 nm. The partial receptors (560 and 610 nm), based by the cone photopigment, did the green-red separation in the three ranges of visible spectrum parted by the neutral points of tritanope at 460 and 575 nm. At least a fourth independent channel has been shown to be required to provide simultaneously all of the colors in a scene for the spectrally-correct reproduction.