Showing papers on "Angular aperture published in 2016"

Optical imaging lens

Abstract: Present embodiments provide for an optical imaging lens. The optical imaging lens comprises a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element positioned in an order from an object side to an image side. Through controlling the convex or concave shape of the surfaces of the lens elements and designing parameters satisfying at least one inequality, the optical imaging lens shows better optical characteristics and enlarge field angle the total length of the optical imaging lens is shortened.

Optical beam shifts in graphene and single-layer boron-nitride

Abstract: Optical beam shifts from a freestanding 2D atomic crystal are investigated. In contrast with a 3D crystal, the magnitude of the Goos–Hanchen shift depends on the surface susceptibility of the crystal and not on the wavelength of the incident light beam. The surface conductivity of the atomically thin crystal is less important in this context because it enters in the expression of the shifts only as a second-order parameter. In analogy to a 3D crystal, the magnitudes of the Imbert–Fedorov shift and of the angular shifts depend, respectively, on the wavelength and on the square of the beam angular aperture.

Optical beam shifts in graphene and single-layer boron-nitride

Abstract: Optical beam shifts from a free-standing two-dimensional atomic crystal are investigated. In contrast to a three-dimensional crystal the magnitude of the Goos-H$\rm \ddot{a}$nchen shift depends on the surface susceptibility of the crystal and not on the wavelength of the incident light beam. The surface conductivity of the atomically thin crystal is less important in this context because it enters in the expression of the shifts only as a second order parameter. In analogy to a three-dimensional crystal the magnitudes of the Imbert-Fedorov shift and of the angular shifts depend respectively on the wavelength and on the square of the beam angular aperture.

A universal design to realize a tunable perfect absorber from infrared to microwaves

Abstract: We propose a design for an universal absorber, characterized by a resonance frequency that can be tuned from visible to microwave frequencies independently of the choice of the metal and the dielectrics involved. An almost perfect absorption up to 99.8% is demonstrated at resonance for all polarization states of light and for a very wide angular aperture. These properties originate from a magnetic Fabry-Perot mode that is confined in a dielectric spacer of λ/100 thickness by a metamaterial layer and a mirror. An extraordinary large funneling through nano-slits explains how light can be trapped in the structure. Simple scaling laws can be used as a recipe to design ultra-thin perfect absorbers whatever the materials and the desired resonance wavelength, making our design truly universal.

High energy electron radiography system design and simulation study of beam angle-position correlation and aperture effect on the images

Abstract: A beam line dedicated to high-energy electron radiography experimental research with linear achromat and imaging lens systems has been designed. The field of view requirement on the target and the beam angle-position correlation correction can be achieved by fine-tuning the fields of the quadrupoles used in the achromat in combination with already existing six quadrupoles before the achromat. The radiography system is designed by fully considering the space limitation of the laboratory and the beam diagnostics devices. Two kinds of imaging lens system, a quadruplet and an octuplet system are integrated into one beam line with the same object plane and image plane but with different magnification factor. The beam angle-position correlation on the target required by the imaging lens system and the aperture effect on the images are studied with particle tracking simulation. It is shown that the aperture position is also correlated to the beam angle-position on the target. With matched beam on the target, corresponding aperture position and suitable aperture radius, clear pictures can be imaged by both lens systems. The aperture is very important for the imaging. The details of the beam optical requirements, optimized parameters and the simulation results are presented.

Full-wavefield marine survey design using all multiples

Abstract: Despite a tremendous leap in efficiency and wavefield sampling over the past two decades, it is sometimes still difficult to achieve adequate coverage and resolution with marine streamer acquisition. It is therefore necessary to carefully study the acquisition geometry, especially with respect to resolution and image quality in the crossline direction. We have extended the existing focal beam method to analyze marine streamer geometries with and without using all multiples. The focal beam analysis method provides a direct link between the acquisition parameters at the surface (number of sources, source locations, number of detectors, detector locations, and which sources are sensed by which detectors) and the image quality at a target location in the subsurface. We have further derived the concept of weighted focal beams to assess the angular aperture available for a specific acquisition configuration at the considered depth point. So far, this method has only addressed illumination by primaries. ...

Simulation of aperture-optimised refractive lenses for hard X-ray full field microscopy

Abstract: The aperture of refractive X-ray lenses is limited by absorption and geometry. We introduce a specific simulation method to develop an aperture-optimized lens design for hard X-ray full field microscopy. The aperture-optimized lens, referred to as Taille-lens, allows for high spatial resolution as well as homogeneous image quality. This is achieved by the individual adaptation of the apertures of hundreds of lens elements of an X-ray imaging lens to the respective microscopy setup. For full field microscopy, the simulations result in lenses with both a large entrance and exit aperture and lens elements with smaller apertures in the middle of the lens.

Optical system and imaging system

Abstract: An optical system, which may include a fish-eye lens including a whole view angle larger than 180 degrees, includes in order from an object-side to an imaging-side, a first lens group including a negative focal distance, an aperture, and a second lens group including a positive focal distance An infrared cutting coat is coated on a lens surface that includes curvature of a lens among lenses included in the second lens group

Resolution in crosswell traveltime tomography: The dependence on illumination

Abstract: The key aspect limiting resolution in crosswell traveltime tomography is illumination, a well-known result but not well-exemplified. We have revisited resolution in the 2D case using a simple geometric approach based on the angular aperture distribution and the Radon transform properties. We have analytically found that if an isolated interface had dips contained in the angular aperture limits, it could be reconstructed using just one particular projection. By inversion of synthetic data, we found that a slowness field could be approximately reconstructed from a set of projections if the interfaces delimiting the slowness field had dips contained in the available angular apertures. On the one hand, isolated artifacts might be present when the dip is near the illumination limit. On the other hand, in the inverse sense, if an interface is interpretable from a tomogram, there is no guarantee that it corresponds to a true interface. Similarly, if a body is present in the interwell region, it is diffusely imaged, but its interfaces, particularly vertical edges, cannot be resolved and additional artifacts might be present. Again, in the inverse sense, there is no guarantee that an isolated anomaly corresponds to a true anomalous body, because this anomaly could be an artifact. These results are typical of ill-posed inverse problems: an absence of a guarantee of correspondence to the true distribution. The limitations due to illumination may not be solved by the use of constraints. Crosswell tomograms derived with the use of sparsity constraints, using the discrete cosine transform and Daubechies bases, essentially reproduce the same features seen in tomograms obtained with the smoothness constraint. Interpretation must be done taking into consideration a priori information and the particular limitations due to illumination, as we have determined with a real data case.

Angle-invariant imaging using a total internal reflection virtual aperture.

Abstract: Conventional lens stops, implemented with an absorptive physical aperture, have an angle-dependent projection that introduces field dependent loss and reduces diffraction-limited resolution. Retro-telephoto lenses obtain uniform response using aberration vignetting, but this results in low wide-angle resolution and significant lens volume. However, an angle-independent "virtual" aperture can be created by total internal reflection (TIR) from a thin low index layer inside the lens. We apply this to monocentric wide-angle imaging and find a simple relationship between the filtering layer index and radius and the resulting lens F/#. We provide two detailed designs of lenses with 12 mm focal length and a F/2.5 TIR stop, one using a low index adhesive within a solid fixed-focus lens, the other using an air cavity within an adjustable focus lens. We show the designs provide absolutely uniform resolution and light collection over an angle range of 84° and 106°, respectively, resulting in a dramatic improvement of both light collection and angular resolution per unit volume over conventional wide-angle lenses.

Optical aperture area determination for accurate illuminance and luminous efficacy measurements of LED lamps

Abstract: The measurement uncertainty of illuminance and, consequently, luminous flux and luminous efficacy of LED lamps can be reduced with a recently introduced method based on the predictable quantum efficient detector (PQED). One of the most critical factors affecting the measurement uncertainty with the PQED method is the determination of the aperture area. This paper describes an upgrade to an optical method for direct determination of aperture area where superposition of equally spaced Gaussian laser beams is used to form a uniform irradiance distribution. In practice, this is accomplished by scanning the aperture in front of an intensity-stabilized laser beam. In the upgraded method, the aperture is attached to the PQED and the whole package is transversely scanned relative to the laser beam. This has the benefit of having identical geometry in the laser scanning of the aperture area and in the actual photometric measurement. Further, the aperture and detector assembly does not have to be dismantled for the aperture calibration. However, due to small acceptance angle of the PQED, differences between the diffraction effects of an overfilling plane wave and of a combination of Gaussian laser beams at the circular aperture need to be taken into account. A numerical calculation method for studying these effects is discussed in this paper. The calculation utilizes the Rayleigh–Sommerfeld diffraction integral, which is applied to the geometry of the PQED and the aperture. Calculation results for various aperture diameters and two different aperture-to-detector distances are presented.

Ultra-wide angle lens design with relative illumination analysis

Abstract: An ultra-wide angle lens design with relative illumination analysis is presented. The half field angle of 80°, the relative illumination of the image plane will be reduced. It is necessary to increase the image numerical aperture ratio for X and Y direction, and decrease the angle between the chief ray and optical axis in the image space. However the ultra-wide angle lens induces great barrel distortion causing image extrusion. Therefore, we use F-theta distortion to replace optical distortion. Seven lenses and two pieces of flat glass are used for a sensor 1/6” sensor with 2.1 million pixels. The final result for the lens is a half viewing angle of 80°, F/2.4, a focal length 1.1 mm, a length of 22.37 mm, F-theta distortion of less than 2%, and relative illumination greater than 83%.

Wave processes in the near-field zone of large aperture antenna

Abstract: Theoretical investigation of the amplitude and phase vectors of the electric and magnetic field in near and intermediate zones of the observation of large aperture antennas electrical sizes. It is shown that is formed near such searchlight beam antennas, wherein the amplitude of the wave is about the same as in the middle of the radiating aperture of the antenna, regardless of its size.

Structural-optical integrated analysis on the large aperture mirror with active mounting

Abstract: Deformation of the large aperture mirror caused by the external environment load seriously affects the optical performance of the optical system, and there is a limit to develop the shape quality of large aperture mirror with traditional mounting method. It is effective way to reduce the optical mirror distortion with active support method, and the structural-optical integrated method is the effective means to assess the merits of the mounting for large aperture mirror. Firstly, we proposes a new support scheme that uses specific boundary constraints on the large lens edges and imposes flexible torque to resist deformation induced by gravity to improve surface quantity of large aperture mirror. We calculate distortion of the large aperture mirror at the edges of the flexible torque respectively with the finite element method; secondly, we extract distortion value within clear aperture of the mirror with MATLAB, solve the corresponding Zernike polynomial coefficients; lastly, we obtain the peak-valley value (PV) and root mean square value (RMS) with optical-structural integrated analysis . The results for the 690x400x100mm mirror show that PV and RMS values within the clear aperture with 0.4MPa torques than the case without applying a flexible torque reduces 82.7% and 72.9% respectively. The active mounting on the edge of the large aperture mirror can greatly improve the surface quality of the large aperture mirror.

Super-wide angle lens and photographing lens having the same

Abstract: A super-wide angle lens and a photographing apparatus including the super-wide angle lens are provided. The super-wide angle lens includes a first lens having a negative refractive power and a second lens having a positive refractive power, wherein the first lens and the second lens are disposed in sequential order from an object side to an image side, and wherein the super-wide angle lens has a half view angle of 80 degrees or greater.

The solid angle (geometry factor) for a spherical surface source and an arbitrary detector aperture

Abstract: It is proved that the solid angle (or geometry factor, also called the geometrical efficiency) for a spherically symmetric outward-directed surface source with an arbitrary radius and polar angle distribution and an arbitrary detector aperture is equal to the solid angle for an isotropic point source located at the center of the spherical surface source and the same detector aperture.

Multiple charged particle beam apparatus

Abstract: A multiple charged particle beam apparatus includes: a first aperture array substrate to form multiple beams; a first grating lens that constitutes a concave lens by using the first aperture array substrate as a grating; a second aperture array substrate that allows the multiple beams to pass through; and a first limiting aperture substrate arranged in a position of a convergent point of the multiple beams between the first aperture array substrate and the second aperture array substrate, wherein a first aperture array image having passed through the first shaping aperture array substrate is formed on the second aperture array substrate by a lens action including a magnetic field distribution generated between the first aperture array substrate and the second aperture array substrate and having opposite signs and same magnitude and an electric field distribution generated by the first grating lens.

Etendue-preserving light coupling system having light output aperture smaller than light input aperture

Abstract: This disclosure provides systems, methods and apparatus for providing illumination. In one aspect, an etendue preserving optical coupling system configured to: receive incident light through an input aperture; and emit the incident light through an output aperture having an area smaller than an area of the input aperture is provided. The light output from the optical coupling system is coupled into a light receiving system including material having substantially the same refractive index as the refractive index of the material of the optical coupling system. The light receiving system includes a light guide configured to internally propagate the redirected light and to release light to illuminate the ambient environment.

Acoustic measurements in the far field during QM-2 solid rocket motor static firing

Abstract: The five-segment Space Launch System solid rocket motor was recently tested at Orbital ATK. Far-field acoustical measurements were performed at angles between 80° and 120° relative to the rocket exhaust at a distance of roughly 2500 m from the rocket, approximately 800 nozzle diameters. The angular aperture allows for evaluating spatial variation in acoustic properties and a comparison with similar tests in the past, including the 2015 test of the same rocket motor. Although terrain variations introduce uncertainty, an approximate 10 dB change in level is seen throughout the aperture, consistent with previous studies. In addition, at low frequencies a high degree of correlation is seen. Near the peak radiation direction high levels of derivative skewness indicate significant shock content and crackle. This dataset also presents the opportunity to test a new method for processing acoustic vector intensity. [Thomas et al., JASA 137, 3366-3376 (2015)] Comparison with the traditional method shows an increase ...

Plane wave diffraction by a large rectangular aperture in a thick conducting screen

Abstract: Based on the application of the exact solution for the plane wave diffraction by a rectangular hole, the transmission property of a rectangular aperture less than the half-wavelength is investigated by calculating the transmitted power for various aperture sizes and screen's thicknesses, and we derive a useful formula for predicting the transmitted power by fitting lines to the asymptotes of the plots of the transmission coefficients. We also visualize the power flow near the aperture by means of the 2D vector plot and the behavior of the diffracted wave is examined. The results for various screen's thicknesses and aperture sizes provide some understanding of the diffraction phenomena for the strong power transmission.

Shielding effectiveness of enclosures with aperture arrays excited by obliquely incident plane wave

Abstract: An accurate model is developed to predict the shielding effectiveness of enclosures with aperture arrays. The impedance of the aperture array is expressed as a function of the spacing between apertures, the diameter of apertures, the incident angle, and the thickness of the perforated plate. The model outperforms the traditional models in that it can consider the thickness of the perforated plate, the spacing between apertures, the mutual coupling between apertures, the incident angle, and the polarization angle at the same time.

Influence of frequency on sub-mirror apertures and the surrounded apertures for the Golay3 sparse aperture

Abstract: This paper analyzes the modulation transfer function of three sub-mirror sparse aperture optical system (Golay3) among the low contrast with the central part, the side lobe peak and the sub-mirror aperture. It is shown that the sparse aperture system can be achieved higher frequency information while the optical imaging system is designed and the side lobe is moved or low contrast of the central part is reduced or contrast of the higher frequency part is increased by changing the position of sub mirrors or size of surrounded apertures.

Frequency performance of 4-layer discretized Luneburg antennas

Abstract: A series of 8λ 0 to 14λ 0 radius 4-layer stepped approximation Luneburg lenses were designed for the same scalar feed positioned at 1.1 lens radii. The relative permittivities and normalized thicknesses of the matching layers of each lens were close but not equal. The lenses were simulated in commercially available full wave simulators. The aperture efficiencies decreased as the lens radii was increased, showing that minor variations in layer thickness and relative permittivity were unable to compensate for decreased excitation aperture illumination. Achieving high aperture efficiencies requires optimization of both lens and feed, the best here been 80% across 15% bandwidth for the 8λ 0 lens. The peak cross-polarized radiation within the main lobe was found to be in the 45° plane and to be an artifact of the scalar feed, and not the lens designs.

Equivalent plane of reflection in graphene and single-layer Boron-Nitride

Abstract: Optical beam shifts from a free-standing two-dimensional atomic crystal are investigated In contrast to a three-dimensional crystal the magnitude of the Goos-H$\rm \ddot{a}$nchen shift depends on the surface susceptibility of the crystal and not on the wavelength of the incident light beam The surface conductivity of the atomically thin crystal is less important in this context because it enters in the expression of the shifts only as a second order parameter In analogy to a three-dimensional crystal the magnitudes of the Imbert-Fedorov shift and of the angular shifts depend respectively on the wavelength and on the square of the beam angular aperture

Numerical optimization of the discrete Mikaelian lens

Abstract: The method of the inhomogeneous Mikaelian lens constructing is presented and investigated. The lens is implemented as a discrete medium which is a stack of figured layers of certain geometry, similar to flower with petals. The dependence of aperture efficiency on layer thickness t and the number of the "petals" N was investigated. It was found that discontinuities of the discrete structure representing the lens can exceed the wavelength still retaining high value of aperture efficiency. It was demonstrated that numerical optimization of "petal" profile along with anisotropy accounting can significantly increase the aperture efficiency of the Mikaelian lens.

Design of adjustable laser beam high-resolution particle size measuring lens

Abstract: On the basis of research on the theory of the Fourier transform lens, according to the observation and test requirements of a fine particle and the geometrical optics aberration theory, a particle size measuring lens of adjustable high resolution laser beam that worked for wavelength of 660 nm is designed, the laser beam can be controlled through the aperture adjusting device of the lens, and can high definition imaging for the semiconductor fiber laser that core diameter is 4.5μm, numerical aperture N.A is 0.13, the output wavelength is 660nm. In the case of object distance for the next 129.5mm, the spot diameter approximately equal to the theoretical amplification value, the main image spot is clear and no flare.

Investigation on beamwidth reduction of aperture radiation with anisotropic ENZ metamaterials

Abstract: The aperture radiation of TEM mode waveguide of two different sizes has been studied. Simulated results show that when the aperture is covered with an effective bulk epsilon-near-zero (ENZ) metamaterial block with the component along the normal of the aperture of the permittivity tensor approaching zero, the beamwidth of the E-plane can be significantly reduced. The effective bulk ENZ block has been implemented by the electric-LC-resonator (ELC) array as well.

Optimization of transmit parameters for two-dimensional cardiac strain estimation with coherent compounding in silico, in vitro, and in vivo

Abstract: Coherent compounding has been investigated as a possible means of increasing strain estimation accuracy while retaining high frame rate; however, the optimal parameters that yield the best strain estimate have yet to be determined. Three transmit parameters were investigated: the number of transmits, the subaperture size, and the angular aperture. Field II simulations of an annular region mimicking cross-sectional views of the systolic left ventricle were imaged. The highest number of transmits evaluated (15), the smallest subaperture (11 elements), and the narrowest angular aperture (60°) were found to yield the smallest axial and lateral interframe strain errors. A hemiellipsoid PVA phantom was inflated and deflated in a water tank to generate wall strain, and the in silico results were corroborated by the phantom results. Finally, a canine infarct model was employed wherein the LAD was ligated, and open chest images of the myocardium were acquired four days later. In silico and in vivo results were used to design an optimized compounding sequence featuring 11 transmits, a 21 element subaperture, and a 90° angular aperture. Based on TTC staining of the excised heart, the optimized sequence was able to distinguish between healthy and infarcted tissue, whereas the single diverging wave sequence incorrectly estimated strain in several regions. This optimization study indicates that a higher number of transmits, a small subaperture, and a narrow angular aperture yield the most accurate strain estimate.