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Showing papers on "Angular aperture published in 2000"


Journal ArticleDOI
TL;DR: It is shown that, in the particular case of a tightly focused, radially polarized beam, the polarization shows large inhomogeneities in the focal region, while the azimuthally polarized beam is purely transverse even at very high numerical apertures.
Abstract: Cylindrical-vector beams are of increasing recent interest for their role in novel laser resonators and their applications to electron acceleration and scanning microscopy. In this paper, we calculate cylindrical-vector fields, near the focal region of an aplanatic lens, and briefly discuss some applications. We show that, in the particular case of a tightly focused, radially polarized beam, the polarization shows large inhomogeneities in the focal region, while the azimuthally polarized beam is purely transverse even at very high numerical apertures.

1,472 citations


Journal ArticleDOI
TL;DR: In this article, a method employing ferroelectric monomolecular layers was proposed to measure the light field polarization in the focus of a lens, which allowed to noninvasively establish the perpendicularly oriented focal field that is anticipated at high apertures.
Abstract: We introduce a method employing ferroelectric monomolecular layers, by which it is possible to measure the light field polarization in the focus of a lens. This method allowed us to noninvasively establish the perpendicularly oriented focal field that is anticipated at high apertures. For a numerical aperture 1.4 oil immersion lens illuminated with linearly polarized plane waves, the integral of the modulus square of the perpendicular component amounts to (1.51±0.2) % of that of the initial polarization. It is proven that depolarization decreases with decreasing aperture angle. Whereas for regular imaging conditions depolarization is largely negligible, it plays a significant role in microscopy of highest resolution, microspectroscopy, and single molecule studies.

51 citations


Patent
23 May 2000
TL;DR: In this article, a non-collimating lens attached to the emitting end of a broad-band antenna feed is proposed to receive and focus the broadband wireless signals from any reflector configuration to any antenna feed.
Abstract: An antenna feed system capable of simultaneously transmitting and receiving in multiple frequency bands. In one embodiment, the feed system comprises a non-collimating lens attached to the emitting end of a broad-band antenna feed. The lens is positioned to receive and focus the broad-band wireless signals from any reflector configuration to any antenna feed. It is also positioned to transmit and focus the broad-band wireless signals from any antenna feed to any reflector configuration. A method for illuminating a reflector configuration through an antenna feed with the lens is disclosed. A wireless sensor system is also disclosed. In one embodiment, the non-collimating lens may be used as part of a wireless signal sensor unit used to increase or decrease the angular aperture of the sensor unit.

30 citations


Patent
31 Jan 2000
TL;DR: In this paper, a projection lens for use with LCD or DMD panels is provided, which satisfies the following relationships: f 0 /|f 1 |<0.6; and BFL/f 0 > 0.3 where (i) f 0 is the effective focal length of the combination of the first, second, and third lens units, and (ii) f 1 is the back focal length for an object located at infinity along the long conjugate side of the projection lens.
Abstract: A projection lens for use with LCD or DMD panels is provided. The lens has three lens units, the first unit having a weak power and at least one aspheric surface, the second unit having a positive power, a high dispersion negative lens element, and a low dispersion positive lens element, and the third unit having a negative power, a positive meniscus lens element and a negative lens element. The projection lens satisfies the following relationships: f 0 /|f 1 |<0.6; and BFL/f 0 >0.3 where (i) f 0 is the effective focal length of the combination of the first, second, and third lens units; (ii) f 1 is the effective focal length of the first lens unit; and (iii) BFL is the back focal length of the combination of the first, second, and third lens units for an object located at infinity along the long conjugate side of the projection lens.

29 citations


Journal ArticleDOI
TL;DR: In this article, a non-contact method for measuring aperture areas using a laser beam focused on the aperture surface was described, which implicitly determines the laser focus diameter, so reducing the corresponding uncertainty and making it possible to determine aperture diameter with standard uncertainties of less than 0.2 µm.
Abstract: Beam-limiting apertures with accurately known areas are required when measuring the radiance and irradiance of sources. We have already described a non-contact method for measuring aperture areas using a laser beam focused on the aperture surface. By shifting the aperture relative to the laser beam, and collecting and monitoring the reflected light, the onset of reflection was used to indicate the position of the aperture edges. We have now improved this approach by evaluating the position-dependence of the reflection signal recorded across the aperture edge. Whereas the former approach required a determination of the laser focus diameter to correct the measured aperture diameter, the quantity that makes the main contribution to the overall uncertainty of the aperture area, the new approach implicitly determines the laser focus diameter, so reducing the corresponding uncertainty and making it possible to determine aperture diameters with standard uncertainties of less than 0.2 µm. Measurements made in 1998 for aluminium apertures are compared with results obtained in 1995 using the same apertures.

23 citations


Journal ArticleDOI
TL;DR: It is concluded that it rotates for small beam size and that increasing beam diameter causes the focused distribution to rotate and shear, i.e., to distort, and that the distortion of the distribution increases with increasing numerical aperture.
Abstract: A scalar treatment for Gaussian beams offset from the optic axis and then focused by a high-numerical-aperture lens is presented. Such a theory is required for describing certain types of Doppler microscopes, i.e., when the measurement is simultaneously performed by more than a single beam axially offset and then focused by a lens. Analytic expressions for the intensity in the focal region of the high-aperture lens are derived. From these expressions we calculate the intensity in the focal region with parameters of beam size, beam offset, and the numerical aperture of the lens. The relative location and variation of the intensity around the focal region are discussed in detail. We show that for small-diameter Gaussian beams the Strehl ratio increases above unity as the beam is offset from the optic axis. This is explained by the increase in the effective numerical aperture of the offset beam compared with the one collinear with the optic axis. From examining the focal distribution, we conclude that it rotates for small beam size and that increasing beam diameter causes the focused distribution to rotate and shear, i.e., to distort. We also show that the distortion of the distribution increases with increasing numerical aperture.

19 citations


Patent
Chia-Yu Ai1
20 Oct 2000
TL;DR: In this paper, a wavefront sensor is provided to determine characteristics of an incoming distorted energy beam, such as a tilt angle and/or a degree of focus, and a beam detector detects the resulted focal point(s) of the energy beam passing through the corresponding aperture(s).
Abstract: A wavefront sensor is provided to determine characteristics of an incoming distorted energy beam, such as a tilt angle and/or a degree of focus. The sensor includes a multi-lens array, a screen, and a beam detector. The multi-lens array focuses the energy beam to a multiple focal points. The screen, positioned adjacent to the multi-lens array, has at least one aperture to allow a portion of the energy beam to pass, while blocking the remainder of the energy beam from arriving at the multi-lens array. Each aperture is aligned with a lens of the multi-lens array. The beam detector detects the resulted focal point(s) of the energy beam passing through the corresponding aperture(s) and determines the characteristics of the passing energy beam. The screen may include a central aperture to measure a local tilt angle of a segment of incoming wavefront entering a lens of the lens array. The screen may also include a plurality sets of apertures configured to align in a plurality of directions, each set of apertures measuring a degree of focus of the incoming wavefront along the corresponding direction. The screen may further include a combination of central aperture and a plurality sets of apertures aligned in a plurality of directions to simultaneously measure the local tilt angle and degree of focus of the incoming wavefront.

17 citations


Patent
20 Jun 2000
TL;DR: A viewing enhancement lens (NAIL) as discussed by the authors increases the resolution of a system by a factor between n, and n2, where n is the index of refraction of the lens substrate.
Abstract: A viewing enhancement lens (18 - NAIL) which functions to increase the numerical aperture or light gathering or focusing power of viewing optics such as a microscope (26) used to view structure within a substrate such as a semiconductor wafer or chip or of imaging optics such as media recorders. The result is to increase the resolution of the system by a factor of between n, and n2, where n is the index of refraction of the lens substrate.

13 citations


Journal ArticleDOI
TL;DR: An anomalous behavior in a diffractive lens is shown in which the spot size at the focus reaches a minimum at a numerical aperture of ~0.5 and then increases significantly at higher values, along with a comparison with refractive aplanatic lenses, inWhich the anomaly does not appear to exist.
Abstract: We show an anomalous behavior in a diffractive lens in which the spot size at the focus reaches a minimum at a numerical aperture of ∼0.5 and then increases significantly at higher values. Theoretical and experimental results are presented, along with a comparison with refractive aplanatic lenses, in which the anomaly does not appear to exist.

12 citations


Journal ArticleDOI
TL;DR: In this article, the standard Fresnel diffraction wave field from an aperture in a plane screen is reduced to an aperture edge integral instead, which can be considered as the reduction of the ‘Maggi-Rubinovics’ edge formula from Kirchhoff optics to paraxial (i.e. Fresnel) optics.
Abstract: The standard Fresnel diffraction wave field from an aperture in a plane screen involves an integral over the aperture area. Here it is reduced to an aperture edge integral instead. The reduction really amounts to performing one integral but can be considered as the reduction of the ‘Maggi-Rubinovics’ edge formula from Kirchhoff optics to paraxial (i.e. Fresnel) optics.

12 citations


Patent
11 Jan 2000
TL;DR: A dual lens camera has a lens carrier with a shorter focal length and a longer focal length lens for alternatively positioning only one of the lenses at a picture-taking axis as discussed by the authors.
Abstract: A dual lens camera has a lens carrier with a shorter focal length lens and a longer focal length lens for alternatively positioning only one of the lenses at a picture-taking axis. A single aperture for each one of the lenses is movable forward and rearward along the picture taking axis. The lens carrier is movable forward and rearward along the picture-taking axis in unity with the aperture, and is movable relative to the aperture to position the shorter focal length lens at the picture-taking axis when the aperture is moved rearward along the picture-taking axis and to position the longer focal length lens at the picture-taking axis when the aperture is moved forward along the picture-taking axis.

Proceedings ArticleDOI
22 Oct 2000
TL;DR: In this paper, two focused large angular aperture transducers are used in this technique and received voltage V(x,t) is acquired during the relative transducers translation along the specimen surface.
Abstract: In this paper, a new method for the measurement of the acoustical parameters of the laterally uniform specimen is considered. Two focused large angular aperture transducers are used in this technique. Foci of the transducers are placed on the specimen surface and received voltage V(x,t) is acquired during the relative transducers translation along the specimen surface. Due to geometry of the ultrasonic system, angular range of the generated and detected waves can be close to (0, /spl pi//2) and the length of the recording distance is unlimited. Velocity and attenuation of the leaky wave measured by this method do not depend on the temperature of the immersion liquid. Also, contrary to V(z) method, angular resolution of the V(x,t) method is better for small incident angles.

Patent
20 Oct 2000
TL;DR: In this paper, an aperture card is provided for single surgical use for surgical precautionary considerations and to achieve the highest quality ablations, in addition to reproducibility, in a path between the laser system and the eye.
Abstract: An aperture card is provided for insertion into a laser refractive ablation system for use in laser ablating the cornea. The aperture card is designed for single surgical use for surgical precautionary considerations and to achieve the highest quality ablations, in addition to reproducibility. The aperture card is loaded into the laser refractive ablation system in a path between the laser system and the eye. The aperture card is precisely located by positioning means and ablative lasing action is inhibited if the card is not positioned within tolerance. Alternatively, the laser system can determine the position of the aperture card and adjust a computed ablation profile or otherwise adjust the optical system to adapt for any misalignment of the apertures in the aperture card. The card contains a “soft spot” aperture capable of shaping a spatial intensity distribution with a unique profile. The profile has a substantially flat top while the sides of the profile slope until an ablation intensity threshold is reached, at which point the sides become substantially vertical. The card can contain more than one soft spot aperture along with a “hard spot” aperture that creates a square-shaped profile used for testing fluence. Each soft spot aperture is formed by a central aperture and a plurality of holes of different sizes surrounding the central aperture and arranged such that the overall diffractive effect produces a soft spot spatial intensity profile compared to the hard, square-sided profile.

Patent
16 Nov 2000
TL;DR: The projection lens has a system screen near the last convexity on the image side as mentioned in this paper, where the first negative lens is a concave meniscus on the aperture diaphragm side.
Abstract: The projection lens has a system screen near the last convexity on the image side. The first negative lens following the aperture diaphragm plane in the beam path is a concave meniscus on the aperture diaphragm side. Each constriction has a lens group with negative refractive power; each bulge has a lens group with positive refractive power. At least two and preferably three positive lenses of the lens group of the third bulge are positioned in front of the aperture diaphragm plane. Near the third bulge in front of the aperture diaphragm plane is at least one spherically over-correcting air gap between adjacent lenses.

Patent
Hiroshi Nishikawa1
14 Mar 2000
TL;DR: In this article, a lens inspection system for evaluating an objective lens system of an optical data recording/reproducing device by measuring a wave front of a light beam emerged from the system is provided with a laser source and a conversion lens.
Abstract: A lens inspection system for evaluating an objective lens system of an optical data recording/reproducing device by measuring a wave front of a light beam emerged from the objective lens system is provided with a laser source and a conversion lens. A laser beam is emitted by the laser source, and is incident on the objective optical system of the optical data recording/reproducing device. Further provided is an interferometer for measuring the wave front. A numerical aperture of an objective lens of the interferometer is smaller than a numerical aperture of the objective lens system of the optical data recording/reproducing device. The conversion lens receives the light beam emerged from the objective lens system of the optical data recording/reproducing device and emerges a light beam to the objective lens of the interferometer such that all the light beam emerged from the conversion lens enters the objective lens of the interferometer.

Patent
07 Apr 2000
TL;DR: In this paper, an apparatus for projection lithography with at least one magnetic doublet lens is described, and two magnetic clamps are configured to prevent substantial overlap of the magnetic lens fields.
Abstract: An apparatus for projection lithography is disclosed. The apparatus has at least one magnetic doublet lens. An aperture scatter filter is interposed between the two lenses of the magnetic doublet lens. The aperture scatter filter is in the back focal plane of the magnetic doublet lens system, or in an equivalent conjugate plane thereof. The apparatus also has two magnetic clamps interposed between the two lenses in the magnetic doublet lens. The clamps are positioned and configured to prevent substantial overlap of the magnetic lens fields. The magnetic clamps are positioned so that the magnetic fields from the lenses in the magnetic doublet lens do not extend to the aperture scatter filter.

Patent
04 Feb 2000
TL;DR: In this article, an x-ray radiation source in which a focused electron beam impinges upon a target positioned in front of the focal point of the electron beam and the radiation emitted by the target travels through the aperture of an aperture diaphragm is considered.
Abstract: An x-ray radiation source in which a focused electron beam impinges upon a target positioned in front of the focal point of the electron beam and the radiation emitted by the target travels through the aperture of an aperture diaphragm with the aperture disposed at the focal point of the electron beam.

Patent
30 Aug 2000
TL;DR: An aperture and lens mechanism for a camera includes a rotatably mounted lens barrel supporting a lens and moveable in a direction parallel to the optical axis of the lens in response to rotation as mentioned in this paper.
Abstract: An aperture and lens mechanism for a camera, includes a rotatably mounted lens barrel supporting a lens and moveable in a direction parallel to the optical axis of the lens in response to rotation; an aperture support mounted for movement parallel to the optical axis of the lens and spring biased into contact with the lens barrel for movement therewith; and an aperture blade defining an aperture, the aperture blade being mounted on the aperture support for movement between a first position where the aperture is centered on the optical axis of the lens and a second position away from the optical axis of the lens.

Patent
28 Sep 2000
TL;DR: In this paper, a horn has an input aperture and an output aperture, and comprises a conductive inner surface formed by rotating a curve about a central axis, which is then optimized to provide a mode conversion which maximizes the power transfer of input energy to the Gaussian mode at the output aperture.
Abstract: A horn has an input aperture and an output aperture, and comprises a conductive inner surface formed by rotating a curve about a central axis. The curve comprises a first arc having an input aperture end and a transition end, and a second arc having a transition end and an output aperture end. When rotated about the central axis, the first arc input aperture end forms an input aperture, and the second arc output aperture end forms an output aperture. The curve is then optimized to provide a mode conversion which maximizes the power transfer of input energy to the Gaussian mode at the output aperture.

Patent
17 Mar 2000
TL;DR: In this article, the authors present an imaging tool for use with a mask with features oriented along at least an x-axis or a y-axis where the x axis extends in directions substantially perpendicular to the directions of the y axis.
Abstract: A imaging tool for use with a mask with features oriented along at least an x-axis or a y-axis where the x-axis extends in directions substantially perpendicular to the directions of the y-axis. The tool has a condenser lens and an objective lens. The condenser lens has a condenser aperture with four-sides and four comers that are located in a condenser lens pupil plane. The sides of the condenser aperture are oriented in substantially the same direction as either the x-axis or the y-axis. The condenser lens is positioned to place at least a portion of any illumination on the mask and then into an objective lens pupil plane of the objective lens. At least one of the comers of the condenser aperture in the condenser plate may have a substantially rounded shape. Additionally, the mask may have at least one artifact added to at least one comer of the features for optical proximity correction.

Patent
Shohei Suzuki1
18 May 2000
TL;DR: In this article, an approach for charged-particle-beam (CPB) microlithography using a hollow beam is described, where the charged particle beam is passed through a scattering aperture, and particles incident on the scattering aperture plate are scattered and become a scattered beam.
Abstract: Apparatus and methods are disclosed for charged-particle-beam (CPB) microlithography using a hollow beam. The hollow beam is produced by passing the charged particle beam through a scattering aperture. However, passage of the beam is performed in a manner by which the scattering aperture is prevented from overheating. Also, the scattering aperture can be made from a material that is micro-machined easily. The scattering aperture can be configured as a beam-scattering aperture plate defining voids that collectively define an annular aperture. The scattering aperture is situated at a beam-crossover plane. As the charged particle beam strikes the scattering aperture, particles pass readily through the voids as a “transmitted beam.” Particles incident on the scattering aperture plate are scattered and become a “scattered beam.” The transmitted beam passes readily through a downstream blocking aperture, whereas most particles of the scattered beam are absorbed by the blocking aperture.

Patent
20 Oct 2000
TL;DR: In this article, an aperture card is provided for single surgical use for surgical precautionary considerations and to achieve the highest quality ablations, in addition to reproducibility, for use in laser ablating the cornea.
Abstract: An aperture card is provided for insertion into a laser refractive ablation system for use in laser ablating the cornea. The aperture card is designed for single surgical use for surgical precautionary considerations and to achieve the highest quality ablations, in addition to reproducibility. The aperture card is loaded into the laser refractive ablation system in a path between the laser system and the eye. The aperture card is precisely located by positioning means and ablative lasing action is inhibited if the card is not positioned within tolerance. Alternatively, the laser system can determine the position of the aperture card and adjust a computed ablation profile or otherwise adjust the optical system to adapt for any misalignment of the apertures in the aperture card. The card contains a 'soft spot' aperture capable of shaping a spatial intensity distribution with a unique profile. The profile has a substantially flat top while the sides of the profile slope until an ablation intensity threshold is reached, at which point the sides become substantially vertical. The card can contain more than one soft spot aperture along with a 'hard spot' aperture that creates a square-shaped profile used for testing fluence. Each soft spot aperture is formed by a central aperture and a plurality of holes of different sizes surrounding the central aperture and arranged such that the overall diffractive effect produces a soft spot spatial intensity profile compared to the hard, square-sided profile.

Journal ArticleDOI
TL;DR: A cone of light extending from a centered point on the specimen to the diameter of the objective lens is the Angular Aperture (A.A.). A.A. ranges from 10° for long focus low powered objectives to 140° for short focus high power objectives as discussed by the authors.
Abstract: Microscope immersion oil is used in light microscopy to improve imaging. The use of microscope immersion oil as part of a microscope lens system will produce a brighter and sharper image than a similar design not using immersion oil. The reason is that this oil replaces the air gaps between the condenser and the bottom of the slide and between the top of the slide or cover glass and the objective lens with a medium that has a refractive index equal to the lowest refractive index of these glass components. How does this work? There is a cone of light extending from a centered point on the specimen to the diameter of the objective lens. The angle of this cone is the Angular Aperture (A.A.). A.A. ranges from 10° for long focus low powered objectives to 140° for short focus high power objectives.

Patent
27 Jan 2000
TL;DR: In this paper, a plurality of aperture restriction devices are disposed in the optical path of a light beam that is emitted from a light source and illuminated onto an optical disk by a pair of first partial arcs.
Abstract: An optical pickup device has one or a plurality of aperture restriction devices that are disposed in the optical path of a light beam that is emitted from a light source and illuminated onto an optical disk. The aperture restriction device restricts the cross-sectional shape of the light beam corresponding to the aperture in the time axis direction in comparison to that corresponding to the aperture in the radial direction and restricts the light beam in the radial direction of the optical disk by a pair of first partial arcs.

Patent
20 Oct 2000
TL;DR: In this paper, an aperture card is provided for single surgical use for surgical precautionary considerations and to achieve the highest quality ablations, in addition to reproducibility, for use in laser ablating the cornea.
Abstract: An aperture card is provided for insertion into a laser refractive ablation system for use in laser ablating the cornea. The aperture card is designed for single surgical use for surgical precautionary considerations and to achieve the highest quality ablations, in addition to reproducibility. The aperture card is loaded into the laser refractive ablation system in a path between the laser system and the eye. The aperture card is precisely located by positioning means and ablative lasing action is inhibited if the card is not positioned within tolerance. Alternatively, the laser system can determine the position of the aperture card and adjust a computed ablation profile or otherwise adjust the optical system to adapt for any misalignment of the apertures in the aperture card. The card contains a "soft spot" aperture capable of shaping a spatial intensity distribution with a unique profile. The profile has a substantially flat top while the sides of the profile slope until an ablation intensity threshold is reached, at which point the sides become substantially vertical. The card can contain more than one soft spot aperture along with a "hard spot" aperture that creates a square-shaped profile used for testing fluence. Each soft spot aperture is formed by a central aperture and a plurality of holes of different sizes surrounding the central aperture and arranged such that the overall diffractive effect produces a soft spot spatial intensity profile compared to the hard, square-sided profile.

Patent
09 Mar 2000
TL;DR: In this article, an aperture is enclosed by or is formed in a first mirror surface that reflects the incident light not falling on the aperture to an optical system that feeds the light back to the aperture altered, especially at a different angle, shifted with respect to the incident, and/or magnified or reduced.
Abstract: The arrangement has an aperture that only passes an output light beam or fan with a reduced beam product. The aperture is enclosed by or is formed in a first mirror surface (6) that reflects the incident light (3) not falling on the aperture to an optical system that feeds the light back to the aperture altered, especially at a different angle, shifted with respect to the incident light and/or magnified or reduced. An Independent claim is also included for a cascade of arrangements for improving a beam product.

Patent
21 Dec 2000
TL;DR: In this paper, an objective lens device (20) consisting of one aspherical lens element and one holographic lens element was proposed to compensate for chromatism due to a change in wavelength of laser light.
Abstract: An objective lens device (20) includes an aspherical lens element (21) facing a disk (10) and having a predetermined first focal distance and a predetermined numerical aperture, and a holographic lens (22) installed adjacent to the aspherical lens element (21) and having a second focal distance longer than that of the first focal distance and having a diffraction lattice for compensating for chromatism due to a change in wavelength of laser light having a wavelength of 670 nm or less. Thus, during the shift between recoding and reproduction of a DVD or an HD-DVD, the change in wavelength due to the change in power of the laser light and aberration according to the change can be effectively corrected. Also, since the objective lens device (10) is formed of one aspherical lens element (21) and one holographic lens element (22), the material for each of the lens elements (21, 22) can be easily selected and also the structure of the optical pickup device adopting the objective lens device (20) according to the present invention can be simplified.

Patent
Katsumi Ogino1, 克美 荻野
24 Jan 2000
TL;DR: In this paper, the image of an observation object is observed by scanning with spot light irradiating the observation object through a confocal type microscope, which is provided with the aperture diaphragm by which the numerical aperture of the objective lens is adjusted.
Abstract: PROBLEM TO BE SOLVED: To obtain a maximum-contrast image in a short time by setting an aperture diaphragm corresponding to the height of ruggedness on the surface of a sample. SOLUTION: The image of an observation object is observed by scanning with spot light irradiating the observation object through a objective lens in this confocal type microscope, which is provided with the aperture diaphragm by which the numerical aperture of the objective lens is adjusted and a control part calculating the contrast of the image of the observation object corresponding to the focal position of the objective lens while changing the focal position of the objective lens in an optical axis direction, obtaining the height of the ruggedness on the surface of the observation object from the change of the contrast and setting the aperture diaphragm so that the depth of focus may be nearly equal to the height of the ruggedness. The height of the ruggedness on the surface of the observation object is measured by utilizing the sectioning function of the confocal type microscope and the aperture diaphragm is automatically set so that the depth of focus may be equivalent to the height of the ruggedness of the observation object, so that the optimum-contrast image is obtained in a short time.

Journal ArticleDOI
TL;DR: The theoretical formalism for inversion is algebraic in nature, requires no integral equation, and possesses a number of advantages for the implementation of a Gauss-Newton type of inversion that was used in this study.
Abstract: Reported in this paper are reconstructions of shape and material parameters of two-dimensional, homogeneous, acoustic, penetrable obstacles of arbitrary cross-sections which are immersed in an infinite, homogeneous ambience. Reconstructions are based on the far-field scattering patterns of multiple incident plane acoustic waves. For remotely acquired data, practical necessities require not only that the entire data collection region be less than 2π, but also that each received “sees” the object over as narrow an angular aperture as possible. The inversions presented here were obtained under such conditions. Two types of data were used for each incidence namely, “near-monostatic” fields of narrow angular apertures (the narrowest aperture reported is 2°), and a “duostatic” geometry consisting of backscatter plus one other receiver angle. These data sets were acquired for a series of incident angles. The theoretical formalism for inversion is algebraic in nature, requires no integral equation, and possesses ...

Proceedings ArticleDOI
01 Oct 2000
TL;DR: In this article, perturbing the roots of a Chesley double-difference pattern allows determination of a circular aperture distribution with side lobes of individually adjusted height, which is useful for main beam ECCM applications.
Abstract: The double-difference beam is a four-lobed far-field antenna response formed by an aperture illumination that has an antisymmetrical phase property in both dimensions of a planar antenna. Such a beam is useful for main beam ECCM applications. In this paper, we found that perturbing the roots of a Chesley double-difference pattern allows determination of a circular aperture distribution affording a double-difference pattern with side lobes of individually adjusted height.