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Showing papers on "Angular aperture published in 1990"


Journal ArticleDOI
M.A. Kumakhov1
TL;DR: In this article, the basic concepts of multiple reflection X-ray optics were formulated and a broad angular aperture was shown, i.e., of the order of many times the angles of total external reflection.

309 citations


Journal ArticleDOI
J.J. Maciel1, L.B. Felsen
TL;DR: In this article, the authors studied the high-frequency propagation of electromagnetic wavefields from an extended planar aperture distribution through a complicated environment, and showed that narrow-waisted beams can reconstruct the correct transmitted field in these cases, as established independently by numerical evaluation of an exact spectral integral.
Abstract: High-frequency propagation of electromagnetic wavefields from an extended planar aperture distribution through a complicated environment is addressed. Geometric optical ray tracing provides a versatile approximate approach to the class of problems, but it fails in transition regions surrounding shadow boundaries and caustics. The uniformity required there can be established by field tracking with Gaussian beams. The basic theory is summarized and applied to the two-dimensional test problem of transmission of radiation from a finite one-dimensional plane aperture through a planar dielectric layer. For a truncated uniform or focused aperture illumination, tracking the edge or caustic transition regions through the layer when it is located within the Fresnel zone of the aperture poses a problem of substantial complexity. It is shown that narrow-waisted beams, which can be propagated in their far zone as complex ray fields, reconstruct the correct transmitted field in these cases, as established independently by numerical evaluation of an exact spectral integral. >

65 citations


Journal ArticleDOI
J.J. Maciel1, L.B. Felsen
TL;DR: In this article, the authors apply the theory developed in pt.I of this paper for transmission of fields from an extended planar aperture through a plane dielectric layer is applied to transmission from such an aperture through an arbitrarily located cylindrical layer.
Abstract: For pt.I see ibid., vol.38, no.10, p.1607-17 (1990). The theory developed in pt.I of this paper for transmission of fields from an extended planar aperture through a plane dielectric layer is applied to transmission from such an aperture through an arbitrarily located cylindrical dielectric layer. By the self-consistency considerations enunciated previously, it is argued that the narrow-beam algorithm for near and far zone fields is truly predictive, although no other reference solution is now available for an independent check. As in pt.I, the aperture distributions are smoothly tapered or abruptly truncated, and they may generate beam tilts and focusing in the layer or its vicinity. >

39 citations


Patent
15 Feb 1990
TL;DR: In this article, a spatial light modulator is disclosed with a first lens array disposed adjacent to a matrix of light modulators, and in proximity to a liquid crystal light valve containing a photoconductive element.
Abstract: A spatial light modulator is disclosed with a first lens array disposed adjacent to a matrix of light modulators, and in proximity to a liquid crystal light valve containing a photoconductive element. Low intensity light is collimated by a lens element to illuminate an optical aperture which has geometric configuration similar to that of the matrix element. The first lens array focuses light from the illuminated aperture into the pupil of a matrix addressed spatial light modulator element. The second lens array collects light emitting from the light modulator element, and focuses the image of the aperture onto the photoconductive element of the liquid crystal light valve so as to preserve the geometrical and positional configuration of the optical aperture, and magnify the size of the illuminated region on the photoconductor. The design of the optics is such that when adjacent apertures are imaged onto the photoconductor, the proximate boundaries of the illuminated regions are contiguous.

39 citations


Journal ArticleDOI
TL;DR: The wave-front diffraction integral was developed for both the classical paraxial and the recently developed exact solutions to the scalar wave equation for a Gaussian beam as mentioned in this paper.
Abstract: The Huygens–Fresnel diffraction integral has been formulated for incident Gaussian laser beams by using the Kirchhoff obliquity factor with the wave front instead of the aperture plane as the surface of integration. Accurate numerical-integration calculations were used to investigate the Fresnel field diffraction region for the much-studied case of a circular aperture. It is shown that the classical aperture-plane formulation becomes inaccurate when the wave front, as truncated at the aperture, has any degree of curvature to it, whereas the newly developed wave-front formulation produces accurate results for as much as one aperture diameter behind the aperture plane. The wave-front diffraction integral was developed for both the classical paraxial and the recently developed exact solutions to the scalar wave equation for a Gaussian beam. Detailed comparisons of these two diffraction solutions show that they are essentially identical for the typical laboratory laser. The typical laboratory laser is defined as having a wavelength in the near-infrared-through-visible range, a beam diameter as large as several millimeters, and a beam divergence angle as large as several milliradians.

18 citations


Patent
24 Dec 1990
TL;DR: In this paper, a radial GRIN lens element having a concave surface on the image side and a positive refractive power at the most image side location in the third lens component was designed to have a high aperture ratio and favorably corrected coma.
Abstract: An imaging lens system comprising, in the order from the object side, a first lens component having a convex surface on the object side and a positive refractive power, a second lens component having a concave surface on the image side and a negative refractive power, and a third lens component. Through the imaging lens system is of a triplet or Tessar type, the lens system is designed so as to have a high aperture ratio and favorably corrected coma by arranging a radial GRIN lens element having a concave surface on the image side and a positive refractive power at the most image side location in the third lens component.

18 citations


Patent
22 Oct 1990
TL;DR: In this article, a ring reticle is interposed in the optical path between the light source and the lens at a distance from the lens substantially equal to its focal length, which is indicative of the tilt of the surface around an axis essentially perpendicular to the axis of the incident light.
Abstract: In the distance and tilt sensing apparatus disclosed herein, an image of a light source is projected by a lens obliquely onto a surface to be sensed. A ring reticle is interposed in the optical path between the light source and the lens at a distance from the lens substantially equal to its focal length. A second lens projects a remote image of the first object image onto a detector. The light projected from the second lens is split into two paths. An aperture reticle is interposed in one of the paths at a distance from the second lens substantially equal to its focal length, an image of the center of the ring reticle being formed on the aperture reticle. A position responsive optical detector aligned with the aperture reticle senses the position of the image of the center of the ring reticle relative to the center of the aperture and that position is indicative of the tilt of the surface around an axis essentially perpendicular to the axis of the incident light.

14 citations


Patent
11 May 1990
TL;DR: In this article, a linear senor is used to project and shift an image of a target onto a linear sensor, in such a way that the field of acquisition of the homing device has a section, by a plane perpendicular to the line of sight, that is ring-shaped having a diameter corresponding to a wide field aperture at the moment when the missile is launched, so that the target is definitely intercepted in the field-of-acquisition, and then having diameter that is variable as a function of time.
Abstract: The disclosed device can be used to determine coordinates expressing the angular deviation between the direction in which a missile is located and a line of sight in which a target is located. The device comprises means to project and shift an image on a linear senor, in such a way that the field of acquisition of the homing device has a section, by a plane perpendicular to the line of sight, that is ring-shaped having a diameter corresponding to a wide field aperture at the moment when the missile is launched, so that the missile is definitely intercepted in the field of acquisition, and then having a diameter that is variable as a function of time in such a way that the ring follows the missile as and when it approaches the line of sight through the action of a remote control system or a directive beam system. Finally, the section of the field is reduced to a simple disk, corresponding to a field having a very small angular aperture, giving a better range than standard homing devices and giving a low probability of false alarms arising out of the presence of the sun or of decoys. The device can be applied to weapons systems.

14 citations


Journal ArticleDOI
TL;DR: In this article, a self-aligned quadrupole correction lens with lower aperture aberration coefficients was developed for an electron-beam lithography system, which consists of three-stage electrostatic quadrupoles, and aperture electrodes placed between quadrapoles.
Abstract: A new type of quadrupole correction-lens system with lower aperture aberration coefficients has been developed for an electron-beam lithography system. The new lens is called a self-aligned quadrupole correction lens and consists of three-stage electrostatic quadrupoles, and aperture electrodes placed between quadrupoles. An octupole field for correction of aperture aberration is automatically created and aligned with a quadrupole field by supplying a voltage to the aperture electrode, and it has its peak near the edge portion of the quadrupole. A new mechanical construction of the quadrupole correction-lens system is developed for realizing high-precision alignment of the multistage lens electrodes. The optical properties of the new correction lens are exactly calculated by using simulated potential distributions. Aperture aberration coefficients of the new correction lens can be corrected to less than 0.1 mm. It is confirmed experimentally that the probe size is improved remarkably by excitations of the aperture electrodes.

13 citations


Patent
15 May 1990
TL;DR: In this article, the authors proposed a dry objective for microscopes in which aperture aberration is corrected, at the same time, both for the visible spectrum and for a selected UV-wavelength.
Abstract: An UV-capable dry objective for microscopes in which aperture aberration is corrected, at the same time, both for the visible spectrum and for a selected UV-wavelength. The objective comprises two lens groups separated by an air gap which is varied in size by relative movement between the two lens groups. The size of the air gap is adjusted to correct aperture aberration for the selected UV-wavelength. The objective is designed so that the mathematical sign is the same for both (i) the corrections required as the illumination moves toward the longer-wave portion of the visible spectrum, and (ii) for the corrections required as the illumination moves toward the shorter-wave portion of the UV-spectrum. The objective has an aperture of at least 0.7 and a magnification of more than 60×.

11 citations


Patent
Mitsugu Sato1
28 Mar 1990
TL;DR: In this article, a field emission scanning electron microscope (FESEM) was used to detect deviations of the focal point taking place in accompanying a change of a virtual electron source position caused by the control of the probe current.
Abstract: A field emission scanning electron microscope in which an aperture plate (4) is disposed in a high-vacuum region between an accelerating electrode (3) and a condenser lens (5). Since a probe current can not be controlled by a lens system with the abovementioned structure, the probe current is controlled by controlling an extracting voltage applied to an extracting electrode (2). Deviation of the focal point taking place in accompanying a change of a virtual electron source position as brought about by the control of the probe current is corrected by controlling the focal length of a condenser lens (5) such that the electron beam has a constant spread on the principal plane of an objective lens (8) to thereby maintain a beam aperture angle (αi) at a specimen (9) to be constant.

Proceedings ArticleDOI
K. Wu1, S. Parekh
07 May 1990
TL;DR: In this article, a method of transforming Fresnel-region fields to far region fields for circular aperture antennas consisting of arbitrary aperture field distributions is presented. But this method can be directly applied to a planar antenna of any shape by defining the aperture diameter as the largest dimension of the antenna.
Abstract: A method of transforming Fresnel-region fields to far-region fields for circular aperture antennas consisting of arbitrary aperture field distributions is presented. In addition, this method can be directly applied to a planar antenna of any shape by defining the aperture diameter as the largest dimension of the antenna. The accuracy of this technique was demonstrated on a 32-element planar array. >

Patent
17 Apr 1990
TL;DR: In this paper, the conic constants of those aspherical surfaces are specified as shown by inequalities I - 3 and I - 4 for wide field angle, high contrast, and high aperture efficiency.
Abstract: PURPOSE: To obtain the lens which is bright and has a wide field angle and superior resolving power by making a 1st, a 6th, and a 10th lens surfaces, which are counted from the object side, aspherical and specifying the conic constants of those aspherical surfaces CONSTITUTION: A 1st group consists of the 1st positive lens 10 and a 2nd negative lens 12, a 2nd group consists of a 3rd meniscus lens 14 which has a convex surface of the object side, and a 3rd group consists of a 4th meniscus lens 18 which has a convex surface of the image side and the 6th positive lens 20 Further, a 5th group is a 7th lens 22 which is parallel plane glass, ie cover glass for the photodetection surface of a solid image pickup element in concrete, and a stop 15 is arranged between the 3rd lens 14 constituting the 2nd group and the 4th lens 16 constituting the 3rd group Then the 1st, 6th, and 10th lens surfaces which are counted from the object side are made aspehrical and the conic constants of those aspehrical surfaces are specified as shown by inequalities I - 3 Consequently, the wide field angle, a high contrast, and high aperture efficiency are obtained COPYRIGHT: (C)1991,JPO&Japio

Patent
30 Nov 1990
TL;DR: In this article, the authors proposed to prevent a deterioration in image quality by forming a thin noble metal film such as platinum on an aperture plate by means of ion sputter coating or the like.
Abstract: PURPOSE: To prevent a deterioration in image quality by forming a thin noble metal film such as platinum on an aperture plate by means of ion sputter coating or the like. CONSTITUTION: In an aperture device for determining an angular aperture of an electron beam applied apparatus, after an aperture plate 2 is subjected to heating (approximately 2000°C) in a vacuum, a thin noble metal film 7 such as platinum is formed on a surface of the aperture plate 2 by means of ion sputter coating or the like. Since noble metal such as platinum is applied on the surface of the aperture plate 2 as a result, good conductivity can be provided even if an oxide film 5 or the like exists on the aperture plate 2, and also such a structure that the oxide film 5 or the like is not likely to be formed can be obtained. Thus a deterioration in image quality in a low acceleration voltage region can be prevented, while reliability and performance of the device can be largely improved. COPYRIGHT: (C)1992,JPO&Japio

Patent
13 Feb 1990
TL;DR: In this article, a wide-angle objective for a picture-taking lens of an aerial mapping camera, consisting of 11 lenses and 14 glass-air surfaces, is presented, where the first optical element of which after the center aperture on the picture side is a converging fluorspar or fluorpar-like lens.
Abstract: A wide-angle objective for a picture-taking lens of an aerial mapping camera, consisting of 11 lenses and 14 glass-air surfaces, the first optical element of which after the center aperture on the picture side is a converging fluorspar or fluorspar-like lens. Due to the large refractive index difference between this lens and the following meniscus lens and due to the provision of a triple group of high refractive index on the object side before the center aperture, a high resolution, low residual distortion and minimal lateral chromatic aberration are achieved.

Patent
17 Oct 1990
TL;DR: In this article, an electron beam lithography apparatus consisting of an upper aperture, a lower aperture, an optical lens for converging the electron beam passed through the lower aperture onto a specimen, and means for measuring an electron reflected from a position mark installed on a stage, calculating a correction value of the section and the measured reflectional electron and controlling the deflector according to the correction value.
Abstract: An electron beam lithography apparatus comprising an upper aperture, a lower aperture, a deflector disposed between the upper aperture and the lower aperture, an optical lens for converging the electron beam passed through the lower aperture onto a specimen, and means for measuring an electron reflected from a position mark installed on a stage when the electron beam scans the position mark, calculating a correction value of the section and the measured reflectional electron and controlling the deflector according to the correction value. As the shapes of the electron beam are corrected by detecting the reflectional electron from the position mark and measuring the positional error of the sectional shape of the electron beam corresponding to the set sectional shapes, the sectional shapes are corrected in high accuracy.

01 Jan 1990
TL;DR: In this paper, an enhanced elliptical aperture (EA) lens was developed for large screen color picture tubes and the effective lens diameter of the EA lens was 10.4mm, 30% larger than that of a conventional EA lens.
Abstract: An enhanced EA (elliptical aperture) lens gun is developed for large screen color picture tubes. The effective lens diameter of the enhanced EA lens is 10.4mm, 30% larger than that of a conventional EA lens. This increase in lens diameter reduces spherical aberration and, thus, spot diameter. Spot diameter at center of the screen is about 20% smaller with the enhanced EA lens than that with the conventional lens. At the screen periphery, the spot diameter is also reduced by aid of an improved dynamic quadrupole lens system. The structure of the quadrupole lens is quite simple and easy to assemble, and a high sensitivity to correct deflection defocusing (astigmatism and field curvature) is achieved. With application of a dynamic voltage under 1 kVp-p, the aorrection can be acomplished over the entire area of the screen. Dimensions of elliptical apertures and the quadrupole lens are optimized with help of a 3-dimensional electron beam simulation.

Proceedings ArticleDOI
07 May 1990
TL;DR: In this article, the spherical reflector antenna of the Arecibo Observatory will be provided with a new dual-reflector feed to provide an illuminated aperture with an elliptical shape.
Abstract: The spherical reflector antenna of the Arecibo Observatory will be provided with a new dual-reflector feed. The author discusses how to synthesize this dual-reflector feed to provide an illuminated aperture with an elliptical shape. It is shown that an elliptical aperture can give 0.85 dB more gain than a circular aperture. >

Patent
Robert Alan Hoult1
25 Oct 1990
TL;DR: In this paper, an optical grating is formed of alternating transparent and opaque stripes having equal widths having respective subpluralities of the stripes located in an aperture area in the aperture plane, so that incident light rays on the aperture area are at least partially passed as beams by the transparent strips.
Abstract: In optical device for measuring displacement an optical grating is formed of alternating transparent and opaque stripes having equal widths. The grating is in an aperture plane with the stripes parallel to a central plane that is perpendicular to the aperture plane. Respective subpluralities of the stripes are located in an aperture area in the aperture plane, so that incident light rays on the aperture area are at least partially passed as beams by the transparent strips in the aperture area. A concave mirror has it center of curvature at the aperture area so as to return the beams back to the aperture area. The return beams are further passed by the transparent strips in the aperture area as return light. The grating is displaceable laterally to the cental plane, such that a corresponding responsiveness of the return light intensity to the lateral position provides a measure of displacement of the grating relative to the central plane. Alternative device with reflecting strips function similarly.

Patent
22 Jan 1990
TL;DR: In this article, an acoustic zone plate is placed on an acoustic input face of an acousto-optic device to increase the angular spread of acoustic energy within the device.
Abstract: A method and apparatus for increasing the angular aperture of an acousto-optic device employing an acoustic zone plate positioned on an acoustic input face of an acousto-optic device. The angular spread of acoustic energy within the acousto-optic device is increased over the angular spread obtainable with a single transducer of the same length; thus providing an increased angular aperture for the resultant acousto-optic device.

Journal ArticleDOI
TL;DR: In this article, a general formulation of acousto-optic diffraction is presented for predicting the Bragg angles of noncollinear wide-angular-aperture AO configurations in biaxial crystals.
Abstract: A general formulation of acousto-optic (AO) diffraction is presented for predicting the Bragg angles of noncollinear wide-angular-aperture AO configurations in biaxial crystals. The Bragg angles are determined explicitly without resorting to any trial configuration.

Patent
04 May 1990
TL;DR: In this article, the angular distance between the direction in which a target is located and a line of sight in which it is situated is estimated by using a linear sensor, where an image of the target is projected on and moved over the linear sensor.
Abstract: The invention concerns a device making it possible to determine coordinates giving the angular distance between the direction in which a missile (1) is located and a line of sight in which a target is situated The device comprises means whereby an image may be projected on and moved over a linear sensor (11) so that the field of acquisition of the homing device has a cross-section through a plane perpendicular to the line of sight in the shape of a ring having a diameter corresponding to a large field aperture (10a) at the time when the missile (1) is launched: this is so that the missile (1) will be definitely intercepted by occurring in the field of acquisition After that, the diameter of the ring is varied with time, so that the ring (10b) follows the missile (1) as it gets nearer the line of sight (o): the variation is produced by the action of a system of remote control or a beam riding system Finally, the cross-section of the field is reduced to a simple disc (10c) corresponding to a field with a very small angular aperture: this ensures a more accurate location than conventional homing devices and produces a low probability of false alarms due to the sun or to chaff dropped by an enemy Application to weapon systems

Patent
05 Jun 1990
TL;DR: In this article, an improved focussing of the laser beam through the decoupling mirror is obtained using the mode aperture with the expanded beam received by an absorber made of heat conducting material.
Abstract: The laser has a resonator that has a decoupling mirror (1), end mirror (2) and an active medium (3), such as Nd; YAG. A laser beam is generated along the axis of the unit. Improved focussing of the laser beam through the decoupling mirror is obtained using the mode aperture (4) with the expanded beam (6) received by an absorber made of heat conducting material (7). ADVANTAGE - Increased operational life.

Proceedings ArticleDOI
01 Jan 1990
TL;DR: The approach uses aperture variation to obtain a sequence of images differing only in depth of field, thus avoiding the 'correspondence problem associated with stereo and optical flow techniques.
Abstract: This paper describes a method of extracting depth information about a scene from a single, static viewpoint. The. approach uses aperture variation to obtain a sequence of images differing only in depth of field, thus avoiding the 'correspondence problem associated with stereo and optical flow techniques. These images contain the necessary coded depth information. By using one image (that with the smallest aperture) as a reference and using knowledge of the. Point Spread function (PSF) of (he system, we can compare the images and hence obtain a depth map for all those points in the image which have sufficient grey-level gradient. We propose a r-alislic model for the system. Several methods of depth extraction from the data are suggested.

Proceedings ArticleDOI
01 Sep 1990
TL;DR: The three-dimensional properties of an optical microscope are analyzed and a defocusing technique is proposed to recover the spatial distribution of the specimens under investigation and to represent side views of an object within the angular aperture range of the microscope.
Abstract: The three-dimensional properties of an optical microscope are analyzed and a defocusing technique is proposed to recover the spatial distribution of the specimens under investigation. Limitations and real capabilities of the 3D reconstruction are pointed out. As a result lateral views are obtained by means of operations in the spatial frequency domain. In such a way it is possible to represent side views of an object within the angular aperture range of the microscope. A theory concerning image formation is discussed and simulations of side view reconstructions are reported.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Proceedings ArticleDOI
04 Dec 1990
TL;DR: In this article, a method for the determination of wide angular aperture AEOTF (acousto-electro-optic tunable filter) configurations in LiNbO/sub 3/ crystals is developed.
Abstract: A formulation which leads to the determination of wide angular aperture AEOTF (acousto-electro-optic tunable filter) configurations in LiNbO/sub 3/ crystals is developed. It is shown that for certain orientations of the bias electric field the LiNbO/sub 3/ crystal becomes optically biaxial. The Bragg angles of noncollinear tunable filter configurations in the artificially biaxial LiNbO/sub 3/ are determined explicitly and their dependences on the intensity of the bias electric field and the acoustic wave propagation direction are treated analytically. It is shown that for, bias electric field intensities widely used in LiNbO/sub 3/ devices, 10 kV/cm to 100 kV/cm, up to four noncollinear AEOTF configurations can be obtained for certain directions of acoustic wave propagation. >

Patent
16 Aug 1990
TL;DR: In this article, the angular aperture (sector aperture) of the adjustable rotary disc shutter is specified as a function of the instantaneous film transport speed, the product of the transport speed and angular aperture being equal to a predeterminable value.
Abstract: Method for controlling the exposure and transport speed of a motion picture film by means of a motion picture camera whose film transport motor is connected to a speed-regulating device and has an adjustable rotary disc shutter. A desired value of the angular aperture (sector aperture) of the adjustable rotary disc shutter is specified as a function of the instantaneous film transport speed, the product of the film transport speed and the angular aperture being equal to a predeterminable value.

Journal ArticleDOI
TL;DR: In this paper, the spectral characteristics of a wide-aperture noncollinear filter based on a paratellurite crystal and the dependence of the transmission linewidth on the size of the angular aperture were studied.
Abstract: In this paper we study the spectral characteristics of a wide-aperture noncollinear filter based on a paratellurite crystal and the dependence of the transmission linewidth on the size of the angular aperture. The vector diagram of the AO interaction is shown in Fig. la, where Ke and Ko are the wave vectors of the incident and diffracted light. The wave vector of the shifted US wave K= makes an angle a with the [ii0] direction. The light and sound interact in the (ii0) plane of the TeO 2 crystal. It is well known that for such an interaction geometry the relation between the wavelength of the diffracted light ~ and the acoustic frequency f and the angle of incidence of the radiation on the US lattice 0 is given by