Showing papers on "Angular aperture published in 1979"

Acoustical image reconstruction in parallel‐processing analog electronic systems

Abstract: Ultrafast cardiac‐valve ultrasonic tomography requires parallel multichannel processing of received echoes. In parallel processing the level of secondary ’’ghost’’ images due to spatial undersampling is much higher than in slower series processors which use a selective field insonification. The paper describes a 20‐channel moving‐focus parallel‐processing analog electronic system, which is realized in our laboratory. It is shown analytically that the secondary‐image level is reduced and remains unchanged when the receiver angular aperture (aperture relative to distance) is limited and kept constant during the whole observation time.

Method and apparatus for forming a variable size electron beam

Abstract: In electron beam apparatus having a souce of electrons and a target area toward which the electrons are directed, electron beam forming means are provided along the path from the source to the target. These forming means include a first beam shaping member having a first spot shaping aperture therein, a second beam shaping member having a second spot shaping aperture therein, and means focusing the image of the first aperture in the plane of the second aperture to thereby form a composite spot shape defined by the image of the first aperture and the second aperture. Further means are provided for focusing the image of the composite spot in the target area. Preferably, the apertures are square shaped. Thus, by varying the position of the superimposed image of the first aperture with respect to the second aperture, a wide variety of rectangular shaped composite spots with different dimensions is obtainable. This permits the exposure of rectilinear patterns, e.g., in photoresists of integrated circuit fabrication, by the electron beam with a minimum of exposure steps and substantially no exposure overlap. The result is greatly increased speed in the total exposure of such rectilinear areas to the electron beam as well as a minimum of the "blooming effects" produced by exposure overlap.

Recording optical system

Abstract: A recording optical system comprising a semi-conductor laser of substantially single mode as the light source, an objective lens of which the focal point is located substantially at the beam divergent position of said semi-conductor laser in a plane perpendicular to the junction plane thereof, an afocal cylindrical lens composed of an element having a refractive power only in a plane parallel to said junction plane, an imaging lens, an aperture limiting the beam entering said imaging lens, and a photosensitive medium positioned in the vicinity of the focal point of said imaging lens.

Optical system with an afocal focusing group

Abstract: The present invention refers to an optical system consisting of an objective lens, an aperture stop, a fixed lens and a movable lens group, whereby the aperture stop corresponds to the primary focal plane of the fixed lens group so that the pupil through which the light beam emerges is formed at the infinite distance. The movable lens group consists of two lenses whose focal planes correspond to each other and even if the movable lens group is moved along, the direction of the optical axis for focusing the position and the dimension of the pupil of the optical system do not change.

Scanning optical system for formation of a half tone image

Abstract: A scanning optical system having an optical system capable of controlling formation of a half tone image which is constructed with a light source, a first aperture which restricts a light beam of the light source, an image focusing optical system provided at the opposite side of the light source relative to the first aperture, a second aperture provided at an optically conjugative position with the first aperture with respect to the image forming optical system, a deflector composed of a crystal interposed between the first aperture and the second aperture, a collimator lens which collimates the light beam from the second aperture, and a scanning device which scans the light beam from the collimator lens in a certain definite direction.

Dual offset reflectors shaped for zero cross-polarisation and prescribed aperture illumination

Abstract: The problem of shaping dual offset reflectors, fed by a linearly polarised rotationally symmetric feed horn, to produce a parallel beam over a non-circular aperture with zero cross-polarisation, is considered under the assumptions of geometrical optics. The condition for zero cross-polarisation leads to a partial differential equation, which hitherto has been solved numerically, but is shown here to possess an analytical solution. For uniqueness an additional constraint is put on systems with a plane of symmetry by prescribing the power distribution along the aperture line of symmetry. A suitable choice yields a uniform aperture edge illumination.

Range swath coverage method for synthetic aperture radar

Abstract: A synthetic aperture radar antenna, which is mechanically scanned through the squint mode, is operated to a selected roll angle to optimize the alignment of the antenna beam axis or isogain line, and the line of constant doppler frequency or isodop line. The roll angle is selected as a function of the angular position of the antenna in azimuth and elevation.

Thin-film tunable optical filtering using anisotropic and noncollinear acoustooptic interaction in LiNbO 3 waveguides

Abstract: Theoretical and experimental studies of optical filtering which utilize anisotropic and noncollinear acoustooptic interaction in a Y -cut LiNbO 3 waveguide are reported. A guided-light beam from either an He-Ne laser at 6328 A or an argon laser at around 5000 A, propagating at an angle centering around 70° from the Z(c) axis of the LiNbO 3 crystal, was Bragg diffracted by the surface acoustic wave with 500 MHz center frequency and propagating at 16° from the x axis of the crystal. High optical resolving power, large optical angular aperture, and good spatial separation between the filtered light and the unfiltered light have been simultaneously achieved. An optical passband of 16 A and an angular aperture of 9° have been measured for the case in which the undiffracted and diffracted light propagate in TE 0 mode and TM 0 mode, respectively. Furthermore, by varying the acoustic frequency from 350 to 670 MHz, the filtered optical wavelength may be tuned from 8300 to 5000 A.

Retro-focus type wide angle lens

Abstract: The present invention relates to a retro-focus type wide angle lens which is compact despite its remarkably large field of view and well compensated for various aberrations. This lens system consists of the first divergent lens group and the second convergent lens group in sequence from the side of the object, whereby the first divergent group consists of a plural number of meniscus lenses convex to the object in such a manner that the distortion is compensated for and a compact lens system is realized by forming the object side surface of the substantially zero first order power lens in the meniscus lenses non spherical. The meniscus lens with non-spherical surface is formed from plastic material, resulting in an inexpensive and light retro-focus type wide angle lens. Further, the second convergent lens group is divided into two lens groups with a diaphragm as boundary, whereby in the object side lens group a meniscus lens concave to the object and a biconvex lens are arranged in sequence from the diaphragm to the object side so as to form an air lens having a divergent effect between both lenses, while in the image plane side lens group a lens concave to the image is arranged so as to eliminate the astigmatism and the spherical aberration.

Processor for optical information

Abstract: PURPOSE:To form the spot of all directions on the disc efficiently and to enable to increase the range of automatic focus drawing, by increasing the numerical aperture of coupling lens and locating the prism at the post stage of the coupling lens. CONSTITUTION:To the semiconductor laser element 1 having non-isotropic spread angle, the coupling lens has greate automatic focussing drawing range to greater numberical aperture allowing to realize perfect automatic focussing to the up and down movement of the disc 4. Then, by using the coupling lens 2 having greater numerical aperture and inserting the prism 7 immediately after the coupling lens 2, the conversion of isotropic beam can be made. This light beam can obtain the isotropic spot 5 on the disc 4 by means of the objective lens 3, and since the numerical aperture of the coupling lens 2 is taken greater, the feedback of reflection light to the semiconductor laser 1 is greater, allowing to extend the range of automatic focus drawing.

Molecular beams and effusive flows

Abstract: Molecular flux emanating from an aperture in a beam oven and incident on a point on the beam axis is discussed. The vector flux density is characterized by its vector‐velocity (rather than speed) probability distribution. As a consequence, the integrals of the velocity components orthogonal to the beam axis yield the observed dependences of beam intensity upon aperture area and distance from the aperture. Both rectangular and circular apertures are considered. The velocity integrals for the circular aperture are exact and demonstrate how the velocity distribution of the flux density gradually changes from that of the Maxwell flux at the aperture to that of a beam flux at large distances from the aperture. (This cannot be shown with the speed distribution.) An expression then is obtained for the flux from a circular aperture incident on an off‐axis point by making use of the concept of a virtual aperture which simplifies the problem considerably. This expression then is used to calculate both the normal flux density distribution and the total flux incident on a finite plane collector. These treatments may be applied to systems with apertures and collectors of almost any shape and/or size.

Diaphragm device of a photographic lens

Abstract: This specification discloses the diaphragm device of a photographic lens in which the stop-down operating performance over the entire area from the maximum aperture to the minimum aperture is made uniform and no aperture error occurs in the practical aperture range.

Tesser type objective lens system having a rear aperture stop

Abstract: An improved tesser type objective lens system having a rear aperture stop with a relatively wide field angle of about 60° and an F-number of about F 2.8 is provided. The thickness of the second negative lens in the lens system is increased relative to the total axial distance of the lens system which permits the reduction of the Petzval sum while maintaining a balance correction of spherical aberration and coma.

Acoustic variable focal length lens assembly

Abstract: A lens assembly exhibiting a certain fixed relative aperture is comprised of a physical acoustic lens having a given physical aperture and a fixed relatively short focal length serially spaced from an electronic acoustic lens having any selected one of a plurality of different relatively long focal lengths and simultaneously controlling the physical aperture of the electronic acoustic lens such that the relative aperture of the assembly as a whole remains fixed regardless of the selected one of the long focal lengths. Such a lens assembly is suitable for use in a pulse-echo ultrasonic-imaging system for imaging a deep structure.

Inverse Methods for Reflector Mapping and Sound Speed Profiling

Abstract: Over the past few years, the present authors have been engaged in a coordinated research program on inverse problems.

Large aperture ratio interchangeable lens for a single lens reflex camera

Abstract: A large aperture ratio interchangeable lens for a single lens reflex camera comprises a lens body, a preset aperture ring provided for rotation with respect to the lens body, a first signal member operatively associated with the preset aperture ring to transmit a corrected difference signal (f-f O -Δf) to the camera body, and a second signal member for transmitting a corrected open value signal (f O +Δf) to the camera body.

Appearance of conjugate images in a volume reflection hologram

Abstract: A study is made of the mechanism of the appearance, in the radiation reconstructed from a volume reflection hologram, of not only the original object field but also of a field traveling in the opposite direction (conjugate object wave). This effect owes its origin to the interaction of fields with a complex angular aperture in the interior of a hologram and may ensure a relatively high efficiency of conversion into the conjugate wave. The calculations are made within the framework of the mode theory.

Another look through the Heisenberg microscope

Abstract: Conditions are examined for measurement of the position and momentum of a particle by Compton scattering from various directions. In addition to the usual uncertainty relation that emerges from this analysis, it is shown that, for a given initial frequency, there is generally a critical angular aperture at which the error in position is a minimum.

6 Mm Ultra-fiche lens

Abstract: A short focal length high magnification lens system for projecting ultra-fiche images as a large aperture with substantially diffraction limited resolution in the visual spectrum and a compact vertex-to-vertex distance.

Instrumentation: Progress and Problems

Abstract: The electron microscopes currently available are designed to transfer information down to resolutions of 2–3 A or in terms of spatial frequencies, 0.3–0.5 A−1. Our present problems relate to efforts directed toward instrumentation that will provide a better specimen environment, on the one hand, and that will extend the contrast transfer function (CTF) of the instrument to 1 A−1 or better, on the other. The instrumental problems and their importance related to specimen environment in high resolution electron microscopy will be discussed in the later part of this contribution. Basic optical parameters such as electron wavelength and angular aperture of the objectives lens can be changed to enhance the CTF and the necessary means are well known, but their execution is far from routine. The electron wavelength can be decreased to give greater resolving power by going to higher accelerating voltages. Spherical and chromatic aberration coefficients can be minimized by using a system of multipoles and when corrected, larger angular apertures can be used to obtain better resolution. These are basic instrumental approaches to the problem and are bemg tried by different groups [1, 2, 3]. Special imaging modes such as tilt or rotatory cone illumination, and phase plates have also been tried [4, 5, 6] and involve special problems of instrumentation. In principle, computer or analogue processing of the electron microscope image also can be used to enhance the information obtained, but this whole area is a subject that is being considered in another contribution in this volume.