Showing papers on "Angular aperture published in 1976"
TL;DR: An anisotropic Bragg diffraction is studied applying simple design expressions to a tilt type in which an acoustic wave is launched a little off the [110] axis.
Abstract: Noncollinear acoustooptic tunable filters using TeO(2) crystals are described. An anisotropic Bragg diffraction is studied applying simple design expressions to a tilt type in which an acoustic wave is launched a little off the [110] axis. Tuning property, filter bandwidth, angular aperture, required acoustic power, deflection angle, divergenceless configuration, and rapid spectrum scanning have been discussed. These filter properties have been confirmed with measurements using three kinds of filter devices: a basic type, an acoustically enhanced type, and a large angular aperture type. A 5-A bandwidth at 4000 A was obtained by slow scanning. A 32-A separation at 4000 A was observed by a rapid scanning of 0.5 msec throughout the visible region with an extremely low electric drive power.
106 citations
TL;DR: In this article, a one-parameter circular aperture distribution is developed which provides an optimum compromise between narrow beamwidth, low sidelobes, and low aperture Q. The pattern is a modified J_{1}(x)/x, analogous to the Taylor oneparameter modified sin (x/x) line source distribution.
Abstract: A one-parameter circular aperture distribution is developed which provides an optimum compromise between narrow beamwidth, low sidelobes, and low aperture Q . The pattern is a modified J_{1}(x)/x , analogous to the Taylor one-parameter modified sin (x)/x line source distribution. Sidelobe envelope taper is essentially that of a uniformly excited circular aperture; hence the aperture is low Q . The aperture distribution which is rotationally symmetric is given by a modified Bessel function of zero order. Like all high efficiency distributions, it has a pedestal. All antenna quantities, sidelobe ratio, beamwidth, aperture efficiency, and edge taper, are uniquely related to the parameter H . A table of these quantities is given for sidelobe ratios up to 50 dB. A typical pattern and several distributions are graphed. This new distribution allows tradeoff studies to be made against any design quantity, with all other quantities determined through the one-parameter.
50 citations
TL;DR: The focal properties of uncorrected geodesic lenses in ion‐exchanged glass waveguides are reported and revealed a 40‐μ spot size when the input aperture was 5 mm, and a spot size of 7.7 μ when the aperture was reduced to 1 mm.
Abstract: The focal properties of uncorrected geodesic lenses in ion‐exchanged glass waveguides are reported. A 13.8‐mm‐focal‐length lens resolved by beams with an angular separation of 27.6 mrad, while a 28‐mm‐focal‐length lens resolved beams with an angular separation of only 3.3 mrad. Intensity profiles of the focal region of the former lens revealed a 40‐μ spot size when the input aperture was 5 mm, and a spot size of 7.7 μ when the aperture was reduced to 1 mm. This value is close to the diffraction‐limited spot size of 5.7 μ.
36 citations
01 Aug 1976
TL;DR: In this paper, a computer program is developed for the problem of transmission of electromagnetic waves from a rectangular waveguide into half space through a rectangular aperture, where the aperture may cover all or part of the waveguide cross section.
Abstract: : A computer program is developed for the problem of transmission of electromagnetic waves from a rectangular waveguide into half space through a rectangular aperture. The aperture may cover all or part of the waveguide cross section, but the sides of the aperture are parallel to those of the waveguide cross section. The solution uses the moment method applied to the integral equation for the equivalent magnetic current in the aperture. The expansion and testing functions are triangles in the direction of current, and pulses transverse to the direction of current. Quantities computed are the equivalent magnetic current, the reflection coefficient and equivalent aperture admittance seen by the incident mode, and the radiation gain pattern. The computer program is described and listed with sample input-output data.
24 citations
TL;DR: It is shown, theoretically and experimentally, that an object traveling through an interference field formed by two coherent point sources can be imaged via synthetic aperture techniques.
Abstract: It is shown, theoretically and experimentally, that an object traveling through an interference field formed by two coherent point sources can be imaged via synthetic aperture techniques. The time varying signal scattered by the object is electronically detected and then recorded spatially such that the recording is a one-dimensional hologram of the object. The synthetic angular aperture of the hologram is proportional to the angle subtended by the pathlength of the object and is dependent on the geometrical arrangement of the point sources with respect to the position and velocity of the object.
22 citations
Patent•
15 Dec 1976
TL;DR: In this paper, a mechanism for a zoom lens of the type in which the aperture defining diaphragm mechanism moves axially of the lens and changes the position of the exit pupil was proposed.
Abstract: A mechanism for a zoom lens of the type in which the aperture defining diaphragm mechanism moves axially of the lens and changes the position of the exit pupil, where the mechanism modifies the aperture with changing focal length to maintain constant relative aperture at full relative aperture and further predetermines the stop down of the diaphragm mechanism as a function of selected relative aperture and focal length.
18 citations
Patent•
23 Feb 1976
TL;DR: A large-aperture photographic lens system of variant Gauss type with a back focal distance nearly as long as 70% of the total focal distance of the entire lens system and wherein aberrations are favorably corrected is described in this article.
Abstract: A large-aperture photographic lens system of variant Gauss type which has a back focal distance nearly as long as 70% of the total focal distance of the entire lens system and wherein aberrations are favorably corrected.
7 citations
Patent•
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01 Oct 1976
TL;DR: A wide angle lens system of the retrofocus type having a ratio of back focal length to equivalent focal length of greater than two and a large relative aperture was proposed in this paper.
Abstract: A wide angle lens system of the retrofocus type having a ratio of back focal length to equivalent focal length of greater than two and a large relative aperture. The lens system comprises 13 elements in nine groups including four consecutive doublets and is capable of focusing to an object distance of eleven equivalent focal lengths from the front vertex thereof.
6 citations
TL;DR: In this paper, the authors discussed the importance of the aperture size in determining the off-axis behavior of a spherically spreading, conical primary beam of finite initial aperture.
Abstract: It is well known that the beam pattern of a parametric acoustic source whose difference frequency is generated largely within the nearfield of the primary beam includes a multiplicative aperture factor that can be important at large angles when ka≳1 (k is the difference frequency wave number, a is the aperture radius). Not so well known, however, is the fact that the same aperture factor arises in the case of a spherically spreading, conical primary beam of finite initial aperture. The importance of the aperture size in determining the off‐axis behavior of parametric sources is discussed.Subject Classification: [43]25.35; [43]20.30; [43]30.75.
6 citations
TL;DR: In this paper, the first-order properties of a symmetrical three-tube lens were determined as a function of applied potentials for different geometrical parameters, such as focal length, the mid focal length and the thickness of the lens.
Abstract: For pt.1 see ibid., vol.9, p.837 (1976). The first-order properties for the symmetrical three-tube lens are determined as a function of applied potentials for different geometrical parameters. Focal length, the mid focal length and the thickness of the lens are calculated from the paraxial ray paths, obtained by numerical integration of the ray equation. The accurate axial potential function for a three-tube lens is used.
5 citations
TL;DR: An integral equation analogous to the Abel integral equation for the derivation of volume emission coefficient from side-on observations, which takes account of finite optical aperture, was developed in this article, and the solution was used to examine the effect of the aperture on the emission coefficient.
Abstract: An integral equation, analogous to the Abel integral equation for the derivation of volume emission coefficient from side-on observations, is developed which takes account of finite optical aperture. This integral equation is partially inverted and the solution is used to examine the effect of finite optical aperture for two simple distributions of volume emission coefficient. It appears that the error arising from the effect of finite optical aperture is negligible in most practical cases. One important and interesting result that emerges from this treatment is that the volume emission coefficient derived on the axis ( r =0) is independent of optical aperture and is therefore correct whatever the aperture.
TL;DR: In this article, a cylindrical acoustic lens, inserted into the sound cell of a Bragg-diffraction imaging system, can substantially improve the resolution of the image, eliminating the need for several optical components in the system and providing directly for an image with a correct aspect ratio.
Abstract: A cylindrical acoustic lens, inserted into the sound cell of a Bragg‐diffraction imaging system, can substantially improve the resolution. In the conventional system, the resolution for an object which spatially modulates the isonifying beam in a direction parallel to the propagation of the laser light is determined by the numerical aperture of the wedge‐forming optical lens. However, with the cylindrical acoustic lens in the system, the above resolution is instead determined by the numerical aperture of this acoustic lens. The use of this lens also eliminates the need for several optical components in the system and provides directly for an image with a correct aspect ratio.
Patent•
27 Jul 1976TL;DR: In this article, a large aperture optical system of short focal length was proposed for efficiently transmitting monochromatic light rays in optical instruments with an extraordinarily high degree of correction over a prescribed field.
Abstract: This invention relates to a large aperture optical system of short focal length primarily intended for efficiently transmitting monochromatic light rays in optical instruments with an extraordinarily high degree of correction over a prescribed field.
Patent•
28 Oct 1976
TL;DR: In this article, a simple Land camera consists of a positive meniscus with at least one aspherical refracting surface and a diaphragm in the vicinity of the coma free position of the menisus.
Abstract: A camera lens, for a simple Land camera consists of a positive meniscus with at least one aspherical refracting surface and a diaphragm in the vicinity of the coma free position of the meniscus. A second diaphragm (20) is located centrally between the first diaphragm (18) and the meniscus (16). The first diaphragm can be the aperture diaphragm and the second, a vignetting diaphragm. The aperture of the vignetting diaphragm can be slightly larger than that of the aperture diaphragm. The useful image area may extend over a half field angle of 26 deg. The lens may be fixed in either of two positions in the camera one for near objects and one for remote objects.
TL;DR: In this paper, the effects of non-uniform illumination on the two-point resolution of a semi-transparent and pi-phase annular aperture microscope were studied and the best resolution was obtained in a good contrast image when the illumination was of the type (1- rho 2)-12/, rho being the radial coordinate in the lens aperture.
Abstract: Presents a theoretical study of the effects of non-uniform illumination on the two-point resolution of a semi-transparent and pi -phase annular aperture microscope. It has been observed that the limiting separation exhibits an oscillatory character around the incoherent limit. The best resolution is obtained in a good contrast image when the illumination is of the type (1- rho 2)-12/, rho being the radial coordinate in the lens aperture.
TL;DR: In this article, the backward radiation from a planar circular aperture antenna is obtained by considering the planar tangential magnetic field outside the aperture, which is the same as the magnetic field inside the aperture.
Abstract: Radiation in the forward direction from a planar aperture in an infinite perfectly conducting plane can be calculated readily by means of aperture field theory. This paper shows how it is possible to obtain the backward radiation from a planar circular aperture antenna by considering the planar tangential magnetic field outside the aperture.