Showing papers on "Angular aperture published in 1980"

Broadband group delay waveguide lens

Abstract: A broadband group delay waveguide lens utilizing an array of half wave plates is disclosed. The lens is comprised of an array of uniformly spaced sections of waveguide having various lengths. The waveguide lengths are selected so as to provide an equal time delay to all rays from the focal point to the aperture plane of the lens. Since equal time delay does not ensure equality of phase at the aperture plane, half wave plates are inserted in the waveguide elements for adjusting the phase of each ray to obtain a constant phase plane over the aperture plane at the design frequency. The inner surface of the lens is spherical with the radius of the sphere equalling the focal length of the lens. The outer surface may be ellipsoidal having a semi-minor axis equal to the focal length and the semi-major axis is dependent upon the waveguide cross section dimensions and the design frequency. Such a lens has a low aperture phase error over a relatively large frequency range.

Transverse tunable acousto-optic filter

Abstract: An electronically tunable optical filter utilizing noncollinear acousto-optic interaction in a birefringent crystal. The directions of optical and acoustic waves are chosen so that large angular aperture is obtained for an interaction geometry wherein the light beam is perpendicular to the group velocity of the acoustic wave. The transverse configuration provides maximum optical aperture for the tunable acousto-optic filter.

Aperture antenna having the improved cross-polarization performance

Abstract: An aperture antenna having the improved phase performance of radiated co- and cross-polarization has been found. The present antenna has, at least, a horn for radiating an electro-magnetic wave, and means for focusing the electromagnetic wave. The focusing means is actually implemented by a reflector or a dielectric lens, and is designed so that the phase distribution of an electric field on an aperture plane of the focusing means has the period of π/2 and the maximum phase at (2m-1) π/8 from the reference plane of one polarized wave in the polar coordinates system on the aperture plane, where m is an integer.

Aperture stop assembly for a laser beam optical system

Abstract: An aperture stop assembly is shown which may be utilized within a laser beam optical system whose laser beam has been split into zero, first and second order beams. A lens is provided to focus the split beams upon a focal plane where an aperture stop is mounted having an aperture aligned with the desired first order beams. The reflective surface of the aperture is arranged at an angle to reflect the unwanted zero and second order beams into a series of absorption baffles found within the aperture stop housing or the aperture stop may absorb unwanted beams directly.

Gauss type large aperture photographic objective

Abstract: In the device disclosed, eight elements form a Gauss type wide or large aperture objective. The first element counting from the front is a positive meniscus lens of forward convexity, the second is a positive lens of convex curvature toward the front, the third is cemented to the second and is a negative lens of concave curvature toward the rear, the fourth is a negative lens of concave curvature toward the front, the fifth is cemented to the fourth and is a positive lens of convex curvature toward the rear, the sixth is a positive meniscus lens of rearward convexity, the seventh is a bi-convex lens with the rear surface of stronger curvature, and the eighth is a positive lens. The front surface of the second lens is aspherical so that as the distance from the optical axis increases, the deviation of the surface from the spherical surface of paraxial radius increases in a direction toward the front.

On the Contribution of Multiple Scattering to Lidar Returns from Homogeneous Fogs and Its Dependence on the Lidar Range and on the Receiver Angular Aperture

Abstract: For a monostatic Lidar the ratio S m/S 1 between the contribution of the mth order of scattering and the contribution of the single scattering to Lidar returns from homogeneous fogs is proportional to tm-1, where t is the time interval between the emission of the laser pulse and the instant at which the received power is considered. The results of calculation, performed for the second and the third order of scattering by choosing several models of scalar phase scattering functions, also show a simple dependence of the received power on the receiver aperture.

Axis aligning method of electronic optical lens barrel

Abstract: PURPOSE:To efficiently realize the axis aligning with high accuracy, by scanning on an aperture mask with the electron beam and detecting simultaneously with this scanning the electron beam that transmits through the aperture mask and reach the surface of a sample. CONSTITUTION:The electron beam given from an electronic gun 1 is made incident to the center of a condenser lens 3 by an axis aligning coil 2 and then converged to irradiate a beam aperture 4. An aperture image of the electron beam which is formed by the apeture 4 is projected to the 2nd beam shaping aperture 6 by an electronic lens 5. In this case, the electron beam receives the control of an axis aligning coil 7 to pass through the center of the lens 5 and is then made incident to the center of a reducing lens 9. This electron beam then receives the control of an axis aligning coil 10 to be made incident to the center position of an objective lens aperture 11. This aperture image is led to the aperture 11 via deflecting systems 12a and 12b having a 2-tier constitution and then irradiated on the sample surface 13.

Photographic lens system having an auxiliary lens

Abstract: Disclosed is a lens system having a principal lens, a photographic film and an auxiliary lens which can be mounted between the principal lens and the photographic lens and has a negative refractive power. The auxiliary lens consisting of a first positive lens having a front surface with large radius and a convex rear surface at the image side, a second bi-concave lens and a third positive lens having a convex front surface at the object side and a rear surface with large radius in sequence from the object side, while the axial distance between the first positive lens and the second bi-concave lens is larger than that between the second bi-concave lens and the third positive lens and the second bi-concave lens and the third positive lens have a negative composed refraction power.

Tessor type lens systems for facsimile

Abstract: An improved tessor type lens system for facsimile having a large aperture ratio and a high contrast are provided. The lens system comprises for components between object and image as follows; a first positive meniscus lens element, a second biconcave lens element, a third meniscus shaped doublet. The entire lens system is capable of providing an aperture ratio greater than 90% and a half angle of image of approximately 18° with an f number of 4.5.

Development Of A Cryogenic Infrared Acousto-Optic Tunable Spectral Filter

Abstract: This paper describes the development of advanced Acousto -Optic Tunable spectral Filter(AOTF) for infrared imaging applications. The device is made of Te02 and operates at 80Kand covers a range from 2 to 5.2 pm. The filter bandpass width is 1% in this region.IntroductionThis paper will describe the development of an advanced acousto -optic tunable spectralfilter (AOTF) for infrared imaging applications. This development was motivated by theneed for active optical devices of this type to enhance the performance of future opticalsystems. Most of the emphasis on smart sensor development has been placed on increasedsophistication of detectors and signal processing electronics. It must be realized thatsome of this sophistication can be circumvented by appropriate preprocessing of the incom-ing signal. Indeed, many applications, such as those that require spectral bandcomparisons or large amounts of spectral data cannot be performed at all without anelectrically tunable spectral filter. The alternative is to sacrifice some othercapability of the system, such as spatial resolution.The development described here has addressed one of the most difficult areas of tunablespectral filter application, that of a low power, cryogenic devices capable of operatingwith advanced mosaic focal planes. In addition to these requirements, most applicationsdemand high in -band transmission, high out -of -band rejection, wide tuning range, largegeometric aperture, wide angular aperture, rapid tuning time and narrow or variablespectral passband width.In this paper we will briefly describe our approach to these issues and show data whichillustrates the performance of a device we have developed. Details of the associatedtechnology efforts will be described elsewhere.Device design and fabricationThe device we have developed utilizes a non - collinear acousto -optical interaction firstdescribed by Yano et al.1 and I. C. Chang.2 Figure 1 shows schematically how the device isconstructed. In this interaction, the incoming broadband light is initially polarized, andlight at the selected spectral wavelength is scattered by the acoustic wave within thecrystal to the orthogonal polarization. Spectral selection is accomplished by changing theacoustic wavelength within the bulk acousto -optic material. An analyzer placed at the exitface of the crystal passes only that spectral component which has been polarization con-verted and reflects the remaining broadband signal out of the system. Detectors placedbehind this analyzer then will sense only that spectral component of the incoming lightwhich has been polarization converted.The key components of the tunable filter subsystem are the acousto -optic crystal, thepolarizer and analyzer, the acoustic transducer, the drive electronics and the mountingstructure.The material chosen for the acousto -optical material is Te02. This material has alarge acousto -optic figure -of- merit, it is transparent from the visible to beyond 5micrometers and is commercially available in high transparency single crystals. Aphotograph of a fabricated crystal is shown in Fig. 2.In the particular configuration shown here. the acoustic group velocity within thecrystal is perpendicular to the center ray of the optical system. This design makesoptimum use of the crystal material, since the acoustic strain fills the entire volume ofthe crystal. The angles at the acoustic faces are uniquely determined by the designcriteria For optimizing bandwidth and angular aperture. The value of the angle is just thecomplement of the walk -off between the acoustic phase velocity and the acoustic groupvelocity. Figure 3 shows the calculated slowness curves of Te02 at 70K and 300K. For thecrystal cut shown in Fig. 2, the shear wave acoustic phase velocity is directed at 18" fromthe (110) direction. Note that for this material, the walkoff is substantial (nearly 60 ")resulting in rather acute angles in the crystal.

Shadow casting electron-beam system

Abstract: Disclosed is an electron-beam system comprised of an iris having an aperture of predetermined shape; a cathode for emitting electrons from an area which is substantially smaller than the aperture; a lens system for directing the emitted electrons along a path through the aperture to form a magnified image of the aperture; and a target for the electrons which is placed along the path of the aperture's demagnified shadow.

Aperture number converting convex lens and optical transmission line using said lens

Abstract: PURPOSE:To improve a coupling efficiency to a fiber, by forming a refractive index distribution type lens so that one end and the other end become flat and convex, respectively, and decreasing the refractive index gradually toward the convex surface side from the flat side. CONSTITUTION:To a terminal part of a core part 6 of a communication optical fiber 3 is connected a convex lens 2 for converting the aperture number, which has been formed so that a connecting part to said terminal, and its opposite side become flat and convex 1, respectively. This convex lens 2 has such a refractive index distribution as a refractive index is decreased toward the convex surface side from the flat side, and a light beam 5 which has been made incident at an angle of theta against an optical axis is made incident to a communication optical fiber 6 with a projecting angle which is much smaller than theta, therefore, an intense light beam is inputted even if the aperture number of the fiber 6 itself is small.

Photographic camera lens system having a short total length

Abstract: A behind-stop type photographic camera lens system designed for an aperture ratio of F/2.8, a field angle of 60 DEG , a short total length less than 0.37 f and favorably corrected aberrations, and comprising a first positive meniscus lens component, a second positive meniscus lens component, a third negative lens component, a fourth cemented lens component consisting of a biconvex lens element and a negative lens element.

Diffraction by a rectangular aperture

Abstract: The diffraction of an acoustic wave by a rectangular aperture in a soft plane screen is examined by a method which uses orthogonal functions and Fourier transformations. Numerical results of the plane‐wave transmission coefficients for normal incidence are given for b/a=1∠8 and ka=0∠2, where 2a and 2b are the side lengths of the aperture and k is the wavenumber.

Analysis of advanced CI applications and systems performance

Abstract: : This report examines two problems. The first is that of scaling previously developed probabilities of a good short exposure to other resolution conditions. The second is of combining low resolution adaptive optics with speckle techniques. Results previously developed for the probability that at some instant the random wavefront distortion over a circular aperture will be less than one radian squared (averaged over the aperture at that instant) are extended to apply to other values than one radian squared. These probabilistic results are then combined with estimates of the relationship between short exposure resolution and residual wavefront error to provide results for the probability of achieving some desired resolution as a function of aperture diameter. It is found that the optimum aperture diameter to achieve a desired level of resolution is almost exactly twice the diameter for which the diffraction limited resolution is equal to the desired resolution, and that the probability of obtaining the desired resolution with that aperture diameter is equal to the probability, previously evaluated, of having one radian squared residual wavefront error on a single short exposure with that aperture diameter. The second part develops an expression for the power spectrum of the focal plane intensity in an adaptive optics two aperture (i.e.,) Michelson stellar interferometer) system acting on a turbulence-distorted single-point-source wavefront. The adaptive optics elements for this system are assumed to correspond to each single aperture of this two aperture system. It is found that no improvement in performance is achieved in speckle interferometry with adaptive optics over conventional optics, in as much as the power spectrum is virtually unchanged.

Interferometer with large angular aperture and broad frequency pass band

Abstract: Coupling between aerials is avoided by the use of at least three aerials, each of which is at a distance greater than lambda /2 from its nearest neighbour, where lambda is the wavelength received by the interferometer. Application to locating a signal with great accuracy.

Aperture synthesis in devices with spatial light-beam control

Abstract: A theoretical investigation is made into the possibility of increasing the resolution of a light deflector by the aperture synthesis method using diffraction gratings. It is shown that a scanning beam becomes narrower when diffraction gratings are used to increase the spatial modulation depth of the light wave.