Showing papers on "Angular aperture published in 1998"

Alternative to Gabor's representation of plane aperture radiation

Abstract: An exact procedure based on frame discretisation is proposed as an alternative for overcoming the inherent limitations of the well-known Gabor expansion. Numerical comparisons of these two phase-space methods are presented in the context of aperture radiation to demonstrate the stability, efficiency and accuracy of the frame decomposition, thereby emphasising its advantages over the Gabor representation.

Particle analyzer and composite lens formed by integrally joining plural lens elements of different focal points

Abstract: A flow cell 2, a composite lens 15, and first to third detectors 16 to 18 are arranged in this sequence in the light pathway of light emitted from a laser light source 1. The composite lens 15 is configured by a convex lens 15a, and lens elements 15b and 15c. These lenses have different focal lengths. When the posture of the composite lens is correct, light impinging on the convex lens forms an image on the first detector. Therefore, the positioning of the composite lens is enabled. When particles in the flow cell are irradiated with laser light, forward scatter is produced. Forward small angle scatter having a small scattering angle impinges on the first lens element 15b to be collected thereby, and is then received by the second detector 17. Forward large angle scatter having a large scattering angle impinges on the second lens element 15c in the outermost periphery to be collected thereby, and is then received by the third detector 18 which is remotest from the composite lens.

Magnetic beam deflection devices

Abstract: A device (10) for changing the divergence of a beam of microwave radiation comprises a ferrite body (12) having an aperture through which the beam passes. Magnetic means in the form of a plurality of wires (20) passing both through the body (12) and across the aperture or in the form of a coil on either side of the aperture causes a differential phase delay as the beam passes through the aperture which broadens or narrows the beam.

A new optical method for high-accuracy determination of aperture area

Abstract: We have developed a direct optical method for aperture area measurement, based on constant, known irradiance over the aperture. The method is described and results of test measurements are given, including wavelength dependence of the effective aperture area. Systematic uncertainty components are studied experimentally to reach a relative uncertainty of 10-4 for aperture sizes down to 3 mm in diameter. The most important advantages of the direct optical method are that it does not require any reference aperture, it can be applied to apertures of any shape, and the calibration setup is similar to the actual use of the apertures in filter radiometers.

Large aperture diffractive space telescope

Abstract: A large (10's of meters) aperture space telescope including two separate spacecraft—an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass “aiming” at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets which may be either earth bound or celestial.

Dependence of focal shift on Fresnel number and angular aperture

Abstract: The effect of angular aperture on the focal shift in optical systems of finite Fresnel number is considered. It is shown that the focal shift for a given Fresnel number decreases with increasing angular aperture.

Bright wide-angle lens

Abstract: A compact, bright wide-angle lens including at least five lens elements, as follows, in order from the object side: a negative lens element, a positive lens element, a negative lens element, a positive lens element and a negative lens element. The large aperture, wide-angle lens is provided with favorable image formation capability throughout the entire field of view by arranging, as the negative lens element on the extreme object side, a meniscus lens with its concave surface on the object side, the meniscus lens having at least one aspherical surface and satisfying the following condition: -0.9<(R.sub.1 -R.sub.2)/(R.sub.1 +R.sub.2) where R 1 is the radius of curvature of the surface on the object side of the meniscus lens, and R 2 is the radius of curvature of the surface of the image side of the meniscus lens.

Optical device and image reading apparatus

Abstract: In an image sensor having a photoelectric conversion element for receiving light, an illumination unit, and a lens array in which a plurality of gradient index lens elements for focusing light reflected by an original onto the photoelectric conversion element are arrayed, part of the peripheral portion of the lens of the gradient index lens element in the radius direction contains a light absorber for absorbing light having a predetermined wavelength other than the wavelength distribution of light emitted by the illumination unit. With this arrangement, since the optical influences of the peripheral portion of the lens element, which degrade the lens resolution can be eliminated, and the lens elements can be accurately arrayed, there can be provided an image sensor which is free from crosstalk between the lens elements although the lens elements are arrayed in tight contact with each other, and has a large focal depth by changing the angular aperture, high performance, and hardly any performance variations in mass production, and an information processing system using the image sensor.

Wide-angle lens system

Abstract: The invention provides an inexpensive wide-angle lens system which is well corrected for longitudinal chromatic aberration and chromatic aberration of magnification without recourse to any anomalous dispersion glass while a long enough back focus is fully ensured. The wide-angle lens system comprises a front lens group comprising at least one positive lens and having negative power as a whole, an aperture stop 10, and a rear lens group comprising at least one negative lens and a diffractive optical element 11 having a diffractive surface of positive power, and having positive power as a whole, and satisfies 0.005

Dependence of Fresnel number on aperture stop position

Abstract: The influence of aperture stop position on the focusing properties of a lens is investigated. Expressions are obtained for the optical coordinates in terms of the system geometry. If the aperture stop is placed in the front focal plane of the lens, the effective Fresnel number is infinite. For other positions, the effective Fresnel number can be made either positive or negative, corresponding to focal shift either toward or away from the lens and a resulting coordinate rescaling.

Confocal scanning microscope with angled objective lenses for improved axial resolution

Abstract: A confocal microscope has an illuminating aperture (10) and a detecting aperture (20), whose optical axes (12, 22) intersect at an angle Multiplication of a predominantly transverse section of the point spread function (14') of one aperture with the predominantly axial section of the point spread function (24') of the other aperture results in improved axial resolution to the extent that the transverse section is narrower than the axial section

Light beats the diffraction limit

Abstract: Physicists have long been fascinated by the propagation of light through small apertures – from simple pinhole cameras to the more complex diffraction patterns of peacock feathers. Diffraction results from the interference of electromagnetic waves emerging from an aperture larger than the wavelength of the incident light. As the size of the aperture approaches the wavelength of the light, the aperture begins to resemble a point source of spherical waves. And when the aperture is smaller than the wavelength – beyond the diffraction limit – transmission is greatly reduced.

Method and apparatus for surface inspection

Abstract: PROBLEM TO BE SOLVED: To measure the shape of an uneven pattern by a method wherein illumination light is irradiated from an oblique part in a region to be measured, reflected light is formed as an image by an object-side or image-side telecentric optical system in which an object-sides angular aperture with reference to one point in the region is set at a prescribed angle, the image is imaged, luminance data on every point is acquired so as to be frequency-decomposed and a prescribed frequency component is extracted and synthesized. SOLUTION: A point light source is formed of a point light source 111 and of an aperture diaphragm 112, and an object-side angular aperture is set in such a way that reflected light on a face parallel to a plane at right angles to an incident direction is wholly incident on an opening in an aperture diaphragm 310 at an angular-aperture variable mans 330. The reflected light is formed as an image at a luminance according to an angle of incidence in every point in the region, to be measured, by illumination light by using an object-side telecentric optical system 300, and the image is imaged by an imaging part 400. Luminance data on every pixel is acquired by a procession part 510. The processing part 510 instructs a data conversion part 520 about a prescribed direction, and frequency data on a high-frequency component is inverse-Fourier-transformed by the conversion part so as to be sent to the processing part 510. A frequency component is extracted from the image which is imaged by the imaging part 400, and an uneven pattern is obtained.

Focusing a light beam more than thirty focal depths from the aplanatic point with a plano-convex lens

Abstract: A device is described for optically scanning a record carrier with a radiation beam having a high numerical aperture. The radiation beam is focused on the record carrier by means of an objective lens and a plano-convex lens. The plano-convex lens has a gap with the record carrier of several tens of micrometers. It focuses the radiation beam to a point at least 30 focal depths away from an aplanatic point of the plano-convex lens. As a consequence, the lens has a relatively large tolerance for sideways movements.

Illumination deflection system for E-beam projection

Abstract: An electron beam projection system comprises a source of an electron beam, a first doublet of condenser lenses with a first symmetry plane, a first aperture comprising a trim aperture located at the first symmetry plane of the first doublet also serving as a first blanking aperture. A second aperture comprises a shaping aperture located below the trim aperture. A second doublet of condenser lenses with a second symmetry plane is located below the second aperture, the second doublet having a symmetry plane. A third aperture is located at the symmetry plane of the second doublet wherein the third aperture comprises another blanking aperture. There are first blanking plates between the first condenser lens and the trim aperture, and second electrostatic alignment plates between the trim aperture and the second aperture. The second doublet comprises a pair of illuminator lenses including deflectors coaxial therewith and located inside the radius of the lenses and shielding rings located along the inner surfaces of the lenses, and correctors located coaxial with the deflectors and inside or outside of the radii thereof including stigmators, focus coils and a hexapole.

Aperture for multiple reflection raster output scanning system to reduce bow

Abstract: An aperture and a field lens are positioned between the collimator and the rotating polygon mirror of a multiple reflection, multiple beam raster output scanner to eliminate differential scan line bow. The aperture and the field lens will be positioned where the multiple beams cross the optical axis of the raster output scanner optical system. The multiple beams are telecentric.

High numerical aperture objective lens

Abstract: A high numerical aperture objective lens for focusing a laser beam consists of a first lens element of positive optical power intercepting the laser beam and a second lens element of positive optical power located adjacent to the first lens element. The first lens element and the second lens element have identical surface profiles.

Focal length variable type lens device

Abstract: PROBLEM TO BE SOLVED: To obtain a focal length variable type lens device in which a zoom unit is used by only one, whose angle of view is 60 deg., whose aperture ratio is large and which is constituted of small number of lenses by providing 1st and 2nd lens units either of which is fixed type and the other of which is movable type, and which are adjacent to each other and arranged in order from a subject side to an image-formation surface. SOLUTION: The 1st lens unit 110 having diffusion refractive power and the 2nd lens unit 120 having convergence refractive power are adjacent to each other. The 1st lens unit 110 is a front lens unit and is constituted of one negative lens 112. The lens 112 is a single meniscus lens which is concave to a formed image and whose surface facing to the subject side is an aspherical surface S1 in order to make distortion minimum, and which is made of low dispersion glass, then desirably whose V value (Abbe number) is >=55. The 2nd lens unit 120 is constituted of at least two lenses 122 and 124 having positive power and a diaphragm lens 123 intervening between both lenses 122 and 124.

Illuminating optical apparatus

Abstract: An illumination mechanism is disclosed which has a high efficiency of illumination and which is compact. The mechanism includes a reflector, a light source, a first lens array with plural lens cells arranged in rows in a direction perpendicular to an optical axis thereof in which each lens cell is similar in shape to a liquid crystal panel, and a second lens array similar in construction to the first lens array, the lens arrays being disposed along the optical axis. The reflector is divided radially about the optical axis, and has a plurality of partial reflecting surfaces. Each partial reflecting surface is part of a rotation paraboloid with its center being on the optical axis. The light source is placed at a focal position of each partial reflecting surface. The focal length of each partial reflecting surface is generally inversely proportional to a distance from an aperture center of the lens cell of the second lens array to an aperture edge thereof in which the distance is parallel to the direction in which the optical axis and each partial reflecting surface are connected together perpendicularly to the optical axis.

Focusing more than 30 depths from an aplanatic point of a plano-convex lens

Abstract: A device for optically scanning a record carrier with radiation beam having a high numerical aperture. The radiation beam is focused on the record carrier by an objective lens and a plano-convex lens. The plano-convex lens has a gap with the record carrier of several tens of micorometers. It focuses the radiation beam to a point at least 30 focal depths away from an aplanatic point of the plano-convex lens. As a consequence, the lens has a relatively large tolerance for sideways movements.

Blanking system for electron beam projection system

Abstract: A charged particle beam projection system includes a source of charged particles and a first doublet of condenser lenses with a first symmetry plane through which the beam is directed, located lower on the column. A trim aperture element is located at the first symmetry plane of the first doublet wherein the trim aperture serves as a first blanking aperture. Below the trim aperture there is a shaping aperture. Next is a second doublet of condenser lenses with a second symmetry plane. A third aperture, which is located at the symmetry plane of the second doublet serves as another blanking aperture.

Taking lens and camera equipped with the same

Abstract: A taking lens consisting of a positive power single lens element positioned behind an aperture stop of a photographic camera having an image format of 16.7×30.2 mm, and having an object side surface which includes an annular marginal section surrounding a core section defined by an effective aperture thereof. The taking lens satisfies the following conditions: Dr<1.0 Dc<0.75 Ds<3.0 where Dr is the radial width of the annular margin; Dc is the thickness of the core section in an extension of a straight line connecting the outer periphery of the core section and the center of curvature of an image side surface of the single lens element; and Ds is the air space between the image side surface and the aperture stop.

Far-Field Pattern of a Focal-Plane Array-Lens Antenna at Millimeter Wavelengths

Abstract: In this paper an analysis of the far-field pattern of a focal-plane array in the case of two different lenses, a coma-free lens and a hyperbolic lens, and their comparison, are presented. Ray tracing and aperture integration are used. The calculated field pattern at W band is presented. The focal-plane elements are assumed to be corrugated horn. The f / D of the lens is 1.3. The coma-free lens is designed by step integration. The calculation results show that the coma-free lens is superior to the hyperbolic lens in the imaging performance. The coma-free lens can contain more pixels under the condition that the beam size and beam quality are almost constant over the range of angles scanned and the differences among beams gain less 1.8 dB. The aperture efficiency and directivity are also presented.

Variable shaped electron beam exposure system and method of writing a pattern by a variable shaped electron beam

Abstract: An aperture member in a variable shaped electron beam exposure system to be used in combination with a counterpart aperture member is provided for a variable shaped electron beam exposure. The counterpart aperture member has a first aperture and the aperture member has a second aperture for shaping an electron beam, wherein the aperture member further has at least one aperture mask pattern having a shape different from a shape of the second aperture and the at least one aperture mask pattern has a smaller size than the first aperture so that the electron beam is shaped in accordance with the shape of the at least one aperture mask pattern except when the electron beam is shaped by a combination of the first and second apertures for the variable shaped electron beam exposure.

Particle analyser and composite lens formed by lens elements of different focal points

Abstract: A flow cell (2), a composite lens (15), and first to third detectors (16) to (18) are arranged in this sequence in the light pathway of light emitted from a laser light source (1). The composite lens (15) is configured by a convex lens (15a), and lens elements (15b) and (15c). These lenses have different focal lengths. When the posture of the composite lens is correct, light impinging on the convex lens forms an image on the first detector. Therefore, the positioning of the composite lens is enabled. When particles in the flow cell are irradiated with laser light, forward scatter is produced. Forward small angle scatter having a small scattering angle impinges on the first lens element (15b) to be collected thereby, and is then received by the second detector (17). Forward large angle scatter having a large scattering angle impinges on the second lens element (15c) in the outermost periphery to be collected thereby, and is then received by the third detector (18) which is remotest from the composite lens.

A high resolution, holographically corrected microscope with a Fresnel lens objective at large working distances.

Abstract: We present details of a microscope which incorporates an inexpensive, high numerical aperture Fresnel lens objective. The system aberrations are corrected by the use of an image hologram of the lens recorded using a point source of coherent illumination. This device gives high resolution, real time imaging while maintaining a large working distance. The same microscope can be used for micromachining and photolithography in situations where close proximity to the sample is impossible or undesirable.

Macro lens system with focusing lens group

Abstract: The focusing lens group (10,20) is movable along the optical axis of the macro lens system between a position corresponding to an infinity focusing near one image plane (I) and a position removed from the image plane and corresponding to a close-up adjustment. A screen (S) has a changeable full aperture diameter. A drive mechanism (30) move the focusing lens group and screen independently of each other

Spread function of acousto-optic filter with high-speed spectral image analysis

Abstract: The contradictory requirements are presented to acousto- optic tunable filters (AOF) of spectral image analysis. On the one hand AOF should have high speed. On the other hand it should have good spectral resolution and wide angular aperture. Thus when AOF is fastly tuned with chirp transients, the diffracted wave intensity at different moments of transient process can considerably diverge form its quasistatic level. It means that spread function (SF) depends on the velocity of frequency tuning, i.e., it is described by 2D function with variables - wave length and velocity of frequency tuning. In Cartesian frame this dependence is presented by some surface being dynamic SF (DSF). It characterizes speed and selectivity properties of AOF. In this work DCF mathematical model was constructed and basic properties of spectral image analysis AOF were investigated. It has been established that the greatest distortions of DSF occur if velocity of frequency tuning has exceeded some critical value connected with acousto-optic interaction geometry and aperture sizes of beams. In this case the side lobes of SF will make 'false' maxima which begin to prevail over the basic. In addition under the conditions of phase mismatch DSF loses the symmetry to position of the main maximum. These effects reduce the accuracy of spectral measurements when tuning velocity is high.

Fringe visibility and localization in hologram interferometry

Abstract: In a theoretical treatment it is shown that in general there is no well defined region of localization for wedge fringes; an expression is given for the angular aperture of a viewing system which will give fringes of good contrast when focussed on the surface of which displacements are to be observed.

Columnar focal lens

Abstract: A lens is described that produces a columnar focus comprised of a continuum of focal points at varying distances from the principal plane of the lens aligned along the axis of the lens. The lens refracts an incident wavefront with a focal length that is dependent upon the radial distance from the axis of the lens. The radii of curvature of the primary surface of the lens is dependent upon the desired length of the focal column.