Showing papers on "Angular aperture published in 2001"

Confocal microscope and wide field microscope

Abstract: A confocal microscope for observing the image of an object to be observed by scanning a spot light for illuminating the object through an objective lens, comprises an aperture stop for adjusting the numerical aperture of the objective lens; and a control unit for calculating a contrast of the image of the object corresponding to each focal position while varying the focal position of the objective lens along the direction of the optical axis so as to determine the height of the unevenness on the surface of the object from a change of the contrast, thereby setting the aperture stop to have the focal depth substantially equal to the height of the unevenness.

Generalization of the Ludwig-3 definition for linear copolarization and cross polarization

Abstract: This article presents a generalization of Ludwig's (1973) third definition that introduces a /spl theta/-dependence that is absent from Ludwig's original definition. Our generalization is based on the nonconformal mapping between the electric field vector lying in the propagation plane (i.e., the probe aperture plane) and the projection of this vector onto the aperture plane (i.e., the AUT aperture plane). We show the error incurred by the two definitions for both the E-field and the H-field aperture models. Ludwig's definition incurs the same level of error for both models while our generalized definition incurs slightly more error for the H-field aperture model but no error for the E-field aperture model.

Validity of the paraxial approximation in the focal region of a small-f-number lens.

Abstract: For small-f-number lenses, whereas the paraxial approximation cannot be used for a description of propagation of light from the lens to the focal region, it is shown that the approximation is still valid for propagation of light over relatively small distances in the region near the focus.

Objective lens for optical disk

Abstract: There is disclosed an objective lens for an optical disk, comprising a bi-aspherical single lens having a numerical aperture of 0.7 or more, wherein a center thickness of the lens is larger than a focal distance.

Diffraction by a subwavelength-sized aperture in a metal plane.

Abstract: We present an experimental study on the diffraction of light by an aperture small compared with the wavelength. The aperture is illuminated by laser light guided in a metal-clad tapered optical fiber. We investigate different orientations of the aperture in the plane: normal to the cleaved plane, oblique to the cleaved plane, and off-center. We measure the far-field, two-dimensional intensity distributions of the diffracted light as functions of angle coordinates theta and phi in a full half-space for various polarization states and analyze the patterns by using low-order multipole fields. We also examine the near- and far-field effects of placing small periodic corrugations near the aperture, focusing on the role of surface-wave excitations. We measure the near-field intensity distributions near the aperture with a near-field scanning optical microscope and discuss their relation to the far-field diffracted fields.

Diffraction of an Ultrashort Pulse by an Aperture

Abstract: The scalar problem of diffraction of an infinitely short pulse by a plane screen is solved within Kirchhoff’s approximation. The response of an infinitely small aperture is calculated, and the explicit solution is found for the case of a circular aperture.

Cross-spectral density propagated through a circular aperture

Abstract: A method is presented for evaluating the cross-spectral density diffracted by a circular aperture in the Fresnel approximation. Our proposal is a generalization to partially coherent illumination of the classical solution to the problem of near-field diffraction due to a circular aperture. We show that our generalization covers particular cases already reported in the literature and present numerical and experimental results that verify our proposal. This work is a contribution to the treatment of diffraction by multiple apertures.

Methods and devices for achieving alignment of a beam-propagation axis with a center of an aperture in a charged-particle-beam optical system

Abstract: Methods and devices are disclosed for aligning a beam-propagation axis with the center of an aperture, especially an aperture configured to limit the aperture angle of the charged particle beam. In an exemplary method, an alignment-measurement aperture is provided at an imaging plane of a charged-particle-beam (CPB) optical system, and a beam detector is downstream of the alignment-measurement aperture. A scanning deflector is energized to cause the beam to be scanned in two dimensions, transverse to an optical axis, over the aperture. Meanwhile, the beam detector obtains an image of beam intensity in the two dimensions. In the image a maximum-intensity point is identified, corresponding to the propagation axis. Based on the two-dimensional image, the beam is deflected as required to align the propagation axis with the aperture center.

Rod lens array for line scanning

Abstract: A rod lens array for line scanning is provided that can reduce the degradation of image quality (i.e., vertical stripes (streaks) in the sub-scanning direction of an output image) caused by a periodic irregularity in the light quantity, considering an angular aperture and the positional deviation of an image line in the sub-scanning direction. A rod lens array for one-to-one imaging is used as the rod lens array for line scanning, including a plurality of columnar rod lenses having a refractive index distribution in the radial direction that are arranged in one row in the main scanning direction with their optical axes in parallel. The effective overlapping degree m is in the range defined by (1.55+0.5 j ) D/d≦m≦ (1.80+0.5 j ) D/d Eq. 37 where d is the lens diameter of the rod lens and D is the array pitch of the rod lenses.

Focal point dislocation detecting method and optical pickup apparatus

Abstract: The focal point detection method detects focal point dislocation of a coupling objective lens in accordance with a light beam passing a 60% to 80% region of a light beam effective diameter, which is centered with respect to an optical axis OZ of a light beam passing through the coupling objective lens, and which is regulated by a numerical aperture of the coupling objective lens. In this manner, focal point dislocation of a converging optical system can be performed without an offset, thereby accurately forming a focal point of the converging optical system on an information recording layer of an optical recording medium.

Radiation source producing a collimated beam

Abstract: This invention concerns the production of a large-area collimated beam of radiation for use in displays. A highly reflective diffusely illuminated cavity source (11) has apertures (12) which allow the selected radiation to pass through directly over a first range of angles. Each aperture (12) has a finite depth and angled sides tapering outwardly so that the radiation which enters the aperture at a second, larger range of angles impinges on the walls (6) of the aperture and is redirected into a preferred direction by reflection at the walls of the aperture. Any radiation not entering an aperture is reflected inside the reflective cavity from the wall which has low absorption and is diffusely reflected from another cavity wall (30), so that it has a finite probability of entering any one of the array of apertures. In this way the light that has not entered an aperture will be randomly reflected back to try again.

Large numerical aperture objective lens and night vision optical device using the same

Abstract: A large numerical aperture objective lens is disclosed having three lens groups. In order from the object side, these lens groups include: a first lens group of positive refractive power that is formed of two positive lens elements and an achromatic set of paired lens elements formed of a lens element of negative refractive power and a lens element of positive refractive power, respectively; a second lens group of negative refractive power; and a third lens group of positive refractive power, with the surface of the third lens group nearest the object side being convex. Specified conditions are satisfied in order to provide a compact, large numerical aperture objective lens having its aberrations favorably corrected as well as to correct for shifts of focus caused by expansion/contraction of the lens barrel with changes in temperature. The objective lens of the invention is particularly suitable for use in a night vision optical device having a photoelectron amplifier tube and an eyepiece, wherein aberrations in the eyepiece are balanced by aberrations of the objective lens.

Apparatus and methods for blocking highly scattered charged particles in a patterned beam in a charged-particle-beam microlithography system

Abstract: Apparatus and methods are disclosed pertaining to microlithography performed using a charged particle beam. In an exemplary apparatus, the projection-optical system includes a first projection lens situated downstream of a pattern-defining reticle and a second projection lens situated downstream of the first projection lens. Between the first and second projection lenses is a back focal plane of the first projection lens, at which focal plane a beam crossover is formed. The projection-optical system includes a cutoff-plate assembly, including at least one aperture-defining cutoff plate, located between the reticle and the back focal plane. The respective aperture in each cutoff plate is wider than an aperture in a scattering aperture conventionally located at the back focal plane. If the cutoff-plate assembly includes multiple cutoff plates, the aperture defined in the cutoff plate closer to the reticle is wider than the aperture defined in the more downstream cutoff plate. At least one of the cutoff plates defines an aperture that is laterally extended in a beam-deflection direction in the projection-optical system.

Increase in the prompt radiated field from an IRA by aperture design techniques

Abstract: Recent results are reported that improve the prompt radiated response from reflector and lens impulse radiating antennas (IRAs) by improved control of the aperture fields of the TEM mode distribution. Both reflector and lens IRAs benefit from trimming the aperture to eliminate portions where the vertical component of the electric field is oriented in the wrong direction. Reflector IRAs can further benefit from reorientation of the TEM feed arm angles as well as the relative size of the feed arms to the maximum aperture radius. Significant improvements over 45-degree feed arms can be realized by making 200-Ohm reflector IRAs with feed arms at 30 degrees from the vertical with the circle of symmetry slightly inside the aperture outer boundary and small amounts of aperture trimming.

Improvement of beam-adjustment accuracy by beam-intensity distribution measurement on a second shaping aperture in electron-beam writing systems

Abstract: We proposed a new adjustment method for the beam-intensity distribution. On the 2nd shaping aperture plate, a small aperture is positioned sufficiently apart from the aperture for variable shaping. The center of the 1st shaping aperture image is moved to the small aperture by adjusting an alignment coil. The beam current, which passes through the small aperture, is measured by the Faraday cup on the target while the 1st shaping aperture image is scanned over the small aperture by operating the shaping deflector. Using this method the beam-intensity distribution of the 1st shaping aperture image on the 2nd shaping aperture plane is obtained. The beam-intensity distribution obtained is ideally a series of concentric circles and the maximum value is reached at the center circle. The center is shifted when the alignment of the limit aperture at the illumination or at the 1st shaping aperture is incorrect. The position of the maximum in the beam intensity is adjusted to the center of the 1st shaping aperture image. At the beam-current-density of 20 A/cm 2 , the slope of the distribution is usually under 1 percent. To evaluate the adjustment accuracy, resist profile of drawn pattern is measured by AFM. The resist profiles in a beam shot coincide well with the beam intensity distribution.

High-Numerical-Aperture Objective Lens for Blue Laser Disk System

Abstract: The authors have developed and prototyped an adjustment-free two-component objective lens for a blue laser disk system (numerical aperture = 0.85, disk thickness = 0.1 mm). The lens is designed to be sufficiently tolerant to the relative position, i.e., the decentering, tilt and spacing inaccuracy between the two lenses, and does not require adjustment of the two lenses. We have carried out some experiments and the tolerance of our newly developed objective lens has been experimentally verified.

Diffraction of an electromagnetic beam by an aperture in a conducting screen

Abstract: An electromagnetic beam that is not the solution to the paraxial wave equation but is the solution to Maxwell’s equation is simulated directly by the finite-difference time-domain method. Electrical and magnetic field components of the beam are presented graphically. Then the diffraction of the electromagnetic beam pulse by an aperture in a conducting screen is analyzed. The fraction of the beam power through the aperture is defined and calculated. The fields in the time domain near the aperture, which show the diffraction by the aperture, are presented graphically.

Large aperture Fresnel optical lens design and manufacturing

Abstract: The large aperture six components Fresnel optical lens design principle and overall manufacturing scheme are presented. Calculating and fabricating method for each spherical ring are reported. The optical cementing and final cutting method are discussed. The final testing results of the Fresnel optical lens are given.

Objective lens for optical write/read head e.g. for optical memory/storage disc equipment, has lens surface divided into exclusion zone for light beam of first numerical aperture and a common zone for light beam of second numerical aperture

Abstract: Objective lenses for optical memory disc systems can suffer from spherical aberration even though the objective lens is designed for the minimum spherical aberration with a digital versatile disc (DVD) but is used for information reproduction of a CD, then the spherical aberration can increase so much that information replay is impossible. The lens surface (11) must be divided into an exclusion zone (RE) designed for a high numerical aperture through which a light beam with a first numerical aperture enters, which is required for an optical memory disc with a first recording density, and a common zone (RC) through which enters a light beam having a second numerical aperture, which is smaller than the first.

Phase contrast microscope has polarizer between light source and ring aperture, polarization filter between objective and tube lens, compensator and analyzer between tube lens image plane

Abstract: The microscope has at least one illumination source followed by a ring aperture and condenser and an objective, tubular lens and an image plane in the path of the light after interaction with the object. A polarizer is arranged between the light source and the ring aperture. A polarization filter is arranged between the objective and tube lens. A compensator and an analyzer are arranged between the tube lens and image plane. The microscope has at least one illumination source with a ring aperture (4) and condenser arranged after it and an objective, tubular lens and an image plane in the path of the light after interaction with the object under investigation. A polarizer (2) is arranged in the light path between the light source and the ring aperture and a polarization filter (8) is arranged in the light path between the objective (7) and tube lens (9). A compensator (10) and an analyzer (11) are arranged in the light path between the tube lens and image plane (12).

The position sensitive 1D-160 detector for high resolution powder diffraction

Abstract: A detector with an angular aperture of 160° based on multi-wire proportion chamber is presented. The detector can work either in full-aperture mode or in scanning mode with restricted aperture. In the first one, which is used for the investigation of fast-running processes, angular resolution is 0.05°. In the other mode for high resolution powder diffraction, angular resolution is 0.002°. The count rate is 1 MHz per channel. The detector operates in the “movies” mode with as many as 8000 frames and a minimum frame time of 10 μs .

Beam array scattering by wedges and rectangular cylinders

Abstract: Scattering by an obstacle in the near field of a radiating aperture can be obtained by superimposing many much simpler omnidirectional scattering solutions. These sources must be closely spaced in the aperture with relative amplitudes corresponding to the aperture field distribution. Highly accurate results can also be obtained with fewer basis solutions if they are beam solutions with the beams arranged in a Gabor lattice. Beam solutions are obtained from omnidirectional source solutions by substituting appropriate complex source coordinates for the real source coordinates. This procedure has already been used for antenna aperture scattering by local half planes and wide slits, where the main results are for forward scattered fields, and also for rectangular cylinders where backscattered fields are also shown. Back radiation from an aperture depends on aperture edge diffraction. This is not specified in a beam array representation, so the total backscattered field cannot be known. Here we revisit earlier solutions to determine how seriously back radiation from the aperture affects the numerical results and to improve our representation of both the radiation fields of an aperture in isolation and the total back scattered fields of an obstacle in the vicinity of the aperture.

Annular Aperture in a Plane

Abstract: The polarizability of various aperture shapes in a conducting plane finds practical applications in low-frequency microwave scattering and penetration problems [1]. For instance, when an aperture size is small compared to an incident wavelength, the polarizability is a useful concept to estimate a field penetration into apertures. The behavior of polarizability for an annular aperture in a conducting plane has been well studied in [2–3] based on the variational method. In the present section we will revisit the problem of polarizability of an annular aperture in a thick conducting plane and analyze its static potential distribution through an annular aperture.

Ion optics system for a Time-of-Flight mass spectrometer

Abstract: In a first aspect there is provided an extraction lens for a TOF mass spectrometer ion source, said lens including an element having an aperture, said aperture extending through the element so as to form a through channel, such that, in use, ions may pass from one side of the element to the opposite side of the element by passing through said through channel; characterised in that said through channel has a length equal to or greater than 8/10 of the diameter of said aperture. This provides an extraction lens which leads to improved extraction and spatial focussing of ions. In addition, as the length of the through channel formed by the aperture is at least equal to 8/10 of its diameter, field penetration through the extraction lens aperture into the region in front of the sample plate is kept at a low level and ions are not prematurely extracted. The aperture can thus be made larger than would otherwise be possible. A larger aperture is advantageous because compared to a smaller aperture, it does not become quickly contaminated with material sputtered from the sample. It is also easier to direct a laser or other light source through a larger aperture. This is useful when it is desired to direct a light beam onto the sample plate, along a path at a small angle to or substantially coincident with the spectrometer's ion-optical axis.

A Novel Design for a Low-Backscatter Optical Aperture

Abstract: : Conventional flat aperture designs introduce error and noise in optical/electro-optical applications when the aperture is placed in close proximity to a light source located within the system Rays that are reflected off the blocked portion of The aperture and then are reflected again off of the light source and reenter the optical path introduce this error A novel design for a low-backscatter aperture has been introduced and validated for a light measurement application The new concept is predicated on a V- or cone-shaped aperture design that uses the law of reflection to direct blocked light rays away from the optical path A light source application was used to validate the new design

Resonant waveguide-grating filters incorporating first-order feedback gratings

Abstract: Summary form only given. Resonant waveguide-grating filters are of interest for a range of potential applications (Wang and Magnusson, 1993; Shin et al, 1998). Although such filters exhibit high reflectance under a plane wave incidence, reflectance reduction and spatial modification of the beam profile occur under a practical finite beam illumination. This stems from the narrow angular linewidth of the filter (Avrutsky and Sychugov, 1989). Incorporation of a first-order Bragg grating widens the angular aperture (Lemarchand et al, 1998) and improves filter properties as the calculations presented in this paper illustrate. The results presented pertain to TE-polarized beams at normal incidence.

3-D Pre-Stack Depth Migration of the Baldpate Field Using MAA Travel-times

Abstract: We have previously introduced a new approach for generating single-valued travel-times for Kirchhoff migration which we call the maximum angular aperture (MAA) selection rule. In Stieglitz and Morton (2000), we applied the MAA approach to several synthetic examples and observed an improvement in image quality over the industry standard selection rules: minimum-time, maximum-amplitude and shortest-path (see also Stieglitz, 2001).

Double-exposure specklegrams obtained by using scaled aperture pupils

Abstract: In speckle photography the pupil aperture is usually not modified between exposures. In our work, the change of the pupil aperture scale between exposures is analyzed on the basis of double-exposed image speckle, before and after a diffuse in-plane displacement is done. The apertures have the same shape but its scale is modified between exposures. Note that the relative position of the aperture is maintained. In particular, we analyze a simple case that uses a circular aperture whose diameter is modified for recording each image. The intensity in the image plane and the fringe visibility are evaluated, in terms of the geometric characteristics of the pupils.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.