Showing papers on "Angular aperture published in 2003"

The theory of diffraction-limited resolution in microparticle image velocimetry

Abstract: A theory of diffraction-limited spot size is developed for infinity-corrected microscope optics. Previously reported formulae were originally derived using a single-lens system. In addition, the previously reported relationship between f-number and numerical aperture assumed a paraxial approximation and was limited to air-immersion lenses. Here, a new relationship between f-number and numerical aperture is developed, and is valid for all numerical apertures and all immersion media. In addition, a new theory is developed that estimates the effective numerical aperture of an oil-immersion lens when imaging into fluid of a lower refractive index, such as water. The results indicated that when imaging into water, high numerical aperture NA = 1.0 or 1.2 water-immersion lenses provide comparable and sometimes better diffraction-limited resolution than NA = 1.4 oil-immersion lenses. In addition, when imaging into water, water-immersion lenses may provide superior image quality, because they are corrected for aberrations resulting from the water/glass interface.

Three-dimensional tracking of small spheres in focused laser beams: influence of the detection angular aperture.

Abstract: Back-focal-plane interferometry is a method capable of determining the three-dimensional position of a particle with high precision ( 07 should be used only for dielectric spheres with diameters approximately equal to the laser wavelength Harmonic optical traps can be calibrated by measurement of the thermal motion of the sphere We performed Brownian dynamics simulations and subsequent thermal noise analyses to prove that the wrong sinα incorrectly suggests an increased and nonharmonic axial trapping potential

An Exact Theory of Imaging with a Parabolic Continuously Refractive X-ray Lens

Abstract: A theory is developed of image formation with an X-ray lens that consists of a large number of elements. Each element has a biconcave parabolic profile and weakly refracts an X-ray beam. Since such a lens can have a relatively large length comparable to the focal length, the thin-lens approximation is inapplicable. An exact expression for the propagator of a continuously refractive lens is derived that describes the transfer of radiation through a refractive parabolic medium. We calculate the image propagator that describes the focusing of a parallel beam and the image transfer (the focusing of a microobject), as well as the Fourier transform of the transmission function for a microobject with a lens, is calculated. The effective aperture of an X-ray lens is completely determined by the absorption of radiation and does not depend on its geometrical cross-sectional sizes. If we write the complex refractive index as n=1− δ+iβ, then the beam diameter at the focus is approximately a factor of 0.8β/δ smaller than the diameter of the effective aperture, with the index depending only slightly on the wavelength. A continuously refractive lens has no aberrations in the sense that all of the rays that passed through the lens aperture are focused at a single point. The lens can focus radiation inside it and has the properties of a waveguide; i.e., it can reconstruct the beam structure for some lengths to within the absorption-caused distortions. Nonuniform X-ray absorption in the lens leads to the interesting visualization effect of transparent microobjects when their image is focused. In this case, the phase shift gradient produced by the microobject is imaged. We discuss the properties of the Fourier transform pertaining to the absorption of radiation in the lens.

Fast-response variable focusing micromirror array lens

Abstract: A reflective type Fresnel lens using an array of micromirrors is designed and fabricated using the MUMPs® surface micromachining process. The focal length of the lens can be rapidly changed by controlling both the rotation and translation of electrostatically actuated micromirrors. The rotation converges rays and the translation adjusts the optical path length difference of the rays to be integer multiples of the wavelength. The suspension spring, pedestal and electrodes are located under the mirror to maximize the optical efficiency. Relations are provided for the fill-factor and the numerical aperture as functions of the lens diameter, the mirror size, and the tolerances specified by the MUMPs® design rules. The fabricated lens is 1.8mm in diameter, and each micromirror is approximately 100mm x 100mm. The lens fill-factor is 83.7%, the numerical aperture is 0.018 for a wavelength of 632.8nm, and the resolution is approximately 22mm, whereas the resolution of a perfect aberration-free lens is 21.4μm for a NA of 0.018. The focal length ranges from 11.3mm to infinity. The simulated Strehl ratio, which is the ratio of the point spread function maximum intensity to the theoretical diffraction-limited PSF maximum intensity, is 31.2%. A mechanical analysis was performed using the finite element code IDEAS. The combined maximum rotation and translation produces a maximum stress of 301MPa, below the yield strength of polysilicon, 1.21 to 1.65GPa. Potential applications include adaptive microscope lenses for scanning particle imaging velocimetry and a visually aided micro-assembly.

Angular aperture shaped beam system and method

Abstract: The present invention provides improved angular aperture schemes for generating shaped beam spots having a desired geometric shape from rectangular, elliptical, and semi-elliptical apertures having one sharp edge. A sharper beam edge can be generated by offsetting the rectangular or elliptical aperture in combination with under or over focus. In the spherical aberration limit, under-focused semi-circle apertures provide a sharp, flat edge. The sharp edge can be made resolute enough for precision milling applications, and at the same time, the spot can be made large enough with enough overall current and current density to efficiently mill away material in either a production or laboratory environment. Depending on the particular beam spot that is desired, combinations of techniques including defocusing, aperture offsetting, and stigmation adjustment, can be used in both spherical aberration dominant and chromatic aberration dominant environments to achieve a desired beam for a desired application.

Focal shift in small-Fresnel-number focusing systems of different relative aperture.

Abstract: Axial irradiance distribution arising from the diffraction of a uniform, converging, spherical wave at a circular aperture is studied on the basis of scalar boundary-diffraction wave theory. The combined effects of Fresnel number and angular aperture on the focal shift are evaluated, and the validity of the results is checked against the Kirchhoff boundary conditions.

Image formation optical system and image reading apparatus using the same

Abstract: To provide an image formation optical system which is excellent in image formation performance while reducing an opening angle of an anamorphic lens, and an image reading apparatus using the same. When a thickness of an anamorphic lens is d a , a thickness of a meniscus lens arranged adjacent to the anamorphic lens is d m , an interval between the anamorphic lens and the meniscus lens adjacent thereto is t in , and a distance between a lens surface of the lens, of both the lenses, nearest an aperture stop, and a lens surface of the lens, other than both the lenses, facing that lens surface is t out , the constituent elements are set so as to satisfy the following condition: t in

Near-field line-integral representation of the Kirchhoff-type aperture radiation for a parabolic reflector

Abstract: A line-integral representation is presented for a linearly polarized Kirchhoff-type aperture radiation from a parabolic reflector antenna. The main purpose of this result is concerned with the acceleration of the numerical integration for calculating the near field of large reflector antennas. The formulation, which is rigorous for a uniform aperture field, is based on the application of the equivalence principle to a projecting surface, which allows the analytical evaluation in a closed form of a twofold surface integral which defines the radiated field at any space point; the extension to a slowly varying primary feed pattern is based on an asymptotic approximation, which is proved to be accurate in the proximity of the aperture to -30 dB of amplitude edge illumination. The present formulation is well suited to be improved by fringe diffraction contributions in the framework of edge-wave theories such as the physical theory of diffraction (PTD) and the incremental theory of diffraction (ITD).

Focal shift and focal switch of flattened Gaussian beams in passage through an aperture bifocal lens

Abstract: A detailed study of the focal shift and accompanying focal switch of flattened Gaussian beams (FGBs) passing through an aperture bifocal lens is presented. It is shown that by suitably choosing the parameters of the optical system and beam, there exists two axial irradiance maxima for focused FGBs, which vary with the Fresnel number of the aperture. The focal switch can take place when the Fresnel number decreases gradually. The focal switch of Gaussian beams is treated as a special case of FGBs. From the axial irradiance distribution of focused FGBs, a physical explanation of the focal switch is given. A comparison with previous work is also made.

Imaging lens system

Abstract: An imaging lens system includes a first lens 2 which is a meniscus lens with its convex face turned toward the object side and having a positive power, a diaphragm 3 , and a second lens 4 which is a meniscus lens with its concave face turned toward the object side. The first lens 2 , the diaphragm 3 and the second lens 4 are disposed sequentially in the named order from the side of the object toward an image surface. In the imaging lens system, the following conditional expressions are satisfied: 1.25×fl≧L≧0.8×fl; 1.26×fl≧f 1 ≧0.85×fl; 0.8×d 1 ≧d 2 ≧0.35×d 1 ; L≦6.25 mm; d 1 ≧0.225×fl; and d 3 ≧0.225×fl, wherein L is a distance of the entire length of the lens system; fl is a focal length of the entire lens system; f 1 is a focal length of the first lens; d 1 is a thickness of the center of the first lens; d 2 is a distance between the first and second lenses; and d 3 is a thickness of the center of the second lens.

An Efficient Dynamic Multi-Angular Feature Points Matcher for Catadioptric Views

Abstract: A new efficient matching algorithm dedicated to catadioptric sensors is proposed in this paper. The presented approach is designed to overcome the varying resolution of the mirror. The aim of this work is to provide a matcher that gives reliable results similar to the ones obtained by classical operators on planar projection images. The matching is based on a dynamical size windows extraction, computed from the viewing angular aperture of the neighborhood around the points of interest. An angular scaling of this angular aperture provides a certain number of different neighborhood resolution around the same considered point. A combinatory cost method is introduced in order to determine the best match between the different angular neighborhood patches of two interest points. Results are presented on sparse matched corner points, that can be used to estimate the epipolar geometry of the scene in order to provide a dense 3D map of the observed environment.

Image pick-up lens

Abstract: A low-cost bright image-pick up lens of a small size is provided which is short in total length, wherein the angle of field is beyond 30°; the angle of incidence onto the image pickup device is narrowed; and various aberrations are appropriately corrected. The image-pick up lens comprises, from the side of an object, an aperture stop, a biconvex positive lens, and a meniscus lens having a concave surface on the object side, and each of the lenses includes at least one aspheric surface.

Effect of numerical aperture on the spectral splitting feature near phase singularities of focused waves

Abstract: We demonstrate that because of the depolarization effect associated with a high-numerical-aperture lens, the recently predicted spectral splitting phenomenon near phase singularities of focused waves [G. Gbur, T. D. Visser, and E. Wolf, Phys. Rev. Lett. 88, 013901 (2002)] disappears when the numerical aperture is higher than critical values that are different between the incident polarization direction and the axial direction.

Differential optical synthetic aperture radar

Abstract: A new differential technique for forming optical images using a synthetic aperture is introduced. This differential technique utilizes a single aperture to obtain unique (N) phases that can be processed to produce a synthetic aperture image at points along a trajectory. This is accomplished by dividing the aperture into two equal “subapertures”, each having a width that is less than the actual aperture, along the direction of flight. As the platform flies along a given trajectory, a source illuminates objects and the two subapertures are configured to collect return signals. The techniques of the invention is designed to cancel common-mode errors, trajectory deviations from a straight line, and laser phase noise to provide the set of resultant (N) phases that can produce an image having a spatial resolution corresponding to a synthetic aperture.

Microscopic observation method and microscope used therefor

Abstract: PROBLEM TO BE SOLVED: To provide a microscopic observation method realizing observation in a wide range, and a microscope for using it. SOLUTION: An aperture unit 40 having an annular aperture 41 is arranged at the pupil position 25 of a condenser lens 14. The aperture 41 is projected to be nearly inscribed in the outer periphery of the pupil of an objective 15 and observed by moving the position of the object 15 in either forward or backward direction by a very small amount with respect to an observation object 4 from an ordinary focusing position. COPYRIGHT: (C)2005,JPO&NCIPI

Three dimensional fully polarimetric W-band ISAR imagery of scale-model tactical targets using a 1.56THz compact range

Abstract: Using the high-frequency terahertz compact range developed recently for measurement of polarimetric return of scale modesl of tactical targets, we have developed several techniques to produce 3D data sets. Fully polarimetric 3D ISAR data has been collected on several 1/16th scale model tactical targets in free space at individual look angles. The 3D scattering coordinates are calculated by viewing the target through a 2D angular aperture in both azimuth and elevation while simultaneously performing a linear frequency chirp to measure the down-range coordinate. Due to the high frequency of W-band radar, this technique produces high-resolution cross-range images from relatively small (approximately 1 degree) angular integrations. Several techniques for calculation of the 3D coordinates have been developed. In addition to the technique described above, a new method utilizing the phase change of the scattering centers due to differentially small changes in angle will be described. Data collected using this technique can be processed to produce 3D scattering information similar to that obtained by monopulse systems. Results from this analysis will be shown.

High Spatial Resolution and Throughput Potential of an Optical Head with a Triangular Aperture for Near-Field Optical Data Storage

Abstract: A near-field optical head with a triangular aperture has been precisely analyzed on the basis of a three-dimensional finite-difference time-domain method in order to obtain both higher spatial resolution and signal output performance for a near-field optical data storage system. The numerical analysis revealed that in contrast to a conventional aperture, this triangular-shaped aperture can successfully enhance energy distribution intensity at only the side perpendicular to the incident polarization direction, generating an extremely small optical spot not limited by its entire aperture size. The read-out performance was also simulated for the aperture passing over a space-patterned metal medium, resulting in both superior spatial resolution and signal output.

Transparent ploycrystalline aluminium oxide

Abstract: The present invention relates to highly dense translucent and transparent aluminium oxide components for applications, e.g. in the lighting industry, where a fine crystal size has to be obtained and stabilized for use at temperatures of 800 °C or more. Disclosed are high-strength polycrystalline alumina products which include 0.001 - 0.5 weight- % ZrO2 stabilizing a fine crystal size 30 % measured over an angular aperture of at most 0.5° at a sample thickness of 0.8 mm and with a monochromatic wavelength of lightλ, preferably, of 645 run.

Parabolic Mirror and Air-Coupled Transducer for Multimodal Plate Wave Detection

Abstract: A conventional contact piezoelectric transducer, excited by a broadband burst (chirp) that covers its whole frequency bandwidth, is used as a transmitter to simultaneously generate several Lamb waves in a plate Throughout the propagation, these modes leak energy into the ambient air, producing bulk waves in many directions The association of a parabolic mirror and an air‐coupled transducer (PMAT) allows these waves to be received in air with a large angular aperture By displacing the PMAT in a direction parallel to the plate, but without changing its orientation like when standard air‐coupled receivers are used, a series of temporal waveforms are captured Signal processing then allows the phase velocity of the several Lamb waves to be measured in large wave number and frequency domains These resulting data are used to identify the moduli of elasticity for composite plates made of long glass fibers and polymer matrix

Improved 3D Imaging System using Reflectors

Abstract: An improved 3D Imaging System Using Reflectors is provided. The device includes a beam splitter system comprising an even number of mirrors. The device also includes a lens panel that has two independent image forming lenses, and an aperture panel with a pair of apertures. The aperture panel is positioned between the beam splitter and lens plane to project dual images of the subject onto a film exposure or ground glass. The alignment of lens, aperture and beam splitter mirrors creates a pair of divergent light paths from lens pair to exposure plane, which simulates a single lens, permitting accurate light metering and a bright viewfinder image when the device is used with a Single Lens Reflex (SLR) camera.

Image integration and multiple laser source projection

Abstract: An apparatus and method for enhancing an image relayed by a central beam of collimated light centered on the optical axis of a lens with an aperture area of A and focused on the focal plane of the lens. The apparatus having an aperture at least n times as big as A centered on the optical axis of the lens to admit a collimated relay beam including the central beam and a diverter means for separating the relay beam into n collimated facet beams equal to the central beam, but exclusive thereof, and redirecting them through the lens aperture to produce n additional images on the same focal plane. The apparatus also including a processor with a separate opto-electronic device for each image that converts it between electronic and photonic states, the electronic images being stored in the processor.

Electromagnetic scattering from a thick circular aperture

Abstract: Electromagnetic scattering from a circular aperture in a thick conducting plane is analyzed. Numerical computations are performed to evaluate the near and far zone radiation fields in terms of the aperture geometry and incident polarization state. A salient difference in the near-zone field behavior between TM and TE wave incidences is discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 228–231, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10728

Telecentric lens system and image measuring device

Abstract: A telecentric lens system including a front lens unit, a rear lens unit that is disposed so that the front focal point of the rear lens unit coincides with the back focal point of the front lens unit, and a diaphragm mechanism that is disposed at the location where the back focal point of the front lens unit and the front focal point of the rear lens unit coincide. The diaphragm mechanism includes a numerical aperture changer for changing the numerical aperture of the diaphragm mechanism. By changing the numerical aperture, the telecentric lens system can be used in a wide range of applications from observations requiring a large focal depth to observations requiring high resolution. The telecentric lens system that can be used in observations for a wide range of applications and an image measuring device including the telecentric lens system.

Confocal arrangement for e.g. three-dimensional tooth shape measurement, has telecentric aperture arranged in internal focal plane of objective lenses to limit numerical aperture of lens, facing object, around specific value

Abstract: The arrangement has a telecentric aperture (7) and a trifocal diffractive lens (8) both arranged in a common internal focal plane of two objective lenses (6, 9). The diffractive lens outputs light beams exhibiting zero refractive power, negative and positive refractive power, respectively, upon receiving a beam from a light source. The aperture (7) limits numerical aperture of the lens (9), facing an object, around 0.025. An independent claim is also included for a confocal procedure.

Flexible scanning beam imaging system

Abstract: The present invention is directed to a flexible scanning beam imaging system. In specific embodiments, the scanning beam imaging system comprises a mask, and an objective lens having an objective lens focal point disposed between the mask and the objective lens. A field lens device is disposed before the mask to direct a light beam through the mask and focus the light beam at a field lens focal point. The field lens focal point is located between the field lens and the objective lens. One or more scanning mirrors are disposed at or near the objective lens focal point. As a result, the beam will be directed to different locations across the objective lens by the scanning mirror(s), and will travel from the objective lens substantially collimated and parallel toward a surface illuminated by the beam. This substantially collimated and parallel beam provides a large depth of field of the ablation pattern.

Illumination system having a more efficient collector optic

Abstract: An illumination system having a light source is disclosed, the light source having a source size and emitting radiant power in a spatial angle element Ω(α), α indicating the aperture angle, a collector, which collects radiant power from the source up to a first maximum aperture angle αmax(1), a first geometric flux G1 being defined by the source size Q and the first maximum aperture angle αmax(1), a plane to be illuminated having an area A and a numerical aperture NA to be illuminated, the numerical aperture NA to be illuminated defining a second aperture angle α(2), and a second geometric flux G2 being defined by the area A and the second aperture angle α(2), distinguished in that the collector has a first maximum aperture angle αmax(1), which is selected in such a way that the first geometric flux G1 is equal to or larger than, particular preferably more than 15 % larger than the second geometric flux G2.

Synthetic aperture ladar resolution through turbulence

Abstract: The theory is developed for the resolution of a coherent optical synthetic aperture imaging system viewing an object through turbulence. The turbulence induces wave distortions that in turn induce errors in the phase history data collected over the synthetic aperture. The image effects of the phase history errors are space-variant and include broadening of the point spread function as well as geometric distortions. The effect of wave distortions on the intensity image impulse response is related to the usual wave structure function (sum of the log-amplitude and phase structure functions) at the synthetic aperture center frequency. The turbulence-induced limit on resolution is determined for synthetic apertures or any size, without restriction on the size of the real sampling aperture. The results have commonalties to the well-known limit on the resolution of incoherent real aperture imaging systems. A relationship is derived for the resolution of an optical synthetic aperture image forming system relative to the resolution of a passive optical real aperture image forming system viewing through the same inhomogeneous medium.

Fluorescence observation apparatus

Abstract: A fluorescence observation apparatus includes a light source, an illumination optical system conducting irradiation light from the light source to a specimen, an aperture member provided in the illumination optical system, a first wavelength selective member, a light splitter deflecting the irradiation light to conduct the light to the specimen, an objective lens interposed between the light splitter and the specimen, a second wavelength selective member transmitting fluorescent light emanating from the specimen, a detecting device receiving the fluorescent light, and a projection optical system projecting the aperture member at the pupil position of the objective lens. In this case, the aperture member has a partial aperture through which part of the irradiation light passes, and the size of the partial aperture and the magnification of the projection optical system are set to satisfy the following Conditions: 0.5 NA≦NA 1

Projection lens comprising an extremely high aperture

Abstract: The invention relates to a purely refractive projection lens comprising an extremely large aperture. Said projection lens is embodied as a double-convexity system having one convexity on the object side, one convexity on the image side, and a throat (7) which is located between the same. The system diaphragm (5) is arranged at a distance from the image plane in the convexity on the image side. A negative group (LG5) is arranged between the throat and the system diaphragm in the region of the divergent radiation, said negative group having an effective swell with a concave side oriented towards the image plane. The system is characterised by a high numeric aperture, few chromatic aberrations and a compact, material-saving structure.

Method and device for determining projection lens pupil transmission distribution and illumination intensity distribution in photolithographic imaging system

Abstract: A method and device for determining projection lens pupil transmission distribution in a photolithographic imaging system, the device including an illumination source; a transmissive reticle; an aperture layer having an illumination source side and a light emission side and comprising a plurality of openings therethrough; a diffuser mounted on the illumination source side of the aperture layer; a projection lens system; and an image plane, in which a pupil image corresponding to each of the plurality of openings in the aperture layer is formed at the image plane when radiation from the illumination source passes through the reticle, the diffuser, the aperture layer and the projection lens system, the pupil image having a projection lens pupil transmission distribution.