Showing papers on "Angular aperture published in 2008"

Focal shift of focused truncated Lorentz-Gauss beam

Abstract: Based on the Collins diffraction integral formula and the complex Gaussian expansion of the aperture function, an analytical expression for a Lorentz-Gauss beam focused by an optical system with a thin lens and a circular aperture has been derived The focal shift of the focused truncated Lorentz-Gauss beam is investigated with numerical examples, and the dependence of the focal shift on the different parameters of the focused truncated Lorentz-Gauss beam is discussed in detail This research is useful to the applications of highly divergent laser beams

Particle-optical apparatus for simultaneous observing a sample with particles and photons

Abstract: A particle-optical apparatus, such as an ESEM®, for simultaneous observing a sample with particles and photons. A pressure limiting aperture (PLA) is placed in a diaphragm between the objective lens of the ESEM® and the sample position. The distance between the sample position and the aperture is sufficiently small to allow a large collection angle of the photons through this aperture. A mirror is placed between the diaphragm and the objective lens. Due to the large collection angle for photons a large NA is achieved. The small distance between sample position and aperture also result in less scattering of electrons than occurs in ESEM's where a mirror is placed between aperture and sample position, as the electrons have to travel through only a limited length in a high pressure area. Embodiments describe combinations where e.g. an immersion lens is used.

Optical Imaging of Structures Within Highly Scattering Material Using a Lens and Aperture to Form a Spatiofrequency Filter

Abstract: Angular Domain Imaging (ADI) is a high resolution, ballistic imaging method that utilizes the angular spectrum of photons to filter multiply-scattered photons which have a wide distribution of angles from ballistic and quasi-ballistic photons which exit a scattering medium with a small distribution of angles around their original trajectory. Such spatial gating has been previously accomplished using a scanning array of collimating holes micromachined into a silicon wafer section. We now extend that work to include using a wide-beam, full-field, converging lens and pinhole aperture system to capture images in a single exposure. We have developed an analysis of resolution and sensitivity trade-offs of such a system using Fourier optics theory to show that the system resolution is primarily governed by collimation ability at larger aperture sizes and by spatiofrequency (Fourier space-gated) filtering at smaller aperture sizes. It is found that maximum sensitivity is achieved when spatiofrequency resolution and collimation resolution are equal. Planar, high contrast, phantom test objects are observed in 5 cm thick media with effective scattered to ballistic photon ratios >1.25×10 7 :1 using a wide-beam, full-field lens and aperture system. Comparisons are made between ballistic imaging with the lens and aperture system and with the scanning silicon micromachined collimating array. Monte-Carlo simulations with angular tracking validate the experimental results.

Single-lens, single-sensor 3-d imaging device with a central aperture for obtaining camera position

Abstract: A device and method for three-dimensional (3-D) imaging using a defocusing technique is disclosed. The device comprises a lens, a central aperture located along an optical axis for projecting an entire image of a target object, at least one defocusing aperture located off of the optical axis, a sensor operable for capturing electromagnetic radiation transmitted from an object through the lens and the central aperture and the at least one defocusing aperture, and a processor communicatively connected with the sensor for processing the sensor information and producing a 3-D image of the object. Different optical filters can be used for the central aperture and the defocusing apertures respectively, whereby a background image produced by the central aperture can be easily distinguished from defocused images produced by the defocusing apertures.

Spectral resolution enhancement of acousto-optic tunable filter by double-filtering.

Abstract: The development of the large angular aperture noncollinear acousto-optic tunable filter (AOTF) is based on the parallel tangents momentum-matching condition. In this letter, we have introduced a special double-filtering method that leads to an enhancement of the spectral resolution. And the birefringence together with the rotatory property of the interaction material has been considered to ensure the accuracy of designing an AOTF. The principle and availability of double-filtering are discussed in detail. It is confirmed that double-filtering method is effective to enhance the spectral resolution on the condition of keeping the quality of imaging, which is significant in practical applications of imaging AOTF.

Light source module, optical scanning device, and image forming apparatus

Abstract: A coupling lens collimates an optical beam emitted from a laser light source. An aperture shields a peripheral light flux area of the collimated optical beam. A phase adjusting element partially changes a phase of wavefront of the optical beam. An auxiliary aperture is formed on an outer side of a normalized aperture size in at least one of a main scanning direction and a sub-scanning direction. The phase adjusting element is formed in a parallel plate, and changes at least a phase of wavefront of a peripheral portion of the optical beam to compensate decreases of the beam spot size and the depth allowance caused by the auxiliary aperture.

Surface emitting laser element and method of fabricating the same

Abstract: A convex-portion forming layer is formed between a current-confinement aperture and a multilayer mirror, and forms a convex portion on each boundary between layers forming the multilayer mirror. The convex portion includes a plane equal to or larger than a spot size of the laser light, where the spot size is decided by a diameter of the current-confinement aperture, a predetermined diffraction angle of the laser light due to the current-confinement aperture, and a distance from the current-confinement aperture.

Optical system effects for computer graphics

Abstract: Users define the aperture shape and brightness characteristics of a virtual lens system to generate optical system effects in computer graphics images. An image sample point is associated with a aperture point within the aperture. The location of the aperture point may be based on the shape of the aperture. The image sample point value may be scaled based on a brightness value of an associated aperture point. Alternatively, the aperture point location may be based on brightness characteristics of the aperture. An optical system transmission function based on the brightness characteristics of the aperture specifies the density distribution of aperture positions within the aperture. The aperture points locations are distributed according to this optical system transmission function so that the out of focus regions or bokeh of images mimic the shape and brightness characteristics of the aperture. The aperture points, image sample points, and three-dimensional scene data are provided to a renderer to create images including optical system effects.

Detection of blood oxygen level by noninvasive passive spectral imaging of skin

Abstract: A compact optical hyperspectral imager that can detect both spectral and polarization signatures was used for passive noninvasive imaging of human skin. This vibration-insensitive imager uses an acousto-optic tunable filter (AOTF) as a spectral selection element and an electronically tunable liquid crystal variable retarder (LCVR) as a polarization device. Such an imager is ideally suited to provide both agile spectral and polarization signatures and can be readily used for real time in vivo medical imaging applications. Operation of this imager and image acquisition is fully computer controlled. This imager covers visible to near-infrared (VNIR) region from 400 to 800 nm with a 10 nm spectral resolution at 600 nm and uses a TeO2 AOTF with a 15×15 mm2 linear aperture and a 4.2° angular aperture. At each wavelength 640×480 images with two orthogonal polarization are captured and a total of 41 spectral images are collected to form an image cube. A commercial Si CCD camera was used along with off-the-shelf lenses, mirrors and irises. We carried out experiments with a human subject and controlled the blood perfusion in the individual arm and finger by using a pressure cuff and a rubber band, respectively. Images were captured by illuminating the subject with a white light lamp source and imaging it from a distance. When the hyperspectral image analysis was performed we could observe the effects of skin deoxygenation. In this paper we will described our instrument, the experimental setup, the images obtained and the analysis results.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Predictions of Rayleigh's diffraction theory for the effect of focal shift in high-aperture systems

Abstract: In their work on diffraction [J. Opt. Soc. Am.51, 1050 1961], Osterberg and Smith have computed in an exact manner from the Rayleigh-Sommerfeld diffraction integral of the first kind the irradiance distribution along the axis of a converging spherical wave, and they found that in a scalar optical system of high relative aperture and finite value of Fresnel number, the central peak value of the axial irradiance may occur inside, at, or outside the geometrical focal point as the angular semiaperture of the system is less than, equal to, or greater than, respectively, a particular angle that falls near 70°. These findings are now reexamined using a different assumption that takes into account diffraction at the edge of the aperture. Different results are obtained that agree well with the predictions of other theories of diffraction of light and give confidence to the common conclusions drawn by investigators of the effect of focal shift, that the point of the principal maximum of axial irradiance is not at the geometrical focus but shifted toward the aperture in systems of different relative aperture and finite value of Fresnel number.

Fixed-focus lens system

Abstract: A fixed-focus lens system includes, in order from an object side to an image side along an optical axis thereof, an aperture stop, a first positive lens, a second negative lens, a third positive meniscus lens, and a fourth negative lens having increasing negative refractive power from the optical axis toward the periphery. The fixed-focus lens system satisfies the following condition: 0.1

FDTD analysis of resonant transmission in an electrically small circular aperture with a ridge

Abstract: In this paper, we have examined the convergence of the transmitted power of an electrically small aperture to the transmission cross section 3lambda2/4pi of it for a case of a circular aperture with a ridge. This property can be applied for any electrically small aperture regardless of size or shape even though only one example of the circular aperture is shown. Although not shown here, the comparison of the field distributions on the aperture with and without the ridge shows that the aperture fields for the original circular aperture is mainly reactive, while those are radiating for the ridged aperture.

Zoom optical system, image sensing device, and digital apparatus

Abstract: A zoom optical system includes first through fourth lens groups having negative-positive-negative-positive optical powers. Assuming that a curvature radius of an object-side lens surface of a negative lens element in the first lens group is r1, a curvature radius of an image-side lens surface of the negative lens element in the first lens group is r2, a focal length of the third lens group is f3, a focal length of the entirety of the optical system at the wide angle end is fw, a focal length of the entirety of the optical system at the telephoto end is ft, and an average refractive index of positive lens elements in the second lens group is nd2p, the zoom optical system satisfies the conditional expressions: 0<( r 1+ r 2)/( r 1− r 2)<1.0 −0.9< f 3/√{square root over ( )}( fw×ft )<−0.4 1.6

Wide Angle Imaging Lens System with Two Positive Lenses

Abstract: A wide-angle imaging lens system with two positive lenses is revealed. The imaging lens system includes a first lens with positive refractive power that is a biconvex aspherical lens and a second lens having positive refractive power that is a meniscus lens with concave surface facing the image side. In the concave surface of the second lens, the effective diameter range from the lens center to the edge includes at least one inflection point that changes the refractive power of the second lens from positive to negative. Moreover, the following conditions are satisfied by the imaging lens system: 2  ω ≥ 70 ° ; 0.3 ≤ bf TL ≤ 0.6 wherein bf is back focal length, TL is distance from an aperture stop to an image plane, and 2ω is maximum field angle. Thus, the imaging lens system of the present invention has wide angle effects, short back focal length, and reduced overall length.

Experimental observation of the effect of astigmatic aperture lens on the spectral switches of polychromatic Gaussian beam

Abstract: Experimental results of a study, conducted to investigate the effect of an astigmatic aperture lens on the spectral switches observed with spatially coherent polychromatic light, are reported. It is found that the spectrum at the observation plane exhibits anomalous behavior after passing through the astigmatic aperture lens. It is shown that at a particular position of the aperture, the spectrum splits into two halves, while at other positions the spectrum either shifts towards lower frequencies (red shift) or shifts towards higher frequencies (blue shift). These spectral changes take place in the vicinity of the dark region of the diffraction pattern. Experimental observations show that the behavior of the spectral switch is affected by the astigmatism of the lens. It is found that the spectral minimum value and the transition height of the spectral switch change as the astigmatism of the lens changes. Moreover, the critical position of the aperture where spectral switch occurs also changes with the astigmatism of the lens. The results are consistent with the theoretical predictions.

Imaging lens, camera module, and portable terminal apparatus

Abstract: An imaging lens comprises, in order from an object side: a first lens having a positive refractive power and a meniscus shape and having a convex surface directed to the object side; a second lens having a negative refractive power in the vicinity of an optical axis of the imaging lens; and a third lens having a positive refractive power in the vicinity of the optical axis, wherein at least one surface of each of the second lens and the third lens is an aspheric surface; and the imaging lens satisfies the following conditional expression expressions: 0.7

Acousto-optic filters on potassium dihydrogen phosphate with optimal angle aperture and maximum beam deflection

Abstract: Results of a theoretical analysis on tunable acousto-optic im- aging filters using potassium dihydrogen phosphate crystals are pre- sented. It is found that the maximum angular aperture of an imaging filter at the optical wavelength 0.3 m is equal to 3 deg. The diffraction effi- ciency in the examined instrument reaches 30% at moderate levels 2W of electric driving power. This performance may be obtained in a cell based on the 010 plane of acousto-optic interaction with the cut angle 18.8 deg evaluated relative to the 100 axis. The device uses a piezoelectric transducer with dimensions 2.71.1 cm 2 generating a slow shear elastic wave in the crystal. The spectral resolution of the filter is equal to 12 cm 1 ; the spatial resolution is characterized by 550800 resolvable pixels in an image processed by means of the filter with linear aperture 0.81.1 cm 2 . © 2008 Society of Photo-Optical Instrumentation

Imaging lens and capsule type endoscope

Abstract: PROBLEM TO BE SOLVED: To provide an imaging lens for a capsule type endoscope which achieves sufficient corrections in magnification chromatic aberrations and distortion and is compact while being a wide-angle lens. SOLUTION: The imaging lens 21 forms an image of light from a spherical subject 13 on an imaging surface of a planar image pickup device and comprises a first lens L1 having negative refractive power, an aperture diaphragm S6, a second lens L2 having positive (or negative) refractive power, a third lens L3 having positive refractive power, and a fourth lens L4 having positive refractive power. A shape of the distal end of a capsule 12 and a cover glass 18 of the image pickup device 17 are taken into consideration in shapes and arrangements of the lenses L1-L4 and the aperture diaphragm S6 constituting the imaging lens 21, and the first lens L1, wherein the aperture diaphragm S6, the second lens L2, the third lens L3, and the fourth lens L4 are disposed in this order from the side of the subject 13. COPYRIGHT: (C)2010,JPO&INPIT

Extreme UV-projection illumination system for microlithographic imaging, has spectral filter detachably arranged in spectral aperture and/or aperture diaphragm and transparent for extreme UV-radiation

Abstract: The system (1) has a lighting device (2) for illuminating structures arranged on a reticle (3), such that the structures are imaged on a wafer stage (5) by a projection lens (4). A sigma-aperture is provided in the lighting device and/or an aperture diaphragm is provided in the projection lens. A spectral filter is detachably arranged in the spectral aperture and/or aperture diaphragm, and is transparent for extreme UV-radiation. The sigma-aperture is arranged at a pupil reflector or pupil facet reflector.

Coherency effects in nanobeam x-ray diffraction analysis

Abstract: We describe the evolution of the x-ray scattering pattern which forms on an area detector when a divergent, coherent nanobeam is diffracted from a perfect or weakly deformed single crystal. We show that the scattering can be considered as virtual diffraction from an angular aperture in reciprocal space; this is analogous to pinhole diffraction in real space. We define an angular Fresnel number, YA, which allows the categorization of the nanodiffraction image into near-field, intermediate-field, and far-field regimes. We provide equations for YA in simple geometries and show that dynamical scattering artifacts are eliminated through wave interference in the far-field image; this is the only regime where direct analysis of the charge coupled device image using geometrical formulae to transform distances to diffraction angles is possible.

Optical Head Using Single Objective Lens for Four Types of Optical Disks

Abstract: An optical head using a single objective lens for Blu-ray disc (BD), high-density digital versatile disc (HD DVD), digital versatile disc (DVD), and compact disc (CD) has been developed, which is suitable for high-speed recording and reading. A relay lens unit, which consists of two convex lenses and one concave lens, corrects the spherical aberration and realizes high light power efficiency for each disk. A numerical aperture (NA) control element, which contains a liquid crystal aperture and a wavelength selective aperture, controls the NA of the objective lens for each disk. A coma aberration caused by the objective lens shift is detected based on differential phase detection signals for read-only disks and push–pull signals for recordable or rewritable disks, and is corrected by moving one of the lenses in the relay lens unit by an actuator. A diffraction-limited focused spot and good readout signal characteristics were obtained for each disk, and the validity of this optical design has been demonstrated.

Imaging lens system with high resolution and compact size

Abstract: An imaging lens includes, in the order from the object side to the image side, a first lens of positive refraction power, a second lens of negative refraction power, a third lens of positive refraction power, and a fourth lens of negative refraction power. The imaging lens satisfies the formulae (1) 1 4; and (3) S 1 /S 2 >3, where T is the overall length of the imaging lens, F is the focal length of the imaging lens, R 3 is the radius of curvature of the object-side surface of the second lens, S 1 is the vertical distance from the edge to the center of the image-side surface of the third lens, and S 2 is the horizontal distance from the edge to the center of the image-side surface of the third lens.

Two-lens type optical lens system for taking image

Abstract: A two-lens type optical lens system for taking image consists two lens elements with refractive power, from the object side: a positive first lens element with a convex object-side surface and a concave image-side surface, both the object-side surface and the image-side surface of the first lens element being aspheric; a positive second lens element with a concave object-side surface and a convex image-side surface, both the object-side surface and the image-side surface of the second lens element being aspheric, and an aperture stop located in front of the first lens element. A focal length of the first lens element is f1, a focal length of the second lens element is f2, a focal length of the optical lens system is f, a radius of curvature of the object-side surface of the second lens element is R3, and they satisfy the relations: f/f1>0.9; (f/f1)>(f/f2)>0.35; and 1/R3<−0.01 mm −1 .

On the optimum form of an aperture for a confinement of the optically excited electric near field.

Abstract: Summary A triangular nanoaperture in an aluminium film was used previously as a probe in a scanning near-field optical microscope to image single fluorescent molecules with an optical resolution down to 30 nm. The high-resolution capability of the triangular aperture probe is because of a highly confined spot of the electric near field which emerges at an edge of the aperture, when the incident light is polarized perpendicular to this edge. Previous numerical calculations of the near-field distribution of a triangular aperture in a planar metal film using the field susceptibility technique yielded a nearly quantitative agreement with the experimental results. Using the same numerical technique we now explored the possibility for a further confinement of the electric near field and an increase in its intensity by modifications of the form of a triangular aperture. By introducing a kink on an edge pointing into the aperture, an arrow-shaped aperture is formed with one convex and three concave metal corners. It turns out that this form leads to a substantial further confinement of the near-field intensity at the convex corner. By extending the wings of this arrow-shaped aperture a further 5-fold increase of the intensity can be obtained without a deterioration of the confined spot.

Afocal attachment for projection lens

Abstract: A projection apparatus has a spatial light modulator to modulate illumination from a laser light source. A base projection lens has, from its long conjugate side to its short conjugate side, a first lens group with negative focal length and with a first lens element that has a negative focal length and a second lens element of positive focal length, a second lens group of negative focal length and spaced apart from the first lens group and having one or more cemented lens elements, and a third lens group spaced apart from the second lens group and having a lens with a positive focal length. The base projection lens has a first field of view and is telecentric in its short conjugate. An afocal attachment to the base projection lens alters the first field of view by the same amount in both of two orthogonal directions.

Imaging lens and imaging device including the imaging lens

Abstract: It is to provide an imaging lens and an imaging device including the imaging lens that can maintain optical performance and achieve size and weight reduction. The imaging lens comprises, in order from an object side to an image surface side, a first lens 2 that is a meniscus lens having a positive power whose convex surface faces the object side, a diaphragm 3, a second lens 4 that is a meniscus lens having a positive power whose convex surface faces the image surface side, and a third lens 5 that is a biconcave lens having a negative power, wherein a condition expressed by 0.3‰ f 1 /f 2 ‰ 0.86 (where, f 1 : focal distance of the first lens and f 2 : focal distance of the second lens) are to be satisfied.

Objective Aperture Effects for the Quantitative Analysis in Electron Tomography

Abstract: We have evaluated the effects of experimental factors on transmitted electron beam intensities for quantitative analysisin electron tomography. For the correct application of Beer’s law in electron tomography, the transmitted beam intensityshould reflect the net effect of mass properties on beam path. So, the any other effects of the objective aperture and thespecimen holder on beam path should be removed. The cut-off effects of objective aperture were examined using Quanti-foil holey carbon film and a transmission electron microscope operated at 120 kV. The transmitted beam intensities with30μm objective aperture dropped about 16.7% compared to electron beam intensities without the objective aperture. Also,the additional losses of about 14.2% at high tilt angles were occurred by cut-off effects of the objective apertures. For theprecise quantitative analysis in electron tomography, the effect of the objective aperture on transmitted electron beamintensities should be considered. It is desirable that 2-D tilt series images are obtained without the objective aperture forcorrect application of Bee’s law.Keywords : Beer’s law, Cut-off effect, Electron tomography, Objective aperture