Showing papers on "Angular aperture published in 2013"

Experimental high numerical aperture focusing with high contrast gratings

Abstract: We demonstrate high aperture (up to NA∼0.64) three-dimensional focusing in free space based on wavefront-engineered diffraction gratings. The grating lens’ optical response is tailored by spatially varying the grating ridge and groove width in two dimensions to achieve focal lengths of order 100 μm that are crucial for micro-optical applications. The phase profile of the lens includes multiple 2π phase jumps and was obtained by applying an algorithm for finding the optimal path for both phase and amplitude. Experimental measurements reveal a lateral spot size of 5 μm that is close to the size of a corresponding Airy disk.

Zoom lens for projection and projection type display device

Abstract: [Problem] To provide a zoom lens for projection in which a high magnification ratio is maintained, the numerical aperture is fixed across the entire magnification range, and a sufficiently long back focus is maintained. [Solution] A zoom lens for projection comprising at least two mobile lens groups (G2-G5) that move during changes in magnification, and an aperture stop (St), wherein a variable stop, the aperture diameter of which varies such that the numerical aperture of the zoom lens is fixed across the entire magnification range, is used for the aperture stop (St). Furthermore, conditional expressions (1) and (2) are satisfied, where Bf is the reduction side back focus (air-equivalent distance) of the entire system at the wide angle end, Imφ is the maximum effective image circle diameter (image circle diameter) on the reduction side, and L is the distance, along the optical axis, from the lens surface furthest to the enlargement side when the zoom distance is infinity to the lens surface furthest to the reduction side. 2.5

Partitioned aperture wavefront imaging method and system

Abstract: A partitioned aperture wavefront imaging system includes an imaging system comprising a partitioned aperture lens array positioned at the aperture plane or Fourier plane between the entrance plane and camera plane of an imaging system. The partitioned aperture lens array can include 2 or more off-axis lenses symmetrically distributed about an optical axis, and adapted to produce simultaneously at the camera plane at least two images of an object, or intermediate image of an object, presented at the entrance plane. Preferably, the partitioned aperture lens array includes from 3 to 5 off-axis lenses and produces 3 to 5 images at the camera plane from which phase and amplitude information about the light field can be determined. The partitioned aperture wavefront imaging system provides enough information about the light field presented at the entrance plane to enable reconstruction of the light field at other planes relative to the entrance plane.

Widely tunable optical parametric oscillator in a 5 mm thick 5% MgO:PPLN partial cylinder

Abstract: A 5 mm thick and 38 mm long 5% MgO-doped periodically poled lithium niobate (MgO:PPLN) cylinder with a grating period of 28 μm has been engineered as a partial cylinder with an angular aperture of 45°. An optical parametric oscillator based on this crystal and pumped at 1.064 μm is reported. The output energy is comparable to that generated in the same kind of sample cut as a slab, but the wavelength tunability from 1.41 to 4.3 μm is much broader and continuous.

Optical imaging lens assembly and optical imaging device

Abstract: An optical imaging lens assembly includes, in order from the object side to the image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element The first lens element with positive refractive power has a convex object-side surface in a paraxial region The fourth lens element with negative refractive power has a concave object-side surface in a paraxial region The fifth lens element with positive refractive power has a convex image-side surface in a paraxial region The sixth lens element with negative refractive power has a concave object-side surface in a paraxial region, a concave image-side surface in a paraxial region and at least one convex shape in the off-axial region of the image-side surface of the sixth lens element The fifth lens element and the sixth lens element are aspheric lens elements

Sharper Focal Spot for a Radially Polarized Beam Using Ring Aperture with Phase Jump

Abstract: We study analytically and numerically in which way the width of ring aperture containing a phase jump affects the size and intensity of the focal spot generated with a radially polarized beam. It is shown that by means of destructive interference of beams coming from the different-phase rings it becomes possible to overcome the scalar diffraction limit corresponding to the first zero of the zero-order Bessel function. The minimal focal spot size (FWHM ) is found to be attained when the annular aperture width amounts to 20% of the full-aperture radius. In this case, the side-lobe intensity is not larger than 30% of the central peak. A wider annular aperture with the phase jump introduced is also shown to form a focal spot not exceeding the diffraction limit for a narrow annular aperture, simultaneously providing a nearly six times higher intensity. In this case, the side lobes amount to 35% of the central peak.

Wafer and reticle inspection systems and methods for selecting illumination pupil configurations

Abstract: In an optical inspection tool, an illumination aperture is opened at each of a plurality of aperture positions of an illumination pupil area one at a time across the illumination pupil area. For each aperture opening position, an incident beam is directed towards the illumination pupil area so as to selectively pass a corresponding ray bundle of the illumination beam at a corresponding set of one or more incident angles towards the sample and an output beam, which is emitted from the sample in response to the corresponding ray bundle of the incident beam impinging on the sample at the corresponding set of one or more incident angles, is detected. A defect detection characteristic for each aperture position is determined based on the output beam detected for each aperture position. An optimum aperture configuration is determined based on the determined defect detection characteristic for each aperture position.

Optical system and image pickup apparatus including the same

Abstract: An optical system includes a first lens unit, an aperture stop, and a second lens unit having a positive refractive power. The first lens unit includes a first lens having a negative refractive power and a second lens having a positive refractive power. The second lens unit includes a cemented lens, a fifth lens having a negative refractive power and a concave surface facing an object side, and a sixth lens having a positive refractive power and a convex surface facing an image side. In the cemented lens, a third lens having a positive refractive power and a fourth lens having a negative refractive power are cemented. A distance D 1 from an object-side lens surface vertex of the first lens to the aperture stop and a distance Dt from the object-side lens surface vertex of the first lens to an image plane are appropriately set.

Pseudo-nonlinear absorption in z-scan measurements

Abstract: In the present study, pseudo-nonlinear absorption characteristics are numerically demonstrated in z-scan measurements even for samples of pure linear absorption materials. The pseudo-nonlinear absorption curves look similar to the nonlinear absorption curves in an open-aperture z-scan measurement. Numerical results reveal that the plausible nonlinear effects stem from two sources, namely the changes in the incident angle and azimuth polarization of the focused beam during the z-scan measurement. It is found that when the laser beam is focused by a lens with a large numerical aperture, the influence of the pseudo-nonlinear absorption due to the change in incident angle becomes substantial and cannot be ignored, whereas if a lens with a low numerical aperture is used, the deviation caused by the pseudo-nonlinear absorption is negligible. On the other hand, for a laser beam focused by a lens with a large numerical aperture, the polarization azimuth angle of the incident beam can be adjusted to the corresponding critical angle, so that the plausible nonlinearity is eliminated. Finally, the theoretical analysis is verified experimentally with a single BK7 glass slice sample and objective lens with numerical apertures of 0.09, 0.45, and 0.65 using a z-scan setup with a laser at 488 nm wavelength. The findings are useful for improving the z-scan measurement of the nonlinear absorption coefficient in terms of sensitivity and accuracy.

Method of Determining a Focal Point or Beam Profile of a Laser Beam in a Working Field

Abstract: In a method for determining the focal point or the beam profile of a laser beam, which can be deflected in the x and y directions by a scanner optic or an x-y-movement unit and can be displaced in the z direction by a focusing optic or a z-movement unit, at a plurality of measurement points in the two-dimensional working field or three-dimensional working space of the laser beam. An aperture diaphragm, followed by a detector, is arranged at each measurement point. At each measurement point, for x-y-focal point or beam profile measurements, the laser beam is moved by the scanner optic or the x-y-movement unit in an x-y-grid over the measurement aperture in the aperture diaphragm, and, at each grid point, the laser power is measured by the detector, the scanner axis of the scanner optic or the x-y-movement unit being stationary. For z-focal point measurements, the laser beam is displaced by the focusing optic or the z-movement unit in the z direction within the measurement aperture in the aperture diaphragm. The laser power is measured by the detector at each grid point. The focal point and/or the beam profile of the laser beam is then determined at each measurement point from the measurement values.

Development of variable-focus lens with liquid-membrane- liquid structure and 30 mm optical aperture

Abstract: With the purpose of designing a variable-focal lens with large optical aperture, a liquid lens with liquid-membrane-liquid structure and 30mm optical aperture is proposed. Function of the inserted membrane is stated that much stronger elastic force takes place of interface tension, and enlarging aperture size of liquid lens becomes possible. Mechanics analysis of membrane’s deformation and finite element simulation was employed to demonstrate the elastic force maintains the deformation into a parabolic shape. Moreover, a prototype lens was designed and optical performance with a refractive power range of 7.7Diopters, and 7.13line-pair/mm resolution was measured in experiments.

Intensity, Brightness and ´ Etendue of an Aperture Lamp

Abstract: Phosphor molecules are excited by ultraviolet light emitted during the steady electrical discharge of the low-pressure gas inside the lamp, and subsequently de-excite via emission of visible light. Some of this light is absorbed and re-emitted by the phosphor. In this problem, assume that there are no losses in this absorption/re-emission. Compare the intensity, brightness and etendue of the light from an ordinary fluorescent lamp (with no reflector and phosphor over the full azimuth) with that of an aperture lamp, with small angular aperture Δφ, with the same power output in the visible light. You may assume that the phosphor surface emits radiation according to Lambert’s cosine law [2]. Note that the principle of this problem applies equally well to a lamp consisting of an array of light-emitting diodes (which also absorb and re-emit light with little loss). Show that the effect of the phosphor/reflector (optical insulator) is to increase the intensity/brightness/temperature of the light inside the lamp (and the light emitted by it) for a given input power. The phosphors are typically metal oxides with a PO4 radical, often with rare-earth elements. The first variant of an aperture lamp may be from 1936 [1]. See, for example, sec. 4.8 of [3]. The principle also applies to an incandescent lamp in which a reflector (mirrorlike or diffuse) directs some of the light back onto the filament. The small size of tungsten filaments makes this a small effect, which apparently went unnoticed until (2000) [4]). Subsequently it was noted that the principle (there called “light recycling”) applies to extended light sources [5], such as LEDs, and that these sources can also serve as diffuse reflectors as in the fluorescent aperture lamp. The effect of the “light recycling” by the phosphor/reflector is similar to that of insulation of the walls of a house in permitting a higher internal temperature for a given heat input.

Efficient point spread function model for multi-channel collimator in photon imaging including extra-geometric photons

Abstract: The point spread function of a multi-channel collimator is modeled in photon imaging. The geometric aperture used in the point spread function is expanded to account for penetration, scattering, and/or imperfections of the collimator. The aperture is broadened using a weight that is a function of the distance of the source from the collimator. Rather than scaling the point spread function itself, the geometric aperture used in the point spread function is scaled to an effective aperture. The distance and geometric constraints may be used to determine the geometric aperture, but an additional broadening occurs as a function of the distance to account for non-ideal photon paths of travel. This additional broadening may improve the fidelity with respect to measured data relative to purely geometric or Gaussian models.

Thin Light Tube Formation by Tightly Focused Azimuthally Polarized Light Beams

Abstract: Theoretical and numerical analysis of the transmission function of the focusing system with high numerical aperture was conducted. The purpose of the study was to form a thin light tube in a focal area using the azimuthally polarized radiation. It was analytically shown that, due to destructive interference of two beams formed by two narrow rings, it is possible to overcome not only the full aperture diffraction limit but also the circular aperture limit. In this case, however, the intensity at the center of the focal plane is significantly reduced, which practically leads to the tube rupture. It was numerically shown that long thin one-piece tubes may be formed through the aperture apodization with diffractive axicon phase function or with complex transmission function of Laguerre-Gaussian or Airy-Gaussian beams.

Large-aperture refractive lenses for momentum-resolved spectroscopy with hard X-rays

Abstract: One-dimensional kinoform and prism refractive lenses with large aperture and high transmittance at 22 keV have been investigated. A 12.0 µm focus size (full width at half-maximum) and an effective aperture of 0.85 mm, at a focal length of 705 mm and 21.747 keV, were achieved.

Optical system, and image pickup apparatus having the same

Abstract: An optical system includes an aperture diaphragm having such a curved surface shape that an aperture part moves in an optical axis direction as an aperture diameter changes. The aperture diaphragm has a convex shape on an object side when an optical system on the object side of the aperture diaphragm has a negative refractive power, and the aperture diaphragm has a convex shape on an image side when the optical system on the object side of the aperture diaphragm has a positive refractive power.

Dynamic aperture holographic multiplexing

Abstract: Systems and methods for dynamic aperture holographic multiplexing are disclosed. One example process may include recording a set of holograms in a recording medium by varying both the reference beam angular aperture and the signal beam angular aperture. The angular aperture of the signal beam may be dynamically changed such that the closest edge of each signal beam angular aperture is selected to be a threshold angle different than the angular aperture of the reference beam used to record it. In some examples, the dynamic aperture holographic multiplexing process may include dynamic aperture equalization to reduce cross-talk, to improve error correction parity distribution for improved recovery transfer rate, to provide multiple locus aperture sharing for increased recording density, and to provide polarization multiplexed shared aperture multiplexing for increased transfer rate in both recording and recovery.

Compact Range Performance Evaluation Using Aperture Near-Field Angular Spectrums

Abstract: For a compact range (CR), the near-field angular spectrum can be obtained by making an inverse Fourier transform of its aperture spatial near field. The characteristics of the aperture design have been carried by the aperture near-field angular spectrum. The direct wave and edge-diffracted waves from the aperture can be separated and distinguished clearly in the angular domain. Therefore, the CR performance can be evaluated and improved accordingly. In this paper, based on the aperture field convolution method and plane wave spectrum (PWS) theory, near-field angular spectrums for different apertures have been computed. The general criteria for the CR aperture design have been discussed. The selections of the whole aperture shape, the serration height, the serration base length, the serration number, and the serration shape (including isosceles and right-angled triangles) have been compared. At last, the near fields of an optimized serrated-edge aperture and an original circular aperture in different transverse planes have been computed and compared. The width and height of the apertures are all 30 wavelengths in free space. In order to suppress the sidelobes, a Chebyshev window with ${- 50} $ dB sidelobes has been adopted in the spatial-angular transform.

Characteristic analysis of diffractive-refractive lens in the submillimeter focal plane imaging system

Abstract: To reduce transmission loss and improve spatial resolution, a diffractive-refractive lens with an aperture diameter of 120 mm has been designed, fabricated, and demonstrated for the submillimeter focal plane imaging system. We analyze the lens’ characteristics, such as focal length, depth of focus, beams spot size, spatial resolution, and field of view, theoretically and experimentally. It is the first time this is used as a focusing lens in the submillimeter wave imaging system. The results show that the lens’ characteristics are identical with theoretical analysis.

Study of Shielding Properties of a Rectangular Enclosure with Apertures Having Different Shapes but Same Area Using Modal Method of Moments

Abstract: In this study, electric field Shielding Effectiveness (SE) of rectangular enclosure with apertures illuminated by vertical polarization plane wave has been studied by using modal method of moment technique. Electric field SE of enclosure with different shape apertures but same area has been c alculated at three different points inside enclosure. To achieve this, assuming appropriate electric field distribution on the aperture, fields inside the cavity are determined using rectangular cavity Green's function. Electromagnetic fields outside the cavity and scattered due to the aperture are obtained using the free space Green's function. Matching the tangential magnetic field across the apertures, the integral equation with aperture fields as unknown variables is obtained. A very good agreement among the results of the proposed technique, results available in the literature and experimental results is observed. The simulation results show that the electric field SE is seriously affected by calculation points, aperture shape and the number of aperture. It has been shown that usual assumption made in EMC literature that lower electric field SE near the aperture than at location inside the enclosure farther away from the aperture is not always true to square aperture at some frequency and square aperture has higher electric field SE than rectangular aperture even though they have same area.

Propagation equation of Hermite-Gauss beams through a complex optical system with apertures and its application to focal shift

Abstract: Based on the generalized Huygens-Fresnel diffraction integral (Collins' formula), the propagation equation of Hermite-Gauss beams through a complex optical system with a limiting aperture is derived. The elements of the optical system may be all those characterized by an ABCD ray-transfer matrix, as well as any kind of apertures represented by complex transmittance functions. To obtain the analytical expression, we expand the aperture transmittance function into a finite sum of complex Gaussian functions. Thus the limiting aperture is expressed as a superposition of a series of Gaussian-shaped limiting apertures. The advantage of this treatment is that we can treat almost all kinds of apertures in theory. As application, we define the width of the beam and the focal plane using an encircled-energy criterion and calculate the intensity distribution of Hermite-Gauss beams at the actual focus of an aperture lens. 2013 Optical Society of America.

Comparison of Interaural Intensity Differences Evoked by Real and Phantom Sources

Abstract: This study compares interaural intensity differences (IIDs) of a real source and those resulting from a phantom source created by pair-wise amplitude panning in an anechoic environment with a listener situated in the sweet spot. Factors under investigation are (1) the source frequency, (2) the source direction angle, (3) the loudspeaker angular aperture, (4) the influence of headrelated transfer functions (HRTFs) across subjects, and (5) differences between panning laws. The between-subject differences in HRTFs occurred mainly above 1 kHz and were found to be a highly significant factor. For the commonly used loudspeaker angular aperture of 60◦, this source of error accounted for 79% of the overall variance. The results also indicated that the most critical direction angle for the evaluation of panning laws equals approximately half that of the loudspeaker angle. Phantom sources tend to have larger IIDs than real sources for the commonly-used loudspeaker angular aperture of 60◦, and the magnitude of this offset was found to be frequency dependent. For wider apertures (110◦), both larger and smaller phantomsource IIDs were observed, depending on the employed panning law and the frequency of the source signal. Furthermore, substantial errors in IIDs are observed for frequencies at which phase cancellation occurs due to the contribution of two loudspeakers at each ear with a relative time delay. These findings, in relation to the observed between-subject variance, suggest that the accuracy of panning laws can mainly be improved by incorporating frequency and loudspeaker-angle dependent panning functions.

Device, apparatus and method for cosmetic treatment by light

Abstract: The invention relates to a device for cosmetic treatment by light comprising: - a plurality of light emission sources (10, 11), each source emitting a light beam (12, 13) with a given angular aperture (2α); - a screen (2) positioned facing the light sources (10, 11) and suitable for transmitting the light beams of each source, in which the screen (2) comprises at least one imprint (3) integrated into the screen and modifying the angular aperture of the transmitted beam (2β) of at least one light emission source.

Projection lens, projection device and optically-induced microparticle device

Abstract: A projection lens, a projection device and an optically-induced microparticle device are provided. The projection lens includes an aperture, a first and a second lens groups. The aperture, the first and the second lens groups are disposed on a projection path of an image. The aperture is between the first and the second lens groups. The first and the second lens groups are suitable for interchanging with each other to switch the magnification ratio. When in a first state, the first lens group is between the object and the aperture and the second lens group is between the aperture and a projection surface, herein the projection lens has a first magnification ratio. When in a second state, the first lens group is between the aperture and the projection surface, and the second lens group is between the object and the aperture, herein the projection lens has a second magnification ratio.

Offset aperture dual-gimbaled optical system

Abstract: An offset aperture two-axis gimbaled optical system comprises a two-axis gimbal and an optics assembly that is mounted on the inner gimbal and offset radially from the rotation axis of the outer gimbal. The optics assembly is suitably offset so that its optical aperture does not overlap the rotation axis of the outer gimbal and its optical aperture is symmetric about the rotation axis of the inner gimbal. In different applications, the offset aperture provides for reduced optical aberrations and improved utilization of the available packaging volume to accommodate multiple offset aperture optics assemblies.

Variable Focal Length Achromatic Lens System

Abstract: A variable focal length achromatic lens includes a flat liquid crystal diffractive lens and a pressure-controlled fluidic refractive lens. The diffractive lens is composed of a flat binary Fresnel zone structure and a thin liquid crystal layer, producing high efficiency and millisecond switching times while applying a low ac voltage input. The focusing power of the diffractive lens is adjusted by electrically modifying the sub-zones and re-establishing phase wrapping points. The refractive lens includes a fluid chamber with a flat glass surface and an opposing elastic polydimethylsiloxane (PDMS) membrane surface. Inserting fluid volume through a pump system into the clear aperture region alters the membrane curvature and adjusts the refractive lens' focal position. Primary chromatic aberration is remarkably reduced through the coupling of the fluidic and diffractive lenses at a number of selected focal lengths. Potential applications include miniature color imaging systems, medical and ophthalmic devices, or any design that utilizes variable focal length achromats.

Spatial Filter Enhanced Spinning Disk Confocal Microscope

Abstract: A spatial filter includes a first focal plane to receive sample fluorescence and auto-fluorescence from a microscope, a first lens to receive the sample fluorescence and auto-fluorescence and focus rays of the sample fluorescence, a mask aperture positioned in a plane where sample fluorescence rays maximally converge, the mask aperture positioned where such rays converge to pass the rays, the aperture having a size that is a function of characteristics of the microscope, and a second lens positioned to receive the passed rays from the spatial filter and form images at a second focal plane to couple to a camera.

The influence of co-phasing error on image quality in synthesized aperture telescope

Abstract: In this paper, an active co-phasing and aligning synthesized aperture imaging system with three quasi-annulus-sectors segmented mirrors was analyzed. The influence of co-phasing error, especially piston error, on image quality of the synthesized aperture imaging system was studied. The relationship of the Point Spread Function (PSF) and piston errors between the adjacent segments was deduced theoretically within the coherence length of the source. According to this theoretical model, the influence of piston error on the image quality in the synthesized aperture imaging system was known that the PSF changes with the variation of piston error. And more importantly, the cycle of this change is λ/2 (λ is the wavelength of the source) when a certain piston error is introduced between two adjacent segment. Additionally, simulation model of the three segmented synthesized aperture imaging system was set up by ZEMAX and simulation experiments have been carried out to verify the conclusion derived from the theory model deduced above. The results show that the simulation experiments results consistent with the theoretical conclusion deduced above. The results provide theoretical foundation for further study and actual reference of tolerance for a synthesized aperture telescope design and manufacture.

Diffraction of Orbital Angular Momentum Carrying Optical Beams by a Circular Aperture

Abstract: Diffraction of optical Laguerre-Gauss vortex beams by a circular aperture is studied experimentally and unexpected features that depend on orbital angular momentum index and aperture size to beam radius ratio are described.