Showing papers on "Lens (optics) published in 2005"

Physics of negative refractive index materials

Abstract: In the past few years, new developments in structured electromagnetic materials have given rise to negative refractive index materials which have both negative dielectric permittivity and negative magnetic permeability in some frequency ranges. The idea of a negative refractive index opens up new conceptual frontiers in photonics. One much-debated example is the concept of a perfect lens that enables imaging with sub-wavelength image resolution. Here we review the fundamental concepts and ideas of negative refractive index materials. First we present the ideas of structured materials or meta-materials that enable the design of new materials with a negative dielectric permittivity, negative magnetic permeability and negative refractive index. We discuss how a variety of resonance phenomena can be utilized to obtain these materials in various frequency ranges over the electromagnetic spectrum. The choice of the wave-vector in negative refractive index materials and the issues of dispersion, causality and energy transport are analysed. Various issues of wave propagation including nonlinear effects and surface modes in negative refractive materials (NRMs) are discussed. In the latter part of the review, we discuss the concept of a perfect lens consisting of a slab of a NRM. This perfect lens can image the far-field radiative components as well as the nearfield evanescent components, and is not subject to the traditional diffraction limit. Different aspects of this lens such as the surface modes acting as the mechanism for the imaging of the evanescent waves, the limitations imposed by dissipation and dispersion in the negative refractive media, the generalization of this lens to optically complementary media and the possibility of magnification of the near-field images are discussed. Recent experimental developments verifying these ideas are briefly covered. (Some figures in this article are in colour only in the electronic version)

Soft X-ray microscopy at a spatial resolution better than 15 nm

Abstract: The study of nanostructures is creating a need for microscopes that can see beyond the limits of conventional visible light and ultraviolet microscopes. X-ray imaging is a promising option. A new microscope described this week achieves unprecedented resolution, and has the ability to see through containing material. It features a specially made two-component zone plate — a lens with concentric zones rather like the rings in the Fresnel lenses familiar in overhead projectors and elsewhere — that makes use of diffraction to project an image into a CCD camera sensitive to soft X-rays. Spatial resolution of better than 15 nm is possible. Analytical tools that have spatial resolution at the nanometre scale are indispensable for the life and physical sciences. It is desirable that these tools also permit elemental and chemical identification on a scale of 10 nm or less, with large penetration depths. A variety of techniques1,2,3,4,5,6,7 in X-ray imaging are currently being developed that may provide these combined capabilities. Here we report the achievement of sub-15-nm spatial resolution with a soft X-ray microscope—and a clear path to below 10 nm—using an overlay technique for zone plate fabrication. The microscope covers a spectral range from a photon energy of 250 eV (∼5 nm wavelength) to 1.8 keV (∼0.7 nm), so that primary K and L atomic resonances of elements such as C, N, O, Al, Ti, Fe, Co and Ni can be probed. This X-ray microscopy technique is therefore suitable for a wide range of studies: biological imaging in the water window8,9; studies of wet environmental samples10,11; studies of magnetic nanostructures with both elemental and spin-orbit sensitivity12,13,14; studies that require viewing through thin windows, coatings or substrates (such as buried electronic devices in a silicon chip15); and three-dimensional imaging of cryogenically fixed biological cells9,16.

Apparatus for multiple camera devices and method of operating same

Abstract: There are many, many inventions described herein. In one aspect, what is disclosed is a digital camera including a plurality of arrays of photo detectors, including a first array of photo detectors to sample an intensity of light of a first wavelength and a second array of photo detectors to sample an intensity of light of a second wavelength. The digital camera further may also include a first lens disposed in an optical path of the first array of photo detectors, wherein the first lens includes a predetermined optical response to the light of the first wavelength, and a second lens disposed in with an optical path of the second array of photo detectors wherein the second lens includes a predetermined optical response to the light of the second wavelength. In addition, the digital camera may include signal processing circuitry, coupled to the first and second arrays of photo detectors, to generate a composite image using (i) data which is representative of the intensity of light sampled by the first array of photo detectors, and (ii) data which is representative of the intensity of light sampled by the second array of photo detectors; wherein the first array of photo detectors, the second array of photo detectors, and the signal processing circuitry are integrated on or in the same semiconductor substrate.

Canalization of subwavelength images by electromagnetic crystals

Abstract: An original regime of operation for flat superlenses formed by electromagnetic crystals is proposed. This regime does not involve negative refraction and amplification of evanescent waves in contrast to the perfect lenses formed by left-handed media. The sub-wavelength spatial spectrum of a source is canalized by the eigenmodes of the crystal having the same longitudinal components of wave vector and group velocities directed across the slab. The regime is implemented at low frequencies with respect to the crystal period by using capacitively loaded wire media. The resolution of λ/6 is demonstrated. The thickness of the lens is not related with the distance to the source and the lens can be made thick enough.

Wide emitting lens for led useful for backlighting

Abstract: Lenses and certain fabrication techniques are described. A wide-emitting lens refracts light emitted by an LED die to cause a peak intensity to occur within 50-80 degrees off the center axis and an intensity along the center axis to be between 5% and 33% of the peak intensity. The lens is particularly useful in a LCD backlighting application. In one embodiment, the lens is affixed to the backplane on which the LED die is mounted and surrounds the LED die. The lens has a hollow portion that forms an air gap between the LED die and the lens, where the light is bent towards the sides both at the air gap interface and the outer lens surface interface. The lens may be a secondary lens surrounding an interior lens molded directly over the LED die.

Method and apparatus for angular-resolved spectroscopic lithography characterisation

Abstract: An apparatus and method to determine a property of a substrate by measuring, in the pupil plane of a high numerical aperture lens, an angle-resolved spectrum as a result of radiation being reflected off the substrate. The property may be angle and wavelength dependent and may include the intensity of TM- and TE-polarized light and their relative phase difference.

Focusing hard x rays to nanometer dimensions by adiabatically focusing lenses.

Abstract: We address the question of what is the smallest spot size that hard x rays can be focused to using refractive optics. A thick refractive x-ray lens is considered, whose aperture is gradually (adiabatically) adapted to the size of the beam as it converges to the focus. These adiabatically focusing lenses are shown to have a relatively large numerical aperture, focusing hard x rays down to a lateral size of $2\text{ }\mathrm{n}\mathrm{m}$ (FWHM), well below the theoretical limit for focusing with waveguides [C. Bergemann et al., Phys. Rev. Lett. 91, 204801 (2003)].

Compression Molding of Aspherical Glass Lenses–A Combined Experimental and Numerical Analysis

Abstract: Compression molding of glass aspherical lenses has become a viable manufacturing process for precision optics. The widespread use of this process has been hampered by the lack of its fundamental understanding. This research is a part of the ongoing effort to understand some of the issues related to the process. Simple lens molding experiments were performed on a commercial precision lens molding machine. A finite element method (FEM) program was used to create a simple numerical model and analyze the molding process. Experimental results show that this process is capable of producing precision optical components. A comparison of the experimental results with the predicted results indicates that with a more sophisticated numerical model, it is possible to use FEM as a tool for process analysis.

Design, Modeling, Optimization, and Experimental Tests of a Particle Beam Width Probe for the Aerodyne Aerosol Mass Spectrometer

Abstract: Aerodynamic lens inlets have revolutionized aerosol mass spectrometry by allowing the introduction of a very narrow particle beam into a vacuum chamber for subsequent analysis. The real-time measurement of particle beam width after an aerodynamic lens is of interest for two reasons: (1) it allows a correction to be made to the measured particle concentration if the beam is so broad, due to poor focusing by non-spherical particles, that some particles miss the detection system; and (2) under constant lens pressure it can provide a surrogate particle non-sphericity measurement. For these reasons, a beam width probe (BWP) has been designed and implemented for the Aerodyne Aerosol Mass Spectrometer (AMS), although this approach is also applicable to other instruments that use aerodynamic lens inlets. The probe implemented here consists of a thin vertical wire that can be precisely positioned to partially block the particle beam at fixed horizontal locations in order to map out the width of the particle beam. ...

Method and apparatus for angular-resolved spectroscopic lithography characterization

Abstract: According to the present invention, an apparatus and method are disclosed for determining the properties of a substrate by measuring the angle-resolved spectrum as a result of the radiation being reflected off the substrate in the pupil plane of the high numerical aperture lens. The properties may be dependent on angle and wavelength and may include the intensity of TM- and TE-polarized light and their associated phase differences.

Electrowetting-Based Variable-Focus Lens for Miniature Systems

Abstract: The meniscus between two immiscible liquids of different refractive indices can be used as a lens. A change in curvature of this meniscus by electrostatic control of the solid/liquid interfacial tension leads to a change in focal distance. It is demonstrated that two liquids in a tube form a self-centred variable-focus lens. The optical properties of this lens were investigated experimentally. We designed and constructed a miniature camera module based on this variable lens suitable for mobile applications. Furthermore, the liquid lens was applied in a Blu-ray Disc optical recording system to enable dual layer disc reading/writing.

Negative refraction and focusing of circularly polarized waves in optically active media.

Abstract: Analysis indicates that certain types of optically active media are capable of producing negative refraction and focusing of circularly polarized waves. It is established that a slab of such material acts just as Veselago's hypothetical left-handed media lens, providing subwavelength resolution as Sir Pendry's ideal lens, but for circularly polarized waves.

A proof of superlensing in the quasistatic regime, and limitations of superlenses in this regime due to anomalous localized resonance

Abstract: Enlarging upon work of Nicorovici, McPhedran & Milton ([Nicorovici et al . 1994][1] Phys. Rev. B 49 (12), 8479–8482), a rigorous proof is given that in the quasistatic regime a cylindrical superlens can successfully image a dipole line source in the limit as the loss in the lens tends to zero. In this limit it is proved that the field magnitude diverges to infinity in two sometimes overlapping annular anomalously locally resonant regions, one of which extends inside the lens and the other of which extends outside the lens. The wavelength of the oscillations in the locally resonant regimes is set by the geometry and the loss, and goes to zero as the loss goes to zero. If the object or source being imaged responds to an applied field it is argued that it must lie outside the resonant regions to be successfully imaged. If the image is being probed it is argued that the resonant regions created by the probe should not surround the tip of the probe. These conditions taken together make it difficult to directly probe the potential in the near vicinity of the image of a source or object having small extent. The corresponding quasistatic results for the slab lens are also derived. If the source is too close to the slab lens, i.e. lying within the resonant region, then the power dissipation in the lens tends to infinity as the loss goes to zero, which makes the lens impractical for imaging such quasistatic sources. Perfect imaging in a cylindrical superlens is shown to extend to the static equations of magnetoelectricity or thermoelectricity, provided they have a special structure which makes these equations equivalent to the quasistatic equations. [1]: #ref-22

Liquid crystal lens element and optical head device

Abstract: There is provided a liquid crystal lens element having a lens function capable of performing spherical aberration correction including a power component equivalent to a focal point change of the stable incident light in accordance with the voltage applied. One (12) of the two transparent substrates (11, 12) has a transparent electrode (15) and a Fresnel lens surface (17) while the other (11) of the two transparent substrates has a phase correction surface (18) and a transparent electrode (16). Thus, by arranging the Fresnel lens surface (17) and the liquid crystal layer (13) between the two transparent electrodes (15, 16), the substantial refraction factor distribution of the liquid crystal layer (13) is changed according to the voltage applied, so that positive/negative power is given to the wavefront transmitting through the liquid crystal layer (13), the Fresnel lens surface (17), and the phase correction surface (18).

Antenna With Partially Spherical Dielectric Lenses

Abstract: An antenna is provided comprising a first group of part-spherical dielectric lenses supported on a first portion of a conducting ground place arranged to reflect signals emerging from the lens, each of the lenses having a number of associated switchably selectable antenna feed elements arranged around the periphery of at least one sector of the lens for injecting signals into and/or receiving signals propagated by the lens, wherein each lens and the associated feed elements of the first group has a different orientation and may be operated to provide coverage in respect of a different region. The antenna also comprises a second group of one or more spherical or part-spherical dielectric lenses and associated switchably selectable antenna feed elements, oriented and operable to provide coverage to a region other than that covered by lenses of the first group. The first portion of the ground plane may be substantially annular and arranged to surround a well-like region of the antenna in which the second group of one or more lenses may be accommodated.

Planar magnetoinductive lens for three-dimensional subwavelength imaging

Abstract: A planar near-field magnetoinductive lens operating in the microwave range is presented. The proposed device consists of two parallel planar arrays of metallic broadside coupled (BC) split-ring resonators (SRRs), or BC-SRRs. The power coming from a point-like source located in front of the lens is focused into a receiver located in free space beyond the lens. This focus is clearly separated from the back side of the lens, and has a size that is an order of magnitude smaller than the free space wavelength of the incoming field. The imaging properties of the device relies mainly on the excitation of magnetoinductive surface waves on the BC-SRR arrays. By simply scaling the BC-SRRs’ size, as well as the arrays periodicity, the operation frequency of the device can be tuned in a wide frequency range. Thus, the proposed design is potentially useful for many applications ranging from megahertz to terahertz.

Tunable microfluidic microlenses

Abstract: A novel type of liquid microlens, bounded by a microfabricated, distensible membrane and activated by a microfluidic liquid-handling system, is presented. By use of an elastomer membrane fabricated by spin coating onto a dry-etched silicon substrate, the liquid-filled cavity acts as a lens whereby applied pressure changes the membrane distension and thus the focal length. Both plano–convex and plano–concave lenses, individual elements as well as arrays, were fabricated and tested. The lens surface roughness was seen to be ∼9 nm rms, and the focal length could be tuned from 1 to 18 mm. This lens represents a robust, self-contained tunable optical structure suitable for use in, for example, a medical environment.

Antenna system for emc test, test signal generation apparatus and transmission apparatus

Abstract: PROBLEM TO BE SOLVED: To properly irradiate an object to be tested with electric waves for test, without increasing costs, in a transmission apparatus used for an EMC test (in particular for an immunity test). SOLUTION: The transmission apparatus comprises a horn antenna 20 and a dielectric lens 30 for correcting a radiation direction or the like of the horn antenna. The dielectric lens 30 comprises a lens 32, a flange 34 and a projection 36 and is directly fixed in an open end of the horn antenna 20 by abutting the flange 34 to the open end of the horn antenna 20 and screwing the projection 36 with an L-shaped fitting metal 22 welded on the horn antenna 20. As a result, transmission electric waves from the horn antenna 20 are made incident to the dielectric lens 30 without loss, further does not pass through the dielectric lens 30 and is not radiated to the side of an object to be tested. Therefore, it is not necessary to increase a gain of the horn antenna 20 or a shape of the dielectric lens 30, and the transmission apparatus can be accomplished at low cost. COPYRIGHT: (C)2006,JPO&NCIPI

A planar magneto-inductive lens for th ree-dimensional subwavelength imaging

Abstract: A planar near-field magnetoinductive lens operating in the microwave range is presented. The proposed device consists of two parallel planar arrays of metallic broadside coupled (BC-) split ring resonators (SRRs), or BC-SRRs. Power coming from a point-like source located in front of the lens is focused into a receiver located in free space behind the device. This focus is clearly removed from the back side of the lens, and has a size which is an order of magnitude smaller than the free space wavelength of the incoming radiation. The imaging properties of the device mainly relies on the excitation of magnetoinductive surface waves on the BC-SRR arrays. By simply scaling the BC-SRRs size, as well as the arrays periodicity, the frequency of operation of the device can be tuned over a wide frequency range. Thus the proposed design is potentially useful for many applications ranging from megahertzs to terahertzs.

The magic volume lens: an interactive focus+context technique for volume rendering

Abstract: The size and resolution of volume datasets in science and medicine are increasing at a rate much greater than the resolution of the screens used to view them. This limits the amount of data that can be viewed simultaneously, potentially leading to a loss of overall context of the data when the user views or zooms into a particular area of interest. We propose a focus+context framework that uses various standard and advanced magnification lens rendering techniques to magnify the features of interest, while compressing the remaining volume regions without clipping them away completely. Some of these lenses can be interactively configured by the user to specify the desired magnification patterns, while others are feature-adaptive. All our lenses are accelerated on the GPU. They allow the user to interactively manage the available screen area, dedicating more area to the more resolution-important features.

Electro-active intraocular lenses

Abstract: An intraocular lens system is presented that comprises an electro-active lens comprising multiple independently controllable zones or pixels, and a controller capable of being remotely programmed.

Three-dimensional fluorescent particle tracking at micron-scale using a single camera

Abstract: This article reports a new approach to track (x, y, z, t) coordinates of multiple fluorescent particles (diameter range 1–10 μm) simultaneously using a quantitative defocusing method. We find that the defocused image of a 1-μm diameter fluorescent particle formed by the objective lens of a conventional microscope has a bright outer ring due to the spherical aberration of the lens system. The ring radius increases as the particle is moved away from its reference plane and closer to the lens. The reference plane refers to locations of the particle at which the projected image is in focus. The (x, y, z) coordinates of the particle are then inferred from the center location of the image ring as well as the ring radius. The described technique is implemented successfully for obtaining 3D trajectories of swimming Escherichia coli cells.

Variable-focus liquid lens by changing aperture

Abstract: We propose an adaptive liquid-filled lens, which consists of an elastic membrane, a solid plate, and an annular sealing ring; a liquid with a fixed volume stored in lens chamber. The key part is the annular sealing ring which looks like an iris diaphragm. The surfaces of annular sealing ring are sealed with an elastic membrane. The radius of the annular sealing ring is changeable. By tuning the radius of the annular sealing ring, the stored liquid in the lens will be redistributed, thus changing the curvature of the elastic membrane. Therefore, the lens cell causes light to converge or diverge. A liquid lens with a positive variable focus was demonstrated, this kind of lens has the advantages of simple fabrication process, compact structure, easy operation, and low cost.

Multi-lens imaging systems and methods

Abstract: Imaging systems and methods are provided. One exemplary system (300) incorporates multiple lenses that are individually configured to receive visible light from an object to be imaged, and to direct this light upon acorresponding sensor array. Luminance information is then derived from signals generated in one or more of the sensor arrays. When chrominance information is desired, an optical filter is interposed between a lens and the corresponding sensor array. The mosaic pattern contained in the optical filter is tailored to provide advantageous chrominance information. One or more such filters with different mosaic patterns may be employed. The luminance and chrominance information obtained from the sensor arrays are combined to generate an image of the object.

Performance of reduced size substrate lens antennas for Millimeter-wave communications

Abstract: This paper presents the theoretical performance (input impedance, -10 dB return-loss bandwidth, radiation patterns and surface efficiencies) of reduced size substrate lenses fed by aperture-coupled microstrip patch antennas. The diameter of the extended hemispherical homogeneous dielectric (/spl epsiv//sub r,lens/) lenses varies between one and five wavelengths in free-space, in order to obtain radiating structures whose directivity is comprised between 10 and 25 dB. A lot of configurations of lenses are investigated using the finite-difference time-domain methods technique and compared in the 47-50 GHz band as a function of their diameter, extension length and dielectric constant. In particular, the analysis of internal reflections-in time and frequency domains-shows that the latter have potentially a strong influence on the input impedance of small lens antennas, even for low values of /spl epsiv//sub r,lens/(2.2), whereas the usual limit (beyond which anti-reflection coatings are required) is /spl epsiv//sub r,lens/=4. We also demonstrate that the diffraction limit of reduced size lenses is reached for extension lengths varying between 50% and 175% of the extension of synthesized ellipses, depending on the lens material and diameter. Finally, we show that superdirective structures with surface efficiencies reaching 250% can be obtained with small lens diameters, justifying the interest in reduced size lens antennas.

Digital camera using multiple lenses and image sensors to provide an extended zoom range

Abstract: A digital camera includes a first image sensor, a first wide angle lens for forming a first image of a scene on the first image sensor; a second image sensor, a zoom lens for forming a second image of the same scene on the second image sensor, a control element for selecting either a first sensor output from the first image sensor or a second sensor output from the second image sensor, and a processing section for producing the output image from the selected sensor output. In one variation of this embodiment, the first lens is also a zoom lens, where the maximum focal length of the first lens is less than or equal to the minimum focal length of the second zoom lens.

Simulation and testing of a graded negative index of refraction lens

Abstract: A gradient index (GRIN) lens using a negative index of refraction material (NIM) has been designed and tested. The GRIN lens was fabricated using a NIM slab with a variable index of refraction perpendicular to the propagation direction. Ray tracing calculations based on the isotropic Eikonal equation determined the index of refraction gradient required for a given focal length. An electromagnetic code was then used to design the required ring and wire unit cells. Finally, the index of refraction was approximated using ten discrete steps in an effective medium simulation for the GRIN lens that agreed with the experimental measurements.