Showing papers on "Lens (optics) published in 2006"

Adaptive liquid microlenses activated by stimuli-responsive hydrogels

Abstract: The trend towards miniaturization in optical imaging, diagnostics and lab-on-a-chip technology is creating a demand for sophisticated microlenses. A new type of smart liquid microlens has been developed that differs from most current devices in that it is self-focusing. The key component is a stimuli-responsive hydrogel integrated into a microfluidic system and acting as a container for a liquid droplet. The hydrogel simultaneously senses stimuli and actuates a change in droplet shape — and hence focal length. Stimuli can include biological and chemical agents and physical parameters. At this micrometre scale, pinned liquid-liquid interfaces are used to attain stable devices, and response times of ten to a few tens of seconds. Lenses can have virtually any focal length and are readily integrated into arrays. Despite its compactness, the human eye can easily focus on different distances by adjusting the shape of its lens with the help of ciliary muscles1. In contrast, traditional man-made optical systems achieve focusing by physical displacement of the lenses used. But in recent years, advances in miniaturization technology have led to optical systems that no longer require complicated mechanical systems to tune and adjust optical performance. These systems have found wide use in photonics, displays and biomedical systems. They are either based on arrays of microlenses with fixed focal lengths2,3,4,5, or use external control to adjust the microlens focal length6,7,8,9,10,11,12. An intriguing example is the tunable liquid lens, where electrowetting or external pressure manipulates the shape of a liquid droplet and thereby adjusts its optical properties. Here we demonstrate a liquid lens system that allows for autonomous focusing. The central component is a stimuli-responsive hydrogel13 integrated into a microfluidic system and serving as the container for a liquid droplet, with the hydrogel simultaneously sensing the presence of stimuli and actuating adjustments to the shape—and hence focal length—of the droplet. By working at the micrometre scale where ionic diffusion and surface tension scale favourably14, we can use pinned liquid–liquid interfaces to obtain stable devices and realize response times of ten to a few tens of seconds. The microlenses, which can have a focal length ranging from -∞ to +∞ (divergent and convergent), are also readily integrated into arrays that may find use in applications such as sensing, medical diagnostics and lab-on-a-chip technologies15,16,17,18,19.

A generic camera model and calibration method for conventional, wide-angle, and fish-eye lenses

Abstract: Fish-eye lenses are convenient in such applications where a very wide angle of view is needed, but their use for measurement purposes has been limited by the lack of an accurate, generic, and easy-to-use calibration procedure. We hence propose a generic camera model, which is suitable for fish-eye lens cameras as well as for conventional and wide-angle lens cameras, and a calibration method for estimating the parameters of the model. The achieved level of calibration accuracy is comparable to the previously reported state-of-the-art

The Sloan Lens ACS Survey. I. A large spectroscopically selected sample of massive early-type lens galaxies

Abstract: The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple nebular emission lines at a redshift significantly higher than that of the SDSS target galaxy. The SLACS survey is optimized to detect bright early-type lens galaxies with faint lensed sources in order to increase the sample of known gravitational lenses suitable for detailed lensing, photometric, and dynamical modeling. In this paper, the first in a series on the current results of our HST Cycle 13 imaging survey, we present a catalog of 19 newly discovered gravitational lenses, along with nine other observed candidate systems that are either possible lenses, nonlenses, or nondetections. The survey efficiency is thus >=68%. We also present Gemini 8 m and Magellan 6.5 m integral-field spectroscopic data for nine of the SLACS targets, which further support the lensing interpretation. A new method for the effective subtraction of foreground galaxy images to reveal faint background features is presented. We show that the SLACS lens galaxies have colors and ellipticities typical of the spectroscopic parent sample from which they are drawn (SDSS luminous red galaxies and quiescent MAIN sample galaxies), but are somewhat brighter and more centrally concentrated. Several explanations for the latter bias are suggested. The SLACS survey provides the first statistically significant and homogeneously selected sample of bright early-type lens galaxies, furnishing a powerful probe of the structure of early-type galaxies within the half-light radius. The high confirmation rate of lenses in the SLACS survey suggests consideration of spectroscopic lens discovery as an explicit science goal of future spectroscopic galaxy surveys.

Data reader apparatus having an adaptive lens

Abstract: Systems and methods for making and using handheld data readers comprising one or more fluid lenses. One or more fluid lenses are provided to allow a handheld data reader to perform such operations as reading indicia, including such additional operations as zooming, reorienting a viewing direction, focusing, adjusting an optical axis, and correcting for the effects of motion such as hand jitter. The fluid lens or lenses can be operated for example by applying electrical signals to fluid lenses comprising a plurality of fluids including at least one that is conductive and at least one that is non-conductive.

Method and apparatus for angular-resolved spectroscopic lithography characterization

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 radiation and their relative phase difference.

Optical scanner and image forming apparatus

Abstract: An optical scanner includes a light source, an optical coupler, an optical line image unit, a deflector, and an optical scanning unit. The optical scanning unit includes scanning lenses that guide the beams to a surface to be scanned. A surface on the deflector side of the scanning lens closest to a deflection reflecting surface has a negative power in a vertical scanning direction, and is a special toric surface in which a radius of curvature in a vertical scanning changes from an optical axis of the lens surface toward a periphery of the horizontal scanning direction. An F number of the beams toward the surface to be scanned of the scanning lens in the vertical scanning direction is larger in a peripheral part than in a central part in an effective scanning width.

Zoom lens and imaging apparatus

Abstract: An object of the present invention is to provide a low-cost, miniature, wide-angle high-zoom-ratio zoom lens that has high imaging performance, and an imaging apparatus equipped with the zoom lens. To achieve the object, a zoom lens including a first lens group having positive refracting power, a second lens group having negative refracting power and a third lens group having positive refracting power in order from an object side in which a lens group P having positive refracting power is arranged closer to an image plane side than the third lens group.

Numerical parametric lens for shifting, magnification, and complete aberration compensation in digital holographic microscopy

Abstract: The concept of numerical parametric lenses (NPL) is introduced to achieve wavefront reconstruction in digital holography. It is shown that operations usually performed by optical components and described in ray geometrical optics, such as image shifting, magnification, and especially complete aberration compensation (phase aberrations and image distortion), can be mimicked by numerical computation of a NPL. Furthermore, we demonstrate that automatic one-dimensional or two-dimensional fitting procedures allow adjustment of the NPL parameters as expressed in terms of standard or Zernike polynomial coefficients. These coefficients can provide a quantitative evaluation of the aberrations generated by the specimen. Demonstration is given of the reconstruction of the topology of a microlens.

Method of providing an optoelectronic element with a non-protruding lens

Abstract: An optoelectronic component has a lens that is formed in the surface of an encapsulant surrounding a semiconductor diode element. With respect to emitters, the lens reduces internal reflection and reduces dispersion to increase overall efficiency. With respect to detectors, the lens focuses photons on the active area of the detector, increasing detector sensitivity, which allows a detector having a reduced size and reduced cost for a given application. The lens portion of the encapsulant is generally non-protruding from the surrounding portions of the encapsulant reducing contact surface pressure caused by the optoelectronic component. This non-protruding lens is particularly useful in pulse oximetry sensor applications. The lens is advantageously formed with a contoured-tip ejector pin incorporated into the encapsulant transfer mold, and the lens shape facilitates mold release.

Micro-optical artificial compound eyes.

Abstract: Natural compound eyes combine small eye volumes with a large field of view at the cost of comparatively low spatial resolution. For small invertebrates such as flies or moths, compound eyes are the perfectly adapted solution to obtaining sufficient visual information about their environment without overloading their brains with the necessary image processing. However, to date little effort has been made to adopt this principle in optics. Classical imaging always had its archetype in natural single aperture eyes which, for example, human vision is based on. But a high-resolution image is not always required. Often the focus is on very compact, robust and cheap vision systems. The main question is consequently: what is the better approach for extremely miniaturized imaging systems—just scaling of classical lens designs or being inspired by alternative imaging principles evolved by nature in the case of small insects? In this paper, it is shown that such optical systems can be achieved using state-of-the-art micro-optics technology. This enables the generation of highly precise and uniform microlens arrays and their accurate alignment to the subsequent optics-, spacing- and optoelectronics structures. The results are thin, simple and monolithic imaging devices with a high accuracy of photolithography. Two different artificial compound eye concepts for compact vision systems have been investigated in detail: the artificial apposition compound eye and the cluster eye. Novel optical design methods and characterization tools were developed to allow the layout and experimental testing of the planar micro-optical imaging systems, which were fabricated for the first time by micro-optics technology. The artificial apposition compound eye can be considered as a simple imaging optical sensor while the cluster eye is capable of becoming a valid alternative to classical bulk objectives but is much more complex than the first system.

Temperature-dependent refractive index of silicon and germanium

Abstract: Silicon and germanium are perhaps the two most well-understood semiconductor materials in the context of solid state device technologies and more recently micromachining and nanotechnology. Meanwhile, these two materials are also important in the field of infrared lens design. Optical instruments designed for the wavelength range where these two materials are transmissive achieve best performance when cooled to cryogenic temperatures to enhance signal from the scene over instrument background radiation. In order to enable high quality lens designs using silicon and germanium at cryogenic temperatures, we have measured the absolute refractive index of multiple prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For silicon, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 20 to 300 K at wavelengths from 1.1 to 5.6 pin, while for germanium, we cover temperatures ranging from 20 to 300 K and wavelengths from 1.9 to 5.5 microns. We compare our measurements with others in the literature and provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. Citing the wide variety of values for the refractive indices of these two materials found in the literature, we reiterate the importance of measuring the refractive index of a sample from the same batch of raw material from which final optical components are cut when absolute accuracy greater than k5 x 10" is desired.

Nanometer linear focusing of hard x rays by a multilayer Laue lens.

Abstract: We report on a type of linear zone plate for nanometer-scale focusing of hard x rays, a multilayer Laue lens (MLL), produced by sectioning a multilayer and illuminating it in Laue diffraction geometry. Because of its large optical depth, a MLL spans the diffraction regimes applicable to a thin Fresnel zone plate and a crystal. Coupled wave theory calculations indicate that focusing to 5 nm or smaller with high efficiency should be possible. Partial MLL structures with outermost zone widths as small as 10 nm have been fabricated and tested with 19.5 keV synchrotron radiation. Focal sizes as small as 30 nm with efficiencies up to 44% are measured.

Tunable-focus liquid lens controlled using a servo motor

Abstract: We demonstrated a liquid lens whose focal length can be controlled by an actuator. The lens cell is composed of elastic membrane, planar glass plate, a periphery sealing ring, and a liquid with a fixed volume in the lens chamber. Part of the periphery sealing ring is excavated to form a hollow chamber which functions as a reservoir. This hollowed periphery is surrounded by an exterior rubber membrane. The shaft of an actuator is used to deform the elastic rubber. Squeezing the liquid contained in the reservoir into the lens chamber. Excess liquid in the lens chamber will push the lens membrane to outward, resulting in a lens shape change. Due to the compact structure and easy operation, this liquid lens has potential applications in zoom lenses, auto beam steering, and eyeglasses.

Subwavelength microwave imaging using an array of parallel conducting wires as a lens

Abstract: An original realization of a lens capable of transmitting images with subwavelength resolution is proposed. The lens is formed by an array of parallel conducting wires and effectively operates as a telegraph which captures a distribution of the electric field at the front interface of the lens and transmits it to the back side without distortions. This regime of operation is called canalization and is inherent in flat lenses formed by electromagnetic crystals. The theoretical estimations are supported by numerical simulations and experimental verification. The subwavelength resolution of $\ensuremath{\lambda}∕15$ and 18% bandwidth of operation are demonstrated at gigahertz frequencies. The proposed lens is capable of transporting subwavelength images without distortion to nearly unlimited distances since the influence of losses to the lens operation is negligibly small.

All-Angle Negative Refraction for Surface Plasmon Waves Using a Metal-Dielectric-Metal Structure

Abstract: We show that a metal-dielectric-metal structure can function as a negative refraction lens for surface plasmon waves on a metal surface. The structure is uniform with respect to a plane of incidence and operates at the optical frequency range. Using three-dimensional finite-difference time-domain simulations, we demonstrate the imaging operation of the structure with realistic material parameters including dispersions and losses. Our design should facilitate the demonstration of many novel effects associated with negative refraction on chip at optical wavelength ranges. In addition, this structure provides a new way of controlling the propagation of surface plasmons, which are important for nanoscale manipulation of optical waves.

Silicone hydrogel contact lenses and the ocular surface.

Abstract: For 30 years, contact lens research focused on the need for highly oxygen-permeable (Dk) soft lens materials. High Dk silicone hydrogel contact lenses, made available in 1999, met this need. The purpose of this review is to examine how silicone hydrogel lens wear affects the ocular surfaces and to highlight areas in which further research is needed to improve biocompatibility. Silicone hydrogel lenses have eliminated lens-induced hypoxia for the majority of wearers and have a less pronounced effect on corneal homeostasis compared to other lens types; however, mechanical interaction with ocular tissue and the effects on tear film structure and physiology are similar to that found with soft lens wear in general. Although the ocular health benefits of silicone hydrogel lenses have increased the length of time lenses can be worn overnight, the risk of infection is similar to that found with other soft lens types, and overnight wear remains a higher risk factor for infection than daily wear, regardless of lens material. Future contact lens research will focus on gaining a better understanding of the way in which contact lenses interact with the corneal surface, upper eyelid, and the tear film, and the lens-related factors contributing to infection and inflammatory responses.

Method and apparatus for patterned plasma-mediated laser trephination of the lens capsule and three dimensional phaco-segmentation

Abstract: System and method for making incisions in eye tissue at different depths. The system and method focuses light, possibly in a pattern, at various focal points which are at various depths within the eye tissue. A segmented lens can be used to create multiple focal points simultaneously. Optimal incisions can be achieved by sequentially or simultaneously focusing lights at different depths, creating an expanded column of plasma, and creating a beam with an elongated waist.

Automatic lens design and manufacturing system

Abstract: The present invention provides a method for designing and making a customized ophthalmic lens, such as a contact lens or an intraocular lens, capable of correcting high-order aberrations of an eye. The posterior surface of the customized contact lens is designed to accommodate the corneal topography of an eye. The design of the customized ophthalmic lens is evaluated and optimized in an optimizing routine using a computational model eye that reproduces the aberrations and corneal topography of an eye. The present invention also provides a system and method for characterizing the optical metrology of a customized ophthalmic lens that is designed to correct aberrations of an eye. Furthermore, the present invention provides a business model and method for placing an order for a pair of customized ophthalmic lenses.

Projection-based head-mounted display with eye-tracking capabilities

Abstract: Methods, systems, apparatus and devices for the lens design of an HMPD with eye-tracking capabilities. The integration uses a low-level optical configuration in order to achieve a compact, comfortable, easy-to-use system. The optical system is further designed and optimized for sharing of the optical path between the HMD and the Eye-Tracker with minimal performance loss for both tasks.

Apparatus and method for capturing still images and video using coded lens imaging techniques

Abstract: An apparatus for capturing images. In one embodiment, the apparatus comprises: a coded lens array including a plurality of lenses arranged in a coded pattern and with opaque material blocking array elements that do not contain lenses; and a light-sensitive semiconductor sensor coupled to the coded lens array and positioned at a specified distance behind the coded lens array, the light-sensitive sensor configured to sense light transmitted through the lenses in the coded lens array.

Image-capturing apparatus

Abstract: A digital camera enables high-speed zooming operation without use of a zoom lens Light originating from a fixed-focal-length lens is split into two beams by a beam splitter, to thus form respective images on a first image sensor and a second image sensor The first image sensor and the second image sensor are equal to each other in terms of the number of pixels, but differ from each other in terms of a pixel size The first image sensor acquires a wide image, and the second image sensor acquires a telephotography image An output is produced by means of switching between the first image sensor and the second image sensor, in response to zooming operation When the image from the first image sensor is recorded, focus detection is performed by use of an image signal from the second image sensor, to thus effect automatic focusing

Light emitting device provided with lens for controlling light distribution characteristic

Abstract: The light emitting device comprises a substrate (2), a positive electrode (6) and a negative electrode (4) formed on the substrate (2), a light emitting diode (8) connected to the positive electrode (6) and the negative electrode (4), the transparent resin (12 and 14) that covers the light emitting diode (8), a fluorescent material (16) that absorbs at least part of light emitted by the light emitting diode (8) and converts it to light of longer wavelength, and the lens that changes the direction of light emission from the light emitting diode (8) and/or the fluorescent material (16). The resin (12 and 14) includes the fluorescent material (16) and is formed so as to constitute the lens of substantially semi-cylindrical shape, and the fluorescent material (16) included in the resin (12 and 14) is distributed with a higher concentration in a region near the surface of the light emitting diode (8) than in a region near the surface of the portion that constitutes the lens.

Variable focus dielectric liquid droplet lens.

Abstract: A liquid crystal droplet lens driven by the dielectrophoresis (DEP) force was demonstrated. The liquid crystal droplet lens was deformed by the DEP forces under non-uniform AC electric fields. Focal length, hysteresis and electrode design were studied. The focal length varied from 1.6mm to 2.6mm in the range of 0-200V at 1 kHz for electrode spacing of 50μm; that is, the tuning ratio of the focal length was about 60% in maximum. The hysteresis of contact angle was found to be less than 3° and it vanished after 1 minute at the rest state. As the electrode spacing over 200μm, the tuning ratios of the focal length dropped below 5%. The liquid crystal droplet lens that had numerical aperture of about 0.5 consumed power of about 0.1mW. Its response time was measured to be about 220ms.

Lensless Imaging with a Controllable Aperture

Abstract: In this paper we propose a novel, highly flexible camera. The camera consists of an image detector and a special aperture, but no lens. The aperture is a set of parallel light attenuating layers whose transmittances are controllable in space and time. By applying different transmittance patterns to this aperture, it is possible to modulate the incoming light in useful ways and capture images that are impossible to capture with conventional lens-based cameras. For example, the camera can pan and tilt its field of view without the use of any moving parts. It can also capture disjoint regions of interest in the scene without having to capture the regions in between them. In addition, the camera can be used as a computational sensor, where the detector measures the end result of computations performed by the attenuating layers on the scene radiance values. These and other imaging functionalities can be implemented with the same physical camera and the functionalities can be switched from one video frame to the next via software. We have built a prototype camera based on this approach using a bare image detector and a liquid crystal modulator for the aperture. We discuss in detail the merits and limitations of lensless imaging using controllable apertures.

Source camera identification using footprints from lens aberration

Abstract: Source camera identification is the process of discerning which camera has been used to capture a particular image. In this paper, we consider the more fundamental problem of trying to classify images captured by a limited number of camera models. Inspired by the previous work that uses sensor imperfection, we propose to use the intrinsic lens aberration as features in the classification. In particular, we focus on lens radial distortion as the primary distinctive feature. For each image under investigation, parameters from pixel intensities and aberration measurements are obtained. We then employ a classifier to identify the source camera of an image. Simulation is carried out to evaluate the success rate of our method. The results show that this is a viable procedure in source camera identification with a high probability of accuracy. Comparing with the procedures using only image intensities, our approach improves the accuracy from 87% to 91%.

Digital imaging system and method using multiple digital image sensors to produce large high-resolution gapless mosaic images

Abstract: A digital imaging system and method using multiple cameras arranged and aligned to create a much larger virtual image sensor array. Each camera has a lens with an optical axis aligned parallel to the optical axes of the other camera lenses, and a digital image sensor array with one or more non-contiguous pixelated sensors. The non-contiguous sensor arrays are spatially arranged relative to their respective optical axes so that each sensor images a portion of a target region that is substantially different from other portions of the target region imaged by other sensors, and preferably overlaps adjacent portions imaged by the other sensors. In this manner, the portions imaged by one set of sensors completely fill the image gaps found between other portions imaged by other sets of sensors, so that a seamless mosaic image of the target region may be produced.

MEMS-based adaptive optics scanning laser ophthalmoscopy

Abstract: We have developed a compact, robust adaptive optics (AO) scanning laser ophthalmoscope using a microelectromechanical (MEMS) deformable mirror (DM). Facilitated with a Shack-Hartmann wavefront sensor, the MEMS-DM-based AO operates a closed-loop modal wave aberration correction for the human eye and reduces wave aberrations in most eyes to below 0.1 μm rms. Lateral resolution is enhanced, and images reveal a clear cone mosaic near the foveal center. The significant increase in throughput allows for a confocal pinhole whose diameter is less than the Airy disc of the collection lens, thereby fully exploiting the axial resolution capabilities of the system.

Electromagnetic lens antenna device for bistatic radar

Abstract: An electromagnetic lens device includes an electromagnetic lens (2) for transmission, an electromagnetic lens (3) for reception, two primary radiators (4, 5) each located at a focal point of one of the electromagnetic lenses (2, 3) , an arm (12) holding the primary radiators (4, 5) , and a table (8). The arm (12) is rotatable about a first axis (A) that extends through the centers of the electromagnetic lenses (2, 3) . The table (8) is rotatable about a second axis (B) that is perpendicular to the first axis (A) . The primary radiators (4, 5) rotate about the first axis (A) together with the arm (12) , and rotate about the second axis (B) together with the table (8) .

50-GHz passively mode-locked surface-emitting semiconductor laser with 100-mW average output power

Abstract: We have developed a passively mode-locked optically-pumped vertical-external-cavity surface-emitting semiconductor laser (VECSEL) which delivers up to 100 mW of average output power at a repetition rate of 50 GHz in nearly transform-limited 3.3-ps pulses at a wavelength around 960 nm. The high-repetition-rate passive mode locking was achieved with a low-saturation-fluence semiconductor saturable absorber mirror (SESAM) incorporating a single layer of quantum-dots. The output power within a nearly diffraction-limited beam was maximized using a gain structure with a low thermal impedance soldered to a diamond heat spreader. In addition, we systematically optimized the laser resonator to accommodate for the strong thermal lens caused by the optical pumping. We measured the thermal lens dioptric power and present a numerical model which is in good agreement with the measurements and is useful for optimizing resonator designs. The experimental setup is very versatile and its design and construction are discussed in detail

Camera based control

Abstract: A communication device may include a lens and processing logic. The lens may receive a gesture made by a user of the mobile terminal and the processing logic may identify the gesture. The processing logic may also generate a command based on the identified gesture, where the command instructs the mobile terminal or an external device to perform a control action.