Showing papers on "Lens (optics) published in 2007"

The focusing of electron flow and a Veselago lens in graphene p-n junctions.

Abstract: The focusing of electric current by a single p-n junction in graphene is theoretically predicted. Precise focusing may be achieved by fine-tuning the densities of carriers on the n- and p-sides of the junction to equal values. This finding may be useful for the engineering of electronic lenses and focused beam splitters using gate-controlled n-p-n junctions in graphene-based transistors.

Dappled photography: mask enhanced cameras for heterodyned light fields and coded aperture refocusing

Abstract: We describe a theoretical framework for reversibly modulating 4D light fields using an attenuating mask in the optical path of a lens based camera. Based on this framework, we present a novel design to reconstruct the 4D light field from a 2D camera image without any additional refractive elements as required by previous light field cameras. The patterned mask attenuates light rays inside the camera instead of bending them, and the attenuation recoverably encodes the rays on the 2D sensor. Our mask-equipped camera focuses just as a traditional camera to capture conventional 2D photos at full sensor resolution, but the raw pixel values also hold a modulated 4D light field. The light field can be recovered by rearranging the tiles of the 2D Fourier transform of sensor values into 4D planes, and computing the inverse Fourier transform. In addition, one can also recover the full resolution image information for the in-focus parts of the scene. We also show how a broadband mask placed at the lens enables us to compute refocused images at full sensor resolution for layered Lambertian scenes. This partial encoding of 4D ray-space data enables editing of image contents by depth, yet does not require computational recovery of the complete 4D light field.

Particle-optical projection system

Abstract: In a particle-optical projection system a pattern is imaged onto a target by means of energetic electrically charged particles. The pattern is represented in a patterned beam of said charged particles emerging from the object plane through at least one cross-over; it is imaged into an image with a given size and distortion. To compensate for the Z-deviation of the image position from the actual positioning of the target (Z denotes an axial coordinate substantially parallel to the optical axis), without changing the size of the image, the system includes a position detector for measuring the Z-position of several locations of the target, and a controller for calculating modifications of selected lens parameters of the final particle-optical lens and controlling said lens parameters according to said modifications.

Calculation of intraocular lens power: a review.

Abstract: This review describes the principles and practices involved in the calculation of intraocular lens (IOL) power The theories behind formulas for calculating IOL power are described, using regression and optical methods employing 'thin lens' and 'thick lens' models, as well as exact ray-tracing methods Numerical examples are included to illustrate the points made The paper emphasizes the importance of establishing an accurate estimation of corneal power as well as an accurate technique for the measurement of axial length and accurate methods of predicting postoperative anterior chamber depth (ACD) It is concluded that current improvements in diagnostic and surgical technology, combined with the latest generation IOL power formulas, make the calculation and selection of appropriate IOL power among the most effective tools in refractive surgery today

Transmission Efficiency of an Aerodynamic Focusing Lens System: Comparison of Model Calculations and Laboratory Measurements for the Aerodyne Aerosol Mass Spectrometer

Abstract: The size-dependent particle transmission efficiency of the aerodynamic lens system used in the Aerodyne Aerosol Mass Spectrometer (AMS) was investigated with computational fluid dynamics (CFD) calculations and experimental measurements. The CFD calculations revealed that the entire lens system, including the aerodynamic lens itself, the critical orifice which defines the operating lens pressure, and a valve assembly, needs to be considered. Previous calculations considered only the aerodynamic lens. The calculations also investigated the effect of operating the lens system at two different sampling pressures, 7.8 × 104 Pa (585 torr) and 1.0 × 105 Pa (760 torr). Experimental measurements of transmission efficiency were performed with size-selected diethyl hexyl sebacate (DEHS), NH4NO3, and NaNO3 particles on three different AMS instruments at two different ambient sampling pressures (7.8 × 104 Pa, 585 torr and 1.0 × 105 Pa, 760 torr). Comparisons of the measurements and the calculations show qualitative ag...

Frequency of and factors associated with contact lens dissatisfaction and discontinuation.

Abstract: Purpose To determine the frequency of and factors associated with contact lens dissatisfaction and discontinuation. Methods A cross-sectional survey of 730 subjects was conducted using a self-administered survey instrument. The survey collected information about present age and sex, history of contact lens wear, types of lenses worn, age at starting wear, current wearing schedule (hours per day, days per week), self-perceived contact lens satisfaction, and contact lens-related problems. A variety of statistical analyses including analysis of variance, logistic regression, and repeated-measures logistic regression were used to model the data. Results Current or previous experience with contact lenses was reported by 453 (62%) of the subjects. Of these subjects, 119 (26.3%) reported that contact lenses were not the ideal form of visual correction for them (contact lens dissatisfaction) and another 109 (24.1%) had permanently discontinued contact lens wear. Dissatisfied contact lens wearers had reduced self-reported wearing times compared with satisfied contact lens wearers. Previous lens wearers were more likely than current lens wearers to be men, older (by approximately 9.5 years), have started contact lens wear at a later age (approximately 4-5 years later), and have tried either rigid or both soft and rigid lenses. The primary self-reported reason for both contact lens dissatisfaction and discontinuation was ocular symptoms (dryness and discomfort), followed by preference for another corrective modality. Conclusion A significant number of contact lens wearers are not satisfied with contact lenses and are at risk for discontinuation.

4D Light Field Cameras

Abstract: A camera acquires a 4D light field of a scene. The camera includes a lens and sensor. A mask is arranged in a straight optical path between the lens and the sensor. The mask including an attenuation pattern to spatially modulate the 4D light field acquired of the scene by the sensor. The pattern has a low spatial frequency when the mask is arranged near the lens, and a high spatial frequency when the mask is arranged near the sensor.

Camera using multiple lenses and image sensors to provide improved focusing capability

Abstract: An electronic camera for producing an output image of a scene from a captured image signal includes: (a) a first imaging stage comprising a first image sensor for generating a first sensor output; a first lens for forming a first image of the scene on the first image sensor; and a first lens focus adjuster for adjusting focus of the first lens responsive to a first focus detection signal; and (b) a second imaging stage comprising a second image sensor for generating a second sensor output; a second lens for forming a second image of the scene on the second image sensor; and a second lens focus adjuster for adjusting focus of the second lens responsive to a second focus detection signal. A processing stage either (a) selects the sensor output from the first imaging stage as the captured image signal and uses the sensor output from the second imaging stage to generate the first focus detection signal for the selected imaging stage, or (b) selects the sensor output from the second imaging stage as the captured image signal and uses the sensor output from the first imaging stage to generate the second focus detection signal for the selected imaging stage.

Aberration-free optical refocusing in high numerical aperture microscopy

Abstract: We describe a method of optical refocusing for high numerical aperture (NA) systems that is particularly relevant for confocal and multiphoton microscopy. This method avoids the spherical aberration that is common to other optical refocusing systems. We show that aberration-free images can be obtained over an axial scan range of 70 mum for a 1.4 NA objective lens. As refocusing is implemented remotely from the specimen, this method will enable high axial scan speeds without mechanical interference between the objective lens and the specimen.

Lens driving device

Abstract: Disclosed herein is a lens driving device which is able to increase displacement without restriction, does not require a complex structure despite having a low power consumption, solves problems of friction and noise occurring in a gear mechanism, and realizes miniaturization and lightness. The lens driving device of the present invention includes a substrate which generates surface acoustic waves on a surface thereof, and a movable unit which is coupled to an optical lens and executes translation above the substrate using the surface acoustic waves. Therefore, the lens driving device of the present invention can implement translation of a lens without a separate mechanism, unlike conventional driving devices using motors and screws. Furthermore, the present invention satisfies the recent trend towards miniaturization and lightness, thus being usable in a variety of industrial fields that use optical lenses.

Gravitational lens time delays: A statistical assessment of lens model dependences and implications for the global hubble constant

Abstract: Time delays between lensed multiple images have been known to provide an interesting probe of the Hubble constant, but such an application is often limited by degeneracies with the shape of lens potentials. We propose a new statistical approach to examine the dependence of time delays on the complexity of lens potentials, such as higher order perturbations, nonisothermality, and substructures. Specifically, we introduce a dimensionless reduced time delay and explore its behavior analytically and numerically as a function of the image configuration, which is characterized by the asymmetry and opening angle of the image pair. In particular, we derive a realistic conditional probability distribution for a given image configuration from Monte Carlo simulations. We find that the probability distribution is sensitive to the image configuration such that more symmetric and/or smaller opening-angle image pairs are more easily affected by perturbations on the primary lens potential. On average time delays of double lenses are less scattered than those of quadruple lenses. Furthermore, the realistic conditional distribution allows a new statistical method to constrain the Hubble constant from observed time delays. We find that 16 published time delay quasars constrain H0 to be 70 ± 6 km s-1 Mpc-1, where the value and its error are estimated using jackknife resampling. Systematic errors coming from the heterogeneous nature of the quasar sample and the uncertainty of the input distribution of lens potentials can be larger than the statistical error. After including rough estimates of important systematic errors, we find H0 = 68 ± 6(stat.) ± 8(syst.) km s-1 Mpc-1. The reasonable agreement of the value of the Hubble constant with other estimates indicates the usefulness of our new approach as a cosmological and astrophysical probe, particularly in the era of large-scale synoptic surveys.

Fast Computational Camera Based On Two Arrays of Lenses

Abstract: Method and apparatus for a fast (low F/number) computational camera that incorporates two arrays of lenses. The arrays include a lenslet array in front of a photosensor and an objective lens array of two or more lenses. Each lens in the objective lens array captures light from a subject. Each lenslet in the lenslet array captures light from each objective lens and separates the captured light to project microimages corresponding to the objective lenses on a region of the photosensor under the lenslet. Thus, a plurality of microimages are projected onto and captured by the photosensor. The captured microimages may be processed in accordance with the geometry of the objective lenses to align the microimages to generate a final image. One or more other algorithms may be applied to the image data in accordance with radiance information captured by the camera, such as automatic refocusing of an out-of-focus image.

Dielectrically actuated liquid lens

Abstract: A packaged liquid lens driven by the dielectric force was demonstrated. The liquid lens consisted of a low dielectric constant droplet and a high dielectric constant sealing liquid. The two non-conductive liquids were sealed in a chamber under the condition of iso-density. Focal length of a liquid lens with an aperture of 3mm changed from 34mm to 12mm in the range of 0-200V. Hysteresis was observed in the liquid lens, with a maximum value measured of 12.5 degrees at 120 volts in terms of droplet's contact angle. The focal spot size measured approximately 80mum. Rise and fall times were 650ms and 300ms, respectively. The lens consumed 1mW of power when applying a 200 volt, 1 kHz signal. The longitudinal and transverse spherical aberrations were estimated to be nearly invariant when the focal length exceeded 20mm.

Liquid crystal lens with large focal length tunability and low operating voltage.

Abstract: We demonstrate a tunable focus liquid crystal (LC) lens by sandwiching a homogeneous LC layer between a planar electrode and a curved electrode. The curved electrode which is made of conductive polymer has parabolic shape with a large apex distance. Such design dramatically reduces the phase loss which leads to a short focal length (~15 cm). By using a thin top glass substrate on the curved electrode side, the operating voltage of the lens cell for achieving the shortest focal length is reduced to ~23 Vrms. This LC lens has advantages in large focal length tunability, low operating voltage, and good mechanical stability.

Enhanced electro-active lens system

Abstract: A lens system and optical devices that provide enhanced vision correction are disclosed. The lens system includes an electro-active layer that provides correction of at least one higher order aberration. The higher order correction changes dynamically based on a user of the lens system's needs, such as a change by the user's gaze distance, pupil size, or changes in tear film following blinking, among others. Optical devices are also described that use these and other lens systems to provide correction of higher order aberrations. An optical guide is also described that guides the user's line of sight to see through a lens region having a correction for a higher order aberration.

Method and apparatus for operating a dual lens camera to augment an image

Abstract: An electronic camera for producing an output image of a scene from a captured image signal includes a first imaging stage comprising a first image sensor for generating a first sensor output and a first lens for forming a first image of the scene on the first image sensor, and a second imaging stage comprising a second image sensor for generating a second sensor output and a second lens for forming a second image of the scene on the second image sensor. The sensor output from the first imaging stage is used as a primary output image for forming the captured image signal and the sensor output from the second imaging stage is used as a secondary output image for modifying the primary output image, thereby generating an enhanced, captured image signal.

Targeting contact lens induced dryness and discomfort: what properties will make lenses more comfortable.

Abstract: There are about 35 million contact lens wearers in North America, and about half of them are symptomatic of dryness and discomfort, more commonly experienced at the end of the lens wearing day. Most of these contact lens wearers do not suffer from true dry eye, which is a pervasive and ubiquitous disease or condition that affects many millions of people in North America. It seems fairly clear that the lens causes the eye to become uncomfortable or "dry," and unless it is effectively remedied, the patient will most likely discontinue lens wear. This review describes the dryness and discomfort effects of contact lenses and how contact lens properties with novel solutions have the potential for eliminating or alleviating these symptoms.

Bicone pattern shaping device

Abstract: A broadband omni-directional bicone antenna. The antenna can comprise conductive surfaces of conical voids provided within a solid dielectric structure. The outside surface of the solid structure can support a radio frequency (RF) lens geometry operable for beam forming. The beam forming can modify the elevation pattern of the electromagnetic radiation from the bicone antenna. The solid dielectric structure may be machined or molded from a single piece of material. The conical voids provided within the solid structure can be metallized to provide conductive bicone radiators. The outer surface beam shaping lenses can be zoned or continuous and can provide elevation patterns with increased gain, cosecant squared falloff, or various other patterns. The beam shaping lens may be formed from any low-loss dielectric. Alternatively, the lens may be formed from a less dense material such as dielectric foam that can support radial conductive beam forming vanes.

Basic building units and properties of a fluorescence single plane illumination microscope.

Abstract: The critical issue of all fluorescence microscopes is the efficient use of the fluorophores, i.e., to detect as many photons from the excited fluorophores as possible, as well as to excite only the fluorophores that are in focus. This issue is addressed in EMBL’s implementation of a light sheet based microscope [single plane illumination microscope (SPIM)], which illuminates only the fluorophores in the focal plane of the detection objective lens. The light sheet is a beam that is collimated in one and focused in the other direction. Since no fluorophores are excited outside the detectors’ focal plane, the method also provides intrinsic optical sectioning. The total number of observable time points can be improved by several orders of magnitude when compared to a confocal fluorescence microscope. The actual improvement factor depends on the number of planes acquired and required to achieve a certain signal to noise ratio. A SPIM consists of five basic units, which address (1) light detection, (2) illumina...

Wide-field schematic eye models with gradient-index lens

Abstract: We propose a wide-field schematic eye model, which provides a more realistic description of the optical system of the eye in relation to its anatomical structure. The wide-field model incorporates a gradient-index (GRIN) lens, which enables it to fulfill properties of two well-known schematic eye models, namely, Navarro's model for off-axis aberrations and Thibos's chromatic on-axis model (the Indiana eye). These two models are based on extensive experimental data, which makes the derived wide-field eye model also consistent with that data. A mathematical method to construct a GRIN lens with its iso-indicial contours following the optical surfaces of given asphericity is presented. The efficiency of the method is demonstrated with three variants related to different age groups. The role of the GRIN structure in relation to the lens paradox is analyzed. The wide-field model with a GRIN lens can be used as a starting design for the eye inverse problem, i.e., reconstructing the optical structure of the eye from off-axis wavefront measurements. Anatomically more accurate age-dependent optical models of the eye could ultimately help an optical designer to improve wide-field retinal imaging.

Theoretical comparison of aberration-correcting customized and aspheric intraocular lenses.

Abstract: PURPOSE: To assess the performance and optical limitations of standard, aspheric, and wavefront-customized intraocular lenses (IOLs) using clinically verifi ed pseudophakic eye models. METHODS: White light pseudophakic eye models were constructed from physical measurements performed on 46 individual cataract patients and subsequently verifi ed using the clinically measured contrast sensitivity function (CSF) and wavefront aberration of pseudophakic patients implanted with two different types of IOLs. These models are then used to design IOLs that correct the astigmatism and higher order aberrations of each individual eye model’s cornea and to investigate how this correction would affect visual benefi t, subjective tolerance to lens misalignment (tilt, decentration, and rotation), and depth of fi RESULTS: Physiological eye models and clinical outcomes show similar levels of higher order aberration and contrast improvement. Customized correction of ocular wavefront aberrations with an IOL results in contrast improvements on the order of 200% over the control and the Tecnis IOLs. The customized lenses can be, on average, decentered by as much as 0.8 mm, tilted 10°, and rotated as much as 15° before their polychromatic modulation transfer function at 8 cycles/degree is less than that of the Tecnis or spherical control lens. Correction of wavefront aberration results in a narrower through focus curve but better out of focus performance for 0.50 diopters. CONCLUSIONS: The use of realistic eye models that include higher order aberrations and chromatic aberrations are important when determining the impact of new IOL designs. Customized IOLs show the potential to improve visual performance. [J Refract Surg.

Variable imaging arrangements and methods therefor

Abstract: Various approaches to imaging involve selecting directional and spatial resolution. According to an example embodiment, images are computed using an imaging arrangement to facilitate selective directional and spatial aspects of the detection and processing of light data. Light passed through a main lens is directed to photosensors via a plurality of microlenses. The separation between the microlenses and photosensors is set to facilitate directional and/or spatial resolution in recorded light data, and facilitating refocusing power and/or image resolution in images computed from the recorded light data. In one implementation, the separation is varied between zero and one focal length of the microlenses to respectively facilitate spatial and directional resolution (with increasing directional resolution, hence refocusing power, as the separation approaches one focal length).

Discontinuous free-form lens design for prescribed irradiance

Abstract: For the problem of point source forming prescribed irradiance, a new, to the best of our knowledge, method-variable separation mapping method is presented, which establishes separately the correspondence between variables on the light source and the target plane. The role played by the optical surfaces is then to redirect the light rays to their corresponding target points. The surface of the lens is determined by first calculating the surface points and then their normal vectors. Considering that normal deviations are produced in the surface construction process, a normal deviation control method is also presented to restrict the deviation. With this normal deviation control method, discontinuities are introduced onto the lens surface. From these mapping and normal control methods, a fast and efficient algorithm has been developed for several prescribed irradiance problems with simple nonrotational shape of the illuminated region.

Imager module optical focus and assembly method

Abstract: An imager apparatus and methods are described. An embodiment of an imager module includes a plurality of groups of optical lenses, a lens frame, and at least one associated lens barrel configured to position and hold the plurality of groups of optical lenses. At least one of the groups of optical lenses is movable with respect to at least one other group of optical lenses for achieving optical focus. The imager module includes an integrated circuit (IC) imager die in proximity to the plurality of lenses, the imager die containing at least one image capture microelectronic device.

Compound eye camera module and method of producing the same

Abstract: A compound eye camera module where an optical filter array (2) and a light shielding block (6) are arranged between a lens module (7) and imaging regions (4a-4d). The optical filter array (2) has optical filters (2a-2d). The light shielding block (6) has light shielding walls (61a-61d) forming openings (6a-6d) independent from each other. The lens module (7) integrally has lenses (1a-1d) arranged on a single plane. First sliding surfaces (66-69) are provided on the light shielding block. The lens module is provided with second sliding surfaces (56-59) sliding on the first sliding surface, and the lens module is provided so that it can rotate relative to the light shielding block with an axis normal to the imaging regions as the center axis of the rotation. The compound eye camera module is small sized, thin, and low cost.

Camera using multiple lenses and image sensors in a rangefinder configuration to provide a range map

Abstract: An electronic camera for producing an output image of a scene from a captured image signal includes a first imaging stage comprising a first image sensor for generating a first sensor output and a first lens for forming a first image of the scene on the first image sensor, and a second imaging stage comprising a second image sensor for generating a second sensor output and a second lens for forming a second image of the scene on the second image sensor, where the lenses have different focal lengths. A processing stage uses the sensor output from one of the imaging stages as the captured image signal and uses the images from both imaging stages to generate a range map identifying distances to the different portions of the scene.

Graded-index fiber lens proposed for ultrasmall probes used in biomedical imaging

Abstract: The quality and parameters of probing optical beams are extremely important in biomedical imaging systems both for image quality and light coupling efficiency considerations. For example, the shape, size, focal position, and focal range of such beams could have a great impact on the lateral resolution, penetration depth, and signal-to-noise ratio of the image in optical coherence tomography. We present a beam profile characterization of different variations of graded-index (GRIN) fiber lenses, which were recently proposed for biomedical imaging probes. Those GRIN lens modules are made of a single mode fiber and a GRIN fiber lens with or without a fiber spacer between them. We discuss theoretical analysis methods, fabrication techniques, and measured performance compared with theory.

Multi-beam antenna with shared dielectric lens

Abstract: An integrated multi-beam antenna with a shared dielectric lens is disclosed. The antenna is formed by positioning the feed apertures of a plurality of waveguide feeds at positions located on the surface of the shared dielectric lens. The angular direction and shape of radiation beams produced by the waveguide feeds are determined by the physical and dielectric characteristics of the lens, the location of feed apertures of the waveguide feeds on the surface of the lens, and the frequency of electromagnetic energy propagating in the waveguide feeds. The principles of the invention are applied to realiz an inexpensive, integrated multi-feed antenna adapted to provide desired angular areas of coverage for both a long range and short range radar in an automotive radar safety system.

On the ocular refractive components: the Reykjavik Eye Study.

Abstract: . Purpose: To study the correlation between ocular refraction and the refractive components (corneal power, lens power and axial length) in a population-based sample of normal subjects. Methods: We analysed the refractive and biometric findings for 723 right eyes (325 males and 398 females) comprising a population-based random sample of citizens 55 years and older participating in the Reykjavik Eye Study. Measurements of refraction, corneal curvature (by keratometry), anterior chamber depth, lens thickness and axial length (all by ultrasound biometry) were used to calculate crystalline lens power. The correlation and regression between refraction and ocular refractive components (corneal power, anterior chamber depth, lens power and axial length) were studied by distributional statistical methods. Results: Refraction (spherical equivalent) showed a significant negative correlation with axial length (r = –0.59, P < 0.0001), lens power (r = –0.26, P < 0.0001) and corneal power (r = –0.16, P < 0.0001). There were significant negative correlations between axial length and corneal power (r = –0.44, P < 0.0001) and between axial length and lens power (r = –0.44, P < 0.0001). Based on multiple linear regression analysis, refraction could be correlated with corneal power, lens power and axial length in combination with a correlation coefficient of 0.98 (P < 0.0001). Conclusion: This study confirms that ocular refraction is statistically significantly correlated with not only axial length but also lens power and (to a lesser extent) corneal power. The variation and correlations of crystalline lens power were considerable – possibly indicating this component's modulatory effect on ocular refraction during growth. We conclude the refractive error of the eye to be a multifactorial condition involving a complex interplay between the cornea, the lens and the length of the eye.