Showing papers on "Lens (optics) published in 1984"

The Statistics of gravitational lenses: The Distributions of image angular separations and lens redshifts

Abstract: An analytical calculation is presented which determines the probability that the light from a distant quasar can be lensed by objects in a different redshift range. Three types of information are used to make the calculation: (1) the physical properties of the intervening scattering lenses; (2) the intrinsic properties of the quasars and (3) the selection procedures by which the quasar samples are acquired. A series of differential equations is given in which the probability is derived, and a number of recommendations are offered with respect to VLA and Space Telescope observations of quasars lensed in this way.

Focusing by electrical modulation of refraction in a liquid crystal cell

Abstract: The creation of a field-controlled variation of the index of refraction in a liquid crystal cell has been analyzed and experimentally verified. To obtain a spherical lens utilizing a simple electrode structure and capable of focusing arbitrary incoming polarizations requires four flat nematic liquid crystal cells. With electrodes fabricated well within the current capability of photolithography, near diffraction-limited performance in terms of the optical transfer function is predicted. The focusing capability of a liquid crystal lens was demonstrated using a single cell with linear transparent electrodes. A plano-convex cylindrical lens for a single incoming polarization was thus created. While the cell had a crude electrode structure, it affirmed all the major qualitative predictions. The fringing along the edge of the electrodes required for eventually obtaining near diffraction-limited performance was observed.

Continuously variable contact lens

Abstract: A continuously variable multi-focal soft contact lens wherein a continuous optical gradient in a region smaller than the maximum pupil opening is provided. The concave surface is aspheric with a desired optical power for distant viewing at the center which increases to the desired near vision power. The increase is usually about 3 to 5 diopters within 6 mm of the anterior optical zone (AOZ) which is approximately 9.7 mm in diameter when wet. Outside this 6 mm zone the concave surface is essentially spherical. The concave surface is an aspheric curve having a steeper curve in the middle than a base curve r2. The curve at the center is the steepest and is designated as r2 '. Once r2 and r2 ' curves are determined, the thickness of the lens (t) and the radius of curavation for AOZ designated r1 is calculated using the desired optical power at the apex of the lens (Pw) and desired thickness at the junction (JTK) of the AOZ, based on the following equation: ##EQU1## wherein Exp is the expansion factor and n is the index of refraction of the lens when wet, all other dimension in the dry state, before expansion. The lenses may be manufactured by lathe cut and polish means using the squeeze method or may be duplicated by molding and casting.

Comparison of models describing the thermal lens effect

Abstract: A model for the thermal lens which approximates the refractive shape as a parabola is compared with a model which accounts for the aberrant nature of the lens; both models are tested against experimental results. The comparison suggests how the inaccuracies of the parabolic lens model may be corrected while retaining its mathematical simplicity and better predictive power for stronger thermal lenses.

Beam optics of quadrupole probe-forming systems.

Abstract: This book presents the theory of quadrupole focusing with the practical development of microprobe systems in mind. The introductory chapter outlines the analytical processes and provides a background to the problems of designing quadrupole probe-forming systems. Following a description of the quadrupole lens and the mathematical models used to describe the fields within both magnetic and electrostatic quadrupole lenses, the authors describe two techniques for calculating the path of a charged particle through a beam-optical system; matrix methods and numerical raytracing. The minimum spot size achieved by a quadrupole system is influenced strongly by parasitic aberrations due to imperfections in the construction and alignment of the instrument. The authors assess the importance of the various effects by reference to their influence in three existing microprobe systems. Finally, they describe briefly some novel and interesting alternatives to the quadrupole lens as the focusing element. Refs.

Laser adjustable intraocular lens and method of altering lens power

Abstract: A laser beam is utilized to alter, in situ, the power of an implanted intraocular lens. The overall intraocular lens can be of conventional size and shape. The circumference, or outer ring of the lens is manufactured from a non-toxic heat shrinkable plastic. The plastic is preferably colored to permit selective absorption of laser energy thereby causing the shape, and thus the corrective power, of the lens to change. The invention is particularly useful for correcting postoperative astigmatism.

Dual lens antenna with mechanical and electrical beam scanning

Abstract: A mechanically positioned phase steered transfer lens which is illuminatedy a fixed collimation lens. Wide angle scan is accomplished by tilting the movable lens and electronically scanning the beam to the desired angle. The mechanical motion minimizes the required electronic scan angles, thus minimizing the number of phase shifters required.

Multifocal, especially bifocal, intraocular, artificial ophthalmic lens

Abstract: A multifocal, especially bifocal, intraocular, artificial ophthalmic lens of transparent material, whose optical lens portion is divided into near range and far range zones and, each of which is disposed on the optical lens portion with approximately equal surface proportions and symmetrically with the lens axis.

Measuring system employing a measuring method based on the triangulation principle for the non-contact measurement of a distance from the surface of a contoured object to a reference level. _

Abstract: An apparatus for dimensional inspection of an object. The apparatus is adapted to produce a slender beam of measuring radiation for irradiating an object under examination. Reflected light image receiving means are provided including a receiving lens for collecting radiation reflected from an object surface spot irradiated by the measuring beam, and a linear photo-sensitive detector. The receiving lens is dimensioned and disposed relative to the measuring beam and the linear detector as to exclusively project those object surface spots irradiated by a longitudinal section defining a measuring range, of the measuring beam, as focussed dots on the linear photo-sensitive detector area. For improving the resolution of the focussed dots produced on the detector, a beam forming lens is provided for causing the cross-sectional area of the measuring beam to gradually increase over the measuring range. The apparatus is further adapted to image one and same object surface spot irradiated by the measuring means as two separate dots on the detector wherein these dots are uniquely related to each other only, in case a true reflection has been received. Thereby a discrimination can be made between true and false reflections from the object under examination.

Searching and measuring endoscope

Abstract: A searching and measuring endoscope employing two image-transmitting systems in a common housing. One system is fitted with a wide angle, fixed focus objective lens with large depth of field for searching and the other system is fitted with a narrow angle, fixed focus objective lens having a small depth of field and a predetermined working distance and magnification for measuring.

Optical features of flow cytometry apparatus

Abstract: A flow cytometry apparatus includes a transparent liquid flow chamber and a nozzle for providing a stream of particles, to be analyzed, through the flow chamber. A light source is provided along with a lens for focusing the light from the source at a region within the flow chamber through which the particles pass and for collecting light associated with those particles. Photoreceptors and the like are provided for detecting one or more characteristics of the particles related to light which strikes the particles. A spring or like biasing member provides and maintains stability between the lens and the flow chamber to particularly stabilize the relative axial position of the flow chamber and the lens.

All-round viewing device for motor vehicles

Abstract: In a motor vehicle, a display is arranged in the field of vision of the driver of the vehicle. The said display is connected by means of optical waveguides, in particular optical fibres to image sensors which are arranged distributed in the exterior surfaces of the motor vehicle in such a way that the driver of the motor vehicle can monitor all the sectors surrounding the motor vehicle which are of interest. The image sensors are correspondingly aligned funnels in which lens systems are located which focus the incident light on the end face of the optics of the optical fibre. In the individual displays, which are preferably combined in a group, funnel-shaped connecting elements are also provided, which connecting elements contain corresponding lens systems with which the image which emerges from the optical fibres in a grid form is deflected onto the display surface.

Calcium and the physiology of cataract.

Abstract: Calcium has long been known to play a role in cataract formation but techniques have only recently become available for investigating the physiological mechanisms Previous studies showed that lens membrane permeability alters when the external calcium concentration falls below 1 mM, so it was interesting that values for human aqueous from cataract patients ranged from 045 to 20 mM The mean value for the aqueous was one half that for the plasma The calcium concentration in cataractous lenses ranged from 01 to 64 mM and lenses with a high calcium concentration also had a high sodium content In lenses with near normal sodium content the highest calcium concentrations were associated with highly localized opacities, while nuclear cataracts had a low calcium content The relationship between calcium and transparency was investigated in a rat lens system using ion-sensitive microelectrodes The distribution of free calcium in the lens varied with age and was correlated with a change in the sensitivity of the lens to cold cataract and a change in lens birefringence The highest free calcium levels were obtained from lenses incubated in 10 mM-calcium in the absence of glucose and these lenses showed most light scattering Ion-sensitive microelectrode techniques applied to human lenses yielded calcium levels of 01 microM-2 mM In lenses with dense, highly localized opacities the calcium distribution was not uniform and was highest in regions that scattered most light The movement of calcium through individual membrane channels was investigated using patch clamp techniques Three types of ionic channels have been identified in the lens The smallest appears to be a calcium channel; the larger current fluctuations are associated with sodium and potassium movements In organ culture studies of the bovine lens, a marked decrease in protein synthesis and net leakage of proteins was associated more strongly with an increase in calcium than with an increase in sodium The stability of the lens protein gel thus seems to depend on maintaining a low internal level of calcium ions

Optical lens for the human eye

Abstract: An optical lens adapted for use with a human eye having a lens body formed of a top surface and a bottom surface and wherein the lens body has integral therewith a predetermined area which is adapted to selectively intercept and pass light through the lens body in a manner to obtain an optical effect for substitution of the loss of the accommodation of a phakic, aphakic and pseudophakic eye is shown. The optical lens may be used in an intraocular lens configuration having resilient support means operatively coupled to the lens body adapted to slidably engage tissue in the chamber of an eye to position the lens body in a proper optical relationship. Also, the optical lens can be placed over the cornea of the eye or in the cornea directly by a cornea inlay.

Automatic focus control: the astigmatic lens approach.

Abstract: The use of an astigmatic lens to generate a position error signal (PES) suitable for servo control is discussed. A simple computer model was written that can predict adequately the performance of an astigmatic system. The effect of various system parameters on the PES is presented.

Multifocus intraocular lens

Abstract: An intraocular lens that internally alters its focal length with the position of the eye with respect to the horizontal. The lens is comprised of a solid transparent material having a hollow lenticule that encompasses the optical zone of the eye. The lenticule is connected with fluid reservoirs above and below it, and the reservoirs also are interconnected by channels on both sides of the lenticule. By moving fluids of different indices of refraction through the lenticule, the lens can be made to change its power. When the eye is in the horizontal position, the index of refraction of the fluid occupying the lenticule is such that distant objects are in focus, and when the eye is inclined 45°-90° from the horizontal as for reading, the index of refraction of a different fluid occupying the lenticule is such that near objects are in focus.

Apparatus for the contact-free disintegration of calculi

Abstract: The utilization of the apparatus fundamentally lies in the medical sector. An essentially planar shock wave is generated with the assistance of a shock wave tube via a magnetic dynamic effect. This shock wave is focussed by an acoustic convergent lens, whereby the calculus to be pulverized is placed at the focal point (F) of the convergent lens. In order to couple the shock wave to the patient, the space that the shock wave traverses is filled with a coupling agent, for example water. The shock wave tube, the convergent lens and a fine adjustment for the displacement of the convergent lens relative to the shock wave tube are attached to a mounting stand so as to be pivotable in all directions. This disintegration facility comprising a shock wave tube has high operating reliability with respect to high voltage, requires low maintenance, and has only negligible imaging or focussing errors resulting from the shock wave producing membrane and the convergent lens.

A new method of measuring in vivo the lens transmittance, and study of lens scatter, fluorescence and transmittance.

Abstract: We propose a new method to measure in vivo nuclear transmittance using scanning photometry, thus complementing its present application in measuring lens scatter and fluorescence. We compared our method of measuring the transmittance with a previously reported in vivo method and found an adequate correlation. We then measured the fluorescence, scatter and transmittance of lenses without cataract and those with as much as a mild yellowing. The three phenomena correlated with age. In addition, this study allowed a correlation of the three phenomena with each other, indicating that the loss of transmittance of the nucleus cannot be explained by its thickening alone but that changes in its composition must take place. Finally, a preliminary study on diabetics showed early onset of the process responsible for the increase in lens fluorescence. This process did not seem to be accelerated in diabetics in comparison with normals. The nuclear scatter appeared to increase more rapidly with age in nondiabetics as compared to diabetics. This preliminary study suggests mainly that scanning photometry can be used to study aging and pathologic changes in the lens.

Response Characteristics Of Laser Diffraction Particle Size Analyzers: Optical Sample Volume Extent And Lens Effects

Abstract: The response characteristics of laser diffraction particle sizing instruments were studied theoretically and experimentally. In particular, the extent of optical sample volume and the effects of receiving lens properties were investigated in detail. The experimental work was performed with a particle size analyzer using a calibration reticle containing a two-dimensional array of opaque circular disks on a glass substrate. The calibration slide simulated the forward-scattering characteristics of a Rosin-Rammler droplet size distribution. The reticle was analyzed with collection lenses of 63 mm, 100 mm, and 300 mm focal lengths using scattering inversion software that determined best-fit Rosin-Rammler size distribution parameters. The data differed from the predicted response for the reticle by about 10 percent. A set of calibration factor for the detector elements was determined that corrected for the nonideal response of the instrument. The response of the instrument was also measured as a function of reticle position, and the results confirmed a theoretical optical sample volume model presented here.

Wide-angle optical model of the eye.

Abstract: There are two approaches to the design of a wide-angle optical model of the eye. One approach is based upon data on biological and physical characteristics of the eye (cornea, crystalline lens) collected from the literature or from in vivo or in vitro measurements. From these data a model is built whose configuration is as close as possible to that of a living eye. Then the visual function of the model is calculated and checked for its conformity with the living eye. The second design approach starts with measurements of the optical performance of a living eye. Then the unknown parameters (asphericity of the cornea, distribution of the thicknesses of the individual layers of the crystalline lens, their curvatures and refractive indices, and sphericity of the layers) can be calculated by fitting the curve of the corresponding optical performance calculated from the model to the curve measured in vivo. Using this approach, we measured the axial spherical aberrations in 50 emmetropic volunteers (100 eyes), calculated the best fit to all the measurements, and used it as the average curve of axial spherical aberrations of an emmetropic eye. In this paper we present the results and calculations and discuss the validity of this approach.

Optical device for concentrating the light radiation emitted by a light emitting diode, and a light emitting diode comprising a device of this nature

Abstract: A device for optically coupling a light emitting diode and a radiation pickup such as an optical fiber. The light emitting diode element includes at least one emissive section within an active layer where a part of the light irradiation does not emerge from the diode element if it is emitted at an excessive angle of incidence. A lenticular element in the form of either a semi-cylindrical lens or a semi-toroidal lens is associated with the emissive section. In one form, the device includes a circular central lens and a plurality of semi-toroidal lens concentric with respect to the central lens and associated with annular emissive sections.

Method of controlling the ultraviolet polymerization of spin cast lenses

Abstract: A method of controlling the polymerization of spin cast hydrogel contact lenses by controlling the shape of the ultraviolet light beam across the rotating surface of the spin cast lens. To provide polymerization which progresses smoothly from the center to edge of the rotating lens.

Intraocular lens with miniature optic having expandable and contractible glare-reducing means

Abstract: An intraocular lens having an optic of sufficiently small dimension so as to permit its insertion through an incision substantially smaller than 5 mm in length. The lens includes a masking means which is deformable between an expanded condition in which it masks the edge portion of the optic which would otherwise cause a glare effect and a contracted condition in which the masking means is located within the confines of said small dimension of the optic.

Three-dimensional display

Abstract: A three-dimensional display is disclosed which uses a variable focal length lens through which two-dimensional images of an object are viewed. In one embodiment, a sequence of different images representative of cross sections of the object along its depth dimension are presented by a two-dimensional display apparatus such as a high resolution CRT. The viewer sees these two-dimensional images of the object through the variable focal length lens. The focal length of the lens is changed in synchronization with the two-dimensional images such that each cross section image is seen at a different focal length, thus resulting in a three-dimensional image of the object. The rate of change of the two-dimensional images and the focal length of the lens is higher than the retention rate of the eye of the viewer, thus the images presented appear to fuse into a coherent three-dimensional image. Also disclosed is a fluid-filled lens having an optically transparent elastic membrane for one optical surface which changes the lens focal length by changing membrane curvature in response to fluid pressure changes. A controller is used to control the sequence of two-dimensional images presented and the fluid pressure of the lens. The controller may also size particular two-dimensional images of the object to produce a proper perspective in the three-dimensional image.

Display apparatus for elevator car

Abstract: A display apparatus has a light modulator with an electrooptical Pockels cell disposed in a machine room to modulate a laser beam with a modulating signal from a signal source as determined by a piece of image information to be displayed. After its passage through an optical fiber, the modulated laser beam enters an elevator car where it is focussed on a horizontal deflector by a diminishing lens and then reflected to be focussed on a vertical deflector by a collecting lens. The focussed laser beam is collected on an inner surface of an elevator door by an objective lens. Each deflector is a galvanometer mirror attached to a coil and horizontally or vertically deflecting the laser beam through an angle proportional to a saw tooth current flowing through the coil under the control of the signal source. This results in the display of the piece of image information on the inner surface of the elevator door.

Focus detection apparatus

Abstract: A focus detection apparatus which can precisely perform focus detection for phototaking lenses having various exit pupil positions even when a position separated from the optical axis of a phototaking lens is set as the center of a focus detection area. A pair of outputs are selected from those of a plurality of pairs of photoelectric transducer arrays on the basis of pupil position information associated with the exit pupil position of a phototaking lens, and position information associated with the distance between a base line and the optical axis. An arithmetic means detects a relative shift amount of a plurality of pairs of optical images on the basis of the selected pair of focus detection signals, thereby calculating a defocus amount.

Head-mounted coaxial image system for surgeons

Abstract: There is disclosed a head-mounted imaging system which system employs a headband to be worn on the head of a surgeon during a surgical procedure. A surgeon may utilize a microscope eyeglass assembly in order for him to achieve a desired magnification of the operating area. The headband assembly includes an imaging system which imaging system furnishes a beam of light which beam of light is reflected into the operating area by means of a tiltable mirror coupled to the headband assembly. The tiltable mirror receives the reflected image from the operating site. This image is received by the imaging system where it is directed through a zoom lens magnification assembly whereby the magnification of the lens assembly is set to correspond to the microscope eyeglass assembly worn by the surgeon. The image thus directed through the zoom lens assembly is then coupled to a television monitor pickup for eventual viewing on a television monitor to thereby enable observers to view the entire operation as if through the eyes of the surgeon.