Showing papers on "Lens (optics) published in 1982"

Laser-induced thermal lens effect: a new theoretical model.

Abstract: A theoretical model for the laser-induced thermal lens effect in weakly absorbing media is derived. The model predicts the intensity variation in the far field of the laser beam in the presence of the lensing medium and takes into account the aberrant nature of the thermal lens. Some experimental results which support the validity of this approach are presented.

Methods for implantation of deformable intraocular lenses

Abstract: The invention provides an improved intraocular lens structure comprising a deformable optical zone portion with prescribed memory characteristics and methods and devices for implantation of such lens in the eye. The unique optical zone portion of the lens can be deformed by compressing, rolling, folding, stretching, or can be deformed by a combination of these techniques to temporarily reduce the optical zone portion to a diameter of about 80% or less of the cross-sectional diameter of the optical zone portion in an unstressed state. After insertion into the eye, the optical zone portion returns to its original configuration, full size and fixed focal length. The inventive methods and devices for implantation permit insertion of the improved lens through a relatively small incision made in the ocular tissue, thereby providing a safer, more convenient surgical procedure and more comfortable fit for the eye.

Imaging antenna arrays

Abstract: Many millimeter and far-infrared imaging systems are limited in sensitivity and speed because they depend on a single scanned element. Because of recent advances in planar detectors such as Schottky diodes, superconducting tunnel junctions, and micro-boiometers, an attractive approach to this problem is a planar antenna array with integrated detectors. A planar line antenna array and optical system for imaging has been developed by the authors. The significant advances are a "reverse-microscope" optical configuration and a modified bow-tie antenna design. In the "reverse-microscope" configuration, a lens is attached to the bottom of the substrate containing the antennas. Imaging is done through the substrate. This configuration eliminates the troublesome effects of substrate surface waves. The substrate lens has only a single refracting surface, making possible a virtually aplanatic system, with little spherical aberration or coma. The array is characterized by an optical transfer function that is easily measured. An array with 19 dB crosstalk levels between adjacent antennas has been tested and it was found that the array captured 50 percent of the available power. This imaging system was diffraction limited.

In acoustic microscopy

Abstract: It has been well recognized that the leaky surface wave plays an essential role both in imaging mode and in V(z) measuring mode of acoustic microscopy. To get further insight into the behavior and the role of the leaky surface wave we devised an acoustic lens that enables to generate broadband short pulses. With this lens, we could detect the leaky surface wave separately from the axial wave in time domain. The time interval between these two waves AtRdecreased as the velocity of leaky surface wave v increased. An analytical expression for predicting vzin terms of Atp and z was derived along with ray optics and was verified experimentally for glass, metals and ceramics. A new method for velocity measurement of leaky surface wave was developed that can be done without mechanical scanning of the lens nor the sample.

Image sensor assembly

Abstract: A compact image sensor package for use in an endoscope or borescope in which a lens system, a solid state image sensor and a circuit board are mounted in tandem within a cylindrical sealed housing. The assembly is positioned within the viewing head of the instrument so that an image of a given target is recorded on the sensor and an electrical output signal indicative of the image data is transmitted out of the package via either an optical or electrical transmission line.

Packaging system for intraocular lens structures

Abstract: The invention provides an improved autoclavable system for packaging of intraocular lens structures. In one embodied form, the inventive system comprises an outer container having at least two optically clear windows arranged in parallel relationship, an inner holding fixture mounted within the outer container for receiving and supporting an intraocular lens structure in alignment with the windows and a liquid medium within the container which substantially duplicates optical transmission characteristics of fluid in the eye. The unique packaging system provides an autoclavable sterile environment for a wide variety of intraocular lens structures prior to implantation which permits visual inspection and measurement of important optical parameters of the lens structure without removal of the lens from the container. Additionally, in a preferred embodiment of the invention, the lens holding fixture can also be used as a surgical tool and handling device for the intraocular lens during manufacture, inspection prior to implantation, and manipulation for placement of the intraocular lens structure within the eye.

On the structural organization of isolated bovine lens fiber junctions.

Abstract: Junctions between fiber cells of bovine lenses have been isolated in milligram quantities, without using detergents or proteases. The structure of the isolated junctions has been studied by thin-section, negative-stain, and freeze-fracture electron microscopy and by x-ray diffraction. The junctions are large and most often have an undulating surface topology as determined by thin sectioning and freeze-fracture. These undulations resemble the tongue-and-groove interdigitations between lens fiber cells previously seen by others (D. H. Dickson and G. W. Crock, 1972, Invest. Ophthalmol. 11:809-815). In sections, the isolated junctions display a pentalamellar structure approximately 13-14 nm in overall thickness, which is significantly thinner than liver gap junctions. Each junctional membrane contains in the plane of the lipid bilayers distinct units arranged in a square lattice with a center-to-center spacing of 6.6 nm. Freeze-fracture replicas of the junctions fractured transversely show that the repeating units extend across the entire thickness of each membrane. Each unit is probably constructed from four identical subunits, with each subunit containing a protein of an apparent molecular weight of 27,000. We conclude that the lens junctions are structurally and chemically, different from gap junctions and could represent a new kind of intercellular contact, not simply another crystalline state of the gap junction protein.

The field of a focusing source

Abstract: An analytical description for the field of a focusing source is derived. It is valid for spherically concave sources with small aperture angle and large ka (radius a, wavenumber k.) The solution furnishes easy access to the sound distribution along the axis and in the focal plane, as well as to parameters such as focusing gain, width of the focal spot, and phase shifting in the focal region. Experiments conducted with an f/2 lens coupled to a planar array are discussed. The results support the utility of the analytical model for describing the distribution of sound along the acoustic axis and across the focal plane.

Adaptive liquid crystal lens

Abstract: A liquid crystal adaptive lens system wherein the index of refraction profile of the liquid crystal is controlled electrically to bring entering light to focus.

Artificial eye lenses

Abstract: A contact lens has a transmission hologram which provides diffractive power on a wavelength and/or amplitude selective basis whereby light from near and distant objects can be focussed on the retina of a presbyopic wearer. Similarly an implant lens can have a transmission hologram to correct for non-accommodative vision. The invention is particularly useful in providing an artificial eye lens with a bi-focal action without need for distinct near and far vision zones.

Chemically etched conical microlenses for coupling single-mode lasers into single-mode fibers

Abstract: Coupling efficiency between a laser diode and a single-mode fiber can be greatly increased by using a lensing scheme to match their respective modes. We propose a simple method to selectively etch a fiber end to produce a conical lens whose base coincides with the fiber core. If needed, this lens may be fire polished or arc melted into a hemispherical lens of the same diameter. We present a general theoretical design of both these lenses. We find that high coupling efficiency is expected in cases of practical interest. Initial experimental results are reported in which coupling losses as low as 3 dB were obtained.

Posterior chamber implant lens

Abstract: A posterior chamber implant lens as a replacement for the natural lens surgically removed, in particular extracapsularly, from the eye of a living being of a higher order, with a central lens body and holding means arranged on the lens body, extending radially outwards from the periphery of the body and fixing it in its position, of a homogeneous, clear, vulcanized silicone rubber, wherein (a) the lens body is formed as a convex lens, wherein the rear surface facing the rear wall of the lens capsule has a greater, preferably much greater curvature than the front surface facing the iris, (b) a basically radially outwardly extending, thin-walled support which encircles the center point of the lens body and has a diameter of between approx. 9.0 and approx. 12.0 mm, preferably of about 10.0 to 11.0 mm (c) there are several openings in the support element distributed over the element, preferably in the form of round holes (d) the support element has a material thickness of between approx. 0.15 mm and 0.40 mm, preferably of about 0.20 mm to 0.25 mm (e) there is preferably situated an outwardly rounded-off ridge on at least a part of the outer edge of the support element (f) the vulcanized silicone material (organopolysiloxane) has a specific gravity between 1.01 and 1.08 preferably of about 1.02 (g) the vulcanized silicone material has a Shore hardness between about 30 and 60, preferably of about 40 to 50, and (h) the vulcanized silicone material has a temperature resistance, without deformation of the lens and its components of over 356° F. during a longer dry heat treatment lasting at least 100 hours.

Horizontal position detecting device

Abstract: Disclosed is a horizontal position detecting device for maintaining the surface of a body to be inspected vertically to the optical axis of a main objective lens. The device includes an illumination optical system and a condenser lens system. The illumination optical system supplies parallel light rays to the surface of the body from the direction oblique to the optical axis of the objective lens. The condenser lens system condenses the light rays supplied by the illumination optical system and reflected by the surface of the body. The optical axes of the illumination optical system and the condenser lens system are arranged substantially symmetrically with respect to the axis of the objective lens.

An improved design method of Rotman lens antennas

Abstract: A Rotman lens is used to feed a linear array antenna for wideband use. A relationship between design parameters for realizing a Rotman lens has been derived by introducing a new design variable. The design method which minimizes the phase error on the aperture of the linear array antenna has been shown. For large array length, the above phase error due to this method becomes considerably smaller than that due to a conventional method. This improved method makes it possible to design small and low-loss Rotman lens antennas.

Measurements of lens transparency or its disturbances by densitometric image analysis of Scheimpflug photographs.

Abstract: Scheimpflug photography of the anterior eye segment with densitometric image analysis to measure lens transparency has proven its value in long-term follow-up studies of lens changes. The necessary technical conditions of the SL 45 Topcon camera guarantee high reproducibility. The technical control with respect to quality in case of repeated photography is ensured by an internal standard, the camera being equipped with a five-step scale of known density values. External standardization is done by taking the densitometer height of the cornea as standard. The coefficients of variation for internal and external standards were nearly equal (∼ 5%) over the 9-month period of observation of 100 patients (3,200 photos). The coefficients of variation correspond to the standard error found with repeated lens photos of volunteers' eyes evaluated by analysis of variance of the respective data sets. The standard error for distance measurements on the x-axis (cornea thickness, depth of anterior chamber, lens thickness, etc.) is less than 3%. Evaluation of follow-up examinations may most successfully be done by densitometric planimetry, which, in case of follow-up studies on opacified lenses, is superior to the usual measurements of densitometer height. The light scatter registered by Scheimpflug photography is highly individual. This is demonstrated by densitograms of normal lenses of persons of different age groups. Besides linear densitometry, various other procedures of densitometric planimetry are possible. The best results so far were obtained by multilinear densitometry, but the enormous amount of data obtained in this way renders routine application rather difficult.

Bifocal intraocular lens structure and spectacle actuation frame

Abstract: The invention contemplates structure for surgical implantation within an eye and providing the user with more than one focal length, for viewing at correspondingly different object ranges. In the embodiments disclosed, one intraocular device is relatively fixed in the eye to provide a conventionally available viewing range, for example, distance viewing, and another lens element is movably mounted with respect to the fixed distance-viewing lens in such manner as to provide its selective use in combination with the fixed lens, for close-object viewing.

Optical beam deflection thermal imaging

Abstract: The present invention provides a thermal imaging method to evaluate the surface and subsurface properties of a material and is based on techniques of optical beam deflection thermal imaging. The invention uses a localized excitation source, such as an optical beam, to provide localized heating of the sample surface. A surface thermal gradient is induced on the sample surface as heat flows, in three dimensions, from the area of localized excitation into the test material. The surface temperature gradient causes a thermal refractive lens to be generated in the fluid (gas or liquid) adjacent to the sample surface. An optical probe beam is directed through the thermal lens and is deflected by changes in a refractive index of the thermal lens. Changes in the refractive index are induced by variations of the surface temperature. In this manner, a detailed surface temperature profile can be generated which reveals surface and subsurface properties of the material tested.

Gaussian to flat-top intensity distributing lens

Abstract: A system has been designed to convert the Gaussian intensity profile of a laser beam into a more uniform distribution. This paper postulates a number of afocal lens arrangements for this purpose and details the effect of one particular combination in balancing the higher-order terms and achieving collimation of a diffraction limited output between the l/e points.

Optical fluid lens

Abstract: A lens particularly for applications requiring a large lens eliminates costly grinding and polishing operations. The lens embodies an adjustable chamber containing an optical fluid which can be pressurized in varying degrees by altering the size of the chamber. Resilient optical diaphragms at the ends of the chamber have their curvatures changed responsive to changes in the pressure of the fluid in the chamber to produce a lens of fixed or variable focal length.

Computer-Originated Aspheric Holographic Optical Elements

Abstract: Holographic optical elements (HOEs) recorded with arbitrary aspheric wavefronts can now be analyzed with a holographic ray-tracing design program The recording wavefronts are defined by analytical phase functions, for example, a two-dimensional polynomial expansion The coefficients of the functional representations of the HOE recording wavefronts are used as parameters to optimize the performance of an optical system containing the HOE The optimum recording wavefronts are then produced with the help of computer-generated holograms Several useful arbitrary wavefront phase functions are discussed Design predictions and experimental results are presented for a holographic Fourier transform lens recorded with the aid of a computer-generated hologram

Variable-focal-length lens using an electrooptic effect

Abstract: A novel arrangement of variable-focal-length lens using an electrooptic effect is provided. A variable electric field is applied to an electrooptic crystal to produce therein a refractive index distribution having a lens action. The applied electric field is such that the intensity distribution of the lens varies along one direction in a plane normal to the direction of the light incidence but which has a uniform intensity distribution in the direction normal to this direction. A two-dimensional variable-focal-length lens is obtained by combining two such one-dimensional lenses in such manner that the two-lenses intersect each other at right angles with respect to the direction of the lens action. Also, a refractive index distribution having a two-dimensional lens action is produced to form a variable-focal-length lens when an electric field having an intensity distribution which varies within the plane normal to the direction of the incident light is applied to the electrooptic crystal.

Three dimensional projection arrangement

Abstract: A projection arrangement for projecting three-dimensional images of objects into space. The object is illuminated by a source of light, and the light rays reflected from the object are directed so as to be incident on a mirror surface located behind a lens. The mirror surface receives an image from the lens and the combination forms an enlarged three-dimensional image projected into space. The lens can be in the form of a modified Fresnel lens of multiple focal lengths and having spherical zones in the form of strips. The Fresnel lens, which may be used in combination with other optical elements, provides a substantially large field of view suitable for viewing a three-dimensional image of the object by a mass audience. The image projection may be achieved without the use of a screen. The enlarged three-dimensional image appears floating in space visible to unaided eyes of an audience.

Multi-beam optical system using lens array

Abstract: Each laser of a semiconductor laser array of an optical system has its own lens mounted adjacent to it in the space between the laser array and the objective lens of the system. The purpose of the lenses is to change the angle of divergence of the light beams leaving the emitting surface of the laser array so that the light beams can be collected efficiently by the objective lens, thereby providing significant beam power at the light sensitive medium (optical disk, photoconductor, etc.) of the optical system. The focusing power of each lens is chosen to form virtual images behind the emitting surface with spacings approximately corresponding to the spacings of the light beams emitted by the laser array, but with the emitter image size substantially magnified.

Liquid crystal display screen for use in TV

Abstract: A liquid crystal display TV includes a TV housing, and a reflective type liquid crystal display panel installed in the housing. A magnifying lens is disposed for magnifying an image on the display area and a support assembly is provided for supporting the magnifying lens to allow a space where the ambient light enters from above a display area of said liquid crystal display panel when the magnifying lens lens is in use. This arrangement allows full utilization of the ambient light for the optical performance of the liquid crystal display panel.

Intra-optical light beam sighting system for an infrared thermometer

Abstract: A sighting system primarily for use with infrared thermometers and that provides a visible light beam, the geometry of which is congruent with the field of view of the infrared optics of the thermometer to provide the user with an accurate representation of the intersection of the field of view cross-section of the object of which the temperature is being measured by the thermometer. Two novel embodiments are disclosed, one of which utilizes Fresnel lenses and one of which utilizes a Cassegrainian lens system. Both embodiments provide means for accommodating an isolated visible light source and passage of the visible light generated therefrom through the identical lens system used by the infrared detector to develop the signal indicative of the infrared energy and therefore temperature generated by the object to which the infrared thermometer is directed.

Variable focus lens system employing elastomeric lens

Abstract: A variable focus lens system comprising an elastomeric, integrally molded, optical member and mounting arrangements therefor by which the axial position and the shape of a central lens part of the optical member can be changed in correspondence with one another to provide the lens system with focusing action over a predetermined range.

Image pick-up apparatus

Abstract: An apparatus for picking-up an image of an object including a solid state image sensor having a number of image sensing elements and an objective lens for projecting the image of the object onto the image sensor is disclosed. In order to remove a curvature of field of the objective lens, the image sensor is curved into a spherical shape having a radius of curvature equal to that of the curvature of field. The solid state image sensor may be curved in any desired shape to correct various aberrations of the objective lens.

Method and apparatus for measuring natural retinal fluorescence

Abstract: Oxygenation of the retina is determined by measuring the fluorescence of flavoprotein in the retina. A spot of excitation light of a frequency of about 450 nanometers is scanned across the retina. Fluorescent light emitted from the retina at a frequency of about 520 nanometers is detected. The emission light may be detected at two frequencies of about 520 nm and 540 nm to allow for compensation for absorption and transmission variables in the eye. To compensate for fluoresence of the lens of the eye, the center of the pupil is imaged onto scanning mirrors so that the scanning beam of excitation light pivots at the center of the eye lens. Further, the center of the lens is imaged onto an optical stop in the emission optical path so that emitted light which passes back through the lens periphery, and not fluorescent light from the center of the lens, is detected. The emission light detector is a photon counting photomultiplier tube to permit safe limits on the intensity of the excitation light. Through computer controlled electronics, a fluorescent map can be stored in memory.